Monomer-dimer model in two-dimensional rectangular lattices with fixed dimer density

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卟啉及其衍生物的应用2

卟啉及其衍生物的应用2

卟啉及其衍生物的应用摘要:近年来,卟啉及卟啉衍生物在显色反应、分子识别、催化合成反应等领域中有很广泛的应用。

文章就卟啉及卟啉衍生物在分析化学、生命科学和化学合成方面的研究发展作一简要介绍,并提出卟啉化合物今后的发展方向。

关键词:卟啉;金属卟啉;应用卟啉和金属卟啉广泛存在于自然界和生命体中,为高熔点的深色固体,多数不溶于水和碱,但能溶于无机酸。

其溶液有荧光,对热非常稳定。

卟啉化合物在石油产品中主要是以钒卟啉存在。

在生命体系中,血红蛋白、细胞色素等生物分子的结构核心都是卟啉。

它们作为一类特殊的大环共轭芳香体系,在仿生学、药学、医学、催化、材料化学、配位化学、光谱学、电化学、分析化学、有机化学等领域有广阔的应用前景。

近年来这类化合物的性能以及应用引起了科学家的广泛关注。

尤其是金属卟啉,在发展检测气体的高选择性传感物质中是一类很有潜力的分子。

本文就卟啉在分析化学、生命科学、催化等领域的应用作一综述。

1 卟啉的性质及基本结构卟啉是在卟吩环上拥有取代基的一类大环化合物的总称,具有特殊的刚性兀电子离域结构。

卟啉的卟吩环基本上在一个平面上,因此它的性质比较稳定。

卟吩环高度共轭的体系极易受到吡咯环及次甲基的电子效应影响,从而表现为各不相同的电子光谱。

在卟啉大环中,四个氮原子构成了一定空间位置和配位能力的环境,可与金属形成稳定的金属卟啉配合物。

如果在卟啉环上改变取代基、调节4个氮原子的给电子能力,引入不同的中心金属离子或者改变不同亲核性的轴向配体,就会使卟啉和金属卟啉具有不同的性质,因而也具有不同的功能。

由于卟啉具有特殊的结构和功能,因而被应用在多方面。

2 卟啉的应用研究2.1在分析化学中的应用2.1.1测定痕量金属离子卟啉类显色剂能与多种金属离子形成配合物,其摩尔吸光系数一般可达105L/moL.cm。

因此卟啉作为显色剂,测定金属离子灵敏度很高,络合比固定,稳定性好,具有操作简便、测定快速等优点。

自1974年四苯基卟啉三磺酸被作为光度试剂测量铜以来,卟啉试剂被称为“超高灵敏度的显色剂”。

Mathematical Modelling and Numerical Analysis Will be set by the publisher Modelisation Mat

Mathematical Modelling and Numerical Analysis Will be set by the publisher Modelisation Mat
& luskin@
c EDP Sciences, SMAI 1999
2

PAVEL BEL K AND MITCHELL LUSKIN
In general, the analysis of stability is more di cult for transformations with N = 4 such as the tetragonal to monoclinic transformations studied in this paper and N = 6 since the additional wells give the crystal more freedom to deform without the cost of additional energy. In fact, we show here that there are special lattice constants for which the simply laminated microstructure for the tetragonal to monoclinic transformation is not stable. The stability theory can also be used to analyze laminates with varying volume fraction 24 and conforming and nonconforming nite element approximations 25, 27 . We also note that the stability theory was used to analyze the microstructure in ferromagnetic crystals 29 . Related results on the numerical analysis of nonconvex variational problems can be found, for example, in 7 12,14 16,18,19,22,26,30 33 . We give an analysis in this paper of the stability of a laminated microstructure with in nitesimal length scale that oscillates between two compatible variants. We show that for any other deformation satisfying the same boundary conditions as the laminate, we can bound the pertubation of the volume fractions of the variants by the pertubation of the bulk energy. This implies that the volume fractions of the variants for a deformation are close to the volume fractions of the laminate if the bulk energy of the deformation is close to the bulk energy of the laminate. This concept of stability can be applied directly to obtain results on the convergence of nite element approximations and guarantees that any nite element solution with su ciently small bulk energy gives reliable approximations of the stable quantities such as volume fraction. In Section 2, we describe the geometrically nonlinear theory of martensite. We refer the reader to 2,3 and to the introductory article 28 for a more detailed discussion of the geometrically nonlinear theory of martensite. We review the results given in 34, 35 on the transformation strains and possible interfaces for tetragonal to monoclinic transformations corresponding to the shearing of the square and rectangular faces, and we then give the transformation strain and possible interfaces corresponding to the shearing of the plane orthogonal to a diagonal in the square base. In Section 3, we give the main results of this paper which give bounds on the volume fraction of the crystal in which the deformation gradient is in energy wells that are not used in the laminate. These estimates are used in Section 4 to establish a series of error bounds in terms of the elastic energy of deformations for the L2 approximation of the directional derivative of the limiting macroscopic deformation in any direction tangential to the parallel layers of the laminate, for the L2 approximation of the limiting macroscopic deformation, for the approximation of volume fractions of the participating martensitic variants, and for the approximation of nonlinear integrals of deformation gradients. Finally, in Section 5 we give an application of the stability theory to the nite element approximation of the simply laminated microstructure.

第4讲 蛋白质的结构体系III

第4讲 蛋白质的结构体系III

二硫键: 可用还原反应断开之 (是可逆反应) Cys-S-S-Cys → Cys-SH + HS-Cys RNase A (RNA 水解酶): Anfinsen
124 个氨基酸序列中有 四对二硫键 极度坚固


Chaperonin 可诱导蛋白质的正确折叠
Proteasome 则摧毀不正确折叠者
The polypeptide hormone insulin cannot spontaneously re-form if its disulfide bonds are disrupted. It is synthesized as a larger protein (proinsulin) that is cleaved by a proteolytic enzyme after the protein chain has folded into a specific shape. Excision of part of the proinsulin polypeptide chain causes an irretrievable loss of the information needed for the protein to fold spontaneously into its normal conformation.
目前研究发现,大部分的蛋白质不像 RNase 一样地可自由地 变性与复性,二硫键的形成或打断,都需要经由另一种酶的 催化。 而要正确地折迭三级结构,有时需要相当复杂的帮手 来协助,这一群帮手统称为 chaperonin。
分子间 Interchain Disulfide bond
C CH2 SH
Oxidation Reduction

单体和低聚物的含量对聚酰胺6切片性能的影响

单体和低聚物的含量对聚酰胺6切片性能的影响

浙江理工大学学报,第51卷,第2期,2024年3月J o u r n a l o f Z h e j i a n g S c i -T e c h U n i v e r s i t yD O I :10.3969/j.i s s n .1673-3851(n ).2024.02.004收稿日期:2023-04-06 网络出版日期:2023-07-07基金项目:浙江省自然科学基金项目(L D Q 23E 030001)作者简介:郭银涛(1997- ),男,安徽阜阳人,硕士研究生,主要从事再生P A 6性能分析方面的研究㊂通信作者:吕汪洋,E -m a i l :l u w y@z s t u .e d u .c n 单体和低聚物的含量对聚酰胺6切片性能的影响郭银涛,王勇军,吕汪洋(浙江理工大学纺织纤维材料与加工技术国家工程实验室,杭州310018) 摘 要:采用溶解/沉淀法对聚酰胺6(P A 6)中的单体及低聚物进行提取,利用液相色谱/飞行时间质谱/二极管阵列检测器(L C -T O F -M S -P D A )和聚合物色谱/多角度激光散射/示差折光检测器(A P C -M A L L S -R I D )联用方法测定P A 6中单体和低聚物含量㊁低聚物组成及P A 6的分子量和分布;通过热重分析仪㊁差示扫描量热仪和二维广角X 射线衍射仪分析P A 6切片中单体低聚物含量对切片热性能和结晶性能的影响㊂结果表明:物理再生P A 6(pr -P A 6)和化学再生P A 6(c r -P A 6)中单体及环状低聚物含量分别为2.079%和1.578%,比原生P A 6(P A 6)分别高0.683%和0.182%,其中再生P A 6切片中单体㊁环状二聚体和环状三聚体含量高于原生P A 6切片㊂P A 6㊁pr -P A 6和c r -P A 6的分子量分别为19620㊁20840g /m o l 和22210g /m o l ,分子量分布系数分别为1.47㊁1.56和1.49;三种P A 6切片的最大分解温度无明显变化㊂与原生P A 6切片相比,再生P A 6切片的结晶峰温度向高温区偏移,结晶温度从P A 6的176ħ增加至p r -P A 6的185ħ,且pr -P A 6和c r -P A 6切片中α晶型的相对含量增加㊂该研究可为提高P A 6材料的热性能及结晶性能提供理论基础㊂关键词:P A 6切片;单体;低聚物;液相色谱/飞行时间质谱/二极管阵列检测器;结晶中图分类号:T Q 317.2文献标志码:A文章编号:1673-3851(2024)03-0174-06引文格式:郭银涛,王勇军,吕汪洋.单体和低聚物的含量对聚酰胺6切片性能的影响[J ].浙江理工大学学报(自然科学),2024,51(2):174-179.R e f e r e n c e F o r m a t :G U O Y i n t a o ,W A N G Y o n g j u n ,L ÜW a n g y a n g .E f f e c t s o f m o n o m e r a n d o l i go m e r c o n t e n t i n p o l y a m i d e 6p e l l e t s o n t h e i r p r o p e r t i e s [J ].J o u r n a l o f Z h e j i a n g S c i -T e c h U n i v e r s i t y,2024,51(2):174-179.E f f e c t s o f m o n o m e r a n d o l i g o m e r c o n t e n t i n p o l y a m i d e 6p e l l e t s o n t h e i r p r o pe r t i e s G U O Y i n t a o ,W A N G Y o n g j u n ,L ÜW a n g y a n g(N a t i o n a l E n g i n e e r i n g L a b o r a t o r y f o r T e x t i l e F i b e r M a t e r i a l s a n d P r o c e s s i n g T e c h n o l o g y,Z h e j i a n g S c i -T e c h U n i v e r s i t y ,H a n gz h o u 310018,C h i n a ) A b s t r a c t :M o n o m e r s a n d o l i g o m e r s f r o m p o l y a m i d e 6(P A 6)w e r e e x t r a c t e d b y d i s s o l u t i o n /p r e c i p i t a t i o n m e t h o d ,a c o m b i n a t i o n o f l i q u i d c h r o m a t o g r a p h y /t i m e f l i g h t m a s s s p e c t r o m e t r y /ph o t o d i o d e a r r a y d e t e c t o r (L C -T O F -M S -P D A )a n d a p o l y m e r c h r o m a t o g r a p h y /m u l t i -a n g l e l a s e r -l i g h t -s c a t t e r i n g/r e f r a c t i v e i n d e x d e t e c t o r (A P C -M A L L S -R I D )w a s u s e d t o m e a s u r e t h e m o n o m e r a n d o l i go m e r c o n t e n t a n d o l i g o m e r c o m p o s i t i o n o f P A 6,P A 6m o l e c u l a r w e i gh t a n d i t s d i s t r i b u t i o n i n P A 6.T h e e f f e c t s o f t h e m o n o m e r a n d o l i g o m e r c o n t e n t o n t h e t h e r m a l a n d c r y s t a l l i z a t i o n p r o p e r t i e s o f P A 6p e l l e t s w e r e a n a l yz e d b y t h e r m o g r a v i m e t r i c a n a l y z e r ,d i f f e r e n t i a l s c a n n i n g c a l o r i m e t e r a n d t w o -d i m e n s i o n a l w i d e -a n g l e X -r a yd i f f r a c t o me t e r .T h e r e s u l t s i n d i c a t e t h a t t h e m o n o m e r a n d c y c l i c o l i g o m e r c o n t e n t s i n p h y s i c a l l y r e c yc l ed P A 6(p r -P A 6)a n d c he m i c a l l y r e c y c l e d P A 6(c r -P A 6)p e l l e t s w e r e 2.079%a n d 1.578%,r e s p e c t i v e l y,0.683%a n d 0.182%h i g h e r t h a n t h o s e i n t h e o r i g i n a l P A 6(P A 6)p e l l e t s ,w h i l e t h e m o n o m e r ,c yc l i cd i me r a n d c y c l i c t r i m e r c o n t e n t s i n t h e r e c y c l e d P A 6p e l l e t s w e r e h i g h e r t h a n t h o s e of t h e o r i gi n a l P A 6p e l l e t s .T h e m o l e c u l a r w e i gh t s o f P A 6,p r -P A 6a n d c r -P A 6w e r e 19620g /m o l ,20840g /m o l a n d22210g/m o l,r e s p e c t i v e l y,w i t h t h e m o l e c u l a r w e i g h t d i s t r i b u t i o n c o e f f i c i e n t s o f P A6,p r-P A6a n d c r-P A6 b e i n g1.47,1.56a n d1.49,r e s p e c t i v e l y.T h e m a x i m u m d e c o m p o s i t i o n t e m p e r a t u r e s o f t h e t h r e e P A6 p e l l e t s d i d n o t c h a n g e s i g n i f i c a n t l y.C o m p a r e d w i t h t h e o r i g i n a l P A6p e l l e t s,t h e c r y s t a l l i z a t i o n p e a k t e m p e r a t u r e o f r e g e n e r a t e d P A6p e l l e t s s h i f t e d t o t h e h i g h t e m p e r a t u r e r e g i o n,a n d t h e c r y s t a l l i z a t i o n t e m p e r a t u r e i n c r e a s e d f r o m176ħf o r P A6t o185ħf o r p r-P A6,a n d t h e r e l a t i v e c o n t e n t o fαc r y s t a l l i n e f o r m s i n p r-P A6a n d c r-P A6p e l l e t s i n c r e a s e d.T h i s s t u d y c a n p r o v i d e a t h e o r e t i c a l b a s i s f o r i m p r o v i n g t h e t h e r m a l a n d c r y s t a l l i z a t i o n p r o p e r t i e s o f P A6m a t e r i a l s.K e y w o r d s:P A6p e l l e t s;m o n o m e r s;o l i g o m e r s;l i q u i d c h r o m a t o g r a p h y/t i m e f l i g h t m a s s s p e c t r o m e t r y/p h o t o d i o d e a r r a y d e t e c t o r(L C-T O F-M S-P D A);c r y s t a l l i z a t i o n0引言聚酰胺6(P A6)材料广泛应用于日常生活和工业工程,如纺织品㊁轮胎帘子布和渔网等[1-2]㊂因具有优异的耐化学性和耐磨性,导致P A6材料在自然环境中难以分解[3-5]㊂为了缓解环境压力及减少P A6材料的浪费,对其进行回收再利用处理是重要途径[6]㊂P A6材料回收再利用的方法主要有物理法和化学法[7-10]㊂物理法指将废旧P A6材料进行清洗㊁干燥和添加各种助剂进行重新熔融造粒的方法;化学法指将废旧P A6材料降解成相应的小单体,然后重新聚合成P A6的方法㊂然而,无论是物理法还是化学法,均会对P A6的性能产生一定的影响㊂对P A6材料结构性能变化进行相关分析的研究近年来受到广泛关注㊂目前,聚合物材料的结构性能的表征方法有傅里叶变换红外光谱法㊁差示扫描量热法和热重分析法等方法[11-14]㊂然而,这些技术却不能高效准确地表征聚合物中低聚物的含量及组成㊂目前,液相色谱技术在对低聚物含量测试方面具有很大的优势,具有相对较高的速度㊁效率和灵敏度㊂通过将液相色谱与合适的检测仪器联用,例如液相色谱和质谱(L C-M S)联用以及液相色谱和化学发光氮检测耦合联用(H P L C-C L N D)能够显著提高检测能力[15-16]㊂本文拟采用更高效㊁快捷的液相色谱/飞行时间质谱/二极管阵列检测器(L C-T O F-M S-P D A)方法对P A6材料中单体及低聚物的含量进行表征㊂目前,常用提取P A6中低聚物的方法为热水萃取法,该方法需要消耗大量时间,且对单体及低聚物提取不完全,急需发展有效的提取方法㊂本文建立了一种对P A6中单体及低聚物提取较完全的溶剂/沉淀法㊂该方法选择合适的良性溶剂和不良溶剂对P A6材料中的单体及低聚物进行提取㊂在此基础上,进一步分析P A6切片中单体和低聚物含量对其性能的影响㊂综上所述,本文采用溶解/沉淀法对P A6材料中单体及低聚物进行提取,利用L C-T O F-M S-P D A 方法对P A6材料中单体及低聚物含量进行表征,采用先进聚合物色谱/多角度激光光散射/示差折光检测器(A P C-M A L L S-R I D)对样品的分子量及其分布进行分析,并通过热分析仪(T G A)㊁差示扫描量热仪(D S C)和二维广角X射线衍射仪(W A X D)分析再生P A6切片中单体及低聚物对其热性能和结晶性能的影响㊂研究结果可为提高P A6材料的热性能及结晶性能提供一定的理论基础㊂1实验部分1.1实验材料P A6切片来自上海纺织工业技术监督局,包括原生P A6(P A6,相对黏度2.8)㊁物理法再生P A6 (p r-P A6,相对黏度2.8)和化学法再生P A6(c r-P A6,相对黏度3.1)㊂乙腈(M e C N,ȡ99.9%)购自默克试剂公司三氟乙酸钠(色谱纯,ȡ99.7%),六氟异丙醇(H F I P,ȡ99.9%),甲醇(A R,ȡ95%)均购自阿拉丁试剂公司㊂1.2P A6样品中单体及低聚物的提取及P A6粉末样品制备将P A6样品(0.5g)在25ħ下溶解于H F I P (7m L)中,随后边搅拌边缓慢滴加沉淀剂甲醇,待大量沉淀析出后,将剩余液体转移至25m L容量瓶中定容,静置待用㊂将P A6样品先液氮冷冻2m i n,再放入粉碎机中粉碎10m i n,得到P A6粉末样品㊂1.3测试与表征采用液相色谱/飞行时间质谱/二极管阵列检测器(美国W a t e r s公司,型号U P L C S y n a p t G2-S H D M S)分析P A6切片中单体和低聚物的含量,流动相由水(A相)和色谱级乙腈(B相)组成,其中流动相采用梯度洗脱,流动相流速为0.3m L/m i n㊂采用先进聚合物色谱(美国W a t e r s公司,型号571第2期郭银涛等:单体和低聚物的含量对聚酰胺6切片性能的影响W a t e r s1525/2414)结合多角度激光光散射仪和示差折光检测器对P A6切片的分子量及分布进行测定,流动相和溶剂为含5m m o l/L三氟乙酸钠的六氟异丙醇溶液,流动相流速为0.4m L/m i n㊂采用热重分析仪(瑞士M e t t l e r公司,型号T G A1/D S C1)考察P A6切片的热稳定性,N2流速为45m L/m i n,测试温度范围25~550ħ,升温速率为10ħ/m i n㊂采用差示扫描量热仪(瑞士M e t t l e r公司,型号A v a n c eⅡ400)测试P A6样品的结晶性能,N2流速为45m L/m i n,升温测试温度范围25~300ħ,并保温3m i n,降温测试温度范围300~25ħ,升温和降温速率均为10ħ/m i n㊂采用二维广角X射线衍射仪(德国B r u k e r公司,型号D8D i s c o v e r)分析P A6切片的晶体结构,采用C u Kα辐射源,电压和电流分别为40k V和40m A,扫描范围为2ʎ~76ʎ㊂2结果与讨论2.1液相色谱/飞行时间质谱/二极管阵列检测器分析液相色谱/飞行时间质谱/二极管阵列检测器(L C-T O F-M S-P D A)不仅能获得聚合物材料中单体及低聚物的分子量,还可以根据其形状及大小对单体和低聚物进行分离㊂P A6中单体及低聚物L C图如图1所示,从中可以看出,单体和低聚物能被有效地分离㊂溶解/沉淀法能有效提取单体㊁环状二聚体至环状九聚体(C1~C9)等低聚物,且C2㊁C1㊁C3㊁C4㊁C5㊁C6㊁C7㊁C8和C9依次被洗脱出来㊂可以清晰地看出C2保留时间短于C1,这可能是因为C2与色谱柱填料之间存在弱相互作用[17]㊂单体及低聚物相对应的分子质量如表1所示,其中测试相对分子量由飞行时间质谱测得,理论相对分子量由计算机计算得到;C1相对分子量为加H+后的相对分子量,C2~ C9相对分子量为加N a+后的相对分子量㊂P A6分子链中的酰胺键为吸水性基团,故在单体及低聚物含量测试前需进行烘干处理㊂P A6切片样品中单体和低聚物含量(质量含量)见表2㊂从中可以看出单体和低聚物含量随聚合度的增加呈现先下降随后上升再下降的趋势,其中p r-P A6比P A6中单体及低聚物比P A6高约0.683%㊂p r-P A6和c r-P A6切片中C1~C5的低聚物含量均显著增加,p r-P A6比P A6高约0.69%,而c r-P A6比P A6高约0.198%㊂相比P A6切片,p r-P A6和图1单体和环状低聚物对应的L C图表1单体及低聚物的分子量[C n+H/N a]+(n=1,2, ,9)测试相对分子量(m/z)P A6p r-P A6c r-P A6理论相对分子量(m/z) [C1+H]+114.0925114.0925114.0921114.0919 [C2+N a]+249.1583249.1582249.1583249.1579 [C3+N a]+362.2419362.2430362.2430362.2420 [C4+N a]+475.3273475.3278475.3270475.3260 [C5+N a]+588.4115588.4120588.4125588.4101 [C6+N a]+701.4951701.4952701.4955701.4942 [C7+N a]+814.5803814.5789814.5787814.5782 [C8+N a]+927.6641927.6642927.6653927.6623 [C9+N a]+1040.75671040.74781040.75391040.7463 c r-P A6切片中C6~C9的含量变化不明显,三种样品都仅在0.643%左右㊂这是因为在再生过程中,高温熔融会导致P A6材料大分子的分子链断裂,生成分子量较低的低聚物所致㊂c r-P A6中的单体及低聚物总含量高于P A6且低于p r-P A6,这主要是因为在c r-P A6的制备是将材料中分子链解聚成单体或低聚物,然后解聚获得单体及低聚物重新聚合制备c r-P A6材料㊂2.2先进聚合物色谱分析聚合物的分子量过大或过小会影响聚合物的加工性能,故对聚合物分子量测试具有重要意义㊂表3展示了不同切片的平均分子量及多分散指数㊂从中可以看出,P A6切片具有较小的分子量分布系数(重均分子量/数均分子量,M w/M n),对应的M n为19620g/m o l;p r-P A6切片的分子量分布系数最大,对应的M n为20840g/m o l,这与多分散指数会随着低聚物含量的增加而增加的结论吻合㊂P A6中低聚物含量低,因其链长均匀,故而导致分子量分布变窄, M n值也较低㊂图2是示差折光(R I)和光散射(L S)信号图㊂从中可以发现,当样品分子量越大,到达峰值所需的时间越短㊂由于c r-P A6在重聚的过程中加671浙江理工大学学报(自然科学)2024年第51卷入扩链剂,使得分子链长度增加并生成凝胶结构[18],因而c r -P A 6切片的M n 最大,达到22210g /m o l㊂总之,再生过程会使P A 6材料的M n 增加,低聚物的增多会使分子链分布变宽,分子量分布系数增加㊂表2 P A 6切片单体及低聚物含量%样品名称C 1C 2C 3C 4C 5C 6C 7C 8C 9总含量P A 60.1080.0480.1310.1960.2630.2780.2370.1020.0331.396pr -P A 60.6450.0750.1830.2450.2880.2820.2330.1050.0212.079c r -P A 60.1380.0820.1800.2480.2960.2810.2380.0910.0261.578表3 不同切片的平均分子量及多分散指数切片名称M n /(g ㊃m o l -1)M w /M n P A 6196201.47pr -P A 6208401.56c r -P A 6222101.49图2 不同P A 6切片的L S 信号和R I 信号图2.3 P A 6切片热性能分析2.3.1 热重分析仪分析P A 6材料的热稳定性在循环再利用过程也会受到一定的影响㊂P A 6切片热重图如图3所示㊂从中可以看出,P A 6切片的初始分解温度为350ħ,P A 6㊁pr -P A 6及c r -P A 6样品质量损失5%对应的温度分别为407.5㊁402.6ħ和407.2ħ㊂此外,从图3中可以看出,P A 6切片的残留量比c r -P A 6的残留量高约2%,比p r -P A 6的残留量高约5%㊂这是由于P A 6材料中低聚物含量高会使分子量的分布变宽,降低了分子量的均匀性,从而导致该部分在降解过程中更容易发生化学键断裂[19],使pr -P A 6切片在初始阶段的热分解速度加快㊂P A 6切片的热重微分曲线如图4所示㊂从中可以看出P A 6的分解速率最快,但三者的分解温度基本相同,并没有发生较大改变㊂图3 不同P A 6切片的T G 曲线图4 不同P A 6切片D T G 曲线2.3.2 差示扫描量热仪分析采用D S C 对P A 6切片的熔融结晶过程进行研究,结果如图5所示㊂从中可以看出,再生P A 6切片和原生P A 6切片的升温和降温曲线相似[2],表明再生过程对P A 6切片的熔融结晶过程影响很小㊂降温结晶过程曲线如图5(a ),与原生P A 6切片相比,再生P A 6切片的结晶峰温度向高温区偏移,结晶温度从原生P A 6的176ħ增加至p r -P A 6的185ħ㊂造成这种现象的原因是,一方面,p r -P A 6和c r -P A 6中低聚物含量较高使分子量分布变宽,从而低分子化合物含量较高;另一方面,P A 6再加工过程中分子链的断裂导致不完整晶体产生[21]㊂这两个方面都会使再生P A 6切片的结晶速率加快及结晶峰向高温偏移㊂结晶温度升高不利于纺丝过程,主要表现为切片在纺丝过程中的拉伸性能变差,更容易771第2期郭银涛等:单体和低聚物的含量对聚酰胺6切片性能的影响发生断丝和毛丝㊂升温过程曲线如图5(b),再生P A6和原生P A6切片的熔点为222ħ左右,表明再生过程对P A6切片的熔融温度没有明显的影响㊂图5不同P A6切片的D S C图2.4P A6切片二维广角X射线衍射仪分析P A6材料在熔融加工㊁冷却后可形成两种主要晶型,即热力学稳定的α晶型和亚稳态的γ晶型[22]㊂从图6所示样品的二维广角X射线衍射图能够看到明显的衍射环㊂对二维衍射图进行软件处理,可以得到如图7所示的一维衍射强度曲线㊂P A6再生前后出现3个突出的衍射环,衍射环的位置没有改变,分别对应19.8ʎ㊁21.2ʎ和23.1ʎ㊂其中19.8ʎ和23.1ʎ对应于α晶型,而21.2ʎ对应γ晶型[23]㊂这说明3种P A6材料的晶型结构未发生改变㊂对于再生P A6材料, 23.1ʎ处的信号强度相比21.2ʎ更强,这说明该样品中23.1ʎ对应的α晶型的相对含量增加㊂3结论为研究P A6切片中单体及低聚物含量对其性能的影响,采用溶解/沉淀法对P A6材料中单体及低聚物进行提取,利用L C-T O F-M S-P D A联用法分析单体及低聚物含量,通过A P C-M A L L S-R I D测试样品分子量及其分布,结合热性能和结晶性能测试分析单体及低聚物含量对P A6材料性能的影响㊂所得主要结论如下:a)再生P A6中所含单体和低聚物的总量高于图6P A6样品X R D 二维衍射图图7P A6样品X R D一维衍射图原生P A6㊂这主要是再生P A6切片中单体㊁环状二聚体和环状三聚体的含量较高㊂物理再生P A6(p r-P A6)和化学再生P A6(c r-P A6)中单体及环状低聚物含量分别为2.079%和1.578%,比原生P A6 (P A6)分别高0.683%和0.182%㊂b)P A6切片的分子量分布随低聚物含量的增加而变宽,且再生过程能够增加P A6材料分子量㊂P A6㊁p r-P A6和c r-P A6的分子量分别为19620㊁20840g/m o l和22210g/m o l,分子量分布分别为1.47㊁1.56和1.49㊂c)较高含量的低聚物能够提高P A6材料的结晶温度㊁结晶速率以及初始热分解速率㊂结晶温度从原生P A6的176ħ增加至p r-P A6的185ħ,但三种P A6切片的最大分解温度无明显变化㊂871浙江理工大学学报(自然科学)2024年第51卷d)再生前后P A6材料的晶型结构未发生改变㊂当结晶温度从P A6的176ħ增加至p r-P A6的185ħ, p r-P A6和c r-P A6切片中α晶型的相对含量增加㊂参考文献:[1]P e n g C,T a n g X J,G o n g X Y,e t a l.D e v e l o p m e n t a n da p p l i c a t i o n o f a m a s s s p e c t r o m e t r y m e t h o d f o r q u a n t i f y i n g n y l o n m i c r o p l a s t i c s i n e n v i r o n m e n t[J].A n a l y t i c a l C h e m i s t r y,2020,92(20):13930-13935.[2]M o n d r a g o n G,K o r t a b e r r i a G,M e n d i b u r u E,e t a l. 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[13]孔维恒,王琳丽,郝欣,等.便携式拉曼光谱仪快速识别塑料新料与再生料[J].分析仪器,2019(5):109-111.[14]刘能盛.再生塑料检验鉴别技术的研究[D].广州:广东工业大学,2016:20-52.[15]S c h w e i g h u b e r A,G a l l M,F i s c h e r J,e t a l.D e v e l o p m e n t o f a n L C-M S m e t h o d f o r t h e s e m i q u a n t i t a t i v e d e t e r m i n a t i o n o f p o l y a m i d e6c o n t a m i n a t i o n s i n p o l y o l e f i n r e c y c l a t e s[J].A n a l y t i c a l a n d B i o a n a l y t i c a l C h e m i s t r y, 2021,413(4):1091-1098.[16]H e i m r i c h M,Bön s c h M,N i c k l H,e t a l.C y c l i c o l i g o m e r s i n p o l y a m i d e f o r f o o d c o n t a c t m a t e r i a l: Q u a n t i f i c a t i o n b y H P L C-C L N D a n d s i n g l e-s u b s t a n c e c a l i b r a t i o n[J].F o o d A d d i t i v e s&C o n t a m i n a n t s:P a r t A:C h e m i s t r y,A n a l y s i s,C o n t r o l,E x p o s u r e&R i s kA s s e s s m e n,2012,29(5):846-860.[17]M e n g e r i n k Y,P e t e r s R,K e r k h o f f M,e t a l.A n a l y s i s o f l i n e a r a n d c y c l i c o l i g o m e r s i n p o l y a m i d e-6w i t h o u t s a m p l e p r e p a r a t i o n b y l i q u i d c h r o m a t o g r a p h y u s i n g t h e s a n d w i c h i n j e c t i o n m e t h o d[J].J o u r n a l o fC h r o m a t o g r a p h y A,2000,876(1/2):37-50.[18]C a i Q Q,B a i T W,Z h a n g H J,e t a l.C a t a l y s t-f r e e s y n t h e s i s o f p o l y e s t e r s v i a c o n v e n t i o n a l m e l t p o l y c o n d e n s a t i o n[J].M a t e r i a l s T o d a y,2021,51:155-164.[19]L i R G,S h i K H,Y e L,e t a l.I n t e r c a l a t i o n s t r u c t u r ea n d e n h a n c e d t h e r m a l o x i d a t i v e s t ab i l i t y o f p o l y a m i d e 6/g r a p h e n e n a n oc o m p o s i t e s p r e p a r ed t h r o u g h i n s i t u p o l y me r i z a t i o n[J].I n d u s t r i a l&E n g i n e e r i n gC h e m i s t r y R e s e a r c h,2017,56(46):13715-13724.[20]T u n a B,B e n k r e i r a H.C h a i n e x t e n s i o n o f r e c y c l e d P A6 [J].P o l y m e r E n g i n e e r i n g&S c i e n c e,2018,58(7): 1037-1042.[21]S u K H,L i n J H,L i n C C.I n f l u e n c e o f r e p r o c e s s i n g o n t h e m e c h a n i c a l p r o p e r t i e s a n d s t r u c t u r e o f p o l y a m i d e 6[J].J o u r n a l o f M a t e r i a l s P r o c e s s i n g T e c h n o l o g y, 2007,192/193:532-538.[22]L i M Q,Z h a n g Y D,Z h u F,e t a l.I n f l u e n c e o f P A6 p a r t i c l e f i l l e r o n m o r p h o l o g y,c r y s t a l l i z a t i o n b e h a v i o r a n d d y n a m i c m e c h a n i c a l p r o p e r t i e s o f p o l y(ε-c a p r o l a c t o n e)a s a n e f f i c i e n t n u c l e a t i n g a g e n t[J]. J o u r n a l o f P o l y m e r R e s e a r c h,2021,28(12):461.[23]L i X R,H a n P,S o n g G J,e t a l.A s s e m b l y o f p o l y a m i d e6n a n o t u b e a r r a y s w i t h o r d e r e d p a t t e r n s a n d t h e c r y s t a l l i z a t i o n b e h a v i o r[J].M a t e r i a l s L e t t e r s, 2015,141:157-160.(责任编辑:刘国金)971第2期郭银涛等:单体和低聚物的含量对聚酰胺6切片性能的影响。

高分子科学专业英语重点词汇

高分子科学专业英语重点词汇

一、高分子基本概念polymer n.聚合物,高聚物polymeric adj.聚合(物)的copolymer 共聚物homopolymer 均聚物linear ~ 线性聚合物branched ~ 支链聚合物cross-linked ~ 交联聚合物addition ~ 加聚物condensation ~ 缩聚物functional/functionalized ~ 功能聚合物inorganic ~ 无机聚合物polymerization n.聚合copolymerization n.共聚depolymerization n.解聚degree of ~ 聚合度step-growth ~ 逐步聚合ionic ~ 离子型聚合radical ~ 自由基型聚合bulk ~本体聚合solution ~ 溶液聚合living ~ 活性聚合 nitroxide-mediated ~ 硝基氧介导聚合atom transfer radical ~ 原子转移自由基聚合reversible addition-fragmentation chain transfer ~ 可逆加成-断裂链转移聚合polycondensation n.缩(合)聚(合)macromolecule 大分子,高分子intermolecular adj.分子间的interchain adj.链间的monomer n.单体comonomer n.共聚单体dimer n.二聚体 trimer n.三聚体elastomer n.弹性体elastomeric adj.弹性的molecular weight 分子量molecular weight distribution 分子量分布number average molecular weight 数均分子量weight average molecular weight 重均分子量viscosity average molecular weight 粘均分子量functional group 官能团repeating unit 重复单元monofunctional adj.单官能度的polydisperse adj.多分散的polydispersity n.多分散性heterogeneous adj.不均匀的,非均相的statistical adj.统计的二、化学物质名词olefin 烯烃olefinic 烯烃的diolefin 二烯烃polyethylene 聚乙烯polypropylene 聚丙烯polystyrene 聚苯乙烯impact polystyrene 抗冲聚苯乙烯butene 丁烯polybutene 聚丁烯isobutylene/isobutene 异丁烯butadiene 丁二烯2-methyl-1,3-butadiene 2-甲基-1,3-丁二烯dimethylbutadiene 二甲基丁二烯isoprene 异戊二烯cis-1,4-polyisoprene 顺式-1,4-聚异戊二烯chloroprene 氯丁二烯neoprene n.氯丁(二烯)橡胶vinyl 乙烯基polyvinyl alcohol 聚乙烯醇polyvinylchloride 聚氯乙烯vinyl ether 乙烯基醚urethane 氨基甲酸酯isocyanate 异氰酸酯isopropylate 异丙醇金属amino 氨基(的)amine 胺diamine 二(元)胺diacid n.二(元)酸diol n.二(元)醇dibasic 二元的polyamide 聚酰胺amidation (酰胺化作用)acrylic 丙烯酸的methyl 甲基(poly)methylmethacrylate (聚)甲基丙烯酸甲酯= perspex n.有机玻璃polycarbonate 聚碳酸酯acetal 聚甲醛,缩醛aromatic adj.芳香(族)的aliphatic adj.脂肪(族)的polyether n.聚醚polyester n.聚酯esterification n.酯化(作用)polyesterificationn.聚酯化(作用)allyl n.烯丙基chlorine n.氯(气)hydrogen n.氢(气)phosgene n.光气,碳酰氯organometallic compound 有机金属化合物transition-metal compound 过渡金属化合物aluminum alkyl 烷基铝alkyl lithium 烷基锂titanium trichloride/tetrachloride 三氯/四氯化钛tetrahydrofuran 四氢呋喃hydroxyl n.羟基carboxyl n.羧基hydroxyl acid 羟基酸oxonium n.氧phenyllithium n.苯基锂phenyl sodium苯基钠butyllithium n.丁基锂triphenylmethyl potassium 三苯甲基钾tertiary adj.三元的,叔的common salt食盐shellac n.虫胶bitumen n.沥青parkesine n.硝化纤维素塑料celluloid n.赛璐珞,假象牙cellulose acetate 乙酸纤维素phenol-formaldehyde resin 酚醛树脂bakelite 酚醛树脂,电木粉candle wax 烛用蜡hydrocarbon oil 烃油三、高分子化学反应synthetic adj.合成的synthesize v.合成synthesis n.合成powdery adj.粉状的interlink v./n.互相连接interaction n. 相互作用distort v.使……变形,扭曲eliminate v.消除,打开transfer v.(链)转移,(热)传递heat transfer 热传递terminate v.(链)终止chain termination 链终止single bond 单键double bond 双键hydrogen bonding 氢键initiation n.(链)引发initiator n.引发剂radical n.自由基kinetic chain length 动力学链长mechanism n.机理activation n.活化(作用)reactive adj.活性的reactivity n.活性,反应性reactant n.反应物stability n.稳定性stabilizer/stabiliser n.稳定剂reactivity ratio 竞聚率irradiation n.照射,辐射catalyst n.催化剂cocatalyst n.助催化剂support v.(催化剂)负载化complex n.络合物promoter n.促进剂substitution n.取代,代替yield n.产率concentration n.浓度side reaction 副反应simultaneous reaction 平行反应ion n.离子ion exchange resin 离子交换树脂anionic adj.阴(负)离子的cationic adj.阳(正)离子的cation n.阳(正)离子positive adj.正的,阳性的growing chain 生长链neutral adj.中性的dissociate v.离解bond dissociation energy 键断裂能conversion n.转化(率)stoichiometric adj.当量的equilibrium n.平衡parameter n.参数mediate v.传递,媒介undergo v.进行,经历dormant/active species 休眠/活性种四、高分子的结构behavior n.性能,行为performance n.性能,特征peculiarity n.特性specificity n. 特异性,专一性viscosity n.黏度viscous adj.黏稠的tacky adj.发粘的consistency n. 稠度,黏稠性architecture n.结构texture n.结构,组织arrangement n.(空间)排布,排列backbone n.主链pendant group 侧基spacer group 隔离基团porosity n.多孔性,孔隙率contour n.外形,轮廓radius n.半径gyration n.旋转,回旋mean-square end-to-end distance 均方末端距torsion n.转矩attraction n.引力,吸引Van der Waals force 范德瓦耳斯力glass transition temperature 玻璃化温度boundary n.界限,范围rubbery adj.橡胶态的glassy adj.玻璃(态)的glassy state 玻璃态viscoelastic state 黏弹态viscofluid state 黏流态mobility n.流动性mobilize v.运动,流动melt index 熔体流动速率/熔融指数entropy n.熵五、高分子溶液性质dissolution n.溶解dissolve v.使……溶解solvent n.溶剂solubility n.溶解度permeability n.渗透性swell v.溶胀swelling n.溶胀swollen adj.溶胀的settle v.沉淀,澄清decomposition n.分解diffuse v.扩散gel n.凝胶disintegrate v.分解,分散,分离agitation n.搅拌globule n.小球,液滴saturation n.饱和(un)saturated adj.(不)饱和的六、高分子力学性能mechanical property 力学性能strength n.强度tensile strength 抗张强度elastic modulus 弹性模量elastic parameter 弹性指数nonelastic adj.非弹性的storage modulus 储存模量Young’s modulus 杨氏模量deformation n.形变deformability n.变形性,形变能力elongation n.伸长率,延伸率hardness n.硬度compliance n.柔量optimum adj.最佳的n.最佳值colligative adj.依数的density n.密度dimensional stability 尺寸稳定性isotropic adj.各向同性的hydrostatic adj.流体静力学的uniaxial adj.单轴的brittle adj.脆的,易碎的flexible adj.柔软的resilience n.弹性,回弹力transparency n.透明性,透光度embrittlement n.脆裂,脆性cracking n.龟裂,裂纹七、(非)晶态聚合物conformation n.构象segment n.链段random coil 无规线团crystal n.晶体,结晶crystallinity n.结晶性,结晶度crystalline n.晶体,晶态/adj.结晶的semicrystalline n.半晶crystallite n.微晶platelet n.片晶molten adj.熔化(融)的amorphous adj.无定形的,非晶态的morphology n.形态(学)three dimensionally ordered 三维有序的align v.排列成行packing n.堆砌orient v.定向,取向orientation n.定向dislocation n.错位,位错entanglement n.缠结,纠缠stretch v.拉直,拉长retract v.收缩release v.解除,松开controlled release 控制释放fringed-micelle theory 缨状微束理论folded-chain lamella theory 折叠链片晶理论imbed v.嵌入,包埋occluded adj.夹杂的matrix n.基体,母体medium n.介质/adj.中等的,中间的stereoregular adj.有规立构的stereoregularity n.立构规整性atactic adj.无规立构的isotactic adj.等规立构的stereospecific adj.立体定向的,有规立构的fragment n.碎屑,碎片purity n.纯度impurity n.杂质contaminant n.污物defect n.缺陷imperfect adj.不完整的irregularity n.不规则性,不均匀性八、表征测试characterize v.表征infrared spectroscopy 红外光谱nuclear magnetic resonance 核磁共振diffraction n.衍射pattern n.花纹,图样light scattering 光散射ultrasonic n.超声波ultracentrifugation n.超速离心(分离)sedimentation n.沉降fractionation n.分级九、高分子制品plastics n.塑料rubber n.橡胶methyl rubber甲基橡胶polysulphide rubber聚硫橡胶styrene-butadiene rubber 丁苯橡胶butyl rubber 丁基橡胶fiber n.纤维vulcanise/vulcanize v.硫化,硬化vulcanization n.硫化thermoplastic adj.热塑性thermoset adj.热固性modify v.改性conductive adj.导电的char n.炭sponge n.海绵oil-resistance n.耐油性general-purpose adj.通用的lubricant n.润滑剂pigment n.颜料versatile adj.用途广的versatility n.多功能性,通用性十、聚合物反应工程batch reactor 间歇反应器recycle reactor 循环反应器differential tubular reactor (微分)管式反应器autoclave n.高压釜three-neck flask 三颈瓶cell n.比色皿,细胞vat n.大桶scale up (反应器)放大uninterrupted adj.连续的raw product 粗产品precipitate n.沉淀integration n.集成,综合integral adj.必备的,构成整体所需要的conserve v./n.保存,节省incorporate v.合并exploit v.开拓exothermicity n.放热性robust adj.坚固耐用的,强壮的devolatilizer n.脱挥器disengage v.脱离surge tank 聚料仓,缓冲槽instrument v.用仪器装备scheme n./v. 安排,计划off-grade n.等外品ingredient n.组成部分,要素nitration n.硝化hydrolysis n.水解chlorination n.氯化hydrogenation n.加氢pyrolysis n.高温裂解/热解depropagation n.降解unzippering n.开链dehydrogenate v.使脱氢random decomposition 无规降解十一、高分子材料成型加工processing n.成型,加工shaping n.成型mo(u)lding n.模塑成型calendering n.压延成型extrusion n.注射成型coating n.涂覆thermoforming n.热成型dieforming n.口模成型intermittent adj.间歇式的secondary shaping operation 二次成型(操作)parison n.型坯squeeze v.挤压rupture n.断裂十二、非专业相关性词汇variation n.变化improve v.增进,改善thermodynamically adv.热力学地simultaneously adv.同时,同步model n.模型controversy n.争论,争议subdivide v.细分,区分category n.种类,类型categorize v.加以区别,分类hypothetical adj.假定的,有前提的indispensable adj.不可缺少的critical adj.决定性的substantial adj.实质的confront v.面临intractable adj.难处理的tempt v.诱惑,感兴趣supplant n.代替schematic adj.示意性的empirical adj.经验的differential adj.微分的inference n.推论straightforward adj.简单的,直截了当的sophisticated adj.复杂的,尖端的sustain v.维持,持续不变offset n./v.偏移alleviate v.减轻mismatch v.不匹配meaningful adj.意味深长的intrinsic adj.固有的visualize v.想象,观察ingenuity n.创造力,机敏break-through n.突破,重要技术成就synonymous adj.同义的analogy n.比喻,类似blockade n.封锁originate v.起源,首创special-purpose n.特殊用途的,专用的hitherto adv.迄今,向来facilitate v.使容易,便于。

免疫球蛋白

免疫球蛋白
1, IgG2, IgG3, IgG4 IgA:IgA1, IgA2
CL VL
CH1 VH
CH2
CH3
高变区和互补决定区
• 高 变 区 ( hypervariable region , HVR ): V 区内 变化最为剧烈的特定部位。 L链3个,H链3个。
• 因其在空间结构上可与抗 原决定簇形成精密的互补, 故 又 称 互 补 决 定 区 (complementarity determing region , CDR)
2. 人源化抗体(humanized antibody)
(1)、将小鼠的CDR序列移植到人 抗体可变区框架中,产生的抗体称 为CDR移植抗体。 (2)、将小鼠Ig基因敲除,转染人Ig 基因,在小鼠体内产生人Ab,再经 杂交瘤技术,产生大量完全人源化 抗体
3. 单链抗体(single chain antibody)
五、IgE
monomer (H2L2)
C4
特种兵
---血中含量最少,主要有粘膜下淋巴组织中的浆细胞分泌; ---IgE具有很强的亲细胞性,介导Ⅰ型超敏反应 ---可能与机体抗寄生虫免疫有关
第四节、人工制备抗体
一、多克隆抗体 (Polyclonal antibody, pAb)
------含多个抗原表位的抗 原免疫动物,可刺激体内 多个B细胞克隆产生针对 多种抗原表位的抗体,这 种含有多种抗体的混合物, 称为多克隆抗体
用基因工程方法,将抗体重链和 轻链可变区通过一个连接肽连接而 成的重组蛋白。 特点:能保持与抗原结合的性能, 分子量小,穿透性强,体内循环半 衰期短,免疫原性低。
See you next week!
Ab与Ig的联系 1、所有的Ab都是Ig,Ig并非都是Ab 2、免疫球蛋白是结构及化学的概念,而抗体是生物 学及功能的概念

基于GC-IMS分析红曲霉发酵产生的风味物质

基于GC-IMS分析红曲霉发酵产生的风味物质

6I Issue6江西科技师范大学学报Journal of Jiangxi Science&Technology Normal University202012Dec.2020基于GC-IMS分析红曲霉发酵产生的风味物质吾蔚蔚D,龙传南D",崔晶晶3(1.江西科技师范大学生命科学学院,江西南昌330013;2.江西科技师范大学江西省生物加工过程重点实验室,江西南昌330013;3.江西科技师范大学江西省有机功能分子重点实验室,江西南昌330013)摘要:本文研究了红曲霉在以大米粉为底物,分别添加芝麻粕、菜籽粕、豆粕、花生粕发酵产生的风味物质指纹图谱#收集红曲霉发酵6:的样品,根据气相色谱离子迁移谱数据,利用聚类和主成分分析不同样品间风味物质差异$结果表明红曲霉在添加芝麻粕、菜籽粕、豆粕、花生粕发酵过程中风味物质显著不同。

共检测出挥发性物质52种,主要有醇类、酯类、酮类、醛类、酚类等物质$聚类和主成分分析表明通过风味物质可以很好地区分五种不同底物红曲霉发酵样品。

气相色谱离子迁移谱可构建红曲霉发酵过程中风味物质指纹图谱和用于挥发性风味物质的可视化表征,对揭示红曲霉发酵风味形成具有一定理论指导价值。

关键词:红曲霉;发酵;风味物质&GC-IMS;指纹图谱中图分类号:qci文献标识码:A文章编号:2096-854X(2020)06-0065-06GC-IMS Analysis of The Volatile Flavoring Compounds inMonascus Ruber FermentationWu Weiwei1,Long Chuannan1,2,*,Cui Jingjing3(1.School of Life Science,Jiangxi Science STechnology Normal University,Nanchang330013,Jiangxi,P.R.China;2.Jiangxi Key Laboratory of Bioprocess Engineering,Jiangxi Science&Technology Normal University,Nanchang330013,Jiangxi,P.R.China;3.Jiangxi Provincial Key Laboratory of Organic Functional Molecules,Jiangxi Science&Technology Normal University,Nanchang330013,Jiangxi,P.R.China)Abstract:This paper is to study the fingerprints of flavor compounds produced by Monascus ruber which fermented with rice as substrate and adding sesame meal,rapeseed meal,soybean meal and peanut meal respectively.Based on gas chromatography-ion mobility spectrometry(GC-IMS)data,the differences of flavor compounds amongdifferent samples were analyzed by cluster analysis and principal component analysis(PCA).The results showed thatthe flavor compounds of these fermentation sample were significantly different.There were52kinds of volatilecompounds detected,mainly including alcohols,esters,ketones,aldehydes,phenols and so on.Clustering and PCAanalysis showed that five different fermentation samples could be well distinguished by flavor compounds.GC-IMS canbe used to construct the fingerprint of flavor compounds in the fermentation process of Monascus ruber and to visualizethe volatile flavor compounds.It has a certain theoretical guiding value for revealing the flavor formation of M.ruberfermentation.Key words:Monascus ruber;fermentation;flavor compound;GC-IMS;fingerprint收稿日期:2020-09-21修回日期:2020-10-30接受日期:2020-10-30基金项目:国家自然科学基金项目(31860436)、江西省自然科学基金项目(201C1BAB204001)、江西科技师范大学青年拔尖人才项目(201CQNBJRC004)。

The minimal model of fermionic dark matter

The minimal model of fermionic dark matter

where h is the SM Higgs boson and the Yukawa type coupling gψ and shifted mass M are given by M = m0 + v2 , 2Λ gψ = v , Λ (7)
with the electroweak scale v = 246 GeV. Thus gψ is the only bridge between the dark matter sector and the SM sector. In this model, we introduce two new parameter m0 and Λ, or equivalently the physical mass of the singlet ¯ in Eq. (6) contributes to ψ ¯+ψ → h+h fermion M and the coupling gψ . While the dimension-5 term −(1/2Λ)h2 ψψ annihilation process, this channel is not so important for the parameter space considered in this work, i.e, M < mh .
∗ Electronic † Electronic
address: ygkim@muon.kaist.ac.kr address: kylee@muon.kaist.ac.kr
2
II. THE MODEL
We introduce a singlet fermion ψ under the SM gauge group. The Lagrangian consists of L = LSM + LDM + Lint , where the dark matter Lagrangian ¯ ¯ iγ µ ∂µ ψ − m0 ψψ. LDM = ψ The leading interaction term between the dark matter and the SM fields is given by the dimension-5 term 1 ¯ Lint = − H † H ψψ, Λ (4) (3) (2)

219401828_沙棘酸奶挥发性风味物质的GC-IMS表征

219401828_沙棘酸奶挥发性风味物质的GC-IMS表征

杨秉坤,剧柠,丁雨红,等. 沙棘酸奶挥发性风味物质的GC-IMS 表征[J]. 食品工业科技,2023,44(13):308−315. doi:10.13386/j.issn1002-0306.2022080120YANG Bingkun, JU Ning, DING Yuhong, et al. Characterization of Volatile Flavors of Fermented Sea-buckthorn Yoghurt Using Gas Chromatography-Ion Mobility Spectroscopy[J]. Science and Technology of Food Industry, 2023, 44(13): 308−315. (in Chinese with English abstract). doi: 10.13386/j.issn1002-0306.2022080120· 分析检测 ·沙棘酸奶挥发性风味物质的GC-IMS 表征杨秉坤,剧 柠*,丁雨红,郭 蓉,龚绵红(宁夏大学食品科学与工程学院,宁夏银川 750021)摘 要:为探究沙棘酸奶中的挥发性风味物质,明确复配沙棘进行发酵对酸奶感官和风味物质的影响,通过感官评价与顶空-固相微萃取-气相色谱-离子迁移谱法(HS-SPME-GC-IMS )结合多元统计分析方法对发酵沙棘酸奶的挥发性化合物进行分析,实现特征挥发性化合物的表征。

结果表明,沙棘酸奶产生了多种挥发性物质,酯类、酮类和醛类为主要挥发性物质来源。

发酵过程减弱了沙棘原浆带来的酸涩味道,使滋味更加柔和,香气更加浓郁、典型。

主成分分析筛选出了对香气贡献较大的化合物,聚类分析将挥发性化合物分成三类。

其中2, 2, 4, 6, 6-五甲基庚烷、乙酸乙酯(单体)、2-甲基丁酸乙酯、丁酸丙酯、甲酸丁酯(二聚体)、糠硫醇、甲酸异戊酯、乙酸乙酯(二聚体)和甲酸丁酯(单体)为发酵沙棘酸奶的主要风味物质。

高分子材料工程专业英语词汇及部分课文翻译

高分子材料工程专业英语词汇及部分课文翻译

专业英语词汇accordion手风琴activation活化(作用)additionpolymer加成聚合物,加聚物aggravate加重,恶化agitation搅拌agrochemical农药,化肥Alfincatalyst醇(碱金属)烯催化剂align排列成行aliphatic脂肪(族)的alkalimetal碱金属allyl烯丙基aluminumalkyl烷基铝amidation酰胺化(作用)amino氨基,氨基的amorphous无定型的,非晶体的anionic阴(负)离子的antioxidant抗氧剂antistaticagent抗静电剂aromatic芳香(族)的arrangement(空间)排布,排列atactic无规立构的attraction引力,吸引backbone 主链,骨干behavior性能,行为biological生物(学)的biomedical生物医学的bonddissociationenergy键断裂能boundary界限,范围brittle脆的,易碎的butadiene丁二烯butyllithium丁基锂calendering压延成型calendering压延carboxyl羧基carrier载体catalyst催化剂,触媒categorization分类(法)category种类,类型cation正[阳]离子cationic阳(正)离子的centrifuge离心chainreaction连锁反应chaintermination链终止char 炭characterize表征成为…的特征chilledwater冷冻水chlorine氯(气)coating涂覆cocatalyst 助催化剂coil线团coiling线团状的colligative依数性colloid胶体commence开始,着手commonsalt食盐complex络合物compliance柔量condensationpolymer缩合聚合物,缩聚物conductivematerial导电材料conformation构象consistency稠度,粘稠度contaminant污物contour外形,轮廓controlledrelease控制释放controversy争论,争议conversion转化率conversion转化copolymer 共聚物copolymerization共聚(合)corrosioninhibitor缓释剂countercurrent逆流crosslinking 交联crystal基体,结晶crystalline晶体,晶态,结晶的,晶态的crystalline结晶的crystallinity结晶性,结晶度crystallite微晶decomposition分解defect缺陷deformability变形性,变形能力deformation形变deformation变形degreeofpolymerization聚合度dehydrogenate使脱氢density密度depolymerization解聚deposit堆积物,沉积depropagation降解dewater脱水diacid二(元)酸diamine二(元)胺dibasic二元的dieforming口模成型diffraction衍射diffuse 扩散dimension尺寸dimensionalstability尺寸稳定性dimer二聚物(体)diol二(元)醇diolefin 二烯烃disintegrate分解,分散,分离dislocation错位,位错dispersant分散剂dissociate离解dissolution溶解dissolve使…溶解distort使…变形,扭曲doublebond双键dough(生)面团,揉好的面drug药品,药物elasticmodulus弹性模量elastomer弹性体eliminate消除,打开,除去elongation伸长率,延伸率entanglement缠结,纠缠entropy熵equilibrium平衡esterification酯化(作用)evacuate 撤出extrusion注射成型extrusion挤出fiber纤维flameretardant阻燃剂flexible柔软的flocculatingagent絮凝剂folded-chainlamellatheory折叠链片晶理论formulation配方fractionation分级fragment碎屑,碎片fringed-micelletheory缨状微束理论functionalgroup官能团functionalpolymer功能聚合物functionalizedpolymer功能聚合物gel凝胶glasstransitiontemperature玻璃化温度glassy玻璃(态)的glassy玻璃态的glassystate玻璃态globule小球,液滴,颗粒growingchain生长链,活性链gyration旋转,回旋hardness硬度heattransfer热传递heterogeneous不均匀的,非均匀的hydocyacid羧基酸hydrogen氢(气)hydrogenbonding氢键hydrostatic流体静力学hydroxyl烃基hypothetical假定的,理想的,有前提的ideal理想的,概念的imagine想象,推测imbed嵌入,埋入,包埋imperfect不完全的improve增进,改善impurity杂质indispensable 不了或缺的infraredspectroscopy红外光谱法ingredient成分initiation(链)引发initiator引发剂inorganicpolymer无机聚合物interaction相互作用interchain链间的interlink把…相互连接起来连接intermittent间歇式的intermolecular(作用于)分子间的intrinsic固有的ion离子ionexchangeresin离子交换树脂ionic离子的ionicpolymerization离子型聚合irradiation照射,辐射irregularity不规则性,不均匀的isobutylene异丁烯isocyanate异氰酸酯isopropylate异丙醇金属,异丙氧化金属isotactic等规立构的isotropic各项同性的kineticchainlength动力学链长kinetics动力学latent 潜在的lightscattering光散射line衬里,贴面liquidcrystal液晶macromelecule大分子,高分子matrix基体,母体,基质,矩阵mean-aquareend-to-enddistance 均方末端距mechanicalproperty力学性能,机械性能mechanism机理medium介质中等的,中间的minimise最小化minimum最小值,最小的mo(u)lding模型mobility流动性mobilize运动,流动model模型modify改性molecularweight分子量molecularweightdistribution分子量分布molten熔化的monofunctional单官能度的monomer单体morphology形态(学)moulding模塑成型neutral 中性的nonelastic非弹性的nuclearmagneticresonance核磁共振nucleartrackdetector核径迹探测器numberaveragemolecularweight数均分子量occluded夹杂(带)的olefinic烯烃的optimum最佳的,最佳值[点,状态]orient定向,取向orientation定向oxonium氧鎓羊packing 堆砌parameter参数parison型柸pattern花纹,图样式样peculiarity特性pendantgroup侧基performance性能,特征permeability 渗透性pharmaceutical药品,药物,药物的,医药的phenylsodium苯基钠phenyllithium苯基锂phosgene光气,碳酰氯photosensitizer光敏剂plastics塑料platelet片晶polyamide聚酰胺polybutene聚丁烯polycondensation缩(合)聚(合)polydisperse多分散的polydispersity多分散性polyesterification聚酯化(作用)polyethylene聚乙烯polyfunctional多官能度的polymer聚合物【体】,高聚物polymeric聚合(物)的polypropylene聚苯烯polystyrene聚苯乙烯polyvinylalcohol聚乙烯醇polyvinylchloride聚氯乙烯porosity多孔性,孔隙率positive正的,阳(性)的powdery粉状的processing加工,成型purity纯度pyrolysis热解radical自由基radicalpolymerization自由基聚合radius半径randomcoil无规线团randomdecomposition无规降解reactent反应物,试剂reactive反应性的,活性的reactivity反应性,活性reactivityratio竞聚率real真是的release 解除,松开repeatingunit重复单元retract收缩rubber橡胶rubbery橡胶态的rupture断裂saturation饱和scalp筛子,筛分seal密封secondaryshapingoperation二次成型sedimentation沉降(法)segment链段segment链段semicrystalline半晶settle沉淀,澄清shaping成型sidereaction副作用simultaneously同时,同步singlebond单键slasticparameter弹性指数slurry淤浆solarenergy太阳能solubility溶解度solvent溶剂spacergroup隔离基团sprinkle喷洒squeeze挤压srereoregularity立构规整性【度】stability稳定性stabilizer稳定剂statistical统计的step-growthpolymerization逐步聚合stereoregular有规立构的,立构规整性的stoichiometric当量的,化学计算量的strength强度stretch拉直,拉长strippingtower脱单塔subdivide细分区分substitution取代,代替surfactant 表面活性剂swell溶胀swollen溶胀的synthesis合成synthesize合成synthetic合成的tacky(表面)发粘的,粘连性tanker油轮,槽车tensilestrength抗张强度terminate(链)终止tertiary三元的,叔(特)的tetrahydrofuran四氢呋喃texture结构,组织thermoforming热成型thermondynamically热力学地thermoplastic热塑性的thermoset热固性的three-dimensionallyordered三维有序的titaniumtetrachloride四氯化钛titaniumtrichloride三氯化铁torsion转矩transfer(链)转移,(热)传递triethyloxonium-borofluoride三乙基硼氟酸羊trimer三聚物(体)triphenylenthylpotassium三苯甲基钾ultracentrifugation超速离心(分离)ultrasonic超声波uncross-linked非交联的uniaxial单轴的unsaturated不饱和的unzippering开链urethane氨基甲酸酯variation变化,改变vinyl乙烯基(的)vinylchloride氯乙烯vinylether乙烯基醚viscoelastic黏弹性的viscoelasticstate黏弹态viscofluidstate黏流态viscosity黏度viscosityaveragemolecularweight黏均分子量viscous粘稠的vulcanization硫化weightaveragemolecularweight重均分子量X-rayx射线x光yield产率Young'smodulus杨氏模量课文翻译第一单元什么是高聚物什么是高聚物首先,他们是合成物和大分子,而且不同于低分子化合物,譬如说普通的盐。

医学微生物学试题及答案

医学微生物学试题及答案

一、选择题每题1分,共30分A型题: 每一考题有A、B、C、D、E五个备选答案,请从中选择一个最佳答案填入题干后括号内;1.细菌的革兰染色性主要决定于:A.核质结构B.细胞壁结构C.细胞膜结构D.磷壁酸的有无E.中介体的有无2.溶原性细菌是指:A.带有前噬菌体基因组的细菌B.带有毒性噬菌体的细菌C.带有温和噬菌体的细菌D.带有R质粒的细菌E.带有F质粒的细菌3.能引起内毒素性休克的细菌成分是:A.肽聚糖B.磷壁酸C.LPS D.菌体抗原E.荚膜多糖4.顿挫感染,下列叙述中哪项正确A. 因宿主细胞内有相应抑制物B. 因宿主细胞DNA有关基因激活C. 因宿主细胞缺乏有关酶D. 因感染病毒有核酸缺失E. 因感染病毒抗原性转变5.细菌芽胞特有的、并与其高度耐热性有关的成分是:A.磷脂B.肽聚糖C.磷壁酸D.二氨基庚二酸E.吡啶二羧酸6.下列哪种实验可用来检测致癌物质A.Ames test B.transformation testC.fluctuation test D.replica plating testE.Widal test7.杀灭包括芽胞的所有微生物的方法称作:A.消毒B.无菌C.灭菌D.灭活E.防腐8. 下列无芽胞的细菌中,抵抗力最强的是:A. 乙型溶血性链球菌B. 金黄色葡萄球菌C. 淋病奈瑟菌D. 肺炎球菌E. 脑膜炎奈瑟菌9. 下列哪项不是病毒在细胞内增殖的指标A. 细胞病变效应B. 红细胞吸附C. 细胞代谢的改变D. 干扰现象E. 细胞培养液混浊10.霍乱弧菌能粘附定植于小肠粘膜上皮细胞是因为具有:A.鞭毛B.LTAC.菌毛D.K抗原E.Vi抗原11.对青霉素产生耐药性的最常见的细菌是:A.Streptococcus B.Staphylococcus C.Meningococcus D.Gonococcus E.Pneumococcus12.分枝杆菌属最突出的特点是:A.胞壁含大量脂质B.无特殊结构C.呈分枝生长D.一般不易着色E.抗盐酸乙醇脱色13. 下列哪种物质与结核结节和干酪样坏死有关A.分枝菌酸B.蜡质DC.磷脂D.索状因子E.硫酸脑苷脂14.下列哪种细菌不会引起食物中毒:A. 鼠伤寒沙门菌B. 志贺菌C. 蜡样芽胞杆菌D. 希氏沙门菌E. 产肠毒素的金黄色葡萄球菌15.从有正常菌群存在的部位所采取的标本应接种在哪种培养基中分离培养病原菌A.增菌培养基B.营养培养基C.选择鉴别培养基D.基础培养基E.特殊培养基16.衣原体与病毒的相同点是:A.含有RNA和DNA B.有核糖体C.严格细胞内寄生D.二分裂方式繁殖E.对抗生素敏感17.新生隐球菌致病物质主要是:A.荚膜多糖B.芽生孢子C.细胞壁D.假菌丝E.侵袭性酶18.真菌的假菌丝是由哪种孢子延长而形成的A.芽生孢子B.大分生孢子C.小分生孢子D.关节孢子E.厚膜孢子19.The main infection source of epidemic type B encephalitis virus is:A. patientB. health carrierC. young pigD. culicine库蚊E. louse20.The main type of infection caused by Poliovirus is:A.inappareent infection B.acute infection C.chronic infectionD.latent infection E.slow virus infection21.At an office visit, a 38-year-old man complains of jaundice黄疸, dark urine, anorexia厌食, abdominal pain, and malaise不适. Serologic tests are positive for both HBeAg and HBsAg. Which statement most accurately describes the virus responsible for these findingsA. Its genome is a messenger RNA mRNA that encodes a polyprotein.B. Its genome is linear double-stranded DNA.C. Its genome is RNA, but it replicates through a DNA intermediate.D. Its replication requires a helper virus.E. Its replication requires an RNA-dependent DNA polymerase.22. Which step in viral replication is inhibited by protease inhibitorA. PenetrationB. UncoatingC. TranscriptionD. ReplicationE. Viral assembly23. A 48-year-old man has been receiving blood products for hemophilia血友病since childhood. He is now suffering from a low-grade fever, weight loss, thrush鹅口疮, serious bouts of diarrhea, and symptoms of pneumonia. A deficiency in the production of which substance would be most pronounced in this patientA. Complement componentsB. Immunoglobulin G IgGC. Interferon-alpha IFN-αD. Interferon-gamma IFN-γE. Interleukin-1 IL-124.A neonate is born with a small head, intracerebral calcification脑内钙化, rash, and swollen liver and spleen. Cells with a basophilic nuclear inclusion body are obtained fromthe patient’s urine, which condition describes the most prevalent consequenence of adult infection with this agentA. Immunosuppression and susceptibility to opportunistic diseasesB. Mild arthritic condition with a fine lacy rashC. Mononucleosis with production of antibody to sheep red blood cellsD. No serious, definable disease symptomsE. Pharyngoconjunctivitis咽结膜炎25.A virus isolated from a patient with liver disease is detergent去污剂-sensitive, and its genome is infectious, Which virus do these findings describeA. EchovirusB. Hepatitis A virusC. Hepatitis C virusD. Hepatitis E virusE. PapillomavirusX型题: 每一考题有A、B、C、D、E五个备选答案,请将所有正确答案填入题干后括号内,多选或少选均为错误;26.可从粪便标本中分离的病毒有:A.甲型肝炎病毒B.麻疹病毒C.脊髓灰质炎病毒D.人类轮状病毒E.ECHO病毒27.SARS病毒的描述,下列哪些是正确的A.主要通过飞沫传播B.有包膜,对乙醚等脂溶剂敏感C.临床表现以发热为基本特征D.病毒分离培养为常规检查方法E.人群对SARS病毒无天然免疫力,普遍易感28.被狂犬咬伤的伤口,下列哪些处理正确A.立即用20%肥皂水清洗伤口B.用70%酒精及碘酒涂擦伤口C.使用大量抗生素D.局部注射高效价抗狂犬病病毒血清E.注射狂犬病疫苗29.下列哪些真菌属于深部感染的条件致病性真菌A.白假丝酵母菌B.新生隐球菌C.曲霉D.毛霉E.组织胞浆菌30. 下列哪些病原体感染后主要依赖细胞免疫发挥抗感染作用A.疱疹病毒B.甲型肝炎病毒C.结核分枝杆菌D.伤寒沙门菌E.麻疹病毒二、填空题每空0.5分,共10分1.细菌细胞壁特有的化学成分是__________, 真菌细胞壁特有的化学成分是__________;2.R质粒由和两部分组成,分别编码和; 3.一般只在局部繁殖而不进入血流引起菌血症的细菌有_____________和___________等;一般只在局部增殖而不进入血流引起病毒血症的病毒有____________和__________等; 4.与宫颈癌发生密切相关的病毒主要是______________和______________;5. 90%以上金黄色葡萄球菌均存在一种能与IgG的Fc段结合的抗原,称__________;鉴别肠杆菌科致病菌与非致病菌常选用的生化试验是:_____________7. 列举3种基因组分节段的RNA病毒:_____________,_____________ ,___________;8. 列举3种引起自然疫源性疾病的病原体,细菌如_____________,病毒如____________和_____________;三、名词解释每题3分,共18分mesosome2. high frequency recombinant3. dysbacteriosis4. Dane particle5. Weil-Felix reaction6. subacute sclerosing panencephalitis四、简答题每题5分,共20分1.细菌的合成代谢产物有哪些在医学上有何实际意义2.简述破伤风梭菌的感染条件及致病机制;3.简述HIV进入靶细胞的机制;4.简述PrPc 和PrPsc的主要区别;五、论述题共22分1. 以性接触为主要传播途径的原核细胞型微生物有哪些各引起何种疾病任举一例阐述其致病机制;10分2. 试述流感病毒的结构,并比较甲、乙、丙三型流感病毒在生物学特性、致病性和药物敏感性等方面的差异;12分一、选择题每题1分1. B 2 . A 3. C 4. C 5. E 6. A 7. C 8. B 9. E 10. C11. B 12. E 13. C 14. B 15. C 16. C 17. A 18. A 19. C 20. A21. E 22. E 23. D 24. D 25. C 26. ACDE 27. ABCE 28. ABDE29. ABCD 30. ACDE二、填空题每空0.5分1.肽聚糖几丁质纤维素2.耐药转移因子耐药决定因子性菌毛耐药性3.痢疾志贺菌白喉棒状杆菌肉毒梭菌;轮状病毒HPV狂犬病毒,流感病毒4.HPV HSV-25.SPA6.乳糖发酵试验7.流感病毒轮状病毒汉坦病毒8.钩端螺旋体流行性乙型脑炎病毒汉坦病毒三、名词解释每题3分,共18分1. mesosome中介体:细菌部分细胞膜内陷、折叠、卷曲形成的囊状物,多见于革兰阳性细菌;中介体参与细菌的分裂和能量的产生,有类似于真核细胞纺锤丝与线粒体的作用;2. high frequency recombinant高频重组菌:有少部分F质粒进入受体菌后,可整合到受体菌的染色体中,与染色体一起复制;整合有F质粒的细菌能高效地转移染色体上的基因,故称之高频重组菌;3. dysbacteriosis菌群失调症:当正常菌群的组成和数量发生明显改变时,称为菌群失调,菌群失调进一步发展,引起的一系列症状和体征,就称之为菌群失凋症;4. Dane particle存在于HBV感染者血液中的结构完整、有感染性的HBV颗粒,直径42nm;由Dane首先发现,故又称Dane颗粒;5. Weil-Felix reaction外斐反应:利用斑疹伤寒等立克次体的脂多糖与变形杆菌某些菌株如OX19和OX2等的菌体抗原有共同抗原成分而应用变形杆菌OX19和OX2及OXk菌株的菌体抗原代替立克次体的抗原检测患者体内相应抗体的交叉凝集试验,可供斑疹伤寒和恙虫病的辅助诊断;6. subacute sclerosing panencephalitis亚急性硬化性全脑炎;是麻疹病毒感染所致的一种晚期中枢神经系统并发症;发生率极低;儿童患麻疹后,在极少数病例中缺陷性麻疹病毒并未完全清除,而是持续存在于脑组织中,经过平均7年时间后,患者大脑功能发生渐进性衰退,最后昏迷死亡;四、简答题每题5分,共20分1. 细菌的合成代谢产物有哪些在医学上有何实际意义1热原质:与致病有关,在制备生物制品和注射用水等制剂中,必须使用无热原质水;2毒素与酶:细菌可产生内毒素与外毒素及侵袭性酶,与细菌的致病性密切相关,并有助于某些病原菌的鉴定;3色素:有些细菌产生色素,对细菌的鉴别具有一定的意义;4抗生素:与治疗有关;5细菌素:可用于细菌分型和流行病学调查;2.简述破伤风梭菌的感染条件及致病机制;破伤风梭菌引起破伤风的条件:伤口形成厌氧微环境,细菌才能生长繁殖产生痉挛毒素而致病;破伤风痉挛毒素是神经毒素,对中枢神经系统特别是对脑干和脊髓前角运动神经细胞有很高亲和力,通过其重链与神经肌肉终点处运动神经元表面受体结合,使毒素进入细胞内的小泡中,小泡从外周神经末梢沿神经轴突逆行至运动神经元细胞体,然后通过跨突触运动,小泡从运动神经元进入传入神经末梢从而进入中枢神经系统,再通过重链介导产生膜的转位使轻链进入胞质中,作为锌内肽酶裂解小泡上膜蛋白特异性肽键, 使膜蛋白发生改变,从而阻止抑制性中间神经元和RenShaw细胞释放抑制性神经介质, 使肌肉痉挛而引起破伤风的特有症状;3.简述HIV进入靶细胞的机制;首先,HIV病毒体的包膜糖蛋白gp120与靶细胞膜上的受体CD4分子结合,gp120分子发生变构,暴露出辅受体CXCR4或CCR5结合位点,使其与辅受体结合,然后gp41分子发生构型变化,插入靶细胞膜,使病毒包膜与细胞膜发生融合,核衣壳进入细胞内;4.简述PrPc 和PrPsc的主要区别;PrPcPrPscMolecular configuration3α-helix42%2 β-sheet3%2α-helix30%4 β-sheet43%PatternMonomer or dimerPolymer fibrilsLocation in or on cellsCytoplasmic membraneCytoplasmic vesicles and extracellular milieuhostNormal and infected humans and animalsInfected humans and animalsProtease k resistanceNoYesPathogenicityNoYesInfectivityNoYes五、论述题共22分1. 以性接触为主要传播途径的原核细胞型微生物有哪些各引起何种疾病任举一例阐述其致病机制;10分细菌淋病奈瑟菌淋病螺旋体梅毒螺旋体梅毒支原体溶脲脲原体人型支原体生殖器支原体泌尿生殖道感染衣原体沙眼衣原体泌尿生殖道感染性病淋巴肉芽肿机制4.5分2. 试述流感病毒的结构,并比较甲、乙、丙三型流感病毒的在生物学特性、致病性和药物敏感性等方面的差异;12分流感病毒的结构由核心和包膜两部分组成;1核心:由核酸、核蛋白和RNA聚合酶组成;核酸类型为单负链RNA,其特点在于核心RNA 分7~8个节段,与核蛋白和RNA聚合酶结合在一起构成核衣壳;2包膜:其特点是包膜分两层,内层为基质蛋白,外层脂质双层膜上镶嵌有HA和NA两种糖蛋白刺突;Type A Type B Type Cseverity of illness +++ ++ +animal reservoir yes no nohuman pandemics yes yes nohuman epidemics yes no nosporadicantigenic changes draft or shift drift driftsegmented genome yes8 yes8 yes7amantadine, rimantidine sensitive no effect no effectzanamivir,oseltamivir sensitive sensitivesurface glycoproteins HA/NA HA/NA NA。

XAFS分析Ni在碳纳米管上特性

XAFS分析Ni在碳纳米管上特性

X-ray absorptionfine structure(XAFS)analyses of Ni species trapped in graphene sheet ofcarbon nanofibersMayuko Ushiro,Kanae Uno,and Takashi Fujikawa*Graduate School for Science,Chiba University,Yayoi-cho1-33,Inage-ku,Chiba263-8522,JapanYoshinori Sato and Kazuyuki TohjiGraduate School of Environmental Studies,Tohoku University,Aoba,Sendai980-8579,JapanFumio WatariGraduate School of Dental Medicine,Department of Biomedical,Dental Materials and Engineering,Hokkaido University,Kita13Nishi7,Sapporo,060-8586,JapanWang-Jae ChunCatalysis Research Center,Hokkaido University and Core Research for Evolution Science and Technology,Japan Science and Technology Corporation,Kita21Nishi11,Sapporo,001-0021,JapanYuichiro Koike and Kiyotaka AsakuraCatalysis Research Center,Department of Quantum Science and Engineering,Hokkaido University,Kita21Nishi11,Sapporo,001-0021,Japan͑Received28October2005;revised manuscript received28December2005;published10April2006͒Metal impurities in the carbon nanotubes and carbon nanofibers play an important role in understanding theirphysical and chemical properties.We apply the Ni K-edge x-ray absorptionfine structure analyses to the localelectronic and geometric structures around embedded Ni impurities used as catalysts in a carbon nanofiber incombination with multiple scattering analyses.Wefind almost Ni catalysts as metal particles are removed bythe purification treatment.Even after the purification,residual100ppm Ni species are still absorbed;most ofthem are in monomer structure with Ni-C bond length1.83Å,and each of them is substituted for a carbonatom in a graphene sheet.DOI:10.1103/PhysRevB.73.144103PACS number͑s͒:61.10.Ht,87.64.Fb,87.64.Gb,61.46.ϪwI.INTRODUCTIONCarbon nanotubes͑CNTs͒1,2and carbon nanofibers ͑CNFs͒3,4are promising nano materials for electric devices, hydrogen reservoir,reinforce composites,medical usages and so on.There are several preparation methods to produce CNTs/CNFs,where the metal catalysts play a decisive role in their production processes.Although most of them can be removed from the CNTs/CNFs by acid treatments,5a small amount of impurities are left in the CNTs/CNFs after the purification processes.6The metals are intimately associated with the nanotube samples.6These impurities are reported to affect a giant thermopower due to a Kondo effect,7quantum conductance,8and anomalous temperature dependence of the resistivity.9In addition to the modification of the physical properties of CNTs/CNFs some metals such as Ni show biotoxic effects on a human body when they are used in medical applications such as drag delivery systems,medical implants and scaffolds.10–12In order to understand the effect of metal atoms on the physical properties as well as the re-moval of these impurities,the structure of metal species left in the CNT will be important.Furthermore the knowledge about the local structure will provide a hint to the formation mechanism for the CNTs/CNFs.From these standpoints of view the structures of metal species trapped in CNTs and CNFs have intensively been discussed theoretically.Several adsorption sites and model structures are proposed such as adsorption on Stone-Wales defects,13monomer or dimer adsorption model on the graphene sheet,14metal adsorption on atop of C atom9,15or on axial C-C bond,16a substitutional site of graphene sheet.17,18Lee et al.propose Ni-C␴bond is formed during the catalytic formation reaction of a single wall CNT and a Ni may be trapped at a substitutional position in the CNT wall.19However,we have had no definite conclusion for the location of metal atoms due to the lack of direct experimen-tal evidence about the local structure around the metal impu-rities.Recently Asakura et al.reported a letter concerning ex-tended x-ray absorptionfine structure͑EXAFS͒studies on the structure of Ni impurities left in a CNF after the purification.20Ni is one of the important catalyst to prepare CNTs and CNFs.They concluded that the dimer species were embedded in the CNFs with covalent Ni-C bonds. However,there are two criticisms on their conclusions.͑1͒Where are these Ni atoms located?͑2͒Are they really in dimers?Thefirst question comes from the fact that EXAFS is a one-dimensional local structure analysis sensitive to the short range order around the metal within about3Å.The second question arises based on the Ni-Ni distance2.48Åfound in the EXAFS analysis,the distance is almost equal to that of Ni foil.The Ni-Ni bonds they observed could be due to thosePHYSICAL REVIEW B73,144103͑2006͒of trace amount of Ni particles left after the purification.X-ray absorption near edge structure͑XANES͒spectra provide longer range information͑typicallyϷ5Å͒than EX-AFS spectra,and stereochemical information.21,22Although XANES contains more information than EXAFS,22XANES analysis is difficult because it requires multiple scattering calculations.Hence,XANES has often been used as afin-gerprint by comparing it with those of reference compounds. Fujikawa et al.have developed a reliable XANES theory based on the short range order full multiple scattering approach.23They have successfully determined several ma-terial structures by simulating XANES spectra.24–28Asakura et al.have measured the XANES spectra of these species and have observed prominent spectral features after the purifica-tion.The spectral features are different from those found in Ni foil or Ni oxide,and are characteristic of Ni species in CNFs after the purification treatment.The detailed XANES analyses will provide important information about the above criticisms.In this paper we report x-ray absorptionfine structure ͑XAFS͒analyses on the local structures around Ni in a CNF. First we describe EXAFS analyses of the Ni residue involved in a CNF before and after the purification in details.Second we explain the XANES analyses and investigate plausible structures.Wefind Ni atoms substitute carbon atoms in the CNF framework.Finally we compare the present result with the previous theoretical works,and discuss the merits of XANES in the material science.II.EXPERIMENTCNF is synthesized by a CVD method using Ni catalyst following a previous literature.29The CNF used here is hat-stacked carbon nanofiber͑HSCNF͒that is composed of graphene hats stacked toward the needle axis.12The diameter and the length of the CNF is25–100nm and0.1–5.0␮m, respectively.It is purified by a calcination in atmosphere followed by6.0M HCl treatment for6hours in order to remove the carbon nanoparticles and Ni catalysts.XAFS measurements are carried out at the BL9A in the Institute for Structure Material Science’s Photon Factory ͑KEK-PF͒using a Si͑111͒double crystal monochromator͑99G280,2001G117,and2003G2477͒.A pair of bentconicalFIG.1.Ni K-edge EXAFS oscillations͑x͒͑x=a,b,c,d͒and their Fourier transforms͑xЈ͒͑xЈ=aЈ,bЈ,cЈ,dЈ͒of reference compounds:͑a͒͑aЈ͒Ni foil,͑b͒͑bЈ͒NiO,͑c͒͑cЈ͒Ni͑H2O͒6͑NO3͒2,and͑d͒͑dЈ͒Ni͑cp͒2. USHIRO et al.PHYSICAL REVIEW B73,144103͑2006͒mirrors focus the x-ray beam on the sample and remove higher harmonics.30The incident and transmitted x rays are monitored by ionization chambers filled with nitrogen.The fluorescence x rays are detected by a 19element SSD ͑Solid State Detector,Camberra Co.͒.The dead times of SSD are corrected according to the literature.31The XAFS analyses are carried out by REX2000͑Rigaku Co.͒32,33using phase shift and amplitude functions obtained from FEFF8.21The Fourier transformation of k 3-weighted ␹͑k ͒is carried out over the range k =3–13Å−1.The peaks are Fourier filtered with ⌬r =1.2–2.2Åfor the first shell with a Hamming win-dow function,and the curve fitting analyses are carried out in the k -space.The goodness of fit is estimated by use of the R -factor defined byR ͑%͒=͚͓k 3␹o ͑k ͒−k 3␹c ͑k ͔͒2͚͓k 3␹o͑k ͔͒2ϫ100,͑1͒where ␹o and ␹c are the observed and the calculated fitting EXAFS oscillations.III.THEORYThe XANES theory used in this paper is based on the short-range-order full multiple scattering theory proposed by Fujikawa et al.34Later,this theory was modified by a parti-tioning technique in order to reduce the computation time.23,35–37Here,we summarize the theoretical methods.The x-ray absorption intensity ␴from the core orbital␾c ͑r ͒=R l c ͑r ͒Y L c ͑rˆ͒,L c =͑l c ,m c ͒at site A ͑x-ray absorbing atom ͒is given by Eq.͑2͒for photoelectron kinetic energy ⑀k =k 2/2.We assume excitation by a linearly polarized x ray in the z direction,23␴=−83Im ͚ͩL ,L Ј,L ci l −l Јexp ͓i ͑␦l A +␦l ЈA͔͒␳c ͑l ͒␳c ͑l Ј͒ϫG ͑L c 10͉L ͒G ͑L c 10͉L Ј͒͑t −1͒LLAA͓͑1−X ͒−1͔LL ЈAAͪ,͑2͒where G ͑LL Ј͉L Љ͒is Gaunt’s integral and ␳c ͑l ͒is the radialdipole integral between the radial part of ␾c ͑r ͒and the l th partial wave of photoelectrons R l ͑r ͒at site A.The phase shift of the l th partial wave at site A is represented by ␦l A .We introduce the matrix X specified with site index ␣and angu-lar momentum L and so on;it is defined asX LL Ј␣␤=t l ␣G LL Ј͑R ␣−R ␤͒͑1−␦␣␤͒,͑3͒where t l ␣and G LL Јrepresent the T -matrix at site ␣and the Green’s function in an angular momentum representation.The inverse matrix ͑1−X ͒−1includes an infinite order of the full multiple scattering inside the cluster we are considering.The phase shifts in t l ␣͕=−͓exp ͑2i ␦l ␣͒−1͔/2ik ͖are one of the most important features and reflect the electronic structure of the surrounding atoms,which are calculated within the Hartree-Fock approximation.The Green’s function G LL Јre-flects the geometrical structure.The clusters used in the present work include all surrounding atoms up to about 5Åfor the carbide model and about 7Åfor other models around an x-ray absorption atom.IV .RESULTS AND DISCUSSIONA.EXAFSWe measure the x-ray spectra of Ni foil,NiO,Ni ͑H 2O ͒6͑NO 3͒2,Ni ͑cp ͒2͑cp=cyclopentadienyl ͒,as refer-ence compounds whose EXAFS oscillations and Fourier transforms are given in Fig.1.We carry out curve fitting analyses to check the validity of FEFF calculations and to obtain the correction parameters,S ,for coordination num-bers.The results are summarized in Table I:The curve fitting analyses can provide 0.02Åaccuracy in the bond length.The coordination numbers are a little scattered but the reduc-tion factor S can be determined within 10%precision.We obtain the averaged reduction factors S =0.9±0.1for Ni-Ni,and S =1.0±0.1for Ni-C and Ni-O.Figure 2shows the observed Ni K -edge EXAFS spectra,their Fourier transforms and curve fitting results of Ni in the CNFs before and after the purification.Before the purifica-tion,the EXAFS oscillation is found to be similar to that ofTABLE I.Curve fitting results for reference compounds.r is the distance to the neighbor,␴is the Debye-Waller factor,⌬E is a shift in edge energy,R is R -factor defined by Eq.͑1͒,S is an amplitude reduction factor.Sample Bond N r /Å␴/10−2Å⌬E /eV R /%S Ni foil Ni-Ni 9.7±1.212a 2.47±0.022.49a 7.1±2.0−11±5 1.00.80±0.1NiONi-O 5.8±0.46a2.07±0.012.084a 8.0±1.0−4.8±50.70.93±0.06͑Ref.53͒Ni-Ni12.4±1.012a 2.95±0.022.954a 8.1±1.0−3.5±3 1.0±0.1͑Ref.53͒Ni ͑H 2O ͒6͑NO 3͒2Ni-O 6.2±0.46a2.04±0.012.063a 8.0±0.9−2.0±1.03.5 1.0±0.1͑Ref.54͒Ni ͑C 5H 5͒2Ni-C10.8±1.210a2.17±0.012.196a8.6±1.0−5.7±3.03.01.1±0.1͑Ref.55͒Thediffraction data.X-RAY ABSORPTION FINE STRUCTURE ͑XAFS ͒¼PHYSICAL REVIEW B 73,144103͑2006͒Ni foil up to high k region;this result indicates the presence of Ni particles.Its Fourier transform has several peaks cor-responding to those for Ni foil:Shape and pattern in 0–6Årange are similar to those of the foil.The Ni particle size is estimated to be longer than 50Åaccording to the Greegor’s relationship between the size and the coordination numbers.38The result is consistent with the XRD and SEM data.12Table II shows the curve fitting results for the first shell of Ni in the CNF before purification.The coordination number is 10.8after the reduction factor correction,which is slightly reduced from 12.This result may be caused by the intrinsic disorder in the Ni particles or the effect of impurity which is hardly observed in the EXAFS Fourier transform.As shown later,we still observe some deviation in the XANES spectrum before the purification from that of Ni foil,which indicate the presence of Ni-O bonding.We carry out two-shell fitting including Ni-O and Ni-Ni,and find better fitting results for the parameters listed in Table II,where R -factor 0.65%for the two-shell fitting is much smaller than 1.0%for the one shell fitting.The fitting EXAFS curve shows the excellent agreement with the observed one as shown in Fig.2͑a Љ͒.After the purification,the EXAFS oscillation is different from that before the purification.The Fourier transform ͓Fig.2͑b Ј͔͒shows that the Ni-Ni peak at 2.1Ådecreases and a new peak appears around 1.4Åwhich may correspond to the coordination of light atoms such as oxygen or carbon.As will be discussed in the XANES section,the peak corre-sponds to the Ni-C bond and we carry out the curve fitting analyses using carbon atoms:Results are shown in Table II.The coordination number and bond distance are 2.5and 1.83Å,respectively.For various Ni-C systems Ni-carbon bond distances are listed in Table III.The Ni-C in the CNF is shorter than Ni-C bonds found in Ni ͑cp ͒2͑␲bond ͒and other ␲bonding compounds.Thus we can rule out the possibility that Ni species form ␲bonds with carbon atoms in graphene aromatic rings.This means that the Ni-C bond is strongly bound to CNF through ␴bond.Since bond lengths for the Ni-C “single bond”are longer than 1.90Å,the “multiple bond”or some strong specific ␴bond as formed in Ni ͑CO ͒4is presumably formed:Actually bond lengths for the Ni-C “double bonds”are in the range of 1.83–1.89Å,and Ni-C distance is 1.82Åin Ni ͑CO ͒4.The Ni impurities should occupy substitution site in the graphene sheet or edge site with strong Ni-C bonds.Such strong Ni-C bonds prevent the Ni atoms from being removed by the purification.In addition to the short Ni-C bonds,we find other peak around 2.3Å,which corresponds totheFIG. 2.͑Color online ͒Ni K -edge EXAFS spectra ͑a,b ͒,their Fourier transforms ͑a Ј,b Ј͒and curve fitting results ͑a Љ,b Љ͒before ͑a,a Ј,a Љ͒and after the purification ͑b,b Ј,b Љ͒.In ͑a Љ͒and ͑b Љ͒the solid lines show the Fourier fil-tered EXAFS whereas the dashed lines show the fitted EXAFS.TABLE II.Curve fitting results for Ni species in CNF.r is the distance to the neighbor,␴is the Debye-Waller factor,⌬E is a shift in edge energy,R is R -factor defined by Eq.͑1͒.Sample Bond N a r /Å␴/10−2Å⌬E /eV R /%BeforeNi-Ni 10.8±1.6 2.47±0.02 6.9±3.0−7±7 1.0One shell Ni-Ni 10.3±1.6 2.47±0.02 6.8±3.0−7±7Two shell Ni-O 0.8±0.4 2.01±0.037.3±3.5−4±10.65Two shellAfterNi-C 2.4±0.8 1.83±0.05 6.0±3.03±5 5.6Ni-Ni0.8±0.32.48±0.055.5±2.07±7Coordination numbers are corrected by the factor S .S Ni-Ni =0.9and S Ni-C =1.0are used.USHIRO et al.PHYSICAL REVIEW B 73,144103͑2006͒Ni-Ni bond distance in Ni foil.Curve fitting analysis shows that the bond distance is 2.48Åand coordination number is 0.8.In our previous paper,20we thought the peak indicated the formation of the Ni dimer in the CNT,but the peak might rather be due to the Ni-Ni bonds in the residual Ni particles because the bond length is quite close to that in Ni foil.This point will be again discussed in the XANES section.Further EXAFS analyses about the location and the detailed structure can be limited because of the one-dimensional information inherent to EXAFS analysis and of the Ni low concentration.Thus we switch our attention to the XANES analysis.B.XANESFigure 3shows the K -edge XANES spectra of Ni species in the CNFs before and after the purification together with that of Ni foil.20All the experimental data are normalized to the absorption intensity at 8400eV,and the calculated atomic absorption cross sections are also normalized in the same way.The XANES spectrum after the purification shows prominent difference from that before the treatment which is quite similar to that for Ni foil.However,the peak at 8350eV is a little larger than that at 8360eV.Since Ni ͑H 2O ͒6͑NO 3͒2has a peak around 8350eV,we infer the presence of a small amount of Ni ͑H 2O ͒62+species.We ana-lyze the observed data on the basis of a regression method using two reference spectra of Ni foil and of Ni ͑H 2O ͒6͑NO 3͒2by adjusting the coefficients,c 1and c 2,␮Ni CNF =c 1␮foil +c 2␮Ni ͑H 2O ͒6,͑4͒c 1+c 2=1,͑5͒where ␮Ni CNF ,␮foil ,and ␮Ni ͑H 2O ͒6are the Ni K -edge x-ray absorption intensities of Ni species in CNF,of Ni foil and of Ni ͑H 2O ͒6.The best fit is obtained when we choose c 1=0.88±0.05as shown in Fig.4,which supports thepresenceFIG.3.The observed Ni K -edge XANES spectra of Ni species in the CNF before and after the purification together with that of Ni foil.The experimental data are normalized to the absorption inten-sity at 8400eV.FIG.4.͑Color online ͒͑a ͒the regression analysis of Ni species in the CNF before the purification.Solid line and circles are ob-served and best fitted data,respectively.Lines ͑b ͒and ͑c ͒are the spectra of Ni foil and Ni ͑H 2O ͒6͑NO 3͒2.TABLE III.Ni-C bond length for various Ni-C systems.r is the distance to the neighbor.Bond typer /ÅReferences Single ␴bond1.90–2.0156–59␴bond with aromatic ring 1.90–1.9360–63“Double bond”1.83–1.8962and 64␴bond in metallocycle 1.81–1.9159,65,and 66␲bond with “double bond”2.00–2.2164,67,and 68␲bond with “triple bond” 1.87–1.9969–71␲bond with allyl 1.93–2.1172and 68␲with aromatic ring 1.95–2.1672and 73Ni 3C 1.8639Ni ͑CO ͒4 1.8274Ni ͑C 5H 5͒22.19655X-RAY ABSORPTION FINE STRUCTURE ͑XAFS ͒¼PHYSICAL REVIEW B 73,144103͑2006͒of Ni ͑H 2O ͒6species.This conclusion does not contradict the EXAFS results obtained in the preceding section.The ex-pected coordination number for Ni-Ni and Ni-O based on the c 1and c 2are 10.8±0.6and 0.72±0.04,respectively,which are in good agreement with the estimated ones 10.3±1.6and 0.8±0.4by the EXAFS analyses shown in TableII.FIG.5.Local structures of a carbide model ͑a ͒and a diamond model ͑b ͒.In ͑a ͒each Ni atom is surrounded by two carbon atoms.In ͑b ͒each Ni atom is absorbed in the diamond and surrounded by four carbon atoms.In ͑c ͒and ͑d ͒edge models,and in ͑e ͒and ͑f ͒substitution models are shown.USHIRO et al.PHYSICAL REVIEW B 73,144103͑2006͒C.Multiple scattering analysis of XANESThe XANES spectrum after the purification is different from that before the purification.There are two characteristic peaks at the absorption edge regions.This characteristic structure should be the fingerprint for the calculated XANES spectra using multiple scattering theory for several model structures given in Figs.5and 9.We investigate the follow-ing possible models referring to other experimental findings and theoretical studies:͑1͒a carbide model or a diamond model,͑2͒an edge model,͑3͒a substitution model,͑4͒a Stone-Wales defect model.In these calculations the Ni atoms are assumed to be neu-tral as supported by our DFT calculations.1.A carbide model or a diamond modelAlthough the carbide,Ni 3C contains a quite large number of Ni-Ni pairs ͑coordination number 12͒at 2.63Å,39we con-sider the carbide model because carbide has often been ob-served during the catalytic reactions of Ni with CO and hy-drocarbons.Figure 6͑a ͒shows the calculated Ni K -edge XANES spectrum for the carbide model shown in Fig.5͑a ͒compared with the experimental spectrum after the purifica-tion.The agreement is quite poor as expected,since no spe-cific peak is observed in the calculated spectrum.Hayakawa et al.have reported micro XANES spectrum for the Ni impurities in the synthetic diamond.40They find similar two peaks in the near edge region of the Ni K -edge.The second peak appears at a little higher energy than the corresponding peak in the spectrum of the Ni species in theCNF.They propose a substitution model for the Ni site,i.e.,a carbon is replaced by a Ni atom and the replaced Ni is surrounded by four carbon atoms in a tetrahedral symmetry.The model is shown in Fig.5͑b ͒:Ni-C distance is assumed to be 1.8Åwith coordination number 4.The calculated XANES spectrum shown in Fig.6͑b ͒gives rise to two small peaks.However,the second peak position of thecalculatedFIG.7.The calculated XANES spectra for the edge models ͑c ͒and ͑d ͒shown in Fig.5compared with the experimental Ni K -edge XANES after the purification.The energy is measured from the onset of the K -edgeabsorption.FIG.8.Calculated Ni K -edge XANES spectra for the substitu-tion models ͑e ͒a monomer model and ͑f ͒a dimer model compared with the observed spectrum after the purification.The energy is measured from the onset of the K -edgeabsorption.FIG.6.Calculated XANES spectra for the carbide model ͑a ͒and a diamond model ͑b ͒shown in Fig.5compared with the ex-perimental Ni K -edge XANES after the purification.The energy is measured from the onset of the K -edge absorption.X-RAY ABSORPTION FINE STRUCTURE ͑XAFS ͒¼PHYSICAL REVIEW B 73,144103͑2006͒XANES spectrum in Fig.6͑b͒is different from that of Niatoms in CNFs measured in this paper.Thus the diamondmodel is also rejected.Ni in diamond has been investigated because Ni is a goodcatalyst for the synthesis of diamond and Ni is efficientlysubstituted into the diamond to modify the optical and physi-cal properties.Hitherto EPR and theoretical studies haveproposed several model structures for Ni impurities in dia-mond,which support the presence of substitutional Ni.40,42However,recent theoretical and ESR results show thatthe substitutional Ni are not so stable and they are accompa-nied with defects͑one or two vacancies͒or impurities ͑nitrogen͒.41,43–46Further analyses of Ni K-edge XANES in diamond should be necessary to confirm their local struc-tures.2.Edge modelsSharp has discussed the catalytic reaction mechanism forthe synthesis of CNT based on the organometallicchemistry.47They propose metallocyclic species as an inter-mediate.At edges of graphene sheets carbon atoms havedangling bonds:Ni atoms can adsorb on the edge of agraphene sheet,forming covalent bonds with C atoms at theedges.We study two different edge models as shown in Figs.5͑c͒and5͑d͒.In both models the Ni-C distance is assumedto be1.8Åwith coordination number1.In the latter modelNi dimer structure is assumed with the Ni-Ni distance2.5Å.The calculated spectra are shown in Fig.7.Both models givenearly the same spectra which show quite small shoulders at 7and16eV,and too rapid decrease above30eV.Thesemodels cannot sufficiently reproduce the observed features.3.Substitution modelsNi can be on a substitution site in the graphene sheet.Meng et al.study the metal-graphene sheet interaction byHartree-Fock calculations with approximate exchangepotential.13Their results show strong attractive interactionand bonding with a graphene sheet due to the unfilled3dshell for transition metals.A different theoretical work alsosupports the substitutional Ni atom in a CNT.17We consider two substitution models—monomer anddimer.In the monomer model as shown in Fig.5͑e͒,Ni isbound to a graphene sheet through three C-Ni bonds withdistance of1.8Å.In the dimer model shown in Fig.5͑f͒,aNi dimer forms the two C-Ni bonds with the same distance ͑1.8Å͒and the coordination number2.In the dimer the Ni-Ni distance is2.5Åwith coordination number1.Thesevalues are in accordance with the EXAFS results.20Figure8shows the calculated XANES for the monomer and dimermodels shown in Figs.5͑e͒and5͑f͒.We can well reproducethe two characteristic peaks at7and16eV by the monomermodel,although the peak at7eV is a little weaker than theobserved one.The peak at7eV is located just at the begin-ning of the edge rise and should have a contribution from theatomic bound state that cannot be fully taken into account bythe present method.The16eV peak is in the continuumcharacter and can successfully be calculated by the multiplescattering theory.The dimer model shows two features at7and16eV but the peak intensities are one-half of theNiFIG.9.Four defects modelsaround the Stone-Wales defects.In the model͑a͒and͑b͒one Niatom adsorbs on the7and5ring,respectively.In model͑c͒and͑d͒two Ni atoms adsorb on the7and5rings,respectively.USHIRO et al.PHYSICAL REVIEW B73,144103͑2006͒monomer structure.The structure above 30eV region is not well fitted to the observed one in the dimer structure.The CNF is composed of multilayer with interlayer distance 3.4Å.12,48We add another sheet ͑two-sheet model ͒,but we cannot find its remarkable effect on the calculated spectra since the bond length of the Ni-C in the next sheet is quite large.We thus conclude that most of Ni impurities are in mono-mer structures in a graphene sheet;each of them substitutes a carbon atom.4.Stone-Wales defect modelsAn important defect in the CNT is a Stone-Wales defect where a pair of 5–7rings can be created by rotating a C-C bond in the hexagonal network by 90°.49Recent molecular orbital calculations show that the introduction of Stone-Wales defects would benefit the adsorption capacity of B,N,F,and Si among 10foreign atoms ͑H,B,C,N,O,F,Si,P,Li,and Na ͒.50This result suggests that the Stone-Wales defects can be the Ni adsorption sites.͑See Figs.9and 10.͒Figure 10shows the XANES spectra based on the four models shown in Fig.9.The adsorption models around the Stone-Wales defects ͑a ͒–͑d ͒fail to explain the two specific peaks at 7and 16eV,and we can rule out the above models.parison with literatureIn our calculations,the substitution model shown in Fig.5͑e ͒gives good fit to the observed data.Takenaka et al.have also observed the two peaks discussed in this paper in theXANES spectra of the heavily deactivated Ni catalyst after the CH 4decomposition reaction to carbon filament.51They compared the XANES and EXAFS of the “Ni carbide”with those of the known Ni 3C,and found that both spectra were completely different.This result clearly shows that the Ni carbide prepared from the methane decomposition is not the Ni 3C species.They were not able to determine the structure because the strong Ni-Ni peak in Fourier transformed EX-AFS spectra for Ni particles were observed at the same time.Judging from the peak positions in the XANES spectra and Fourier transform peaks in the EXAFS,the deactivated Ni they observed should be the same one discussed in this work.The proposed structure as shown in Fig.5͑e ͒has already been suggested by Banhart et al.in the onionlike graphitic networks.18They observe Ni atoms in graphitic carbon on-ions by TEM and observed a zigzag structure,which indi-cates the formation of a new C-Ni phase.Their first principle calculations show that the Ni-substituted graphite structure with C-Ni distance 1.8Åis quite consistent with our XAFS results.Their Car-Pallinello simulation suggests the high sta-bility of this substituted Ni atom in the graphene sheet.An-driotis et al.study Ni in a CNT framework using atightFIG.11.Two tube models and the calculated XANES spectra.The tube type is armchair which is ͑10,10͒tube with 14Åin diam-eter.We assume that Ni atoms are present at the substitution sites whose local adsorption structures are nearly the same as those shown in Fig.5͑e ͒.In model ͑a ͒the Ni is located outside of the tube,and in model ͑b ͒the Ni is located inside the tube.Calculated Ni K -edge XANES spectra are shown for the two tubemodels.FIG.10.Calculated Ni K -edge XANES spectra for the four models shown in Fig.9compared with the experimental spectrum after the purification.For the comparison the calculated spectrum for the model ͑e ͒in Fig.8is shown as ͑8-e ͒.The energy is mea-sured from the onset of the K -edge absorption.X-RAY ABSORPTION FINE STRUCTURE ͑XAFS ͒¼PHYSICAL REVIEW B 73,144103͑2006͒。

MHD simulations of the collapsar model for GRBs

MHD simulations of the collapsar model for GRBs

a r X i v :a s t r o -p h /0312319v 1 11 D e c 2003MHD simulations of the collapsar model for GRBs.Daniel Proga ∗,Andrew I.MacFadyen †,Philip J.Armitage ∗and Mitchell C.Begelman ∗∗JILA,University of Colorado,Boulder,CO 80309-0440,USA †California Institute of Technology,Mail Code 130-33,Pasadena,CA 9112Abstract.We present results from axisymmetric,time-dependent magnetohydrodynamic (MHD)simulations of the collapsar model for gamma-ray bursts.Our main conclusion is that,within the collapsar model,MHD effects alone are able to launch,accelerate and sustain a strong polar outflow.We also find that the outflow is Poynting flux-dominated,and note that this provides favorable initial conditions for the subsequent production of a baryon-poor fireball.INTRODUCTION The collapsar model is one of most promising scenarios to explain the huge release of energy in a matter of seconds,associated with gamma-ray bursts (GRBs;[1];[2];[3];[4];[5]).In this model,the collapsed iron core of a massive star accretes gas at a high rate (∼1M ⊙s −1)producing a large neutrino flux,a powerful outflow,and a GRB.Although the association of long duration GRBs with stellar collapse is now secure ([6];[7]),basic properties of the central engine are uncertain.In part,this is because previous numerical studies of the collapsar model did not explicitly include magnetic fields,although they are commonly accepted as a key element of accretion flows and outflows.We present a study of the time evolution of 2.5-dimensional,magnetohydrodynamic (MHD)flows in the collapsar model.This study is an extension of existing models of MHD accretion flows onto a black hole (BH;[8]).In particular,we include a realisticequation of state,photodisintegration of bound nuclei and cooling due to neutrino emis-sion.Our study is also an extension of collapsar simulations by [3],as we consider very similar neutrino physics and initial conditions but solve MHD instead of hydrodynami-cal equations.MODELSWe begin the simulations after the 1.7M ⊙iron core of a 25M ⊙presupernova star has collapsed and study the ensuing accretion of the 7M ⊙helium envelope onto the central black hole formed by the collapsed iron core.We consider a spherically symmetric progenitor model,but with spherical symmetry broken by the introduction of a small,latitude-dependent angular momentum and a weak radial magnetic field.For moredetails,see[9]).RESULTSWefind that after a transient episode of infall,lasting0.13s,the gas with l>∼2R S c piles up outside the black hole and forms a thick torus bounded by a centrifugal barrier near the rotation axis.Soon after the torus forms(i.e.,within a couple of orbital times at the inner edge),the magneticfield is amplified by the magnetorotational instability (MRI,e.g.,[10])and shear.We have verified that most of the inner torus is unstable to MRI,and that our simulations have enough resolution to resolve,albeit marginally, the fastest growing MRI mode.The torus starts evolving rapidly and accretes onto the black hole.Another important effect of magneticfields is that the torus produces a magnetized corona and an outflow.The presence of the corona and outflow is essential to the evolution of the innerflow at all times and the entireflow close to the rotational axis during the latter phase of the evolution.Wefind that the outflow very quickly becomes sufficiently strong to overcome supersonically infalling gas(the radial Mach number in the polar funnel near the inner radius is∼5)and makes its way outward,reaching the outer boundary at t=0.25s.Due to limited computing time,our simulations were stopped at t=0.28215s,which corresponds to6705orbits of theflow near the inner boundary.We expect the accretion to continue much longer,roughly the collapse timescale of the Helium core(∼10s),as in[3].Figure1shows theflow pattern of the inner part of theflow at t=0.2437s.The left and middle panels show density and|Bφ|maps,respectively.The two maps are overlaid with the direction of the poloidal velocity.The right panel shows theflow domains of different polarity of Bφoverlaid with the direction of the poloidal magneticfield.The polar regions of low density and high Bφcoincide with the region of an outflow.We note that during the latter phase of the evolution not all of the material in the outflow originated in the innermost part of the torus–a part of the outflow is“peeled off”the infalling gas at large radii by the magnetic pressure(see Fig.2in[9]).We imposed a weak poloidalfield of a given polarity at the outer boundary.This means that initially Bφchanges sign only across the equator,which is a relatively unfavorable configuration for subsequently producing Bφreversals in the jet.Nevertheless,wefind that the polarity of Bφchanges with time.This is because theflow loses memory of the initial polarity by the time it reaches the inner MRI-dominated regions where the jet is formed.Sikora et al.(2003)[11]argue that Poyntingflux-dominated jets with reversing B-fields provide a natural and efficient way to dissipate energy via the reconnection process.Poyntingflux dominated jets have been found in previous numerical simulations whereas jets with reversing B-fields appear as a relatively new result.Therefore,we have reviewed results from[8]to check whether polar outflows generated during adiabatic accretion onto BHs also exhibit reversing Bφ.Simulations reported by[8]are suitable to study theflow pattern on relatively large length scales because they have been continued for a few dynamical time scales at a distance of∼103BH radii.Fig.2shows theflow domains of different polarity of Bφoverlaid with the direction of the poloidal velocity and magneticfield(left and right panel,respectively)for run DFIGURE1.Maps of logarithmic density,toroidal magneticfield,and toroidal magneticfield domains with different polarity(white and grey regions)for Proga et al.’s GRB simulation at t=0.2437s(left, middle,and right panel,respectively).The arrows in the left and middle panels indicate the direction of the poloidal velocity while the arrows in right panel indicate the direction of the poloidal magneticfield. The length scale is in units of the BH radius(i.e.,r′=r/R S and z′=z/R Sin[8].It appears then that reversing B-fields are not unique to our GRB simulations and that domains with different polarity can be relatively large and long-lived.CONCLUSIONSWe have performed time-dependent two-dimensional MHD simulations of the collapsar model.Our simulations show that:1)soon after the rotationally supported torus forms, the magneticfield very quickly starts deviating from purely radial due to MRI and shear. This leads to fast growth of the toroidal magneticfield asfield lines wind up due to the torus rotation;2)The toroidalfield dominates over the poloidalfield and the gradient of the former drives a polar outflow against supersonically accreting gas through the polar funnel;3)The polar outflow is Poyntingflux-dominated;4)The polarity of the toroidalfield can change with time;5)The polar outflow reaches the outer boundary of the computational domain(5×108cm)with an expansion velocity of0.2c;6)The polar outflow is in a form of a relatively narrow jet(when the jet breaks through the outer boundary its half opening angle is5◦);7)Most of the energy released during the accretion is in neutrinos,Lν=2×1052erg s−1.Neutrino driving will increase the outflow energy(e.g.,[12]and references therein),but could also increase the mass loading of the outflow if the energy is deposited in the torus.FIGURE2.Maps of toroidal magneticfield domains with different polarity(white and grey regions) overplotted with the direction of the poloidal velocity(left panel)and the direction of the poloidal magneticfield(right panel)at the end of Proga&Begelman’s simulation of adiabatic accretion onto a BH(run D in[8]).The length scale is also in units of the BH radius;the same as in Fig.1.Note however the difference in the r′and z′ranges.ACKNOWLEDGMENTSDP acknowledges support from NASA under LTSA grants NAG5-11736and NAG5-12867.MCB acknowledges support from NSF grants AST-9876887and AST-0307502.REFERENCES1.Woosley,S.E.,1993,ApJ,405,2732.Paczy´n ski,B.,1998,ApJ,494,L453.MacFadyen,A.,Woosley,S.E.,1999,ApJ,524,2624.Popham,R.,Woosley,S.E.,Fryer,C.,1999,ApJ,518,3565.MacFadyen,A.,Woosley,S.E.,Heger,A.,2001,ApJ,550,4106.Hjorth,J.,et al.,2003,Nature,423,8477.Stanek,K.Z.,et al.,2003,ApJ,591,L178.Proga,D.,Begelman,M.C.,2003,ApJ,592,7679.Proga,D.,MacFadyen,A.I.,Armitage,P.J.,Begelman M.C.,2003,ApJ,599,L510.Balbus,S.A.,Hawley,J.F.,1991,ApJ,376,21411.Sikora M.,Begelman M.C.,Coppi P.,Proga D.,2003,submitted to ApJ Letters(astro-ph/0309504)12.Fryer,C.L.,Mészáros,P.,2003,ApJ,588,L25。

高分子科学导论-绪论

高分子科学导论-绪论

comprises the multiple repetition of units derived, actually or conceptually, from
molecules of low relative molecular mass. 相对高分子质量的分子,其结构主要是由相对低分子质量的分子按实际
高分子物理 (Polymer Physics)
高分子的结构与性能:高分子链的构型与构象,高分子的聚集态及 分子运动、固态与液态聚合物的物性(热学、力学、电学、光学、 磁学、流变学等性能),高分子溶液与分子量等;
高分子工程 (Polymer Engineering)
高分子成型加工与聚合反应工程:高分子成形加工的理论基础及方
4.0
包装箱/容器
148.7
11.8
5.3
日用品
301.9
22.9
10.8
其他
675.0
14.5
合计
2,801.9
17.9
24.1
8
100
Introduction to Polymer Science
高分子科学的基本内涵
高分子化学 (Polymer Chemistry)
高分子的合成和化学反应:聚合反应理论,新的聚合方法及改性方 法,高分子的基团反应,高分子的降解、老化与交联等;
O
O O
O
NH2 NN H2N N NH2
L-lactide Dimer of L-lactic acid
Melamine
15
Trimer of cyanamide
Introduction to Polymer Science
Definition and Foundation

[精品]HLM多层线性模型简介解析教案资料

[精品]HLM多层线性模型简介解析教案资料
同一单位内的观测,具有更大的相似性。同一 个班级的学生由于受相同的班级环境等因素的 影响有更大的相似性。
嵌套于背景(contextual)特征 的多层数据举例
学生水平特征的观测,嵌套于班级或学校 兄弟姊妹特征的观测,嵌套于家庭 个体之间的观测嵌套于社区 个体不同时间点的重复测量嵌套于个体 病人嵌套于医院 参数的估计嵌套于不同的研究 (元分析,meta-analysis)
第一水平: Yij 0 j eij
第二水平: 0 j g 00 u0 j
合并模型:
Yij g 00 uoj eij
HLM常用模型类型
无条件模型:模型中没任何预测变量的多层分析模型
模型表示与随机效应的方差分析模型相同。在无条件模 型中:
00
00 2
上式的相关系数描述了水平2单位内个体之间的相关 (intra level 2-unit correlation),它测量了学校之间方差 占总方差的比例,或者说在总的变异中由水平二解释 的方差的比例。
模型的特征
注意到: 我们有:
ij = uj + rij
Var(ij)
= Var(uj + rij) = Var(uj) + Var(rij) + 2*Cov(uj,rij) = Var(uj) + Var(rij)
模型的特征
Yij 的值可能存在第二水平(组间)的差异 对于 uj和 rij没有定义其分布.
(4)对73所学校分别做回归分析, 得到如图4的结果,如图4所示,从 图中结果可以看出,不同学校回归 直线的截距和斜率均不同,即:不 同学校学生平均高考成绩之间存在 差异,入学学业成绩对高考成绩的 影响强度不同。
图4:考虑不同学校平均成绩差异 和入学对毕业成绩影 响程度差异的回归直线

Intermediate filaments

Intermediate filaments

anino terminus 35 8-14
1B -螺旋
101
L12
L2




区 2A 区
-螺旋
8
9 16-17
2B -螺旋
121
C-端
Carboxyl terminus
直径介与微管与微丝之间,故得名中等纤维(中间纤维 IF) 8——10nm。 IF结构稳定:既不受秋水仙素也不受细胞松弛B素影响,并且也没有极性。
monomer
coiled-coil dimer
Staggered tetramer of two coiled-coil dimers
Two tetramers packed together(nonpolarized intermediate fialiament)
三 .中等纤维的组装
NH2
2.A. A cross-section through a microtubule demonstrates a ring composed of 13 protofilaments. B. A cross-section through a cilium or flagellum reveals a core of microtubules referred to as an axoneme. The axoneme is composed of two central singlet microtubules surrounded by nine doublet microtubules. C. A cross-section through the basal body of a cilium or flagellum or through the centriole reveals a ring composed of nine triplet microtubules.

巨细胞病毒感染小鼠结肠中肠三叶因子的表达及更昔洛韦的干预作用

巨细胞病毒感染小鼠结肠中肠三叶因子的表达及更昔洛韦的干预作用

巨细胞病毒感染小鼠结肠中肠三叶因子的表达及更昔洛韦的干预作用刘芹;王军;叶黎离;郑玉艳;刘文强;杨倩倩【摘要】目的:观察肠三叶因子(ITF/TFF3)在鼠巨细胞病毒(MCMV)感染小鼠结肠中的表达及更昔洛韦的干预作用。

方法将48只4周龄BALB/c小鼠,随机分为空白组、病毒组及更昔洛韦(GCV)组,每组8只。

病毒组和GCV组分别腹腔接种致半数细胞感染量(TCID50=105.31/mL)的MCMV病毒悬液100μL ,GCV组在接种MCMV 24 h后GCV 50 mg/kg ,每天1次,腹腔注射,连续14 d ,同时病毒组和空白组分别给予同等剂量的生理盐水作为对照。

定量PCR检测肝脏、结肠MCMV-DNA ;采用实时定量逆转录-聚合酶链反应(RT-PCR)法检测ITF mRNA表达水平。

结果病毒组小鼠明显出现食欲差、活动少;皮毛稀松、对刺激反应迟钝、生长迟缓、体质量不增等表现。

病毒组肝脏、结肠组织有MCMV-DNA表达,GCV组亦有表达,但弱于病毒组。

GCV组与病毒组相比ITF mRNA表达升高,差异有统计学意义(P<0.05);病毒组与空白组相比ITF mRNA表达水平升高,差异有统计学意义(P<0.05)。

结论 ITF是一类较新的肠黏膜保护因子,在MCMV感染后所导致的急性肠道炎症损伤过程中发挥着重要的保护作用。

%Objective To observe the expression of ITF in colon of mice infected by mouse cytomegalovirus (MCMV) and the in-volvement of ganciclovir(GCV) .Methods Forty-eight BALB/c young mice were randomly divided into blank group ,virus group and GCV group ,each with 8mice .Mice in virus group and GCV group received injection of 100 μL MCMV virus suspension (TCID50105 .31 /mL) ,and GCV group was given intraperitoneal injection of GCV once a day at the dose of 50 mg/kg fromday 0 (24 hours after vaccination of virus ) ,for 14 days .At the same time the virus group and blank group were given the same dose of normal saline as controls .Murine cytomegalovirus loads in livers and colons were measured by PCR .The expression levels of ITF in mRNA in colon were detected by RT-PCR .Results After MCMV injection ,mice in virus group manifested aggressively apparent poor appetite ,less activity ,furlaxly ,unresponsiveness to stimuli ,growth retardation ,body weight not increased .All liver and colon tissue MCMV-DNA PCR electrophoresis of virus group had positive strip ,while the blank group did not .GCV group also showed less bright positive strip when compared with the virus group .Expression level of ITF mRNA was significant higher in GCV group than virus group ,there was statistically significantdifference(P<0 .05) .Expression of ITF mRNA in virus group were higher than that in blank group ,there was statisticaldifference(P<0 .05) .Conclusion ITF is regarded as a fast reaction peptide in the course of mucosa impairments ,so ITF plays a protective role in delayed healing process after acute MCMV infection .【期刊名称】《重庆医学》【年(卷),期】2013(000)030【总页数】3页(P3653-3655)【关键词】巨细胞病毒感染;小鼠;结肠;肠三叶因子;更昔洛韦【作者】刘芹;王军;叶黎离;郑玉艳;刘文强;杨倩倩【作者单位】徐州医学院附属医院,江苏徐州,221000;徐州医学院附属医院,江苏徐州,221000;徐州医学院附属医院,江苏徐州,221000;徐州医学院附属医院,江苏徐州,221000;徐州医学院附属医院,江苏徐州,221000;徐州医学院附属医院,江苏徐州,221000【正文语种】中文人巨细胞病毒(human cytomegalovirus,HCMV)属于疱疹病毒亚科,是导致胃肠道感染的常见病原体[1]。

血浆D-二聚体、纤维蛋白单体水平监测在骨科术后对深静脉血栓风险评估的价值

血浆D-二聚体、纤维蛋白单体水平监测在骨科术后对深静脉血栓风险评估的价值

血浆D-二聚体、纤维蛋白单体水平监测在骨科术后对深静脉血栓风险评估的价值摘要】目的:研究血浆D-二聚体(DD)、纤维蛋白单体(FM)水平监测在骨科术后深静脉血栓(DVT)风险评估的价值。

方法:选择本院行骨科手术的54例患者,在术后的第1天、第3天检测血浆DD、FM,探讨DD、FM与术后DVT发生风险评估价值。

结果:术后DVT发生率为14.81%(8/54),DVT组术后第1天、第3天的DD、FM显著高于对照组(P<0.05);DVT组术后第3天的DD、FM较术后第1天有显著升高(P<0.05)。

结论:在术后同时监测DD、TM对骨科术后患者评估DVT发生风险有预测意义,在DD、TM变化后进行早期干预能降低DVT发生率。

【关键词】血浆D-二聚体;纤维蛋白单体;深静脉血栓[Abstract] Objective: To study the value of monitoring plasma D-dimer (DD) and fibrin monomer (FM) levels in risk assessment of deep venous thrombosis (DVT) after orthopaedic surgery.Methods: 54 patients who underwent orthopaedic surgery in our hospital were selected. The plasma DD and FM were measured on the first and third days after operation, and the risk assessment value of DD, FM and DVT after operation was discussed.Results: The incidence of DVT was 14.81% (8/54), and the DD and FM of DVT group on the first and third day after operation were significantly higher than those of control group (P < 0.05); the DD and FM of DVT group on the third day after operation were significantly higher than those on the first day after operation (P <0.05).Conclusion: Monitoring DD and TM simultaneously after operation can predictthe risk of DVT in orthopaedic patients. Early intervention after the changes of DD and TM can reduce the incidence of DVT.[Keywords]plasma D- two dimer, fibrin monomer, deep vein thrombosis[ 中图分类号 ]R2[ 文献标号 ]A[ 文章编号 ]2095-7165(2018)20-0334-01骨科手术有人工髋关节置换术、人工膝关节置换术、髋部周围骨折手术、脊柱手术等,在术后患者的凝血机制充分发挥功能,易发生深静脉血栓(DVT)[1]。

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PACS numbers: 05.50.+q, 02.10.Ox, 02.70.-c
arXiv:cond-mat/0610690v1 [cond-mat.stat-mech] 25 Oct 2006
I.
INTRODUCTION
The monomer-dimer problem has received much attention not only from statistical physics but also from theoretical computer science. As one of the classical lattice statistical mechanics models, the monomer-dimer model was first used to describe the absorption of a binary mixture of molecules of unequal sizes on crystal surface [1]. In the model, the regular lattice sites are either covered by monomers or dimers. The diatomic molecules are modeled as rigid dimers which occupy two adjacent sites in a regular lattice and no lattice site is covered by more than one dimer. The lattice sites that are not covered by the dimers are regarded as occupied by monomers. A central problem of the model is to enumerate the dimer configurations on the lattice. In 1961 an elegant analytical solution was found for a special case of the problem, namely when the planar lattice is completely covered by dimers (the close-packed dimer problem, or dimercovering problem) [2, 3]. For the general monomer-dimer problem where there are vacancies (monomers) in the lattice, there is no exact solution. For three-dimensional lattices, there is even no exact solution for the special case of close-packed dimer problem. One recent advance is an analytic solution to the special case of the problem in -dimensional lattices where there is a single vacancy at certain specific sites on the boundary of the
2 and (2) to use the computational methods to probe the physical properties of the monomer-dimer model, especially at the high dimer density limit (Section VIII). The high dimer density limit is considered to be more difficult and more interesting than the low dimer density limit. The major result is the asymptotic expression Eq. 24. The third purpose of the paper is to introduce the asymptotic theory of Pemantle and Wilson [26], which not only gives a theoretical explanation of the origin of the logarithmic correction term found by computational methods reported in this paper (Section III), but also has the potential to be applicable to other statistical models. The following notation and definitions will be used throughout the paper. The configurational grand canonical partition function of the monomer-dimer system in a m × n two-dimensional lattice is Zm,n (x) = aN (m, n)xN +aN −1 (m, n)xN −1 +· · ·+a0 (m, n) (1) where as (m, n) is the number of distinct ways to arrange s dimers on the m × n lattice, N = ⌊mn/2⌋, and x can be taken as the activity of a dimer. The average number of sites covered by dimers (twice the average number of dimers) of this grand canonical ensemble is given by 2 ∂ ln Zm,n (x) 2 θm,n (x) = = mn ∂ ln x mn
Monomer-dimer model in two-dimensional rectangular lattices with fixed dimer density
Yong Kong∗
Department of Mathematics National University of Singapore Singapore 117543 (Dated: February 6, 2008) The classical monomer-dimer model in two-dimensional lattices has been shown to belong to the “#P-complete” class, which indicates the problem is computationally “intractable”. We use exact computational method to investigate the number of ways to arrange dimers on m × n twodimensional rectangular lattice strips with fixed dimer density ρ. For any dimer density 0 < ρ < 1, we find a logarithmic correction term in the finite-size correction of the free energy per lattice site. The coefficient of the logarithmic correction term is exactly −1/2. This logarithmic correction term is explained by the newly developed asymptotic theory of Pemantle and Wilson. The sequence of the free energy of lattice strips with cylinder boundary condition converges so fast that very accurate free energy f2 (ρ) for large lattices can be obtained. For example, for a half-filled lattice, f2 (1/2) = 0.633195588930, while f2 (1/4) = 0.4413453753046 and f2 (3/4) = 0.64039026. For ρ < 0.65, f2 (ρ) is accurate at least to 10 decimal digits. The function f2 (ρ) reaches the maximum value f2 (ρ∗ ) = 0.662798972834 at ρ∗ = 0.6381231, with 11 correct digits. This is also the monomer-dimer constant for two-dimensional rectangular lattices. The asymptotic expressions of free energy near close packing are investigated for finite and infinite lattice widths. For lattices with finite width, dependence on the parity of the lattice width is found. For infinite lattices, the data support the functional form obtained previously through series expansions.
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