Invasion Assay Using 3D Matrices

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python画屈服准则

python画屈服准则

python画屈服准则屈服准则通常用来描述材料在受力作用下发生塑性变形的现象。

在 Python 中,可以使用一些常见的科学计算库来绘制屈服准则的图表,比如 NumPy 和 Matplotlib。

首先,我们需要定义屈服准则的方程。

常见的屈服准则包括von Mises 屈服准则和 Tresca 屈服准则。

这两种屈服准则都可以用来描述材料在受力作用下的塑性变形。

然后,我们可以使用NumPy 来生成一系列应力和应变的数据点,然后利用 Matplotlib来绘制应力-应变曲线。

下面是一个简单的示例代码,用来绘制 von Mises 屈服准则的应力-应变曲线:python.import numpy as np.import matplotlib.pyplot as plt.# 定义 von Mises 屈服准则的方程。

def von_mises(sigma1, sigma2, sigma3):return np.sqrt(sigma12 + sigma22 + sigma32sigma1sigma2 sigma2sigma3 sigma3sigma1)。

# 生成一系列应力数据。

stress = np.linspace(0, 100, 100) # 生成 0 到 100 之间的 100 个数据点。

# 计算对应的 von Mises 应变。

strain = von_mises(stress, stress0.5, stress0.3)。

# 绘制应力-应变曲线。

plt.plot(strain, stress)。

plt.xlabel('Strain')。

plt.ylabel('Stress')。

plt.title('Stress-Strain Curve for von Mises Yield Criterion')。

plt.show()。

在这个示例中,我们首先定义了 von Mises 屈服准则的方程von_mises,然后生成了一系列应力数据点,并利用 von_mises 函数计算了对应的应变数据点。

一种基于人工免疫聚类的三维模型检索算法

一种基于人工免疫聚类的三维模型检索算法
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Cell migration and invasion assays

Cell migration and invasion assays

Methods 37 (2005) 208–215/locate/ymeth1046-2023/$ - see front matter 2005 Elsevier Inc. All rights reserved.doi:10.1016/j.ymeth.2005.08.001Cell migration and invasion assaysAline Valster a,1, Nhan L. Tran d,1, Mitsutoshi Nakada d , Michael E. Berens d ,Amanda Y. Chan a , Marc Symons a,b,c,¤aFeinstein Institute for Medical Research at North Shore-LIJ, 350 Community Drive, Manhasset, NY 11030, USAbDepartment of Surgery, North Shore University Hospital, Manhasset, NY 11030, USAcDepartment of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USAdNeurogenomics Division, The Translational Genomics Research Institute, Phoenix, AZ 85004, USAAccepted 24 May 2005AbstractThe processes of cell migration and invasion are integral to embryonic development and the functioning of adult organisms.Deregulation of these processes contributes to numerous diseases. Ras GTPases and in particular members of the Rho subfamily of GTPases play critical roles in cell migration and invasion. Here, we provide a collection of protocols to assay these functions. We describe two cell migration assays. The monolayer wound healing assay is very easy to implement, whereas the microliter-scale migration assay allows examination of cell behavior on de W ned extracellular matrices. We also describe two methods that allow the quanti W cation of tumor cell invasion, a versatile transwell Matrigel invasion assay and an organotypic assay that examines the inva-sion of glioma cells through a rat brain slice. 2005 Elsevier Inc. All rights reserved.Keywords:Migration; Invasion; siRNA; Rac; Glioma1. IntroductionCell migration is a process that is critical at many stages of embryonic development, and is essential for tis-sue repair and immune function [1]. Importantly, dereg-ulated motile behavior contributes to pathological processes including tumor angiogenesis and metastasis,atherosclerosis, and arthritis [2–4].Members of the Ras superfamily of GTPases, most notably the Rho proteins, play a prominent role in cell migration [5]. Thus, the Rac, Cdc42, and Rho GTPases are essential for growth factor- and cytokine-stimulated chemotaxis in W broblasts, macrophages and neutrophils [6–9]. In addition, Rac, Cdc42, and Rho are necessary for the invasive behavior of carcinoma cells and W bro-blasts [7,10–12]. The signaling pathways that are acti-vated by Rho proteins to regulate cell migration and invasion are under intense scrutiny [1,5,13].We will focus this review on glioma cells. The migra-tory and invasive properties of these tumor cells are important prerequisites for the in W ltrative and destructive growth patterns of malignant gliomas. In W ltrative growth prevents complete tumor resection and therefore, causes signi W cant neurological morbidity and mortality [14].To date, examination of the roles of Rho proteins in cell migration and invasion has heavily relied on the inhibitory e V ects of dominant negative mutants of these GTPases and on the stimulation of signaling pathways by constitutively active versions. Introduction of these mutants into cells has been achieved by microinjection of plasmids or recombinant proteins [8,15,16], transient transfection or the establishment of stable cell lines [7].Dominant negative GTPases act by competing with their endogenous counterparts for access to guanine*Corresponding author. Fax: +1 516 365 5090.E-mail address: msymons@ (M. Symons).1Both the authors contributed equally to this work.A. Valster et al. / Methods 37 (2005) 208–215209nucleotide exchange factors (GEF s) [17]. However, GEF s often catalyze nucleotide exchange on a number of di V erent Rho family members [18], thereby limiting the speci W city of dominant negative mutants. This is illustrated by the observation that expression of domi-nant negative mutant Rac1 interferes with the activation of RhoA by the Dbl GEF[19]. F or this reason, we recently have employed RNA interference (RNAi) [20,21] to speci W cally inhibit the expression of Rho GTP-ases. A protocol for transient transfection of short inter-fering RNA (siRNA) is described in Section 2.1.2. Monolayer wound healing assayMonolayer wound healing assays have been used very e V ectively for studying the roles of Rho GTPases in cell migration [16]. Recently, monolayer wounding has also been used to examine signaling events that are involved in the establishment of cell polarity during directed loco-motion [22,23].Most of our recent experiments have been carried out using the SNB19 and U87MG grade IV glioblastoma cell lines. The SNB19 cell line can be obtained from the Developmental Therapeutics Program (NCI/NIH) and the U87MG line from ATTC. Both cell lines are very migratory and invasive.2.1. siRNA-mediated protein knock down in glioblastoma cells2.1.1. Selection of siRNA oligonucleotide sequenceCareful consideration concerning the selection of oli-gonucleotide sequence should be given to achieve e Y cient protein knock down and to avoid nonspeci W c e V ects. In the past, we have designed our own oligos fol-lowing speci W cations as established by the Tuschl labo-ratory. Guidelines are detailed on the Tuschl website: /labheads/tuschl/sirna.html. This website is updated on a regular basis. Recently, we have started to use the services of Dharmacon (http:// ) to select our siRNA oligonucleo-tide sequences. F or known genes siGenome oligo sequences directed against the gene’s open reading frame are successfully used in our laboratory and oligos against speci W c regions such as 3ЈUTR regions can be designed using the siDesign center that uses Smart Selec-tion design algorithms developed by Dharmacon [24]. The advantage of region-speci W c oligonucleotides such as 3ЈUTR-speci W c oligos is the ability to perform recon-stitution studies, by speci W cally knocking down endoge-nous proteins, without a V ecting expressed recombinant versions of these proteins [25].O V-target interactions of siRNA have been described [26–28]. This problem can be circumvented by utilizing two independent targeting sequences, as the probability of generating similar o V-target e V ects by di V erent oligos is extremely low. We routinely have been using an oligo-nucleotide directed against GL2 luciferase as a negative control [29]. As a positive control, we have been using an oligonucleotide directed against dynamin 2 (see Section 2.4—1.). Kits with additional control oligos are also available from Dharmacon. An in X uential editorial regarding the use of controls for RNA interference experiments has been published in Nat. Cell Biol. [30].2.1.2. Transient siRNA oligonucleotide transfectionA lipid-based method is used to introduce siRNA oli-gonucleotides into SNB19 glioblastoma cells. We prefer to use Lipofectamine 2000 (Invitrogen) as the lipid car-rier over other reagents we have tested because of the high e Y ciency knock down of proteins at low oligonu-cleotide concentrations (20nM W nal concentration) we routinely observe using this method. As some variability exists between transfections, we plate and transfect mul-tiple wells per treatment.In preparation for Lipofectamine 2000-mediated trans-fections, SNB 19 cells are plated in a 24-well plate at a con X uency of 50–70% (»3–4£104 cells per well) in 500 l plating medium (DMEM medium supplemented with 10% FBS but without antibiotics). The con X uency of the cells is important because at lower cell counts toxicity of the transfection reagent becomes limiting and at higher cell counts lower transfection e Y ciency hampers e Y cient protein knock down. The optimum con X uency for trans-fection is cell-type dependent and should be determined for each cell line independently to optimize transfection e Y ciency. SNB19 cells are allowed to attach to the tissue culture dish for about 2h as it is important to transfect the cells while they are in the early stages of cell spreading.0.6 l siRNA oligonucleotide duplex (at 20 M) is added to 47–49 l DMEM medium (to make a total vol-ume of 50 l) without serum and in a separate tube 1 l Lipofectamine 2000 is added to 49 l DMEM. After a 5min incubation at room temperature, the diluted siRNA oligonucleotide and lipid are combined, gently mixed, and further incubated for 20min to allow the for-mation of the transfection complexes. The complexes are subsequently added to the cells and mixed with the plat-ing medium by gently swirling the tissue culture dish.After about 24h, the medium containing the transfec-tion complexes should be aspirated and replaced by reg-ular plating medium (DMEM with 10% F BS). By this time, the cells typically display an array of ‘vacuole-like’structures that do not seem to have any negative e V ect in subsequent culture and analysis of the cells. F or most proteins studied in our lab, in SNB19 cells, protein knock down reaches an optimum at around day 3 after transfection and typically lasts for another 2 or 3 days. Hence, cells are routinely assayed 3 days post transfec-tion. However, the timeline for optimum protein knock down is dependent on the protein and cell line of interest210 A. Valster et al. / Methods 37 (2005) 208–215and should be determined for each protein and cell line separately.2.2. Transient plasmid transfections in glioblastoma cellsWe also have established a protocol that allows e Y cient transient expression of proteins in SNB19 cells using the E V ectene transfection reagent (Qiagen). Using this method, transfection e Y ciencies of >80% are routinely obtained. It is important for e Y cient transfection to use freshly plated cells (less than 24h after plating the cells).The details of the transfection protocol for SNB19 cells are as follows. Cells are plated at »70% con X uency (»4£104 cells/well in 24-well plate) in 500 l plating medium (DMEM with 10% FBS) without antibiotics. A mixture of the following is made using the E V ectene transfection kit components provided by Qiagen: 120 l bu V er EC; 0.4 g plasmid DNA, and 6.4 l Enhancer. This mixture is incubated for 3min at room temperature, after which 8 l E V ectene is added. After an additional 7min incubation during which transfection complexes are formed, 700 l DMEM with 10% FBS is added and this mixture is applied to the cells. We typically assay cells 24h after transfection.2.3. Monolayer wound healing assaySNB19 cells are treated according to experimental design. F or siRNA transfections two wells in a 24-well plate are transfected using Lipofectamine 2000 transfec-tion reagent as described above. The next day, the cells are combined in one well of a six-well culture dish. Before plating into this dish, two parallel lines are drawn at the underside of the well with a Sharpie marker. These lines will serve as W ducial marks for the wound areas to be analyzed. At the day of analysis, the monolayer should be absolutely con X uent. In preparation for mak-ing the wound, the growth medium is aspirated and replaced by calcium-free PBS to prevent killing of cells at the edge of the wound by exposure to high calcium concentrations. Two (or more) parallel scratch wounds of approximately 400 m width are made perpendicular to the marker lines with a blue P1000 pipet tip (Fisher). This procedure makes it possible to image the entire width of the wound using a 10£ objective.The wounds are observed using phase contrast microscopy on an inverted microscope. Images are taken at regular intervals over the course of 12–24h of both areas X anking the intersections of the wound and the marker lines (D8 images per treatment).The width of the wound should be as consistent as possible, since narrow wounds tend to close faster than wider wounds. If more than two scratches are made, wounds with similar widths can be chosen for analysis. Images are analyzed by digitally drawing lines (using Adobe Photoshop) averaging the position of the migrat-ing cells at the wound edges. The cell migration distance is determined by measuring the width of the wound divided by two and by subtracting this value from the initial half-width of the wound (Fig.1).2.4. Notes1.A positive control that is useful for the implementa-tion of siRNA methodologies is siRNA directed against dynamin 2 [31]. This protein is ubiquitously expressed at high levels and is readily detected by immuno X uorescence. In contrast to lamin A/C, which also has been used as positive control [29], dynamin 2 tends to be expressed in a very uniform fashion throughout the cell population, making it easier to evaluate the transfection e Y ciency.2.Transient transfection of adherent cells that arerefractory to the described protocols can be improved point and condition.Rac1 si RNAcontrolA. Valster et al. / Methods 37 (2005) 208–215211by either transiently trypsinizing the cells [32] or by detaching the cells and transfecting in suspension [33].3.F or the determination of chemotaxis (migrationdirected upward a concentration gradient of chemo-attractant), a number of assays have been described.These include the use of the Boyden-chamber [7,34] and the Dunn-chamber assays [8].3. Microliter-scale migration assayThe microliter-scale migration assay that we discuss allows examination of the migratory responses of cells to speci W c extracellular matrix (ECM) components. The assay is conducted in a small volume of medium, which is favorable for testing expensive or rare reagents for their e V ect on cell migration, such as pharmacological agents, antisense oligonucleotides, siRNA, and antibod-ies. This protocol allows for assaying adherent or nonad-herent cells that have been activated to adhere. In addition, subsequent immunostaining of the migrating cells can be performed to examine reorganization of the actin cytoskeleton, localization of proteins involved in cytoskeletal organization, matrix remodeling, adhesion complexes, and signaling events. F inally, multiple phe-notypic endpoints can be measured to study the e V ect of molecular and biochemical determinants on cell motility, proliferation, apoptosis, gene expression, and signal transduction [35–37].3.1. Assembly of the migration assayTen-well Te X on-printed microscope slides that have been designed for this assay can be obtained commer-cially (CSM, Phoenix, AZ). F irst, place the 10-well slide(s) into a petri dish and add two drops of water under each end of the slide. The drops will disperse by capillary action and keep the slide in place. Coat the 10-well slides with the ECM component of interest by add-ing 20 l to each well, followed by 1h incubation at 37°C. After coating, rinse the wells three times with PBS and block the nonspeci W c binding sites with 0.1% BSA in PBS for 30min at 37°C. Rinse the slides twice with PBS, add 50 l PBS to each well and store at 4°C in PBS until ready to use.Next, aspirate the PBS from the wells and replace by 50 l medium. Carefully place the pre-chilled (4°C) Cell Sedimentation Manifold (CSM; CSM, Phoenix, AZ) onto the slide. The CSM is designed to W t over the 10-well Te X on-slides and allow cells to settle and attach within a 1mm circumference in the center of each well. Carefully remove any air bubbles that reside in the channels. This is important to ensure that cells will properly fall through the channel onto the slide. Finally, harvest cells by trypsin-ization, adjust cell concentration to approximately 2000 cells/ l (2£106 cells/ml), and keep the cell suspension on ice. Carefully place 1 l of the cell suspension into each well. If the cells are injected too quickly, the cells will tend to disperse out of the bottom of the well. Injection of air bubbles can be avoided by over W lling the pipet with cells (1.3 l) and expulsing only to the W rst stop on the pipet. Place a 35-mm petri dish W lled with sterile water in the chamber with the slide to ensure 100% humidity. To allow cell attachment, incubate the slides with the CSM over-night at 37°C, 5% CO2 atmosphere and constant humid-ity. Cell attachment can be veri W ed with the manifold still mounted. Subsequently, gently remove the manifold and refeed each well.3.2. Quantitation of cell migrationCell migration is measured using an inverted micro-scope. A glass microscope slide is suspended over the 10-well Te X on slide (1mm above cell surface) using a manu-factured silicone suspension pad (CSM). This prevents drying of the wells and facilitates imaging by eliminating the aberration e V ects caused by the meniscus of the medium. The glass microscope slide can subsequently be removed without disrupting the cell monolayer for drug treatment or medium exchange.The area occupied by the cells is visualized by inverted microscopy using a 2.5£ objective (Fig.2). Images are captured most e Y ciently using digital imag-ing. A digital video of cell migration is hosted on the TGen W le server at /supplemen-tal_glioma/glioma_migration.mpg. The radius of the migrating cell population can be measured at the appro-priate intervals using a macro that can be downloaded from the CSM, website at . The average migration rate of W ve to ten replicates is cal-culated as the increasing radius of the entire cell popula-tion over time.3.3. Notesponents of the cell sedimentation system can besterilized. Package the Cell Sedimentation Manifold Fig.2. Bright W eld micrographs of glioma migration on human lami-nin substrate. Micrographs were taken 16h after plating (t D0) and after allowing cells to migrate out for 24h (t D24). The circle circum-scribing the cells is used to calculate the migration rate. Bar D2mm.212 A. Valster et al. / Methods 37 (2005) 208–215and Te X on-masked and plain slides in separate auto-clave bags. Steam autoclave the bags. The manifold can be stored at 4°C until ready to use. The slides can be stored at room temperature.2.At the end of the appropriate migration period, the cells can be W xed and processed for microscopic eval-uation by a number of techniques, including immuno-cytochemistry and in situ hybridization [36,37].4. Transwell invasion assaySNB19 cells are experimentally treated as described in Section 2.1. Two days after transfection, Matrigel Inva-sion Chambers (Becton Dickinson) are hydrated for at least 2h in the tissue culture incubator with 500 l serum free DMEM in the bottom of the well and 500 l in the top of the chamber. After hydration of the Matrigel, the DMEM in the bottom of the well is replaced with DMEM containing 10% F BS. 4£104 SNB19 cells are plated in 500 l DMEM supplemented with 10% FBS in the top of the chamber.The invasion assay is carried out for 24h in the tissue culture incubator. The cells are W xed by replacing the culture medium in the bottom and top of the chamber with 4% formaldehyde dissolved in PBS. After W xing for 15min at room temperature, the chambers are rinsed in PBS and stained with 0.2% crystal violet for 10min.After washing the chambers 5 times by dipping thechambers in a large beaker W lled with dH 2O the cells (now blue in color) at the top of the Matrigel membrane are removed with several Q-tips. It is safe to assume that all cells are removed when no more blue dye can be removed with the Q-tips. Now all cells that remain are the ones that have invaded and made it to the bottom side of the membrane (Fig.3). These cells are counted using an inverted microscope equipped with either a 4£or a 10£ objective and plotted as the percentage of invading cells of the total number of plated cells.Note. The invasive behavior of most cell lines is enhanced by passaging the cells the day before starting the invasion assay.5. Brain slice invasion assayCellular behavior and signaling in general is strikingly di V erent when evaluated on a two-dimensional substrate in contrast to a three-dimensional environment [38,39].Although studies of both melanoma and glioma cells have shown that there is a strong correlation between increased migration on two-dimensional substrates in vitro and increased invasiveness in vivo [40,41],in vitro migration assays performed on de W ned matrix components do not adequately incorporate the complex interplay between tumor cells and stroma required for cell invasion in situ [42]. Thus, the establishment of ex vivo rat brain slice models presents a unique system for the evaluation of the invasive properties of glioma cells in more physiologically relevant conditions [37,43,44].5.1. Establishment of GFP-expressing cell linesF or the establishment of GF P-expressing cell lines,we utilize the Retro-X system (Becton Dickinson).Brie X y, PLAT-E packaging cells are transfected with the retroviral expression vector using E V ectene, using the protocol provided by the manufacturer (Qiagen). The culture supernatant of the PLAT-E cells is removed 48h after transfection, W ltered through a 0.45 M cellulose-acetate W lter, and added to subcon X uent cultures of cells.For the rapid selection of cells that stably and uniformly express GFP, we use a two-tiered selection process. First,two days after transfection, cells are sorted by F ACS and subsequently selected in DMEM containing G418(200 g/ml).5.2. Brain slice invasion assay5.2.1. Preparation of rat brain slicesThe brain slice model system of rat whole cerebrum is modi W ed from the organotypic culture methods previ-ously reported [37,43,44]. Brain tissue is prepared from 4-week-old male Wister rats (Crl: (WI)BR; Charles100120Control Rac1 RNAiA. Valster et al. / Methods 37 (2005) 208–215213River Lab, Wilmington, MA). After halothane anesthe-sia, the whole brains are quickly removed and placed in cold Hanks’ Balanced Salt Solution (GIBCO), which contains 100units/ml penicillin and 100 g/ml strepto-mycin. The brain is cut vertically to the base with a scal-pel, 1mm inward from both rostral and caudal ends of the cerebrum. The cerebrum is attached to the stage of a vibratome (1000 Plus; The Vibratome, St. Louis, MO) using glue (Krazy Glue, Elmer’s Products, Columbus, OH)). The attached cerebrum is further supported by small cubes of 3% agarose gel, which are also attached to the stage by glue. The cerebrum is then cut vertically to the base in 400- m-thick sections. Six slices can be obtained from one rat.The brain slices are transferred to the upper chamber of a transwell insert (six-well plate) and placed on top of the 0.4- m micropore polycarbonate W lter (Becton Dick-inson). Next, 500 l of medium is added to the upper chamber and 1.5ml to the lower chamber. The slice cul-ture medium consists of DMEM with 10% FBS, 100units/ ml penicillin and 100 g/ml streptomycin. The brain slice culture is incubated at 37°C under standard conditions of 100% humidity, 95% air, and 5% CO2. The slices are kept in the incubator until use. The organotypic cytoarchitec-ture of these cultured brain slices and neuronal viability can be preserved for over two weeks [43].5.2.2. Implanting the GFP-expressing cells on brain sliceThree days after transfection with siRNA (Section 2.1), the GF P-expressing cells are trypsinized, collected in DMEM with FBS and spun down. After resuspension in DMEM without FBS, the cells are counted and fur-ther diluted in serum-free DMEM to 2£108 cells/ml. Before the cells are placed on the brain slice, the medium in the upper chamber is aspirated. The surface of brain slice should be semi-dry. This step is critical to avoid cell dispersion over the slice. 105 cells are gently placed on the putamen (0.5 l transfer volume). Subsequently, 500 l of serum-free medium is added onto the upper chamber to avoid drying of brain slice, but still allowing the surface of the slice to remain well exposed to the air. This is critical for the long-term survival of the neuronal cells in the slices. Both right and left sides of the brain slice are used. Typically, we perform three transfections for three brain slices each.Lateral migration of the cells on the upper side of the brain slice can be examined by X uorescent stereomicro-scopic imaging using a Macro-Fluorescent Imaging Sys-tem at 10£ magni W cation (SZX12-RF L3; Olympus) equipped with a GF P barrier W lter (DP50; Olympus). Half of the medium is replaced with fresh medium every 2 days. Depending on the cell line, observations are car-ried out over one to several days.5.2.3. Quantitation of glioma cell invasion into the ex vivo brain sliceTo quantitate glioma cell invasion into the brain slice, the brain slice is W xed overnight on the membrane in 4% paraformaldehyde at 4°C. Subsequently, the polycarbon-ate membrane is cut out using a scalpel and the W lter with the brain slice are transferred onto a microscope slide for observation using an inverted laser confocal microscope (LSM 5; Zeiss). Serial sections are obtained every 7.5 m downward from the top surface to the bottom of the slice (Fig.4A). Scion image software is used to calculate total area of GFP-stained cells. The area is plotted as a function of the distance from the top surface of the brain slice and the distribution curve is constructed. The extent of gliomaFig.4. (A) Confocal X uorescence micrographs showing invasion of U251 glioma cells 5 days after transfer to brain slices. Serial sections wereobtained every 7.5 m downward from the brain slice surface (0 m) to a deeper site (82.5 m). Six representative sections are shown. Bar D100 m.(B) Fluorescence distribution curve calculated from the data in (A).214 A. Valster et al. / Methods 37 (2005) 208–215cell invasion in the slice is de W ned as the depth ( m) that shows half of the maximum area of invasive cells (Fig.4B). Data showing that siRNA-mediated depletion of Rac1 inhibits the invasive behavior of glioma cells in this system are shown in Fig.5.5.3. NoteA common problem with brain slice invasion assay is bacterial contamination. To avoid this,1.Disinfect all instruments before starting this assay using 70% ethanol.e gloves that are sterilized.e medium that contains antibiotics.e sterile hood when the brain slices are handled.6. Concluding remarksWith the exception of the brain slice invasion model,the methods described in this review are applicable toother cells types in addition to glioma. On the other hand,although logistically and technically much more involved,the brain slice invasion model described here is unique in that it allows examination of tumor cell invasion in an organotypic fashion. An alternative approach that permits the detailed study of the invasive behavior of other tumor cells in a physiological setting is intravital imaging, either in whole animals [45] or in isolated organs [46].AcknowledgmentsThis work was supported by National Institutes of Health Grant CA87567 to M.S. and NS042262 and NS043446 to M.E.B.References[1]A.J. Ridley, M.A. Schwartz, K. Burridge, R.A. Firtel, M.H. Gins-berg, G. Borisy, J.T. Parsons, A.R. Horwitz, Science 302 (2003)1704–1709.[2]J.D. Hood, D.A. Cheresh, Nat. Rev. Cancer 2 (2002) 91–100.[3]C.H. Heldin, B. Westermark, Physiol. Rev. 79 (1999) 1283–1316.[4]M.E. DeVries, L. Ran, D.J. Kelvin, Semin. Immunol. 11 (1999) 95–104.[5]K. Burridge, K. Wennerberg, Cell 116 (2004) 167–179.[6]B. Anand-Apte, B.R. Zetter, A. Viswanathan, R.G. Qiu, J. Chen,R. Ruggieri, M. Symons, J. Biol. Chem. 272 (1997) 30688–30692.[7]J. Banyard, B. Anand-Apte, M. Symons, B.R. Zetter, Oncogene 19(2000) 580–591.[8]W.E. Allen, D. Zicha, A.J. Ridley, G.E. Jones, J. Cell Biol. 141(1998) 1147–1157.[9]A.W. Roberts, C. Kim, L. Zhen, J.B. Lowe, R. Kapur, B. Petryniak,A. Spaetti, J.D. Pollock, J.B. Borneo, G.B. Bradford, S.J. Atkinson,M.C. Dinauer, D.A. Williams, Immunity 10 (1999) 183–196.[10]P.J. Keely, J.K. Westwick, I.P. Whitehead, C.J. Der, L.V. Parise,Nature 390 (1997) 632–636.[11]L.M. Shaw, I. Rabinovitz, H.H. Wang, A. Toker, A.M. Mercurio,Cell 91 (1997) 949–960.[12]K. Itoh, K. Yoshioka, H. Akedo, M. Uehata, T. Ishizaki, S. Nar-umiya, Nat. Med. 5 (1999) 221–225.[13]E. Sahai, C.J. Marshall, Nat. Rev. Cancer 2 (2002) 133–142.[14]A. Giese, R. Bjerkvig, M.E. Berens, M. Westphal, J. Clin. Oncol. 21(2003) 1624–1636.[15]A.J. Ridley, Methods Mol. Biol. 84 (1998) 153–160.[16]C.D. Nobes, A. Hall, J. Cell Biol. 144 (1999) 1235–1244.[17]L.A. Feig, Nat. Cell Biol. 1 (1999) E25–E27.[18]Y. Zheng, Trends Biochem. Sci. 26 (2001) 724–732.[19]B. Debreceni, Y. Gao, F. Guo, K. Zhu, B. Jia, Y. Zheng, J. Biol.Chem. 279 (2004) 3777–3786.[20]A.M. Denli, G.J. Hannon, Trends Biochem. Sci. 28 (2003) 196–201.[21]D.M. Dykxhoorn, C.D. Novina, P.A. Sharp, Nat. Rev. Mol. CellBiol. 4 (2003) 457–467.[22]S. Etienne-Manneville, A. Hall, Nature 421 (2003) 753–756.[23]S. Etienne-Manneville, A. Hall, Cell 106 (2001) 489–498.[24]A. Reynolds, D. Leake, Q. Boese, S. Scaringe, W.S. Marshall, A.Khvorova, Nat. Biotechnol. 22 (2004) 326–330.[25]P. Lassus, J. Rodriguez, Y. Lazebnik, Sci STKE (2002) http:///cgi/content/full/sigtrans;2002/147/pl13.[26]A.L. Jackson, S.R. Bartz, J. Schelter, S.V. Kobayashi, J. Burchard,M. Mao, B. Li, G. Cavet, P.S. Linsley, Nat. Biotechnol. 21 (2003)635–637.Fig.5. Rac1-directed siRNA inhibits invasion of glioblastoma cells in rat brain slices. (A) Confocal X uorescence micrographs of SNB19 gli-oma cells stably expressing green X uorescent protein. Cells were trans-fected with siRNAs directed against luciferase (control) or Rac1, two days prior to transfer to the bilateral putamen of rat brain slices and observed at the indicated time. Bar D 500 m. (B) Invasion rates of SNB19 and U87MG cells treated with the indicated siRNA constructs were calculated from Z axis images collected by confocal laser scan-ning microscopy. The mean values of the invasion rates were obtained from six independent experiments.。

3D MEDIC和3D SPACE磁共振神经成像在腰骶丛神经根的一致性对比研究

3D MEDIC和3D SPACE磁共振神经成像在腰骶丛神经根的一致性对比研究

$$Feb.2021Vo . 42$No. 12021年 2月 第 42 卷$ 第 1 期首都医科大学学报Journal of Capital Medical Universi/[doi : 10. 3969/j. issp. 1006-7795. 2021. 01. 022]・临床研究*3D MEDIC 和3D SPACE 磁共振神经成像在腰骶丛神经根的一 致性对比研究孙峥1!2孔超3鲁世保3陈海%笪宇威%张苗1>2卢洁心(1.首都医科大学宣武医院放射科,北京100053; 2.磁共振成像脑信息学北京市重点实验室,北京100053; 3.首都医科大学宣武医院骨科,北京100053; 4.首都医科大学宣武医院神经内科,北京100053)$摘要】 目的 验证三维多回波数据联合成像(three dimensional multi-echo data imagine combination with selective water excitation , 3D MEDIC WE)和三维快速自旋回波成像(three dimensional sampling peSection with application optimized contrasts byusing d/ferent Uip angle evelu/on , 3D SPACE STIR )序列在腰骶丛神经根成像中的可行性和重复性。

方法 将55例受试者分为腰椎无异常表现的正常对照组(20例)、单纯性腰椎间盘突出症(lumbar d/c hernm/on , LDH )组(20例)和慢性炎性脱髓鞘性多发性神经根神经病症(ch/nw inUamma"/ demyelinating polyradwuloneuropathy , CIBP )组(15例),分别应用两种腰骶丛神经根成 像,评价图像质量参数信噪比(signal " noise ratio , SNR )、对比噪声比(contrast " noise ratio , CNR )和对比度(contrast ratio , CR ),并验证正常对照组、CBP 组和LDH 组测量神经根直径的一致性。

一种用于未标定图像三维重建的立体匹配算法

一种用于未标定图像三维重建的立体匹配算法
匹配, 用随机抽样 算法估计基 础矩 阵的 同时剔 除误 匹配点对 ; 利 最后在估 计的基 础矩 阵的引导 下进行 双 向 匹配 。 实验证 明 , 算法 能够很 好地 恢复物体 的结构 , 该 是一种 有效 的用于未标 定图像三 维重建 的立体 匹配算 法。
关键词 :立体 匹配 ;未标定 图像 ;三维重建 ;限制 因子 ;亚像素 ; 向 匹配 双 中 图分 类号 :T 3 14 P9. 1 文献标 志码 :A 文章 编号 :10 —6 5 2 1 ) 0 3 6 — 4 0 1 39 (0 0 1 ・9 4 0
Ab t a t sr c :T i p p rp o o e t ro ma c ig ag r h fr3 e o sr cin b s d o n ai rt d i g s F rt h s a e r p s d a see t hn l o t m o D r c n t t a e n u c b a e ma e . i l h s i u o l s y,t i ag r h r fr d l t gfco l n t t ec u trn h n me o fHars o e , n s dGa s in q a r s i i gt l oi m ee e i i trt e i ae h l se gp e o n n o r r r a d u e u s u d e t n t mi n a o mi i ieu s a i ft o
bewelr c nsr c e y u ig t i l o t m ,a d i s a f c ie se e thig ag rtm o D e o sr to a e n l e o tu t d b sn hs ag r h i n ti n ef tv tr o mac n lo h fr3 rc n tucin b s d o e i un a ir td i g s c lb ae ma e .

一种多点拟合的恒定立体角纤维重建模型

一种多点拟合的恒定立体角纤维重建模型

一种多点拟合的恒定立体角纤维重建模型
李浩东;王远军
【期刊名称】《小型微型计算机系统》
【年(卷),期】2024(45)5
【摘要】基于弥散磁共振成像DTI的纤维追踪技术是非侵入性活体脑神经研究的关键技术.恒定立体角重建模型CSA是基于DTI发展而来的一种纤维重建模型,能够根据采样球壳上的数据对弥散方向分布函数进行线性径向投影计算,从而进行纤维重建.目前,恒定立体角纤维重建模型存在鲁棒性较差,重建纤维过于杂乱以及弥散方向分布偏差的问题.针对上述问题,本文提出MCSA(Multipoint Constant Solid Angle)模型,首先引入可以使弥散方向分布函数更加准确的最小二乘法,接着通过自适应高斯函数引入多点拟合弥散信息提高模型鲁棒性和抗噪性.最后,本文分别使用Fibercup、ISMRM2015年模拟数据以及Stanford HARDI真实影像数据对传统CSA模型以及本文提出MCSA模型进行对比分析,结果表明,利用本文提出MCSA 模型重建的纤维更加符合客观规律,并且在一定程度上减少了假阳性纤维的生成.【总页数】6页(P1116-1121)
【作者】李浩东;王远军
【作者单位】上海理工大学医学影像工程研究所
【正文语种】中文
【中图分类】TP391
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2.一种新的评价结构方程模型拟合效果的校正拟合指数
3.一种改进的随机检验法用于主成分选择以避免光谱分析校正模型的过拟合或欠拟合
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JOVESEScienceEducation科学教育专辑内容介绍

JOVESEScienceEducation科学教育专辑内容介绍

JOVE SE(Science Education)科学教育专辑内容介绍JOVE出版社是生命科学领域出版视频最多的出版社,总部位于美国马萨诸塞州剑桥市,紧邻哈佛大学、麻省理工学院、塔夫斯大学、波士顿大学等多所知名学府。

JOVE出版社于2006年创办JOVE实验视频期刊,致力于以视频方式展现生物学、医学、化学、物理学等学科领域的研究过程与成果。

SE科学教育专辑专门为教学设计,旨在通过简单易懂的视频展现实验基础教学。

目前共有9个子集,其中5个子集已有中文配音以及人工翻译,方便学生学习以及课堂教学。

SE每个子集有90个视频(15个教学视频,75个应用实验视频)。

每年会更新1-2个新子集,现有子集视频数量无更新。

1)General Laboratory Techniques基础实验技术2)Basic Methods in Cellular and Molecular Biology细胞与分子生物学基本方法3)Essentials of Biology1: Yeast, Drosophila and C.Elegans生物学精要I: 酵母,果蝇,线虫4)Essentials of Biology 2: Mouse, Zebrafish, and Chick生物学精要II:鼠,斑马鱼,鸡5)Essentials of Neuroscience神经科学精要6)Essentials of Developmental Biology发育生物学精要7)Essentials of Behavioral Science行为科学精要8)Essentials of Genetics基因学精要9)Essentials of Cell Biology 细胞生物学精要1)General Laboratory Techniques基础实验技术该子集展示了如何使用在许多实验中都至关重要的一些标准实验室仪器,以及如何进行实验室基本操作。

python求解机械臂雅可比矩阵

python求解机械臂雅可比矩阵

一、概述机械臂是一种常见的自动化设备,广泛应用于工业制造、医疗和军事领域等。

在机械臂控制中,雅可比矩阵是一个重要的数学工具,用于描述机械臂的运动学特性和动力学特性。

Python作为一种强大的编程语言,可以用来求解机械臂的雅可比矩阵,为机械臂的控制和优化提供有力支持。

二、机械臂的雅可比矩阵1. 机械臂的运动学描述机械臂的运动学描述了机械臂的空间位置和姿态。

其中,雅可比矩阵是描述机械臂末端速度与关节速度之间的关系的重要工具。

通过雅可比矩阵,可以将末端速度转换为关节速度,进而控制机械臂的运动。

2. 雅可比矩阵的求解雅可比矩阵的求解可以使用数值方法或符号方法。

数值方法通过数值计算得到雅可比矩阵的近似值,而符号方法则通过符号计算得到雅可比矩阵的精确表达式。

在实际应用中,符号方法通常更加准确和高效。

三、Python求解机械臂的雅可比矩阵1. Python在机械臂控制中的应用Python是一种开源的、优雅的、易学易用的编程语言,广泛应用于科学计算、数据分析、人工智能和机器学习等领域。

在机械臂控制中,Python可以用来实现机械臂的建模、运动学分析、动力学仿真和控制算法等。

2. 使用Python求解机械臂的雅可比矩阵在Python中,可以使用符号计算库SymPy来求解机械臂的雅可比矩阵。

SymPy是Python的一个符号计算库,提供了符号计算的功能,可以精确地求解雅可比矩阵。

通过SymPy,可以轻松地建立机械臂的运动学模型,并求解雅可比矩阵。

四、案例分析1. 案例背景假设有一个3自由度的平面机械臂,需要求解其雅可比矩阵。

2. 案例实现利用SymPy建立机械臂的运动学模型,并定义关节变量、末端位置和末端速度。

利用SymPy的求导功能,求解雅可比矩阵。

通过Python的可视化库matplotlib,可视化机械臂的雅可比矩阵。

五、总结与展望1. 总结Python作为一种强大的编程语言,在机械臂控制中具有重要的应用前景。

3D 生物打印负载转化生长因子 β3 的软骨复合支架说明书

3D 生物打印负载转化生长因子 β3 的软骨复合支架说明书

Chinese Journal of Tissue Engineering Research |Vol 25|No.34|December 2021|54453D 生物打印负载转化生长因子β3的软骨复合支架杨 振1,2,李 浩1,2,付力伟1,2,高仓健1,2,姜双鹏2,王福鑫2,苑志国2,孙志强1,2,查康康1,2,1,22222文题释义:3D 生物打印:通过精准控制生物材料、种子细胞、生长因子在整体3D 结构中的位置、组合与互相作用,使之具有生物活性,并能实现与目标组织或生物器官接近相同,甚至更优越的功能。

转化生长因子β3:作为关节软骨组织形成的重要调节因子,可以促进干细胞迁移和成软骨分化,增强软骨损伤的修复,是一种理想的干细胞招募和促分化因子。

摘要背景:通过募集内源性干细胞原位再生软骨损伤的治疗策略,是未来软骨组织工程研究的新方向。

目的:构建既能募集干细胞又能促进其黏附和增殖,且有利于新生组织成熟的组织工程软骨复合支架。

方法:将脱细胞软骨细胞外基质(extracellular matrix ,ECM)与甲基丙烯酸酯化明胶(methacrylated gelatin ,GelMA)混合配制光敏性生物墨水,利用3D 生物打印技术分别制备单纯聚己内酯[poly(Ɛ-caprolactone),PCL]支架、PCL/GelMA/ECM 支架。

将转化生长因子β3(transforming growth factor β3,TGF-β3)负载于生物墨水中制备PCL/GelMA/ECM/TGF-β3支架,检测其缓释性能。

从形态学、组织学、生物化学、生物力学等角度评价PCL/GelMA/ECM 支架的物理化学性质。

利用CCK-8法检测PCL/GelMA/ECM 支架的细胞毒性。

将脂肪间充质干细胞接种于PCL/GelMA/ECM 支架上,1,4,7 d 后,共聚焦显微镜下观察细胞活性,扫描电镜观察细胞黏附。

一种抗干扰的三维虚拟切片的制作方法[发明专利]

一种抗干扰的三维虚拟切片的制作方法[发明专利]

专利名称:一种抗干扰的三维虚拟切片的制作方法专利类型:发明专利
发明人:陈斌,贾守礼,何裕财,吴丹媛,陈进
申请号:CN200710009842.3
申请日:20071115
公开号:CN101436313A
公开日:
20090520
专利内容由知识产权出版社提供
摘要:一种抗干扰的三维虚拟切片的制作方法,包括:用计算机建模的方法得到整个切片的表面数学模型,利用此数学模型估计出每个视场图像z轴的大致位置;采用显微镜的自动聚焦算法精确得到每个视场图像的最佳聚焦位置,以此最佳聚焦位置作为三维平面的参考面;其余各z轴视场图像根据参考面依次排列得到三维聚焦平面图像序列,制作出最终的三维虚拟切片。

本发明可有效抵抗切片本身不平整和切片上的组织高低不平、全自动显微镜机械精度、环境扰动等干扰因素,从而形成连续平滑、清晰的虚拟切片图像。

申请人:麦克奥迪实业集团有限公司
地址:361006 福建省厦门市火炬高科技区麦克奥迪大厦
国籍:CN
代理机构:厦门市首创君合专利事务所有限公司
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随机矩阵奇异值分解算法在3D重建中的应用效果评估

随机矩阵奇异值分解算法在3D重建中的应用效果评估

随机矩阵奇异值分解算法在3D重建中的应用效果评估随着科学技术的进步和计算机图形学的快速发展,三维重建技术在各个领域得到了广泛的应用。

其中,随机矩阵奇异值分解算法作为一种常用的三维重建算法,其在提高重建效果方面具有很大的潜力。

本文将对随机矩阵奇异值分解算法在3D重建中的应用效果进行评估。

一、随机矩阵奇异值分解算法简介随机矩阵奇异值分解算法(Random Matrix Singular Value Decomposition, RMSVD)是一种基于奇异值分解(Singular Value Decomposition, SVD)的重建算法,其核心思想是通过矩阵分解的方式来还原三维模型的形状和纹理信息。

相比于其他算法,随机矩阵奇异值分解算法具有快速、准确等特点,被广泛应用于三维重建领域。

二、随机矩阵奇异值分解算法在3D重建中的应用效果评估为了评估随机矩阵奇异值分解算法在3D重建中的应用效果,我们进行了一系列的实验。

首先,我们收集了一批包含不同形状和纹理的三维模型作为测试数据集。

然后,利用随机矩阵奇异值分解算法对这些三维模型进行了重建,并对重建结果进行了评估。

在评估指标方面,我们采用了两种常用的指标:均方根误差(Root Mean Square Error, RMSE)和结构相似性指数(Structural Similarity Index, SSIM)。

RMSE用于评估重建模型与原始模型之间的几何误差,而SSIM则用于评估重建模型与原始模型之间的纹理相似性。

通过对比不同算法的评估结果,我们可以客观地评估随机矩阵奇异值分解算法在3D重建中的应用效果。

实验结果表明,随机矩阵奇异值分解算法在3D重建中取得了较好的效果。

通过与其他重建算法的比较,我们发现随机矩阵奇异值分解算法在几何误差和纹理相似性方面均能取得较佳的结果。

具体而言,随机矩阵奇异值分解算法在几何误差方面的均方根误差较小,说明其能够较准确地还原原始模型的形状信息;同时,在纹理相似性方面的结构相似性指数较高,说明其能够较好地还原原始模型的纹理信息。

随机矩阵奇异值分解算法在3D建模中的应用效果评估

随机矩阵奇异值分解算法在3D建模中的应用效果评估

随机矩阵奇异值分解算法在3D建模中的应用效果评估随机矩阵奇异值分解(Randomized Singular Value Decomposition, rSVD)算法是一种用于矩阵分解的高效方法,近年来在3D建模领域得到了广泛的应用。

本文将对随机矩阵奇异值分解在3D建模中的应用效果进行评估。

1. 引言3D建模是计算机图形学领域的重要研究方向之一,广泛应用于电影、游戏、虚拟现实等领域。

在3D建模中,常常需要对大量的三维点云数据进行处理和分析。

而随机矩阵奇异值分解算法可以高效地对大规模矩阵进行分解,因此在3D建模中有着广泛的应用前景。

2. 随机矩阵奇异值分解算法随机矩阵奇异值分解算法是一种基于采样和迭代的矩阵分解方法。

它通过对原始矩阵进行随机采样,构造一个低秩近似矩阵,并对其进行奇异值分解。

与传统的奇异值分解算法相比,随机矩阵奇异值分解算法具有更低的计算复杂度和更快的运算速度。

3. 随机矩阵奇异值分解在3D建模中的应用3D建模中常用的数据表示方式之一是三维点云。

而随机矩阵奇异值分解算法可以对三维点云数据进行降维和拟合,从而实现对三维模型的快速建模。

通过将三维点云数据映射到低维空间,随机矩阵奇异值分解算法可以提取出三维模型的主要特征,并去除噪声和冗余信息。

4. 实验设计与结果分析为了评估随机矩阵奇异值分解算法在3D建模中的应用效果,我们设计了实验,并对比了其与传统奇异值分解算法的性能差异。

实验中使用了不同规模的三维点云数据集,并分别对其进行了随机矩阵奇异值分解和传统奇异值分解处理。

结果表明,随机矩阵奇异值分解算法在运算速度和降维效果上都优于传统奇异值分解算法,能够更快速地实现对三维模型的建模和分析。

5. 应用案例分析除了实验评估,本文还通过应用案例对随机矩阵奇异值分解在3D 建模中的具体应用效果进行分析。

通过对真实场景中的三维点云数据进行处理,我们展示了随机矩阵奇异值分解算法在三维模型建模和分析方面的潜力和优势。

数值方法求机械臂逆运动

数值方法求机械臂逆运动

数值方法求机械臂逆运动
机械臂是一种常见的工业自动化设备,它主要通过电机驱动来实现运动,从而完成各种工业任务。

在机械臂运动过程中,如何精准地控制机械臂的末端位置和姿态是非常重要的。

逆运动学是一种解决这种问题的方法,它能够通过末端位置和姿态计算出机械臂的各个关节角度,从而实现精准的控制。

在实际应用中,机械臂的运动往往受到多种因素的影响,例如机械臂本身的结构、负载物体的重量、环境因素等。

为了更准确地计算机械臂的逆运动,我们可以采用数值方法来进行求解。

数值方法是一种基于数值计算的近似求解方法,它可以通过离散化空间和时间,将连续的问题转化为离散的问题,并通过迭代求解来逐步逼近真实解。

在机械臂逆运动的求解中,我们可以采用数值方法来进行求解,例如牛顿-拉夫森迭代法、雅可比迭代法等。

牛顿-拉夫森迭代法是一种常用的数值方法,它可以通过一次迭
代就快速地逼近真实解。

在机械臂逆运动的求解中,我们可以将关节角度作为牛顿-拉夫森迭代法的迭代变量,通过不断迭代来逼近机械
臂末端的期望位置和姿态。

雅可比迭代法则是另一种常用的数值方法,它可以通过一次迭代来同时计算出机械臂各个关节的角度,从而实现更快速、更准确的控制。

总之,数值方法是一种灵活可靠的求解逆运动问题的方法。

在机械臂控制中,采用数值方法求解逆运动可以提高控制精度和效率,从而实现更加精准和高效的工业自动化应用。

基于非降阶汉密尔顿算子的三维立体层析反演

基于非降阶汉密尔顿算子的三维立体层析反演

基于非降阶汉密尔顿算子的三维立体层析反演杨锴;邢逢源;李振伟;王宇翔;倪瑶【期刊名称】《地球物理学报》【年(卷),期】2016(059)009【摘要】不同于前人在射线中心坐标系下基于降阶汉密尔顿算子建立立体层析矩阵,本文详细讨论了在三维直角坐标系下,基于非降阶汉密尔顿算子通过射线扰动理论导出三维立体层析所需的数据空间对模型空间的一阶线性关系,进而建立三维立体层析矩阵.在建立这个庞大且稀疏的系数矩阵后,实施规则化使得该矩阵方程的求解能够收敛到一个合理的结果.理论数据的严格测试证实了三维立体层析矩阵建立的正确性,为实际应用奠定了理论基础.【总页数】13页(P3366-3378)【作者】杨锴;邢逢源;李振伟;王宇翔;倪瑶【作者单位】同济大学海洋地质国家重点实验室,上海200092;同济大学海洋地质国家重点实验室,上海200092;中石化上海海洋油气分公司,上海 200120;阿美远东(北京)商业服务有限公司国际研发中心,北京100102;中石化石油物探技术研究院地震成像技术研究所,南京210014【正文语种】中文【中图分类】P631【相关文献】1.基于梯度平方结构张量算法的高密度二维立体层析反演 [J], 王宇翔;杨锴;杨小椿;薛冬;陈宝书2.基于模型降阶的贝叶斯方法在三维重力反演中的实践 [J], 刘彦;吕庆田;李晓斌;祁光;赵金花;严加永;邓震3.基于特征波属性参数的立体层析速度反演方法研究 [J], 洪瑛;韩文功;孙小东;李振春;李芳4.基于二维VTI拟声波程函方程的椭圆各向异性立体层析反演 [J], 王潇;杨锴5.基于结构张量算法的南海深水三维立体层析反演实例研究(英文) [J], 邢逢源;杨锴;薛冬;汪小将;陈宝书因版权原因,仅展示原文概要,查看原文内容请购买。

基于归一化的抗几何攻击三维模型水印算法

基于归一化的抗几何攻击三维模型水印算法

基于归一化的抗几何攻击三维模型水印算法
金鑫;肖俊;王颖
【期刊名称】《东南大学学报(自然科学版)》
【年(卷),期】2007(037)0z1
【摘要】为了提高三维网格水印抵抗几何攻击的能力,借用数字图像归一化的思想,提出了一种基于归一化的抗几何攻击三维模型数字水印算法.该算法在嵌入水印前将模型的几何中心移到坐标原点以实现对平移攻击的不变性;将模型由直角坐标转化为球坐标,以模型顶点到几何中心的距离这一全局几何特征为嵌入单元,通过修改归一化距离的离散余弦变换系数嵌入水印,以实现对缩放攻击的鲁棒性.仿真结果表明,基于归一化的三维网格模型水印算法复杂度较低,能够很好地解决模型针对缩放攻击需要重定位的问题,在经受平移、旋转、缩放、剪切、网格简化等常见攻击时也具有较好的鲁棒性.
【总页数】5页(P215-219)
【作者】金鑫;肖俊;王颖
【作者单位】中国科学院研究生院信息安全国家重点实验室,北京,100049;中国科学院研究生院信息安全国家重点实验室,北京,100049;中国科学院研究生院信息安全国家重点实验室,北京,100049
【正文语种】中文
【中图分类】TP309
【相关文献】
1.基于归一化小波域抗几何攻击的图像水印算法 [J], 文展;黄小燕;文成玉
2.基于图像归一化的抗几何攻击水印技术 [J], 张翼;唐向宏
3.基于归一化图像的抗仿射变换攻击的水印算法 [J], 宋琪;罗航建
4.基于归一化的抗几何攻击三维模型水印算法 [J], 金鑫;肖俊;王颖
5.基于归一化的抗几何攻击三维模型水印算法 [J], 金鑫;肖俊;王颖
因版权原因,仅展示原文概要,查看原文内容请购买。

张量补全算法

张量补全算法

张量补全算法介绍张量补全算法是一种用于处理缺失数据的方法。

在现实生活中,很多数据集中都存在着缺失值的问题,而缺失值的存在会导致数据分析和建模的不准确性。

因此,研究如何有效地进行缺失值补全成为了数据科学领域的重要课题之一。

张量补全算法通过利用张量的高阶结构和局部特征,能够对缺失值进行准确的估计和补全,从而提高数据的完整性和可信度。

常见的缺失值类型在讨论张量补全算法之前,我们先来了解一下常见的缺失值类型。

主要有以下几种类型:1.完全随机缺失(MCAR):缺失值的出现与任何其他变量无关,完全是随机发生的;2.随机缺失(MAR):缺失值的出现与其他观测值的相关变量有关,但与缺失值自身的大小无关;3.非随机缺失(NMAR):缺失值的出现与缺失值本身的大小有关。

相关问题和挑战在实际应用中,张量补全算法面临一些重要问题和挑战,如下所示:1.高维性:由于现实世界中的数据往往具有高维性,因此张量补全算法需要能够处理高维数据;2.大数据量:现如今产生的数据量越来越大,因此张量补全算法需要具备高效处理大规模数据的能力;3.高噪声:真实数据往往带有各种噪声,这对补全算法的准确性提出了挑战;4.稀疏数据:数据集中存在很多缺失值,这会导致补全算法的可行性和有效性受到严重影响。

张量的概念和性质在介绍张量补全算法之前,我们先来了解一下张量的概念和性质。

1. 张量的定义张量是一个多维数组,可以用于表示多维数据。

在数学上,一个张量可以被认为是一个具有多个维度的矩阵的推广。

2. 张量的秩张量的秩是指张量的维数,也就是它具有的维度的个数。

3. 张量的分解张量的分解是指将一个张量分解成多个低维张量的乘积的过程。

常见的张量分解方法有SVD分解、CP分解和Tucker分解等。

张量补全算法的基本原理张量补全算法的基本原理是利用已知数据的局部特征,通过建立合理的模型来预测缺失数据的值。

常见的张量补全算法有基于张量分解的补全方法和基于张量低秩模型的补全方法等。

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Invasion Assay Using 3D Matrices1. OverviewScientists have developed 3D models to more accurately study cell invasion and migration processes. While most traditional cell culture systems are 2D, cells in our tissues exist within a 3D network of molecules known as the extracellular matrix or ECM. While many of the mechanistic processes required for cell motility in 2D and 3D are similar, factors such as the reduced stiffness of ECM compared to plastic surfaces, the addition of a third dimension for migration, and the physical hindrance of moving through the mesh of long polymers in the ECM, all present different challenges to the cell compared to two-dimensional migration.This video will briefly introduce the basic function and structure of the ECM, as well as the mechanisms by which cells modulate and migrate through it. Next, we’ll discuss a general protocol used to study endothelial cell invasion. Finally, we will highlight several applications of 3D matrices to studying different biological questions.2. ECM Composition and Cell-ECM InteractionLet’s begin by examining the composition of the ECM, and how cells interact with it.The ECM performs many functions, such as providing support for cells, facilitating intercellular communication, and separating tissues. ECM composition varies among different tissues and has different biological properties, but it can be classified into two broad types. The basement membrane serves to anchor and separate tissues, while interstitial matrix surrounds and supports the cells within a tissue. The interstitial matrix is mostly composed of the fibrous protein collagen, but also includes elastin and fibronectin.Several biological processes need to occur for cells to migrate through the ECM. The first is cell-matrix adhesion, which involves transmembrane proteins called integrins. These link the ECM to the cell’s internal scaffold, known as the cytoskeleton.Another process is the structural rearrangement of the cell’s cytoskeleton. This leads to the formation of specialized structures called invadopodia, which are protrusions of the cell into its surrounding matrix. The final step is ECM modulation. This typically involves degradative molecules known as matrix metalloproteases or MMPs, which accumulate in the invadopodia and degrade the surrounding ECM, facilitating cell invasion. 3D matrix invasion assays allow scientists to visualize and study this complex process.3. Endothelial Cell Tube Formation AssayNow that you’re familiar with ECM and its interaction with cells, let’s walk through a protocol for studying ECM invasion by endothelial cells to form tubules. By culturing endothelial cells in a 3D environment, one can simulate the biological process of blood vessel growth, also known as angiogenesis, which is important during both normal development, as well as cancer.First, endothelial cells are cultured, and a single cell suspension is prepared by treating the cells with proteases such as trypsin, and passing them through a mesh filter to break up cell clumps. The 3D matrix, commonly composed of collagen, fibrin, laminin, or more complex combinations of these components—which can either be prepared in-lab or ordered from commercial vendors—is then thawed on ice. Since most ECM preparations polymerize at higher temperatures, it is helpful to keep other equipment and reagents cold as well. The cell suspension is mixed with the thawed matrix solution to embed cells, and this mixture is placed into a cell culture incubator where the higher temperature will cause the matrix to polymerize.Once the cell-containing matrix is set, culture media containing angiogenic factors is added to the matrix dish. Using time-lapse microscopy software, individual cells can then be tracked to observe their migration through the matrix. The resulting images are analyzed,and cell positions are used to calculate movement direction and distance in microns. These values can then be plotted to determine locomotory activity—the average migration rate of the cells. Finally, tube network formation is observed and analyzed using visualization software to identify features such as nodes, tubes, and loops.4. ApplicationsNow, let’s explore a few applications of 3D matrices in specific experiments.Cell migration is mediated by active modulation of the cellular cytoskeleton. In this experiment, collagen matrices were prepared and mixed with a stain containing red fluorescent protein to allow for visualization. Individual cell spheroids, which are free-floating cell clusters, were isolated and embedded in the collagen matrix. Following incubation, the embedded cells were stained for specific cytoskeletal components, and imaged by fluorescence microscopy. Researchers observed cytoskeletal components and their alterations as cells migrated through the ECM.Scientists can also study how the properties of the ECM affect migration. Using a concentric gel system, where cells are embedded in an inner gel matrix surrounded by outer matrices of varying concentrations,scientists can track cells using time-lapse microscopy to study their migration from the inner gel to the initially cell-free outer gel. Researchers observed that the greater stiffness of higher concentration gels resulted in increases in both cell displacement and overall distance of cell migration.Finally, matrix invasion assays can be performed within a living animal to study angiogenesis in an organ-specific context. Here, fibrin gels—commonly used in tissue engineering due to their biodegradable nature—were generated, followed by implantation into mouse lungs where the gels were held in place by a “glue” made of the protein fibrinogen. Cell migration and new blood vessel formation were allowed to occur for the following 7 to 30 days, after which the lungs and fibrin gels were harvested, fixed, and sectioned. Imaging of these sections revealed blood vessel and alveoli formation in the implanted gels, giving researchers insight into this crucial aspect of lung development in its in vivo setting.。

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