The radial basis function (RBF) interpolation approach proposed by Freedman is used to solve inverse problems encountered in well-logging and other petrophysical issues. The approach is to predict petrophysical prop...The radial basis function (RBF) interpolation approach proposed by Freedman is used to solve inverse problems encountered in well-logging and other petrophysical issues. The approach is to predict petrophysical properties in the laboratory on the basis of physical rock datasets, which include the formation factor, viscosity, permeability, and molecular composition. However, this approach does not consider the effect of spatial distribution of the calibration data on the interpolation result. This study proposes a new RBF interpolation approach based on the Freedman's RBF interpolation approach, by which the unit basis functions are uniformly populated in the space domain. The inverse results of the two approaches are comparatively analyzed by using our datasets. We determine that although the interpolation effects of the two approaches are equivalent, the new approach is more flexible and beneficial for reducing the number of basis functions when the database is large, resulting in simplification of the interpolation function expression. However, the predicted results of the central data are not sufficiently satisfied when the data clusters are far apart.展开更多
Recently a Hybrid Carrier (HC) scheme based on Weighted-type Fractional Fourier Transform (WFRFT) was proposed and developed, which contains Single Carrier (SC) and Multi-Carrier (MC) synergetie transmission. ...Recently a Hybrid Carrier (HC) scheme based on Weighted-type Fractional Fourier Transform (WFRFT) was proposed and developed, which contains Single Carrier (SC) and Multi-Carrier (MC) synergetie transmission. The wide interest is primarily due to its appealing characteristics, such as the robust performances in different types of selective fading channels and a great deal of potential for secure communications. According to the literatures, the HC signal and SC or MC signal probability distributions are different. In particular, some benefits of this HC scheme are brought by the quasi-Gaussian distribution of WFRFT signals. However, until now researchers have only presented statistic properties through computer simulations, and the accurate expressions of signals are not derived yet. In this paper, we derive the accu- rate and rigorously established closed-form expressions of Probability Density Function (PDF) of WFRFT signal real and imaginary parts with a large number of QPSK subcarriers, and this PDF can describe the behavior of data modulated by WFRFT, avoiding the complex computation for extensive computer simulations. Furthermore, the components of PDF expression are described and analyzed, and it is revealed that the tendency of signal quasi-Gaussian changes with the increasing of the parameter a (a in (0,1]). To validate the analytical results, extensive simulations have been conducted, showing a very good match between the analytical results and the real situations. The contribution of this paper may be useful to deduce the closed form expressions of Bit Error Ratio (BER), the Complementary Cumulative Distribution Function (CCDF) of Peak to Average Power Ratio (PAPR), and other analytical studies which adopt the PDF.展开更多
Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom,were considered.This problem of diffraction by th...Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom,were considered.This problem of diffraction by these two cylinders,which were considered as idealization of a buoy and a circular plate,can be considered as a wave energy device.The wave energy that is created and transferred by this device can be appropriately used in many applications in lieu of conventional energy.Method of separation of variables was used to obtain the analytical expressions for the diffracted potentials in four clearly identified regions.By applying the appropriate matching conditions along the three virtual boundaries between the regions,a system of linear equations was obtained,which was solved for the unknown coefficients.The potentials allowed us to obtain the exciting forces acting on both cylinders.Sets of exciting forces were obtained for different radii of the cylinders and for different gaps between the cylinders.It was observed that changes in radius and the gap had significant effect on the forces.It was found that mostly the exciting forces were significant only at lower frequencies.The exciting forces almost vanished at higher frequencies.The problem was also investigated for the base case of no plate arrangement,i.e.,the case having only the floating cylinder tethered to the sea-bed.Comparison of forces for both arrangements was carried out.In order to take care of the radiation of the cylinders due to surge motion,the corresponding added mass and the damping coefficients for both cylinders were also computed.All the results were depicted graphically and compared with available results.展开更多
Network traffic classification plays an important role and benefits many practical network issues,such as Next-Generation Firewalls(NGFW),Quality of Service(QoS),etc.To face the challenges brought by modern high speed...Network traffic classification plays an important role and benefits many practical network issues,such as Next-Generation Firewalls(NGFW),Quality of Service(QoS),etc.To face the challenges brought by modern high speed networks,many inspiring solutions have been proposed to enhance traffic classification.However,taking many factual network conditions into consideration,e.g.,diversity of network environment,traffic classification methods based on Deep Inspection(DI) technique still occupy the top spot in actual usage.In this paper,we propose a novel classification system employing Deep Inspection technique,aiming to achieve Parallel Protocol Parsing(PPP).We start with an analytical study of the existing popular DI methods,namely,regular expression based methods and protocol parsing based methods.Motivated by their relative merits,we extend traditional protocol parsers to achieve parallel matching,which is the representative merit of regular expression.We build a prototype system,and evaluation results show that significant improvement has been made comparing to existing open-source solutions in terms of both memory usage and throughput.展开更多
Human pluripotent stem cells represent a potentially unlimited source of functional pancreatic endocrine lineage cells. Here we report a highly efficient approach to induce human embryonic stem (ES) cells and induce...Human pluripotent stem cells represent a potentially unlimited source of functional pancreatic endocrine lineage cells. Here we report a highly efficient approach to induce human embryonic stem (ES) cells and induced pluripo- tent stem (iPS) cells to differentiate into mature insulin-producing cells in a chemical-defined culture system. The differentiated human ES cells obtained by this approach comprised nearly 25% insulin-positive cells as assayed by flow cytometry analysis, which released insulin/C-peptide in response to glucose stimuli in a manner comparable to that of adult human islets. Most of these insulin-producing cells co-expressed mature β cell-specific markers such as NKX6-1 and PDX1, indicating a similar gene expression pattern to adult islet β cells in vivo. In this study, we also demonstrated that EGF facilitates the expansion of PDXl-positive pancreatic progenitors. Moreover, our protocol also succeeded in efficiently inducing human iPS cells to differentiate into insuIin-producing ceils. Therefore, this work not only provides a new model to study the mechanism of human pancreatic specialization and maturation in vitro, but also enhances the possibility of utilizing patient-specific iPS cells for the treatment of diabetes.展开更多
This paper presents an improved Voice Activity Detection (VAD) algorithm which uses the Signal-to-Noise Ratio (SNR) measure. We assume that noise Power Spectral Density (PSD) in each spectral bin follows a Rayle...This paper presents an improved Voice Activity Detection (VAD) algorithm which uses the Signal-to-Noise Ratio (SNR) measure. We assume that noise Power Spectral Density (PSD) in each spectral bin follows a Rayleigh distribution. Rayleigh distributions with its asymmetric tail characteristics give a better description of the noise PSD distribution than Gaussian distribution. Under this asstlmption, a new threshold updating expression is derived. Since the analytical integral of the false alarm probability, the threshold updating expression can be represented without the inverse complementary error function and low computational complexity is achieved in our system. Experimental results show that the proposed VAD outperforms or at least is comparable with the VAD scheme presented by Davis under several noise environments and has a lower computational complexity.展开更多
Regenerative medicine, including cell-replacement strategies, may have an important role in the treatment of type 1 diabetes which is associated with decreased islet cell mass. To date, significant progress has been m...Regenerative medicine, including cell-replacement strategies, may have an important role in the treatment of type 1 diabetes which is associated with decreased islet cell mass. To date, significant progress has been made in generating insulin-secreting 13 cells from pluripotent mouse embryonic stem cells (ESCs).The aim of this study is to explore the potential of regulating the differentiation of ESCs into pancreatic endocrine cells capable of synthesizing the pancreatic hormones including insulin, glucagon, somatostatin and pancreatic polypeptide under proper conditions. Undifferentiated ES cell line was stably transfected with mouse RIP-YFP plasmid construction in serum-free medium using LipofectamineTM 2000 Reagents. We tested pancreatic specific gene expression and characterized these ESC-derived pancreatic endocrine cells. Most of these insulin-secreting cells co-expressed many of the phenotypic markers characteristic of 13 cells such as insulinl, insulin2, Isletl, MafA, insulinoma-associated antigen 1 (IA1) and so on, indicating a similar gene expression pattern to adult islet 13 cells in vivo. Characterization of this population revealed that it consisted predominantly of pancreatic endocrine cells that were able to undergo pancreatic specification under the appropriate conditions. We also demonstrated that zinc supplementation mediated up-regulation of insulin-secreting cells as an effective inducer promoted the development of ESC-derived diabetes therapy. In conclusion, this work not only established an efficient pancreatic differentiation strategy from ESCs to pancreatic endocrine lineage in vitro, but also leaded to the development of new strategies to derive transplantable islet-replacement 13 cells from embryonic stem cells for the future applications of a stem cell based therapy of diabetes.展开更多
The approximate expressions of the travelling wave solutions for a class of nonlinear disturbed long-wave system are constructed using the generalized variational iteration method.
Objective:The aim of this study was to study the expression and the clinical pathological relationship of p27 and Skp2 in the tissues of colorectal cancer,discuss the correlation between them.Methods:To determine the ...Objective:The aim of this study was to study the expression and the clinical pathological relationship of p27 and Skp2 in the tissues of colorectal cancer,discuss the correlation between them.Methods:To determine the expressions of p27 and Skp2 among 30 cases of colorectal cancer tissue specimen and 18 cases of normal colorectal tissue samples with immunohistochemistry SP method.Results:The average positive rate of p27 among the normal colorectal tissue samples was 55.2%,which was obviously higher than that of colorectal cancer tissue samples(27.5%,P < 0.05).The correlation between the expression of p27 and the degree of differentiation of colorectal cancer;Dukes stage and lymph node metastasis were distinctly negative(P < 0.05).The average positive rate of Skp2 among the colorectal cancer tissue specimens was 9.5%,which was obviously higher than that of normal colorectal tissue samples(1.8%,P < 0.05).There was an obviously negative correlation between the expression of Skp2 and the degree of differentiation of colorectal cancer(P < 0.05),and the expression of Skp2 had no significant correlation with patients' age,sex,Dukes stage and lymph node metastasis(P > 0.05).There was an negative correlation between the expression of p27 and Skp2(r =-0.806,P < 0.01).Conclusion:The expression of Skp2 in the colorectal cancer tissues is correlative with the degradation of p27;Skp2,the oncogene of colorectal cancer,is involved in colorectal carcinogenesis,which may be the new target for the treatment of colorectal cancer.展开更多
The paper aimed to study the effect of lysyl oxidase-like 2 (LOXL2) on hepatocellular carcinoma (HCC) and explore the biological mechanisms of tumorigenicity and progression in HCC. The authors used four HCC cell ...The paper aimed to study the effect of lysyl oxidase-like 2 (LOXL2) on hepatocellular carcinoma (HCC) and explore the biological mechanisms of tumorigenicity and progression in HCC. The authors used four HCC cell lines to identify LOXL2. A lentiviral vector containing LOXL2-siRNA was constructed to silence the LOXL2 gene in SMMC-7721 cell line, and mRNA of the target gene was detected by real-time polymerase chain reaction (RT-PCR). The effect of LOXL2 silencing on the growth of SMMC-7721 cells was explored with flow cytometry profiling and BrdU labeling. Downstream genes of LOXL2 were selected by microarray and verified by Western Blotting. In the results, LOXL2 expression was significantly up-regulated in four types of HCC cell lines, therefore, SMMC-7721 cell line was selected for further exploration. When SMMC-7721 cell line was infected with LOXL2-siRNA, the expression of LOXL2 mRNA decreased. The silencing of LOXL2 resulted in the cell cycle arrest at the G 1-phase, the increased apoptosis and the decreased growth of SMMC-7721 cells on the indicated days by BrdU. Moreover, the MDM2, BIRC3, CDC42, FOS and TGFBR2 genes were selected and verified to be the downstream genes of LOXL2. In conclusion, LOXL2 contributes to the genesis and progression of HCC cells and works by regulating downstream genes of LOXL2 in certain pathways. Therefore, LOXL2 may play an important role in the progression and prognosis of HCC.展开更多
Nowadays the answer to the question "what is logic?" seems very simple and obvious--"logic is a science," and after that usually one says what is this science about. As for the expressions "logic is an art" or ...Nowadays the answer to the question "what is logic?" seems very simple and obvious--"logic is a science," and after that usually one says what is this science about. As for the expressions "logic is an art" or "the art of logic," then they are only metaphors or some kind of "facon de parler" used in serious scientific discourse. One of my aims here is to trace (on the base of as authentic texts as a commentator literature) the line of development of dichotomy "logic as an art--logic as a science" and to demonstrate that both these feat uses of logic have fundamental historical roots and play very important conceptual role in any theorizing about logic. Despite the fact that (modern) logic is undoubtedly a science, it can be interpreted as an art, moreover, the analysis of logic from this point of view expands, it seems to me, the researching possibilities in the field of the philosophy of logic at least in better understanding what is logic, what creates its unity independently from the historical period of its development, topics, and methods.展开更多
The first aim of this work is to provide an analytical expression to calculate the rate of spread of surface fires under no wind and no slope conditions. A previous simplified model was improved for this particular ca...The first aim of this work is to provide an analytical expression to calculate the rate of spread of surface fires under no wind and no slope conditions. A previous simplified model was improved for this particular case of fire propagation. The test of this proposed model was performed by using two complete sets of experimental results with several fuel beds and variable parameters such as moisture content or bulk density. The second aim of this article is to highlight two conditions that allow stopping a fire: the low leaf area and the high value of the moisture content.展开更多
This study quantifies the main characteristics of a terrain-following, G-coordinate through mathematical analyses of its covariant and contravariant basis vectors as well as the vertical coordinate of σ. A 3-D schema...This study quantifies the main characteristics of a terrain-following, G-coordinate through mathematical analyses of its covariant and contravariant basis vectors as well as the vertical coordinate of σ. A 3-D schematic of the σ-coordinate in a curvilinear coordinate system is provided in this study. The characteristics of the basis vectors were broken down into their "local vector charac- teristics" and "spatial distribution characteristics", and the exact expressions of the covariant; in addition, the con- travariant basis vectors of the G-coordinate used to eluci- date their detailed characteristics were properly solved. Through rewriting the expression of the vertical coordi- nate of G, a mathematical expression of all the cr-coor- dinate surfaces was found, thereby quantifying the so- called terrain-following characteristics and lack of flexi- bility to adjust the slope variation of G-coordinate sur- faces for the classic definition of G. Finally, an analysis on the range value of the vertical coordinate demonstrated that the general value range of G could be obtained by eliminating the G-coordinate surfaces below the Earth's surface. All these quantitative descriptions of the charac- teristics of G-coordinate were the foundation for improv- ing the G-coordinate or creating a new one.展开更多
Glutathione S-transferases (GSTs) are a class of enzymes that facilitate the detoxification of xenobiotics, and also play important roles in antioxidant defense. We identified two glutathione S-transferase isoforms (V...Glutathione S-transferases (GSTs) are a class of enzymes that facilitate the detoxification of xenobiotics, and also play important roles in antioxidant defense. We identified two glutathione S-transferase isoforms (VpGSTS, sigma GST; VpGSTO, omega GST) from Venerupis philippinarum by RACE approaches. The open reading frames of VpGSTS and VpGSTO were of 612 bp and 729 bp, encoding 203 and 242 amino acids with an estimated molecular mass of 22.88 and 27.94 kDa, respectively. The expression profiles of VpGSTS and VpGSTO responded to heavy metals and benzo[a]pyrene (B[a]P) exposure were investigated by quantitative real-time RT-PCR. The expression of VpGSTS and VpGSTO were both rapidly up-regulated, however, they showed differential expression patterns to different toxicants. Cd displayed stronger induction of VpGSTS expression with an approximately 12-fold increase than that of VpGSTO with a maximum 6.4-fold rise. Cu exposure resulted in similar expression patterns for both VpGSTS and VpGSTO. For B[a]P exposure, the maximum induction of VpGSTO was approximately two times higher than that of VpGSTS. Altogether, these findings implied the involvement of VpGSTS and VpGSTO in host antioxidant responses, and highlighted their potential as a biomarker to Cd and B[a]P exposure.展开更多
Objective This work aims to investigate the expression pattern and clinicopathologic significance of centromere protein H(CENP-H) in uterine cervical cancer(UCC). Methods The level of CENP-H expression in the paraffin...Objective This work aims to investigate the expression pattern and clinicopathologic significance of centromere protein H(CENP-H) in uterine cervical cancer(UCC). Methods The level of CENP-H expression in the paraffin sections of 62 UCC cases was determined by the SP immunohistochemical method,with complete clinicopathologic data in all cases.Statistical analysis was conducted to evaluate the prognostic and diagnostic significance of CENP-H using SPSS13.0 software package. Results Immunohistochemical assay showed strong CENP-H expression in 61.29% (38/62) of the paraffin-embedded cervical cancer tissues.Statistical analysis revealed a strong correlation between the CENP-H expression and the clinical classification(P=0.038) of the cervical carcinoma.The expression increased with rise of the stages.The analysis of Cox proportional hazards regression model suggested that CENP-H expression(P=0.002) and tumor stage(P=0.001) were independent prognostic markers for the survival of UCC patients.The survival analysis showed that the survival rate was significantly lower in patients with high expression of CENP-H than in those with low expression of CENP-H(P=0.001). Conclusions CENP-H is likely to be a valuable marker for carcinogenesis and progression of UCC.It might be used as the important diagnostic and prognostic marker for cervical carcinoma patients,especially for those at early stage.展开更多
Metalloproteinases have a critical role in a broad spectrum of cellular processesranging from the break-down of extracellular matrix to the processing of signaltransduction-related proteins.These hydrolytic functions ...Metalloproteinases have a critical role in a broad spectrum of cellular processesranging from the break-down of extracellular matrix to the processing of signaltransduction-related proteins.These hydrolytic functions underlie a variety of mechanisms related to developmental processes as well as disease states.Structural analysis of metalloproteinases from both invertebrate and vertebrate species indicates that these enzymes are highly conserved and arose early during metazoan evolution.In this regard,studies from vari-ous laboratories have reported that a number of classes of metalloproteinases are found in hydra,a member of Cnidaria,the second oldest of existing animal phyla.These studies demonstrate that the hydra genome contains at least three classes of metalloproteinases to include members of the 1)astacin class,2)matrix met-alloproteinase class,and 3)neprilysin class.Functional studies indicate that these metalloproteinases play diverse and important roles in hydra morphogenesis and cell differentiation as well as specialized functions in adult polyps.This article will review the structure,expression,and function of these metalloproteinases in hydra.展开更多
The purpose of this paper is to show the influence of the edge-effect on the electric field distribution, and hence on the inner capacitance and outer capacitance of a cylindrical capacitor surrounded by an insulating...The purpose of this paper is to show the influence of the edge-effect on the electric field distribution, and hence on the inner capacitance and outer capacitance of a cylindrical capacitor surrounded by an insulating medium. To generalize the results, a two-dimensional axisymmetric finite element model of a cylindrical capacitor has been generated and the problem has been resolved taking into account the distance between the conductors for a complete set of dimensions. The available obtained results have been compared with previous published works. Finally, using statistical tools, the mathematical expression for computing the relationship between capacitance and insulation gap and cylindrical plates dimensions has been obtained.展开更多
In this paper we elaborate a general expression of the conditional expectation related to pricing problem of the American options using the Malliavin derivative (without localization). This work is a generalization ...In this paper we elaborate a general expression of the conditional expectation related to pricing problem of the American options using the Malliavin derivative (without localization). This work is a generalization of paper of Bally et al. (2005) [ 1 ] for the one dimensional case. Basing on the density function of the asset price, Bally and al. used the Malliavin calculus to evaluate the conditional expectation related to pricing American option problem, but in our work we use the Malliavin derivative to resolve the previous problem.展开更多
基金supported by the National Science and Technology Major Projects(No.2011ZX05020-008)Well Logging Advanced Technique and Application Basis Research Project of Petrochina Company(No.2011A-3901)
文摘The radial basis function (RBF) interpolation approach proposed by Freedman is used to solve inverse problems encountered in well-logging and other petrophysical issues. The approach is to predict petrophysical properties in the laboratory on the basis of physical rock datasets, which include the formation factor, viscosity, permeability, and molecular composition. However, this approach does not consider the effect of spatial distribution of the calibration data on the interpolation result. This study proposes a new RBF interpolation approach based on the Freedman's RBF interpolation approach, by which the unit basis functions are uniformly populated in the space domain. The inverse results of the two approaches are comparatively analyzed by using our datasets. We determine that although the interpolation effects of the two approaches are equivalent, the new approach is more flexible and beneficial for reducing the number of basis functions when the database is large, resulting in simplification of the interpolation function expression. However, the predicted results of the central data are not sufficiently satisfied when the data clusters are far apart.
基金supported by the National Natural Science Foundation General Program of China(No.61201146)the National Basic Research Program of China(2013CB329003)the Fundamental Research Funds for the Central Universities(HIT.NSRIF.2015022)
文摘Recently a Hybrid Carrier (HC) scheme based on Weighted-type Fractional Fourier Transform (WFRFT) was proposed and developed, which contains Single Carrier (SC) and Multi-Carrier (MC) synergetie transmission. The wide interest is primarily due to its appealing characteristics, such as the robust performances in different types of selective fading channels and a great deal of potential for secure communications. According to the literatures, the HC signal and SC or MC signal probability distributions are different. In particular, some benefits of this HC scheme are brought by the quasi-Gaussian distribution of WFRFT signals. However, until now researchers have only presented statistic properties through computer simulations, and the accurate expressions of signals are not derived yet. In this paper, we derive the accu- rate and rigorously established closed-form expressions of Probability Density Function (PDF) of WFRFT signal real and imaginary parts with a large number of QPSK subcarriers, and this PDF can describe the behavior of data modulated by WFRFT, avoiding the complex computation for extensive computer simulations. Furthermore, the components of PDF expression are described and analyzed, and it is revealed that the tendency of signal quasi-Gaussian changes with the increasing of the parameter a (a in (0,1]). To validate the analytical results, extensive simulations have been conducted, showing a very good match between the analytical results and the real situations. The contribution of this paper may be useful to deduce the closed form expressions of Bit Error Ratio (BER), the Complementary Cumulative Distribution Function (CCDF) of Peak to Average Power Ratio (PAPR), and other analytical studies which adopt the PDF.
文摘Two coaxial vertical cylinders-one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom,were considered.This problem of diffraction by these two cylinders,which were considered as idealization of a buoy and a circular plate,can be considered as a wave energy device.The wave energy that is created and transferred by this device can be appropriately used in many applications in lieu of conventional energy.Method of separation of variables was used to obtain the analytical expressions for the diffracted potentials in four clearly identified regions.By applying the appropriate matching conditions along the three virtual boundaries between the regions,a system of linear equations was obtained,which was solved for the unknown coefficients.The potentials allowed us to obtain the exciting forces acting on both cylinders.Sets of exciting forces were obtained for different radii of the cylinders and for different gaps between the cylinders.It was observed that changes in radius and the gap had significant effect on the forces.It was found that mostly the exciting forces were significant only at lower frequencies.The exciting forces almost vanished at higher frequencies.The problem was also investigated for the base case of no plate arrangement,i.e.,the case having only the floating cylinder tethered to the sea-bed.Comparison of forces for both arrangements was carried out.In order to take care of the radiation of the cylinders due to surge motion,the corresponding added mass and the damping coefficients for both cylinders were also computed.All the results were depicted graphically and compared with available results.
基金supported by the National Key Technology R&D Program of China under Grant No.2012BAH46B04
文摘Network traffic classification plays an important role and benefits many practical network issues,such as Next-Generation Firewalls(NGFW),Quality of Service(QoS),etc.To face the challenges brought by modern high speed networks,many inspiring solutions have been proposed to enhance traffic classification.However,taking many factual network conditions into consideration,e.g.,diversity of network environment,traffic classification methods based on Deep Inspection(DI) technique still occupy the top spot in actual usage.In this paper,we propose a novel classification system employing Deep Inspection technique,aiming to achieve Parallel Protocol Parsing(PPP).We start with an analytical study of the existing popular DI methods,namely,regular expression based methods and protocol parsing based methods.Motivated by their relative merits,we extend traditional protocol parsers to achieve parallel matching,which is the representative merit of regular expression.We build a prototype system,and evaluation results show that significant improvement has been made comparing to existing open-source solutions in terms of both memory usage and throughput.
文摘Human pluripotent stem cells represent a potentially unlimited source of functional pancreatic endocrine lineage cells. Here we report a highly efficient approach to induce human embryonic stem (ES) cells and induced pluripo- tent stem (iPS) cells to differentiate into mature insulin-producing cells in a chemical-defined culture system. The differentiated human ES cells obtained by this approach comprised nearly 25% insulin-positive cells as assayed by flow cytometry analysis, which released insulin/C-peptide in response to glucose stimuli in a manner comparable to that of adult human islets. Most of these insulin-producing cells co-expressed mature β cell-specific markers such as NKX6-1 and PDX1, indicating a similar gene expression pattern to adult islet β cells in vivo. In this study, we also demonstrated that EGF facilitates the expansion of PDXl-positive pancreatic progenitors. Moreover, our protocol also succeeded in efficiently inducing human iPS cells to differentiate into insuIin-producing ceils. Therefore, this work not only provides a new model to study the mechanism of human pancreatic specialization and maturation in vitro, but also enhances the possibility of utilizing patient-specific iPS cells for the treatment of diabetes.
基金Supported by the National Natural Science Foundation of China (No. 60874060)
文摘This paper presents an improved Voice Activity Detection (VAD) algorithm which uses the Signal-to-Noise Ratio (SNR) measure. We assume that noise Power Spectral Density (PSD) in each spectral bin follows a Rayleigh distribution. Rayleigh distributions with its asymmetric tail characteristics give a better description of the noise PSD distribution than Gaussian distribution. Under this asstlmption, a new threshold updating expression is derived. Since the analytical integral of the false alarm probability, the threshold updating expression can be represented without the inverse complementary error function and low computational complexity is achieved in our system. Experimental results show that the proposed VAD outperforms or at least is comparable with the VAD scheme presented by Davis under several noise environments and has a lower computational complexity.
文摘Regenerative medicine, including cell-replacement strategies, may have an important role in the treatment of type 1 diabetes which is associated with decreased islet cell mass. To date, significant progress has been made in generating insulin-secreting 13 cells from pluripotent mouse embryonic stem cells (ESCs).The aim of this study is to explore the potential of regulating the differentiation of ESCs into pancreatic endocrine cells capable of synthesizing the pancreatic hormones including insulin, glucagon, somatostatin and pancreatic polypeptide under proper conditions. Undifferentiated ES cell line was stably transfected with mouse RIP-YFP plasmid construction in serum-free medium using LipofectamineTM 2000 Reagents. We tested pancreatic specific gene expression and characterized these ESC-derived pancreatic endocrine cells. Most of these insulin-secreting cells co-expressed many of the phenotypic markers characteristic of 13 cells such as insulinl, insulin2, Isletl, MafA, insulinoma-associated antigen 1 (IA1) and so on, indicating a similar gene expression pattern to adult islet 13 cells in vivo. Characterization of this population revealed that it consisted predominantly of pancreatic endocrine cells that were able to undergo pancreatic specification under the appropriate conditions. We also demonstrated that zinc supplementation mediated up-regulation of insulin-secreting cells as an effective inducer promoted the development of ESC-derived diabetes therapy. In conclusion, this work not only established an efficient pancreatic differentiation strategy from ESCs to pancreatic endocrine lineage in vitro, but also leaded to the development of new strategies to derive transplantable islet-replacement 13 cells from embryonic stem cells for the future applications of a stem cell based therapy of diabetes.
基金*Supported by the National Natural Science Foundation of China under Grant No. 40876010, the Main Direction Program of the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No. KZCX2-YW-Q03-08, the R &: D Special Fund for Public Welfare Industry (Meteorology) under Grant No. GYHY200806010, the LASG State Key Laboratory Special Fund and the Foundation of E-Institutes of Shanghai Municipal Education Commission (E03004)
文摘The approximate expressions of the travelling wave solutions for a class of nonlinear disturbed long-wave system are constructed using the generalized variational iteration method.
文摘Objective:The aim of this study was to study the expression and the clinical pathological relationship of p27 and Skp2 in the tissues of colorectal cancer,discuss the correlation between them.Methods:To determine the expressions of p27 and Skp2 among 30 cases of colorectal cancer tissue specimen and 18 cases of normal colorectal tissue samples with immunohistochemistry SP method.Results:The average positive rate of p27 among the normal colorectal tissue samples was 55.2%,which was obviously higher than that of colorectal cancer tissue samples(27.5%,P < 0.05).The correlation between the expression of p27 and the degree of differentiation of colorectal cancer;Dukes stage and lymph node metastasis were distinctly negative(P < 0.05).The average positive rate of Skp2 among the colorectal cancer tissue specimens was 9.5%,which was obviously higher than that of normal colorectal tissue samples(1.8%,P < 0.05).There was an obviously negative correlation between the expression of Skp2 and the degree of differentiation of colorectal cancer(P < 0.05),and the expression of Skp2 had no significant correlation with patients' age,sex,Dukes stage and lymph node metastasis(P > 0.05).There was an negative correlation between the expression of p27 and Skp2(r =-0.806,P < 0.01).Conclusion:The expression of Skp2 in the colorectal cancer tissues is correlative with the degradation of p27;Skp2,the oncogene of colorectal cancer,is involved in colorectal carcinogenesis,which may be the new target for the treatment of colorectal cancer.
文摘The paper aimed to study the effect of lysyl oxidase-like 2 (LOXL2) on hepatocellular carcinoma (HCC) and explore the biological mechanisms of tumorigenicity and progression in HCC. The authors used four HCC cell lines to identify LOXL2. A lentiviral vector containing LOXL2-siRNA was constructed to silence the LOXL2 gene in SMMC-7721 cell line, and mRNA of the target gene was detected by real-time polymerase chain reaction (RT-PCR). The effect of LOXL2 silencing on the growth of SMMC-7721 cells was explored with flow cytometry profiling and BrdU labeling. Downstream genes of LOXL2 were selected by microarray and verified by Western Blotting. In the results, LOXL2 expression was significantly up-regulated in four types of HCC cell lines, therefore, SMMC-7721 cell line was selected for further exploration. When SMMC-7721 cell line was infected with LOXL2-siRNA, the expression of LOXL2 mRNA decreased. The silencing of LOXL2 resulted in the cell cycle arrest at the G 1-phase, the increased apoptosis and the decreased growth of SMMC-7721 cells on the indicated days by BrdU. Moreover, the MDM2, BIRC3, CDC42, FOS and TGFBR2 genes were selected and verified to be the downstream genes of LOXL2. In conclusion, LOXL2 contributes to the genesis and progression of HCC cells and works by regulating downstream genes of LOXL2 in certain pathways. Therefore, LOXL2 may play an important role in the progression and prognosis of HCC.
文摘Nowadays the answer to the question "what is logic?" seems very simple and obvious--"logic is a science," and after that usually one says what is this science about. As for the expressions "logic is an art" or "the art of logic," then they are only metaphors or some kind of "facon de parler" used in serious scientific discourse. One of my aims here is to trace (on the base of as authentic texts as a commentator literature) the line of development of dichotomy "logic as an art--logic as a science" and to demonstrate that both these feat uses of logic have fundamental historical roots and play very important conceptual role in any theorizing about logic. Despite the fact that (modern) logic is undoubtedly a science, it can be interpreted as an art, moreover, the analysis of logic from this point of view expands, it seems to me, the researching possibilities in the field of the philosophy of logic at least in better understanding what is logic, what creates its unity independently from the historical period of its development, topics, and methods.
文摘The first aim of this work is to provide an analytical expression to calculate the rate of spread of surface fires under no wind and no slope conditions. A previous simplified model was improved for this particular case of fire propagation. The test of this proposed model was performed by using two complete sets of experimental results with several fuel beds and variable parameters such as moisture content or bulk density. The second aim of this article is to highlight two conditions that allow stopping a fire: the low leaf area and the high value of the moisture content.
基金supported by the National Natural Science Foundation of China under Grant Nos. 40821092,40633016,and 40875022
文摘This study quantifies the main characteristics of a terrain-following, G-coordinate through mathematical analyses of its covariant and contravariant basis vectors as well as the vertical coordinate of σ. A 3-D schematic of the σ-coordinate in a curvilinear coordinate system is provided in this study. The characteristics of the basis vectors were broken down into their "local vector charac- teristics" and "spatial distribution characteristics", and the exact expressions of the covariant; in addition, the con- travariant basis vectors of the G-coordinate used to eluci- date their detailed characteristics were properly solved. Through rewriting the expression of the vertical coordi- nate of G, a mathematical expression of all the cr-coor- dinate surfaces was found, thereby quantifying the so- called terrain-following characteristics and lack of flexi- bility to adjust the slope variation of G-coordinate sur- faces for the classic definition of G. Finally, an analysis on the range value of the vertical coordinate demonstrated that the general value range of G could be obtained by eliminating the G-coordinate surfaces below the Earth's surface. All these quantitative descriptions of the charac- teristics of G-coordinate were the foundation for improv- ing the G-coordinate or creating a new one.
基金Supported by the 100 Talents Program of Chinese Academy of Sciences and Key Laboratory of Marine Spill Oil Identification and Damage Assessment Technology (No. 201115)the State Oceanic Administration of China
文摘Glutathione S-transferases (GSTs) are a class of enzymes that facilitate the detoxification of xenobiotics, and also play important roles in antioxidant defense. We identified two glutathione S-transferase isoforms (VpGSTS, sigma GST; VpGSTO, omega GST) from Venerupis philippinarum by RACE approaches. The open reading frames of VpGSTS and VpGSTO were of 612 bp and 729 bp, encoding 203 and 242 amino acids with an estimated molecular mass of 22.88 and 27.94 kDa, respectively. The expression profiles of VpGSTS and VpGSTO responded to heavy metals and benzo[a]pyrene (B[a]P) exposure were investigated by quantitative real-time RT-PCR. The expression of VpGSTS and VpGSTO were both rapidly up-regulated, however, they showed differential expression patterns to different toxicants. Cd displayed stronger induction of VpGSTS expression with an approximately 12-fold increase than that of VpGSTO with a maximum 6.4-fold rise. Cu exposure resulted in similar expression patterns for both VpGSTS and VpGSTO. For B[a]P exposure, the maximum induction of VpGSTO was approximately two times higher than that of VpGSTS. Altogether, these findings implied the involvement of VpGSTS and VpGSTO in host antioxidant responses, and highlighted their potential as a biomarker to Cd and B[a]P exposure.
基金supported by grants from the Social Development Projects of Guangdong SciTech Planning (No.2010B031600201)
文摘Objective This work aims to investigate the expression pattern and clinicopathologic significance of centromere protein H(CENP-H) in uterine cervical cancer(UCC). Methods The level of CENP-H expression in the paraffin sections of 62 UCC cases was determined by the SP immunohistochemical method,with complete clinicopathologic data in all cases.Statistical analysis was conducted to evaluate the prognostic and diagnostic significance of CENP-H using SPSS13.0 software package. Results Immunohistochemical assay showed strong CENP-H expression in 61.29% (38/62) of the paraffin-embedded cervical cancer tissues.Statistical analysis revealed a strong correlation between the CENP-H expression and the clinical classification(P=0.038) of the cervical carcinoma.The expression increased with rise of the stages.The analysis of Cox proportional hazards regression model suggested that CENP-H expression(P=0.002) and tumor stage(P=0.001) were independent prognostic markers for the survival of UCC patients.The survival analysis showed that the survival rate was significantly lower in patients with high expression of CENP-H than in those with low expression of CENP-H(P=0.001). Conclusions CENP-H is likely to be a valuable marker for carcinogenesis and progression of UCC.It might be used as the important diagnostic and prognostic marker for cervical carcinoma patients,especially for those at early stage.
文摘Metalloproteinases have a critical role in a broad spectrum of cellular processesranging from the break-down of extracellular matrix to the processing of signaltransduction-related proteins.These hydrolytic functions underlie a variety of mechanisms related to developmental processes as well as disease states.Structural analysis of metalloproteinases from both invertebrate and vertebrate species indicates that these enzymes are highly conserved and arose early during metazoan evolution.In this regard,studies from vari-ous laboratories have reported that a number of classes of metalloproteinases are found in hydra,a member of Cnidaria,the second oldest of existing animal phyla.These studies demonstrate that the hydra genome contains at least three classes of metalloproteinases to include members of the 1)astacin class,2)matrix met-alloproteinase class,and 3)neprilysin class.Functional studies indicate that these metalloproteinases play diverse and important roles in hydra morphogenesis and cell differentiation as well as specialized functions in adult polyps.This article will review the structure,expression,and function of these metalloproteinases in hydra.
文摘The purpose of this paper is to show the influence of the edge-effect on the electric field distribution, and hence on the inner capacitance and outer capacitance of a cylindrical capacitor surrounded by an insulating medium. To generalize the results, a two-dimensional axisymmetric finite element model of a cylindrical capacitor has been generated and the problem has been resolved taking into account the distance between the conductors for a complete set of dimensions. The available obtained results have been compared with previous published works. Finally, using statistical tools, the mathematical expression for computing the relationship between capacitance and insulation gap and cylindrical plates dimensions has been obtained.
文摘In this paper we elaborate a general expression of the conditional expectation related to pricing problem of the American options using the Malliavin derivative (without localization). This work is a generalization of paper of Bally et al. (2005) [ 1 ] for the one dimensional case. Basing on the density function of the asset price, Bally and al. used the Malliavin calculus to evaluate the conditional expectation related to pricing American option problem, but in our work we use the Malliavin derivative to resolve the previous problem.