Differential diagnosis of pancreatic cancer by single-shot echo-planar imaging diffusion-weighted imaging

AIM: To investigate the diagnostic ability of single-shot echo-planar imaging(EPI) diffusion-weighted imaging (DWI) to differentiate between malignant and benign pancreatic lesions. METHODS: A computerized search was performed on Pub Med, MEDLINE and EMBASE up to August 2014. Nine studies(10 sets of data) with a total of 304 malignant pancreatic lesions and 188 benign pancreatic lesions were included. The characteristics of each study included the study name, year of publication, magnetic resonance modalities used, patient population, strength of field, pulse time, repetition time, echo time(TE), maximum b factor, mean age, mean body weight, fat suppression, number of benign and malignant lesions, and true positive, true negative, false positive and false negative results. All analyses were performed using Meta-Di Sc and Stata 11.0.RESULTS: The pooled sensitivity and specificity of singleshot EPI DWI were 0.83(95%CI: 0.79-0.87) and 0.77(95%CI: 0.70-0.83), respectively. The positive likelihood ratio and negative likelihood ratio were 5.09(95%CI: 2.19-11.84) and 0.23(95%CI: 0.15-0.36), respectively. The P value for the χ2 heterogeneity for all pooled estimates was < 0.05. From the fitted summary receiver operating characteristic curve, the area under the curve and Q* index were 0.89 and 0.82, respectively. Publication bias was not present(t = 0.58, P = 0.58). Meta-regression analysis indicated that fat suppression, mean age, TE, and maximum b factor were not sources of heterogeneity(all P > 0.05). CONCLUSION: Single-shot EPI DWI is useful to differentiate between malignant and benign pancreatic lesions. Lesion size ≥ 2 cm is the limit for the diagnosis of early lesions.

Adaptive Single Piecewise Interpolation Reproducing Kernel Method for Solving Fractional Partial Differential Equation

It is well-known that using the traditional reproducing kernel method(TRKM) for solving the fractional partial differential equation(FPDE) is very intractable. In this study, the adaptive single piecewise interpolation reproducing kernel method(ASPIRKM) is determined to solve the FPDE. This improved method not only improves the calculation accuracy, but also reduces the waste of time. Two numerical examples show that the ASPIRKM is a more time-saving numerical method than the TRKM.

Spin-dependent negative differential conductance in transport through single-molecule magnets

Transport properties are theoretically studied through an anisotropy single-molecule magnet symmetrically connected to two identical ferromagnetic leads. It is found that even though in parallel configuration of leads’ magnetizations, the total current still greatly depends on the spin polarization of leads at certain particular bias region, and thus for large polarization a prominent negative differential conductance （NDC） emerges. This originates from the joint effect of single-direction transitions and spin polarization, which removes the symmetry between spin-up and spin-down transitions. The present mechanism of NDC is remarkably different from the previously reported mechanisms. To clarify the physics of the NDC, we further monitored the shot noise spectroscopy and found that the appearance of the NDC is accompanied by the rapid decrease of Fano factor.

New Numerical Integration Formulations for Ordinary Differential Equations

An entirely new framework is established for developing various single- and multi-step formulations for the numerical integration of ordinary differential equations. Besides polynomials, unconventional base-functions with trigonometric and exponential terms satisfying different conditions are employed to generate a number of formulations. Performances of the new schemes are tested against well-known numerical integrators for selected test cases with quite satisfactory results. Convergence and stability issues of the new formulations are not addressed as the treatment of these aspects requires a separate work. The general approach introduced herein opens a wide vista for producing virtually unlimited number of formulations.

Triple differential cross sections of magnesium in doubly symmetric geometry

A dynamically screened three-Coulomb-wave （DS3C） method is applied to study the single ionization of magnesium by electron impact. Triple differential cross sections （TDCS） are calculated in doubly symmetric geometry at incident energies of 13.65, 17.65, 22.65, 27.65, 37.65, 47.65, 57.65, and 67.65 eV. Comparisons are made with experimental data and theoretical predictions from a three-Coulomb-wave function （3C） approach and distorted-wave Born approximation （DWBA）. The overall agreement between the predictions of the DS3C model and the DWBA approach with the experimen- tal data is satisfactory.

Robust identification of regulatory variants(eQTLs)using a differential expression framework developed for RNA‑sequencing

Background A gap currently exists between genetic variants and the underlying cell and tissue biology of a trait,and expression quantitative trait loci(eQTL)studies provide important information to help close that gap.However,two concerns that arise with eQTL analyses using RNA-sequencing data are normalization of data across samples and the data not following a normal distribution.Multiple pipelines have been suggested to address this.For instance,the most recent analysis of the human and farm Genotype-Tissue Expression(GTEx)project proposes using trimmed means of M-values(TMM)to normalize the data followed by an inverse normal transformation.Results In this study,we reasoned that eQTL analysis could be carried out using the same framework used for dif-ferential gene expression(DGE),which uses a negative binomial model,a statistical test feasible for count data.Using the GTEx framework,we identified 35 significant eQTLs(P<5×10^(–8))following the ANOVA model and 39 significant eQTLs(P<5×10^(–8))following the additive model.Using a differential gene expression framework,we identified 930 and six significant eQTLs(P<5×10^(–8))following an analytical framework equivalent to the ANOVA and additive model,respectively.When we compared the two approaches,there was no overlap of significant eQTLs between the two frameworks.Because we defined specific contrasts,we identified trans eQTLs that more closely resembled what we expect from genetic variants showing complete dominance between alleles.Yet,these were not identified by the GTEx framework.Conclusions Our results show that transforming RNA-sequencing data to fit a normal distribution prior to eQTL analysis is not required when the DGE framework is employed.Our proposed approach detected biologically relevant variants that otherwise would not have been identified due to data transformation to fit a normal distribution.

Analysis of Population Genetic Change to Single Oospore Strains of Phytophthora infestans

The occurrence of sexual reproduction accelerates the population genetic variation of Phytophthora infestans and makes it more difficult to control.The systematic analysis of the differentiation of phenotype(mating type and metalaxyl sensitivity)and genotype(mtDNA haplotype and SSR genotype)of 65 single oospore strains of P.infestans was carried out in this article.Five test strains were isolated from Heilongjiang Province and Mongolia Autonomous Region.The experiment results showed that the isolation ratio of metalaxyl resistance(MR:HR)of single oospore strains produced through the cross of medium resistance and high resistant parents was 18:13;the isolation ratio of the metalaxyl resistance(S:MR:HR)of single oospore strains produced through the cross of sensitive and high resistant parents was 4:12:7.The progenies of single oospore strains produced through self-fertility parents with medium resistance were all of the medium resistance.The mating types A1:A2 was greater than 1:1 in single oospore strains of the progenies,which did not conform to the Mendel's law of inheritance.All single oospore strains of the progenies inherited mitochondrial DNA fragments from only one parent.Sexual recombination of single oospore strains was verified by using two pairs of SSR primers(Pi4B and Pi4G).At the locus of Pi4B and Pi4G in the cross of KS-37 and KS-25,the separation frequencies of allele were 19:12 and 14:17,respectively.They produced two new genotype strains.This study could provide a basis for formulating disease control strategies.

Research on the Relationship between Density of States and Conducting Properties of Single-walled Carbon Nanotubes

The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The distinctive properties of the DOS, the normalized differential conductivity and the current us bias for SWNTs are deduced and analyzed theoretically. The singularities in the DOS (or in the normalized differential conductivity) predict that the jump structure of current (or conductance)-bias of SWNTs exists. All conclusions from the theoretical analysis are in well agreement with the experimental results of SWNT's electronic structure and electronic transport. In other words, the simple theoretical model in this paper can be applied to understand a range of spectroscopic and other measurement data related to the DOS of SWNTs.

A Thermal-Hydraulic Coolant Channel Module (CCM) for Single- and Two-Phase Flow

A theoretical “drift-flux based thermal-hydraulic mixture-fluid coolant channel model” is presented. It is the basis to a corresponding digital “Coolant Channel Module (CCM)”. This purpose derived “Separate-Region Mixture Fluid Approach” should yield an alternative platform to the currently dominant “Separate-Phase Models” where each phase is treated separately. Contrary to it, a direct procedure could be established with the objective to simulate in an as general as possible way the steady state and transient behaviour of characteristic parameters of single- and/or (now non-separated) two-phase fluids flowing within any type of heated or non-heated coolant channels. Their validity could be confirmed by a wide range of verification and validation runs, showing very satisfactory results. The resulting universally applicable code package CCM should provide a fundamental element for the simulation of thermal-hydraulic situations over a wide range of complex systems (such as different types of heat exchangers and steam generators as being applied in both conventional but also nuclear power stations, 1D and 3D nuclear reactor cores etc). Thereby the derived set of equations for different coolant channels (distinguished by their key numbers) as appearing in these systems can be combined with other ODE-s and non-linear algebraic relations from additional parts of such an overall model. And these can then to be solved by applying an appropriate integration routine. Within the solution procedure, however, mathematical discontinuities can arise. This due to the fact that along such a coolant channel transitions from single- to two-phase flow regimes and vice versa could take place. To circumvent these difficulties it will in the presented approach be proposed that the basic coolant channel (BC) is subdivided into a number of sub-channels (SC-s), each of them being occupied exclusively by only a single or a two-phase flow regime. After an appropriate nodalization of the BC (and thus its SC-s) and after applying a “modified finite volume method” together with other special activities the fundamental set of non-linear thermal-hydraulic partial differential equations together with corresponding constitutive relations can be solved for each SC separately. As a result of such a spatial discretization for each SC type (and thus the entire BC) the wanted set of non-linear ordinary differential equations of 1st order could be established. Obviously, special attention had to be given to the varying SC entrance or outlet positions, describing the movement of boiling boundaries or mixture levels along the channel. Including even the possibility of SC-s to disappear or be created anew during a transient.

Differential gene network analysis from single cell RNA-seq

Study of gene expression has been arguably the most active research field in functional genomics.Over the last two decades,various high-throughput technologies,from gene expression microarray to RNA-seq,have been widely applied to the wholegenome profiling of gene expression.The commonality of these experiments is that they measure the gene expression levels of"bulk"sample,which pools a large number(often in the scale of millions)of cells,and thus the measurements reflect the average expression

DFCluster:An efficient algorithm to mine maximal differential biclusters for single pilot operations task synthesis safety analysis

With the continuous advancement of the avionics system,crew members are correspondingly reduced,and Single Pilot Operations(SPO)has attracted widespread attention from scholars.To meet the flight requirements in SPO mode,it is necessary to further strengthen air-ground coordination system integration,but at the same time,there will be some safety issues caused by resource integration,function fusion,and task synthesis.Aimed at the safety problems caused by task synthesis,an efficient differential bicluster mining algorithm--DFCluster algorithm is proposed in this paper to discover potential hazardous elements or propagation mechanisms through mining the resource-function matrixes.To mine efficiently,several pruning techniques are designed for generating maximal biclusters without candidate maintenance.The experimental results show that the DFCluster algorithm is more efficient than the existing differential biclustering algorithms under different scales of artificial datasets and public datasets.Then,a typical flight scenario is designed based on SPO air-ground collaborative system architecture,and combined with our proposed DFCluster algorithm for task synthesis safety analysis.Based on the mining results,the SPO airground collaborative system architecture is modified,which ultimately improves the safety of the SPO system.

Linear Quadratic Differential Game Strategies with Two-pursuit Versus Single-evader

In order to intercept the future targets that are characterized by high maneuverability, multiple interceptors may be launched and aimed at single target. The scenario of two missiles P and Q intercepting a single target is modeled as a two-pursuit single-evader non-zero-sum linear quadratic differential game. The intercept space is decomposed into three subspaces which are mutually disjoint and their union covers the entire intercept space. The effect of adding the second interceptor arises in the intercept space of both P and Q （PQ-intercept space）. A guidance law is derived from the Nash equilibrium strategy set （NESS） of the game. Simulation studies are focused on the PQ-intercept space. It is indicated that 1） increasing the target＇s maneuverability will enlarge PQ-intercept space; 2） the handover conditions will be released if the initial zero-effort-miss （ZEM） of both interceptors has opposite sign; 3） overvaluation of the target＇s maneuverability by choosing a small weight coefficient will generate robust performance with respect to the target maneuvering command switch time and decrease the fuel requirement; and 4） cooperation between interceptors increases the interception probability.

Differential expression analyses for single-ce RNA-Seq： old questions on new data

Single-cell RNA sequencing （scRNA-seq） is an emerging technology that enables high resolution detection of heterogeneities between ceils. One important application of scRNA-seq data is to detect differential expression （DE） of genes. Currently, some researchers still use DE analysis methods developed for bulk RNA-Seq data on single-cell data, and some new methods for scRNA-seq data have also been developed. Bulk and single-cell RNA-seq data have different characteristics. A systematic evaluation of the two types of methods on scRNA-seq data is needed. Results： In this study, we conducted a series of experiments on scRNA-seq data to quantitatively evaluate 14 popular DE analysis methods, including both of traditional methods developed for bulk RNA-seq data and new methods specifically designed for scRNA-seq data. We obtained observations and recommendations for the methods under different situations. Conclusions： DE analysis methods should be chosen for scRNA-seq data with great caution with regard to different situations of data. Different strategies should be taken for data with different sample sizes and/or different strengths of the expected signals. Several methods for scRNA-seq data show advantages in some aspects, and DEGSeq tends to outperform other methods with respect to consistency, reproducibility and accuracy of predictions on scRNA-seq data.

A single-to-differential low-noise amplifier with low differential output imbalance

This paper presents a single-ended input differential output low-noise amplifier intended for GPS applications. We propose a method to reduce the gain/amplitude and phase imbalance of a differential output exploiting the inductive coupling of a transformer or center-tapped differential inductor.A detailed analysis of the theory of imbalance reduction,as well as a discussion on the principle of choosing the dimensions of a transformer,are given.An LNA has been implemented using TSMC 0.18μm technology with ESD-protected.Measurement on board shows a voltage gain of 24.6 dB at 1.575 GHz and a noise figure of 3.2 dB.The gain imbalance is below 0.2 dB and phase imbalance is less than 2 degrees.The LNA consumes 5.2 mA from a 1.8 V supply.

平面并联机器人离线PID控制优化研究

为了使平面并联机器人在闭环控制系统中具有更稳定的控制性能。对此,这里构建了平面五杆并联机器人动力学模型及其控制系统模型,给出了控制系统的增益矢量p。对机器人系统模型进行离线PID控制优化,通过控制增益来设计控制系统中的增益矢量p,从而实现非线性单目标动态优化(NLMODOP)。在NLMODOP中加入动态约束,采用带约束处理机制的差分进化(DE)算法求解平面并联机器人的非线性规划问题,进而处理不稳定的动态优化。对机器人模型中的五个连杆进行仿真实验,并对有无DE算法控制的仿真结果进行了比较。结果表明:相比于无DE算法,采用DE算法下的机器人系统模型的连杆跟踪位移基本无跟踪误差。说明基于差分进化算法的平面并联机器人离线PID控制优化具有较好的控制精度和跟踪性能。

基于单芯移相变压器的差动保护配置研究

移相变压器能够有效调控潮流,为保障电力系统安全可靠运行,为移相变压器配置性能优良的保护不可或缺。以某示范工程的35 kV单芯对称型移相变压器为研究对象,提出相应的本体保护方案。首先,基于基尔霍夫电流定律和电磁感应定律分析其运行特性。然后,结合其拓扑结构,设计了保护用电流互感器的安装位置,构建了电平衡差动保护和磁平衡差动保护方案。此方案可覆盖单芯移相变压器内部各绕组和绕组引线相间故障以及各绕组匝间故障。最后,基于Matlab/Simulink平台搭建单芯移相变压器模型,通过设置本体内部典型故障,验证了提出的两种差动保护配置方案的有效性。

5个宽体金线蛭种群遗传多样性和遗传分化的SNP分析

为了解宽体金线蛭(Whitmania pigra)群体的遗传特征,本研究使用单核苷酸多态性标记法对5个地点的宽体金钱蛭(W.pigra)群体(江西抚州AH、安徽太和TH、江西南昌JX、山东微山WSH、山东济南JN)进行遗传多样性和群体遗传结构分析。种群结构分析和主成分分析表明5个宽体金钱蛭种群可追溯至3个不同的种群来源。系统发育树分析结果显示AH种群与TH种群存在部分分支交叉,JX种群、WSH种群和JN种群单独成支。5个群体的成对FST值在0.03~0.20之间,群体两两之间遗传距离在0.03~0.22之间,单核苷酸多态性(π)为0.003974~0.004131,群体间遗传分化程度较低,多态性信息含量(PIC)的含量在0.16~0.20,观测杂合度(Ho)含量在0.18~0.27,近交系数(F)的含量值为-0.07912~0.09063,宽体金钱蛭5个群体有比较低的遗传多样性。Tajima's D值均值为正值,即群体处于稳定状态。群体间遗传变异主要来自群体内部,群体间具有较低的遗传多样性,推测可能是宽体金线蛭在养殖过程中进行了频繁的苗种移养或亲本引种。

新型波形钢腹板组合箱梁畸变效应

为研究新型波形钢腹板(CSW)组合箱梁的畸变效应,以板梁框架法和位移法为基础,建立单箱多室新型CSW组合箱梁的畸变控制微分方程和边界条件,得到畸变正应力解析解,并采用有限元法检验推导结果的正确性。应用推导结果对比分析新型CSW组合箱梁与传统CSW组合箱梁的畸变性能,以及截面高度、箱室宽度和钢底板厚度对新型CSW组合箱梁畸变效应的影响。结果表明:解析解计算得到的畸变正应力与有限元模型计算的结果吻合较好,畸变角的变化规律与有限元模型计算结果一致;与传统CSW组合箱梁相比,新型CSW组合箱梁的畸变翘曲刚度减小了38.89%,畸变框架刚度减小了71.84%,抗畸变能力减弱;随着截面高度和箱室宽度增加,新型CSW组合箱梁跨中畸变角和跨中畸变双力矩均逐渐增大,且箱室宽度的影响更为明显;随着钢底板厚度增加,新型CSW组合箱梁跨中畸变角逐渐减小,跨中畸变双力矩逐渐增大。

梨形环棱螺6个地理种群遗传多样性与遗传分化分析

本研究旨在探究国内不同地理种群梨形环棱螺(Bellamya purificata)的遗传特征,以了解其遗传多样性和群体结构。选取了安徽芜湖(ASY)、江苏淮安(CX)、广西南海(GZT)、江苏江阴(JY)、江苏常州(RS)、广西柳州(ZZR)6个地区的梨形环棱螺样本进行比较研究。研究发现,这6个群体的遗传多样性均较高,单核苷酸多态性(π)为0.005976~0.007760。其中GZT群体和ASY群体的遗传多样性相对更高,而ZZR群体遗传多样性较低,RS群体与GZT种群之间存在较大的分离,ZZR群体与ASY种群之间分离较小,其余种群之间分离均不明显,说明梨形环棱螺种群虽然分布广,但不同地理种群之间的遗传分化不大。

昆明犬IGF1基因在肝脏中的表达特征及遗传多样性分析

为了探究IGF1基因在不同生长发育阶段昆明犬肝脏中的表达特征,并筛选与昆明犬体重和体尺性状相关的单核苷酸多态性(single nucleotide polymorphism,SNP)位点,试验首先采用实时荧光定量PCR方法检测IGF1基因在不同年龄段昆明犬肝脏中的mRNA表达水平,然后分别针对IGF1基因5′和3′侧翼序列、外显子1~4和内含子1设计引物,采用PCR-单链构象多态性(SSCP)技术对昆明犬IGF1基因单核苷酸多态性(SNP)位点进行筛查,通过测序分析其突变情况,统计该SNP位点的基因型频率和基因频率及遗传多样性指标[纯合度(homozygosity,Ho)、杂合度(heterozygosity,He)和有效等位基因数(number of effective alleles,Ne)],最后分析该SNP位点与昆明犬体重和体尺性状的关联性。结果表明:IGF1基因在5个年龄段的昆明犬肝脏中均有表达,且表达量随着月龄的增大呈现逐渐下降的趋势;与2月龄比较,6,12,20,30月龄昆明犬肝脏中IGF1基因的相对表达量均极显著降低(P<0.001)。昆明犬IGF1基因仅外显子3中识别到1个SNP位点,其他区域未识别到SNP位点。该位点位于外显子3第464位核苷酸处,发生了T→C的点突变,但氨基酸未变,命名为T464C位点。T464C位点在昆明犬群体中共存在两种基因型,分别为TT纯合型和TC杂合型,其中优势基因型为TT纯合型,优势等位基因为T,表现为低度多态(PIC<0.25),Ho为0.97,He为0.03,Ne为1.03,在昆明犬群体中处于Hardy-Weinberg平衡状态。昆明犬IGF1基因T464C位点TT纯合型个体胸深、头长显著高于TC杂合型个体(P<0.05)。说明IGF1基因在昆明犬生长发育过程中具有重要作用,T464C位点可作为昆明犬品种培育的潜在辅助选择标记。