双能CT彩色编码技术对痛风患者尿酸盐沉积的应用价值研究

目的:探讨双源双能量CT(DECT)彩色编码技术对痛风患者不同临床时期尿酸盐结晶与血尿酸的关系,进而评估双能CT成像在痛风筛查中的应用价值。方法:回顾性分析120例高尿酸血症或痛风患者的双能CT成像特点及临床资料,根据临床分期分为两组,男92例,女28例;对照组为非痛风患者30例,男26例,女4例。所有患者手、足均行DECT非增强扫描,薄层重组后将原始数据传至MMWP工作站选择Dual Energy GOUT软件,进行影像后处理,比较痛风患者两期尿酸盐沉积的差异与尿酸值相关性,以及DECT检测尿酸盐沉积部位与临床评估的差异。采用t检验、χ2检验、Fisher精确概率进行统计学分析。结果:三组性别及年龄比较,差异无统计学意义(P_年龄=0.236,P_性别=0.613,P>0.005)。高尿酸组尿酸盐沉积量明显高于尿酸正常组,两组有显著统计学意义(P=0.000,P<0.001);痛风组检出率与对照组相比,差异有显著统计学意义(P=0.000,P<0.001)。结论:DECT成像技术对尿酸盐结晶沉积有很好的显示能力,对高尿酸血症、痛风早期、疑似痛风患者均有较高的检出率,可作为痛风筛选的常规检查项目,具有较高的临床应用价值。      

Survival of an invasive aquatic snail to overland translocation in non-aquatic media: Implications for spreading

Invasive species are a threat to aquatic ecosystems worldwide. Aquatic snails have a limited ability for an active dispersal. Therefore, their ability to survive to transport in non-aquatic media may help explain their spread across unconnected habitats. We assessed the ability of New Zealand Mud Snail (NZMS) (Potamopyrgus antipodarum) to survive attached to different materials. Two studies were conducted: (1) a laboratory study to assess the tolerance of a laboratory population of NZMS to non-aquatic media attaching snails to leaf litter, sediment and clay and (2) a field-laboratory study to assess the survival of an invasive field population after being left imbedded in clay in the laboratory and subsequently transferred to a new river reach. All laboratory animals died after 3 days in leaf litter, while in the case of sediment and clay all snails died after 5 days. After being imbedded in clay and subsequently transferred to the river, the survival of the field population was lower than that of the laboratory populations. We conclude that NZMS can be dispersed by mechanisms which imply spending some time in non-aquatic media, and that this species has a relatively high tolerance to translocation between reaches with contrasting environmental properties.     

大兴安岭中北段森林沼泽丘陵景观区的1∶5万化探方法技术研究

在森林沼泽水系较不发育区开展土壤测量时,部分区段存在厚度为1~3 m的黏土层,采样困难,大家选用采样介质不一。通过对比研究残积土、腐殖土、黏土的粒级分布特征、元素分布特征及同点采集的样品元素含量的对比研究,认为在大兴安岭中北段森林沼泽丘陵景观区开展1∶5万化探时采用的方法为:采样介质为残坡积土;采样粒级为-10~+60目;采样密度为9点/km²;野外样品加工方法为水筛。     

Mathematical modeling of colloid and virus cotransport in porous media: Application to experimental data

A conceptual mathematical model was developed to describe the simultaneous transport (cotransport) of viruses and colloids in three-dimensional, water saturated, homogeneous porous media with uniform flow. The model accounts for the migration of individual virus and colloid particles as well as viruses attached onto colloids. Viruses can be suspended in the aqueous phase, attached onto suspended colloids and the solid matrix, and attached onto colloids previously attached on the solid matrix. Colloids can be suspended in the aqueous phase or attached on the solid matrix. Viruses in all four phases (suspended in the aqueous phase, attached onto suspended colloid particles, attached on the solid matrix, and attached onto colloids previously attached on the solid matrix) may undergo inactivation with different inactivation coefficients. The governing coupled partial differential equations were solved numerically using finite difference methods, which were implemented explicitly or implicitly so that both stability and speed factors were satisfied. Furthermore, the experimental data collected by Syngouna and Chrysikopoulos [1] were satisfactorily fitted by the newly developed cotransport model.     

An efficient numerical model for hydrodynamic parameterization in 2D fractured dual-porosity media

This paper presents a robust and efficient numerical model for the parameterization of the hydrodynamic in fractured porous media. The developed model is based upon the refinement indicators algorithm for adaptive multi-scale parameterization. For each level of refinement, the Levenberg–Marquardt method is used to minimize the difference between the measured and predicted data that are obtained by solving the direct problem with the mixed finite element method. Sensitivities of state variables with respect to the parameters are calculated by the sensitivity method. The adjoint-state method is used to calculate the local gradients of the objective function necessary for the computation of the refinement indicators. Validity and efficiency of the proposed model are demonstrated by means of several numerical experiments. The developed numerical model provides encouraging results, even for noisy data and/or with a reduced number of measured heads.     

First-order doubly-asymptotic formulation of the direct stiffness method for elastodynamic problems

A first-order formulation to analyze the dynamic response of layered soil profiles is presented as an alternative to the widely used second-order thin-layer method by the direct stiffness approach, including an efficient simulation of the underlaying elastic half-space. In contrast to the thin-layer method where response is expressed through a combination of second-order propagation modes, the proposed procedure uses first-order modal parameters that have the capacity to provide a good approximation in the complete wave number domain k, including the exact stiffness values for k=0 and k→∞, thus justifying its designation of doubly-asymptotic. This feature allows obtaining the exact soil profile response for static loads, while the proposed treatment of the elastic half-space reproduces naturally the radiation condition without a need of artificial damping. The capacity of the proposed formulation to solve elastodynamic problems is assessed by comparing its results with those of exact solutions available in the literature, and numerical solutions of rigid disks supported on the surface of different soil profiles.     

Inertial effects during irreversible meniscus reconfiguration in angular pores

In porous media, the dynamics of the invading front between two immiscible fluids is often characterized by abrupt reconfigurations caused by local instabilities of the interface. As a prototype of these phenomena we consider the dynamics of a meniscus in a corner as it can be encountered in angular pores. We investigate this process in detail by means of direct numerical simulations that solve the Navier–Stokes equations in the pore space and employ the Volume of Fluid method (VOF) to track the evolution of the interface. We show that for a quasi-static displacement, the numerically calculated surface energy agrees well with the analytical solutions that we have derived for pores with circular and square cross sections. However, the spontaneous reconfigurations are irreversible and cannot be controlled by the injection rate: they are characterized by the amount of surface energy that is spontaneously released and transformed into kinetic energy. The resulting local velocities can be orders of magnitude larger than the injection velocity and they induce damped oscillations of the interface that possess their own time scales and depend only on fluid properties and pore geometry. In complex media (we consider a network of cubic pores) reconfigurations are so frequent and oscillations last long enough that increasing inertial effects leads to a different fluid distribution by influencing the selection of the next pore to be invaded. This calls into question simple pore-filling rules based only on capillary forces. Also, we demonstrate that inertial effects during irreversible reconfigurations can influence the work done by the external forces that is related to the pressure drop in Darcy’s law. This suggests that these phenomena have to be considered when upscaling multiphase flow because local oscillations of the menisci affect macroscopic quantities and modify the constitutive relationships to be used in macro-scale models. These results can be extrapolated to other interface instabilities that are at the origin of fast pore-scale events, such as Haines jumps, snap-off and coalescence.     

Interpretation and nonuniqueness of CTRW transition distributions: Insights from an alternative solute transport formulation

The continuous time random walk (CTRW) has both an elegant mathematical theory and a successful record at modeling solute transport in the subsurface. However, there are some interpretation ambiguities relating to the relationship between the discrete CTRW transition distributions and the underlying continuous movement of solute that have not been addressed in existing literature. These include the exact definition of “transition”, and the extent to which transition probability distributions are unique/quantifiable from data. Here, we present some theoretical results which address these uncertainties in systems with an advective bias. Simultaneously, we present an alternative, reduced parameter CTRW formulation for general advective transport in heterogeneous porous media, which models early- and late-time transport by use of random transition times between sparse, imaginary planes normal to flow. We show that even in the context of this reduced-parameter formulation there is nonuniqueness in the definitions of both transition lengths and waiting time distributions, and that neither may be uniquely determined from experimental data. For practical use of this formulation, we suggest Pareto transition time distributions, leading to a two-degree-of-freedom modeling approach. We then demonstrate the power of this approach in fitting two sets of existing experimental data. While the primary focus is the presentation of new results, the discussion is designed to be pedagogical and to provide a good entry point into practical modeling of solute transport with the CTRW.     

双路点对点视频会议系统设计与实现

地震系统实现与政府相关应急部门的单路点对点视频会议,为满足双方双路甚至多路的视频会议需求,采用编解码器的模数/数模转化技术,通过增加音视频切换器模块、音视频分配器模块和双绞线传输器模块,最终实现地震局值班室与应急办、指挥大厅与应急办的双路点对点视频会议,同时实现上海市地震局多路视频源信号与应急办传输功能,拓展沟通渠道,丰富通讯信息,保证信息传输及时有效.     

自动管电流调制技术在双源CT冠状动脉成像中降低辐射剂量的价值

目的：探讨双源CT自动管电流调制（ATCM）技术在冠状动脉成像中降低辐射剂量的价值。方法：回顾性分析134例双源CT冠脉成像资料,根据体重指数（BMI〈18.5,18.5≤BMI≤24,BMI〉24）将受试者分三组,每组分别为28例,50例及56例。每组各随机抽取一半受试者为实验组,根据体重指数手动调节管电流,同时使用ACTM技术（勾选Care Dose 4D）进行扫描;另一半为对照组,仅根据体重指数手动调节管电流。计算所有患者CTA检查的辐射剂量,对冠脉节段进行图像质量评分。结果：实验组及对照组图像质量和图像噪声无显著差异。三组中CTDIvol、DLP、ED值之间差异有统计学意义,实验组比对照组均下降约50%（详细数据见表1）;体重指数偏大组SD值实验组略大于对照组。结论：在图像质量无明显下降的情况下,双源CT冠状动脉成像中使用ATCM能明显降低患者检查的剂量。