Calcium3D: a visual software package for the simulation of calcium buffered diffusion in neuroendocrine cells

We present Calcium3D, a user-friendly software package for simulating calcium triggered processes in neuroendocrine cells. We use Monte Carlo methods for the simulation of the basic processes involved: entry of calcium into the cytoplasm, the diffusion of ions and mobile intracellular calcium buffers inside the intracellular medium, and the kinetics of the reaction of calcium with these buffers. The outputs of the simulation are calcium and buffer concentrations as a function of time and for different depths from the cellular membrane.     

石灰石的氧化钙含量超标的原因分析

某燃煤电厂烟气脱硫采用石灰石—石膏湿法脱硫工艺。针对在石灰石氧化钙含量测定时发现一批次的石灰石氧化钙含量超标,氧化钙含量高达60%,且折算成碳酸钙含量则大幅超过100%,明显不符合常理的问题。通过一系列的化学分析试验,验证了试验方法、检测试剂、试验过程以及铁铝杂质含量并不是造成氧化钙含量超标的原因。最后通过对检测原理的进一步分析和试验,得出主要原因是石灰石中掺入了生石灰或熟石灰,人为添加钙成分类似于牛奶中添加三聚氰胺,干扰了石灰石中氧化钙的测定。通过定性检测样品的水溶液是否含有钙离子,可快速有效的检测石灰石中是否掺入了生石灰或熟石灰,保证了石灰石的质量验收和脱硫系统的安全运行,很大程度上弥补了国标测定方法《化工用石灰石中氧化钙和氧化镁含量的测定》的不足     

神经元钙振荡的非线性动力学研究

在神经元的生理实验中经常观察到丰富的钙振荡模式,本文详细综述了产生这些现象的钙流交换机理和各类通道调节机理,以及描述这些生理机理的数学表达式.介绍三类典型的研究钙振荡的非线性动力学模型,即电压动力学与钙动力学相耦合的模型,多个钙存储单元之间钙流平衡的模型和考虑信使物质IP3的振荡与钙振荡相互作用的模型;并针对第一个模型简要地讨论其复杂的动力学行为;最后对神经元钙振荡的非线性动力学研究提出了一些展望.     

Modeling deterioration of cementitious materials exposed to calcium leaching in non-isothermal conditions

The paper presents a new mathematical model of hydro-thermo-chemo-mechanical behavior of cementitious materials exposed to contact with the deionized water. For analyzing the calcium leaching process, an equation describing kinetics of the process is used instead of an equilibrium curve commonly used in previous isothermal models. This allows taking directly into account the temperature dependence of characteristic times of calcium leaching from different components of concrete what affects the process kinetics, especially that with a relatively fast decrease of the concentration of calcium in pore water. Constitutive relationships describing the transport and strength properties of concrete during chemical degradation at non-isothermal conditions are discussed. The governing equations of the model and boundary conditions are expressed in terms of the state variables: gas pressure, capillary pressure, temperature, calcium concentration and displacement vector. Numerical solution of the model equations with the Finite Element Method, as well as several examples of application of the model for analysis of some test problems, are presented.     

耕地土壤交换性钙镁比值的研究

对沈阳市郊区1994个耕地表土(0～20cm)样点和4个典型剖面中交换性Ca/Mg的比值进行了对比研究。结果表明:不同土属耕层土壤中Ca、Mg交换量有较大差别,交换性Ca/Mg的比值主要受母质等成土因素的影响;棕壤的各个土属的Ca/Mg在4左右,石灰性草甸土和草甸沼泽土的Ca/Mg则在8以上。棕壤和草甸土典型剖面不同层次中的Ca/Mg比值有着随深度加深而降低的趋势;由于Ca的植物返还率较Mg高,同一土壤类型中Ca/Mg比值的最大值出现在表土层,母质层中的Ca/Mg则相对稳定。对土壤Ca/Mg进行研究可以丰富土壤离子交换性能研究和土壤发生学特性研究的内容。     

氯化焙烧回收高铁硫酸烧渣中有价金属的实验研究

从高铁硫酸渣本身的特点出发,选用氯化挥发法进行有色金属分离的实验。结果表明:氯化剂的含量、焙烧温度、焙烧时间均会对有价金属的挥发产生影响;随着氯化剂的含量的增加,金、银、铜、铅、锌挥发率均会提高,挥发率达到最大值后稳定;金、银达到最大挥发率所需氯化剂分别为4%、6%,而铜、锌需9%;高温会促进氯化剂的分解,最重要的是促进金属氯化物的挥发,从而提高挥发率,但是在高氯化剂含量（9%）的情况下,焙烧温度超过1150℃后,随着温度的升高铜、铅、锌的挥发率反而会降低;焙烧时金属氯化物挥发需20 min,而氯化剂完全分解需60 min。综合考虑后最终选择的条件是烧渣中加入9%CaCl₂在1100℃下焙烧,在此条件下焙烧后金、银品位及挥发率分别为:0.17g/t、91.26%、6.24g/t、80.05%,其它元素的含量也都达标。     

The muscle fatigue fiber model

The aim of this study was to integrate the effect of muscle fatigue into the skeletal muscle fiber model, which was previously developed in our laboratory and was based on the modified Huxley equation with the calcium activation taken into account. The cellular mechanisms such as (i) the attachment of myosin heads to the actin binding sites, (ii) the actin filament activation, (iii) the sensitivity of myofilaments to calcium ions and (iv) the calcium handling; which influence the force generated by the muscle fiber and are affected during fatigue, became the base stone for the development of the muscle fatigue fiber model.     

中性载体钙微电极的特性改进及蛙心肌细胞外光释放游离钙的瞬时测定

中性载体钙微电极的应用,被局限于活体组织(包括单细胞)中静止Ca~(2+)活度的测定,其主要原因是电极的响应速度不够快。本文研究影响电极响应速度的各种因素,提出了改进电极响应特性的有效办法。业将改进后的钙微电极成功地应用于心肌细胞外受紫外脉冲光激发、由DM—硝基酚钙络合物释放的钙的瞬时跟踪测定。改进后的钙微电极可作为研究细胞膜Ca~(2+)通道动力学机制的有效工具。     

Surface studies of the Medicus nickel matrix cathode

It is shown that activation of the Medicus nickel matrix cathode results in the development of a surface microstructure consisting of alkaline earth oxide-rich regions, 20–40 μm in diameter, distributed over the nickel-rich cathode coating. An in situ correlation between thermionic emission current and surface composition indicates a primary dependence upon the relative Ba to Ni concentration. A time dependent increase in the average calcium concentration at the surface has also been observed; compositional analyses of material evaporating from the cathode revealed that this calcium may accumulate at the surface due to the preferential release of barium and strontium. The accumulation of calcium at the surface, as well as the loss of barium, are believed to contribute to emission degradation during cathode life. Ion sputtering studies suggest the dispensing of barium and the dependence of the surface microstructure upon the initial thermal/ electrolytic activation. Although barium concentrations in excess of the oxide stoichiometry are measured, the presence of elemental barium monolayers has not been verified. It is concluded that owing to these chemical, compositional and morphological effects, the nickel matrix cathode should not be viewed simply as an oxide cathode physically supported by a metal matrix.     

基于激光诱导的细胞荧光成像系统研制

分析了激光诱导荧光法检测钙离子浓度的原理.并利用微流控芯片在细胞培养和检测上的独特优越性,设计实现了基于微流控芯片的测量细胞内钙离子浓度变化的显微荧光成像系统.在对微流控芯片技术研究的基础上设计制作了微流控芯片,并设计了显微系统、快速波长切换系统、CCD成像系统等.利用这套显微荧光成像系统对活体细胞的荧光图像进行采集....     

A hybrid approach for fabrication of polymeric BIOMEMS devices

Polymeric microfluidic chips are an enabling component for cost-effective, point of care analytical devices for pharmaceutical, agriculture, health, biological and medical applications. The microfluidic structures can be completed with active elements like pumps and valves as well as sensor components for more complex so called total analysis systems. Often, systems are designed as reader and disposable cartridge where the fluidic structures are simple devices that will be inserted into the reader, which executes the analytical protocol and displays the information in digital form, and disposed after completion of the analysis. In this paper, a hybrid fabrication approach was employed to build a polymeric microfluidic device, so-called sweatstick, suitable for collecting small, precise amounts (600 μl) of human sweat, which were further analyzed for the amount of calcium ions indicating bone mass loss. The device was assembled from different parts fabricated by ultra deep X-ray lithography, precision micro-milling, and molding. Surface treatment of liquid exposed surfaces by oxygen plasma ensures hydrophilic behavior and proper capillary action. Preliminary testing of the device was performed by collecting defined amounts of sweat simulant and determining the calcium ion content using a fluorescent technique. The results for low calcium ion concentration typical for human sweat were excellent and repeatable with variation less than 5% demonstrating the ability to perform indirect bone loss measurements.     

耦合pre-B tzinger复合体神经元中混合簇放电的多时间尺度动力学分析

Pre-B tzinger复合体是新生哺乳动物呼吸节律起源的关键部位,是呼吸节律产生的中枢.本文以pre-B tzinger复合体中两个耦合的神经元为研究对象,并考虑钙离子动力学的耦合神经元模型.利用多时间尺度动力学、快慢尺度分解和分岔分析,研究混合簇同步放电模式及其产生机制,并研究了耦合神经元同相和反相簇放电类型及其同步转迁.结果表明钙离子的周期性波动对混合簇放电模式的产生有极大的影响,钙离子波动导致的时间尺度变化及分岔曲线相对位置的改变是混合簇放电产生的主要原因.本文的研究对认识pre-B tzinger中大规模网络的动力学有着重要的意义,为进一步探索呼吸节律的产生机制提供了一些有益的思考和见解.     

Performance evaluation of 3D polystyrene 96-well plates with human neural stem cells in a calcium assay

In this study, we have generated a high-throughput screening (HTS)-compatible 3D cell culture platform by chemically "welding" polystyrene scaffolds into standard 2D polystyrene 96-well plates. The variability of scaffolds was minimized by introducing automation into the fabrication process. The fabricated 3D cell culture plates were compared with several commercially available 3D cell culture platforms with light and scanning electron microscopy. Voltage-gated calcium channel functionality was used to access the Z' factors of all plates, including a 2D standard plate control. It was found that with the No-Wash Fluo-4 calcium assay and neural progenitor cells, all plates display acceptable Z' factors for use in HTS. The plates with "welded" polystyrene scaffolds have several advantages, such as being versatile and economical, and are ready to use off the shelf. These characteristics are especially desired in HTS preclinical drug discovery applications.     

葡聚六糖诱导后黄瓜幼苗细胞内Ca2+水平变化的细胞化学研究

采用改进的焦锑酸钙细胞化学方法 ,探讨了葡聚六糖诱导后Ca2 在黄瓜幼苗细胞中超微结构定位变化动态。结果表明 ,在正常情况下 ,黄瓜幼苗的细胞壁和细胞间隙存在大量Ca2 。葡聚六糖诱导后2h,细胞壁和细胞间隙Ca2 沉淀物明显减少 ;诱导后4h ,细胞壁和细胞间隙只偶尔能看到有少量Ca2 沉淀物 ,细胞质中Ca2 沉淀物增多 ;诱导后7h ,Ca2 又重新流回细胞壁和细胞间隙     

生物细胞超短脉冲电场传感器

描述了生物细胞的电模型。细胞内生物电效应的实验观察包括细胞颗粒的破裂而又不能使细胞膜受到永久性伤害,细胞内游离钙值的突然升高和基因表现的增强。在较高场强时,亚微秒脉冲的作用是感应生物细胞凋亡（编程细胞死亡）和抑制肿瘤细胞的生长。细胞内电效应的应用包括增强基因向细胞核的释放,肿瘤医疗诊断和控制细胞功能（如生物细胞“冻结”,但不一定死亡）。     

Visualization of calcium activity in nerve cells

Calcium plays an important role in many cellular functions. This investigation of its role in nervous system behavior uses imaging techniques, confocal microscopy, and the VolVis volume visualization system. The use of VolVis provided substantial assistance in the study of cellular calcium dynamics and in monitoring neural network activity. It yielded geometric details that facilitated our understanding of the behavior of calcium indicators inside nerve cells and led to a new view of the calcium permeability of the nuclear envelope. It has also produced anatomical details that significantly facilitated the development of a technique to directly visualize the activity of neuron populations while simultaneously observing vertebrate behavior     

Rigorous modeling of gypsum solubility in Na–Ca–Mg–Fe–Al–H–Cl–H2O system at elevated temperatures

Precipitation and scaling of calcium sulfate have been known as major problems facing process industries and oilfield operations. Most scale prediction models are based on aqueous thermodynamics and solubility behavior of salts in aqueous electrolyte solutions. There is yet a huge interest in developing reliable, simple, and accurate solubility prediction models. In this study, a comprehensive model based on least-squares support vector machine (LS-SVM) is presented, which is mainly devoted to calcium sulfate dihydrate (or gypsum) solubility in aqueous solutions of mixed electrolytes covering wide temperature ranges. In this respect, an aggregate of 880 experimental data were gathered from the open literature in order to construct and evaluate the reliability of presented model. Solubility values predicted by LS-SVM model are in well accordance with the observed values yielding a squared correlation coefficient (R ²) of 0.994. Sensitivity of the model for some important parameters is also checked to ascertain whether the learning process has succeeded. At the end, outlier diagnosis was performed using the method of leverage value statistics to find and eliminate the falsely recorded measurements from assembled dataset. Results obtained from this study indicate that LS-SVM model can successfully be applied in predicting accurate solubility of calcium sulfate dihydrate in Na–Ca–Mg–Fe–Al–H–Cl–H₂O system over temperatures ranging from 283.15 to 371.15 K.     

软测量在电石生产中的应用

针对电石生产中比电阻难于测量的问题,从工艺上对这一关键参数加以分析,提出了采用线性回归分析的方法来建立其软测量模型的方法与步骤,并且在实际中以其为控制目标加以应用,现场的反馈数据表明这种软测量方法在电石生产中是行之有效的。     

PLC在电石炉控制系统中的应用

电石冶炼炉是一个大量消耗电能、炉内状况变化大、现场工作环境恶劣的冶炼设备。它工作的稳定与否直接关系到电石产品的质量。对电石炉生产过程进行自动控制是冶炼厂提高产品质量和节能降耗的重要手段之一。本文介绍了一种基于PLC的电石炉控制系统组成及生产控制策略,采取优先调整偏离设定值最大相和协调控制的原则,有效的解决了负载波动大和负载耦合的问题。该系统在实际应用中能有效提高电石产品质量,减少能源损耗,降低工人劳动强度。     

DFT,QTAIM, and NBO studies on the trimeric interactions in the protrusion domain of a piscine betanodavirus

Crystal structure of the protrusion domain (P-domain) of the grouper nervous necrosis virus (GNNV) shows the presence of three-fold trimeric protrusions with two asymmetrical calcium cations along the non-crystallographic three-fold axis. The trimeric interaction natures of the interacting residues and the calcium cations with the neighboring residues within the trimeric interface have been studied by the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses in the framework of the density-functional theory (DFT) approach. The results revealed that residues Leu259, Val274, Trp280, and Gln322 of subunit A, Arg261, Asp275, Ala277, and Gln322 of subunit B, Leu259, Asp260, Arg261, Ala277, Val278, and Leu324 of subunit C are the main residues involved in the trimeric interactions. Charge-dipole, dipole-dipole, and hydrogen bonding interactions make the significant contributions to these trimeric interactions. Among different interacting residues within trimeric interface, residue pair Arg261 B-Leu259C forms the strongest hydrogen bond inside the interface between subunits B and C. It was also found that calcium cations interact with residues Asp273, Val274, and Asp275 of subunits A, B, and C through charge-charge and charge transfer interactions.