Bifurcation analysis in a diffusive Segel–Jackson model

Bifurcations of spatially nonhomogeneous periodic orbits and steady state solutions are rigorously proved for a reaction–diffusion system modeling predator–prey interaction. The existence of these patterned solutions shows the richness of the spatiotemporal dynamics such as oscillatory behavior and spatial patterns.     

基于液体碳氢燃料的旋转爆轰燃烧特性研究

为了探索液体碳氢燃料参与旋转爆轰所产生的不完全燃烧现象,采用守恒元与求解元方法,开展柱坐标系下的汽油/空气两相旋转爆轰燃烧室三维数值模拟研究,针对燃料喷注压力和反应物当量比对旋转爆轰流场结构及燃烧室性能的影响进行分析。分析结果表明:保持总当量比为1.00,随着燃料喷注压力的上升,燃烧室内燃料不均匀分布增强,产生局部富燃区,燃料在燃烧室未能完全反应,导致燃烧室燃料比冲下降;保持喷注压力不变,减小当量比,在贫燃工况下依然存在局部富燃区,导致燃烧室内出现不完全燃烧现象,降低燃烧室比冲性能。由此可知,反应物喷注方案对气液两相旋转爆轰的不完全燃烧有显著影响。     

Inactivation of lymphocytes in blood products using riboflavin photochemical treatment with visible light

Abstract Immunocompetent lymphocytes present in blood products are an important cause of immune reactions following blood transfusion such as transfusion-associated graft-versus-host disease (TA-GVHD). In this study the effects of riboflavin photochemical treatment (RPT) on lymphocyte proliferation and cytokine production in vitro were measured to establish whether RPT of blood products can be used to prevent immune reactions resulting from transfused lymphocytes. Lymphocytes and riboflavin were added together in medical PVC transparent bags and then exposed to visible light. Control lymphocytes were exposed to light in the absence of riboflavin. Lymphocytes exposed to riboflavin photochemical treatment (RPT-lymphocytes) and control lymphocytes were tested for the proliferative ability and the production of several cytokines upon stimulation with antigens. Upon stimulation by phytohemagglutinin (PHA) the proliferation of RPT-lymphocytes was inhibited. Using flow cytometry it was shown that RPT-lymphocytes were unable to enter the S-phase of the cell cycle following PHA stimulation. The level of cytokines present in the supernatant of RPT-lymphocytes after stimulation by antigens was significantly lower than those present in the corresponding supernatant of control lymphocytes. RPT with visible light inactivates lymphocytes, inhibits lymphocyte proliferation and the production of cytokines. It appears to be a promising method to prevent immune reactions such as TA-GVHD.     

高效液相色谱-串联质谱法测定盐酸二甲双胍及其制剂中痕量N -亚硝基二甲胺

建立了高效液相色谱-串联质谱（HPLC-MS/MS）检测盐酸二甲双胍原料和制剂中N -亚硝基二甲胺（NDMA）含量的方法。样品以水为提取溶剂,经涡旋混匀、恒温振荡、高速离心、微孔过滤后进行HPLC-MS/MS分析。采用ACE EXCEL 3 C18-AR色谱柱（150 mm×4.6 mm,3 μm）分离,流动相为均含0.1%甲酸的水和甲醇溶液,梯度洗脱,流速0.8 mL/min,柱温40℃,自动进样器温度10℃。采用阀切换技术保护质谱仪,设置六通阀切换使保留时间2.85~7.00 min的流动相进入质谱,其余时间流动相进入废液。质谱部分采用大气压化学电离（APCI）源,在正离子、MRM模式下扫描,雾化器流量为3 L/min,加热器流量为10 L/min,接口温度为300℃,脱溶剂管温度为250℃,加热块温度为400℃,干燥器流量为10 L/min。NDMA定量离子对为m /z 75.0→43.1,碰撞能量（CE）为-17.0 eV,定性离子对为m /z 75.0→58.2,CE为-16.0 eV。采用外标法定量。对方法进行了详细的方法学验证,结果表明,该法专属性良好,溶剂和辅料对NDMA测定无干扰。NDMA峰面积与其质量浓度在1.00~100.00 ng/mL范围内呈现良好的线性关系,相关系数（r ）>0.9999;低、中、高3个水平下NDMA的回收率为94.55%~114.67%,RSD为4.73%~13.46%;检出限和定量限分别为0.20 ng/mL和1.00 ng/mL;NDMA在自动进样器放置0、8、24 h的峰面积RSD为2.08%。使用该方法对113批盐酸二甲双胍原料和制剂供试品中的NDMA进行测定,发现原料药中NDMA检出量不超限,但有8批二甲双胍制剂超过了限度。该法灵敏、准确,操作简便,可用于盐酸二甲双胍原料及制剂中的NDMA检测。     

通气空泡生成和溃灭特性试验研究

为了研究通气流量对超空泡生成和溃灭的影响,在西北工业大学高速水洞实验室进行了系列通气超空泡生成和渍灭特征的试验.结果表明:空泡生成过程中,空泡长度和直径的变化特性与空泡溃灭时的变化特性相反;通气流量对空泡生成和溃灭均有较大影响,数据显示通气量对空泡生成的影响大于对空泡溃灭的影响.此研究为进一步研究超空泡的快速稳定生成提供了实验基础.     

The newsvendor problem: Review and directions for future research

In this paper, we review the contributions to date for analyzing the newsvendor problem. Our focus is on examining the specific extensions for analyzing this problem in the context of modeling customer demand, supplier costs, and the buyer risk profile. More specifically, we analyze the impact of market price, marketing effort, and stocking quantity on customer demand; how supplier prices can serve as a coordination mechanism in a supply chain setting; integrating alternative supplier pricing policies within the newsvendor framework; and how the buyer’s risk profile moderates the newsvendor order quantity decision. For each of these areas, we summarize the current literature and develop extensions. Finally, we also propose directions for future research.     

Molecular dynamics simulation of thermal conductivity of Cu–Ar nanofluid using EAM potential for Cu–Cu interactions

Mechanism of heat conduction in copper-argon nanofluids is studied by molecular dynamics simulation and the thermal conductivity was obtained using the Green–Kubo method. While the interatomic potential between argon atoms is described using the well-known Lennard–Jones (L–J) potential, a more accurate embedded atom method (EAM) potential is used in describing the interatomic interaction between copper atoms. It is found that the heat current autocorrelation function obtained using L–J potential to describe the copper-copper interatomic interaction fluctuates periodically due to periodic oscillation of the instantaneous microscopic heat fluxes. Thermal conductivities of nanofluids using EAM potentials were calculated with different volume fractions but the same nanoparticle size. The results show that thermal conductivity of nanofluids are almost a linear function of the volume fraction and slightly higher than the results predicted by the conventional effective media theory for a well-dispersed solution. A solid-like base fluid liquid layer with a thickness of 0.6 nm was found in the simulation and this layer is believed to account for the small discrepancy between the results of MD simulation and the conventional effective media theory.     

Nanochemoprevention by encapsulation of (-)-epigallocatechin-3-gallate with bioactive peptides/chitosan nanoparticles for enhancement of its bioavailability

Nanochemoprevention by oral consumption was developed by the encapsulation of (-)-epigallocatechin-3-gallate (EGCG) with nanoparticles that were electrostatically assembled from bioactive caseinophosphopeptides and chitosan, which was highly biocompatible and able to enhance the bioavailability of EGCG.     

1,3,5-三[(4’-乙炔基苯基)乙炔基]苯的合成

设计了多种合成路线制备芳香炔基树枝状化合物中间体1,3,5-三[(4’-乙炔基苯基)乙炔基]苯,通过一系列的合成路线和反应条件的对比,发现多官能团的端基炔化合物与芳基溴化合物之间发生多重Sonogashira反应时,常会生成不同取代程度的极性相似化合物,因而难以分离.采用多官能团的端基炔化合物与芳基碘化合物反应可以避免这种情况.最终确定以1,3,5-三溴苯和2-甲基-3-丁炔-2-醇为原料,制得中间产物1,3,5-三乙炔基苯;再以对碘苯胺和三甲基硅乙炔为原料,经重氮化化、卤代反应制得4-三甲基硅乙炔基碘苯;后者与1,3,5-三乙炔苯经Sonogashira反应、裂解去保护反应,制得化合物1,3,5-三[(4’-乙炔基苯基)乙炔基]苯.用1H NMR,13C NMR,元素分析等表征手段确认了中间体及最终产物的结构.