Momentum-diffusive model for gas transfer in granular media

The development of controlled atmosphere storage technology for insect control requires an accurate prediction of the distribution of introduced gases in bulk grain. The published models are based on either diffusion theory or convective-diffusion theory. The momentum transport of gases, which is a key driving force for the gas mixture movements, has been neglected. In this paper, all the driving forces for gas transfer were investigated. A momentum-diffusive model is proposed. The model is based on the combined effects of concentration gradients, pressure gradients, and gravity on the transport of gases in the bulk grain. The experimental data for CO₂ transfer through connected columns of hot and cold wheat were used to validate the model. The equations were solved using the finite difference method, and the predictions from the proposed model were in good agreement with the experimental results.     

Synthesis of Brightly PEGylated Luminescent Magnetic Upconversion Nanophosphors for Deep Tissue and Dual MRI Imaging

A method is developed to fabricate monodispersed biocompatible Yb/Er or Yb/Tm doped β‐NaGdF₄ upconversion phosphors using polyelectrolytes to prevent irreversible particle aggregation during conversion of the precursor, Gd₂O(CO₃)₂?H₂O:Yb/Er or Yb/Tm, to β‐NaGdF₄:Yb/Er or Yb/Tm. The polyelectrolyte on the outer surface of nanophosphors also provided an amine tag for PEGylation. This method is also employed to fabricate PEGylated magnetic upconversion phosphors with Fe₃O₄ as the core and β‐NaGdF₄ as a shell. These magnetic upconversion nanophosphors have relatively high saturation magnetization (7.0 emu g^?1) and magnetic susceptibility (1.7 × 10^?2 emu g^?1 Oe^?1), providing them with large magnetophoretic mobilities. The magnetic properties for separation and controlled release in flow, their optical properties for cell labeling, deep tissue imaging, and their T₁‐ and T₂‐weighted magnetic resonance imaging (MRI) relaxivities are studied. The magnetic upconversion phosphors display both strong magnetophoresis, dual MRI imaging (r₁ = 2.9 mM^?1 s^?1, r₂ = 204 mM^?1 s^?1), and bright luminescence under 1 cm chicken breast tissue.     

Bacterial Killing by Light‐Triggered Release of Silver from Biomimetic Metal Nanorods

Illumination of noble metal nanoparticles at the plasmon resonance causes substantial heat generation, and the transient and highly localized temperature increases that result from this energy conversion can be exploited for photothermal therapy by plasmonically heating gold nanorods (NRs) bound to cell surfaces. Here, plasmonic heating is used for the first time to locally release silver from gold core/silver shell (Au@Ag) NRs targeted to bacterial cell walls. A novel biomimetic method of preparing Au@Ag core–shell NRs is employed, involving deposition of a thin organic polydopamine (PD) primer onto Au NR surfaces, followed by spontaneous electroless silver metallization, and conjugation of antibacterial antibodies and passivating polymers for targeting to gram‐negative and gram‐positive bacteria. Dramatic cytotoxicity of S. epidermidis and E. coli cells targeted with Au@Ag NRs is observed upon exposure to light as a result of the combined antibacterial effects of plasmonic heating and silver release. The antibacterial effect is much greater than with either plasmonic heating or silver alone, implying a strong therapeutic synergy between cell‐targeted plasmonic heating and the associated silver release upon irradiation. The findings suggest a potential antibacterial use of Au@Ag NRs when coupled with light irradiation, which has not been previously described.     

Analysis of mixed-mode dynamic crack propagation by interface element based on virtual crack closure technique

An interface element tailored for the virtual crack closure technique (VCCT) was used to study an example of dynamic crack propagation under mixed mode loading. Through this interfacial element approach, VCCT can be implemented into a commercial finite element analysis (FEA) code having user subroutines without interrupting the main code. Further, with the implementation of relevant fracture criteria, this interface element can be used to simulate a wide range of fracture problems by utilizing the enhanced capabilities available by the commercial FEA codes. For illustration, this element has been implemented with the commercial FEA software ABAQUS^® through the user defined element (UEL). One example of fast crack propagation at constant speed and under mixed-mode loading was examined by comparison to the other’s numerical results using singular moving elements. No convergence difficulty was encountered for all the cases with different values of crack velocity. Neither singular element, nor the collapsed element was required. Therefore, due to its simplicity, the VCCT interface element as demonstrated could be a potential tool for engineers to practice dynamic fracture analysis in conjunction with commercial FEA codes.     

Q355钢板对接接头裂纹扩展所致焊接残余应力重分布研究

目的 定量研究裂纹扩展导致的焊接残余应力重分布效应,得到残余应力随裂纹扩展的变化规律。方法 首先采用盲孔法测试了Q355钢板对接接头的初始残余应力;其次利用线切割技术模拟了平行以及垂直于焊缝的裂纹扩展情况,并测试了裂纹扩展导致的残余应力变化量;最后根据测试数据提出了残余应力释放量Δσ与裂纹长度a之间的函数关系式,进一步得到了基于裂纹扩展的应力重分布计算公式。结果 Q355钢板对接焊的焊缝区纵向(沿焊缝方向)存在较大的残余拉应力,拉应力峰值出现在焊趾处,为屈服强度的1.13倍。焊缝区横向存在梯度较大、拉压交替变化的残余应力,压应力峰值出现在焊趾处,大小为52.6 MPa,拉应力峰值出现在距焊缝中心线17 mm处,大小为63.5 MPa。裂纹扩展能显著释放残余拉应力:裂纹沿焊缝中心扩展,横向残余拉应力峰值降低了45.8%;裂纹沿垂直于焊缝方向扩展,焊趾处的拉应力峰值降低了63.3%。结论 裂纹扩展会显著影响焊接构件的残余应力分布,根据实测数据提出的裂纹扩展应力重分布计算公式能够较好地反映残余应力重分布情况。     

株六复线高边坡深路堑石方控制爆破和安全技术

株六铁路复线K40 1地段扩堑 ,由于边坡高、路堑深、方量大、距电接触网近 ,爆破施工十分困难。本文主要介绍了该段复杂地形和环境条件下石方控制爆破的设计与施工 ,以及安全防护措施 ;论述了浅孔台阶法和中深孔分层爆破法的爆破参数设计、药量计算、起爆技术 ;详细地阐述了钢管排架和“炮被”等安全设施的结构和作用 ;概述了几点认识和体会。     

联体砖混结构圆筒仓的控制爆破拆除

介绍了设有提升机房的联体砖混圆筒仓的控制爆破拆除。对圆筒仓间仓壁重叠部前端的"x"型部分进行了爆破预拆除,充分考虑爆破切口形状的影响合理选择爆破参数,利用中间通道作定向窗,设置减荷窗及合理的延时时间,保证了联体结构的整体失稳,避免了筒仓整体下坐而产生后坐或倒塌不充分。可为同类工程提供借鉴。     

己酰化乙二醇壳聚糖/泊洛沙姆复合水凝胶的制备及其药物缓释性能

为减少泊洛沙姆水凝胶的溶胶-凝胶转变温度对浓度的依赖性,以泊洛沙姆(P₄₀₇)为基材,将己酰化乙二醇壳聚糖(HGC)与泊洛沙姆复合,制备了己酰化乙二醇壳聚糖/泊洛沙姆(HGC/P₄₀₇)复合水凝胶,利用FTIR、SEM及试管反转法探讨了HGC/P₄₀₇复合水凝胶的性能,并利用紫外-可见分光光度计(UV-vis)对HGC/P₄₀₇复合水凝胶的体外药物缓释性能进行表征。结果表明,通过控制HGC的加入量,基于3%泊洛沙姆的HGC/P₄₀₇复合水凝胶即可发生溶胶-凝胶转变现象,并使HGC/P₄₀₇复合水凝胶的溶胶-凝胶转变温度处于32~37℃。HGC/P₄₀₇复合水凝胶具有高度孔隙率,孔隙之间相互连通,孔径大小处于10~90μm的范围之内。HGC/P₄₀₇复合水凝胶对抗癌药物吉西他滨的释药量达到82.4%~90.6%,缓释时间可达80 h左右。HGC/P₄₀₇复合水凝胶在可注射药物载体领域具有重要的应用前景。     

The Acute Antiallodynic Effect of Tolperisone in Rat Neuropathic Pain and Evaluation of Its Mechanism of Action

Current treatment approaches to manage neuropathic pain have a slow onset and their use is largely hampered by side-effects, thus there is a significant need for finding new medications. Tolperisone, a centrally acting muscle relaxant with a favorable side effect profile, has been reported to affect ion channels, which are targets for current first-line medications in neuropathic pain. Our aim was to explore its antinociceptive potency in rats developing neuropathic pain evoked by partial sciatic nerve ligation and the mechanisms involved. Acute oral tolperisone restores both the decreased paw pressure threshold and the elevated glutamate level in cerebrospinal fluid in neuropathic rats. These effects were comparable to those of pregabalin, a first-line medication in neuropathy. Tolperisone also inhibits release of glutamate from rat brain synaptosomes primarily by blockade of voltage-dependent sodium channels, although inhibition of calcium channels may also be involved at higher concentrations. However, pregabalin fails to affect glutamate release under our present conditions, indicating a different mechanism of action. These results lay the foundation of the avenue for repurposing tolperisone as an analgesic drug to relieve neuropathic pain.     

Rate of release of spruce budworm pheromone from virgin females and synthetic lures

The rate of pheromone [(E)- and (Z)-11-tetradecenal] release from calling virginChoristoneura fumiferana females and synthetic lures was determined in both static and aerated atmospheres. In a static system ca. 2 ng/hr was recovered per female. Owing to the > 75% adsorption onto the females' bodies in static atmospheres, the actual release rate has to be corrected to roughly 9–27 ng/hr, depending on the percentage adsorbed. In the air-flow system, females were found to release between 4 and 20 ng/hr. On a 168 light-dark cycle, calling began 1–2 hr before lights-off and continued nonstop until lights-on. Pheromone was emitted throughout calling, while no pheromone was detected during the noncalling periods.Lepidoptera: Tortricidae.Published as Journal Article No. 10258 of the Michigan Agricultural Experiment Station.