Age is more than just a number: implications for an aging workforce in the US transportation sector

The US workforce is aging. At the same time, there are a record number of open positions in the transportation sector, which has traditionally been a well-paying, but stressful and schedule-dependent, occupation. Due to increasing longevity, need, and ability to work, a possible solution to the transportation workforce shortfall may lie within the retention and recruitment of older workers. This paper uses a socio-technical framework to examine the pertinent, though scant, literature and data related to older workforce demographics and operational needs, the regulatory environment, requisite knowledge, skills and abilities, and application of support technology and training. Although there is evidence of age-related changes in physiology and cognition, the current science remains unable to resolve how an older workforce may most appropriately be applied to transportation to maximize system safety and minimize negative impact to worker well-being.     

不同功能单体制备水杨酸分子印迹聚合物的分子模拟研究

采用分子模拟技术,研究水杨酸分子制备印迹聚合物过程中,水杨酸(SA)与不同功能单体之间的结合能.作者等先计算水杨酸与常用功能单体之间的结合能,再选出适合制备水杨酸分子印迹聚合物的功能单体.其次详细讨论丙烯酰胺(AM)和甲基丙烯酸(MAA)与SA的结合能以及聚合物与水杨酸分子之问的结合能.发现,(1)制备分子印迹聚合物过程中,水杨酸的作用功能基团是-COOH,AM、MAA的作用功能基团分别是-NH2、-COOH.(2)SA与AM形成的复合物结合能大于与MAA形成复合物的结合能.由此,推断以AM为功能单体的水杨酸分子印迹聚合物,比以MAA为功能单体的水杨酸分子印迹聚合物的吸附量大,与实验结果一致.     

计算机曲线拟合求解析氢反应的动力学参数

应用电化学稳态极化方法,研究1M NaOH电解液中镍硫合金电极表面析氢反应电催化活性与沉积层中含硫量之间的关系.根据析氢反应机理,用理论电化学极化方程拟合实验稳态极化曲线,得到不同含硫量的镍硫合金电极表面氢原子吸附和脱附反应的速率常数、反应对称系数等动力学参数.     

一种三维刚架—桁架静力分析有限元程序

介绍了三维刚架计算原理以及作者所编制的一种应用于ＰＣ微机的有限元程序．本程序用＂ＦＯＲＴＲＡＮ＂语言编写,采用半动态一维存储．引入了单元整体形函数矩阵,简化了单元非结点载荷与结点载荷的转换过程．可用于计算三维及二维刚架或桁架在多种载荷条件下的位移及杆端内力并可绘出结构的有限元模型、支承、受载及变形状况．通过一系列算例验证了程序的正确性．     

Characteristics of Fe/AlPO4-5 catalyst prepared with organic solution

The Fe/AlPO₄-5 catalysts are prepared by impregnation with aqueous and organic solution (acetic acid, alcohol and acetone) of iron(III) nitrite respectively. The characterization of catalyst by means of XPS, Mössbauer spectroscopy, TPR and CO hydrogenation is reported. The catalyst prepared with the aqueous solution has no activity for CO hydrogenation because the Fe(III) in the catalyst cannot be reduced to -Fe. However, the catalysts prepared with organic solution possess obvious hydrogenation activity, in which -Fe is present in the initial reduced catalyst besides Fe³⁺ and Fe²⁺. The results may be explained by the interaction degrees between the metal and the support induced by the different impregnation solvents.     

Localization effects in transition-metal doped Bi2Sr2CaCu2O8+y high-temperature superconductors

Doping Bi₂Sr₂Ca₁Cu₂O_8+y with Co causes a superconductor-insulator transition. We study correlations between changes in the electrical resistivity _ab(T) and the electronic bandstructure using identical single crystalline samples. For undoped samples the resistivity is linear in temperature and has a vanishing residual resistivity. In angle resolved photoemission these samples show dispersing band-like states. Co-doping decreases T_c and causes and increase in the residual resistivity. Above a threshold Co-concentration the resistivity is metallic (d_ab/dT>0) at room temperature, turns insulating below a characteristic temperature T_min and becomes superconducting at even lower temperature. These changes in the resistivity correlate with the disappearance of the dispersing band-like states in angle resolved photoemission. We show that Anderson localization caused by the impurity potential of the doped Co-atoms provides a consistent explanation of all experimental features. The coexistance of insulating (d_ab/dT <0) normal state behavior and superconductivity indicates that the superconducting ground state is formed out of spatially almost localized carriers.     

Lymphocyte subpopulations of workers in a plant producing plastic materials (preliminary study)

Lymphocyte subpopulations were studied in 31 men working in a plant producing plastic materials in relation with control groups of similar age and smoking habit. 8 workers (group A) were exposed to solvents (mainly methylethylketone and dimethylformamide), 8 men (group B) to dust containing particles of calcium carbonate, polyvinylchloride, phtalates, unsaturated oils, paraffin wax, iron oxides, titanium bioxides, barium, zinc and lead and 15 men (group C), working in the same department as group B, were studied after a period of 16 months during which lead chromate was employed in the preparation of colors. The lymphocyte subpopulations were normal in group A, while in B there was a significant increase of HLA-DR + cells (monocytes, B and activated T lymphocytes). In group C, T helper/inducer lymphocytes (mainly CD4(+)-CD45RO- "virgin" lymphocytes), CD19+ B lymphocytes, CD3-HLADR+ and CD3-CD25+ (activated B lymphocytes and monocytes) were significantly reduced without changes of serum IgM, IgG and IgA. Highly significant correlation was found between B lymphocytes (reduced in the workers about 40%) and CD4(+)-CD45R0+ "memory" lymphocytes (reduced about 20%). Moreover, blood lead (correlated with urinary chromium) showed a highly significant negative correlation with the B lymphocytes. This study demonstrates that combined exposure to toxic agents produces specific modifications in the lymphocyte subsets without changes in immunoglobulins and confirms the results of previous researches showing that the exposure to lead or chromate induces reduction of lymphocytes in the peripheral blood.     

Solution-Mediated Hybrid FAPbI3 Perovskite Quantum Dots for Over 15% Efficient Solar Cell

Organic–inorganic formamidinium lead triiodide (FAPbI₃) hybrid perovskite quantum dot (QD) is of great interest to photovoltaic (PV) community due to its narrow band gap, higher ambient stability, and long carrier lifetime. However, the surface ligand management of FAPbI₃ QD is still a key hurdle that impedes the design of high-efficiency solar cells. Herein, this study first develops a solution-mediated ligand exchange (SMLE) for preparing FAPbI₃ QD film with enhanced electronic coupling. By dissolving optimal methylammonium iodide (MAI) into antisolvent to treat the FAPbI₃ QD solution, the SMLE can not only effectively replace the long-chain ligands, but also passivate the A- and X-site vacancies. By combining experimental and theoretical results, this study demonstrates that the SMLE engineered FAPbI₃ QD exhibits lower defect density, which is beneficial for fabricating high-quality QD arrays with desired morphology and carrier transport. Consequently, the SMLE FAPbI₃ QD based solar cell outputs a champion efficiency of 15.10% together with improved long-term ambient storage stability, which is currently the highest reported value for hybrid perovskite QD solar cells. These results would provide new design principle of hybrid perovskite QDs toward high-performance optoelectronic application.