大学物理实验教学改革

对比于国内现状．介绍了国外大学在大学物理实验教学中一些比较有意义的做法,指出学习借鉴的必要性。     

沥青基球形活性炭对葡萄糖分子的吸附行为研究

考察了沥青基球形活性炭(PSAC)对葡萄糖分子的吸附行为,以探讨其治疗糖尿病的可能性.在不同吸附时间、不同活性炭用量及不同浓度等条件下,测定沥青基球形活性炭对葡萄糖分子的吸附量,根据Langmuir和Freundlich等温线方程对吸附等温线数据进行拟合,检验实验数据与方程的吻合度,确定方程参数.同时,研究了葡萄糖和α-淀粉酶在沥青基球形活性炭上的竞争吸附行为.结果表明,所选用沥青基球形活性炭对葡萄糖分子的吸附在5h内达到吸附平衡;葡萄糖的初始浓度为3g/时,平衡吸附量为71mg/g;平衡吸附量受葡萄糖分子空间构象的影响,且随葡萄糖浓度的升高而增加,吸附等温线数据与Langmuir方程吻合,说明该吸附为单分子层吸附.在葡萄糖分子和α-淀粉酶的共存环境下,沥青基球形活性炭对葡萄糖有较好的吸附选择性.     

Significantly enhanced rate capability in supercapacitors using carbide-derived carbons electrode with superior microstructure

Mesoporous carbide-derived carbons (CDC) with hierarchical pore structure were fabricated by chlorine etching of mesoporous titanium carbides. Their capacitive behaviors for electrochemical capacitor were investigated in comparison to those of purely microporous CDC. The as-prepared mesoporous CDC exhibited not only uniform micropores formed by leaching out titanium atoms but a 3-D mesoporous network inherited from their parent carbides. These mesoporous CDC could deliver a high specific capacitance of 120 F g⁻¹ in 1 M tetraethylammonium tetrafluoroborate dissolved in propylene carbonate. Moreover, they owned excellent frequency response and superior rate capability with capacitance retention ratio of 91% at current density of 10 A g⁻¹. A high energy density of 16.3 Wh kg⁻¹ was obtained even though power density was raised up to 4,300 W kg⁻¹. The distinctive capacitive performance of mesoporous CDC would be attributed to their superior microstructure, in which the uniform micropores contributed to high charge storage while the 3-D mesoporous network and nanometer-scaled dimension of particles facilitated ions transfer as well as shortened electrolyte diffusion distance.     

Sorption and desorption of radioselenium on red earth and its solid components

The effect of organic matter and iron oxides as solid components of the red earth on the retention of SeO₃ has been investigated by a batch technique and selective extraction method. The sorption and desorption isotherms of SeO₃ on the untreated red earth and the three treated soils were determined at 20°C, pH 6.8 or 7.2 and in the presence of 0.01M CaCl₂. It was found that the sorption-desorption hysteresis for untreated an treated soils is obvious and the clays play an important role in the sorption-desorption hysteresis, and that the retention of SeO₃ on red earth is attributed to the iron oxides to a great extent.     

Dynamic trapping and high-throughput patterning of cells using pneumatic microstructures in an integrated microfluidic device

Microfluidic trapping methods create significant opportunities to establish highly controlled cell positioning and arrangement for the microscale study of numerous cellular physiological and pathological activities. However, a simple, straightforward, dynamic, and high-throughput method for cell trapping is not yet well established. In the present paper, we report a direct active trapping method using an integrated microfluidic device with pneumatic microstructures (PμSs) for both operationally and quantitatively dynamic localization of cells, as well as for high-throughput cell patterning. We designed and fabricated U-shape PμS arrays to replace the conventional fixed microstructures for reversible trapping. Multidimensional dynamics and spatial consistency of the PμSs were optically characterized and quantitatively demonstrated. Furthermore, we performed a systematic trapping investigation of the PμSs actuated at a pressure range of 0 psi to 20 psi using three types of popularly applied mammalian cells, namely, human lung adenocarcinoma A549 cells, human hepatocellular liver carcinoma HepG2 cells, and human breast adenocarcinoma MCF-7 cells. The cells were quantitatively trapped and controlled by the U-shape PμSs in a programmatic and parallel manner, and could be opportunely released. The trapped cells with high viability were hydrodynamically protected by the real-time actuation of specifically designed umbrella-like PμSs. We demonstrate that PμSs can be applied as an active microfluidic component for large-scale cell patterning and manipulation, which could be useful in many cell-based tissue organization, immunosensor, and high-throughput imaging and screening.     

A simple method for the production of hydrogels based on hemicellulose in aqueous solution

A simple method of bamboo hemicellulose-based hydrogel with multiple responses properties was proposed employing glow discharge electrolysis plasma (GDEP). The network of hydrogels was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The mechanical properties, swelling, and stimuli responses were also investigated. The results showed that swelling ratio of hydrogel under 570 V and 90 s was 903.6 g/g. Too long discharge time or high discharge voltage indicated high compression stress and modulus. The hydrogels exhibited excellent sensitivity to pH and salts, which indicated their widely application such as adsorption, separation, and drug release systems.     

Sorption and desorption of radiocesium on calcareous soil: Results from batch and column investigations

The sorption and desorption of radiocesium on a calcareous soil from Jiuqian County of Gansu Province (China) were studied by using batch and column experiments. The sorption-desorption isotherms and the breakthrough curves, displacement curves on the whole soil and two treated soils were determined. Based on these results, it was found that the sorption and retention of cesium are mainly determined by the clay minerals, that the sorption-desorption hysteresis of cesium on the calcareous soil is obvious and that the organic matter has a little positive contribution and the calcium carbonate has a little negative contribution to the sorption of cesium on the whole soil. The results from batch experiments were consistent with the results from column experiments.     

On the transience and recurrence of Lamperti's random walk on Galton-Watson trees

Science China Mathematics - In a Galton-Watson tree generated by a supercritical branching process with offspring N and EN:= m > 1, the conductance assigned to the edge between the vertex x...     

Manufacturer cooperation in supplier development under risk

Supplier development involves efforts undertaken by manufacturing firms to improve their suppliers’ capabilities and performance. These improvement efforts can be targeted at a variety of areas such as quality management, product development, and cost reduction. Since supplier development requires investments on the part of the manufacturer, it is important to optimally allocate investment dollars among multiple suppliers to minimize risk while maintaining an acceptable level of return. This paper presents a set of optimization models that address this issue. We consider two scenarios: single-manufacturer and multiple suppliers (SMMS) and two-manufacturer and multiple suppliers (TMMS). In the SMMS case, we suggest optimal investments in various suppliers by effectively considering risk and return. The TMMS case investigates whether manufacturers with differing capabilities could gain risk reduction benefits from cooperating with each other in supplier development. Through illustrative applications, we identify conditions in which both cooperation and non-cooperation are beneficial for manufacturers. Under conditions of cooperation, we propose optimal investments for manufacturers to achieve high levels of risk reduction benefits.