Mathematical model for mixing reactants in a capillary microreactor by transverse diffusion of laminar flow profiles

Transverse diffusion of laminar flow profiles (TDLFP) was recently suggested as a generic approach for mixing reactants inside a capillary microreactor. Conceptually, solutions of reactants are injected inside the capillary by high pressure as a series of consecutive plugs. Because of the laminar nature of the flow inside the capillary, the nondiffused plugs have parabolic profiles with predominantly longitudinal interfaces between the plugs. After the injection, the reactants are mixed by transverse diffusion across the longitudinal interfaces. TDLFP-based mixing is still in its infancy as only the principle was proved. Here, we develop the theory of TDLFP and introduce a dimensionless parameter, York number, which can be used in predicting the quality of TDLFP-based mixing. The theory uses a single simplifying assumption that the longitudinal diffusion is negligible; this assumption is readily satisfied. We then develop a numerical model of TDLFP and use it to simulate the concentration profiles of three reactants mixed by TDLFP in the capillary. The correlation between the York number and quality of mixing is analyzed. Two ways of improving the quality of TDLFP-based mixing are suggested and studied: (i) increasing the longitudinal interface between the plugs by a long last plug of a solvent and (ii) "shaking" the injected reactants by a series of alternating negative and positive pressure pulses. The developed theory and computational simulation of TDLFP will stimulate the practical use of capillary microreactors.     

便携式医疗设计中的无线发展趋势和解决方案

医疗产业渴望拥有更多的功能和互操作性,当然还需要无线接口,本文将探讨无线发展趋势及其挑战,包括在采用无线模块时,现在设计中的标准和频率以及功率考虑事项。单节可充电电池的应用将会是通用终端应用的产品,     

The Formation of a 12-Hydroxystearic Acid/Vegetable Oil Organogel Under Shear and Thermal Fields

External laminar oscillatory shear applied during crystallization in combination with different temperature fields was used to modify the microstructure and physical properties of edible oil organogels. Crystallization at a high cooling rate (30 °C/min) resulted in a spherulitic microstructure with a higher oil-binding capacity, lower storage modulus and lower yield stress compared with a material (with a fibrillar microstructure) crystallized at a slow cooling rate (1 °C/min). The application of an oscillatory shear resulted in the formation of novel microstructures depending on the cooling regime used. The application of an oscillatory shear (strain > 500 % and frequency = 1 Hz) resulted in the thickening of fibers observed in the slow-cooled material and an increased incidence of spherulite nucleation in the rapidly cooled material. Increasing the frequency of the oscillatory shear applied did not change the microstructure for the slow-cooled gel but further increased the incidence of nucleation for the rapidly cooled gel. The application of controlled-strain oscillatory shear to the crystallizing gel at either cooling rates resulted in an oily and very soft, paste-like material. This material had a lower storage modulus and poorer oil-binding capacity compared with the same gel crystallized statically. Reduction of the oscillatory strain from a maximum of 1500 to 500 % moderately mitigated the loss of mechanical properties and oil-binding capacity although these properties were in no way comparable to those obtained from static crystallization. The study shows that the application of oscillatory shear and different cooling regimes can be used to tailor a crystalline organogel. However, the application of continuous shear must be done with care as application of excessive shear can result in a complete breakdown in gel structure and large amounts of oil loss.     

Chemical Reactivity Factor for Metallic Sulfide Lubricants

Wear data for molybdenum lubricated with various metallic sulfides have been analyzed. It is found that wear life in the Falex Lubricant Tester depends greatly upon chemical reactions, which apparently form MoS₂ in situ. With the possible exception of WS₂, none of the metal sulfides except MoS₂ are lubricants per se. Water solubility as an index of reactivity shows that compounds exhibiting pronounced water solubility function as more effective lubricants for molybdenum than less soluble compounds. There is also some evidence that wear life of alloy pins in the Falex wear test correlate with performance characteristics of ball bearings in high-speed bearing tests for several different alloy retainer materials.     

An energy approach for predicting springback of metal sheets after double-curvature forming, Part I: axisymmetric stamping

In our previous study (Xue P, Yu TX, Shu E. International Journal of Materials Processing Technology 1999; 89-90:65-71.), based on the membrane theory of shells of revolution and an energy method a mechanics model and corresponding analytical procedure have been proposed to predict springback of circular and square metal sheets after a double-curvature forming operation. The strain hardening of the material is incorporated into the mechanics model. In the present paper, the method is extended to the cases, in which bending effect, as well as bending-and-unbending effect are taken into account. It is shown that the procedure developed is capable of quantitatively predicting the strain distribution and springback of metal sheets after axisymmetric stamping with a relatively minor effort of calculation and a good accuracy. The effect of stretching force applied at the edge of the plate on springback is also considered. Excellent agreement is found between the theoretical prediction of springback and experiment results.     

The impact of the Veterans Health Administration (VHA) reorganization on psychology programs: A survey of VHA psychology leaders.

Because the Veterans Health Administration (VHA) is the nation's largest health care system and employer and trainer of psychologists, changes in VHA psychology have implications for the rest of the profession. A national survey of 127 VHA psychology leaders (91% response rate) documented that many psychologists now are managed by a psychiatrist, deliver more outpatient services, and do less personality testing. In the context of a 10% reduction in psychology staffing, morale is rated lower than 2 years earlier. Diversified professional roles are associated with higher status of psychology and management support for mental health programs. Psychologists need to understand and respond adaptively to the organizational and economic forces affecting their practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Supported Metallocene Catalysts

Single-site olefin polymerization catalysts have been researched extensively and are now achieving wide acceptance in the polyolefin industry. To achieve commercial significance in the majority of today's commercial processes, these soluble catalysts must be immobilized on a carrier. The challenges of supporting metallocene catalysts have been addressed in many creative ways and are the topic of this paper.     

Pyrene Tags for the Detection of Carbohydrates by Label-Assisted Laser Desorption/Ionisation Mass Spectrometry**

Matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) is widely used for the analysis of biomolecules. Label-assisted laser desorption/ionisation mass spectrometry (LALDI-MS) is a matrix-free variant of MALDI-MS, in which only analytes covalently attached to a laser desorption/ionisation (LDI) enhancer are detected. LALDI-MS has shown promise in overcoming the limitations of MALDI-MS in terms of sample preparation and MS analysis. In this work, we have developed a series of pyrene-based LDI reagents (LALDI tags) that can be used for labelling and LALDI-MS analysis of reducing carbohydrates from complex (biological) samples without the need for additional chemical derivatisation or purification. We have systematically explored the suitability of four pyrene-based LDI enhancers and three aldehyde-reactive handles, optimised sample preparation, and demonstrated the use of LALDI tags for the detection of lactose. We have also exemplified the potential of LALDI tags for labelling carbohydrates in biological samples by direct detection of lactose in cow's milk. These results demonstrate that LALDI-MS is a promising technique for the analysis of reducing carbohydrates in biological samples, and pave the way for the development of LALDI-MS for glycomics and diagnostics.