Coupled flow and reaction during natural convection PCR

Polymerase chain reaction (PCR) in a microfluidic Rayleigh–Benard convection cell represents a promising route towards portable PCR for point-of-care uses. In the present contribution, the coupled fluid mechanics and heat transport processes are solved numerically for a 2-D flow cell. The resultant velocity and temperature fields serve as the inputs to a convection-diffusion-reaction model for the DNA amplification, wherein the reaction kinetics are modeled by Gaussian distributions around the conventional bulk PCR reaction temperatures. These evolution equations are integrated to determine the exponential growth rate of the double-stranded DNA concentration. The predicted doubling time is approximately 10–25 s, increasing with the Péclet number. This effect is attributed to low velocity, slow kinetics “dead zones” located at the center of the reactor. The latter observation provides an alternative rationalization for the use of loop-based natural convection PCR systems.     

Environmental barrier coatings using low pressure plasma spray process

Yb₂Si₂O₇/Si bilayer environmental barrier coatings (EBCs) on SiC ceramic substrate were produced by low pressure plasma spray (LPPS) process. Phase composition, microstructure, and thermal durability of LPPS Yb₂Si₂O₇/Si coating were investigated. XRD analysis indicated that the coating is mainly composed of Yb₂Si₂O₇ with ~15.5v% Yb₂SiO₅ phases. The LPPS EBCs have a dense microstructure with porosity less than 4%. Adhesion strength measurement indicated the LPPS EBCs have an average adhesion strength of 29.1 ± 0.8 MPa. Furnace cycle test (FCT) on the coatings in air at 1316°C was performed and the test ran for 900 cycles and there was no coating spallation/failure for LPPS Yb₂Si₂O₇/Si EBCs. The FCT results demonstrated the excellent thermal cycle durability of LPPS EBCs. Oxidation kinetics investigation of LPPS EBCs in flowing 90% H₂O (g)+10% air at 1316°C showed that the thermally grown oxide (TGO) growth rate is close to the oxidation rate of pure Si in dry air and is significantly lower than that in water vapor environment. The LPPS process is promising in making highly durable Yb2Si2O7-based dense EBCs by impeding diffusion and ingression of water vapor/O₂.     

遗传工程在食品上的应用

重组DNA的研究对食品工业有显著的作用,这是因为工程化的微生物能够合成众多的食品成份--酶、营养添加剂、调味品和其他物质。目前在食品发酵行业用以防腐和调味剂的一些酵母以及其他微生物从理论上讲是能够通过重组DNA技术有效地得到改良。     

Next Generation Thermal Barrier Coatings for the Gas Turbine Industry

The aim of this study is to develop the next generation of production ready air plasma sprayed thermal barrier coating with a low conductivity and long lifetime. A number of coating architectures were produced using commercially available plasma spray guns. Modifications were made to powder chemistry, including high purity powders, dysprosia stabilized zirconia powders, and powders containing porosity formers. Agglomerated & sintered and homogenized oven spheroidized powder morphologies were used to attain beneficial microstructures. Dual layer coatings were produced using the two powders. Laser flash technique was used to evaluate the thermal conductivity of the coating systems from room temperature to 1200 °C. Tests were performed on as-sprayed samples and samples were heat treated for 100 h at 1150 °C. Thermal conductivity results were correlated to the coating microstructure using image analysis of porosity and cracks. The results show the influence of beneficial porosity on reducing the thermal conductivity of the produced coatings.     

Aging effects on memory encoding in the frontal lobes.

Functional magnetic resonance imaging (fMRI) was used to compare frontal-lobe activation in younger and older adults during encoding of words into memory. Participants made semantic or nonsemantic judgements about words. Younger adults exhibited greater activation for semantic relative to nonsemantic judgements in several regions, with the largest activation in the left inferior frontal gyrus. Older adults exhibited greater activation for semantic judgments in the same regions, but the extent of activation was reduced in left prefrontal regions. In older adults, there was a significant association between behavioral tests of declarative and working memory and extent of frontal activation. These results suggest that age-associated decreases in memory ability may be due to decreased frontal-lobe contributions to the initial encoding of experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Critical parameters of percolation in metal-dielectric diamond-like composites of atomic scale

The stabilized atomic scale composites ‘diamond-like carbon-metal’ are virtually ideal metal-dielectric percolating systems. The metals may be introduced in the diamond-like dielectric during its growth in a combined plasma and molecular beam deposition process. The maximum metal concentration and temperature limiting the composite stability depend on the atom radius and metal-matrix interaction. The percolation threshold in ([Cr,Fe,Ni]-C) composites corresponds to the theoretical value X_c=0.25 with critical exponent t=1.44, while in (W–C), (Hf–C), (Nb–C) composites the critical parameters of percolation are X_c=0.10, 1.25≤t≤2.0. A possible reason for this giant shift of percolation threshold is a self-organized redistribution of relatively large metallic atoms.     

Chondrosarcoma of the short tubular bones of the hands and feet

OBJECTIVE: To report 12 cases of chondrosarcoma in a rare location, the short tubular bones of the hands and feet, as well as 12 cases of enchondroma in similar locations, emphasizing the radiologic and histopathologic features. DESIGN AND PATIENTS: All relevant cases that had both histologic slides and radiographs available were taken from the files of one orthopedic referral hospital and the personal files of one of the authors. A similar number of enchondroma cases was selected at random from the files. RESULTS AND CONCLUSIONS: One malignancy arose in a background of enchondromatosis, with all the others being solitary lesions. A pathologic diagnosis of malignancy is often difficult in the absence of radiologic signs of malignancy (cortical destruction with or without soft tissue extension). However, three cases were unusual in that the initial radiograph demonstrated a benign appearance. Another group of three malignancies was surprisingly indolent biologically. The treatment of choice is ray resection (or more limited amputation in a lesion of the middle or distal phalanx).