Microstructural Characterization and Mechanical Properties of Si3N4 Formed by Fused Deposition of Ceramics

We present processing (green and sintered), part shrinkage and warping, microstructural characterization, and mechanical properties of Si₃N₄ made by fused deposition of ceramics (FDC), using optical microscopy, scanning electron microscopy, and X-ray diffraction. The mechanical properties (fracture strength, fracture toughness, and Weibull modulus) are also reported. Proper FDC build parameters resulted in dense, homogeneous, near-net-shape Si₃N₄, with microstructures and mechanical properties similar to conventionally processed material. Mechanical properties are shown to be isotropic, while there is some degree of microstructural texturing (preferred β-Si₃N₄ grain orientation) in sintered components.     

Enhancing the performance of solar cells via luminescent down-shifting of the incident spectrum: A review

The application of a luminescent down-shifting (LDS) layer has been proposed as a method for improving the poor spectral response (SR) of solar cells to short-wavelength light. The LDS layer absorbs photons, typically in the 300-500 nm range, and re-emits them at a longer wavelength where the photovoltaic (PV) device exhibits a significantly better response. This paper reviews the progress in this area over the last three decades, starting from early experiments that yielded promising results but being limited by the luminescent materials available at the time, to modern materials that exhibit higher luminescent quantum efficiencies and better photostability. The candidate materials are considered and their potential is reviewed for a wide range of PV technologies. A particular opportunity is the ability to use the existing polymer encapsulation layer of certain PV technologies as a LDS layer as well.     

High Dietary Fat Exacerbates Weight Gain and Obesity in Female Liver Fatty Acid Binding Protein Gene-Ablated Mice

Since liver fatty acid binding protein (L-FABP) facilitates uptake/oxidation of long-chain fatty acids in cultured transfected cells and primary hepatocytes, loss of L-FABP was expected to exacerbate weight gain and/or obesity in response to high dietary fat. Male and female wild-type (WT) and L-FABP gene-ablated mice, pair-fed a defined isocaloric control or high fat diet for 12 weeks, consumed equal amounts of food by weight and kcal. Male WT mice gained weight faster than their female WT counterparts regardless of diet. L-FABP gene ablation enhanced weight gain more in female than male mice—an effect exacerbated by high fat diet. Dual emission X-ray absorptiometry revealed high-fat fed male and female WT mice gained mostly fat tissue mass (FTM). L-FABP gene ablation increased FTM in female, but not male, mice—an effect also exacerbated by high fat diet. Concomitantly, L-FABP gene ablation decreased serum β-hydroxybutyrate in male and female mice fed the control diet and, even more so, on the high-fat diet. Thus, L-FABP gene ablation decreased fat oxidation and sensitized all mice to weight gain as whole body FTM and LTM—with the most gain observed in FTM of control vs high-fat fed female L-FABP null mice. Taken together, these results indicate loss of L-FABP exacerbates weight gain and/or obesity in response to high dietary fat.     

Association between homeobox-containing gene MSX1 and the occurrence of limb deficiency

Impaired exercise capacity is a common finding in chronic obstructive pulmonary disease (COPD) patients. This reduction is not a simple consequence of airflow limitation. Peripheral muscle weakness, deconditioning and impaired gas exchange, were recognized as important contributors to exercise intolerance. In this overview, the contribution of peripheral muscle function and muscle training to exercise performance is discussed by means of three questions: 1) Is peripheral muscle dysfunction contributing to exercise limitation in COPD? 2) How do we measure peripheral muscle function? 3) Are peripheral muscle training modalities effective? At present, there is substantial evidence for peripheral muscle dysfunction. Both reduced force generating capacity as well as impaired muscle metabolism were observed and these findings contributed substantially to the reduced exercise capacity in COPD. Peripheral muscle strength measurements are feasible with mechanical or electronic devices and revealed muscle weakness in COPD patients. However, this weakness is not uniform for all muscle groups. Upper arm and leg muscles were more affected than hand muscles. This may, at least in part, be related to differences in the levels of inactivity between leg and hand muscles. In addition, muscle weakness is associated with impaired exercise capacity and symptoms of increased exertion during exercise. Endurance exercise training, i.e. cycling and treadmill walking, improved exercise capacity and was associated with alterations in muscle metabolism. Strength training of peripheral muscles showed increases in submaximal exercise performance and quality of life measures. These improvements were observed independently of the degree of airflow obstruction. The optimal training regimen (strength or endurance), and the muscle groups to be trained, remain to be determined.     

The metabolism of neutral lipids in the spur dogfish,Squalus acanthias

Cell free studies have shown that liver and intestine are the major sites of synthesis of triacyl glycerols inSqualus acanthias. The liver and to a lesser extent the intestine and stomach are major sites of wax ester synthesis. Muscle does not synthesize either triacyl glycerols or wax esters significantly. In vivo studies have shown that intravenously injected (³H) fatty alcohol is massively oxidized to (³H) fatty acid, the bulk of which appears in muscle. Liver appears to export both free fatty acids and triacyl glycerols to serum and thence to muscle. Free fatty acids, triacyl glycerols, wax esters and cholesteryl esters are all turned over within 48 hr inSqualus serum. The turnover of triacyl glycerols greatly exceeds the turnover of alkyl diacyl glycerols.     

Preservation of algal and higher plant ribosomal RNA integrity during extraction and electrophoretic quantitation

Isolation of high molecular weight ribosomal RNA from the wall-less alga Olisthodiscus luteus and the angiospermous plant Sauromatum guttatum is described. It has been found that a buffer which contains magnesium must be used to successfully isolate Olisthodiscus rRNA whereas the isolation of intact Sauromatum rRNA requires a buffer system containing a high amount of the chelator EDTA. Sauromatum but not Olisthodiscus extracts were contaminated with ribonuclease unless the inhibitor diethylpyrocarbonate was used during the ribonucleic acid extraction procedure. Nuclease levels were monitored by coincubating [3H]-labeled Escherichia coli ribosomal RNA with the experimental RNA samples. The effects of detergents on the isolation and quantitation of RNA are presented, and methods to avoid loss of highly thermolabile plant ribosomal RNA species are discussed.     

Fractionation and analysis of rat liver14CH3-lecithins labeled in vivo

The¹⁴CH₃-lecithins were biosynthesized by normal adult rats injected with¹⁴CH₃-methionine. About 20% of the dose was incorporated into liver lecithins. The¹⁴CH₃-lecithins were isolated by thin-layer chromatography. Separation of lecithins on AgNO₃-treated silica gel yielded lecithins containing a saturated fatty acid in combination with mainly one unsaturated fatty acid, namely, oleic, linoleic, eicosatrienoic, or arachidonic acid. These fractions were eluted with methanolic choline chloride, which prevented elution of AgNO₃. The lecithins, after extraction into petroleum ether, were analyzed for radioactivity and for fatty acid composition. Yields were about 75%, based upon fatty acids or radioactivity applied to the plate. Specific activities differed sharply between the fractions, and arachidonoyllecithins had the highest specific activity. The sum of the activities contributed by each of the fractions agreed well with the specific activity of total lecithins, indicating the recovery of intact lecithin molecules. The recovery of intact molecules allows this procedure to be used with lecithins containing any isotopic labels. The high specific activity of arachidonoyl-lecithins relative to the other fractions indicates a high degree of specificity in the metabolic reactions which lead to the formation of rat liver lecithins.