Development of a density-tapered capillary gas cell for laser wakefield acceleration.

A capillary gas cell for laser wakefield acceleration was developed with the aid of three-dimensional computational fluid dynamics simulations. The gas cell was specially designed to provide upward density tapering in the longitudinal direction, which is expected to suppress the dephasing problem in laser wakefield acceleration by keeping the accelerated electrons in the acceleration phase of the wake wave. The density-tapered capillary gas cell was fabricated by sapphire plates, and its performance characteristics were tested. The capillary gas cell was filled with a few hundred millibars of hydrogen gas, and a Ti:sapphire laser pulse with a peak power of 3.8 TW and a pulse duration of 40 fs (full width at half maximum) was sent through the capillary hole, which has a length of 7 mm and a square cross section of 350 × 350 µm2. The laser-produced hydrogen plasma in the capillary hole was then diagnosed two-dimensionally by using a transverse Mach-Zehnder interferometer. The capillary gas cell was found to provide an upward plasma density tapering in the range of 1018 cm-3-1019 cm-3, which has a potential to enhance the electron beam energy in laser wakefield acceleration experiments.

Protein expression and oxygen consumption rate of early postmortem mitochondria relate to meat tenderness.

Oxygen consumption rate (OCR) of muscle fibers from bovine semimembranosus muscle of 41 animals was investigated 3 to 4 h and 3 wk postmortem. Significant relations (P < 0.05) were found between OCR measurements and Warner-Bratzler shear force measurement. Muscles with high mitochondrial OCR after 3 to 4 h and low nonmitochondrial oxygen consumption gave more tender meat. Tender (22.92 ± 2.2 N/cm2) and tough (72.98 ± 7.2 N/cm2) meat samples (4 samples each), separated based on their OCR measurements, were selected for proteomic studies using mitochondria isolated approximately 2.5 h postmortem. Twenty-six differently expressed proteins (P < 0.05) were identified in tender meat and 19 in tough meat. In tender meat, the more prevalent antioxidant and chaperon enzymes may reduce reactive oxygen species and prolong oxygen removal by the electron transport system (ETS). Glycolytic, Krebs cycle, and ETS enzymes were also more abundant in tender meat

Lipid oxidation in minced beef meat with added Krebs cycle substrates to stabilise colour.

Krebs cycle substrates (KCS) can stabilise the colour of packaged meat by oxygen reduction. This study tested whether this reduction releases reactive oxygen species that may lead to lipid oxidation in minced meat under two different storage conditions. KCS combinations of succinate and glutamate increased peroxide forming potential (PFP, 1.18-1.32 mmol peroxides/kg mince) and thiobarbituric acid reactive substances (TBARS, 0.30-0.38 mg malondialdehyde (MDA) equivalents/kg mince) under low oxygen storage conditions. Both succinate and glutamate were metabolised. Moreover, under high oxygen (75%) storage conditions, KCS combinations of glutamate, citrate and malate increased PFP (from 1.22 to 1.29 mmol peroxides/kg) and TBARS (from 0.37 to 0.40 mg MDA equivalents/kg mince). Only glutamate was metabolised. The KCS combinations that were added to stabilise colour were metabolised during storage, and acted as pro-oxidants that promoted lipid oxidation in both high and low oxygen conditions.

Mitochondrial oxygen consumption in permeabilized fibers and its link to colour changes in bovine M. semimembranosus muscle.

Animal and muscle characteristics were recorded for 41 cattle. The oxygen consumption rate (OCR) of M. semimembranosus was measured between 3.0-6.4h post mortem (PM3-6) and after 3 weeks in a vacuum pack at 4°C. Colour change measurements were performed following the 3 weeks using reflectance spectra (400-1,100 nm) and the colour coordinates L, a and b, with the samples being packaged in oxygen permeable film and stored at 4°C for 167 h. Significant individual animal differences in OCR at PM3-6 were found for mitochondrial complexes I and II. OCR of complex I declined with increased temperature and time PM, while residual oxygen-consuming side-reactions (ROX) did not. OCR of stored muscles was dominated by complex II respiration. A three-way regression between samples, colour variables collected upon air exposure and OCR of 3 weeks old fibres revealed a positive relationship between OCR and complex II activity and also between OCR and OCR(ROX). The presence of complex I and ß-oxidation activities increased metmyoglobin formation.

Glycoconjugates in normal human kidney. A histochemical study using 13 biotinylated lectins.

The avidin-biotin-peroxidase complex technique was used with 13 lectins to study the glycoconjugates of normal human renal tissue. The evaluated lectins included Triticum vulgaris (WGA), Concanavalin ensiformis (ConA), Phaseolus vulgaris leukoagglutinin and erythroagglutinin (PHA-L and PHA-E), Lens culinaris (LCA), Pisum sativum (PSA), Dolichos biflorus (DBA), Glycine max (SBA), Arachis hypogaea (PNA), Sophora japonica (SJA), Bandeiraea simplicifolia I (BSL-I), Ulex europaeus I (UEA-I) and Ricinus communis I (RCA-I). Characteristic and reproducible staining patterns were observed. WGA and ConA stained all tubules; PHA-L, PHA-E, LCA, PSA stained predominantly proximal tubules; DBA, SBA, PNA, SJA and BSL-I stained predominantly distal portions of nephrons. In glomeruli, WGA and PHA-L stained predominantly visceral epithelial cells; ConA stained predominantly basement membranes and UEA-I stained exclusively endothelial cells. UEA-I also stained endothelial cells of other blood vessels and medullary collecting ducts. Sialidase treatment before staining caused marked changes of the binding patterns of several lectins including a focal loss of glomerular and tubular staining by WGA; an acquired staining of endothelium by PNA and SBA; and of glomeruli by PNA, SBA, PHA-E, LCA, PSA and RCA-I. The known saccharide specificities and binding patterns of the lectins employed in this study allowed some conclusions about the nature and the distribution of the sugar residues in the oligosaccharide chains of renal glycoconjugates. The technique used in this report may be applicable to other studies such as evaluation of normal renal maturation, classification of renal cysts and pathogenesis of nephrotic syndrome. The observations herein reported may serve as a reference for these studies.