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61.
We have studied the effect of retinoic acid on the expression of the neurotrophin receptors trkA, trkC, and p75 by neuroblasts and neurons at different axial levels along the embryonic mouse paravertebral sympathetic chain. In dissociated cultures of sympathetic neuroblasts, retinoic acid inhibited the developmental increase in trkA mRNA expression and the developmental decrease in trkC mRNA expression that normally occurs in these cells but did not affect p75 mRNA expression. At higher concentrations, retinoic acid also increased the proliferation of sympathetic neuroblasts. After sympathetic neuroblasts became postmitotic, retinoic acid no longer affected receptor expression. Studies with retinoic acid receptor agonists and antagonists indicated that the effects of retinoic acid on neurotrophin receptor expression were mediated mainly by alpha retinoic acid receptors, not beta or gamma receptors. The observation that alpha-antagonists increased trkA mRNA expression in intact sympathetic ganglion explants suggests that endogenous retinoic acid is a physiological regulator of trkA receptor expression. 相似文献
62.
R. Lemus-Mondaca M. Miranda A. Andres Grau V. Briones R. Villalobos 《Drying Technology》2013,31(10):1105-1115
The effect of osmotic pretreatment on the mass transfer kinetics and quality of dried rehydrated Chilean papaya was researched. Osmotic treatments were sucrose solutions of 40, 50, and 60% w/w and dried at 60°C; non-pretreated samples were dried at different temperatures (40, 60, and 80°C). Quality parameters were analyzed: proximal composition, rehydration ratio, water-holding capacity, color, vitamin C content, firmness, and microstructure. Non-pretreated samples showed a clear turgor loss, color loss. and low ascorbic acid retention when rehydrated. Osmotic pretreatment improved the quality of rehydrated papayas, showing higher ascorbic acid retention and best firmness and color. Microstructure is better preserved in the pretreated papayas than in the non-pretreated samples, although this difference is minimal. 相似文献
63.
N. Chawla U. Habel Y. -L. Shen C. Andres J. W. Jones J. E. Allison 《Metallurgical and Materials Transactions A》2000,31(2):531-540
The effect of matrix microstructure on the stress-controlled fatigue behavior of a 2080 Al alloy reinforced with 30 pct SiC
particles was investigated. A thermomechanical heat treatment (T8) produced a fine and homogeneous distribution of S′ precipitates,
while a thermal heat treatment (T6) resulted in coarser and inhomogeneously distributed S′ precipitates. The cyclic and monotonic
strength, as well as the cyclic stress-strain response, were found to be significantly affected by the microstructure of the
matrix. Because of the finer and more-closely spaced precipitates, the composite given the T8 treatment exhibited higher yield
strengths than the T6 materials. Despite its lower yield strength, the T6 matrix composite exhibited higher fatigue resistance
than the T8 matrix composite. The cyclic deformation behavior of the composites is compared to monotonic deformation behavior
and is explained in terms of microstructural instabilities that cause cyclic hardening or softening. The effect of precipitate
spacing and size has a significant effect on fatigue behavior and is discussed. The interactive role of matrix strength and
SiC reinforcement on stress within “rogue” inclusions was quantified using a finite-element analysis (FEA) unit-cell model. 相似文献
64.
Y.O. Barmenkov A.V. Kir'yanov J. Mora J.L. Cruz M.V. Andres 《Photonics Technology Letters, IEEE》2005,17(1):28-30
We present a compact diode-pumped single-frequency single-polarization erbium-doped fiber laser with fiber Bragg gratings (FBGs) written in the active fiber itself. The single-polarization regime was obtained by applying uni-axial stress to one of the two FBGs forming the cavity. The laser is shown to operate in two regimes-quasi-continuous-wave regime with a few-percent of modulation in the output power and a giant-pulse regime accessible under sinusoidal pump modulation. 相似文献
65.
66.
Seddik Karim G. Kwasinski Andres Liu K. J. Ray 《Mobile Computing, IEEE Transactions on》2010,9(2):270-287
A key challenge in the design of real-time wireless multimedia systems is the presence of fading coupled with strict delay constraints. A very effective answer to this problem is the use of diversity achieving techniques to overcome the fading nature of the wireless channels caused by the mobility of the nodes. The mobility of the nodes gives rise to the need of cooperation among the nodes to enhance the system performance. This paper focuses on comparing systems that exhibit diversity of three forms: source coding diversity, channel coding diversity, and user cooperation diversity implemented through multihop or relay channels with amplify-and-forward or decode-and-forward protocols. Commonly used in multimedia communications, performance is measured in terms of the distortion exponent, which measures the rate of decay of the end-to-end distortion at asymptotically high signal-to-noise ratio (SNR). For the case of repetition coding at the relay nodes, we prove that having more relays is not always beneficial. For the general case of having a large number of relays that can help the source using repetition coding, the optimum number of relay nodes that maximizes the distortion exponent is determined in this paper. This optimum number of relay nodes will depend on the system bandwidth as well as the channel quality. The derived result shows a trade-off between the quality (resolution) of the source encoder and the amount of cooperation (number of relay nodes). Also, the performances of the channel coding diversity-based scheme and the source coding diversity-based scheme are compared. The results show that for both relay and multihop channels, channel coding diversity provides the best performance, followed by the source coding diversity. 相似文献
67.
Biosecurity Measures to Control Salmonella and Other Infectious Agents in Pig Farms: A Review
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Victor M. Andres Rob H. Davies 《Comprehensive Reviews in Food Science and Food Safety》2015,14(4):317-335
Salmonellosis is the 2nd most common cause of human bacterial food poisoning and can be acquired from meat or eggs, either via direct consumption or cross‐contamination in the kitchen. The European Commission has set the criteria to control Salmonella infections within the poultry sector and it is proposed that the swine sector should follow. Pork is considered, after eggs, the major source of infection in humans in the EU, with Salmonella typhimurium, including monophasic strains, being frequently implicated. Good control measures at the farm level are likely to correspond with lower prevalence of Salmonella infection and, subsequently, a reduction of cross‐contamination of carcasses processed at the slaughterhouse and a reduction in human salmonellosis. This review focuses on biosecurity measures in pig farms that can help to control important pig diseases at the same time as reducing the within‐herd prevalence of Salmonella. This information is likely to provide an economic incentive for farmers to apply improved general standards of farm biosecurity and hygiene management that would have a positive impact in food safety. 相似文献
68.
Andres A. Amell Hernando A. YepesFrancisco J. Cadavid 《International Journal of Hydrogen Energy》2014
The laminar burning velocity of syngas mixtures has been studied by various researches. However, most of these studies have been conducted in atmospheric conditions at sea level. In the present study, the effect of sub atmospheric pressure was evaluated on the laminar burning velocity for a mixture of H2, CO and N2 (20:20:60 vol%) in real sub atmospheric condition. The measurements was conducted in an altitude of 2130 m.a.s.l (0.766 atm) and 21 m.a.s.l (0.994 atm) to evaluate the effect of pressure, the temperature and relative humidity were controlled using an air conditioning unit and was maintained in 295 ± 1 K and 62.6 ± 2.7% respectively. The Flames were generated using contoured slot-type nozzle burner, and an ICCD camera was used to capture chemiluminescence emitted by OH∗-CH∗ radicals present in the flame and thus obtain the flame front and determinate the laminar burning velocity using the angle method. The experimental results were compared with numerical calculations, conducted using the detailed mechanisms of Li et al. and the GRI-Mech 3.0. It was found that the laminar burning velocity increases at lower pressure, for an equivalence ratio of 1.1, the laminar burning velocity increases by almost 23% respect to the sea level conditions. 相似文献
69.
The flow in a recess of a hydrostatic journal bearing is studied in detail. The Navier-Stokes equations for the laminar flow of an incompressible liquid are solved numerically in a two-dimensional plane of a typical bearing recess. Pressure- and shear-induced flows, as well as a combination of these two flow conditions, are analyzed. Recess friction, pressure-ram effects at discontinuities in the flow region, and film entrance pressure loss effects are calculated. Entrance pressure loss coefficients over a forward-facing step are presented as functions of the mean flow Reynolds number for pure-pressure and shear-induced laminar flows. 相似文献
70.
Aqueous solutions of poly(vinyl alcohol) and poly(vinyl pyrrolidone) are blended and films are produced by casting method with the further intention of being used as bio‐materials with latent medical application. Glutaraldehyde, 4,4′‐diazido‐2,2′‐stilbenedisulfonic acid disodium salt tetra‐hydrate are used as crosslinker agents, whereas lactic acid is the plasticizer in the blend. The obtained films are characterized by differential scanning calorimetry (DSC), mechanical properties, swelling and solubility behavior. DSC measurements show that the blends exhibit a single glass transition temperature indicating that they are miscible, even in the presence of the plasticizer and crosslinker agents. By the combination of all mentioned additives, a relevant enhancement of the swelling is observed, accompanied by a stabilization of the solubility during the tested time. Finally, mechanical properties show an appropriate performance in the studied parameters. As a consequence, the obtained films could be suitable for use as medium or long‐term implants. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献