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51.
Viral quasispecies are closely related (but nonidentical) mutant and recombinant viral genomes subjected to continuous genetic variation, competition, and selection. Quasispecies structure and dynamics of replicating RNA enable virus populations to persist in their hosts and cause disease. We review mechanisms of viral persistence in cells, organisms, and populations of organisms and suggest that the critical interplay between host and viral influences (including in some cases the quasispecies organization) is the main driving force for long-term survival of viruses in nature. 相似文献
52.
The aim of this study was to assess the influence of bioflavonoids from the radix of Scurellaria baicalensis on the level of lipids, via the determination of the concentrations of triglycerides, total cholesterol and high-density lipoprotein (HDL) cholesterol in the plasma of laboratory rats fed high-fat and high-cholesterol diets, and via the calculation of their atherogenic index. We also studied the influence of bioflavonoids on their physical development by measuring the increase in their body mass and liver mass. The rats were fed a diet with a 15% content of fresh or oxidized lard or sunflower oil, along with 0.5% added cholesterol. 0.05% S. baicalensis radix extract was added to the diet of half of the rats as the source of bioflavonoids. In the group of rats fed a diet containing oxidized oil we observed a significantly lower increase in body mass (15.5 +/- 7.6 g/4 weeks/rat) than that observed for the control rats (77.0 +/- 15.7 g/4 weeks/rat). The addition of S. baicalensis radix extract to the diet raised the increase in body mass in the groups receiving oil as the source of fat; those receiving fresh oil had a 40% increase, and those receiving oxidized oil showed a 300% increase relative to the appropriate controls. In all the groups of rats fed a diet with bioflavonoids added, a beneficial decrease in the plasma triglyceride content was observed relative to the appropriate controls. In the plasma of rats on a diet containing the extract and fresh or oxidized oil or fresh lard, we observed a beneficial reduction in the total cholesterol level relative to the appropriate controls. The atherogenic index was higher for the group of animals fed with fresh lard than for those fed with fresh oil, and higher for those fed with oxidized oil than for those fed with oxidized lard. The addition of bioflavonoids to the diet beneficially reduced the atherogenic index value in the group fed with fresh oil, and increased its value in the group fed with oxidized lard. 相似文献
53.
Jadwiga N. Bilchak Guillaume Caron Marie-Pascale Ct 《International journal of molecular sciences》2021,22(9)
Spinal cord injury (SCI) leads to numerous chronic and debilitating functional deficits that greatly affect quality of life. While many pharmacological interventions have been explored, the current unsurpassed therapy for most SCI sequalae is exercise. Exercise has an expansive influence on peripheral health and function, and by activating the relevant neural pathways, exercise also ameliorates numerous disorders of the central nervous system (CNS). While the exact mechanisms by which this occurs are still being delineated, major strides have been made in the past decade to understand the molecular underpinnings of this essential treatment. Exercise rapidly and prominently affects dendritic sprouting, synaptic connections, neurotransmitter production and regulation, and ionic homeostasis, with recent literature implicating an exercise-induced increase in neurotrophins as the cornerstone that binds many of these effects together. The field encompasses vast complexity, and as the data accumulate, disentangling these molecular pathways and how they interact will facilitate the optimization of intervention strategies and improve quality of life for individuals affected by SCI. This review describes the known molecular effects of exercise and how they alter the CNS to pacify the injury environment, increase neuronal survival and regeneration, restore normal neural excitability, create new functional circuits, and ultimately improve motor function following SCI. 相似文献
54.
The X-ray structures of polycrystalline barium hollandite with cesium partially substituting for barium (viz [BaxCsy] [Al2x+yTi8 ? 2x ? y]O16) have been determined using the Rietveld refinement technique. Electron microprobe results indicate that the level of cesium substitution is constrained by the condition that the total volume occupied per unit cell by the cesium and barium ions remains substantially constant. X-ray refinement revealed that the structural parameters defining the positions of the titanium, aluminium and oxygen ions are not affected greatly by cesium substitution. The only significant change occurs in the parameter z which defines the average Cs/Ba position. This increases with the level of cesium indicating that these ions tend to occupy a more central location with respect to their coordinating oxygen ions. An analysis of the (Cs/Ba)-O bond lengths suggests a limit of structural stability corresponding to 0.25 cesium ions per unit cell. 相似文献
55.
Jadwiga Bucheska 《应用聚合物科学杂志》1995,58(10):1901-1911
The grafting of polyacrylamide (PAM) onto PA6 knitted fabric in aqueous systems under the atmosphere of nitrogen or air was examined. The grafting process was initiated by oxidation with air oxygen, forming hydroperoxide groups. Effects of time and temperature of oxidation and of the grafting conditions, such as concentration of monomer, temperature, and time, on the rate and degree of grafting were determined. The optimum grafting conditions, ensuring the minimum amount of homopolymer, were found (oxidation temperature 413 K, oxidation time 10 min, grafting temperature under nitrogen 353–373 K, grafting time 1 h, monomer concentration 0.7 mol/dm3). The activation energy of the grafting under nitrogen and air at 313–373 K was found to be 25.74 and 42.25 kJ/mol, respectively. The hydroscopicity, capillarity, disperse dye absorption, and electrical resistance of the modified PA-6 fabrics were determined. Some improvement of these properties was observed, depending on the degree of PAM grafting and the type of posttreatment with hydrazine and 3-bromopropionic acid. © 1995 John Wiley & Sons, Inc. 相似文献
56.
Salazar Laura Teresa Hernandez; Laska Matthias; Luna Ernesto Rodriguez 《Canadian Metallurgical Quarterly》2003,117(6):1142
Using a conditioning paradigm, the authors investigated the olfactory sensitivity of 3 spider monkeys (Ateles geoffroyi) for a homologous series of aliphatic esters (ethyl acetate to n-octyl acetate) and isomeric forms of some of these substances. With all odorants, the monkeys significantly discriminated concentrations below 1 ppm from the odorless solvent, and in several cases, individual monkeys even demonstrated thresholds below 1 ppb. The results showed spider monkeys to have a high olfactory sensitivity for aliphatic esters, which for the majority of substances matches or even is better than that of species such as the rat, the mouse, or the dog. These findings support the assumption that between-species comparisons of neuroanatomical features are poor predictors of olfactory performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
57.
Iwona Konopka ucja Fornal Danuta Abramczyk Jadwiga Rothkaehl & Daniela Rotkiewicz 《International Journal of Food Science & Technology》2004,39(1):11-20
Forty‐two Polish wheat flour were used to establish correlation coefficients between protein content, Zeleny test, falling number value, amylograph viscosity, farinograph water absorption, bread volume and rheological properties of dough, as shown by use of a extrusion chamber and alveograph. The equations expressing the changes of bread volume and flour water absorption as a function of significantly correlated parameters were calculated. The correlations and their significance depended on wheat quality and the alveographic parameters were significantly correlated with the dough extrusion parameters. The dough extrusion parameters were significantly correlated only with the water absorption of soft wheats. The dough rheological tests were correlated to a greater extent with the values of the Zeleny test than to the protein content. The prediction of the bread volume as a function of flour quality parameters and dough rheological properties was best done by grouping wheat varieties into specific qualitative classes. 相似文献
58.
Thermal barrier coatings (TBC) of yttria stabilized zirconia were deposited on the γ-TiAl based alloy Ti–45Al–8Nb (at.%) using electron-beam physical vapor deposition. The bond coats used were 10 μm thick intermetallic Ti–Al–Cr layers with additions of the reactive elements Y and Zr produced by magnetron sputtering. Cyclic oxidation tests at 900 and 1,000 °C in air revealed excellent oxidation resistance of the Ti–Al–Cr–Y bond coat associated with the precipitation of Y-rich particles in the thermally grown alumina scale as well as in the intermetallic layer. A less protective behavior was found with the zirconium containing bond coat. Lifetimes exceeding 1,000 1-h cycles were determined for both TBC systems at 900 °C. Edge chipping of the zirconia topcoat occurred at 1,000 °C. As observed by cross-sectional examination, a continuous alumina scale was still present on the samples with Ti–Al–Cr–Y bond coat, whereas the Ti–Al–Cr–Zr layer was severely degraded and a thick mixed oxide scale formed after 1,000 cycles at 1,000 °C. 相似文献
59.
HeinrichHora CangYu HeXiantu ZhangJie F.Osman J.Badziak F.P.Boody S.Gammino R.Hoepfl K.Jungwirth B.Kralikova J.Kraska L.Laska LiuHong G.H.Miley P.Parys PengHansheng M.Pfeifer K.Rohlena J.Skala Z.Skladanowski L.Torrisi J.Ullschmied J.Wolowski ZhangWeiyan 《等离子体科学和技术》2004,6(1):2172-2178
The discovery of the essential difference of maximum ion energy for TW-ps laser plasma interaction compared with the 100 ns laser pulses led to the theory of a skin layer model where the control of prepulses suppressed the usual relativistic self-focusing.The subsequent generation of two nonlinear force driven blocks has been demonstrated experimentally and in extensive numerical studies where one block moves against the laser light and the other block into the irradiated target.These blocks of nearly solid state density DT plasma correspond to ion beam current densities exceeding 10^10 A/cm^2 where the ion velocity can be chosen up to highly relativistic values.Using the results of the expected ignition of DT fuel by light ion beams,a selfsustained fusion reaction front may be generated even into uncompressed solid DT fuel similar to the Nuckolls-Wood scheme where 10 kJ laser pulses produce 100 MJ fusion energy.This new and simplified scheme of laser-ICF needs and optimisation of the involved parameters. 相似文献
60.
Emilia Smiechowicz Piotr Kulpinski Barbara Niekraszewicz Jadwiga Bemska Jerzy Morgiel 《Coloration Technology》2014,130(6):424-431
Silver nanoparticles were embedded into cellulose fibres using N‐methylmorpholine N‐oxide as a direct cellulose solvent that was also the system from which silver nanoparticles were generated. The process of generation of silver nanoparticles in the N‐methylmorpholine N‐oxide enables the properties of cellulose fibres to be modified without any additional reducing agent, which makes this process more environmentally friendly. By varying the reaction time of the precursor with the N‐methylmorpholine N‐oxide, a range of nanoparticle sizes was obtained. The fibres contain the same concentration of silver, but, on account of the varying morphology of the nanoparticles, they show a range of colour shades. The primary aim of this study was to show how temperature and reaction time affect the basic parameters of the obtained nanoparticles (shape, size, and distribution in the polymer matrix of fibres), which consequently influences the colour of the modified cellulose fibres. Nanoparticles were characterised by dynamic light scattering and transmission electron microscopy methods, while the fibre hues were estimated by colorimetric analysis. Trichromatic coordinates of colour x, y were delineated, and the colour was identified by positioning the x and y values in the CIE chromaticity diagram. It is noted that many parameters, especially the diameter and shape of the silver nanoparticles, influence the colour of the fibre obtained. 相似文献