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排序方式: 共有501条查询结果,搜索用时 31 毫秒
61.
Kucera SA McGinity JW Zheng W Shah NH Malick AW Infeld MH 《Drug development and industrial pharmacy》2007,33(7):717-726
The objective of this study was to investigate the influence of two proteins, albumin and type B gelatin, on the physical aging of EUDRAGIT® RS 30 D and RL 30 D coated theophylline pellets. The physicomechanical properties of sprayed films, thermal properties of cast films, influence of proteins on the zeta potential and particle size of the dispersion, and the release of proteins from cast films under simulated dissolution conditions were investigated. The release rate of theophylline decreased significantly over time from pellets coated with an acrylic dispersion containing 10% albumin when there was no acidification of the acrylic dispersion; however, when pellets were coated with an acidified EUDRAGIT®/albumin dispersion, the theophylline release rate was stable for dosage forms stored in the absence of humidity. The drug release rate was faster for pellets coated with acrylic dispersions containing 10% gelatin compared to the albumin-containing formulations. When sprayed films were stored at 40°C/75% RH, the water vapor permeability decreased significantly for both EUDRAGIT® films and those containing EUDRAGIT® and albumin; however, there was no significant change in this parameter when 10% gelatin was present. Albumin was released from the acrylic films when the pH of the dissolution media was below the isoelectric point of the protein while no quantitative release of gelatin was observed in pH 1.2 or 7.4 media. The effect of gelatin to prevent the decrease in drug release rate was due to stabilization in water vapor permeability of the film. Acidification of the polymeric dispersion resulted in electrostatic repulsive forces between albumin and the acrylic polymer, which stabilized the drug release rate when the dosage forms were stored in aluminum induction sealed containers at both 40°C/75% RH and 25°C/60% RH. 相似文献
62.
Khai Gene Leong Elyce Ozols John Kanellis Shawn S. Badal John T. Liles David J. Nikolic-Paterson Frank Y. Ma 《International journal of molecular sciences》2021,22(1)
Cyclophilins have important homeostatic roles, but following tissue injury, cyclophilin A (CypA) can promote leukocyte recruitment and inflammation, while CypD can facilitate mitochondrial-dependent cell death. This study investigated the therapeutic potential of a selective cyclophilin inhibitor (GS-642362), which does not block calcineurin function, in mouse models of tubular cell necrosis and renal fibrosis. Mice underwent bilateral renal ischemia/reperfusion injury (IRI) and were killed 24 h later: treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. In the second model, mice underwent unilateral ureteric obstruction (UUO) surgery and were killed 7 days later; treatment with 10 or 30 mg/kg/BID GS-642362 (or vehicle) began 1 h before surgery. GS-642362 treatment gave a profound and dose-dependent protection from acute renal failure in the IRI model. This protection was associated with reduced tubular cell death, including a dramatic reduction in neutrophil infiltration. In the UUO model, GS-642362 treatment significantly reduced tubular cell death, macrophage infiltration, and renal fibrosis. This protective effect was independent of the upregulation of IL-2 and activation of the stress-activated protein kinases (p38 and JNK). In conclusion, GS-642362 was effective in suppressing both acute kidney injury and renal fibrosis. These findings support further investigation of cyclophilin blockade in other types of acute and chronic kidney disease. 相似文献
63.
Harmful algal blooms are occurring in large river ecosystems and at the mouth of large rivers with increasing frequency. In lentic systems, the chemical and physical conditions that promote harmful algal blooms are somewhat predictable but tracking prevalence and conditions that promote harmful algal blooms in lotic systems is much more difficult. We captured two of the most extreme discharge years within the last 20 years occurring in the Upper Mississippi River, allowing a natural experiment that evaluated how major shifts in discharge drive environmental variation and associated shifts in phytoplankton. Statistical models describing significant environmental covariates for phytoplankton assemblages and specific taxa were developed and used to identify management‐relevant numeric breakpoints at which environmental variables may promote the growth of specific phytoplankton and/or cyanobacteria. Our analyses supported that potentially toxin‐producing cyanobacteria dominate under high phosphorus concentration, low nitrogen concentration, low nitrogen‐to‐phosphorus ratio, low turbulence, low flushing, adequate light and warm temperatures. Cyanobacteria dominated in 2009 when low discharge and low flushing likely led to optimal growth environments for Dolichospermum, Aphanizomenon and Microcystis. Rarely will a single factor lead to the dominance, but multiple positive factors working in concert can lead to cyanobacteria proliferation in large rivers. Certain isolated backwaters with high phosphorus, low nitrogen, warm water temperatures and low potential for flushing could benefit from increased connection to channel inputs to reduce cyanobacterial dominance. Numerous examples of this type of habitat currently exist in the Upper Mississippi River and could benefit from reconnection to channel habitats. 相似文献
64.
65.
Mahesh Mani Brandon M. Lane M. Alkan Donmez Shaw C. Feng Shawn P. Moylan 《国际生产研究杂志》2017,55(5):1400-1418
Additive manufacturing technologies are increasingly used in the development of new products. However, variations in part quality in terms of material properties, dimensional tolerances, surface roughness and defects limit its broader acceptance. Process control today based on heuristics and experimental data yields limited improvement in part quality. In an effort to identify the needed measurement science for real-time closed-loop control of additive manufacturing (AM) processes, this paper presents a literature review on the current AM control schemes, process measurements and modelling and simulation methods as it applies to the powder bed fusion process, though results from other processes are reviewed where applicable. We present our research findings to identify the correlations between process parameters, process signatures and product quality. We also present research recommendations on the key control issues to serve as a technical basis for standards development in this area. Complimentary details to this paper with summary tables, range of values, preliminary correlations and correlation figures can be accessed from a National Institute of Standards and Technology Report (http://nvlpubs.nist.gov/nistpubs/ir/2015/NIST.IR.8036.pdf). This paper is developed based on the report. 相似文献
66.
Johnny Guzman Alexandre Madureira Marcus Sarkis Shawn Walker 《Journal of scientific computing》2018,77(3):1736-1761
We derive error estimates for the piecewise linear finite element approximation of the Laplace–Beltrami operator on a bounded, orientable, \(C^3\), surface without boundary on general shape regular meshes. As an application, we consider a problem where the domain is split into two regions: one which has relatively high curvature and one that has low curvature. Using a graded mesh we prove error estimates that do not depend on the curvature on the high curvature region. Numerical experiments are provided. 相似文献
67.
Three-Dimensional Magnesia-Based Nanocrystal Assemblies Via Low-Temperature Magnesiothermic Reaction of Diatom Microshells 总被引:1,自引:0,他引:1
Ye Cai Shawn M. Allan Kenneth H. Sandhage Frank M. Zalar 《Journal of the American Ceramic Society》2005,88(7):2005-2010
A low-temperature (≤700°C) magnesiothermic reaction has been used for the first time to convert three-dimensional (3-D) silica-based diatom microshells into nanocrystalline magnesia-based replicas. Exposure of diatom microshells to Mg( g ) at only 650°–700°C resulted in the initial (direct) formation of MgO and Si nanocrystals (≤5 nm), that is, no intermediate magnesium silicate compounds were detected. Further reaction of Si with Mg( g ) led to the formation of Mg2 Si, and then a Mg–Si liquid that sweated away to yield free-standing, nanocrystalline MgO-based replicas. Such direct low-temperature magnesiothermic conversion of diatom microshells enables the synthesis of large numbers of 3-D nanocrystal assemblies with well-controlled morphologies for catalytic/chemical, biological, optical, and other applications. 相似文献
68.
William L. Porter Karen R. Conca Walter G. Yeomans Shawn Diotte Amy Lynch Jennifer Tate 《Journal of the American Oil Chemists' Society》2006,83(8):697-705
Inhibition of pyrazine formation by natural antioxidants and the foods containing them was measured in a microwaved glucose/glycine
model system. Inhibition of lipid oxidation by the same materials was assayed in both bulk and emulsion systems. Pyrazines
were determined by solid-phase micro extraction followed by GC. Lipid oxidation volatiles were assayed by polyamide fluorescence
produced by either a bulk oil display or a hematin- or 2,2′-azobis-(2-amidino=propane) dihydrochloride-accelerated lecithin
or fish oil emulsion. It was shown that (i) the inhibition of pyrazine formation depends on high concentrations of water-soluble
antioxidants; (ii) such antioxidants occur naturally in some foods and are usually polyphenols; (iii) during pyrazine inhibition,
oxidized polyphenols show enhanced nonfluorescing browning similar to enzymic browning products; (iv) monophenols, which structurally
cannot form quinone polymers on oxidation, inhibit pyrazines with less browning; (v) during the final pyrazine-forming phase
of the Maillard reaction, polyphenolics and reducing agents such as glutathione and ascorbic acid are partially consumed with
some nutritional loss; (vi) fruit powders of grape seed, grape skin, and red wine are highly pyrazine-inhibitory, steeped
blueberry strongly so, but plum purees are moderately pro-pyrazine, and freeze-dried vegetables strongly pro-pyrazine; and
(vii) black and green tea infusions are highly inhibitory, whereas spices have mixed effects. 相似文献
69.
Melt blending of polylactide and linear low‐density polyethylene (LLDPE) was performed in an effort to toughen polylactide. In addition, two model polylactide‐polyethylene (PLLA‐PE) block copolymers were investigated as compatibilizers. The LLDPE particle size and the impact resistance of binary and ternary blends were measured to determine the extent of compatibilization. For the amorphous polylactide (PLA), toughening was achieved only when a PLLA‐PE block copolymer was used as a compatibilizer. For the semicrystalline polylactide (PLLA), toughening was achieved in the absence of block copolymer. To decrease the variability in the impact resistance of the PLLA/LLDPE binary blend, as little as 0.5 wt % of a PLLA–;PE block copolymer was effective. The differences that were seen between the PLA and PLLA binary blends were investigated with adhesion testing. The semicrystalline PLLA did show significantly better adhesion to the LLDPE. We propose that tacticty effects on the entanglement molecular weight or miscibility of polylactide allow for the improved adhesion between the PLLA and LLDPE. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3757–3768, 2003 相似文献
70.
Utsey Shawn O.; Giesbrecht Norman; Hook Joshua; Stanard Pia M. 《Canadian Metallurgical Quarterly》2008,55(1):49
This study tested a sociocultural model of stress and coping in a sample of 215 African Americans. Psychological resources (optimism, ego resilience) were modeled as a "nested self" (S. E. Hobfoll, 2001), supported by social resources (family adaptability and cohesion) and cultural resources (racial pride, religiosity). Race-related stress was a significantly more powerful risk factor than stressful life events for psychological distress. Structural equation modeling results confirmed the hypotheses that psychological resources had a significant direct effect in minimizing psychological distress, and social resources had a significant stress-suppressing effect on race-related stress. Theoretical and practical implications for counseling psychologists are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献