337 research outputs found
AN EMERGING NICHE FOR FIRMS IN WESTERN REGIONS OF CHINA IN THE PERIOD OF TRANSITION ECONOMY TO DEVELOP RENEWABLE ENERGY INDUSTRY: A PERSPECTIVE FROM INSTITUTIONAL ENTREPRENEURSHIP
This paper explores the enabling role of institutional entrepreneurship in western regions of China in the context of transition economy. Considering the widely emerging concerns to develop environment friendly technologies and industries, which could contribute to the achievement of sustainable development both economically and ecologically, this paper proposes that western regions are standing in front of a great opportunity by stimulating development of the emerging renewable energy industry. In this process, institutional entrepreneurships under the massive institutional change, i.e, the Grand Western Development Program, could have the “path defining” effect through leveraging the emerging great niche and redirecting western regions to an innovative path instead of following the traditional resource-based development path. Key words: Western Regions, China, transition economy, renewable energy industry, institutional entrepreneurshi
Low-energy, Mobile Grain Boundaries in Magnesium
The strong basal texture that is commonly developed during the rolling of magnesium alloy and can even increase during annealing motivates atomic-level study of dislocation structures of both \u3c0001\u3e tilt and twist grain boundaries (GBs) in Magnesium. Both symmetrical tilt and twist GBs over the entire range of rotation angles θ between 0° and 60° are found to have an ordered atomic structure and can be described with grain boundary dislocation models. In particular, 30° tilt and twist GBs are corresponding to energy minima. The 30° tilt GB is characterized with an array of Shockley partial dislocations bp:- bp on every basal plane and the 30° twist GB is characterized with a stacking faulted structure. More interesting, molecular dynamics simulations explored that both 30° tilt and twist GBs are highly mobile associated with collective glide of Shockley partial dislocations. This could be responsible for the formation of the strong basal texture and a significant number of 30° misorientation GBs in Mg alloy during grain growth
Linear combination methods for prediction of drug skin permeation
YesMany in-vitro methods for prediction of skin permeability have been reported in literature. Cerasome electrokinetic chromatography is one of the most sophisticated approaches representing a maximum level of similarity to the lipid phase of the stratum corneum. One goal of this study was to investigate the affinity pattern of Cerasome and to compare it with the permeability profile of human skin. Another purpose was to study the applicability of Hansen solubility parameters for modelling skin permeation and to investigate the predictive and explanatory potential of this method. Visualisation in Hansen diagrams revealed very similar profiles of Cerasome electrokinetic chromatography retention factors and skin permeability coefficients. In both cases, the characteristic pattern with two clusters of highly retained or highly permeable substances could be shown to be mainly caused by two groups of compounds, one of them with high affinity to ceramides, fatty acids and lecithin and the other being more affine to cholesterol. If based on a sufficiently comprehensive experimental dataset, model-independent predictions of skin permeability data using three-component Hansen solubility parameters are able to achieve similar accuracy as calculations made with an Abraham linear free energy relationship model in which the compounds are characterized by seven physicochemical descriptors
An Equation for the Prediction of Human Skin Permeability of Neutral Molecules, Ions and Ionic Species
yesExperimental values of permeability coefficients, as log Kp, of chemical compounds across human skin were collected by carefully screening the literature, and adjusted to 37 °C for the effect of temperature. The values of log Kp for partially ionized acids and bases were separated into those for their neutral and ionic species, forming a total data set of 247 compounds and species (including 35 ionic species). The obtained log Kp values have been regressed against Abraham solute descriptors to yield a correlation equation with R2 = 0.866 and SD = 0.432 log units. The equation can provide valid predictions for log Kp of neutral molecules, ions and ionic species, with predictive R2 = 0.858 and predictive SD = 0.445 log units calculated by the leave-one-out statistics. The predicted log Kp values for Na+ and Et4N+ are in good agreement with the observed values. We calculated the values of log Kp of ketoprofen as a function of the pH of the donor solution, and found that log Kp markedly varies only when ketoprofen is largely ionized. This explains why models that neglect ionization of permeants still yield reasonable statistical results. The effect of skin thickness on log Kp was investigated by inclusion of two indicator variables, one for intermediate thickness skin and one for full thickness skin, into the above equation. The newly obtained equations were found to be statistically very close to the above equation. Therefore, the thickness of human skin used makes little difference to the experimental values of log Kp
High-throughput chromatographic approaches to assess drug partition into biomembranes
Modern drug design and discovery not only focus on the pharmacological activity of a compound, but also take its pharmacokinetic behavior into account. The prediction of in vivo barrier permeation, particularly intestinal absorption and blood-brain barrier passage, are substantial concerns in the development of new drug compounds. For several decades, lipophilicity expressed as n-octanol/water partition coefficient (log Poct) dominated absorption prediction schemes, since partitioning in this solvent system is traditionally accepted as an informative model of membrane partitioning. Recent advances in automated synthesis and combinatorial chemistry result in a vast number of potential drug candidates, and thus the demand for fast and reliable methods to measure this parameter has grown rapidly in recent years. However, in many relevant cases especially for the structurally unrelated or ionized compounds, log Poct can not give a good estimate of a drug´s absorption or permeation. Indeed, the isotropic n-octanol/water system can only roughly mimic natural membrane barriers, which are made of ordered and anisotropic lipid membranes. Therefore bio-mimicking artificial membrane systems have been developed for a better prediction of drug absorption. The objective of this work is to further develop the present high-throughput techniques to measure relevant lipophilicity indices, and more importantly to understand the structural properties encoded in lipophilicity indices derived from different systems. This is important for designing better-suited drugs for medical therapy by improving the biopharmaceutical properties of the drugs via their chemical structure modifications. Chapter 1 gives a brief description of drug permeation and lipophilicity, and the relationship between them. Chapter 2 reviews the high-throughput chromatographic approaches to assess drug partition into biomembranes
Morph-specific differences in life history traits between the winged and wingless morphs of the aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae)
Life history traits were evaluated in the wing polyphenic aphid, Sitobion avenae (Fabricius), by rearing the winged and wingless morphs under the laboratory conditions. Winged morph with large thoraces exhibited a significantly greater morphological investment in flight apparatus than wingless morph with small thoraces. Compared to the winged morph, the wingless morph produced significantlymore nymphs and exhibited significantly faster nymph development rates. In addition, the age at which reproduction first occurred for the winged morph was significantly delayed, and higher mortality was recorded.The results suggest that the fitness differences associated with wingsmay be related to nymph development, adult fecundity, and mortality. Based on these results, the trends and exceptions of life history traits for the wing polyphenic insects are discussed
Determination of solute lipophilicity by reversed-phase high-performance liquid chromatography (RP-HPLC)
Lipophilicity was evaluated by the high-throughput RP-HPLC method. A set of 40 solutes with well-defined solvatochromic parameters were selected in this study. The chromatographic results show that, under the conditions of study, the lipophilicity index log kw was highly correlated with the experimental log Poct
The prediction of blood–tissue partitions, water–skin partitions and skin permeation for agrochemicals
YesBACKGROUND: There is considerable interest in the blood–tissue distribution of agrochemicals, and a number of researchershave developed experimental methods for in vitro distribution. These methods involve the determination of saline–blood andsaline–tissue partitions; not only are they indirect, but they do not yield the required in vivo distribution.RESULTS: The authors set out equations for gas–tissue and blood–tissue distribution, for partition from water into skin andfor permeation from water through human skin. Together with Abraham descriptors for the agrochemicals, these equationscan be used to predict values for all of these processes. The present predictions compare favourably with experimental in vivoblood–tissue distribution where available. The predictions require no more than simple arithmetic.CONCLUSIONS: The present method represents a much easier and much more economic way of estimating blood–tissuepartitions than the method that uses saline–blood and saline–tissue partitions. It has the added advantages of yielding therequired in vivo partitions and being easily extended to the prediction of partition of agrochemicals from water into skin andpermeation from water through skin
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