3,628 research outputs found
Anomalies in non-stoichiometric uranium dioxide induced by pseudo-phase transition of point defects
A uniform distribution of point defects in an otherwise perfect
crystallographic structure usually describes a unique pseudo phase of that
state of a non-stoichiometric material. With off-stoichiometric uranium dioxide
as a prototype, we show that analogous to a conventional phase transition,
these pseudo phases also will transform from one state into another via
changing the predominant defect species when external conditions of pressure,
temperature, or chemical composition are varied. This exotic transition is
numerically observed along shock Hugoniots and isothermal compression curves in
UO2 with first-principles calculations. At low temperatures, it leads to
anomalies (or quasi-discontinuities) in thermodynamic properties and electronic
structures. In particular, the anomaly is pronounced in both shock temperature
and the specific heat at constant pressure. With increasing of the temperature,
however, it transforms gradually to a smooth cross-over, and becomes less
discernible. The underlying physical mechanism and characteristics of this type
of transition are encoded in the Gibbs free energy, and are elucidated clearly
by analyzing the correlation with the variation of defect populations as a
function of pressure and temperature. The opportunities and challenges for a
possible experimental observation of this phase change are also discussed.Comment: 11 pages, 5 figure
Enhanced Steroid Metabolites Production by Resting Cell Phytosterol Bioconversion
The steroid metabolites 9-hydroxy-androstenedione (9-OH-AD), androstadienedione (ADD) and androstenedione (AD) are important steroidal pharmaceuticals. In order to raise the production of steroid metabolites, an efficient resting cell phytosterol bioconversion process was developed to produce 9-OH-AD in the presence of hydroxypropyl-β-cyclodextrin (HP-β-CD). Cell growth medium containing phytosterol as an inducer positively improved cell activity. Under aerobic conditions, bioconversion proceeded at 70 g L–1 phytosterol in the presence of HP-β-CD (the optimized molar ratio of HP-β-CD/phytosterol was 1:1) with 30 g L–1 resting Mycobacterium neoaurum NwIB-yV cells (cell dry mass) in a 5-L bioreactor, where 9-OH-AD production and space-time yield reached 36.4 g L–1 and 9.1 g L–1 d–1, respectively. The recycling of cells and HP-β-CD enables cost-saving and industrial applications. This bioprocess was also applied for the production of ADD and AD. The production of these steroid metabolites was much higher than that reported in previous studies
Modelo de cálculo del rendimiento a compresión y capacidad de carga de columnas con pequeñas excentricidades reforzadas con mortero reforzado con textiles (TRM)
To study the compression performance of TRM-strengthened columns with small eccentricities, a total of 9 reinforced concrete (RC) columns with end corbels were subjected to compression testing. The test parameters are as follows: the number of textile layers, the ratio of longitudinal reinforcement, and polyvinyl alcohol (PVA) short-cut fiber volume fraction. The experimental results indicated that, compared to the control, columns with three layers of textile exhibited an approximately 10.66% increase in the bearing capacity. However, the effect increased only slightly when the number of textile layers increased to 4. Besides, the effect was improved with the increase in the ratio of longitudinal reinforcement and PVA fiber volume fraction. Finally, based on laboratory tests and related research results, a model for calculating normal section bearing capacity of TRM-strengthened columns with small eccentricities was presented. A comparison of the theoretical and experimental data demonstrated the applicability of the proposed model.En este trabajo se estudió el rendimiento a compresión de columnas reforzadas con TRM con pequeñas excentricidades, y para ello, se sometieron a pruebas de compresión a nueve columnas de hormigón armado (RC) con ménsulas finales. Los parámetros estudiados fueron: el número de capas textiles, la relación de refuerzo longitudinal y la fracción en volumen de fibras cortas de alcohol polivinílico (PVA). Los resultados experimentales indicaron que, en comparación con el control, las columnas con tres capas de textiles mostraron un aumento de aproximadamente el 10,66% en la capacidad de carga. Sin embargo, el aumento fue ligero cuando el número de capas textiles aumentó a cuatro. Además, el efecto mejoró con el aumento en la proporción de refuerzo longitudinal y la fracción en volumen de fibras de PVA. Finalmente, basándonos en las pruebas de laboratorio y resultados de investigación previos, se presentó un modelo para calcular la capacidad de carga de la sección normal de columnas reforzadas con TRM con pequeñas excentricidades. Una comparación de los datos teóricos y experimentales demostró la aplicabilidad del modelo propuesto
Flavonoids and volatiles in Chrysanthemum morifolium Ramat flower from Tongxiang County in China
Flavonoids and volatiles in a traditional herbal medicine Chrysanthemum morifolium Ramat flower were determined by HPLC and GC/MS, respectively. Eight flavonoids and fifty eight volatiles were identified. Luteolin-7-glucoside and quercitrin were the most abundant flavonoids and they amounted for 85.7% of the total detected flavonoids. -Humulene was the most abundant volatile and ledene oxide-(I) the next abundant one and the two volatiles were 16.3 and 9.0% of total volatiles, respectively. The bioactivities of the partial components in C. morifolium Ramat flower were discussed. It is considered that the health benefits of C. morifolium Ramat might be related to its abundant flavonoids and volatiles
Bridgeness: A Local Index on Edge Significance in Maintaining Global Connectivity
Edges in a network can be divided into two kinds according to their different
roles: some enhance the locality like the ones inside a cluster while others
contribute to the global connectivity like the ones connecting two clusters. A
recent study by Onnela et al uncovered the weak ties effects in mobile
communication. In this article, we provide complementary results on document
networks, that is, the edges connecting less similar nodes in content are more
significant in maintaining the global connectivity. We propose an index named
bridgeness to quantify the edge significance in maintaining connectivity, which
only depends on local information of network topology. We compare the
bridgeness with content similarity and some other structural indices according
to an edge percolation process. Experimental results on document networks show
that the bridgeness outperforms content similarity in characterizing the edge
significance. Furthermore, extensive numerical results on disparate networks
indicate that the bridgeness is also better than some well-known indices on
edge significance, including the Jaccard coefficient, degree product and
betweenness centrality.Comment: 10 pages, 4 figures, 1 tabl
In-shoe plantar prressure measurement and analysis system based on fabric pressure sensing array
Author name used in this publication: David Dagan Feng2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
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