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1.
Yuxiang Mo Sitaram Aryal Paul Rulis Wai‐Yim Ching 《Journal of the American Ceramic Society》2014,97(8):2646-2653
The term “MAX phase” refers to a very interesting and important class of layered ternary transition‐metal carbides and nitrides with a novel combination of both metal and ceramic‐like properties that have made these materials highly regarded candidates for numerous technological and engineering applications. Using (Cr2Hf)2Al3C3 as an example, we demonstrate the possibility of incorporating more types of elements into a MAX phase while maintaining the crystallinity, instead of creating solid solution phases. The crystal structure and elastic properties of MAX phase‐like (Cr2Hf)2Al3C3 are studied using the Vienna ab initio Simulation Package. Unlike MAX phases with a hexagonal symmetry (P63/mmc, #194), (Cr2Hf)2Al3C3 crystallizes in the monoclinic space group of P21/m (#11) with lattice parameters of a = 5.1739 Å, b = 5.1974 Å, c = 12.8019 Å; α = β = 90°, γ = 119.8509°. Its structure is found to be energetically much more favorable with an energy (per formula unit) of ?102.11 eV, significantly lower than those of the allotropic segregation (?100.05 eV) and solid solution (?100.13 eV) phases. Calculations using a stress versus strain approach and the VRH approximation for polycrystals also show that (Cr2Hf)2Al3C3 has outstanding elastic moduli. 相似文献
2.
Seepage effects on the stability, mobility, and incipient motion of sand-bed particles are experimentally investigated. Seepage through a sand bed in a downward direction (suction) reduces the stability of particles, and it can even initiate their movement. The bed erosion is increased with the increased rates of suction. Whereas the seepage in an upward direction (injection) increases the stability of bed particles, it does not aid initiating their movement. The rate of bed erosion is reduced or even stopped by the increased injection rates. Hydrodynamic conditions leading to the so-called “pseudoincipient motion” with suction (for the initiation of particles movement that are otherwise at rest under no-seepage conditions), and with injection (for only arresting the particles movement that are otherwise moving initially) are evaluated. The conventional Shields curve cannot be used to predict such pseudoincipient motion conditions with seepage. The concepts thus developed are useful for a better understanding of the sediment transport mechanics and in the design of stable alluvial channels affected by seepage. 相似文献
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4.
Hanne Hjorth Tønnesen Jan Karlsen Sitaram R. Adhikary Rita Pandey 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1989,189(2):116-118
Summary The content of curcuminoids inCurcuma longa L. before, during and after a normal harvesting period was investigated. The plant material was grown in the Kathmandu area. Bis-demethoxycurcumin was found to be the main constituent. No significant change in the curcuminoid content was observed during a 17-week sampling period.
Studien über Curcumin und Curcuminoide. XVII. Veränderung des Gehaltes an Curcuminoiden inCurcuma longa L. (Zingiberaceae) aus Nepal warend der Ernte
Zusammenfassung Der Gehalt an Curcuminoiden inCurcuma longa L. (Zingiberaceae) wurde vor, während und nach der normalen Erntezeit untersucht. Das Pflanzenmaterial stammt aus dim Kathmandu-Tal in Nepal. Der Hauptinhaltsstoff ist Bisdemethoxycurcumin. Im Laufe von 17 Wochen konnten keine signifikante Schwankungen observiert werden.相似文献
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6.
Gogl D. Arndt C. Barwin J.C. Bette A. DeBrosse J. Gow E. Hoenigschmid H. Lammers S. Lamorey M. Yu Lu Maffitt T. Maloney K. Obermaier W. Sturm A. Viehmann H. Willmott D. Wood M. Gallagher W.J. Mueller G. Sitaram A.R. 《Solid-State Circuits, IEEE Journal of》2005,40(4):902-908
A 16-Mb magnetic random access memory (MRAM) is demonstrated in 0.18-/spl mu/m three-Cu-level CMOS with a three-level MRAM process adder. The chip, the highest density MRAM reported to date, utilizes a 1.42/spl mu/m/sup 2/ 1-transistor 1-magnetic tunnel junction (1T1MTJ) cell, measures 79 mm/sup 2/ and features a /spl times/16 asynchronous SRAM-like interface. The paper describes the cell, architecture, and circuit techniques unique to multi-Mb MRAM design, including a novel bootstrapped write driver circuit. Hardware results are presented. 相似文献
7.
Faulkner JR Hussaini SR Blankenship JD Pal S Branan BM Grossman RB Schardl CL 《Chembiochem : a European journal of chemical biology》2006,7(7):1078-1088
Loline alkaloids are saturated pyrrolizidines with an oxygen bridge between carbon atoms C‐2 and C‐7 and an amino group on C‐1. They are bioprotective alkaloids produced by Epichloë and Neotyphodium species, mutualistic fungal endophytes that are symbiotic with cool‐season grasses. The sequence of bond formation in loline alkaloid biosynthesis was determined by synthesizing deuterated forms of potential intermediates and feeding them to cultures of the endophyte Neotyphodium uncinatum. These cultures incorporated deuterium from labeled N‐(3‐amino‐3‐carboxypropyl)proline and exo‐1‐aminopyrrolizidine into N‐formylloline. The first result suggests that N‐(3‐amino‐3‐carboxypropyl)proline is the first committed intermediate in loline biosynthesis, and the second result demonstrates that the pyrrolizidine rings form before the ether bridge. The incorporation of these two compounds into lolines and the lack of incorporation of several related compounds clarify the order of bond formation in loline alkaloid biosynthesis. 相似文献
8.
Alok Singh Sitaram Dash Mohammed Kamruddin Puthupparampil K. Ajikumar Ashok K. Tyagi Vinjamoor S. Raghunathan Baldev Raj 《Journal of the American Ceramic Society》2002,85(4):927-932
Formation of nanocrystalline calcia from calcite has been studied in situ via transmission electron microscopy. The crystallographic transformation occurred via two mechanisms: the first is by distortion of the cleaved rhombohedron of calcite, formed by {104} planes in hexagonal coordinates, into a cube. This produced a microstructure of oriented, elongated nanocrystals of calcia with planar boundaries. In the second mechanism, the micrometer-sized parent calcite particles broke up into nano-sized grains as the decomposition began, leading to irregularly shaped, randomly oriented nanocrystals of calcia. 相似文献
9.
Cervid species represent a growing livestock enterprise in the United States of America (USA). The zoonotic threat of bovine tuberculosis (Mycobacterium bovis) is the only significant public health risk posed by this alternative livestock industry. This paper examines the potential sources of tuberculosis exposure as related to public health and compares and contrasts the status of tuberculosis in Cervidae with the situation in the cattle industry in the USA. Based on the existing prevalence of the disease and the limited potential of human exposure to infected meat or meat products, bovine tuberculosis in Cervidae poses a minimal threat to public health. The only significant public health concern is exposure to infected free-ranging cervids of hunters who field-dress carcasses and may unknowingly incise tuberculous lesions. This risk is mitigated only by the small size of the cervid population at risk when compared to the general population of cervids hunted yearly. 相似文献
10.
Walk interaction formalism in the graph theory has been applied for the calculation of volumetric properties of liquids and liquid mixtures. By regression analysis, the parameters of the expression V = ΣΣxyxy, Vyy, are obtained from the data on pure liquids at different temperatures. Only 3 Vyy, parameters are required for n-alkanes and the standard deviation of calculated volumes is 0.02 cm3/mol as compared with the experimental accuracy of ± 0.05 cm3/mol. The calculated thermal expansion coefficients also agree well with the experimental ones. The properties of mixtures and hence the excess volumes are calculable using the same Vyy, parameters established for pure liquids. Excellent agreement is observed between the calculated and experimental excess volumes of n-alkane mixtures. 相似文献