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排序方式: 共有324条查询结果,搜索用时 15 毫秒
91.
R.V. SuganthiK. Elayaraja M.I. Ahymah JoshyV. Sarath Chandra E.K. GirijaS. Narayana Kalkura 《Materials science & engineering. C, Materials for biological applications》2011,31(3):593-599
The effect of strontium on the crystallization of helical ribbon of hydroxyapatite (HAp) was investigated by single diffusion technique in silica gel matrix at 27 °C and physiological pH. Fibers of HAp were obtained on addition of strontium. The length of the HAp fibers, were found to decrease as the strontium substitution increases. The presence of strontium ion increased the crystallinity as well as crystallite size of HAp. The strontium substituted HAp (Sr-HAp) has similar stoichiometry to that of biological apatite. Sr-HAp was found to have increased surface area (35%) compared to control. Further, strontium substitution leads to an enhancement of in vitro bioactivity. The cumulative in-vitro amoxicillin drug release in phosphate buffer solution (PBS, pH 7.2) showed a prolonged release profile for Sr-HAp. 相似文献
92.
Akchheta Karki Gert‐Jan A. H. Wetzelaer Gollapalli Narayana Manjunatha Reddy Vojtech Ndady Martin Seifrid Franz Schauer Guillermo C. Bazan Bradley F. Chmelka Paul W. M. Blom Thuc‐Quyen Nguyen 《Advanced functional materials》2019,29(20)
Characterizing the density of states (DOS) width accurately is critical in understanding the charge‐transport properties of organic semiconducting materials as broader DOS distributions lead to an inferior transport. From a morphological standpoint, the relative densities of ordered and disordered regions are known to affect charge‐transport properties in films; however, a comparison between molecular structures showing quantifiable ordered and disordered regions at an atomic level and its impact on DOS widths and charge‐transport properties has yet to be made. In this work, for the first time, the DOS distribution widths of two model conjugated polymer systems are characterized using three different techniques. A quantitative correlation between energetic disorder from band‐bending measurements and charge transport is established, providing direct experimental evidence that charge‐carrier mobility in disordered materials is compromised due to the relaxation of carriers into the tail states of the DOS. Distinction and quantification of ordered and disordered regions of thin films at an atomic level is achieved using solid‐state NMR spectroscopy. An ability to compare solid‐state film morphologies of organic semiconducting polymers to energetic disorder, and in turn charge transport, can provide useful guidelines for applications of organic conjugated polymers in pertinent devices. 相似文献
93.
R. N. Kar L. B. Sukla K. M. Swamy V. V. Panchanadikar K. L. Narayana 《Metallurgical and Materials Transactions B》1996,27(3):351-354
The bioleaching of nickel from lateritic ore of Orissa, India, using a nativeAspergillus niger strain was studied with and without ultrasound. Different parameters, such as spore concentration, amount of dextrose in the medium, pulp densities, and sonication time, were studied for maximizing the extraction of nickel. Enhanced recoveries and reduction in leaching time were demonstrated using ultrasound. The highest amount of nickel, 95 pct, was extracted in 14 days with an inoculum size of 106 spore/mL and 2 pct dextrose in the medium under 30 minutes ultrasonic pretreatment using 43 KHz frequency at 1.5 W/cm2 intensity. It was also found that ultrasound assists in selective leaching of nickel over iron. 相似文献
94.
K. V. Narayana A. Venugopal K. S. Rama Rao V. Venkat Rao S. Khaja Masthan P. Kanta Rao 《Applied Catalysis A: General》1997,150(2):269-278
A series of titania (anatase)-supported vanadia catalysts ranging in V2O5 content from 0.4 to 9.9 mol% was prepared by wet impregnation technique, characterized by BET surface area measurement and X-ray diffraction, and evaluated for ammoxidation of 3-picoline. The average oxidation number of vanadium in the fresh and used catalysts was determined by titrimetric methods. The ammoxidation activity and the average oxidation number were observed to increase with vanadia loading up to 3.4 mol% in the catalyst which corresponds to a monolayer coverage. The phase transformation of anatase to rutile after the reaction was observed at a V2O5 loading of 5.9 mol%. The slow decrease of ammoxidation activity beyond 3.4 mol% V2O5 was attributed to the coverage of active monomeric VOx species on the support by bulk vanadia and by other oxides, and also to compound formation with ammonia. 相似文献
95.
Narayana Garimella Yongho Sohn M. P. Brady 《Journal of Phase Equilibria and Diffusion》2006,27(6):665-670
Interdiffusion in nickel (Ni)-chromium (Cr) (face-centered cubic γ phase) alloys with small additions of aluminum (Al), silicon
(Si), germanium (Ge), or palladium (Pd) was investigated using solid-to-solid diffusion couples. Ni-Cr-X alloys having compositions of Ni-22at.% Cr, Ni-21at.%Cr-6.2at.%Al, Ni-22at.%Cr-4.0at.%Si, Ni-22at.%Cr-1.6at.%Ge, and Ni-22at.%Cr-1.6at.%Pd
were manufactured by arc casting. The diffusion couples were assembled in an Invar steel jig, encapsulated in Ar after several
hydrogen purges, and annealed at 900 °C in a three-zone tube furnace for 168 h. Experimental concentration profiles were determined
from polished cross sections of these couples by using electron probe microanalysis with pure element standards. Interdiffusion
fluxes of individual components were calculated directly from the experimental concentration profiles, and the moments of
interdiffusion fluxes were examined to determine the average ternary interdiffusion coefficients. The effects of ternary alloying
additions on the diffusional behavior of Ni-Cr-X alloys are presented in the light of the diffusional interactions and the
formation of a protective Cr2O3 scale.
This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was
held during TMS 2006, the 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized
by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard
D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University. 相似文献
96.
New synthesized reagent 2,6-diacetylpyridine bis-4-phenyl-3-thiosemicarbazone (2,6-DAPBPTSC) is proposed as a sensitive and selective analytical reagent for the spectrophotometric determination of copper(II) at pH 3.0 to form a yellowish orange colored 1:1 chelate complex. The maximum absorbance was measured at 370 nm. This method obeys Beer’s law in the concentration range 0.63–6.30 g ml−1 and the correlation coefficient of Cu(II)–2,6-DAPBPTSC complex is 0.942, which indicates an adequate linearity between the two variables with good molar absorptivity and Sandell’s sensitivity, 0.847 × 104 l mol−1 cm−1 and 0.0075 g cm−2, respectively. The instability constant of complex calculated from Asmus′ method is 1.415 × 10−4 at room temperature. The precision and accuracy of the method is checked with calculation of relative standard deviation (n = 5), 0.777% and the detection limit value is 0.0056 g ml−1. The interfering effect of various cations and anions has also been studied. The method was successfully applied for the determination of Cu(II) in food samples. The performance of present method was evaluated in terms of Student ‘t’ test and Variance ‘f’ test, which is indicates the significance of present method is an inter comparison of the experimental values, using atomic absorption spectrometer (AAS). 相似文献
97.
K. V. Narayana A. Martin U. Bentrup B. Lücke J. Sans 《Applied Catalysis A: General》2004,270(1-2):57-64
The present contribution is a brief account of investigations carried out on the ammoxidation of o-xylene over a few VPO and V2O5 based catalysts. The desired reaction product is phthalonitrile, however, phthalimide is the main product in most cases besides carbon oxides. The product distribution between nitrile and imide mainly depends on the reaction conditions and the nature of catalyst used. Influence of various reaction parameters such as effects of (i) reaction temperature, (ii) water vapour addition in the feed gas, (iii) NH3/o-xylene mole ratio and (iv) space velocity were studied. It is interesting to note that the removal of water vapour from the feed gas has a highly pronounced promotional effect on the selectivity of phthalonitrile. The nitrile selectivity increased from 2.1 to 34% at the expense of phthalimide (decreased from 53 to 9%) with the complete removal of water vapour in the reactant feed mixture. This observation gives an indication that phthalonitrile being formed in the reaction is further getting hydrolysed to phthalimide via amide intermediate in presence of water vapour. Another interesting aspect of the present investigation is that the titania supported catalysts always gave significantly higher selectivities of phthalimide compared to phthalonitrile. Phthalimide yields up to 80% were reached on a VPO/TiO2 catalyst. 相似文献
98.
V Narayana PL Roberson AT Pu H Sandler RH Winfield PW McLaughlin 《Canadian Metallurgical Quarterly》1997,37(5):1181-1185
PURPOSE: Both ultrasound (US) and computerized tomography (CT) images have been used in the planning of prostate interstitial therapy. Ultrasound images more clearly define the apex and capsule of the prostate, while CT images define seed positions for postimplant dosimetry. Proper registration of the US volume with the CT volume is critical to the assessment of dosimetry. We therefore compared US and CT prostate volumes to determine if differences were significant. METHODS AND MATERIALS: Ten consecutive patients entered in an interstitial implant program were studied by pretreatment US. In addition, pretreatment CT scans were obtained and three physicians independently outlined the dimensions of the prostate on these images. The patients subsequently underwent placement of radioactive 125I or 103Pd. Postimplant CT images were obtained the next day and the postimplant prostate volumes were outlined by the same three physicians. Seven of 10 patients underwent late CT scans 9-14 months postimplant for comparison of preimplant and immediate postimplant CT studies. RESULTS: There were differences between US and CT volumes. Although the physician-to-physician variation was significant, the trends were consistent, with US prostate volume typically smaller (47%) than the preimplant CT volume and markedly smaller (120%) than the postimplant CT volume. Prostate volumes derived from late CT images did not consistently return to preimplant levels. CONCLUSIONS: Significant differences in volume of the prostate structure were found between US and CT images. The data suggests that: (a) Implants planned on CT tend to overestimate the size of the prostate and may lead to unnecessary implantation of the urogenital diaphragm and penile urethra. (b) Registration of initial US and postimplant CT prostate volumes required for accurate dosimetry is difficult due to the increased volume of prostate secondary to trauma. (c) Further study to determine the optimal time for the postimplant CT is necessary. 相似文献
99.
This paper describes a novel application of singular value decomposition (SVD) of subsets of the phase-space trajectory for
calculation of the attractor dimension of a small data set. A certain number of local centres (M) are chosen randomly on the attractor and an adequate number of nearest neighbours (q=50) are ordered around each centre. The local intrinsic dimension of a local centre is determined by the number of significant
singular values and the attractor dimension (D
2) by the average of the local intrinsic dimensions of the local centres. The SVD method has been evaluated for model data
and EEG. The results indicate that the SVD method is a reliable approach for estimation of attractor dimension at moderate
signal to noise ratios. The paper emphasises the importance of SVD approach to EEG analysis. 相似文献
100.
Sanjeev Kumar Singh Yadav Vinod Yadava V. Lakshmi Narayana 《The International Journal of Advanced Manufacturing Technology》2008,36(1-2):34-42
Electrical discharge diamond grinding (EDDG), which integrates diamond grinding and electro-discharge machining (EDM), is
a new hybrid machining process for shaping electrically conductive very hard materials. The process employs synergetic interactive
effect of electro-discharge action and abrasion action to increase machining performance. This paper presents an investigation
on the experimental study and machining parameter design of electro-discharge diamond grinding (EDDG). The EDDG setup was
designed and fabricated, and experiments were conducted on high speed steel (HSS) workpiece under varying current, pulse-ontime,
duty factor and wheel speed. The settings of machining parameters were determined by using the Taguchi experimental design
method. The level of the machining parameters on the MRR is determined by using analysis of variance (ANOVA). The optimum
machining parameter combination was obtained by using the evaluated S/N ratio. 相似文献