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291.
We present a systematic study of the photo-absorption spectra of various SinHm clusters using the time-dependent density functional theory (TDDFT). The method uses a real-time, real-space implementation of TDDFT involving full propagation of the time dependent Kohn-Sham equations. Our results for SiH4 and Si2H6 show good agreement with the earlier calculations and experimental data. We study the photo-absorption spectra of silicon clusters as a function of hydrogenation. For single hydrogenation, we find that in general, the absorption optical gap decreases showing a significant red shift for small sized clusters and as the number of silicon atoms increases the effect of a single hydrogen atom on the optical gap diminishes. For further hydrogenation the optical gap increases and for the fully hydrogenated clusters the optical gap is larger compared to corresponding pure silicon clusters corresponding to a blue shifted spectra. 相似文献
292.
Neeraj Dwivedi Sushil Kumar C. M. S. Rauthan O. S. Panwar 《Applied Physics A: Materials Science & Processing》2011,102(1):225-230
Nanoindentation testing was performed on nitrogen (N2) incorporated diamond-like carbon (N-DLC) films and deposited using radio-frequency plasma-enhanced chemical vapor deposition
technique, with varied percentage of nitrogen partial pressures of 0, 44.4, 66.6, and 76.1%. The values of nanohardness (H) and elastic modulus (E) of these films were obtained from 38 to 22 GPa and 462 to 330 GPa, respectively, as the partial pressure of N2 increases from 0 to 76.1%. Further, these films were studied for % elastic recovery, ratio between residual displacement
after load removal and displacement at maximum load (d
res/d
max ), plastic deformation energy and plasticity index parameter (H/E). Both hardness per unit stress and plasticity index per unit stress were found to be maximum at N2 partial pressure of 76.1%. X-ray photoelectron spectroscopy measurements confirmed the presence of N2 in these films. 相似文献
293.
Field emission, morphological and mechanical properties of variety of diamond-like carbon thin films
Neeraj Dwivedi Sushil Kumar R. K. Tripathi H. K. Malik O. S. Panwar 《Applied Physics A: Materials Science & Processing》2011,105(2):417-425
The effect of nitrogen incorporation and sandwich titanium and copper layers, on field emission, morphological and mechanical
properties of diamond-like carbon (DLC) thin films is explored. The introduction of foreign element (N2) and sandwich Cu and Ti layers changed the amorphous morphology to nanostructured, reduced the stress, enhanced the hardness
(except N2 incorporated DLC film) and improved the field emission (except Ti/DLC bilayer) of modified DLC films. The associated versatile
electrical and mechanical properties of modified DLC film made it a material of great utility in the development of field
emission display panels and also lead to its application as a hard and protective coating on cutting tools, automobile parts
etc. It is important to mention that DLC-based electronic materials may replace currently used soft electronic materials (such
as Si) due to their enhanced stability under high energy radiation. 相似文献
294.
Sushil Gupta 《European Journal of Operational Research》2011,211(1):47-56
The research work on supply-chain management has primarily focused on the study of materials flow and very little work has been done on the study of upstream flow of money. In this paper we study the flow of money in a supply chain from the viewpoint of a supply chain partner who receives money from the downstream partners and makes payments to the upstream partners. The objective is to schedule all payments within the constraints of the receipt of the money. A penalty is to be paid if payments are not made within the specified time. Any unused money in a given period can be invested to earn an interest. The problem is computationally complex and non-intuitive because of its dynamic nature. The incoming and outgoing monetary flows never stop and are sometimes unpredictable. For tractability purposes we first develop an integer programming model to represent the static problem, where monetary in-flows and out-flows are known before hand. We demonstrate that even the static problem is NP-Complete. First we develop a heuristic to solve this static problem. Next, the insights derived from the static problem analysis are used to develop two heuristics to solve the various level of dynamism of the problem. The performances of all these heuristics are measured and presented. 相似文献
295.
Jadhav SV Bandyopadhyay A Benke SN Mali SM Gopi HN 《Organic & biomolecular chemistry》2011,9(11):4182-4187
A facile, efficient and racemization-free method for the synthesis of N-protected β-amino alcohols and peptaibols using N-hydroxysuccinimide active esters is described. Using this method, dipeptide, tripeptide and pentapeptide alcohols were isolated in high yields. The conformations in crystals of β-amino alcohol, dipeptide and tripeptide alcohols were analysed, with a well-defined type III β-turn being observed in the tripeptide alcohol crystals. This method is found to be compatible with Fmoc-, Boc- and other side-chain protecting groups. 相似文献
296.
Saha UC Dhara K Chattopadhyay B Mandal SK Mondal S Sen S Mukherjee M van Smaalen S Chattopadhyay P 《Organic letters》2011,13(17):4510-4513
A new probe, 3-[(3-benzyloxypyridin-2-ylimino)methyl]-2-hydroxy-5-methylbenzaldehyde (1-H) behaves as a highly selective fluorescent pH sensor in a Britton-Robinson buffer at 25 °C. The pH titrations show a 250-fold increase in fluorescence intensity within the pH range of 4.2 to 8.3 with a pK(a) value of 6.63 which is valuable for studying many of the biological organelles. 相似文献
297.
Santosh K. Tripathi Bishan L. Khandelwal Sushil K. Gupta 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2285-2293
A new series of 24- and 28-membered macrocyclic systems associated with "hard" (N and O) and "soft" (Se or Te) donor atoms have been developed via template free (2 + 2) condensation reactions of bis(aminoalkyl)selenides/tellurides, {NH 2 (CH 2 ) n } 2 E (E = Se, Te; n = 2,3) with 2,6-diacetyl-4-methylphenol. A macroacycle, Se{(CH 2 ) 2 N=C(CH 3 )C 6 H 2 (OH)(CH 3 )C=O(CH 3 )} 2 , has also been obtained. These compounds have been characterized by ESMS, IR, and 1 H, 13 C, and 77 Se NMR spectroscopy. 相似文献
298.
Enantiopure ferrocenyl-β, and bis-β-amino acids [(R)-(+)-1 and (R, R)-(+)-2] were prepared from (S)-(+)-sulfinimine (3) and (S, S)-(+)-bis-sulfinimine (4) respectively. The desired sulfinimines [(S)-(+)-3 and (S, S)-(+)-4] were prepared from (S)-Andersen reagent (5) and ferrocenecarboxaldehyde (6) and 1, 1 -ferrocenedicarboxaldehyde (7). 相似文献
299.
Lu H Akgun B Wei X Li L Satija SK Russell TP 《Langmuir : the ACS journal of surfaces and colloids》2011,27(20):12443-12450
In situ neutron reflectivity was used to study thermally induced structural changes of the lamellae-forming polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer thin films floating on the surface of an ionic liquid (IL). The IL, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, is a nonsolvent for PS and a temperature-tunable solvent for P2VP, and, as such, micellization can be induced at the air-IL interface by changing the temperature. Transmission electron microscopy and scanning force microscopy were used to investigate the resultant morphologies of the micellar films. It was found that highly ordered nanostructures consisting of spherical micelles with a PS core surrounded by a P2VP corona were produced. In addition, bilayer films of PS homopolymer on top of a PS-b-P2VP layer also underwent micellization with increasing temperature but the micellization was strongly dependent on the thickness of the PS and PS-b-P2VP layers. 相似文献
300.
M. Kumar T. Nautiyal S. Auluck 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,73(3):423-432
We report a systematic study of the electronic, optical, and magneto-optical
properties of the Fe4−xCox (x = 1–3) compounds using the
full-potential linearized augmented plane waves (FPLAPW) method within the
local spin density approximation (LSDA). Pure Fe (x = 0) and Co (x = 4) have
also been studied, the latter in hcp as well as bcc structure, to offer a
better comparison. A good agreement is obtained between calculated optical
conductivity spectra and experimental data. We note that the magneto-optical
properties of these compounds are found to be more akin to those of
bcc Co (which has MOKE very similar to that of bcc Fe) than to those of hcp
Co. This shows strong impact of the environment on the MOKE of these
compounds. With respect to the elemental values, the magnetic moments at Fe
sites are found to be larger in general, while those at Co sites are almost
the same. However, interestingly, despite their larger magnetic moment, the
Kerr rotation remains comparable to that of bcc Fe for most of the energy
range. The origin of Kerr spectra has been explained in terms of optical
transitions. 相似文献