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161.
In this paper, necessary and sufficient conditions for the oscillation and asymptotic behaviour of solutions of the second
order neutral delay differential equation (NDDE)
are obtained, where q, h ∈ C([0, ∞), ℝ) such that q(t) ≥ 0, r ∈ C
(1) ([0, ∞), (0, ∞)), p ∈ C ([0, ∞), ℝ), G ∈ C (ℝ, ℝ) and τ ∈ ℝ+. Since the results of this paper hold when r(t) ≡ 1 and G(u) ≡ u, therefore it extends, generalizes and improves some known results.
相似文献
162.
163.
X‐ray diffraction and transmission electron microscopy experiments were carried out to study the structure of rapidly solidified as‐cast and annealed Al55Cu35V10 alloy. The as‐cast Al55Cu35V10 alloy shows the presence of a new f.c.c. τ2 phase (a=0.58nm) along with a b.c.c. (a = 0.89 nm) phase which after subsequent annealing transforms into single f.c.c. phase (a = 0.58 nm). In this paper, it is also reported that these phases are crystalline approximants to an icosahedral phase on the basis of e/a (valence electron per atom) constant line. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
164.
Sambhu N. Datta Anirban Misra R. Vinodhkumar 《International journal of quantum chemistry》2000,79(5):308-324
The qualitative rules for the existence of high‐spin ground states in extended systems and molecular crystals are examined here on a firmer theoretical footing. Extended systems have been categorized into three groups, namely, type I, type II, and type III, depending on the type of bonding interactions. The general form of the spin Hamiltonian operators have been written down. The active spaces have been restricted to the minimum size for each of these three types of spin systems. The zeroth‐order state vectors and the Hartree–Fock ground‐state energies have been identified for unit species of each type. The extended system Hamiltonian operators are further truncated in such a way that only the nearest‐neighbor interactions are retained. Expressions have been derived for the energy gap from a molecular orbital approach. The relatively small effects of electron correlation on the energy gaps have been estimated for the type I systems, which belong to the systems of solid‐state physics. In particular, it has been shown that for the type I systems the singlet–triplet gap, and hence the ferromagnetic coupling constant, primarily depends upon the difference of one‐electron kinetic energies and not on the two‐electron exchange integrals. This result agrees with the concept of kinetic exchange that was introduced in the context of a resonating valence‐bond formalism. Type II systems are exemplified by extended systems that can be prepared from conjugated molecules while organic molecular crystals form examples of type III species. For these systems, however, the Coulomb exchange interaction has been shown to dominate the energy gap. A quick review of the Heisenberg spin Hamiltonian for the H2 molecule is sufficient to point out that the sign of the calculated ferromagnetic coupling constant depends on the method of calculation, the nature of the basis set, and the bond length. This is amply supported by ab initio calculations on this species. Numerical data have also been obtained from computations on m‐phenylene‐coupled nitroxy radicals and stacks of α‐nitronyl nitroxide, but these calculations have been based on a semiempirical quantum chemical methodology (INDO) since some of the species involved are exceedingly large. Computed energy gaps are in good agreement with experimental and other theoretical (AM1, PM3) results. Nevertheless, for the dimer, trimer, tetramer, and pentamer of the type II specimen, the important π orbitals are far from being degenerate. The quantitative results clearly deviate from the criterion of degeneracy that was suggested from qualitative theories for the existence of a high‐spin ground state. Therefore, the criteria for the existence of high spins have been reformulated in terms of the monomer orbitals. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 79: 308–324, 2000 相似文献
165.
Nadanathangam Vigneshwaran Gopalakrishnapillai Bijukumar Nivedita Karmakar Sneh Anand Anoop Misra 《Macromolecular Symposia》2003,193(1):119-128
Isoelectric focusing (IEF) of glycated hemoglobin (GHb) was carried out in ultra-thin polyacrylamide gels to separate the hemoglobin-advanced glycation endproducts (Hb-AGEs) from the hemoglobin-A1C (HbA1C) fraction. Precast polyacrylamide gels (Ampholine® PAGplate) were used in Pharmacia LKB Multiphor II for this purpose. The separated bands for Hb-AGE and HbA1C based on their isoelectric point (pI), were confirmed with the purifed fractions obtained from the cation exchange chromatographic technique. From the calibration curve, the pI values were found to be 6.748 and 6.495 for HbA1C and Hb-AGE, respectively. The lowering of pI values for glycated hemoglobin, when compared to unglycated hemoglobin (pI = 6.852), can be attributed to the glycation at the amino terminals of the peptide chains. Increased reduction in pI value for Hb-AGE can be attributed to the effect of glycation of amino groups at various sites on the peptide chains, apart from the terminal amino groups. Fluorescence analysis was carried out for the purified fraction of Hb-AGE which showed the formation of a new fluorophor adduct having the excitation and emission maxima at 308 nm and 345 nm, respectively. Time-dependent formation of Hb-AGE under in vitro conditions was monitored by fluorescence (308/345 nm) over a period of 120 days, which showed its formation only after 3 weeks of incubation. 相似文献
166.
The force on a charged dust grain in a plasma due to polarization of thermal ions and degenerate electrons around the grain is derived in the limits of weakly relativistic and ultra-relativistic degeneracy of electrons. It is found that in both these cases, the magnitude of the polarization force is enhanced compared to that in classical plasmas. The influence of this force on dust-acoustic(DA) modes is examined and discussed. It is shown that the DA wave frequency in degenerate plasmas is significantly reduced compared to the classical DA mode. 相似文献
167.
Sushil K. Misra S. I. Andronenko A. Punnoose Dmitry Tipikin J. H. Freed 《Applied magnetic resonance》2009,36(2-4):291-295
High-frequency (236 GHz) electron paramagnetic resonance (EPR) studies of Fe3+ ions at 255 K are reported in a Sn1?x Fe x O2 powder with x = 0.005, which is a ferromagnetic semiconductor at room temperature. The observed EPR spectrum can be simulated reasonably well as the overlap of spectra due to four magnetically inequivalent high-spin (HS) Fe3+ ions (S = 5/2). The spectrum intensity is calculated, using the overlap I(BL) + (I(HS1) + I(HS2) + I(HS3) + I(HS4)) × exp(?0.00001B), where B is the magnetic field intensity in Gauss, I represents the intensity of an EPR line (HS1, HS2, HS3, HS4), and BL stands for the baseline (the exponential factor, as found by fitting to the experimental spectrum, is related to the Boltzmann population distribution of energy levels at 255 K, which is the temperature of the sample in the spectrometer). These high-frequency EPR results are significantly different from those at X-band. The large values of the zero-field splitting parameter (D) observed here for the four centers at the high frequency of 236 GHz are beyond the capability of X-band, which can only record spectra of ions with much smaller D values than those reported here. 相似文献
168.
Nanoscale laser processing and diagnostics 总被引:2,自引:0,他引:2
David Hwang Sang-Gil Ryu Nipun Misra Hojeong Jeon Costas P. Grigoropoulos 《Applied Physics A: Materials Science & Processing》2009,96(2):289-306
The article summarizes research activities of the Laser Thermal Laboratory on pulsed nanosecond and femtosecond laser-based
processing of materials and diagnostics at the nanoscale using optical-near-field processing. Both apertureless and apertured
near-field probes can deliver highly confined irradiation at sufficiently high intensities to impart morphological and structural
changes in materials at the nanometric level. Processing examples include nanoscale selective subtractive (ablation), additive
(chemical vapor deposition), crystallization, and electric, magnetic activation. In the context of nanoscale diagnostics,
optical-near-field-ablation-induced plasma emission was utilized for chemical species analysis by laser-induced breakdown
spectroscopy. Furthermore, optical-near-field irradiation greatly improved sensitivity and reliability of electrical conductance
atomic force microscopy enabling characterization of electron tunneling through the oxide shell on silicon nanowires. Efficient
in-situ monitoring greatly benefits optical-near-field processing. Due to close proximity of the probe tip with respect to
the sample under processing, frequent degradation of the probe end occurs leading to unstable processing conditions. Optical-fiber-based
probes have been coupled to a dual-beam (scanning electron microscopy and focused ion beam) system in order to achieve in-situ
monitoring and probe repair. 相似文献
169.
Enhanced field emission from pulsed laser deposited nanocrystalline ZnO thin films on Re and W 总被引:1,自引:0,他引:1
Dattatray J. Late Pankaj Misra B. N. Singh Lalit M. Kukreja Dilip S. Joag Mahendra A. More 《Applied Physics A: Materials Science & Processing》2009,95(2):613-620
Nanocrystalline ZnO thin films have been deposited on rhenium and tungsten pointed and flat substrates by pulsed laser deposition
method. An emission current of 1 nA with an onset voltage of 120 V was observed repeatedly and maximum current density ∼1.3 A/cm2 and 9.3 mA/cm2 has been drawn from ZnO/Re and ZnO/W pointed emitters at an applied voltage of 12.8 and 14 kV, respectively. In case of planar
emitters (ZnO deposited on flat substrates), the onset field required to draw 1 nA emission current is observed to be 0.87
and 1.2 V/μm for ZnO/Re and ZnO/W planar emitters, respectively. The Fowler–Nordheim plots of both the emitters show nonlinear
behaviour, typical for a semiconducting field emitter. The field enhancement factor β is estimated to be ∼2.15×105 cm−1 and 2.16×105 cm−1 for pointed and 3.2×104 and 1.74×104 for planar ZnO/Re and ZnO/W emitters, respectively. The high value of β factor suggests that the emission is from the nanometric features of the emitter surface. The emission current–time plots
exhibit good stability of emission current over a period of more than three hours. The post field emission surface morphology
studies show no significant deterioration of the emitter surface indicating that the ZnO thin film has a very strong adherence
to both the substrates and exhibits a remarkable structural stability against high-field-induced mechanical stresses and ion
bombardment. The results reveal that PLD offers unprecedented advantages in fabricating the ZnO field emitters for practical
applications in field-emission-based electron sources. 相似文献
170.
A. Dwivedi S. A. Siddiqui O. Prasad L. Sinhal N. Misra 《Journal of Applied Spectroscopy》2009,76(5):623-629
The molecular geometry and vibrational frequencies of 5-phenyl-2-(4-pyridyl)pyrimidine in the ground state have been calculated
by the density functional theory with B3LYP/6-311G(d) as the basis set. The observed frequencies of 5-phenyl-2-(4-pyridyl)pyrimidine
and those calculated are nearly the same. The form of the modes for all fundamentals is based on potential energy distribution
calculations. 相似文献