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991.
X-band electron paramagnetic resonance (EPR) studies are carried out on Fe3+ ions doped in ammonium dihydrogen phosphate (ADP) single crystals at room temperature. The crystal field and spin Hamiltonian parameters are evaluated from the resonance lines obtained at different angular rotations. The obtained values of spin Hamiltonian and zero-field parameters of the Fe3+ ion in ADP are: g = 1.994 ± 0.002, |D| = (220 ± 5) × 10?4 cm?1 and a = (640 ± 5) × 10?4 cm?1. On the basis of EPR data, the site symmetry of the Fe3+ ion in the crystal is discussed. The Fe3+ ion enters the lattice substitutionally replacing the NH4 + sites. The optical absorption of the crystal is also studied at room temperature in the wavelength range of 195–925 nm. The energy values of different orbital levels are calculated. The observed bands are assigned as transitions from the 6 A 1g (S) ground state to various excited quartet levels of the Fe3+ ion in a cubic crystalline field. From the observed band positions, Racah interelectronic repulsion parameters (B and C), cubic crystal field splitting parameter (D q ) and Trees correction are calculated. There values are: B = 970, C = 1,923, D q = 1,380 cm?1 and α = 90 cm?1, respectively. On the basis of EPR and optical data, the nature of bonding in the crystal is discussed. The zero-field splitting (ZFS) parameters are also determined theoretically using B kq parameters estimated from the superposition model. The values of ZFS parameters thus obtained are |D| = (213 ± 5) × 10?4 cm?1 and |E| = (21 ± 5) × 10?4 cm?1. 相似文献
992.
Ultrasonic attenuation for the longitudinal and shear waves due to phonon-phonon interaction and thermoelastic mechanism have
been evaluated in B2 structured intermetallic compounds AgMg, CuZr, AuMg, AuTi, AuMn, AuZn and AuCd along 〈100〉, 〈111〉 and
〈110〉 crystallographic directions at room temperature. For the same evaluations, second- and third-order elastic constants,
ultrasonic velocities, Grüneisen parameters, non-linearity parameter, Debye temperature and thermal relaxation time are also
computed. Although the molecular weight of these materials increases from AgMg to AuCd, the obtained results are affected
with the deviation number. Attenuation of ultrasonic waves due to phonon-phonon interaction is predominant over thermoelastic
loss. Results are compared with available theoretical and experimental results. The results with other well-known physical
properties are useful for industrial purposes.
相似文献
993.
Few phenomena are as complex as the teaching-learning (TL) process. The instruction efficiency and information on the state of knowledge of the student group are some key variables in this process. Guided by Shannon’s definition of information we propose an entropy based performance index (Sp) for monitoring the teaching-learning process. Our index is based on item response curves (IRCs) which have been recently employed in physics education research. Our proposed index is an explicit function of the ability θ. A preliminary survey indicates that Sp is low (high) for high (low) ability student groups. We propose a simple model to explain this. We have also carried out a number of controlled studies to study the dependence of Sp on student ability, peer instruction and collaborative learning. Our studies indicate that Sp plays a role analogous to entropy in statistical mechanics, with student ability being akin to inverse temperature, peer instruction to an ordering (magnetic) field and collaborative learning to interacting components. 相似文献
994.
Sinha S Misra A Rathi M Kumar V Pandey RM Luthra K Jagannathan NR 《Magnetic resonance imaging》2009,27(1):94-100
We report the determination of intramyocellular lipids (IMCLs) of the soleus muscle of patients with type 2 diabetes mellitus (T2DM) using proton magnetic resonance spectroscopy. In addition, the various anthropometric and biochemical profiles of these patients were determined, including estimation of C-reactive protein (CRP), an inflammatory marker of coronary heart disease, and insulin resistance [Homeostasis Model Assessment (HOMA-IR)]. The estimated CRP level and the IMCL content in these patients were correlated with body mass index, percentage of body fat, other measures of abdominal obesity, serum lipoproteins, fasting and post-oral glucose load serum insulin levels and other surrogate markers of insulin resistance. The IMCL content (P=.04), CRP (P=.008) and insulin resistance (P=.0007) were significantly higher in T2DM patients compared to healthy controls. However, IMCL content did not correlate with values of fasting insulin, HOMA-IR or CRP in either group. These findings have strong implications of increased cardiovascular risk in Asian Indians with T2DM. The absence of relationship between CRP and IMCL needs to be explored further in a study using a large sample size. 相似文献
995.
Mallika Somayajulu-Ni?u Jagdeep K Sandhu Jerome Cohen Marianna Sikorska TS Sridhar Anca Matei Henryk Borowy-Borowski Siyaram Pandey 《BMC neuroscience》2009,10(1):88
Background
Parkinson's disease, for which currently there is no cure, develops as a result of progressive loss of dopamine neurons in the brain; thus, identification of any potential therapeutic intervention for disease management is of a great importance. 相似文献996.
David Groh Ravindra Pandey Munima B. Sahariah Isabelle Baraille 《Journal of Physics and Chemistry of Solids》2009,70(5):789-795
Optical properties such as the dynamic dielectric function, reflectance, and energy-loss function of beryllium oxide (BeO) in its ambient and high-pressure phases are reported for a wide energy range of 0-50 eV. The calculations of optical properties employ first-principles methods based on all-electron density functional theory together with sum over states and finite-field methods. Our results show subtle differences in the calculated optical properties of the wurtzite, zincblende, rocksalt and CsCl phases of BeO, which may be attributed to the higher symmetry and packing density of these phases. For the wurtzite phase, the calculated band gap of 10.4 eV corresponds well with the experimental value of 10.6 eV and the calculated (average) index of refraction of 1.70 shows excellent agreement with the experimental value of 1.72. 相似文献
997.
Pandey PC 《Analytica chimica acta》2006,568(1-2):47-56
The aim of this article is to provide insight on the use of a biological molecule--bacteriorhodopsin (bR) having all the basic properties necessary for the assembly of nanoscale electronic devices. Recent developments made during last decade supported by key references are reviewed in this contribution. Major emphasis on bR-based observations conducted in our laboratory has been elaborated. Important issues concerning structure, widely accepted photocycle of bR has been summarized. The possibility of nano-devices emanating from this biomolecule is briefly presented. 相似文献
998.
Covalent immobilization of cholesterol esterase and cholesterol oxidase on polyaniline films for application to cholesterol biosensor 总被引:2,自引:0,他引:2
Cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) have been covalently immobilized on electrochemically prepared polyaniline (PANI) films. These PANI/ChEt/ChOx enzyme films have been characterized using UV-visible, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Electrochemical behavior of these films has been studied using cyclic voltammetry (CV) and amperometric techniques, respectively. The PANI/ChEt/ChOx enzyme films show broad oxidation peak from 0.2 to 0.5 V. These PANI/ChEt/ChOx biosensing electrodes have a response time of about 40s, linearity from 50 to 500 mg/dl of cholesterol oleate concentration. These PANI/ChEt/ChOx films are thermally stable up to 46 degrees C. This polyaniline based cholesterol biosensor has optimum pH in the range of 6.5-7.5, sensitivity as 7.5x10(-4) nA/mg dl and a lifetime of about 6 weeks. 相似文献
999.
This paper discusses the approximate controllability of a neutral functional integro-differential inclusion involving Caputo fractional derivative in a Hilbert space under the assumptions that the corresponding linear system is approximately controllable. A new set of sufficient conditions for approximate controllability of neutral fractional stochastic functional integro-differential inclusions are formulated and established by utilizing stochastic analysis theory, fractional calculus and the technique of fixed point theorem with analytic compact resolvent operator. An example is also considered for illustrating the discussed theory. 相似文献
1000.
Fourier transform infrared (FT-IR) spectra of xBaO–15Na2O–(70−x)B2O3–15SiO2 glass system with x=0, 5, 10, 15 and 20 (mol%) has been measured in the spectral range 400–4000 cm−1 at room temperature in order to understand the characteristic frequencies of the chemical bonds and bonding mechanisms, which are susceptible to the structural and spectral changes. The effect of gamma irradiation in the dose range 0.1 kGy–60 kGy on the infrared absorption spectra of these glasses is also reported. The change in the glass structure due to the effect of composition is also discussed. It has been observed that irradiation of the glasses with the gamma rays increases the BO3 groups and the non bridging oxygens which make the network loose. 相似文献