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61.
Orientational order parameter S is evaluated in the nematic phase of six liquid crystal compounds, N-(p-n-propyl benzylidene)-p-n-alkoxy anilines, 3.Om and N-(p-n-propyloxy benzylidene)-p-n-alkoxy anilines, 3O.Om compounds with m = 6, 7 and 8, using different methods. The techniques employed are S from birefringence δn, Haller's approximation from (1?T/Tc) β, effective geometry parameter αg and Vuks’ scaling factor SC. The values of S obtained using the above methods are compared with one another and with the results on a number of liquid crystals; the liquid crystals favor isotropic Vuks’ method. 相似文献
62.
S Prasad P Zhao J Huang J J Fitzgerald J S Shore 《Solid state nuclear magnetic resonance》2001,19(1-2):45-62
93Nb (I = 9/2) multiple-quantum magic-angle spinning (MQMAS) NMR spectra of a series of inorganic niobates have been measured. 93Nb MQMAS spectroscopy yields spectra with typically an order of magnitude higher resolution than that obtainable with 93Nb MAS spectroscopy and 93Nb dynamic-angle spinning (DAS) spectroscopy. For example, the full-width at half-maximums of the 93Nb resonances of LiNbO3 were 9 (MAS), 5.8 (DAS), and 0.7 kHz (MQMAS). Broadening of the 93Nb MAS and DAS spectra is due to the second-order quadrupolar and homonuclear dipolar interactions, respectively. The quadrupolar products (P(O)) and isotropic chemical shifts (delta(iso)) of the 93Nb resonances of LiNbO3, NaNbO3, PbNb2O6, Pb2Nb2O7, Pb3Nb2O8, Pb3Nb4O15, Pb3Nb4O13, and Pb1.83Nb1.71Mg0.29O6.39 were determined from MQMAS spectra and range from 13.6 to 26.8 MHz and from -951 to -1113 ppm, respectively. Resonances with relatively large quadrupolar coupling constants (> 30 MHz) were not observed using MQMAS spectroscopy, but were detected using nutation spectroscopy. The applicability and limitations of MQMAS spectroscopy in studying inorganic niobates containing multiple 93Nb resonances are addressed and compared with those of MAS, nutation, and DAS spectroscopies. 相似文献
63.
Anomalous phase synchronization in nonidentical interacting oscillators is manifest as the increase of frequency disorder prior to synchronization. We show that this effect can be enhanced when a time-delay is included in the coupling. In systems of limit-cycle and chaotic oscillators we find that the regions of phase disorder and phase synchronization can be interwoven in the parameter space such that as a function of coupling or time-delay the system shows transitions from phase ordering to disorder and back. 相似文献
64.
Sandeep Sundriyal Smriti Khanna Rikta Saha Prasad V. Bharatam 《Journal of Physical Organic Chemistry》2008,21(1):30-33
This theoretical study attempts to find out similarity between metformin and glitazone class of antidiabetic drugs. It was found that some tautomeric forms of both metformin and thiazolidinedione ring of glitazones have similar molecular electrostatic potential (MESP) surface and may bind to a common complementary surface. Complexation and docking studies were also carried out in order to support this hypothesis. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
65.
In this paper, a rigorous theoretical analysis has been made to study the dispersion relation of EM waves in periodic ternary one-dimensional photonic crystal having two different structures. In one case we have chosen glass-plasma and ZnS in one unit cell and in other case we have considered glass-plasma and MgF2 in one unit cell. Using Kronig-Penney model the dispersion relation for proposed structures has been obtained and numerical results are presented in the form of dispersion curves. The dependence of photonic band gap (PBG) characteristics on plasma frequency, plasma width and the width of dielectric media are discussed in the light of frequency gap and cutoffs of binary one-dimensional plasma photonic crystal. An attempt has been made to show how the PBG characteristic of a particular structure changes when the dielectric materials of its unit cell is changed by the other dielectric material. It is found that the structure having glass-plasma-ZnS in unit cell is more useful for broad band filtering and other plasma functioning devices compared to the structure having glass-plasma-MgF2 in one unit cell. 相似文献
66.
A chemically modified poly(fluorene-alt-benzothiadiazole) (PFBT) polymer film is reported to exhibit high two-photon absorbing capability and chemical/physical stability upon the action of high-power laser pulses of ~780 nm wavelength and ~160 fs duration. A nonlinear transmission measurement is conducted by varying the input intensity from ~20 to ~600 GW/cm2, the corresponding nonlinear transmission of a ~70 μm thick film is reduced from ~0.8 to 0.18, indicating a superior optical limiting behavior. In the meantime, intensity fluctuation of laser pulses can be significantly reduced after passing through the same film sample. Based on the intensity-dependent nonlinear attenuation mechanism, a straightforward optical reshaping effect on spatio-temporal profiles of the laser pulses has also been demonstrated. 相似文献
67.
It is proposed to construct a spallation neutron source (SNS) at Centre for Advanced Technology (CAT) based on a 1 GeV proton
synchrotron with 100 MeV H− LINAC as injector. Additionally, the LINAC can form the first 100 MeV part of a 1 GeV proton LINAC to be built in future
for accelerator driven system (ADS) applications. We are exploring a configuration of the 100 MeV LINAC which will consist
of an H− ion source, a 4–6 MeV RFQ followed either by a 20 MeV drift tube LINAC (DTL) and 100 MeV separated function drift tube LINAC
(SDTL) or a coupled cavity drift tube LINAC (CCDTL) structure. In this paper, we present the results of our preliminary physics
design studies of the RFQ-SDTL, RFQ-CCDTL and RFQ-DTL-SDTL configurations. The design of the 4.5 MeV RFQ is discussed along
with the matching sections between the RFQ-SDTL/DTL and RFQ-CCDTL. The choice of the accelerator configuration and that of
various parameters of the individual accelerator structures under consideration are discussed. The design objectives are to
arrive at a configuration which eases heat removal for CW operation and which is less prone to halo formation in order to
reduce the beam loss at higher energies. 相似文献
68.
Subash Khushu Poonam Rana Tarun Sekhri Gopalakrishnan Sripathy Rajendra Prasad Tripathi 《Magnetic resonance imaging》2010
Mitochondrial metabolism particularly oxidative phosphorylation is greatly influenced by thyroid hormones. Earlier studies have described neuromuscular symptoms as well as impaired muscle metabolism in hypothyroid and hyperthyroid patients. In this study, we intend to look in to the muscle bioenergetics including phosphocreatine recovery kinetics based oxidative metabolism in thyroid dysfunction using in vivo 31P nuclear magnetic resonance spectroscopy (MRS). 31P MRS was carried out at resting state on 32 hypothyroid, 10 hyperthyroid patients and 25 control subjects. Nine out of 32 hypothyroid patients and 17 out of 25 control subjects under went exercise protocol for oxidative metabolism study and performed plantar flexion exercise while lying supine in 1.5 T magnetic resonance scanner using custom built exercise device. MRS measurements of inorganic phosphate (Pi), phosphocreatine (PCr), phosphodiesters (PDE) and adenosine triphosphate (ATP) of the calf muscle were acquired during rest, exercise and recovery phase. PCr recovery rate constant (kPCr) and oxidative capacity were calculated by monoexponential fit of PCr versus time (t) at the beginning of recovery. During resting condition in hypothyroid patients, PCr/Pi ratio was reduced whereas PDE/ATP and Pi/ATP were increased. However, in case of hyperthyroidism, an increased PCr/Pi ratio and reduced PDE/ATP and Pi/ATP were observed. The results confirmed differential energy status of the muscle due to increased or decreased levels of thyroid hormone. Our results also demonstrate reduced oxidative metabolism in hypothyroid patients based on PCr recovery kinetics. PCr recovery kinetics study after exercise revealed decreased PCr recovery rate constant (kPCr) in hypothyroid patients compared to controls that resulted in decrease in oxidative capacity of muscle by 50% in hypothyroids. These findings are consistent with a defect of high energy phosphate mitochondrial metabolism in thyroid dysfunction. 相似文献
69.
The energy spectrum and dipole matrix elements of a multiple quantum well (MQW) system has been calculated numerically by solving the time-independent Schrödinger equation using finite difference method, in the presence of magnetic field. The effect of barrier width is also investigated. The energy difference between the levels of various minibands and the energy difference between various levels of the same miniband is calculated for different number of wells in the MQW. Finally, the dynamics of the system in short laser pulses has been calculated numerically by solving the time-dependent Schrödinger equation. The effect of magnetic field on the dynamics is clearly shown and explained. 相似文献
70.
Anamika Bajpai Kashi Nath Prasad Priyanka Mishra Rakesh Kumar Gupta Aloukick K. Singh Bal Krishna Ojha 《Magnetic resonance imaging》2014