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41.
Charagundla SR Borthakur A Leigh JS Reddy R 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2003,162(1):113-121
Significant artifacts arise in T(1rho)-weighted imaging when nutation angles suffer small deviations from their expected values. These artifacts vary with spin-locking time and amplitude, severely limiting attempts to perform quantitative imaging or measurement of T(1rho) relaxation times. A theoretical model explaining the origin of these artifacts is presented in the context of a T(1rho)-prepared fast spin-echo imaging sequence. Experimentally obtained artifacts are compared to those predicted by theory and related to B(1) inhomogeneity. Finally, a "self-compensating" spin-locking preparatory pulse cluster is presented, in which the second half of the spin-locking pulse is phase-shifted by 180 degrees. Use of this pulse sequence maintains relatively uniform signal intensity despite large variations in flip angle, greatly reducing artifacts in T(1rho)-weighted imaging. 相似文献
42.
K. Sridhar 《Pramana》2007,69(5):719-725
The international linear collider (ILC) is likely to provide us important insights into physics sector that may supersede
our current paradigm, viz., the standard model. In anticipation of the possibility that the ILC may come up in the middle
of the next decade, several groups are vigourously investigating its potential to explore this new sector of physics. The
Linear Collider Workshop in Bangalore (LCWS06) had several presentations of such studies which looked at supersymmetry, extra
dimensions and other exotic possibilities which the ILC may help us discover or understand. Some papers also looked at the
understanding of cosmology that may emerge from studies at the ILC. This paper summarises these presentations.
相似文献
43.
The thermal lensing effect of the Copper Vapor Laser (CVL) was studied by considering both its windows and the active medium. The equivalent combined focal length of the active medium and windows was measured to be 52 mts under operating conditions for a 35W CVL. The variation of focal length with the operating parameters was studied. 相似文献
44.
Wei Yang Itır Z. Karaesmen Pınar Keskinocak Sridhar Tayur 《Annals of Operations Research》2008,159(1):415-431
Fractional aircraft ownership programs, where individuals or corporations own a fraction of an aircraft, have revolutionized
the corporate aviation industry. Fractional management companies (FMC) manage all aspects of aircraft operations enabling
the owners to enjoy the benefits of private aviation without the associated responsibilities. We describe here the development
of a scheduling decision support tool for a leading FMC. We present mathematical models, exact and heuristic solution methods.
Our computational results using real and randomly generated data indicate that these models are quite effective in finding
optimal or near-optimal solutions. The first phase of the implementation of one of these models at the FMC led to a significant
improvement in effective utilization of the aircraft, reduction of costs due to reduced empty moves, and hence increased profits. 相似文献
45.
Biswanath Das Kongara Ravinder Reddy Bommena Ravikanth Akella Venkata Subrahmanya Sarma Balasubramanian Sridhar 《Helvetica chimica acta》2008,91(6):1137-1143
Chemical investigation on two samples of the flowers of Parthenium hysterophorus afforded two new pseudoguaianolides (one from each sample) together with several known constituents. The structures of the new compounds were established by extensive spectroscopic (1D‐ and 2D‐NMR) studies. The X‐ray crystallographic analysis of one of these compounds was also accomplished. 相似文献
46.
Sridhar S. KannurpattiMichael A. Motes Bart RypmaBharat B. Biswal 《Magnetic resonance imaging》2011,29(1):140-146
Block and event-related stimulus designs are typically used in fMRI studies depending on the importance of detection power or estimation efficiency. The extent of vascular contribution to variability in block and event-related fMRI-BOLD response is not known. With scaling, the extent of vascular variability in the fMRI-BOLD response during block and event-related design tasks was investigated. Blood oxygen level-dependent (BOLD) contrast data from healthy volunteers performing a block design motor task and an event-related memory task requiring performance of a motor response were analyzed from the regions of interest (ROIs) surrounding the primary and supplementary motor cortices. Average BOLD signal change was significantly larger during the block design compared to the event-related design. In each subject, BOLD signal change across voxels in the ROIs had higher variation during the block design task compared to the event-related design task. Scaling using the resting state fluctuation of amplitude (RSFA) and breath-hold (BH), which minimizes BOLD variation due to vascular origins, reduced the within-subject BOLD variability in every subject during both tasks but significantly reduced BOLD variability across subjects only during the block design task. The strong non-neural source of intra- and intersubject variability of BOLD response during the block design compared to event-related task indicates that study designs optimizing for statistical power through enhancement of the BOLD contrast (for, e.g., block design) can be affected by enhancement of non-neural sources of BOLD variability. 相似文献
47.
48.
Dehydration of 1,4-dioxane through blend membranes of poly(vinyl alcohol) and chitosan by pervaporation 总被引:1,自引:0,他引:1
D. Anjali Devi B. Smitha S. Sridhar T.M. Aminabhavi 《Journal of membrane science》2006,280(1-2):138-147
Blend membranes prepared from poly(vinyl alcohol) (PVA) and chitosan (CS) were crosslinked with glutaraldehyde and used in the pervaporation dehydration of 1,4-dioxane. Membranes were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (X-RD) to assess, respectively, the intermolecular interactions, thermal stability and crystallinity. Equilibrium sorption studies were carried out in pure liquids and binary mixtures of different compositions of water + 1,4-dioxane mixtures to assess the polymer–liquid interactions. The crosslinked membrane showed a good potential in breaking the azeotrope of 82 wt.% aqueous 1,4-dioxane giving a selectivity of 117 with a reasonable water flux of 0.37 kg/m2 h. The effect of operating parameters such as feed composition, membrane thickness and permeate pressure was evaluated. 相似文献
49.
50.
K. Sridhar 《Zeitschrift fur Physik C Particles and Fields》1992,55(3):401-408
Largep T direct photon and dimuon production in experiments using nuclear targets have been studied in detail. We show that, by a careful choice of kinematic configurations in these experiments, very good estimates of nuclear quark and gluon densities can be obtained. Information on the cumulative region of the nuclear structure functions i.e. the regionx>1 can also be obtained by considering semi-integrated cross sections. 相似文献