631 research outputs found
Augmented space recursion for partially disordered systems
Off-stoichiometric alloys exhibit partial disorder, in the sense that only
some of the sublattices of the stoichiometric ordered alloy become disordered.
This paper puts forward a generalization of the augmented space recursion (ASR)
(introduced earlier by one of us (Mookerjee et al 1997(*))) for systems with
many atoms per unit cell. In order to justify the convergence properties of ASR
we have studied the convergence of various moments of local density of states
and other physical quantities like Fermi energy and band energy. We have also
looked at the convergence of the magnetic moment of Ni, which is very sensitive
to numerical approximations towards the k-space value 0.6 with the
number of recursion steps prior to termination.Comment: Latex 2e, 21 Pages, 13 Figures, iopb style file attache
Vibrational properties of phonons in random binary alloys: An augmented space recursive technique in the k-representation
We present here an augmented space recursive technique in the
k-representation which include diagonal, off-diagonal and the environmental
disorder explicitly : an analytic, translationally invariant, multiple
scattering theory for phonons in random binary alloys.We propose the augmented
space recursion (ASR) as a computationally fast and accurate technique which
will incorporate configuration fluctuations over a large local environment. We
apply the formalism to , Ni_{88}Cr_12} and
alloys which is not a random choice. Numerical results on spectral functions,
coherent structure factors, dispersion curves and disordered induced FWHM's are
presented. Finally the results are compared with the recent itinerant coherent
potential approximation (ICPA) and also with experiments.Comment: 20 pages, LaTeX, 23 figure
Inelastic neutron scattering in random binary alloys : an augmented space approach
Combining the augmented space representation for phonons with a generalized
version of Yonezawa-Matsubara diagrammatic technique, we have set up a
formalism to seperate the coherent and incoherent part of the total intensity
of thermal neutron scattering from disordered alloys. This is done exacly
without taking any recourse to mean-field like approximation (as done
previously). The formalism includes disorder in masses, force constants and
scattering lengths. Implementation of the formalism to realistic situations is
performed by an augmented space Block recursion which calculates entire Green
matrix and self energy matrix which in turn is needed to evaluate the coherent
and incoherent intensities. we apply the formalism to NiPd and NiPt alloys.
Numerical results on coherent and incoherent scattering cross sections are
presented along the highest symmetry directions. Finally the incoherent
intensities are compared with the CPA and also with experiments.Comment: 18 pages, 13 figure
Worsening of cerebral hyperemia by the administration of terlipressin in acute liver failure with severe hepatic encephalopathy
There is increasing evidence that terlipressin is useful in patients with cirrhosis and
hepatorenal syndrome, but there are no data of its use in patients with acute liver
failure (ALF) in whom hepatorenal syndrome is common. Although terlipressin
produces systemic vasoconstriction, it produces cerebral vasodilatation and may
increase cerebral blood flow (CBF). Increased CBF contributes to intracranial
hypertension in patients with ALF. The aim of this study was to evaluate the safety of
terlipressin in patients with ALF with respect to cerebral haemodynamics. Six
successive patients with ALF were electively ventilated for grade IV hepatic
encephalopathy. Patients were monitored invasively and CBF was measured (Kety-
Schmidt technique). Measurements were made before, at 1, 3 hour and 5 hours after
intravenous (single bolus) administration of terlipressin (0.005 mg/kg) )intravenously
(single bolus), median 0.25mg (range 0.2-0.3). There was no significant change in
heart rate, mean arterial pressure or cardiac output. CBF and jugular venous oxygen
saturation both increased significantly at 1 hour (p<0.0=0.016) respectively.
Intracranial pressure increased significantly at 21 hours (p<0=.0.031), returning back
to baseline values at 42 hours. This study shows that administration of terlipressin, at
a dose that did not alter systemic haemodynamicshemodynamics, resulted in
worsening of cerebral hyperemia and intracranial hypertension in patients with ALF
and severe hepatic encephalopathy. These data suggest the need to exercise extreme
caution in the use of terlipressin in these patients in view of its potentially deleterious
consequences on cerebral haemodynamics
Development of a Computerized App Based on Fitness Norms of University Students
Please view abstract in the attached PDF fil
65 The CD4 peptide analogue 802-2 inhibits proliferation of both TH1 and TH2 cells in response to allogeneic stimulation
Structure, bonding and magnetism in cobalt clusters
The structural, electronic and magnetic properties of Co clusters
(20) have been investigated using density functional theory within the
pseudopotential plane wave method. An unusual hexagonal growth pattern has been
observed in the intermediate size range, 20. The cobalt atoms are
ferromagnetically ordered and the calculated magnetic moments are found to be
higher than that of corresponding hcp bulk value, which are in good agreement
with the recent Stern-Gerlach experiments. The average coordination number is
found to dominate over the average bond length to determine the effective
hybridization and consequently the cluster magnetic moment.Comment: 12 pages and 9 figure
Emergence of noncollinear magnetic ordering in small magnetic clusters: Mn and As@Mn
Using first-principles density functional calculations, we have studied the
magnetic ordering in pure Mn (10, 13, 15, 19) and As@Mn
(10) clusters. Although, for both pure and doped manganese clusters,
there exists many collinear and noncollinear isomers close in energy, the
smaller clusters with 5 have collinear magnetic ground state and
the emergence of noncollinear ground states is seen for 6 clusters.
Due to strong hybridization in As@Mn clusters, the binding energy is
substantially enhanced and the magnetic moment is reduced compared to the
corresponding pure Mn clusters.Comment: 10 Pages and 5 Figure
An augmented space recursion study of the electronic structure of rough epitaxial overlayers
In this communication we propose the use of the Augmented Space Recursion as
an ideal methodology for the study of electronic and magnetic structures of
rough surfaces, interfaces and overlayers. The method can take into account
roughness, short-ranged clustering effects, surface dilatation and
interdiffusion. We illustrate our method by an application of Fe overlayer on
Ag (100) surface.Comment: 22 pages, Latex, 6 postscript figure
Minimising ambient illumination via ambient subtraction: Smartphone assessment of jaundice in liver patients via sclera images
Using smartphone images to quantify color presents a noninvasive way to assess jaundice and other color-related biomarkers of the human body. Here we focus on assessing jaundice through accurate bilirubin measurement in adult liver patients, the first time optical imaging has been applied to this cohort. These patients can suffer from very high levels of bilirubin, indicating their severity of liver disease. A smartphone assessment technique for jaundice based around the color of the sclera (white of the eye) extracted from images is being developed, as smartphone imaging enables cheap, non-invasive and quantitative readings. Variations in ambient light cause large changes to recorded pixel values so must be accounted for to ensure that any changes detected are due to changes in jaundice level. Here we suggest the use of an ambient subtraction approach to minimise the effects of ambient light. Pairs of flash/no-flash images are captured and the extracted values subtracted to yield data as though under a pure flash illumination. We present data demonstrating the technique with a group of healthy adult volunteers. We also present data from a patient study involving adults with liver disease. Images were captured and the bilirubin (jaundice) level predicted from these images before and after subtraction was compared to the ground truth value obtained via blood test. The linear correlation coefficient increased from 0.47 to 0.85 (p<0.001 in both cases) upon application of subtraction, demonstrating the effectiveness of the technique
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