2,040 research outputs found
Ferrodistorsive orbital ordering in the layered nickelate NaNiO_2: A density-functional study
The electronic structure and magnetism in the sodium nickelate NaNiO_2 in the
low-temperature phase is studied from density-functional calculations using the
linear muffin-tin orbitals method. An antiferromagnetic solution with a
magnetic moment of 0.7 m_B per Ni ion is found. A ferrodistorsive orbital
ordering is shown to occur due to the Jahn-Teller distortion around the Ni^{3+}
ion in agreement with the orbital ordering inferred from neutron diffraction.
While the intralayer exchange is ferromagnetic, the interlayer exchange is
weakly antiferromagnetic, mediated by a long Ni-O-Na-O-Ni superexchange path.Comment: 4 pages, 5 figures Submitted to MMM2004 conference Proceeding
Saturation properties and incompressibility of nuclear matter: A consistent determination from nuclear masses
Starting with a two-body effective nucleon-nucleon interaction, it is shown
that the infinite nuclear matter model of atomic nuclei is more appropriate
than the conventional Bethe-Weizsacker like mass formulae to extract saturation
properties of nuclear matter from nuclear masses. In particular, the saturation
density thus obtained agrees with that of electron scattering data and the
Hartree-Fock calculations. For the first time using nuclear mass formula, the
radius constant =1.138 fm and binding energy per nucleon = -16.11
MeV, corresponding to the infinite nuclear matter, are consistently obtained
from the same source. An important offshoot of this study is the determination
of nuclear matter incompressibility to be 288 28 MeV using
the same source of nuclear masses as input.Comment: 14 latex pages, five figures available on request ( to appear in Phy.
Rev. C
Spin excitations in ferromagnetic manganites
An effective one-band Hamiltonian for colossal-magnetoresistance (CMR)
manganites is constructed and the spin excitations are determined. Fitting the
experimental data by the derived spin-wave dispersion gives an e_g -electron
hopping amplitude of about 0.2 eV in agreement with LDA band calculations.Comment: 2 pages, 1 figur
Epidemiological investigation into the source of water contamination at a tertiary care cancer hospital
Background: Water quality impacts the performance of the hospitals and leads to drastic health service deterioration affecting infection control programs, along with safety of the patients and staff. Good quality water is an essential prerequisite to ensure optimal patient care, and the well-being of the staff and visitors in a hospital environment. Objectives was to study the current water supply and treatment system in the cancer hospital. Also, to carryout root cause analysis of the causes of episodes of diarrhoea amongst patients and staff and to identify the source of infection and suggest improvement in the existing system to prevent recurrence.Methods: There were 25 reported cases of diarrhoea and other gastrointestinal symptoms between May 12 and June 2 2017, allegedly due to water contamination occurring in admitted patients and staff of a tertiary care cancer hospital in north India. This was reported to Hospital Administration, which prompted an epidemiological investigation.Results: Formation of Biofilms on the plastic taps was found to be the main reason for contamination of water.Conclusions: It was very clear that deposition of biofilm within the plastic taps was the main reason of diarrhea among the patients
Multiplex PCR for Detection of Herpes Simplex Viruses Type-1 and Type-2, Cytomegalovirus, Varicella-zoster Virus, and Adenovirus in Ocular Viral Infections
Purpose: Most common viruses causing ocular infections are Herpes Simplex Viruses (HSV) type 1 and type 2, Cytomegalovirus (CMV), Varicella-zoster Virus (VZV), and few strains of Adenovirus. Diagnosis of these infections through clinical manifestations and using conventional methods has a number of limitations. The purpose of this study was to develop a multiplex Polymerase Chain Reaction (PCR) for simultaneous detection of all pathogenic viruses from ocular infections.
Methods: Ten uniplex PCRs were standardized, two each for HSV type 1 (HSV-1) and type 2 (HSV-2), CMV, VZV, and Adenovirus. Various multiplexing combinations of above PCRs were put to finalize targets and reaction conditions enabling diagnosis of all in a single reaction. The uniplex and multiplex PCRs were run for known positive and negative controls, and samples from clinically suspected patients and healthy controls.
Results: Out of the 170 samples from suspected ocular infections, 24.7% were positive by uniplex PCR and 22.9% were correctly identified by multiplex PCR. None of the samples negative by uniplex PCRs was positive by the multiplex PCR. The sensitivity and specificity of multiplex PCR compared to the commonly used uniplex PCRs as gold standard was 92.86% and 100%, respectively. The prevalence of different viral pathogens was 13.5% for HSV-1, followed by 5.9% for Adenovirus, 2.4% for VZV, 1.8% for HSV-2, and 1.2% for CMV.
Conclusion: The establishment of multiplex PCR has found immediate application in diagnosing ocular viral pathogens in a single reaction, thus saving time, manpower, and resources by fivefold
Caloric curve in Au + Au collisions
Realistic caloric curves are obtained for reaction with
incident energy ranging from 35 to 130 MeV/nucleon in the dynamic statistical
multifragmentation model. It is shown that for excitation energy 3 to 8
MeV/nucleon, the temperature remains constant in the range 5 to 6 MeV, which is
close to experiment. The mechanism of energy deposition through the
tripartition of colliding system envisaged in this model together with
inter-fragment nuclear interaction are found to play important role. A possible
signature of liquid-gas phase transition is seen in the specific heat
distribution calculated from these caloric curves, and the critical temperature
is found to be 6 to 6.5 MeV.Comment: Revtex, 10 pages, 4 postscipt figures, To appear in Phys. Rev. C
(Rapid Communications
Electronic structure of spinel-type LiV_2O_4
The band structure of the cubic spinel compound LiV_2O_4, which has been
reported recently to show heavy Fermion behavior, has been calculated within
the local-density approximation using a full-potential version of the linear
augmented-plane-wave method. The results show that partially-filled V 3d bands
are located about 1.9 eV above the O 2p bands and the V 3d bands are split into
a lower partially-filled t_{2g} complex and an upper unoccupied e_{g} manifold.
The fact that the conduction electrons originate solely from the t_{2g} bands
suggests that the mechanism for the mass enhancement in this system is
different from that in the 4f heavy Fermion systems, where these effects are
attributed to the hybridization between the localized 4f levels and itinerant
spd bands.Comment: 5 pages, revte
Magnetic reconstruction at (001) CaMnO surface
The Mn-terminated (001) surface of the stable anti-ferromagnetic insulating
phase of cubic perovskite CaMnO is found to undergo a magnetic
reconstruction consisting on a spin-flip process at surface: each Mn spin at
the surface flips to pair with that of Mn in the subsurface layer. In spite of
very little Mn-O charge transfer at surface, the surface behavior is driven by
the states due to charge redistribution. These
results, based on local spin density theory, give a double exchange like
coupling that is driven by character, not additional charge, and may have
relevance to CMR materials.Comment: 4 pages, 5 figures reference added Fig. 3 modified. Caption of Fig. 5
modifie
Spin Excitation Spectrum of LaMnO
As an effective model to describe perovskite-type manganates (La,)MnO,
the double-exchange model on a cubic lattice is investigated. Spin excitation
spectrum of the model in the ground state is studied using the spin wave
approximation. Spin wave dispersion relation observed in the inelastic neutron
scattering experiment of LaPbMnO is reproduced. Effective
values for the electron bandwidth as well as Hund's coupling is estimated from
the data.Comment: 10 pages LaTeX including 4 PS figure
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