1,314 research outputs found
Effect of disorder on the electronic properties of graphene: a theoretical approach
In order to manipulate the properties of graphene, its very important to
understand the electronic structure in presence of disorder. We investigate,
within a tight-binding description, the effects of disorder in the on-site
(diagonal disorder) term in the Hamiltonian as well as in the hopping integral
(off-diagonal disorder) on the electronic dispersion and density of states by
augmented space recursion method. Extrinsic off-diagonal disorder is shown to
have dramatic effects on the two-dimensional Dirac-cone, including asymmetries
in the band structures as well as the presence of discontinuous bands in
certain limits. Disorder-induced broadening, related to the scattering length
(or life-time) of electrons, is modified significantly with the increasing
strength of disorder. We propose that our theory is suitable to study the
effects of disorder in other 2D materials, e.g., a boron nitride monolayer.Comment: 11 pages, 8 figure
Lattice thermal conductivity of disordered binary alloys : a formulation
We present here a formulation for the calculation of the configuration
averaged lattice thermal conductivity in random alloys. Our formulation is
based on the augmented-space theorem, introduced by one of us, combined with a
generalized diagrammatic technique. The diagrammatic approach simplifies the
problem of including effects of disorder corrections to a great extent. The
approach allows us to obtain an expression for the effective heat current in
case of disordered alloys, which in turn is used in a Kubo-Greenwood type
formula for the thermal conductivity. We show that disorder scattering
renormalizes the phonon propagators as well as the heat currents. The
corrections to the current terms have been shown to be related to the
self-energy of the propagators. We also study the effect of vertex corrections
in a simplified ladder diagram approximation. A mode dependent diffusivity
and then a total thermal diffusivity averaged over different modes
are defined. Schemes for implementing the said formalism are discussed. A few
initial numerical results on the frequency and temperature dependence of
lattice thermal conductivity are presented for NiPd alloy and are also compared
with experiment. We also display numerical results on the frequency dependence
of thermal diffusivity averaged over modes.Comment: 16 pages, 17 figure
Source code embedded (SCEM) security framework
Security in the Software Development Life Cycle (SDLC) has become imperative due to the variety of threats posed during and after system design. In this paper we have studied the security in system design in general and software development in particular, and have proposed strategies for integration of security in the SDLC. The paper highlights the needs of embedding security right from the earlier processes in the SDLC because patches and controls after the software delivery are more expensive to fix. We propose Source Code EMbedded (SCEM) security framework to improve the design of security policies and standards for the software development process to ensure the security and reliability in government departments such as taxation, auditing, national security, social security, and immigration. It is also envisaged that the implementation of SCEM security framework will ensure commercial and public trust in the software development process within Australia and worldwide, saving enormous redevelopment costs
Enhancing the rheological properties and shale inhibition behavior of water-based mud using nanosilica, multi-walled carbon nanotube, and graphene nanoplatelet
Five different drilling mud systems namely potassium chloride (KCl) as a basic mud, KCl/partial hydrolytic polyacrylamide (PHPA), KCl/graphene nanoplatelet (GNP), KCl/nanosilica and KCl/multi-walled carbon nano tube (MWCNT) were prepared and investigated for enhancement of rheological properties and shale inhibition. Nanoparticles were characterized in drilling mud using transmission electron microscope (TEM) analysis. Mineralogical analysis of shale was examined by X-ray diffraction (XRD). Five shale plugs were prepared using compactor cell for the determination of shale swelling. Shale swelling was determined using the linear swell meter (LSM) for 20 hours. Results revealed that basic mud and KCl/polymer mud systems shows 30% and 24% change in shale volume. MWCNT, nanosilica and GNP were added separately in the KCl mud system. 0.1 ppb of each MWCNT and nanosilica showed 32% and 33% change in shale volume. However, when the shale was interacted with WBM containing 0.1 ppb of GNP, it was found that only 10% change in shale volume occurred. The results showed that the addition of nanoparticles in the KCl mud system improved the shale inhibition. API, HPHT filtrate loss volume, plastic viscosity (PV) and yield point (YP) were improved using GNP. It is learned from the experimental work that small concentration of KCl with GNP can mitigate shale swelling compared to the mud contains higher concentration of KCl and PHPA in WBM. Thus, GNP can be a better choice for enhancement of WBM performance
Mortality caused by aqueous extract of the leaves of Datura stramineus to goat biting louse, Bovicola caprae (Phthiraptera)
Extensive and indiscriminate use of organic lousicides is leading to environmental hazards i.e. persistence of residues, development of resistance and targeting of non-target beneficial organism. Hence, phytotherapy is emerging as effective tool for louse control, due to ecofriendly and biodegradable nature of plant extracts. In the present study the mortality and repellency caused by five concentration of aqueous extract of the leaves of commonly available Datura stramineus were tested against goat biting louse, Bovicola caprae. Fifteen percent concentration of extract prepared from leaves of aforesaid plant imparted 77% mortality and 66% repellency to goat biting louse
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
Impaired IFN-γ Production by Viral Immunodominant Peptide-specific Tetramer+ CD8+ T Cells in HIV-1 Infected Patients is not Secondary to HAART
Studies on PBMC samples from HIV-1 infected patients have shown that despite
substantial number of HIV specific CTLs, these patients gradually progress to AIDS.
The present study was conducted to determine whether this paradox was secondary
to the influence of protease inhibitors being utilized by these patients. Thus, aliquots
of PBMC samples from 10 HIV infected humans with no prior history of anti-retroviral
drug therapy (ART) and 6 HIV-infected patients that had been on HAART for >1 year
were analyzed for the frequency of HIV-1 Nef and Gag dominant peptide specific
tetramer+ cells, respectively. The tetramer+ PBMCs were analyzed for their ability
to synthesize specific peptide induced IFN-γ utilizing both the ELISPOT and the
intracellular cytokine (ICC) assays. Results of the studies showed that there was
an overall correlation between the frequency of Nef and Gag peptide tetramer+
cells and the frequency of IFN-γ synthesizing cells as assayed by either ICC or
ELISPOT assay, markedly reduced values of IFN-γ synthesizing cells per unit
tetramer+ cells were noted in both group of patients. These data suggest that
the frequency of HIV-specific CD8+T cells is maintained during the chronic phase
of infection, their ability to function is compromised and is not a reflection of ART.
While the addition of IL-2, anti-CD40L and allogeneic cells led to partial increase
in the ability of the tetramer+ cells to synthesize IFN-γ, the addition of IL-4, IL-12,
anti-CD28 or a cocktail of anti-TGF-β, TNF-α and IL-10 failed to augment the IFN-γ response
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Recommendations for coronavirus infection in rheumatic diseases treated with biologic therapy.
The Coronavirus-associated disease, that was first identified in 2019 in China (CoViD-19), is a pandemic caused by a bat-derived beta-coronavirus, named SARS-CoV2. It shares homology with SARS and MERS-CoV, responsible for past outbreaks in China and in Middle East. SARS-CoV2 spread from China where the first infections were described in December 2019 and is responsible for the respiratory symptoms that can lead to acute respiratory distress syndrome. A cytokine storm has been shown in patients who develop fatal complications, as observed in past coronavirus infections. The management includes ventilatory support and broad-spectrum antiviral drugs, empirically utilized, as a targeted therapy and vaccines have not been developed. Based upon our limited knowledge on the pathogenesis of CoViD-19, a potential role of some anti-rheumatic drugs may be hypothesized, acting as direct antivirals or targeting host immune response. Antimalarial drugs, commonly used in rheumatology, may alter the lysosomal proteases that mediates the viral entry into the cell and have demonstrated efficacy in improving the infection. Anti-IL-1 and anti-IL-6 may interfere with the cytokine storm in severe cases and use of tocilizumab has shown good outcomes in a small cohort. Baricitinib has both antiviral and anti-inflammatory properties. Checkpoints inhibitors such as anti-CD200 and anti-PD1 could have a role in the treatment of CoViD-19. Rheumatic disease patients taking immunosuppressive drugs should be recommended to maintain the chronic therapy, prevent infection by avoiding social contacts and pausing immunosuppressants in case of infection. National and international registries are being created to collect data on rheumatic patients with CoViD-19
A Gaussian Process Approach for Extended Object Tracking with Random Shapes and for Dealing with Intractable Likelihoods
Tracking of arbitrarily shaped extended objects is a complex task due to the intractable analytical expression of measurement to object associations. The presence of sensor noise and clutter worsens the situation. Although a significant work has been done on the extended object tracking (EOT) problems, most of the developed methods are restricted by assumptions on the shape of the object such as stick, circle, or other axis-symmetric properties etc. This paper proposes a novel Gaussian process approach for tracking an extended object using a convolution particle filter (CPF). The new approach is shown to track irregularly shaped objects efficiently in presence of measurement noise and clutter. The mean recall and precision values for the shape, calculated by the proposed method on simulated data are around 0.9, respectively, by using 1000 particles
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