Reducing numerical diffusion for incompressible flow calculations

A number of approaches for improving the accuracy of incompressible, steady-state flow calculations are examined. Two improved differencing schemes, Quadratic Upstream Interpolation for Convective Kinematics (QUICK) and Skew-Upwind Differencing (SUD), are applied to the convective terms in the Navier-Stokes equations and compared with results obtained using hybrid differencing. In a number of test calculations, it is illustrated that no single scheme exhibits superior performance for all flow situations. However, both SUD and QUICK are shown to be generally more accurate than hybrid differencing

MPEG-4 video transmission using distributed TDMA MAC protocol over IEEE 802.15.4 wireless technology

The issues of green technology nowadays give an inspiration to the researcher to make all the future design to be energy efficient. Medium Access Control (MAC) layer is the most effective layer to provide energy efficient due to its ability to control the physical radio directly. One of the important applications in the future is a video transmission that can be transmitted with low-cost and low power consumption. MPEG-4 is one of the international standards for moving video. MPEG-4 provide better compression and primarily design at low bit rate communication. In order to achieve good quality for video application, the design at MAC layer must be strong. Therefore, to increase the performance of the MPEG-4 in IEEE 802.15.4, in this paper we propose a cross layer design between MAC layer and Application layer. A priority queue will be implemented at MAC scheduling depends on the level of frame important in MPEG-4 format frame. A distributed Time division Multiple Access (TDMA) will be used for MAC protocol to provide reliable data transmission for high priority frame

Island Size Selectivity during 2D Ag Island Coarsening on Ag (111)

We report on early stages of submonolayer Ag island coarsening on Ag(111) surface at room temperature ($300$ K) carried out using realistic kinetic Monte Carlo (KMC) simulations. We find that during early stages, coarsening proceeds as a sequence of selected island sizes creating peaks and valleys in the island size distribution. We find that island-size selectivity is due to formation of kinetically stable islands for certain sizes because of adatom detachment/attachment processes and large activation barrier for kink detachment. In addition, we find that the ratio of number of adatom attachment to detachment processes to be independent of parameters of initial configuration and also on the initial shapes of the islands confirming that island-size selectivity is independent of initial conditions.These simulations were carried out using a very large database of processes identified by their local environment and whose activation barriers were calculated using the embedded-atom method

Pool boiling on modified surfaces using R-123

This article has been made available through the Brunel Open Access Publishing Fund.Saturated pool boiling of R-123 was investigated for five horizontal copper surfaces modified by different treatments, namely, an emery-polished surface, a fine sandblasted surface, a rough sandblasted surface, an electron beam-enhanced surface, and a sintered surface. Each 40-mm-diameter heating surface formed the upper face of an oxygen-free copper block, electrically heated by embedded cartridge heaters. The experiments were performed from the natural convection regime through nucleate boiling up to the critical heat flux, with both increasing and decreasing heat flux, at 1.01 bar, and additionally at 2 bar and 4 bar for the emery-polished surface. Significant enhancement of heat transfer with increasing surface modification was demonstrated, particularly for the electron beam-enhanced and sintered surfaces. The emery-polished and sandblasted surface results are compared with nucleate boiling correlations and other published data. © 2014 Syed W. Ahmad, John S. Lewis, Ryan J. McGlen, and Tassos G. Karayiannis Published with license by Taylor & Francis

Disorder mediated splitting of the cyclotron resonance in two-dimensional electron systems

We perform a direct study of the magnitude of the anomalous splitting in the cyclotron resonance (CR) of a two-dimensional electron system (2DES) as a function of sample disorder. In a series of AlGaAs/GaAs quantum wells, identical except for a range of carbon doping in the well, we find the CR splitting to vanish at high sample mobilities but to increase dramatically with increasing impurity density and electron scattering rates. This observation lends strong support to the conjecture that the non-zero wavevector, roton-like minimum in the dispersion of 2D magnetoplasmons comes into resonance with the CR, with the two modes being coupled via disorder.Comment: accepted to PRB Rapid Com

Acoustic phonon scattering in a low density, high mobility AlGaN/GaN field effect transistor

We report on the temperature dependence of the mobility, $\mu$, of the two-dimensional electron gas in a variable density AlGaN/GaN field effect transistor, with carrier densities ranging from 0.4$\times10^{12}$ cm$^{-2}$ to 3.0$\times10^{12}$ cm$^{-2}$ and a peak mobility of 80,000 cm$^{2}$/Vs. Between 20 K and 50 K we observe a linear dependence $\mu_{ac}^{-1} = \alpha$T indicating that acoustic phonon scattering dominates the temperature dependence of the mobility, with $\alpha$ being a monotonically increasing function of decreasing 2D electron density. This behavior is contrary to predictions of scattering in a degenerate electron gas, but consistent with calculations which account for thermal broadening and the temperature dependence of the electron screening. Our data imply a deformation potential D = 12-15 eV.Comment: 3 pages, 2 figures, RevTeX. Submitted to Appl Phys Let

In Vitro Antioxidant and In Vivo Hepatoprotective Activity of Leave Extract of Raphanus Sativus in Rats Using CCL4 Model

Background: Raphanus sativus is reported to have a variety of biological activities. This work screened the hepato-protective and antioxidant activity of ethanol (ERS), and aqueous (ARS), extracts of leaves of Raphanus sativus in Carbon tetrachloride (CCl4), model in rats.Material and Methods: The extracts were subjected to antioxidant tests (Total reducing power and Total phenolic content), and preliminary phytochemical screening. A pilot study was done on 100 and 300 mg/kg extracts, form which 300 mg was chosen for further experiments. The albino rats (200-250 grams), were divided into 5 groups of 6 animals each (n=6). There were three control groups comprising of normal control (normal saline -1ml/kg), negative control group (CCl4 1ml/kg in olive oil in a ratio of 1:1 v/v), and positive control group (Silymarin 50mg/kg). The Test drugs were given in a dose of 300 mg/kg for both ERS and ARS extract for 7 days. Biochemical parameters (AST, ALT, Alkaline phosphatase, Total Bilirubin), histo-pathological examination of liver and in vivo antioxidant tests [CAT, GSH and MDA] were done.Results: The phytochemical study showed the presence of flavanoids, terpenoids, alkaloids, saponins and sterols. A dose dependent increase in the oxidative potential was observed in both the extracts with total phenolic content 70.1 and 44.4 GAE/g extract for ERS and ARS respectively. ERS 300mg/kg showed a significant (p<0.001) increase in levels of AST, ALT and alkaline phosphatase as compared to negative control (percentage hepatoprotection =45.3%) while ARS 300 mg/kg (p<.01) group showed 30% hepatoprotection. The GSH (p<0.001) and CAT (p<0.05) in ERS and ARS were significantly increased while MDA levels were decreased (P< 0.01), as compared negative control. The findings were confirmed histo-pathological examination.Conclusion: The ethanol and aqueous extract of Raphanus sativus have partial hepatoprotection against CCl4 toxicity.Key words: Raphanus sativus, hepatoprotection, CCl4, antioxidant

Bacterial Profiles of Subgingival Plaques in Periodontitis

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142259/1/jper0447.pd

Microcanonical entropies and radiative strength functions of 50,51^{50,51}V

The level densities and radiative strength functions (RSFs) of $^{50,51}$V have been extracted using the ($^3$He,$\alpha \gamma$) and ($^3$He,$^3$He$^{\prime} \gamma$) reactions, respectively. From the level densities, microcanonical entropies are deduced. The high $\gamma$-energy part of the RSF is described by the giant electric dipole resonance. A significant enhancement over the predicted strength in the region of $E_{\gamma} \lesssim 3$ MeV is seen, which at present has no theoretical explanation.Comment: 16 pages including 9 figure

Alternative splicing and protein diversity: plants versus animals

Plants, unlike animals, exhibit a very high degree of plasticity in their growth and development and employ diverse strategies to cope with the variations during diurnal cycles and stressful conditions. Plants and animals, despite their remarkable morphological and physiological differences, share many basic cellular processes and regulatory mechanisms. Alternative splicing (AS) is one such gene regulatory mechanism that modulates gene expression in multiple ways. It is now well established that AS is prevalent in all multicellular eukaryotes including plants and humans. Emerging evidence indicates that in plants, as in animals, transcription and splicing are coupled. Here, we reviewed recent evidence in support of co-transcriptional splicing in plants and highlighted similarities and differences between plants and humans. An unsettled question in the field of AS is the extent to which splice isoforms contribute to protein diversity. To take a critical look at this question, we presented a comprehensive summary of the current status of research in this area in both plants and humans, discussed limitations with the currently used approaches and suggested improvements to current methods and alternative approaches. We end with a discussion on the potential role of epigenetic modifications and chromatin state in splicing memory in plants primed with stresses