Vacuum ultraviolet photoabsorption of prime ice analogues of Pluto and Charon

Here we present the first Vacuum UltraViolet (VUV) photoabsorption spectra of ice analogues of Pluto and Charon ice mixtures. For Pluto the ice analogue is an icy mixture containing nitrogen (N2), carbon monoxide (CO), methane (CH4) and water (H2O) prepared with a 100:1:1:3 ratio, respectively. Photoabsorption of icy mixtures with and without H2O were recorded and no significant changes in the spectra due to presence of H2O were observed. For Charon a VUV photoabsorption spectra of an ice analogue containing ammonia (NH3) and H2O prepared with a 1:1 ratio was recorded, a spectrum of ammonium hydroxide (NH4OH) was also recorded. These spectra may help to interpret the P-Alice data from New Horizons

Evaluation of the Blood-Glucose Reducing Effects of Aqueous Extracts of the Selected Umbelliferous Fruits Used in Culinary Practices

Purpose: Oxidative stress in diabetes coexists with a reduction in the antioxidant status, which can increase the deleterious effects of free radicals. Many plant extracts and plant products have been shown to have significant antioxidant activity. The role of antioxidant plants in diabetes has not been studied. Food additives like spices, which have free radical scavenging activity, may also be useful in maintaining normal glucose levels in diabetic patients. The objective of the study is to evaluate the aqueous extracts of selected umbelliferous fruits for hypoglycaemic and antidiabetic activities in normal and diabetic rats respectively. Methods: All the aqueous extracts of (Caraway) CA, (Coriander) CO, (Cumin) CU, (Dill) DI and (Fennel) FE were administered at dose levels of 300 mg/kg body weight orally to different groups each containing 5 animals. A control group was also maintained simultaneously and received distilled water orally.Blood samples were collected from retro-orbital plexus of each rat before and at 2, 4, 6 and 8 h after extract administration and were analyzed for glucose content by using glucose oxidase peroxidase (GOD-POD) method using a visible spectrophotometer at 505 nm. Results: In normal rats only caraway extract produced significant hypoglycaemic action. The rest of the extracts produced hypoglycaemia, which was not significant different from that of control animals. In diabetic rats also the caraway was found to be the best among the extracts. Conclusion: The study indicates that since the umbelliferous fruits are used in the preparation of foods, they may be useful in the control of postprandial rise of blood glucose particularly in diabetic condition. Additionally, their daily use may help in reducing complications associated with chronic diabetes. Keywords: Diabetes, Oxidative stress, Glucose Oxidase – Peroxidase (GOD-POD), Antioxidants. > Tropical Journal of Pharmaceutical Research Vol. 5 (2) 2006: pp. 613-61

SEPIC Converter based-Drive for Unipolar BLDC Motor

Front-end single-ended primary inductance converter (SEPIC) and a switch in series with each phase is proposed for driving a permanent magnet brushless dc (BLDC) motor with unipolar currents. All the switches are ground-referenced, which simplifies their gate drives. The available input voltage can be boosted for better current regulation, which is an advantage for low voltage applications. The SEPIC converter is designed to operate in the discontinuous conduction mode for operation with an ac supply. In this operation mode, the line current follows the line voltage waveform to a certain extent. The reduction in low-order harmonics and improved power factor is achieved without the use of any voltage or current sensors. The simplicity and reduced parts count of the proposed topology make it an attractive low-cost choice for many variable speed drive applications. The proposed topology is simulated and verified by using MATLAB/SIMULINK.DOI:http://dx.doi.org/10.11591/ijece.v2i2.30

Electron states and electron-phonon coupling in the BEDT-TTF-based organic superconductors

URL:http://link.aps.org/doi/10.1103/PhysRevB.53.6677 DOI:10.1103/PhysRevB.53.6677The electronic structure and the coupling of electrons to the vibrational modes of a single bis (ethylenedithio)-tetrathiafulvalene (BEDT-TTF) molecule, the building block of a class of organic superconductors, are studied from quantum chemical calculations. We find that the molecular orbital structure near the Fermi energy can be described with a simple tight-binding model involving only the out-of-plane p orbitals on the carbon and sulfur atoms in the central part of the molecule. Just three of the vibrational modes of Ag symmetry couple strongly to the electron states resulting in a frequency shift of typically 10% for these modes. The high-frequency Ag(11) mode is predicted to be broadened the most by the coupling, by an amount of ∼8%. The calculated electron-phonon coupling constant in the solid, λ∼0.4, is strong enough to produce a superconducting transition temperature Tc∼3-10 K as estimated from McMillan's formula, indicating that the superconductivity in the BEDT-TTF compounds can be explained within the standard BCS electron-phonon coupling theory.Financial support was in part provided by the Research Board of the University of Missouri

Production and characterization of titanium carbide particulate reinforced AA6061 aluminum alloy composites using stir casting

Abstract: Stir casting is an economical method to produce aluminum matrix composites. In the present work, composites of aluminum alloy AA6061 reinforced with various amounts (0, 5, 10 and 15wt. %) of TiC particles were prepared by stir casting technique. X-ray diffraction patterns of the prepared composites clearly revealed the incorporation of TiC particles without the presence of any other compounds. The microstructures of the composites were studied using optical and scanning electron microscopy. It was observed that the TiC particles distributed all over the composite and properly bonded to the matrix alloy. Local clusters of TiC particle were also seen in a few places. The result shows that the reinforcement of TiC particles enhances the microhardness, ultimate tensile strength and wear resistance of the composite. The details of fracture morphology, worn surface and wear debris are also presented in this paper

Predicting the influence of process parameters on tensile strength of AA6061/TiC aluminum matrix composites produced using stir casting

Abstract: Stir casting is an economical method to produce aluminum matrix composites (AMCs). In this work, stir casting was used to produce AA6061/15wt. % TiC AMCs. An empirical relationship was developed to predict the effect of stir casting parameters on the ultimate tensile strength (UTS) of AA6061/TiC AMCs. A central composite rotatable design consisting of four factors and five levels was used to minimize the number of experiments i.e. castings. The factors considered were stirrer speed, stirring time, blade angle and casting temperature. The effect of those factors on the UTS of AA6061/TiC AMCs was derived using the developed empirical relationship and elucidated using microstructural characterization. Each factor significantly influenced the UTS. A higher or lower values of those factors resulted in poor tensile strength. The variation in the UTS was attributed to porosity content, cluster formation, segregation of TiC particles at the grain boundaries and 2 homogenous distribution in the aluminum matrix. The UTS was high when the porosity content was low and the distribution was homogenous. The present work concludes that a careful selection and control of stir casting parameters are necessary to reduce porosity content and obtain uniform distribution to improve the load bearing capacity of the AA6061/TiC AMCs

R^2 Corrections to Asymptotically Lifshitz Spacetimes

We study $R^{2}$ corrections to five-dimensional asymptotically Lifshitz spacetimes by adding Gauss-Bonnet terms in the effective action. For the zero-temperature backgrounds we obtain exact solutions in both pure Gauss-Bonnet gravity and Gauss-Bonnet gravity with non-trivial matter. The dynamical exponent undergoes finite renormalization in the latter case. For the finite-temperature backgrounds we obtain black brane solutions perturbatively and calculate the ratio of shear viscosity to entropy density $\eta/s$. The KSS bound is still violated but unlike the relativistic counterparts, the causality of the boundary field theory cannot be taken as a constraint.Comment: 24 pages, Latex, typos fixed, accepted by JHE

Out-of-plane dielectric constant and insulator-superconductor transition in Bi_2Sr_2Dy_{1-x}Er_xCu_2O_8 single crystals

The out-of-plane dielectric constant of the parent insulator of the high-temperature superconductor Bi_2Sr_2(Dy,Er)Cu_2O_8 was measured and analysed from 80 to 300 K in the frequency range of 10^6-10^9 Hz. All the samples were found to show a fairly large value of 10-60, implying some kind of charge inhomogeneity in the CuO_2 plane. Considering that the superconducting sample Bi_2Sr_2(Ca,Pr)Cu_2O_8 also shows a similar dielectric constant, the charge inhomogeneity plays an important role in the insulator-superconductor transition.Comment: RevTex4 format, 5 pages, 3 figures, submitted to J. Phys. Condens. Ma

Quantum phase transition in a Dp-Dq system

Using the top-down approach, we study intersecting Dp-Dq brane configuration in string theory and find examples, where there can be a quantum phase transition at zero temperature induced by the violation of the Breitenlohner-Freedman (BF) bound at IR, which is done essentially by a combination of charge density and magnetic fields. In particular, there exists a Berezinskii-Kosterlitz-Thouless (BKT) type of transition for D3-D5 and D5-D5 systems. The study of the BKT type of transition is initiated by Jensen et al. [Phys. Rev. Lett. {\bf 105}, 041601 (2010) ] for a D3-D5 system with nonzero charge density and a magnetic field. Here, we show that one can have the BKT transition for a D3-D5 system even in the absence of charge density but requires multiple magnetic fields. In this case the field theory lives in 2+1 dimensions, whereas for the D5-D5 type, the transition requires the presence of both the charge density and magnetic fields and the dual field theory lives on a 3+1 dimensional spacetime. We also study the D3-D7 system but it does not show the BKT type of transition.Comment: 1+37 pages; v2 Chern-Simon term for D3-D5 case presented, typos fixed and a reference added; v3 Minor corrections, Chern-Simon term for D2-D4, D4-D6, and D5-D7 added, also an appendix and few references added; v4 Journal versio

Qualitative observation of reversible phase change in astrochemical ethanethiol ices using infrared spectroscopy

Here we report the first evidence for a reversible phase change in an ethanethiol ice prepared under astrochemical conditions. InfraRed (IR) spectroscopy was used to monitor the morphology of the ice using the Ssingle bondH stretching vibration, a characteristic vibration of thiol molecules. The deposited sample was able to switch between amorphous and crystalline phases repeatedly under temperature cycles between 10 K and 130 K with subsequent loss of molecules in every phase change. Such an effect is dependent upon the original thickness of the ice. Further work on quantitative analysis is to be carried out in due course whereas here we are reporting the first results obtained