Energy dependent wavelength of the ion induced nanoscale ripple

Wavelength variation of ion beam induced nanoscale ripple structure has received much attention recently due to its possible application in nanotechnology. We present here results of Ar$^+$ bombarded Si in the energy range 50 to 140 keV to demonstrate that with beam scanning the ripple wavelength increases with ion energy and decreases with energy for irradiation without ion beam scanning. An expression for the energy dependence of ripple wavelength is proposed taking into simultaneous effect of thermally activated surface diffusion and ion induced effective surface diffusion.Comment: REVTeX (4 pages), 3 EPS figure

Constraints on Fluid Dynamics from Equilibrium Partition Functions

We study the thermal partition function of quantum field theories on arbitrary stationary background spacetime, and with arbitrary stationary background gauge fields, in the long wavelength expansion. We demonstrate that the equations of relativistic hydrodynamics are significantly constrained by the requirement of consistency with any partition function. In examples at low orders in the derivative expansion we demonstrate that these constraints coincide precisely with the equalities between hydrodynamical transport coefficients that follow from the local form of the second law of thermodynamics. In particular we recover the results of Son and Surowka on the chiral magnetic and chiral vorticity flows, starting from a local partition function that manifestly reproduces the field theory anomaly, without making any reference to an entropy current. We conjecture that the relations between transport coefficients that follow from the second law of thermodynamics agree to all orders in the derivative expansion with the constraints described in this paper.Comment: Typos corrected, References adde

Effect of Fibonacci Modulation On Superconductivity

We have studied finite-sized single band models with short range pairing interactions between electrons in presence of diagonal Fibonacci modulation in one dimension. Two models, namely the attractive Hubbard model and the Penson-Kolb model, have been investigated at half-filling at zero temperature by solving the Bogoliubov-de Gennes equations in real space within a mean field approximation. The competition between ``disorder'' and the pairing interaction leads to a suppression of superconductivity (of usual pairs with zero centre-of-mass momenta) in the strong-coupling limit while an enhancement of the pairing correlation is observed in the weak-coupling regime for both the models. However, the dissimilarity of the pairing mechanisms in these two models brings about notable difference in the results. The extent to which the bond ordered wave and the $\eta$-paired (of pairs with centre-of-mass momenta = $\pi$) phases of the Penson-Kolb model are affected by the disorder has also been studied in the present calculation. Some finite size effects are also identified.Comment: 14 pages, 13 figure

Constraints on Superfluid Hydrodynamics from Equilibrium Partition Functions

Following up on recent work in the context of ordinary fluids, we study the equilibrium partition function of a 3+1 dimensional superfluid on an arbitrary stationary background spacetime, and with arbitrary stationary background gauge fields, in the long wavelength expansion. We argue that this partition function is generated by a 3 dimensional Euclidean effective action for the massless Goldstone field. We parameterize the general form of this action at first order in the derivative expansion. We demonstrate that the constitutive relations of relativistic superfluid hydrodynamics are significantly constrained by the requirement of consistency with such an effective action. At first order in the derivative expansion we demonstrate that the resultant constraints on constitutive relations coincide precisely with the equalities between hydrodynamical transport coefficients recently derived from the second law of thermodynamics.Comment: 46 page

Utilización del insaponificable de destilados de ácidos grasos de aceites de salvado de arroz para la preparación de oleogeles ricos en antioxidantes y evaluación de sus propiedades

Rice bran oil fatty acid distillate (RBOFAD) is an important by-product obtained from the physical refining process. This fatty acid distillate contains high a amount of Unsaponifiable Matter (γ-oryzanol 3.27 gm/100gm UM; total tocopherol 10.93 mg/100 g UM; total phytosterol 21.81 g/100g UM; squalene 1.15 g/100 g UM and total fatty alcohol 73.34 g/100 g UM) and free fatty acids. Antioxidant-rich Oleogels were obtained from rice bran wax (RBW), rice bran oil fatty acid distillate (RBOFAD) and refined rice bran oil. The main objective of this study was to utilize the antioxidant-rich unsaponifiable matter of RBOFAD (UMRBOFAD) as an organogelator along with rice bran wax, which also acts as a good organogelator. Antioxidant-rich oleogel was prepared using UMRBFAD, ethylcellulose (EC) and RBW at 2%, 2%, 3% on weight basis, respectively, in refined rice bran oil and this antioxidant-rich oleogel was compared with rice bran oil oleogel using RBW at 7% on weight basis of rice bran oil. These oleogels were evaluated using a combination of techniques such as differential scanning calorimetry (DSC), polarized light microscopy (PLM), Viscosity, synchrotron radiation X-ray diffraction (SR-XRD) and FTIR Spectroscopy. The differential scanning calorimetry (DSC) measured the thermal properties of rice bran oil oleogel and high antioxidant-rich oleogel. Polarized light microscopy images revealed needle-like crystals for RBW. SR-XRD measurements were used for clarification of the crystal structures of the building blocks of these oleogels. The antioxidant activities of oleogels were evaluated involving DPPH and ABTS assays.El destilado de ácidos grasos de aceites de salvado de arroz (RBOFAD) es un subproducto importante que se obtiene en el proceso de refinación física. Este destilado contiene una gran cantidad de materia insaponificable (γ-oryzanol 3.27 g/100g UM; tocoferol total 10.93 mg/100 g UM; phytosterol total 21.81 g/100g UM; escualeno 1.15 g/100 g UM y alcohol graso total 73.34 g/100 g UM) y ácidos grasos libres. Los oleogeles ricos en antioxidantes se obtuvieron de la cera del salvado de arroz (RBW), de destilados de ácidos grasos de aceite de salvado de arroz (RBOFAD) y de aceite de salvado de arroz refinado. El objetivo principal de este estudio fue utilizar materia insaponificable de RBOFAD (UMRBOFAD) ricos en antioxidantes como organogelador junto con cera de salvado de arroz que actúa también como un buen organogelador. El oleogel rico en antioxidantes se preparó usando UMRBFAD, etilcelulosa (EC) y RBW al 2%, 2%, 3% en peso respectivamente en aceite de salvado de arroz refinado y este oleogel rico en antioxidantes se comparó con el oleogel de aceite de salvado de arroz usando RBW al 7% en peso de aceite de salvado de arroz. Estos oleogeles se evaluaron utilizando una combinación de técnicas como la calorimetría diferencial de barrido (DSC), microscopía de luz polarizada (PLM), viscosidad, difracción de rayos X por radiación de sincrotrón (SR-XRD) y espectroscopía FTIR. La calorimetría diferencial de barrido (DSC) midió las propiedades térmicas del oleogel de aceite de salvado de arroz y el oleogel rico en antioxidantes. Las imágenes de microscopía de luz polarizada revelaron una aguja como el cristal para RBW. Las medidas de SR-XRD se usaron para la clarificación de las estructuras cristalinas de los bloques de construcción de estos oleogeles. Se evaluaron las actividades antioxidantes de los oleogeles con ensayos de DPPH y ABTS

Search for optical bursts from the gamma ray burst source GBS 0526-66

Attempts were made to detect optical bursts from the gamma-ray burst source GBS 0526-66 during Dec. 31, 1984 to Jan. 2, 1985 and Feb. 23 to Feb. 24, 1985, using the one meter reflector of the Kavalur Observatory. Jan. 1, 1985 coincided with the zero phase of the predicted 164 day period of burst activity from the source (Rothschild and Lingenfelter, 1984). A new optical burst photon counting system with adjustable trigger threshold was used in parallel with a high speed photometer for the observations. The best time resolution was 1 ms and maximum count rate capability was 255,000 counts s(-1). Details of the instrumentation and observational results are presented

Phase diagram for non-axisymmetric plasma balls

Plasma balls and rings emerge as fluid holographic duals of black holes and black rings in the hydrodynamic/gravity correspondence for the Scherk-Schwarz AdS system. Recently, plasma balls spinning above a critical rotation were found to be unstable against m-lobed perturbations. In the phase diagram of stationary solutions the threshold of the instability signals a bifurcation to a new phase of non-axisymmetric configurations. We find explicitly this family of solutions and represent them in the phase diagram. We discuss the implications of our results for the gravitational system. Rotating non-axisymmetric black holes necessarily radiate gravitational waves. We thus emphasize that it would be important, albeit possibly out of present reach, to have a better understanding of the hydrodynamic description of gravitational waves and of the gravitational interaction between two bodies. We also argue that it might well be that a non-axisymmetric m-lobed instability is also present in Myers-Perry black holes for rotations below the recently found ultraspinning instability.Comment: 1+22 pages, 3 figures. v2: minor corrections and improvements, matches published versio

Search for TeV γ\gamma -rays from H1426+428 during 2004-07 with the TACTIC telescope

The BL Lac object H1426+428 ($z\equiv 0.129$) is an established source of TeV $\gamma$-rays and detections of these photons from this object also have important implications for estimating the Extragalactic Background Light (EBL) in addition to the understanding of the particle acceleration and $\gamma$-ray production mechanisms in the AGN jets. We have observed this source for about 244h in 2004, 2006 and 2007 with the TACTIC $\gamma$-ray telescope located at Mt. Abu, India. Detailed analysis of these data do not indicate the presence of any statistically significant TeV $\gamma$-ray signal from the source direction. Accordingly, we have placed an upper limit of $\leq1.18\times10^{-12}$ $photons$ $cm^{-2}$ $s^{-1}$ on the integrated $\gamma$-ray flux at 3$\sigma$ significance level.Comment: 11 pages, 5 figures accepted for publication in Journal of Physics G: Nuclear and Particle Physic

Supersymmetric hydrodynamics from the AdS/CFT correspondence

We compute holographically the dispersion relation for a hydrodynamic mode of fluctuation (the phonino) of the density of supersymmetry current in N = 4 SYM at strong coupling. The mode appears as a pole at low frequency and momentum in the correlator of supercurrents. It has a wave-like propagation, and we find its speed and coefficient of attenuation.Comment: 17 page