Mini-clusters

Experimental results of mini-clusters observed in Chacaltaya emulsion chamber no.19 are summarized. The study was made on 54 single core shower upper and 91 shower clusters of E(gamma) 10 TeV from 30 families which are visible energy greater than 80 TeV and penetrate through both upper and lower detectors of the two-story chamber. The association of hadrons in mini-cluster is made clear from their penetrative nature and microscopic observation of shower continuation in lower chamber. Small P sub t (gamma) of hadrons in mini-clusters remained in puzzle

Comparison of Bond Character in Hydrocarbons and Fullerenes

We present a comparison of the bond polarizabilities for carbon-carbon bonds in hydrocarbons and fullerenes, using two different models for the fullerene Raman spectrum and the results of Raman measurements on ethane and ethylene. We find that the polarizabilities for single bonds in fullerenes and hydrocarbons compare well, while the double bonds in fullerenes have greater polarizability than in ethylene.Comment: 7 pages, no figures, uses RevTeX. (To appear in Phys. Rev. B.

Role of multiple subband renormalization in the electronic transport of correlated oxide superlattices

Metallic behavior of band-insulator/ Mott-insulator interfaces was observed in artificial perovskite superlattices such as in nanoscale SrTiO3/LaTiO3 multilayers. Applying a semiclassical perspective to the parallel electronic transport we identify two major ingredients relevant for such systems: i) the quantum confinement of the conduction electrons (superlattice modulation) leads to a complex, quasi-two dimensional subband structure with both hole- and electron-like Fermi surfaces. ii) strong electron-electron interaction requires a substantial renormalization of the quasi-particle dispersion. We characterize this renormalization by two sets of parameters, namely, the quasi-particle weight and the induced particle-hole asymmetry of each partially filled subband. In our study, the quasi-particle dispersion is calculated self-consistently as function of microscopic parameters using the slave-boson mean-field approximation introduced by Kotliar and Ruckenstein. We discuss the consequences of strong local correlations on the normal-state free-carrier response in the optical conductivity and on the thermoelectric effects.Comment: 11 pages, 4 figure

Quantum-mechanical model for particles carrying electric charge and magnetic flux in two dimensions

We propose a simple quantum mechanical equation for $n$ particles in two dimensions, each particle carrying electric charge and magnetic flux. Such particles appear in (2+1)-dimensional Chern-Simons field theories as charged vortex soliton solutions, where the ratio of charge to flux is a constant independent of the specific solution. As an approximation, the charge-flux interaction is described here by the Aharonov-Bohm potential, and the charge-charge interaction by the Coulomb one. The equation for two particles, one with charge and flux ($q, \Phi/Z$) and the other with ($-Zq, -\Phi$) where $Z$ is a pure number is studied in detail. The bound state problem is solved exactly for arbitrary $q$ and $\Phi$ when $Z>0$. The scattering problem is exactly solved in parabolic coordinates in special cases when $q\Phi/2\pi\hbar c$ takes integers or half integers. In both cases the cross sections obtained are rather different from that for pure Coulomb scattering.Comment: 12 pages, REVTeX, no figur

Tuning of metal-insulator transition of two-dimensional electrons at parylene/SrTiO3_3 interface by electric field

Electrostatic carrier doping using a field-effect-transistor structure is an intriguing approach to explore electronic phases by critical control of carrier concentration. We demonstrate the reversible control of the insulator-metal transition (IMT) in a two dimensional (2D) electron gas at the interface of insulating SrTiO$_3$ single crystals. Superconductivity was observed in a limited number of devices doped far beyond the IMT, which may imply the presence of 2D metal-superconductor transition. This realization of a two-dimensional metallic state on the most widely-used perovskite oxide is the best manifestation of the potential of oxide electronics

Internal states of model isotropic granular packings. III. Elastic properties

In this third and final paper of a series, elastic properties of numerically simulated isotropic packings of spherical beads assembled by different procedures and subjected to a varying confining pressure P are investigated. In addition P, which determines the stiffness of contacts by Hertz's law, elastic moduli are chiefly sensitive to the coordination number, the possible values of which are not necessarily correlated with the density. Comparisons of numerical and experimental results for glass beads in the 10kPa-10MPa range reveal similar differences between dry samples compacted by vibrations and lubricated packings. The greater stiffness of the latter, in spite of their lower density, can hence be attributed to a larger coordination number. Voigt and Reuss bounds bracket bulk modulus B accurately, but simple estimation schemes fail for shear modulus G, especially in poorly coordinated configurations under low P. Tenuous, fragile networks respond differently to changes in load direction, as compared to load intensity. The shear modulus, in poorly coordinated packings, tends to vary proportionally to the degree of force indeterminacy per unit volume. The elastic range extends to small strain intervals, in agreement with experimental observations. The origins of nonelastic response are discussed. We conclude that elastic moduli provide access to mechanically important information about coordination numbers, which escape direct measurement techniques, and indicate further perspectives.Comment: Published in Physical Review E 25 page

Compact q-gram Profiling of Compressed Strings

We consider the problem of computing the q-gram profile of a string \str of size $N$ compressed by a context-free grammar with $n$ production rules. We present an algorithm that runs in $O(N-\alpha)$ expected time and uses O(n+q+\kq) space, where $N-\alpha\leq qn$ is the exact number of characters decompressed by the algorithm and \kq\leq N-\alpha is the number of distinct q-grams in \str. This simultaneously matches the current best known time bound and improves the best known space bound. Our space bound is asymptotically optimal in the sense that any algorithm storing the grammar and the q-gram profile must use \Omega(n+q+\kq) space. To achieve this we introduce the q-gram graph that space-efficiently captures the structure of a string with respect to its q-grams, and show how to construct it from a grammar

Anti-inflammatory effect of glucose—mannose binding lectins isolated from Brazilian beans

Selectins are essential for leukocyte recruitment in inflammation. Because of a lectin domain present in the selectin structure, we investigated the anti-inflammtory activity of six mannose–glucose binding lectins from brazilian beans: Dioclea guianensis-DguiL; D. grandiflora-DgL; Cratylia floribunda-CfL; D. violacea-D.vL; D. virgata-DvirL and Canavalia brasiliensis-ConBr. The lectins were injected intravenously (i.v.) into rats (0.1 and 1.0 mg/kg; 30 min before irritants) and its activities compared to E. coli endotoxin (LPS,30 μg/kg i.v.). Three lectins (DvL, CfL and DguiL), although less intense than LPS, inhibited the neutrophil migration induced by carrageenan (Cg, 300 μg) in a dose-dependent manner (0.1 and 1.0 mg/kg). DvL activity was reversed by 0.1 M α-D-methyl-mannoside (α-CH3), but not by 0.1 M α-D-galactose. The fMLP (44 ng)-induced neutrophil migration was also reduced by these lectins. Endotoxin contamination of lectin samples could be excluded since α-CH3 treatment reversed the DvL effect, but did not modify LPS inhibitory activity. Carrageenan (300 μg)-induced paw oedema was also reduced by LPS or lectin treatments. Conversely, none of the tested lectins inhibited dextran (Dex, 300 μg)-induced paw oedema, a classical leukocyte independent model, or zymosan (Zy, 1.0 mg)-induced peritonitis and paw oedema. LPS showed no effect upon Dex-induced paw oedema and barely reduced (25%) the oedematogenic effects of zymosan. As proposed for LPS, the lectin inhibitory activity was better observed on neutrophil-mediated inflammatory reactions. We speculate that the plant lectin antiinflammatory activity is probably due to a competitive blockage of a common leukocyte and/or endothelial selectin carbohydrate ligand

Rewritable nanoscale oxide photodetector

Nanophotonic devices seek to generate, guide, and/or detect light using structures whose nanoscale dimensions are closely tied to their functionality. Semiconducting nanowires, grown with tailored optoelectronic properties, have been successfully placed into devices for a variety of applications. However, the integration of photonic nanostructures with electronic circuitry has always been one of the most challenging aspects of device development. Here we report the development of rewritable nanoscale photodetectors created at the interface between LaAlO3 and SrTiO3. Nanowire junctions with characteristic dimensions 2-3 nm are created using a reversible AFM writing technique. These nanoscale devices exhibit a remarkably high gain for their size, in part because of the large electric fields produced in the gap region. The photoconductive response is gate-tunable and spans the visible-to-near-infrared regime. The ability to integrate rewritable nanoscale photodetectors with nanowires and transistors in a single materials platform foreshadows new families of integrated optoelectronic devices and applications.Comment: 5 pages, 5 figures. Supplementary Information 7 pages, 9 figure

The spectral energy distribution of the redshift 7.1 quasar ULAS J1120+0641

We present new observations of the highest-redshift quasar known, ULAS J1120+0641, redshift $z=7.084$, obtained in the optical, at near-, mid-, and far-infrared wavelengths, and in the sub-mm. We combine these results with published X-ray and radio observations to create the multiwavelength spectral energy distribution (SED), with the goals of measuring the bolometric luminosity $L_{\rm bol}$, and quantifying the respective contributions from the AGN and star formation. We find three components are needed to fit the data over the wavelength range $0.12-1000\,\mu$m: the unobscured quasar accretion disk and broad-line region, a dusty clumpy AGN torus, and a cool 47K modified black body to characterise star formation. Despite the low signal-to-noise ratio of the new long-wavelength data, the normalisation of any dusty torus model is constrained within $\pm40\%$. We measure a bolometric luminosity $L_{\rm bol}=2.6\pm0.6\times10^{47}\,$erg$\,$s$^{-1}=6.7 \pm 1.6\times10^{13}L_{\odot}$, to which the three components contribute $31\%,32\%,3\%$, respectively, with the remainder provided by the extreme UV $<0.12\,\mu$m. We tabulate the best-fit model SED. We use local scaling relations to estimate a star formation rate (SFR) in the range $60-270\,{\rm M}_\odot$/yr from the [C$\,{\scriptsize \rm II}$] line luminosity and the $158\,\mu$m continuum luminosity. An analysis of the equivalent widths of the [C$\,{\scriptsize \rm II}$] line in a sample of $z>5.7$ quasars suggests that these indicators are promising tools for estimating the SFR in high-redshift quasars in general. At the time observed the black hole was growing in mass more than 100 times faster than the stellar bulge, relative to the mass ratio measured in the local universe, i.e. compared to ${M_{\rm BH}}/{M_{\rm bulge}} \simeq 1.4\times10^{-3}$, for ULAS J1120+0641 we measure ${\dot{M}_{\rm BH}}/{\dot{M}_{\rm bulge}} \simeq 0.2$.Comment: Accepted for publication in A&A. 10 pages, 5 figures, 5 table