Transistorized Marx bank pulse circuit provides voltage multiplication with nanosecond rise-time

Base-triggered avalanche transistor circuit used in a Marx bank pulser configuration provides voltage multiplication with nanosecond rise-time. The avalanche-mode transistors replace conventional spark gaps in the Marx bank. The delay time from an input signal to the output signal to the output is typically 6 nanoseconds

The Dark Matter Radial Profile in the Core of the Relaxed Cluster A2589

We present an analysis of a Chandra--ACIS observation of the galaxy cluster A2589 to constrain the radial distribution of the total gravitating matter and the dark matter in the core of the cluster. A2589 is especially well-suited for this analysis because the hot gas in its core region (r < ~0.1 Rvir) is undisturbed by interactions with a central radio source. From the largest radius probed (r=0.07 Rvir) down to r ~0.02 Rvir dark matter dominates the gravitating mass. Over this region the radial profiles of the gravitating and dark matter are fitted well by the NFW and Hernquist profiles predicted by CDM. The density profiles are also described well by power laws, rho ~r^{-alpha}, where alpha=1.37 +/- 0.14 for the gravitating matter and alpha=1.35 +/- 0.21 for the dark matter. These values are consistent with profiles of CDM halos but are significantly larger than alpha ~0.5 found in LSB galaxies and expected from self-interacting dark matter models.Comment: 10 pages, 6 figures, To Appear in The Astrophysical Journal, March 20 issue, a few very minor changes to match copyedited versio

Size-dependent oxygen-related electronic states in silicon nanocrystals

Silicon nanocrystals embedded in SiO2 were isolated with a selective etching procedure, and the isolated nanocrystals' excitonic emission energy was studied during controlled oxidation. Nanocrystals having initial diameters, d(0), of similar to 2.9-3.4 nm showed a photoluminescence (PL) blueshift upon oxidatively induced size reduction, as expected from models of quantum confinement. Oxidation of smaller Si nanocrystals (d(0)similar to 2.5-2.8 nm) also initially resulted in a PL blueshift, but a redshift in the PL was then observed after growth of similar to 0.3 monolayers of native oxide. This decrease in excitonic emission energy during oxidation is consistent with the theoretically predicted formation of an oxygen-related excitonic recombination state

Signatures of hermitian forms and the Knebusch Trace Formula

Signatures of quadratic forms have been generalized to hermitian forms over algebras with involution. In the literature this is done via Morita theory, which causes sign ambiguities in certain cases. In this paper, a hermitian version of the Knebusch Trace Formula is established and used as a main tool to resolve these ambiguities. The last page is an erratum for the published version. We inadvertently (I) gave an incorrect definition of adjoint involutions; (II) omitted dealing with the case $(H\times H, \widehat{\phantom{m}}\,)$. As $W(H\times H, \widehat{\phantom{m}}\,)= W(R\times R, \widehat{\phantom{m}}\,)=0$, the omission does not affect our reasoning or our results. For the sake of completeness we point out where some small changes should be made in the published version.Comment: This is the final version before publication. The last page is an updated erratum for the published versio

On the accretion origin of a vast extended stellar disk around the Andromeda galaxy

We present the discovery of an inhomogenous, low-surface brightness, extended disk-like structure around the Andromeda galaxy (M31) based on a large kinematic survey of more than 2800 stars with the Keck/DEIMOS spectrograph. The stellar structure spans radii from 15 kpc out to ~40 kpc, with detections out to R ~ 70 kpc. The constituent stars lag the expected velocity of circular orbits in the plane of the M31 disk by ~40 kms and have a velocity dispersion of ~30 kms. The color range on the upper RGB shows a large spread indicative of a population with a significant range of metallicity. The mean metallicity of the population, measured from Ca II equivalent widths, is [Fe/H] = -0.9 +/- 0.2. The morphology of the structure is irregular at large radii, and shows a wealth of substructures which must be transitory in nature, and are almost certainly tidal debris. The presence of these substructures indicates that the global entity was formed by accretion. This extended disk follows smoothly on from the central parts of M31 disk with an exponential density law of scale-length of 5.1 +/- 0.1 kpc, similar to that of the bright inner disk. The population possesses similar kinematic and abundance properties over the entire region where it is detected in the survey. We estimate that the structure accounts for approximately 10% of the total luminosity of the M31 disk, and given the huge scale, contains ~30% of the total disk angular momentum. This finding indicates that at least some galactic stellar disks are vastly larger than previously thought and are formed, at least in their outer regions, primarily by accretion. [abridged]Comment: 20 pages, 30 figures, ApJ submitte

A comparison of calculated and measured background noise rates in hard X-ray telescopes at balloon altitude

An actively shielded hard X-ray astronomical telescope has been flown on stratospheric balloons. An attempt is made to compare the measured spectral distribution of the background noise counting rates over the energy loss range 20-300 keV with the contributions estimated from a series of Monte Carlo and other computations. The relative contributions of individual particle interactions are assessed

Barrierless procedure for substitutionally doping graphene sheets with boron atoms: ab initio calculations

Using ab initio methods, we propose a simple and effective way to substitutionally dope graphene sheets with Boron. The method consists of selectively exposing each side of the graphene sheet to different elements. We first expose one side of the membrane to Boron, while the other side is exposed to Nitrogen. Proceeding this way, the B atoms will be spontaneously incorporated into the graphene membrane, without any activation barrier. In a second step, the system should be exposed to a H-rich environment, that will remove the CN radical from the layer and form HCN, leading to a perfect substitutional doping.Comment: Accepted Physical Review

Asymptotic formula for the moments of Minkowski question mark function in the interval [0,1]

In this paper we prove the asymptotic formula for the moments of Minkowski question mark function, which describes the distribution of rationals in the Farey tree. The main idea is to demonstrate that certain a variation of a Laplace method is applicable in this problem, hence the task reduces to a number of technical calculations.Comment: 11 pages, 1 figure (final version). Lithuanian Math. J. (to appear

The Andromeda Stream

The existence of a stream of tidally stripped stars from the Sagittarius Dwarf galaxy demonstrates that the Milky Way is still in the process of accreting mass. More recently, an extensive stream of stars has been uncovered in the halo of the Andromeda galaxy (M31), revealing that it too is cannibalizing a small companion. This paper reports the recent observations of this stream, determining it spatial and kinematic properties, and tracing its three-dimensional structure, as well as describing future observations and what we may learn about the Andromeda galaxy from this giant tidal stream.Comment: 3 Pages. Refereed contribution to the 5th Galacto Chemodynamics conference held in Swinburne, July 2003. Accepted for publication in PAS

Elastic precursor of the transformation from glycolipid-nanotube to -vesicle

By the combination of optical tweezer manipulation and digital video microscopy, the flexural rigidity of single glycolipid "nano" tubes has been measured below the transition temperature at which the lipid tubules are transformed into vesicles. Consequently, we have found a clear reduction of the rigidity obviously before the transition as temperature increasing. Further experiments of infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) have suggested a microscopic change of the tube walls, synchronizing with the precursory softening of the nanotubes.Comment: 9 pages, 6 figure