Thickness dependent magnetotransport in ultra-thin manganite films

To understand the near-interface magnetism in manganites, uniform, ultra-thin films of La_{0.67}Sr_{0.33}MnO_3 were grown epitaxially on single crystal (001) LaAlO_3 and (110) NdGaO_3 substrates. The temperature and magnetic field dependent film resistance is used to probe the film's structural and magnetic properties. A surface and/or interface related dead-layer is inferred from the thickness dependent resistance and magnetoresistance. The total thickness of the dead layer is estimated to be $\sim 30 \AA$ for films on NdGaO_3 and $\sim 50 \AA$ for films on LaAlO_3.Comment: 11 pages, 4 figure

The true nature of the alleged planetary nebula W16-185

We report the discovery of a small cluster of massive stars embedded in a NIR nebula in the direction of the IRAS15411-5352 point source, which is related to the alleged planetary nebula W16-185. The majority of the stars present large NIR excess characteristic of young stellar objects and have bright counterparts in the Spitzer IRAC images; the most luminous star (IRS1) is the NIR counterpart of the IRAS source. We found very strong unresolved Brgamma emission at the IRS1 position and more diluted and extended emission across the continuum nebula. From the sizes and electron volume densities we concluded that they represent ultra-compact and compact HII regions, respectively. Comparing the Brgamma emission with the 7 mm free-free emission, we estimated that the visual extinction ranges between 14 and 20 mag. We found that only one star (IRS1) can provide the number of UV photons necessary to ionize the nebula.Comment: 30 pages, 15 figures, 2 tables V3: minor grammatical changes. Figure 4 is available in pdf file. Accepted for publication in AJ, April / 200

The Poisson Bracket for Poisson Forms in Multisymplectic Field Theory

We present a general definition of the Poisson bracket between differential forms on the extended multiphase space appearing in the geometric formulation of first order classical field theories and, more generally, on exact multisymplectic manifolds. It is well defined for a certain class of differential forms that we propose to call Poisson forms and turns the space of Poisson forms into a Lie superalgebra.Comment: 40 pages LaTe

Generic local distinguishability and completely entangled subspaces

A subspace of a multipartite Hilbert space is completely entangled if it contains no product states. Such subspaces can be large with a known maximum size, S, approaching the full dimension of the system, D. We show that almost all subspaces with dimension less than or equal to S are completely entangled, and then use this fact to prove that n random pure quantum states are unambiguously locally distinguishable if and only if n does not exceed D-S. This condition holds for almost all sets of states of all multipartite systems, and reveals something surprising. The criterion is identical for separable and for nonseparable states: entanglement makes no difference.Comment: 12 page

Variation of turbulent burning rate of methane, methanol, and iso-octane air mixtures with equivalence ratio at elevated pressure

Turbulent burning velocities for premixed methane, methanol, and iso-octane/air mixtures have been experimentally determined for an rms turbulent velocity of 2 m/s and pressure of 0.5 MPa for a wide range of equivalence ratios. Turbulent burning velocity data were derived using high-speed schlieren photography and transient pressure recording; measurements were processed to yield a turbulent mass rate burning velocity, utr. The consistency between the values derived using the two techniques, for all fuels for both fuel-lean and fuel-rich mixtures, was good. Laminar burning measurements were made at the same pressure, temperature, and equivalence ratios as the turbulent cases and laminar burning velocities and Markstein numbers were determined. The equivalence ratio (φ) for peak turbulent burning velocity proved not always coincident with that for laminar burning velocity for the same fuel; for isooctane, the turbulent burning velocity unexpectedly remained high over the range φ = 1 to 2. The ratio of turbulent to laminar burning velocity proved remarkably high for very rich iso-octane/air and lean methane/air mixtures

Supertubes

It is shown that a IIA superstring carrying D0-brane charge can be `blown-up', in a {\it Minkowski vacuum} background, to a (1/4)-supersymmetric tubular D2-brane, supported against collapse by the angular momentum generated by crossed electric and magnetic Born-Infeld fields. This `supertube' can be viewed as a worldvolume realization of the sigma-model Q-lump.Comment: Revision includes mention of some configurations dual to the supertub

Microwave Electronics

Contains reports on two research projects.U. S. ArmyLincoln Laboratory, Purchase Order DDL B-00306U. S. Navy (Office of Naval Research) under Contract Nonr-1841(49)U. S. Air Force under Air Force Contract AF19(604)-5200U. S. Nav

Evidence for Evolving Spheroidals in the Hubble Deep Fields North and South

We investigate the dispersion in the internal colours of faint spheroidals in the HDFs North and South. We find that a remarkably large fraction ~30% of the morphologically classified spheroidals with I<24 mag show strong variations in internal colour, which we take as evidence for recent episodes of star-formation. In most cases these colour variations manifest themselves via the presence of blue cores, an effect of opposite sign to that expected from metallicity gradients. Examining similarly-selected ellipticals in five rich clusters with 0.37<z<0.83 we find a significant lower dispersion in their internal colours. This suggests that the colour inhomogeneities have a strong environmental dependence being weakest in dense environments where spheroidal formation was presumably accelerated at early times. We use the trends defined by the cluster sample to define an empirical model based on a high-redshift of formation and estimate that at z~1 about half the field spheroidals must be undergoing recent episodes of star-formation. Using spectral synthesis models, we construct the time dependence of the density of star-formation. Although the samples are currently small, we find evidence for an increase in $\rho_{SFR}$ between z=0 to z=1. We discuss the implications of this rise in the context of that observed in the similar rise in the abundance of galaxies with irregular morphology. Regardless of whether there is a connection our results provide strong evidence for the continued formation of field spheroidals over 0<z<1.Comment: 13 pages, 11 figures. To appear in MNRAS in response to referee's Report. Figures and paper also available at http://www.ast.cam.ac.uk/~fmenante/HDFs