Snowpack ground truth: Radar test site, Steamboat Springs, Colorado, 8-16 April 1976

Ground-truth data taken at Steamboat Springs, Colorado is presented. Data taken during the period April 8, 1976 - April 16, 1976 included the following: (1) snow depths and densities at selected locations (using a Mount Rose snow tube); (2) snow pits for temperature, density, and liquid water determinations using the freezing calorimetry technique and vertical layer classification; (3) snow walls were also constructed of various cross sections and documented with respect to sizes and snow characteristics; (4) soil moisture at selected locations; and (5) appropriate air temperature and weather data

Random Antiferromagnetic SU(N) Spin Chains

We analyze random isotropic antiferromagnetic SU(N) spin chains using the real space renormalization group. We find that they are governed at low energies by a universal infinite randomness fixed point different from the one of random spin-1/2 chains. We determine analytically the important exponents: the energy-length scale relation is $\Omega\sim\exp(-L^{\psi})$, where $\psi=1/N$, and the mean correlation function is given by $\bar{C_{ij}}\sim(-1)^{i-j}/|i-j|^{\phi}$, where $\phi=4/N$. Our analysis shows that the infinite-N limit is unable to capture the behavior obtained at any finite N.Comment: 4 pages, 3 figure

Modeling the gravitational wave signature of neutron star black hole coalescences: PhenomNSBH

Accurate gravitational-wave (GW) signal models exist for black-hole binary (BBH) and neutron-star binary (BNS) systems, which are consistent with all of the published GW observations to date. Detections of a third class of compact-binary systems, neutron-star-black-hole (NSBH) binaries, have not yet been confirmed, but are eagerly awaited in the near future. For NSBH systems, GW models do not exist across the viable parameter space of signals. In this work we present the frequency-domain phenomenological model, PhenomNSBH, for GWs produced by NSBH systems with mass ratios from equal-mass up to 15, spin on the black hole up to a dimensionless spin of $|\chi|=0.5$, and tidal deformabilities ranging from 0 (the BBH limit) to 5000. We extend previous work on a phenomenological amplitude model for NSBH systems to produce an amplitude model that is parameterized by a single tidal deformability parameter. This amplitude model is combined with an analytic phase model describing tidal corrections. The resulting approximant is accurate enough to be used to measure the properties of NSBH systems for signal-to-noise ratios (SNRs) up to 50, and is compared to publicly-available NSBH numerical-relativity simulations and hybrid waveforms constructed from numerical-relativity simulations and tidal inspiral approximants. For most signals observed by second-generation ground-based detectors within this SNR limit, it will be difficult to use the GW signal alone to distinguish single NSBH systems from either BNSs or BBHs, and therefore to unambiguously identify an NSBH system

Topology of the Spin-polarized Charge Density in bcc and fcc Iron

We investigate the topology of the spin-polarized charge density in bcc and fcc iron. While the total spin-density is found to possess the topology of the non-magnetic prototypical structures, in some cases the spin-polarized densities are characterized by unique topologies; for example, the spin-polarized charge densities of bcc and high-spin fcc iron are atypical of any known for non-magnetic materials. In these cases, the two spin-densities are correlated: the spin-minority electrons have directional bond paths with deep minima in the minority density, while the spin-majority electrons fill these holes, reducing bond directionality. The presence of two distinct spin topologies suggests that a well-known magnetic phase transition in iron can be fruitfully reexamined in light of these topological changes. We show that the two phase changes seen in fcc iron (paramagnetic to low-spin and low-spin to high-spin) are different. The former follows the Landau symmetry-breaking paradigm and proceeds without a topological transformation, while the latter also involves a topological catastrophe.Comment: 5 pages, 3 figures. Phys. Rev. Lett. (in press

Parts of Quantum States

It is shown that generic N-party pure quantum states (with equidimensional subsystems) are uniquely determined by their reduced states of just over half the parties; in other words, all the information in almost all N-party pure states is in the set of reduced states of just over half the parties. For N even, the reduced states in fewer than N/2 parties are shown to be an insufficient description of almost all states (similar results hold when N is odd). It is noted that Real Algebraic Geometry is a natural framework for any analysis of parts of quantum states: two simple polynomials, a quadratic and a cubic, contain all of their structure. Algorithmic techniques are described which can provide conditions for sets of reduced states to belong to pure or mixed states.Comment: 10 pages, 1 figur

Variations of the Mid-IR Aromatic Features Inside and Among Galaxies

We present the results of a systematic study of mid-IR spectra of Galactic regions, Magellanic HII regions, and galaxies of various types (dwarf, spiral, starburst), observed by the satellites ISO and Spitzer. We study the relative variations of the 6.2, 7.7, 8.6 and 11.3 micron features inside spatially resolved objects (such as M82, M51, 30 Doradus, M17 and the Orion Bar), as well as among 90 integrated spectra of 50 objects. Our main results are that the 6.2, 7.7 and 8.6 micron bands are essentially tied together, while the ratios between these bands and the 11.3 micron band varies by one order of magnitude. This implies that the properties of the PAHs are remarkably universal throughout our sample, and that the relative variations of the band ratios are mainly controled by the fraction of ionized PAHs. In particular, we show that we can rule out both the modification of the PAH size distribution, and the mid-infrared extinction, as an explanation of these variations. Using a few well-studied Galactic regions (including the spectral image of the Orion Bar), we give an empirical relation between the I(6.2)/I(11.3) ratio and the ionization/recombination ratio G0/ne.Tgas^0.5, therefore providing a useful quantitative diagnostic tool of the physical conditions in the regions where the PAH emission originates. Finally, we discuss the physical interpretation of the I(6.2)/I(11.3) ratio, on galactic size scales.Comment: Accepted by the ApJ, 67 pages, 70 figure

Reinforced structural plastics

Reinforced polyimide structures are described. Reinforcing materials are impregnated with a suspension of polyimide prepolymer and bonded together by heat and pressure to form a cured, hard-reinforced, polyimide structure

New rapid-curing, stable polyimide polymers with high-temperature strength and thermal stability

Additive-type polymerization reaction forms thermally stable polyimide polymers, thereby eliminating the volatile matter attendant with the condensation reaction. It is based on the utilization of reactive alicyclic rings positioned on the ends of polyimide prepolymers having relatively low molecular weights

Radio Emission from a Young Supernova Remnant Interacting with an Interstellar Cloud: MHD Simulation with Relativistic Electrons

We present two-dimensional MHD simulations of the evolution of a young Type Ia supernova remnant during its interaction with an interstellar cloud of comparable size at impact. We include for the first time in such simulations explicit relativistic electron transport, including spectral information using a simple but effective scheme that follows their acceleration at shocks and subsequent transport. From this information we also model radio synchrotron emission, including spectra. The principal conclusions from these experiments are: 1) Independent of the cloud interaction, the SNR reverse shock can be an efficient site for particle acceleration in a young SNR. 2) At these early times the synchrotron spectral index due to electrons accelerated at the primary shocks should be close to 0.5 unless those shocks are modified by cosmic-ray pressures. However, interaction with the cloud generates regions of distinctly steeper spectra, which may complicate interpretation in terms of global dynamical models for SNR evolution. 3) The internal motions within the SNR become highly turbulent following the cloud interaction. 4) An initially uniform interstellar magnetic field is preferentially amplified along the magnetic equator of the SNR, primarily due to biased amplification by instabilities. Independent of the external field configuration, there is a net radial direction to this field inside the SNR. 5) Filamentary radio structures correlate well with magnetic filaments, while diffuse emission follows the electron distribution. 6) Interaction with the cloud enhances both the electron population and the radio emission.Comment: 29 pages of Latex generated text with 6 figures in gif format. Accepted for publication in the Astrophysical Journal. High resolution postscript figures can be obtained by anonymous ftp from ftp://ftp.msi.umn.edu/pub/users/twj/sn