A study to develop improved spacecraft show survey methods using Skylab/EREP data: Demonstration of the utility of the S190 and S192 data

The author has identified the following significant results. This interim report provides a demonstration of the utility of spacecraft acquired Skylab S190A and S190B photography and S192 imagery for mapping areal extent of snow cover in western United States test site areas. The data sample is from the SL-2 mission flown in June 1973. Results of the investigation indicate that areal snow cover extent can be mapped more accurately from the S190A and S190B photography than from any other spacecraft system, including ERTS. The results of a qualitative analysis of the S192 imagery indicate considerable potential for the utility of multispectral snow cover analysis; the potential for distinguishing snow from clouds automatically is particularly significant

The application of ERTS imagery to mapping snow cover in the western United States

The author has identified the following significant results. In much of the western United States a large part of the utilized water comes from accumulated mountain snowpacks; thus, accurate measurements of snow distributions are required for input to streamflow prediction models. The application of ERTS-1 imagery for mapping snow has been evaluated for two geographic areas, the Salt-Verde watershed in central Arizona and the southern Sierra Nevada in California. Techniques have been developed to identify snow and to differentiate between snow and cloud. The snow extent for these two drainage areas has been mapped from the MSS-5 (0.6 - 0.7 microns) imagery and compared with aerial survey snow charts, aircraft photography, and ground-based snow measurements. The results indicate that ERTS imagery has substantial practical applications for snow mapping. Snow extent can be mapped from ERTS-1 imagery in more detail than is depicted on aerial survey snow charts. Moreover, in Arizona and southern California cloud obscuration does not appear to be a serious deterrent to the use of satellite data for snow survey. The costs involved in deriving snow maps from ERTS-1 imagery appear to be very reasonable in comparison with existing data collection methods

The application of Heat Capacity Mapping Mission (HCMM) thermal data to snow hydrology

The application of HCMM thermal infrared data to snow hydrology and the prediction of snowmelt runoff was evaluated. Data for the Salt Verde watershed in central Arizona and the southern Sierra Nevada in California were analyzed and compared to LANDSAT and NOAA satellite data, U-2 thermal data, and other correlative data. It was determined that HCMM thermal imagery provides data as accurate for snow mapping as does visible imagery, and that in comparison with the reslution of other satellite imagery, it may be the most useful. Data from the HCMM thermal channel, with careful calibration, provides useful snow surface temperature data for hydrological purposes. An approach to an automated method of analysis is presented

Two-dimensional colloidal fluids exhibiting pattern formation

Fluids with competing short range attraction and long range repulsive interactions between the particles can exhibit a variety of microphase separated structures. We develop a lattice-gas (generalised Ising) model and analyse the phase diagram using Monte Carlo computer simulations and also with density functional theory (DFT). The DFT predictions for the structures formed are in good agreement with the results from the simulations, which occur in the portion of the phase diagram where the theory predicts the uniform fluid to be linearly unstable. However, the mean-field DFT does not correctly describe the transitions between the different morphologies, which the simulations show to be analogous to micelle formation. We determine how the heat capacity varies as the model parameters are changed. There are peaks in the heat capacity at state points where the morphology changes occur. We also map the lattice model onto a continuum DFT that facilitates a simplification of the stability analysis of the uniform fluid.Comment: 13 pages, 15 figure

Iron(III)-catalyzed chlorination of activated arenes

A general and regioselective method for the chlorination of activated arenes has been developed. The transformation uses iron(III) triflimide as a powerful Lewis acid for the activation of N-chlorosuccinimide and the subsequent chlorination of a wide range of anisole, aniline, acetanilide and phenol derivatives. The reaction was utilized for the late-stage mono- and di-chlorination of a range of target compounds such as the natural product nitrofungin, the antibacterial agent chloroxylenol and the herbicide chloroxynil. The facile nature of this transformation was demonstrated with the development of one-pot tandem iron-catalyzed dihalogenation processes allowing highly regioselective formation of different carbon-halogen bonds. The synthetic utility of the resulting dihalogenated aryl compounds as building blocks was established with the synthesis of natural products and pharmaceutically relevant targets

Ideal Bose gas in fractal dimensions and superfluid 4^4He in porous media

Physical properties of ideal Bose gas with the fractal dimensionality between D=2 and D=3 are theoretically investigated. Calculation shows that the characteristic features of the specific heat and the superfluid density of ideal Bose gas in fractal dimensions are strikingly similar to those of superfluid Helium-4 in porous media. This result indicates that the geometrical factor is dominant over mutual interactions in determining physical properties of Helium-4 in porous media.Comment: 13 pages, 6 figure

Hidden spin-current conservation in 2d Fermi liquids

We report the existence of regimes of the two dimensional Fermi liquid that show unusual conservation of the spin current and may be tuned by varying some parameter like the density of fermions. We show that for reasonable models of the effective interaction the spin current may be conserved in general in 2d, not only for a particular regime. Low temperature spin waves propagate distinctively in these regimes and entirely new ``spin-acoustic'' modes are predicted for scattering-dominated temperature ranges. These new high-temperature propagating spin waves provide a clear signature for the experimental search of such regimes.Comment: 4 pages, no figures, revised version, accepted for pub. in the PR

Rayleigh-Taylor instability of crystallization waves at the superfluid-solid 4He interface

At the superfluid-solid 4He interface there exist crystallization waves having much in common with gravitational-capillary waves at the interface between two normal fluids. The Rayleigh-Taylor instability is an instability of the interface which can be realized when the lighter fluid is propelling the heavier one. We investigate here the analogues of the Rayleigh-Taylor instability for the superfluid-solid 4He interface. In the case of a uniformly accelerated interface the instability occurs only for a growing solid phase when the magnitude of the acceleration exceeds some critical value independent of the surface stiffness. For the Richtmyer-Meshkov limiting case of an impulsively accelerated interface, the onset of instability does not depend on the sign of the interface acceleration. In both cases the effect of crystallization wave damping is to reduce the perturbation growth-rate of the Taylor unstable interface.Comment: 8 pages, 2 figures, RevTe

XY models with disorder and symmetry-breaking fields in two dimensions

The combined effect of disorder and symmetry-breaking fields on the two-dimensional XY model is examined. The study includes disorder in the interaction among spins in the form of random phase shifts as well as disorder in the local orientation of the field. The phase diagrams are determined and the properties of the various phases and phase transitions are calculated. We use a renormalization group approach in the Coulomb gas representation of the model. Our results differ from those obtained for special cases in previous works. In particular, we find a changed topology of the phase diagram that is composed of phases with long-range order, quasi-long-range order, and short-range order. The discrepancies can be ascribed to a breakdown of the fugacity expansion in the Coulomb gas representation. Implications for physical systems such as planar Josephson junctions and the faceting of crystal surfaces are discussed.Comment: 17 pages Latex with 5 eps figures, change: acknowledgment extende