Observations of thunder with the Arecibo VHF radar

An experiment was carried out at the Arecibo Observatory in Puerto Rico in August 1985 to study Doppler velocities in a thunderstorm environment with a beam pointed 2.5 degrees off-vertical. Researchers detected two types of echoes associated with lightning. The first was associated with scattering from the lightning channel itself and had characteristics similar to those observed previously with meteorological radars. The second appeared to be due to scattering from the turbulence organized by phase fronts of an acoustic wave generated by lightning. The observations were consistent with a wave traveling at a velocity near the speed of sound and having a vertical phase velocity component of 40 m/s

Observations of vertical velocity power spectra with the SOUSY VHF radar

A data set taken with the SOUSY VHF radar from October 28 to November 13, 1981 was used to calculate the power spectrum of the vertical velocities directly from the vertical beam measurements. The spectral slopes for the frequency spectra have been determined out to periods of several days and have been found to have values near -1 in the troposphere and shallower slopes in the lower stratosphere. The value of -1 is in agreement with the value found by Larsen et al. (1985) and Balsley and Carter (1982) in the range from a few minutes to 1 hr

Cosmological Solution in M-theory on S^1/Z_2

We provide the first example of a cosmological solution of the Horava-Witten supergravity. This solution is obtained by exchanging the role of time with the radial coordinate of the transverse space to the five-brane soliton. On the boundary this corresponds to rotating an instanton solution into a tunneling process in a space with Lorentzian signature, leading to an expanding universe. Due to the freedom to choose different non-trivial Yang-Mills backgrounds on the boundaries, the two walls of the universe ( visible and hidden worlds) expand differently. However at late times the anisotropy is washed away by gravitational interactions.Comment: 10 pages, latex, no figur

A Young Globular Cluster in the Galaxy NGC 6946

A globular cluster ~15 My old that contains 5x10^5 Msun of stars inside an 11 pc radius has been found in the nearby spiral galaxy NGC 6946, surrounded by clouds of dust and smaller young clusters inside a giant circular bubble 300 pc in radius. At the edge of the bubble is an arc of regularly-spaced clusters that could have been triggered during the bubble's formation. The region is at the end of a spiral arm, suggesting an origin by the asymmetric collapse of spiral arm gas. The globular is one of the nearest examples of a cluster that is similar to the massive old globulars in the Milky Way. We consider the energetics of the bubble and possible formation mechanisms for the globular cluster, including the coalescence of smaller clusters.Comment: 20 pages, 7 figures, accepted for Astrophysical Journal Vol 535, June 1 200

UHF and VHF radar observations of thunderstorms

A study of thunderstorms was made in the Summer of 1985 with the 430-MHz and 50-MHz radars at the Arecibo Observatory in Puerto Rico. Both radars use the 300-meter dish, which gives a beam width of less than 2 degrees even at these long wavelengths. Though the radars are steerable, only vertical beams were used in this experiment. The height resolution was 300 and 150 meters for the UHF and VHF, respectively. Lightning echoes, as well as returns from precipitation and clear-air turbulence were detected with both wavelengths. Large increases in the returned power were found to be coincident with increasing downward vertical velocities at UHF, whereas at VHF the total power returned was relatively constant during the life of a storm. This was attributed to the fact that the VHF is more sensitive to scattering from the turbulence-induced inhomogeneities in the refractive index and less sensitive to scatter from precipitation particles. On occasion, the shape of the Doppler spectra was observed to change with the occurrence of a lightning discharge in the pulse volume. Though the total power and mean reflectivity weighted Doppler velocity changed little during these events, the power is Doppler frequency bins near that corresponding to the updraft did increase substantially within a fraction of a second after a discharge was detected in the beam. This suggests some interaction between precipitation and lightning

From p-branes to Cosmology

We study the relationship between static p-brane solitons and cosmological solutions of string theory or M-theory. We discuss two different ways in which extremal p-branes can be generalised to non-extremal ones, and show how wide classes of recently discussed cosmological models can be mapped into non-extremal p-brane solutions of one of these two kinds. We also extend previous discussions of cosmological solutions to include some that make use of cosmological-type terms in the effective action that can arise from the generalised dimensional reduction of string theory or M-theory.Comment: Latex, 24 pages, no figur

Black Hole Hair Removal: Non-linear Analysis

BMPV black holes in flat transverse space and in Taub-NUT space have identical near horizon geometries but different microscopic degeneracies. It has been proposed that this difference can be accounted for by different contribution to the degeneracies of these black holes from hair modes, -- degrees of freedom living outside the horizon. In this paper we explicitly construct the hair modes of these two black holes as finite bosonic and fermionic deformations of the black hole solution satisfying the full non-linear equations of motion of supergravity and preserving the supersymmetry of the original solutions. Special care is taken to ensure that these solutions do not have any curvature singularity at the future horizon when viewed as the full ten dimensional geometry. We show that after removing the contribution due to the hair degrees of freedom from the microscopic partition function, the partition functions of the two black holes agree.Comment: 40 pages, LaTe

q-Deformed de Sitter/Conformal Field Theory Correspondence

Unitary principal series representations of the conformal group appear in the dS/CFT correspondence. These are infinite dimensional irreducible representations, without highest weights. In earlier work of Guijosa and the author it was shown for the case of two-dimensional de Sitter, there was a natural q-deformation of the conformal group, with q a root of unity, where the unitary principal series representations become finite-dimensional cyclic unitary representations. Formulating a version of the dS/CFT correspondence using these representations can lead to a description with a finite-dimensional Hilbert space and unitary evolution. In the present work, we generalize to the case of quantum-deformed three-dimensional de Sitter spacetime and compute the entanglement entropy of a quantum field across the cosmological horizon.Comment: 18 pages, 2 figures, revtex, (v2 reference added

Rapid communication: Linkage and physical mapping of the porcine melanocortin-4 receptor (MC4R) gene

Genus and Species. Sus scrofa. Locus. Pig Melanocortin-4 Receptor (MC4R) gene. Source and Description of Primers. Primers were designed from well-conserved sequence regions between the human and rat MC4R genes (Genbank accession no. S77415 and U67863, respectively). The primers were used to amplify approximately 760 bp of the porcine MC4R gene from genomic DNA. The sequence of the PCR product showed 92.2 and 97.6% identities at the nucleotide and amino acid levels, respectively, to the corresponding human sequence. The porcine MC4R sequence has been submitted to GenBank (accession no. AF087937). Using this sequence, pig-specific primers were designed

Rapid Communication: Genetic Linkage Mapping of the Porcine Fibroblast Growth Factor 7 (FGF7) Gene

Source and Description of Primers. The forward primer was developed from a human fibroblast growth factor ( FGF7) cDNA sequence (GenBank accession no. L06243), and the reverse primer was a published primer (Kelley et al., 1992). These primers were used to amplify a 1.3-kb fragment from porcine genomic DNA. This fragment included regions corresponding to exon 2, exon 3, and the intron flanked by these two exons. Sequences were obtained from both ends of the PCR fragment and compared with a human sequence showing 95.9% identity at the amino acid level in a 73-amino acid overlap. Sequences produced in this experiment have been submitted to GenBank (accession no. AF052657)