Study of the system of middle atmosphere-ionosphere using remote-sensing data

In the present investigation, the methods of statistical spectral analysis are employed for a study of the quasi-periodic changes of state parameters of the middle atmosphere and the ionosphere, taking into account oscillations with periods of several days. The considered oscillations are typical for planetary waves. The theory and empirical findings regarding transient planetary waves are utilized as a basis for the concepts employed in the data analysis and for the interpretation of the results. The results of the investigation show a presence of coherent variations in the time series of radiation density measurements and other state parameters for the middle atmosphere and the ionosphere. The existence of presumably dynamic coupling processes can be recognized in oscillations with periods of about 16 or 5 days

Andreev reflections on Y1-xCaxBa2Cu3O7-delta evidence for an unusual proximity effect

We have measured Andreev reflections between an Au tip and Y_{1-x}Ca_{x}Ba_{2}Cu_{3}O_{7 - \delta} thin films in the in-plane orientation. The conductance spectra are best fitted with a pair potential having the "d_{x^{2}-y^{2}+is" symmetry. We find that the amplitude of the "is" component is enhanced as the contact transparency is increased. This is an indication for an unusual proximity effect that modifies the pair potential in the superconductor near the surface with the normal metal.Comment: 4 pages, 4 figure

Noncyclic covers of knot complements

Hempel has shown that the fundamental groups of knot complements are residually finite. This implies that every nontrivial knot must have a finite-sheeted, noncyclic cover. We give an explicit bound, $\Phi (c)$, such that if $K$ is a nontrivial knot in the three-sphere with a diagram with $c$ crossings and a particularly simple JSJ decomposition then the complement of $K$ has a finite-sheeted, noncyclic cover with at most $\Phi (c)$ sheets.Comment: 29 pages, 8 figures, from Ph.D. thesis at Columbia University; Acknowledgments added; Content correcte

The Computational Complexity of Knot and Link Problems

We consider the problem of deciding whether a polygonal knot in 3-dimensional Euclidean space is unknotted, capable of being continuously deformed without self-intersection so that it lies in a plane. We show that this problem, {\sc unknotting problem} is in {\bf NP}. We also consider the problem, {\sc unknotting problem} of determining whether two or more such polygons can be split, or continuously deformed without self-intersection so that they occupy both sides of a plane without intersecting it. We show that it also is in NP. Finally, we show that the problem of determining the genus of a polygonal knot (a generalization of the problem of determining whether it is unknotted) is in {\bf PSPACE}. We also give exponential worst-case running time bounds for deterministic algorithms to solve each of these problems. These algorithms are based on the use of normal surfaces and decision procedures due to W. Haken, with recent extensions by W. Jaco and J. L. Tollefson.Comment: 32 pages, 1 figur

A New Precision Measurement of the 3He(4He,gamma)7Be Cross section

The 3He(4He,gamma)7Be reaction plays an important role in determining the high energy solar neutrino flux and in understanding the abundances of primordial 7Li. The present paper reports a new precision measurement of the cross sections of this direct capture reaction, determined by measuring the ensuing 7Be activity in the region of Ec.m.=400 keV to 950 keV. Various recent theoretical fits to our data result in a consistent extrapolated value of S34(0)=0.53(2)(1).Comment: 10 pages 3 figure

Confirmation of Parity Violation in the Gamma Decay of 180Hfm^{180}Hf^{m}

This paper reports measurements using the technique of On Line Nuclear Orientation (OLNO) which reexamine the gamma decay of isomeric $^{\rm 180}$Hf$^{\rm m}$ and specifically the 501 keV 8$^{\rm -}$ -- 6$^{\rm +}$ transition. The irregular admixture of E2 to M2/E3 multipolarity in this transition, deduced from the forward-backward asymmetry of its angular distribution, has for decades stood as the prime evidence for parity mixing in nuclear states. The experiment, based on ion implantation of the newly developed mass-separated $^{\rm 180}$Hf$^{\rm m}$ beam at ISOLDE, CERN into an iron foil maintained at millikelvin temperatures, produces higher degrees of polarization than were achieved in previous studies of this system. The value found for the E2/M2 mixing ratio, $\epsilon$ = -0.0324(16)(17), is in close agreement with the previous published average value $\epsilon$ = - 0.030(2), in full confirmation of the presence of the irregular E2 admixture in the 501 keV transition. The temperature dependence of the forward-backward asymmetry has been measured over a more extended range of nuclear polarization than previously possible, giving further evidence for parity mixing of the 8$^{\rm -}$ and 8$^{\rm +}$ levels and the deduced E2/M2 mixing ratio.Comment: 28 pages, 9 figures, accepted for publication in Physical Review

Consumo dos frutos e dispersão de sementes de Dimorphandra mollis Benth. (Leguminosae) pela anta no cerrado do Brasil Central

A frutificação de Dimorphandra mollis e o destino dos frutos foram analisados por 7 meses em uma área de cerrado stricto sensu no Distrito Federal. Analisamos 81 amostras de fezes de anta (Tapirus terrestris) coletadas em 6 áreas de cerrado no Brasil Central e oferecemos frutos a 5 antas no zoológico de Brasília. As fezes foram coletadas e as sementes usadas em testes de germinação. A anta é importante consumidor dos frutos e potencial dispersor das sementes. Contudo, o consumo de frutos no campo foi reduzido provavelmente em razão da palatabilidade dos frutos e da baixa densidade de frugívoros, especialmente antas. Discutimos a possibilidade de os dispersores originais pertencerem à megafauna extinta de mamíferos da América do Sul.Fruit phenology observations and consumption of Dimorphandra mollis (Leguminosae) were analyzed during seven months in an area of cerrado stricto sensu. We analysed 81 fecal samples collected at six different places of lowland tapirs (Tapirus terrestris) in central Brazilian cerrado. In addition, from the feces of five tapirs at the Brasília Zoo to which fruit had been offered, seeds were collected and used in germination tests. The results suggest that the tapir is an important fruit consumer and a potential seed disperser of D. mollis. In the field, however, fruit consumption was found to be very low, probably because of both fruit palatability and the low density of frugivores, especially tapirs. The possibility that the original dispersal agents of D. mollis seeds belonged to the South American Pleistocene megafauna is discussed

Experimental evidence of strong phonon scattering in isotopical disordered systems: The case of LiH_xD_{1-x} crystals

The observation of the local - mode vibration, the two - mode behavior of the LO phonons at large isotope concentration, as well as large line broadening in LIH - D mixed crystals directly evidence strong additional phonon scattering due to the isotope - induced disorder.Comment: 9 pages, 4 figure

The Optical Design and Characterization of the Microwave Anisotropy Probe

The primary goal of the MAP satellite, now in orbit, is to make high fidelity polarization sensitive maps of the full sky in five frequency bands between 20 and 100 GHz. From these maps we will characterize the properties of the cosmic microwave background (CMB) anisotropy and Galactic and extragalactic emission on angular scales ranging from the effective beam size, <0.23 degree, to the full sky. MAP is a differential microwave radiometer. Two back-to-back shaped offset Gregorian telescopes feed two mirror symmetric arrays of ten corrugated feeds. We describe the prelaunch design and characterization of the optical system, compare the optical models to the measurements, and consider multiple possible sources of systematic error.Comment: ApJ in press; 22 pages with 11 low resolution figures; paper is available with higher quality figures at http://map.gsfc.nasa.gov/m_mm/tp_links.htm