Thermoelectric Effect in Single Crystal Zinc Wires

The work reported is a continuation of measurements published in the Physical Review for October, 1925. The thermol e.m.f. of the zinc crystals against copper has been measured from -182°C to 480°C for crystals having orientations from about 10° to 90°. The relation between thermoelectric power and temperature is definitely not linear, but may he represented fairly well by a second degree equation. The nature of the effect in the neighborhood of the melting point will be discussed

Thermoelectric Effect in Single Crystal Zinc Wires

Single crystal zinc wires of any desired orientation may be prepared by the method of Gomperz. The thermo-electric power of such crystals against a standard metal is a function of the orientation of the crystal lattice. The method of growing the crystals is described and data are given on the thermoelectric power against copper of wires of various orientations

Seeing Darkness: the New Cosmology

We present some useful ways to visualize the nature of dark energy and the effects of the accelerating expansion on cosmological quantities. Expansion probes such as Type Ia supernovae distances and growth probes such as weak gravitational lensing and the evolution of large scale structure provide powerful tests in complementarity. We present a ``ladder'' diagram, showing that in addition to dramatic improvements in precision, next generation probes will provide insight through an increasing ability to test assumptions of the cosmological framework, including gravity beyond general relativity.Comment: plenary talk at TAUP2005; to appear in Journal of Physics; 7 page

The massive star binary fraction in young open clusters I. NGC 6231 revisited

We present the results of a long-term high-resolution spectroscopy campaign on the O-type stars in NGC 6231. We revise the spectral classification and multiplicity of these objects and we constrain the fundamental properties of the O-star population. Almost three quarters of the O-type stars in the cluster are members of a binary system. The minimum binary fraction is 0.63, with half the O-type binaries having an orbital period of the order of a few days. The eccentricities of all the short-period binaries are revised downward, and henceforth match a normal period-eccentricity distribution. The mass-ratio distribution shows a large preference for O+OB binaries, ruling out the possibility that, in NGC 6231, the companion of an O-type star is randomly drawn from a standard IMF. Obtained from a complete and homogeneous population of O-type stars, our conclusions provide interesting observational constraints to be confronted with the formation and early-evolution theories of O stars.Comment: 16 pages, 14 figures. Accepted by MNRA

Quick-look guide to the crustal dynamics project's data information system

Described are the contents of the Crustal Dynamics Project Data Information System (DIS) and instructions on the use of this facility. The main purpose of the DIS is to store all geodetic data products acquired by the Project in a central data bank and to maintain information about the archive of all Project-related data. Access and use of the DIS menu-driven system is described as well as procedures for contacting DIS staff and submitting data requests

The Struve-Sahade effect in the optical spectra of O-type binaries I. Main-sequence systems

We present a spectroscopic analysis of four massive binary systems that are known or are good candidates to display the Struve-Sahade effect (defined as the apparent strengthening of the secondary spectrum of the binary when the star is approaching, and the corresponding weakening of the lines when it is receding). We use high resolution optical spectra to determine new orbital solutions and spectral types of HD 165052, HD 100213, HD 159176 and DH Cep. As good knowledge of the fundamental parameters of the considered systems is necessary to examine the Struve-Sahade effect. We then study equivalent width variations in the lines of both components of these binaries during their orbital cycle. In the case of these four systems, variations appear in the equivalent widths of some lines during the orbital cycle, but the definition given above can any longer be valid, since it is now clear that the effect modifies the primary spectrum as much as the secondary spectrum. Furthermore, the lines affected, and the way in which they are affected, depend on the considered system. For at least two of them (HD 100213 and HD 159176) these variations probably reflect the ellipsoidal variable nature of the system.Comment: 12 pages, 20 figures, in press A&

Cosmic Growth History and Expansion History

The cosmic expansion history tests the dynamics of the global evolution of the universe and its energy density contents, while the cosmic growth history tests the evolution of the inhomogeneous part of the energy density. Precision comparison of the two histories can distinguish the nature of the physics responsible for the accelerating cosmic expansion: an additional smooth component - dark energy - or a modification of the gravitational field equations. With the aid of a new fitting formula for linear perturbation growth accurate to 0.05-0.2%, we separate out the growth dependence on the expansion history and introduce a new growth index parameter \gamma that quantifies the gravitational modification.Comment: 8 pages, 3 figures; minor changes to match version accepted to PR

Unconventional superconductivity on a topological insulator

We study proximity-induced superconductivity on the surface of a topological insulator (TI), focusing on unconventional pairing. We find that the excitation spectrum becomes gapless for any spin-triplet pairing, such that both subgap bound states and Andreev reflection is strongly suppressed. For spin-singlet pairing, the zero-energy surface state in the $d_{xy}$-wave case becomes a Majorana fermion, in contrast to the situation realized in the topologically trivial high-$T_c$ cuprates. We also study the influence of a Zeeman field on the surface states. Both the magnitude and direction of this field is shown to strongly influence the transport properties, in contrast to the case without TI. We predict an experimental signature of the Majorana states via conductance spectroscopy.Comment: 4 pages, 3 figures. Accepted for publication in Phys. Rev. Let

AN EVALUATION OF INTEGRATED PEST MANAGEMENT WITH HETEROGENEOUS PARTICIPATION

Principal component analysis in employed to develop indices that distinguish between participants and nonparticipants in Integrated Pest Management (IPM) programs. Results of incorporating these indices into yield, net return, and production cost functions for cotton producers indicate that both yield and costs increase as the degree of producer participation in IPM increases. Although these results are inconsistent with previous research, they are consistent with the theoretical relationship between IPM and conventional input usage.Crop Production/Industries,

Standards of Capacity

In order to calibrate with precision condensers for use in radio frequency measurements, three standard condensers of coaxial cylindrical plates were made after the manner described by the former Lord Rayleigh. The three condensers were of capacities 25, 50, and 100 micro-micro-farads. By means of continuous wave radio frequency currents from an electron tube generator a variable air condenser with a vernier was calibrated by a step by step method. This was used as a secondary standard. The measurements were accurate to less than one-half micro-micro-farad, and the calibration was correct to considerably less than one per cent, for capacities greater than twenty micro-micro-farads. Measurements showed that isolated metal spheres and metal discs could not be readily used as standards, that is, their calculated and measured capacities were not in agreement because of unavoidable capacity effects. On the other hand, the capacities of small parallel plate variable condensers were found to be in close agreement with the values calculated from the dimensions of the plates and the distance apart of the plates. The plates were of brass 2.5 mm in thickness, the back surfaces being beveled until the edges were thin. The plates were circular, those of one condenser being 7 cms in diameter, of another 10 cms. The distance apart of the plates was varied by a slow screw adjustment