Hydrostatic pressure study of single-crystalline UNi0.5Sb2

We studied single-crystals of the antiferromagnetic compound UNi0.5Sb2 (TN ~ 161 K) by means of measurements of magnetic susceptibility (chi), specific heat (Cp), and electrical resistivity (rho) at ambient pressure, and resistivity under hydrostatic pressures up to 20 kbar, in the temperature range from 1.9 to 300 K. The thermal coefficient of the electrical resistivity (drho/dT) changes drastically from positive below TN to negative above, reflecting the loss of spin-disorder scattering in the ordered phase. Two small features in the rho vs T data centered near 40 and 85 K correlate well in temperature with features in the magnetic susceptibility and are consistent with other data in the literature. These features are quite hysteretic in temperature, i.e., the difference between the warming and cooling cycles are about 10 and 6 K, respectively. The effect of pressure is to raise TN at the approximate rate of 0.76 K/kbar, while progressively suppressing the amplitude of the small features in rho vs T at lower temperatures and increasing the thermal hysteresis.Comment: 9 pages, 3 figues, 2007-mmm conferenc

Behavioral and Economic Reasons for Homeowners’ Reticence to Install Alternative Solar Energy Systems

Institutional and Behavioral Economics,

CLIMATE AND COOPERATION: A NEW PERSPECTIVE ON THE MANAGEMENT OF SHARED FISH STOCKS

Climate regime shifts occur at irregular intervals and have profound and persistent impacts on ocean temperature and circulation patterns and on the dynamics of marine fish populations. Despite a growing scientific literature and some attention to the implications of such regime shifts for domestic fisheries, the issue has received little attention in the context of international fishery management. This paper presents evidence for the significance of climatic regime shifts, and draws upon the recent history of conflict between Canada and the United States over Pacific salmon management to illustrate the dangers that unpredicted, unanticipated environmental regime shifts pose for efforts to maintain international cooperation. This suggests a need for greater attention to this issue. Fishery agreements can be made more resilient to the impacts of such environmental changes by explicitly building in flexibility — for example, by allowing the use of side payments. In addition, pre-agreements on procedures to be followed in the event of sustained changes in fish stock productivity or migration patterns, and cooperation on developing common scientific understandings, can help to prevent destructive conflicts. Finally, the literature employing game theoretic shared-fishery models could be further developed to focus on providing practical guidance for maintaining cooperation in the presence of unpredictable and persistent environmental changes.climate regimes, shared fisheries, potential conflicts, uncertainty, Q21, Q22, Resource /Energy Economics and Policy,

Real photon structure at an e^+e^- linear collider

Previous studies of the kinematic coverage for measuring the photon structure function F_2^gamma at a future 500 GeV e^+e^- linear collider are updated using current estimates of luminosities and important detector parameters. The perturbative expansion for the evolution of F_2^gamma is briefly recalled in view of a recent claim that all existing next-to-leading order analyses of the photon structure are incorrect. A simple illustration is given of the different sensitivities of hadronic and photonic structure functions on the strong coupling constant alpha_s.Comment: 6 pages LaTeX including 7 eps-figures, uses espcrc2.sty (included). Talk presented at PHOTON'99, Freiburg (Germany), May 1999. To appear in the proceedings [Nucl. Phys. B (Proc. Suppl.)

СЛОВО ПРО ПРОФЕСОРА В. В. КРУТІКОВА

The electronic structures of “Ti9-nFe2+nRu18B8” (n = 0, 0.5, 1, 2, 3), in connection to the recently synthesized Ti9-nFe2+nRu18B8 (n = 1, 2), have been investigated and analyzed using LSDA tight-binding calculations to elucidate the distribution of Fe and Ti, to determine the maximum Fe content, and to explore possible magnetic structures to interpret experimental magnetization results. Through a combination of calculations on specific models and using the rigid band approximation, which is validated by the DOS curves for “Ti9-nFe2+nRu18B8” (n = 0, 0.5, 1, 2, 3), mixing of Fe and Ti is anticipated at both the 2b- and 4h-chain sites. The model “Ti8.5Fe2.5Ru18B8” (n = 0.5) revealed that both Brewer-type Ti−Ru interactions as well as ligand field splitting of the Fe 3d orbitals regulated the observed valence electron counts between 220 and 228 electrons/formula unit. Finally, models of magnetic structures were created using “Ti6Fe5Ru18B8” (n = 3). A rigid band analysis of the LSDA DOS curves concluded preferred ferromagnetic ordering at low Fe content (n ≤ 0.75) and ferrimagnetic ordering at higher Fe content (n \u3e 0.75). Ferrimagnetism arises from antiferromagnetic exchange coupling in the scaffold of Fe1-ladder and 4h-chain sites

Расчет магнитного поля, созданного проводником с током в прямоугольном пазу

На основе прямого вариационного метода Канторовича получена приближенная аналитическая формула для векторного магнитного потенциала в области сечения прямоугольного паза с ферромагнитными стенками. Поле создается прямолинейным проводником с током при обычных допущениях: бесконечно большая магнитная проницаемость ферромагнитной среды и отсутствие выпучивания потока у открытой стороны паза

Electrical resistivity, electronic heat capacity, and electronic structure of Gd5Ge4

Temperature and dc magnetic-field dependencies of the electrical resistivity (4.3–300 K, 0–40 kOe) and heat capacity (3.5–14 K, 0–100 kOe) of polycrystalline Gd5Ge4 have been measured. The electrical resistivity of Gd5Ge4 shows a transition between the low-temperature metallic and high-temperature insulatorlike states at ∼130 K. In the low-temperature metallic state both the resistivity and electronic heat capacity of Gd5Ge4 indicate a possible presence of a narrow conduction band. Both low- and high-temperature behaviors of the electrical resistivity of Gd5Ge4 correlate with the crystallographic and magnetic phase transitions induced by temperature and/or magnetic field. Several models, which can describe the unusual behavior of the electrical resistance of Gd5Ge4 above 130 K, are discussed. Preliminary tight-binding linear muffin-tin orbital calculations show that Gd5Ge4 behaves as a metal in the low-temperature magnetically ordered state, and as a Mott-Hubbard “semiconductor” in the high-temperature magnetically disordered state

Phase Transformation Driven by Valence Electron Concentration: Tuning Interslab Bond Distances in Gd5GaxGe4-x

X-ray single crystal and powder diffraction studies on the Gd5GaxGe4-x system with 0 ≤ x ≤ 2.2 reveal dependence of interslab T−T dimer distances and crystal structures themselves on valence electron concentration (T is a mixture of Ga and Ge atoms). While the Gd5GaxGe4-x phases with 0 ≤ x ≤ 0.6 and valence electron concentration of 30.4−31 e-/formula crystallize with the Sm5Ge4-type structure, in which all interslab T−T dimers are broken (distances exceeding 3.4 Å), the phases with 1 ≤ x ≤ 2.2 and valence electron concentration of 28.8−30 e-/formula adopt the Pu5Rh4- or Gd5Si4-type structures with T−T dimers between the slabs. An orthorhombic Pu5Rh4-type structure, which is intermediate between the Gd5Si4- and Sm5Ge4-type structures, has been identified for the Gd5GaGe3 composition. Tight-binding linear-muffin-tin-orbital calculations show that substitution of three-valent Ga by four-valent Ge leads to larger population of the antibonding states within the dimers and, thus, to dimer stretching and eventually to dimer cleavage