Boundary condition for Ginzburg-Landau theory of superconducting layers

Electrostatic charging changes the critical temperature of superconducting thin layers. To understand the basic mechanism, it is possible to use the Ginzburg-Landau theory with the boundary condition derived by de Gennes from the BCS theory. Here we show that a similar boundary condition can be obtained from the principle of minimum free energy. We compare the two boundary conditions and use the Budd-Vannimenus theorem as a test of approximations.Comment: 6 pages, 4 figure

Aquatic Exercise Programs for Children and Adolescents with Cerebral Palsy: What Do We Know and Where Do We Go?

Aquatic exercise programs may be a beneficial form of therapy for children and adolescents with cerebral palsy (CP), particularly for those with significant movement limitations where land-based physical activity is difficult. The most recently published systematic review (2005) on aquatic interventions in children with CP found supportive but insufficient evidence on its effectiveness. The aim of this paper is to review recently published literature since 2005 with a focus on aquatic exercise for children with CP. In total, six new studies were published with a main focus on aerobic aquatic interventions in higher functioning children and adolescents with CP. Swimming is one of the most frequently reported physical activities in children and adolescents with CP. Therefore, information on its safety and benefits is highly needed, for those with more severe CP in particular. Research design issues are discussed to help guide future research and practice

Vacancies and residential search in an empirical equilibrium search model

As is well known housing has a unique set of characteristics which interact to cause the operation of the housing market to be significantly different from that of other markets. On the demand side individuals have to search for vacancies and its characteristics. Due to the high dimensionality of housing considerable search costs are involved. On the supply side, complicated interactions exist in the housing market whereby frictions occur frequently. In the labour market similar behaviour has been explained with search and matching models, where vacancies and turnovers are explicitly considered. Wheaton (1990) remarks that these search and matching models from the labour market would seem particularly applicable to housing. In this paper we formulate an equilibrium search model of the housing market that deals with search and prices. We beleive that an equilibrium searchmodel could be an important step forward into the analysis of vacancies and residential search. Using this framework we formulate an empirical model for the Dutch housing market.

Hoe wordt Nederland Miss Europe?

De Nederlandse welvaartsstaat is niet voldoende toegesneden op de toekomst. De vergrijzing jaagt de kosten van de oudedagsvoorziening en de zorg op, waardoor de spanning tussen jong en oud groeit. Tegelijkertijd dreigen economische integratie en technologische ontwikkeling de positie van laaggeschoolden op de arbeidsmarkt te verslechteren (Nahuis en De Groot, 2003). Verder is de verzorgingsstaat onvoldoende aangepast aan de toegenomen heterogeniteit in de samenleving en werken instituties langdurige inactiviteit in de hand. Er moet daarom verder worden hervormd in de Nederlandse verzorgingsstaat. Maar hoe

Electrostatic potential in a superconductor

The electrostatic potential in a superconductor is studied. To this end Bardeen's extension of the Ginzburg-Landau theory to low temperatures is used to derive three Ginzburg-Landau equations - the Maxwell equation for the vector potential, the Schroedinger equation for the wave function and the Poisson equation for the electrostatic potential. The electrostatic and the thermodynamic potential compensate each other to a great extent resulting into an effective potential acting on the superconducting condensate. For the Abrikosov vortex lattice in Niobium, numerical solutions are presented and the different contributions to the electrostatic potential and the related charge distribution are discussed.Comment: 19 pages, 11 figure

The Determination of Technology and Commodity Policy in the U.S. Dairy Industry

United States dairy policy includes both predatory and productive components. The milk price support program is designed to transfer income to dairy farmers while research and extension expenditures are designed to increase social welfare. The purpose of this chapter is to provide an empirical example of the theory developed in the previous chapter. It has long been recognized the government research and extension policies have been significant contributors to technological advance in agriculture (Evenson and Kislev 1976, Evenson, Waggoner, and Ruttan 1979). The advent of technological change on agriculture and its policy implications was first noted by Schultz (1945, 1953). Some, like Cochrane (1958) in characterizing his famous technological treadmill thesis, argued for price supports in order to compensate farmers for the adverse effects of research on farmers\u27 welfare. Indeed, commentators like Thurow (1981) and Schlesinger (1984) argue that public good provision in agriculture is one of the few major economic success stories of government intervention in the history of the United States. Nevertheless, one of the most stylized facts in government policy intervention in agriculture is the pervasive level and overwhelming evidence of underinvestment in public research (Ruttan 1982). Concomitant to this notion, economists have alleged that governments \u27overinvest\u27 in commodity policies because of the associated deadweight losses generated

Cooperation in a modified version of the finitely repeated prisoners' dilemma game

In this paper we consider a series of finitely repeated prisoners' dilemma games in which the payoff the players receive in a period depends on how they have played the game in the past. We show that this modification of the finitely repeated prisoners' dilemma game makes cooperation a feasible equilibrium configuration in the beginning of play

Early Permian Zircon Ages from the \u3cem\u3eP. confluens\u3c/em\u3e and \u3cem\u3eP. pseudoreticulata\u3c/em\u3e Spore-Pollen Zones in the Southern Bonaparte and Canning Basins, Northwestern Australia

The Pseudoreticulatispora confluens–P. pseudoreticulata spore-pollen zonal datum typically coincides with the end of widespread Permian glacial deposits in Western Australia. Although previously attributed to the mid-Sakmarian, chemical abrasion isotope dilution thermal ionisation mass spectrometry (TIMS) dating of zircons from volcanic tuffs in the Ditji Formation of the Bonaparte Basin and the Grant Group in the Canning Basin point to an Asselian age of about 295.25 Ma for this datum. All dated zircons from the Ditji Formation came from petroleum well cuttings but the accompanying palynology was mostly from sidewall cores; however, all Grant Group samples were from conventional core. TIMS dates from the Ditji Formation range in age from 295.2 to 292.7 Ma whereas the only productive tuff from the Grant Group yielded a 296.26 Ma date. By comparison, there are no zircon dates to constrain the onset of glacial deposition in Australia. The Bonaparte Basin ages overlap with those for the Edie Tuff (296.1–294.5 Ma) in Queensland’s Galilee Basin, approximately 2000 km to the southeast, which also lies close to the base of the P. pseudoreticulata Zone. To date the only fossil group within the P. confluens Zone in Western Australia to provide independent age control, albeit loosely, are goniatites from the northern Perth Basin (Uraloceras irwinense and Juresanites jacksoni) that have consistently been attributed to the Sakmarian; these require a reassessment of their affinity with Russian faunas and therefore to global stratotypes. The position of the Carboniferous–Permian boundary is elusive in Australia and will remain so until additional volcanic tuffs containing young datable zircons are found; however, spore-pollen and zircon dates from Namibia place this boundary within the P. confluens Zone