437 research outputs found
Integer Quantum Hall Effect in Double-Layer Systems
We consider the localization of independent electron orbitals in double-layer
two-dimensional electron systems in the strong magnetic field limit. Our study
is based on numerical Thouless number calculations for realistic microscopic
models and on transfer matrix calculations for phenomenological network models.
The microscopic calculations indicate a crossover regime for weak interlayer
tunneling in which the correlation length exponent appears to increase.
Comparison of network model calculations with microscopic calculations casts
doubt on their generic applicability.Comment: 14 pages, 12 figures included, RevTeX 3.0 and epsf. Additional
reference
The superconductor-insulator transition in 2D dirty boson systems
Universal properties of the zero temperature superconductor-insulator
transition in two-dimensional amorphous films are studied by extensive Monte
Carlo simulations of bosons in a disordered medium. We report results for both
short-range and long-range Coulomb interactions for several different points in
parameter space. In all cases we observe a transition from a superconducting
phase to an insulating Bose glass phase. {}From finite-size scaling of our
Monte Carlo data we determine the universal conductivity and the
critical exponents at the transition. The result for bosons with long-range Coulomb interaction is roughly consistent
with experiments reported so far. We also find for bosons with short-range interactions.Comment: Revtex 3.0, 54 pages, 17 figures included, UBCTP-93-01
Business constraints and growth potential of micro and small manufacturing enterprises in Uganda
Ugandan micro and small enterprises (MSEs) still perform poorly. Studies associating poor performance of manufacturers with lack of finance and low investment ignore micro enterprises. Those focusing on MSEs are either exploratory in nature or employ a descriptive analysis, which cannot show the extent to which business constraints explain the performance of MSEs. Thus, this paper tries to examine the extent to which the growth of MSEs is associated with business constraints while controlling for owners’ attributes and firms’ characteristics. The results reveal that MSEs’ growth potential is negatively associated with limited access to productive resources (finance and business development services), high taxes and lack of market access
Lipolysis drives expression of the constitutively active receptor GPR3 to induce adipose thermogenesis
Thermogenic adipocytes possess a therapeutically appealing, energy-expending capacity, which is canonically cold-induced by ligand-dependent activation of β-adrenergic G protein-coupled receptors (GPCRs). Here, we uncover an alternate paradigm of GPCR-mediated adipose thermogenesis through the constitutively active receptor, GPR3. We show that the N terminus of GPR3 confers intrinsic signaling activity, resulting in continuous Gs-coupling and cAMP production without an exogenous ligand. Thus, transcriptional induction of Gpr3 represents the regulatory parallel to ligand-binding of conventional GPCRs. Consequently, increasing Gpr3 expression in thermogenic adipocytes is alone sufficient to drive energy expenditure and counteract metabolic disease in mice. Gpr3 transcription is cold-stimulated by a lipolytic signal, and dietary fat potentiates GPR3-dependent thermogenesis to amplify the response to caloric excess. Moreover, we find GPR3 to be an essential, adrenergic-independent regulator of human brown adipocytes. Taken together, our findings reveal a noncanonical mechanism of GPCR control and thermogenic activation through the lipolysis-induced expression of constitutively active GPR3
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