One-dimensional Josephson arrays as superlattices for single Cooper pairs

We investigate uniform one-dimensional arrays of small Josephson junctions ($E_J \ll E_C$, $E_C = (2e)^2/2C$) with a realistic Coulomb interaction $U(x) = E_C \lambda \exp( - |x|/\lambda)$ (here $\lambda \gg 1$ is the screening length in units of the lattice constant of the array). At low energies this system can be described in terms of interacting Bose particles (extra single Cooper pairs) on the lattice. With increasing concentration $\nu$ of extra Cooper pairs, a crossover from the Bose gas phase to the Wigner crystal phase and then to the superlattice regime occurs. The phase diagram in the superlattice regime consists of commensurable insulating phases with $\nu = 1/l$ ($l$ is integer) separated by superconducting regions where the current is carried by excitations with {\em fractional} electric charge $q = \pm 2e/l$. The Josephson current through a ring-shaped array pierced by magnetic flux is calculated for all of the phases.Comment: 4 pages (LATEX), 2 figure

Political Regimes and Sovereign Credit Risk in Europe, 1750-1913

This article uses a new panel data set to perform a statistical analysis of political regimes and sovereign credit risk in Europe from 1750 to 1913. Old Regime polities typically suffered from fiscal fragmentation and absolutist rule. By the start of World War I, however, many such countries had centralized institutions and limited government. Panel regressions indicate that centralized and?or limited regimes were associated with significant improvements in credit risk relative to fragmented and absolutist ones. Structural break tests also reveal close relationships between major turning points in yield series and political transformations

Fast Algorithms For Josephson Junction Arrays : Bus--bars and Defects

We critically review the fast algorithms for the numerical study of two--dimensional Josephson junction arrays and develop the analogy of such systems with electrostatics. We extend these procedures to arrays with bus--bars and defects in the form of missing bonds. The role of boundaries and of the guage choice in determing the Green's function of the system is clarified. The extension of the Green's function approach to other situations is also discussed.Comment: Uuencoded 1 Revtex file (11 Pages), 3 Figures : Postscript Uuencode

ABCC1: a gateway for pharmacological compounds to the ischaemic brain

By preventing access of drugs to the CNS, the blood-brain barrier hampers developments in brain pharmacotherapy. Strong efforts are currently being made to identify drugs that accumulate more efficaciously in ischaemic brain tissue. We identified an ATP-binding cassette (ABC) transporter, ABCC1, which is expressed on the abluminal surface of the brain capillary endothelium and mildly downregulated in response to focal cerebral ischaemia, induced by intraluminal middle cerebral artery occlusion. In biodistribution studies we show that ABCC1 promotes the accumulation of known neuroprotective and neurotoxic compounds in the ischaemic and non-ischaemic brain, ABCC1 deactivation reducing tissue concentrations by up to two orders of magnitude. As such, ABCC1's expression and functionality in the brain differs from the liver, spleen and testis, where ABCC1 is strongly expressed on parenchymal cells, resulting -- in case of liver and testis -- in directed transport from the tissue into the blood. After focal cerebral ischaemia, ABCC1 deactivation abolished the efficacy of both neuroprotective and neurotoxic compounds. Our data indicate that ABCC1 acts as gateway for pharmacological compounds to the stroke brain. We suggest that the tailoring of compounds binding to abluminal but not luminal ABC transporters may facilitate stroke pharmacotherap

Five-Year Outcomes of the SuperB Trial:A Multicenter Randomized Controlled Trial Comparing Heparin-Bonded Endograft to Surgical Femoropopliteal Bypass

Objective: This study aims to compare the 5-year outcomes of endoluminal bypass (EB) using heparin-bonded self-expanding covered stents versus bypass surgery for extensive femoropopliteal disease, including technical and clinical outcomes and health status. Background: The surgical femoropopliteal bypass was the gold standard to treat peripheral arterial disease (PAD) for decades; however, endovascular treatment modalities are now recommended for most femoropopliteal lesions. One-year data of a randomized controlled trial comparing EB with surgical bypass (SB) have shown a faster recovery, less morbidity, and comparable patency rates between the two techniques. To date, long-term randomized controlled data regarding both techniques are lacking. Methods: Five-year results of a multicenter randomized controlled trial comparing EB with SB in patients with femoropopliteal artery disease were evaluated based on intention-to-treat and per-protocol analyses. Results: At 5-year follow-up, primary, primary-assisted, and secondary patency rates were 36.2%, 52.4%, and 68.1% for EB and 49.4%, 72.2%, and 77.8% for SB, respectively (p=0.608). Freedom from target lesion revascularization (fTLR) was 34.1% for EB and 57.6% for SB (p=0.365). In both groups, the ankle-brachial index, Rutherford classification, and walking distance significantly improved compared with baseline without differences between groups at follow-up. Freedom from major amputation rate was 92.6% in the EB group and 96.2% in the SB group (p=0.361). The 36-Item Short-Form Health Survey showed no significant differences between groups. Conclusion: Treatment of extensive femoropopliteal disease with self-expanding covered stents provides comparable clinical-related and health-related questionnaire outcomes when compared with SB through 5 years of follow-up. However, the EB is related to a higher number of reinterventions. Clinical Impact: This present study is the first to report five-year outcomes comparing an endoluminal (EB) using heparin-bonded self-expanding covered stents with surgical bypass (SB) for long and complex femoropopliteal disease. Although the advantages of treatment with EB are mostly seen in the early period after treatment, the outcomes support the use of EB for this indication and seems to be a valid and safe alternative for bypass surgery. Future trials comparing various endovascular strategies may provide further guidance for the development of an evidence-based treatment algorithm.</p

SUrgical versus PERcutaneous Bypass: SUPERB-trial; Heparin-bonded endoluminal versus surgical femoro-popliteal bypass: study protocol for a randomized controlled trial

Contains fulltext : 96315.pdf (publisher's version ) (Open Access)BACKGROUND: Endovascular treatment options for the superficial femoral artery are evolving rapidly. For long lesions, the venous femoropopliteal bypass considered to be superior above the prosthetic bypass. An endoluminal bypass, however, may provide equal patency rates compared to the prosthetic above knee bypass. The introduction of heparin-bonded endografts may further improve patency rates. The SUrgical versus PERcutaneous Bypass (SuperB) study is designed to assess whether a heparin-bonded endoluminal bypass provides equal patency rates compared to the venous bypass and to prove that it is associated with improved quality of life, related to a decreased complication rate, or not. METHODS/DESIGN: Two-hundred-twenty-two patients with peripheral arterial occlusive disease, category 3-6 according to Rutherford, will be randomized in two treatment arms; 1. the surgical femoro-popliteal bypass, venous whenever possible, and 2. the heparin-bonded endoluminal bypass. The power analysis was based on a non-inferiority principle, with an effect size of 90% and 10% margins (alpha 5%, power 80%). Patients will be recruited from 5 teaching hospitals in the Netherlands during a 2-year period. The primary endpoint is primary patency and quality of life evaluated by the RAND-36 questionnaire and the Walking Impairment Questionnaire. Secondary endpoints include secondary patency, freedom-from-TLR and complications. DISCUSSION: The SuperB trial is a multicentre randomized controlled trial designed to show non-inferiority in patency rates of the heparin-bonded endograft compared to the surgical bypass for treatment of long SFA lesions, and to prove a better quality of life using the heparin bonded-endograft compared to surgically treatment, related to a reduction in complications. TRIAL REGISTRATION: Clinicaltrials: NCT01220245

Critical properties of two-dimensional Josephson junction arrays with zero-point quantum fluctuations

We present results from an extensive analytic and numerical study of a two-dimensional model of a square array of ultrasmall Josephson junctions. We include the ultrasmall self and mutual capacitances of the junctions, for the same parameter ranges as those produced in the experiments. The model Hamiltonian studied includes the Josephson, $E_J$, as well as the charging, $E_C$, energies between superconducting islands. The corresponding quantum partition function is expressed in different calculationally convenient ways within its path-integral representation. The phase diagram is analytically studied using a WKB renormalization group (WKB-RG) plus a self-consistent harmonic approximation (SCHA) analysis, together with non-perturbative quantum Monte Carlo simulations. Most of the results presented here pertain to the superconductor to normal (S-N) region, although some results for the insulating to normal (I-N) region are also included. We find very good agreement between the WKB-RG and QMC results when compared to the experimental data. To fit the data, we only used the experimentally determined capacitances as fitting parameters. The WKB-RG analysis in the S-N region predicts a low temperature instability i.e. a Quantum Induced Transition (QUIT). We carefully simulations and carry out a finite size analysis of $T_{QUIT}$ as a function of the magnitude of imaginary time axis $L_\tau$. We find that for some relatively large values of $\alpha=E_C/E_J$ ($1\leq \alpha \leq 2.25)$, the $L_\tau\to\infty$ limit does appear to give a {\it non-zero} $T_{QUIT}$, while for $\alpha \ge 2.5$, $T_{QUIT}=0$. We use the SCHA to analytically understand the $L_\tau$ dependence of the QMC results with good agreement between them. Finally, we also carried out a WKB-RG analysis in the I-N region and found no evidence of a low temperature QUIT, up to lowest order in ${\alpha}^{-1}$Comment: 39 pages, 18 postscript figures, to appear in Phys. Rev.

Quantum-Phase Transitions of Interacting Bosons and the Supersolid Phase

We investigate the properties of strongly interacting bosons in two dimensions at zero temperature using mean-field theory, a variational Ansatz for the ground state wave function, and Monte Carlo methods. With on-site and short-range interactions a rich phase diagram is obtained. Apart from the homogeneous superfluid and Mott-insulating phases, inhomogeneous charge-density wave phases appear, that are stabilized by the finite-range interaction. Furthermore, our analysis demonstrates the existence of a supersolid phase, in which both long-range order (related to the charge-density wave) and off-diagonal long-range order coexist. We also obtain the critical exponents for the various phase transitions.Comment: RevTex, 20 pages, 10 PostScript figures include

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 $\sigma^*$ and the critical exponents at the transition. The result $\sigma^* = (0.55 \pm 0.06) (2e)^2/h$ for bosons with long-range Coulomb interaction is roughly consistent with experiments reported so far. We also find $\sigma^* = (0.14 \pm 0.03) (2e)^2/h$ for bosons with short-range interactions.Comment: Revtex 3.0, 54 pages, 17 figures included, UBCTP-93-01

Developmental seizures and mortality result from reducing GABAᴀ receptor α2-subunit interaction with collybistin

Fast inhibitory synaptic transmission is mediated by γ-aminobutyric acid type A receptors (GABAARs) that are enriched at functionally diverse synapses via mechanisms that remain unclear. Using isothermal titration calorimetry and complementary methods we demonstrate an exclusive low micromolar binding of collybistin to the α2-subunit of GABAARs. To explore the biological relevance of collybistin-α2-subunit selectivity, we generate mice with a mutation in the α2-subunit-collybistin binding region (Gabra2-1). The mutation results in loss of a distinct subset of inhibitory synapses and decreased amplitude of inhibitory synaptic currents. Gabra2–1 mice have a striking phenotype characterized by increased susceptibility to seizures and early mortality. Surviving Gabra2-1 mice show anxiety and elevations in electroencephalogram δ power, which are ameliorated by treatment with the α2/α3-selective positive modulator, AZD7325. Taken together, our results demonstrate an α2-subunit selective binding of collybistin, which plays a key role in patterned brain activity, particularly during development