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We develop an engineered microwave environment for coupling high Q superconducting resonators to quantum dots using a multilayer fabrication stack for the dot control wiring. Analytic and numerical models are presented to understand how parasitic capacitive coupling to the dot bias leads can result in microwave energy leakage and low resonator quality factors. We show that by controlling the characteristic impedance of the dot bias wiring, on-chip quality factors of 8140 can be attained without the addition of explicit filtering. Using this approach we demonstrate single electron occupation in double and triple dots detected via dipole or quadrupole coupling to a superconducting resonator. Additionally, by using multilayer fabrication we are able to improve ground plane integrity and keep microwave crosstalk below -20 dB out to 18 GHz while maintaining high wire density which will be necessary for future circuit quantum electrodyanmics (cQED) quantum dot processors., Comment: 5 pages, 3 figures

We present in detail a method we recently introduced (PRL. 103, 176404 (2009)) to describe finite systems in and out of equilibrium, where the evolution in time is performed via the Kadanoff-Baym Equations (KBE) within Many-Body Perturbation Theory (MBPT). The main property we analyze is the time-dependent density. We also study is the exchange-correlation potential of TDDFT, obtained via reverse engineering from the time-dependent density. Our systems consist of small, strongly correlated clusters, described by a Hubbard Hamiltonian within the Hartree-Fock, second Born, GW and T-matrix approximations. We compare the results from the KBE dynamics to those from exact numerical solutions. The outcome of our comparisons is that, among the many-body schemes considered, the T-matrix approximation is overall superior at all electron densities. Such comparisons permit a general assessment of the whole idea of applying MBPT, in the KBE sense, to finite systems. A striking outcome of our analysis is that when the system evolves under a strong external field, the KBE develop a steady-state solution as a consequence of a correlation-induced damping. This damping is present both in isolated (finite) systems, where it is purely artificial, as well as in clusters contacted to (infinite) macroscopic leads. To illustrate this point we present selected results for a system coupled to contacts within the T-matrix and second Born approximation. The extensive characterization we performed indicates that this behavior is present whenever approximate self energies, based upon infinite partial summations, are used. A second important result is that, for isolated clusters, the steady state reached is not unique but depends on how one switches on the external field. This may also true for clusters connected to leads., Comment: 18 pages, 15 figures

Spin blockade occurs when an electron is unable to access an energetically favorable path through a quantum dot due to spin conservation, resulting in a blockade of the current through the dot. Spin blockade is the basis of a number of recent advances in spintronics, including the measurement and the manipulation of individual electron spins. We report measurements of the spin blockade regime in a silicon double quantum dot, revealing a complementary phenomenon: lifetime-enhanced transport. We argue that our observations arise because the decay times for electron spins in silicon are long, enabling the electron to maintain its spin throughout its transit across the quantum dot and access fast paths that exist in some spin channels but not in others. Such long spin lifetimes are important for applications such as quantum computation and, more generally, spintronics., Comment: Published version. Supplementary Information in appendices

We measured magnetization, M, of a twin-aligned single crystal of YBa2Cu 3Ox (YBaCuO), with Tc = 91 K, as a function of temperature, T, and magnetic field, H, with H applied along the ab planes. Isothermal M-vs.-H and M-vs.-time curves were obtained with H applied parallel and perpendicular to the twin boundary, TB, direction. M-vs.-H curves exhibited two minimums below 38 K, which resembled similar curves that have been obtained in YBaCuO for H parallel to c axis. Above 12 K, the field positions of the minimums for H||TB and HperpTB were quite similar. Below 12 K, the position of the second minimum, Hmin, occurred at a higher field value with H||TB. Below 6 K, only one minimum appeared for both field directions. At low temperatures, these minimums in the M-vs.-H curves produced maximums in the critical current. It was determined that vortex lines were expelled more easily for H||TB than for HperpTB, and, therefore, below a certain field value, that Jc(HperpTB) was larger than Jc(H||TB) . At T, 7 pages, 6 figures. to appear in PRB Dec. 2004

SummaryHeparin neutralizing activity (HNA) was increased in plasma of patients with end-stage renal disease treated by maintenance haemodialysis. It was not raised in non-dialyzed patients with chronic renal failure, nor in patients with normal renal function who had been exposed to the extracorporeal circulation of the heart-lung bypass 48–72 hr before testing. It is postulated that the trauma of extracorporeal circulation causes platelets to release HNA which is not cleared by the dialysis membranes of the artificial kidney but is by the human kidney. This may have therapeutic implications for heparin dosage schedules during haemodialysis.

These studies clearly indicate that heparin has 2 antagonistic effects in this platelet-foreign surface interaction; it acts directly on platelets to increase retention, while acting on the foreign surface to reduce platelet retention, perhaps by competing for cationic sites. This study also suggests that it is unlikely that heparin bonding confers reduced surface thrombogenicity by virtue of the ability to leach off that surface and that further studies in heparin bonding or other surface modification should consider the antiplatelet effect which can easily be studied in vitro.

These studies clearly indicate that heparin has 2 antagonistic effects in this platelet-foreign surface interaction; it acts directly on platelets to increase retention, while acting on the foreign surface to reduce platelet retention, perhaps by competing for cationic sites. This study also suggests that it is unlikely that heparin bonding confers reduced surface thrombogenicity by virtue of the ability to leach off that surface and that further studies in heparin bonding or other surface modification should consider the antiplatelet effect which can easily be studied in vitro.

Contains fulltext : 51396.pdf (Publisher’s version ) (Closed access) Vitamin C is an antioxidant and inhibitor of carcinogenic N-nitroso compound production in the stomach. Higher dietary vitamin C consumption is associated with decreased risk of gastric cancer (GC) in numerous case-control studies, but data from prospective studies are limited, particularly so for blood measures of vitamin C. The objective of this study was to determine the association of plasma and dietary vitamin C levels with the risk of GC in a case-control study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC), a large cohort involving 10 European countries. Using a fluorometric method, vitamin C was measured in pre-diagnostic plasma from 215 GC cases (matched controls = 416). Conditional logistic regression models adjusted by body mass index, total energy intake, smoking status/duration/intensity and Helicobacter pylori infection status were used to estimate relative cancer risks. No association with GC risk was observed for dietary vitamin C, whereas an inverse GC risk was observed in the highest versus lowest quartile of plasma vitamin C [odds ratio (OR) = 0.55, 95% confidence interval (CI) = 0.31-0.97, P(trend) = 0.043], which was maintained after exclusion of cases with