On the theory of resonances in non-relativistic QED and related models

We study the mathematical theory of quantum resonances in the standard model of non-relativistic QED and in Nelson's model. In particular, we estimate the survival probability of metastable states corresponding to quantum resonances and relate the resonances to poles of an analytic continuation of matrix elements of the resolvent of the quantum Hamiltonian.Comment: 28 page

Pluto: A Monte Carlo Simulation Tool for Hadronic Physics

Pluto is a Monte-Carlo event generator designed for hadronic interactions from Pion production threshold to intermediate energies of a few GeV per nucleon, as well as for studies of heavy ion reactions. This report gives an overview of the design of the package, the included models and the user interface.Comment: XI International Workshop on Advanced Computing and Analysis Techniques in Physics Research, April 23-27 2007, Amsterdam, the Netherland

Nonlocal Effects on the Magnetic Penetration Depth in d-wave Superconductors

We show that, under certain conditions, the low temperature behavior of the magnetic penetration depth $\lambda(T)$ of a pure d-wave superconductor is determined by nonlocal electrodynamics and, contrary to the general belief, the deviation $\Delta\lambda(T) = \lambda(T)-\lambda(0)$ is proportional to T^2 and not T. We predict that the $\Delta\lambda(T)\propto T^2$ dependence, due to nonlocality, should be observable experimentally in nominally clean high-T_c superconductors below a crossover temperature $T^* = (\xi_o/\lambda_o)\Delta_o \sim 1 K$. Possible complications due to impurities, surface quality and crystal axes orientation are discussed.Comment: REVTeX3.0; 4 pages, 1 EPS figure (included); Submitted to Phys. Rev. Let

Hidden potential in predicting wintertime temperature anomalies in the Northern Hemisphere

Variability of the North Atlantic Oscillation (NAO) drives wintertime temperature anomalies in the Northern Hemisphere. Dynamical seasonal prediction systems can skilfully predict the winter NAO. However, prediction of the NAO-dependent air temperature anomalies remains elusive, partially due to the low variability of predicted NAO. Here, we demonstrate a hidden potential of a multi-model ensemble of operational seasonal prediction systems for predicting wintertime temperature by increasing the variability of predicted NAO. We identify and subsample those ensemble members which are close to NAO index statistically estimated from initial autumn conditions. In our novel multi-model approach, the correlation prediction skill for wintertime Central Europe temperature is improved from 0.25 to 0.66, accompanied by an increased winter NAO prediction skill of 0.9. Thereby, temperature anomalies can be skilfully predicted for the upcoming winter over a large part of the Northern Hemisphere through increased variability and skill of predicted NAO

Aqueous Black Colloids of Reticular Nanostructured Gold

Since ancient times, noble gold has continuously contributed to several aspects of life from medicine to electronics. It perpetually reveals its new features. We report the finding of a unique form of gold, reticular nanostructured gold (RNG), as an aqueous black colloid, for which we present a one-step synthesis. The reticules consist of gold crystals that interconnect to form compact strands. RNG exhibits high conductivity and low reflection and these features, coupled with the high specific surface area of the material, could prove valuable for applications in electronics and catalysis. Due to high absorption throughout the visible and infrared domain, RNG has the potential to be applied in the construction of sensitive solar cells or as a substrate for Raman spectroscopy

“Bull's-eye” sign on gadolinium-enhanced magnetic resonance venography determines thrombus presence and age: A preliminary study

AbstractPurpose: Venous thrombosis is associated with a significant inflammatory response, which can be visualized by gadolinium magnetic resonance venography (MRV). Gadolinium extravasates into tissue during inflammation, producing perithrombus enhancement on magnetic resonance scanning. This study determines (1) whether gadolinium enhancement occurs during deep venous thrombosis (DVT); and (2) whether this enhancement changes with time and can therefore establish the age of thrombus.Methods: Patients with a diagnosis of iliofemoral DVT by duplex ultrasound who were referred for MRV to document central thrombus extent were studied. T1 weighted images were obtained before and after gadolinium injection (0.1 mmol/kg); repeat scans were obtained up to 3 months thereafter. At the level of maximum thrombus, measurements of signal intensity were made at the periphery (rim), and the center of the thrombosed vein, as well as the contralateral normal vein, on images after gadolinium enhancement. Rim-center vein signal intensity ratios were then calculated and followed.Results: A total of 39 scans were obtained in 14 patients (eight men, six women). The thrombosed veins were enlarged, with a peripheral rim of enhancement (“bull's-eye” sign). The rim-center ratio for thrombosed veins (2.16 ± 0.18) was different from that of normal veins (0.66 ± 0.10; n = 39; p < 0.001). For all acute studies (≤14 days) the rim-center ratio was 2.38 ± 0.17 (n = 31), whereas for all chronic studies (>14 days) the rim-center ratio was 1.29 ± 0.44 (n = 8; p = 0.001). Among patients who underwent both early and late studies, the rim-center ratio dropped significantly, from 2.33 ± 0.20 acutely to 1.29 ± 0.44 in chronic studies (n = 8; p = 0.03). One patient with active malignancy had a paradoxic increase in rim-center ratio over time and a clinical recurrence of symptoms, suggesting active thrombosis.Conclusions: We conclude that (1) a pattern of peripheral gadolinium enhancement (bull's-eye sign) is seen around acutely thrombosed veins on gadolinium-enhanced MRV, facilitating DVT diagnosis; and (2) the ratio of signal intensity at the rim versus the center of the thrombosed vein may be a good discriminator of acute compared with chronic DVT, which may help direct therapy. (J Vasc Surg 1997;26:809-16.

Dynamic testbed laboratory and micro-optics

Objectives of this research are as follows: to understand the three classes of superresolution and their behavior in optical data storage systems; to investigate new and improved components and techniques in the optical system for data detection and servo control; to apply micro-optic components to the optical system to reduce size and weight; to investigate techniques, such as near-field optical probes, for recording data densities beyond that possible with superresolution; and to understand and find solutions for problems associated with dynamic testing, especially those that arise when evaluating blue-sensitive media

Roots of the derivative of the Riemann zeta function and of characteristic polynomials

We investigate the horizontal distribution of zeros of the derivative of the Riemann zeta function and compare this to the radial distribution of zeros of the derivative of the characteristic polynomial of a random unitary matrix. Both cases show a surprising bimodal distribution which has yet to be explained. We show by example that the bimodality is a general phenomenon. For the unitary matrix case we prove a conjecture of Mezzadri concerning the leading order behavior, and we show that the same follows from the random matrix conjectures for the zeros of the zeta function.Comment: 24 pages, 6 figure

Indication of a deeply bound compact K-pp state formed in the pp -> p Lambda K+ reaction at 2.85 GeV

We have analyzed data of the DISTO experiment on the exclusive pp -> p Lambda K+ reaction at 2.85 GeV to search for a strongly bound compact K-pp (= X) state to be formed in the pp -> K+ + X reaction. The observed spectra of the K+ missing-mass and the p Lambda invariant-mass with high transverse momenta of p and K+ revealed a broad distinct peak with a mass M_X = 2265 +- 2 (stat) +- 5 (syst) MeV/c2 and a width Gamma_X = 118 +- 8 (stat) +- 10 (syst) MeV.Comment: 4 pages, 4 figure