Electron Self Energy for Higher Excited S Levels

A nonperturbative numerical evaluation of the one-photon electron self energy for the 3S and 4S states with charge numbers Z=1 to 5 is described. The numerical results are in agreement with known terms in the expansion of the self energy in powers of Zalpha.Comment: 3 pages, RevTeX, to appear in Phys. Rev.

Two-Loop Bethe Logarithms

We calculate the two-loop Bethe logarithm correction to atomic energy levels in hydrogen-like systems. The two-loop Bethe logarithm is a low-energy quantum electrodynamic (QED) effect involving multiple summations over virtual excited atomic states. Although much smaller in absolute magnitude than the well-known one-loop Bethe logarithm, the two-loop analog is quite significant when compared to the current experimental accuracy of the 1S-2S transition: it contributes -8.19 and -0.84 kHz for the 1S and the 2S state, respectively. The two-loop Bethe logarithm has been the largest unknown correction to the hydrogen Lamb shift to date. Together with the ongoing measurement of the proton charge radius at the Paul Scherrer Institute its calculation will bring theoretical and experimental accuracy for the Lamb shift in atomic hydrogen to the level of 10^(-7).Comment: 4 pages, RevTe

Electromagnetic radiation screening of microcircuits for long life applications

The utility of X-rays as a stimulus for screening high reliability semiconductor microcircuits was studied. The theory of the interaction of X-rays with semiconductor materials and devices was considered. Experimental measurements of photovoltages, photocurrents, and effects on specified parameters were made on discrete devices and on microcircuits. The test specimens included discrete devices with certain types of identified flaws and symptoms of flaws, and microcircuits exhibiting deviant electrical behavior. With a necessarily limited sample of test specimens, no useful correlation could be found between the X-ray-induced electrical response and the known or suspected presence of flaws

NASA rotor system research aircraft flight-test data report: Helicopter and compound configuration

The flight test activities of the Rotor System Research Aircraft (RSRA), NASA 740, from June 30, 1981 to August 5, 1982 are reported. Tests were conducted in both the helicopter and compound configurations. Compound tests reconfirmed the Sikorsky flight envelope except that main rotor blade bending loads reached endurance at a speed about 10 knots lower than previously. Wing incidence changes were made from 0 to 10 deg

Single-cell physiological structure and growth rates of heterotrophic bacteria in a temperate estuary (Waquoit Bay, Massachusetts)

Author Posting. © American Society of Limnology and Oceanography, 2011. This article is posted here by permission of American Society of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 56 (2011): 37-48, doi:10.4319/lo.2011.56.1.0037.Flow cytometric determinations of membrane integrity, nucleic acid content, and respiratory activity were combined with dilution cultures in Waquoit Bay Estuary (Massachusetts) to estimate specific growth rates of total, live, high (HNA), and low (LNA) nucleic acid content and actively respiring (CTC+) cells. Bacterial abundance ranged from 106 to 107 cells mL-1, with live cells generally contributing > 85% to total numbers, 42-82% HNA cells, and 3-36% CTC+ cells. Specific growth rates (µ) from all physiological groups were positively correlated, but they showed different temperature dependences, with activation energies ranging from 0.28 (live) to 0.97 eV (LNA). The µ values of live cells (0.14-2.40 d-1) were similar to those of total bacteria (0.06-1.53 d-1). LNA bacteria were not dormant but showed positive growth in most experiments, although HNA cells greatly outgrew LNA cells (µ ranges of 0.28-2.26 d-1 vs. 0-0.69 d-1), and CTC+ cells showed the highest values (0.12-2.65 d-1). Positive correlations of HNA bacteria µ with total and phytoplankton-derived dissolved organic carbon support the previously hypothesized strong bottom-up control of HNA cells. Bacterial production estimated from leucine incorporation and empirical conversion factors agreed well with estimates based on growth rates. HNA cells were always responsible for the largest share of bacterial production in the estuary. The contribution of CTC+ cells significantly increased with temperature in the 7-27°C range, reaching values of 40% at temperatures higher than 20°C.This study was supported by the Spanish Ministry of Science and Innovation (MICINN) sabbatical stay program (to X.A.G.M.), National Science Foundation Office of Polar Programs grant 0823101 to H.W.D., and by the Marine Biological Laboratory

Spurious phase in a model for traffic on a bridge

We present high-precision Monte Carlo data for the phase diagram of a two-species driven diffusive system, reminiscent of traffic across a narrow bridge. Earlier studies reported two phases with broken symmetry; the existence of one of these has been the subject of some debate. We show that the disputed phase disappears for sufficiently large systems and/or sufficiently low bulk mobility.Comment: 8 pages, 3 figures, JPA styl

Charge Exchange Spectra of Hydrogenic and He-like Iron

We present H-like Fe XXVI and He-like Fe XXV charge-exchange spectra resulting from collisions of highly charged iron with N2 gas at an energy of 10 eV/amu in an electron beam ion trap. Although individual high-n emission lines are not resolved in our measurements, we observe that the most likely level for Fe25+ --> Fe24+ electron capture is n~9, in line with expectations, while the most likely value for Fe26+ --> Fe25+ charge exchange is significantly higher. In the Fe XXV spectrum, the K-alpha emission feature dominates, whether produced via charge exchange or collisional excitation. The K-alpha centroid is lower in energy for the former case than the latter (6666 versus 6685 eV, respectively), as expected because of the strong enhancement of emission from the forbidden and intercombination lines, relative to the resonance line, in charge-exchange spectra. In contrast, the Fe XXVI high-n Lyman lines have a summed intensity greater than that of Ly-alpha, and are substantially stronger than predicted from theoretical calculations of charge exchange with atomic H. We conclude that the angular momentum distribution resulting from electron capture using a multi-electron target gas is significantly different from that obtained with H, resulting in the observed high-n enhancement. A discussion is presented of the relevance of our results to studies of diffuse Fe emission in the Galactic Center and Galactic Ridge, particularly with ASTRO-E2/Suzaku.Comment: 16 pages, 4 figures (3 color), accepted by Ap

An intelligent, free-flying robot

The ground based demonstration of the extensive extravehicular activity (EVA) Retriever, a voice-supervised, intelligent, free flying robot, is designed to evaluate the capability to retrieve objects (astronauts, equipment, and tools) which have accidentally separated from the Space Station. The major objective of the EVA Retriever Project is to design, develop, and evaluate an integrated robotic hardware and on-board software system which autonomously: (1) performs system activation and check-out; (2) searches for and acquires the target; (3) plans and executes a rendezvous while continuously tracking the target; (4) avoids stationary and moving obstacles; (5) reaches for and grapples the target; (6) returns to transfer the object; and (7) returns to base

Precise calculation of transition frequencies of hydrogen and deuterium based on a least-squares analysis

We combine a limited number of accurately measured transition frequencies in hydrogen and deuterium, recent quantum electrodynamics (QED) calculations, and, as an essential additional ingredient, a generalized least-squares analysis, to obtain precise and optimal predictions for hydrogen and deuterium transition frequencies. Some of the predicted transition frequencies have relative uncertainties more than an order of magnitude smaller than that of the g-factor of the electron, which was previously the most accurate prediction of QED.Comment: 4 pages, RevTe