Resonance Contributions to η\eta Photoproduction on Protons Found Using Dispersion Relations and an Isobar Model

The contributions of the resonances $D_{13}(1520)$, $S_{11}(1535)$, $S_{11}(1650)$, $D_{15}(1675)$, $F_{15}(1680)$, $D_{13}(1700)$, $P_{11}(1710)$, $P_{13}(1720)$ to $\gamma p\to \eta p$ are found from the data on cross sections, beam and target asymmetries using two approaches: fixed-t dispersion relations and an isobar model. Utilization of the two approaches and comparison of the results obtained with different parametrizations of the resonance contributions allowed us to make conclusions about the model-dependence of these contributions. We conclude that the results for the contributions of the resonances $D_{13}(1520)$, $S_{11}(1535)$, $F_{15}(1680)$ to corresponding multipole amplitudes are stable. With this the results for $D_{13}(1520)$ and $F_{15}(1680)$, combined with their PDG photoexcitation helicity amplitudes, allowed us to find the branching ratios $Br (D_{13}(1520)\to \eta N)=0.05\pm 0.02$, $Br (F_{15}(1680)\to \eta N)=0.16\pm0.04$ which have significantly better accuracy than the PDG data. The total Breit-Wigner width of the $S_{11}(1535)$ is model-dependent, we have obtained $\Gamma (S_{11}(1520))=142 MeV$ and $195 MeV$ using dispersion relations and the isobar model, respectively. The results for the $S_{11}(1650)$, $D_{15}(1675)$, $P_{11}(1710)$, $P_{13}(1720)$ are model dependent, only the signs and orders of magnitude of their contributions to multipole amplitudes are determined. The results for the $D_{13}(1700)$ are strongly model-dependent.Comment: 26 pages, 6 figure

Design and characteristics of the twice-over rotation grazing system

R-1006; This circular focuses on designing twice-over rotation grazin

The 8^8B Neutrino Spectrum

Knowledge of the energy spectrum of $^8$B neutrinos is an important ingredient for interpreting experiments that detect energetic neutrinos from the Sun. The neutrino spectrum deviates from the allowed approximation because of the broad alpha-unstable $^8$Be final state and recoil order corrections to the beta decay. We have measured the total energy of the alpha particles emitted following the beta decay of $^8$B. The measured spectrum is inconsistent with some previous measurements, in particular with a recent experiment of comparable precision. The beta decay strength function for the transition from $^8$B to the accessible excitation energies in $^8$Be is fit to the alpha energy spectrum using the R-matrix approach. Both the positron and neutrino energy spectra, corrected for recoil order effects, are constructed from the strength function. The positron spectrum is in good agreement with a previous direct measurement. The neutrino spectrum disagrees with previous experiments, particularly for neutrino energies above 12 MeV.Comment: 15 pages, 13 figures, 4 tables, submitted to Phys. Rev. C, typos correcte

Addressing Undernutrition in Nigeria: What Next?

This briefing sets out the Priorities for Action that emerged from an online discussion amongst experts from central and sub-national government, multilateral and bilateral development agencies, national and international non-governmental organisations, civil society organisations, and research institutions operating in different sectors and levels in Nigeria, and who share the same goal of ending undernutrition in Nigeria. Those advocating within and outside government for commitment and action to address undernutrition in Nigeria are encouraged to adopt and use these Priorities for Action to inform and guide their advocacy efforts

Nodeless superconductivity in the cage-type superconductor Sc5Ru6Sn18 with preserved time-reversal symmetry

We report the single-crystal synthesis and detailed investigations of the cage-type superconductor Sc5Ru6Sn18, using powder x-ray diffraction (XRD), magnetization, specific-heat and muon-spin relaxation (muSR) measurements. Sc5Ru6Sn18 crystallizes in a tetragonal structure (space group I41/acd) with the lattice parameters a = 1.387(3) nm and c = 2.641(5) nm. Both DC and AC magnetization measurements prove the type-II superconductivity in Sc5Ru6Sn18 with Tc = 3.5(1) K, a lower critical field H_c1 (0) = 157(9) Oe and an upper critical field, H_c2 (0) = 26(1) kOe. The zero-field electronic specific-heat data are well fitted using a single-gap BCS model, with superconducting gap = 0.64(1) meV. The Sommerfeld constant varies linearly with the applied magnetic field, indicating s-wave superconductivity in Sc5Ru6Sn18. Specific-heat and transverse-field (TF) muSR measurements reveal that Sc5Ru6Sn18 is a superconductor with strong electron-phonon coupling, with TF-muSR also suggesting the single-gap s-wave character of the superconductivity. Furthermore, zero-field muSR measurements do not detect spontaneous magnetic fields below Tc, hence implying that time-reversal symmetry is preserved in Sc5Ru6Sn18.Comment: 23 pages, 11 figure

Tracked vehicle effects on vegetation and soil characteristics

A 3-year experiment to evaluate tracked vehicle effects on vegetation and soil characteristics was established on the Gilbert C. Grafton South State Military Reservation (CGS) in North Dakota. Study objectives were to evaluate the effects of 3 tracked vehicle use intensity treatments on plant species cover and frequency, and soil compaction. The 3 treatments evaluated include heavy use (74 passes), moderate use (37 passes) and no use. The moderate use treatment represents a typical use of 1 battalion unit at CGS with the heavy use treatment classified as 2 battalion units. This land area comprised a 50 by 150 meter block subdivided into three, 50 by 50 meter blocks. Each 50 by 50 meter block was subdivided into three, 16.7 by 50 meter blocks with each block treated with 1 of the 3 treatments. Soil bulk density increased (P \u3c 0.05) on the moderate and heavy use treatments in the 0 to 15, 30 to 45, and 45 to 60 cm soil depths. Kentucky bluegrass (Poa pratensis L.) cover (P \u3c 0.05) decreased in 1996 on both the moderate and heavy use treatments but was not (P \u3e 0.05) different among all treatments in 1997. The tracked vehicle use on the heavy and moderate treatments did not change species composition or litter amounts after 2 years; however, bulk density and bare ground increased on both treatments in 1996 and 1997. Se establecio un experimento de 3 aiios en la Reservacion Militar Estatal Gilbert C. Grafon (CGS) de North Dakota para evaluar los efectos del paso de vehaiculos militares en la vegetacion y suelo. Los objetivos del estudio fueron evaluar los efectos de 3 intensidades de paso de vehaiculos militares en la cobertura y frecuencia de especies vegetales y la compactacion del suelo. Los 3 tratamientos evaluados fueron: uso alto (74 pasos), uso moderado (37 pasos) y sin uso. El uso moderado representa el uso taipico de una unidad de batallon en el CGS y el tratamiento de uso alto representa el paso de dos unidades de batallon. El aea experimental fue un bloque de 50 x 150 m dividido en tres bloques, cada bloque de 50 x 50 m se subdividido en 3 bloques de 16.7 x 50 m y en cada uno de estos bloque se aplico uno de los tratamientos. La densidad aparente del suelo a las profundidades de 0-15, 30-45 y 45-60 cm aumento (P \u3c 0.05) en los tratamientos de uso moderado y alto. En 1996, la cobertura del zacate Kentucky bluegrass (Poa pratensis L.) disminuyo (P \u3c 0 .05) en los tratamientos de uso moderado y alto, pero en 1997 la cobertura de esta especie no difirio entre tratamientos (P \u3e 0.05). Despues de 2 anios, el uso moderado y alto de vehaiculos militares no cambio la composicion de especies ni la cantidad de mantillo; sin embargo, la densidad aparente y el suelo desnudo aumento en ambos tratamientos en 1996 y 1997

Does gravity cause load-bearing bridges in colloidal and granular systems?

We study structures which can bear loads, "bridges", in particulate packings. To investigate the relationship between bridges and gravity, we experimentally determine bridge statistics in colloidal packings. We vary the effective magnitude and direction of gravity, volume fraction, and interactions, and find that the bridge size distributions depend only on the mean number of neighbors. We identify a universal distribution, in agreement with simulation results for granulars, suggesting that applied loads merely exploit preexisting bridges, which are inherent in dense packings

Optimizations of sub-100 nm Si/SiGe MODFETs for high linearity RF applications

Based on careful calibration in respect of 70 nm n-type strained Si channel S/SiGe modulation doped FETs (MODFETs) fabricated by Daimler Chrysler, numerical simulations have been used to study the impact of the device geometry and various doping strategies on device performance and linearity. The device geometry is sensitive to both RF performance and device linearity. Doped channel devices are found to be promising for high linearity applications. Trade-off design strategies are required for reconciling the demands of high device performance and high linearity simultaneously. The simulations also suggest that gate length scaling helps to achieve higher RF performance, but decreases the linearity

Coalescence of Two Spinning Black Holes: An Effective One-Body Approach

We generalize to the case of spinning black holes a recently introduced ``effective one-body'' approach to the general relativistic dynamics of binary systems. The combination of the effective one-body approach, and of a Pad\'e definition of some crucial effective radial functions, is shown to define a dynamics with much improved post-Newtonian convergence properties, even for black hole separations of the order of $6 GM / c^2$. We discuss the approximate existence of a two-parameter family of ``spherical orbits'' (with constant radius), and, of a corresponding one-parameter family of ``last stable spherical orbits'' (LSSO). These orbits are of special interest for forthcoming LIGO/VIRGO/GEO gravitational wave observations. It is argued that for most (but not all) of the parameter space of two spinning holes the effective one-body approach gives a reliable analytical tool for describing the dynamics of the last orbits before coalescence. This tool predicts, in a quantitative way, how certain spin orientations increase the binding energy of the LSSO. This leads to a detection bias, in LIGO/VIRGO/GEO observations, favouring spinning black hole systems, and makes it urgent to complete the conservative effective one-body dynamics given here by adding (resummed) radiation reaction effects, and by constructing gravitational waveform templates that include spin effects. Finally, our approach predicts that the spin of the final hole formed by the coalescence of two arbitrarily spinning holes never approaches extremality.Comment: 26 pages, two eps figures, accepted in Phys. Rev. D, minor updating of the text, clarifications added and inclusion of a few new reference

The visual nonverbal memory trace is fragile when actively maintained, but endures passively for tens of seconds

Despite attempts at active maintenance in the focus of attention, the fragile nature of the visual nonverbal memory trace may be revealed when the retention interval between target memoranda and probed recall on a trial is extended. In contrast, a passively maintained or unattended visual memory trace may be revealed as persisting proactive interference extending across quite extended intervals between trials in a recent probes task. The present study, comprising five experiments, used this task to explore the persistence of such a passive visual memory trace over time. Participants viewed some target visual items (for example, abstract colored patterns) followed by a variable retention interval and a probe item. The task was to report whether the probe matched one of the targets or not. A decaying active memory trace was indicated by poorer performance as the memory retention interval was extended on a trial. However, when the probe was a member of the target set from the preceding trial, task performance was poorer than a comparison novel probe, demonstrating proactive interference. Manipulations of the intertrial interval revealed that the temporal persistence of the passive memory trace of an old target was impressive, and proactive interference was largely resilient to a simple ‘cued forgetting’ manipulation. These data support the proposed two-process memory conception (active–passive memory) contrasting fragile active memory traces decaying over a few seconds with robust passive traces extending to tens of seconds