Isovector deformation and its link to the neutron shell closure

DWBA analysis of the inelastic $^{30-40}$S$(p,p')$ and $^{18-22}$O$(p,p')$ scattering data measured in the inverse kinematics has been performed to determine the isoscalar ($\delta_0$) and isovector ($\delta_1$) deformation lengths of the 2$^+_1$ excitations in the Sulfur and Oxygen isotopes using a compact folding approach. A systematic $N$-dependence of $\delta_0$ and $\delta_1$ has been established which shows a link between $\delta_1$ and the neutron-shell closure. Strong isovector deformations were found in several cases, e.g., the 2$^+_1$ state in $^{20}$O where $\delta_1$ is nearly three times larger than $\delta_0$. These results confirm the relation $\delta_1>\delta_0$ anticipated from the core polarization by the valence neutrons in the open-shell (neutron rich) nuclei. The effect of neutron shell closure at N=14 or 16 has been discussed based on the folding model analysis of the inelastic $^{22}$O+$p$ scattering data at 46.6 MeV/u measured recently at GANIL.Comment: Talk given at RNB7 conference (Cortina d'Ampezzo, Italy, July 3-7, 2006); 4 pages, 4 figures, to appear in Eur. Phys. Journal

Management of coastal fisheries in Vietnam

The fisheries sector of Vietnam plays an important role in the social and economic development of the country. The sector contributes about 3% of the GDP and fish contributes about 40% of animal protein consumption in the country. In 1999, total fisheries production amounted to 1.8 million t. Of this, 1.2 million t was derived from marine capture fisheries and 0.6 million t from aquaculture. Fish exports were valued at US$971.12 million in the same year. VietnamÆs marine fisheries and coastal aquaculture have further potential for development. However, overfishing in coastal areas, degradation of the marine environment and conflicts between small-scale and large scale fishers must be resolved to realize the sectorÆs potential. This report presents the status of coastal fisheries resources, reviews government fisheries policies and suggested management measures. Based on the recommendations from a multisectoral consultative workshop conducted among the key experts on fisheries and resource management in Vietnam, the following fisheries management objectives were suggested for sustainable development of coastal fisheries in Vietnam: (1) optimization of productivity and efficiency of the fisheries exploitation regime; (2) ensuring that the benefits of production are distributed equitably; (3) ensuring that the productivity generated results in minimum damage to the resource base and the supporting natural environment; and (4) upgrading and strengthening the related institutions. Indicative action programs for improved management are also presented.Fishery resources, Catch/effort, Population characteristics, Coastal fisheries, Marine fisheries, Ecosystems, Economic benefits, Fishery industry, Capture fishery economics, Fish consumption, Fishery policy, Legislation, Fishery management, Demersal fisheries, Pelagic fisheries, Cephalopod fisheries, Socioeconomic aspects, Surveys, Marketing, Fishery organizations, Fishing gear, Cephalopod fisheries, Trade, ISEW, Vietnam,

Probing the isoscalar excitations of 12C with inelastic alpha scattering

The robust (spin and isospin zero) $\alpha$-particle remains one of the best projectiles to probe the nuclear isoscalar excitations. In the present work, a microscopic folding model analysis of the \ac inelastic scattering to the 2$^+$ (4.44 MeV), 0$^+$ (7.65 MeV), 3$^-$ (9.64 MeV), 0$^+$ (10.3 MeV) and 1$^-$ (10.84 MeV) states in $^{12}$C has been performed using the 3-$\alpha$ resonating group method wave functions. The isoscalar transition strengths of these states were carefully studied based on the coupled-channel analysis using the microscopic folded form factors. A correlation between the weak binding and/or short lifetime of the excited state and absorption in the exit channel of inelastic scattering has been established.Comment: Talk given at SOTANCP Workshop, Strasbourg, May 2008; to appear in International Journal of Modern Physics

Probing the isovector transition strength of the low-lying nuclear excitations induced by inverse kinematics proton scattering

A compact approach based on the folding model is suggested for the determination of the isoscalar and isovector transition strengths of the low-lying ($\Delta S=\Delta T=0$) excitations induced by inelastic proton scattering measured with exotic beams. Our analysis of the recently measured inelastic $^{18,20}$O+p scattering data at $E_{\rm lab}=30$ and 43 MeV/nucleon has given for the first time an accurate estimate of the isoscalar $\beta_0$ and isovector $\beta_1$ deformation parameters (which cannot be determined from the (p,p') data alone by standard methods) for 2$^+_1$ and $3^-_1$ excited states in $^{18,20}$O. Quite strong isovector mixing was found in the 2$^+_1$ inelastic $^{20}$O+p scattering channel, where the strength of the isovector form factor $F_1$ (prototype of the Lane potential) corresponds to a $\beta_1$ value almost 3 times larger than $\beta_0$ and a ratio of nuclear transition matrix elements $M_n/M_p\simeq 4.2$.Comment: 5 pages, 3 figure

Space debris measurement program at Phillips Laboratory

Ground-based optical sensing was identified as a technique for measuring space debris complementary to radar in the critical debris size range of 1 to 10 cm. The Phillips Laboratory is building a staring optical sensor for space debris measurement and considering search and track optical measurement at additional sites. The staring sensor is implemented in collaboration with Wright Laboratory using the 2.5 m telescope at Wright Patterson AFB, Dayton, Ohio. The search and track sensor is designed to detect and track orbital debris in tasked orbits. A progress report and a discussion of sensor performance and search and track strategies will be given

Electrical Characterization of Deuterium-Doped Gallium Antimonide Grown on Silicon Substrates

In the world today, there exists the need for advances in high speed, energy efficient electronic applications. In the fields of lasers, transistors, and thermophotovoltaic systems, one potential improvement that is currently being explored is the use of gallium antimonide (GaSb), a III-V semiconducting material that has interesting electrical properties. GaSb is a material to be considered because it has a direct band gap of 0.726eV, as well as a relatively high electron mobility (≤ 3000 cm2 V-1 s-1), which makes its use possible in high speed electronic applications [1]. In this research, GaSb will be grown as a thin-film on Si substrates because the cost of pure GaSb substrates is very high relative to that of Si [2]. Although GaSb has a high electron mobility, there exists a native defect in its lattice, causing the material to be intrinsically p-type. Prior research has suggested that doping GaSb with deuterium, an isotope of hydrogen, would correct this defect [3,4]. In a 2006 study performed by Tim Fennessey at the University of Vermont, the passivation of this defect was investigated using van der Pauw Hall measurements. In Fennessey’s research, it was believed that with the addition of hydrogen, samples of GaSb would change from intrinsically p-type to ­n-type. Although several samples displayed a change in intrinsic carrier type, some did not, and the results were inconclusive. In an effort to clarify the results, this supplemental research seeks to resolve the effects of deuterium on thin-film GaSb devices in order to gain a more comprehensive understanding of semiconducting materials as a whole