Development of a new model of feeding strategy analysis of fish incorporating resource availability and use data

A feeding strategy model is proposed using stomach content and resource availability data as a modification to Costello (1990) and Amundsen et al. (1996). Incorporation of feeding electivity index (E) instead of the prey-specific abundance signifies the importance of resource availability in prey selection as well as the predator's ability to specialize, generalize or avoid particular prey items at the individual and population level

Niche measures and feeding strategies of Barbodes gonionotus Bleeker and Oreochromis spp. from a ricefield in Bangladesh

Intra-and interspecific virtual niche measures and feeding strategies of Barbodes gonionotus and Oreochromis spp. were studied from a rice field in Bangladesh. Appropriateness and ease of interpretation of different indices were evaluated. Small sizes of both species had a relatively wider dietary breadth and used many of the resource categories available to them than the large size groups, though none were generalist feeder. The dietary overlap of large B. gonionotus on the small was greater than the reverse, but biologically insignificant. While the dietary overlap of large Oreochromis spp. on the small was significantly greater. Interspecific dietary width was relatively broader for B. gonionotus than Oreochromis spp. and overlap of B. gonionotus on Oreochromis spp. was significantly greater than the reverse. Evidence of significant intraspecific dietary overlap between the two sizes of tilapia reflects strong competition and cautions for mixed-size stocking in rice-fish system. Besides, there seem fewer opportunities for habitat segregation between B. gonionotus and Oreochromis spp., due to the significant interspecific dietary overlap of the former on the latter in rice-fish system. Tilapia specialized on periphytic detrital aggregate while silver barb tended to consume aquatic macrophytes and molluscs. Small sizes of B. gonionotus should be preferred for rice-fish integration over the Oreochromis spp. due to their broader niche width and pronounced ontogenetic dietary shifts with the aging of the stock

Direct measurments of (p,γ) cross sections at astrophysical energies using radioactive beams and the Daresbury Recoil Separator

There are a number of astrophysical environments in which the path of nucleosynthesis proceeds through proton-rich nuclei. Radioactive nuclei have traditionally not been available as beams, and thus proton-capture reactions on these nuclei could only be studied indirectly. At the Holifield Radioactive Ion Beam Facility (HRIBF), some of the first direct measurements of (p,γ) cross sections on radioactive beams have been made. The Daresbury Recoil Separator (DRS) has been used to separate the recoils of interest from the unreacted primary beam and identify them in an isobutane-filled ionization counter. Data from 17F(p,γ)18Ne and 7Be(p,γ)8B measurements are presented

Neutron hole states in ¹³¹Sn and spin-orbit splitting in neutron-rich nuclei

In atomic nuclei, the spin-orbit interaction originates from the coupling of the orbital motion of a nucleon with its intrinsic spin. Recent experimental and theoretical works have suggested a weakening of the spin-orbit interaction in neutron-rich nuclei far from stability. To study this phenomenon, we have investigated the spin-orbit energy splittings of single-hole and single-particle valence neutron orbits of 132Sn. The spectroscopic strength of single-hole states in 131Sn was determined from the measured differential cross sections of the tritons from the neutron-removing 132Sn(d, t)131Sn reaction, which was studied in inverse kinematics at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The spectroscopic factors of the lowest 3/2+, 1/2+ and 5/2+ states were found to be consistent with their maximal values of (2j + 1), confirming the robust N = 82 shell closure at 132Sn. We compared the spin-orbit splitting of neutron single-hole states in 131Sn to those of single-particle states in 133Sn determined in a recent measurement of the 132Sn(d, p)133Sn reaction. We found a significant reduction of the energy splitting of the weakly bound 3p orbits compared to the well-bound 2d orbits, and that all the observed energy splittings can be reproduced remarkably well by calculations using a one-body spin-orbit interaction and a Woods–Saxon potential of standard radius and diffuseness. The observed reduction of spin-orbit splitting can be explained by the extended radial wavefunctions of the weakly bound orbits, without invoking a weakening of the spin-orbit strength

The first science result with the JENSA gas-jet target: Confirmation and study of a strong subthreshold F18(p,α)O15 resonance

The astrophysical F18(p,α)O15 rate determines, in large part, the extent to which the observable radioisotope 18F is produced in novae. This rate, however, has been extremely uncertain owing to the unknown properties of a strong subthreshold resonance and its possible interference with higher-lying resonances. The new Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas-jet target has been used for the first time to determine the spin of this important resonance and significantly reduce uncertainties in the F18(p,α)O15 rate