PubMed Health⌕ Search

Biomedical subjects

A Navin

Publications and source records attributed to A Navin.

13 recordsLinked to original sources
PubMed2002

Angular momentum and cross sections for fusion with weakly bound nuclei: breakup, a coherent effect.

Results for the cross section and average angular momentum for complete fusion at energies around the Coulomb barrier are presented for 7Li with 165Ho. Comparison of the cross sections with a one-dimensional barrier penetration model, using a potential consistent with the measured elastic scattering, showed a reduction above the barrier and an enhancement below it. An increase in the measured average angular momentum, , above the barrier and its consistency with that obtained from the fusion excitation function for weakly bound nuclei, is reported. These results together with a reanalysis of existing data conclusively demonstrate that the effect of breakup on fusion is coherent, like coupling to any nonelastic channel.

Journal Article↗
PubMed2000

Direct evidence for the breakdown of the N = 8 shell closure in 12Be

Partial cross sections and corresponding momentum distributions have been studied in the one-neutron knockout reaction ( 12Be,11Be+gamma) on a 9Be target at 78 MeV/nucleon. The resulting spectroscopic factors for the only two bound states of 11Be are 0.42+/-0.06 ( 1/2(+)) and 0.37+/-0.06 ( 1/2(-)), where the errors are experimental only. This result shows that N = 8 is not a good closed shell in the neutron-rich 12Be and that the last neutron pair is two-thirds in the ( 1s(2)+0d(2)) intruder configuration.

Journal Article↗
PubMed2000

One-neutron knockout from individual single-particle states of 11Be

The structure of the halo nucleus 11Be has been studied using the reaction 9Be(11Be,10Be+gamma)X at 60 MeV/nucleon. The ground state structure of 11Be is determined by comparing the experimental cross sections to a calculation combining spectroscopic factors from the shell model with l-dependent single-particle cross sections obtained in an eikonal model. This experiment shows the dominant 1s single-particle character of the 11Be ground state and indicates a small contribution of 0d admixture in the wave function. After correction for the approximately 22% intensity to excited levels, a clean and precise distribution of parallel momentum for knockout from the 1s halo wave function is obtained for the first time.

Journal Article↗
PubMed1996

Mouse Y-specific repeats isolated by whole chromosome representational difference analysis.

Representational difference analysis (RDA) was used to generate Y-specific probes by enriching for and cloning the differences between the male (XY) and the female (XX) C57BL/6J mouse genomes. Characterization of 35 clones revealed 12 families related by sequence similarity. One clone from each family was chosen for detailed analysis by Southern blot hybridization, polymerase chain reaction (PCR) on normal and aberrant genomes (Sxr), and fluorescence in situ hybridization. From one difference product we have characterized 12 Y-specific probes for hybridization, created seven male-specific PCR assays, mapped all repeat families, and identified one repeat with a distinct XY homology. We report the first cloning of a Y-specific long interspersed repeat element (LINE) fragment. In total, RDA has identified six novel Y Chromosome repeat families and allowed us to extend the characterization of six known Y repeats. We conclude that this novel use of RDA for whole chromosome subtraction successfully enriches chromosome-specific sequences and is suitable for the rapid generation of new Y Chromosome-specific probes.

Animals↗
PubMed1994

PCR-amplification of simple sequence repeat variants from pooled DNA samples for rapidly mapping new mutations of the mouse.

A novel strategy for rapidly mapping new mutations of the mouse is presented and tested. The inbred Mus musculus castaneus strain CAST/Ei is used as a tester stock. Separate DNA pools are made from mutant and wildtype intercross (F2) progeny and analyzed using simple sequence repeat (SSR) variants detected using PCR amplification. Linkage is indicated if the mutant DNA pool is enriched for the mutant-strain SSR allelic fragment in comparison with the wildtype pool and controls. The expected contributions of the tester stock to mutant and wildtype pools as a function of recombination frequency are derived for both intercross and backcross progeny segregating for a recessive mutant gene. The sensitivity and reliability of this method is investigated using arbitrary DNA mixtures and also mutant and wildtype pools from a (CAST/Ei x MEV) intercross segregating for the dilute coat color mutation. It is concluded that linkages as great as 20 cM can be reliably detected by this method provided that sufficient progeny contribute to the pools. A set of 39 SSR variants, resolvable by agarose gel electrophoresis and suitable for pooled-SSR analysis, is identified. These are expected to screen 94% of the autosomal genome in crosses between CAST/Ei and common laboratory strains.

Animals↗