16 research outputs found
Nodes of the Gap Function and Anomalies in Thermodynamic Properties of Superfluid He
Departures of thermodynamic properties of three-dimensional superfluid He
from the predictions of BCS theory are analyzed. Attention is focused on
deviations of the ratios and
from their BCS values, where is the pairing gap at zero
temperature, is the critical temperature, and and are the
superfluid and normal specific heats. We attribute these deviations to the
momentum dependence of the gap function , which becomes well
pronounced when this function has a pair of nodes lying on either side of the
Fermi surface. We demonstrate that such a situation arises if the P-wave
pairing interaction , evaluated at the Fermi surface, has a sign
opposite to that anticipated in BCS theory. Taking account of the momentum
structure of the gap function, we derive a closed relation between the two
ratios that contains no adjustable parameters and agrees with the experimental
data. Some important features of the effective pairing interaction are inferred
from the analysis.Comment: 17 pages, 4 figure
Bovine somatic cell nuclear transfer using recipient oocytes recovered by ovum pick up. Effect of maternal lineage of oocyte donors.
The efficiency of bovine nuclear transfer using recipient oocytes recovered by ultrasound-guided follicle aspiration (ovum pick-up [OPU]) was investigated. Oocyte donors were selected from 2 distinct maternal lineages (A and B) differing in 11 nucleotide positions of the mitochondrial DNA control region. A total of 1342 cumulus-oocyte complexes (COCs) were recovered. The numbers of total COCs and class I/II COCs recovered from donors of lineage A were higher (P < 0.001) than those obtained from lineage B. Follicle aspiration once per week yielded a higher (P < 0.001) total number of COCs per session than aspiration twice per week, whereas the reproduction status of donors (heifer vs. cow) had no effect on OPU results. Of the 1342 oocytes recovered, 733 (55%) were successfully matured in vitro and used for nuclear transfer. Fusion was achieved in 550 (75%) karyoplast-cytoplast complexes (KCCs), resulting in 277 (50%) cleaved embryos on Day 3. On Day 7 of culture, 84 transferable embryos (15% based on fused KCCs) were obtained. After 38 transfers (10 single, 22 double, and 6 triple transfers), 9 recipients (8 double and 1 triple transfer) were diagnosed as pregnant on Day 28, corresponding to a pregnancy rate of 24%. The proportion of transferable embryos on Day 7 was significantly (P < 0.05) influenced by maternal lineage of oocyte donors and by the frequency of follicle aspiration. Our study demonstrates the feasibility of generating nuclear transfer embryos with defined cytoplasmic background. These will be valuable tools to experimentally dissect the effects of nuclear and cytoplasmic components on embryonic, fetal, and postnatal development.Katja Brüggerhoff, Valeri Zakhartchenko, Hendrik Wenigerkind, Horst-Dieter Reichenbach, Katja Prelle, Wolfgang Schernthaner, Ramiro Alberio, Helmut Küchenhoff, Miodrag Stojkovic, Gottfried Brem, Stefan Hiendleder, and Eckhard Wol