1,022 research outputs found
Magnetic and electrical properties of dhcp NpPd3 and U(1-x)Np(x)Pd3
We have made an extensive study of the magnetic and electrical properties of
double-hexagonal closepacked NpPd3 and a range of U(1-x)Np(x)Pd3 compounds with
x=0.01, 0.02, 0.05, and 0.50 using magnetization, magnetic susceptibility,
electrical resistivity, and heat capacity measurements on polycrystalline
samples, performed in the temperature range 2-300 K and in magnetic fields up
to 9 T. Two transitions are observed in NpPd3 at T=10 and 30 K. Dilute Np
samples (x<0.05) exhibit quadrupolar transitions, with the transition
temperatures reduced from those of pure UPd3.Comment: 10 pages, 18 figure
Evidence of increased axillary blood flow velocity without increased handgrip strength and endurance in persons with a fibromuscular axillary arch
Background: The purpose of this in vivo study was to compare axillary artery blood flow velocity, and maximal handgrip strength and endurance performance in young subjects with and without an axillary arch (AA).
Materials and methods: One hundred and fifty-six young adults were screened for the presence of an AA on their dominant arm side. After physical examination subjects were checked using diagnostic echography for the presence of an AA. Sixteen subjects with an AA and 15 without an AA had their axillary artery peak systolic velocity quantified in 3 different arm positions using Doppler ultrasound. Maximal handgrip strength and endurance performance was quantified in the same positions using a functional rehabilitation system.
Results: Mean peak systolic velocity was significantly higher in the AA group compared to controls in abduction/external rotation of the arm during muscle relaxation (p = 0.003) and contraction (p = 0.01). No significant differences between groups were found for maximal handgrip strength and endurance performance.
Conclusions: This study provides evidence for a transient axillary artery compression by the AA in a throwing position. This is not reinforced by additional contraction of the shoulder muscles along with the AA. Axillary artery compression does not influence maximal handgrip strength and endurance performance in symptom-free young adults
Influence of myocardial oxygen demand on the coronary vascular response to arterial blood gas changes in humans
It remains unclear if the human coronary vasculature is inherently sensitive to changes in arterial PO2 and PCO2 or if coronary vascular responses are the result of concomitant increases in myocardial O2 consumption/demand (MVO2). We hypothesized that the coronary vascular response to PO2 and PCO2 would be attenuated in healthy men when MVO2 was attenuated with β1-adrenergic receptor blockade. Healthy men (n=11; age: 25 {plus minus} 1 years) received intravenous esmolol (β1-adrenergic receptor antagonist) or volume-matched saline in a double-blind, randomized, crossover study, and were exposed to poikilocapnic hypoxia, isocapnic hypoxia, and hypercapnic hypoxia. Measurements made at baseline and following 5-min of steady state at each gas manipulation included left anterior descending coronary blood velocity (LADV; Doppler echocardiography), heart rate and arterial blood pressure. LADV values at the end of each hypoxic condition were compared between esmolol and placebo. Rate pressure product (RPP) and left-ventricular mechanical energy (MELV) were calculated as indices of MVO2. All gas manipulations augmented RPP, MELV, and LADV but only RPP and MELV were attenuated (4-18%) following β1-adrenergic receptor blockade (P<0.05). Despite attenuated RPP and MELV responses, β1-adrenergic receptor blockade did not attenuate the mean LADV vasodilatory response when compared to placebo during poikilocapnic hypoxia (29.4{plus minus}2.2 vs. 27.3{plus minus}1.6 cm/s) and isocapnic hypoxia (29.5{plus minus}1.5 vs. 30.3{plus minus}2.2 cm/s). Hypercapnic hypoxia elicited a feed-forward coronary dilation that was blocked by β1-adrenergic receptor blockade. These results indicate a direct influence of arterial PO2 on coronary vascular regulation that is independent of MVO2
Magnetism, Spin-Orbit Coupling, and Superconducting Pairing in UGe
A consistent picture on the mean-field level of the magnetic properties and
electronic structure of the superconducting itinerant ferromagnet UGe is
shown to require inclusion of correlation effects beyond the local density
approximation (LDA). The "LDA+U" approach reproduces both the magnitude of the
observed moment, composed of strongly opposing spin and orbital parts, and the
magnetocrystalline anisotropy. The largest Fermi surface sheet is comprised
primarily of spin majority states with orbital projection =0,
suggesting a much simpler picture of the pairing than is possible for general
strong spin-orbit coupled materials. This occurrence, and the
quasi-two-dimensional geometry of the Fermi surface, support the likelihood of
magnetically mediated p-wave triplet pairing.Comment: accepted for publication in Phys. Rev. Lett; URL for better quality
image of Fig.3 (2MB) at http://yammer.ucdavis.edu/public/UGe2/fig3.ep
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