Universal temperature dependence, flux extinction, and the role of 3He impurities in superfluid mass transport through solid 4He.

The mass flux, F, carried by as-grown solid (4)He in the range 25.6-26.3 bar rises with falling temperature, and at a concentration-dependent temperature, T(d), the flux decreases sharply within a few mK. We study F as a function of (3)He impurity concentration, χ. We find that T(d) is an increasing function of increasing χ. At temperatures above T(d) the flux has a universal temperature dependence and the flux terminates in a narrow window near a characteristic temperature T(h) ≈ 625 mK, which is independent of χ.

Beyond spontaneously broken symmetry in Bose-Einstein condensates.

Spontaneous symmetry breaking (SSB) for Bose-Einstein condensates cannot treat phase off-diagonal effects, and thus cannot explain Bell inequality violations. We describe another situation that is beyond a SSB treatment: an experiment where particles from two (possibly macroscopic) condensate sources are used for conjugate measurements of the relative phase and populations. Off-diagonal phase effects are characterized by a "quantum angle" and observed via "population oscillations," signaling quantum interference of macroscopically distinct states.

Nonlocal quantum effects with Bose-Einstein condensates.

We study theoretically the properties of two Bose-Einstein condensates in different spin states, represented by a double Fock state. Individual measurements of the spins of the particles are performed in transverse directions, giving access to the relative phase of the condensates. Initially, this phase is completely undefined, and the first measurements provide random results. But a fixed value of this phase rapidly emerges under the effect of the successive quantum measurements, giving rise to a quasiclassical situation where all spins have parallel transverse orientations. If the number of measurements reaches its maximum (the number of particles), quantum effects show up again, giving rise to violations of Bell type inequalities. The violation of Bell-Clauser-Horne-Shimony-Holt inequalities with an arbitrarily large number of spins may be comparable (or even equal) to that obtained with two spins.

Giant viscosity enhancement in a spin-polarized fermi liquid.

The viscosity is measured for a Fermi liquid, a dilute 3He-4He mixture, under extremely high magnetic field/temperature conditions (Bor=1.5 mK). The spin-splitting energy microB is substantially greater than the Fermi energy kBTF; as a consequence the polarization tends to unity and s-wave quasiparticle scattering is suppressed for T<

New evidence for zero-temperature relaxation in a spin-polarized fermi liquid.

Spin-echo experiments are reported for 3He-4He solutions under extremely high B/T conditions, B=14.75 T and T>or=1.73 mK. The 3He concentration x(3) was adjusted close to the value x(c) approximately 3.8% at which the spin-rotation parameter muM0 vanishes. In this way the transverse and longitudinal spin-diffusion coefficients D( perpendicular ),D( parallel ) were measured while keeping |muM(0)|<1. It is found that the temperature dependence of D( perpendicular ) deviates strongly from 1/T(2), with anisotropy temperature T(a)=4.26(+0.18)(-0.44) mK. This value is close to the theoretical prediction for dilute solutions and suggests that spin current relaxation remains finite as the temperature tends to zero.

Study of soybean seed coat components and their relationship to water absorption.

The occurrence of hard or "stone" seeds in shipments of food grade soybeans can cause serious problems in processing, particularly in the preparation of fermented soy products. Climatic conditions during the growing season and as the seed matures may trigger the production of hard seeds. Total water absorption of soybeans is also a significant parameter in assessing quality for export markets. The seed coats of six varieties of soybeans, covering a wide range of water absorption and stone seed content, were analyzed for ash and cations, protein, lignin, and complex carbohydrates. The water absorption characteristics and macrochemical constituents of the whole seed were also determined. The results indicated that there was no correlation between the concentration of any of the cations and the occurrence of hard seeds. The results from analysis of the complex carbohydrates indicated there were differences in hemicellulose content of seed coat fractions, particularly xylans, that correlated with the water uptake ratio and the occurrence of hard seeds.

Magnetic resonance evaluation of recurrent disc herniation: is gadolinium necessary?

STUDY DESIGN: Evaluation of magnetic resonance images (MRIs) with surgical reference standard. OBJECTIVES: To determine whether the addition of contrast-enhanced MRI scans increases diagnostic efficacy in the evaluation of recurrent disc herniation. SUMMARY OF BACKGROUND DATA: Many centers now routinely use gadolinium-enhanced examinations in the evaluation of recurrent disc herniation. Others, noting the additional expense of contrast injection, advocate a more limited role for contrast injection and emphasize the importance of T2-weighted axial sequences. METHODS: The study included 165 consecutive patients who were referred to the authors' outpatient imaging center and had a history of previous lumbar discectomy and recurrent back and/or leg pain. The scanning protocol included sagittal and axial T1-weighted spin-echo pre- and postcontrast injection images and sagittal and axial T2-weighted fast spin-echo images. Twenty-eight patients (32 vertebral levels) had subsequent surgical exploration of a disc margin that had previously undergone discectomy. The surgical findings formed the reference standard. Three spine radiologists interpreted the MRI examinations without knowledge of the surgical results. They first interpreted the unenhanced studies, indicated whether they felt contrast injection would be helpful in further evaluation, and then (regardless of this determination) read the postcontrast study. RESULTS: On pre- and post-contrast examinations Reader 1 had a sensitivity of 95% (20/21), a specificity of 100% (10/10), and an accuracy of 97% (30/31). Reader 2 had a sensitivity of 95% (20/21), a specificity of 90% (9/10), and an accuracy of 94% (29/31). Reader 3 had a sensitivity of 90% (19/21), a specificity of 100% (10/10), and an accuracy of 94% on the precontrast examinations. His postcontrast performance demonstrated a sensitivity of 86% (18/21), a specificity of 100% (10/10), and an accuracy of 90% (28/31). In the nine interpretations wherein the readers thought that a contrast-enhanced examination might provide useful additional information, they did not change their interpretations in three cases, improved their interpretations in two, and made their interpretations worse in four on the basis of addition of the enhanced images. CONCLUSIONS: Routine use of contrast-enhanced examinations in patients who have had prior lumbar surgery probably adds little diagnostic value and may be confusing.

Bone contusions of the knee: increased lesion detection with fast spin-echo MR imaging with spectroscopic fat saturation.

PURPOSE: To demonstrate that T2-weighted fast spin-echo (FSE) imaging with spectroscopic fat saturation (FS-FSE) increases the conspicuity between normal marrow and bone contusions in posttraumatic knees. MATERIALS AND METHODS: Seventy-six magnetic resonance (MR) studies of the knee were prospectively evaluated in 73 consecutive patients with knee pain. Conspicuity of regions of microtrabecular trauma (bone contusions) was evaluated with conventional T2-weighted imaging in the sagittal plane, T2-weighted FSE imaging in the coronal plane, T2-weighted FS-FSE imaging in the sagittal plane, and conventional T1-weighted imaging in the sagittal plane. RESULTS: Twenty-six foci of bone contusion were identified in 21 knees with the FS-FSE technique. Only 16 foci were demonstrated with conventional T2-weighted imaging. Six of the sites of bone contusion were not demonstrated with the FSE technique alone (without fat saturation). Four of the bone contusions were not seen on T1-weighted images; these sites of bone contusion were substantially more conspicuous on the FS-FSE images. In addition, FS-FSE imaging was more sensitive in demonstrating the extent of microtrabecular trauma. CONCLUSION: T2-weighted FS-FSE imaging is a sensitive and rapid method of identifying and assessing the extent of microtrabecular trauma about the knee.

Adaptive responses of rats trained with reductions in exercise heart rate.

This study was designed to test the hypothesis that rats trained with marked reductions in exercise heart rate respond with adaptations indicative of increased intrinsic myocardial performance. Therefore, we measured changes in maximum work capacity (VO2max), biochemical-functional indexes of cardiac contractile capacity, and skeletal muscle oxidative capacity in normal-trained (NT) rats and in rats trained while receiving the selective cardiac beta 1-blocking drug atenolol (AT). Training consisted of treadmill running at approximately 80% VO2max (untrained) for 1-h duration, 6 days/wk, for a total of 8 wk. Exercise heart rate of the AT group was markedly reduced and averaged 140 beats/min below the NT group for any given session. Compared with sedentary controls, VO2max was increased by 11%, and red vastus lateralis muscle citrate synthase activity was increased by 28% in both AT and NT groups (P less than 0.05). There were no differences between trained and nontrained groups with regard to Ca2+-regulated myofibril adenosinetriphosphatase. In situ derived left ventricular pressure and the maximum rate of left ventricular pressure development were not augmented relative to sedentary control values when the trained hearts were either stimulated inotropically or maximally afterloaded . These findings suggest that maximum exercise capacity can be enhanced in rodents conditioned with and without limited elevation in exercise heart rate; however, this reduction of exercise heart rate acceleration does not provide a stimulus to enhance the intrinsic functional capacity of the rodent heart.

Exercise and cardiac performance capacity in rats with partial sympathectomy.

This study was undertaken to examine maximal oxygen uptake (VO2 max) and heart rate (HR) during exercise, in situ derived cardiac contractile capacity, and Ca2+ regulation of cardiac myofibril ATPase in normal female rats and in rats with partial sympathectomy (SYMX) induced by chronic injections of guanethidine. Also, normal control (NC) rats were studied during exercise with and without the beta 1-blocking drug atenolol. The results show that SYMX did not have any effect on Ca2+-regulated cardiac myofibril ATPase activity. Also similar cardiac functional capacity, as reflected in left ventricular pressure development and +dP/dtmax, was observed for both groups when the heart was stressed by either exogenous norepinephrine or maximal afterload (aortic constriction). Exercise VO2 max was reduced by 15% (P less than 0.05) in the SYMX compared to the NC group. Although this reduction in VO2 max corresponded to a parallel reduction in HRmax, NC rats with cardiac beta-blockade attained normal VO2 max even though their exercise HRmax was below the SYMX group. These findings suggest that normal rats with attenuated HR and contractility have a better capacity to acutely maintain VO2 max during exercise than rats with chemical sympathectomy.

Exercise capacity and cardiac function of rats with drug-induced cardiac enlargement.

A study was undertaken to determine if sustained administration of isoproterenol (ISO) alters biochemical and functional properties of hearts and the submaximal and maximal exercise capacity of rodents. Compared with sham-treated controls of the same age, sex, and body weight, 4 wk of ISO (0.2--0.4 mg/kg sc) produced an approximate 30% increase in combined ventricle wet weight (P less than 0.001). Respiratory capacity of homogenates, total muscle protein concentration, and actomyosin and myofibril ATPase of heart muscle of the ISO-treated group were the same as in the control group. Various cardiac function parameters in situ, obtained under control conditions and in response to tyramine-induced norepinephrine release, were similar for the two groups. ISO-treated rats had slightly greater endurance for running submaximally on a treadmill than the control rats (P less than 0.10), but their maximal capacity to utilize oxygen (VO2max) was not different from controls. These findings suggest that rodent hearts moderately enlarged by relatively low doses of isoproterenol possess normal metabolic and functional capacity. However, this cardiac enlargement had no apparent effect on maximal exercise performance of the whole animal.

Exercise capacity and cardiac function in trained and untrained thyroid-deficient rats.

This study was undertaken to ascertain the extent that impairments in a) the oxidative capacity of skeletal muscle, b) cardiac functional and biochemical correlates of contractile capacity, and c) maximal oxygen consumption (VO2 max) can be reversed in thyroid-deficient (TD) female rats subjected to an 8-wk physical training (running) program. Compared with a normal control (NC) group, thyroid deficiency caused reductions in the following: VO2 max (-32%), skeletal muscle homogenate respiratory capacity (-50%), cardiac myosin ATPase (-58%), and in situ-derived ventricular dP/dt max (-58%) (P < 0.001). The training program restored to within normal limits skeletal muscle oxidative capacity and VO2 max, but it did not improve cardiac myosin ATPase, Ca2+ regulation of myofibril ATPase, and dP/dt max relative to TD sedentary rats. However, the heart weight-to-body weight ratio was highest among the three groups in the TD trained group. These findings suggest that maximal oxygen utilization capacity of TD rats can be normalized by physical training, even though intrinsic contractile capacity of the heart could not.

The effects of graded forelimb afferent volleys on acetylcholine release from cat sensorimotor cortex.

1. The acetylcholine (ACh)-releasing system in the cerebral cortex of pentobarbital anaesthetized cats was investigated by examining the effect of graded afferent volleys in forelimb nerves on ACh release from the sensorimotor cortices contralateral and ipsilateral to the site of stimulation. 2. Cortical ACh release was determined by bio-assay of neostigmine-containing perfusates which had been in contact with the cortical surfaces for 5-10 min periods. 3. Afferent volleys, generated by stimuli that were effective in activating as many fibres of a fibre group as possible without stimulating fibres in the group with the next highest threshold for activation, were monitored from dorsal roots C7 or C8 before entering the spinal cord. 4. Stimulation of the deep (DR) and superficial (SR) radial nerves and the radial (R) nerve proximal to the junction of the DR and SR were effective in enhancing ACh release only when either group III or groups III and IV fibres were included in the afferent volley. 5. The rates of ACh release from the primary receiving area of the sensorimotor cortex contralateral to the site of stimulation did not differ from those from the same area of the ipsilateral sensorimotor cortex. 6. The pertinence of this data to the various hypotheses concerning the nature of the ACh-releasing pathways to the cerebral cortex is discussed.