Biography:

In the past U. Weiss has collaborated on articles with F. Napoli and G.E. Theintz. One of their most recent publications is Energy loss in quantum tunnelling. Which was published in journal Physics Letters A.

More information about U. Weiss research including statistics on their citations can be found on their Copernicus Academic profile page.

U. Weiss's Articles: (5)

Energy loss in quantum tunnelling

AbstractThe energy dissipated during the quantum decay of a metastable system which interacts with an environment at zero temperature is considered. It is found that quantum effects reduce the energy loss as compared to simple semiclassical estimates and that the decay is always possible for energetical reasons. Explicit results for the decay rate are obtained from the functional integral of the partition function.

Two-phonon processes in the two-state dynamics

AbstractWe study the influence of phonons on the dynamics of a symmetric two-state system. The spectral density of the environmental excitations is explicitly evaluated, taking into account single- and two-phonon processes. The interplay between these two different interactions is studied both in the coherent and incoherent tunneling regime. Attention is focused on the behavior of the crossover temperature as function of the coupling constants. The renormalized tunneling level splitting and the relaxation rates are evaluated as function of temperature in the physically relevant region of the parameters.

Evidence for a reduction of growth potential in adolescent female gymnasts†

The goal of this prospective study was to assess whether intensive physicaltraining during puberty could alter the growth potential of adolescent female athletes. Helght, sitting height, leg length, weight, body fat, and pubertal stage of 22 gymnasts aged 12.3±0.2 years (mean±SEM), with an average training period of 22 hr/wk, and of 21 swimmers aged 12.3±0.3 years (average training period 8hr/wk) were recorded half-yearly for a mean period of 2.35 years (range 2.0 to 3.7 years). Adult height predictions were performed with the methods of Bayler and Pinneau; Roche, Wainer, and Thissen, and Tanner et al. Growth velocity of gymnasts was significantly lower than that of swimmers from 11 to 13 years of bone age (p<0.05), with a mean peak height velocity of 5.48±0.32 cm/yr versus 8.0±0.50 cm/yr for swimmers. Height standard deviation score decreased significantly in gymnasts with time (r=−0.747; p<0.001). This observation was not associated with a significant alteration of chronologic age/bone age ratio. By contrast, height standard deviation score remained unchanged in swimmers (r=−0.165; p=0.1). A marked stunting of leg-length growth was observed in gymnasts from 12 years of bone age, resulting in a marked difference in overall sitting-height/leg-length ratio (gymnasts 1.054±0.005 vs swimmers 1.100±0.005; p<0.001). Concomitantly, predicted height of gymnasts decreased significantly with time (Tanner et al.: r=0.63, p<0.001; Bayley-Pinneau: r=0.44, p<0.001), whereas those of swimmers did not change. We conclude that heavy training in gymnastics (>18 hr/wk), starting before puberty and maintained throughout puberty, can alter growth rate to such an extent that full adult height will not be reached. The mechanisms underlying these observations are not settled; we suggest that prolonged inhibition of the hypothalamic-pituitary-gonadal axis by exercise, together with or because of the metabolic effects of dieting, is responsible for them.

Pharmacology lettersThe impact of diets with different magnesium contents on magnesium and calcium in serum and tissues of the rat

AbstractThe impact of three different magnesium diets (70, 1000 and 9000 ppm) on total, ionized and bound magnesium as well as ionized calcium in serum and total calcium and magnesium in femoral bone, skeletal muscle, heart and liver of male Sprague-Dawley rats was investigated. The percentage of ionized serum magnesium was unproportionally high in rats fed a low magnesium (70 ppm) diet. Femoral magnesium was correlated with ionized and total serum magnesium. In contrast, there was generally no correlation between total serum magnesium and the magnesium fractions in skeletal muscle, heart and liver. In rats fed the magnesium deficient diet, total cardiac concentration of magnesium was even significantly increased along with total calcium content, while there were no effects on total muscle and liver magnesium. Within the single groups, ionized serum calcium was never proportional to dietary magnesium, but in all three magnesium diet groups together, it was inversely correlated with dietary magnesium. Moreover, ionized serum calcium was inversely correlated with both ionized and total serum magnesium. In all 3 groups together, the concentrations of total calcium and magnesium in heart and skeletal muscle were correlated, within the single groups correlation existed only in the 1000 ppm group. Magnesium influx via calcium channels during low magnesium intake has been seen in non cardiac tissues [35,36], but nothing similar is known about non selective channels for divalent cations in the heart [33]. Thus, magnesium uptake by cardiac cells along with calcium seems to be possible, especially at low intracellular magnesium concentrations, but is still poorly investigated. We suggest that the calcium-antagonistic effect of magnesium is related to the turnover rate of magnesium rather than to its tissue concentrations.

Differential amygdala activation in schizophrenia during sadness

AbstractSeveral studies have reported impaired emotion processing in schizophrenic patients. However, the corresponding functional cerebral correlates of such impairment have not been fully understood, leaving the neurobiological basis of their affective symptoms unknown. Functional magnetic resonance imaging (fMRI) was utilized to examine brain activity in subcortical and cortical regions of 13 medicated male schizophrenic patients and 13 matched healthy controls during happy and sad mood induction. Results show brain activity in the amygdala of normal controls during negative affect, which is in line with previous neuroimaging findings. Unlike controls, schizophrenic patients have not demonstrated amygdala activation during sadness despite matched ratings to normal controls indicating a similar negative affect. Recognizing that structural abnormalities exist in the amygdala of schizophrenic patients, our results provide new evidence of functional abnormalities in the limbic system.

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