616 research outputs found
Investigation of line-of-sight propagation in dense atmosphere, phase 3, part 1
The investigation of microwave absorption in the 1 to 10 GHz frequency band by the Jovian atmosphere has continued, and an estimate of the strength of signal fading at these frequencies due to layers of turbulence in Jupiter's atmosphere is given. The microwave absorption due to gaseous ammonia is estimated both in terms of a power loss in dB/km, and in total power loss in dB for slant-path communication with a probe at altitudes down to pressures of several tens of atmospheres. The graphs indicate a frequency-squared scaling of the absorption, and appreciable losses at altitudes where the pressure is several atmospheres. An estimate of turbulence strength is given. This may turn out to be quite crude considering the absence of any relevant data. A planetary scaling law which appears to hold reasonably well for Earth to Venus, is extrapolated to Jupiter. No reasonable modifications of the estimate can alter the conclusion that direct-path fading is negligible for pressure regimes up to 20 atm
Canine liver transplantation under nva cyclosporine versus cyclosporine
The immunosuppressive qualities and other features of a new cyclosporine (CsA) analogue, Nva 2-cyclosporine (Nva 2-CsA) were examined using canine orthotopic liver allografts. The mean survival time was 11.8±9.6 (SD) days in dogs without treatment, 60.8±34.4 days with Nva 2-CsA and 65.1±33.0 days with CsA. Functional abnormalities indicating toxic side effects were not noted either with Nva 2-CsA or with CsA. Using the same oral dose, the rate of blood level rise and the amount of the rise were greater with Nva2-CsA. Histopathologically, Nva2-CsA the treatment was associated with the same degree of hydropic vocuolation in the pars recta of the proximal tubules as CsA treatment. Thus, in the dog, Nva2-CsA had identical immunosuppressive properties as CsA, with no functionally detectable toxicity affecting the liver and kidney. © 1986 by The Williams & Wilkins Co
Low flow venovenous bypasses in small dogs and pediatric patients undergoing replacement of the liver
A venovenous bypass for transplantation of the liver was developed and evaluated in dogs and applied clinically, with flows that averaged less than 500 milliliters per minute. Fatal pulmonary emboli were seen in two of 40 experiments. The venovenous flow in the four pediatric recipients was 200 to 1,200 milliliters per minute, and there were no complications
Development of Locomotor-Related Movements in Early Infancy
This mini-review focuses on the emergence of locomotor-related movements in early infancy. In particular, we consider multiples precursor behaviors of locomotion as a manifestation of the development of the neuronal networks and their link in the establishment of precocious locomotor skills. Despite the large variability of motor behavior observed in human babies, as in animals, afferent information is already processed to shape the behavior to specific situations and environments. Specifically, we argue that the closed-loop interaction between the neural output and the physical dynamics of the mechanical system should be considered to explore the complexity and flexibility of pattern generation in human and animal neonates
Differential activation of lumbar and sacral motor pools during walking at different speeds and slopes
Organization of spinal motor output has become of interest for investigating differential activation of lumbar and sacral motor pools during locomotor tasks. Motor pools are associated with functional grouping of motoneurons of the lower limb muscles. Here we examined how the spatiotemporal organization of lumbar and sacral motor pool activity during walking is orchestrated with slope of terrain and speed of progression. Ten subjects walked on an instrumented treadmill at different slopes and imposed speeds. Kinetics, kinematics, and electromyography of 16 lower limb muscles were recorded. The spinal locomotor output was assessed by decomposing the coordinated muscle activation profiles into a small set of common factors and by mapping them onto the rostrocaudal location of the motoneuron pools. Our results show that lumbar and sacral motor pool activity depend on slope and speed. Compared with level walking, sacral motor pools decrease their activity at negative slopes and increase at positive slopes, whereas lumbar motor pools increase their engagement when both positive and negative slope increase. These findings are consistent with a differential involvement of the lumbar and the sacral motor pools in relation to changes in positive and negative center of body mass mechanical power production due to slope and speed.NEW & NOTEWORTHY In this study, the spatiotemporal maps of motoneuron activity in the spinal cord were assessed during walking at different slopes and speeds. We found differential involvement of lumbar and sacral motor pools in relation to changes in positive and negative center of body mass power production due to slope and speed. The results are consistent with recent findings about the specialization of neuronal networks located at different segments of the spinal cord for performing specific locomotor tasks
Erraticity of Rapidity Gaps
The use of rapidity gaps is proposed as a measure of the spatial pattern of
an event. When the event multiplicity is low, the gaps between neighboring
particles carry far more information about an event than multiplicity spikes,
which may occur very rarely. Two moments of the gap distrubiton are suggested
for characterizing an event. The fluctuations of those moments from event to
event are then quantified by an entropy-like measure, which serves to describe
erraticity. We use ECOMB to simulate the exclusive rapidity distribution of
each event, from which the erraticity measures are calculated. The dependences
of those measures on the order of of the moments provide single-parameter
characterizations of erraticity.Comment: 10 pages LaTeX + 5 figures p
Universal behavior of multiplicity differences in quark-hadron phase transition
The scaling behavior of factorial moments of the differences in
multiplicities between well separated bins in heavy-ion collisions is proposed
as a probe of quark-hadron phase transition. The method takes into account some
of the physical features of nuclear collisions that cause some difficulty in
the application of the usual method. It is shown in the Ginzburg-Landau theory
that a numerical value of the scaling exponent can be determined
independent of the parameters in the problem. The universality of
characterizes quark-hadron phase transition, and can be tested directly by
appropriately analyzed data.Comment: 15 pages, including 4 figures (in epsf file), Latex, submitted to
Phys. Rev.
- …