Primary Orthostatic Tremor in Adolescence

Tremor is an involuntary rhythmic muscle contraction, which causes a regular oscillation of a part of the body. Orthostatic tremor is a rare neurological movement disorder characterized by unsteadiness while standing that is relieved when sitting, walking, or lying down. Neurological examination of primary orthostatic tremor is reported to be normal. The pathophysiological mechanism of this condition is not entirely unknown. Symptoms usually start in the sixth decade. Clonazepam is widely used as a first-line medication in the treatment. A 14-year-old girl patient was admitted due to tremor activated on standing, absent while seated or lying, and improved by walking or leaning. Her brain magnetic resonance imaging and laboratory workup were normal. Tremor completely disappeared with clonazepam in 10 days. I report a case of primary orthostatic tremor in adolescence.

Mapping circuit dynamics during function and dysfunction

Neural circuits can generate many spike patterns, but only some are functional. The study of how circuits generate and maintain functional dynamics is hindered by a poverty of description of circuit dynamics across functional and dysfunctional states. For example, although the regular oscillation of a central pattern generator is well characterized by its frequency and the phase relationships between its neurons, these metrics are ineffective descriptors of the irregular and aperiodic dynamics that circuits can generate under perturbation or in disease states. By recording the circuit dynamics of the well-studied pyloric circuit in C. borealis, we used statistical features of spike times from neurons in the circuit to visualize the spike patterns generated by this circuit under a variety of conditions. This unsupervised approach captures both the variability of functional rhythms and the diversity of atypical dynamics in a single map. Clusters in the map identify qualitatively different spike patterns hinting at different dynamical states in the circuit. State probability and the statistics of the transitions between states varied with environmental perturbations, removal of descending neuromodulation, and the addition of exogenous neuromodulators. This analysis reveals strong mechanistically interpretable links between complex changes in the collective behavior of a neural circuit and specific experimental manipulations, and can constrain hypotheses of how circuits generate functional dynamics despite variability in circuit architecture and environmental perturbations.

Feedbacks Driving Interdecadal Variability in Southern Ocean Convection in Climate Models: A Coupled Oscillator Mechanism

Numerous climate models display large-amplitude, long-period variability associated with quasiperiodic convection in the Southern Ocean, but the mechanisms responsible for producing such oscillatory convection are poorly understood. In this paper we identify three feedbacks that help generate such oscillations within an Earth system model with a particularly regular oscillation. The first feedback involves increased (decreased) upward mixing of warm interior water to the surface, resulting in more (less) evaporation and loss of heat to the atmosphere which produces more (less) mixing. This positive feedback helps explain why temperature anomalies are not damped out by surface forcing. A second key mechanism involves convective (nonconvective) events in the Weddell Sea causing a relaxation (intensification) of westerly winds, which at some later time results in a pattern of currents that reduces (increases) the advection of freshwater out of the Weddell Sea. This allows for the surface to become lighter (denser) which in turn can dampen (trigger) convection—so that the overall feedback is a negative one with a delay—helping to produce a multidecadal oscillation time scale. The decrease (increase) in winds associated with convective (nonconvective) states also results in a decrease (increase) in the upward mixing of salt in the Eastern Weddell Sea, creating a negative (positive) salinity anomaly that propagates into the Western Weddell Sea and dampens (triggers) convection—again producing a negative feedback with a delay. A principal oscillatory pattern analysis yields a reasonable prediction for the period of oscillation. Strengths of the feedbacks are sensitive to parameterization of mesoscale eddies.

Features of the Operation of Powered Resonance Tube Actuators: Experiments and Simulations

There has been a recent surge of interest in powered resonance tube actuators for flow control applications. Additional features of powered resonance tube actuators (both experiments and simulations) are presented in this paper. A Powered Resonance Tube (PRT) is a device based on aeroacoustics principles, capable of producing intense perturbation levels for use in active flow control. The PRT described here is capable of producing frequencies ranging from 1600 to 15,000 Hz at amplitudes as high as 160 dB near the source. Our detailed experiments aimed at understanding the PRT phenomenon are complemented by improved direct numerical simulations. We provide a detailed characterization of the unsteady pressures in the nearfield of the actuator using phase averaged pressure measurements. The measurements revealed that propagating fluctuations were biased towards the upstream direction (relative to the supply jet) for some frequencies. However, this feature depended on the frequency at which the device was operated. The simulations that were performed earlier at a Reynolds number 490 times lower than that in the experiment have been refined. The current simulations are performed at 49 times lower than that in the experiments and show that a finer scale structure develops at higher Reynolds numbers and a more regular oscillation is present at low Reynolds numbers.

Food intake, growth and body composition in Australian Merino sheep selected for high and low weaning weight. 1. Food intake, food efficiency and growth

ABSTRACTChanges in the pattern of food intake, food conversion efficiency and growth from weaning to maturity, were examined in 35 rams and ewes from flocks of Merino sheep selected for high (weight-plus) and low (weight-minus) weaning weight and from a randomly bred control flock. The sheep were individually fed a pelleted ration ad libitum for at least 72 weeks and up to 90 weeks post weaning. Weekly food intake was described as an increasing exponential function of age with a linearly declining asymptote, about which a regular oscillation occurred, and weekly body-weight gain was described as an increasing exponential function of weekly food intake, about which a regular oscillation also occurred.The oscillations in weekly food intake had a period of about 52 weeks and appeared to be largely associated with seasonal variations in temperature, with an increased food intake during winter and a decreased food intake during summer. The oscillations in both the food-intake and body-weight functions were of similar phase and period and it was suggested that the body-weight oscillations were due to variation in gut-fill, a result of the seasonal oscillations in food intake.Selection for weaning weight changed the shape and magnitude of the food-intake curve, with the weight-plus having a greater rate of food intake (i.e. appetite) in the early stages of growth and a greater asymptote than the weight-minus animals. Selection for high and low weaning weight also resulted in an increase and a decrease in mature weight. Both strains had a similar growth efficiency, although when calculated as gross food conversion efficiency the weight-plus were higher than the weight-minus animals at the same body weight, whereas there was no difference between strains at the same age.The rams had both a higher asymptote and a slower rate of decline in food intake than the ewes. Rams had a higher mature weight than the ewes, although ewes had a slightly greater growth efficiency. However, when calculated as gross food conversion efficiency, ewes tended to be lower than rams, when compared either at the same age, or at the same body weight.When the food-intake curves were standardized for differences in mature size, strain differences in the magnitude of the food-intake curves were reduced, although differences in the shape were still apparent. Shape differences in the food-intake curves were reflected in the shape of the standardized growth curves, with the weight-plus maturing at a faster rate than the weight-minus animals. There was little difference between the sexes in the initial shape of the food-intake curve, although at later ages ewes had a lower food intake than rams. There was little difference between the sexes in the shape of the standardized growth curves.