THE TOUCH-DOWN AND TAKE-OFF ANGLES IN DIFFERENT PHASES OF 100 M SPRINT RUN

The variation in running velocity over a 100 m dash has been studied extensively in the last decade. Very few studies, however, have dealt with the changes in technique occurring between the second acceleration (from the normal sprinting position of run the maximal velocity until is reached), maximal velocity and deceleration phases. The purpose of this study was to quantify the touch-down (TO) and take-off (TO) angles in a 100 m sprint run, before, during and after the maximal velocity phase. Ten sprinters were filmed during these phases using a high-speed video camera operating at 250 Hz in a 100 m dash. The results of this study suggest that the Trunk Angle at TO influenced the TO angle. Furthermore, the horizontal distance between the centre of gravity and the Foot at TO, is an important technical characteristic influencing the stride length and the stride rate which provoke the running velocity variation

NGC 2362: a Template for Early Stellar Evolution

We present UBVRI photometry for the young open cluster NGC 2362. From analysis of the appropriate color-color and color-magnitude diagrams we derive the fundamental parameters of the NGC 2362 cluster to be: age = 5 (+1-2) Myr, distance = 1480 pc, E(B-V)=0.10 mag. The cluster age was independently determined for both high mass (2.1 - 36Msun) and low mass (0.7 - 1.2Msun) stars with excellent agreement between the ages derived using post-main sequence and pre-main sequence evolutionary tracks for the high and low mass stars respectively. Analysis of this cluster's color-magnitude diagram reveals a well defined pre-main sequence (covering DeltaV ~ 9 magnitudes in V and extending from early A stars to near the hydrogen burning limit) which makes this cluster an ideal laboratory for pre-main sequence evolution studies.Comment: 9 pages, 3 figures, to be published in ApJ

Generalized Ladder Operators for Shape-invariant Potentials

A general form for ladder operators is used to construct a method to solve bound-state Schr\"odinger equations. The characteristics of supersymmetry and shape invariance of the system are the start point of the approach. To show the elegance and the utility of the method we use it to obtain energy spectra and eigenfunctions for the one-dimensional harmonic oscillator and Morse potentials and for the radial harmonic oscillator and Coulomb potentials.Comment: in Revte

Kidney Abscess During Pregnancy. A Case Report

Apesar das infecções urinárias serem relativamente frequentes durante a gravidez, a ocorrência de um abcesso renal é muito raro. A patogénese do abcesso renal tem mudado ao longo dos anos. Actualmente, mais de 75% dos casos têm origem numa infecção do aparelho urinário. Os autores apresentam o caso clínico de uma grávida de 35 anos, internada às 38 semanas e cinco dias de gestação por febre, náuseas, vómitos e dor lombar à direita. Os dados clínicos e os exames complementares realizados levaram ao diagnóstico de abcesso renal. É feita uma revisão da literatura acerca do tema

The Dynamical State of Barnard 68: A Thermally Supported, Pulsating Dark Cloud

We report sensitive, high resolution molecular-line observations of the dark cloud Barnard 68 obtained with the IRAM 30-m telescope. We analyze spectral-line observations of C18O, CS(2--1), C34S(2--1), and N2H+(1--0) in order to investigate the kinematics and dynamical state of the cloud. We find extremely narrow linewidths in the central regions of the cloud. These narrow lines are consistent with thermally broadened profiles for the measured gas temperature of 10.5 K. We determine the thermal pressure to be a factor 4 -- 5 times greater than the non-thermal (turbulent) pressure in the central regions of the cloud, indicating that thermal pressure is the primary source of support against gravity in this cloud. This confirms the inference of a thermally supported cloud drawn previously from deep infrared extinction measurements. The rotational kinetic energy is found to be only a few percent of the gravitational potential energy, indicating that the contribution of rotation to the overall stability of the cloud is insignificant. Finally, our observations show that CS line is optically thick and self-reversed across nearly the entire projected surface of the cloud. The shapes of the self-reversed profiles are asymmetric and are found to vary across the cloud in such a manner that the presence of both inward and outward motions are observed within the cloud. Moreover, these motions appear to be globally organized in a clear and systematic alternating spatial pattern which is suggestive of a small amplitude, non-radial oscillation or pulsation of the outer layers of the cloud about an equilibrium configuration.Comment: To appear in the Astrophysical Journal; 23 pages, 8 figures; Manuscript and higher resolution images can be obtained at http://cfa-www.harvard.edu/~ebergin/pubs_html/b68_vel.htm