Search results for "TF"
showing 10 items of 1652 documents
X-rays from protostellar jets: emission from continuous flows
2006
Recently X-ray emission from protostellar jets has been detected with both XMM-Newton and Chandra satellites, but the physical mechanism which can give rise to this emission is still unclear. We performed an extensive exploration of a wide space of the main parameters influencing the jet/ambient interaction. Aims include: 1) to constrain the jet/ambient interaction regimes leading to the X-ray emission observed in Herbig-Haro objects in terms of the emission by a shock forming at the interaction front between a continuous supersonic jet and the surrounding medium; 2) to derive detailed predictions to be compared with optical and X-ray observations of protostellar jets; 3) to get insight int…
The diagnostic potential of Fe lines applied to protostellar jets
2013
We investigate the diagnostic capabilities of the iron lines for tracing the physical conditions of the shock-excited gas in jets driven by pre-main sequence stars. We have analyzed the 300-2500 nm X-shooter spectra of two jets driven by the pre-main sequence stars ESO-Halpha 574 and Par-Lup 3-4. Both spectra are very rich in [FeII] lines over the whole spectral range; in addition, lines from [FeIII] are detected in the ESO-H\alpha 574 spectrum. NLTE codes along with codes for the ionization equilibrium are used to derive the gas excitation conditions of electron temperature and density, and fractional ionization. The iron gas-phase abundance is provided by comparing the iron lines emissivi…
Do p annihilations at rest choose the Eightfold way?
1993
Dynamical selection rules observed in pp annihilation at rest are linked to relations between SU(3) invariant amplitudes. The ϱπ puzzle, the KK suppression in P wave, and the unexplained production rates of πa2 (1320) are shown to be manifestions of one SU(3) amplitude ratio. The dynamical selection rules observed in the production of strange mesons lead to symmetries in SU(3) amplitudes. We conjecture that these symmetries reflect the underlying quark-gluon dynamic. It is shown that the contribution of annihilation diagrams to important annihilation channels like ϱ0π0 or ηω is small or vanishes. Hence rearrangement must play an important role. The use of SU(3) relations in the context of N…
Force-Time Characteristics and Running Velocity of Male Sprinters during the Acceleration Phase of Sprinting
1988
Abstract In an effort to investigate the force-time characteristics during the acceleration phase of the sprint start, eight male sprinters were used as subjects. Runs up to 3 m were analyzed from film, and force-time parameters were measured on a force platform. In a starting stance the reaction time of the group was .118 ± .016 s and the force production lasted .342 ± .022 s. The maximal resultant force at the moment of maximal horizontal force was 19.3 ± 2.2 N x kg1, and the direction of the force was 32 ± 7°. In the very last instant before leaving the blocks the velocity of the center of gravity was 3.46 ± .32 m x s−1. In the first contact after leaving the blocks there was a braking p…
On the Azimuthal Stability of Shock Waves around Black Holes
1998
Analytical studies and numerical simulations of time dependent axially symmetric flows onto black holes have shown that it is possible to produce stationary shock waves with a stable position both for ideal inviscid and for moderately viscous accretion disks. We perform several two dimensional numerical simulations of accretion flows in the equatorial plane to study shock stability against non-axisymmetric azimuthal perturbations. We find a peculiar new result. A very small perturbation seems to produce an instability as it crosses the shock, but after some small oscillations, the shock wave suddenly transforms into an asymmetric closed pattern, and it stabilizes with a finite radial extent…
An X-shooter survey of star forming regions: Low-mass stars and sub-stellar objects
2011
We present preliminary results of our X-shooter survey in star forming regions. In this contribution we focus on sub-samples of young stellar and sub-stellar objects (YSOs) in the Lupus star forming region and in the TW Hya association. We show that the X-shooter spectra are suitable for conducting several parallel studies such as YSO + disk fundamental parameters, accretion and outflow activity in the very low-mass (VLM) and sub-stellar regimes, as well as magnetic activity in young VLM YSOs, and Li abundance determinations. The capabilities of X-shooter in terms of wide spectral coverage, resolution and limiting magnitudes, allow us to assess simultaneously the accretion/outflow, magnetic…
Stock markets and quantum dynamics: A second quantized description
2009
In this paper we continue our description of stock markets in terms of some non-abelian operators which are used to describe the portfolio of the various traders and other observable quantities. After a first prototype model with only two traders, we discuss a more realistic model of market involving an arbitrary number of traders. For both models we find approximated solutions for the time evolution of the portfolio of each trader. In particular, for the more realistic model, we use the stochastic limit approach and a fixed point like approximation. © 2007 Elsevier B.V. All rights reserved
Body composition in children and adolescents residing in southern Europe: Prevalence of overweight and obesity according to different international r…
2019
The objective was to analyze body composition in children and adolescents of Southern Europe to identify prevalence of overweight and obesity. This investigation involved 512 girls and 488 boys between 7-to 19-years. Variables evaluated were Body Mass Index (BMI) and Fat Mass (FM; electrical bioimpedance). The references used to establish prevalence according to BMI were those of the World Health Organization (WHO) and the International Obesity Task Force (IOTF); in the case of FM, the Child Growth Foundation (CGF) reference was used. There were significant differences (p < 0.05) in the prevalence of overweight and obesity between the three classifications (32.3% according to IOTF, 37.3%…
Effects of sesame seed meal and bambaranut meal on growth, feed utilization and body composition of juvenile African catfish Clarias gariepinus
2014
Plant proteins are plausible fishmeal substitutes but are deficient in some essential amino acids (EAA) like lysine and methionine. Combination of different plant proteins with complimentary EAA could be a useful alternative. Bambaranut (Voandzeia subterranea) contains high amount of lysine while methionine is in sesame seed (Sesamum indicum). This experiment tested effects of combining sesame seed meal (SSM) and bambaranut meal (BNM) on juvenile African catfish Clarias gariepinus. Inclusion levels (%) of SSM:BNM in four novel diets were feed 1 (F1) 0:35, feed 2 (F2) 11.7:23.3, feed 3 (F3) 23.3:11.7, feed 4 (F4) 35:0. Catfish (initial weight ± SD 11.7 ± 0.56 g) were stocked in four replicat…
Mechanical power and segmental contribution to force impulses in long jump take-off
1979
Changes in total mechanical work, its partitioning into different energy states, mechanical power, force-time characteristics, force impulses of body segments and mass center's pathway characteristics during long jump take-off were investigated on four national and six ordinary level athletes. Both cinematographic and force-platform techniques were used. The data showed that the national level jumpers had higher run-up and higher take-off (release) velocities in horizontal and vertical directions. In addition, they were able to utilize efficiently the elastic energy stored in the leg extensor muscles at take-off impact. This was seen in high support leg eccentric and concentric forces, whic…