Seal-off assembly permits rapid evacuation of air from containers

Seal-off assembly which permits rapid container evacuation using large diameter tubing has a vacuum valve that permits sealing plate transfer from the vacuum valve stem to the container after evacuation. The sealing plate can be reused repeatedly. This device can repump in case of a small leak without exposing the container to the atmosphere

Location and Calibration of Lightning Pulses from LOFAR Radiation Measurements

Lightning has the power to shock and awe as an incredible force of nature, yet so many phenomena surrounding lightning are still not well-understood. In fact, the very physics regarding what actually sparks a lightning strike remain poorly defined. In an effort to understand how lightning initiation is achieved, data collected from the Low Frequency Array in the Netherlands were calibrated and interferometry performed to map the flash in 4D space. The calibration process itself is explored, from choosing lightning sources to calibrate, to the various stages of calibration leading to a fully calibrated flash ready for interferometric analysis. Using these calibrations, other researchers will be able to explore initiation and other lightning phenomena

Behavior of the Escape Rate Function in Hyperbolic Dynamical Systems

For a fixed initial reference measure, we study the dependence of the escape rate on the hole for a smooth or piecewise smooth hyperbolic map. First, we prove the existence and Holder continuity of the escape rate for systems with small holes admitting Young towers. Then we consider general holes for Anosov diffeomorphisms, without size or Markovian restrictions. We prove bounds on the upper and lower escape rates using the notion of pressure on the survivor set and show that a variational principle holds under generic conditions. However, we also show that the escape rate function forms a devil's staircase with jumps along sequences of regular holes and present examples to elucidate some of the difficulties involved in formulating a general theory.Comment: 21 pages. v2 differs from v1 only by additions to the acknowledgment

The elusive old population of the dwarf spheroidal galaxy Leo I

We report the discovery of a significant old population in the dwarf spheroidal (dSph) galaxy Leo I as a result of a wide-area search with the ESO New Technology Telescope. Studies of the stellar content of Local Group dwarf galaxies have shown the presence of an old stellar population in almost all of the dwarf spheroidals. The only exception was Leo I, which alone appeared to have delayed its initial star formation episode until just a few Gyr ago. The color-magnitude diagram of Leo I now reveals an extended horizontal branch, unambiguously indicating the presence of an old, metal-poor population in the outer regions of this galaxy. Yet we find little evidence for a stellar population gradient, at least outside R > 2' (0.16 kpc), since the old horizontal branch stars of Leo I are radially distributed as their more numerous intermediate-age helium-burning counterparts. The discovery of a definitely old population in the predominantly young dwarf spheroidal galaxy Leo I points to a sharply defined first epoch of star formation common to all of the Local Group dSph's as well as to the halo of the Milky Way.Comment: 4 pages, 3 postscript figures, uses apjfonts.sty, emulateapj.sty. Accepted for publication in ApJ Letter

Near infrared spectroscopy of starburst galaxies

(Abridged) We present new K-band spectroscopy for a sample of 48 starburst galaxies, obtained using UKIRT in Hawaii. This constitutes a fair sample of the most common types of starburst galaxies found in the nearby Universe. The variety of near infrared spectral features shown by these galaxies implies different bursts characteristics, which suggests that we survey galaxies with different star formation histories or at different stages of their burst evolution. Using synthetic starburst models, we conclude that the best ensemble of parameters which describe starburst galaxies in the nearby universe are a constant rate of star formation, a Salpeter IMF with an upper mass cutoff equal to 30 solar mass and bursts ages between 10 Myr and 1 Gyr. The model is fully consistent with the differences observed in the optical and FIR between the different types of starbursts. It suggests that HII galaxies have younger bursts and lower metallicities than SBNGs, while LIRGs have younger bursts but higher metallicities. Our observations suggest that the starburst phenomenon must be a sustained or self--sustained phenomenon: either star formation is continuous in time or multiple bursts happen in sequence over a relatively long period of time. The generality of our observations implies that this is a characteristic of starburst galaxies in the nearby Universe.Comment: 19 pages, Latex, 12 encapsulated Postscript figures, Accepted for publication in MNRA

A Wide-Field Survey of the Fornax Dwarf Spheroidal Galaxy

The results of a photometric survey of the Fornax dwarf spheroidal galaxy are presented herein. Accurate photometry in two colours (V and I) was collected over a 10 square degree area centred on the Fornax system with the aim of searching for extra-tidal structure. The data were complete to a magnitude of V=20, or approximately one magnitude brighter than the Fornax red clump stars. Stars were selected with a colour and magnitude lying near the Fornax red giant branch, thereby reducing contamination from the field star population. We were thus able to probe the outer structure of this dwarf galaxy. Immediately visible was a shell-like structure located 1.3 degrees NW from the centre of Fornax, approximately 30 arcmin beyond the nominal tidal radius at this position angle. We have measured the absolute visual magnitude of this feature to be M_V ~ -7. The feature is aligned with a previously reported shell (age approximately 2 Gyr) located near the core radius of Fornax. A statistical analysis of the extra-tidal stellar distribution further revealed two lobes situated on the Fornax minor axis which are aligned with the two shell-like features. The two-lobed structure combined with the two shells provide strong evidence that Fornax has experienced a merger event in the relatively recent past.Comment: 79 pages including 24 figures. Accepted for publication in AJ, scheduled for the March 2005 issue. Some figures are low resolution, and a full version of the paper is available at the ftp address: ftp://ftp.mso.anu.edu.au/pub/coleman

Magellanic Cloud Periphery Carbon Stars IV: The SMC

The kinematics of 150 carbon stars observed at moderate dispersion on the periphery of the Small Magellanic Cloud are compared with the motions of neutral hydrogen and early type stars in the Inter-Cloud region. The distribution of radial velocities implies a configuration of these stars as a sheet inclined at 73+/-4 degrees to the plane of the sky. The near side, to the South, is dominated by a stellar component; to the North, the far side contains fewer carbon stars, and is dominated by the neutral gas. The upper velocity envelope of the stars is closely the same as that of the gas. This configuration is shown to be consistent with the known extension of the SMC along the line of sight, and is attributed to a tidally induced disruption of the SMC that originated in a close encounter with the LMC some 0.3 to 0.4 Gyr ago. The dearth of gas on the near side of the sheet is attributed to ablation processes akin to those inferred by Weiner & Williams (1996) to collisional excitation of the leading edges of Magellanic Stream clouds. Comparison with pre LMC/SMC encounter kinematic data of Hardy, Suntzeff, & Azzopardi (1989) of carbon stars, with data of stars formed after the encounter, of Maurice et al. (1989), and Mathewson et al. (a986, 1988) leaves little doubt that forces other than gravity play a role in the dynamics of the H I.Comment: 30 pages; 7 figures, latex compiled, 1 table; to appear in AJ (June 2000

Black hole entropy and renormalization

Using a new regulator, we examine 't Hooft's approach for evaluating black hole entropy through a statistical-mechanical counting of states for a scalar field propagating outside the event horizon. We find that this calculation yields precisely the one-loop renormalization of the standard Bekenstein-Hawking formula, S={\Cal A}/(4G). Thus our result provides evidence confirming a suggestion by Susskind and Uglum regarding black hole entropy

Performance Kinetics During Repeated Sprints Is Influenced by Knowledge of Task Endpoint and Associated Peripheral Fatigue

International Journal of Exercise Science 16(1): 987-998, 2023. The regulation of exercise intensity allows an athlete to perform an exercise in the fastest possible time while avoiding debilitating neuromuscular fatigue development. This phenomenon is less studied during intermittent activities. To investigate anticipatory and real-time regulation of motor output and neuromuscular fatigue during repeated-sprint exercise, twelve males randomly performed one (S1), two (S2), four (S4) and six (S6) sets of five 5-s cycling sprints. Mechanical work and electromyographic activity were assessed during sprints. Potentiated quadriceps twitch force (ΔQtw,pot) and central activation ratio (QCAR) were quantified from response to supra-maximal magnetic femoral nerve stimulation pre- vs post-exercise. Compared with S1, mechanical work developed in the first sprint and in the entire first set was reduced in S6 (–7.8% and –5.1%, respectively, P \u3c 0.05). Work developed in the last set was similar in S4 and S6 (P = 0.82). Similar results were observed for EMG activity. The QCAR was also more reduced in S4 (–5.8%, P \u3c 0.05) and S6 (–8.3%, P \u3c 0.05) than in S1. However, ΔQtw,pot was not significantly different across all trials (–33.1% to –41.9%, P = 0.46). Perceived exhaustion increased across sprints to reach a maximal and similar level in S2, S4 and S6 (all 19.2, P \u3c 0.01 vs S1). These results suggest that the regulation of performance, exerted at the beginning and continuously during repeated sprints, is based on the task endpoint, presumably to avoid excessive peripheral muscle and associated conscious overwhelming sensations