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1.
Int J Sports Med ; 35(9): 725-30, 2014 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-24577860

RESUMEN

This study examined the effect of exercise-induced dehydration by ~4% body mass loss on 5-km cycling time trial (TT) performance and neuromuscular drive, independent of hyperthermia. 7 active males were dehydrated on 2 occasions, separated by 7 d. Participants remained dehydrated (DEH, -3.8±0.5%) or were rehydrated (REH, 0.2±0.6%) over 2 h before completing the TT at 18-25 °C, 20-30% relative humidity. Neuromuscular function was determined before dehydration and immediately prior the TT. The TT started at the same core temperature (DEH, 37.3±0.3°C; REH, 37.0±0.2 °C (P>0.05). Neither TT performance (DEH, 7.31±1.5 min; REH, 7.10±1.3 min (P>0.05)) or % voluntary activation were affected by dehydration (DEH, 88.7±6.4%; REH, 90.6±6.1% (P>0.05)). Quadriceps peak torque was significantly elevated in both trials prior to the TT (P<0.05), while a 19% increase in the rate of potentiated peak twitch torque development (P<0.05) was observed in the DEH trial only. All other neuromuscular measures were similar between trials. Short duration TT performance and neuromuscular function are not reduced by dehydration, independent of hyperthermia.


Asunto(s)
Rendimiento Atlético/fisiología , Ciclismo/fisiología , Deshidratación/fisiopatología , Músculo Esquelético/fisiología , Adulto , Índice de Masa Corporal , Temperatura Corporal/fisiología , Prueba de Esfuerzo , Fluidoterapia , Humanos , Masculino , Contracción Muscular/fisiología , Músculo Esquelético/inervación , Análisis y Desempeño de Tareas , Factores de Tiempo , Adulto Joven
2.
Rev Sci Instrum ; 95(6)2024 Jun 01.
Artículo en Inglés | MEDLINE | ID: mdl-38921059

RESUMEN

Superconducting magnets based on Rare Earth Barium Copper Oxides (REBCO) offer transformative capabilities in the fields of fusion energy, high energy physics, and space exploration. A challenge shared by these applications is the limited lifetime of REBCO due to radiation damage sustained during operation. Here we present a new ion-beam facility that enables simultaneous cryogenic irradiation and in situ characterization of commercial REBCO tapes. The ion source provides spatially uniform fluxes up to 1018 protons/m2s with kinetic energies up to 3.4 MeV, in addition to helium and higher-Z species. Using this facility, we can induce uniform damage profiles in the first 10-20 µm of REBCO tapes with less than 0.25 appm of hydrogen implanted in REBCO after a dose of 1020 protons/m2. The tape can be held between 20 and 300 K with an accuracy of ±0.1 K and is connected to a four-point probe measuring the critical current, Ic, and critical temperature, Tc, before, during, and after irradiation with transport current ranging from 100 nA to 100 A, and a typical voltage noise less than 0.1 µV. These capabilities are presently used to study the effect of irradiation temperature on REBCO performance change during and after proton bombardment, to assess the possibility of Ic and Tc recovery after irradiation through thermal annealing, and to explore the instantaneous and recoverable suppression of Ic and Tc observed during irradiation.

3.
Phys Rev Lett ; 106(21): 215001, 2011 May 27.
Artículo en Inglés | MEDLINE | ID: mdl-21699305

RESUMEN

Intrinsic rotation has been observed in I-mode plasmas from the C-Mod tokamak, and is found to be similar to that in H mode, both in its edge origin and in the scaling with global pressure. Since both plasmas have similar edge ∇T, but completely different edge ∇n, it may be concluded that the drive of the intrinsic rotation is the edge ∇T rather than ∇P. Evidence suggests that the connection between gradients and rotation is the residual stress, and a scaling for the rotation from conversion of free energy to macroscopic flow is calculated.

4.
Rev Sci Instrum ; 89(10): 10J106, 2018 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-30399747

RESUMEN

Plasma facing component (PFC) conditioning dramatically affects plasma performance in magnetic confinement fusion experiments. Lithium (Li) has been used in several machines to condition PFC with subsequent improvements to plasma performance. Multiple studies have investigated the interactions of Li with deuterium (D) and oxygen (O) in order to ascertain the mechanisms behind the enhanced plasma performance. Ion Beam Analysis (IBA) is a useful tool to interrogate PFC surfaces as they interact with plasmas. Dynamics of ion implantation and sputtering of surfaces (DIONISOS) is a linear plasma device, capable of generating discharges with fluxes ∼1021 m-2 s-1 and Te ∼6 eV, coupled to an ion accelerator. DIONISOS is capable of analyzing samples using Elastic Recoil Detection (ERD) and Rutherford Backscattering Spectroscopy (RBS) during plasma exposures. The facility has been equipped with a Li deposition system for evaporation of thin coatings on different substrates. The evaporator enables real time ERD and RBS measurements of deposition and erosion of Li coatings on different substrates and the interaction of the Li with the vacuum and plasma. Considerations for ERD, e.g., ion species, energy, and data acquisition frequency, are presented. This work is the basis for further investigation of He, H, and D retention in solid and liquid Li.

5.
Rev Sci Instrum ; 85(2): 023503, 2014 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-24593357

RESUMEN

A major impediment towards a better understanding of the complex plasma-surface interaction is the limited diagnostic access to the material surface while it is undergoing plasma exposure. The Dynamics of ION Implantation and Sputtering Of Surfaces (DIONISOS) experiment overcomes this limitation by uniquely combining powerful, non-perturbing ion beam analysis techniques with a steady-state helicon plasma exposure chamber, allowing for real-time, depth-resolved in situ measurements of material compositions during plasma exposure. Design solutions are described that provide compatibility between the ion beam analysis requirements in the presence of a high-intensity helicon plasma. The three primary ion beam analysis techniques, Rutherford backscattering spectroscopy, elastic recoil detection, and nuclear reaction analysis, are successfully implemented on targets during plasma exposure in DIONISOS. These techniques measure parameters of interest for plasma-material interactions such as erosion/deposition rates of materials and the concentration of plasma fuel species in the material surface.

6.
Rev Sci Instrum ; 81(10): 10E106, 2010 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-21033971

RESUMEN

The ideal in situ plasma facing component (PFC) diagnostic for magnetic fusion devices would perform surface element and isotope composition measurements on a shot-to-shot (∼10 min) time scale with ∼1 µm depth and ∼1 cm spatial resolution over large areas of PFCs. To this end, the experimental adaptation of the customary laboratory surface diagnostic--nuclear scattering of MeV ions--to the Alcator C-Mod tokamak is being guided by ACRONYM, a Geant4 synthetic diagnostic. The diagnostic technique and ACRONYM are described, and synthetic measurements of film thickness for boron-coated PFCs are presented.

7.
Rev Sci Instrum ; 81(10): 10E111, 2010 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-21033976

RESUMEN

An ion sensitive probe (ISP) is developed as a robust diagnostic for measuring plasma potentials (Φ(P)) in magnetized plasmas. The ISP relies on the large difference between the ion and electron gyroradii (ρ(i)/ρ(e)∼60) to reduce the electron collection at a collector recessed behind a separately biased wall distance ∼ρ(i). We develop a new ISP method to measure the plasma potential that is independent of the precise position and shape of the collector. Φ(P) is found as the wall potential when charged current to the probe collector vanishes during the voltage sweep. The plasma potentials obtained from the ISP match Φ(P) measured with an emissive probe over a wide range of plasma conditions in a small magnetized plasma.

8.
Rev Sci Instrum ; 80(4): 043501, 2009 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-19405654

RESUMEN

A probe has been designed, constructed, and successfully used to inject methane into the DIII-D lower divertor in a manner imitating natural release by chemical erosion. This porous plug injector (PPI) probe consists of a self-contained gas reservoir with an integrated pressure gauge and a 3 cm diameter porous surface through which gas is injected into the lower divertor of the tokamak. The probe is positioned flush with the divertor target surface by means of the divertor materials evaluation system. Two gas delivery systems were developed: in the first, gas flow is regulated by a remotely controlled microvalve and in the second by a fixed micro-orifice flow restrictor. Because of the large area of the porous surface through which gas is admitted, the injected hydrocarbon molecules see a local carbon surface (>90% carbon) similar to that seen by hydrocarbons being emitted by chemical sputtering from surrounding carbon tiles. The distributed gas source also reduces the disturbance to the local plasma while providing sufficient signal for spectroscopic detection. In situ spectroscopic measurements with the PPI in DIII-D allow the direct calibration of response for measured plasma conditions from a known influx of gas.

9.
Thorax ; 31(4): 456-9, 1976 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-968804

RESUMEN

A case of acute thoracic inlet obstruction presenting as a rare complication of achalasia is described. The probable mechanism, diagnosis, and management are discussed.


Asunto(s)
Acalasia del Esófago/complicaciones , Estenosis Traqueal/etiología , Anciano , Acalasia del Esófago/diagnóstico por imagen , Acalasia del Esófago/cirugía , Femenino , Humanos , Radiografía
10.
Br Med J ; 1(5637): 142-4, 1969 Jan 18.
Artículo en Inglés | MEDLINE | ID: mdl-5762273

RESUMEN

A new method of acute urography suitable for use in any general hospital is described. It takes only 30 minutes and can be performed by the duty radiographer.The method has proved invaluable in the diagnosis and differentiation of renal colic. With radiation safeguards, it may be of value in pregnancy. It has been found useful in renal trauma and in the differential diagnosis of haematuria.


Asunto(s)
Urografía , Adulto , Anciano , Diagnóstico Diferencial , Femenino , Hematuria/diagnóstico por imagen , Humanos , Riñón/lesiones , Enfermedades Renales/diagnóstico por imagen , Masculino , Métodos , Persona de Mediana Edad , Embarazo , Complicaciones del Embarazo/diagnóstico por imagen , Cálculos Ureterales/diagnóstico por imagen , Obstrucción Ureteral/diagnóstico por imagen , Neoplasias de la Vejiga Urinaria/diagnóstico por imagen
11.
Phys Rev Lett ; 89(5): 055001, 2002 Jul 29.
Artículo en Inglés | MEDLINE | ID: mdl-12144446

RESUMEN

High-pressure gas-jet injection of neon and argon is shown to be a simple and robust method to mitigate the deleterious effects of disruptions on the DIII-D tokamak. The gas jet penetrates to the central plasma at its sonic velocity. The deposited species dissipates >95% of the plasma by radiation and substantially reduces mechanical stresses on the vessel caused by poloidal halo currents. The gas-jet species-charge distribution can include >50% fraction neutral species which inhibits runaway electrons. The favorable scaling of this technique to burning fusion plasmas is discussed.

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