11,423 research outputs found
EXCITATION AND DELAYED ANNIHILATION OF PS IN A LASER FIELD
No full textFaisal F, RAY PS. EXCITATION AND DELAYED ANNIHILATION OF PS IN A LASER FIELD. JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS. 1981;14(21):L715-L719
Streaking and splashing: design of a grazing incidence x-ray streak camera and time-resolved measurements of the structure of water
No full textThe performance of cesium iodide photocathodes has been characterized for use with grazing incidence soft x-rays. The total electron yield and pulsed quantum efficiency has been measured in a reflection geometry as a function of photon energy (100 eV to 1 keV), angle of incidence, and the electric field between the anode and photocathode. The total electron yield and pulsed quantum efficiency increase as the x-ray penetration depth approaches the secondary electron escape depth Unit quantum efficiency in a grazing incidence geometry is demonstrated. A weak electnc-field dependence is observed for the total yield measurements, while no significant dependence is found for the pulsed quantum efficiency. The effect of the pulse height distribution on the detective quantum efficiency is discussed Theoretical predictions agree accurately with expenment.
Demonstrated unit quantum efficiency in a reflection geometry motivated the development of a grazing incidence x-ray streak camera for the Ultrafast X-ray Science beamline, under construction at the Advanced Light Source, Lawrence Berkeley National Laboratory, USA Design considerations particular to synchrotron radiation sources are discussed. An analytical model and particle simulation for a camera incorporating magnetostatic imaging and meander sweep plates is presented. The camera is characterised with the third harmonic from a titanium-sapphire based laser system, 70 ps intrinsic and 150 fs “sliced” x-ray photon pulses from a synchrotron bend magnet source. A grazing incidence x-ray streak camera with an instrument temporal response of 6 ps is demonstrated.
Dynamical changes in the structure factor of liquid water are measured using time-resolved x-ray diffraction techniques with 100 ps resolution. On short time scales, before the system has had time to expand following femtosecond optical excitation, temperatureinduced changes associated with rearrangements of the hydrogen-bonded structure at constant volume are observed. Transient changes in the pair correlation function associated with isochonc heating effects are extracted and interpreted in terms of a decrease in the local tetrahedral ordering in the liquid
CONDENSATION OF LIGHT BOSONS IN GAUGE-THEORIES
No full textMiller D, RAY PS. CONDENSATION OF LIGHT BOSONS IN GAUGE-THEORIES. PHYSICS LETTERS B. 1984;149(1-3):179-181
THERMODYNAMICS OF A RELATIVISTIC FERMI GAS IN A STRONG MAGNETIC-FIELD
No full textMiller D, RAY PS. THERMODYNAMICS OF A RELATIVISTIC FERMI GAS IN A STRONG MAGNETIC-FIELD. HELVETICA PHYSICA ACTA. 1984;57(1):96-100
CONDENSATION OF A CHARGES RELATIVISTIC BOSE-GAS IN THE PRESENCE OF A MAGNETIC-FIELD
No full textMiller D, RAY PS. CONDENSATION OF A CHARGES RELATIVISTIC BOSE-GAS IN THE PRESENCE OF A MAGNETIC-FIELD. PHYSICAL REVIEW A. 1986;33(3):1990-1995
LIMITING PARTICLE DENSITY OF A RELATIVISTIC FERMI GAS IN A MAGNETIC-FIELD
No full textMiller D, RAY PS. LIMITING PARTICLE DENSITY OF A RELATIVISTIC FERMI GAS IN A MAGNETIC-FIELD. HELVETICA PHYSICA ACTA. 1984;57(6):704-707
LINE-SHAPE FUNCTION FOR THE MICROWAVE-INDUCED HYPERFINE-LEVEL TRANSITION IN POSITRONIUM
No full textFaisal F, RAY PS. LINE-SHAPE FUNCTION FOR THE MICROWAVE-INDUCED HYPERFINE-LEVEL TRANSITION IN POSITRONIUM. PHYSICAL REVIEW A. 1984;30(5):2316-2322
Wavelength tunable 10-GHz 3-ps pulse source using a dispersion decreasing fiber-based nonlinear optical loop mirror
No full textWe experimentally demonstrate the use of a dispersion decreasing fiber (DDF)-based nonlinear optical loop mirror (NOLM) for the generation of wavelength tunable soliton-like pulses at a repetition rate of 10 GHz. We compress ~12 ps Gaussian pulses from an electro-absorption modulator (EAM) (followed by 125 m of DCF for preliminary linear dispersion compensation) into 3 ps pedestal-free pulses using both high-order soliton compression and nonlinear switching effects within an 8.5 km DDF-based loop mirror. The output pulses from the DDF-based NOLM show considerable pedestal reduction compared to those obtained by directly compressing the EAM seed pulses via a single passage through the DDF. Wavelength tuning of the compressed pulses over a ~15 nm bandwidth (from 1541 to 1556 nm) is demonstrated without a significant increase in pulse duration or degradation in pulse quality
Blendas PET/PS: efeito do compatibilizante SMA e da reciclagem nas propriedades microscópicas /
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas.Neste trabalho foram estudados os efeitos da adição de agente compatibilizante, poli[(estireno)-co-(anidirido maleico)] [SMA] e dos ciclos de reciclagem à blenda PET/PS. Inicialmente foi avaliada a miscibilidade da blenda de poli(tereftalatode etileno) [PET] com poliestireno [PS]. Sendo esta blenda imiscível em toda a faixa de composição, foi estudada a influência da adição de SMA nas propriedades térmicas e na morfologia da blenda PET/PS/SMA. O parâmetro de interação de Flory-Huggings (c12), cujo valor está relacionado com as interações específicas entre os componentes, foi calculado a partir das temperaturas de fusão de equilíbrio do componente semicristalino puro e na blenda, como igual a +0,024. O valor positivo sugere interações desfavoráveis entre os componentes, em concordância com os outros métodos. A viabilidade de reutilização do PET em mistura com outro polímero, foi analisada através de sucessivos processos de extusão, de maneira que as propriedades microscópicas dos componentes puros e das blendas foram estudadas. A pequena redução da massa molar média do PET, não deve prejudicar o reaproveitamento do PET pós-consumo. Para as blendas PET/PS/SMA, o aumento da adesão interfacial, de certo modo, minimiza o efeito causado pela redução de massa molar durante o processo de reciclagem
Ray Barger
No full textPhotograph of Ray Barger standing outside his house in Botetourt County. He is a former member of the Roanoke Jug Band playing guitar for them through the late 1920's and early 1930's
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