86,537 research outputs found
AN ENDOR STUDY OF THE TEMPERATURE-DEPENDENCE OF METHYL TUNNELING
No full textWe have studied the motion of the methyl group in the free radical obtained by gamma-irradiation of 4-methyl-2,6-di-t-butylphenol (MDBP). The ENDOR spectra have been measured in the temperature range 4.5 to 200 K. The positions of the methyl proton lines are temperature dependent. Their variation is accounted for by considering the transition from the quantum regime of motion of the methyl group at low temperature to the classic regime at higher temperature. This transition is found to occur in a temperature range narrower than that anticipated by Allen's theory
EPR AND ENDOR RELAXATION STUDY OF MOLECULAR MOTIONS OF A KETONE UREA INCLUSION COMPOUND
No full textThe radical obtained by gamma irradiation of the 10-nonadecanone/urea inclusion compound has been studied by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy. The EPR line widths have been analyzed, and the characteristics and the rates of the molecular motions of the included molecule have been obtained in the temperature range 160-290 K. Two different types of motion have been detected: the wobbling motion of the methylene groups about the carbon-carbon bond modulates the beta proton isotropic hyperfine interactions, while overall uniaxial rotation inside the host channel mainly modulates the anisotropic dipolar interaction of the alpha proton. The internal motion is faster and has higher activation energy than molecular rotation. These results have been confirmed by the analysis of the amplitudes of the ENDOR lines of the gamma and zeta protons, which shows that the internal motion rate is just in the range of the electron spin Larmor frequency, while the rotation rate is lower
ENDOR spectroscopy: a tool for the study of radical structures and motions in the solid state.
No full textWe show that the analysis of ENDOR lineshapes and enhancements can give valuable information on the dynamics of radicals in the solid state. The basic advantage of ENDOR with respect to EPR spectroscopy resides in its greater spectral resolution, which positively affects also its potentiality in studying molecular motions in solids. In fact, we show that the dynamical effects on the lineshapes are detectable by using ENDOR spectroscopy in a larger range of correlation times. The range can be still more wide if the radical dynamics gives rise to an efficient relaxation mechanism which influences the spin populations. In this case, the motions can be studied through the analysis of the ENDOR enhancements, which in some cases became a very sensitive probe
An ENDOR study of methyl dynamics at low temperature
No full textWe have studied the motion of the methyl group in the free radical obtained by gamma-irradiation of 4-methyl-2,6-di-t-butylphenol. The ENDOR spectra have been measured in thetemperature range 6 to 200 K. The height of hindering potential barrier has been obtained from the shift of the ENDOR lines at low temperature
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
[Newspaper Clipping: Author Claims Evidence of Second JFK Assassin #1]
No full textNewspaper article titled "Author Claims Evidence of Second JFK Assassin." The article states that author Richard J. Whalen concluded "that there is circumstantial evidence to support the theory of a second assassin in the shooting of President John F. Kennedy.
Also By The Same Author: AKTiveAuthor, a Citation Graph Approach to Name Disambiguation
No full textThe desire for definitive data and the semantic web drive for inference over heterogeneous data sources requires co-reference resolution to be performed on those data. In particular, name disambiguation is required to allow accurate publication lists, citation counts and impact measures to be determined. This paper describes a graph-based approach to author disambiguation on large-scale citation networks. Using self-citation, co-authorship and document source analyses, AKTiveAuthor clusters papers, achieving precision of 0.997 and recall of 0.818 over a test group of eight surname clusters
John F. Kennedy telegram to Roosevelt
No full textJersey Homesteads (later the Borough of Roosevelt) was established in the 1930s as an agro-industrial cooperative community. It was established specifically for urban Jewish garment workers, many of whom had emigrated from Europe. President John F. Kennedy sent a telegram to the citizens of Roosevelt, New Jersey, apologizing for not being able to attend the memorial dedication in honor of former President Franklin Delano Roosevelt. (Jersey Homesteads became Roosevelt in 1945 in honor of the president.) President Kennedy expressed his gratitude to the people of Roosevelt for constructing the memorial, and commented that it will serve as a constant reminder of Roosevelt's good works
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
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