Benchmark calculations for reduced density-matrix functional theory

Reduced density-matrix functional theory (RDMFT) is a promising alternative approach to the problem of electron correlation. Like standard density functional theory, it contains an unknown exchange-correlation functional, for which several approximations have been proposed in the last years. In this article, we benchmark some of these functionals in an extended set of molecules with respect to total and atomization energies. Our results show that the most recent RDMFT functionals give very satisfactory results compared to more involved quantum chemistry and density functional approaches.Comment: 17 pages, 1 figur

RC J1148+0455 identification: gravitational lens or group of galaxies ?

The structure of the radio source RC B1146+052 of the ``Cold'' catalogue is investigated by data of the MIT-GB-VLA survey at 4850 MHz. This source belongs to the steep spectrum radio sources subsample of the RC catalogue. Its spectral index is $\alpha$ = -1.04. The optical image of this source obtained with 6m telescope is analysed. The radio source center is situated in a group of 8 galaxies of about 24$^m$ in the R-filter. The possible explanations of the complex structure of radio components are considered.Comment: 6 pages, 5 figures, uses psfig.sty. This was the poster as presented on Gamow Memorial Internat. Conference GMIC'99 "Early Universe: Cosmological Problems and Instrumental Technologies" in St.Petersburg, 23-27 Aug., 1999. Submitted to Proceedings to be published in A&A Transaction

Electron Inertial Effects on Rapid Energy Redistribution at Magnetic X-points

The evolution of non-potential perturbations to a current-free magnetic X-point configuration is studied, taking into account electron inertial effects as well as resistivity. Electron inertia is shown to have a negligible effect on the evolution of the system whenever the collisionless skin depth is less than the resistive scale length. Non-potential magnetic field energy in this resistive MHD limit initially reaches equipartition with flow energy, in accordance with ideal MHD, and is then dissipated extremely rapidly, on an Alfvenic timescale that is essentially independent of Lundquist number. In agreement with resistive MHD results obtained by previous authors, the magnetic field energy and kinetic energy are then observed to decay on a longer timescale and exhibit oscillatory behavior, reflecting the existence of discrete normal modes with finite real frequency. When the collisionless skin depth exceeds the resistive scale length, the system again evolves initially according to ideal MHD. At the end of this ideal phase, the field energy decays typically on an Alfvenic timescale, while the kinetic energy (which is equally partitioned between ions and electrons in this case) is dissipated on the electron collision timescale. The oscillatory decay in the energy observed in the resistive case is absent, but short wavelength structures appear in the field and velocity profiles, suggesting the possibility of particle acceleration in oppositely-directed current channels. The model provides a possible framework for interpreting observations of energy release and particle acceleration on timescales down to less than a second in the impulsive phase of solar flares.Comment: 30 pages, 8 figure

Destruction of chain-superconductivity in YBa_2Cu_4O_8 in a weak magnetic field

We report measurements of the temperature dependent components of the magnetic penetration depth {\lambda}(T) in single crystal samples of YBa_2Cu_4O_8 using a radio frequency tunnel diode oscillator technique. We observe a downturn in {\lambda}(T) at low temperatures for currents flowing along the b and c axes but not along the a axis. The downturn in {\lambda}_b is suppressed by a small dc field of ~0.25 T. This and the zero field anisotropy of {\lambda}(T) likely result from proximity induced superconducting on the CuO chains, however we also discuss the possibility that a significant part of the anisotropy might originate from the CuO2 planes.Comment: 5 page

Does diet mediate associations of volume and bouts of sedentary time with cardiometabolic health indicators in adolescents?

Objective: Examine the mediating role of diet in the relationship between volume and duration of sedentary time with cardiometabolic health in adolescents. Methods: Adolescents (12-19 years) participating in the 2003/04 and 2005/06 U.S. National Health and Nutrition Examination Survey (NHANES) were examined. Cardiometabolic health indicators were body mass index z-scores (zBMI) (n 5 1,797) and metabolic syndrome (MetS) (n 5 812). An ActiGraph hip-worn accelerometer was used to derive total sedentary time and usual sedentary bout duration. Dietary intake was assessed using two 24-hour dietary recalls. Mediation analyses were conducted to examine five dietary mediators [total energy intake, discretionary foods, sugar-sweetened beverages (SSB), fruits and vegetables, and dietary quality] of the relationship between total sedentary time and usual sedentary bout duration with zBMI and MetS. Results: Total sedentary time was inversely associated with zBMI (b 5 21.33; 95% CI 22.53 to 20.13) but attenuated after adjusting for moderate-to-vigorous physical activity. No significant associations were observed between usual sedentary bout duration with zBMI or either sedentary measure with MetS. None of the five dietary variables mediated any of the relationships examined. Conclusions: Further studies are needed to explore associations of specific time periods (e.g., after school) and bout durations with both cardiometabolic health indicators and dietary behaviors

Iteration of quasiregular tangent functions in three dimensions

We define a new quasiregular mapping T in three dimensions that generalizes the tangent function on the complex plane and shares a number of its geometric properties. We investigate the dynamics of the family \lambda T for \lambda>0, establishing results analogous to those of Devaney and Keen for the meromorphic family \lambda tan z, \lambda>0, although the methods used are necessarily original.Comment: 24 pages, 3 figure