The Detection of a 3.5-h Period in the Classical Nova Velorum 1999 (V382 Vel) and the Long Term Behavior of the Nova Light Curve

We present CCD photometry, light curve and time series analysis of the classical nova V382 Vel (N Vel 1999). The source was observed for 2 nights in 2000, 21 nights in 2001 and 7 nights in 2002 using clear filters. We report the detection of a distinct period in the light curve of the nova P=0.146126(18) d (3.5 h). The period is evident in all data sets, and we interpret it as the binary period of the system. We also measured an increase in the amplitude modulation of the optical light (in magnitude) by more than 55% from 2000 to 2001 and about 64% from 2001 to 2002. The pulse profiles in 2001 show deviations from a pure sinusoidal shape which progressively become more sinusoidal by 2002. The main cause of the variations in 2001 and 2002 can be explained with the occultation of the accretion disk by the secondary star. We interpret the observed deviations from a pure sinusoidal shape as additional flux resulting from the aspect variations of the irradiated face of the secondary star.Comment: 16 pages and 4 figures, accepted as it stands to be published in the Astronomical Journal (AJ

Wess-Zumino-Witten model off criticality

We study the renormalization group flow properties of the Wess-Zumino-Witten model in the region of couplings between $g^2=0$ and $g^2=4\pi/k$, by evaluating the two-loop Zamolodchikov's $c$-function. We also discuss the region of negative couplings.Comment: 8 page

Theoretical investigation of magnetic order in ReOFeAs, Re = Ce, Pr

Density functional theory (DFT) calculations are carried out on ReOFeAs, Re = Ce, Pr, the parent compounds of the high-T$_c$ superconductors ReO$_{1-x}$F$_{x}$FeAs, in order to determine the magnetic order of the ground state. It is found that the magnetic moments on the Fe sites adopt a collinear antiferromagnetic order, similar to the case of LaOFeAs. Within the generalized gradient approximation along with Coulomb onsite repulsion (GGA+U), we show that the Re magnetic moments also adopt an antiferromagnetic order for which, within the ReO layer, same spin Re sites lie along a zigzag line perpendicular to the Fe spin stripes. While within GGA the Re 4f band crosses the Fermi level, upon inclusion of onsite Coulomb interaction the 4f band splits and moves away from the Fermi level, making ReOFeAs a Mott insulator.Comment: 5 pages, 4 figure

Ferromagnetism below 10 K in Mn doped BiTe

Ferromagnetism is observed below 10 K in [Bi0.75Te0.125Mn0.125]Te. This material has the BiTe structure, which is made from the stacking of two Te-Bi-Te-Bi-Te blocks and one Bi-Bi block per unit cell. Crystal structure analysis shows that Mn is localized in the Bi2 blocks, and is accompanied by an equal amount of TeBi anti-site occupancy in the Bi2Te3 blocks. These TeBi anti-site defects greatly enhance the Mn solubility. This is demonstrated by comparison of the [Bi1-xMnx]Te and [Bi1-2xTexMnx]Te series; in the former, the solubility is limited to x = 0.067, while the latter has xmax = 0.125. The magnetism in [Bi1-xMnx]Te changes little with x, while that for [Bi1-2xTexMnx]Te shows a clear variation, leading to ferromagnetism for x > 0.067. Magnetic hysteresis and the anomalous Hall Effect are observed for the ferromagnetic samples.Comment: Accepted for publication in Phys. Rev.

Decay of scalar variance in isotropic turbulence in a bounded domain

The decay of scalar variance in isotropic turbulence in a bounded domain is investigated. Extending the study of Touil, Bertoglio and Shao (2002; Journal of Turbulence, 03, 49) to the case of a passive scalar, the effect of the finite size of the domain on the lengthscales of turbulent eddies and scalar structures is studied by truncating the infrared range of the wavenumber spectra. Analytical arguments based on a simple model for the spectral distributions show that the decay exponent for the variance of scalar fluctuations is proportional to the ratio of the Kolmogorov constant to the Corrsin-Obukhov constant. This result is verified by closure calculations in which the Corrsin-Obukhov constant is artificially varied. Large-eddy simulations provide support to the results and give an estimation of the value of the decay exponent and of the scalar to velocity time scale ratio

Octet Baryon Magnetic Moments in the Chiral Quark Model with Configuration Mixing

The Coleman-Glashow sum-rule for magnetic moments is always fulfilled in the chiral quark model, independently of SU(3) symmetry breaking. This is due to the structure of the wave functions, coming from the non-relativistic quark model. Experimentally, the Coleman-Glashow sum-rule is violated by about ten standard deviations. To overcome this problem, two models of wave functions with configuration mixing are studied. One of these models violates the Coleman-Glashow sum-rule to the right degree and also reproduces the octet baryon magnetic moments rather accurately.Comment: 22 pages, RevTe

Seasonality of mood and affect in a large general population sample

Mood and behaviour are thought to be under considerable influence of the seasons, but evidence is not unequivocal. The purpose of this study was to investigate whether mood and affect are related to the seasons, and what is the role of neuroticism in this association. In a national internet-based crowdsourcing project in the Dutch general population, individuals were invited to assess themselves on several domains of mental health. ANCOVA was used to test for differences between the seasons in mean scores on the Positive and Negative Affect Schedule (PANAS) and Quick Inventory of Depressive Symptomatology (QIDS). Within-subject seasonal differences were tested as well, in a subgroup that completed the PANAS twice. The role of neuroticism as a potential moderator of seasonality was examined. Participants (n = 5,282) scored significantly higher on positive affect (PANAS) and lower on depressive symptoms (QIDS) in spring compared to summer, autumn and winter. They also scored significantly lower on negative affect in spring compared to autumn. Effect sizes were small or very small. Neuroticism moderated the effect of the seasons, with only participants higher on neuroticism showing seasonality. There was no within-subject seasonal effect for participants who completed the questionnaires twice (n = 503), nor was neuroticism a significant moderator of this within-subjects effect. The findings of this study in a general population sample participating in an online crowdsourcing study do not support the widespread belief that seasons influence mood to a great extent. For, as far as the seasons did influence mood, this only applied to highly neurotic participants and not to low-neurotic participants. The underlying mechanism of cognitive attribution may explain the perceived relation between seasonality and neuroticism

Some applications of enthalpimetric detection in flow injection analysis

A flow injection manifold is described based on a flow-through arrangement of thermistors for measuring heat effects of chemical reactions. Temperature changes down to 10−3 °C can be measured reproducibly. The working range for the determination of a component is dependent on the reaction enthalpy and can vary from 10−3 to 10 mol/l for acids and bases, from 10 to 1000 ppm for e.g., alkylhydroperoxides. Sample frequencies up to 150 samples per hour can be realized