QZ Serpentis: A Dwarf Nova with a 2-Hour Orbital Period and an Anomalously Hot, Bright Secondary Star

We present spectroscopy and time-series photometry of the dwarf nova QZ Ser. The spectrum shows a rich absorption line spectrum of type K4 +- 2. K-type secondary stars are generally seen in dwarf novae with orbital periods P-orb around 6 h, but in QZ Ser the absorption radial velocities show an obvious modulation (semi-amplitude 207(5) km/s) at P-orb = 119.752(2) min, much shorter than typical for such a relatively warm and prominent secondary spectrum. The H-alpha emission-line velocity is modulated at the same period and roughly opposite phase. Time-series photometry shows flickering superposed on a modulation with two humps per orbit, consistent with ellipsoidal variation of the secondary's light. QZ Ser is a second example of a relatively short-period dwarf nova with a surprisingly warm secondary. Model calculations suggest that the secondary is strongly enhanced in helium, and had already undergone significant nuclear evolution when mass transfer began. Several sodium absorption features in the secondary spectrum are unusually strong, which may indicate that the present-day surface was the site of CNO-cycle hydrogen burning in the past.Comment: 11 pages, 3 postscript figures, 1 jpeg greyscale figure. Accepted for publication in PAS

XTE J2123-058: A New Neutron Star X-Ray Transient

We report on optical and RXTE observations of a new high-latitude bursting X-ray transient, XTE J2123-058. We identified the optical counterpart, measured the 5.9573 hr orbital period and constrained the binary inclination and the source distance. The distance lower limit indicates that the source is at least 2.6 kpc from the Galactic plane, which is unusual for an LMXB. RXTE observations were made between June and August 1998 during the first detected outburst from this source. We describe correlations between X-ray timing and spectral properties and discuss the possibility that the propeller mechanism turned on during the decay of the outburst. During one of the RXTE observations, we detect a pair of high frequency QPOs at 847.1 +/- 5.5 Hz and 1102 +/- 13 Hz simultaneously. According to the beat frequency model, the QPO separation implies a neutron star spin period near 3.9 ms. As the X-ray flux decreases at the end of the outburst, the amplitude of the optical modulation increases significantly. This behavior can be explained if the size of the accretion disk decreases during the decay of the outburst.Comment: 24 pages, 9 figures, accepted by Ap

Are there eco-metrics for fisheries?

Author Posting. © The Author, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Fisheries Research 77 (2006): 1-3, doi:10.1016/j.fishres.2005.11.003.Ecosystem based management of marine resources is a worthy ideal. At present, however, the science is unable to measure and relate the fundamental concepts of diversity, productivity and resilience required for management decisions. Further, we do not have legal or fiscal measures that would allow us to allocate these resources to reserves, fishing quotas or fish farms. A proper appreciation of these shortcomings is needed

On the center-vortex baryonic area law

We correct an unfortunate error in an earlier work of the author, and show that in center-vortex QCD (gauge group SU(3)) the baryonic area law is the so-called $Y$ law, described by a minimal area with three surfaces spanning the three quark world lines and meeting at a central Steiner line joining the two common meeting points of the world lines. (The earlier claim was that this area law was a so-called $\Delta$ law, involving three extremal areas spanning the three pairs of quark world lines.) We give a preliminary discussion of the extension of these results to $SU(N), N>3$. These results are based on the (correct) baryonic Stokes' theorem given in the earlier work claiming a $\Delta$ law. The $Y$-form area law for SU(3) is in agreement with the most recent lattice calculations.Comment: 5 pages, RevTeX4, 5 .eps figure

Amelioration of Binge Eating by Nucleus Accumbens Shell Deep Brain Stimulation in Mice Involves D2 Receptor Modulation

Hedonic overconsumption contributing to obesity involves altered activation within the mesolimbic dopamine system. Dysregulation of dopamine signaling in the nucleus accumbens shell (NAS) has been implicated in reward-seeking behaviors, such as binge eating, which contributes to treatment resistance in obesity (Wise, 2012). Direct modulation of the NAS with deep brain stimulation (DBS), a surgical procedure currently under investigation in humans for the treatment of major depression, obsessive–compulsive disorder, and addiction, may also be effective in ameliorating binge eating. Therefore, we examined the ability of DBS of the NAS to block this behavior in mice. c-Fos immunoreactivity was assessed as a marker of DBS-mediated neuronal activation. NAS DBS was found to reduce binge eating and increased c-Fos levels in this region. DBS of the dorsal striatum had no influence on this behavior, demonstrating anatomical specificity for this effect. The dopamine D2 receptor antagonist, raclopride, attenuated the action of DBS, whereas the D1 receptor antagonist, SCH-23390, was ineffective, suggesting that dopamine signaling involving D2 receptors underlies the effect of NAS DBS. To determine the potential translational relevance to the obese state, chronic NAS DBS was also examined in diet-induced obese mice and was found to acutely reduce caloric intake and induce weight loss. Together, these findings support the involvement of the mesolimbic dopamine pathways in the hedonic mechanisms contributing to obesity, and the efficacy of NAS DBS to modulate this system

Working with simple machines

A set of examples is provided that illustrate the use of work as applied to simple machines. The ramp, pulley, lever and hydraulic press are common experiences in the life of a student and their theoretical analysis therefore makes the abstract concept of work more real. The mechanical advantage of each of these systems is also discussed so that students can evaluate their usefulness as machines.Comment: 9 pages, 4 figure

Genetic Interactions in Zebrafish Midline Development

AbstractMutational analyses have shown that the genesno tail(ntl, Brachyuryhomolog),floating head(flh,aNothomeobox gene), andcyclops(cyc) play direct and essential roles in the development of midline structures in the zebrafish. In bothntlandflhmutants a notochord does not develop, and incycmutants the floor plate is nearly entirely missing. We made double mutants to learn how these genes might interact. Midline development is disrupted to a greater extent incyc;flhdouble mutants than in eithercycorflhsingle mutants; their effects appear additive. Both the notochord and floor plate are completely lacking, and other phenotypic disturbances suggest that midline signaling functions are severely reduced. On the other hand, trunk midline defects inflh;ntldouble mutants are not additive, but are most often similar to those inntlsingle mutants. This finding reveals that loss ofntlfunction can suppress phenotypic defects due to mutation atflh,and we interpret it to mean that the wild-type allele ofntl(ntl+) functions upstream toflhin a regulatory hierarchy. Loss of function ofntlalso strongly suppresses the floor plate deficiency incycmutants, for we found trunk floor plate to be present incyc;ntldouble mutants. From these findings we propose thatntl+plays an early role in cell fate choice at the dorsal midline, mediated by the Ntl protein acting to antagonize floor plate development as well as to promote notochord development

The Cosmology Large Angular Scale Surveyor

The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array designed to characterize relic primordial gravitational waves from inflation and the optical depth to reionization through a measurement of the polarized cosmic microwave background (CMB) on the largest angular scales. The frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high atmospheric emission and span the minimum of the polarized Galactic foregrounds: synchrotron emission at lower frequencies and dust emission at higher frequencies. Low-noise transition edge sensor detectors and a rapid front-end polarization modulator provide a unique combination of high sensitivity, stability, and control of systematics. The CLASS site, at 5200 m in the Chilean Atacama desert, allows for daily mapping of up to 70\% of the sky and enables the characterization of CMB polarization at the largest angular scales. Using this combination of a broad frequency range, large sky coverage, control over systematics, and high sensitivity, CLASS will observe the reionization and recombination peaks of the CMB E- and B-mode power spectra. CLASS will make a cosmic variance limited measurement of the optical depth to reionization and will measure or place upper limits on the tensor-to-scalar ratio, $r$, down to a level of 0.01 (95\% C.L.)