On the Inheritance of Resistance to Fowl Typhoid in Chickens

Studies at the Iowa Experiment Station during 1927 and 1928 indicate very clearly that selection is effective in increasing resistance to this disease

The Inheritance of Leg-Feathering in the Chicken

The inheritance of leg-feathering in crosses of the Black Langshan (feathered) with the White Plymouth Rock and Buff Orpington breeds (non-feathered) has been found to be dependent upon two dominant duplicate factors (S1 and S2). This relationship has been verified from data secured from F2 and backcross generations. Of five F1 males used in these studies three proved to be heterozygous for both factors S1 and S2 and two for but one of these factors, while six F1 females proved to be heterozygous for both factors and ten for but one factor. These data indicate, therefore, that the Black Langshan is often heterozygous for at least one pair of these factors

Simultaneous X-ray and Ultraviolet Observations of the SW Sextantis Star DW Ursae Majoris

We present the first pointed X-ray observation of DW Ursae Majoris, a novalike cataclysmic variable (CV) and one of the archetype members of the SW Sextantis class, obtained with the XMM-Newton satellite. These data provide the first detailed look at an SW Sex star in the X-ray regime (with previous X-ray knowledge of the SW Sex stars limited primarily to weak or non-detections in the ROSAT All Sky Survey). It is also one of only a few XMM-Newton observations (to date) of any high mass transfer rate novalike CV, and the only one in the evolutionarily important 3-4 hr orbital period range. The observed X-ray spectrum of DW UMa is very soft, with ~95% of the detected X-ray photons at energies <2 keV. The spectrum can be fit equally well by a one-component cooling flow model, with a temperature range of 0.2-3.5 keV, or a two-component, two-temperature thermal plasma model, containing hard (~5-6 keV) and soft (~0.8 keV) components. The X-ray light curve of DW UMa shows a likely partial eclipse, implying X-ray reprocessing in a vertically extended region, and an orbital modulation, implying a structural asymmetry in the X-ray reprocessing site (e.g., it cannot be a uniform corona). We also obtained a simultaneous near-ultraviolet light curve of DW UMa using the Optical Monitor on XMM-Newton. This light curve is similar in appearance to published optical-UV light curves of DW UMa and shows a prominent deep eclipse. Regardless of the exact nature of the X-ray reprocessing site in DW UMa, the lack of a prominent hard X-ray total eclipse and very low fraction of high energy X-rays point to the presence of an optically and geometrically thick accretion disk that obscures the boundary layer and modifies the X-ray spectrum emitted near the white dwarf

A Self-Occulting Accretion Disk in the SW Sex Star DW UMa

We present the ultraviolet spectrum of the SW Sex star and nova-like variable DW UMa in an optical low state, as observed with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope (HST). The data are well described by a synthetic white dwarf (WD) spectrum with T_eff = 46,000 +/- 1000 K, log g = 7.60 +/- 0.15, v*sin(i) = 370 +/- 100 km/s and Z/Z_solar = 0.47 +/- 0.15. For this combination of T_eff and log g, WD models predict M_WD = 0.48 +/- 0.06 M_solar and R_WD = (1.27 +/- 0.18) * 10^9 cm. Combining the radius estimate with the normalization of the spectral fit, we obtain a distance estimate of d = 830 +/-150 pc. During our observations, DW UMa was approximately 3 magnitudes fainter in V than in the high state. A comparison of our low-state HST spectrum to a high-state spectrum obtained with the International Ultraviolet Explorer shows that the former is much bluer and has a higher continuum level shortward of 1450 A. Since DW UMa is an eclipsing system, this suggests that an optically thick accretion disk rim blocks our view of the WD primary in the high state. If self-occulting accretion disks are common among the SW Sex stars, we can account for (i) the preference for high-inclination systems within the class and (ii) their V-shaped continuum eclipses. Moreover, even though the emission lines produced by a self-obscured disk are generally still double-peaked, they are weaker and narrower than those produced by an unobscured disk. This may allow a secondary line emission mechanism to dominate and produce the single-peaked, optical lines that are a distinguishing characteristic of the SW Sex stars.Comment: 9 pages, including 2 figures; accepted for publication in Astrophysical Journal Letters; New version matches version in press (footnote added to discussion section; figures now use color

Excitonic resonances in the 2D extended Falicov-Kimball model

Using the projector-based renormalization method we investigate the formation of the excitonic insulator phase in the two-dimensional (2D) spinless Falicov-Kimball model with dispersive $f$ electrons and address the existence of excitonic bound states at high temperatures on the semiconductor side of the semimetal-semiconductor transition. To this end we calculate the imaginary part of the dynamical electron-hole pair susceptibility and analyze the wave-vector and energy dependence of excitonic resonances emerging in the band gap. We thereby confirm the existence of the exciton insulator and its exciton environment within a generic two-band lattice model with local Coulomb attraction.Comment: 6 pages, 5 figures, final versio

Observations of the SW Sextantis star DW Ursae Majoris with the Far Ultraviolet Spectroscopic Explorer

We present an analysis of the first far-ultraviolet observations of the SW Sextantis-type cataclysmic variable DW Ursae Majoris, obtained in November 2001 with the Far Ultraviolet Spectroscopic Explorer. The time-averaged spectrum of DW UMa shows a rich assortment of emission lines (plus some contamination from interstellar absorption lines including molecular hydrogen). Accretion disk model spectra do not provide an adequate fit to the far-ultraviolet spectrum of DW UMa. We constructed a light curve by summing far-ultraviolet spectra extracted in 60-sec bins; this shows a modulation on the orbital period, with a maximum near photometric phase 0.93 and a minimum half an orbit later. No other periodic variability was found in the light curve data. We also extracted spectra in bins spanning 0.1 in orbital phase; these show substantial variation in the profile shapes and velocity shifts of the emission lines during an orbital cycle of DW UMa. Finally, we discuss possible physical models that can qualitatively account for the observed far-ultraviolet behavior of DW UMa, in the context of recent observational evidence for the presence of a self-occulting disk in DW UMa and the possibility that the SW Sex stars may be the intermediate polars with the highest mass transfer rates and/or weakest magnetic fields.Comment: accepted by the Astronomical Journal; 36 pages, including 12 figures and 4 table

Searching For Integrated Sachs-Wolfe Effect Beyond Temperature Anisotropies: CMB E-mode Polarization-Galaxy Cross Correlation

The cross-correlation between cosmic microwave background (CMB) temperature anisotropies and the large scale structure (LSS) traced by the galaxy distribution, or sources at different wavelengths, is now well known. This correlation results from the integrated Sachs-Wolfe (ISW) effect in CMB anisotropies generated at late times due to the dark energy component of the Universe. In a reionized universe, the ISW quadrupole rescatters and contributes to the large-scale polarization signal. Thus, in principle, the large-scale polarization bump in the E-mode should also be correlated with the galaxy distribution. Unlike CMB temperature-LSS correlation that peaks for tracers at low redshifts this correlation peaks mostly at redshifts between 1 and 3. Under certain conditions, mostly involving a low optical depth to reionization, if the Universe reionized at a redshift around 6, the cross polarization-source signal is marginally detectable, though challenging as it requires all-sky maps of the large scale structure at redshifts between 1 and 3. If the Universe reionized at a redshift higher than 10, it is unlikely that this correlation will be detectable even with no instrumental noise all-sky maps. While our estimates do not guarantee a detection unknown physics related to the dark energy as well as still uncertain issues related to the large angular scale CMB and polarization anisotropies may motivate attempts to measure this correlation using upcoming CMB polarization E-mode maps.Comment: 13 pages; 3 figure panels, JCAP submitte

The Imprint of Gravitational Waves in Models Dominated by a Dynamical Cosmic Scalar Field

An alternative to the standard cold dark matter model has been recently proposed in which a significant fraction of the energy density of the universe is due to a dynamical scalar field ($Q$) whose effective equation-of-state differs from that of matter, radiation or cosmological constant ($\Lambda$). In this paper, we determine how the Q-component modifies the primordial inflation gravitational wave (tensor metric) contribution to the cosmic microwave background anisotropy and, thereby, one of the key tests of inflation.Comment: 15 pages, 14 figures, revtex, submitted to Phys. Rev.