The enigmatic He-sdB pulsator LS IV−-14∘^\circ116: new insights from the VLT

The intermediate Helium subdwarf B star LS IV$-$14$^\circ$116 is a unique object showing extremely peculiar atmospheric abundances as well as long-period pulsations that cannot be explained in terms of the usual opacity mechanism. One hypothesis invoked was that a strong magnetic field may be responsible. We discredit this possibility on the basis of FORS2 spectro-polarimetry, which allows us to rule out a mean longitudinal magnetic field down to 300 G. Using the same data, we derive the atmospheric parameters for LS IV$-$14$^\circ$116 to be $T_{\rm eff}$ = 35,150$\pm$111 K, $\log{g}$ = 5.88$\pm$0.02 and $\log{N(\rm He)/N(\rm H)}$ = $-$0.62$\pm$0.01. The high surface gravity in particular is at odds with the theory that LS IV$-$14$^\circ$116 has not yet settled onto the Helium Main Sequence, and that the pulsations are excited by an $\epsilon$ mechanism acting on the Helium-burning shells present after the main Helium flash. Archival UVES spectroscopy reveals LS IV$-$14$^\circ$116 to have a radial velocity of 149.1$\pm$2.1 km/s. Running a full kinematic analysis, we find that it is on a retrograde orbit around the Galactic centre, with a Galactic radial velocity component $U$=13.23$\pm$8.28 km/s and a Galactic rotational velocity component $V$=$-$55.56$\pm$22.13 km/s. This implies that LS IV$-$14$^\circ$116 belongs to the halo population, an intriguing discovery.Comment: accepted for publication in A&

A Prospective Longitudinal Assessment of Medical Records for Diagnostic Substitution among Subjects Diagnosed with a Pervasive Developmental Disorder in the United States

Background: Previously, investigators suggested that diagnostic substitution from other diagnoses, e.g., mental retardation (MR) and/or cerebral palsy (CP) to pervasive developmental disorder (PDD) is a driving factor behind increases in PDD. This study evaluated potential diagnostic substitution among subjects diagnosed with PDD vs MR or CP by examining birth characteristic overlap.Methods: SAS® and StatsDirect software examined medical records for subjects within the Vaccine Safety Datalink (VSD) database who were Health Maintenance Organization (HMO)-enrolled from birth until diagnosed with an International Classification of Disease, 9th revision (ICD-9) outcome of PDD (299.xx, n=84), CP (343.xx, n=300), or MR (317.xx, 318.xx, or 319.xx, n=51).Results: Subjects with PDD had significantly (p<0.01) increased: male/female ratio (PDD=5.5 vs CP=1.5 or MR=1.3), mean age of initial diagnosis in years (PDD=3.13 vs CP=1.09 or MR=1.62), mean gestational age in weeks at birth (PDD=38.73 vs CP=36.20 or MR=34.84), mean birth weight in grams (PDD=3,368 vs CP=2,767 or MR=2,406), and mean Appearance-Pulse-Grimace-Activity-Respiration (APGAR) scores at 1 minute (PDD=7.82 vs CP=6.37 or MR=6.76) and 5 minutes (PDD=8.77 vs CP=7.92 or MR=8.04), as compared to subjects diagnosed with CP or MR.Conclusion: This study suggests diagnostic substitution cannot fully explain increased PDD prevalence during the 1990s within the United States

Cooperative behavior between oscillatory and excitable units: the peculiar role of positive coupling-frequency correlations

We study the collective dynamics of noise-driven excitable elements, so-called active rotators. Crucially here, the natural frequencies and the individual coupling strengths are drawn from some joint probability distribution. Combining a mean-field treatment with a Gaussian approximation allows us to find examples where the infinite-dimensional system is reduced to a few ordinary differential equations. Our focus lies in the cooperative behavior in a population consisting of two parts, where one is composed of excitable elements, while the other one contains only self-oscillatory units. Surprisingly, excitable behavior in the whole system sets in only if the excitable elements have a smaller coupling strength than the self-oscillating units. In this way positive local correlations between natural frequencies and couplings shape the global behavior of mixed populations of excitable and oscillatory elements.Comment: 10 pages, 6 figures, published in Eur. Phys. J.

Two candidate brown dwarf companions around core helium-burning stars

Hot subdwarf stars of spectral type B (sdBs) are evolved, core helium-burning objects. The formation of those objects is puzzling, because the progenitor star has to lose almost its entire hydrogen envelope in the red-giant phase. Binary interactions have been invoked, but single sdBs exist as well. We report the discovery of two close hot subdwarf binaries with small radial velocity amplitudes. Follow-up photometry revealed reflection effects originating from cool irradiated companions, but no eclipses. The lower mass limits for the companions of CPD-64$^{\circ}$481 ($0.048\,M_{\rm \odot}$) and PHL\,457 ($0.027\,M_{\rm \odot}$) are significantly below the stellar mass limit. Hence they could be brown dwarfs unless the inclination is unfavourable. Two very similar systems have already been reported. The probability that none of them is a brown dwarf is very small, 0.02%. Hence we provide further evidence that substellar companions with masses that low are able to eject a common envelope and form an sdB star. Furthermore, we find that the properties of the observed sample of hot subdwarfs in reflection effect binaries is consistent with a scenario where single sdBs can still be formed via common envelope events, but their low-mass substellar companions do not survive.Comment: accepted to A&

A longitudinal cohort study of the relationship between Thimerosal-containing hepatitis B vaccination and specific delays in development in the United States: Assessment of attributable risk and lifetime care costs

AbstractEpidemiological evidence suggests a link between mercury (Hg) exposure from Thimerosal-containing vaccines and specific delays in development. A hypothesis-testing longitudinal cohort study (n=49,835) using medical records in the Vaccine Safety Datalink (VSD) was undertaken to evaluate the relationship between exposure to Hg from Thimerosal-containing hepatitis B vaccines (T-HBVs) administered at specific intervals in the first 6months of life and specific delays in development [International Classification of Disease, 9th revision (ICD-9): 315.xx] among children born between 1991 and 1994 and continuously enrolled from birth for at least 5.81years. Infants receiving increased Hg doses from T-HBVs administered within the first month, the first 2months, and the first 6months of life were significantly more likely to be diagnosed with specific delays in development than infants receiving no Hg doses from T-HBVs. During the decade in which T-HBVs were routinely recommended and administered to US infants (1991–2001), an estimated 0.5–1million additional US children were diagnosed with specific delays in development as a consequence of 25μg or 37.5μg organic Hg from T-HBVs administered within the first 6months of life. The resulting lifetime costs to the United States may exceed $1 trillion

Optical/near-infrared selection of red QSOs: Evidence for steep extinction curves towards galactic centers?

We present the results of a search for red QSOs using a selection based on optical imaging from SDSS and near-infrared imaging from UKIDSS. For a sample of 58 candidates 46 (79%) are confirmed to be QSOs. The QSOs are predominantly dust-reddened except a handul at redshifts z>3.5. The dust is most likely located in the QSO host galaxies. 4 (7%) of the candidates turned out to be late-type stars, and another 4 (7%) are compact galaxies. The remaining 4 objects we could not identify. In terms of their optical spectra the QSOs are similar to the QSOs selected in the FIRST-2MASS red Quasar survey except they are on average fainter, more distant and only two are detected in the FIRST survey. We estimate the amount of extinction using the SDSS QSO template reddened by SMC-like dust. It is possible to get a good match to the observed (restframe ultraviolet) spectra, but for nearly all the reddened QSOs it is not possible to match the near-IR photometry from UKIDSS. The likely reasons are that the SDSS QSO template is too red at optical wavelengths due to contaminating host galaxy light and that the assumed SMC extinction curve is too shallow. Our survey has demonstrated that selection of QSOs based on near-IR photometry is an efficent way to select QSOs, including reddened QSOs, with only small contamination from late-type stars and compact galaxies. This will be useful with ongoing and future wide-field near-IR surveys such as the VISTA and EUCLID surveys. [Abridged]Comment: 74 pages, 6 figures. Accepted for for publication in ApJ