Measuring the Radiative Histories of QSOs with the Transverse Proximity Effect

Since the photons that stream from QSOs alter the ionization state of the gas they traverse, any changes to a QSO's luminosity will produce outward-propagating ionization gradients in the surrounding intergalactic gas. This paper shows that at redshift z~3 the gradients will alter the gas's Lyman-alpha absorption opacity enough to produce a detectable signature in the spectra of faint background galaxies. By obtaining noisy (S:N~4) low-resolution (~7A) spectra of a several dozen background galaxies in an R~20' field surrounding an isotropically radiating 18th magnitude QSO at z=3, it should be possible to detect any order-of-magnitude changes to the QSO's luminosity over the previous 50--100 Myr and to measure the time t_Q since the onset of the QSO's current luminous outburst with an accuracy of ~5 Myr for t_Q<~50 Myr. Smaller fields-of-view are acceptable for shorter QSO lifetimes. The major uncertainty, aside from cosmic variance, will be the shape and orientation of the QSO's ionization cone. This can be determined from the data if the number of background sources is increased by a factor of a few. The method will then provide a direct test of unification models for AGN.Comment: Accepted for publication in the ApJ. 16 page

Heating in the Accreted Neutron Star Ocean: Implications for Superburst Ignition

We perform a self-consistent calculation of the thermal structure in the crust of a superbursting neutron star. In particular, we follow the nucleosynthetic evolution of an accreted fluid element from its deposition into the atmosphere down to a depth where the electron Fermi energy is 20 MeV. We include temperature-dependent continuum electron capture rates and realistic sources of heat loss by thermal neutrino emission from the crust and core. We show that, in contrast to previous calculations, electron captures to excited states and subsequent gamma-emission significantly reduce the local heat loss due to weak-interaction neutrinos. Depending on the initial composition these reactions release up to a factor of 10 times more heat at densities < 10^{11} g/cc than obtained previously. This heating reduces the ignition depth of superbursts. In particular, it reduces the discrepancy noted by Cumming et al. between the temperatures needed for unstable 12C ignition on timescales consistent with observations and the reduction in crust temperature from Cooper pair neutrino emission.Comment: 10 pages, 11 figures, the Astrophysical Journal, in press (scheduled for v. 662). Revised from v1 in response to referee's comment

Aging predicts decline in explicit and implicit memory: a life-span study

Explicit memory declines with age, but age effects on implicit memory are debated. This issue is important because if implicit memory is age-invariant, it may support effective interventions in individuals experiencing memory decline. This study overcame several methodological issues in past research to clarify age effects on implicit memory (priming) and their relationship to explicit memory (recognition, source memory). It aimed to (1) recruit a large lifespan sample of participants (N=1072) during a residency at the Science Museum, London, (2) employ an implicit task that is unaffected by explicit contamination, and (3) systematically manipulate depth-of-processing and attention to assess their contribution to age effects. Participants witnessed a succession of overlapping colored objects, attending to one colour stream and ignoring the other, and at test identified masked objects before judging whether they were previously attended, unattended, or new. Age significantly predicted decline in both explicit and implicit memory for attended objects

First Results from the Large Area Lyman Alpha Survey

We report on a new survey for z=4.5 Lyman alpha sources, the Large Area Lyman Alpha (LALA) survey. Our survey achieves an unprecedented combination of volume and sensitivity by using narrow-band filters on the new 8192x8192 pixel CCD Mosaic Camera at the 4 meter Mayall telescope of Kitt Peak National Observatory. Well-detected sources with flux and equivalent width matching known high redshift Lyman alpha galaxies (i.e., observed equivalent width above 80 Angstroms and line+continuum flux between 2.6e-17 and 5.2e-17 erg/cm^2/sec in an 80 Angstrom filter) have an observed surface density corresponding to 11000 +- 700 per square degree per unit redshift at z=4.5. Spatial variation in this surface density is apparent on comparison between counts in 6561 and 6730 Angstrom filters. Early spectroscopic followup results from the Keck telescope included three sources meeting our criteria for good Lyman alpha candidates. Of these, one is confirmed as a z=4.52 source, while another remains consistent with either z=4.55 or z=0.81. We infer that 30 to 50% of our good candidates are bona fide Lyman alpha emitters, implying a net density of about 4000 Lyman alpha galaxies per square degree per unit redshift.Comment: 10 pages, 2 figures (3 .ps files), uses AASTeX 4. Submitted to The Astrophysical Journal Letter

Seeking the Ultraviolet Ionizing Background at z~3 with the Keck Telescope

We describe the initial results of a deep long-slit emission line search for redshifted (2.7<z<4.1) Lyman-alpha. These observations are used to constrain the fluorescent Ly-alpha emission from the population of clouds whose absorption produces the higher-column-density component of the Ly-alpha forest in quasar spectra. We use the results to set an upper limit on the ultraviolet ionizing background. Our spectroscopic data obtained with the Keck II telescope at lambda/(Delta lambda FWHM)~2000 reveals no candidate Ly-alpha emission over the wavelength range of 4500-6200 Ang along a 3 arcmin slit in a 5400 s integration. Our 3 sigma upper bound on the mean intensity of the ionizing background at the Lyman limit is J(nu 0) < 2E-21 erg/s/cm**2/Hz/sr for 2.7<z<3.1 (where we are most sensitive), assuming Lyman limit systems have typical radii of 70 kpc (q_0=0.5, H_0=50 km/s/Mpc). This constraint is more than an order of magnitude more stringent than any previously published direct limit. However, it is still a factor of three above the ultraviolet background level expected due to the integrated light of known quasars at z~3. This pilot study confirms the conclusion of Gould \& Weinberg (1996) that integrations of several hours on a 10-m class telescope should be capable of measuring J(nu 0) at high redshift.Comment: 22 pages, 2 postscipt figures. Latex requires aaspp4.sty and epsf.sty (included). Accepted for publication in the Astronomical Journal (Nov 1998

Deuterium-Stabilized (R)-Pioglitazone, PXL065, for Treatment of X-Linked Adrenoleukodystrophy (ALD)

Background and aims: X-linked Adrenoleukodystrophy (ALD) is a rare neurometabolic disorder caused by ABCD1- gene mutations, leading to Very-Long-Chain Fatty Acids (VLCFA; in particular C26:0) accumulation, inflammation, mitochondrial impairment and demyelination. PXL065, a clinical-stage deuterium-stabilized(R)-stereoisomer of pioglitazone, retains pioglitazone non-genomic actions but lacks PPARγ activity. As pioglitazone exhibits beneficial effects in ALD models and PXL065 may avoid PPARγ- related side effects, we investigated PXL065 effects of in preclinical models. Methods: Patient-derived fibroblasts and lymphocytes and Abcd1-KO mouse glial cells were exposed to PXL065 (5-10μM) and pioglitazone (10μM) for 7 days. VLCFA content was measured by mass spectrometry, selected gene expression by RT-qPCR, and mitochondrial function using a Seahorse Analyzer (after 72hr). PXL065 or pioglitazone (15mg/kg QD) were administered to 6-8-week or 13-month old Abcd1-KO mice for 8 and 12 weeks, respectively. VLCFA content (mass spectrometry), sciatic nerve axonal morphology (electronic microscopy), and locomotor function (open field test) were measured. Results: In patient and mouse glial cells, PXL065 and pioglitazone corrected C26:0, improved mitochondrial function, increased compensatory Abcd2-3 transporter gene expression, and decreased inflammatory gene expression. In Abcd1-KO mice, C26:0 levels were normalized in plasma and decreased in spinal cord (-55%, p\u3c0.01) and brain (-49%, p\u3c0.0001). Pioglitazone had no effect in spinal cord. Following PXL065 and pioglitazone treatment, abnormal axonal morphology (stellate-shaped cells) was improved but only PXL065 showed significantly improved locomotor test results. Conclusion: Despite reduced PPARγ activity, PXL065 showed substantial signs of efficacy and superior therapeutic potential vs. pioglitazone (in vivo) supporting clinical development for ALD. A Phase 2a study is planned in 2022

Ellipticals with Kinematically-Distinct Cores: (V-I) Color Images with WFPC2

We have analysed HST/WFPC2 F555W and F814W images for fifteen elliptical galaxies with kinematically-distinct cores. For each of them we have derived surface brightness and isophotal parameter profiles in the two bands, color maps, and radial profiles in (V-I). We have detected photometric evidence for faint stellar disks, on scales of a few tens to a few arcseconds, in seven galaxies, namely NGC 1427, 1439, 1700, 4365, 4406, 4494 and 5322. In NGC 1700, the isophotes are slightly boxy at the scale of the counter-rotating component, and disky at larger radii. We find no difference in (V-I) color greater than 0.02 mag between these disks and the surrounding galactic regions. Hence the stellar populations in the kinematically distinct cores are not strongly deviant from the population of the main body. For one galaxy, NGC 4365, the innermost region is bluer than the surrounding regions. This area extends to about 15pc, and contains a luminosity of 2.5x10^6 L$_\odot$. If interpreted as a stellar population effect, an age difference of $\sim$ 3-4 Gyrs, or an $[Fe/H]$ variation of about 0.2 dex, is derived. The nuclear intensity profiles show a large variety: some galaxies have steep cusp profiles, others have shallow cusps and a ``break radius''. The nuclear cusps of galaxies with kinematically-distinct cores follow the same trends as the nuclei of normal galaxies. We have not been able to identify a unique, qualifying feature in the WFPC2 images which distinguish the galaxies with kinematically distinct cores from the kinematically normal cores. [shortened]Comment: 56 pages, latex, 17 figures; figure 1 available upon request; ApJ, 481 in pres

FISSION DYNAMICS WITH MICROSCOPIC LEVEL DENSITIES

We present a consistent framework for treating the energy and angularmomentum dependence of the shape evolution in the nuclear fission. It combines microscopically calculated level densities with the Metropolis-walk method, has no new parameters, and can elucidate the energy-dependent influence of pairing and shell effects on the dynamics of warm nuclei