@article{4259, abstract = {We extend current multilocus models to describe the effects of migration, recombination, selection, and nonrandom mating on sets of genes in diploids with varied modes of inheritance, allowing us to consider the patterns of nuclear and cytonuclear associations (disequilibria) under various models of migration. We show the relationship between the multilocus notation recently presented by Kirkpatrick, Johnson, and Barton (developed from previous work by Barton and Turelli) and the cytonuclear parameterization of Asmussen, Arnold, and Avise and extend this notation to describe associations between cytoplasmic elements and multiple nuclear genes. Under models with sexual symmetry, both nuclear-nuclear and cytonuclear disequilibria are equivalent. They differ, however, in cases involving some type of sexual asymmetry, which is then reflected in the asymmetric inheritance of cytoplasmic markers. An example given is the case of different migration rates in males and females; simulations using 2, 3, 4, or 5 unlinked autosomal markers with a maternally inherited cytoplasmic marker illustrate how nuclear-nuclear and cytonuclear associations can be used to separately estimate female and male migration rates. The general framework developed here allows us to investigate conditions where associations between loci with different modes of inheritance are not equivalent and to use this nonequivalence to test for deviations from simple models of admixture. }, author = {Orive, Maria and Barton, Nicholas H}, issn = {0016-6731}, journal = {Genetics}, number = {3}, pages = {1469 -- 1485}, publisher = {Genetics Society of America}, title = {{Associations between cytoplasmic and nuclear loci in hybridizing populations}}, doi = {10.1093/genetics/162.3.1469}, volume = {162}, year = {2002}, } @article{4260, abstract = {We calculate the fixation probability of a beneficial allele that arises as the result of a unique mutation in an asexual population that is subject to recurrent deleterious mutation at rate U. Our analysis is an extension of previous works, which make a biologically restrictive assumption that selection against deleterious alleles is stronger than that on the beneficial allele of interest. We show that when selection against deleterious alleles is weak, beneficial alleles that confer a selective advantage that is small relative to U have greatly reduced probabilities of fixation. We discuss the consequences of this effect for the distribution of effects of alleles fixed during adaptation. We show that a selective sweep will increase the fixation probabilities of other beneficial mutations arising during some short interval afterward. We use the calculated fixation probabilities to estimate the expected rate of fitness improvement in an asexual population when beneficial alleles arise continually at some low rate proportional to U. We estimate the rate of mutation that is optimal in the sense that it maximizes this rate of fitness improvement. Again, this analysis relaxes the assumption made previously that selection against deleterious alleles is stronger than on beneficial alleles. }, author = {Johnson, Toby and Barton, Nicholas H}, issn = {0016-6731}, journal = {Genetics}, number = {1}, pages = {395 -- 411}, publisher = {Genetics Society of America}, title = {{The effect of deleterious alleles on adaptation in asexual populations}}, doi = {10.1093/genetics/162.1.395}, volume = {162}, year = {2002}, } @article{4261, abstract = {Until recently, it was impracticable to identify the genes that are responsible for variation in continuous traits, or to directly observe the effects of their different alleles. Now, the abundance of genetic markers has made it possible to identify quantitative trait loci (QTL) — the regions of a chromosome or, ideally, individual sequence variants that are responsible for trait variation. What kind of QTL do we expect to find and what can our observations of QTL tell us about how organisms evolve? The key to understanding the evolutionary significance of QTL is to understand the nature of inherited variation, not in the immediate mechanistic sense of how genes influence phenotype, but, rather, to know what evolutionary forces maintain genetic variability.}, author = {Barton, Nicholas H and Keightley, Peter}, issn = {1471-0056}, journal = {Nature Reviews Genetics}, pages = {11 -- 21}, publisher = {Nature Publishing Group}, title = {{Understanding quantitative genetic variation}}, doi = {10.1038/nrg700}, volume = {3}, year = {2002}, } @article{4262, abstract = {Natural populations are structured spatially into local populations and genetically into diverse ‘genetic backgrounds’ defined by different combinations of selected alleles. If selection maintains genetic backgrounds at constant frequency then neutral diversity is enhanced. By contrast, if background frequencies fluctuate then diversity is reduced. Provided that the population size of each background is large enough, these effects can be described by the structured coalescent process. Almost all the extant results based on the coalescent deal with a single selected locus. Yet we know that very large numbers of genes are under selection and that any substantial effects are likely to be due to the cumulative effects of many loci. Here, we set up a general framework for the extension of the coalescent to multilocus scenarios and we use it to study the simplest model, where strong balancing selection acting on a set of n loci maintains 2n backgrounds at constant frequencies and at linkage equilibrium. Analytical results show that the expected linked neutral diversity increases exponentially with the number of selected loci and can become extremely large. However, simulation results reveal that the structured coalescent approach breaks down when the number of backgrounds approaches the population size, because of stochastic fluctuations in background frequencies. A new method is needed to extend the structured coalescent to cases with large numbers of backgrounds.}, author = {Barton, Nicholas H and Navarro, Arcadio}, issn = {0016-6723}, journal = {Genetical Research}, number = {2}, pages = {129 -- 139}, publisher = {Cambridge University Press}, title = {{Extending the coalescent to multilocus systems: the case of balancing selection}}, doi = {10.1017/S0016672301005493}, volume = {79}, year = {2002}, } @article{4263, abstract = {We introduce a general recursion for the probability of identity in state of two individuals sampled from a population subject to mutation, migration, and random drift in a two-dimensional continuum. The recursion allows for the interactions induced by density-dependent regulation of the population, which are inevitable in a continuous population. We give explicit series expansions for large neighbourhood size and for low mutation rates respectively and investigate the accuracy of the classical Malécot formula for these general models. When neighbourhood size is small, this formula does not give the identity even over large scales. However, for large neighbourhood size, it is an accurate approximation which summarises the local population structure in terms of three quantities: the effective dispersal rate, σe; the effective population density, ρe; and a local scale, κ, at which local interactions become significant. The results are illustrated by simulations.}, author = {Barton, Nicholas H and Depaulis, Frantz and Etheridge, Alison}, issn = {0040-5809}, journal = {Theoretical Population Biology}, number = {1}, pages = {31 -- 48}, publisher = {Academic Press}, title = {{Neutral evolution in spatially continuous populations}}, doi = {10.1006/tpbi.2001.1557}, volume = {61}, year = {2002}, } @article{1737, abstract = {A new solvent-free composite polymer electrolyte consisting of high-molecular mass polyethylene oxide (PEO) filled with titanium oxide and containing LiI and I2 was developed. The introduction of the inorganic filler (TiO2 Degussa P25) into the polymer matrix produces dramatic morphological changes to the host polymer structure. Upon addition of the inorganic oxide, the surface roughness increases, with respect to the original polymer and in parallel, the fractal dimension decreases. Both the thermograms and the atomic force microscope (AFM) pictures confirm the amorphicity of the composite electrolyte. The polymer sub-units are held together in a parallel orientation, forming straight long chains of about 500 nm in width, along which TiO2 spherical particles of about 20-25 nm in diameter are distributed. The polymer chains separated by the titania particles are arranged in a three-dimensional, mechanically stable network, that creates free space and voids into which the iodide/triodide anions can easily migrate. All solid-state dye-sensitized solar cells fabricated using this composite electrolyte present high efficiencies (typical maximum incident photon to current efficiency (IPCE) as high as 40% at 520 nm and overall conversion efficiency (η) of 0.96% (Voc = 0.67 V, Jsc = 2.050 mA/cm2, FF = 39%) under direct solar irradiation. Further improvement of the photovoltaic performance is expected by optimization of the electrolyte parameters and of the cell assembly.}, author = {Katsaros, Georgios and Stergiopoulos, Thomas and Arabatzis, Iannis and Papadokostaki, Kyriaki and Falaras, Polycarpos}, issn = {1010-6030}, journal = {Journal of Photochemistry and Photobiology A: Chemistry}, number = {1-3}, pages = {191 -- 198}, publisher = {Elsevier}, title = {{A solvent-free composite polymer/inorganic oxide electrolyte for high efficiency solid-state dye-sensitized solar cells}}, doi = {10.1016/S1010-6030(02)00027-8}, volume = {149}, year = {2002}, } @inproceedings{1738, abstract = {New dyes of the type Ru(II)(bdmpp)(bpy) [where bdmpp is 2,6-bis(3,5-dimethyl-N-pyrazoyl)pyridine and bpy is 2,2′-bipyridine-4,4′-dicarboxylic acid] are prepared and characterized by infra-red (IR), mass (MS) and electrospray mass spectroscopy (ES-MS) as well as 1H NMR (1D and 2D) spectroscopies. The compounds present broad and very high intensity MLCT absorption bands in the visible and can be chemically anchored on TiO2 films via ester-like linkage involving carboxylato groups. These complexes have been tested with success as potential molecular antennas in dye-sensitized solar cells. Both opaque and transparent nanocrystalline TiO2 thin film electrodes obtained by a doctor blade technique sensitized by these complexes were incorporated in a sandwich type regenerative photoelectrochemical solar cell containing 0.1M LiI +0.01M I2 in propylene carbonate as well as a platinized conductive glass counter electrode. The cell was characterized by Raman spectroscopy under anodic and cathodic bias. Two new vibration bands were observed in the lower frequency region. The first one at 112 cm-1 is due to tri-iodide formed on the photoactive electrode, and the second one at 167 cm-1 is a sign of the dye/iodide interaction and corresponds to a vibration in a chemically stable "DI" intermediate species. Under direct sunlight illumination (solar irradiance of 60 mW/cm2) by using a composite polymer solid state electrolyte, the cell ITO/TiO2/[Ru(II)(bdmpp)(bpy)(NCS)](PF6)/electrolyte/Pt-ITO produced a continuous photocurrent as high as 4.29mA/cm2, and gave IPCE values about half of the corresponding values obtained by the standard N3 dye under the same conditions. The photovoltage is about 600 mV and the overall energy conversion cell's efficiency is as high as 1.72%.}, author = {Falaras, Polycarpos and Chryssou, Katerina and Stergiopoulos, Thomas and Arabatzis, Ioannis M and Georgios Katsaros and Catalano, Vincent J and Kurtaran, Raif and Hugot-Le Goff, Anne and Bernard, Marie C}, pages = {125 -- 135}, publisher = {SPIE}, title = {{Dye-sensitization of titanium dioxide thin films by Ru(II)-bpp-bpy complexes}}, doi = {10.1117/12.452446}, volume = {4801}, year = {2002}, } @article{1739, abstract = {Poly(ethylene oxide)/titania polymer electrolyte based photoelectrochemical cells have been fabricated with Ru(dcbpy)2(NCS)2 complex as the sensitizer and nanoporous TiO2 films as photoanodes. The introduction of the titania filler into the poly(ethylene oxide) matrix reduces the crystallinity of the polymer and enhances the mobility of the 1-/13 - redox couple, resulting in outstanding overall conversion efficiency (4.2% under direct sunlight illumination) of the corresponding dye-sensitized nanocrystalline TiO2 solar cell, one of the best efficiencies reported to date for a solid-state device.}, author = {Stergiopoulos, Thomas and Arabatzis, Iannis M and Georgios Katsaros and Falaras, Polycarpos}, journal = {Nano Letters}, number = {11}, pages = {1259 -- 1261}, publisher = {American Chemical Society}, title = {{Binary Polyethylene Oxide/Titania Solid-State Redox Electrolyte for Highly Efficient Nanocrystalline TiO2 Photoelectrochemical Cells}}, doi = {10.1021/nl025798u}, volume = {2}, year = {2002}, } @article{17723, abstract = {The recent discovery of bright quasars around redshift z=6 suggests that black holes (BHs) with masses in excess of 10^9 Msun have already assembled at a very early stage in the evolution of the universe. An alternative interpretation is that these quasars are powered by less massive BHs, but their fluxes are strongly magnified through gravitational lensing by intervening galaxies. Here we analyze the flux distribution of the Ly alpha emission of the quasar with the highest known redshift, SDSS 1030+0524, at z=6.28. We show that this object could not have been magnified by lensing by more than a factor of five. The constraint arises from the large observed size, 30 (comoving) Mpc, of the ionized region around this quasar, and relies crucially only on the assumption that the quasar is embedded in a largely neutral IGM. Based on the line/continuum ratio of SDSS 1030+0524, we argue further that this quasar also cannot be beamed by a significant factor. We conclude that the minimum mass for its resident BH is 4 x 10^8 Msun (for magnification by a factor of five); if the mass is this low, then the quasars had to switch on prior to redshift z=9. From the size of the ionized region, we are also able to place an absolute lower bound on the age of this quasar at t > 2 x 10^7 years.}, author = {Haiman, Zoltán and Cen, Renyue}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {702--707}, publisher = {American Astronomical Society}, title = {{A constraint on the gravitational lensing magnification and age of the redshift z = 6.28 Quasar SDSS 1030+0524}}, doi = {10.1086/342610}, volume = {578}, year = {2002}, } @article{17739, abstract = {An extensive sample of galaxy clusters will be available in the coming years, detected through their Sunyaev-Zeldovich effect (SZE). We use a semianalytic model to study the scientific yield of combining SZE data with X-ray and optical follow-up observations. If clusters at a given redshift z0 can be identified with virialized, spherical halos, they populate a well-defined "fundamental plane" (FP) in the parameter space of the three observables virial temperature (T), total Sunyaev-Zeldovich flux decrement (ΔSν), and angular size (θ). The location and orientation of the FP, as well as its redshift evolution, are sensitive to both the internal evolution of clusters and to the underlying cosmological parameters. We show that if clusters are not standard candles (e.g., because of feedback or energy injection), then this can be inferred from the FP. Likewise, we study the dependence of the FP on the cosmological parameters h, σ8, and Ω0, and quantify future constraints on these parameters. We also show that in the absence of any nongravitational effects, the scatter in the (ΔSν,T)-plane is significantly smaller than in either the (θ,T) or the (θ,ΔSν) planes. As a result, the ΔSν-T relation can be an exceptionally sensitive probe of both cluster physics and cosmological parameters. A comparison of the amount of scatter in these three scaling relations will test the origin (cosmological vs. stochastic) of the scatter.}, author = {Verde, Licia and Haiman, Zoltán and Spergel, David N.}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {5--19}, publisher = {American Astronomical Society}, title = {{Are clusters standard candles? Galaxy cluster scaling relations with the Sunyaev‐Zeldovich effect}}, doi = {10.1086/344134}, volume = {581}, year = {2002}, } @article{17746, abstract = {For a source of Lyα radiation embedded in a neutral intergalactic medium (IGM) prior to the reionization epoch, the Lyα emission line is strongly suppressed by the intervening IGM. The damping wing of the so-called Gunn-Peterson trough can extend to the red side of the emission line and erase a significant fraction of the total line flux. However, the transmitted fraction increases with the size of the local cosmological H II region surrounding the source, and therefore with the ionizing luminosity and age of the source. Motivated by the recent discovery of a Lyα-emitting galaxy at a redshift z = 6.56 (Hu et al.), possibly prior to the reionization of the IGM, we revisit the effects of a neutral IGM on the Lyα emission line. We show that for faint sources with little or even no ionizing continuum, a sufficiently broad (Δv ≳ 300 km s^-1) emission line can still remain observable. In particular, the line detected by Hu et al. is consistent with a source embedded in a neutral IGM. We provide characterizations of the asymmetry and total transmitted flux of the Lyα line as functions of the ionizing emissivity of its source. We argue that a statistical sample of Lyα emitters extending beyond the reionization redshift can be a useful probe of reionization.}, author = {Haiman, Zoltán}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {1}, pages = {L1--L4}, publisher = {American Astronomical Society}, title = {{The detectability of high-redshift Lyα emission lines prior to the reionization of the universe}}, doi = {10.1086/343101}, volume = {576}, year = {2002}, } @article{17779, abstract = {The first generation of stars is thought to have formed in low-mass halos with Tvir < 10^4 K where H2 cooling is paramount. However, the efficiency of H2 formation and cooling in these halos may have been severely limited by feedback processes. In this paper we investigate the radiative cooling and collapse of halos with virial temperatures Tvir > 10^4 K, i.e., those that can cool in the absence of H2 via neutral atomic lines. The evolution of these halos differs from their less massive counterparts. Efficient atomic line radiation allows rapid cooling to ~8000 K; subsequently the gas can contract nearly isothermally at this temperature. In the absence of H2 molecules, the gas would likely settle into a locally stable disk, and only disks with unusually low spin would be unstable. However, we find that the initial atomic line cooling leaves a large, out-of-equilibrium residual free electron fraction. This allows the molecular fraction to build up to a universal value of x ≈ 10^-3, almost independently of initial density and temperature. We show that this is a nonequilibrium freeze-out value that can be understood in terms of timescale arguments. Unlike in less massive halos, H2 formation and cooling is largely impervious to feedback from external UV fields, due to the high initial densities achieved by atomic cooling. The newly formed molecules cool the gas further to ~100 K and allow the gas to fragment on scales of a few times 100 M☉. We investigate the importance of various feedback effects such as H2 photodissociation from internal UV fields and radiation pressure due to Lyα photon trapping, which are likely to regulate the efficiency of star formation.}, author = {Oh, S. Peng and Haiman, Zoltán}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, pages = {558--572}, publisher = {American Astronomical Society}, title = {{Second‐generation objects in the universe: Radiative cooling and collapse of halos with virial temperatures above 10^4 K}}, doi = {10.1086/339393}, volume = {569}, year = {2002}, } @article{17798, abstract = {Recent discoveries by the Sloan Digital Sky Survey (SDSS) of four bright z ~ 6 quasars could constrain the mechanism by which the supermassive black holes powering these sources are assembled. Here we compute the probability that the fluxes of the quasars are strongly amplified by gravitational lensing and therefore the likelihood that the black hole masses are overestimated when they are inferred assuming Eddington luminosities. The poorly constrained shape of the intrinsic quasar luminosity function (LF) at redshift ~6 results in a large range of possible lensing probabilities. If the LF is either steep or extends to faint magnitudes, the probability for amplification by a factor μ ≳ 10 (and with only one image detectable by SDSS) can reach essentially 100%. We show that future observations, in particular, of either the current four quasars at the high angular resolution provided by the Hubble Space Telescope or an increased sample of ~20 z ~ 6 quasars at the current angular resolution, should either discover several gravitational lenses or else provide interesting new constraints on the shape of the z ~ 6 quasar LF.}, author = {Comerford, Julia M. and Haiman, Zoltán and Schaye, Joop}, issn = {1538-4357}, journal = {The Astrophysical Journal}, pages = {63--72}, publisher = {American Astronomical Society}, title = {{Constraining the Redshift z ~ 6 quasar luminosity function using gravitational lensing}}, doi = {10.1086/343116}, volume = {580}, year = {2002}, } @article{17799, abstract = {The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of ≈106 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg2 of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux- and wavelength-calibrated, with 4096 pixels from 3800 to 9200 Å at R ≈ 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.}, author = {Stoughton, Chris and Lupton, Robert H. and Bernardi, Mariangela and Blanton, Michael R. and Burles, Scott and Castander, Francisco J. and Connolly, A. J. and Eisenstein, Daniel J. and Frieman, Joshua A. and Hennessy, G. S. and Hindsley, Robert B. and Ivezić, Željko and Kent, Stephen and Kunszt, Peter Z. and Lee, Brian C. and Meiksin, Avery and Munn, Jeffrey A. and Newberg, Heidi Jo and Nichol, R. C. and Nicinski, Tom and Pier, Jeffrey R. and Richards, Gordon T. and Richmond, Michael W. and Schlegel, David J. and Smith, J. Allyn and Strauss, Michael A. and SubbaRao, Mark and Szalay, Alexander S. and Thakar, Aniruddha R. and Tucker, Douglas L. and Vanden Berk, Daniel E. and Yanny, Brian and Adelman, Jennifer K. and Anderson, Jr., John E. and Anderson, Scott F. and Annis, James and Bahcall, Neta A. and Bakken, J. A. and Bartelmann, Matthias and Bastian, Steven and Bauer, Amanda and Berman, Eileen and Böhringer, Hans and Boroski, William N. and Bracker, Steve and Briegel, Charlie and Briggs, John W. and Brinkmann, J. and Brunner, Robert and Carey, Larry and Carr, Michael A. and Chen, Bing and Christian, Damian and Colestock, Patrick L. and Crocker, J. H. and Csabai, István and Czarapata, Paul C. and Dalcanton, Julianne and Davidsen, Arthur F. and Davis, John Eric and Dehnen, Walter and Dodelson, Scott and Doi, Mamoru and Dombeck, Tom and Donahue, Megan and Ellman, Nancy and Elms, Brian R. and Evans, Michael L. and Eyer, Laurent and Fan, Xiaohui and Federwitz, Glenn R. and Friedman, Scott and Fukugita, Masataka and Gal, Roy and Gillespie, Bruce and Glazebrook, Karl and Gray, Jim and Grebel, Eva K. and Greenawalt, Bruce and Greene, Gretchen and Gunn, James E. and de Haas, Ernst and Haiman, Zoltán and Haldeman, Merle and Hall, Patrick B. and Hamabe, Masaru and Hansen, Brad and Harris, Frederick H. and Harris, Hugh and Harvanek, Michael and Hawley, Suzanne L. and Hayes, J. J. E. and Heckman, Timothy M. and Helmi, Amina and Henden, Arne and Hogan, Craig J. and Hogg, David W. and Holmgren, Donald J. and Holtzman, Jon and Huang, Chih-Hao and Hull, Charles and Ichikawa, Shin-Ichi and Ichikawa, Takashi and Johnston, David E. and Kauffmann, Guinevere and Kim, Rita S. J. and Kimball, Tim and Kinney, E. and Klaene, Mark and Kleinman, S. J. and Klypin, Anatoly and Knapp, G. R. and Korienek, John and Krolik, Julian and Kron, Richard G. and Krzesiński, Jurek and Lamb, D. Q. and Leger, R. French and Limmongkol, Siriluk and Lindenmeyer, Carl and Long, Daniel C. and Loomis, Craig and Loveday, Jon and MacKinnon, Bryan and Mannery, Edward J. and Mantsch, P. M. and Margon, Bruce and McGehee, Peregrine and McKay, Timothy A. and McLean, Brian and Menou, Kristen and Merelli, Aronne and Mo, H. J. and Monet, David G. and Nakamura, Osamu and Narayanan, Vijay K. and Nash, Thomas and Neilsen, Jr., Eric H. and Newman, Peter R. and Nitta, Atsuko and Odenkirchen, Michael and Okada, Norio and Okamura, Sadanori and Ostriker, Jeremiah P. and Owen, Russell and Pauls, A. George and Peoples, John and Peterson, R. S. and Petravick, Donald and Pope, Adrian and Pordes, Ruth and Postman, Marc and Prosapio, Angela and Quinn, Thomas R. and Rechenmacher, Ron and Rivetta, Claudio H. and Rix, Hans-Walter and Rockosi, Constance M. and Rosner, Robert and Ruthmansdorfer, Kurt and Sandford, Dale and Schneider, Donald P. and Scranton, Ryan and Sekiguchi, Maki and Sergey, Gary and Sheth, Ravi and Shimasaku, Kazuhiro and Smee, Stephen and Snedden, Stephanie A. and Stebbins, Albert and Stubbs, Christopher and Szapudi, István and Szkody, Paula and Szokoly, Gyula P. and Tabachnik, Serge and Tsvetanov, Zlatan and Uomoto, Alan and Vogeley, Michael S. and Voges, Wolfgang and Waddell, Patrick and Walterbos, René and Wang, Shu-i and Watanabe, Masaru and Weinberg, David H. and White, Richard L. and White, Simon D. M. and Wilhite, Brian and Wolfe, David and Yasuda, Naoki and York, Donald G. and Zehavi, Idit and Zheng, Wei}, issn = {1538-3881}, journal = {The Astronomical Journal}, number = {1}, pages = {485--548}, publisher = {American Astronomical Society}, title = {{Sloan digital sky survey: Early data release}}, doi = {10.1086/324741}, volume = {123}, year = {2002}, } @article{17802, abstract = {The Sloan Digital Sky Survey has confirmed the existence of populations of broad absorption line (BAL) quasars with various unusual properties. We present and discuss 23 such objects and consider the implications of their wide range of properties for models of BAL outflows and quasars in general. We have discovered one BAL quasar with a record number of absorption lines. Two other similarly complex objects with many narrow troughs show broad Mg II absorption extending longward of their systemic host galaxy redshifts. This can be explained as absorption of an extended continuum source by the rotation-dominated base of a disk wind. Five other objects have absorption that removes an unprecedented ∼90% of all flux shortward of Mg II. The absorption in one of them has varied across the ultraviolet with an amplitude and rate of change as great as ever seen. This same object may also show broad Hβ absorption. Numerous reddened BAL quasars have been found, including at least one reddened mini-BAL quasar with very strong Fe II emission. The five reddest objects have continuum reddenings of E(B-V) ≃ 0.5, and in two of them we find strong evidence that the reddening curve is even steeper than that of the SMC. We have found at least one object with absorption from Fe III but not Fe II. This may be due to a high column density of moderately high ionization gas, but the Fe III level populations must also be affected by some sort of resonance. Finally, we have found two luminous, probably reddened high-redshift objects that may be BAL quasars whose troughs partially cover different regions of the continuum source as a function of velocity.}, author = {Hall, Patrick B. and Anderson, Scott F. and Strauss, Michael A. and York, Donald G. and Richards, Gordon T. and Fan, Xiaohui and Knapp, G. R. and Schneider, Donald P. and Vanden Berk, Daniel E. and Geballe, T. R. and Bauer, Amanda E. and Becker, Robert H. and Davis, Marc and Rix, Hans‐Walter and Nichol, R. C. and Bahcall, Neta A. and Brinkmann, J. and Brunner, Robert and Connolly, A. J. and Csabai, Istvan and Doi, Mamoru and Fukugita, Masataka and Gunn, James E. and Haiman, Zoltán and Harvanek, Michael and Heckman, Timothy M. and Hennessy, G. S. and Inada, Naohisa and Ivezić, Željko and Johnston, David and Kleinman, S. and Krolik, Julian H. and Krzesinski, Jurek and Kunszt, Peter Z. and Lamb, D. Q. and Long, Daniel C. and Lupton, Robert H. and Miknaitis, Gajus and Munn, Jeffrey A. and Narayanan, Vijay K. and Neilsen, Eric and Newman, P. R. and Nitta, Atsuko and Okamura, Sadanori and Pentericci, Laura and Pier, Jeffrey R. and Schlegel, David J. and Snedden, S. and Szalay, Alexander S. and Thakar, Anirudda R. and Tsvetanov, Zlatan and White, Richard L. and Zheng, Wei}, issn = {1538-4365}, journal = {The Astrophysical Journal Supplement Series}, number = {2}, pages = {267--309}, publisher = {American Astronomical Society}, title = {{Unusual broad absorption line quasars from the sloan digital sky survey}}, doi = {10.1086/340546}, volume = {141}, year = {2002}, } @article{17803, abstract = {We reassess constraints on the cosmological baryon density from observations of the mean decrement and power spectrum of the Lyα forest, taking into account uncertainties in all free parameters in the simplest gravitational instability model. The uncertainty is dominated by that of the photoionizing background, but incomplete knowledge of the thermal state of the intergalactic medium also contributes significantly to the error budget. While current estimates of the baryon fraction from the forest do prefer values that are somewhat higher than the big bang nucleosynthesis value of Ωb h2 = 0.02 ± 0.001, the discrepancy is at most about 3 σ. For instance, assuming the highest estimate of the ionizing background, as indicated by recent measurements of a large escape fraction from Lyman break galaxies by Steidel, Pettini, & Adelberger, we find Ωbh2 = 0.045 ± 0.008. A recent measurement of the ionizing background from the proximity effect by Scott et al., on the other hand, implies Ωbh2 = 0.03 ± 0.01. We provide an expression from which future likelihoods for Ωb h2 can be derived as measurements of the ionizing background improve—consistency among constraints from the forest, nucleosynthesis, and the microwave background will provide a powerful test of the gravitational instability model for the forest and for large-scale structure in general. We also develop a formalism that treats lower bounds on the baryon density in a statistical manner, which is appropriate if only a lower bound on the ionizing background is known. Finally, we discuss the implications of the escape fraction measurement for the age, structure, and stellar content of Lyman break galaxies. We show that the observed hard spectrum from Lyman break galaxies requires a very young age (less than about 1 million years) and/or a top-heavy initial mass function. We also build a model in which an extended (non-disk-like) gas distribution allows a large escape fraction.}, author = {Hui, Lam and Haiman, Zoltán and Zaldarriaga, Matias and Alexander, Tal}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, pages = {525--533}, publisher = {American Astronomical Society}, title = {{Connections between the cosmic baryon fraction, the extragalactic ionizing background, and Lyman break galaxies}}, doi = {10.1086/324401}, volume = {564}, year = {2002}, } @article{18369, author = {Bronstein, Michael M. and Bronstein, Alexander}, issn = {0028-0836}, journal = {Nature}, number = {6917}, pages = {739--739}, publisher = {Springer Nature}, title = {{Biometrics was no match for hair-raising tricks}}, doi = {10.1038/420739a}, volume = {420}, year = {2002}, } @inproceedings{18382, abstract = {Detection of high-energy photons emitted as the result of positron decay is one of the most important low-level stages in PET imaging. In this paper we consider a detector based on the Anger scintillation camera. Incident high-energy gamma quanta, generated due to positron decay, produce scintillation effect in the crystal. As a result, a shower of low energy photons in the visible and UV spectra is emitted. These photons are collected by an array of photo-multipliers (PMTs), optically coupled to the scintillation crystal, and invoke electric impulses in them. The PMT responses are utilized in estimation of the scintillation point coordinates. Our work incorporates side information on the photon incidence angle into the process of position estimation. We use localized, asymptotically optimal, nonlinear estimators, implemented by feedforward and radial basis function (RBF) neural networks. As a byproduct, we get accurate position estimation over the entire area of the detector including the edges. This is difficult to obtain with centroid arithmetic algorithms. We present a comparison of algorithms on a Monte Carlo simulation and discuss the prospects for practical implementation.}, author = {Bronstein, Alexander and Bronstein, M.M. and Zibulevsky, M. and Zeevi, Y.Y.}, booktitle = {The 22nd Convention on Electrical and Electronics Engineers in Israel}, isbn = {0780376935}, location = {Tel-Aviv, Israel}, pages = {341--344}, publisher = {IEEE}, title = {{Optimal non-linear line-of-flight estimation in positron emission tomography}}, doi = {10.1109/eeei.2002.1178493}, volume = {2002-January}, year = {2002}, } @inproceedings{18383, author = {Bronstein, M.M. and Bronstein, Alexander and Zibulevsky, M. and Azhari, H.}, booktitle = {The 22nd Convention on Electrical and Electronics Engineers in Israel}, isbn = {0780376935}, location = {Tel-Aviv, Israel}, pages = {345--347}, publisher = {IEEE}, title = {{Application of the NUFFT for reconstruction problems in diffraction tomography}}, doi = {10.1109/eeei.2002.1178495}, volume = {2002-January}, year = {2002}, } @inproceedings{18404, abstract = {We consider detection of high-energy photons in PET using thick scintillation crystals. Parallax effect and multiple Compton interactions in this type of crystals significantly reduce the accuracy of conventional detection methods. In order to estimate the scintillation point coordinates based on photomultiplier responses, we use asymptotically optimal nonlinear techniques, implemented by feed-forward neural networks, radial basis functions (RBF) networks, and neuro-fuzzy systems. Incorporation of information about angles of incidence of photons, significantly improves accuracy of estimation. The proposed estimators are fast enough to perform detection, using conventional computers.}, author = {Bronstein, Alexander and Bronstein, M. and Zibulevsky, M. and Zeevi, Y.Y.}, booktitle = {Proceedings IEEE International Symposium on Biomedical Imaging}, isbn = {078037584X}, location = {Washington, DC, United States}, pages = {541--544}, publisher = {IEEE}, title = {{Optimal nonlinear estimation of photon coordinates in PET}}, doi = {10.1109/isbi.2002.1029314}, volume = {2002-January}, year = {2002}, }