Radio Observations of Infrared Luminous High Redshift QSOs

We present Very Large Array (VLA) observations at 1.4 GHz and 5 GHz of a sample of 12 Quasi-stellar Objects (QSOs) at z = 3.99 to 4.46. The sources were selected as the brightest sources at 250 GHz from the recent survey of Omont et al. (2001). We detect seven sources at 1.4 GHz with flux densities, S_{1.4} > 50 microJy. These centimeter (cm) wavelength observations imply that the millimeter (mm) emission is most likely thermal dust emission. The radio-through-optical spectral energy distributions for these sources are within the broad range defined by lower redshift, lower optical luminosity QSOs. For two sources the radio continuum luminosities and morphologies indicate steep spectrum, radio loud emission from a jet-driven radio source. For the remaining 10 sources the 1.4 GHz flux densities, or limits, are consistent with those expected for active star forming galaxies. If the radio emission is powered by star formation in these systems, then the implied star formation rates are of order 1e3 M_solar/year. We discuss the angular sizes and spatial distributions of the radio emitting regions, and we consider briefly these results in the context of co-eval black hole and stellar bulge formation in galaxies.Comment: to appear in the A

The Deficit of Distant Galaxy Clusters in the RIXOS X-ray Survey

Clusters of galaxies are the largest gravitationally bound systems and therefore provide an important way of studying the formation and evolution of the large scale structure of the Universe. Cluster evolution can be inferred from observations of the X-ray emission of the gas in distant clusters, but interpreting these data is not straightforward. In a simplified view, clusters grow from perturbations in the matter distribution: their intracluster gas is compressed and shock-heated by the gravitational collapse$^{1}$. The resulting X-ray emission is determined by the hydrostatic equilibrium of the gas in the changing gravitational potential. However, if processes such as radiative cooling or pre-collapse heating of the gas are important, then the X-ray evolution will be strongly influenced by the thermal history of the gas. Here we present the first results from a faint flux-limited sample of X-ray selected clusters compiled as part of the ROSAT International X-ray and Optical Survey (RIXOS). Very few distant clusters have been identified. Most importantly, their redshift distribution appears to be inconsistent with simple models based on the evolution of the gravitational potential. Our results suggest that radiative cooling or non-gravitational heating of the intracluster gas must play an important role in the evolution of clusters.Comment: uuencoded compressed postscript. The preprint is also available at http://www.ast.cam.ac.uk/preprint/PrePrint.htm

The external benefits of higher education

The private market benefits of education are widely studied at the micro level, although the magnitude of their macroeconomic impact is disputed. However, there are additional benefits of education, which are less well understood. In this paper the macroeconomic effects of external benefits of higher education are estimated using the “micro-to-macro” simulation approach. Two types of externalities are explored: technology spillovers and productivity spillovers in the labour market. These links are illustrated and the results suggest they could be very large. However, this is qualified by the dearth of microeconomic evidence, for which we hope to encourage further work

Exercises for improving quick perception grades I, II, III.

Thesis (Ed.M.)--Boston University N.B.: Page 242 is misnumbered. No content is missing from thesis

Total energy calculation of high pressure selenium: The origin of incommensurate modulations in Se-IV and the instability of proposed Se-II

We present calculation of the high pressure crystal structures in selenium, including rational approximants to the recently reported incommensurate phases. We show how the incommensurate phases can be intuitively explained in terms of imaginary phonon frequencies arising from Kohn anomalies in the putative undistorted phase. We also find inconsistencies between the calculated and experimental Se-II phase - the calculations show it to be a metastable metal while the experiment finds a stable semiconductor. We propose that the experimentally reported structure is probably in error.Comment: 4 pages 4 figure

Resolving the Submillimeter Background: the 850-micron Galaxy Counts

Recent deep blank field submillimeter surveys have revealed a population of luminous high redshift galaxies that emit most of their energy in the submillimeter. The results suggest that much of the star formation at high redshift may be hidden to optical observations. In this paper we present wide-area 850-micron SCUBA data on the Hawaii Survey Fields SSA13, SSA17, and SSA22. Combining these new data with our previous deep field data, we establish the 850-micron galaxy counts from 2 mJy to 10 mJy with a >3-sigma detection limit. The area coverage is 104 square arcmin to 8 mJy and 7.7 square arcmin to 2.3 mJy. The differential 850-micron counts are well described by the function n(S)=N_0/(a+S^3.2), where S is the flux in mJy, N_0=3.0 x 10^4 per square degree per mJy, and a=0.4-1.0 is chosen to match the 850-micron extragalactic background light. Between 20 to 30 per cent of the 850-micron background resides in sources brighter than 2 mJy. Using an empirical fit to our >2 mJy data constrained by the EBL at lower fluxes, we argue that the bulk of the 850-micron extragalactic background light resides in sources with fluxes near 1 mJy. The submillimeter sources are plausible progenitors of the present-day spheroidal population.Comment: 5 pages, accepted by The Astrophysical Journal Letter

Optical and X-ray properties of the RIXOS AGN: II - Emission lines

We present the optical and UV emission line properties of 160 X-ray selected AGN taken from the RIXOS survey (including Halpha, Hbeta, [OIII]5007, MgII2798 and CIII]1909). This sample is believed to contain a mixture of absorbed and unabsorbed objects, with column densities up to 4e21 cm-2. Although the distribution of the [OIII] EW for the RIXOS AGN is typical of optically selected samples, the Balmer line EWs are relatively low. This is consistent with the presence of a dust absorber between the broad and narrow line regions (eg. a molecular torus), and intrinsically weak optical line emission. We find Baldwin effects in CIII] and MgII, and a positive response of the MgII line to its ionizing continuum. There is a strong correlation between the EW and FWHM of MgII, which may be similar to that seen in other samples for Hbeta. We demonstrate that this is consistent with models which suggest two line-emitting zones, a `very broad line region' (VBLR) and an `intermediate line region' (ILR). The correlation between EW and FWHM in MgII may be a physical characteristic of the ILR or it may reflect a geometric dependence. We found no correlation between the Hbeta FWHM and the slope of the X-ray spectrum, however this may be due to the effects of dust absorption which suppresses the broad Hbeta component, masking any relationship. The Halpha FWHM does tend to be narrow when alpha_X is soft, and broadens as alpha_X hardens, although the formal probability for this correlation is low (91 per cent). If the distribution of alpha_X in the RIXOS sample reflects the level of intrinsic absorption in these AGN, the data suggest a possible link between the velocity of the Balmer line-emitting region and the amount of absorbing material beyond.Comment: 29 pages, 14 figures, to be published in Monthly Notices of the Royal Astronomical Society. Also available from http://www.mssl.ucl.ac.uk/www_astro/preprints/preprints.htm

TarO : a target optimisation system for structural biology

This work was funded by the UK Biotechnology and Biological Sciences Research Council (BBSRC) Structural Proteomics of Rational Targets (SPoRT) initiative, (Grant BBS/B/14434). Funding to pay the Open Access publication charges for this article was provided by BBSRC.TarO (http://www.compbio.dundee.ac.uk/taro) offers a single point of reference for key bioinformatics analyses relevant to selecting proteins or domains for study by structural biology techniques. The protein sequence is analysed by 17 algorithms and compared to 8 databases. TarO gathers putative homologues, including orthologues, and then obtains predictions of properties for these sequences including crystallisation propensity, protein disorder and post-translational modifications. Analyses are run on a high-performance computing cluster, the results integrated, stored in a database and accessed through a web-based user interface. Output is in tabulated format and in the form of an annotated multiple sequence alignment (MSA) that may be edited interactively in the program Jalview. TarO also simplifies the gathering of additional annotations via the Distributed Annotation System, both from the MSA in Jalview and through links to Dasty2. Routes to other information gateways are included, for example to relevant pages from UniProt, COG and the Conserved Domains Database. Open access to TarO is available from a guest account with private accounts for academic use available on request. Future development of TarO will include further analysis steps and integration with the Protein Information Management System (PIMS), a sister project in the BBSRC Structural Proteomics of Rational Targets initiative.Publisher PDFPeer reviewe

Hyperplastic Polyps Are Innocuous Lesions in Hereditary Nonpolyposis Colorectal Cancers

Aims. To compare methylation profiles, protein expression, and microsatellite instability (MSI) of sporadic, HNPCC, and familial hyperplastic polyps (HPs). Methods. Methylation-specific PCR (MSP) and pyrosequencing assessed p16, MGMT, hMLH-1, MINT 1, and MINT 31 methylation. IHC (Immunohistochemistry) assessed Ki67, CK20, hMLH-1, hMSH-2, and hMSH-6 protein expression. MSI analysis was performed on those polyps with adequate DNA remaining. Results. 124 HPs were identified 78 sporadic, 21 HNPCC, 25 familial, and the HNPCC group demonstrated no significant differences in overall methylation (P = .186 Chi2). The familial group demonstrated significantly less over all methylation levels (P = .004 Chi2). Conclusions. HPs that occur in HNPCC have no more worrying features at a molecular level than those patients with HPs in a sporadic setting