University of California, Santa Cruz

About: University of California, Santa Cruz is a education organization based out in Santa Cruz, California, United States. It is known for research contribution in the topics: Galaxy & Population. The organization has 15541 authors who have published 44120 publications receiving 2759983 citations. The organization is also known as: UCSC & UC, Santa Cruz.

Damped Lyman alpha Systems

Abstract: Observations of damped Lyman alpha systems offer a unique window on the neutral-gas reservoirs that gave rise to galaxies at high redshifts. This review focuses on critical properties such as the H I and metal content of the gas and on independent evidence for star formation. Together, these provide an emerging picture of gravitationally bound objects in which accretion of gas from the IGM replenishes gas consumed by star formation. Other properties such as dust content, molecular content, ionized-gas content, gas kinematics, and galaxy identifications are also reviewed. These properties point to a multiphase ISM in which radiative and hydrodynamic feedback processes are present. Numerical simulations and other types of models used to describe damped Lyman alpha systems within the context of galaxy formation are also discussed.

General considerations for skin test procedures in the diagnosis of drug hypersensitivity

Abstract: K. Brockow, A. Romano, M. Blanca, J. Ring, W. Pichler, P. Demoly Klinik und Poliklinik fur Dermatologie und Allergologie, Muenchen, Germany; Department of Internal Medicine and Geriatrics, UCSC, Allergy Unit, CI Columbus, Rome and IRCS Oasi Maria SS, Troina, Italy; Research Unit for Allergic Diseases, Carlos Haya Hospital, Malaga, Spain; Clinic for Rheumatology and Clinical Immunology/Allergology, Inselspital, Bern, Switzerland; Maladies Respiratoires, Hopital Arnaud de Villeneuve, Montpellier, France

The mass assembly history of field galaxies: detection of an evolving mass limit for star forming galaxies

Abstract: We characterize the mass-dependent evolution of more than 8000 galaxies using spectroscopic redshifts from the DEEP2 Galaxy Redshift Survey in the range 0.4 < z < 1.4 and stellar masses calculated from K-band photometry obtained at Palomar Observatory. This sample spans more than 1.5 deg^2 in four independent fields. Using rest-frame U - B color and [O II] equivalent widths, we distinguish star-forming from passive populations in order to explore the nature of "downsizing"—a pattern in which the sites of active star formation shift from high-mass galaxies at early times to lower mass systems at later epochs. We identify a mass limit, M_Q, above which star formation appears to be quenched and show that the physical mechanisms responsible for downsizing can thus be empirically quantified by charting the evolution in this threshold mass. We find that M_Q decreases with time by a factor of ~3 across our redshift range according to M_Q α (1 + z)^(3.5). To further constrain possible quenching mechanisms, we investigate how downsizing depends on local galaxy environment using the projected third-nearest-neighbor statistic D_(p,3). For the majority of galaxies near the median density, there is no significant correlation between downsizing and environment. However, a trend is observed in the comparison between environments that are more than 3 times overdense or underdense relative to the median. Here, downsizing appears accelerated in overdense regions that host higher numbers of massive, early-type galaxies as compared to the underdense regions. Our results significantly constrain recent suggestions for the origin of downsizing and indicate that the process for quenching star formation must, primarily, be internally driven

Unusual resistance of peptidyl transferase to protein extraction procedures

Abstract: Peptidyl transferase, the ribosomal activity responsible for catalysis of peptide bond formation, is resistant to vigorous procedures that are conventionally employed to remove proteins from protein-nucleic acid complexes. When the "fragment reaction" was used as a model assay for peptide bond formation, Escherichia coli ribosomes or 50S subunits retained 20 to 40 percent activity after extensive treatment with proteinase K and SDS, but lost activity after extraction with phenol or exposure to EDTA. Ribosomes from the thermophilic eubacterium Thermus aquaticus remained more than 80 percent active after treatment with proteinase K and SDS, which was followed by vigorous extraction with phenol. This activity is attributable to peptidyl transferase, as judged by specific inhibition by the peptidyl transferase-specific antibiotics chloramphenicol and carbomycin. In contrast, activity is abolished by treatment with ribonuclease T1. These findings support the possibility that 23S ribosomal RNA participates in the peptidyl transferase function.