California Institute of Technology

About: California Institute of Technology is a education organization based out in Pasadena, California, United States. It is known for research contribution in the topics: Galaxy & Population. The organization has 57649 authors who have published 146691 publications receiving 8620287 citations. The organization is also known as: Caltech & Cal Tech.

New Hubble Space Telescope Discoveries of Type Ia Supernovae at z ≥ 1: Narrowing Constraints on the Early Behavior of Dark Energy*

Abstract: We have discovered 21 new Type Ia supernovae (SNe Ia) with the Hubble Space Telescope (HST) and have used them to trace the history of cosmic expansion over the last 10 billion yr. These objects, which include 13 spectroscopicallyconfirmedSNeIaat z � 1,werediscoveredduring14epochsofreimagingoftheGOODSfieldsNorthand South over 2 yr with the Advanced Camera for Surveys on HST. Together with a recalibration of our previous HSTdiscovered SNe Ia, the full sample of 23 SNe Ia at z � 1 provides the highest redshift sample known. Combining these data with previous SN Ia data sets, we measured Hz ðÞ at discrete, uncorrelated epochs, reducing the uncertainty of Hz >1 ðÞ from 50% to under 20%, strengthening the evidence for a cosmic jerk—the transition from deceleration in the past to acceleration in thepresent. The uniqueleverage of theHSThigh-redshift SNe Ia provides thefirstmeaningful constraint on the dark energy equation-of-state parameter at z � 1. The result remains consistent with a cosmological constant [ wz ðÞ ¼� 1] and rules out rapidly evolving dark energy (dw/dz 31). The defining property of dark energy, its negative pressure, appears to be present at z > 1, in the epoch preceding acceleration, with � 98% confidenceinourprimaryfit.Moreover,thez > 1sample-averagedspectralenergydistributionisconsistentwiththat of thetypicalSNIaoverthelast10Gyr,indicatingthatanyspectralevolutionofthepropertiesof SNeIawithredshift is still below our detection threshold.

The Cosmic Evolution Survey (COSMOS): Overview*

Abstract: The Cosmic Evolution Survey (COSMOS) is designed to probe the correlated evolution of galaxies, star formation, active galactic nuclei (AGNs), and dark matter (DM) with large-scale structure (LSS) over the redshift range z > 0.5-6. The survey includes multiwavelength imaging and spectroscopy from X-ray-to-radio wavelengths covering a 2 deg^2 area, including HST imaging. Given the very high sensitivity and resolution of these data sets, COSMOS also provides unprecedented samples of objects at high redshift with greatly reduced cosmic variance, compared to earlier surveys. Here we provide a brief overview of the survey strategy, the characteristics of the major COSMOS data sets, and a summary the science goals.

Sickle Cell Anemia, a Molecular Disease

Abstract: The erythrocytes of certain individuals possess the capacity to undergo reversible changes in shape in response to changes in the partial pressure of oxygen. When the oxygen pressure is lowered, these cells change their forms from the normal biconcave disk to crescent, holly wreath, and other forms. This process is known as sickling. About 8 percent of American Negroes possess this characteristic; usually they exhibit no pathological consequences ascribable to it. These people are said to have sicklemia, or sickle cell trait. However, about 1 in 40 (4) of these individuals whose cells are capable of sickling suffer from a severe chronic anemia resulting from excessive destruction of their erythrocytes; the term sickle cell anemia is applied to their condition.

Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies: Evaluation Number 18

Abstract: This is the eighteenth in a series of evaluated sets of rate constants, photochemical cross sections, heterogeneous parameters, and thermochemical parameters compiled by the NASA Panel for Data Evaluation. The data are used primarily to model stratospheric and upper tropospheric processes, with particular emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena. The evaluation is available in electronic form from the following Internet URL: http://jpldataeval.jpl.nasa.gov/