Probing Dark Energy via Weak Gravitational Lensing with the Supernova Acceleration Probe (SNAP)

SNAP is a candidate for the Joint Dark Energy Mission (JDEM) that seeks to place constraints on the dark energy using two distinct methods. The first, Type Ia SN, is discussed in a separate white paper. The second method is weak gravitational lensing, which relies on the coherent distortions in the shapes of background galaxies by foreground mass structures. The excellent spatial resolution and photometric accuracy afforded by a 2-meter space-based observatory are crucial for achieving the high surface density of resolved galaxies, the tight control of systematic errors in the telescope's Point Spread Function (PSF), and the exquisite redshift accuracy and depth required by this project. These are achieved by the elimination of atmospheric distortion and much of the thermal and gravity loads on the telescope. The SN and WL methods for probing dark energy are highly complementary and the error contours from the two methods are largely orthogonal. The nominal SNAP weak lensing survey covers 1000 square degrees per year of operation in six optical and three near infrared filters (NIR) spanning the range 350 nm to 1.7 {micro}m. This survey will reach a depth of 26.6 AB magnitude in each of the nine filters and allow for approximately 100 resolved galaxies per square arcminute, {approx} 3 times that available from the best ground-based surveys. Photometric redshifts will be measured with statistical accuracy that enables scientific applications for even the faint, high redshift end of the sample. Ongoing work aims to meet the requirements on systematics in galaxy shape measurement, photometric redshift biases, and theoretical predictions

Seeing the Nature of the Accelerating Physics: It's a SNAP

For true insight into the nature of dark energy, measurements of the precision and accuracy of the Supernova/Acceleration Probe (SNAP) are required. Precursor or scaled-down experiments are unavoidably limited, even for distinguishing the cosmological constant. They can pave the way for, but should not delay, SNAP by developing calibration, refinement, and systematics control (and they will also provide important, exciting astrophysics)

Expression and activity of multidrug resistance protein 1 in a murine thymoma cell line

Multidrug resistance proteins [MRPs and P-glycoprotein (Pgp)] are members of the family of ATP-binding cassette (ABC) transport proteins, originally described as being involved in the resistance against anti-cancer agents in tumour cells. These proteins act as ATP-dependent efflux pumps and have now been described in normal cells where they exert physiological roles. The aim of this work was to investigate the expression and activity of MRP and Pgp in the thymoma cell line, EL4. It was observed that EL4 cells expressed mRNA for MRP1, but not for MRP2, MRP3 or Pgp. The activity of ABC transport proteins was evaluated by using the efflux of the fluorescent probes carboxy-2′-7′-dichlorofluorescein diacetate (CFDA) and rhodamine 123 (Rho 123). EL4 cells did not retain CFDA intracellularly, and MRP inhibitors (probenecid, indomethacin and MK 571) decreased MRP1 activity in a concentration-dependent manner. As expected, EL4 cells accumulated Rho 123, and the presence of cyclosporin A and verapamil did not modify this accumulation. Most importantly, when EL4 cells were incubated in the presence of the MRP1 inhibitors indomethacin and MK 571 for 6 days, they started to express CD4 and CD8 molecules on their surface, producing double-positive cells and CD8 single-positive cells. Our results suggest that MRP activity is important for the maintenance of the undifferentiated state in this cell type. This finding might have implications in the physiological process of normal thymocyte maturation

Supernova Acceleration Probe: Studying Dark Energy with Type Ia Supernovae

The Supernova Acceleration Probe (SNAP) will use Type Ia supernovae (SNe Ia) as distance indicators to measure the effect of dark energy on the expansion history of the Universe. (SNAP's weak-lensing program is described in a separate White Paper.) The experiment exploits supernova distance measurements up to their fundamental systematic limit; strict requirements on the monitoring of each supernova's properties leads to the need for a space-based mission. Results from pre-SNAP experiments, which characterize fundamental SN Ia properties, will be used to optimize the SNAP observing strategy to yield data, which minimize both systematic and statistical uncertainties. With early R&D funding, we have achieved technological readiness and the collaboration is poised to begin construction. Pre-JDEM AO R&D support will further reduce technical and cost risk. Specific details on the SNAP mission can be found in Aldering et al. (2004, 2005). The primary goal of the SNAP supernova program is to provide a dataset which gives tight constraints on parameters which characterize the dark-energy, e.g. w{sub 0} and w{sub a} where w(a) = w{sub 0} + w{sub a}(1-a). SNAP data can also be used to directly test and discriminate among specific dark energy models. We will do so by building the Hubble diagram of high-redshift supernovae, the same methodology used in the original discovery of the acceleration of the expansion of the Universe that established the existence of dark energy (Perlmutter et al. 1998; Garnavich et al. 1998; Riess et al. 1998; Perlmutter et al. 1999). The SNAP SN Ia program focuses on minimizing the systematic floor of the supernova method through the use of characterized supernovae that can be sorted into subsets based on subtle signatures of heterogeneity. Subsets may be defined based on host-galaxy morphology, spectral-feature strength and velocity, early-time behavior, inter alia. Independent cosmological analysis of each subset of ''like'' supernovae can be compared to give confidence that the results are free from significant systematics. Conversely, analysis between supernova subsets at the same redshift can identify further systematics controls. While theories of the supernova progenitor and explosion mechanism can guide the establishment of subset criteria, such understanding is not required--only comprehensive measurements are--for robustness of the cosmological results. The level of robustness is tied to the quality of data with which supernovae are distinguished. Statistical mission requirements are fundamentally bound by the systematic limitations of the experiment

Time-dependent in-situ neutron diffraction investigation of a Li(Co 0.16Mn1.84)O4 cathode

10.1021/jp2026237Journal of Physical Chemistry C1154321473-2148