Evaluation of a planned program of word analysis in grade two

Thesis (Ed.M.)--Boston Universit

Probing the Reionization History of the Universe using the Cosmic Microwave Background Polarization

The recent discovery of a Gunn--Peterson (GP) trough in the spectrum of the redshift 6.28 SDSS quasar has raised the tantalizing possibility that we have detected the reionization of the universe. However, a neutral fraction (of hydrogen) as small as 0.1% is sufficient to cause the GP trough, hence its detection alone cannot rule out reionization at a much earlier epoch. The Cosmic Microwave Background (CMB) polarization anisotropy offers an alternative way to explore the dark age of the universe. We show that for most models constrained by the current CMB data and by the discovery of a GP trough (showing that reionization occurred at z > 6.3), MAP can detect the reionization signature in the polarization power spectrum. The expected 1-sigma error on the measurement of the electron optical depth is around 0.03 with a weak dependence on the value of that optical depth. Such a constraint on the optical depth will allow MAP to achieve a 1-sigma error on the amplitude of the primordial power spectrum of 6%. MAP with two years (Planck with one year) of observation can distinguish a model with 50% (6%) partial ionization between redshifts of 6.3 and 20 from a model in which hydrogen was completely neutral at redshifts greater than 6.3. Planck will be able to distinguish between different reionization histories even when they imply the same optical depth to electron scattering for the CMB photons.Comment: ApJ version. Added Figure 2 and reference

Testing General Relativity with Atom Interferometry

The unprecedented precision of atom interferometry will soon lead to laboratory tests of general relativity to levels that will rival or exceed those reached by astrophysical observations. We propose such an experiment that will initially test the equivalence principle to 1 part in 10^15 (300 times better than the current limit), and 1 part in 10^17 in the future. It will also probe general relativistic effects--such as the non-linear three-graviton coupling, the gravity of an atom's kinetic energy, and the falling of light--to several decimals. Further, in contrast to astrophysical observations, laboratory tests can isolate these effects via their different functional dependence on experimental variables.Comment: 4 pages, 1 figure; v2: Minor changes made for publicatio

Efficient operation of a high-power X-band gyroklystron

Experimental studies of amplification in a two-cavity X-band gyroklystron are reported. The system utilizes a thermionic magnetron injection gun at voltages up to 440 kV and currents up to 190 A in 1-μs pulses. Optimum performance is achieved by tapering the magnetic-field profile. Peak powers of 20 MW in the TE01 mode at 9.87 GHz are measured with calibrated crystals and with methanol calorimetry. Resultant efficiencies are in excess of 31% and large-signal gains surpass 26 dB. The experimental results are in good agreement with simulated results from a partially self-consistent, nonlinear, steady-state code

Effects of leukemia inhibitory factor on 3T3-L1 adipocytes

Leukemia inhibitory factor (LIF) is a member of the gp130 cytokine family and signals through the receptor complex of gp130 and the LIF receptor (LIFR) to activate the JAK/STAT signaling cascade. Since LIF activates STATs 1 and 3 in adipocytes, we examined the effects of LIF on 3T3-L1 adipocytes. Our studies clearly demonstrate that LIF treatment had minimal effects on adipocyte differentiation as judged by marker gene expression, but did inhibit triacylglyceride (TAG) accumulation during adipogenesis. Acute treatment with LIF resulted in increased expression of suppressors of cytokine signaling-3 (SOCS3) and CCAAT/enhancer-binding protein-δ (C/EBPδ) mRNA in 3T3-L1 adipocytes. Moreover, the upregulation of C/EBPδ correlated with binding to three sites in the C/EBPδ promoter by LIF-activated protein complexes that contained STAT1 and not STAT3. Chronic treatment with LIF resulted in decreased protein levels of sterol regulatory element binding protein-1 (SREBP1) and fatty acid synthase (FAS), but had no effect on the expression of other adipocyte marker proteins or on TAG levels in mature 3T3-L1 adipocytes. LIF had a small effect on insulin-stimulated glucose uptake in 3T3-L1 adipocytes, but did not cause insulin resistance following chronic treatment. These findings indicate that LIF has similar and distinct effects in comparison with the effects of other gp130 cytokines on cultured fat cells. In summary, our results support a role for LIF in the regulation of proteins involved in lipid synthesis and in the modulation of signal transduction pathways in 3T3-L1 adipocytes. © 2005 Society for Endocrinology

The regulation of fatty acid synthase by STAT5A

Growth hormone (GH) diminishes adipose tissue mass in vivo and decreases expression and activity of fatty acid synthase (FAS) in adipocytes. GH and prolactin (PRL) are potent activators of STAT5 and exert adipogenic and antiadipogenic effects in adipocytes. In this study, we demonstrate that GH and PRL decrease the mRNA and protein levels of FAS in 3T3-L1 adipocytes. We present evidence that indicates that FAS is repressed at the level of transcription. In addition, PRL responsiveness was shown to exist between -1,594 and -700 of the rat FAS promoter. Moreover, responsiveness to PRL was abolished with mutation of a site at position -908 to -893, which we have shown to bind STAT5A in a PRL-dependent manner. Taken together, these data strongly suggest that PRL directly represses expression of FAS in adipocytes through STAT5A binding to the -908 to -893 site. Furthermore, our results indicate that STAT5A has an antilipogenic function in adipocytes and may contribute to the regulation of energy balance. © 2005 by the American Diabetes Association