Differential Imaging with a Multicolor Detector Assembly: A New ExoPlanet Finder Concept

Simultaneous spectral differential imaging is a high contrast technique by which subtraction of simultaneous images reduces noise from atmospheric speckles and optical aberrations. Small non-common wave front errors between channels can seriously degrade its performance. We present a new concept, a multicolor detector assembly (MCDA), which can eliminate this problem. The device consists of an infrared detector and a microlens array onto the flat side of which a checkerboard pattern of narrow-band micro-filters is deposited, each micro-filter coinciding with a microlens. Practical considerations for successful implementation of the technique are mentioned. Numerical simulations predict a noise attenuation of 10^-3 at 0.5" for a 10^5 seconds integration on a mH=5 star of Strehl ratio 0.9 taken with an 8-m telescope. This reaches a contrast of 10^-7 at an angular distance of 0.5" from the center of the star image.Comment: 13 pages, 5 figures, accepted APJ

Time-varying volatility in Canadian and U.S. stock index and index futures markets: A multivariate analysis

We use a multivariate generalized autoregressive heteroskedasticity model (M-GARCH) to examine three stock indexes and their associated futures prices: the New York Stock Exchange Composite, Standard and Poor's 500, and Toronto 35. The North American context is significant because markets in Canada and the United States share similar structures and regulatory environments. Our model allows examination of dependence in volatility as it captures time variation in volatility and cross-market influences. Estimated time-variation in volatility is significant, and the volatilities are highly positively correlated. Yet, we find that the correlation in North American index and futures markets has declined over time.Financial markets ; Futures ; Stock market

Reassessing the WIC Effect: Evidence from the Pregnancy Nutrition Surveillance System

Recent analyses differ on how effective the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) is at improving infant health. We use data from nine states that participate in the Pregnancy Nutrition Surveillance System to address limitations in previous work. With information on the mother's timing of WIC enrollment, we test whether greater exposure to WIC is associated with less smoking, improved weight gain during pregnancy, better birth outcomes, and greater likelihood of breastfeeding. Our results suggest that much of the often-reported association between WIC and lower rates of preterm birth is likely spurious, the result of gestational age bias. We find modest effects of WIC on fetal growth, inconsistent associations between WIC and smoking, limited associations with gestational weight gain, and some relationship with breast feeding. A WIC effect exists, but on fewer margins and with less impact than has been claimed by policy analysts and advocates.

Λ\LambdaCDM or self-interacting neutrinos? - how CMB data can tell the two models apart

Of the many proposed extensions to the $\Lambda$CDM paradigm, a model in which neutrinos self-interact until close to the epoch of matter-radiation equality has been shown to provide a good fit to current cosmic microwave background (CMB) data, while at the same time alleviating tensions with late-time measurements of the expansion rate and matter fluctuation amplitude. Interestingly, CMB fits to this model either pick out a specific large value of the neutrino interaction strength, or are consistent with the extremely weak neutrino interaction found in $\Lambda$CDM, resulting in a bimodal posterior distribution for the neutrino self-interaction cross section. In this paper, we explore why current cosmological data select this particular large neutrino self-interaction strength, and by consequence, disfavor intermediate values of the self-interaction cross section. We show how it is the $\ell \gtrsim 1000$ CMB temperature anisotropies, most recently measured by the Planck satellite, that produce this bimodality. We also establish that smaller scale temperature data, and improved polarization data measuring the temperature-polarization cross-correlation, will best constrain the neutrino self-interaction strength. We forecast that the upcoming Simons Observatory should be capable of distinguishing between the models.Comment: 7 pages, 7 figures, comments welcome, references added, version submitted to PR

Time-varying volatility in Canadian and U.S. stock index and index futures markets: A multivariate analysis

We use a multivariate generalized autoregressive heteroskedasticity model (M-GARCH) to examine three stock indexes and their associated futures prices: the New York Stock Exchange Composite, Standard and Poor's 500, and Toronto 35. The North American context is significant because markets in Canada and the United States share similar structures and regulatory environments. Our model allows examination of dependence in volatility as it captures time variation in volatility and cross-market influences. Estimated time-variation in volatility is significant, and the volatilities are highly positively correlated. Yet, we find that the correlation in North American index and futures markets has declined over time

On EM Reconstruction of a Multi Channel Shielded Applicator for Cervical Cancer Brachytherapy: A Feasibility Study

Electromagnetic tracking (EMT) is a promising technology for automated catheter and applicator reconstruc- 10 tions in brachytherapy. In this work, a proof-of-concept is presented for reconstruction of the individual channels of a shielded tandem applicator dedicated to intensity modulated brachytherapy. All six channels of a straight prototype was reconstructed and the distance between two opposite channels was measured. A study was also conducted on the influence of the shield on the data fluctuation of the EMT system. The differences with the CAD specified dimensions are under 2 mm. The pair of channels which has one of it more distant from the generator have 15 higher inter-channel distance with higher variability. In the first 110 cm reconstruction, all inter-channel distances are within the geometrical tolerances. According to a paired Student t-test, the data given by the EM system with and without the shield applicator tip are not significantly different. This study shows that the reconstruction of channel path within the mechanical accuracy of the applicator is possible.Comment: 3 pages, 3 figure

Interaction of yeast eIF4G with spliceosome components Implications in pre-mRNA processing events

International audienceAs evidenced from mammalian cells the eukaryotic translation initiation factor eIF4G has a putative role in nuclear RNA metabolism. Here we investigate whether this role is conserved in the yeast Saccharomyces cerevisiae. Using a combination of in vitro and in vivo methods, we show that, similar to mammalian eIF4G, yeast eIF4G homologues, Tif4631p and Tif4632p, are present both in the nucleus and the cytoplasm. We show that both eIF4G proteins interact efficiently in vitro with UsnRNP components of the splicing machinery. More specifically, Tif4631p and Tif4632p interact efficiently with U1 snRNA in vitro. In addition, Tif4631p and Tif4632p associate with protein components of the splicing machinery, namely Snu71p and Prp11p. To further delineate these interactions, we map the regions of Tif4631p and Tif4632p that are important for the interaction with Prp11p and Snu71p and we show that addition of these regions to splicing reactions in vitro has a dominant inhibitory effect. The observed interactions implicate eIF4G in aspects of pre-mRNA processing. In support of this hypothesis, deletion of one of the eIF4G isoforms results in accumulation of un-spliced precursors for a number of endogenous genes, in vivo. In conclusion these observations are suggestive of the involvement of yeast eIF4G in pre-mRNA metabolism

Effects of Quasi-Static Aberrations in Faint Companion Searches

We present the first results obtained at CFHT with the TRIDENT infrared camera, dedicated to the detection of faint companions close to bright nearby stars. The camera's main feature is the acquisition of three simultaneous images in three wavelengths (simultaneous differential imaging) across the methane absorption bandhead at 1.6 micron, that enables a precise subtraction of the primary star PSF while keeping the companion signal. The main limitation is non-common path aberrations between the three optical paths that slightly decorrelate the PSFs. Two types of PSF calibrations are combined with the differential simultaneous imaging technique to further attenuate the PSF: reference star subtraction and instrument rotation to smooth aberrations. It is shown that a faint companion with a DeltaH of 10 magnitudes would be detected at 0.5 arcsec from the primary.Comment: 12 pages, 10 figures, to appear in Astronomy with High Contrast Imaging, EAS Publications Serie

The Impact of Prenatal Exposure to Cocaine on Newborn Costs and Length of Stay

This paper determines newborn costs and lengths of stay attributable to prenatal exposure to cocaine and other illicit drugs, using as a data source all parturients who delivered at a large municipal hospital in New York City between November 18, 1991 and April 11, 1992. We performed a cross-sectional analysis in which multivariate, loglinear regressions were used to analyze differences in costs and length of stay between infants exposed and unexposed prenatally to cocaine and other illicit drugs adjusting for maternal race, age, prenatal care, tobacco, parity, type of delivery, birth weight, prematurity, and newborn infection. Urine specimens, with linked obstetric sheets and discharge abstracts provided information on exposure, prenatal behaviors, costs, length of stay and discharge disposition. Our principal findings show that infants exposed to cocaine and some other illicit drug stay approximately 7 days longer at a cost of $7,731 more than infants unexposed. Approximately 60 percent of these costs are indirect, the result of adverse birth outcomes and newborn infection. Hospital screening as recorded on discharge abstracts substantially underestimates prevalence at delivery, but overestimates its impact on costs.