Weak Lensing Mass Reconstruction: Flexion vs Shear

Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the Universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of a shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone not be used to do convergence map reconstruction, even on small scales.Comment: Submitted to Ap

Bac-pool Sequencing And Assembly Of 19 Mb Of The Complex Sugarcane Genome

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Sequencing plant genomes are often challenging because of their complex architecture and high content of repetitive sequences. Sugarcane has one of the most complex genomes. It is highly polyploid, preserves intact homeologous chromosomes from its parental species and contains 55% repetitive sequences. Although bacterial artificial chromosome (BAC) libraries have emerged as an alternative for accessing the sugarcane genome, sequencing individual clones is laborious and expensive. Here, we present a strategy for sequencing and assembly reads produced from the DNA of pooled BAC clones. A set of 178 BAC clones, randomly sampled from the SP80-3280 sugarcane BAC library, was pooled and sequenced using the Illumina HiSeq2000 and PacBio platforms. A hybrid assembly strategy was used to generate 2,451 scaffolds comprising 19.2 MB of assembled genome sequence. Scaffolds of >= 20 Kb corresponded to 80% of the assembled sequences, and the full sequences of forty BACs were recovered in one or two contigs. Alignment of the BAC scaffolds with the chromosome sequences of sorghum showed a high degree of collinearity and gene order. The alignment of the BAC scaffolds to the 10 sorghum chromosomes suggests that the genome of the SP80-3280 sugarcane variety is similar to 19% contracted in relation to the sorghum genome. In conclusion, our data show that sequencing pools composed of high numbers of BAC clones may help to construct a reference scaffold map of the sugarcane genome.7[FAPESP - 10/50114-4]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Gravitational Flexion by Elliptical Dark Matter Haloes

We present equations for the gravitational lensing flexion expected for an elliptical lens mass distribution. These can be reduced to one-dimensional finite integrals, thus saving significant computing time over a full two-dimensional calculation. We estimate constraints on galaxy halo ellipticities for a range of potential future surveys, finding that the constraints from the two different types of flexion are comparable and are up to two orders of magnitude tighter than those from shear. Flexion therefore appears to be a very promising potential tool for constraining the shapes of galaxy haloes from future surveys.Comment: 7 pages, 5 figures, submitted to MNRA

A New Constraint on the Lyα\alpha Fraction of UV Very Bright Galaxies at Redshift 7

We study the extent to which very bright (-23.0 < MUV < -21.75) Lyman-break selected galaxies at redshifts z~7 display detectable Lya emission. To explore this issue, we have obtained follow-up optical spectroscopy of 9 z~7 galaxies from a parent sample of 24 z~7 galaxy candidates selected from the 1.65 sq.deg COSMOS-UltraVISTA and SXDS-UDS survey fields using the latest near-infrared public survey data, and new ultra-deep Subaru z'-band imaging (which we also present and describe in this paper). Our spectroscopy has yielded only one possible detection of Lya at z=7.168 with a rest-frame equivalent width EW_0 = 3.7 (+1.7/-1.1) Angstrom. The relative weakness of this line, combined with our failure to detect Lya emission from the other spectroscopic targets allows us to place a new upper limit on the prevalence of strong Lya emission at these redshifts. For conservative calculation and to facilitate comparison with previous studies at lower redshifts, we derive a 1-sigma upper limit on the fraction of UV bright galaxies at z~7 that display EW_0 > 50 Angstrom, which we estimate to be < 0.23. This result may indicate a weak trend where the fraction of strong Lya emitters ceases to rise, and possibly falls between z~6 and z~7. Our results also leave open the possibility that strong Lya may still be more prevalent in the brightest galaxies in the reionization era than their fainter counterparts. A larger spectroscopic sample of galaxies is required to derive a more reliable constraint on the neutral hydrogen fraction at z~7 based on the Lya fraction in the bright galaxies.Comment: 20 pages, 7 figures, accepted for publication in Ap

Probiotics in Diverticular Disease of the Colon: an Open Label Study

Aim: To investigate the effectiveness and safety of a symbiotic mixture in preventing recurrence of constipation-related abdominal pain in patients with uncomplicated diverticular disease of the colon. Methods: Forty-six consecutive patients (10 men, 36 women, mean age 62.5 years, range 49 to 77 years), previously affected by symptomatic uncomplicated diverticular disease of the colon, were enrolled in a 6-month follow-up study in a prospective, randomized, open-label study. The following symptoms were assessed at entry and through follow-up by using a quantitative scale: constipation, diarrhoea and abdominal pain. After recruitment, the patients were assigned to the following treatment: SCM-III symbiotic mixture, 10ml three times a day. The colonization of ingested Lactobacillus acidophilus 145 and Bifidobacterium spp. 420 was assessed by specie-specific PCR. Forty-five patients completed the study (97%). Results: Thirty-one patients (68%) were still symptom free after the 6th month of treatment. Treatment with SCM-III was regarded as "effective" or "very effective" in more than 78% of the patients altogether (p<0.01 vs baseline values). The microbiological study showed that, as compared to baseline values, SCM-III enabled a significant increase of the lactobacilli and bifidobacteria counting and a trend decrease of clostridia. Genomic analysis confirmed the survivability of the ingested strain as long as treatment was given. Conclusions: The present symbiotic mixture seems to be effective in preventing recurrence of symptomatic uncomplicated diverticular disease of the colon, especially in those patients with constipation-predominant features

Impact of Diabetes on Work Cessation: Data from the GAZEL cohort study

International audienceOBJECTIVE: To measure the impact of diabetes on work cessation, i.e., on the risks of work disability, early retirement, and death while in the labor force. RESEARCH DESIGN AND METHODS: We used data from the GAZEL prospective cohort of 20,625 employees of the French national gas and electricity company "EDF-GDF." We identified 506 employees with diabetes and randomly selected 2,530 nondiabetic employed control subjects matched for major sociodemographic and occupational characteristics. Using a multistate Cox model, we estimated hazard ratios (HRs) comparing the risks of transition from employment to disability, retirement, and death over time between participants with versus without diabetes. RESULTS: Employment rate decreased more rapidly in participants with diabetes (51.9 and 10.1% at 55 and 60 years, respectively) compared with nondiabetic participants (66.5 and 13.4%, respectively). Participants with diabetes had significantly increased risks of transition from employment to disability (HR 1.7 [95% CI 1.0-2.9]), retirement (HR 1.6 [1.5-1.8]), and death (HR 7.3 [3.6-14.6]) compared with participants without diabetes. Between 35 and 60 years, each participant with diabetes lost an estimated mean time of 1.1 year in the workforce (95% CI 0.99-1.14) compared with a nondiabetic participant. CONCLUSIONS: Our results provide evidence for a profound negative impact of diabetes on workforce participation in France. Social and economic consequences are major for patients, employers, and society-a burden that is likely to increase as diabetes becomes more and more common in the working-aged population

Constraining primordial non-Gaussianity with cosmological weak lensing: shear and flexion

We examine the cosmological constraining power of future large-scale weak lensing surveys on the model of \emph{Euclid}, with particular reference to primordial non-Gaussianity. Our analysis considers several different estimators of the projected matter power spectrum, based on both shear and flexion, for which we review the covariances and Fisher matrices. The bounds provided by cosmic shear alone for the local bispectrum shape, marginalized over $\sigma_8$, are at the level of $\Delta f_\mathrm{NL} \sim 100$. We consider three additional bispectrum shapes, for which the cosmic shear constraints range from $\Delta f_\mathrm{NL}\sim 340$ (equilateral shape) up to $\Delta f_\mathrm{NL}\sim 500$ (orthogonal shape). The competitiveness of cosmic flexion constraints against cosmic shear ones depends on the galaxy intrinsic flexion noise, that is still virtually unconstrained. Adopting the very high value that has been occasionally used in the literature results in the flexion contribution being basically negligible with respect to the shear one, and for realistic configurations the former does not improve significantly the constraining power of the latter. Since the flexion noise decreases with decreasing scale, by extending the analysis up to $\ell_\mathrm{max} = 20,000$ cosmic flexion, while being still subdominant, improves the shear constraints by $\sim 10$ when added. However on such small scales the highly non-linear clustering of matter and the impact of baryonic physics make any error estimation uncertain. By considering lower, and possibly more realistic, values of the flexion intrinsic shape noise results in flexion constraining power being a factor of $\sim 2$ better than that of shear, and the bounds on $\sigma_8$ and $f_\mathrm{NL}$ being improved by a factor of $\sim 3$ upon their combination. (abridged)Comment: 30 pages, 4 figures, 4 tables. To appear on JCA

GREAT3 results I: systematic errors in shear estimation and the impact of real galaxy morphology

We present first results from the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, the third in a sequence of challenges for testing methods of inferring weak gravitational lensing shear distortions from simulated galaxy images. GREAT3 was divided into experiments to test three specific questions, and included simulated space- and ground-based data with constant or cosmologically-varying shear fields. The simplest (control) experiment included parametric galaxies with a realistic distribution of signal-to-noise, size, and ellipticity, and a complex point spread function (PSF). The other experiments tested the additional impact of realistic galaxy morphology, multiple exposure imaging, and the uncertainty about a spatially-varying PSF; the last two questions will be explored in Paper II. The 24 participating teams competed to estimate lensing shears to within systematic error tolerances for upcoming Stage-IV dark energy surveys, making 1525 submissions overall. GREAT3 saw considerable variety and innovation in the types of methods applied. Several teams now meet or exceed the targets in many of the tests conducted (to within the statistical errors). We conclude that the presence of realistic galaxy morphology in simulations changes shear calibration biases by $\sim 1$ per cent for a wide range of methods. Other effects such as truncation biases due to finite galaxy postage stamps, and the impact of galaxy type as measured by the S\'{e}rsic index, are quantified for the first time. Our results generalize previous studies regarding sensitivities to galaxy size and signal-to-noise, and to PSF properties such as seeing and defocus. Almost all methods' results support the simple model in which additive shear biases depend linearly on PSF ellipticity.Comment: 32 pages + 15 pages of technical appendices; 28 figures; submitted to MNRAS; latest version has minor updates in presentation of 4 figures, no changes in content or conclusion