Gravitational Lensing as Signal and Noise in Lyman-alpha Forest Measurements

In Lyman-alpha forest measurements it is generally assumed that quasars are mere background light sources which are uncorrelated with the forest. Gravitational lensing of the quasars violates this assumption. This effect leads to a measurement bias, but more interestingly it provides a valuable signal. The lensing signal can be extracted by correlating quasar magnitudes with the flux power spectrum and with the flux decrement. These correlations will be challenging to measure but their detection provides a direct measure of how features in the Lyman-alpha forest trace the underlying mass density field. Observing them will test the fundamental hypothesis that fluctuations in the forest are predominantly driven by fluctuations in mass, rather than in the ionizing background, helium reionization or winds. We discuss ways to disentangle the lensing signal from other sources of such correlations, including dust, continuum and background residuals. The lensing-induced measurement bias arises from sample selection: one preferentially collects spectra of magnified quasars which are behind overdense regions. This measurement bias is ~0.1-1% for the flux power spectrum, optical depth and the flux probability distribution. Since the effect is systematic, quantities such as the amplitude of the flux power spectrum averaged across scales should be interpreted with care.Comment: 22 pages, 8 figures; v2: references added, discussion expanded, matches PRD accepted versio

Factors Associated with Long-Term Oral Hypoglycemic Agent Responsiveness in Korean Patients with Type 2 Diabetes Mellitus

BackgroundThis study was performed to determine the factors associated with long-term oral hypoglycemic agent (OHA) responsiveness in Korean type 2 diabetic patients.MethodsTwo groups of patients were selected among the type 2 diabetic patients who were followed for more than two years at a university hospital diabetes clinic. The OHA responsive group consisted of 197 patients whose HbA1c levels were maintained at ≤7% with OHA for more than two years. The OHA failure group consisted of 180 patients whose HbA1c levels were >8% in spite of optimal combined OHA therapy or patients who required insulin therapy within the two years of the study.ResultsThe OHA failure group had higher baseline values of fasting and postprandial glucose, HbA1c, and lower fasting, postprandial, and delta C-peptide compared to those of the OHA responsive group. The OHA failure group also had a higher proportion of female patients, longer diabetic duration, and more family history of diabetes. There were no significant differences in body mass index (BMI) or insulin resistance index between the two groups. Multiple logistic regression analysis showed that the highest quartile of baseline fasting, postprandial glucose, and HbA1c and the lowest quartile of postprandial and delta C-peptide were associated with an increased odds ratio of OHA failure after adjustment for age, sex, body mass index, and family history of diabetes.ConclusionLower baseline values of postprandial and delta C-peptide and elevated fasting glucose and HbA1c are associated with long-term OHA responsiveness in Korean patients with type 2 diabetes mellitus

Digital Opportunities Within the Aboriginal Teacher Education Program: A Study of Preservice Teachers' Attitudes and Proficiency in Technology Integration

This article explores changes that occurred in preservice teachers' thinking about the use of educational technology in a post-secondary, Aboriginal, elementary teacher education program. The research explores relationships associated with changes in preservice teachers' attitudes and perceived proficiency with technology integration. Quantitative results indicate significant increases in several attitude constructs as well as overall computer proficiency over the course of the project. Supplemental qualitative analysis reveals participants' perception of technology integration as a contributing factor in this positive change. The findings from this study represent a research effort to better prepare teachers to meet the educational needs of Aboriginal students in a 21st century context. Cet article explore l’évolution dans les idées des stagiaires quant à l’emploi des technologies éducatives dans un programme postsecondaire de formation pour enseignants autochtones à l’élémentaire. La recherche porte sur des rapports associés aux changements dans les attitudes des stagiaires et leur perception de leur compétence relative à l’intégration technologique. Les résultats quantitatifs révèlent des augmentations significatives tant dans les attitudes que la compétence technologique globale au cours du projet. Une analyse qualitative supplémentaire indique que la perception des participants quant à l’intégration technologique constitue un facteur contributif dans ce changement positif. Les résultats de cette étude représentent un effort de recherche visant une meilleure préparation des enseignants de sorte à répondre aux besoins pédagogiques des étudiants autochtones au 21e siècle

Comparison of bacterial genome assembly software for MinION data and their applicability to medical microbiology.

Translating the Oxford Nanopore MinION sequencing technology into medical microbiology requires on-going analysis that keeps pace with technological improvements to the instrument and release of associated analysis software. Here, we use a multidrug-resistant Enterobacter kobei isolate as a model organism to compare open source software for the assembly of genome data, and relate this to the time taken to generate actionable information. Three software tools (PBcR, Canu and miniasm) were used to assemble MinION data and a fourth (SPAdes) was used to combine MinION and Illumina data to produce a hybrid assembly. All four had a similar number of contigs and were more contiguous than the assembly using Illumina data alone, with SPAdes producing a single chromosomal contig. Evaluation of the four assemblies to represent the genome structure revealed a single large inversion in the SPAdes assembly, which also incorrectly integrated a plasmid into the chromosomal contig. Almost 50 %, 80 % and 90 % of MinION pass reads were generated in the first 6, 9 and 12 h, respectively. Using data from the first 6 h alone led to a less accurate, fragmented assembly, but data from the first 9 or 12 h generated similar assemblies to that from 48 h sequencing. Assemblies were generated in 2 h using Canu, indicating that going from isolate to assembled data is possible in less than 48 h. MinION data identified that genes responsible for resistance were carried by two plasmids encoding resistance to carbapenem and to sulphonamides, rifampicin and aminoglycosides, respectively.Health Innovation Challenge Fund (WT098600, HICF-T5-342) (Department of Health, Wellcome Trust)This is the final version of the article. It first appeared from the Microbiology Society via http://dx.doi.org/10.1099/mgen.0.00008

Large Scale Magnetic Fields: Galaxy Two-Point correlation function

We study the effect of large scale tangled magnetic fields on the galaxy two-point correlation function in the redshift space. We show that (a) the magnetic field effects can be comparable the gravity-induced clustering for present magnetic field strength $B_0 \simeq 5 \times 10^{-8}$ G, (b) the absence of this signal from the present data gives an upper bound B_0 \la 3 \times 10^{-8} G, (c) the future data can probe the magnetic fields of $\simeq 10^{-8}$ G. A comparison with other constraints on the present magnetic field shows that they are marginally compatible.However if the magenetic fields corresponding to $B_0 \simeq 10^{-8}$ G existed at the last scattering surface they will cause unacceptably large CMBR anisotropies.Comment: 10 pages, 4 figures, accepted for publication in MNRA

Higher order moments of the density field in a parameterized sequence of non-gaussian theories

We calculate the higher order moments in a sequence of models where the initial density fluctuations are drawn from a chi^2_nu distribution with a power-law power spectrum. For large values of nu the distribution is approximately gaussian, and we reproduce the values known from perturbation theory. As \nu is lowered the distribution becomes progressively more non-gaussian, approximating models with rare, high-amplitude peaks. The limit nu=1 is a realization of recently proposed isocurvature models for producing early galaxy formation where the density perturbations are quadratic in a gaussian field.Comment: 7 pages, 7 figures, to appear in MNRA

Topology of non-linear structure in the 2dF Galaxy Redshift Survey

We study the evolution of non-linear structure as a function of scale in samples from the 2dF Galaxy Redshift Survey, constituting over 221 000 galaxies at a median redshift of z=0.11. The two flux-limited galaxy samples, located near the southern galactic pole and the galactic equator, are smoothed with Gaussian filters of width ranging from 5 to 8 Mpc/h to produce a continuous galaxy density field. The topological genus statistic is used to measure the relative abundance of overdense clusters to void regions at each scale; these results are compared to the predictions of analytic theory, in the form of the genus statistic for i) the linear regime case of a Gaussian random field; and ii) a first-order perturbative expansion of the weakly non-linear evolved field. The measurements demonstrate a statistically significant detection of an asymmetry in the genus statistic between regions corresponding to low- and high-density volumes of the universe. We attribute the asymmetry to the non-linear effects of gravitational evolution and biased galaxy formation, and demonstrate that these effects evolve as a function of scale. We find that neither analytic prescription satisfactorily reproduces the measurements, though the weakly non-linear theory yields substantially better results in some cases, and we discuss the potential explanations for this result.Comment: 13 pages, matching proof to be published in MNRAS; new version adds reference and corrects figure

Large scale bias and the inaccuracy of the peak-background split

The peak-background split argument is commonly used to relate the abundance of dark matter halos to their spatial clustering. Testing this argument requires an accurate determination of the halo mass function. We present a Maximum Likelihood method for fitting parametric functional forms to halo abundances which differs from previous work because it does not require binned counts. Our conclusions do not depend on whether we use our method or more conventional ones. In addition, halo abundances depend on how halos are defined. Our conclusions do not depend on the choice of link length associated with the friends-of-friends halo-finder, nor do they change if we identify halos using a spherical overdensity algorithm instead. The large scale halo bias measured from the matter-halo cross spectrum b_x and the halo autocorrelation function b_xi (on scales k~0.03h/Mpc and r ~50 Mpc/h) can differ by as much as 5% for halos that are significantly more massive than the characteristic mass M*. At these large masses, the peak background split estimate of the linear bias factor b1 is 3-5% smaller than b_xi, which is 5% smaller than b_x. We discuss the origin of these discrepancies: deterministic nonlinear local bias, with parameters determined by the peak-background split argument, is unable to account for the discrepancies we see. A simple linear but nonlocal bias model, motivated by peaks theory, may also be difficult to reconcile with our measurements. More work on such nonlocal bias models may be needed to understand the nature of halo bias at this level of precision.Comment: MNRAS accepted. New section with Spherical Overdensity identified halos included. Appendix enlarge