386 research outputs found
Variability selected high-redshift quasars on SDSS Stripe 82
The SDSS-III BOSS Quasar survey will attempt to observe z>2.15 quasars at a
density of at least 15 per square degree to yield the first measurement of the
Baryon Acoustic Oscillations in the Ly-alpha forest. To help reaching this
goal, we have developed a method to identify quasars based on their variability
in the u g r i z optical bands. The method has been applied to the selection of
quasar targets in the SDSS region known as Stripe 82 (the Southern equatorial
stripe), where numerous photometric observations are available over a 10-year
baseline. This area was observed by BOSS during September and October 2010.
Only 8% of the objects selected via variability are not quasars, while 90% of
the previously identified high-redshift quasar population is recovered. The
method allows for a significant increase in the z>2.15 quasar density over
previous strategies based on optical (ugriz) colors, achieving a density of
24.0 deg^{-2} on average down to g~22 over the 220 deg^2 area of Stripe 82. We
applied this method to simulated data from the Palomar Transient Factory and
from Pan-STARRS, and showed that even with data that have sparser time sampling
than what is available in Stripe 82, including variability in future quasar
selection strategies would lead to increased target selection efficiency in the
z>2.15 redshift range. We also found that Broad Absorption Line quasars are
preferentially present in a variability than in a color selection.Comment: 14 pages, 21 figures, accepted for publication in A&
The magnetic fields of large Virgo Cluster spirals
Because of its proximity the Virgo Cluster is an excellent target for
studying interactions of galaxies with the cluster environment. Both the
high-velocity tidal interactions and effects of ram pressure stripping by the
intracluster gas can be investigated. Optical and/or \ion{H}{i} observations do
not always show effects of weak interactions between galaxies and their
encounters with the cluster medium. For this reason we searched for possible
anomalies in the magnetic field structure in Virgo Cluster spirals which could
be attributed to perturbations in their gas distribution and kinematics. Five
angularly large Virgo Cluster spiral galaxies (NGC 4501, NGC 4438, NGC 4535,
NGC 4548 and NGC 4654) were the targets for a sensitive total power and
polarization study using the 100-m radio telescope in Effelsberg at 4.85 GHz.
For two objects polarization data at higher frequencies have been obtained
allowing Faraday rotation analysis. Distorted magnetic field structures were
identified in all galaxies. Interaction-induced magnetized outflows were found
in NGC 4438 (due to nuclear activity) and NGC 4654 (a combination of tidal
tails and ram pressure effects). Almost all objects (except the anaemic NGC
4548) exhibit distortions in polarized radio continuum attributable to
influence of the ambient gas. For some galaxies they agree with observations of
other species, but sometimes (NGC 4535) the magnetic field is the only tracer
of the interaction with the cluster environment. The cluster environment
clearly affects the evolution of the galaxies due to ram pressure and tidal
effects. Magnetic fields provide a very long-lasting memory of past
interactions. Therefore, they are a good tracer of weak interactions which are
difficult to detect by other observations.Comment: 13 pages, 12 figure
The inflammatory microenvironment in colorectal neoplasia
Peer reviewedPublisher PD
EFSA NDA Panel (EFSA Panel on Dietetic Products, Nutrition and Allergies), 2013 . Scientific opinion on Dietary Reference Values for fluoride
Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies (NDA) derived Dietary Reference Values (DRVs) for fluoride, which are provided as Adequate Intake (AI) from all sources, including non-dietary sources. Fluoride is not an essential nutrient. Therefore, no Average Requirement for the performance of essential physiological functions can be defined. Nevertheless, the Panel considered that the setting of an AI is appropriate because of the beneficial effects of dietary fluoride on prevention of dental caries. The AI is based on epidemiological studies (performed before the 1970s) showing an inverse relationship between the fluoride concentration of water and caries prevalence. As the basis for defining the AI, estimates of mean fluoride intakes of children via diet and drinking water with fluoride concentrations at which the caries preventive effect approached its maximum whilst the risk of dental fluorosis approached its minimum were chosen. Except for one confirmatory longitudinal study in US children, more recent studies were not taken into account as they did not provide information on total dietary fluoride intake, were potentially confounded by the use of fluoride-containing dental hygiene products, and did not permit a conclusion to be drawn on a dose-response relationship between fluoride intake and caries risk. The AI of fluoride from all sources (including non-dietary sources) is 0.05 mg/kg body weight per day for both children and adults, including pregnant and lactating women. For pregnant and lactating women, the AI is based on the body weight before pregnancy and lactation. Reliable and representative data on the total fluoride intake of the European population are not available
DNA Methylation Dynamics in Human Induced Pluripotent Stem Cells over Time
Epigenetic reprogramming is a critical event in the generation of induced pluripotent stem cells (iPSCs). Here, we determined the DNA methylation profiles of 22 human iPSC lines derived from five different cell types (human endometrium, placental artery endothelium, amnion, fetal lung fibroblast, and menstrual blood cell) and five human embryonic stem cell (ESC) lines, and we followed the aberrant methylation sites in iPSCs for up to 42 weeks. The iPSCs exhibited distinct epigenetic differences from ESCs, which were caused by aberrant methylation at early passages. Multiple appearances and then disappearances of random aberrant methylation were detected throughout iPSC reprogramming. Continuous passaging of the iPSCs diminished the differences between iPSCs and ESCs, implying that iPSCs lose the characteristics inherited from the parent cells and adapt to very closely resemble ESCs over time. Human iPSCs were gradually reprogrammed through the “convergence” of aberrant hyper-methylation events that continuously appeared in a de novo manner. This iPS reprogramming consisted of stochastic de novo methylation and selection/fixation of methylation in an environment suitable for ESCs. Taken together, random methylation and convergence are driving forces for long-term reprogramming of iPSCs to ESCs
Dispersal Routes and Habitat Utilization of Juvenile Atlantic Bluefin Tuna, Thunnus thynnus, Tracked with Mini PSAT and Archival Tags
Between 2005 and 2009, we deployed 58 miniature pop-up satellite archival tags (PSAT) and 132 implanted archival tags on juvenile Atlantic bluefin tuna (age 2–5) in the northwest Atlantic Ocean. Data returned from these efforts (n = 26 PSATs, 1 archival tag) revealed their dispersal routes, horizontal and vertical movements and habitat utilization. All of the tagged bluefin tuna remained in the northwest Atlantic for the duration observed, and in summer months exhibited core-use of coastal seas extending from Maryland to Cape Cod, MA, (USA) out to the shelf break. Their winter distributions were more spatially disaggregated, ranging south to the South Atlantic Bight, northern Bahamas and Gulf Stream. Vertical habitat patterns showed that juvenile bluefin tuna mainly occupied shallow depths (mean = 5–12 m, sd = 15–23.7 m) and relatively warm water masses in summer (mean = 17.9–20.9°C, sd = 4.2–2.6°C) and had deeper and more variable depth patterns in winter (mean = 41–58 m, sd = 48.9–62.2 m). Our tagging results reveal annual dispersal patterns, behavior and oceanographic associations of juvenile Atlantic bluefin tuna that were only surmised in earlier studies. Fishery independent profiling from electronic tagging also provide spatially and temporally explicit information for evaluating dispersals rates, population structure and fisheries catch patterns
Global Chromatin Architecture Reflects Pluripotency and Lineage Commitment in the Early Mouse Embryo
An open chromatin architecture devoid of compact chromatin is thought to be associated with pluripotency in embryonic stem cells. Establishing this distinct epigenetic state may also be required for somatic cell reprogramming. However, there has been little direct examination of global structural domains of chromatin during the founding and loss of pluripotency that occurs in preimplantation mouse development. Here, we used electron spectroscopic imaging to examine large-scale chromatin structural changes during the transition from one-cell to early postimplantation stage embryos. In one-cell embryos chromatin was extensively dispersed with no noticeable accumulation at the nuclear envelope. Major changes were observed from one-cell to two-cell stage embryos, where chromatin became confined to discrete blocks of compaction and with an increased concentration at the nuclear envelope. In eight-cell embryos and pluripotent epiblast cells, chromatin was primarily distributed as an extended meshwork of uncompacted fibres and was indistinguishable from chromatin organization in embryonic stem cells. In contrast, lineage-committed trophectoderm and primitive endoderm cells, and the stem cell lines derived from these tissues, displayed higher levels of chromatin compaction, suggesting an association between developmental potential and chromatin organisation. We examined this association in vivo and found that deletion of Oct4, a factor required for pluripotency, caused the formation of large blocks of compact chromatin in putative epiblast cells. Together, these studies show that an open chromatin architecture is established in the embryonic lineages during development and is sufficient to distinguish pluripotent cells from tissue-restricted progenitor cells
Different Mechanisms Underlie Post-menarchial Increase in Depression and Weight
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99254.pdf (publisher's version ) (Open Access)Background Depression and being overweight are correlated health problems in adulthood. Adolescence is a significant period for the onset and increase of depression and obesity, especially among girls. Pubertal development also occurs with concomitant increases in weight. Thus, it is not yet clear whether the association between depression and being overweight can be explained by pubertal development.
Purpose We examined the association between depressive mood, body weight, and pubertal status in adolescent girls.
Method The design was cross-sectional. In 962 young adolescent Dutch girls (age range, 11.9-15.9) weight and height measurements were used to calculate height, age, and gender-standardized body weight (zBMI). Questionnaires assessed depressive mood (the Center for Epidemiological Studies-Depression, CES-D, inventory) and menarcheal status (pre or post).
Results The correlation between menarcheal status and body weight (r = 0.34, p < 0.001) was not affected by depressive mood, and the correlation between menarcheal status and depressive mood (r = 0.20, p < 0.001) was not affected by body weight. A small correlation between depressive mood and body weight (r = 0.12, p < 0.01) largely disappeared after controlling for menarche.
Conclusion Menarcheal status largely explains the association between weight and depression. It is independently associated with both BMI and depression, suggesting that different mechanisms underlie the post-menarcheal increased prevalence of depression and overweight.6 p
Adaptive Evolution of Escherichia coli to an α-Peptide/β-Peptoid Peptidomimetic Induces Stable Resistance.
Antimicrobial peptides (AMPs) and synthetic analogues thereof target conserved structures of bacterial cell envelopes and hence, development of resistance has been considered an unlikely event. However, recently bacterial resistance to AMPs has been observed, and the aim of the present study was to determine whether bacterial resistance may also evolve against synthetic AMP analogues, e.g. α-peptide/β-peptoid peptidomimetics. E. coli ATCC 25922 was exposed to increasing concentrations of a peptidomimetic (10 lineages), polymyxin B (10 lineages), or MilliQ water (4 lineages) in a re-inoculation culturing setup covering approx. 500 generations. All 10 lineages exposed to the peptidomimetic adapted to 32 × MIC while this occurred for 8 out of 10 of the polymyxin B-exposed lineages. All lineages exposed to 32 × MIC of either the peptidomimetic or polymyxin B had a significantly increased MIC (16-32 ×) to the selection agent. Five transfers (≈ 35 generations) in unsupplemented media did not abolish resistance indicating that resistance was heritable. Single isolates from peptidomimetic-exposed lineage populations displayed MICs against the peptidomimetic from wild-type MIC to 32 × MIC revealing heterogeneous populations. Resistant isolates showed no cross-resistance against a panel of membrane-active AMPs. These isolates were highly susceptible to blood plasma antibacterial activity and were killed when plasma concentrations exceeded ≈ 30%. Notably, MIC of the peptidomimetic against resistant isolates returned to wild-type level upon addition of 25% plasma. Whole-genome sequencing of twenty isolates from four resistant lineages revealed mutations, in murein transglycosylase D (mltD) and outer-membrane proteins, which were conserved within and between lineages. However, no common resistance-conferring mutation was identified. We hypothesise that alterations in cell envelope structure result in peptidomimetic resistance, and that this may occur via several distinct mechanisms. Interestingly, this type of resistance result in a concomitant high susceptibility towards plasma, and therefore the present study does not infer additional concern for peptidomimetics as future therapeutics
Study protocol: an early intervention program to improve motor outcome in preterm infants: a randomized controlled trial and a qualitative study of physiotherapy performance and parental experiences
Background Knowledge about early physiotherapy to preterm infants is sparse, given the risk of delayed motor development and cerebral palsy. Methods/Design A pragmatic randomized controlled study has been designed to assess the effect of a preventative physiotherapy program carried out in the neonatal intensive care unit. Moreover, a qualitative study is carried out to assess the physiotherapy performance and parents' experiences with the intervention. The aim of the physiotherapy program is to improve motor development i.e. postural control and selective movements in these infants. 150 infants will be included and randomized to either intervention or standard follow-up. The infants in the intervention group will be given specific stimulation to facilitate movements based on the individual infant's development, behavior and needs. The physiotherapist teaches the parents how to do the intervention and the parents receive a booklet with photos and descriptions of the intervention. Intervention is carried out twice a day for three weeks (week 34, 35, 36 postmenstrual age). Standardized tests are carried out at baseline, term age and at three, six, 12 and 24 months corrected age. In addition eight triads (infant, parent and physiotherapist) are observed and videotaped in four clinical encounters each to assess the process of physiotherapy performance. The parents are also interviewed on their experiences with the intervention and how it influences on the parent-child relationship. Eight parents from the follow up group are interviewed about their experience. The interviews are performed according to the same schedule as the standardized measurements. Primary outcome is at two years corrected age. Discussion The paper presents the protocol for a randomized controlled trial designed to study the effect of physiotherapy to preterm infants at neonatal intensive care units. It also studies physiotherapy performance and the parent's experiences with the intervention
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