321 research outputs found
The influence of the food environment on overweight and obesity in young children : a systematic review
The increasing prevalence of childhood obesity has led to interest in its prevention, particularly through school-based and family-based interventions in the early years. Most evidence reviews, to date, have focused on individual behaviour change rather than the âobesogenic environmentâ. This paper reviews the evidence on the influence of the food environment on overweight and obesity in children up to 8â
years. Electronic databases (including MEDLINE, EMBASE, Cochrane Controlled Trials Register (CCTR), DARE, CINAHL and Psycho-Info) and reference lists of original studies and reviews were searched for all papers published up to 31 August 2011. Study designs included were either population-based intervention studies or a longitudinal study. Studies were included if the majority of the children studied were under 9â
years, if they related to diet and if they focused on prevention rather than treatment in clinical settings. Data included in the tables were characteristics of participants, aim, and key outcome results. Quality assessment of the selected studies was carried out to identify potential bias and an evidence ranking exercise carried out to prioritise areas for future public health interventions. Thirty-five studies (twenty-five intervention studies and ten longitudinal studies) were selected for the review. There was moderately strong evidence to support interventions on food promotion, large portion sizes and sugar-sweetened soft drinks. Reducing food promotion to young children, increasing the availability of smaller portions and providing alternatives to sugar-sweetened soft drinks should be considered in obesity prevention programmes aimed at younger children. These environment-level interventions would support individual and family-level behaviour change
UV-optical from space
The following subject areas are covered: (1) the science program (star formation and origins of planetary systems; structure and evolution of the interstellar medium; stellar population; the galactic and extragalactic distance scale; nature of galaxy nuclei, AGNs, and QSOs; formation and evolution of galaxies at high redshifts; and cosmology); (2) implementation of the science program; (3) the observatory-class missions (HST; LST - the 6m successor to HST; and next-generation 16m telescope); (4) moderate and small missions (Delta-class Explorers; imaging astrometric interferometer; small Explorers; optics development and demonstrations; and supporting ground-based capabilities); (5) prerequisites - the current science program (Lyman-FUSE; HTS optimization; the near-term science program; data analysis, modeling, and theory funding; and archives); (6) technologies for the next century; and (7) lunar-based telescopes and instruments
Witnessing the formation of a brightest cluster galaxy at z>2
We present deep observations taken with the HST Advanced Camera for Surveys
of the central massive galaxy in a forming cluster at z=2.2. The galaxy hosting
the powerful radio source MRC 1138-262 is associated with one of the most
extensive merger systems known in the early universe. Our HST/ACS image shows
many star-forming galaxies merging within a ~200 kpc region that emits both
diffuse line emission and continuum in the rest-frame UV. Because this galaxy
lives in an overdense environment, it represents a rare view of a brightest
cluster galaxy in formation at z>2 which may serve as a testbed for predictions
of massive cluster galaxy formation.Comment: Contribution to the proceedings of "The Fate of Gas in Galaxies",
Dwingeloo, July 2006, with 2 colour figures. To appear in New Astronomy
Reviews, Vol. 51 (2007), eds. Morganti, Oosterloo, Villar-Martin & van Gorko
Spatio-temporal trends in normal-fault segmentation recorded by low-temperature thermochronology: Livingstone fault scarp, Malawi Rift, East African Rift System
The evolution of through-going normal-fault arrays from initial nucleation to growth and subsequent interaction and mechanical linkage is well documented in many extensional provinces. Over time, these processes lead to predictable spatial and temporal variations in the amount and rate of displacement accumulated along strike of individual fault segments, which should be manifested in the patterns of footwall exhumation. Here, we investigate the along-strike and vertical distribution of low-temperature apatite (UâTh)/He (AHe) cooling ages along the bounding fault system, the Livingstone fault, of the Karonga Basin of the northern Malawi Rift. The fault evolution and linkage from rift initiation to the present day has been previously constrained through investigations of the hanging wall basin fill. The new cooling ages from the footwall of the Livingstone fault can be related to the adjacent depocentre evolution and across a relay zone between two palaeo-fault segments. Our data are complimented by published apatite fission-track (AFT) data and reveal significant variation in rock cooling history along-strike: the centre of the footwall yields younger cooling ages than the former tips of earlier fault segments that are now linked. This suggests that low-temperature thermochronology can detect fault interactions along strike. That these former segment boundaries are preserved within exhumed footwall rocks is a function of the relatively recent linkage of the system. Our study highlights that changes in AHe (and potentially AFT) ages associated with the along-strike displacement profile can occur over relatively short horizontal distances (of a few kilometres). This is fundamentally important in the assessment of the vertical cooling history of footwalls in extensional systems: temporal differences in the rate of tectonically driven exhumation at a given location along fault strike may be of greater importance in controlling changes in rates of vertical exhumation than commonly invoked climatic fluctuations
An XMM-Newton Study of the Hard X-ray Sky
We report on the spectral properties of a sample of 90 hard X-ray selected
serendipitous sources detected in 12 XMM observations with 1<F(2-10)<80
10^(-14) erg/cm2/s. Approximately 40% of the sources are optically identified
with 0.1<z<2 and most of them are classified as broad line AGNs. A simple model
consisting of power law modified by Galactic absorption offers an acceptable
fit to ~65% of the source spectra. This fit yields an average photon index of
~1.55 over the whole sample. We also find that the mean slope of the
QSOs in our sample turns out to remain nearly constant (~1.8-1.9)
between 0<z<2, with no hints of particular trends emerging along z. An
additional cold absorption component with 10^(21)<Nh<10^(23) cm^(-2) is
required in ~30% of the sources. Considering only subsamples that are complete
in flux, we find that the observed fraction of absorbed sources (i.e. with
Nh>~10^(22) cm^(-2)) is ~30%, with little evolution in the range 2<F(2-10)<80
10^(-14) erg/cm2/s. Interestingly, this value is a factor ~2 lower than
predicted by the synthesis models of the CXB. This finding, detected for the
first time in this survey, therefore suggests that most of the heavily obscured
objects which make up the bulk of the CXB will be found at lower fluxes
(F(2-10)< 10^(-14) erg/cm2/s). This mismatch together with other recent
observational evidences which contrast with CXB model predictions suggest that
one (or more) of the assumptions usually included in these models need to be
revised.Comment: 20 pages, 13 figures, accepted for publication in A&
Glucose Excursions Between States of Glycemia With Progression to Type 1 Diabetes in the Diabetes Prevention TrialâType 1 (DPT-1)
Quasars: the characteristic spectrum and the induced radiative heating
Using information on the cosmic X-ray background and the cumulative light of
active galactic nuclei at infrared wavelengths, the estimated local mass
density of galactic massive black holes (MBHs) and published AGN composite
spectra in the optical, UV and X-ray, we compute the characteristic
angular-integrated, broad-band spectral energy distribution of the average
quasar in the universe. We demonstrate that the radiation from such sources can
photoionize and Compton heat the plasma surrounding them up to an equilibrium
Compton temperature (Tc) of 2x10^7 K. It is shown that circumnuclear
obscuration cannot significantly affect the net gas Compton heating and cooling
rates, so that the above Tc value is approximately characteristic of both
obscured and unobscured quasars. This temperature is above typical gas
temperatures in elliptical galaxies and just above the virial temperatures of
giant ellipticals. The general results of this work can be used for accurate
calculations of the feedback effect of MBHs on both their immediate environs
and the more distant interstellar medium of their host galaxies.Comment: 15 pages, 5 figures. Revised version accepted for publication in
MNRA
Numerical modelling of Non-Transform Discontinuity geometry: Implication for ridge structure, volcano-tectonic fabric development and hydrothermal activity at segment ends.
Ocean ridge discontinuities partition and offset spreading centres at a range of scales. Large scale discontinuities (10'sâ100's km) are synonymous with first-order transform faults, which have well defined linear fault zone valleys. In contrast, Non-Transform Discontinuities (NTDs) are diffuse, smaller scale offsets (0 to b20 km), characterised by central basins or topographic highs. The geometry of NTD offsets can be categorised by the sense of offset, either right-stepping or left-stepping, and by the relative positions of the segment tips. The segment tip configurations include under-lapping, over-lapping or simple across-axis jumps or stepping in the ridge axis. In this study finite difference software is used to model segment geometry at a slow-spreading ridge under a normal tensile-stress within a homogeneous and isotropic medium. Along- and across-axis segment separations were varied incrementally for left- and right-stepping senses. The results show that the ratio of along-axis to across-axis segment tip separation is a dominant control of stress field rotation within an NTD. Features which most clearly show rotation within an NTD include basins and tectonically controlled constructional ridges. The obliquity of these features along with measurements of the surrounding fault fabrics are used as a way of observing and determining stress rotations within NTDs along the Central Indian Ridge (CIR). These rotations were used to obtain segment geometries from models where the central tensor showed an equivalentrotation. The results show that geometry has a profound effect on stress field rotation under which large- and small-scale volcanotectonic fabrics form. In addition, a shortfall of the predicted model tip relative to interpreted positions, along with morphology and observation of the ridge fabrics at the terminations to some segments, suggests the existence of a zone, broadly analogous to theprocess zone observed in fracture mechanics, which we call a damage zone. Given the criteria for the promotion of hydrothermal circulation, this damage zone would have a greater potential for hosting hydrothermal activity.<br/
Using VO tools to investigate distant radio starbursts hosting obscured AGN in the HDF(N) region
A 10-arcmin field around the HDF(N) contains 92 radio sources >40 uJy,
resolved by MERLIN+VLA at 0".2-2".0 resolution. 55 have Chandra X-ray
counterparts including 18 with a hard X-ray photon index and high luminosity
characteristic of a type-II (obscured) AGN. >70% of the radio sources have been
classified as starbursts or AGN using radio morphologies, spectral indices and
comparisons with optical appearance and MIR emission. Starbursts outnumber
radio AGN 3:1. This study extends the VO methods previously used to identify
X-ray-selected obscured type-II AGN to investigate whether very luminous radio
and X-ray emission originates from different phenomena in the same galaxy. The
high-redshift starbursts have typical sizes of 5--10 kpc and star formation
rates of ~1000 Msun/yr. There is no correlation between radio and X-ray
luminosities nor spectral indices at z>~1.3. ~70% of both the radio-selected
AGN and the starburst samples were detected by Chandra. The X-ray luminosity
indicates the presence of an AGN in at least half of the 45 cross-matched radio
starbursts, of which 11 are type-II AGN including 7 at z>1.5. This distribution
overlaps closely with the X-ray detected radio sources which were also detected
by SCUBA. Stacked 1.4-GHz emission at the positions of radio-faint X-ray
sources is correlated with X-ray hardness. Most extended radio starbursts at
z>1.3 host X-ray selected obscured AGN. Radio emission from most of these
ultra-luminous objects is dominated by star formation but it contributes less
than 1/3 of their X-ray luminosity. Our results support the inferences from
SCUBA and IR data, that at z>1.5, star formation is an order of magnitude more
extended and more copious, it is closely linked to AGN activity and it is
triggered differently, compared with star formation at lower redshifts.Comment: 24 pages, 12 figures, uses graphicx, rotating, natbib, supertabular
packages and aa.cls. Accepted for publication in A&
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