Spatial mode detection by frequency upconversion

The efficient creation and detection of spatial modes of light has become topical of late, driven by the need to increase photon-bit-rates in classical and quantum communications. Such mode creation/detection is traditionally achieved with tools based on linear optics. Here we put forward a new spatial mode detection technique based on the nonlinear optical process of sum-frequency generation. We outline the concept theoretically and demonstrate it experimentally with intense laser beams carrying orbital angular momentum and Hermite-Gaussian modes. Finally, we show that the method can be used to transfer an image from the infrared band to the visible, which implies the efficient conversion of many spatial modes.Comment: Published version, 4 pages, 5 figure

X-Ray Emission from Rotating Elliptical Galaxies

The slow inward flow of the hot gas in elliptical galaxy cooling flows is nearly impossible to detect directly due to instrumental limitations. However, in rotating galaxies, if the inflowing gas conserves angular momentum, it will eventually form a disk. The X-ray signature of this phenomenon is a flattening of the X-ray isophotes in the inner 1-10 kpc region. This effect is observable, so we have searched for it in X-ray observations of six rotating and non-rotating early-type galaxies, obtained mainly with the ROSAT PSPC and HRI imagers. The ellipticities of the X-ray emission never increase toward the central region, nor are the X-ray ellipticities significantly greater than the ellipticities for the optical stellar emission. Central ellipticities in excess of 0.5 were expected in rotating ellipticals whereas values of 0-0.2 are measured. The failure to detect the expected signature requires a modification to the standard cooling flow picture, possibly including partial galactic winds, rapid mass drop-out, or turbulent redistribution of angular momentum.Comment: 34 postscript pages; ApJ, in press (Feb 10,2000

The SLUGGS Survey: Calcium Triplet-based Spectroscopic Metallicities for Over 900 Globular Clusters

Although the colour distribution of globular clusters in massive galaxies is well known to be bimodal, the spectroscopic metallicity distribution has been measured in only a few galaxies. After redefining the calcium triplet index-metallicity relation, we use our relation to derive the metallicity of 903 globular clusters in 11 early-type galaxies. This is the largest sample of spectroscopic globular cluster metallicities yet assembled. We compare these metallicities with those derived from Lick indices finding good agreement. In 6 of the 8 galaxies with sufficient numbers of high quality spectra we find bimodality in the spectroscopic metallicity distribution. Our results imply that most massive early-type galaxies have bimodal metallicity, as well as colour, distributions. This bimodality suggests that most massive galaxies early-type galaxies experienced two periods of star formation.Comment: 23 pages, 13 figures. Accepted for publication in MNRAS. For more information about the SLUGGS Survey please see http://sluggs.swin.edu.a

Interventions targeted at women to encourage the uptake of cervical screening

BACKGROUND World-wide, cervical cancer is the second most common cancer in women. Increasing the uptake of screening, alongside increasing informed choice is of great importance in controlling this disease through prevention and early detection. OBJECTIVES To assess the effectiveness of interventions aimed at women, to increase the uptake, including informed uptake, of cervical cancer screening. SEARCH STRATEGY We searched the Cochrane Gynaecological Cancer Group Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), Issue 1, 2009. MEDLINE, EMBASE and LILACS databases up to March 2009. We also searched registers of clinical trials, abstracts of scientific meetings, reference lists of included studies and contacted experts in the field. SELECTION CRITERIA Randomised controlled trials (RCTs) of interventions to increase uptake/informed uptake of cervical cancer screening. DATA COLLECTION AND ANALYSIS Two review authors independently abstracted data and assessed risk of bias. Where possible the data were synthesised in a meta-analysis. MAIN RESULTS Thirty-eight trials met our inclusion criteria. These trials assessed the effectiveness of invitational and educational interventions, counselling, risk factor assessment and procedural interventions. Heterogeneity between trials limited statistical pooling of data. Overall, however, invitations appear to be effective methods of increasing uptake. In addition, there is limited evidence to support the use of educational materials. Secondary outcomes including cost data were incompletely documented so evidence was limited. Most trials were at moderate risk of bias. Informed uptake of cervical screening was not reported in any trials. AUTHORS' CONCLUSIONS There is evidence to support the use of invitation letters to increase the uptake of cervical screening. There is limited evidence to support educational interventions but it is unclear what format is most effective. The majority of the studies are from developed countries and so the relevance to developing countries is unclear.Output Type: Revie

Bioelectrical Impedance Analysis (BIA)-derived Phase Angle (PA) is a practical aid to nutritional assessment in hospital in-patients

Background: Nutritional status can be difficult to assess. Bioelectrical impedance analysis (BIA)-derived phase angle (PA), and the plasma markers citrulline and transthyretin (pre-albumin) have the potential to assist, but the protocol of fasting and resting for BIA renders the investigation impractical for routine use, especially so in populations at high risk of malnutrition.  Aims: 1- To clarify whether starving and resting are necessary for reliable measurement of PA. 2- To identify whether PA, citrulline and transthyretin correlate with nutritional status.  Methods: Eighty consenting adult in-patients were recruited. Nutritional status was determined by subjective global assessment (SGA) used as gold standard. The Malnutrition Universal Screening Tool (MUST) was used and anthropometric measurements were performed. Serum was analysed for citrulline and transthyretin. PA was measured using Bodystat 4000. The PA was considered to define malnutrition when lower than reference ranges for sex and age, and severe malnutrition if more than 2 integers below the lower limit. Anthropometric measurements were categorised according to WHO reference centiles. Ordinal logistic regression estimated the strength of association of PA, citrulline and transthyretin with SGA. PA values in the different metabolic states were compared using paired t tests.  Results: All 80 subjects completed the BIA and the nutritional assessments in the 3 different states; 14 declined to provide blood samples for the biochemical assays. Malnutrition was identified in 32 cases, severe malnutrition in 14 cases, the remaining 34 cases were deemed not to be malnourished. PA was strongly inversely associated with SGA (Odds Ratio [OR] per unit increase = 0.21, CI 0.12-0.37, p < 0.001). PA was not influenced by exercise (p=0.134) or food intake (p=0.184). Transthyretin was inversely associated with malnourished/severely malnourished states (OR = 0.98, 95% CI 0.97 – 0.99, p = 0.001), but had poorer predictive values than PA. There was no significant association between citrulline concentration and SGA (OR = 1.01, 95% CI 0.99-1.04, p = 0.348).  Conclusions: The BIA-derived PA reliably identifies malnutrition. It is strongly associated with SGA but requires less skill and experience, and out-performs circulating transthyretin, rendering it a promising and less operator-dependent tool for assessing nutritional status in hospital patients. Our novel demonstration that fasting and bed-rest are unnecessary consolidates that position

Dynamical Evolution of Globular Clusters in Hierarchical Cosmology

We probe the evolution of globular clusters that could form in giant molecular clouds within high-redshift galaxies. Numerical simulations demonstrate that the large and dense enough gas clouds assemble naturally in current hierarchical models of galaxy formation. These clouds are enriched with heavy elements from earlier stars and could produce star clusters in a similar way to nearby molecular clouds. The masses and sizes of the model clusters are in excellent agreement with the observations of young massive clusters. Do these model clusters evolve into globular clusters that we see in our and external galaxies? In order to study their dynamical evolution, we calculate the orbits of model clusters using the outputs of the cosmological simulation of a Milky Way-sized galaxy. We find that at present the orbits are isotropic in the inner 50 kpc of the Galaxy and preferentially radial at larger distances. All clusters located outside 10 kpc from the center formed in the now-disrupted satellite galaxies. The spatial distribution of model clusters is spheroidal, with a power-law density profile consistent with observations. The combination of two-body scattering, tidal shocks, and stellar evolution results in the evolution of the cluster mass function from an initial power law to the observed log-normal distribution.Comment: 5 pages, proceedings of IAU 246 "Dynamical Evolution of Dense Stellar Systems", eds. Vesperini, Giersz, Sill

Dissecting the Red Sequence--II. Star Formation Histories of Early-Type Galaxies Throughout the Fundamental Plane

This analysis uses spectra of ~16,000 nearby SDSS quiescent galaxies to track variations in galaxy star formation histories along and perpendicular to the Fundamental Plane (FP). We sort galaxies by their FP properties (sigma, R_e, and I_e) and construct high S/N mean galaxy spectra that span the breadth and thickness of the FP. From these spectra, we determine mean luminosity-weighted ages, [Fe/H], [Mg/H], and [Mg/Fe] based on single stellar population models using the method described in Graves & Schiavon (2008). In agreement with previous work, the star formation histories of early-type galaxies are found to form a two-parameter family. The major trend is that mean age, [Fe/H], [Mg/H], and [Mg/Fe] all increase with sigma. However, no stellar population property shows any dependence on R_e at fixed sigma, suggesting that sigma and not dynamical mass (M_dyn ~ sigma^2 R_e) is the better predictor of past star formation history. In addition to the main trend with sigma, galaxies also show a range of population properties at fixed sigma that are strongly correlated with surface brightness residuals from the FP, such that higher surface brightness galaxies have younger mean ages, higher [Fe/H], higher [Mg/H], and lower [Mg/Fe] than lower-surface brightness galaxies. These latter trends are a major new constraint on star-formation histories.Comment: 23 pages, 14 figures. Accepted to Ap

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Seed degeneration in potato : the need for an integrated seed health strategy to mitigate the problem in developing countries

Seed potato degeneration, the reduction in yield or quality caused by an accumulation of pathogens and pests in planting material due to successive cycles of vegetative propagation, has been a long-standing production challenge for potato growers around the world. In developed countries this problem has been overcome by general access to and frequent use of seed, produced by specialized growers, that has been certified to have pathogen and pest incidence below established thresholds, often referred to as certified seed. The success of certified seed in developed countries has concentrated the research and development agenda on the establishment of similar systems in developing countries. Despite these efforts, certified seed has had little penetration into the informal seed systems currently in place in most developing countries. Small-scale farmers in these countries continue to plant seed tubers acquired through the informal seed system, i.e. produced on-farm or acquired from neighbours or local markets. Informal seed tubers frequently have poor health status, leading to significant reductions in yield and/or market value. This review emphasizes the need to refocus management efforts in developing countries on improving the health status of seed tubers in the informal system by integrating disease resistance and on-farm management tools with strategic seed replacement. This 'integrated seed health strategy' can also prolong the good health status of plants derived from certified seed, which would otherwise be diminished due to potential rapid infection from neighbouring fields. Knowledge gaps, development challenges and impacts of this integrated seed health strategy are discussed.PostprintPeer reviewe

Globular cluster formation within the Aquarius simulation

The Aquarius project is a very high-resolution simulation capable of resolving the full mass range of potential globular cluster (GC) formation sites. With a particle mass mp= 1.4 × 104 M¿, Aquarius yields more than 100 million particles within the virial radius of the central halo which has a mass of 1.8 × 1012 M¿, similar to that of the Milky Way. With this particle mass, dark matter concentrations (haloes) that give rise to GCs via our formation criteria contain a minimum of ~2000 particles. Here, we use this simulation to test a model of metal-poor GC formation based on collapse physics. In our model, GCs form when the virial temperatures of haloes first exceed 104 K as this is when electronic transitions allow the gas to cool efficiently. We calculate the ionizing flux from the stars in these first clusters and stop the formation of new clusters when all the baryonic gas of the Galaxy is ionized. This is achieved by adopting reasonable values for the star formation efficiencies and escape fraction of ionizing photons which result in similar numbers and masses of clusters to those found in the Milky Way. The model is successful in that it predicts ages (peak age ~13.3 Gyr) and a spatial distribution of metal-poor GCs which are consistent with the observed populations in the Milky Way. The model also predicts that less than 5 per cent of GCs within a radius of 100 kpc have a surviving dark matter halo, but the more distant clusters are all found in dark matter concentrations. We then test a scenario of metal-rich cluster formation by examining mergers that trigger star formation within central gas discs. This results in younger (~7¿13.3 Gyr), more centrally located clusters (40 metal-rich GCs within 18 kpc from the centre of the host) which are consistent with the Galactic metal-rich population. We test an alternate model in which metal-rich GCs form in dwarf galaxies that become stripped as they merge with the main halo. This process is inconsistent with observed metal-rich globulars in the Milky Way because it predicts spatial distributions that are far too extended