Finite-Size Scaling Exponents in the Dicke Model

We consider the finite-size corrections in the Dicke model and determine the scaling exponents at the critical point for several quantities such as the ground state energy or the gap. Therefore, we use the Holstein-Primakoff representation of the angular momentum and introduce a nonlinear transformation to diagonalize the Hamiltonian in the normal phase. As already observed in several systems, these corrections turn out to be singular at the transition point and thus lead to nontrivial exponents. We show that for the atomic observables, these exponents are the same as in the Lipkin-Meshkov-Glick model, in agreement with numerical results. We also investigate the behavior of the order parameter related to the radiation mode and show that it is driven by the same scaling variable as the atomic one.Comment: 4 pages, published versio

Factors Associated with Haemoglobin Concentration among Timor-Leste Children Aged 6–59 Months

The study was conducted to assess the prevalence of and factors associated with haemoglobin (Hb) concentrations among children aged 6–59 months in Timor-Leste. The 2003 Demographic and Health Survey was a multi-stage cluster survey of 4,320 households from four different geographic regions in Timor-Leste. In total, 4,514 children aged 6–59 months were included in the analysis. The prevalence of anaemia (Hb concentration <11.0g/dL) was 38.2% (638/1,668) for children aged 6–23 months and 22.6% (644/2,846) for older children (p<0.001). Girls had a higher mean Hb concentration than boys (11.9g/dL vs 11.7g/dL, p<0.006) and children who had diarrhoea in the previous two weeks had a lower Hb concentration than children without diarrhoea (11.5g/dL vs 11.9g/dL, p<0.001). Children from the richest and middle-class households had a lower average Hb concentration than those from the poorest households (11.8g/dL, 11.7g/dL vs 12.0g/dL, p<0.001). Children of mothers with some secondary or more education had a lower mean Hb concentration than children of mothers with completed primary, some primary and no education (11.7 g/dL vs 11.9 g/dL, 11.8 g/dL, and 11.9 g/dL, p=0.002). Children from severely-anaemic mothers had a lower mean Hb concentration than children from moderately-, mild and not anaemic mothers (10.5 g/dL vs 11.1 g/dL, 11.6 g/dL, 12.0 g/dL, p<0.001). After backward stepwise hierarchical multiple regression, wasting, male sex, recent diarrhoea, household wealth index (richest and middle-class), maternal educational status (some secondary or more and some primary), and maternal anaemic status were significantly associated with a lower Hb concentration in children and increased age of child and duration of breastfeeding (6 months) with a higher Hb concentration. Anaemia-prevention programmes among children in Timor-Leste should focus on those children aged less than two years, children with recent diarrhoea, wasted children, high socioeconomic status, and anaemic mothers

Phytoplankton communities and acclimation in a cyclonic eddy in the southwest Indian Ocean

A study of phytoplankton in a cyclonic eddy was undertaken in the Mozambique Basin between Madagascar and southern Africa during austral winter. CHEMTAX analysis of pigment data indicated that the community comprised mainly haptophytes and diatoms, with Prochlorococcus, prasinophytes and pelagophytes also being prominent to the east and west of the eddy. There was little difference in community structure, chlorophyll-specific absorption [a*ph(440)] and pigment:TChla ratios between the surface and the sub-surface chlorophyll maximum (SCM), reflecting acclimation to fluctuating light conditions in a well mixed upper layer. Values for a*ph(440) were low for diatom dominance, high where prokaryote proportion was high, and intermediate for flagellate dominated communities. Chlorophyll c and fucoxanthin:TChla ratios were elevated over most of the eddy, while 19′-hexanoyloxyfucoxanthin ratios increased in the eastern and western sectors. In a community comprising mainly flagellates and Prochlorococcus to the west of the eddy, there was high a*ph(440) at the surface and elevated ratios for divinyl chlorophyll a, chlorophyll b and 19′-hexanoyloxyfucoxanthin at the SCM. An increase in diadinoxanthin:TChla ratios and a decline in the quantum efficiency of photochemistry in PSII under high light conditions, indicated some photoprotection and photoinhibition at the surface even in a well mixed environment. Diadinoxanthin was the main photoprotective carotenoid within the eddy, while zeaxanthin was the dominant photoprotective pigment outside the eddy. The results of this study will be useful inputs into appropriate remote sensing models for estimating primary production and the size class distribution of phytoplankton in eddies in the southwest Indian Ocean

Factors Associated with Haemoglobin Concentration among Timor-Leste Children Aged 6-59 Months

The study was conducted to assess the prevalence of and factors associated with haemoglobin (Hb) concentrations among children aged 6-59 months in Timor-Leste. The 2003 Demographic and Health Survey was a multi-stage cluster survey of 4,320 households from four different geographic regions in Timor-Leste. In total, 4,514 children aged 6-59 months were included in the analysis. The prevalence of anaemia (Hb concentration &lt;11.0g/dL) was 38.2% (638/1,668) for children aged 6-23 months and 22.6% (644/2,846) for older children (p&lt;0.001). Girls had a higher mean Hb concentration than boys (11.9g/dL vs 11.7g/ dL, p&lt;0.006) and children who had diarrhoea in the previous two weeks had a lower Hb concentration than children without diarrhoea (11.5g/dL vs 11.9g/dL, p&lt;0.001). Children from the richest and middleclass households had a lower average Hb concentration than those from the poorest households (11.8g/ dL, 11.7g/dL vs 12.0g/dL, p&lt;0.001). Children of mothers with some secondary or more education had a lower mean Hb concentration than children of mothers with completed primary, some primary and no education (11.7 g/dL vs 11.9 g/dL, 11.8 g/dL, and 11.9 g/dL, p=0.002). Children from severely-anaemic mothers had a lower mean Hb concentration than children from moderately-, mild and not anaemic mothers (10.5 g/dL vs 11.1 g/dL, 11.6 g/dL, 12.0 g/dL, p&lt;0.001). After backward stepwise hierarchical multiple regression, wasting, male sex, recent diarrhoea, household wealth index (richest and middle-class), maternal educational status (some secondary or more and some primary), and maternal anaemic status were significantly associated with a lower Hb concentration in children and increased age of child and duration of breastfeeding (6 months) with a higher Hb concentration. Anaemia-prevention programmes among children in Timor-Leste should focus on those children aged less than two years, children with recent diarrhoea, wasted children, high socioeconomic status, and anaemic mothers

Patient safety in developing countries: retrospective estimation of scale and nature of harm to patients in hospital

OBJECTIVE: To assess the frequency and nature of adverse events to patients in selected hospitals in developing or transitional economies. DESIGN: Retrospective medical record review of hospital admissions during 2005 in eight countries. SETTING: Ministries of Health of Egypt, Jordan, Kenya, Morocco, Tunisia, Sudan, South Africa and Yemen; the World Health Organisation (WHO) Eastern Mediterranean and African Regions (EMRO and AFRO), and WHO Patient Safety. PARTICIPANTS: Convenience sample of 26 hospitals from which 15,548 patient records were randomly sampled. MAIN OUTCOME MEASURES: Two stage screening. Initial screening based on 18 explicit criteria. Records that screened positive were then reviewed by a senior physician for determination of adverse event, its preventability, and the resulting disability. RESULTS: Of the 15,548 records reviewed, 8.2% showed at least one adverse event, with a range of 2.5% to 18.4% per country. Of these events, 83% were judged to be preventable, while about 30% were associated with death of the patient. About 34% adverse events were from therapeutic errors in relatively non-complex clinical situations. Inadequate training and supervision of clinical staff or the failure to follow policies or protocols contributed to most events. CONCLUSIONS: Unsafe patient care represents a serious and considerable danger to patients in the hospitals that were studied, and hence should be a high priority public health problem. Many other developing and transitional economies will probably share similar rates of harm and similar contributory factors. The convenience sampling of hospitals might limit the interpretation of results, but the identified adverse event rates show an estimate that should stimulate and facilitate the urgent institution of appropriate remedial action and also to trigger more research. Prevention of these adverse events will be complex and involves improving basic clinical processes and does not simply depend on the provision of more resources

Cross sectional study of performance indicators for English Primary Care Trusts: testing construct validity and identifying explanatory variables

BACKGROUND: The performance of Primary Care Trusts in England is assessed and published using a number of different performance indicators. Our study has two broad purposes. Firstly, to find out whether pairs of indicators that purport to measure similar aspects of quality are correlated (as would be expected if they are both valid measures of the same construct). Secondly, we wanted to find out whether broad (global) indicators correlated with any particular features of Primary Care Trusts, such as expenditure per capita. METHODS: Cross sectional quantitative analysis using data from six 2004/05 PCT performance indicators for 303 English Primary Care Trusts from four sources in the public domain: Star Rating, aggregated Quality and Outcomes Framework scores, Dr Foster mortality index, Dr Foster equity index (heart by-pass and hip replacements), NHS Litigation Authority Risk Management standards and Patient Satisfaction scores from the Star Ratings. Forward stepwise multiple regression analysis to determine the effect of Primary Care Trust characteristics on performance. RESULTS: Star Rating and Quality and Outcomes Framework total, both summary measures of global quality, were not correlated with each other (F = 0.66, p = 0.57). There were however positive correlations between Quality and Outcomes Framework total and patient satisfaction (r = 0.61, p < 0.001) and between screening/'additional services' indicators on the Star Ratings and Quality and Outcomes Framework (F = 24, p < 0.001). There was no correlation between different measures of access to services. Likewise we found no relationship between either Star Rating or Litigation Authority Standards and hospital mortality (F = 0.61, p = 0.61; F = 0.31, p = 0.73). CONCLUSION: Performance assessment in healthcare remains on the Government's agenda, with new core and developmental standards set to replace the Star Ratings in 2006. Yet the results of this analysis provide little evidence that the current indicators have sufficient construct validity to measure the underlying concept of quality, except when the specific area of screening is considered

Environmental influence on phytoplankton communities in the northern Benguela ecosystem

An investigation of surface phytoplankton communities was undertaken on the shelf of the northern Benguela upwelling ecosystem during austral autumn (May) and spring (September), along latitudinal transects at 20° S and 23° S, from 2 to 70 nautical miles offshore, as well as on a zigzag grid located between these transects. Microscopic identification of the phytoplankton and CHEMTAX analysis of pigment biomarkers were used to characterise the community composition. During May 2014, warmer, more-saline water with a shallower upper mixed layer corresponding to periods of less-intense offshore Ekman transport was encountered on the shelf. Satellite imagery indicated high phytoplankton biomass extending for a considerable distance from the coast, and CHEMTAX indicated diatoms as dominant at most of the stations (52–92%), although dinoflagellates were dominant at some inshore localities (57–74%). Species of Chaetoceros, Bacteriastrum and Cylindrotheca were the most abundant, with abundance of the Pseudo-nitzschia ‘seriata-group’ being particularly high at a number of stations. In September 2014, more-intense wind-forcing resulted in a deeper upper mixed layer and stronger upwelling of colder, less-saline water. Elevated phytoplankton biomass was confined close to the coast, where diatoms accounted for most of the population (54–87%), whereas small flagellates, such as prasinophytes, haptophytes and cryptophytes, as well as the cyanobacterium Synechococcus, dominated the communities (58–90%) farther from the coast. It is hypothesised that stronger upwelling and deeper vertical mixing in September of that year were not conducive for widespread diatom growth, and that small flagellates populated the water column by being entrained from offshore onto the shelf in the upwelled water that moved in towards the coast

Long-Time Tails and Anomalous Slowing Down in the Relaxation of Spatially Inhomogeneous Excitations in Quantum Spin Chains

Exact analytic calculations in spin-1/2 XY chains, show the presence of long-time tails in the asymptotic dynamics of spatially inhomogeneous excitations. The decay of inhomogeneities, for $t\to \infty$, is given in the form of a power law $$(t/\tau_{Q}) ^{-\nu_{Q}}$$ where the relaxation time $\tau_{Q}$ and the exponent $\nu_{Q}$ depend on the wave vector $Q$, characterizing the spatial modulation of the initial excitation. We consider several variants of the XY model (dimerized, with staggered magnetic field, with bond alternation, and with isotropic and uniform interactions), that are grouped into two families, whether the energy spectrum has a gap or not. Once the initial condition is given, the non-equilibrium problem for the magnetization is solved in closed form, without any other assumption. The long-time behavior for $t\to \infty$ can be obtained systematically in a form of an asymptotic series through the stationary phase method. We found that gapped models show critical behavior with respect to $Q$, in the sense that there exist critical values $Q_{c}$, where the relaxation time $\tau_{Q}$ diverges and the exponent $\nu_{Q}$ changes discontinuously. At those points, a slowing down of the relaxation process is induced, similarly to phenomena occurring near phase transitions. Long-lived excitations are identified as incommensurate spin density waves that emerge in systems undergoing the Peierls transition. In contrast, gapless models do not present the above anomalies as a function of the wave vector $Q$.Comment: 25 pages, 2 postscript figures. Manuscript submitted to Physical Review

The most dangerous hospital or the most dangerous equation?

<p>Abstract</p> <p>Background</p> <p>Hospital mortality rates are one of the most frequently selected indicators for measuring the performance of NHS Trusts. A recent article in a national newspaper named the hospital with the highest or lowest mortality in the 2005/6 financial year; a report by the organization Dr Foster Intelligence provided information with regard to the performance of all NHS Trusts in England.</p> <p>Methods</p> <p>Basic statistical theory and computer simulations were used to explore the relationship between the variations in the performance of NHS Trusts and the sizes of the Trusts. Data of hospital standardised mortality ratio (HSMR) of 152 English NHS Trusts for 2005/6 were re-analysed.</p> <p>Results</p> <p>A close examination of the information reveals a pattern which is consistent with a statistical phenomenon, discovered by the French mathematician de Moivre nearly 300 years ago, described in every introductory statistics textbook: namely that variation in performance indicators is expected to be greater in small Trusts and smaller in large Trusts. From a statistical viewpoint, the number of deaths in a hospital is not in proportion to the size of the hospital, but is proportional to the square root of its size. Therefore, it is not surprising to note that small hospitals are more likely to occur at the top and the bottom of league tables, whilst mortality rates are independent of hospital sizes.</p> <p>Conclusion</p> <p>This statistical phenomenon needs to be taken into account in the comparison of hospital Trusts performance, especially with regard to policy decisions.</p

Health behaviours associated with healthy body composition among Aboriginal adolescents in Australia in the ‘Next Generation: Youth Well-being study’

OnlinePublThis study described the distribution of healthy body composition among Aboriginal adolescents in Australia aged 10–24 years and examined associations with health behaviours and self-rated health. Data were crosssectional from the ‘Next Generation: Youth Well-being study’ baseline (N = 1294). We used robust Poisson regression to quantify associations of self-reported health behaviours (physical activity, screen time, sleep, consumption of vegetables, fruit, soft drinks and fast food, and tobacco smoking and alcohol) and self-rated health to healthy body mass index (BMI) and waist/height ratio (WHtR). Overall, 48% of participants had healthy BMI and 64% healthy WHtR, with healthy body composition more common among younger adolescents. Higher physical activity was associated with healthy body composition (5–7 days last week vs none; adjusted prevalence ratio (aPR) healthy BMI 1.31 [95% CI 1.05–1.64], and healthy WHtR 1.30 [1.10–1.54]), as was recommended sleep duration (vs not; aPR healthy BMI 1.56 [1.19–2.05], and healthy WHtR 1.37 [1.13–1.67]). There was a trend for higher proportion of healthy body composition with more frequent fast food consumption. Healthy body composition was also associated with higher self-rated health (‘very good/excellent’ vs ‘poor/fair’; aPR healthy BMI 1.87 [1.45–2.42], and healthy WHtR 1.71 [1.40–2.10]). Culturally appropriate community health interventions with a focus on physical activity and sleep may hold promise for improving body composition among Aboriginal adolescents.Christopher D. McKay, Lina Gubhaju, Alison J. Gibberd, Bridgette J. McNamara, Rona Macniven, Grace Joshy, Robert Roseby, Robyn Williams, Aryati Yashadhana, Ted Fields, Bobby Porykali, Peter Azzopardi, Emily Banks, Sandra J. Eade