An Extremely Luminous Galaxy at z=5.74

We report the discovery of an extremely luminous galaxy lying at a redshift of z=5.74, SSA22-HCM1. The object was found in narrowband imaging of the SSA22 field using a 105 Angstrom bandpass filter centered at 8185 Angstroms during the course of the Hawaii narrowband survey using LRIS on the 10 m Keck II Telescope, and was identified by the equivalent width of the emission W_lambda(observed)=175 Angstroms, flux = 1.7 x 10^{-17} erg cm^{-2} s^{-1}). Comparison with broadband colors shows the presence of an extremely strong break (> 4.2 at the 2 sigma level) between the Z band above the line, where the AB magnitude is 25.5, and the R band below, where the object is no longer visible at a 2 sigma upper limit of 27.1 (AB mags). These properties are only consistent with this object's being a high-z Ly alpha emitter. A 10,800 s spectrum obtained with LRIS yields a redshift of 5.74. The object is similar in its continuum shape, line properties, and observed equivalent width to the z=5.60 galaxy, HDF 4-473.0, as recently described by Weymann et al. (1998), but is 2-3 times more luminous in the line and in the red continuum. For H_0 = 65 km s^{-1} Mpc^{-1} and q_0 = (0.02, 0.5) we would require star formation rates of around (40, 7) solar masses per year to produce the UV continuum in the absence of extinction.Comment: 5 pages, 4 figures, Latex with emulateapj style file; to appear in the Astrophysical Journal (Letters

Cytokine gene polymorphisms in preterm infants with necrotising enterocolitis: genetic association study

BACKGROUND The inflammatory cytokine cascade is implicated in the pathogenesis of necrotising enterocolitis (NEC). Genetic association studies of cytokine polymorphisms may help to detect molecular mechanisms that are causally related to the disease process. AIM To examine associations between the common genetic variants in candidate inflammatory cytokine genes and NEC in preterm infants. METHODS Multi-centre case-control and genetic association study. DNA samples were collected from 50 preterm infants with NEC and 50 controls matched for gestational age and ethnic group recruited to a multi-centre case-control study. Ten candidate single-nucleotide polymorphisms in cytokines previously associated with infectious or inflammatory diseases were genotyped. The findings were included in random-effects meta-analyses with data from previous genetic association studies. RESULTS All allele distributions were in Hardy-Weinberg equilibrium. None of the studied cytokine polymorphisms was significantly associated with NEC. Four previous genetic association studies of cytokine polymorphisms and NEC in preterm infants were found. Meta-analyses were possible for several single-nucleotide polymorphisms. These increased the precision of the estimates of effect size but did not reveal any significant associations. CONCLUSIONS The available data are not consistent with more than modest associations between these candidate cytokine variant alleles and NEC in preterm infants. Data from future association studies of these polymorphisms may be added to the meta-analyses to obtain more precise estimates of effects sizes.The study was funded by Tenovus (Scotland)

The Density of Lyman-alpha Emitters at Very High Redshift

We describe narrowband and spectroscopic searches for emission-line star forming galaxies in the redshift range 3 to 6 with the 10 m Keck II Telescope. These searches yield a substantial population of objects with only a single strong (equivalent width >> 100 Angstrom) emission line, lying in the 4000 - 10,000 Angstrom range. Spectra of the objects found in narrowband-selected samples at lambda ~5390 Angstroms and ~6741 Angstroms show that these very high equivalent width emission lines are generally redshifted Lyman alpha 1216 Angstrom at z~3.4 and 4.5. The density of these emitters above the 5 sigma detection limit of 1.5 e-17 ergs/cm^2/s is roughly 15,000 per square degree per unit redshift interval at both z~3.4 and 4.5. A complementary deeper (1 sigma \~1.0 e-18 ergs/cm^2/s) slit spectroscopic search covering a wide redshift range but a more limited spatial area (200 square arcminutes) shows such objects can be found over the redshift range 3 to 6, with the currently highest redshift detected being at z=5.64. The Lyman alpha flux distribution can be used to estimate a minimum star formation rate in the absence of reddening of roughly 0.01 solar masses/Mpc^3/year (H_0 = 65 km/s/Mpc and q_0 = 0.5). Corrections for reddening are likely to be no larger than a factor of two, since observed equivalent widths are close to the maximum values obtainable from ionization by a massive star population. Within the still significant uncertainties, the star formation rate from the Lyman alpha-selected sample is comparable to that of the color-break-selected samples at z~3, but may represent an increasing fraction of the total rates at higher redshifts. This higher-z population can be readily studied with large ground-based telescopes.Comment: 7 pages, 5 encapsulated figures; aastex, emulateapj, psfig and lscape style files. Separate gif files for 2 gray-scale images also available at http://www.ifa.hawaii.edu/faculty/hu/emitters.html . Added discussion of foreground contaminants. Updated discussion of comparison with external surveys (Sec. 5 and Fig. 5). Note: continuum break strength limits (Fig. 3 caption) are correct here -- published ApJL text has a sign erro

Managing an Ageing Population: Challenging Oral Epidemiology

Global population projections indicate that the proportion of older people is increasing and will continue to do so for the foreseeable future. Many countries are already experiencing the challenges of managing an ageing population, including increased pension contributions from workers, rises to national retirement ages, and spiralling healthcare costs. In oral health terms, in addition to simply an ageing population, epidemiological studies have demonstrated significant changes in the oral health of older adults in recent years. As the numbers of edentulous older adults has declined, there has been a significant increase in the number of partially dentate elderly. Changing attitudes, improved access to dental care and more effective preventative programmes have meant that large numbers of patients are now retaining natural teeth into old age. However, as older patients retain natural teeth for longer, the dental profession is charged with controlling chronic dental diseases in an increasingly challenging oral environment

Physical Conditions of Accreting Gas in T Tauri Star Systems

We present results from a low resolution (R~300) near-infrared spectroscopic variability survey of actively accreting T Tauri stars (TTS) in the Taurus-Auriga star forming region. Paschen and Brackett series H I recombination lines were detected in 73 spectra of 15 classical T Tauri systems. The values of the Pan/PaB, Brn/BrG, and BrG/Pan H I line ratios for all observations exhibit a scatter of < 20% about the weighted mean, not only from source to source, but also for epoch-to-epoch variations in the same source. A representative or `global' value was determined for each ratio in both the Paschen and Brackett series as well as the BrG/Pan line ratios. A comparison of observed line ratio values was made to those predicted by the temperature and electron density dependent models of Case B hydrogen recombination line theory. The measured line ratios are statistically well-fit by a tightly constrained range of temperatures (T < 2000 K) and electron densities 1e9 < n_e < 1e10 cm^-3. A comparison of the observed line ratio values to the values predicted by the optically thick and thin local thermodynamic equilibrium cases rules out these conditions for the emitting H I gas. Therefore, the emission is consistent with having an origin in a non-LTE recombining gas. While the range of electron densities is consistent with the gas densities predicted by existing magnetospheric accretion models, the temperature range constrained by the Case B comparison is considerably lower than that expected for accreting gas. The cooler gas temperatures will require a non-thermal excitation process (e.g., coronal/accretion-related X-rays and UV photons) to power the observed line emission.Comment: 12 pages, emulateapj format, Accepted for publication in Ap

The effect of collisional enhancement of Balmer lines on the determination of the primordial helium abundance

This paper describes a new determination of the primordial helium abundance (Y_P), based on the abundance analysis of five metal-poor extragalactic HII regions. For three regions of the sample (SBS 0335-052, I Zw 18, and H29) we present tailored photoionization models based on improved calculations with respect to previous models. In particular, we use the photoionization models to study quantitatively the effect of collisional excitation of Balmer lines on the determination of the helium abundance (Y) in the individual regions. This effect is twofold: first, the intensities of the Balmer lines are enhanced with respect to the pure recombination value, mimicking a higher hydrogen abundance; second, the observed reddening is larger than the true extinction, due to the differential effect of collisions on different Balmer lines. In addition to these effects, our analysis takes into account the following features of HII regions: (i) the temperature structure, (ii) the density structure, (iii) the presence of neutral helium, (iv) the collisional excitation of the HeI lines, (v) the underlying absorption of the HeI lines, and (vi) the optical thickness of the HeI lines. The object that shows the highest increase in Y after the inclusion of collisional effects in the analysis is SBS 0335-052, whose helium abundance has been revised by Delta Y = +0.0107. The revised Y values for the five objects in our sample yield an increase of +0.0035 in Y_P, giving Y_P = 0.2391 +/- 0.0020.Comment: 59 pages, 8 figures. AAS Latex. Accepted for publication in the Astrophysical Journa

Dental Attendances to General Medical Practitioners in Wales: a 44 Year Analysis

One-third of the UK population is composed of problem-oriented dental attenders, seeking dental care only when they have acute dental pain or problems. Patients seek urgent dental care from a range of health care professionals, including general medical practitioners. This study aimed to identify trends in dental attendance at Welsh medical practices over a 44-y period, specifically in relation to dental policy change and factors associated with repeat attendance. A retrospective observational study was completed via the nationwide Secure Anonymised Information Linkage (SAIL) Databank of visits to general medical practice in Wales. Read codes associated with dental diagnoses were extracted for patients attending their general medical practitioner between 1974 and 2017. Data were analyzed with descriptive statistics and univariate and multivariable logistic regression. Over the 44-y period, there were 439,361 dental Read codes, accounting for 288,147 patient attendances. The overall attendance rate was 2.60 attendances per 1,000 patient-years (95% CI, 2.59 to 2.61). The attendance rate was negligible through 1987 but increased sharply to 5.0 per 1,000 patient-years in 2006 (95% CI, 4.94 to 5.09) before almost halving to 2.6 per 1,000 in 2017 (95% CI, 2.53 to 2.63) to a pattern that coincided with changes to National Health Service policies. Overall 26,312 patients were repeat attenders and were associated with living in an area classified as urban and deprived (odds ratio [OR], 1.22; 95% CI, 1.19 to 1.25; P < 0.0001) or rural (OR, 0.84; 95% CI, 0.83 to 0.85; P < 0.0001). Repeat attendance was associated with greater odds of having received an antibiotic prescription (OR, 2.53; 95% CI, 2.50 to 2.56; P < 0.0001) but lower odds of having been referred to another service (OR, 0.75; 95% CI, 0.70 to 0.81; P < 0.0001). Welsh patients’ reliance on medical care for dental problems was influenced by social deprivation and health policy. This indicates that future interventions to discourage dental attendance at medical practitioners should be targeted at those in the most deprived urban areas or rural areas. In addition, health policy may influence attendance rates positively and negatively and should be considered in the future when decisions related to policy change are made

Theoretical He I Emissivities in the Case B Approximation

We calculate the He I case B recombination cascade spectrum using improved radiative and collisional data. We present new emissivities over a range of electron temperatures and densities. The differences between our results and the current standard are large enough to have a significant effect not only on the interpretation of observed spectra of a wide variety of objects but also on determinations of the primordial helium abundance.Comment: Accepted to ApJ

The primordial Helium-4 abundance determination: systematic effects

By extrapolating to O/H = N/H = 0 the empirical correlations Y-O/H and Y-N/H defined by a relatively large sample of ~ 45 Blue Compact Dwarfs (BCDs), we have obtained a primordial 4Helium mass fraction Yp= 0.2443+/-0.0015 with dY/dZ = 2.4+/-1.0. This result is in excellent agreement with the average Yp= 0.2452+/-0.0015 determined in the two most metal-deficient BCDs known, I Zw 18 (Zsun/50) and SBS 0335-052 (Zsun/41), where the correction for He production is smallest. The quoted error (1sigma) of < 1% is statistical and does not include systematic effects. We examine various systematic effects including collisional excitation of Hydrogen lines, ionization structure and temperature fluctuation effects, and underlying stellar HeI absorption, and conclude that combining all systematic effects, our Yp may be underestimated by ~ 2-4%. Taken at face value, our Yp implies a baryon-to-photon number ratio eta = 4.7x10^-10 and a baryon mass fraction Omega_b h^2_{100} = 0.017+/-0.005 (2sigma), consistent with the values obtained from deuterium and Cosmic Microwave Background measurements. Correcting Yp upward by 2-4% would make the agreement even better.Comment: 12 pages, 5 PS figures, to appear in "Matter in the Universe", ed P. Jetzer, K. Pretzl and R. von Steiger, Kluwer, Dordrecht (2002