8,456 research outputs found
Intraday credit: risk, value, and pricing
An abstract for this article is not availableElectronic funds transfers ; Payment systems ; Overdrafts
More than the sum of its parts: Cumulative risk effects on school functioning in middle childhood.
BACKGROUND: Risk factors for poor school functioning rarely occur in isolation, but instead are likely to cluster together. As they accumulate, cumulative risk theory (CRT) predicts that the likelihood of negative outcomes increases, often disproportionately. AIMS: We build upon and extend previous research by (i) examining two critical aspects of school functioning (reading attainment and behavioural difficulties); (ii) utilizing a large number of candidate risk factors across multiple ecological domains; (iii) testing the two core assumptions of CRT; and (iv) formally examining the functional form of the risk-outcome relationships. SAMPLE: Participants were NÂ =Â 3084 children aged 6-7 attending 77 mainstream primary schools in England. METHODS: Sixteen candidate risk factors (e.g., familial poverty) were modelled using data from the National Pupil Database. Reading attainment and behavioural difficulties data were generated via teachers' reading assessment scores and the Teacher Observation of Children's Adaptation Checklist (disruptive behaviour subscale), respectively. A cumulative risk score was generated for each pupil. Multilevel modelling was utilized for analysis. RESULTS: Six risk factors were identified for behaviour and seven for reading attainment. A cumulative risk effect was found for both outcomes, and the two core assumptions of CRT were supported. Quadratic relationships were found for both aspects of school functioning, indicative of a threshold effect. CONCLUSIONS: As the number of risk factors increases, difficulties in school functioning increase disproportionately. Consistent with CRT, our results suggest that the number of risks is more important than their nature. This has implications for future risk research and the implementation of school-based interventions
Hydrogen-silicon carbide interactions
A study of the thermochemistry and kinetics of hydrogen environmental attack of silicon carbide was conducted for temperatures in the range from 1100 C to 1400 C. Thermodynamic maps based on the parameters of pressure and oxygen/moisture content were constructed. With increasing moisture levels, four distinct regions of attack were identified. Each region is defined by the thermodynamically stable solid phases. The theoretically stable solid phases of Region 1 are silicon carbide and silicon. Experimental evidence is provided to support this thermodynamic prediction. Silicon carbide is the single stable solid phase in Region 2. Active attack of the silicon carbide in this region occurs by the formation of gases of SiO, CO, CH4, SiH4, and SiH. Analysis of the kinetics of reaction for Region 2 at 1300 C show the attack of the silicon carbide to be controlled by gas phase diffusion of H2O to the sample. Silicon carbide and silica are the stable phases common to Regions 3 and 4. These two regions are characterized by the passive oxidation of silicon carbide and formation of a protective silica layer
Deep spectroscopy of the FUV-optical emission lines from a sample of radio galaxies at z~2.5: metallicity and ionization
We present long-slit NIR spectra, obtained using the ISAAC instrument at the
Very Large Telescope, for nine radio galaxies at z~2.5. One-dimensional spectra
have been extracted and cross calibrated with optical spectra from the
literature to produce line spectra spanning a rest wavelength of ~1200-7000 A.
We have also produced a composite of the rest-frame UV-optical line fluxes of
powerful, z~2.5 radio galaxies. We have investigated the relative strengths of
Ly-alpha, H-beta, H-alpha, HeII 1640 and HeII 4687, and we find that Av can
vary significantly from object to object. In addition, we identify new line
ratios to calculate electron temperature: [NeV] 1575/[NeV] 3426, [NeIV]
1602/[NeIV] 2423, OIII] 1663/[OIII] 5008 and [OII] 2471/[OII]3728. We model the
emission line spectra and conclude they are best explained by
AGN-photoionization with the ionization parameter U varying between objects.
Single slab photoionization models are unable to reproduce the high- and the
low-ionization lines simultaneously: this may be alleviated either by combining
two or more single slab photoionization models with different U, or by using
mixed-medium models such as those of Binette, Wilson & Storchi-Bergmann (1996).
On the basis of NV/NIV] and NIV]/CIV we argue that shocks make a fractional
contribution to the ionization of the EELR. We find that in the EELR of z~2
radio galaxies the N/H abundance ratio is close to its solar value. We conclude
that N/H and metallicity do not vary by more than a factor of two in our
sample. This is consistent with the idea that massive ellipticals are assembled
very early in the history of the universe, and then evolve relatively passively
up to the present day.Comment: Accepted for publication by MNRA
Oral health in Late Pleistocene and Holocene North West Africa
Archaeological sites in North West Africa have yielded a rich record of human occupation, including well dated human burials from the Late Pleistocene Iberomaurusian and early Holocene Capsian periods. The transition broadly coincides with climatic amelioration at the end of the Holocene enabling expansion into slighter dryer inland areas. Here we investigate possible changes in oral health and subsistence behaviours during the transition between the Iberomaurusian (n = 109 individuals) and the Capsian (n = 19 individuals), based on the study of dental remains. Frequencies in oral pathologies (caries, abscesses, periodontal disease and antemortem tooth loss) were studied to assess possible differences between the late Pleistocene and early Holocene. The Late Pleistocene Iberomaurusians were characterised by high caries frequencies (60% of observed teeth). The Capsians displayed very similar patterns in oral pathologies but a slightly lower percentage of carious teeth (49%). The similarity in oral health in Iberomaurusian and Capsian populations is consistent with similarities in diet and oral hygiene. The implication of cultural and biological continuity between the Iberomaurusian and Capsian periods is supported by indicators, such as exploitation of wild plants and snails, tooth evulsion and craniofacial and dental morphology. © 201
- …