Systematic errors in global air-sea CO2 flux caused by temporal averaging of sea-level pressure

International audienceLong-term temporal averaging of meteorological data, such as wind speed and air pressure, can cause large errors in air-sea carbon flux estimates. Other researchers have already shown that time averaging of wind speed data creates large errors in flux due to the non-linear dependence of the gas transfer velocity on wind speed (Bates and Merlivat, 2001). However, in general, wind speed is negatively correlated with air pressure, and a given fractional change in the pressure of dry air produces an equivalent fractional change in the atmospheric partial pressure of carbon dioxide (<i>p</i>CO_2air). Thus low pressure systems cause a drop in <i>p</i>CO_2air, which together with the associated high winds, promotes outgassing/reduces uptake of CO₂ from the ocean. Here we quantify the errors in global carbon flux estimates caused by using monthly or climatological pressure data to calculate <i>p</i>CO_2air (and thus ignoring the covariance of wind and pressure) over the period 1990?1999, using two common parameterisations for gas transfer velocity (Wanninkhof, 1992 (W92) and Wanninkhof and McGillis, 1999 (WM99)). Results show that on average, compared with estimates made using 6 hourly pressure data, the global oceanic sink is systematically overestimated by 7% (W92) and 10% (WM99) when monthly mean pressure is used, and 9% (W92) and 12% (WM99) when climatological pressure is used

Paediatric burns in a rural South African district hospital

Objectives. To describe the epidemiology, clinical features, management and outcome of children with burns admitted to a rural district hospital. Design. A retrospective analysis of the case notes of consecutive cases of paediatric burns. Setting. Hlabisa Hospital, KwaZulu-Natal - a 450-bed rural district hospital serving approximately 200 000 people. Subjects. All cases of paediatric burns (age < 12 years) admitted to Hlabisa Hospital in 1994. Main outcome measures. Number of admissions, month of admission, age, sex, time to presentation, site of burn, complications, number of surgical procedures, adherence to management protocol and outcome. Results. One hundred and forty-nine children presented to the outpatient department in 1994 and 88 (59%) were admitted, The median age of those admitted was 36 months with 66 (75%) aged less than 5 years; 42 (48%) were boys, Thirty-nine children (44%) were admitted during the four winter months of May to August, The average interval from the tirne of the burn to presentation at hospital was 42 hours (range 1 - 120). Sixty-eight burns (77%) were due to hot fluid or food burning the legs, trunk or arms, There was a high level of morbidity, Nineteen (22%) children developed wound infections, 5 (6%) developed contractures and 20 (23%) required a total of 32 surgical procedures, There was 1 death, Burns were responsible for more paediatric patient days spent in hospital than any condition other than malnutrition, and a longer length of stay was associated with delay in presentation, Children presenting within 24 hours of the burn had a mean length of stay of 12.8 days, compared with 25.2 days (P = 0.03) for children presenting 24 hours or more after the burn. Twenty of the 22 children who stayed for longer than 3 weeks or who required transfer were judged to have been managed inadequately in at least one respect compared with 3 of 48 who were discharged within 2 weeks or not transferred (P < 0.001). Conclusion. This study shows that paediatric burns are an important cause of morbidity and contribute significantly to inpatient stay in this rural setting. The lengthy delay from time of burn to presentation at hospital is of serious concern and our results show that this delay is associated with increased hospital stay. As most burns were due to spillage of hot fluids or food there seems to be significant potential for preventive interventions. Community-based studies would help to estimate the true incidence of burns and would contribute to an understanding of the reasons for delay in presentation. The information gathered is being used to inform the development of a burns prevention programme.4 page(s

B-meson decay constants: a more complete picture from full lattice QCD

We extend the picture of $B$-meson decay constants obtained in lattice QCD beyond those of the $B$, $B_s$ and $B_c$ to give the first full lattice QCD results for the $B^*$, $B^*_s$ and $B^*_c$. We use improved NonRelativistic QCD for the valence $b$ quark and the Highly Improved Staggered Quark (HISQ) action for the lighter quarks on gluon field configurations that include the effect of $u/d$, $s$ and $c$ quarks in the sea with $u/d$ quark masses going down to physical values. For the ratio of vector to pseudoscalar decay constants, we find $f_{B^*}/f_B$ = 0.941(26), $f_{B^*_s}/f_{B_s}$ = 0.953(23) (both $2\sigma$ less than 1.0) and $f_{B^*_c}/f_{B_c}$ = 0.988(27). Taking correlated uncertainties into account we see clear indications that the ratio increases as the mass of the lighter quark increases. We compare our results to those using the HISQ formalism for all quarks and find good agreement both on decay constant values when the heaviest quark is a $b$ and on the dependence on the mass of the heaviest quark in the region of the $b$. Finally, we give an overview plot of decay constants for gold-plated mesons, the most complete picture of these hadronic parameters to date.Comment: 20 pages, 9 figures. Minor updates to the discussion in several places and some additional reference

Voltage Control of Exchange Coupling in Phosphorus Doped Silicon

Motivated by applications to quantum computer architectures we study the change in the exchange interaction between neighbouring phosphorus donor electrons in silicon due to the application of voltage biases to surface control electrodes. These voltage biases create electro-static fields within the crystal substrate, perturbing the states of the donor electrons and thus altering the strength of the exchange interaction between them. We find that control gates of this kind can be used to either enhance, or reduce the strength of the interaction, by an amount that depends both on the magnitude and orientation of the donor separation.Comment: 5 Pages, 5 Figure

Multicycle dynamics of fault systems and static and dynamic triggering of earthquakes

Dynamic simulations of rupture propagation and multiple earthquake cycles for varying fault geometries are presented. We investigate the role of both dynamic and static stress changes on earthquake triggering. Dynamic stress triggering of earthquakes is caused by the passage of seismic waves, whereas static stress triggering is due to net slippage on a fault resulting from an earthquake. Static stress changes represented by a Coulomb failure function and its relationship to seismicity rate change is a relatively well-known mechanism, whereas the physical origin of dynamic triggering remains one of the least understood aspects of earthquake nucleation. We investigate these mechanisms by analysing seismicity patterns with varying fault separation, geometry and with and without dynamic triggering present

A statistical model for sea surface diurnal warming driven by numercial weather predictions fluxes and winds

A statistical model is derived relating the diurnal variation of sea surface temperature (SST) to the net surface heat flux and surface wind speed from a numerical weather prediction (NWP) model. The model is derived using fluxes and winds from the European Centre for Medium-Range Weather Forecasting (ECMWF) NWP model and SSTs from the Spinning Enhanced Visible and Infrared Imager (SEVIRI). In the model, diurnal warming has a linear dependence on the net surface heat flux integrated since (approximately) dawn and an inverse quadratic dependence on the maximum of the surface wind speed in the same period. The model coefficients are found by matching, for a given integrated heat flux, the frequency distributions of the maximum wind speed and the observed warming. Diurnal cooling, where it occurs, is modelled as proportional to the integrated heat flux divided by the heat capacity of the seasonal mixed layer. The model reproduces the statistics (mean, standard deviation, and 95-percentile) of the diurnal variation of SST seen by SEVIRI and reproduces the geographical pattern of mean warming seen by the Advanced Microwave Scanning Radiometer (AMSR-E). We use the functional dependencies in the statistical model to test the behaviour of two physical model of diurnal warming that display contrasting systematic errors

‘I would rather be having my leg cut off than a little needle’: A supplementary qualitative analysis of dentally anxious children’s experiences of needle fear

Fear of needles is common in childhood, with up to 50% being affected to some degree. In individuals who are dentally anxious, the prevalence may be as high as 91%. Fear of needles, and therefore intra-oral injections can have negative impacts on children’s quality of life and healthcare experiences, including a requirement for pharmacological methods to facilitate dental treatment. The aim of this study is to identify whether dentally anxious children report fear of injections and explore how these children experience a fear of needles in a dental setting. A supplementary analysis of interviews collected as part of two previous studies relating to children with dental anxiety. Five main themes were identified: feelings about needles; the nature of needle fear; the context of the fear, its consequences and how children tried to control the process. Children showed a desire to have control of their healthcare interventions, and wanted to trust the healthcare professionals giving the injections. There is evidence that children with dental anxiety also experience fear of needles, including intra-oral injections. Further primary qualitative research is needed to explore this topic in more depth and to design appropriate child centred interventions to reduce needle fear

Improvement of the deep UV sensor performance of a β-Ga2O3 photodiode by coupling of two planar diodes

β -Ga 2 O 3 is one of the promising semiconductor materials that has been widely used in power electronics and ultraviolet (UV) detectors due to its wide bandgap and high sensitivity to UV light. Specifically, for the UV detection application, it has been reported that the photocurrent was in the scale of microamps ( μA ), which normally requires sophisticated signal processing units. In this work, a novel approach based upon coupling of two Schottky diodes is reported, leads to a substantial increase in photocurrent (~186 times) when benchmarked against a conventional planar UV photodiode. The detectivity and responsivity of the new device have also been significantly increased; the rectification ratio of this device was measured to be 1.7×107 with ultralow dark current, when measured in the reverse bias. The results confirm that the approach of coupling two Schottky diodes has enormous potential for improving the optical performance of deep UV sensors

Chemical changes in PCPDTBT:PCBM solar cells using XPS and TOF-SIMS and use of inverted device structure for improving lifetime performance

Analysis of the degradation routes for poly[(4,4-bis(2-ethylhexyl)-cyclopenta-[2,1-b;3,4-b′]dithiophene)-2,6-diyl-alt-2,1,3-benzothiadiazole-4,7-diyl] (PCPDTBT)-based solar cells under illumination and in the presence of air have been conducted using a combination of X-ray Photoelectron Spectroscopy (XPS), Time-Of-Flight Secondary Ion Mass Spectrometry (TOF-SIMs) and solar cell device data. After ageing, XPS studies show that PCPDTBT appears as an oxygen-containing polymer, with data indicating that a break-up in the aromatic rings, formation of sulphates at the thiophene ring, chain scission in the polymer backbone and also loss of side chains. XPS studies have also been conducted on Phenyl-C71-butyric acid methyl ester (PC71BM) films and show a breakage of the fullerene cage, loss of molecular shape and oxidation of carbon atoms in the fullerene cage and side chains after ageing. XPS studies on active layers blends of PCPDTBT and PCBM also show significant changes in the vertical composition during ageing, with increased enrichment of PCPDTBT observed at the top surface and that the use of a processing additive (ODT) has a negative impact on the morphological stability. Based on these studies, it shown that inverted structures are better suited than non-inverted devices for PCPDTBT:PCBM solar cells. An additional advantage of inverted devices is shown using TOF-SIMS; electrode degradation during ageing experiments leads to migration of indium and tin ions into the active layer in non-inverted devices, but is eliminated for inverted devices.HW would like to thank Bangor University for financial support through his “125 scholarship” from the University. ZD is supported from the “SteelPV” project, which is funded from the EC’s Research Fund for Coal and Steel (RFCS) research programme under grant agreement number RFSR-CT-2014-00014. Finally, JK would like to thank the Royal Academy of Engineering for funding via the Newton Research Collaboration Programme (NRCP/1415/28)