Improving Guideline-Based Streptococcal Pharyngitis Testing: A Quality Improvement Initiative.

BACKGROUND AND OBJECTIVES: Acute pharyngitis is a common diagnosis in ambulatory pediatrics. The Infectious Diseases Society of America (IDSA) clinical practice guideline for group A streptococcal (GAS) pharyngitis recommends strict criteria for GAS testing to avoid misdiagnosis and unnecessary treatment of children who are colonized with group A Streptococcus. We sought to improve adherence to the IDSA guideline for testing and treatment of GAS pharyngitis in a large community pediatrics practice. METHODS: The Model for Improvement was used, and iterative Plan-Do-Study-Act cycles were completed. The quality improvement project was approved for American Board of Pediatrics Part 4 Maintenance of Certification credit. Interventions included provider education, modification of existing office procedure, communication strategies, and patient and family education. Outcomes were assessed by using statistical process control charts. RESULTS: An absolute reduction in unnecessary GAS testing of 23.5% (from 64% to 40.5%) was observed during the project. Presence of viral symptoms was the primary reason for unnecessary testing. Appropriate antibiotic use for GAS pharyngitis did not significantly change during the project; although, inappropriate use was primarily related to unnecessary testing. At the end of the intervention period, the majority of providers perceived an improvement in their ability to communicate with families about the need for GAS pharyngitis testing and about antibiotic use. CONCLUSIONS: The majority of GAS pharyngitis testing in this practice before intervention was inconsistent with IDSA guideline recommendations. A quality improvement initiative, which was approved for Part 4 Maintenance of Certification credit, led to improvement in guideline-based testing for GAS pharyngitis.

Phase stability, electronic structures and elastic properties of (U,Np)O2 and (Th,Np)O2 mixed oxides.

Mixing enthalpies (ΔHmix) of U1-xNpxO2 and Th1-xNpxO2 solid solutions are derived from atomic scale simulations based on density functional theory (DFT) employing the generalised gradient approximation corrected with an effective Hubbard parameter (Ueff). The variation of structural and electronic properties of UO2 and NpO2 with collinear ferromagnetic (FM), collinear anti-ferromagnetic (AFM) and non-collinear anti-ferromagnetic arrangements of the uranium and neptunium magnetic moments are investigated while ramping up Ueff from 0 eV to 4 eV (the Ueff-ramping method). A combination of the Ueff-ramping method to treat the presence of metastable magnetic states and special-quasirandom structures (SQS) for the random distribution of Np atoms in UO2 and ThO2 is employed to calculate ΔHmix of U1-xNpxO2 and Th1-xNpxO2 mixed oxides (MOX). The effect of collinear FM and AFM ordering is also considered in determining the ΔHmix. The calculated ΔHmix of Th1-xNpxO2 MOX were positive compared to the end members and nearly symmetric around x = 0.5 and ΔHmix of the AFM configuration were higher compared to the FM configuration maximum by 0.19 kJ mol-1. The ΔHmix of U1-xNpxO2 MOX were negative up to U0.50Np0.50O2 with a maximum value of -1.21 kJ mol-1 for U0.4375Np0.5625O2 whereas Np-rich (U,Np)O2 MOX compositions exhibited ΔHmix close to zero. Values of ΔHmix for (Th,Np)O2 are consistent with a simple miscibility-gap phase diagram while those for (U,Np)O2 suggest more complex behaviour. Nevertheless, lattice parameter variation with composition still follows a Vegard's law relationship. Finally, single crystal elastic constants of pure oxides and MOX are reported. The linear-elasticity models describe the mixing energies to within an accuracy of approximately 1 kJ mol-1 for the U1-xNpxO2 and Th1-xNpxO2 MOX systems.

High temperature measurements and condensed matter analysis of the thermo-physical properties of ThO2.

Values are presented for thermal conductivity, specific heat, spectral and total hemispherical emissivity of ThO2 (a potential nuclear fuel material) in a temperature range representative of a nuclear accident - 2000 K to 3050 K. For the first time direct measurements of thermal conductivity have been carried out on ThO2 at such high temperatures, clearly showing the property does not decrease above 2000 K. This could be understood in terms of an electronic contribution (arising from defect induced donor/acceptor states) compensating the degradation of lattice thermal conductivity. The increase in total hemispherical emissivity and visible/near-infrared spectral emissivity is consistent with the formation of donor/acceptor states in the band gap of ThO2. The electronic population of these defect states increases with temperature and hence more incoming photons (in the visible and near-infrared wavelength range) can be absorbed. A solid state physics model is used to interpret the experimental results. Specific heat and thermal expansion coefficient increase at high temperatures due to the formation of defects, in particular oxygen Frenkel pairs. Prior to melting a gradual increase to a maximum value is predicted in both properties. These maxima mark the onset of saturation of oxygen interstitial sites.

Advances in the development of a dissolution method for the attribution of iridium source materials.

To assist in nuclear forensic investigations, new techniques are required to evaluate radioactive materials that may be discovered outside of regulatory control. Using a recently developed pressure digestion method for iridium powder, assessments have been made of this techniques suitability for undertaking iridium target material evaluations. In addition to determining the reaction conditions necessary for total dissolution, these investigations have provided an insight into the elemental impurities that are present within unirradiated iridium targets that are used in QSA Global radiography sources, and established the speciation of the iridium solutions that are formed during this process.

A retrospective cohort analysis of hypoglycaemic and cardiovascular agent use in young adults in the Irish primary care setting.

AIM: The prevalence of type 2 diabetes in young adults is increasing, yet little is known about medication use in this population. This study aimed to describe hypoglycaemic and cardiovascular treatment patterns in young adults newly treated with oral hypoglycaemic agents. METHODS: A retrospective cohort study from 2008-2011 was conducted using the Irish national pharmacy claims database. Subjects aged 15-39 years were analysed for use of hypoglycaemic therapy, subsequent regimen changes, and any co-prescription of cardiovascular agents 1 year after treatment initiation. Cox-proportional-hazards regression and logistic regression were used to examine factors associated with non-persistence to initial hypoglycaemic therapy (in males only), insulin use as a regimen change, and use of cardiovascular agents. Hazard ratios (HR), odds ratios (OR), and 95 % confidence intervals (CI) are presented. RESULTS: There were 5284 individuals initiated on hypoglycaemic agents. Most were initiated on metformin (88 %); 13 % of subjects received a hypoglycaemic agent regimen change, with insulin being used in 26 % of these cases. A total of 38 % of males were non-persistent with their initial hypoglycaemic agent, with males aged 15-29 years and those on sulphonylureas significantly more likely to be non-persistent with therapy. Over 40 % of subjects were initiated on cardiovascular agents. Females were less likely to receive cardiovascular agents [OR 0.50 (95 % CI 0.42-0.83)]. CONCLUSIONS: Treatment patterns were found to be associated with high levels of non-persistence, substantial use of insulin, and a low use of cardiovascular agents. This may pose problems for the management of the long-term complications associated with type 2 diabetes.

A computational study on the superionic behaviour of ThO2.

This study reports the density functional theory (DFT) and classical molecular dynamics (MD) study of the lattice dynamical, mechanical and anionic transport behaviours of ThO2 in the superionic state. DFT calculations of phonon frequencies were performed at different levels of approximation as a function of isotropic dilation (ε) in the lattice parameter. With the expansion of the lattice parameter, there is a softening of B1u and Eu phonon modes at the X symmetry point of the Brillouin zone. As a result of the nonlinear decrease at the X point, the B1u and Eu phonon modes cross each other at ε = 0.03, which is associated with a sharp increase in the narrow peak of the phonon density of states, signifying a higher occupation and hence a higher coupling of these modes at high temperatures. The mode crossing also indicates anionic conductivity in the 〈001〉 direction leading to occupation of interstitial sites. Moreover, MD and nudged elastic band calculated diffusion barriers indicate that 〈001〉 is the easy direction for anion migration in the normal and superionic states. With a further increase in the lattice parameter, the B1u mode continues to soften and becomes imaginary at a strain (ε) of 0.036 corresponding to a temperature of 3430 K. The calculated temperature variation of single crystal elastic constants shows that the fluorite phase of ThO2 remains elastically stable up to the superionic regime, though the B1u phonon mode is imaginary in that state. This leads to anionic disorder at elevated temperatures. Tracking of anion positions in the superionic state as a function of time in MD simulations suggests a hopping model in which the oxygen ions migrate from one tetrahedral site to another via octahedral interstitial sites.

Thermophysical properties and oxygen transport in (Thx,Pu1-x)O2.

Using Molecular Dynamics, this paper investigates the thermophysical properties and oxygen transport of (Thx,Pu1-x)O2 (0 ≤ x ≤ 1) between 300-3500 K. In particular, the superionic transition is investigated and viewed via the thermal dependence of lattice parameter, linear thermal expansion coefficient, enthalpy and specific heat at constant pressure. Oxygen diffusivity and activation enthalpy are also investigated. Below the superionic temperature an increase of oxygen diffusivity for certain compositions of (Thx,Pu1-x)O2 compared to the pure end members is predicted. Oxygen defect formation enthalpies are also examined, as they underpin the superionic transition temperature and the increase in oxygen diffusivity. The increase in oxygen diffusivity for (Thx,Pu1-x)O2 is explained in terms of lower oxygen defect formation enthalpies for (Thx,Pu1-x)O2 than PuO2 and ThO2, while links are drawn between the superionic transition temperature and oxygen Frenkel disorder.

Development of Xe and Kr empirical potentials for CeO2, ThO2, UO2 and PuO2, combining DFT with high temperature MD.

The development of embedded atom method (EAM) many-body potentials for actinide oxides and associated mixed oxide (MOX) systems has motivated the development of a complementary parameter set for gas-actinide and gas-oxygen interactions. A comprehensive set of density functional theory (DFT) calculations were used to study Xe and Kr incorporation at a number of sites in CeO2, ThO2, UO2 and PuO2. These structures were used to fit a potential, which was used to generate molecular dynamics (MD) configurations incorporating Xe and Kr at 300 K, 1500 K, 3000 K and 5000 K. Subsequent matching to the forces predicted by DFT for these MD configurations was used to refine the potential set. This fitting approach ensured weighted fitting to configurations that are thermodynamically significant over a broad temperature range, while avoiding computationally expensive DFT-MD calculations. The resultant gas potentials were validated against DFT trapping energies and are suitable for simulating combinations of Xe and Kr in solid solutions of CeO2, ThO2, UO2 and PuO2, providing a powerful tool for the atomistic simulation of conventional nuclear reactor fuel UO2 as well as advanced MOX fuels.

Pipe and grain boundary diffusion of He in UO2.

Molecular dynamics simulations have been conducted to study the effects of dislocations and grain boundaries on He diffusion in [Formula: see text]. Calculations were carried out for the {1 0 0}, {1 1 0} and {1 1 1} [Formula: see text] edge dislocations, the screw [Formula: see text] dislocation and Σ5, Σ13, Σ19 and Σ25 tilt grain boundaries. He diffusivity as a function of distance from the dislocation core and grain boundaries was investigated for the temperature range 2300-3000 K. An enhancement in diffusivity was predicted within 20 Å of the dislocations or grain boundaries. Further investigation showed that He diffusion in the edge dislocations follows anisotropic behaviour along the dislocation core, suggesting that pipe diffusion occurs. An Arrhenius plot of He diffusivity against the inverse of temperature was also presented and the activation energy calculated for each structure, as a function of distance from the dislocation or grain boundary.

The impact of initial antidiabetic agent and use of monitoring agents on prescription costs in newly treated type 2 diabetes: A retrospective cohort analysis.

AIMS: To measure the costs associated with the use of antidiabetic agents, monitoring materials and cardiovascular disease (CVD) agents in the management of newly treated type 2 diabetes, and to investigate the factors associated with these costs. METHODS: A population-based retrospective cohort study was conducted using the Irish national pharmacy claims database. Newly treated patients were identified for 2012 and followed for one year post treatment initiation. Factors associated with costs were assessed using a generalised linear model with gamma family and log-link function. Cost ratios (CR) and 95% CIs were used to determine the contributors of prescription costs. Adjusted odd ratios (OR) and 95% CIs were used to investigate factors associated with high frequency self-monitoring of blood glucose (SMBG). RESULTS: Mean prescription costs for the 12,941 subjects was €871, while total costs were €11 million. CVD agents accounted for 58% of total costs; 22% of costs were for SMBG; antidiabetic agents accounted for 17% of costs. SMBG resulted in costs that were 80% higher than those without, CR 1.80 (95% CI 1.76-1.84). No significant differences were observed between initiation on metformin or sulphonylureas and high frequency SMBG (OR 1.01 95% CI 0.97-1.04 vs reference). Initiation on newer antidiabetic agents was a significant positive predictors of prescription costs (CR 2.36 95% CI 2.21-2.51 vs metformin). CONCLUSIONS: Type of initial antidiabetic agent, and SMBG were significant predictors of prescription costs. SMBG represent a major proportion of total costs; however, its use in combination with antidiabetic agents that do not cause hypoglycaemia is questionable.

Genetics of superionic conductivity in lithium lanthanum titanates.

The self-diffusion of ions is a fundamental mass transport process in solids and has a profound impact on the performance of electrochemical devices such as the solid oxide fuel cell, batteries and electrolysers. The perovskite system lithium lanthanum titanate, La2/3-xLi3xTiO3 (LLTO) has been the subject of much academic interest as it displays very high lattice conductivity for a solid state Li conductor; making it a material of great technological interest for deployment in safe durable mobile power applications. However, so far, a clear picture of the structural features that lead to efficient ion diffusion pathways in LLTO, has not been fully developed. In this work we show that a genetic algorithm in conjunction with molecular dynamics can be employed to elucidate diffusion mechanisms in systems such as LLTO. Based on our simulations we provide evidence that there is a three-dimensional percolated network of Li diffusion pathways. The present approach not only reproduces experimental ionic conductivity results but the method also promises straightforward investigation and optimisation of the properties relating to superionic conductivity in materials such as LLTO. Furthermore, this method could be used to provide insights into related materials with structural disorder.

Thermal conductivity and energetic recoils in UO2 using a many-body potential model.

Classical molecular dynamics simulations have been performed on uranium dioxide (UO2) employing a recently developed many-body potential model. Thermal conductivities are computed for a defect free UO2 lattice and a radiation-damaged, defect containing lattice at 300 K, 1000 K and 1500 K. Defects significantly degrade the thermal conductivity of UO2 as does the presence of amorphous UO2, which has a largely temperature independent thermal conductivity of ∼1.4 Wm(-1) K(-1). The model yields a pre-melting superionic transition temperature at 2600 K, very close to the experimental value and the mechanical melting temperature of 3600 K, slightly lower than those generated with other empirical potentials. The average threshold displacement energy was calculated to be 37 eV. Although the spatial extent of a 1 keV U cascade is very similar to those generated with other empirical potentials and the number of Frenkel pairs generated is close to that from the Basak potential, the vacancy and interstitial cluster distribution is different.

A many-body potential approach to modelling the thermomechanical properties of actinide oxides.

A many-body potential model for the description of actinide oxide systems, which is robust at high temperatures, is reported for the first time. The embedded atom method is used to describe many-body interactions ensuring good reproduction of a range of thermophysical properties (lattice parameter, bulk modulus, enthalpy and specific heat) between 300 and 3000 K for AmO2, CeO2, CmO2, NpO2, ThO2, PuO2 and UO2. Additionally, the model predicts a melting point for UO2 between 3000 and 3100 K, in close agreement with experiment. Oxygen-oxygen interactions are fixed across the actinide oxide series because it facilitates the modelling of oxide solid solutions. The new potential is also used to predict the energies of Schottky and Frenkel pair disorder processes.

Computed tomography in patients with abdominal pain and diarrhoea: does the benefit outweigh the drawbacks?

The role of computed tomography (CT) in the evaluation of abdominal pain is well established. However, concern exists in regard to procedure-related radiation levels, contrast-medium toxicity and costs. We sought to determine whether the use of abdominal CT caused major changes in the management of patients who had abdominal pain and diarrhoea. We reviewed all abdominal CT examinations that were performed at our hospital from October through December 2010. We selected 574 scans that had been performed in patients who presented with or without diarrhoea. We examined the selected medical records to determine whether the CT scan changed patients' management. A scan was considered to be management changing if a decisive intervention occurred on the basis of the scan results. Among 124 scans in patients with diarrhoea and 450 scans in patients without diarrhoea, the scan results changed management in 13 of the patients with diarrhoea (11%) and in 233 of those without diarrhoea (52%) (P < 0.001). When management changed, the changes resulted from findings unrelated to diarrhoea. Despite its defined role in the assessment of abdominal pain, CT of patients that also had diarrhoea seldom caused a major change in management. The probability of CT causing such a change does not outweigh the cost, radiation risk or potential for contrast-induced nephropathy.

Point defect engineering strategies to retard phosphorous diffusion in germanium.

The diffusion of phosphorous in germanium is very fast, requiring point defect engineering strategies to retard it in support of technological application. Density functional theory corroborated with hybrid density functional calculations are used to investigate the influence of the isovalent codopants tin and hafnium in the migration of phosphorous via the vacancy-mediated diffusion process. The migration energy barriers for phosphorous are increased significantly in the presence of oversized isovalent codopants. Therefore, it is proposed that tin and in particular hafnium codoping are efficient point defect engineering strategies to retard phosphorous migration.

Strain-induced changes to the electronic structure of germanium.

Density functional theory calculations (DFT) are used to investigate the strain-induced changes to the electronic structure of biaxially strained (parallel to the (001), (110) and (111) planes) and uniaxially strained (along the [001], [110] and [111] directions) germanium (Ge). It is calculated that a moderate uniaxial strain parallel to the [111] direction can efficiently transform Ge to a direct bandgap material with a bandgap energy useful for technological applications.

Defect processes in orthorhombic LnBaCo2O5.5 double perovskites.

Static atomistic simulations based on the Born model were used to investigate intrinsic defect processes in orthorhombic LnBaCo(2)O(5.5) (Ln = Y, La, Pr, Nd, Sm, Gd, Dy, Ho, Er, and Yb) double perovskites. It was found that Ln/Ba antisite disorder is the lowest energy defect reaction, with the large Ln cations giving rise to smaller antisite energies. On the oxygen sublattice the oxygen Frenkel disorder dominates and also decreases in energy with increasing Ln cation size. The lowest energy oxygen vacancy and interstitial positions are in the LnO(0.5) and CoO(2) layers respectively. Interestingly, the calculations indicate that oxygen vacancies cluster with Ba antisite defects (occupying Ln sites). This suggests that the transport of oxygen vacancies will be influenced not only by the oxygen Frenkel energy but also the antisite energy. We propose that PrBaCo(2)O(5.5) most efficiently balances these two competing effects as it has an oxygen Frenkel energy of just 0.24 eV per defect combined with a high antisite energy (0.94 eV), which ensures that the A cation sublattice will remain more ordered.

A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel.

Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials. The structure and energetics of the defects were investigated using density functional theory (DFT) and the results compared to simulations using empirical fixed charge potentials. Each point defect was studied in a variety of supercell sizes in order to ensure convergence. It was found that empirical potential simulations significantly overestimate formation energies, but that the type and relative stability of the defects are well predicted by the empirical potentials both for point defects and small defect clusters.

A retrospective study to determine the impact of medical- and lifestyle-based contraindications to a prescribed HAART regimen on clinical outcomes and adherence.

OBJECTIVE: To determine whether patients who are prescribed a highly active antiretroviral therapy regimen, that minimizes medical and lifestyle contraindications, will be better able to adhere to their drug regimens and will have better clinical outcomes, than patients who do not have such a regimen. METHODS: A retrospective chart review of patients' prescription renewals and changes in viral load and CD4(+) count and a comparison of these changes with patients' self-identified contraindications. Contraindications were identified by a questionnaire with 35 questions relating to medical history/concurrently prescribed medication and 16 questions on lifestyle. Main outcome measures are adherence assessed by prescription renewals, change in plasma HIV-1 RNA viral loads, and change in CD4(+) T-lymphocyte counts. Logistic and linear regression and student t-test were used to identify associations between outcome measurements and number of contraindications. RESULTS: A total of 203 patients (72% male, 74% African-American, 7% Hispanic) completed the questionnaire. Seventy-four per cent of the patients had at least one medical/drug contraindication and 78% had at least one lifestyle contraindication. Increases in CD4 counts were reduced by an average of 13 cells/mm(3) (P = 0.033) for each medical/drug contraindication and viral load decreases was significant even with one medical contraindication vs. none (P = 0.042). Patients with fewer lifestyle contraindications were more likely to have at least a 1 log drop in viral load (P = 0.036). For each increase in the number of contraindications, there was a corresponding 2% decrease in the rate of adherence (P = 0.048). CONCLUSIONS: The results suggest that using a patient administered questionnaire it is possible to identify contraindications in prescribed regimens that impact on adherence and on treatment effects on viral load and CD4 counts.