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We establish a solid/water interface model which treats ionic defects in solids and ions in water uniformly, allowing one to study the space charge layer and the electric double layer profiles under doping and pH effects.

Purpose To conduct a systematic review to evaluate the clinical parameters for periodontal diseases in individuals with cleft lip and/or palate (CL/P). Methods The authors searched six indexed databases without language restriction through July 2021. The eligibility criteria were observational studies that compared the periodontal clinical measures of individuals with CL/P to those without CL/P. Meta-analysis was conducted using random-effects models with inverse variance weighting. Results The literature search generated 1277 records, and 40 full-text articles were reviewed. Twenty-three studies comprising 3,235 individuals from 4 continents fulfilled our selection criteria. The meta-analysis revealed significant difference in mean plaque index scores (MD = 0.31, 95%CI = 0.22, 0.41), gingival index scores (MD = 0.50, 95%CI = 0.24, 0.77) and periodontal pocket depth (MD = 0.64, 95%CI = 0.12, 1.16) between individuals with and without CL/P. A slight increase in clinical attachment loss was detected among individuals with CL/P; however, such an increase may have little clinical significance. Conclusions As age is positively related to periodontal disease progression, and individuals with CL/P are more likely to present with more plaque accumulation and gingival inflammation, clinicians should reinforce preventive dental care from an early age.

In order to assess C. difficile/AMR dissemination between humans, animals and the environment, studies were conducted on samples from 4 countries (2 HOALs Portugal, Austria, 1 agricultural facility Estonia, single compartments Ireland). The results obtained allowed to perform a classification of pig farm compartments according to their role in the epidemiology of C. difficile, which was identified in all the following ecosystems: pig barn (faeces), manure (pig), wild animals, soil (agricultural fields), river water, ground water, wastewater treatment plant and air. In addition, in each HOAL, a different toxigenic C. difficile RT (RT033, RT078 and RT049, respectively) was dominant, reflecting well-established transmission chains and a resilient source. Overall, the results obtained from the 3 HOALs/agricultural facility showing the presence of dominant clones in compartments associated with the pig production unit suggest a transmission chain involving these animals. They contribute to unveiling the role played by animal and environmental reservoirs within the C. difficile epidemiology.

Automation of surface well-testing solutions has enabled the oil and gas industry to safely explore and produce high-risk wells and formations with unprecedentedly high levels of process assurance and quality. Surface well-testing operations are regularly performed throughout the lifecycle of oil and gas wells to evaluate potential reserves in exploration wells initially, and later to monitor changes in well or reservoir parameters in producing wells. The collected information is critical to optimizing hydrocarbon asset management. Such surface well-testing operations present risk associated with control, evaluation, and disposal of produced hydrocarbon at the rig/wellsite. Additionally, these operations can be demanding in terms of manpower because considerably large crews are necessary to operate equipment safely and efficiently. Furthermore, risks are elevated when high levels of hydrogen sulfide (H2S) gas are present in well effluent because it can present imminent and elevated hazards to personnel health and equipment integrity. To help address risks associated with high H2S concentrations in an exploration well located in a remote desert location, A new automated surface well-testing technologies for automated control and operation of critical surface well-testing equipment was recently deployed. Incorporated as part of this automated process was a zero-emission gas sampling and analysis technology. Additionally, new criteria for equipment selection and acceptance were adopted to help reduce risks to as low as reasonable when flowing hydrocarbon at the surface with such ultrahigh concentrations of H2S. Using automated well-testing, sampling, and analysis technologies enabled the safe and efficient completion of three well tests with observed H2S concentrations up to 40% while reducing crew size and removing them from the red-zone area; there were also zero emissions in the working area.

This paper studies comprehensively the defect chemistry of and cation diffusion in α-Fe2O3. Defect formation energies and migration barriers are calculated using density functional theory with a theoretically calibrated Hubbard U correction. The established model shows a good agreement with experimental off-stoichiometry and cation diffusivities available in the literature. At any temperature, and are the predominant ionic defects in hematite at the two extremes of oxygen partial pressure (pO2) range, reducing and oxidizing, respectively. Between these two extremes, an intrinsic electronic regime exists where small polaronic electrons and holes are the dominant charge carriers. The calculated migration barriers show that Fe ions favor the diffusion along the 〈111〉 direction in the primitive cell through an interstitial crowdion-like mechanism. Our model suggests that cation diffusion in hematite is mainly controlled by the migration of , while may contribute to cation diffusion at extremely low pO2. Our analysis in the presence of two sample donor dopants Ti and Sn indicates that high temperature annealing at T > 1100 K is needed to prepare n-type hematite at ambient pO2, consistently with prior experimental findings. Alternatively, annealing at lower temperatures requires much lower pO2 to avoid compensating the donors with Fe vacancies. A synergistic comparison of our theoretical model and the experimental results on Ti-doped hematite led us to propose that free electrons and small polarons coexist and both contribute to n-type conductivity. Our validated model of defective hematite is a foundation to study hematite in applications such as corrosion and water splitting.

Digital twins are seen as one of the key technologies of Industry 4.0. Although many research groups focus on digital twins and create meaningful outputs, the technology has not yet reached a broad application in the industry. The main reasons for this imbalance are the complexity of the topic, the lack of specialists, and the unawareness of the twin opportunities. The project 'Digital Twin Academy' aims to overcome these barriers by focusing on three actions: Building a digital twin community for discussion and exchange, offering multi-stage training for various knowledge levels, and implementing realworld use cases for deeper insights and guidance. In this work, we focus on creating a flexible learning platform that allows the user to select a training path adjusted to personal knowledge and needs. Therefore, a mix of basic and advanced modules is created and expanded by individual feedback options. The usage of personas supports the selection of the appropriate modules.

The low-temperature defect chemistry of monoclinic and tetragonal ZrO2 and hematite Fe2O3 is studied in the non-equilibrium state of thermochemical quenching; that is, rapid cooling starting from a certain high temperature and oxygen chemical potential. This non-equilibrium state is of great interest because many metal oxides are used at low temperatures below their growth temperatures. This paper addresses the importance of considering this non-equilibrium state rather than applying equilibrium thermodynamics as commonly used when studying point defects from first principles. Based on point defect formation energies calculated previously using density functional theory, we compare the type of dominant defects at equilibrium to those at a quenched state originating from a certain initial growth temperature and oxygen partial pressure. The comparison is facilitated by casting the dominant defects in a dominance diagram on the temperature – oxygen partial pressure plane. We consider two scenarios to model the quenched state. In the first, only electronic defects equilibrate whereas all ionic defects are frozen. Whereas, in the second, electronic defects and interstitials are allowed to equilibrate under the assumption of mobile interstitials at low temperatures. We find that new ionic charge compensation modes can appear on the dominance diagram after quenching. Additionally, purely ionic charge compensation modes consisting of vacancies and/or interstitials expand in the dominance diagram at the expense of purely electronic compensation modes. For the ZrO2 phases, we argue that scenario 2 is more realistic and leads to difficulty in achieving n-type doping by thermochemical quenching. For Fe2O3, and regardless of the quenching scenario, iron vacancies occupy a wider zone of domination, which limits the performance of this oxide as a water splitting photoanode. Our study shows that by controlling the growth thermochemical conditions, it is possible to tune the Fermi level of oxides over a considerable range within the band gap by quenching. This provides an extra tool to tune the electric conductivity of metal oxides beyond traditional extrinsic doping. This work indicates that non-equilibrium thermodynamic analysis is necessary to understand and control defect chemistry at low temperatures.

This paper studies comprehensively the defect chemistry of and cation diffusion in α-Fe

Polarization of ionic and electronic defects in response to high electric fields plays an essential role in determining properties of materials in applications such as memristive devices. However, isolating the polarization response of individual defects has been challenging for both models and measurements. Here the authors quantify the nonlinear dielectric response of neutral oxygen vacancies, comprised of strongly localized electrons at an oxygen vacancy site, in perovskite oxides of the form ABO

Research interest in multi-principal element high entropy alloys (HEAs) has increased drastically since the field was first formally introduced in 2004. Since then, HEAs have become important candidate materials for many key applications. However, despite the progress made in this field, there remains much ambiguity surrounding HEA phase stabilities. To that end, the calculation of phase diagrams (CALPHAD) method was used to construct extensive temperature-composition phase diagrams of the CoCrFeNi x Ti2−x , Co x CrFeNiTi2−x , CoCrFe x NiTi2−x , and CoCr x FeNiTi2−x HEA systems. Due to its potentially favorable properties, the current work was focused on the single face-centered cubic (fcc) solid solution phase and an extensive thermodynamic analysis was carried out to examine the underlying thermodynamic factors of its stabilization. The mixing enthalpies and entropies of the alloys in the studied systems were calculated, where it was found that the single fcc solid solution phase can be either enthalpy- or entropy-stabilized depending on the temperature. The deviation of these quantities from the ideal solid solution thermodynamic behavior was considered, and it was found that close to and within the single fcc solid solution regions, the deviation is smallest in all systems. Furthermore, a preliminary exploration of the impact of interstitial nonmetals such as C, N, and O showed noticeable alteration of the phase equilibria of the studied systems. This work emphasizes the importance of exploring non-equiatomic compositions of HEAs as well as the necessity of a comprehensive thermodynamic analysis to understand HEAs phase stabilities.

The low electronic conductivity of hematite (α-Fe2O3) limits its best performance in many applications. Though highly reducing conditions induce an intrinsic n-type behavior, reaching extremely low oxygen partial pressure [Formula: see text] values is not practical. Alternatively, certain dopants provide hematite with excess electrons at practical [Formula: see text] values. This study employs density functional theory with thermodynamic analysis to compute the concentration of electronic defects in hematite as a function of [Formula: see text], upon doping with 1% of 3d, 4d, and 5d transition metals. Isothermal Kröger–Vink diagrams at 1100 K are plotted to reveal the charge compensation mechanism controlling the electronic carriers in doped hematite and the maximum attainable [Formula: see text] value, which achieves approximately one electron per dopant. A higher [Formula: see text] value is a metric for an effective donor. Ti, Zr, Hf, Nb, Ta, Mo, and W are shown to be effective donors, especially Nb, Ta, and W, which achieve a 1:1 electron/dopant ratio around atmospheric pressure and a maximum electron/dopant ratio greater than one. The latter is a new metric introduced in this study to quantify the doping efficacy of a donor. Moreover, our study shows that W, Ta, and Nb co-doping in specific percentages with any of the other investigated dopants ensures the n-type behavior of the co-doped hematite while opening the possibility of improving other properties via the other dopant. The other dopant can be Ni or Co to enhance the surface catalytic properties or Zn to increase the minority hole carriers. Both properties are desirable in applications such as photoelectrochemical cells.

The design of solid management systems (SMS) facilities for offshore big bore HP/HT sour gas well cleanup is an industry challenge, mainly it is due to solid erosion (sand), potential high pressure H2S release, heat radiation from flare, SO2 exposure, vibration, noise, including risk of piping or facilities blockage, and corrosion (facility integrity) that might hinder safety, operability and environmental issues. The objective of this paper is to develop a solid handling management decision making process especially during early facilities development, identify the merit and limitation on each handling option. As methodology; firstly, technology screening and benchmarking will be performed. Then characterize solid composition, determine the expected solid/ mud flow back during well clean up, erosion and deposition study, hydraulic flow assurance and heat impact mapping. The next process is, develop a decision-making workflow based on solid handling option scenarios including offshore, onshore or a combination of them. Moreover, a hydrocyclone solid removal simulation is performed, and for the onshore application; flow loop experimental work is carried out on a small scale to prove the solid removal efficiency. Various flow rate, pressure and mud with different particle size and concentration from 7% to 15% with mixture of base fluid component are tested during the flow loop test. It is found that factors such as safety (operability), reservoir, well type, solid mud properties, the availability of infrastructure and footprint are playing important roles in the decision of well clean up strategy. Having offshore and onshore SMS will help solid management further robust. Based on the flow loop test study, solids management system with multi-stage separation process has a capability to remove more than 90% solids separation and in addition, differential pressure across stage need to be maintained.

The current era is characterized with knowledge and technological expansion in the use of the Internet. This made the world an e-village. Countries have begun to feel the growing importance of information upbringing through providing an interactive learning and training environment that attracts the attention of individuals in an era characterized with the continuous development and change through functioning the information technology and the Internet in education. The problem of research can be determined in the following questions: 1 - What is the extent of utilizing the World Wide Web in the implementation of clothes techniques? 2 - What is the effectiveness of the pilot unit of the proposed channel in providing the female students with the skills included in the experimental unit? 3- What is the effectiveness of the proposed educational channel in learning the techniques of implementing clothes for the third level female students in the Department of Fashion Design and Textile? Objectives of the research: The research aims to the following: 1. Designing the presentation of the content of a specialized educational channel on the world wide web to teach the techniques of the implementation of clothes. 2 - Measurement of the effectiveness of an educational unit within the specialized educational channel proposed in the education of techniques for the implementation of clothes regarding the skills aspects. Significance of the research: The techniques of implementation of clothes are considered the cornerstone in the way of fashion designer and sewing lovers .Their mastery requires of a lot of knowledge and skills and their foundations in addition to patience to repeat training, redoing and experience until the implemented piece reaches the required form. Methodology of the research: - This research follows the semi-experimental methodology due to its relevance to the objectives of the research and verifying its hypotheses.

Chemomechanical coupling is a hallmark of the functional oxides that are used widely for energy conversion and storage applications including solid oxide fuel cells (SOFCs). These oxides rely on the presence of oxygen vacancies to enable important properties including ionic conductivity and gas exchange reactivity. However, such defects can also facilitate chemical expansion, or coupling between material volume and defect content. Such chemomechanical coupling is particularly relevant with the recent interest in thin film SOFCs which have the potential to decrease operating temperatures and enable portable applications. Thin films present a particular challenge for modelling, as experimental results indicate that film defect chemistry can differ significantly from bulk counterparts under the same experimental conditions. In this study, we explore the influence of point defects, including oxygen vacancies and cation dopants, on the elastic properties of a model material, PrxCe1-xO2-δ (PCO), using density functional theory (DFT + U) simulations. Previously, we showed that PCO films exhibit a decrease in Young’s elastic modulus E due to chemical expansion, but that this decrease can be larger than predicted based on bulk defect models. Here, we apply DFT + U to show that the biaxial elastic modulus of PCO decreases with increased oxygen vacancy content in both bulk and membrane forms. We consider the relative influences of oxygen vacancies and cation dopants on this trend, and highlight local structural changes in the presence of such defects. By relating our computational and experimental results, we evaluate the relative importance of increased oxygen vacancy content and finite thickness on the mechanical properties of oxides that are subject to chemical expansion under operando conditions. This work informs the design of μ-SOFCs, emphasizing the need to characterize thin films separately from bulk counterparts and demonstrating how functional defect content can influence development of stress and strain in devices by changing both material volume and elastic properties.

We present a multi-scale approach to predict equilibrium defect concentrations across oxide/oxide hetero-interfaces. There are three factors that need to be taken into account simultaneously for computing defect redistribution around the hetero-interfaces: the variation of local bonding environment at the interface as epitomized in defect segregation energies, the band offset at the interface, and the equilibration of the chemical potentials of species and electrons via ionic and electronic drift-diffusion fluxes. By including these three factors from the level of first principles calculation, we build a continuum model for defect redistribution by concurrent solution of Poisson's equation for the electrostatic potential and the steady-state equilibrium drift-diffusion equation for each defect. This model solves for and preserves the continuity of the electric displacement field throughout the interfacial core zone and the extended space charge zones. We implement this computational framework to a model hetero-interface between the monoclinic zirconium oxide, m-ZrO2, and the chromium oxide Cr2O3. This interface forms upon the oxidation of zirconium alloys containing chromium secondary phase particles. The model explains the beneficial effect of the oxidized Cr particles on the corrosion and hydrogen resistance of Zr alloys. Under oxygen rich conditions, the ZrO2/Cr2O3 heterojunction depletes the oxygen vacancies and the sum of electrons and holes in the extended space charge zone in ZrO2. This reduces the transport of oxygen and electrons thorough ZrO2 and slows down the metal oxidation rate. The enrichment of free electrons in the space charge zone is expected to decrease the hydrogen uptake through ZrO2. Moreover, our analysis provides a clear anatomy of the components of interfacial electric properties; a zero-Kelvin defect-free contribution and a finite temperature defect contribution. The thorough analytical and numerical treatment presented here quantifies the rich coupling between defect chemistry, thermodynamics and electrostatics which can be used to design and control oxide hetero-interfaces.

Understanding the response of functional oxides to extrinsic ion insertion is important for technological applications including electrochemical energy storage and conversion, corrosion, and electronic materials in neuromorphic computing devices. Decoupling the complicated chemical and mechanical effects of ion insertion is difficult experimentally. In this work, we assessed the effect of lithium incorporation in zirconium oxide as a model system, by performing first-principles based calculations. The chemical effect of lithium is to change the equilibria of charged defects. Lithium exists in $\mathrm{Zr}{\mathrm{O}}_{2}$ as a positively charged interstitial defect, and raises the concentration of free electrons, negatively charged oxygen interstitials, and zirconium vacancies. As a result, oxygen diffusion becomes faster by five orders of magnitude, and the total electronic conduction increases by up to five orders of magnitude in the low oxygen partial pressure regime. In the context of Zr metal oxidation, this effect accelerates oxide growth kinetics. In the context of electronic materials, it has implications for resistance modulations via ion incorporation. The mechanical effect of lithium is in changing the volume and equilibrium phase of the oxide. Lithium interstitials together with zirconium vacancies shrink the volume of the oxide matrix, release the compressive stress that is needed for stabilizing the tetragonal phase $\mathrm{Zr}{\mathrm{O}}_{2}$ at low temperature, and promote tetragonal-to-monoclinic phase transformation. By identifying these factors, we are able to mechanistically interpret experimental results in the literature for zirconium alloy corrosion in different alkali-metal hydroxide solutions. These results provide a mechanistic and quantitative understanding of lithium-accelerated corrosion of zirconium alloy, as well as, and more broadly, show the importance of considering coupled electro-chemo-mechanical effects of cation insertion in functional oxides.

We present a multi-scale approach to predict equilibrium defect concentrations across oxide/oxide hetero-interfaces. There are three factors that need to be taken into account simultaneously for computing defect redistribution around the hetero-interfaces: the variation of local bonding environment at the interface as epitomized in defect segregation energies, the band offset at the interface, and the equilibration of the chemical potentials of species and electrons via ionic and electronic drift-diffusion fluxes. By including these three factors from the level of first principles calculation, we build a continuum model for defect redistribution by concurrent solution of Poisson's equation for the electrostatic potential and the steady-state equilibrium drift-diffusion equation for each defect. This model solves for and preserves the continuity of the electric displacement field throughout the interfacial core zone and the extended space charge zones. We implement this computational framework to a model hetero-interface between the monoclinic zirconium oxide, m-ZrO[subscript 2], and the chromium oxide Cr[subscript 2]O[subscript 3]. This interface forms upon the oxidation of zirconium alloys containing chromium secondary phase particles. The model explains the beneficial effect of the oxidized Cr particles on the corrosion and hydrogen resistance of Zr alloys. Under oxygen rich conditions, the ZrO[subscript 2]/Cr[subscript 2]O[subscript 3] heterojunction depletes the oxygen vacancies and the sum of electrons and holes in the extended space charge zone in ZrO[subscript 2]. This reduces the transport of oxygen and electrons thorough ZrO[subscript 2] and slows down the metal oxidation rate. The enrichment of free electrons in the space charge zone is expected to decrease the hydrogen uptake through ZrO[subscript 2]. Moreover, our analysis provides a clear anatomy of the components of interfacial electric properties; a zero-Kelvin defect-free contribution and a finite temperature defect contribution. The thorough analytical and numerical treatment presented here quantifies the rich coupling between defect chemistry, thermodynamics and electrostatics which can be used to design and control oxide hetero-interfaces.

We demonstrate a thermodynamic formulation to quantify defect formation energetics in an insulator under high electric field. As a model system, we analyzed neutral oxygen vacancies (color centers) in alkaline-earth-metal binary oxides using density functional theory, Berry phase calculations, and maximally localized Wannier functions. Work of polarization lowers the field dependent electric Gibbs energy of formation of this defect. This is attributed mainly to the ease of polarizing the two electrons trapped in the vacant site, and secondarily to the defect induced reduction in bond stiffness and softening of phonon modes. The formulation and analysis have implications for understanding the behavior of insulating oxides in electronic, magnetic, catalytic, and electrocaloric devices under high electric field., This paper was accepted for publication in Physical Review Letters. A Link to the accepted abstract: https://journals.aps.org/prl/accepted/d7070Yf1Mfe1975061178757351719ba020145107

We predict a predominance diagram for electron defects in the temperature-hydrostatic stress space for $\mathrm{SrTi}{\mathrm{O}}_{3}$ by combining density functional theory and the quasiharmonic approximation. We discovered two regimes where small polarons dominate: under tensile stress at lower temperature due to a larger relaxation volume of the defect $\mathrm{\ensuremath{\Omega}}$, and under compressive stress at higher temperature due to a smaller $\mathrm{\ensuremath{\Omega}}$ and larger formation entropy. This provides a means to modulate the electronic conductivity via controlling the underlying charge carrier. Furthermore, the results challenge the common association between larger $\mathrm{\ensuremath{\Omega}}$ and charge localization by demonstrating that at high temperature the free electron can induce larger $\mathrm{\ensuremath{\Omega}}$ compared to the small polaron. This finding is attributed to the ability of the free electron to generate greater vibrational entropy upon finite isothermal expansion.

Zirconium–niobium alloys are currently proposed for applications in water-cooled nuclear reactors. However, the mechanisms by which Nb impacts the corrosion resistance of these alloys are yet to be clarified. In this work, we utilize a thermodynamic framework informed by density functional theory calculations to predict the effect of Nb on the equilibria of charged defects in tetragonal ZrO2, and discuss how the changes in the defect concentrations affect the protectiveness of this oxide that grows natively on Zr alloys during oxidation. Our analysis shows that Nb dissolves predominantly in the oxidation state 5+ as a substitutional defect on the Zr sublattice, with charge compensation achieved by the negatively charged Zr vacancies. Moreover, Nb dissolution is limited to the oxygen-rich conditions, i.e., in the oxide surface facing oxidizing environment. We validate this finding by performing X-ray photoelectron spectroscopy on oxidized Zr–Nb alloys. The introduction of Nb in tetragonal ZrO2 is found to ...

Cementitious materials are considered to be a waste form for the ultimate disposal of radioactive materials in geological repositories. We investigated by means of atomistic simulations the encapsulation of strontium-90, an important radionuclide, in calcium–silicate–hydrate (C–S–H) and its crystalline analog, the 9 A-tobermorite. C–S–H is the major binding phase of cement. Strontium was shown to energetically favor substituting calcium in the interlayer sites in C–S–H and 9 A-tobermorite with the trend more pronounced in the latter. The integrity of the silicate chains in both cementitious waste forms were not affected by strontium substitution within the time span of molecular dynamics simulation. Finally, we observed a limited degradation of the mechanical properties in the strontium-containing cementitious waste form with the increasing strontium concentration. These results suggest the cement hydrate as a good candidate for immobilizing radioactive strontium.

A mesoscopic chemical reaction kinetics model to predict the formation of zirconium oxide and hydride accumulation light-water reactor (LWR) fuel clad is presented. The model is designed to include thermodynamic information from ab initio electronic structure methods as well as parametric information in terms of diffusion coefficients, thermal conductivities and reaction constants. In contrast to approaches where the experimentally observed time exponents are captured by the models by design, our approach is designed to be predictive and to provide an improved understanding of the corrosion process. We calculate the time evolution of the oxide/metal interface and evaluate the order of the chemical reactions that are conducive to a t 1/3 dependence. We also show calculations of hydrogen cluster accumulation as a function of temperature and depth using spatially dependent cluster dynamics. Strategies to further cohesively integrate the different elements of the model are provided.

Hydrogen embrittlement of metallic alloys is critical to the aging and failure of components in power plants and infrastructure. Embrittlement begins with hydrogen penetrating the protective oxide film that naturally grows on a surface in air. The authors apply concepts from semiconductor defect physics and catalysis to develop materials engineering strategies for thwarting hydrogen uptake. For ZrO${}_{2}$ film on a Zr alloy, a model system that is important for materials in nuclear reactors, they demonstrate that one can use doping to tune the chemical potential of electrons in ZrO${}_{2}$ either to minimize the solubility of hydrogen, or to facilitate its evolution as H${}_{2}$ gas from the surface.

We present the structural and dynamic nature of water ultraconfined in the quasi-two-dimensional nanopores of the highly disordered calcium-silicate-hydrate (C-S-H), the major binding phase in cement. Our approach is based on classical molecular simulations. We demonstrate that the C-S-H nanopore space is hydrophilic, particularly because of the nonbridging oxygen atoms on the disordered silicate chains which serve as hydrogen-bond acceptor sites, directionally orienting the hydrogen atoms of the interfacial water molecules toward the calcium-silicate layers. The water in this interlayer space adopts a unique multirange structure: a distorted tetrahedral coordination at short range up to 2.7 Å, a disordered structure similar to that of dense fluids and supercooled phases at intermediate range up to 4.2 Å, and persisting spatial correlations through dipole-dipole interactions up to 10 Å. A three-stage dynamics governs the mean square displacement (MSD) of water molecules, with a clear cage stage characteristic of the dynamics in supercooled liquids and glasses, consistent with its intermediate-range structure identified here. At the intermediate time scales corresponding to the β-relaxation of glassy materials, coincident with the cage stage in MSD, the non-Gaussian parameter indicates a significant heterogeneity in the translational dynamics. This dynamic heterogeneity is induced primarily because of the heterogeneity in the distribution of hydrogen bond strengths. The strongly attractive interactions of water molecules with the calcium silicate walls serve to constrain their motion. Our findings have important implications on describing the cohesion and mechanical behavior of cement from its setting to its aging.

Coronary bypass grafting for ischemic heart disease in achondroplastic dwarfs is very rare. Shortage of veins and inadequate vein quality may cause difficulties during surgery. Only 2 cases of coronary bypass surgery in an achondroplastic dwarf, in which the left internal mammary artery and vein grafts were used, have been reported. We describe the case of a 55-year-old male achondroplastic dwarf who had triple-vessel coronary disease and underwent successful coronary bypass surgery using one saphenous vein graft and bilateral internal mammary artery grafts. The anatomic and surgical challenges in achondroplasia are highlighted.

Theoretical prediction of self-diffusion in a metal oxide in a wide range of thermodynamic conditions has been a long-standing challenge. Here, we establish that combining the formation free energies and migration barriers of all charged oxygen defects as calculated by density functional theory, within the random-walk diffusion theory framework, is a viable approach to predicting oxygen self-diffusion in metal oxides. We demonstrate this approach on tetragonal ZrO${}_{2}$ by calculating oxygen self-diffusivity as a function of temperature and oxygen partial pressure or, alternatively, temperature and off-stoichiometry. Arrhenius analysis on the isobaric (or constant off-stoichiometry) self-diffusivities yields a spectrum of effective activation barriers and prefactors. This provides reconciliation for the wide scatter in the experimentally determined activation barriers and prefactors for many oxides.

In the energy-structure paradigm, we analyzed the defects that can arise in tetragonal zirconium oxide (T-ZrO2) involving the hydrogen atom or the hydrogen molecule using density functional theory. Our results indicate that the dominant hydrogen defect under reducing conditions is H(·)(0), a complex formed between the hydride ion and a doubly charged oxygen vacancy. This result is consistent with the experimental observation that under reducing conditions, the solubility of hydrogen is proportional to the degree of hypostoichiometry of T-ZrO2. Under oxidizing conditions we found three different hydrogen defects, each predominating in a specific range of the chemical potential of electrons. Starting from the valence band top toward the conduction band bottom, these defects are the interstitial proton, H(·)(i), a complex formed between two hydrogen species and a zirconium vacancy with a net effective charge of (2-), (2H)"(Zr), and finally a complex similar to the latter but with a net effective charge of (4-), (H(2))'''(Zr). In (2H)"(Zr)the two hydrogens exist in the form of hydroxyl groups, while in (H(2))" " (Zr) they exist in the form of a hydrogen molecule. In addition, we found that up to three hydrogen species can favorably accumulate in a zirconium vacancy under oxidizing conditions. The clustering of hydrogen in cation vacancies can be a precursor for the deleterious effects of hydrogen on the mechanical properties and stability of metal oxides, in analogy with hydrogen embrittlement in metals. Finally we observed a red-shift and a blue-shift for the vibrational frequencies of all the hydroxyl groups and all the hydrogen molecules, respectively, in T-ZrO2 when compared to the gas phase frequencies. This is an important characteristic for guiding future experimental efforts to detect and identify hydrogen defects in T-ZrO2. The insights presented in this work advance our predictive understanding of the degradation behavior of T-ZrO2 as a corrosion resistant passive layer, as a gate dielectric and in biomedical applications.

Pre-hospital delay has a significant impact on patients' mortality and morbidity in ST segment elevation myocardial infarction (STEMI). Internationally many factors including female gender have been implicated, but no research has been conducted in Arab cultures. We aimed to explore the factors contributing to pre-hospital delay among female STEMI patients in Saudi Arabia.This sequential, explanatory mixed methods study comprised a consecutive sample of 311 patients, presenting with STEMI to three hospitals in Riyadh, from March 2011-August 2011. Of these, 189 patients (36 females) were eligible and interviewed using the Response to Symptoms Questionnaire. A purposive sample of 18 patients (9 females) then participated in qualitative interviews that were taped and transcribed prior to thematic analysis.The median pre-hospital delay for males was 5 h and 12.9 h for females (p0.002). Standard multiple regression determined female gender as the strongest predictor of transfer delay-from decision to seek help to hospital arrival. Qualitative analysis produced five gender-related themes: (a) women require a male relative's permission to seek medical help; (b) women cannot travel to hospital unless accompanied by a male relative; (c) women prioritise family responsibilities over seeking help; (d) women lack knowledge of myocardial infarction (MI) symptoms and treatment; and (e) perception that women should not attract attention.This study provides new insight into how cultural factors increase pre-hospital delay for women within Saudi Arabia. While the quantitative data demonstrates that women experience much longer delays, the qualitative interviews confirm that cultural factors are implicated. Further research is urgently required.

We present a density functional theory (DFT) framework taking into account the finite temperature effects to quantitatively understand and predict charged defect equilibria in a metal oxide. Demonstration of this approach was performed on the technologically important tetragonal zirconium oxide, T-ZrO${}_{2}$. We showed that phonon free energy and electronic entropy at finite temperatures add a nonnegligible contribution to the free energy of formation of the defects. Defect equilibria were conveniently cast in Kr\"oger--Vink diagrams to facilitate realistic comparison with experiments. Consistent with experiments, our DFT-based results indicate the predominance of free electrons at low oxygen partial pressure (${P}_{{\mathrm{O}}_{2}}\ensuremath{\le}{10}^{\ensuremath{-}6}$ atm) and low temperature ($T\ensuremath{\le}1500\phantom{\rule{0.28em}{0ex}}\mathrm{K}$). In the same regime of ${P}_{{\mathrm{O}}_{2}}$ but at higher temperatures, we discovered that the neutral oxygen vacancies (F-centers) predominate. The nature of the predominant defect at high oxygen partial pressure has been a long-standing controversy in the experimental literature. Our results revealed this range to be dominated by the doubly charged oxygen vacancies at low temperatures ($T\ensuremath{\le}1500$ K) and free electrons at high temperatures. T-ZrO${}_{2}$ was found to be hypostoichiometric over all ranges of $T$ and ${P}_{{\mathrm{O}}_{2}}$, mainly because of the doubly charged oxygen vacancies, which are responsible for inducing $n$-type conductivity via a self-doping effect. A range of 1.3 eV in the band gap of T-ZrO${}_{2}$ starting from the middle of the gap toward the conduction band is accessible to the chemical potential of electrons (Fermi level) by varying $T$ and ${P}_{{\mathrm{O}}_{2}}$ without extrinsic doping. The approach presented here can be used to determine the thermodynamic conditions that extremize certain desirable or undesirable defects to attain the optimal catalytic and electronic performance of oxides.

The electronic conductivity and the redox activity of metal oxides depend on the extent of the wave function spread of the electronic charge carriers. Delocalized (free) electrons and holes lead to large electronic conductivity, whereas self-trapped (small polaron) electrons and holes provide active centers for charge transfer and redox reactions. It is possible to control the state of the electronic charge carriers in metal oxides, free vs. self-trapped, by utilizing mechanical stress and strain. Tensile stresses tend to favor trapping, and the critical tensile stress above which trapping occurs also depends strongly on temperature. Here we adopt SrTiO3 as a model system and computationally predict regimes of trapping or delocalization for electrons and holes as a function of hydrostatic stress and temperature. SrTiO3 is a representative of the perovskite family of metal oxides, and itself is a widely used crystal for electronic studies. Starting from density functional theory (DFT), we parametrized on-site Hubbard terms (+U) for Ti 3d states and O 2p states that adhere to the generalized Koopman’s theorem. This adherence qualifies DFT equipped with the selected U to accurately describe trapped electrons and holes. Using this DFT+U approach we found that in SrTiO3 at zero temperature and zero stress, trapped holes on oxygen ions are favored by 170 meV, whereas free electrons are favored by 110 meV. Using the quasiharmonic approximation we extend these results to finite temperature and finite hydrostatic stress. In particular we calculate the Gibbs free energy of formation of electrons and holes in both trapped and free states. Based on these free energies, we build a stress-temperature diagram for the predominant electronic defect state. The analysis we present here for SrTiO3 is broadly applicable to other semiconducting metal oxides, and illustrates how strain (or stress) can serve as a modulator of electronic charge carriers.

In a CO2-rich anoxic aqueous environment as in some oil fields, a layer of siderite (FeCO3) grows on carbon steel as a byproduct of steel corrosion. This layer acts as a resistive barrier that kinetically slows down further corrosion of steel. Understanding and predicting the rates of progression of both general and pitting corrosion requires a fundamental understanding of defect equilibria and diffusion in the passive film [1]. In this work we address this need by modelling point defect equilibria and mobility using a combination of density functional theory (DFT) and thermodynamic analysis. The defects of interest in this study are the native cation and anion vacancies and extrinsic chlorine defects whose concentrations vary depending on temperature and the chemical potential gradient from the steel/siderite interface (iron rich) to the siderite/water interface (carbonate rich). Defect formation energies were calculated using the DFT+U approach and defect mobility’s were computed the nudged elastic band method. Preliminary results indicate that iron vacancies are predominantly fully ionized (2- charge state), whereas oxygen vacancies are mainly neutral and carbon vacancies are never fully ionized (charge state less than 4-) as shown in Figure 1. In addition we identified hole polarons localized on iron cations to be a predominant electronic defect that participate in the equilibria of charged defects in this material. The predictions of point defects thermodynamics and kinetics in FeCO3 is major step toward an atomistics-informed corrosion model of carbon steel in oil fields. [1] D. D. Macdonald, Pure Appl. Chem., 71, 951, (1999). Figure 1

Background — Platelet glycoprotein IIb/IIIa receptor blockade with abciximab decreases ischemic events after percutaneous coronary intervention (PCI); however, the mechanism of this benefit has not been fully elucidated. The present study was designed to assess endothelium-dependent vasomotion after coronary stenting and to determine if abciximab alters this response. Methods and Results — The study group consisted of 48 patients (59±10 years of age) with discrete coronary stenoses who underwent stenting alone (n=28) or stenting plus abciximab (n=20). A control group consisted of 31 additional patients who had vasomotor testing on a non-PCI vessel. Coronary blood flow (CBF) was measured (0.014-inch Doppler wire) 30 minutes after uncomplicated PCI and in response to the intracoronary infusion of acetylcholine (Ach) (10 −7 , 10 −6 mol/L Ach) and adenosine (24 μg). Ach-mediated increase in CBF was impaired after stent insertion when compared with the control group (41±52% versus 70±48%; P P P Conclusions — Abciximab preserves the CBF response to Ach after coronary stenting. The preservation of microvascular endothelial function may help explain the beneficial clinical effect of this agent in patients undergoing PCI.

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