Carbonate Coprecipitation for Cd and Zn Treatment and Evaluation of Heavy Metal Stability Under Acidic Conditions.

Mining wastes or combustion ash are materials of high carbon sequestration potential but are also known for their toxicity in terms of heavy metal content. To utilize such waste materials for engineered carbon mineralization purposes, there is a need to investigate the fate and mobility of toxic metals. This is a study of the coprecipitation of metals with calcium carbonate for environmental heavy metal mitigation. The study also examines the stability of precipitated phases under environmentally relevant acid conditions. For a wide range of cadmium (Cd) and zinc (Zn) concentrations (10 to 5000 mg/L), induced coprecipitation led to greater than 99% uptake from water. The calcium carbonate phases were found to contain amounts as high as 9.9 wt % (Cd) and 17 wt % (Zn), as determined by novel synchrotron techniques, including X-ray fluorescence element mapping and three-dimensional (3D) nanotransmission X-ray microscopy (TXM). TXM imaging revealed first-of-a-kind observations of chemical gradients and internal nanoporosity within particles. These observations provided new insights into the mechanisms leading to the retention of coprecipitated heavy metals during the dissolution of calcite in acidic (pH 4) solutions. These observations highlight the feasibility of utilizing carbonate coprecipitation as an engineered approach to the durable sequestration of toxic metals.

Peak grain forecasts for the US High Plains amid withering waters.

Irrigated agriculture contributes 40% of total global food production. In the US High Plains, which produces more than 50 million tons per year of grain, as much as 90% of irrigation originates from groundwater resources, including the Ogallala aquifer. In parts of the High Plains, groundwater resources are being depleted so rapidly that they are considered nonrenewable, compromising food security. When groundwater becomes scarce, groundwater withdrawals peak, causing a subsequent peak in crop production. Previous descriptions of finite natural resource depletion have utilized the Hubbert curve. By coupling the dynamics of groundwater pumping, recharge, and crop production, Hubbert-like curves emerge, responding to the linked variations in groundwater pumping and grain production. On a state level, this approach predicted when groundwater withdrawal and grain production peaked and the lag between them. The lags increased with the adoption of efficient irrigation practices and higher recharge rates. Results indicate that, in Texas, withdrawals peaked in 1966, followed by a peak in grain production 9 y later. After better irrigation technologies were adopted, the lag increased to 15 y from 1997 to 2012. In Kansas, where these technologies were employed concurrently with the rise of irrigated grain production, this lag was predicted to be 24 y starting in 1994. In Nebraska, grain production is projected to continue rising through 2050 because of high recharge rates. While Texas and Nebraska had equal irrigated output in 1975, by 2050, it is projected that Nebraska will have almost 10 times the groundwater-based production of Texas.

Early supported discharge for older adults admitted to hospital with medical complaints: a systematic review and meta-analysis.

INTRODUCTION: Early supported discharge (ESD) aims to link acute and community care, allowing hospital inpatients to return home and continue to receive the necessary input from healthcare professionals that they would otherwise receive in hospital. It has been researched extensively in the stroke population, showing reduced length of stay for patients and improved functional outcomes. This systematic review aims to explore the totality of evidence for the use of ESD in an older adult population who have been hospitalised with medical complaints. METHODS: Systematic searches were conducted in MEDLINE, CINAHL, Ebsco, Cochrane Library and EMBASE. Randomised controlled trials (RCTs) and quasi-RCTs were included if they provided an ESD intervention to older adults admitted to hospital for medical complaints compared with usual inpatient care. Patient and process outcomes were explored. The Cochrane Risk of Bias Tool was used to assess methodological quality. A meta-analysis was conducted using RevMan 5.4.1. RESULTS: Five RCTs met the inclusion criteria. The quality of the trials was mixed overall, with high levels of heterogeneity. ESD demonstrated a statistically significant reduction in length of stay (MD -6.04 days, 95% CI -9.76 to -2.32) and improvements in function, cognition, and health-related quality of life, with no increased risk of long-term care admission, hospital re-admission or mortality in the ESD interventions versus usual care groups. DISCUSSION: This review demonstrates that ESD positively impacts patient and process outcomes for older adults. Further consideration should be given to exploring the experiences of those involved in ESD including older adults, family members/caregivers as well as healthcare professionals.

A biallelic loss-of-function PDIA6 variant in a second patient with polycystic kidney disease, infancy-onset diabetes, and microcephaly.

We report a second patient with intrauterine growth retardation, congenital polycystic kidney disease, infancy-onset diabetes, microcephaly, and liver fibrosis caused by a homozygous PDIA6 loss-of-function variant. Our study further defines the genetic and clinical features of this rare syndromic form of infancy-onset diabetes.

Sexual Shame as a Unique Distress Outcome of Morally Incongruent Pornography Use: Modifications and Methodological Considerations.

Researchers focused on the model of pornography problems due to moral incongruence (PPMI) have suggested that perceptions of addiction, stemming from a misalignment between one's moral values and online sexual behavior, may lead to heightened sexual shame. Even so, it has been suggested that the associations found in previous models of PPMI may have been inflated by the inclusion of the emotional distress subscale in the widely used Cyber Pornography Use Inventory (CPUI-9), leading many to use the abridged 4-item version (i.e., the CPUI-4), which excludes emotional distress. Prior models assessing sexual shame have yet to fully address this potential methodological limitation. Considering advances in the conceptualization of PPMI and recommendations concerning best practices, a sample of participants (N = 296) that reported using pornography in the last six months was utilized to compare findings from two moderated mediation models. The first model assessed the differential strength of effects when the subscales of the CPUI-9 were assessed as separate mediators of the associations between moral incongruence and sexual shame, while the second model examined whether such associations persisted when using the recommended CPUI-4. Model results provide further justification for previous findings, indicating that associations between constructs were not the sole result of emotional distress, which supports the utility of the CPUI-4 in models that include sexual shame. Findings provide added support for sexual shame as a unique outcome among those who, due to moral incongruence, perceive that they are addicted to Internet pornography.

Early supported discharge for older adults admitted to hospital with medical complaints: a systematic review and meta-analysis.

INTRODUCTION: Early supported discharge (ESD) aims to link acute and community care, allowing hospital inpatients to return home and continue to receive the necessary input from healthcare professionals that they would otherwise receive in hospital. The concept has shown reduced length of stay and improved functional outcomes in stroke patients. This systematic review aims to explore the totality of evidence for the use of early supported discharge in older adults hospitalised with medical complaints. METHODS: A literature search of CINAHL in EBSCO, Cochrane Central Register of Controlled Trials in the Cochrane Library (CENTRAL), EMBASE and MEDLINE in EBSCO was carried out. Randomised controlled trials or quasi-randomised controlled trials were included. The Cochrane Risk of Bias Tool 2.0 was used for quality assessment. The primary outcome measure was hospital length of stay. Secondary outcomes included mortality, function, health related quality of life, hospital readmissions, long-term care admissions and cognition. A pooled meta-analysis was conducted using RevMan software 5.4.1. RESULTS: Five studies met the inclusion criteria. All studies were of some concern in terms of their risk of bias. Statistically significant effects favouring ESD interventions were only seen in terms of length of stay (REM, MD = -6.04, 95% CI -9.76 to -2.32, I2 = 90%, P = 0.001). No statistically significant effects favouring ESD interventions were established in secondary outcomes. CONCLUSION: ESD interventions can have a statistically significant impact on the length of stay of older adults admitted to hospital for medical reasons. There is a need for further higher quality research in the area, with standardised interventions and outcome measures used.

The SARS-CoV-2 pandemic is associated with increased severity of presentation of childhood onset type 1 diabetes mellitus: A multi-centre study of the first COVID-19 wave.

OBJECTIVE: Children are usually mildly affected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19). However, the pandemic has caused collateral damage to those with non-COVID-19 diseases. We aimed to determine the impact of the COVID-19 pandemic on the presentation of newly diagnosed childhood onset type 1 diabetes. METHODS: This was a cross-sectional study conducted over a 1-year period. We compared the severity of presentation of new-onset type 1 diabetes in children under the age of 18 presenting to the multi-centre North Central London diabetes network before (1 July 2019 to 22 March 2020) and during (23 March 2020 to 30 June 2020) the first wave of the COVID-19 pandemic in the United Kingdom. RESULTS: Over the 1-year study period, a total of 30 children presented with new-onset type 1 diabetes during the pre-pandemic period and 17 presented during the first COVID-19 wave. Children presented more frequently in diabetic ketoacidosis (DKA) during the first COVID-19 wave compared with pre-pandemic (pre-pandemic: mild 13%, moderate 6.7%, severe 10%; first COVID-19 wave: mild 5.9%, moderate 24%, severe 47%; p = 0.002). During the first COVID-19 wave, DKA presentations in children with a family history of type 1 diabetes were fewer compared to those without a family history (33.3% vs. 100.0%; p = 0.006). Children presenting in severe DKA pre-pandemic were younger than those not in severe DKA (3.9 years vs. 12.2 years, p < 0.001) but this difference was not significant during the first COVID-19 wave (10.1 years vs. 11.2 years, p = 0.568). Presenting HbA1c measurement was higher in those presenting during the first COVID-19 wave (13.0 ± 1.7 vs. 10.4 ± 3.2%; 119 ± 19 vs. 90 ± 35 mmol/mol; p = 0.008). CONCLUSION: The COVID-19 pandemic is associated with increased severity of presentation of childhood onset type 1 diabetes. Whatever the context, young people with suspected new-onset type 1 diabetes should be referred for urgent clinical review.

Global Environmental Engineering for and with Historically Marginalized Communities.

Marginalized communities lack full participation in social, economic, and political life, and they disproportionately bear the burden of environmental and health risks. This special issue of Environmental Engineering Science, the official journal of the Association of Environmental Engineering and Science Professors (AEESP), reports research on the unique environmental challenges faced by historically marginalized communities around the world. The results of community-based participatory research with an Afro-descendant community in Columbia, Native American communities in Alaska, United States, villagers in the Philippines, disadvantaged communities in California, United States, rural communities in Mexico and Costa Rica, homeless encampments in the San Diego River (United States) watershed entrepreneurs in Durban, South Africa, and remote communities in the island nation of Fiji are presented. The research reported in this special issue is transdisciplinary, bringing engineers together with anthropologists, sociologists, economists, and public health experts. In the 13 articles in this special issue, some of the topics covered include inexpensive technologies for water treatment, novel agricultural strategies for reversing biodiversity losses, and strategies for climate change adaptation. In addition, one article covered educational strategies for teaching ethics to prepare students for humanitarian engineering, including topics of poverty, sustainability, social justice, and engineering decisions under uncertainty. Finally, an article presented ways that environmental engineering professors can engage and promote the success of underrepresented minority students and enable faculty engaged in community-based participatory research.

Acid Erosion of Carbonate Fractures and Accessibility of Arsenic-Bearing Minerals: In Operando Synchrotron-Based Microfluidic Experiment.

Underground flows of acidic fluids through fractured rock can create new porosity and increase accessibility to hazardous trace elements such as arsenic. In this study, we developed a custom microfluidic cell for an in operando synchrotron experiment using X-ray attenuation. The experiment mimics reactive fracture flow by passing an acidic fluid over a surface of mineralogically heterogeneous rock from the Eagle Ford shale. Over 48 h, calcite was preferentially dissolved, forming an altered layer 200-500 µm thick with a porosity of 63-68% and surface area >10× higher than that in the unreacted shale as shown by xCT analyses. Calcite dissolution rate quantified from the attenuation data was 3 × 10-4 mol/m2s and decreased to 3 × 10-5 mol/m2s after 24 h because of increasing diffusion limitations. Erosion of the fracture surface increased access to iron-rich minerals, thereby increasing access to toxic metals such as arsenic. Quantification using XRF and XANES microspectroscopy indicated up to 0.5 wt % of As(-I) in arsenopyrite and 1.2 wt % of As(V) associated with ferrihydrite. This study provides valuable contributions for understanding and predicting fracture alteration and changes to the mobilization potential of hazardous metals and metalloids.

Metals Coprecipitation with Barite: Nano-XRF Observation of Enhanced Strontium Incorporation.

Coprecipitation can be an effective treatment method for the removal of environmentally relevant metals from industrial wastewaters such as produced waters from the oil and gas industry. The precipitation of barite, BaSO4, through the addition of sulfate removes barium while coprecipitating strontium and other alkaline earth metals even when these are present at concentrations below their solubility limit. Among other analytical methods, X-ray fluorescence (XRF) nanospectroscopy at the Hard X-ray Nanoprobe (HXN) beamline at the National Synchrotron Light Source II (NSLS-II) was used to quantify Sr incorporation into barite. Thermodynamic modeling of (Ba,Sr)SO4 solid solutions was done using solid solution-aqueous solution (SS-AS) theory. The quantitative, high-resolution nano-XRF data show clearly that the Sr content in (Ba,Sr)SO4 solid solutions varies widely among particles and even within a single particle. We observed substantial Sr incorporation that is far larger than thermodynamic models predict, likely indicating the formation of metastable solid solutions. We also observed that increasing barite supersaturation of the aqueous phase led to increased Sr incorporation, as predicted by available kinetic models. These results suggest that coprecipitation offers significant potential for designing treatment systems for aqueous metals' removal in desired metastable compositions. Solution conditions may be optimized to enhance the incorporation of Sr by increasing sulfate addition such that the barite saturation index remains above ∼3 or by increasing the aqueous Sr to Ba ratio.

Targeted Permeability Control in the Subsurface via Calcium Silicate Carbonation.

Efforts to develop safe and effective next-generation energy and carbon-storage technologies in the subsurface require novel means to control undesired fluid migration. Here we demonstrate that the carbonation of calcium silicates can produce reaction products that dramatically reduce the permeability of porous media and that are stable. Most calcium silicates react with CO2 to form solid carbonates but some polymorphs (here, pseudowollastonite, CaSiO3) can react to form a range of crystalline calcium silicate hydrates (CCSHs) at intermediate pH. High-pressure (1.1-15.5 MPa) column and batch experiments were conducted at a range of temperatures (75-150 °C) and reaction products were characterized using SEM-EDS and synchrotron µXRD and µXRF. Two characteristics of CCSH precipitation were observed, revealing unique properties for permeability control relative to carbonate precipitates. First, precipitation of CCSHs tends to occur on the surface of sand grains and into pore throats, indicating that small amounts of precipitation relative to the total pore volume can effectively block flow, compared to carbonates which precipitate uniformly throughout the pore space. Second, the precipitated CCSHs are more stable at low pH conditions, which may form more secure barriers to flow, compared to carbonates, which dissolve under acidic conditions.

Reactive Transport Simulation of Fracture Channelization and Transmissivity Evolution.

Underground fractures serve as flow conduits, and they may produce unwanted migration of water and other fluids in the subsurface. An example is the migration and leakage of greenhouse gases in the context of geologic carbon sequestration. This study has generated new understanding about how acids erode carbonate fracture surfaces and the positive feedback between reaction and flow. A two-dimensional reactive transport model was developed and used to investigate the extent to which geochemical factors influence fracture permeability and transmissivity evolution in carbonate rocks. The only mineral modeled as reactive is calcite, a fast-reacting mineral that is abundant in subsurface formations. The X-ray computed tomography dataset from a previous experimental study of fractured cores exposed to carbonic acid served as a testbed to benchmark the model simulation results. The model was able to capture not only erosion of fracture surfaces but also the specific phenomenon of channelization, which produces accelerating transmissivity increase. Results corroborated experimental findings that higher reactivity of the influent solution leads to strong channelization without substantial mineral dissolution. Simulations using mineral maps of calcite in a specimen of Amherstburg limestone demonstrated that mineral heterogeneity can either facilitate or suppress the development of flow channels depending on the spatial patterns of reactive mineral. In these cases, fracture transmissivity may increase rapidly, increase slowly, or stay constant, and for all these possibilities, the calcite mineral continues to dissolve. Collectively, these results illustrate that fluid chemistry and mineral spatial patterns need to be considered in predictions of reaction-induced fracture alteration and risks of fluid migration.

Influence of Rock Mineralogy on Reactive Fracture Evolution in Carbonate-Rich Caprocks.

Fractures present environmental risks for subsurface engineering activities, such as geologic storage of greenhouse gases, because of the possibility of unwanted upward fluid migration. The risks of fluid leakage may be exacerbated if fractures are subjected to physical and chemical perturbations that alter their geometry. This study investigated this by constructing a 2D fracture model to numerically simulate fluid flow, acid-driven reactions, and mechanical deformation. Three rock mineralogies were simulated: a limestone with 100% calcite, a limestone with 68% calcite, and a banded shale with 34% calcite. One might expect transmissivity to increase fastest for rocks with more calcite due to its high solubility and fast reaction rate. Yet, results show that initially transmissivity increases fastest for rocks with less calcite because of their ability to deliver unbuffered-acid downstream faster. Moreover, less reactive minerals become persistent asperities that sustain mechanical support within the fracture. However, later in the simulations, the spatial pattern of less reactive mineral, not abundance, controls transmissivity evolution. Results show that a banded mineral pattern creates persistent bottlenecks, prevents channelization, and stabilizes transmissivity. For sites for geologic storage of CO2 that have carbonate caprocks, banded mineral variation may limit reactive evolution of fracture transmissivity and increase storage reliability.

Impact of deprivation, ethnicity, and insulin pump therapy on developmental trajectories of diabetes control in COB type 1 diabetes.

BACKGROUND: There is marked variation in diabetes outcomes for children and adolescents across the UK. We used modelling techniques to examine the independent contributions of deprivation, ethnicity, insulin pump use, and health service use on HbA1c trajectories across adolescence. METHODS: Prospective data from a large UK Paediatric & Adolescent Diabetes Service on subjects with type 1 diabetes (T1D) aged 9-17 years from January 2008 to December 2013: 2560 HbA1c datapoints were available on 384 patients [193 (50.4%) female]. Sequential multilevel growth models assessed the effects of sex, duration of diabetes, deprivation, ethnicity, insulin pump use, and health service use on HbA1c . Growth mixture models were used to identify discrete HbA1c trajectories across adolescence. RESULTS: Mean clinic HbA1c decreased from 2008 to 2013 by 0.122% (95% confidence interval: 0.034, 0.210; P = .007) per year. The optimal multilevel growth model showed mean HbA1c increased with age (B = 0.414, P < .0001), and that mean HbA1c was predicted by white/British ethnicity (B = -0.748, P = .004), clinic visits (B = 0.041, P = .04), and pump use (B = -0.568, P < .0001) but not deprivation. The optimal mixture model was a four trajectory group solution, with 45.1% in Good Control, 39.6% with Deteriorating Control, 6.5% with Rapidly Deteriorating Control, and 8.8% in Poor Control across adolescence. Only pump use predicted trajectory group membership, being protective against membership of all other trajectories compared with Good Control. CONCLUSIONS: Increasing uptake of insulin pumps and ensuring access to health services are likely to be the most effective means of reducing inequalities in outcomes of T1D in children and young people.

The Leakage Risk Monetization Model for Geologic CO2 Storage.

We developed the Leakage Risk Monetization Model (LRiMM) which integrates simulation of CO2 leakage from geologic CO2 storage reservoirs with estimation of monetized leakage risk (MLR). Using geospatial data, LRiMM quantifies financial responsibility if leaked CO2 or brine interferes with subsurface resources, and estimates the MLR reduction achievable by remediating leaks. We demonstrate LRiMM with simulations of 30 years of injection into the Mt. Simon sandstone at two locations that differ primarily in their proximity to existing wells that could be leakage pathways. The peak MLR for the site nearest the leakage pathways ($7.5/tCO2) was 190x larger than for the farther injection site, illustrating how careful siting would minimize MLR in heavily used sedimentary basins. Our MLR projections are at least an order of magnitude below overall CO2 storage costs at well-sited locations, but some stakeholders may incur substantial costs. Reliable methods to detect and remediate leaks could further minimize MLR. For both sites, the risk of CO2 migrating to potable aquifers or reaching the atmosphere was negligible due to secondary trapping, whereby multiple impervious sedimentary layers trap CO2 that has leaked through the primary seal of the storage formation.

Management of Cushing syndrome in children and adolescents: experience of a single tertiary centre.

UNLABELLED: The diagnosis and management of paediatric Cushing syndrome (CS) is highly challenging. This study aims to characterise its presentation, diagnosis, management and outcome by a retrospective case review of 30 patients (14 females) followed at a single tertiary paediatric endocrinology centre over a 30-year period. At presentation, median age was 8.9 years (0.2-15.5) and the commonest manifestations were weight gain (23/30), hirsutism (17/30), acne (15/30) and hypertension (15/30). Growth retardation was present in 11/30. Median body mass index (BMI) was +2.1 standard deviation score (SDS) (-6.5 to +4.6). Urinary free cortisol (UFC) was abnormal in 17/18 (94 %), midnight cortisol in 27/27 (100 %) and low-dose dexamethasone suppression (LDDS) test in 20/20 (100 %). High-dose dexamethasone suppression (HDDS) test was abnormal in 6/6 (100 %) of adrenal tumours, 1/10 (10 %) of Cushing disease (CD) and 1/2 (50 %) of ectopic tumours. Bilateral inferior petrosal sinus sampling (IPSS) identified five CD cases and one ectopic tumour. All patients underwent surgery and subsequently required cortisol replacement. Final diagnoses were 16 CD, 11 adrenal disease, 2 ectopic ACTH-secreting lesions and 1 case of unidentified aetiology. One year post-diagnosis, median BMI was 0.5 SDS (-2.5 to +3.7), hypertension was present in 4/14 (28 %), and 43 % (12/30) of individuals were off hydrocortisone. CONCLUSION: The prevalence of the clinical manifestations differs from that reported in other series. Screening tests were highly sensitive, with UFC, midnight cortisol and LDDS performing well. One year post-treatment, BMI and BP normalised in the majority of patients and almost half of them were able to discontinue replacement hydrocortisone. WHAT IS KNOWN: •Cushing syndrome is an extremely rare entity in the paediatric and adolescent age groups, so not many cohort studies have been published in this population. •Several tests can be employed to firstly diagnose hypercortisolaemia and secondly identify the source of origin of it. The efficacy and safety of these tests in children is still uncertain. What is New: •This study includes cases due to the different aetiologies of endogenous hypercortisolaemia (pituitary, adrenal and ectopic hypercortisolaemia) allowing us to compare the differences in presentation, diagnosis, management and long-term outcome between the groups. •There is a difference in the prevalence of Cushing syndrome symptoms and in the performance of the tests in our cohort compared to previously published studies in the literature.

Mitigating Climate Change at the Carbon Water Nexus: A Call to Action for the Environmental Engineering Community.

Environmental engineers have played a critical role in improving human and ecosystem health over the past several decades. These contributions have focused on providing clean water and air as well as managing waste streams and remediating polluted sites. As environmental problems have become more global in scale and more deeply entrenched in sociotechnical systems, the discipline of environmental engineering must grow to be ready to respond to the challenges of the coming decades. Here we make the case that environmental engineers should play a leadership role in the development of climate change mitigation technologies at the carbon-water nexus (CWN). Climate change, driven largely by unfettered emissions of fossil carbon into the atmosphere, is a far-reaching and enormously complex environmental risk with the potential to negatively affect food security, human health, infrastructure, and other systems. Solving this problem will require a massive mobilization of existing and innovative new technology. The environmental engineering community is uniquely positioned to do pioneering work at the CWN using a skillset that has been honed, solving related problems. The focus of this special issue, on "The science and innovation of emerging subsurface energy technologies," provides one example domain within which environmental engineers and related disciplines are beginning to make important contributions at the CWN. In this article, we define the CWN and describe how environmental engineers can bring their considerable expertise to bear in this area. Then we review some of the topics that appear in this special issue, for example, mitigating the impacts of hydraulic fracturing and geologic carbon storage, and we provide perspective on emergent research directions, for example, enhanced geothermal energy, energy storage in sedimentary formations, and others.

Alterations of Fractures in Carbonate Rocks by CO2-Acidified Brines.

Fractures in geological formations may enable migration of environmentally relevant fluids, as in leakage of CO2 through caprocks in geologic carbon sequestration. We investigated geochemically induced alterations of fracture geometry in Indiana Limestone specimens. Experiments were the first of their kind, with periodic high-resolution imaging using X-ray computed tomography (xCT) scanning while maintaining high pore pressure (100 bar). We studied two CO2-acidified brines having the same pH (3.3) and comparable thermodynamic disequilibrium but different equilibrated pressures of CO2 (PCO2 values of 12 and 77 bar). High-PCO2 brine has a faster calcite dissolution kinetic rate because of the accelerating effect of carbonic acid. Contrary to expectations, dissolution extents were comparable in the two experiments. However, progressive xCT images revealed extensive channelization for high PCO2, explained by strong positive feedback between ongoing flow and reaction. The pronounced channel increasingly directed flow to a small region of the fracture, which explains why the overall dissolution was lower than expected. Despite this, flow simulations revealed large increases in permeability in the high-PCO2 experiment. This study shows that the permeability evolution of dissolving fractures will be larger for faster-reacting fluids. The overall mechanism is not because more rock dissolves, as would be commonly assumed, but because of accelerated fracture channelization.

Cardiovascular risk factors in children and adolescents with congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

OBJECTIVE: The prevalence of cardiovascular risk factors in congenital adrenal hyperplasia (CAH) varies widely. In the light of recent changes in treatment regimens, we have reassessed the prevalence of these risk factors in our current cohort of patients with CAH due to P450c21 deficiency. METHODS: A retrospective cross-sectional study of 107 children (39 m) with CAH aged 9·2 years (range 0·4-20·5 years). Anthropometric, systolic (SBP) and diastolic (DBP) blood pressure data were collected and expressed as standard deviation scores (SDS) using UK growth reference data and the Fourth Task Force data set, respectively. Fasting blood glucose with plasma insulin and lipids was measured, and insulin resistance (HOMA IR) calculated using the homoeostasis assessment model. RESULTS: 23·6% (33% men; 18% women) of the cohort were obese (BMI SDS>2). BMI SDS was significantly higher (P < 0·001) when compared with the UK population. Nineteen (20·9%) of 91 patients (20% men; 21% women) had systolic hypertension and 8 [8·8% (8·6% men; 8·9% women)] had diastolic hypertension. Mean SBP [108 (SD 13·5)] mm Hg was significantly higher than the normal population (P < 0·001), but mean DBP was not (P = 0·07). Both SBP SDS and DBP SDS were not related to BMI SDS. 9·5% of the subjects had hyperlipidaemia, but HOMA IR was more favourable compared with the normal population. CONCLUSION: Despite a reduction in steroid doses over the last decade, a number of children with CAH are still obese and hypertensive. Whether this reflects general population trends or indicates a need to further optimize treatment regimens remains to be determined.

Impacts of diffusive transport on carbonate mineral formation from magnesium silicate-CO2-water reactions.

Reactions of CO2 with magnesium silicate minerals to precipitate magnesium carbonates can result in stable carbon sequestration. This process can be employed in ex situ reactors or during geologic carbon sequestration in magnesium-rich formations. The reaction of aqueous CO2 with the magnesium silicate mineral forsterite was studied in systems with transport controlled by diffusion. The approach integrated bench-scale experiments, an in situ spectroscopic technique, and reactive transport modeling. Experiments were performed using a tube packed with forsterite and open at one end to a CO2-rich solution. The location and amounts of carbonate minerals that formed were determined by postexperiment characterization of the solids. Complementing this ex situ characterization, (13)C NMR spectroscopy tracked the inorganic carbon transport and speciation in situ. The data were compared with the output of reactive transport simulations that accounted for diffusive transport processes, aqueous speciation, and the forsterite dissolution rate. All three approaches found that the onset of magnesium carbonate precipitation was spatially localized about 1 cm from the opening of the forsterite bed. Magnesite was the dominant reaction product. Geochemical gradients that developed in the diffusion-limited zones led to locally supersaturated conditions at specific locations even while the volume-averaged properties of the system remained undersaturated.