Equilibrium isotope fractionation factors of H exchange between steam and soil clay fractions

Rationale Steam equilibration overcomes the problem of the traditional measurements of H isotope compositions, which leave an arbitrary amount of adsorbed water in the sample, by controlling for the entire exchangeable H pool, including adsorbed water and hydroxyl-H. However, the use of steam equilibration to determine nonexchangeable stable H isotope compositions in environmental media (expressed as δ2Hn values) by mathematically eliminating the influence of exchangeable H after sample equilibration with waters of known H-isotopic composition requires the knowledge of the equilibrium isotope fractionation factor between steam-H and exchangeable H of the sample (αex-w), which is frequently unknown. Methods We developed a new method to determine the αex-w values for clay minerals, topsoil clay fractions, and mica by manipulating the contributions of exchangeable H to the total H pool via different degrees of post-equilibration sample drying. We measured the δ2H values of steam-equilibrated mineral and soil samples using elemental analyzer-pyrolysis-isotope ratio mass spectrometry. Results The αex-w values of seven clay minerals ranged from 1.071 to 1.140, and those of 19 topsoil clay fractions ranged from 0.885 to 1.216. The αex-w value of USGS57 biotite, USGS58 muscovite, and of cellulose was 0.965, 0.871, and 1.175, respectively. The method did not work for kaolinite, because its small exchangeable H pool did not respond to the selected drying conditions. Structurally different mineral groups such as two- and three-layer clay minerals or mica showed systematically different αex-w values. The αex-w value of the topsoil clay fractions correlated with the soil clay content (r = 0.63, P = 0.004), the local mean annual temperature (r = 0.68, P = 0.001), and the δ2H values of local precipitation (r = 0.72, P < 0.001), likely to reflect the different clay mineralogy under different weathering regimes. Conclusions Our new αex-w determination method yielded realistic results in line with the few previously published values for cellulose. The determined αex-w values were similar to the widely assumed values of 1.00–1.08 in the literature, suggesting that the adoption of one of these values in steam equilibration approaches is appropriate

Non‐exchangeable stable hydrogen isotope ratios in clay minerals and soil clay fractions: A method test

Stable hydrogen isotope ratios (δ$^{2}$H values) in structural hydroxyl groups of pedogenic clay minerals are inherited from the surrounding water at the time of their formation. Only non-exchangeable H preserves the environmental forensic and paleoclimate information (δ$^{2}$H$_{n}$ value). To measure δ$^{2}$H$_{n}$ values in structural H of clay minerals and soil clay fractions, we adapted a steam equilibration method by accounting for high hygroscopicity. Our δ$^{2}$H$_{n}$ values for USGS57 biotite (−95.3 ± SD 0.9‰) and USGS58 muscovite (30.7 ± 1.4‰) differed slightly but significantly from the reported δ$^{2}$H values (−91.5 ± 2.4‰ and −28.4 ± 1.6‰), because the minerals contained 1.1%–4.4% of exchangeable H. The low SD of replicate measurements (n = 3) confirmed a high precision. The clay separation method including destruction of Fe oxides, carbonates and soil organic matter, and dispersion did not significantly change the δ$^{2}$H$_{n}$ values of five different clay minerals. However, we were unable to remove all organic matter from the soil clay fractions resulting in an estimated bias of 1‰ in two samples and 15‰ in the carbon-richest sample. Our results demonstrate that δ$^{2}$H$_{n}$ values of structural H of clay minerals and soil clay fractions can be reliably measured without interference from atmospheric water and the method used to separate the soil clay fraction

Quantitative TaqMan® real-time PCR assays for gene expression normalisation in feline tissues

ABSTRACT: BACKGROUND: Gene expression analysis is an important tool in contemporary research, with real-time PCR as the method of choice for quantifying transcription levels. Co-analysis of suitable reference genes is crucial for accurate expression normalisation. Reference gene expression may vary, e.g., among species or tissues; thus, candidate genes must be tested prior to use in expression studies. The domestic cat is an important study subject in both medical research and veterinary medicine. The aim of the present study was to develop TaqMan(R) real-time PCR assays for eight potential reference genes and to test their applicability for feline samples, including blood, lymphoid, endocrine, and gastrointestinal tissues from healthy cats, and neoplastic tissues from FeLV-infected cats. RESULTS: RNA extraction from tissues was optimised for minimal genomic DNA (gDNA) contamination without use of a DNase treatment. Real-time PCR assays were established and optimised for v-abl Abelson murine leukaemia viral oncogene homolog (ABL), beta-actin (ACTB), beta-2-microglobulin (B2M), beta-glucuronidase (GUSB), hydroxymethyl-bilane synthase (HMBS), hypoxanthine phosphoribosyltransferase (HPRT), ribosomal protein S7 (RPS7), and tryptophan 5-monooxygenase activation protein, zeta polypeptide (YWHAZ). The presence of pseudogenes was confirmed for four of the eight investigated genes (ACTB, HPRT, RPS7, and YWHAZ). The assays were tested together with previously developed TaqMan(R) assays for feline glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the universal 18S rRNA gene. Significant differences were found among the expression levels of the ten candidate reference genes, with a ~10;6-fold expression difference between the most abundant (18S rRNA) and the least abundant genes (ABL, GUSB, and HMBS). The expression stability determined by the geNorm and NormFinder programs differed significantly. Using the ANOVA-based NormFinder program, RPS7 was the most stable gene in the tissues studied, followed by ACTB and ABL; B2M, HPRT, and the 18S rRNA genes were the least stable ones. CONCLUSION: The reference gene expression stability varied considerably among the feline tissues investigated. No tested gene was optimal for normalisation in all tissues. For the majority of the tissues, two to three reference genes were necessary for accurate normalisation. The present study yields essential information on the correct choice of feline reference genes depending on the tissues analysed

Signed zeros of Gaussian vector fields-density, correlation functions and curvature

We calculate correlation functions of the (signed) density of zeros of Gaussian distributed vector fields. We are able to express correlation functions of arbitrary order through the curvature tensor of a certain abstract Riemann-Cartan or Riemannian manifold. As an application, we discuss one- and two-point functions. The zeros of a two-dimensional Gaussian vector field model the distribution of topological defects in the high-temperature phase of two-dimensional systems with orientational degrees of freedom, such as superfluid films, thin superconductors and liquid crystals.Comment: 14 pages, 1 figure, uses iopart.cls, improved presentation, to appear in J. Phys.

The inter-relationship of adolescent unhappiness and parental mental distress

Purpose Substantial evidence supports the hypothesis that parental well-being impacts upon child well-being and that this relationship is bidirectional. Here we explore how, in a large, nationally representative sample, both parents' mental distress relates over time to each other's mental distress and to their adolescent child's unhappiness, and vice versa. Methods Analyses were conducted using data from waves one to five (2009/10–2014/15) of Understanding Society, the UK Household Longitudinal Study. Understanding Society collects data on adults' mental distress (General Health Questionnaire), and on youths' (age: 10–15 years) unhappiness in relation to their school work, appearance, family, friends, school, and life as a whole. We use repeated-measures structural equation models to investigate the reciprocal relationships between both parents' distress and their child's unhappiness, using both longitudinal cross-lagged and nonrecursive contemporaneous specifications. The analytic sample is 1,883 triads (adolescent child, mother, and father) with data at two or more consecutive time points. Analyses are stratified by adolescent gender. Results Our results show that parental mental distress predicts unhappiness of girls but not that of boys. Reciprocal associations of maternal and paternal mental distress are evident in families with an adolescent daughter. Unhappiness of adolescents does not predict their parents' mental distress. Results are similar whether examined contemporaneously or over time. Conclusions Our findings support the suggestion that the family should be considered as a dynamic system, for instance when planning clinical interventions. This is particularly pertinent in families with an adolescent daughter present

A longitudinal examination of maternal, family, and area-level experiences of racism on children's socioemotional development: patterns and possible explanations

The association between experienced racial discrimination and poor health is now well documented, particularly among adult populations. However, longitudinal studies of the association between racism and child health are limited, and evidence on how racial discrimination experienced by members of children's immediate environment impact on child development, and the mechanisms by which this occurs, is scarce. We examined the longitudinal association between maternal, family, and area-level experiences of racial discrimination, and children's socioemotional development. We proposed that exposure to racial discrimination would be detrimental to children's socioemotional development via two mother-centred stress pathways: a worsening in maternal mental health, and an increase in harsh parenting practices. Data on ethnic minority mothers and their children were drawn from waves 3 to 5 (2006–2012) of the UK Millennium Cohort Study. Results of longitudinal path analyses show a strong association between maternal and family experiences of racial discrimination in wave 3, and a worsening in mother's mental health in wave 4. Maternal and family experiences of racial discrimination at wave 3 had an indirect effect on children's socioemotional development at wave 5. This occurred mainly via a worsening in mother's mental health, although some events of racial discrimination experienced by the mother and other family members also impacted negatively on children's socioemotional development via an increase in harsh parenting practices. We found a direct effect of maternal and family experiences of racial discrimination on children's socioemotional development. Our findings document the harm of growing up in a racist environment on the socioemotional development of children, and provide some evidence for the role of mother-centred stress mechanisms in linking vicarious exposure to racial discrimination to children's socioemotional development

The epidemiology and natural history of depressive disorders in Hong Kong's primary care

Background: Depressive disorders are commonly managed in primary care and family physicians are ideally placed to serve as central providers to these patients. Around the world, the prevalence of depressive disorders in patients presenting to primary care is between 10-20%, of which around 50% remain undiagnosed. In Hong Kong, many barriers exist preventing the optimal treatment and management of patients with depressive disorders. The pathways of care, the long term outcomes and the factors affecting prognosis of these patients requires closer examination. Methods/Design. The aim of this study is to examine the prevalence, incidence and natural history of depressive disorders in primary care and the factors influencing diagnosis, management and outcomes using a cross-sectional study followed by a longitudinal cohort study. Doctors working in primary care settings across Hong Kong have been invited to participate in this study. On one day each month over twelve months, patients in the doctor's waiting room are invited to complete a questionnaire containing items on socio-demography, co-morbidity, family history, previous doctor-diagnosed mental illness, recent mental and other health care utilization, symptoms of depression and health-related quality of life. Following the consultation, the doctors provide information regarding presenting problem, whether they think the patient has depression, and if so, whether the diagnosis is new or old, and the duration of the depressive illness if not a new diagnosis. If the doctor detects a depressive disorder, they are asked to provide information regarding patient management. Patients who consent are followed up by telephone at 2, 12, 26 and 52 weeks. Discussion. The study will provide information regarding cross-sectional prevalence, 12 month incidence, remission rate, outcomes and factors affecting outcomes of patients with depressive disorders in primary care. The epidemiology, outcomes, pathways of care, predictors for prognosis and service needs for primary care patients with depressive disorders will be described and recommendations made for policy and service planning. © 2011 Chin et al; licensee BioMed Central Ltd.published_or_final_versio

A randomised controlled trial assessing the use of citalopram, sertraline, fluoxetine and mirtazapine in preventing relapse in primary care patients who are taking long-term maintenance antidepressants (ANTLER : ANTidepressants to prevent reLapse in dEpRession): study protocol for a randomised controlled trial

BACKGROUND: Antidepressants are used both for treating acute episodes and for prophylaxis to prevent future episodes of depression, also called maintenance treatment. This article describes the protocol for a randomised controlled trial (ANTLER: ANTidepressants to prevent reLapse in dEpRession) to investigate the clinical effectiveness and cost-effectiveness in UK primary care of continuing on long-term maintenance antidepressants compared with a placebo in preventing relapse of depression in those who have taken antidepressants for more than 9 months and who are currently well enough to consider stopping maintenance treatment. METHODS/DESIGN: The ANTLER trial is an individually randomised, double-blind, placebo-controlled trial in which participants are randomised to remain on active medication or to take an identical placebo after a tapering period of 2 months. Eligible participants are those who: are between the ages of 18 and 74 years; have had at least two episodes of depression; and have been taking antidepressants for 9 months or more and are currently taking citalopram 20 mg, sertraline 100 mg, fluoxetine 20 mg or mirtazapine 30 mg but are well enough to consider stopping their medication. The participants will be followed up at 6, 12, 26, 39 and 52 weeks. The primary outcome will be the time in weeks to the beginning of the first episode of depression after randomisation. This will be measured using a retrospective version of the Clinical Interview Schedule-Revised administered at 12, 26, 39 and 52 weeks. Secondary outcomes will include depressive and anxiety symptoms, adverse effects, withdrawal symptoms, emotional processing tasks, quality of life and the resources and costs used. We will also perform a cost-effectiveness analysis based on results of the trial. DISCUSSION: The ANTLER trial findings will inform primary care prescribing practice by providing a valid and generalisable estimate of the clinical effectiveness and cost-effectiveness of long-term maintenance treatment with antidepressants in UK primary care. TRIAL REGISTRATION: Controlled Trials ISRCTN Registry, ISRCTN15969819. Registered on 21 September 2015

The Patient Health Questionnaire-9 for detection of major depressive disorder in primary care: consequences of current thresholds in a crosssectional study

<p>Abstract</p> <p>Background</p> <p>There is a need for brief instruments to ascertain the diagnosis of major depressive disorder. In this study, we present the reliability, construct validity and accuracy of the PHQ-9 and PHQ-2 to detect major depressive disorder in primary care.</p> <p>Methods</p> <p>Cross-sectional analyses within a large prospective cohort study (PREDICT-NL). Data was collected in seven large general practices in the centre of the Netherlands. 1338 subjects were recruited in the general practice waiting room, irrespective of their presenting complaint. The diagnostic accuracy (the area under the ROC curve and sensitivities and specificities for various thresholds) was calculated against a diagnosis of major depressive disorder determined with the Composite International Diagnostic Interview (CIDI).</p> <p>Results</p> <p>The PHQ-9 showed a high degree of internal consistency (ICC = 0.88) and test-retest reliability (correlation = 0.94). With respect to construct validity, it showed a clear association with functional status measurements, sick days and number of consultations. The discriminative ability was good for the PHQ-9 (area under the ROC curve = 0.87, 95% CI: 0.84-0.90) and the PHQ-2 (ROC area = 0.83, 95% CI 0.80-0.87). Sensitivities at the recommended thresholds were 0.49 for the PHQ-9 at a score of 10 and 0.28 for a categorical algorithm. Adjustment of the threshold and the algorithm improved sensitivities to 0.82 and 0.84 respectively but the specificity decreased from 0.95 to 0.82 (threshold) and from 0.98 to 0.81 (algorithm). Similar results were found for the PHQ-2: the recommended threshold of 3 had a sensitivity of 0.42 and lowering the threshold resulted in an improved sensitivity of 0.81.</p> <p>Conclusion</p> <p>The PHQ-9 and the PHQ-2 are useful instruments to detect major depressive disorder in primary care, provided a high score is followed by an additional diagnostic work-up. However, often recommended thresholds for the PHQ-9 and the PHQ-2 resulted in many undetected major depressive disorders.</p

Assessing hospitals' clinical risk management: Development of a monitoring instrument

<p>Abstract</p> <p>Background</p> <p>Clinical risk management (CRM) plays a crucial role in enabling hospitals to identify, contain, and manage risks related to patient safety. So far, no instruments are available to measure and monitor the level of implementation of CRM. Therefore, our objective was to develop an instrument for assessing CRM in hospitals.</p> <p>Methods</p> <p>The instrument was developed based on a literature review, which identified key elements of CRM. These elements were then discussed with a panel of patient safety experts. A theoretical model was used to describe the level to which CRM elements have been implemented within the organization. Interviews with CRM practitioners and a pilot evaluation were conducted to revise the instrument. The first nationwide application of the instrument (138 participating Swiss hospitals) was complemented by in-depth interviews with 25 CRM practitioners in selected hospitals, for validation purposes.</p> <p>Results</p> <p>The monitoring instrument consists of 28 main questions organized in three sections: 1) Implementation and organizational integration of CRM, 2) Strategic objectives and operational implementation of CRM at hospital level, and 3) Overview of CRM in different services. The instrument is available in four languages (English, German, French, and Italian). It allows hospitals to gather comprehensive and systematic data on their CRM practice and to identify areas for further improvement.</p> <p>Conclusions</p> <p>We have developed an instrument for assessing development stages of CRM in hospitals that should be feasible for a continuous monitoring of developments in this important area of patient safety.</p