A generalized linear mixed model for longitudinal binary data with a marginal logit link function

Longitudinal studies of a binary outcome are common in the health, social, and behavioral sciences. In general, a feature of random effects logistic regression models for longitudinal binary data is that the marginal functional form, when integrated over the distribution of the random effects, is no longer of logistic form. Recently, Wang and Louis [Biometrika 90 (2003) 765--775] proposed a random intercept model in the clustered binary data setting where the marginal model has a logistic form. An acknowledged limitation of their model is that it allows only a single random effect that varies from cluster to cluster. In this paper we propose a modification of their model to handle longitudinal data, allowing separate, but correlated, random intercepts at each measurement occasion. The proposed model allows for a flexible correlation structure among the random intercepts, where the correlations can be interpreted in terms of Kendall's $\tau$. For example, the marginal correlations among the repeated binary outcomes can decline with increasing time separation, while the model retains the property of having matching conditional and marginal logit link functions. Finally, the proposed method is used to analyze data from a longitudinal study designed to monitor cardiac abnormalities in children born to HIV-infected women.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS390 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Factors affecting psychological well-being: Evidence from two nationally representative surveys

Financial status is thought to be an important determinant of psychological well-being. We investigate this relationship, and the effect of other factors, using a parametric mixed modelling approach for panel data, controlling the problem of unobservable heterogeneity. Two nationally representative surveys, the British Household Panel Survey (BHPS) and the Understanding Society Survey (USS), were used to construct a unified data set which measured psychological well-being and associated factors using the 12-item General Health Questionnaire (GHQ-12). The GHQ-12 score for the head of the household was used as the dependant variable and its relationship with multiple independent demographic and financial status variables was investigated. Following assessment of growth curve characteristics with linear, curvilinear and higher-order polynomial modelling; several variance-covariance structures were tested to assess the error covariance structure of the longitudinal data. The random intercept and random slope were allowed to vary across participants, and methods such as natural splines and B-splines were used to improve the fit of some variables. Our final model demonstrated the most important variables affecting self-reported psychological well-being, as determined by GHQ-12, were perception and expectation of future financial situation and problems meeting household expenditure. Gender, age, marital status, number of children at home, highest qualification and job status were also significantly implicated. Unlike previous studies however we did not find that size of income was significant. These results provide further strong evidence of the impact that financial concerns have on self-reported measures of psychological well-being

A performance comparison of the contiguous allocation strategies in 3D mesh connected multicomputers

The performance of contiguous allocation strategies can be significantly affected by the distribution of job execution times. In this paper, the performance of the existing contiguous allocation strategies for 3D mesh multicomputers is re-visited in the context of heavy-tailed distributions (e.g., a Bounded Pareto distribution). The strategies are evaluated and compared using simulation experiments for both First-Come-First-Served (FCFS) and Shortest-Service-Demand (SSD) scheduling strategies under a variety of system loads and system sizes. The results show that the performance of the allocation strategies degrades considerably when job execution times follow a heavy-tailed distribution. Moreover, SSD copes much better than FCFS scheduling strategy in the presence of heavy-tailed job execution times. The results also show that the strategies that depend on a list of allocated sub-meshes for both allocation and deallocation have lower allocation overhead and deliver good system performance in terms of average turnaround time and mean system utilization

In vitro digestibility of field pea as influenced by processing methods

Field pea meals exposed to different treatments (flaking, extrusion, expansion, dry heating at 150°C/15' or 30', dry heating at 150°C/30' after addition of 1% of xylose, 4% NaOH addition, microwave irradiation at 800 W for 6' or 9') were controlled for their 6 and 24 hours in vitro fermentability by the gas production (GP) technique. Flaking and extrusion accelerated initial fermentation but tended to reduce 24h GP, whereas dry heating and microwaves mainly improved final gas volume, but NaOH had the opposite effect. Apparent dry matter digestion at 6h was lowered by dry heating, NaOH addition and the shorter microwave irradiation. Xylose addition did not substantially change the effects of dry heating, but lowered the initial disappearance. Ammonia concentration was in general lowered by the treatments, suggesting a reduction in protein degradability but also a possible higher microbial uptake for protein synthesis. Microwave irradiation had limited effects on all the parameters. Dry heating, with or without xylose addition, seems interesting to increase rumen escaping protein fraction without accelerating starch fermentation that could expose to higher risks of rumen acidosis

Selenium-containing enzymes in mammals: chemical perspectives

The chemical and biochemical route to the synthesis of the 21st amino acid in living systems, selenocysteine, is described. The incorporation of this rare amino acid residue into proteins is described with emphasis on the role of monoselenophosphate as selenium source. The role of selenocysteine moiety in natural mammalian enzymes such as glutathione peroxidase (GPx), iodothyronine deiodinase (ID) and thioredoxin reductase (TrxR) is highlighted and the effect of other amino acid residues located in close proximity to selenocysteine is described. It is evident from various studies that two amino acid residues, tryptophan and glutamine, appear in identical positions in all known members of the GPx family. According to the three-dimensional structure established for bovine GPx, these residues could constitute a catalytic triad in which the selenol group of the selenocysteine is both stabilized and activated by hydrogen bonding with the imino group of the tryptophan (Trp) residue and with the amido group of the glutamine (Gln) residue. The ID enzymes, on the other hand, do not possess any Trp or Gln residues in close proximity to selenium, but contain several histidine residues, which may play important roles in the catalysis. The TrxR enzymes also possess some basic histidines, but the most important amino acid residues are the cysteines which constitute the internal cofactor systems along with the catalytically active selenocysteine. The catalytic activity and substrate specificity of all three selenoenzymes are described. The reactivity of selenocysteine residues in selenoenzymes towards metal-based drugs such as goldthioglucose is also described

An unusual presentation of erythema multiforme in a paediatric patient

Background: Erythema multiforme (EM) is an acute, vesiculobullous disease of skin and mucous membranes with symptoms ranging from mild to severe. A complex interaction of different factors has been implicated the condition; the majority with a preceding herpes simplex infection. This report describes an unusual presentation of erythema multiforme affecting the lips and oral mucosa of a healthy 7-year-old boy in the form of lip adherence. Case report: Two weeks following eruption of oral ulcerations, a 7-year-old healthy boy developed severe erosive ulceration of both lips, causing complete lip adherence. This was accompanied by marked bilateral submandibular and cervical lymphadenopathy, tremor and sweating. Clinical and laboratory investigations led to a diagnosis of erythema multiforme. The patient was treated initially with gentle application of Vaseline between the lips using cotton buds in an attempt to release lip adhesion, followed by surgical release of the lips under general anaesthesia. Analgesics and topical steroid mouthwash were provided. Follow-up: Seven months later, the patient presented with a recurrence of his EM which included lesions on the skin. The patient was treated with antivirals, topical and systematic steroids to suppress the recurrent attacks of EM. Eighteen months following the initial presentation the patient and parent reported considerable decrease in the frequency, severity and duration of the occurrence of intra-oral ulcers, with no major episode of target lesions on the skin. Conclusion: Erythema multiforme is rare in children, however it should be considered in the differential diagnosis of recurrent erosive oral ulcerative lesions especially when the oral lesions resemble those of primary herpetic gingivostomatitis

Charting the value and limits of other effective conservation measures (OECMs) for marine conservation: A Delphi study

Other effective conservation measures (OECMs) will play an important role in the Post-2020 Global Biodiversity Framework as a way for governments to achieve “30 × 30” (30% protection of land and oceans by 2030). However, the policy tool remains relatively new, is expanding from multiple perspectives, and requires clarification. We conducted a Delphi study – a structured technique designed to elicit the insights of a panel of experts – to chart the value and limits of OECMs for marine conservation. Results of the Delphi reveal a high degree of consensus on several core areas of this emerging policy tool. Experts agreed that OECMs can advance equitable and effective conservation. Realizing these opportunities will require strengthening local and Indigenous rights and prioritizing principles of social equity. The panel also agreed on five key challenges, ranging from ensuring that the burden to prove effectiveness does not fall to local communities to securing adequate resources to support OECMs. In contrast, no consensus was reached on how to measure the effectiveness of OECMs, highlighting the need to develop shared monitoring guidelines. Taken together, these findings outline a clear policy and research agenda to support the contributions of OECMs towards equitable, effective, and enduring conservation

Application of FT-IR spectroscopy to analyze casein in cow milk

AbstractInfrared spectrometry is, at present, the most frequently applied methodology for the composition analysis of milk and dairy products. The determination of fat, protein and lactose has been described during recent decades. The introduction of Fourier Transform Infra-red (FT-IR) technology in combination with the application of multi-dimensional procedures (i.e. principal component regression, partial least squares) has improved this methodology, opening new perspectives for the simultaneous and routinely determination of many new parameters such as casein, urea, specific sugars, etc.. The aim of our study was to develop on MilkoScanTM FT 120 (Foss Electric, Hillerod, Denmark) a calibration curve for the analysis of casein in cow milk and to execute a preliminary validation. The calibration curve was developed on 89 individual milk samples collected from 4 dairy herds in the Grana-Padano cheese district. In order to obtain a higher variability of milk protein content and composition, in each herd m..

First In-Situ Measurements of Plume Chemistry at Mount Garet Volcano, Island of Gaua (Vanuatu)

Recent volcanic gas compilations have urged the need to expand in-situ plume measurements to poorly studied, remote volcanic regions. Despite being recognized as one of the main volcanic epicenters on the planet, the Vanuatu arc remains poorly characterized for its subaerial emissions and their chemical imprints. Here, we report on the first plume chemistry data for Mount Garet, on the island of Gaua, one of the few persistent volatile emitters along the Vanuatu arc. Data were collected with a multi-component gas analyzer system (multi-GAS) during a field campaign in December 2018. The average volcanic gas chemistry is characterized by mean molar CO2/SO2, H2O/SO2, H2S/SO2 and H2/SO2 ratios of 0.87, 47.2, 0.13 and 0.01, respectively. Molar proportions in the gas plume are estimated at 95.9 ± 11.6, 1.8 ± 0.5, 2.0 ± 0.01, 0.26 ± 0.02 and 0.06 ± 0.01, for H2O, CO2, SO2, H2S and H2. Using the satellite-based 10-year (2005–2015) averaged SO2 flux of ~434 t d−1 for Mt. Garet, we estimate a total volatile output of about 6482 t d−1 (CO2 ~259 t d−1; H2O ~5758 t d−1; H2S ~30 t d−1; H2 ~0.5 t d−1). This may be representative of a quiescent, yet persistent degassing period at Mt. Garet; whilst, as indicated by SO2 flux reports for the 2009–2010 unrest, emissions can be much higher during eruptive episodes. Our estimated emission rates and gas composition for Mount Garet provide insightful information on volcanic gas signatures in the northernmost part of the Vanuatu Arc Segment. The apparent CO2-poor signature of high-temperature plume degassing at Mount Garet raises questions on the nature of sediments being subducted in this region of the arc and the possible role of the slab as the source of subaerial CO2. In order to better address the dynamics of along-arc volatile recycling, more volcanic gas surveys are needed focusing on northern Vanuatu volcanoes