390 research outputs found
Recent Accumulation Variability in Northwest Greenland from Ground-Penetrating Radar and Shallow Cores along the Greenland Inland Traverse
Accumulation is a key parameter governing the mass balance of the Greenland ice sheet. Several studies have documented the spatial variability of accumulation over wide spatial scales, primarily using point data, remote sensing or modeling. Direct measurements of spatially extensive, detailed profiles of accumulation in Greenland, however, are rare. We used 400 MHz ground-penetrating radar along the 1009 km route of the Greenland Inland Traverse from Thule to Summit during April and May of 2011, to image continuous internal reflecting horizons. We dated these horizons using ice-core chemistry at each end of the traverse. Using density profiles measured along the traverse, we determined the depth to the horizons and the corresponding water-equivalent accumulation rates. The measured accumulation rates vary from ~0.1 m w.e. a–1 in the interior to ~0.7 m w.e. a–1 near the coast, and correspond broadly with existing published model results, though there are some excursions. Comparison of our recent accumulation rates with those collected along a similar route in the 1950s shows a ~10% increase in accumulation rates over the past 52 years along most of the traverse route. This implies that the increased water vapor capacity of warmer air is increasing accumulation in the interior of Greenland
Physical and optical characteristics of heavily melted “rotten” Arctic sea ice
Field investigations of the properties of heavily melted “rotten” Arctic
sea ice were carried out on shorefast and drifting ice off the coast of
Utqiaġvik (formerly Barrow), Alaska, during the melt season. While no
formal criteria exist to qualify when ice becomes rotten, the objective
of this study was to sample melting ice at the point at which its structural and
optical properties are sufficiently advanced beyond the peak of the summer
season. Baseline data on the physical (temperature, salinity, density,
microstructure) and optical (light scattering) properties of shorefast ice
were recorded in May and June 2015. In July of both 2015 and 2017, small
boats were used to access drifting rotten ice within ∼32 km of Utqiaġvik. Measurements showed that pore space increased as ice
temperature increased (−8 to 0 ∘C), ice salinity
decreased (10 to 0 ppt), and bulk density decreased (0.9 to
0.6 g cm−3). Changes in pore space were characterized with thin-section
microphotography and X-ray micro-computed tomography in the laboratory. These
analyses yielded changes in average brine inclusion number density (which
decreased from 32 to 0.01 mm−3), mean pore size (which
increased from 80 µm to 3 mm), and total porosity (increased from
0 % to > 45 %) and structural anisotropy (variable, with
values of generally less than 0.7). Additionally, light-scattering coefficients
of the ice increased from approximately 0.06 to > 0.35 cm−1 as the ice melt progressed. Together, these findings indicate that
the properties of Arctic sea ice at the end of melt season are significantly
distinct from those of often-studied summertime ice. If such rotten ice were
to become more prevalent in a warmer Arctic with longer melt seasons, this
could have implications for the exchange of fluid and heat at the ocean
surface.</p
Collective Animal Behavior from Bayesian Estimation and Probability Matching
Animals living in groups make movement decisions that depend, among other factors, on social interactions with other group members. Our present understanding of social rules in animal collectives is based on empirical fits to observations and we lack first-principles approaches that allow their derivation. Here we show that patterns of collective decisions can be derived from the basic ability of animals to make probabilistic estimations in the presence of uncertainty. We build a decision-making model with two stages: Bayesian estimation and probabilistic matching.
In the first stage, each animal makes a Bayesian estimation of which behavior is best to perform taking into account personal information about the environment and social information collected by observing the behaviors of other animals. In the probability matching stage, each animal chooses a behavior with a probability given by the Bayesian estimation that this behavior is the most appropriate one. This model derives very simple rules of interaction in animal collectives that depend only on two types of reliability parameters, one that each animal assigns to the other animals and another given by the quality of the non-social information. We test our model by obtaining theoretically a rich set of observed collective patterns of decisions in three-spined sticklebacks, Gasterosteus aculeatus, a shoaling fish species. The quantitative link shown between probabilistic estimation and collective rules of behavior allows a better contact with other fields such as foraging, mate selection, neurobiology and psychology, and gives predictions for experiments directly testing the relationship between estimation and collective behavior
Adaptative Potential of the Lactococcus Lactis IL594 Strain Encoded in Its 7 Plasmids
The extrachromosomal gene pool plays a significant role both in evolution and in the environmental adaptation of bacteria. The L. lactis subsp. lactis IL594 strain contains seven plasmids, named pIL1 to pIL7, and is the parental strain of the plasmid-free L. lactis IL1403, which is one of the best characterized lactococcal strains of LAB. Complete nucleotide sequences of pIL1 (6,382 bp), pIL2 (8,277 bp), pIL3 (19,244 bp), pIL4 (48,979), pIL5 (23,395), pIL6 (28,435 bp) and pIL7 (28,546) were established and deposited in the generally accessible database (GeneBank). Nine highly homologous repB-containing replicons, belonging to the lactococcal theta-type replicons, have been identified on the seven plasmids. Moreover, a putative region involved in conjugative plasmid mobilization was found on four plasmids, through identification of the presence of mob genes and/or oriT sequences. Detailed bioinformatic analysis of the plasmid nucleotide sequences provided new insight into the repertoire of plasmid-encoded functions in L. lactis, and indicated that plasmid genes from IL594 strain can be important for L. lactis adaptation to specific environmental conditions (e.g. genes coding for proteins involved in DNA repair or cold shock response) as well as for technological processes (e.g. genes encoding citrate and lactose utilization, oligopeptide transport, restriction-modification system). Moreover, global gene analysis indicated cooperation between plasmid- and chromosome-encoded metabolic pathways
Performance status is the most powerful risk factor for early death among patients with advanced soft tissue sarcoma The European Organisation for Research and Treatment of Cancer – Soft Tissue and Bone Sarcoma Group (STBSG) and French Sarcoma Group (FSG) study
BACKGROUND: We investigated prognostic factors (PFs) for 90-day mortality in a large cohort of advanced/metastatic soft tissue sarcoma (STS) patients treated with first-line chemotherapy. METHODS: The PFs were identified by both logistic regression analysis and probability tree analysis in patients captured in the Soft Tissue and Bone Sarcoma Group (STBSG) database (3002 patients). Scores derived from the logistic regression analysis and algorithms derived from probability tree analysis were subsequently validated in an independent study cohort from the French Sarcoma Group (FSG) database (404 patients). RESULTS: The 90-day mortality rate was 8.6 and 4.5% in both cohorts. The logistic regression analysis retained performance status (PS; odds ratio (OR) = 3.83 if PS = 1, OR = 12.00 if PS >= 2), presence of liver metastasis (OR = 2.37) and rare site metastasis (OR = 2.00) as PFs for early death. The CHAID analysis retained PS as a major discriminator followed by histological grade (only for patients with PS >= 2). In both models, PS was the most powerful PF for 90-day mortality. CONCLUSION: Performance status has to be taken into account in the design of further clinical trials and is one of the most important parameters to guide patient management. For those patients with poor PS, expected benefits from therapy should be weighed up carefully against the anticipated toxicities. British Journal of Cancer (2011) 104, 1544-1550. doi: 10.1038/bjc.2011.136 www.bjcancer.com Published online 19 April 2011 (C) 2011 Cancer Research U
Simple methodology for the quantitative analysis of fatty acids in human red blood cells
In the last years, there has been an increasing
interest in evaluating possible relations between fatty acid
(FA) patterns and the risk for chronic diseases. Due to the
long life span (120 days) of red blood cells (RBCs), their
FA profile reflects a longer term dietary intake and was
recently suggested to be used as an appropriate biomarker
to investigate correlations between FA metabolism and diseases.
Therefore, the aim of this work was to develop and
validate a simple and fast methodology for the quantification
of a broad range of FAs in RBCs using gas chromatography
with flame ionization detector, as a more common
and affordable equipment suitable for biomedical and
nutritional studies including a large number of samples. For
this purpose, different sample preparation protocols were
tested and compared, including a classic two-step method
(Folch method) with modifications and different one-step methods, in which lipid extraction and derivatization were
performed simultaneously. For the one-step methods, different
methylation periods and the inclusion of a saponification
reaction were evaluated. Differences in absolute FA
concentrations were observed among the tested methods,
in particular for some metabolically relevant FAs such as
trans elaidic acid and eicosapentaenoic acid. The one-step
method with saponification and 60 min of methylation time
was selected since it allowed the identification of a higher
number of FAs, and was further submitted to in-house validation.
The proposed methodology provides a simple, fast
and accurate tool to quantitatively analyse FAs in human
RBCs, useful for clinical and nutritional studies.This work received financial support from the
European Union (FEDER funds through COMPETE) and National
Funds (FCT, Fundação para a Ciência e Tecnologia) through project
PTDC/SAU-ENB/116929/2010 and EXPL/EMS-SIS/2215/2013.
ROR acknowledges PhD scholarship SFRH/BD/97658/2013 attributed
by FCT (Fundação para a Ciência e Tecnologia).info:eu-repo/semantics/publishedVersio
Valence-dependent influence of serotonin depletion on model-based choice strategy.
Human decision-making arises from both reflective and reflexive mechanisms, which underpin goal-directed and habitual behavioural control. Computationally, these two systems of behavioural control have been described by different learning algorithms, model-based and model-free learning, respectively. Here, we investigated the effect of diminished serotonin (5-hydroxytryptamine) neurotransmission using dietary tryptophan depletion (TD) in healthy volunteers on the performance of a two-stage decision-making task, which allows discrimination between model-free and model-based behavioural strategies. A novel version of the task was used, which not only examined choice balance for monetary reward but also for punishment (monetary loss). TD impaired goal-directed (model-based) behaviour in the reward condition, but promoted it under punishment. This effect on appetitive and aversive goal-directed behaviour is likely mediated by alteration of the average reward representation produced by TD, which is consistent with previous studies. Overall, the major implication of this study is that serotonin differentially affects goal-directed learning as a function of affective valence. These findings are relevant for a further understanding of psychiatric disorders associated with breakdown of goal-directed behavioural control such as obsessive-compulsive disorders or addictions.This research was funded by Wellcome Trust Grants awarded to VV (Intermediate WT Fellowship) and Programme Grant (089589/Z/09/Z) awarded to TWR, BJE, ACR, JWD and BJS. It was conducted at the Behavioural and Clinical Neuroscience Institute, which is supported by a joint award from the Medical Research Council and Wellcome Trust (G00001354). YW was supported by the Fyssen Foundation. SP is supported by Marie Curie Intra-European Fellowship (FP7-People-2012-IEF).This is the final version of the article. It first appeared from NPG via http://dx.doi.org/10.1038/mp.2015.4
Avoidable mortality across Canada from 1975 to 1999
BACKGROUND: The concept of 'avoidable' mortality (AM) has been proposed as a performance measure of health care systems. In this study we examined mortality in five geographic regions of Canada from 1975 to 1999 for previously defined avoidable disease groups that are amenable to medical care and public health. These trends were compared to mortality from other causes. METHODS: National and regional age-standardized mortality rates for ages less than 65 years were estimated for avoidable and other causes of death for consecutive periods (1975–1979, 1980–1985, 1985–1989, 1990–1994, and 1995–1999). The proportion of all-cause mortality attributable to avoidable causes was also determined. RESULTS: From 1975–1979 to 1995–1999, the AM decrease (46.9%) was more pronounced compared to mortality from other causes (24.9%). There were persistent regional AM differences, with consistently lower AM in Ontario and British Columbia compared to the Atlantic, Quebec, and Prairies regions. This trend was not apparent when mortality from other causes was examined. Injuries, ischaemic heart disease, and lung cancer strongly influenced the overall AM trends. CONCLUSION: The regional differences in mortality for ages less than 65 years was attributable to causes of death amenable to medical care and public health, especially from causes responsive to public health
Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990-2013: A systematic analysis for the Global Burden of Disease Study 2013
Background Up-to-date evidence on levels and trends for age-sex-specific all-cause and cause-specific mortality is essential for the formation of global, regional, and national health policies. In the Global Burden of Disease Study 2013 (GBD 2013) we estimated yearly deaths for 188 countries between 1990, and 2013. We used the results to assess whether there is epidemiological convergence across countries. Methods We estimated age-sex-specific all-cause mortality using the GBD 2010 methods with some refinements to improve accuracy applied to an updated database of vital registration, survey, and census data. We generally estimated cause of death as in the GBD 2010. Key improvements included the addition of more recent vital registration data for 72 countries, an updated verbal autopsy literature review, two new and detailed data systems for China, and more detail for Mexico, UK, Turkey, and Russia. We improved statistical models for garbage code redistribution. We used six different modelling strategies across the 240 causes; cause of death ensemble modelling (CODEm) was the dominant strategy for causes with sufficient information. Trends for Alzheimer's disease and other dementias were informed by meta-regression of prevalence studies. For pathogen-specific causes of diarrhoea and lower respiratory infections we used a counterfactual approach. We computed two measures of convergence (inequality) across countries: the average relative difference across all pairs of countries (Gini coefficient) and the average absolute difference across countries. To summarise broad findings, we used multiple decrement life-tables to decompose probabilities of death from birth to exact age 15 years, from exact age 15 years to exact age 50 years, and from exact age 50 years to exact age 75 years, and life expectancy at birth into major causes. For all quantities reported, we computed 95% uncertainty intervals (UIs). We constrained cause-specific fractions within each age-sex-country-year group to sum to all-cause mortality based on draws from the uncertainty distributions. Findings Global life expectancy for both sexes increased from 65·3 years (UI 65·0-65·6) in 1990, to 71·5 years (UI 71·0-71·9) in 2013, while the number of deaths increased from 47·5 million (UI 46·8-48·2) to 54·9 million (UI 53·6-56·3) over the same interval. Global progress masked variation by age and sex: for children, average absolute differences between countries decreased but relative differences increased. For women aged 25-39 years and older than 75 years and for men aged 20-49 years and 65 years and older, both absolute and relative differences increased. Decomposition of global and regional life expectancy showed the prominent role of reductions in age-standardised death rates for cardiovascular diseases and cancers in high-income regions, and reductions in child deaths from diarrhoea, lower respiratory infections, and neonatal causes in low-income regions. HIV/AIDS reduced life expectancy in southern sub-Saharan Africa. For most communicable causes of death both numbers of deaths and age-standardised death rates fell whereas for most non-communicable causes, demographic shifts have increased numbers of deaths but decreased age-standardised death rates. Global deaths from injury increased by 10·7%, from 4·3 million deaths in 1990 to 4·8 million in 2013; but age-standardised rates declined over the same period by 21%. For some causes of more than 100 000 deaths per year in 2013, age-standardised death rates increased between 1990 and 2013, including HIV/AIDS, pancreatic cancer, atrial fibrillation and flutter, drug use disorders, diabetes, chronic kidney disease, and sickle-cell anaemias. Diarrhoeal diseases, lower respiratory infections, neonatal causes, and malaria are still in the top five causes of death in children younger than 5 years. The most important pathogens are rotavirus for diarrhoea and pneumococcus for lower respiratory infections. Country-specific probabilities of death over three phases of life were substantially varied between and within regions. Interpretation For most countries, the general pattern of reductions in age-sex specific mortality has been associated with a progressive shift towards a larger share of the remaining deaths caused by non-communicable disease and injuries. Assessing epidemiological convergence across countries depends on whether an absolute or relative measure of inequality is used. Nevertheless, age-standardised death rates for seven substantial causes are increasing, suggesting the potential for reversals in some countries. Important gaps exist in the empirical data for cause of death estimates for some countries; for example, no national data for India are available for the past decade. Funding Bill & Melinda Gates Foundation
- …