651 research outputs found

    The 27-day versus 13.5-day variations in the solar Lyman-alpha radiation and the radio wave absorption in the lower ionosphere over Europe

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    In order to clarify the question of solar periods in absorption, the pattern was studied of the solar Lyman-alpha radiation (the principal ionizing agent of the lower ionosphere) and of the radio wave absorption at five widely spaced places in Europe. When the solar Lyman-alpha flux variability is very well developed, then it dominates in the lower ionospheric variability. The most pronounced Lyman-alpha variation on time scale day-month is the solar rotation variation (about 27 days). When the Lyman-alpha variability is developed rather poorly, as it is typical for periods dominated by the 13.5 day variability, then the lower ionospheric variability appears to be dominated by variations of meteorological origin. The conclusions hold for all five widely spaced placed in Europe

    Survival of closing-wedge high tibial osteotomy - Good outcome in men with low-grade osteoarthritis after 10-16 years

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    BACKGROUND AND PURPOSE: High tibial valgus osteotomy (HTO) is a well-accepted treatment for medial unicompartmental osteoarthritis of the knee with varus alignment in relatively young and active patients. Controversies about the factors affecting survival of HTO still exist. We assessed preoperative risk factors for failure of closing-wedge HTO at long-term follow-up. PATIENTS AND METHODS: A cohort of 100 patients with a mean age of 49 (24-67) years, who had closing-wedge HTO performed between January 1991 and December 1996, were analyzed retrospectively. A survival analysis was carried out according to the Kaplan-Meier method. Logistic regression analysis was used to assess the association between failure of the osteotomy and known potential preoperative risk factors. RESULTS: The probability of survival for HTO was 75% (SD 4%) at 10 years with knee replacement as the endpoint. Female sex and osteoarthritis of grade > or = 2 were identified as preoperative risk factors for conversion to arthroplasty 10 years after HTO. INTERPRETATION: Our findings suggest that ideal candidates for corrective osteotomy are men with symptomatic medial compartmental osteoarthritis of Ahlback grade 1, who, 10 years after surgery, have an almost tenfold lower probability of failure of HTO than women with more advanced osteoarthritis

    How grass keeps growing : an integrated analysis of hormonal crosstalk in the maize leaf growth zone

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    We studied the maize leaf to understand how long-distance signals, auxin and cytokinin, control leaf growth dynamics. We constructed a mathematical model describing the transport of these hormones along the leaf growth zone and their interaction with the local gibberellin (GA) metabolism in the control of cell division. Assuming gradually declining auxin and cytokinin supply at the leaf base, the model generated spatiotemporal hormone distribution and growth patterns that matched experimental data. At the cellular level, the model predicted a basal leaf growth as a result of cell division driven by auxin and cytokinin. Superimposed on this, GA synthesis regulated growth through the control of the size of the region of active cell division. The predicted hormone and cell length distributions closely matched experimental data. To correctly predict the leaf growth profiles and final organ size of lines with reduced or elevated GA production, the model required a signal proportional to the size of the emerged part of the leaf that inhibited the basal leaf growth driven by auxin and cytokinin. Excision and shading of the emerged part of the growing leaf allowed us to demonstrate that this signal exists and depends on the perception of light intensity

    Trends in caesarean section and instrumental deliveries in relation to Body Mass Index: a clinical survey during 1978 - 2001

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    <p>Abstract</p> <p>Background</p> <p>During the last 20 years the rate of CS has increased in Sweden as it has in many other countries. The proportion of pregnant women suffering from a high BMI has also increased rapidly during the same time period. It would therefore be of interest to study both how and if these two observations are related to each other. The aim was therefore to study trends in mode of caesarean section (CS) and instrumental deliveries among women in three BMI groups over a time span of almost 25 years with special focus on the observed body weight of pregnant women.</p> <p>Method</p> <p>The design is a retrospective cohort study using medical records of consecutively delivered women at two delivery wards in South East Sweden during the years 1978, 1986, 1992, 1997 and 2001.</p> <p>Results</p> <p>No significant time-trends were found for CS and instrumental delivery within each BMI-group for the time period studied. The proportion of women with BMI ≥ 25 delivered by means of CS or instrumental delivery increased quite dramatically from 1978 to 2001 (χ<sup>2 </sup>test for trend; p < 0.001 for both CS and instrumental deliveries). The mean birth weight in relation to BMI and year of study among women delivered by means of CS decreased, a trend that was most evident between 1997 and 2001 (F-test; p = 0.005, p = 0.004, and p = 0.003 for BMI < 20, 20-24.9, and ≥ 25, respectively).</p> <p>Conclusion</p> <p>Overweight and obese pregnant women constitute a rapidly growing proportion of the total number of CS and instrumental deliveries. Planning and allocation of health resources must be adjusted to this fact and its implications.</p

    Under pressure: Response urgency modulates striatal and insula activity during decision-making under risk

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    When deciding whether to bet in situations that involve potential monetary loss or gain (mixed gambles), a subjective sense of pressure can influence the evaluation of the expected utility associated with each choice option. Here, we explored how gambling decisions, their psychophysiological and neural counterparts are modulated by an induced sense of urgency to respond. Urgency influenced decision times and evoked heart rate responses, interacting with the expected value of each gamble. Using functional MRI, we observed that this interaction was associated with changes in the activity of the striatum, a critical region for both reward and choice selection, and within the insula, a region implicated as the substrate of affective feelings arising from interoceptive signals which influence motivational behavior. Our findings bridge current psychophysiological and neurobiological models of value representation and action-programming, identifying the striatum and insular cortex as the key substrates of decision-making under risk and urgency

    Improved annotation of 3' untranslated regions and complex loci by combination of strand-specific direct RNA sequencing, RNA-seq and ESTs

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    The reference annotations made for a genome sequence provide the framework for all subsequent analyses of the genome. Correct annotation is particularly important when interpreting the results of RNA-seq experiments where short sequence reads are mapped against the genome and assigned to genes according to the annotation. Inconsistencies in annotations between the reference and the experimental system can lead to incorrect interpretation of the effect on RNA expression of an experimental treatment or mutation in the system under study. Until recently, the genome-wide annotation of 3-prime untranslated regions received less attention than coding regions and the delineation of intron/exon boundaries. In this paper, data produced for samples in Human, Chicken and A. thaliana by the novel single-molecule, strand-specific, Direct RNA Sequencing technology from Helicos Biosciences which locates 3-prime polyadenylation sites to within +/- 2 nt, were combined with archival EST and RNA-Seq data. Nine examples are illustrated where this combination of data allowed: (1) gene and 3-prime UTR re-annotation (including extension of one 3-prime UTR by 5.9 kb); (2) disentangling of gene expression in complex regions; (3) clearer interpretation of small RNA expression and (4) identification of novel genes. While the specific examples displayed here may become obsolete as genome sequences and their annotations are refined, the principles laid out in this paper will be of general use both to those annotating genomes and those seeking to interpret existing publically available annotations in the context of their own experimental dataComment: 44 pages, 9 figure

    Particles and fields in fluid turbulence

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    The understanding of fluid turbulence has considerably progressed in recent years. The application of the methods of statistical mechanics to the description of the motion of fluid particles, i.e. to the Lagrangian dynamics, has led to a new quantitative theory of intermittency in turbulent transport. The first analytical description of anomalous scaling laws in turbulence has been obtained. The underlying physical mechanism reveals the role of statistical integrals of motion in non-equilibrium systems. For turbulent transport, the statistical conservation laws are hidden in the evolution of groups of fluid particles and arise from the competition between the expansion of a group and the change of its geometry. By breaking the scale-invariance symmetry, the statistically conserved quantities lead to the observed anomalous scaling of transported fields. Lagrangian methods also shed new light on some practical issues, such as mixing and turbulent magnetic dynamo.Comment: 165 pages, review article for Rev. Mod. Phy

    DNA methylation-based classification of glioneuronal tumours synergises with histology and radiology to refine accurate molecular stratification.

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    AIMS: Glioneuronal tumours (GNTs) are poorly distinguished by their histology and lack robust diagnostic indicators. Previously, we showed that common GNTs comprise two molecularly distinct groups, correlating poorly with histology. To refine diagnosis, we constructed a methylation-based model for GNT classification, subsequently evaluating standards for molecular stratification by methylation, histology and radiology. METHODS: We comprehensively analysed methylation, radiology and histology for 83 GNT samples: a training cohort of 49, previously classified into molecularly defined groups by genomic profiles, plus a validation cohort of 34. We identified histological and radiological correlates to molecular classification and constructed a methylation-based support vector machine (SVM) model for prediction. Subsequently, we contrasted methylation, radiological and histological classifications in validation GNTs. RESULTS: By methylation clustering, all training and 23/34 validation GNTs segregated into two groups, the remaining 11 clustering alongside control cortex. Histological review identified prominent astrocytic/oligodendrocyte-like components, dysplastic neurons and a specific glioneuronal element as discriminators between groups. However, these were present in only a subset of tumours. Radiological review identified location, margin definition, enhancement and T2 FLAIR-rim sign as discriminators. When validation GNTs were classified by SVM, 22/23 classified correctly, comparing favourably against histology and radiology that resolved 17/22 and 15/21, respectively, where data were available for comparison. CONCLUSIONS: Diagnostic criteria inadequately reflect glioneuronal tumour biology, leaving a proportion unresolvable. In the largest cohort of molecularly defined glioneuronal tumours, we develop molecular, histological and radiological approaches for biologically meaningful classification and demonstrate almost all cases are resolvable, emphasising the importance of an integrated diagnostic approach
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