75,082 research outputs found
The Swift satellite and redshifts of long gamma-ray bursts
No full textUntil 6 October 2005 sixteen redshifts had been measured of long gamma-ray bursts discovered by the Swift satellite. Further 45 redshifts have been measured of the long gamma- ray bursts discovered by other satellites. Here we perform five statistical tests comparing the redshift distributions of these two samples assuming as the null hypothesis an identical distribution for the two samples. Three tests (Student's t-test, Mann-Whitney test, Kolmogorov-Smirnov test) reject the null hypothesis at significance levels between 97.19 and 98.55%. Two different comparisons of the medians show extreme (99.78 - 99.99994)% significance levels of rejection. This means that the redshifts of the Swift sample and the redshifts of the non-Swift sample are distributed differently - in the Swift sample the redshifts are on average larger. This statistical result suggests that the long GRBs should on average be at the higher redshifts of the Swift sample
Testing the randomness in the sky-distribution of gamma-ray bursts
No full textWe have studied the complete randomness of the angular distribution of gamma-ray bursts (GRBs) detected by the Burst and Transient Source Experiment (BATSE). Because GRBs seem to be a mixture of objects of different physical nature, we divided the BATSE sample into five subsamples (short1, short2, intermediate, long1, long2) based on their durations and peak fluxes, and we studied the angular distributions separately. We used three methods, Voronoi tesselation, minimal spanning tree and multifractal spectra, to search for non-randomness in the subsamples. To investigate the eventual non-randomness in the subsamples, we defined 13 test variables (nine from the Voronoi tesselation, three from the minimal spanning tree and one from the multifractal spectrum). Assuming that the point patterns obtained from the BATSE subsamples are fully random, we made Monte Carlo simulations taking into account the BATSE's sky-exposure function. The Monte Carlo simulations enabled us to test the null hypothesis (i.e. that the angular distributions are fully random). We tested the randomness using a binomial test and by introducing squared Euclidean distances in the parameter space of the test variables. We concluded that the short1 and short2 groups deviate significantly (99.90 and 99.98 per cent, respectively) from the full randomness in the distribution of the squared Euclidean distances; however, this is not the case for the long samples. For the intermediate group, the squared Euclidean distances also give a significant deviation (98.51 per cent)
Novel aspects of factor XIII deficiency
No full textPURPOSE OF REVIEW
Here we review recent developments concerning the diagnosis, classification and treatment of factor XIII (FXIII) deficiency and new findings related to the pathogenesis of the disease.
RECENT FINDINGS
Most recently, the International Society on Thrombosis and Haemostasis, Scientific and Standardization Committee published a guideline for the diagnosis and classification of FXIII deficiencies. Since 2009, three novel mutations causing severe bleeding diathesis were discovered in the FXIII-A gene and one in the FXIII-B gene. A newly described FXIII-A deficiency was of the extremely rare qualitative type II deficiency. The first well established founder effect was reported for a causative FXIII-A mutation. More than a quarter of all FXIII-A deficiencies are due to autoantibody, among them the first case of deficiency caused by anti-FXIII-B autoantibody was reported in the last 2 years. The safety and effectiveness of plasma FXIII concentrate for prophylaxis and treatment is now well established. The new recombinant FXIII product is currently in phase III clinical trial and the preliminary data are promising.
SUMMARY
FXIII deficiency is considered the most underdiagnosed bleeding diathesis. The recommended algorithm for its diagnosis and classification could improve the diagnostic efficiency. The preferred choice for substitution therapy is FXIII concentrate (plasma-derived or, in the future, recombinant)
Classification of Swift's gamma-ray bursts
No full textContext. Two classes of gamma-ray bursts have been identified in the BATSE catalogs characterized by durations shorter and longer
than about 2 s. There are, however, some indications for the existence of a third class. Swift satellite detectors have different spectral
sensitivity than pre-Swift ones for gamma-ray bursts. Therefore we reanalyze the durations and their distribution and also the classification
of GRBs.
Aims. We analyze the bursts duration distribution, published in The First BAT Catalog, whether it contains two, three or more groups.
Methods. Using The First BAT Catalog the maximum likelihood estimation was used to analyze the duration distribution of GRBs.
Results. The three log-normal fit is significantly (99.54% probability) better than the two for the duration distribution. Monte-Carlo
simulations also confirm this probability (99.2%). Similarly, in previous results we found that the fourth component is not needed.
The relative frequencies of the distribution of the groups are 7% short 35% intermediate and 58% long.
Conclusions. Similarly to the BATSE data, three components are needed to explain the BAT GRBs’ duration distribution. Although
the relative frequencies of the groups are different than in the BATSE GRB sample, the difference in the instrument spectral sensitivities
can explain this bias. This means theoretical models may be needed to explain three different type of gamma-ray bursts
A new definition of the intermediate group of gamma-ray bursts
No full textGamma-ray bursts can be divided into three groups ("short", "intermediate", "long") with respect to their durations. This classification is somewhat imprecise, since the subgroup of intermediate duration has an admixture of both short and long bursts. In this paper a physically more reasonable definition of the intermediate group is presented, using also the hardnesses of the bursts. It is shown again that the existence of the three groups is real, no further groups are needed. The intermediate group is the softest one. From this new definition it follows that 11% of all bursts belong to this group. An anticorrelation between the hardness and the duration is found for this subclass in contrast to the short and long groups. Despite this difference it is not clear yet whether this group represents a physically different phenomenon
On the difference between the short and long gamma-ray bursts
No full textWe argue that the distributions of both the intrinsic fluence and the intrinsic duration of the gamma-ray emission in gamma-ray bursts from the BATSE sample are well represented by log-normal distributions, in which the intrinsic dispersion is much larger than the cosmological time dilatation and redshift effects. We perform separate bivariate log-normal distribution fits to the BATSE short and long burst samples. The bivariate log-normal behaviour results in an ellipsoidal distribution, whose major axis determines an overall statistical relation between the fluence and the duration. We show that this fit provides evidence for a power-law dependence between the fluence and the duration, with a statistically significant different index for the long and short groups. We discuss possible biases, which might affect this result, and argue that the effect is probably real. This may provide a potentially useful constraint for models of long and short bursts
The Benefits of Being Economics Professor A (and not Z)
No full textAlphabetic name ordering on multi-authored academic papers, which is the convention in the economics discipline and various other disciplines, is to the advantage of people whose last name initials are placed early in the alphabet. As it turns out, Professor A, who has been a first author more often than Professor Z, will have published more articles and experienced afaster growth rate over the course of her career as a result of reputation and visibility. Moreover, authors know that name ordering matters and indeed take ordering seriously: Several characteristics of an author group composition determine the decision to deviate from the default alphabetic name order to a significant extent.performance measurement, incentives, economists, name ordering
Final word on Jersey Dutch
No full textIn this article, William Z. Shetter compares and contrasts the dialects that developed between different Dutch colonies in the New World. He explores in-depth the nuances of Jersey Dutch, and provides theories to explain how Dutch and colonial languages blended. The article is reprinted from American Speech, December 1958, Volum XXXIII, No. 4
The teaching of botany in Portugal: an analysis of primary school textbooks (1900-2000)
No full textThe research presented in this chapter aimed at understanding the place of botany within primary school science textbooks used in Portugal over the last century. The study follows a qualitative methodological approach, supported by content analysis and the establishment of a posteriori categories, as well as cluster analysis through the construction of dendograms. The comparison of textbooks took into account pedagogical and didactical orientations, educational and curricular policy recommendations, and the educational and scientific values suggested. Textbooks are of great importance to schools and teaching, with important pedagogical functions, especially in relation to their structural arrangement of the forms and content of pedagogical knowledge, including aspects related to the sequencing and rhythm of knowledge transmission through, for instance, activities that promote and evaluate the forms of knowledge acquired. Textbooks, therefore, can allow access to knowledge about the pedagogical ideology on which they are based, how teaching and learning in the classroom is understood, and how students’ and teachers’ roles are developed. Data analysis showed that changes have occurred in the naming of the teaching of the science and in the organization of the contents. Therefore, one may find various botanical content distributed throughout different botanical dimensions.Este trabalho foi financiado por Fundos Nacionais através da FCT – Fundação para a Ciência e a Tecnologia no âmbito dos projetos do CIEC (Centro de Investigação em Estudos da Criança da Universidade do Minho) com as referências UIDB/00317/2020 e UIDP/00317/2020
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
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