139 research outputs found
Short-lived Nuclei in the Early Solar System: Possible AGB Sources
(Abridged) We review abundances of short-lived nuclides in the early solar
system (ESS) and the methods used to determine them. We compare them to the
inventory for a uniform galactic production model. Within a factor of two,
observed abundances of several isotopes are compatible with this model. I-129
is an exception, with an ESS inventory much lower than expected. The isotopes
Pd-107, Fe-60, Ca-41, Cl-36, Al-26, and Be-10 require late addition to the
solar nebula. Be-10 is the product of particle irradiation of the solar system
as probably is Cl-36. Late injection by a supernova (SN) cannot be responsible
for most short-lived nuclei without excessively producing Mn-53; it can be the
source of Mn-53 and maybe Fe-60. If a late SN is responsible for these two
nuclei, it still cannot make Pd-107 and other isotopes. We emphasize an AGB
star as a source of nuclei, including Fe-60 and explore this possibility with
new stellar models. A dilution factor of about 4e-3 gives reasonable amounts of
many nuclei. We discuss the role of irradiation for Al-26, Cl-36 and Ca-41.
Conflict between scenarios is emphasized as well as the absence of a global
interpretation for the existing data. Abundances of actinides indicate a
quiescent interval of about 1e8 years for actinide group production in order to
explain the data on Pu-244 and new bounds on Cm-247. This interval is not
compatible with Hf-182 data, so a separate type of r-process is needed for at
least the actinides, distinct from the two types previously identified. The
apparent coincidence of the I-129 and trans-actinide time scales suggests that
the last actinide contribution was from an r-process that produced actinides
without fission recycling so that the yields at Ba and below were governed by
fission.Comment: 92 pages, 14 figure files, in press at Nuclear Physics
Social control in online communities of consumption: a framework for community management
Online communities of consumption (OCCs) represent highly diverse groups of consumers whose interests are not always aligned. Social control in OCCs aims to effectively manage problems arising from this heterogeneity. Extant literature on social control in OCCs is fragmented as some studies focus on the principles of social control, while others focus on the implementation. Moreover, the domain is undertheorized. This article integrates the disparate literature on social control in OCCs providing a first unified conceptualization of the topic. The authors conceptualize social control as a system, or configuration, of moderation practices. Moderation practices are executed during interactions operating under different governance structures (market, hierarchy, and clan) and serving different purposes (interaction initiation, maintenance, and termination). From this conceptualization, important areas of future research emerge and research questions are developed. The framework also serves as a community management tool for OCC managers, enabling the diagnosis of social control problems and the elaboration of strategies and tactics to address them
S. <i>mansoni</i> Schistosomula Antigens Induce Th1/Proinflammatory Cytokine Responses
Larvae of Schistosoma (schistosomula) are highly susceptible to host immune responses and are attractive prophylactic vaccine targets, although cellular immune responses against schistosomula antigens in endemic human populations are not well characterized. We collected blood and stool from 54 Schistosoma mansoni-infected Ugandans, isolated peripheral blood mononuclear cells and stimulated them for 24 hours with schistosome adult worm and soluble egg antigens (AWA and SEA), along with schistosomula recombinant proteins rSmKK7, Lymphocyte Antigen 6 isoforms (rSmLy6A and rSmLy6B), tetraspanin isoforms (rSmTSP6 and rSmTSP7). Cytokines, chemokines and growth factors were measured in the culture supernatants using a multiplex luminex assay, and infection intensity was determined before and at 1 year after praziquantel (PZQ) treatment using the Kato-Katz method. Cellular responses were grouped and the relationship between groups of correlated cellular responses and infection intensity before and after PZQ treatment was investigated. AWA and SEA induced mainly Th2 responses. In contrast, rSmLy6B, rSmTSP6 and rSmTSP7 induced Th1/pro-inflammatory responses. While recombinant antigens rSmKK7 and rSmLy6A did not induce a Th1/pro-inflammatory response, they had an association with pre-treatment infection intensity after adjusting for age and sex. Testing more schistosomula antigens using this approach could provide immune-epidemiology identifiers necessary for prioritizing next generation schistosomiasis vaccine candidates
CNO in evolved intermediate mass stars
In order to investigate the possible influence of rotation on the efficiency
of the first dredge-up we determined atmospheric parameters, masses, and
abundances of carbon, nitrogen, and oxygen in a sample of evolved intermediate
mass stars. We used high resolution spectra and conducted a model atmosphere
analysis. The abundances were calculated through spectral synthesis and
compared to the predictions of rotating and non-rotating evolutionary models.
Almost all those objects in our sample where carbon and nitrogen abundances
could be determined show signs of internal mixing. The stars, however, seem to
be mixed to different extents. Among the mixed stars we identify five in our
sample with abundances in agreement with the non-rotating models, four stars
that seem to be mixed beyond that, and one star that seems to be slightly less
mixed than predicted for the first dredge-up. There are also five stars that
seem to be slightly more mixed than expected, but their abundances are in
marginal agreement with both rotating and non-rotating models. Such differences
in the extent of the mixing are not predicted by the standard models and imply
the action of other mixing mechanisms than solely the convective dredge-up. We
also identified for the first time an important correlation between the [N/C]
ratio and the stellar mass.Comment: Accepted for publication in A&A. Final version with language
correction
ISO-SWS calibration and the accurate modelling of cool-star atmospheres - IV. G9 to M2 stars
presented. The 2.38 -- 4.08 micron wavelength-range of band 1 of ISO-SWS
(Short-Wavelength Spectrometers on board of the Infrared Space Observatory) in
which many different molecules -- with their own dependence on each of the
stellar parameters -- are absorbing, enables us to estimate the effective
temperature, the gravity, the microturbulence, the metallicity, the
CNO-abundances, the 12C/13C-ratio and the angular diameter from the ISO-SWS
data. Using the Hipparcos' parallax, the radius, luminosity and
gravity-inferred mass are derived. The stellar parameters obtained are in good
agreement with other published values, though also some discrepancies with
values deduced by other authors are noted. For a few stars (Delta Dra, Xi Dra,
Alpha Tuc, H Sco and Alpha Cet) some parameters -- e.g. the CNO-abundances --
are derived for the first time. By examining the correspondence between
different ISO-SWS observations of the same object and between the ISO-SWS data
and the corresponding synthetic spectrum, it is shown that the relative
accuracy of ISO-SWS in band 1 (2.38 -- 4.0 micron) is better than 2% for these
high-flux sources. The high level of correspondence between observations and
theoretical predictions, together with a confrontation of the estimated
Teff(ISO) value with Teff-values derived from colours -- which demonstrates the
consistency between V-K, BC(K), Teff and the angular diameter derived from
optical or IR data -- proves that both the used MARCS models to derive the
stellar quantities and the flux calibration of the ISO-SWS detectors have
reached a high level of reliability.Comment: 19 pages, 15 figures; Astronomy and Astrophysics, in press; preprints
can be obtained by contacting [email protected] or via WWW on
http://www.ster.kuleuven.ac.be/~leen or via anonymous ftp on
ftp://ftp.ster.kuleuven.ac.be/dist/leen/latex/h3318 Appendix electronically
available (26 pages, 22 figures
Selection Signatures in Worldwide Sheep Populations
The diversity of populations in domestic species offers great opportunities to study genome response to selection. The recently published Sheep HapMap dataset is a great example of characterization of the world wide genetic diversity in sheep. In this study, we re-analyzed the Sheep HapMap dataset to identify selection signatures in worldwide sheep populations. Compared to previous analyses, we made use of statistical methods that (i) take account of the hierarchical structure of sheep populations, (ii) make use of linkage disequilibrium information and (iii) focus specifically on either recent or older selection signatures. We show that this allows pinpointing several new selection signatures in the sheep genome and distinguishing those related to modern breeding objectives and to earlier post-domestication constraints. The newly identified regions, together with the ones previously identified, reveal the extensive genome response to selection on morphology, color and adaptation to new environments
Cashew nut allergy: clinical relevance and allergen characterisation
Cashew plant (Anacardium occidentale L.) is the most relevant species of the Anacardium genus. It presents high economic value since it is widely used in human nutrition and in several industrial applications. Cashew nut is a well-appreciated food (belongs to the tree nut group), being widely consumed as snacks and in processed foods by the majority of world's population. However, cashew nut is also classified as a potent allergenic food known to be responsible for triggering severe and systemic immune reactions (e.g. anaphylaxis) in sensitised/allergic individuals that often demand epinephrine treatment and hospitalisation. So far, three groups of allergenic proteins have been identified and characterised in cashew nut: Ana o 1 and Ana o 2 (cupin superfamily) and Ana o 3 (prolamin superfamily), which are all classified as major allergens. The prevalence of cashew nut allergy seems to be rising in industrialised countries with the increasing consumption of this nut. There is still no cure for cashew nut allergy, as well as for other food allergies; thus, the allergic patients are advised to eliminate it from their diets. Accordingly, when carefully choosing processed foods that are commercially available, the allergic consumers have to rely on proper food labelling. In this sense, the control of labelling compliance is much needed, which has prompted the development of proficient analytical methods for allergen analysis. In the recent years, significant research advances in cashew nut allergy have been accomplished, which are highlighted and discussed in this review.This work was supported by FCT/MEC through national funds and co-financed by FEDER, under the Partnership Agreement PT2020 with grant no. UID/QUI/50006/2013–POCI/01/ 0145/FEDER/007265. Joana Costa is grateful to FCT post-doctoral grant (SFRH/BPD/102404/2014) financed by POPH-QREN (subsidised by FSE and MCTES).info:eu-repo/semantics/publishedVersio
Avaliação da embebição e do desenvolvimento inicial das estruturas embrionárias de sementes de milho submetidas a diferentes potenciais hídricos
Substrates with water potentials between O and -12atm, were used to evaluate the behavior of corn seeds during the germination process. Water deficiency treatments were compared with the control (adequate available water) using seeds with and without fungicide treatment. The analysis and the interpretation of the results permitted to conclude that the absorption of water, the emergency and the initial development of the embryonic structures are interdependent and vary with the water deficit. For these cases the reduction of water potential promotes difficulties in the evolution of the processes. The presence of fungicide treatment may not influence quantitatively the processes occurring in the beginning of the germination.Empregando substratos com potenciais hídricos variáveis entre 0 e -12atm, o presente trabalho objetivou avaliar o comportamento das sementes de milho postas a germinar. As situações de deficiência hídrica foram diretamente comparadas à testemunha (plena disponibilidade de água), usando sementes com e sem tratamento fungicida. A análise e a interpretação dos resultados permitiram concluir que a absorção de água, a emergência e o desenvolvimento inicial das estruturas embrionárias são interdependentes e reagem no mesmo sentido ao déficit hídrico; para esses casos, a redução do potencial hídrico promove dificuldades na evolução dos processos. Paralelamente, a presença de tratamento fungicida pode não influenciar, quantitativamente, os fenômenos envolvidos no início da germinação
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