3,514 research outputs found
The s-process weak component: uncertainties due to convective overshooting
Using a new s-nucleosynthesis code, coupled with the stellar evolution code
Star2003, we performed simulations to study the impact of the convection
treatment on the s-process during core He-burning of a 25 Msun star (ZAMS mass)
with an initial metallicity of Z=0.02. Particular attention was devoted to the
impact of the extent of overshooting on the s-process efficiency. The results
show enhancements of about a factor 2-3 in s-process efficiency (measured as
the average overproduction factor of the 6 s-only nuclear species with
) with overshooting parameter values in the range
0.01-0.035, compared to results obtained with the same model but without
overshooting. The impact of these results on the p-process model based on type
II supernovae is discussed.Comment: 7 pages, 4 figures, accepted for publication in Astronomy &
Astrophysic
Convective overshooting and production of s-nuclei in massive stars during their core He-burning phase
With the "post-processing" technique we explore the role of the convective
overshooting on the production of s-nuclei in stellar models of different
initial mass and metallicity (; ), considering a range of values for the parameter , which
determines the overall efficiency of convective overshooting.We find
enhancements in the production of s-nuclei until a factor (measured as
the average overproduction factor of the 6 s-only nuclear species with
) in all our models of different initial mass and
metallicity with in the range (i.e. models with
overshooting) compared to the production obtained with "no-overshooting" models
(i.e. models with the same initial mass and metallicity, but ).
Moreover the results indicate that the link between the overshooting parameter
and the s-process efficiency is essentially monotonic in all our models of
different initial mass and metallicity. Also evident is the higher s-process
efficiency when we progressively increase for a given f value both the mass of
the models from 15 M to 25 M and the Z value from 10 to
0.02. We also briefly discuss the possible consequences of these results for
some open questions linked to the s-process weak component efficiency, as well
as a "rule of thumb" to evaluate the impact of the convective overshooting on
the yields of a generation of stars.Comment: 12 pages, 6 figures, A&A accepted (corrected typos plus minor changes
in order to fulfill the guidelines for A&A manuscripts
A questionnaire-wide association study of personality and mortality:The Vietnam Experience Study
OBJECTIVE: We examined the association between the Minnesota Multiphasic Personality Inventory (MMPI) and all-cause mortality in 4462 middle-aged Vietnam-era veterans.METHODS: We split the study population into half-samples. In each half, we used proportional hazards (Cox) regression to test the 550 MMPI items' associations with mortality over 15years. In all participants, we subjected significant (p<.01) items in both halves to principal-components analysis (PCA). We used Cox regression to test whether these components predicted mortality when controlling for other predictors (demographics, cognitive ability, health behaviors, and mental/physical health).RESULTS: Eighty-nine items were associated with mortality in both half-samples. PCA revealed Neuroticism/Negative Affectivity, Somatic Complaints, Psychotic/Paranoia, and Antisocial components, and a higher-order component, Personal Disturbance. Individually, Neuroticism/Negative Affectivity (HR=1.55; 95% CI=1.39, 1.72), Somatic Complaints (HR=1.66; 95% CI=1.52, 1.80), Psychotic/Paranoid (HR=1.44; 95% CI=1.32, 1.57), Antisocial (HR=1.79; 95% CI=1.59, 2.01), and Personal Disturbance (HR=1.74; 95% CI=1.58, 1.91) were associated with risk. Including covariates attenuated these associations (28.4 to 54.5%), though they were still significant. After entering Personal Disturbance into models with each component, Neuroticism/Negative Affectivity and Somatic Complaints were significant, although Neuroticism/Negative Affectivity's were now protective (HR=0.73; 95% CI=0.58, 0.92). When the four components were entered together with or without covariates, Somatic Complaints and Antisocial were significant risk factors.CONCLUSIONS: Somatic Complaints and Personal Disturbance are associated with increased mortality risk. Other components' effects varied as a function of variables in the model
Nanopercolation
We investigate through direct molecular mechanics calculations the
geometrical properties of hydrocarbon mantles subjected to percolation
disorder. We show that the structures of mantles generated at the critical
percolation point have a fractal dimension . In addition,
the solvent access surface and volume of these molecules follow
power-law behavior, and ,
where is the system size, and with both critical exponents and
being significantly dependent on the radius of the accessing probing
molecule, . Our results from extensive simulations with two distinct
microscopic topologies (i.e., square and honeycomb) indicate the consistency of
the statistical analysis and confirm the self-similar characteristic of the
percolating hydrocarbons. Due to their highly branched topology, some of the
potential applications for this new class of disordered molecules include drug
delivery, catalysis, and supramolecular structures.Comment: 4 pages, 5 figure
Reproductive isolation between two populations of Aglaoctenus lagotis , a funnel-web wolf spider
Aglaoctenus lagotis (Lycosidae: Sosippinae) is a spider that, in contrast to the predominant wandering habit of the family, constructs funnel webs. The species is widely distributed throughout the Neotropics and is credited with high levels of intraspecific variation. Here, we evaluate whether reproductive isolating barriers operate between some populations of A. lagotis. We used heterotypic encounters between individuals from two distant localities: southern Uruguay (SU) and Central Argentina (CA). Additionally, we used spiders from an ntermediate locality, western Uruguay (WU), where both forms of the species overlap (SU.WU was used to describe individuals from WU reminiscent of those from SU; and CA.WU was used to describe individuals from WU reminiscent of those from CA). No copulations occurred between SU and CA individuals, whereas a single and atypical copulation occurred between SU.WU and CA.WU individuals. Attacks (only by females on males) were rare. In tests of choice based on silk cues, SU males did not prefer homotypic cues but almost did not court CA females, whereas CA males preferred homotypic cues but usually courted heterotypic females. These findings, with a previously reported temporal asynchrony between populations, suggest the occurrence of reproductive isolation between both spider forms and a speciation process favoured by the wide distribution and plasticity of the species.Fil: González Pérez, María de la Macarena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Animal I; ArgentinaFil: Peretti, Alfredo Vicente. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Diversidad y Ecología Animal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Diversidad y Ecología Animal; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Animal I; ArgentinaFil: Costa, Fernando G.. Instituto de Investigaciones Biológicas "Clemente Estable"; Urugua
Lower prevalence of protective antibodies for 2015/2016 influenza A(H1)pdm circulating strains comparing to seroprevalence for 2009 influenza A(H1)pdm virus
DDI-INSA em colaboração com a Rede Portuguesa de Laboratórios para o Diagnóstico da GripeBackground:
Since 2009, influenza A(H1)pdm09 is circulating in the human population infecting in different ways specific age groups. The study aims to assess the seroprotection for A/California /07/2009 vaccine strain and evaluate the seroprotection for the circulating A(H1)pdm09 strains (clade 6B) in the Portuguese population. Seroepidemiological data can determine the vulnerable populations to disease and support intervention and action regarding vaccination programmes and other preventive measures, particularly in high-risk groups.
Methods:
To study influenza immunity a non-probabilistic sample was used. Samples were collected from people attending to hospital laboratories (n=13) for other reasons aside from influenza infection. We developed a cross-sectional study based on a convenience sample of 734 sera collected during July 2016, from all age groups (0–4; 5–14; 15–44; 45-64 and ≥65 years old), both genders, covering mainland and Atlantic islands. Sera were randomly selected. All samples were anonymized and recorded data: district residence/sample collection, gender and age.
Antibody titers to A(H1)pdm09 virus strains [A/California /07/2009 and A/Lisboa/58/2015 (clade 6B)] were assessed by hemagglutination inhibition (HI) assay. HI titer>40 were considered protective. Seroprevalence estimates, overall and by age group, were calculated with 95% confidence intervals (95% CI). The HA1 subunit of the hemagglutinin gene from A(H1)pdm09 viruses used in HI were sequenced.
Results:
In July 2016, the prevalence of protective antibodies for influenza A/California/07/2009 was 38% (95% CI: 34–41) and for A/Lisboa /58/2015 was 23% (95% CI: 21–27). Highest seroprevalence was observed in 5-14 age group for both strains, 55% (95% CI: 47–63) for A/California/07/2009 and 42% (95% CI: 35–50) for A/Lisboa/58/2015. The lowest seroprevalences were detected in the 65+ age group for A/California/07/2009 (28%; 95% CI: 22–36) and in the 45-64 for the A/Lisboa /58/2015 (9%; 95% CI: 6-15). Was observed a reduced prevalence of protective antibodies for A/Lisboa /58/2015 for all age groups, although a higher decrease was seen in the adults 45-64 years old (24% drop in seroprevalence). The influenza A/Lisboa/58/2015 presented four amino acid substitutions in antigenic sites: S162N e K163Q (Sa), S185T (Sb) and S203T (Ca1), belonging to 6B.1clade.
Conclusions:
Although 38% of study population have demonstrated to have seroprotection for A(H1)pdm09 vaccine strain this could not represent seroprotection to the currently circulating A(H1)pdm09 strains. Individuals in the age group of 45-64 years old are more susceptible to infection by currently circulating influenza A(H1)pdm09 viruses. The presence of K163Q (Sa), S185T (Sb) substitutions are likely to be involved in antigenic drift, as previously described, allowing the virus to escape from immune response namely the one that could be induced by the vaccine. In future this event should be closely monitored, although WHO recommended a new A(H1)pdm09 strain to be included in the next season flu vaccine.N/
Time-scarcity, ready-meals, ill-health and the obesity epidemic
In this 3-part paper, we firstly review the interaction of time-scarcity with food-choices, specifically ready-meals, and potential health consequences from their consumption. Secondly we review declared nutrients, in relation to the standard 30% of Guideline Daily Amounts, concluding that popular ready-meals from major UK supermarkets are currently nutritionally haphazard. Thirdly, we present a simple scheme to establish standards for nutritional composition of ready-meals: unless otherwise specified, any meal (the smallest unit of nutrition) as recommended to be eaten or as offered should provide 30%+10% of GDA for energy and pro rata for key nutrients (e.g. sodium, sat fat, vitamin C)
Diagnostic Imaging in Intervertebral Disc Disease
Imaging is integral in the diagnosis of canine intervertebral disc disease (IVDD) and in differentiating subtypes of intervertebral disc herniation (IVDH). These include intervertebral disc extrusion (IVDE), intervertebral disc protrusion (IVDP) and more recently recognized forms such as acute non-compressive nucleus pulposus extrusion (ANNPE), hydrated nucleus pulposus extrusion (HNPE), and intradural/intramedullary intervertebral disc extrusion (IIVDE). Many imaging techniques have been described in dogs with roles for survey radiographs, myelography, computed tomography (CT), and magnetic resonance imaging (MRI). Given how common IVDH is in dogs, a thorough understanding of the indications and limitations for each imaging modality to aid in diagnosis, treatment planning and prognosis is essential to successful case management. While radiographs can provide useful information, especially for identifying intervertebral disc degeneration or calcification, there are notable limitations. Myelography addresses some of the constraints of survey radiographs but has largely been supplanted by cross-sectional imaging. Computed tomography with or without myelography and MRI is currently utilized most widely and have become the focus of most contemporary studies on this subject. Novel advanced imaging applications are being explored in dogs but are not yet routinely performed in clinical patients. The following review will provide a comprehensive overview on common imaging modalities reported to aid in the diagnosis of IVDH including IVDE, IVDP, ANNPE, HNPE, and IIVDE. The review focuses primarily on canine IVDH due to its frequency and vast literature as opposed to feline IVDH
Blockchain for the metaverse: A Review
Since Facebook officially changed its name to Meta in Oct. 2021, the metaverse has become a new norm of social networks and three-dimensional (3D) virtual worlds. The metaverse aims to bring 3D immersive and personalized experiences to users by leveraging many pertinent technologies. Despite great attention and benefits, a natural question in the metaverse is how to secure its users’ digital content and data. In this regard, blockchain is a promising solution owing to its distinct features of decentralization, immutability, and transparency. To better understand the role of blockchain in the metaverse, we aim to provide an extensive survey on the applications of blockchain for the metaverse. We first present a preliminary to blockchain and the metaverse and highlight the motivations behind the use of blockchain for the metaverse. Next, we extensively discuss blockchain-based methods for the metaverse from technical perspectives, such as data acquisition, data storage, data sharing, data interoperability, and data privacy preservation. For each perspective, we first discuss the technical challenges of the metaverse and then highlight how blockchain can help. Moreover, we investigate the impact of blockchain on key-enabling technologies in the metaverse, including Internet-of-Things, digital twins, multi-sensory and immersive applications, artificial intelligence, and big data. We also present some major projects to showcase the role of blockchain in metaverse applications and services. Finally, we present some promising directions to drive further research innovations and developments toward the use of blockchain in the metaverse in the future
C and N abundances of MS and SGB stars in NGC 1851
We present the first chemical analysis of stars on the double subgiant branch
(SGB) of the globular cluster NGC 1851. We obtained 48 Magellan IMACS spectra
of subgiants and fainter stars covering the spectral region between
3650-6750\AA, to derive C and N abundances from the spectral features at
4300\AA (G-band) and at ~ 3883\AA (CN). We added to our sample ~ 45 unvevolved
stars previously observed with FORS2 at the VLT. These two datasets were
homogeneously reduced and analyzed. We derived abundances of C and N for a
total of 64 stars and found considerable star-to-star variations in both [C/H]
and [N/H] at all luminosities extending to the red giant branch (RGB) base
(V~18.9). These abundances appear to be strongly anticorrelated, as would be
expected from the CN-cycle enrichment, but we did not detect any bimodality in
the C or N content. We used HST and ground-based photometry to select two
groups of faint- and bright-SGB stars from the visual and Str\"omgren
color-magnitude diagrams. Significant variations in the carbon and nitrogen
abundances are present among stars of each group, which indicates that each SGB
hosts multiple subgenerations of stars. Bright- and faint-SGB stars differ in
the total C+N content, where the fainter SGB have about 2.5 times the C+N
content of the brighter ones. Coupling our results with literature photometric
data and abundance determinations from high-resolution studies, we identify the
fainter SGB with the red-RGB population, which also should be richer on average
in Ba and other s-process elements, as well as in Na and N, when compared to
brighter SGB and the blue-RGB population.Comment: 17 pages, 3 tables, 16 figures; typos corrected, added checks on
temperature scale; A&A accepted (in press
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