1,268 research outputs found
Lithium and magnetic fields in giants. HD 232862 : a magnetic and lithium-rich giant star
We report the detection of an unusually high lithium content in HD 232862, a
field giant classified as a G8II star, and hosting a magnetic field. With the
spectropolarimeters ESPaDOnS at CFHT and NARVAL at TBL, we have collected high
resolution and high signal-to-noise spectra of three giants : HD 232862, KU Peg
and HD 21018. From spectral synthesis we have inferred stellar parameters and
measured lithium abundances that we have compared to predictions from
evolutionary models. We have also analysed Stokes V signatures, looking for a
magnetic field on these giants. HD 232862, presents a very high abundance of
lithium (ALi = 2.45 +/- 0.25 dex), far in excess of the theoretically value
expected at this spectral type and for this luminosity class (i.e, G8II). The
evolutionary stage of HD 232862 has been precised, and it suggests a mass in
the lower part of the [1.0 Msun ; 3.5 Msun ] mass interval, likely 1.5 to 2.0
solar mass, at the bottom of the Red Giant Branch. Besides, a time variable
Stokes V signature has been detected in the data of HD 232862 and KU Peg,
pointing to the presence of a magnetic field at the surface of these two
rapidly rotating active stars.Comment: 11 pages, 9 figures ; accepted by Astronomy and Astrophysic
The familial hypercholesterolaemia phenotype: Monogenic familial hypercholesterolaemia, polygenic hypercholesterolaemia and other causes
Familial Hypercholesterolaemia (FH) is a monogenic disorder characterised by high LDL-C concentrations and increased cardiovascular risk. However, in clinically defined FH cohorts worldwide, an FH-causing variant is only found in 40-50% of the cases. The aim of this work was to characterise the genetic cause of the FH phenotype in Portuguese clinical FH patients. Methods and Results Between 1999 and 2017, 731 index patients (311 children and 420 adults) who met the Simon Broome diagnostic criteria had been referred to our laboratory. LDLR, APOB, PCSK9, APOE, LIPA, LDLRAP1, ABCG5/8 genes were analysed by PCR amplification and Sanger sequencing. The 6-SNP LDL-C genetic risk score (GRS) for polygenic hypercholesterolaemia was validated in the Portuguese population and cases with a GRS over the 25th percentile were considered to have a high likelihood of polygenic hypercholesterolaemia. An FH-causing mutation was found in 39% of patients (94% in LDLR, 5% APOB and 1% PCSK9), while at least 29% have polygenic hypercholesterolaemia and 1% have other lipid disorders. A genetic cause for the FH phenotype was found in 503 patients (69%). All known causes of the FH phenotype should be investigated in FH cohorts to ensure accurate diagnosis and appropriate management. This article is protected by copyright. All rights reserved
A catalog of rotational and radial velocities for evolved stars. IV. Metal-poor stars
The present paper describes the first results of an observational program
intended to refine and extend the existing vsini measurements of metal-poor
stars, with anemphasis on field evolved stars. The survey was carried out with
the FEROS and CORALIE spectrometers. For the vsini measurements, obtained from
spectral synthesis, we estimate an uncertainty of about 2.0 km/s. Precise
rotational velocities vsini are presented for a large sample of 100 metal-poor
stars, most of them evolving off the main-sequence. For the large majority of
the stars composing the present sample, rotational velocities have been
measured for the first time.Comment: 5 pages, 1 Postscript figures, accepted for publication in the A&
The Interplay Between GUT and Flavour Symmetries in a Pati-Salam x S4 Model
Both Grand Unified symmetries and discrete flavour symmetries are appealing
ways to describe apparent structures in the gauge and flavour sectors of the
Standard Model. Both symmetries put constraints on the high energy behaviour of
the theory. This can give rise to unexpected interplay when building models
that possess both symmetries. We investigate on the possibility to combine a
Pati-Salam model with the discrete flavour symmetry that gives rise to
quark-lepton complementarity. Under appropriate assumptions at the GUT scale,
the model reproduces fermion masses and mixings both in the quark and in the
lepton sectors. We show that in particular the Higgs sector and the running
Yukawa couplings are strongly affected by the combined constraints of the Grand
Unified and family symmetries. This in turn reduces the phenomenologically
viable parameter space, with high energy mass scales confined to a small region
and some parameters in the neutrino sector slightly unnatural. In the allowed
regions, we can reproduce the quark masses and the CKM matrix. In the lepton
sector, we reproduce the charged lepton masses, including bottom-tau
unification and the Georgi-Jarlskog relation as well as the two known angles of
the PMNS matrix. The neutrino mass spectrum can present a normal or an inverse
hierarchy, and only allowing the neutrino parameters to spread into a range of
values between and , with .
Finally, our model suggests that the reactor mixing angle is close to its
current experimental bound.Comment: 62 pages, 4 figures; references added, version accepted for
publication in JHE
OBTENÇÃO E CARACTERIZAÇÃO DE NANOPARTÍCULAS DE PLGA PARA VEICULAÇÃO INTRAVENOSA DE PROTEÍNAS
O desenvolvimento de nanopartículas é considerado atualmente um sistema promissor para o carreamento de drogas em sítios específicos. O uso de polímeros na obtenção desse sistema pode ser de origem natural ou sintética desde que seja biocompatível ou biodegradável. Desenvolver sistemas de transportes para carrear proteínas requer cuidado com variáveis como tempo de homogeneização e concentração do surfactante, que interferem diretamente na obtenção destas. As nanopartículas foram obtidas pelo método de dupla emulsificação, onde foram elaborados 6 sistemas (A,B,C,D,E e F), utilizando diferentes concentrações de PVA (0,5; 1 e 1,5%) e tempo de homogeneização de 30 e 60 segundos. Os sistemas foram analisados pela técnica de espalhamento de luz dinâmico. Os resultados mostraram que o sistema D apresentou melhor IPD com 0,638, com tamanho de partícula de 678,3 nm, o que sugere homogeneidade maior em relação aos outros sistemas. Porém, há a necessidade de se otimizar o método para obtenção de partículas de tamanhos menores para a veiculação intravenosa
Accurate mass-radius ratios for Hyades white dwarfs
We use the ESPRESSO spectrograph at the Very Large Telescope to measure velocity shifts and gravitational redshifts of eight bona fide Hyades white dwarfs, with an accuracy better than 1.5 per cent. By comparing the gravitational redshift measurements of the mass-to-radius ratio with the same ratios derived by fitting the Gaia photometry with theoretical models, we find an agreement to better than one per cent. It is possible to reproduce the observed white dwarf cooling sequence and the trend of the mass-to-radius ratios as a function of colour using isochrones with ages between 725 and 800 Myr, tuned for the Hyades. One star, EGGR 29, consistently stands out in all diagrams, indicating that it is possibly the remnant of a blue straggler. We also computed mass-to-radius ratios from published gravities and masses, determined from spectroscopy. The comparison between photometric and spectroscopic stellar parameters reveals that spectroscopic effective temperature and gravity are systematically larger than the photometric values. Spectroscopic mass-to-radius ratios disagree with those measured from gravitational redshift, indicating the presence of systematics affecting the white dwarf parameters derived from the spectroscopic analysis
Cryptosporidium Priming Is More Effective than Vaccine for Protection against Cryptosporidiosis in a Murine Protein Malnutrition Model
Cryptosporidium is a major cause of severe diarrhea, especially in malnourished children. Using a murine model of C. parvum oocyst challenge that recapitulates clinical features of severe cryptosporidiosis during malnutrition, we interrogated the effect of protein malnutrition (PM) on primary and secondary responses to C. parvum challenge, and tested the differential ability of mucosal priming strategies to overcome the PM-induced susceptibility. We determined that while PM fundamentally alters systemic and mucosal primary immune responses to Cryptosporidium, priming with C. parvum (106 oocysts) provides robust protective immunity against re-challenge despite ongoing PM. C. parvum priming restores mucosal Th1-type effectors (CD3+CD8+CD103+ T-cells) and cytokines (IFNγ, and IL12p40) that otherwise decrease with ongoing PM. Vaccination strategies with Cryptosporidium antigens expressed in the S. Typhi vector 908htr, however, do not enhance Th1-type responses to C. parvum challenge during PM, even though vaccination strongly boosts immunity in challenged fully nourished hosts. Remote non-specific exposures to the attenuated S. Typhi vector alone or the TLR9 agonist CpG ODN-1668 can partially attenuate C. parvum severity during PM, but neither as effectively as viable C. parvum priming. We conclude that although PM interferes with basal and vaccine-boosted immune responses to C. parvum, sustained reductions in disease severity are possible through mucosal activators of host defenses, and specifically C. parvum priming can elicit impressively robust Th1-type protective immunity despite ongoing protein malnutrition. These findings add insight into potential correlates of Cryptosporidium immunity and future vaccine strategies in malnourished children
On the influence of a Coulomb-like potential induced by the Lorentz symmetry breaking effects on the Harmonic Oscillator
In this work, we obtain bound states for a nonrelativistic spin-half neutral
particle under the influence of a Coulomb-like potential induced by the Lorentz
symmetry breaking effects. We present a new possible scenario of studying the
Lorentz symmetry breaking effects on a nonrelativistic quantum system defined
by a fixed space-like vector field parallel to the radial direction interacting
with a uniform magnetic field along the z-axis. Furthermore, we also discuss
the influence of a Coulomb-like potential induced by Lorentz symmetry violation
effects on the two-dimensional harmonic oscillator.Comment: 14 pages, no figure, this work has been accepted for publication in
The European Physical Journal Plu
Profiles of Global Gene Expression in Ionizing-Radiation–Damaged Human Diploid Fibroblasts Reveal Synchronization behind the G(1) Checkpoint in a G(0)-like State of Quiescence
Cell cycle arrest and stereotypic transcriptional responses to DNA damage induced by ionizing radiation (IR) were quantified in telomerase-expressing human diploid fibroblasts. Analysis of cytotoxicity demonstrated that 1.5 Gy IR inactivated colony formation by 40–45% in three fibroblast lines; this dose was used in all subsequent analyses. Fibroblasts exhibited > 90% arrest of progression from G(2) to M at 2 hr post-IR and a similarly severe arrest of progression from G(1) to S at 6 and 12 hr post-IR. Normal rates of DNA synthesis and mitosis 6 and 12 hr post-IR caused the S and M compartments to empty by > 70% at 24 hr. Global gene expression was analyzed in IR-treated cells. A microarray analysis algorithm, EPIG, identified nine IR-responsive patterns of gene expression that were common to the three fibroblast lines, including a dominant p53-dependent G(1) checkpoint response. Many p53 target genes, such as CDKN1A, GADD45, BTG2, and PLK3, were significantly up-regulated at 2 hr post-IR. Many genes whose expression is regulated by E2F family transcription factors, including CDK2, CCNE1, CDC6, CDC2, MCM2, were significantly down-regulated at 24 hr post-IR. Numerous genes that participate in DNA metabolism were also markedly repressed in arrested fibroblasts apparently as a result of cell synchronization behind the G(1) checkpoint. However, cluster and principal component analyses of gene expression revealed a profile 24 hr post-IR with similarity to that of G(0) growth quiescence. The results reveal a highly stereotypic pattern of response to IR in human diploid fibroblasts that reflects primarily synchronization behind the G(1) checkpoint but with prominent induction of additional markers of G(0) quiescence such as GAS1
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