Context.
Metal-poor components of dwarf galaxies around the Milky Way could be remnants of the building blocks of the Galactic halo structure. Low-mass stars that are currently observed as metal-poor ...stars are expected to have formed in chemically homogeneous clusters in the early phases of galaxy formation. They should have already disintegrated and should exhibit large scatter in abundance ratios of some sets of elements (e.g., Sr/Ba) in the Milky Way field stars. However, chemical abundance ratios are expected to cluster in very metal-poor stars in dwarf galaxies because the number of clusters formed in individual galaxies in the very early phase is expected to be quite limited.
Aims.
We examine the possible clustering of abundance ratios of Sr and Ba in the Sextans dwarf galaxy to test for the clustering star formation scenario.
Methods.
We investigate a total of 11 elements (C, Mg, Ca, Sc, Ti, Cr, Mn, Ni, Zn, Sr, Ba) in five stars in the Sextans dwarf galaxy. Previous studies suggest that these have similar abundance ratios. In this study, we focus on the abundance ratio of Sr to Ba. The observations are based on high-resolution spectroscopy (
R
= 40 000) using the Subaru Telescope High Dispersion Spectrograph.
Results.
The distribution of
α
/Fe abundance ratios of the Sextans dwarf galaxy stars is slightly lower than the average of the values of stars in the Galactic halo. The Sr/Ba abundance ratios for the five metal-poor stars are in good agreement, and this clumping is distinctive compared to the Sr/Ba spread seen in the metal-poor halo stars. We find that the probability of such clumping is very small if the Sextans stars have distributions of Sr and Ba abundances similar to halo stars.
Conclusions.
In the Sextans dwarf galaxy, five out of six of the extremely metal-poor stars for which abundance ratios are well studied so far show clear clustering in abundance ratios including Sr/Ba. These observations tend to support the hypothesis that these stars were formed from a cloud of homogeneous chemical composition.
Prospects for charged Higgs searches at the LHC Akeroyd, A. G.; Aoki, M.; Arhrib, A. ...
The European physical journal. C, Particles and fields,
05/2017, Letnik:
77, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The goal of this report is to summarize the current situation and discuss possible search strategies for charged scalars, in non-supersymmetric extensions of the Standard Model at the LHC. Such ...scalars appear in Multi-Higgs-Doublet models, in particular in the popular Two-Higgs-Doublet model, allowing for charged and additional neutral Higgs bosons. These models have the attractive property that electroweak precision observables are automatically in agreement with the Standard Model at the tree level. For the most popular version of this framework, Model II, a discovery of a charged Higgs boson remains challenging, since the parameter space is becoming very constrained, and the QCD background is very high. We also briefly comment on models with dark matter which constrain the corresponding charged scalars that occur in these models. The stakes of a possible discovery of an extended scalar sector are very high, and these searches should be pursued in all conceivable channels, at the LHC and at future colliders.
Context. The most metal-poor stars are the relics of the early chemical evolution of the Galaxy. Their chemical composition is an important tool to constrain the nucleosynthesis in the first ...generation of stars. The aim is to observe a sample of extremely metal-poor star (EMP stars) candidates selected from the Sloan Digital Sky Survey Data Release 12 (SDSS DR12) and determine their chemical composition. Aims. We obtain medium resolution spectra of a sample of six stars using the X-shooter spectrograph at the Very Large Telescope (VLT) and we used ATLAS models to compute the abundances. Methods. Five stars of the sample have a metallicity Fe/H between −2.5 dex and −3.2 dex. We confirm the recent discovery of SDSS J002314.00+030758.0 as a star with an extremely low Fe/H ratio. Assuming the α-enhancement Ca/Fe = +0.4 dex, we obtain Fe/H = −6.1 dex. Results. We could also determine its magnesium abundance and found that this star exhibits a very high ratio Mg/Fe≤ +3.60 dex assuming Fe/H = −6.13 dex. We determined the carbon abundance and found A(C) = 6.4 dex. From this carbon abundance, this stars belongs to the lower band of the A(C)–Fe/H diagram.
Mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) is frequently activated in cancers and can be counteracted with the clinical mTORC1 inhibitors everolimus and temsirolimus. Although mTORC1 ...and dual mTORC1/2 inhibitors are currently under development to treat various malignancies, the emergence of drug resistance has proven to be a major complication. Using the cis-Apc/Smad4 mouse model of locally invasive intestinal adenocarcinoma, we show that administration of everolimus or the dual mTORC1/2 inhibitor AZD8055 significantly reduces the growth of intestinal tumors. In contrast, although everolimus treatment at earlier phase of tumor progression delayed invasion of the tumors, both inhibitors exhibited little effect on blocking invasion of the tumors when administered later in their progression. Biochemical and immunohistochemical analyses revealed that treatment of cis-Apc/Smad4 mice with everolimus or AZD8055 induced marked increases in epidermal growth factor receptor (EGFR) and MEK/ERK signaling in tumor epithelial and stromal cells, respectively. Notably, co-administration of AZD8055 and the EGFR inhibitor erlotinib or the MEK inhibitor trametinib was sufficient to suppress tumor invasion in cis-Apc/Smad4 mice. These data indicate that mTOR inhibitor resistance in invasive intestinal tumors involves feedback signaling from both cancer epithelial and stromal cells, highlighting the role of tumor microenvironment in drug resistance, and support that simultaneous inhibition of mTOR and EGFR or MEK may be more effective in treating colon cancer.
Molecular dynamics (MD) methods suitable for treating anisotropic fluctuations in condensed matter are discussed. Barostats with two anisotropic factors to control the simulation cell dynamics are ...introduced in three MD simulation methods; constant pressure, constant surface tension, and canonical hydrostatic. To demonstrate the possibilities of these methods, calculations of two systems, one consisting of anisotropic particles and other consisting of isotropic particles, are presented.
Surgical site infection (SSI) is associated with higher medical expenses and lower patient quality of life.
To identify specific modifiable risk factors for SSI after orthopaedic surgery for ...fractures caused by trauma.
This nested case–control study used a nationwide trauma registry, the Japan Trauma Data Bank (JTDB) database. Patient data from 280 hospitals between January 2004 and May 2019 were retrieved from the JTDB. Patients with SSI and identified patients without SSI as control subjects were included, using propensity score matching adjusted for unmodifiable factors. Risk factors associated with SSI after orthopaedic trauma surgery were assessed using multi-level mixed-effects logistic regression models.
In total, 15,910 patients were included in the analysis. Of these patients, 377 (2.4%) had SSI. After propensity score matching, 258 patients with SSI and 2580 matched patients without SSI were selected. In the multi-level mixed-effects logistic regression analysis, blood transfusion within 24 h (odds ratio (OR): 1.51; 95% confidence interval (CI): 1.06–2.13) was a significant risk factor for SSI following orthopaedic fracture surgery. The OR (95% CI) values for external fixation, transcatheter arterial embolization, and tourniquet for SSI following orthopaedic fracture surgery were 1.40 (0.96–2.03), 1.66 (0.81–3.38), and 2.99 (0.60–14.87), respectively.
These findings highlight the necessity of exercising caution when implementing blood transfusion within 24 h as a risk factor associated with SSI following orthopaedic trauma surgery.
Infectious diseases are caused by the invasion of pathogenic microorganisms such as fungi, bacteria, viruses, and parasites. After infection, disease progression relies on the complex interplay ...between the host immune response and the microorganism evasion strategies. The host’s survival depends on its ability to mount an efficient protective anti-microbial response to accomplish pathogen clearance while simultaneously preventing tissue injury by keeping under control the excessive inflammatory process. The purinergic system has the dual function of regulating the immune response and triggering effector antimicrobial mechanisms. This review provides an overview of the current knowledge of the modulation of innate and adaptive immunity driven by the purinergic system during parasitic, bacterial and viral infections.
Context.
Unevolved metal-poor stars bore witness to the early evolution of the Galaxy, and the determination of their detailed chemical composition is an important tool to understand its chemical ...history. The study of their chemical composition can also be used to constrain the nucleosynthesis of the first generation of supernovae that enriched the interstellar medium.
Aims.
We aim to observe a sample of extremely metal-poor star (EMP stars) candidates selected from the Sloan Digital Sky Survey data release 12 (SDSS DR12) and determine their chemical composition.
Methods.
We obtained high-resolution spectra of a sample of five stars using HDS on Subaru telescope and used standard 1D models to compute the abundances. The stars we analysed have a metallicity Fe/H of between −3.50 and −4.25 dex.
Results.
We confirm that the five metal-poor candidates selected from low-resolution spectra are very metal poor. We present the discovery of a new ultra metal-poor star (UMP star) with a metallicity of Fe/H = −4.25 dex (SDSS J1050032.34−241009.7). We measured in this star an upper limit of lithium (log(Li/H) ≤ 2.0. We found that the four most metal-poor stars of our sample have a lower lithium abundance than the Spite plateau lithium value. We obtain upper limits for carbon in the sample of stars. None of them belong to the high carbon band. We measured abundances of Mg and Ca in most of the stars and found three new
α
-poor stars.
By a molecular dynamics (MD) simulation method which ensures the system will be under hydrostatic pressure, dynamic and elastic properties of glassy metatstable states are investigated. In the MD ...method, the simulation cell fluctuates not only in volume but also in shape under constant hydrostatic pressure and temperature. As observed in experiments for many glass forming materials, metastable states in our simulation show a sharp increase in mean-square-displacement at certain temperatures TD. Dynamic heterogeneity is also observed at TD. Elastic properties are calculated from stress and strain relations obtained from the spontaneous fluctuation of internal stress tensor and simulation cell parameters. Each investigated state shows distinctive dynamics while maintaining solid-like elastic properties. The elastic properties stay intact even above TD. It has been shown that the rigidity and mobility of glassy metastable states are compatible under dynamic heterogeneity.
PDF
