431 research outputs found
Revision of the 15N(p,{\gamma})16O reaction rate and oxygen abundance in H-burning zones
The NO cycle takes place in the deepest layer of a H-burning core or shell,
when the temperature exceeds T {\simeq} 30 {\cdot} 106 K. The O depletion
observed in some globular cluster giant stars, always associated with a Na
enhancement, may be due to either a deep mixing during the RGB (red giant
branch) phase of the star or to the pollution of the primordial gas by an early
population of massive AGB (asymptotic giant branch) stars, whose chemical
composition was modified by the hot bottom burning. In both cases, the NO cycle
is responsible for the O depletion. The activation of this cycle depends on the
rate of the 15N(p,{\gamma})16O reaction. A precise evaluation of this reaction
rate at temperatures as low as experienced in H-burning zones in stellar
interiors is mandatory to understand the observed O abundances. We present a
new measurement of the 15N(p,{\gamma})16O reaction performed at LUNA covering
for the first time the center of mass energy range 70-370 keV, which
corresponds to stellar temperatures between 65 {\cdot} 106 K and 780 {\cdot}106
K. This range includes the 15N(p,{\gamma})16O Gamow-peak energy of explosive
H-burning taking place in the external layer of a nova and the one of the hot
bottom burning (HBB) nucleosynthesis occurring in massive AGB stars. With the
present data, we are also able to confirm the result of the previous R-matrix
extrapolation. In particular, in the temperature range of astrophysical
interest, the new rate is about a factor of 2 smaller than reported in the
widely adopted compilation of reaction rates (NACRE or CF88) and the
uncertainty is now reduced down to the 10% level.Comment: 6 pages, 5 figure
Observable Signatures of Planet Accretion in Red Giant Stars I: Rapid Rotation and Light Element Replenishment
The orbital angular momentum of a close-orbiting giant planet can be
sufficiently large that, if transferred to the envelope of the host star during
the red giant branch (RGB) evolution, it can spin-up the star's rotation to
unusually large speeds. This spin-up mechanism is one possible explanation for
the rapid rotators detected among the population of generally slow-rotating red
giant stars. These rapid rotators thus comprise a unique stellar sample
suitable for searching for signatures of planet accretion in the form of
unusual stellar abundances due to the dissemination of the accreted planet in
the stellar envelope. In this study, we look for signatures of replenishment in
the Li abundances and (to a lesser extent) 12C/13C, which are both normally
lowered during RGB evolution. Accurate abundances were measured from high
signal-to-noise echelle spectra for samples of both slow and rapid rotator red
giant stars. We find that the rapid rotators are on average enriched in lithium
compared to the slow rotators, but both groups of stars have identical
distributions of 12C/13C within our measurement precision. Both of these
abundance results are consistent with the accretion of planets of only a few
Jupiter masses. We also explore alternative scenarios for understanding the
most Li-rich stars in our sample---particularly Li regeneration during various
stages of stellar evolution. Finally, we find that our stellar samples show
non-standard abundances even at early RGB stages, suggesting that initial
protostellar Li abundances and 12C/13C may be more variable than originally
thought.Comment: Accepted for publication in the Astrophysical Journal. 29 pages in
emulateapj format, including 16 figures and 12 tables. Tables 4 and 8 are
provided in their entirety as plain text ancillary files (and will also be
available in the electronic edition of ApJ
The Nuclear Astrophysics program at n-TOF (CERN)
An important experimental program on Nuclear Astrophysics is being carried out at the n-TOF since several years, in order to address the still open issues in stellar and primordial nucleosynthesis. Several neutron capture reactions relevant to s-process nucleosynthesis have been measured so far, some of which on important branching point radioisotopes. Furthermore, the construction of a second experimental area has recently opened the way to challenging measurements of (n, charged particle) reactions on isotopes of short half-life. The Nuclear Astrophysics program of the n-TOF Collaboration is here described, with emphasis on recent results relevant for stellar nucleosynthesis, stellar neutron sources and primordial nucleosynthesis
Differences in the Kinetic of the First Meiotic Division and in Active Mitochondrial Distribution between Prepubertal and Adult Oocytes Mirror Differences in their Developmental Competence in a Sheep Model
Our aim is to verify if oocyte developmental potential is related to the timing of meiotic progression
and to mitochondrial distribution and activity using prepubertal and adult oocytes
as models of low and high developmental capacity respectively. Prepubertal and adult oocytes
were incorporated in an in vitro maturation system to determine meiotic and developmental
competence and to assess at different time points kinetic of meiotic maturation, 2D
protein electrophoresis patterns, ATP content and mitochondria distribution. Maturation and
fertilization rates did not differ between prepubertal and adult oocytes (95.1% vs 96.7% and
66.73% vs 70.62% respectively for prepubertal and adult oocytes). Compared to adults,
prepubertal oocytes showed higher parthenogenesis (17.38% vs 2.08%respectively in prepubertals
and adults; P<0.01) and polispermy (14.30% vs 2.21% respectively in prepubertals
and adults; P<0.01), lower cleavage rates (60.00%vs 67.08% respectively in
prepubertals and adults; P<0.05) and blastocyst output (11.94%vs 34.% respectively in
prepubertals and adults; P<0.01). Prepubertal oocytes reached MI stage 1 hr later than
adults and this delay grows as the first meiotic division proceeds. Simultaneously, the protein
pattern was altered since in prepubertal oocytes it fluctuates, dropping and rising to levels
similar to adults only at 24 hrs. In prepubertal oocytes ATP rise is delayed and did not
reach levels comparable to adult ones. CLSM observations revealed that at MII, in the majority
of prepubertal oocytes, the active mitochondria are homogenously distributed, while in
adults they are aggregated in big clusters. Our work demonstrates that mitochondria and
their functional aggregation during maturation play an active role to provide energy in terms of ATP. The oocyte ATP content determines the timing of the meiotic cycle and the acquisition
of developmental competence. Taken together our data suggest that oocytes with low
developmental competence have a slowed down energetic metabolism which delays later
development
Noncanonical Fungal Autophagy Inhibits Inflammation in Response to IFN-γ via DAPK1
Defects in a form of noncanonical autophagy, known as LC3-associated phagocytosis (LAP), lead to increased inflammatory pathology during fungal infection. Although LAP contributes to fungal degradation, the molecular mechanisms underlying LAP-mediated modulation of inflammation are unknown. We describe a mechanism by which inflammation is regulated during LAP through the death-associated protein kinase 1 (DAPK1). The ATF6/C/EBP-β/DAPK1 axis activated by IFN-γ not only mediates LAP to Aspergillus fumigatus but also concomitantly inhibits Nod-like receptor protein 3 (NLRP3) activation and restrains pathogenic inflammation. In mouse models and patient samples of chronic granulomatous disease, which exhibit defective autophagy and increased inflammasome activity, IFN-γ restores reduced DAPK1 activity and dampens fungal growth. Additionally, in a cohort of hematopoietic stem cell-transplanted patients, a genetic DAPK1 deficiency is associated with increased inflammation and heightened aspergillosis susceptibility. Thus, DAPK1 is a potential drugable player in regulating the inflammatory response during fungal clearance initiated by IFN-γ
Predialysis and dialysis therapies differently affect nitric oxide synthetic pathway in red blood cells from uremic patients: Focus on peritoneal dialysis
European standard clinical practice recommendations for children and adolescents with primary and recurrent osteosarcoma
Osteosarcoma is a challenging disease requiring multidisciplinary management in expert centers for optimal outcome. There are no current international protocols or guidelines specific for pediatric and adolescent osteosarcoma. The European Standard Clinical Practice (ESCP) project is a collaboration between ERN PaedCan and SIOP Europe's Clinical Trial Groups to develop approved clinical recommendations reflecting current best practice. This manuscript is a summary of the full ESCP guideline for patients with osteosarcoma. The manuscript provides evidence graded recommendations for diagnosis, staging, management, response evaluation and follow-up. The methodology as defined in the standard operating procedures of the European Society for Medical Oncology (ESMO) was applied. Experts of the Fight OsteoSarcoma Through European Research (FOSTER) consortium contributed. In summary, the ESCP provides guidance on low-grade, but has a focus on high-grade osteosarcoma. In high-grade osteosarcoma the outcomes of most recent trials for clinical subgroups (e.g., metastatic vs. non-metastatic, resectable vs. non-resectable) are discussed, for treatment-naïve as well as for recurrent/refractory disease. An overview of current evidence also highlights the need for further therapeutic development as patients with primary metastatic or recurrent/refractory high-grade osteosarcoma still have a poor prognosis. Intensified collaborative research is identified as a prerequisite to increase survival and to limit long-term toxicities
Redefining radiologic responses in high-risk soft-tissue sarcomas treated with neoadjuvant chemotherapy: final results of ISG-STS 1001, a randomized clinical trial
Background: We report the results of the pre-planned secondary analysis of radiologic responses (RRs) of ISG-STS 1001, a randomized trial comparing anthracycline + ifosfamide (AI) versus histology-tailored (HT) neoadjuvant chemotherapy for primary localized high-risk soft-tissue sarcomas of the extremities and trunk wall. Patients and methods: Patients with undifferentiated pleomorphic sarcoma (UPS), leiomyosarcoma (LMS), malignant peripheral nerve sheath tumor, synovial sarcoma or myxoid liposarcoma (MLPS) were randomized, whereas patients with myxofibrosarcoma, pleomorphic liposarcoma, pleomorphic rhabdomyosarcoma or unclassified sarcoma were included in the observational arm (O) and treated with AI. Patients with UPS, LMS or MLPS needing concurrent preoperative radiotherapy were included in O. We evaluated associations between: disease-free survival (DFS)/overall survival (OS) and centrally reviewed RR, assessed with RECIST 1.1 and as percent dimensional variation (D; both dichotomized and continuous); DFS/OS and histology; RR and histology. Results: Four hundred and thirty-five patients were included (287 randomized, 148 observed). The analysis of RRs comprised 236 patients (154 randomized, 82 observed) with measurable disease and available for central review. RECIST best responses were: 28 (11.9%) partial response (PR), 195 (82.6%) stable disease (SD), 13 (5.5%) progressive disease (PD). RECIST significantly correlated with DFS [PD versus PR: hazard ratio (HR) 8.18, 95% confidence interval (CI) 2.96-22.58; SD versus PR: HR 2.96, 95% CI 1.30-6.75] and OS (PD versus PR: HR 12.61, 95% CI 3.40-46.84; SD versus PR: HR 4.24, 95% CI 1.34-13.47). The median value of D was −1.6%. Patients with D >−1.6% had worse clinical outcomes than those with D <−1.6% (DFS: HR 1.73, 95% CI 1.19-2.50; OS: HR 1.86, 95% CI 1.21-2.86). D in continuous scale inversely correlated with DFS (HR 1.53, 95% CI 1.25-1.87) and OS (HR 1.78, 95% CI 1.41-2.25). Conclusions: These results confirm the prognostic value of RRs as per RECIST and D and demonstrate that any variation in size predicts the proportional efficacy of treatment
The astrophysical S-factor of the direct 18
We attempted to determine the astrophysical S-factor of the direct part of the 18O(p, γ)19F capture by the indirect method of asymptotic normalization coefficients (ANC). We measured the differential cross section of the transfer reaction 18O(3He, d)19F at a 3He energy of 24.6 MeV. The measurement was realized on the cyclotron of the NPI in Řež, Czech Republic, with the gas target consisting of the high purity 18O (99.9 %). The reaction products were measured by eight ∆E-E telescopes composed from thin and thick silicon surface-barrier detectors. The parameters of the optical model for the input channel were deduced by means of the code ECIS and the analysis of transfer reactions to 12 levels of the 19F nucleus up to 8.014 MeV was made by the code FRESCO. The deduced ANCs were then used to specify the direct contribution to the 18O(p, γ)19F capture process and were compared with the mutually different results of two works
Trabectedin for patients with advanced soft tissue sarcoma: A non-interventional, retrospective, multicenter study of the italian sarcoma group
The Italian Sarcoma Group performed this retrospective analysis of patients with advanced soft tissue sarcoma, pretreated with ≥1 anthracycline-based treatment, and treated with trabectedin every three weeks. Primary endpoint was to describe real-life use of trabectedin across Italy. Secondary endpoints included objective response rate (ORR) and safety. Overall, 512 patients from 20 Italian centers were evaluated. Leiomyosarcoma (37.7%)/liposarcoma (30.3%) were the most prevalent histological types (abbreviated as L-sarcoma). Patients received a median of four trabectedin cycles (range: 1–40), mostly as a second-line treatment (~60% of patients). The ORR was 13.7% superior (p < 0.0001) in patients with L-sarcoma compared with patients with non-L-sarcoma (16.6% vs. 9.0%). Median progression-free survival (PFS) was 5.1 months, whereas median overall survival (OS) was 21.6 months. Significantly better PFS and OS were observed in patients with L-sarcoma, those with objective responses and/or disease stabilization, treated in an early line and treated with reduced dose. Bone marrow toxicity (61.4%) and transaminase increases (21.9%) were the most common grade 3/4 adverse events. The results of this real-life study suggest that trabectedin is an active treatment, which is mostly given as a second-line treatment to patients with a good performance status and high-grade, metastatic L-sarcoma (clinical trial information: NCT02793050)
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