1,200 research outputs found
Yield scaling, size hierarchy and fluctuations of observables in fragmentation of excited heavy nuclei
Multifragmentation properties measured with INDRA are studied for single
sources produced in Xe+Sn reactions in the incident energy range 32-50 A MeV
and quasiprojectiles from Au+Au collisions at 80 A MeV. A comparison for both
types of sources is presented concerning Fisher scaling, Zipf law, fragment
size and fluctuation observables. A Fisher scaling is observed for all the
data. The pseudo-critical energies extracted from the Fisher scaling are
consistent between Xe+Sn central collisions and Au quasi-projectiles. In the
latter case it also corresponds to the energy region at which fluctuations are
maximal. The critical energies deduced from the Zipf analysis are higher than
those from the Fisher analysis.Comment: 30 pages, accepted for publication in Nuclear Physics A, references
correcte
Teleology and Realism in Leibniz's Philosophy of Science
This paper argues for an interpretation of Leibniz’s claim that physics requires both mechanical and teleological principles as a view regarding the interpretation of physical theories. Granting that Leibniz’s fundamental ontology remains non-physical, or mentalistic, it argues that teleological principles nevertheless ground a realist commitment about mechanical descriptions of phenomena. The empirical results of the new sciences, according to Leibniz, have genuine truth conditions: there is a fact of the matter about the regularities observed in experience. Taking this stance, however, requires bringing non-empirical reasons to bear upon mechanical causal claims. This paper first evaluates extant interpretations of Leibniz’s thesis that there are two realms in physics as describing parallel, self-sufficient sets of laws. It then examines Leibniz’s use of teleological principles to interpret scientific results in the context of his interventions in debates in seventeenth-century kinematic theory, and in the teaching of Copernicanism. Leibniz’s use of the principle of continuity and the principle of simplicity, for instance, reveal an underlying commitment to the truth-aptness, or approximate truth-aptness, of the new natural sciences. The paper concludes with a brief remark on the relation between metaphysics, theology, and physics in Leibniz
Microscopic model approaches to fragmentation of nuclei and phase transitions in nuclear matter
The properties of excited nuclear matter and the quest for a phase transition
which is expected to exist in this system are the subject of intensive
investigations. High energy nuclear collisions between finite nuclei which lead
to matter fragmentation are used to investigate these properties. The present
report covers effective work done on the subject over the two last decades. The
analysis of experimental data is confronted with two major problems, the
setting up of thermodynamic equilibrium in a time-dependent fragmentation
process and the finite size of nuclei. The present status concerning the first
point is presented. Simple classical models of disordered systems are derived
starting with the generic bond percolation approach. These lattice and cellular
equilibrium models, like percolation approaches, describe successfully
experimental fragment multiplicity distributions. They also show the properties
of systems which undergo a thermodynamic phase transition. Physical observables
which are devised to show the existence and to fix the order of critical
behaviour are presented. Applications to the models are shown. Thermodynamic
properties of finite systems undergoing critical behaviour are advantageously
described in the framework of the microcanonical ensemble. Applications to the
designed models and to experimental data are presented and analysed.
Perspectives of further developments of the field are suggested.Comment: 150 pages including 28 figures. To be published in Phys. Rep.
Corrected discussion in section 3.2.3 and new Fig.5. New caption of Fig.2
Generalized entropy and temperature in nuclear multifragmentation
In the framework of a 2D Vlasov model, we study the time evolution of the
"coarse-grained" Generalized Entropy (GE) in a nuclear system which undergoes a
multifragmentation (MF) phase transition. We investigate the GE both for the
gas and the fragments (surface and bulk part respectively). We find that the
formation of the surface causes the growth of the GE during the process of
fragmentation. This quantity then characterizes the MF and confirms the crucial
role of deterministic chaos in filling the new available phase-space: at
variance with the exact time evolution, no entropy change is found when the
linear response is applied. Numerical simulations were used also to extract
information about final temperatures of the fragments. From a fitting of the
momentum distribution with a Fermi-Dirac function we extract the temperature of
the fragments at the end of the process. We calculate also the gas temperature
by averaging over the available phase space. The latter is a few times larger
than the former, indicating a gas not in equilibrium. Though the model is very
schematic, this fact seems to be very general and could explain the discrepancy
found in experimental data when using the slope of light particles spectra
instead of the double ratio of isotope yields method in order to extract the
nuclear caloric curve.Comment: 26 pages, 9 postscript figures included, Revtex, some figures and
part of text changed, version accepted for publication in PR
The Female Athlete's Heart: Facts and Fallacies.
Purpose of the review
For many years, competitive sport has been dominated by men. Recent times have witnessed a significant increase in women participating in elite sports. As most studies investigated male athletes, with few reports on female counterparts, it is crucial to have a better understanding on physiological cardiac adaptation to exercise in female athletes, to distinguish normal phenotypes from potentially fatal cardiac diseases. This review reports on cardiac adaptation to exercise in females.
Recent findings
Recent studies show that electrical, structural, and functional cardiac changes due to physiological adaptation to exercise differ in male and female athletes. Women tend to exhibit eccentric hypertrophy, and while concentric hypertrophy or concentric remodeling may be a normal finding in male athletes, it should be evaluated carefully in female athletes as it may be a sign of pathology. Although few studies on veteran female athletes are available, women seem to be affected by atrial fibrillation, coronary atherosclerosis, and myocardial fibrosis less than male counterparts.
Summary
Males and females exhibit many biological, anatomical, and hormonal differences, and cardiac adaptation to exercise is no exception. The increasing participation of women in sports should stimulate the scientific community to develop large, longitudinal studies aimed at a better understanding of cardiac adaptation to exercise in female athletes
Mediastinitis complicating a percutaneous endoscopic gastrostomy: a case report
BACKGROUND: Since its introduction in the early 1980s, percutaneous endoscopic gastrostomy has become the most popular method for performing a gastrostomy for long-term enteral feeding. It has been associated, however, with a lot of minor and major complications. CASE PRESENTATION: A case of mediastinitis with concominant sepsis caused by a masked esophageal perforation after percutaneous endoscopic gastrostomy in a multi-traumatized, brain-injured patient is presented. Ten – fourteen days after the procedure, the patient became febrile and gradually septic with tenderness of the sternum and upper abdomen. Computerized tomography of the thorax revealed mediastinitis. An urgent left thoracotomy and laparotomy were performed for drainage of the mediastinum, removal of the gastrostomy and insertion of a jejunostomy tube. The patient improved soon after the surgery. He was successfully weaned off the ventilator and was discharged from the Intensive Care Unit. CONCLUSION: Perforating mediastinitis is a rare but potentially lethal complication of percutaneous endoscopic gastrostomy. When diagnosed and properly treated it may have a favourable outcome
457 KEYNOTE-495/KeyImPaCT: interim analysis of a randomized, biomarker-directed, phase 2 trial of pembrolizumab-based combination therapy for non–small cell lung cancer (NSCLC)
BackgroundT-cell–inflamed gene expression profile (TcellinfGEP) and tumor mutational burden (TMB) are clinically validated biomarkers that independently predict pembrolizumab response. This study investigated prospective TcellinfGEP and TMB assessment in evaluating first-line pembrolizumab-based combination therapies; the different treatment combinations evaluated may provide insight into the unique biology of each biomarker subgroup.MethodsKEYNOTE-495/KeyImPaCT is a group-sequential, adaptively randomized, multisite, open-label, phase 2 study investigating first-line pembrolizumab plus the VEGF/FGFR inhibitor lenvatinib, CTLA-4 inhibitor quavonlimab (MK-1308), or LAG-3 inhibitor favezelimab (MK-4280) in patients with advanced NSCLC. DNA and RNA were extracted from tumor tissue to determine TcellinfGEP and TMB; patients were assigned to one of four biomarker-defined subgroups (TcellinfGEPlowTMBlow, TcellinfGEPlowTMBhigh, TcellinfGEPhighTMBlow, TcellinfGEPhighTMBhigh) and randomly assigned 1:1:1 to receive pembrolizumab (200mg IV Q3W)+lenvatinib (20mg oral QD), pembrolizumab+quavonlimab (75mg IV Q6W), or pembrolizumab+favezelimab (200mg [n=30] or 800mg [n=34] Q3W; the initial prespecified dose was 200mg but changed to 800mg based on emerging data). The primary end point was investigator-assessed ORR per RECIST v1.1. Multiple interim analyses will be performed until the prespecified clinical signal is observed. The first interim analysis for each combination therapy occurred after ≥10 patients had ≥12 weeks of follow-up.ResultsAt the data cutoff (January 11, 2021), 208 patients were treated (pembrolizumab+lenvatinib, n=72; pembrolizumab+quavonlimab, n=72; pembrolizumab+favezelimab 200mg, n=30; pembrolizumab+favezelimab 800mg, n=34). The overall assay success rate for testing and determining TcellinfGEP and TMB was 94%. In patients treated with pembrolizumab+lenvatinib, pembrolizumab+quavonlimab, or pembrolizumab+favezelimab, ORRs were generally highest in the TcellinfGEPhighTMBhigh subgroup (table 1); response rates were similar across combinations within this subgroup. ORR was low across combinations within the TcellinfGEPlowTMBlow subgroup. Treatment-related adverse events (TRAEs) occurred in 88%, 65%, 57%, and 59% of patients in the pembrolizumab+lenvatinib, pembrolizumab+quavonlimab, pembrolizumab+favezelimab 200mg and pembrolizumab+favezelimab 800mg arms, respectively. Consistent with the known TRAEs of these agents, most TRAEs were grade 1 or 2 in severity except in the pembrolizumab+lenvatinib arm (grade 3–5, 63%). Three deaths from TRAEs occurred (pembrolizumab+lenvatinib [n=2], brain hemorrhage and myocardial infarction; pembrolizumab+favezelimab 800 mg [n=1], pneumonitis).Abstract 457 Table 1Confirmed ORR by Therapy and Biomarker StatusConclusionsThese data demonstrate the feasibility and clinical usefulness of prospective TcellinfGEP and TMB assessment to study the clinical activity of three first-line pembrolizumab-based combination therapies in patients with advanced NSCLC. Although sample sizes were small, the TcellinfGEPhighTMBhigh subgroup demonstrated the best response among the biomarker subgroups for all three combination therapies; further validation is needed to determine additional signals and may be addressed as more mature data become available.AcknowledgementsJeanne Fahey, PhD, of Merck & Co., Inc., Kenilworth, New Jersey, USA, provided critical review of the abstract. Elisha Dettman PhD, Mark Ayers MS, and Andrey Loboda PhD of Merck & Co., Inc., Kenilworth, New Jersey, USA, provided critical review of study translational data. Medical writing and/or editorial assistance was provided by Shane Walton, PhD, and Lei Bai, PhD, of ApotheCom (Yardley, PA, USA). This assistance was funded by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA.Trial RegistrationClinicalTrials.gov, NCT03516981Ethics ApprovalThe study protocol and all amendments were approved by the relevant institutional review board or ethics committee at each study site. All patients provided written informed consent to participate in the clinical trial
A search for the decay modes B+/- to h+/- tau l
We present a search for the lepton flavor violating decay modes B+/- to h+/-
tau l (h= K,pi; l= e,mu) using the BaBar data sample, which corresponds to 472
million BBbar pairs. The search uses events where one B meson is fully
reconstructed in one of several hadronic final states. Using the momenta of the
reconstructed B, h, and l candidates, we are able to fully determine the tau
four-momentum. The resulting tau candidate mass is our main discriminant
against combinatorial background. We see no evidence for B+/- to h+/- tau l
decays and set a 90% confidence level upper limit on each branching fraction at
the level of a few times 10^-5.Comment: 15 pages, 7 figures, submitted to Phys. Rev.
Regional regulators in healthcare service under quality competition: A game theoretical model
In several countries, healthcare services are provided by public and/or private subjects, and they are reimbursed by the Government, on the basis of regulated prices. Thus, providers take prices as given and compete on quality to attract patients. In some countries, regulated prices differ across regions. This paper focuses on the interdependence between regional regulators within a country: it proposes a model of spatial competition to study how price-setters of different regions interact, in a simple but realistic framework. We show that the decentralisation of price regulation implies higher expenditure, but higher patients' welfare
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