Feasability of constraining the curvature parameter of the symmetry energy using elliptic flow data

A QMD type transport model supplemented by a phase-space coalescence model fitted to FOPI experimental multiplicities of free nucleons and light clusters has been used to study the density dependence of the symmetry energy above the saturation point by a comparison with experimental elliptic flow ratios measured by the FOPI-LAND and ASYEOS collaborations in $^{197}$Au+$^{197}$Au collisions at 400 MeV/nucleon impact energy. A previous calculation has proven that neutron-to-proton and neutron-to-charged particles elliptic flow ratios probe on average different densities allowing in principle the extraction of both the slope $L$ and curvature $K_{sym}$ parameters of the symmetry energy. Consequently a Gogny interaction inspired potential has been modified to allow independent changes of $L$ and $K_{sym}$. Comparing theoretical predictions with experimental data for neutron-to-proton and neutron-to-charged particles elliptic flow ratios the following constraints have been extracted: $L$=85$\pm$22(exp)$\pm$20(th)$\pm$12(sys) MeV and $K_{sym}$=96$\pm$315(exp)$\pm$170(th)$\pm$166(sys) MeV. Residual model dependence is accounted for in the magnitude of the quoted theoretical error. Systematical uncertainties are generated by the inability of the transport model to reproduce experimental light-cluster-to-proton multiplicity ratios. A value for $L$, free of systematical theoretical uncertainties, can be extracted from the neutron-to-proton elliptic flow ratio alone: $L$=84$\pm$30(exp)$\pm$19(th) MeV. It has also been demonstrated that elliptic flow ratios reach a maximum sensitivity on the $K_{sym}$ parameter in heavy-ion collisions of about 250 MeV/nucleon impact energy, allowing a reduction of the experimental component of uncertainty to about 150 MeV for this parameter.Comment: 22 pages, 13 figure

Constraining the density dependence of the symmetry energy using the multiplicity and average pTp_T ratios of charged pions

The charged pion multiplicity ratio in intermediate energy heavy-ion collisions, a probe of the density dependence of symmetry energy above the saturation point, has been proven in a previous study to be extremely sensitive to the strength of the isovector $\Delta$(1232) potential in nuclear matter. As there is no knowledge, either from theory or experiment, about the magnitude of this quantity, the extraction of constraints on the slope of the symmetry energy at saturation by using exclusively the mentioned observable is hindered at present. It is shown that, by including the ratio of average $p_T$ of charged pions $\langle p_T^{(\pi^+)}\rangle/\langle p_T^{(\pi^-)}\rangle$ in the list of fitted observables, the noted problem can be circumvented. A realistic description of this observable requires accounting for the interaction of pions with the dense nuclear matter environment by the incorporation of the so called $S$-wave and $P$-wave pion optical potentials. This is performed within the framework of a quantum molecular dynamics transport model that enforces the conservation of the total energy of the system. It is shown that constraints on the slope of the symmetry energy at saturation density and the strength of the $\Delta$(1232) potential can be simultaneously extracted. A symmetry energy with a value of the slope parameter $L>$ 50 MeV is favored, at 1$\sigma$ confidence level, from a comparison with published FOPI experimental data. A precise constraint will require experimental data more accurate than presently available, particularly for the charged pion multiplicity ratio, and better knowledge of the density and momentum dependence of the pion potential for the whole range of these two variables probed in intermediate energy heavy-ion collisions.Comment: 22 pages, 17 figure

Towards a model-independent constraint of the high-density dependence of the symmetry energy

Neutron-proton elliptic flow difference and ratio have been shown to be promising observables in the attempt to constrain the density dependence of the symmetry energy above the saturation point from heavy-ion collision data. Their dependence on model parameters like microscopic nucleon-nucleon cross-sections, compressibility of nuclear matter, optical potential, and symmetry energy parametrization is thoroughly studied. By using a parametrization of the symmetry energy derived from the momentum dependent Gogny force in conjunction with the T\"{u}bingen QMD model and comparing with the experimental FOPI/LAND data for 197Au+197Au collisions at 400 MeV/nucleon, a moderately stiff, x=-1.35 +/- 1.25, symmetry energy is extracted, a result that agrees with that of a similar study that employed the UrQMD transport model and a momentum independent power-law parametrization of the symmetry energy. This contrasts with diverging results extracted from the FOPI $\pi^{-}/\pi^{+}$ ratio available in the literature.Comment: 18 pages, 3 figures, accepted for publication in Phys. Rev.

Flow probe of symmetry energy in relativistic heavy-ion reactions

Flow observables in heavy-ion reactions at incident energies up to about 1 GeV per nucleon have been shown to be very useful for investigating the reaction dynamics and for determining the parameters of reaction models based on transport theory. In particular, the elliptic flow in collisions of neutron-rich heavy-ion systems emerges as an observable sensitive to the strength of the symmetry energy at supra-saturation densities. The comparison of ratios or differences of neutron and proton flows or neutron and hydrogen flows with predictions of transport models favors an approximately linear density dependence, consistent with ab-initio nuclear-matter theories. Extensive parameter searches have shown that the model dependence is comparable to the uncertainties of existing experimental data. Comprehensive new flow data of high accuracy, partly also through providing stronger constraints on model parameters, can thus be expected to improve our knowledge of the equation of state of asymmetric nuclear matter.Comment: 20 pages, 24 figures, review to appear in EPJA special volume on nuclear symmetry energ

Therapeutic alternatives with CPAP in obstructive sleep apnea

Obstructive Sleep Apnea (OSA), characterized by airflow cessation (apnea) or reduction (hypopnea) due to repeated pharyngeal obstructions during sleep, causes frequent disruption of sleep and hypoxic events. The condition is linked to many adverse health related consequences, such as neurocognitive and cardiovascular disorders, and metabolic syndrome. OSA is a chronic condition requiring long-term treatment, so treatment using continuous positive airway pressure (CPAP) has become the gold standard in cases of moderate or severe OSA. However, its effectiveness is influenced by patients’ adherence. Surgery for OSA or treatment with oral appliances can be successful in selected patients, but for the majority, lifestyle changes such as exercise and dietary control may prove useful. However, exercise training remains under-utilized by many clinicians as an alternative treatment for OSA. Other interventions such as oral appliance (OA), upper way stimulation, and oropharyngeal exercises are used in OSA. Because the benefit of all these techniques is heterogeneous, the major challenge is to associate specific OSA therapies with the maximum efficacy and the best patient compliance

Spotted fever group rickettsiae in ticks of migratory birds in Romania

BACKGROUND: Birds are important hosts and dispersers of parasitic arthropods and vector-borne zoonotic pathogens. Particularly migratory species may carry these parasites over long distances in short time periods. Migratory hotspots present ideal conditions to get a snapshot of parasite and pathogen diversity of birds migrating between continents. The aim of this study was to investigate the presence and diversity of Rickettsia spp. in ticks collected from birds at a migratory hot-spot in the Danube Delta, Romania, eastern Europe. METHODS: DNA was extracted from ticks that were collected from migratory birds in the Danube Delta during migratory seasons in 2011–2012. Two 360 bp  fragments of the 16S ribosomal RNA gene and a 381 bp  fragment Gene gltA were PCR amplified and analyzed by sequence analysis (performed at Macrogen Europe, Amsterdam, The Netherlands). Nucleotide sequences were compared to reference sequences available in the GenBank database, using Basic Local Alignment Search Tool. RESULTS: Four hundred ticks of four different species were found on 11 bird species. The prevalence of Rickettsia spp. infection was 14 % (56/400, CI: 11.7–29.1), with significantly more nymphs hosting rickettsial infection compared to larvae (48 vs 7; P < 0.001). Significantly more ticks in nymphal stage were hosting Rickettsia spp. infection in spring, than in autumn. Four different genospecies were found: R. monacensis (29 ticks), R. helvetica (13), R. massiliae (3) and R. slovaca (2). The seasonal distribution of different Rickettsia spp. was heterogeneous; with most of the R. monacensis-infected ticks were found in spring, while more R. helvetica were found in autumn than spring. R. massiliae was found only in autumn and R. slovaca was found only in spring. CONCLUSION: This study has shown that birds migrating through eastern Europe may carry ticks infected with a high diversity of rickettsial pathogens, with four Rickettsia spp. recorded. Migratory direction was important for pathogen burden, with seasonal differences in the occurrence of individual Rickettsia species. Here we report the first individual records of different Rickettsia spp. in H. concinna (R. monacensis), I. arboricola (R. helvetica, R. massiliae) and I. redikorzevi (R. helvetica) and also the first geographical record of occurrence of R. massiliae in Romania, representing the easternmost observation on the continent

Az amurgéb (Perccottus glenii Dybowski, 1877) egy álló- és egy folyóvízi populációjának táplálkozásökológiai vizsgálata

Az utóbbi két évtizedben a Távol‐Keletről származó amurgéb (Perccottus glenii) inváziója figyelhető meg Kelet‐ és Közép‐Európában. Munkánk során az amurgéb évszakonkénti részletes táplálkozásökológiai elemzését tűztük ki célul egy állóvízben (a Rakamaz-Tiszanagyfalui‐Nagy‐morotvában) és egy vízfolyásban (a Lónyay‐főcsatornában). A legjelentősebb táplálékszervezeteknek az árvaszúnyogok (Chironomidae), szitakötők (Odonata), rákok (Crustacea) és kérészek (Ephemeroptera) bizonyultak. A faj táplálkozásának intenzitásában nem tapasztalható méret, évszak és hely által befolyásolt változás. Táplálékának összetételét legfőképp a halak mérete befolyásolja, amelynek hatása erősebbnek bizonyult az élőhelyi és évszakos hatásoknál is. Kutatásaink igazolják, hogy az amurgé a vízi táplálékhálózat számos szintjét (kompartmentjét) befolyásolhatja, elsősorban azonban a makroszkopikus gerinctelen szervezetek hatékony predátora

Search for Bremsstrahlung radiation in quasi-free n p --> n p gamma reactions

Due to the high sensitivity of the N N --> N N gamma reaction to the nucleon-nucleon potential, Bremsstrahlung radiation is used as a tool to investigate details of the nucleon-nucleon interaction. Such investigations can be performed at the cooler synchrotron COSY in the Research Centre Juelich, by dint of the COSY-11 detection system. The results of the identification of Bremsstrahlung radiation emitted via the d p --> d p gamma reaction in data taken with a proton target and a deuteron beam are presented and discussed.Comment: 3 pages; Presented at Meson 2004: 8th International Workshop on Meson Production, Properties and Interaction, Krakow, Poland, 4-8 June 2004; Submitted to International Journal of Modern Physics

In-medium Δ(1232)\Delta(1232) potential, pion production in heavy-ion collisions and the symmetry energy

Using the dcQMD transport model, the isoscalar and isovector in-medium potentials of the $\Delta$(1232) baryon are studied and information regarding their effective strength is obtained from a comparison to experimental pion production data in heavy-ion collisions below 800 MeV/nucleon impact energy. The best description is achieved for an isoscalar potential moderately more attractive than the nucleon optical potential and a rather small isoscalar relative effective mass m$^*_\Delta \approx$ 0.45. For the isovector component only a constraint between the potential's strength at saturation and the isovector effective mass difference can be extracted, which depends on quantities such as the slope of the symmetry energy and the neutron-proton effective mass difference. These results are incompatible with the usual assumption, in transport models, that the $\Delta$(1232) and nucleon potentials are equal. The density dependence of symmetry energy can be studied using the high transverse momentum tail of pion multiplicity ratio spectra. Results are however correlated with the value of neutron-proton effective mass difference. This region of spectra is shown to be affected by uncertain model ingredients such as the pion potential or in-medium correction to inelastic scattering cross-sections at levels smaller than 10$\%$. Extraction of precise constraints for the density dependence of symmetry energy above saturation will require experimental data for pion production in heavy-ion collisions below 800 MeV/nucleon impact energy and experimental values for the high transverse momentum tail of pion multiplicity ratio spectra accurate to better than 5$\%$.Comment: 22 pages, 13 figure

Study of dielectron production in C+C collisions at 1 AGeV

The emission of e+e- pairs from C+C collisions at an incident energy of 1 GeV per nucleon has been investigated. The measured production probabilities, spanning from the pi0-Dalitz to the rho/omega! invariant-mass region, display a strong excess above the cocktail of standard hadronic sources. The bombarding-energy dependence of this excess is found to scale like pion production, rather than like eta production. The data are in good agreement with results obtained in the former DLS experiment.Comment: submitted to Physics Letters