Refine
Year of publication
- 2016 (730) (remove)
Document Type
- Article (730) (remove)
Language
- English (730) (remove)
Has Fulltext
- yes (730)
Is part of the Bibliography
- no (730)
Keywords
- Mitochondria (7)
- crystal structure (7)
- invasion (5)
- Cortex (4)
- Gender (4)
- Invasive species (4)
- apoptosis (4)
- cancer (4)
- management (4)
- Apoptosis (3)
Institute
- Medizin (283)
- Biowissenschaften (70)
- Physik (69)
- Geowissenschaften (61)
- Frankfurt Institute for Advanced Studies (FIAS) (58)
- Biochemie und Chemie (46)
- Informatik (38)
- Biodiversität und Klima Forschungszentrum (BiK-F) (34)
- Institut für Ökologie, Evolution und Diversität (27)
- Senckenbergische Naturforschende Gesellschaft (27)
On the robustness of the r-process in neutron-star mergers against variations of nuclear masses
(2016)
r-process calculations have been performed for matter ejected dynamically in neutron star mergers (NSM), such calculations are based on a complete set of trajectories from a three-dimensional relativistic smoothed particle hydrodynamic (SPH) simulation. Our calculations consider an extended nuclear reaction network, including spontaneous, β- and neutron-induced fission and adopting fission yield distributions from the ABLA code. In this contribution we have studied the sensitivity of the r-process abundances to nuclear masses by using diferent mass models for the calculation of neutron capture cross sections via the statistical model. Most of the trajectories, corresponding to 90% of the ejected mass, follow a relatively slow expansion allowing for all neutrons to be captured. The resulting abundances are very similar to each other and reproduce the general features of the observed r-process abundance (the second and third peaks, the rare-earth peak and the lead peak) for all mass models as they are mainly determined by the fission yields. We find distinct differences in the predictions of the mass models at and just above the third peak, which can be traced back to different predictions of neutron separation energies for r-process nuclei around neutron number N = 130.
A new technique developed for measuring nuclear reactions at low momentum transfer with stored beams in inverse kinematics was successfully used to study isoscalar giant resonances. The experiment was carried out at the experimental heavy-ion storage ring (ESR) at the GSI facility using a stored 58Ni beam at 100 MeV/u and an internal helium gas-jet target. In these measurements, inelastically scattered α-recoils at very forward center-of-mass angles (θcm ≤ 1.5°) were detected with a dedicated setup, including ultra-high vacuum compatible detectors. Experimental results indicate a dominant contribution of the isoscalar giant monopole resonance at this very forward angular range. It was found that the monopole contribution exhausts 79+12−11% of the energy-weighted sum rule (EWSR), which agrees with measurements performed in normal kinematics. This opens up the opportunity to investigate the giant resonances in a large domain of unstable and exotic nuclei in the near future. It is a fundamental milestone towards new nuclear reaction studies with stored ion beams.
Within the SEASTAR project at RIKEN-RIBF, 66Cr and 70,72Fe have been produced via protonknockout reactions, and their first excited 2+ and 4+ states have been discovered. The combination of the liquid-hydrogen target and TPC system MINOS has been used in combination with the DALI2 detector array for the first time. A 345 MeV/u 238U beam with a mean intensity of about 12 pnA impinged on a Be target. Fission fragments were separated and identified using the BigRIPS spectrograph, and reaction products were analyzed using the ZeroDegree spectrograph. A plateau of excitation energies, with a small change in the systematic trends past N = 44, reveals an extension of the N = 40 region of collectivity toward N = 50. Hence, the isotopes of interest are located within the N = 40 island of inversion. An interpretation of the observed trends is offered through large scale shell model calculations.
The elliptic-flow ratio of neutrons with respect to protons or light complex particles in reactions of heavy ions at pre-relativistic energies has been proposed as an observable sensitive to the strength of the symmetry term of the nuclear equation of state at supra-saturation densities. In the ASY-EOS experiment at the GSI laboratory, flows of neutrons and light charged particles were measured for 197Au+197Au collisions at 400 MeV/nucleon. Flow results obtained for the Au+Au system, in comparison with predictions of the UrQMD transport model, confirm the moderately soft to linear density dependence of the symmetry energy deduced from the earlier FOPI-LAND data.
The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process β-decay chains. These nuclei are attributed to the p and rp process.
For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections.
The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.
A heavy-ion detector was developed for decay studies in the Experimental Storage Ring (ESR) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. This detector serves as a prototype for the in-pocket particle detectors for future experiments with the Collector Ring (CR) at FAIR (Facility for Antiproton and Ion Research). The detector includes a stack of six silicon pad sensors, a double-sided silicon strip detector (DSSD), and a CsI(Tl) scintillation detector. It was used successfully in a recent experiment for the detection of the β+-decay of highly charged 142Pm60+ ions. Based on the technique for particle identification and an energy resolution of 0.9% for and 0.5% for E (Full Width at Half Maximum (FWHM)), the detector is well-suited to distinguish neighbouring isobars in the region of interest.
First observation of the competitive double-γ decay process is presented. It is a second-order electromagnetic decay mode. The 662-keV decay transition from the 11/2− isomer of 137Ba to its ground state proceeds at a fraction of 2 × 10−6 by simultaneous emission of two γ quanta instead of one. The observed angular correlation and energy distribution of coincident γ quanta are well described by a dominant M2 – E2 and a minor E3 – M1 contribution to the double-γ decay branch. The data were well accounted for by a calculation using the Quasiparticle Phonon Model.
The Coulomb Dissociation (CD) cross sections of the stable isotopes 92,94,100Mo and of the unstable isotope 93Mo were measured at the LAND/R3B setup at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Experimental data on these isotopes may help to explain the problem of the underproduction of 92,94Mo and 96,98Ru in the models of p-process nucleosynthesis. The CD cross sections obtained for the stable Mo isotopes are in good agreement with experiments performed with real photons, thus validating the method of Coulomb Dissociation. The result for the reaction 93Mo(γ,n) is especially important since the corresponding cross section has not been measured before. A preliminary integral Coulomb Dissociation cross section of the 94Mo(γ,n) reaction is presented. Further analysis will complete the experimental database for the (γ,n) production chain of the p-isotopes of molybdenum.
The process of electron-loss to the continuum (ELC) has been studied for the collision systems U28++H2 at a collision energy of 50 MeV/u, U28++N2 at 30 MeV/u, and U28++Xe at 50 MeV/u. The energy distributions of cusp electrons emitted at an angle of 0∘ with respect to the projectile beam were measured using a magnetic forward-angle electron spectrometer. For these collision systems far from equilibrium charge state, a significantly asymmetric cusp shape is observed. The experimental results are compared to calculations based on first-order perturbation theory, which predict an almost symmetric cusp shape. Some possible reasons for this discrepancy are discussed.
The decay properties of the Pygmy Dipole Resonance (PDR) have been investigated in the semi-magic N=82 nucleus 140Ce using a novel combination of nuclear resonance fluorescence and γ–γ coincidence techniques. Branching ratios for transitions to low-lying excited states are determined in a direct and model-independent way both for individual excited states and for excitation energy intervals. Comparison of the experimental results to microscopic calculations in the quasi-particle phonon model exhibits an excellent agreement, supporting the observation that the Pygmy Dipole Resonance couples to the ground state as well as to low-lying excited states. A 10% mixing of the PDR and the [21+ x PDR] is extracted.
Experimental study of the ¹⁵O(2p,γ)¹⁷Ne cross section by Coulomb dissociation for the rp process
(2016)
The time-reversed reaction 15O(2p, γ)17Ne has been studied by the Coulomb dissociation technique. Secondary 17Ne ion beams at 500 AMeV have been produced by fragmentation reactions of 20Ne in a beryllium production target and dissociated on a secondary Pb target. The incoming beam and the reaction products have been identified with the kinematically complete LAND-R3B experimental setup at GSI. The excitation energy prior to decay has been reconstructed by using the invariant-mass method. The preliminary differential and integral Coulomb Dissociation cross sections (σCoul) have been calculated, which provide a photoabsorption (σphoto) and a radiative capture cross section (σcap). Additionally, important information about the nuclear structure of the 17Ne nucleus will be obtained. The analysis is in progress.
First observation of the competitive double-γ decay process is presented. It is a second-order electromagnetic decay mode. The 662-keV transition from the 11/2− isomer of 137Ba to its ground state proceeds at a fraction of 2 x 10−6 by simultaneous emission of two γ quanta instead of one. The angular correlation and energy distribution of coincident γ quanta are reproduced by a dominant M2-E2 and a minor E3-M1 contribution to the double-γ decay branch. The data are well accounted for by a calculation in the Quasiparticle Phonon Model.
New experimental data for dissociation of relativistic 17Ne projectiles incident on targets of lead, carbon, and polyethylene targets at GSI are presented. Special attention is paid to the excitation and decay of narrow resonant states in 17Ne. Distributions of internal energy in the three-body system have been determined together with angular and partial-energy correlations between the decay products in different energy regions. The analysis was done using existing experimental data on 17Ne and its mirror nucleus 17N. The isobaric multiplet mass equation is used for assignment of observed resonances and their spins and parities. A combination of data from the heavy and light targets yielded cross sections and transition probabilities for the Coulomb excitations of the narrow resonant states. The resulting transition probabilities provide information relevant for a better understanding of the 17Ne structure.
Beyond radicalism and resignation: the competing logics for public participation in policy decisions
(2016)
Participation – like justice or freedom – is a term that can be constructed in multiple ways. However, existing typologies of participation pay little attention to the alternative logics for public participation in policy decisions: either they assume one particular normative bias or categorise by institutional design features without reference to the broader ideology that informs the use of these designs. This paper outlines an alternative approach that connects the variety in participatory practices to competing theories of democracy and public administration. It identifies four archetypes of participation: knowledge transfer; collective decision-making; choice and voice; and arbitration and oversight.
DESPITE A RECENT SLIGHT RECOVERY FROM CRISIS LOW LEVELS, STOCK MARKET PARTICIPATION IN GERMANY IS STILL AT ONLY 14% OF ADULT POPULATION. PREVIOUS RESEARCH SHOWED THAT TRADITIONAL PERSONAL ADVICE – DUE TO HIGH COSTS AND MISALIGNED INCENTIVES – CAN HARDLY ALLEVIATE PRIVATE INVESTORS' INVESTMENT MISTAKES, OF WHICH STOCK MARKET NON-PARTICIPATION IS ONE. ROBOADVICE IS A "HOT TOPIC" IN REGULATORY AND INDUSTRY DISCUSSIONS. THE RESULTS OF THIS STUDY SHOW EMPIRICAL EVIDENCE THAT INVITATIONS TO ROBO-ADVICE INCREASE STOCK MARKET PARTICIPATION.
COMPANIES USE SOCIAL MEDIA IN GENERAL AND MICROBLOGGING IN PARTICULAR FOR DIFFERENT PURPOSES, SUCH AS REPUTATION MANAGEMENT. WE EMPIRICALLY IDENTIFY DIFFERENT SOCIAL MEDIA ACTIVITIES IN TERMS OF SOCIAL MEDIA MANAGEMENT STRATEGIES, ACCOUNT TYPES, AND COMMUNICATIVE APPROACHES. BY ANALYZING A DATA SET OF OVER FIVE MILLION TWITTER MESSAGES, WE FIND POSITIVE EFFECTS OF SOCIAL MEDIA MANAGEMENT TOOLS, BROADCASTING ACCOUNTS, AND CONVERSATIONAL COMMUNICATION ON THE CORPORATE PUBLIC PERCEPTION.
THIS STUDY DOCUMENTS THE ROLE OF BARGAINING POWER IN THE DETERMINATION OF
MORTGAGE RATES BASED ON A UNIQUE ADMINISTRATIVE DATA SET COMPRISING 20,000
MORTGAGE LOAN CONTRACTS. WE USE VARIATION IN THE COMPETITIVE ENVIRONMENT
TO IDENTIFY THE EXTENT TO WHICH DIFFERENTIAL PRICING IS DUE TO RELATIVE BARGAINING POWER. OUR IDENTIFICATION STRATEGY SEPARATES MARKET POWER FROM OTHER SOURCES OF PRICING DIFFERENTIALS, SUCH AS CREDIT RISK, PRODUCT DIFFERENTIATION, OR OTHER COSTS. THE RESULTS INDICATE THAT BARGAINING POWER DETERMINES THE EXTENT OF PRICE DISCRIMINATION ON OBSERVABLE BORROWER CHARACTERISTICS. A REDUCTION IN LENDER BARGAINING POWER REDUCES THE DISADVANTAGE SUFFERED BY BORROWERS WHO REFINANCE THEIR LOAN AND REDUCES THE ADVANTAGE FOR THOSE WHO HAVE THEIR MAIN BANKING RELATIONSHIP AT ANOTHER BANK. SIMULTANEOUSLY, IT INCREASES THE ADVANTAGE FOR BORROWERS FALLING IN THE WEALTHY/HIGH-INCOME SEGMENT. FURTHER ANALYSES POINT TO SEARCH INCENTIVES AS AN IMPORTANT DRIVER OF THE DIRECTION OF THE EFFECT OF BARGAINING POWER.
THIS PAPER PROVIDES EMPIRICAL EVIDENCE ON THE IMPACT OF REVIEWER STATUS ONTHE OBJECTIVITY OF HIS CONTRIBUTIONS IN ONLINE COMMUNITIES. WHILE PREVIOUS RESEARCH INDICATES THAT USER-GENERATED ONLINE REVIEWS GUIDE CONSUMER DECISION MAKING, LITTLE IS KNOWN ABOUT DRIVERS OF THE ACTUAL REVIEW GENERATION PROCESS. UTILIZING A DATA SAMPLE COVERING 413,077 REVIEWS POSTED OVER 12 YEARS ON TRIPADVISOR.COM, WE FIND THAT WITH INCREASED USER STATUS, REVIEW OBJECTIVITY INCREASES. THUS, WE CONTRIBUTE TO THEORY BY GENERALIZING THE SO-CALLED "POPULARITY EFFECT" TO A MULTI-DIMENSIONAL “STATUS EFFECT”.