One- and Two-Nucleon Structure form Green's Function Theory

We review some applications of self-consistent Green's function theory to studies of one- and two-nucleon structure in finite nuclei. Large-scale microscopic calculations that employ realistic nuclear forces are now possible. Effects of long-range correlations are seen to play a dominant role in determining the quenching of absolute spectroscopic factors. They also enhance considerably (e,e'pn) cross sections in superparallel kinematics, in agreement with observations.Comment: Proceedings of the International Symposium on "Forefronts of Researches in Exotic Nuclear Structures" (Niigata2010)

Quasiparticle and quasihole states of nuclei around 56Ni

The single-particle spectral function of 56Ni has been computed within the framework of self-consistent Green's functions theory. The Faddeev random phase approximation method and the G-matrix technique are used to account for the effects of long- and short-range physics on the spectral distribution. Large scale calculations have been performed in spaces including up to ten oscillator shells. The chiral N3LO interaction is used together with a monopole correction that accounts for eventual missing three-nucleon forces. The single-particle energies associated with nucleon transfer to valence 1p0f orbits are found to be almost converged with respect to both the size of the model space and the oscillator frequency. The results support that 56Ni is a good doubly magic nucleus. The absolute spectroscopic factors to the valence states on A=55,57 are also obtained. For the transition between the ground states of 57Ni and 56Ni, the calculations nicely agree with heavy-ion knockout experiments.Comment: Minor comments and references added, accepted for publication on Phys. Rev.

A "kilonova" associated with short-duration gamma-ray burst 130603B

Short-duration gamma-ray bursts (SGRBs) are intense flashes of cosmic gamma-rays, lasting less than ~2 s, whose origin is one of the great unsolved questions of astrophysics today. While the favoured hypothesis for their production, a relativistic jet created by the merger of two compact stellar objects (specifically, two neutron stars, NS-NS, or a neutron star and a black hole, NS-BH), is supported by indirect evidence such as their host galaxy properties, unambiguous confirmation of the model is still lacking. Mergers of this kind are also expected to create significant quantities of neutron-rich radioactive species, whose decay should result in a faint transient in the days following the burst, a so-called "kilonova". Indeed, it is speculated that this mechanism may be the predominant source of stable r-process elements in the Universe. Recent calculations suggest much of the kilonova energy should appear in the near-infrared (nIR) due to the high optical opacity created by these heavy r-process elements. Here we report strong evidence for such an event accompanying SGRB 130603B. If this simplest interpretation of the data is correct, it provides (i) support for the compact object merger hypothesis of SGRBs, (ii) confirmation that such mergers are likely sites of significant r-process production and (iii) quite possibly an alternative, un-beamed electromagnetic signature of the most promising sources for direct detection of gravitational waves.Comment: preprint of paper appearing in Nature (3 Aug 2013

X-ray Emission from the Radio Jet in 3C 120

We report the discovery of X-ray emission from a radio knot at a projected distance of 25" from the nucleus of the Seyfert galaxy, 3C 120. The data were obtained with the ROSAT High Resolution Imager (HRI). Optical upper limits for the knot preclude a simple power law extension of the radio spectrum and we calculate some of the physical parameters for thermal bremsstrahlung and synchrotron self-Compton models. We conclude that no simple model is consistent with the data but if the knot contains small regions with flat spectra, these could produce the observed X-rays (via synchrotron emission) without being detected at other wavebands.Comment: 6 pages latex plus 3 ps/eps figures. Uses 10pt.sty and emulateapj.sty. Accepted for publication in the ApJ (6 Jan 99

Analyse af rejsetidsvariabilitet på danske motorveje

Variabilitet i rejsetider, som betyder at det er vanskeligt at forudsige hvor lang tid en tur tager, er en negativ konsekvens af bl.a. trængsel og hændelser på vejene. I samfundsøkonomiske analyser håndteres det i dag ved, at tidsværdien af forsinkelser er højere end tidsværdien for almindelige rejsetid. Denne metode er dog ikke altid tilfredsstillende, og grundlaget er forholdsvis svagt dokumenteret. Transport DTU og Vejdirektoratet har forsøgt at anvende GPS-data til at kortlægge sammenhængen mellem forsinkelse og variabilitet, for at undersøge om det er muligt at forudsige rejsetidsvariabilitet ud fra forsinkelser. Hvis det er muligt, vil man kunne forudsige ændringer i rejsetidsvariabilitet ud fra output fra trafikmodeller, og variabilitet vil dermed kunne værdisættes mere direkte i den samfundsøkonomiske analyse. Resultaterne af denne analyse viser en tydelig sammenhæng mellem forsinkelse og variabilitet, hvilket betyder, at det måske er muligt at opstille en simpel efterberegningsmodel til LTM, der beregner ændringer i rejsetidsvariabilitet som følge af transport- og infrastrukturprojekter. I forbindelse med analysen er det dog tydeligt, at der er behov for videreudvikling af metoden, før den implementeres i den samfundsøkonomiske analyse

Particle Impact Analysis of Bulk Powder During Pneumatic Conveyance

Fragmentation of powders during transportation is a common problem for manufacturers of food and pharmaceutical products. We illustrate that the primary cause of breakage is due to inter-particle collisions, rather than particle-wall impacts, and provide a statistical mechanics model giving the number of collisions resulting in fragmentation

Direct measurement of dissolved inorganic nitrogen exchange and denitrification in individual polychaete (Nereis virens) burrows

The burrows of macroinfauna are significant sites of sediment-water nitrogen exchange and associated microbial activity. In this study, the exchange of dissolved inorganic nitrogen (DIN) and nitrogen cycle reaction rates were quantified in individual burrows of the estuarine polychaete Nereis virens. Burrow ventilation rate and DIN (NH4+, NO2−, NO3− and N2O) exchange were determined at 22°C in individual, inhabited burrows with and without the presence of C2H2 (an NH4+ oxidation, N2O reduction block). Ventilation cycles were unaffected by C2H2, but worm metabolism (O2 uptake) and excretion of NH4+ were enhanced by ∼100% and ∼50%, respectively. Time-specific DIN exchange patterns were quantitatively modeled by relating burrow water concentration changes, excretion, and ventilation rates. The highest rates were at the start of ventilation periods and decreased or increased (depending on the solute) exponentially to a steady state level. The presence of C2H2 increased NH4+ release from burrows and changed the NO2− flux from a high release (∼300 nmol h−1) to an uptake (∼–30 nmol h−1). Nitrate uptake was independent of C2H2, presumably because overlying water NO3− concentration was high (∼100 μM). Indirect estimates of nitrification corresponded to the burrow release of NO2− without C2H2. Approximately half of the NO2− + NO3− uptake in burrows was due to denitrification. In microcosms with and without N. virens (875 m−2), denitrification was stimulated 3-fold by N. virens and the ratio denitrification/nitrification increased from 0.61 to 1.11. The changes in DIN flux and denitrification caused by N. virens corresponded well to the rates extrapolated from individual burrows to the appropriate worm density of 875 m−2. At the abundance used, N. virens burrows were responsible for 37% and 66% of the total sediment nitrification and denitrification, respectively