Gauge dependence of calculations in relativistic Coulomb excitation

Before a quantum-mechanical calculation involving electromagnetic interactions is performed, a choice must be made of the gauge to be used in expressing the potentials. If the calculation is done exactly, the observable results it predicts will be independent of the choice of gauge. However, in most practical calculations approximations are made, which can destroy the gauge invariance of the predictions. We compare here the results of coupled-channel time-dependent relativistic Coulomb excitation calculations, as performed in either Lorentz or Coulomb gauges. We find significant differences when the bombarding energy per nucleon is $\geq$ 2 GeV, which indicates that the common practice of relying completely on the Lorentz gauge can be dangerous.Comment: 23 pages, 3 figure

A dataset of tracer concentrations and meteorological observations from the Bolzano Tracer EXperiment (BTEX) to characterize pollutant dispersion processes in an Alpine valley

Abstract. The paper describes the dataset of concentrations and related meteorological measurements collected during the field campaign of the Bolzano Tracer Experiment (BTEX). The experiment was performed to characterize the dispersion of pollutants emitted from a waste incinerator in the basin of the city of Bolzano, in the Italian Alps. As part of the experiment, two controlled releases of a passive gas tracer (sulfur hexafluoride, SF6) were performed through the stack of the incinerator on 14 February 2017 for two different time lags, starting, respectively, at 07:00 and 12:45 LST. Samples of ambient air were collected at target sites with vacuum-filled glass bottles and polyvinyl fluoride bags, and they were later analyzed by means of a mass spectrometer (detectability limit 30 pptv). Meteorological conditions were monitored by a network of 15 surface weather stations, 1 microwave temperature profiler, 1 sodar and 1 Doppler wind lidar. The dataset represents one of the few examples available in the literature concerning dispersion processes in a typical mountain valley environment, and it provides a useful benchmark for testing atmospheric dispersion models in complex terrain. The dataset described in this paper is available at https://doi.org/10.1594/PANGAEA.898761 (Falocchi et al., 2019)

A WARM CONVEYOR BELT MECHANISM ACCOMPANYING EXTREME PRECIPITATION EVENTS OVER NORTH-EASTERN ITALY

A Lagrangian methodology for the reconstruction and the analysis of the airstreams governing the transport of water vapour has been applied to analyse three recent extreme precipitation events over the Alps (3-5 November 1966, 16-18 November 2000 and 24-26 November 2002). The analysis outlines that the precipitation over the North-East of Italy is strongly conditioned by the evaporation rate and by properties of airmasses over the Central Mediterranean area. In particular most of the water vapour contributing to the precipitation ending over the Alps originates over Tunisia, the coastal regions in the western Lybia, the Channel of Sicilia, the Gulf of Gabes and the southerly Thyrrenian Sea. A simplified conceptual model is also proposed to visualize the traits of the moist airstreams inside the Mediterranean cyclones. Two patterns of airstreams can be identified, according to the scheme proposed by Browning and Roberts, 1994. The trajectory population of the two portions of WCB is a crucial factor controlling the precipitation production

Coulomb Excitation of Multi-Phonon Levels of the Giant Dipole Resonance

A closed expression is obtained for the cross-section for Coulomb excitation of levels of the giant dipole resonance of given angular momentum and phonon number. Applications are made to the Goldhaber-Teller and Steinwedel-Jensen descriptions of the resonance, at non-relativistic and relativistic bombarding energies.Comment: 16 pages, 5 figure

Quantum derivation of the use of classical electromagnetic potentials in relativistic Coulomb excitation

We prove that a relativistic Coulomb excitation calculation in which the classical electromagnetic field of the projectile is used to induce transitions between target states gives the same target transition amplitudes, to all orders of perturbation theory, as would a calculation in which the interaction between projectile and target is mediated by a quantized electromagnetic field.Comment: 1 .zip file containing LaTex source plus three figures as .eps file

Movement behaviour and mortality in invasive and indigenous mussels: resilience and resistance strategies at different spatial scales

The responses of indigenous and exotic species to environmental factors can differ across spatial and temporal scales, and it is this difference that determines invasion success and the dynamics of co-existence, In South Africa, the indigenous Perna perna and the invasive Mytilus galloprovincialis are the dominant intertidal mussels on the southern coast, where they co-exist. We compared their movement behaviour over 6 mo at small scales (within and at the edge of mussel beds) and at meso scales (in bays and on the open coast). M, galloprovincialis moved more and had higher mortality rates than did P. perna. For both species, mortality was greater at the edge than at the centre of beds, and on the open coast than in bays. Mussels at the edge of beds moved more than those within beds, but, while this was true for M. galloprovincialis in both habitats, P. perna did not show a position effect on the open coast. Cross-correlation analysis showed that movement rates of both species were correlated with mortality rates after a lag of 1. mo. These results suggest that following mortality events, mussels react to increased availability of space and decreased attachment to neighbours by increasing their movement to reorganise into a safer arrangement. However, P. perna and M. galloprovincialis effectively adopt resistance and resilience strategies, respectively. The effectiveness of each strategy depends on environmental conditions in different habitats, influencing the possibility of co-existence. The higher hydrodynamic stresses experienced in open coast habitats and at the edge of a mussel bed are disadvantageous to the more active, less strongly attached invasive species.Claude Harris Leon Foundation; Rhodes University; National Research Foundation of South Afric

LATE FROST EVENTS IN AN ALPINE VALLEY: MEASUREMENTS AND CHARACTERISATION OF THE PROCESS

Under the research project GEPRI, aimed at investigating and characterizing late frost events potentiallydangerous for cultivated areas, in the spring of 2004 an intensive meteorological field experiment has been made in the Adige River Valley in Trentino (Northern Italy). The project is aimed at a better characterization of the mechanism of late frost events in complex topography in order to improve the forecast of the occurrence of nocturnal temperature minima. In this work some preliminary results of the micrometeorological measurements performed at a target area within an appletrees orchard are presented and discussed. Measurements allowed the determination of the complete energy balance, as well as the identification of specific local-scale circulations which appear to be relevant in characterizing the night-time cooling process. In case of fair weather conditions, the latter displays a sequence of at least four different phases which seem to alternate rather than superimpose advective- and radiative-effects

Biogeographical patterns of endolithic infestation in an invasive and an indigenous intertidal marine ecosystem engineer

By altering the phenotypic properties of their hosts, endolithic parasites can modulate the engineering processes of marine ecosystem engineers. Here, we assessed the biogeographical patterns of species assemblages, prevalence and impact of endolithic parasitism in two mussel species that act as important ecosystem engineers in the southern African intertidal habitat, Perna perna and Mytilus galloprovincialis. We conducted large-scale surveys across three biogeographic regions along the South African coast: the subtropical east coast, dominated by the indigenous mussel, P. perna, the warm temperate south coast, where this species coexists with the invasive Mediterranean mussel, M. galloprovincialis, and the cool temperate west coast dominated by M. galloprovincialis. Infestation increased with mussel size, and in the case of M. galloprovincialis we found a significantly higher infestation in the cool temperate bioregion than the warm temperate region. For P. perna, the prevalence of infestation was higher on the warm temperate than the subtropical region, though the difference was marginally non-significant. On the south coast, there was no significant difference in infestation prevalence between species. Endolith-induced mortality rates through shell collapse mirrored the patterns for prevalence. For P. perna, endolith species assemblages revealed clear grouping by bioregions. Our findings indicate that biogeography affects cyanobacteria species composition, but differences between biogeographic regions in their effects are driven by environmental conditions.Agência financiadora Número do subsídio Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) UID/Multi/04326/2019 IF/01413/2014/CP1217/CT0004 South African Research Chairs Initiative (SARChI) of the Department of Science and Technology National Research Foundationinfo:eu-repo/semantics/publishedVersio

Development of a measurement platformon a light airplane and analysis of airborne measurementsin the atmospheric boundary layer

In the present paper we provide an overview of a long term research project aimed at setting up a suitable platform for measurements in the atmospheric boundary layer on a light airplane along with some preliminary results obtained from fi eld campaigns at selected sites. Measurements of air pressure, temperature and relative humidity have been performed in various Alpine valleys up to a height of about 2500 m a.m.s.l. By means of GPS resources and specifi c post-processing procedures careful positioning of measurement points within the explored domain has been achieved. The analysis of collected data allowed detailed investigation of atmospheric vertical structures and dynamics typical of valley environment, such as morning transition from ground based inversion to fully developed well mixed convective boundary layer. Based on data collected along fl ights, 3D fi elds of the explored variables have been detected and identifi ed through application of geostatistical techniques (Kriging). The adopted procedures allowed evaluation of the intrinsic statistical structure of the spatial distribution of measured quantities and the estimate of the values of the same variable at unexplored locations by suitable weighted average of data recorded at close locations. Results thus obtained are presented and discussed

MONTHLY ISOTOPIC SIGNAL OF THE PRECIPITATED WATER IN THE PROVINCE OF TRENTO: LAGRANGIAN ANALYSIS AND DISCUSSION OF MEASUREMENTS

The present work has been performed in the framework of the research project AQUAPAST. The main focus of AQUAPAST is the reconstruction of past climate changes in the atmospheric circulation and in particular in the water vapour transport mechanism over the Mediterranean area starting from the analysis of the isotopic content of cave speleothemes in the Trentino Province (North-East of Italy). A Lagrangian methodology for the reconstruction and the analysis of the airstreams which govern the transport of water vapour has been applied to recent events. The average monthly isotopic signal of the precipitation water sampled in stations located in key geographic settings in the Province of Trento is used as tracer to infer the origin of the precipitating water and to validate the Lagrangian analysis. A comparison between the isotopic signal of November 2002 and November 2003 is here presented, as most of the yearly precipitation falls in November over the Eastern Alps. Hypotheses are proposed about the meteorological factors (e.g. monthly averaged sea surface temperature, atmospheric circulation, etc.) determining different isotopic signals in the two years