Intrinsic quadrupole moment of the nucleon

We address the question of the intrinsic quadrupole moment Q_0 of the nucleon in various models. All models give a positive intrinsic quadrupole moment for the proton. This corresponds to a prolate deformation. We also calculate the intrinsic quadrupole moment of the Delta(1232). All our models lead to a negative intrinsic quadrupole moment of the Delta corresponding to an oblate deformation.Comment: 17 pages, 5 figure

Particle image velocimetry measurements of blood flow in a modeled carotid artery bifurcation

Cardiovascular diseases are on of the leading causes of mortality and morbidity in the western world. Amongst these diseases, atherosclerosis, a progressive narrowing of the arterial wall is one of the most severe and if untreated may lead to stroke or ischemic infarction. Fluid mechanic forces are a key player in the early development and progression of atherosclerosis and a better understanding of the interplay between haemodynamic and vascular diseases is needed. The carotid artery (CA) in one of the predominant sites of atherosclerotic plaque formation. In this work a transparent, scaled model of an average human carotid artery (AHCA) bifurcation was constructed and steady blood flow at Re = 290 and Re = 700 was simulated using an aqueous glycerin solution. Particle Image Velocimetry (PIV) measurements were performed in the plane of bifurcation and three axial planes in the carotid sinus. Flow inside the CA bifurcation was found to be three-dimensional with strong secondary currents due to the curvature of the vessel. An accurate method for wall shear stress (WSS) calculation along the outer internal carotid artery (ICA) wall is introduced. The method was tested against synthetically generated particle images and was found to perform best for an 8x8 pix2 interrogation windows. A large low momentum flow region with low WSS along the outer ICA wall exists, posing the potential for atherosclerotic plaque formation. Calculated WSS ranged between 0 and 21. Pa and compared well with in-vivo data

Radiative decays of decuplet hyperons

We calculate the radiative decay widths of decuplet hyperons in a chiral constituent quark model including electromagnetic exchange currents between quarks. Exchange currents contribute significantly to the E2 transition amplitude, while they largely cancel for the M1 transition amplitude. Strangeness suppression of the radiative hyperon decays is found to be weakened by exchange currents. Differences and similarities between our results and other recent model predictions are discussed.Comment: 11 pages, 1 eps figure, revtex, accepted for publication in Phys. Rev.

Methodological tests of the use of trace elements as tracers to assess root activity

peer-reviewedN.J.H. was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments A, B and G were supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under the grant agreements FP7-266018 (AnimalChange) and FP7- 244983 (MultiSward). Experiment F was supported by the German Science Foundation (FOR 456).Background and aims There is increasing interest in how resource utilisation in grassland ecosystems is affected by changes in plant diversity and abiotic conditions. Research to date has mainly focussed on aboveground responses and there is limited insight into belowground processes. The aim of this study was to test a number of assumptions for the valid use of the trace elements caesium, lithium, rubidium and strontium as tracers to assess the root activity of several grassland species. Methods We carried out a series of experiments addressing the reliability of soil labelling, injection density, incubation time, application rate and the comparability of different tracers in a multiple tracer method. Results The results indicate that it is possible to achieve a reliable labelling of soil depths. Tracer injection density affected the variability but not the mean level of plant tracer concentrations. Tracer application rates should be based on pilot studies, because of site- and species-specific responses. The trace elements did not meet prerequisites to be used in a multiple tracer method. Conclusions The use of trace elements as tracers is potentially a very useful tool to give insight into plant root activity at different soil depths. This work highlights some of the main benefits and pitfalls of the method and provides specific recommendations to assist the design of tracer experiments and interpretation of the results.N.J.H. was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments A, B and G were supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under the grant agreements FP7-266018 (AnimalChange) and FP7- 244983 (MultiSward). Experiment F was supported by the German Science Foundation (FOR 456).European Unio

Airflow in a Domestic Kitchen Oven measured by Particle Image Velocimetry

Particle Image Velocimetry (PIV) was used to map the internal airflow of a domestic kitchen oven. Oven cooking performance is dependant on the airflow within the cavity. Previous flow measurement techniques such as hot wire anemometry and pitot probes are very time consuming and prone to error in the hot recirculating flow in an oven. The oven cavity, a commercially available mid-range oven, was modified for optical access. The PIV system consisted of a CCD camera, light sheet illumination from a pulsed Nd:YAG laser, and propanediol droplets and hollow glass spheres with a Stokes number of less than 0.055. Experiments were conducted in an empty oven at room temperature and at 180oC, and at 180oC with a single cooking tray installed. Velocity fields were measured in seven adjacent, coplanar object planes each on four different planes in the oven. The velocity data was averaged to yield mean flow fields, and the seven coplanar data fields were subsequently collaged to produce a full cross-sectional velocity map for each oven plane. In the cold and hot empty cavity a single vortex centred on the fan axis was seen, with strong radial flow. The maximum measured velocity in the cold oven was 1.8ms-1, which compared well with earlier hot-wire measurements. When a tray was introduced, the single vortex was replaced by three circulatory features. Shear flow was seen on both upper and lower sides of the tray, with a lower velocity and a stagnation point on the upper side

Electromagnetic N->Delta transition and neutron form factors

The C2/M1 ratio of the electromagnetic N->Delta(1232) transition, which is important for determining the geometric shape of the nucleon, is shown to be related to the neutron elastic form factor ratio G_C^n/G_M^n. The proposed relation holds with good accuracy for the entire range of momentum transfers where data are available.Comment: 4 pages, 2 figure

The Matter and the Pseudoscalar Densities in Lattice QCD

The matter and the pseudoscalar densities inside a hadron are calculated via gauge-invariant equal-time correlation functions. A comparison is made between the charge charge and the matter density distributions for the pion, the rho, the nucleon and the $\Delta^+$ within the quenched theory, and with two flavours of dynamical quarks.Comment: Typos corrected; 13 pages, 16 figure

Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

The terrestrial carbon (C) cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual), including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO<sub>2</sub> dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO<sub>2</sub> fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. A further part of the paper is dedicated to physical interactions between soil CO<sub>2</sub> and the soil matrix, such as CO<sub>2</sub> diffusion and dissolution processes within the soil profile. Finally, we highlight state-of-the-art stable isotope methodologies and their latest developments. From the presented evidence we conclude that there exists a tight coupling of physical, chemical and biological processes involved in C cycling and C isotope fluxes in the plant-soil-atmosphere system. Generally, research using information from C isotopes allows an integrated view of the different processes involved. However, complex interactions among the range of processes complicate or currently impede the interpretation of isotopic signals in CO<sub>2</sub> or organic compounds at the plant and ecosystem level. This review tries to identify present knowledge gaps in correctly interpreting carbon stable isotope signals in the plant-soil-atmosphere system and how future research approaches could contribute to closing these gaps