Abstract
The abundance and distribution of
44
Ti tells us about the nature of the core-collapse supernovae explosions. There is a need to understand the nuclear reaction network creating and ...destroying
44
Ti in order to use it as a probe for the explosive mechanism. The
44
Ti(
α, p
)
47
V reaction is a very important reaction and it controls the destruction of
44
Ti. Difficulties with direct measurements have led to an attempt to study this reaction indirectly. Here, the first step of the indirect study which is the identification of levels of the compound nucleus
48
Cr is presented. A 100-MeV proton beam was incident on a
50
Cr target. States in
48
Cr were populated in the
50
Cr(
p, t
)
48
Cr reaction. The tritons were momentum-analysed in the K600 Q2D magnetic spectrometer at iThemba LABS.
Experiments investigating the fine structure of the IsoScalar Giant Monopole Resonance (ISGMR) of 48Ca were carried out with a 200 MeV alpha inelastic-scattering reaction, using the high ...energy-resolution capability and the zero-degree setup at the K600 magnetic spectrometer of iThemba LABS, Cape Town, South Africa. Considerable fine structure is observed in the energy region of the ISGMR. Characteristic energy scales are extracted from the experimental data by means of a wavelet analysis and compared with the state-of-the-art theoretical calculations within a Skyrme-RPA (random phase approximation) approach using the finite-rank separable approximation with the inclusion of phonon-phonon coupling (PPC). Good agreement was observed between the experimental data and the theoretical predictions.
Peatlands store substantial amounts of carbon and are vulnerable to climate change. We present a modified version of the Organising Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE) land surface ...model for simulating the hydrology, surface energy, and CO2 fluxes of peatlands on daily to annual timescales. The model includes a separate soil tile in each 0.5∘ grid cell, defined from a global peatland map and identified with peat-specific soil hydraulic properties. Runoff from non-peat vegetation within a grid cell containing a fraction of peat is routed to this peat soil tile, which maintains shallow water tables. The water table position separates oxic from anoxic decomposition. The model was evaluated against eddy-covariance (EC) observations from 30 northern peatland sites, with the maximum rate of carboxylation (Vcmax) being optimized at each site. Regarding short-term day-to-day variations, the model performance was good for gross primary production (GPP) (r2= 0.76; Nash–Sutcliffe modeling efficiency, MEF = 0.76) and ecosystem respiration (ER, r2= 0.78, MEF = 0.75), with lesser accuracy for latent heat fluxes (LE, r2= 0.42, MEF = 0.14) and and net ecosystem CO2 exchange (NEE, r2= 0.38, MEF = 0.26). Seasonal variations in GPP, ER, NEE, and energy fluxes on monthly scales showed moderate to high r2 values (0.57–0.86). For spatial across-site gradients of annual mean GPP, ER, NEE, and LE, r2 values of 0.93, 0.89, 0.27, and 0.71 were achieved, respectively. Water table (WT) variation was not well predicted (r2 < 0.1), likely due to the uncertain water input to the peat from surrounding areas. However, the poor performance of WT simulation did not greatly affect predictions of ER and NEE. We found a significant relationship between optimized Vcmax and latitude (temperature), which better reflects the spatial gradients of annual NEE than using an average Vcmax value.
Background: Serotonin, a key denominator of the brain-gut axis, is involved in the regulation of gastrointestinal motility, secretion, and perception as well as cognition and mood. Aim: To assess the ...effects of an acutely lowered serotonin synthesis, using the acute tryptophan depletion (ATD) method, on visceral perception, affective memory performance, and mood in diarrhoea predominant irritable bowel syndrome patients (d-IBS) and controls. Methods: In a randomised, double blind, crossover design, 14 d-IBS patients and fourteen matched controls were studied under ATD and placebo conditions, respectively. Perception of urge and pain was scored during rectal distensions. Affective memory performance, mood, and biochemical parameters of serotonergic metabolism were simultaneously assessed. Results: ATD significantly decreased plasma tryptophan (67.0 (2.0) v 24.9 (2.0) μmol/l) and 5-hydroxyindole acetic acid concentrations (29.9 (1.0) v 15.8 (0.6) nmol/l). ATD was associated with significantly increased urge scores specifically in the lower pressure range and overall increased pain scores. ATD significantly lowered the perceptual threshold for first perception compared with placebo (patients 10.6 (1.2) v 13.6 (0.8) mm Hg, controls 12.6 (1.3) v 15.7 (1.2) mm Hg) but not for maximal tolerable discomfort (patients 50.5 (3.6) v 51.6 (3.3) mm Hg, controls 50.9 (3.3) v 48.8 (2.9) mm Hg). ATD induced a significant shift in affective memory bias towards preferential loss of positive material but no significant changes in mood. ATD did not differentially affect the patient or control group. Conclusions: We have provided evidence that serotonergic modulation by ATD affects both visceral perception as well as cognition in d-IBS and controls. Simultaneous measurement of brain and gut function and the application of ATD contribute to the elucidation of the complex pathophysiology of IBS.
Several radionuclide production facilities based on a new generation of high-current, 70 MeV H
cyclotrons have been established in recent years and a number of new facilities are either under ...construction or being planned. In this study, the feasibility to produce
Ac/
Bi and
U/
Th generators via Th + p reactions at such a facility has been investigated. From the perspective of production yields, it has been found useful to compare the relevant reactions on thorium with those on other targets regularly employed in this energy region, in particular the
Mg(p,x)
Na,
Ga(p,x)
Ge, and
Rb(p,x)
Sr reactions that have been exploited with 66 MeV proton beams at iThemba LABS for many years. Therefore, various tandem configurations of thorium with magnesium, gallium and rubidium are discussed based on the relevant nuclear data. In a few cases, the available data were judged to be insufficient in this energy region. New experimental cross sections are presented for
Ac,
Ra, and
Pa in Th + p reactions as well as
Na in
Mg + p reactions. Integral yields have been derived for those radionuclides of main interest. Production yields expected from extended 70 MeV proton bombardments, on selected tandem-target configurations, are presented for
Na,
Ge,
Sr,
Ac, and
Pa. It is concluded that
Ac/
Bi generators can, in principle, be added to a production programme based at a 70 MeV H
cyclotron facility as the production rate is of similar magnitude to those of other well-established radionuclides in this energy region. Also, radio-contaminant levels for
Ac are similar to those found in higher proton-energy windows. The scope for
U/
Th generators, via bulk production of the precursor
Pa, seems to be more limited due to a lower yield but can nevertheless be produced in clinically relevant quantities.
Here, the large-scale production of 88Y with proton-induced reactions has been investigated from the perspective of new generation 70 MeV H – cyclotrons. Tandem target configurations are presented ...for both the direct production of 88Y as well as for producing 88Zr/88Y generators. Based on the relevant excitation functions, physical yields have been derived for 88Y production with Y2O3/SrCO3 tandem targets and 88Zr production with Zr/Y2O3 tandem targets. Yields are presented for optimized targets (i.e. optimum yield) as well as for balanced thermal loads on the individual targets. Liquid 88Zr/88Y generators have been produced using both natural Zr and Nb target materials, the former for dedicated productions and the latter as a byproduct by processing spent irradiated Nb capsules which normally would constitute radioactive waste. These stock solutions, which contain both the target material and 88Zr precursor, are retained virtually unchanged after processing except for the removal of 88Y on AG MP-50 macroporous cation-exchange resin. Methods are presented for the preparation of Nb stock solutions in hydrofluoric acid and Zr stock solutions in sulfuric acid. It is shown that multi-Ci productions of 88Y are feasible at a 70 MeV cyclotron facility, suitable for the needs of fracking applications. In addition, 88Zr/88Y generators can provide 88Y with very high specific activity, suitable for labelling of biomolecules.
Proton inelastic scattering experiments at energy Ep=200 MeV and a spectrometer scattering angle of 0° were performed on 144,146,148,150Nd and 152Sm exciting the IsoVector Giant Dipole Resonance ...(IVGDR). Comparison with results from photo-absorption experiments reveals a shift of resonance maxima towards higher energies for vibrational and transitional nuclei. The extracted photo-absorption cross sections in the most deformed nuclei, 150Nd and 152Sm, exhibit a pronounced asymmetry rather than a distinct double-hump structure expected as a signature of K-splitting. This behaviour may be related to the proximity of these nuclei to the critical point of the phase shape transition from vibrators to rotors with a soft quadrupole deformation potential. Self-consistent random-phase approximation (RPA) calculations using the SLy6 Skyrme force provide a relevant description of the IVGDR shapes deduced from the present data.
Massive amounts of Saharan dust are blown from the coast of northern Africa across the Atlantic Ocean towards the Americas each year. This dust has, depending on its chemistry, direct and indirect ...effects on global climate which include reflection and absorption of solar radiation as well as transport and deposition of nutrients and metals fertilizing both ocean and land. To determine the temporal and spatial variability of Saharan dust transport and deposition and their marine environmental effects across the equatorial North Atlantic Ocean, we have set up a monitoring experiment using deep-ocean sediment traps as well as land-based dust collectors. The sediment traps were deployed at five ocean sites along a transatlantic transect between north-west Africa and the Caribbean along 12° N, in a downwind extension of the land-based dust collectors placed at 19° N on the Mauritanian coast in Iouîk. In this paper, we lay out the setup of the monitoring experiment and present the particle fluxes from sediment trap sampling over 24 continuous and synchronized intervals from October 2012 through to November 2013. We establish the temporal distribution of the particle fluxes deposited in the Atlantic and compare chemical compositions with the land-based dust collectors propagating to the downwind sediment trap sites, and with satellite observations of Saharan dust outbreaks. First-year results show that the total mass fluxes in the ocean are highest at the sampling sites in the east and west, closest to the African continent and the Caribbean, respectively. Element ratios reveal that the lithogenic particles deposited nearest to Africa are most similar in composition to the Saharan dust collected in Iouîk. Downwind increasing Al, Fe and K contents suggest a downwind change in the mineralogical composition of Saharan dust and indicate an increasing contribution of clay minerals towards the west. In the westernmost Atlantic Ocean, admixture of re-suspended clay-sized sediments advected towards the deep sediment trap cannot be excluded. Seasonality is most prominent near both continents but generally weak, with mass fluxes dominated by calcium carbonate and clear seasonal maxima of biogenic silica towards the west. The monitoring experiment is now extended, with autonomous dust sampling buoys for better quantification of Saharan dust transport and deposition from source to sink and their impact on fertilization and carbon export to the deep ocean.
The rising incidence of inflammatory bowel disease (IBD) since the Second World War coincides with profound changes of the dietary pattern. The aim of the study was to investigate the possible ...pathogenic role of some characteristic 'modern life' dietary factors in IBD.
Case-control, studying risk factors in recently diagnosed cases, 290 with Crohn's disease and 398 with ulcerative colitis, compared with 616 population controls. Smoking, age, gender and education were taken into account by using logistic regression analysis.
Hospital cases and population controls.
Questionnaires.
Logistic regression-derived odds ratios.
A positive association with cola drinks OR: 2.2 (95% CI 1.5-3.1), chewing gum OR: 1.5 (95% CI: 1.1-2.1) and chocolate consumption OR: 2.5 (95% CI: 1.8-3.5) and a negative association with citrus fruit consumption OR: 0.5 (95% CI 0.3-0.7) and the development of Crohn's disease were found. Consumption of cola drinks OR: 1.6 (95% CI 1.1-2.3) and chocolate consumption OR: 2.5 (95% CI 1.8-3.5) were positively associated with developing ulcerative colitis. There was a negative association between the intake of citrus fruits OR: 0.5 (95% CI 0.4-0.8) and 'having a stuffed pet' for a period longer than 5 years OR: 0.6 (95% CI 0.4-0.9) and developing the disorder. No association with the frequency of tooth brushing and developing IBD was found.
All the nutritional items mentioned may be true risk factors or they just might be the expression of a modern life-style also involving other risk factors for the development of IBD which at the present are still unknown.
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