Background: Inelastic proton scattering at energies of a few hundred MeV and very-forward angles including \(0^\circ\) has been established as a tool to study electric-dipole strength distributions ...in nuclei. The present work reports a systematic investigation of the chain of stable even-mass Nd isotopes representing a transition from spherical to quadrupole-deformed nuclei. Purpose: Extraction of the equivalent photo-absorption cross sections and analysis of their fine structure in the energy region of the IsoVector Giant Dipole Resonance (IVGDR). Method: Proton inelastic scattering reactions of 200 MeV protons were measured at iThemba LABS in Cape Town, South Africa. The scattering products were momentum-analysed by the K600 magnetic spectrometer positioned at \(\theta_{\mathrm{Lab}}=0^\circ\). Using dispersion-matching techniques, energy resolutions of \(\Delta E \approx 40 - 50\) keV were obtained. After subtraction of background and contributions from other multipoles, the spectra were converted to photo-absorption cross sections using the equivalent virtual-photon method. Results: Wavelet-analysis techniques are used to extract characteristic energy scales of the fine structure of the IVGDR from the experimental data. Comparisons with the Quasiparticle-Phonon Model (QPM) and Skyrme Separable Random Phase Approximation (SSRPA) predictions provide insight into the role of different giant resonance damping mechanisms. Conclusions: Fine structure is observed even for the most deformed nuclei studied. Fragmentation of the one particle-one hole (\(1p1h\)) strength seems to be the main source of fine structure in both spherical and deformed nuclei. Some impact of the spreading due to coupling of the two particle-two hole (\(2p2h\)) states to the \(1p1h\) doorway states is seen in the spherical/transitional nuclei, where calculations beyond the \(1p1h\) level are available.
Peatlands are poorly represented in global Earth system modeling frameworks. Here we add a peatland‐specific land surface hydrology module (PEAT‐CLSM) to the Catchment Land Surface Model (CLSM) of ...the NASA Goddard Earth Observing System (GEOS) framework. The amended TOPMODEL approach of the original CLSM that uses topography characteristics to model catchment processes is discarded, and a peatland‐specific model concept is realized in its place. To facilitate its utilization in operational GEOS efforts, PEAT‐CLSM uses the basic structure of CLSM and the same global input data. Parameters used in PEAT‐CLSM are based on literature data. A suite of CLSM and PEAT‐CLSM simulations for peatland areas between 40°N and 75°N is presented and evaluated against a newly compiled data set of groundwater table depth and eddy covariance observations of latent and sensible heat fluxes in natural and seminatural peatlands. CLSM's simulated groundwater tables are too deep and variable, whereas PEAT‐CLSM simulates a mean groundwater table depth of −0.20 m (snow‐free unfrozen period) with moderate temporal fluctuations (standard deviation of 0.10 m), in significantly better agreement with in situ observations. Relative to an operational CLSM version that simply includes peat as a soil class, the temporal correlation coefficient is increased on average by 0.16 and reaches 0.64 for bogs and 0.66 for fens when driven with global atmospheric forcing data. In PEAT‐CLSM, runoff is increased on average by 38% and evapotranspiration is reduced by 19%. The evapotranspiration reduction constitutes a significant improvement relative to eddy covariance measurements.
Plain Language Summary
Peatlands are wetlands in which plant matter has accumulated over thousands of years under almost permanently water‐logged conditions. Alterations in these conditions as a result of global climate change can lead to the release of the huge peatland carbon pool as carbon dioxide over much shorter timescales than were required for accumulation. The additional emissions would amplify global warming. A better representation of the peatland hydrology in global Earth system models can help quantify how peatlands respond to a changing climate. In this paper, we add a peatland‐specific land surface hydrology module to the land surface model used in NASA's GEOS Earth system modeling framework. Comparisons of numerical simulations encompassing northern peatlands against field observations show that the new model version significantly improves our ability to capture the hydrological dynamics of peatlands. The new peatland representation in GEOS offers new opportunities, including the potential for merging model information and remote sensing observations in a way that improves our understanding of the overall role played by peatlands in the global water and carbon cycles.
Key Points
A peatland‐specific land surface hydrology was added to an Earth system model and constrained by literature data, without parameter tuning
Simulations were evaluated with a data set of groundwater table depth and evapotranspiration with unprecedented coverage in high latitudes
The peatland model version performs significantly better in terms of hydrological variables over peatlands than the operational model
Background: Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder that is frequently seen in gastroenterological practice. Population-based studies have shown that at any point in ...time IBS symptoms are present in about 3%-22% of the general Western population. In general practice, half of all new patients have functional disorders and IBS is responsible for about five consultations per week. General practitioners (GPs) manage the majority of IBS patients, but most knowledge (and research) is based on the smaller percentage of patients managed in secondary care. There is a paucity of literature on differences or similarities between these two groups with regard to clinical characteristics or diagnostic approach. Methods: The literature published in English about IBS in general practice was reviewed. Conclusions: Irritable bowel syndrome is frequently encountered in primary care. Primary care IBS patients, compared to secondary care patients, are likely to be young, female and to have less severe symptoms. But this is only true for some symptoms; for example, non-abdominal complaints are equally reported in both groups. The disorder can be diagnosed safely using internationally agreed symptom-based criteria, such as the Rome II criteria. Additional diagnostic measures will be necessary to support the diagnosis in only a minority of situations. Many primary care IBS patients can be managed given adequate reassurance and education, frequently without additional pharmacological treatment.
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.
Previous studies had shown that the integration of genome wide expression profiles, in metabolic tissues, with genetic and phenotypic variance, provided valuable insight into the underlying molecular ...mechanisms. We used RNA-Seq to characterize hypothalamic transcriptome in 99 inbred strains of mice from the Hybrid Mouse Diversity Panel (HMDP), a reference resource population for cardiovascular and metabolic traits. We report numerous novel transcripts supported by proteomic analyses, as well as novel non coding RNAs. High resolution genetic mapping of transcript levels in HMDP, reveals both
and
expression Quantitative Trait Loci (eQTLs) demonstrating 2
eQTL 'hotspots' associated with expression of hundreds of genes. We also report thousands of alternative splicing events regulated by genetic variants. Finally, comparison with about 150 metabolic and cardiovascular traits revealed many highly significant associations. Our data provide a rich resource for understanding the many physiologic functions mediated by the hypothalamus and their genetic regulation.
Fermentation of dietary fiber in the colon results in the production of short chain fatty acids (mainly propionate, butyrate and acetate). Butyrate modulates a wide range of processes, but its ...mechanism of action is mostly unknown. This study aimed to determine the effects of butyrate on the transcriptional regulation of human colonic mucosa in vivo.
Five hundred genes were found to be differentially expressed after a two week daily butyrate administration with enemas. Pathway analysis showed that the butyrate intervention mainly resulted in an increased transcriptional regulation of the pathways representing fatty acid oxidation, electron transport chain and oxidative stress. In addition, several genes associated with epithelial integrity and apoptosis, were found to be differentially expressed after the butyrate intervention.
Colonic administration of butyrate in concentrations that can be achieved by consumption of a high-fiber diet enhances the maintenance of colonic homeostasis in healthy subjects, by regulating fatty acid metabolism, electron transport and oxidative stress pathways on the transcriptional level and provide for the first time, detailed molecular insight in the transcriptional response of gut mucosa to butyrate.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A sample of goethite was mixed for periods which ranged from 2 hours to 8 weeks with solutions of dilute nitrate salts of Pb, Hg, Cd, Zn, Cu, Ni, Co, Mn, Cr and Al. The amount of sorption after each ...period was measured for an appropriate pH range for each metal. The sorption behaviour was characterized both by using characteristics of the sorption curves such as the pH at which half of the added metal was sorbed (pH₅₀) and by fitting a model in which sorption was mainly characterized by an affinity constant and by a diffusion constant. Initial sorption, whether characterized by the pH₅₀ or by the affinity constant, was closely correlated with the appropriate dissociation constants of the metals. The greater the affinity of the metals for hydroxide ions, the greater their affinity for the goethite surface. The metals differed in the rate at which they continued to react with the goethite. Lead had the slowest continuing reaction, cobalt the fastest. The continuing reaction was due to diffusion into the particles. It was characterized by the fitted diffusion constant and by the change with time in the pH₅₀. For seven of the eight divalent metals, these were correlated with the ionic radius of the metals: the larger the radius, the slower the reaction. For Al and Cr, rates were slower than would be expected from the ionic radii and we suggest this shows that these ions react as the larger M(OH)²⁺ ions. The behaviour of Ni was consistent with oxidation of the surface species and diffusion of Ni(OH)²⁺ ions. The continuing reaction was similar to that observed when metal ions react with soils and suggests that their reaction with iron oxides is important in soils. The results also show that studies in which sorption is measured at only one period of reaction are incomplete and the application of equilibrium models to such results is misleading.
The \(^{22}\)Ne(\(\alpha,n\))\(^{25}\)Mg reaction is an important source of neutrons for the s-process. Due to the difficulty in directly measuring the cross section of this reaction and the ...competing \(^{22}\)Ne(\(\alpha,\gamma\))\(^{26}\)Mg reaction, indirect methods are frequently used to try to instead calculate the relevant reaction rates. Uncertainty, however, persists in the number and properties of the pertinent excited states of \(^{26}\)Mg. In this paper, the results of proton and deuteron scattering from \(^{26}\)Mg are presented, giving a list of levels in \(^{26}\)Mg. In addition, level assignments in \(^{26}\)Mg are discussed, including some possible changes to the previously accepted assignments in \(^{26}\)Mg.
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