910 research outputs found

    Col. John Q. Wilds

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    Dry season foraging preferences of cattle and sheep in a communal area of South Africa.

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    We examined landscape and habitat (vegetation) scale foraging of cattle and sheep at two communal villages in the Eastern Cape, South Africa, to determine the key resources utilised during the dry season. At the landscape scale, cattle at both sites displayed overall preference for the arable lands at this time, although this diminished steadily as the dry season progressed. In contrast, sheep made considerably less use of these areas, showing only sporadic preference. At the vegetation scale, cattle demonstrated greatest preference for crop residues and uncultivated ‘commonage' areas, although foraging in grassland increased considerably in the latter stages of the dry season. Sheep utilised a much smaller range of vegetation types, preferring crop residues and fields that had been recently fallow and avoiding all other vegetation categories. We suggest that given the spatial limitations in planned, communal villages, the arable lands function as key resource areas for livestock during the dry season. It is recommended that management of these areas emphasise greater integration of sheep and cattle grazing and focus on maintaining vegetation heterogeneity in order to facilitate opportunistic ‘switching' in foraging patterns at different stages of the dry season.African Journal of Range & Forage Science 2007, 24(3): 109–12

    Dynamic Capabilities in Media Management Research: A Literature Review

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    Abstract Purpose – This study explores Dynamic Capabilities (DC) as one of the most prolific streams of research within the field of management and looks its applicability for media management research. Argumentation – It argues that reviewing the lineages of DC is a useful exercise for answering questions surrounding the fundamental change in the media industry, the challenges that media organizations and their managers are currently facing under the impact of digital change, and the theoretical grounding DC offers for media management scholars in understand the breadth and complexity of these challenges. Design/Methodology/Approach – This study uses a systematic reviewing methodology on DC in media management research. Findings – The study shows that DC help media research understand how media firms can best respond to changing environments. Research activity published from 2003 to 2019 in the field of media management has grown considerably. In the number of research papers related to the dynamic capabilities concept in the media management field between. Originality/Value – The study qualifies the validity of the DC framework in media management research and discusses conceptual bridges between the fields, its constituencies and perspectives

    A metalloproteomic analysis of interactions between plasma proteins and zinc: elevated fatty acid levels affect zinc distribution

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    Serum albumin is a highly abundant plasma protein associated with the transport of metal ions, pharmaceuticals, fatty acids and a variety of small molecules in the blood. Once thought of as a molecular ‘sponge’, mounting evidence suggests that the albumin-facilitated transport of chemically diverse entities is not independent. One such example is the transport of Zn2+ ions and non-esterified ‘free’ fatty acids (FFAs) by albumin, both of which bind at high affinity sites located in close proximity. Our previous research suggests that their transport in blood plasma is linked via an allosteric mechanism on serum albumin. In direct competition, albumin-bound FFAs significantly decrease the binding capacity of albumin for Zn2+, with one of the predicted consequences being a change in plasma/serum zinc speciation. Using liquid chromatography (LC), ICP-MS and fluorescence assays, our work provides a quantitative assessment of this phenomenon, and finds that in the presence of high FFA concentrations encountered in various physiological conditions, a significant proportion of albumin-bound Zn2+ is re-distributed amongst plasma/serum proteins. Using peptide mass fingerprinting and immunodetection, we identify candidate acceptor proteins for Zn2+ liberated from albumin. These include histidine-rich glycoprotein (HRG), a multifunctional protein associated with the regulation of blood coagulation, and members of the complement system involved in the innate immune response. Our findings highlight how FFA-mediated changes in extracellular metal speciation might contribute to the progression of certain pathological conditions

    Recent Advances in Metalloproteomics

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    Interactions between proteins and metal ions and their complexes are important in many areas of the life sciences, including physiology, medicine, and toxicology. Despite the involvement of essential elements in all major processes necessary for sustaining life, metalloproteomes remain ill-defined. This is not only owing to the complexity of metalloproteomes, but also to the non-covalent character of the complexes that most essential metals form, which complicates analysis. Similar issues may also be encountered for some toxic metals. The review discusses recently developed approaches and current challenges for the study of interactions involving entire (sub-)proteomes with such labile metal ions. In the second part, transition metals from the fourth and fifth periods are examined, most of which are xenobiotic and also tend to form more stable and/or inert complexes. A large research area in this respect concerns metallodrug–protein interactions. Particular attention is paid to separation approaches, as these need to be adapted to the reactivity of the metal under consideration.</p

    Solar Stereoscopy with STEREO/EUVI A and B spacecraft from small (6 deg) to large (170 deg) spacecraft separation angles

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    We performed for the first time stereoscopic triangulation of coronal loops in active regions over the entire range of spacecraft separation angles (αsep≈6∘,43∘,89∘,127∘\alpha_{sep}\approx 6^\circ, 43^\circ, 89^\circ, 127^\circ, and 170∘170^\circ). The accuracy of stereoscopic correlation depends mostly on the viewing angle with respect to the solar surface for each spacecraft, which affects the stereoscopic correspondence identification of loops in image pairs. From a simple theoretical model we predict an optimum range of αsep≈22∘−125∘\alpha_{sep} \approx 22^\circ-125^\circ, which is also experimentally confirmed. The best accuracy is generally obtained when an active region passes the central meridian (viewed from Earth), which yields a symmetric view for both STEREO spacecraft and causes minimum horizontal foreshortening. For the extended angular range of αsep≈6∘−127∘\alpha_{sep}\approx 6^\circ-127^{\circ} we find a mean 3D misalignment angle of μPF≈21∘−39∘\mu_{PF} \approx 21^\circ-39^\circ of stereoscopically triangulated loops with magnetic potential field models, and μFFF≈15∘−21∘\mu_{FFF} \approx 15^\circ-21^\circ for a force-free field model, which is partly caused by stereoscopic uncertainties μSE≈9∘\mu_{SE} \approx 9^\circ. We predict optimum conditions for solar stereoscopy during the time intervals of 2012--2014, 2016--2017, and 2021--2023.Comment: Solar Physics, (in press), 22 pages, 9 figure

    Angular dependence of the bulk nucleation field Hc2 of aligned MgB2 crystallites

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    Studies on the new MgB2 superconductor, with a critical temperature Tc ~ 39 K, have evidenced its potential for applications although intense magnetic relaxation effects limit the critical current density, Jc, at high magnetic fields. This means that effective pinning centers must be added into the material microstructure, in order to halt dissipative flux movements. Concerning the basic microscopic mechanism to explain the superconductivity in MgB2, several experimental and theoretical works have pointed to the relevance of a phonon-mediated interaction, in the framework of the BCS theory. Questions have been raised about the relevant phonon modes, and the gap and Fermi surface anisotropies, in an effort to interpret spectroscopic and thermal data that give values between 2.4 and 4.5 for the gap energy ratio. Preliminary results on the anisotropy of Hc2 have shown a ratio, between the in-plane and perpendicular directions, around 1.7 for aligned MgB2 crystallites and 1.8 for epitaxial thin films. Here we show a study on the angular dependence of Hc2 pointing to a Fermi velocity anisotropy around 2.5. This anisotropy certainly implies the use of texturization techniques to optimize Jc in MgB2 wires and other polycrystalline components.Comment: 10 pages + 4 Figs.; Revised version accepted in Phys. Rev.

    Advances in quadrupole and time-of-flight mass spectrometry for peptide MRM based translational research analysis

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    © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim The application of unit resolution tandem quadrupole and high-resolution orthogonal acceleration ToF mass spectrometers for the quantitation and translational analysis of proteolytic peptides is described. The MS platforms were contrasted in terms of sensitivity and linear response. Moreover, the selectivity of the platforms was investigated and the effect on quantitative precision studied. Chromatographic LC conditions, including gradient length and configuration, were investigated with respect to speed/throughput, while minimizing isobaric interferences, thereby providing information with regard to practical sample cohort size limitations of LC-MS for large cohort experiments. In addition to these fundamental analytical performance metrics, precision and linear dynamic ranges were also studied. An LC-MS configuration that encompasses the best combination of throughput and analytical accuracy for translational studies was chosen, despite the MS platforms giving similar quantitative performance, and instances were identified where alternative combinations were found to be beneficial. This configuration was utilized to demonstrate that proteolytically digested nondepleted samples from heart failure patients could be classified with good discriminative power using a subset of proteins previously suggested as candidate biomarkers for cardiovascular diseases
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