Flow carbonylation of sterically hindered ortho-substituted iodoarenes

The flow synthesis of ortho-substituted carboxylic acids, using carbon monoxide gas, has been studied for a number of substrates. The optimised conditions make use of a simple catalyst system compromising of triphenylphosphine as the ligand and palladium acetate as the pre-catalyst. Carbon monoxide was introduced via a reverse “tube-in-tube” flow reactor at elevated pressures to give yields of carboxylated products that are much higher than those obtained under normal batch conditions

Catalytic Chan–Lam coupling using a ‘tube-in-tube’ reactor to deliver molecular oxygen as an oxidant

A flow system to perform Chan–Lam coupling reactions of various amines and arylboronic acids has been realised employing molecular oxygen as an oxidant for the re-oxidation of the copper catalyst enabling a catalytic process. A tube-in-tube gas reactor has been used to simplify the delivery of the oxygen accelerating the optimisation phase and allowing easy access to elevated pressures. A small exemplification library of heteroaromatic products has been prepared and the process has been shown to be robust over extended reaction times

Self-consistent description of nuclear compressional modes

Isoscalar monopole and dipole compressional modes are computed for a variety of closed-shell nuclei in a relativistic random-phase approximation to three different parametrizations of the Walecka model with scalar self-interactions. Particular emphasis is placed on the role of self-consistency which by itself, and with little else, guarantees the decoupling of the spurious isoscalar-dipole strength from the physical response and the conservation of the vector current. A powerful new relation is introduced to quantify the violation of the vector current in terms of various ground-state form-factors. For the isoscalar-dipole mode two distinct regions are clearly identified: (i) a high-energy component that is sensitive to the size of the nucleus and scales with the compressibility of the model and (ii) a low-energy component that is insensitivity to the nuclear compressibility. A fairly good description of both compressional modes is obtained by using a ``soft'' parametrization having a compression modulus of K=224 MeV.Comment: 28 pages and 10 figures; submitted to PR

Xanthomonas Wilt of banana drives changes in land-use and ecosystem services across Infected landscapes

Changes in land-use have been observed in banana-based systems in the African Great Lakes region affected by Xanthomonas wilt disease (XW) of banana. Through focus group discussions (FGDs) and the 4-cell method (to map the area under production and the number of households involved), changes in land-use were assessed in 13 XW-affected landscapes/villages along a 230 km transect from Masisi (where XW arrived in 2001) to Bukavu (XW arrived around 2014) in the Eastern Democratic Republic of Congo. Farmers’ perceptions on the sustainability of new land uses were also documented. Soil nutrient content and erosion levels were measured for five major land-use options/trajectories on 147 fields across 55 farms in three landscapes along the transect. From banana being ranked the most important crop (92% of landscapes) before XW outbreaks, its importance had declined, with it grown on smaller farms by most households in 36% of the landscapes, while in 64% of cases by few households on smaller plots. Farmers uprooted entire banana mats or fields, expanding land under other crops. Species richness did not change at landscape level, although 21 crops were introduced at farm level. Banana is, however, still perceived as more sustainable due to its multi-functional roles. Soils under banana had better chemical attributes, while high erosion levels (Mg ha−1 year−1) occurred under cassava (1.7–148.9) compared with banana (0.3–10.7) and trees (0.3–5.9). The shifts from banana could thus affect supply of key services and sustainability of the farming systems. This study offers a good basis for interventions in XW-affected landscapes

The neutron radii of Lead and neutron stars

A new relation between the neutron skin of a heavy nucleus and the radius of a neutron star is proposed: the larger the neutron skin of the nucleus the larger the radius of the star. Relativistic models that reproduce a variety of ground-state observables can not determine uniquely the neutron skin of a heavy nucleus. Thus, a large range of neutron skins is generated by supplementing the models with nonlinear couplings between isoscalar and isovector mesons. We illustrate how the correlation between the neutron skin and the radius of the star can be used to place important constraints on the equation of state and how it may help elucidate the existence of a phase transition in the interior of the neutron star.Comment: 4 pages including 4 encapsulated postscript figure

Responding to future regime shifts with agrobiodiversity: A multi-level perspective on small-scale farming in Uganda

We analyse the impact of two large-scale regime shifts caused by disease incidence or climate change, and associated crop productivity and price changes, on banana-based smallholders in Uganda. We evaluate these farmers' vulnerability and assess the potential of using increased crop diversity to improve their resilience. We further explore trade-offs and synergies between environmental, economic and nutritional outcomes faced by the farmers in their decision making when a regime shift occurs. We simulate the large-scale scenarios with the IMPACT model and use the results obtained to assess their effect at the local level using the bio-economic farm-household model, FarmDESIGN. Our results indicate that climate change can lead to a regime shift that expands revenue variance, increases soil erosion and reduces vitamin A yield for farmers. Banana disease can negatively impact income levels and species diversity. We show that under both scenarios farmers have scope to reconfigure their farms and recover farm performance. Specifically, we discuss the benefits of species diversity; increasing agrobiodiversity by adding new crops increases the farm's adaptive capacity and resilience, allowing for much higher revenues, on-farm crop diversity and vitamin A production. The conceptual approach and the method we developed can be applied to assess the local synergies and trade-offs between crop diversity conservation, nutrition, environmental protection and human nutrition that farmers face as a result of global drivers. Our results offer a further understanding of how biodiverse systems respond to regime shifts, which can inform effective policy design. Our method can be also useful to help farmers manage their farms in a way to better meet their complex needs.</p

Pair fluctuation induced pseudogap in the normal phase of the two-dimensional attractive Hubbard model at weak coupling

One-particle spectral properties in the normal phase of the two-dimensional attractive Hubbard model are investigated in the weak coupling regime using the non-selfconsistent T-matrix approximation. The corresponding equations are evaluated numerically directly on the real frequency axis. For temperatures sufficiently close to the superconducting transition temperature a pseudogap in the one-particle spectral function is observed, which can be assigned to the increasing importance of pair fluctuations.Comment: 22 pages, 13 figure

Decoherence scenarios from micro- to macroscopic superpositions

Environment induced decoherence entails the absence of quantum interference phenomena from the macroworld. The loss of coherence between superposed wave packets depends on their separation. The precise temporal course depends on the relative size of the time scales for decoherence and other processes taking place in the open system and its environment. We use the exactly solvable model of an harmonic oscillator coupled to a bath of oscillators to illustrate various decoherence scenarios: These range from exponential golden-rule decay for microscopic superpositions, system-specific decay for larger separations in a crossover regime, and finally universal interaction-dominated decoherence for ever more macroscopic superpositions.Comment: 11 pages, 7 figures, accompanying paper to quant-ph/020412

Proteins and free amino acids in the salivary secretion and hemolymph of the tick Amblyomma hebraeum

Electrophoretic and chromatographic separations of the salivary secretion of Amblyomma hebraeum showed a less complex protein pattern than that of Ornithodoros savignyi. A hyaluronidase active component was isolated. The haemolymph protein pattern showed a major protein fraction with a mobility slightly faster than that of bovine serum albumin.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format