Notes on structural analysis in a distributed collaboratory

The worldwide growth of communication networks and associated technologies provide the basic infrastructure for new ways of executing the engineering process. Collaboration amongst team members seperated in time and location is of particular importance. Two broad themes can be recognized in research pertaining to distributed collaboration. One theme focusses on the technical and technological aspects of distributed work, while the other emphasises human aspects thereof. The case of finite element structural analysis in a distributed collaboratory is examined in this paper. An approach is taken which has its roots in human aspects of the structural analysis task. Based on experience of how structural engineers currently approach and execute this task while utilising standard software designed for use on local workstations only, criteria are stated for a software architechture that could support collaborative structural analysis. Aspects of a pilot application and the results of qualitative performance measurements are discussed

Why agricultural production in sub-Saharan Africa remains low compared to the rest of the world – a historical perspective

Agricultural production in sub-Saharan Africa has, in recent times, remained lower than the rest of the world. Many attribute this to factors inherent to Africa and its people, such as climate, soil quality, slavery and disease. This article traces the role of agriculture through history and argues that these are not the main reasons. Before the arrival of European traders, complex agricultural systems existed, which supported food security, manufacturing and trade. External interference manipulated these systems in pursuit of export crops. Independence has not fundamentally changed this; resource and wealth extraction continue to inhibit economic development for Africans in Africa

The South Atlantic radiation anomaly

Part I. (1) An elementary treatment of the motion of charged particles in a magnetic field is presented. The concept of guiding centre motion is introduced, and is used in outlining the theory of particle drifts. (2 ) The motion of charged particles in the geomagnetic field is discussed, and the concept of adiabatic invariance introduced. (3) Mc Iliwains coordinates for mapping the distribution of charged particles trapped in the geometric field are defined and briefly discussed. (4) A survey of present knowledge of the Van Allen radiation zones is made. Particular attention is given to the distribution, characteristics, and variability of the trapped radiation. (5) The Cape Town magnetic anomaly, the Brazil radiation anomaly and the South Atlantic radiation anomaly are discussed. The electrons entering the South Atlantic radiation anomaly are shown to be those monitored over Iowa by the US satellite Injun I. Part 11. (1) It is shown how the geomagnetic field can, at high altitudes and over relatively short distances, be approximated by the field of a monopole. A new method is developed which enables one to plot the energy absorbed from an electron (which moves in a monopole field in the atmosphere) against altitude, given the initial energy and pitch angle of the electron. Some numerical computations using this method are described, and the results discussed. These results are used, in conjunction with US satellite Injun I for the Iowa region, to estimate the energy inout to the atmosphere in the South Atlantic radiation anomaly. The main approximations and simplifying assumptions made in this treatment, are discussed. (2) Geophysical effects generally recognized to be connected with the precipitation of charged particles are discussed. In the course of this discussion the two main theories of the connection between the radiation zones and the auroras are examined. (3) A preliminary discussion, based on the work summarized in point (1) of detectable geophysical events associated with the precipitation of electrons into the South Atlantic radiation anomaly is given. It is concluded that auroral emission, X-ray bursts, and ionospheric ionization in the E region should be more frequent and pronounced in the South Atlantic radiation anomaly than in any other region of comparable invariant latitudes and that the effects of atmospheric heating by precipitated electrons should be detectable over the anomaly. (4) An assessment is made of the value of the method referred to in point (1). Suggestions for its modification and extension are put forward. It is suggested that if more extensive rocket and satellite data on the low energy component of the electron flux become available, this method can be employed in a rigorous theoretical investigation of the South Atlantic radiation anomaly. Summary, p. 98-100

2-(Biphenyl-4-yl)propan-2-ol

The title compound, C15H16O, crystallizes with two independent mol­ecules in the asymmetric unit. Due to the space-group symmetry, this results in the formation of a tetra­mer where the four mol­ecules are connected by O—H⋯O hydrogen bonds. The mol­ecules pack parallel to the c axis. Both mol­ecules in the asymmetric unit are nonplanar and the dihedral angles between connected aromatic rings in each mol­ecule are 7.96 (12) and 9.75 (13)°. This contrasts with the gas phase density functional theory (DFT) optimized conformation, where this dihedral angle is 39.33°

Orientation of trimethylolethane cyclic phosphite in rhodium complexes : structure of [Rh(CH3COCHCOCH3)(CO)(P(OCH2)3CCH3)]

Density functional theory calculations showed that rotation of the (P(OCH2)3CCH3) group in the rhodium-acetylacetonato complex [Rh(acac)(CO)(P(OCH2)3CCH3)] has a negligible influence on the energy of the complex. Density functional theory calculations further showed that the minimum energy orientation of the cyclic (P(OCH2)3CCH3) group in square planar rhodium- (P(OCH2)3CCH3)-(CO) complexes containing a bidentate ligand that is larger than the acetylacetonato ligand, is with one of the P-O bonds near parallel (within 10°) to the plane defined by the four atoms coordinated to Rh. The three P-O bonds of the rigid (P(OCH2)3CCH3) group adopt a C3-symmetrical conformation around the Rh-P axis. The lowest energy geometry of [Rh(BID)(CO)(P(OCH2)3CCH3)] (BID = bidentate ligand with two O donor atoms and charge -1) complexes is where one P-O bond is aligned near parallel to the Rh-OBID trans to CO bond, while the geometry with a P-O bond orientated near parallel to the Rh-CCO bond, is slightly higher in energy, but still possible experimentally. The highest energy orientation of the (P(OCH2)3CCH3) group in square planar [Rh(BID)(CO)(P(OCH2)3CCH3)] complexes, is with one of the P-O bonds near perpendicular to the plane described by the four atoms coordinated to Rh. The orientation of the cyclic (P(OCH2)3CCH3) group in available experimental structures of square planar [Rh(BID)(CO) (P(OCH2)3CCH3)] complexes, confirms this finding.The South African National Research Foundation and the Central Research Fund of the University of the Free State, Bloemfontein, South Africa.http://www.elsevier.com/locate/poly2017-06-30hb2016Chemistr

Transforming failing smallholder irrigation schemes in Africa: a theory of change

Drawing on the results of the Transforming Irrigation in Southern Africa project, we assess positive transitions in smallholder irrigation schemes. The project’s theory of change is evaluated. Soil monitoring tools and agricultural innovation platforms were introduced in five irrigation schemes in Mozambique, Tanzania and Zimbabwe. The synergies between these interventions increased both crop yields and profitability. This empowered farmers, improved equity, and accelerated social learning and innovation. The resulting, iterative cycles of change improved governance, sustainability and socio-economic outcomes. The challenges of scaling these interventions up and out are outlined