SUNSAT, Stellenbosch University and SA-AMSAT\u27s Remote Sensing and Packet Communications Microsatellite

The Engineering Model of SUNSAT, a 50 kg, 45 cm, Ariane ASAP-compatible microsatellite is scheduled for assembly in December 1993, permitting flight model completion early in 1995. Fifteen M.Eng. students, led by Computer & Control System lecturers at Stellenbosch University, began detail design in January 1992. Most prototype hardware was operating by July 1993, and assembly of the first final-sized PCB\u27s started. A packet radio service, a 2m parrot speech transponder, and Mode A and S transponders, all defined and endorsed by SA-AMSAT, comprise the Amateur Radio communications payload. Verification of the 15-20 m pixel spacing, 3-color, 3456 pixel pushbroom imager capable of stereo imaging, is a major research goal. Data will be downlinked in S-band, or single images stored in a 64Mbyte RAM. Coarse attitude stabilization by gravity gradient and magnetorquing is improved by small reaction wheels during imaging. Continuous attitude sensing is by magnetometers. Sun sensors, visible band horizon sensors, and star sensor provide 1 mrad accuracy when imaging from the sun-synchronous orbit. Average power of 30 W enables images of South Africa to be taken on a daily basis for real time downlinking. Satisfaction of SA electronics companies on our Advisory Board with the engineering model will lead to continued student funding. Demonstration of a working engineering model will then hopefully provide the credibility we need to finalize a launch opportunity. The satellite\u27s layout, block diagram, and expected performance of the imager, downlink, and Amateur packet communications payload are described

Fourier basis for the engineering assessment of cracks in residual stress fields

A theoretical basis is presented for determining the significance of a residual stress distribution of arbitrary shape on the crack tip stress intensity factor for a centre-cracked plate as a function of crack length. The Fourier series based approach enables one to increasingly add more spatial definition to the stress field and thereby determine the level of detailed knowledge of the residual stress required to make a reliable assessment of structural integrity. The approach is applied to examples of measured symmetric distributions of residual stresses in welded plates and used to determine the significance of residual stress lengthscales in fracture mechanics analysis

Mirrored one-nucleon knockout reactions to the T-z = +/- 3/2 A=53 mirror nuclei

Background: The study of excited states in mirror nuclei allows us to extract information on charge-dependent (i.e., isospin-nonconserving) interactions in nuclei. Purpose: To extend previous studies of mirror nuclei in the f72 region, investigating charge symmetry breaking of the strong nuclear force. Methods: γ-ray spectroscopy has been performed for the mirror (Tz=±32) pair Ni53 and Mn53, produced via mirrored one-nucleon knockout reactions. Results: Several new transitions have been identified in Ni53 from which a new level scheme has been constructed. Cross sections for knockout have been analyzed and compared with reaction model calculations where evidence is found for knockout from high-spin isomeric states. Mirror energy differences between isobaric analog states have been computed, compared to large scale shell-model calculations, and interpreted in terms of isospin-nonconserving effects. In addition, lifetimes for the long-lived Jπ=52−1 analog states in both Mn53 and Ni53 have been extracted through lineshape analysis, giving half-lives of t12=120(14) ps and t12=198(12) ps, respectively. Conclusions: The inclusion of a set of isovector isospin-nonconserving matrix elements to the shell-model calculations gave the best agreement with the experimental data

Differential expression of microRNAs and potential targets under drought stress in barley

Drought is a crucial environmental constraint limiting crop production in many parts of the world. microRNA (miRNA) based gene regulation has been shown to act in several pathways, including crop response to drought stress. Sequence based profiling and computational analysis have revealed hundreds of miRNAs and their potential targets in different plant species under various stress conditions, but few have been biologically verified. In this study, eleven candidate miRNAs were tested for their expression profiles in barley. Differences in accumulation of only four miRNAs (Ath-miR169b, Osa-miR1432, Hv-miRx5 and Hv-miR166b/c) were observed between drought-treated and well-watered barley in four genotypes. miRNA targets were predicted using degradome analysis of two, different genotypes and genotype-specific target cleavage was observed. Inverse correlation of mature miRNA accumulation with miRNA target transcripts was also genotype-dependent under drought treatment. Drought-responsive miRNAs accumulated predominantly in mesophyll tissues. Our results demonstrate genotype-specific miRNA regulation under drought stress and evidence for their role in mediating expression of target genes for abiotic stress response in barley.Jannatul Ferdous, Juan Carlos Sanchez-Ferrero, Peter Langridge, Linda Milne, Jamil Chowdhury, Chris Brien, and Penny J. Tricke

Stimulation of colorectal tumour protein synthesis, in vivo, by nutritional support.

Malignant disease is frequently accompanied by weight loss and malnutrition, which are associated with an increase in patient mortality and morbidity

Projected impacts of increased uptake of source control mitigation measures on agricultural diffuse pollution emissions to water and air

The authors gratefully acknowledge the funding provided by Defra project LM0304; Phase 2 of the Avon Demonstration Test Catchment. The DTC farm survey data were collected in conjunction with the Avon (Defra project WQ0211), Wensum (Defra project WQ0212) and Eden (Defra project WQ02010) DTC programmes. The Environment Agency kindly provided access to national GIS layers. The authors thank the experts included in the elicitation exercise for current implementation of source control measures

Mapping immune variation and var gene switching in naive hosts infected with Plasmodium falciparum

Falciparum malaria is clinically heterogeneous and the relative contribution of parasite and host in shaping disease severity remains unclear. We explored the interaction between inflammation and parasite variant surface antigen (VSA) expression, asking whether this relationship underpins the variation observed in controlled human malaria infection (CHMI). We uncovered marked heterogeneity in the host response to blood challenge; some volunteers remained quiescent, others triggered interferon-stimulated inflammation and some showed transcriptional evidence of myeloid cell suppression. Significantly, only inflammatory volunteers experienced hallmark symptoms of malaria. When we tracked temporal changes in parasite VSA expression to ask whether variants associated with severe disease rapidly expand in naive hosts, we found no transcriptional evidence to support this hypothesis. These data indicate that parasite variants that dominate severe malaria do not have an intrinsic growth or survival advantage; instead, they presumably rely upon infection-induced changes in their within-host environment for selection

Optical Light Curves of Supernovae

Photometry is the most easily acquired information about supernovae. The light curves constructed from regular imaging provide signatures not only for the energy input, the radiation escape, the local environment and the progenitor stars, but also for the intervening dust. They are the main tool for the use of supernovae as distance indicators through the determination of the luminosity. The light curve of SN 1987A still is the richest and longest observed example for a core-collapse supernova. Despite the peculiar nature of this object, as explosion of a blue supergiant, it displayed all the characteristics of Type II supernovae. The light curves of Type Ib/c supernovae are more homogeneous, but still display the signatures of explosions in massive stars, among them early interaction with their circumstellar material. Wrinkles in the near-uniform appearance of thermonuclear (Type Ia) supernovae have emerged during the past decade. Subtle differences have been observed especially at near-infrared wavelengths. Interestingly, the light curve shapes appear to correlate with a variety of other characteristics of these supernovae. The construction of bolometric light curves provides the most direct link to theoretical predictions and can yield sorely needed constraints for the models. First steps in this direction have been already made.Comment: To be published in:"Supernovae and Gamma Ray Bursters", Lecture Notes in Physics (http://link.springer.de/series/lnpp