Smith-Purcell radiation from a 50 MeV beam

A 50 MeV electron beam and a 1 mm period, 5{degree} blaze, echelle grating have been used to produce radiation in the mid-infrared spectral region. The emission is highly collimated and forward-directed. The intensity level in the few ps pulse (2 nJ/sr) indicates a degree of coherent enhancement

Book Reviews

Book Review 1Book Title: Reproductive Energetics in MammalsBook Authors: A.S.I. Loudon & P.A. Racey (Eds.)Zoological Society of London Symposia 57, 1987 Clarendon. Press, Oxford. 371 pp.Book Review 2Book Title: Classification of Southern African MammalsBook Authors: J.A.J. Meester, I.L. Rautenbach, N.J. Dippenaar & C.M. BakerTransvaal Museum Monograph No.5. 359 pp.Book Review 3Book Title: Pesticide impact on stream fauna with special reference to macroinvertebratesBook Author: R.C. Muirhead-ThomsonCambridge University Press, 1987. 275 pp.Book Review 4Book Title: Evolution of sex determining mechanismsBook Author: James J. BullBenjamin-Cummings Publ. Company / Addison-Wesley Publishing Group, JohannesburgBook Review 5Book Title: The evolutionary ecology of ant-plant mutualismsBook Author: Andrew J. BeattieCambridge University Press 182 pp.Book Review 6Book Title: The Ecology of SexBook Authors: P.J. Greenwood & J. Adams Edward Arnold, London, 1987. 74 pagesBook Review 7Book Title: The Dinosaur Heresies - a revolutionary view of dinosaursBook Author: Robert BakkerPublished by Longman Scientific and Technical, 1987Book Review 8Book Title: Molecular Biology of the GeneBook Authors: Watson, Hopkins, Roberts, Steitz & WeinerVolumes I and II (Fourth Edition) (Benjamin/Cummings. Menlo Park); Addison-Wesley Publishing Group. Johannesburg 1163 pp.Book Review 9Book Title: Evolutionary BiologyBook Author: Eli C. MinkoffAddison-Wesley Publishing Company, Massachussets, 1983. 627pp.Book Review 10Book Title: An ecosystem approach to aquatic ecology. Mirror Lake and its environmentBook Author: Gene E. Likens (Ed.)Springer-Ver1ag, New York. xiv - 516 pages; 197 figuresBook Review 11Book Title: The Physiological Ecology of SeaweedsBook Authors: C.S. Lobban, P.J. Harrison & M.J. Duncan Cambridge University press, Cambridge, 1985. 242 pagesBook Review 12Book Title: Principles of ecologyBook Authors: R.J.Putman & S.D. WrattenCroom Helm, London, 1984. 388 pages

Anthropogenic forcing increases the water-use efficiency of African trees

Rising atmospheric CO2 concentrations affect climate directly through radiative effects and indirectly by changing plant water-use efficiency. Under global warming scenarios these widely reported changes will have a substantial impact on future bush encroachment, crop yields, river flow and climate feedbacks. Tree-ring intrinsic water-use efficiency (iWUE) records for Africa show a 24.6% increase over the 20th century. As high iWUE can partly counterbalance projected decreases in regional precipitation, this research has important implications for those involved in water resource management and highlights the need for climate models to take physiological forcing into account.National Geographic Society - Science and Exploration Europe (grant GEFNE80-13), the Royal Geographical Society, the Quaternary Research Association, the Palaeo-Anthropological Scientific Trust, the National Research Foundation, SysTem for Analysis, Research and Training (START) and the Climate Change Consortium of Wales.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-14172017-05-31hb2016Mammal Research Institut

Renormalization of Hamiltonian Field Theory; a non-perturbative and non-unitarity approach

Renormalization of Hamiltonian field theory is usually a rather painful algebraic or numerical exercise. By combining a method based on the coupled cluster method, analysed in detail by Suzuki and Okamoto, with a Wilsonian approach to renormalization, we show that a powerful and elegant method exist to solve such problems. The method is in principle non-perturbative, and is not necessarily unitary.Comment: 16 pages, version shortened and improved, references added. To appear in JHE

AfrOBIS: a marine biogeographic information system for sub-Saharan Africa

AfrOBIS is one of 11 global nodes of the Ocean Biogeographic Information System (OBIS), a freely accessible network of databases collating marine data in support of the Census of Marine Life. Versatile graphic products, provided by OBIS, can be used to display the data. To date, AfrOBIS has loaded about3.2 million records of more than 23 000 species located mainly in the seas around southern Africa. This forms part of the 13.2 million records of more than 80 000 species currently stored in OBIS. Scouting for South African data has been successful, whereas locating records in other African countries has been much less so

Search for supersymmetry with a dominant R-parity violating LQDbar couplings in e+e- collisions at centre-of-mass energies of 130GeV to 172 GeV

A search for pair-production of supersymmetric particles under the assumption that R-parity is violated via a dominant LQDbar coupling has been performed using the data collected by ALEPH at centre-of-mass energies of 130-172 GeV. The observed candidate events in the data are in agreement with the Standard Model expectation. This result is translated into lower limits on the masses of charginos, neutralinos, sleptons, sneutrinos and squarks. For instance, for m_0=500 GeV/c^2 and tan(beta)=sqrt(2) charginos with masses smaller than 81 GeV/c^2 and neutralinos with masses smaller than 29 GeV/c^2 are excluded at the 95% confidence level for any generation structure of the LQDbar coupling.Comment: 32 pages, 30 figure

First Measurement of Z/gamma* Production in Compton Scattering of Quasi-real Photons

We report the first observation of Z/gamma* production in Compton scattering of quasi-real photons. This is a subprocess of the reaction e+e- to e+e-Z/gamma*, where one of the final state electrons is undetected. Approximately 55 pb-1 of data collected in the year 1997 at an e+e- centre-of-mass energy of 183 GeV with the OPAL detector at LEP have been analysed. The Z/gamma* from Compton scattering has been detected in the hadronic decay channel. Within well defined kinematic bounds, we measure the product of cross-section and Z/gamma* branching ratio to hadrons to be (0.9+-0.3+-0.1) pb for events with a hadronic mass larger than 60 GeV, dominated by (e)eZ production. In the hadronic mass region between 5 GeV and 60 GeV, dominated by (e)egamma* production, this product is found to be (4.1+-1.6+-0.6) pb. Our results agree with the predictions of two Monte Carlo event generators, grc4f and PYTHIA.Comment: 18 pages, LaTeX, 5 eps figures included, submitted to Physics Letters

Measurement of the Michel Parameters in Leptonic Tau Decays

The Michel parameters of the leptonic tau decays are measured using the OPAL detector at LEP. The Michel parameters are extracted from the energy spectra of the charged decay leptons and from their energy-energy correlations. A new method involving a global likelihood fit of Monte Carlo generated events with complete detector simulation and background treatment has been applied to the data recorded at center-of-mass energies close to sqrt(s) = M(Z) corresponding to an integrated luminosity of 155 pb-1 during the years 1990 to 1995. If e-mu universality is assumed and inferring the tau polarization from neutral current data, the measured Michel parameters are extracted. Limits on non-standard coupling constants and on the masses of new gauge bosons are obtained. The results are in agreement with the V-A prediction of the Standard Model.Comment: 32 pages, LaTeX, 9 eps figures included, submitted to the European Physical Journal

An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics

For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types