The new ALEPH Silicon Vertex Detector

The ALEPH collaboration, in view of the importance of effective vertex detection for the Higgs boson search at LEP 2, decided to upgrade the previous vertex detector. Main changes were an increased length (±20 cm), a higher granularity for rφ view (50 µm), a new preamplifier (MX7 rad hard chip), a polymide (upilex) fan-out on z side to carry the signals from the strips to the front-end electronics outside the fiducial region reducing consequently the passive material in the central region by a factor of two. The detector, the running experience and its performance will be described

The new ALEPH Silicon Vertex Detector

The ALEPH collaboration, in view of the importance of effective vertex detection for the Higgs boson search at LEP 2, decided to upgrade the previous vertex detector. Main changes were an increased length (±20 cm), a higher granularity for rφ view (50 µm), a new preamplifier (MX7 rad hard chip), a polymide (upilex) fan-out on z side to carry the signals from the strips to the front-end electronics outside the fiducial region reducing consequently the passive material in the central region by a factor of two. The detector, the running experience and its performance will be described

A determination of #Delta#(m) from tagged neutral kaons

SIGLEAvailable from British Library Document Supply Centre- DSC:DX174007 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Fen Bilgisi ve Ortaokul Matematik Öğretmen Adaylarının Bilimsel Süreç Becerileri

. Whilst the rate at which mutations occur in artificial evolutionary systems has received considerable attention, there has been little analysis of the mutation operators themselves. Here attention is drawn to the possibility that inherent biases within such operators might artefactually affect the direction of evolutionary change. Biases associated with several mutation operators are detailed and attempts to alleviate them are discussed. Natural evolution is then shown to be subject to analogous mutation "biases". These tendencies are explicable in terms of (i) selection pressure for low mutation rates, and (ii) selection pressure to avoid parenting non-viable offspring. It is concluded that attempts to eradicate mutation biases from artificial evolutionary systems may lead to evolutionary dynamics that are more unnatural, rather than less. Only through increased awareness of the character of mutation biases, and analyses of our models' sensitivity to them, can we guard ..

Deriving the spin rate/orientation from the quiescent spacecraft ABRIXAS using optical observations

SIGLEAvailable from TIB Hannover: RR 7310(2000-24) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Holocene vegetation history of the Sahel: pollen, sedimentological and geochemical data from Jikariya Lake, north-eastern Nigeria

Aim: This study aims to separate regional and local controls on Holocene vegetation development and examine how well pollen records reflect climate change in a semi-arid region. The relative importance of climate and human activity as agents of vegetation change in the Sahel during the late-Holocene is also considered. Location: Jikariya Lake, an interdune depression in the Manga Grasslands of north-eastern Nigeria. Methods: Pollen and charcoal were used to provide a record of Holocene vegetation history. Palaeoclimate and hydrological changes were reconstructed from sedimentary and geochemical data. Regional and local influences were separated by comparing the evidence obtained from Jikariya Lake with previously published data from the Manga Grasslands. Results: The Manga Grasslands experienced a prolonged wet period during the early and mid Holocene during which swamp forest vegetation with Guinean affinities (Alchornea, Syzygium, Uapaca) occupied the interdune depressions. However, variation in the pollen records between sites suggests that their establishment was dependent upon conditions being locally favourable, rather than being directly coupled to regional climate. The pollen records from the Manga Grasslands are more consistent in suggesting the colonisation of the dunefields by trees associated with Sudanian savanna (Combretaceae, Detarium) c. 8700 cal. yrs BP. The Jikariya Lake pollen data are in accordance with the sedimentological and geochemical data from the region in indicating the onset of arid conditions occurred progressively during the late Holocene (from c. 4700 cal. yrs BP). Abrupt changes in pollen stratigraphy, recorded at other Manga Grasslands sites 3500 cal. yrs BP, appear to be the product of the local passing of ecological thresholds. The dunefield vegetation (Sahelian savanna) appears to have been resilient, or at least palynologically silent, to the climatic variability of the late Holocene. Main conclusions: While climate appears to have been the primary control on vegetation development in the Manga Grasslands during the Holocene, local conditions (particularly depression size and sand influx) had a strong influence on the timing of pollen stratigraphic changes. Anthropogenic influences are difficult to detect, even during the late Holocene