Search for heavy neutrinos mixing with tau neutrinos

We report on a search for heavy neutrinos (\nus) produced in the decay D_s\to \tau \nus at the SPS proton target followed by the decay \nudecay in the NOMAD detector. Both decays are expected to occur if \nus is a component of $\nu_{\tau}$.\ From the analysis of the data collected during the 1996-1998 runs with $4.1\times10^{19}$ protons on target, a single candidate event consistent with background expectations was found. This allows to derive an upper limit on the mixing strength between the heavy neutrino and the tau neutrino in the \nus mass range from 10 to 190 $\rm MeV$. Windows between the SN1987a and Big Bang Nucleosynthesis lower limits and our result are still open for future experimental searches. The results obtained are used to constrain an interpretation of the time anomaly observed in the KARMEN1 detector.\Comment: 20 pages, 7 figures, a few comments adde

The NOMAD Experiment at the CERN SPS

The NOMAD experiment is a short base-line search for ν<sub>μ</sub> − ν<sub>τ</sub> oscillations in the CERN neutrino beam. The ν<sub>τ</sub>'s are searched for through their charged current interactions followed by the observation of the resulting τ− through its electronic, muonic or hadronic decays. These decays are recognized using kinematical criteria necessitating the use of a light target which enables the reconstruction of individual particles produced in the neutrino interactions. This paper describes the various components of the NOMAD detector: the target and muon drift chambers, the electromagnetic and hadronic calorimeters, the preshower and transition radiation detectors and the veto and trigger scintillation counters. The beam and data acquisition system are also described. The quality of the reconstruction and individual particles is demonstrated through the ability of NOMAD to observe K<sub>s</sub><sup>0</sup>'s, Λ<sup>0</sup>'s and π<sup>0</sup>'s. Finally, the observation of τ− through its electronic decay being one of the most promising channels in the search, the identification of electrons in NOMAD is discussed

Processing difficulties and instability of carbohydrate microneedle arrays

BACKGROUND: A number of reports have suggested that many of the problems currently associated with the use of microneedle (MN) arrays for transdermal drug delivery could be addressed by using drug-loaded MN arrays prepared by moulding hot melts of carbohydrate materials. METHODS: In this study, we explored the processing, handling, and storage of MN arrays prepared from galactose with a view to clinical application. RESULTS: Galactose required a high processing temperature (160°C), and molten galactose was difficult to work with. Substantial losses of the model drugs 5-aminolevulinic acid (ALA) and bovine serum albumin were incurred during processing. While relatively small forces caused significant reductions in MN height when applied to an aluminium block, this was not observed during their relatively facile insertion into heat-stripped epidermis. Drug release experiments using ALA-loaded MN arrays revealed that less than 0.05% of the total drug loading was released across a model silicone membrane. Similarly, only low amounts of ALA (approximately 0.13%) and undetectable amounts of bovine serum albumin were delivered when galactose arrays were combined with aqueous vehicles. Microscopic inspection of the membrane following release studies revealed that no holes could be observed in the membrane, indicating that the partially dissolved galactose sealed the MN-induced holes, thus limiting drug delivery. Indeed, depth penetration studies into excised porcine skin revealed that there was no significant increase in ALA delivery using galactose MN arrays, compared to control (P value < 0.05). Galactose MNs were unstable at ambient relative humidities and became adhesive. CONCLUSION: The processing difficulties and instability encountered in this study are likely to preclude successful clinical application of carbohydrate MNs. The findings of this study are of particular importance to those in the pharmaceutical industry involved in the design and formulation of transdermal drug delivery systems based on dissolving MN arrays. It is hoped that we have illustrated conclusively the difficulties inherent in the processing and storage of carbohydrate-based dissolving MNs and that those in the industry will now follow alternative approaches

Putting the eco back in ecotourism

[Extract] In the 1980s, alarm began to spread about habitat loss, especially in tropical forests that supported a vast number of species. Fast and accelerating clearing over the previous two decades had reduced, isolated and degraded this habitat type (Aldhous, 1993; Skole & Tucker, 1993). Conservation proponents reacted by buying and protecting forest tracts; however, political will and funds were often insufficient to support viable plant and animal populations, to protect representative forest communities, or even to prevent the neighboring human populations from illicitly using resources in protected tracts (Goodman & Gonzales, 1990; Terborgh, 1999). Ecotourism developed, in part, as a complement to these conventional conservation methods

Tropical forages: An interactive selection tool

A tool for selecting forage species suitable for local conditions in the tropics and subtropics. Invaluable for agricultural researchers and extension officers involved in improving animal production. Allows you to identify forage species suitable for your climate, soils and production system; access comprehensive information on these species with details of adaptation, uses and management; view images of the plants and their use; and search a comprehensive database of scientific references with abstracts. JavaScript must be enabled for use. Works best with Internet Explorer