Absolute measurement of the nitrogen fluorescence yield in air between 300 and 430 nm

The nitrogen fluorescence induced in air is used to detect ultra-high energy cosmic rays and to measure their energy. The precise knowledge of the absolute fluorescence yield is the key quantity to improve the accuracy on the cosmic ray energy. The total yield has been measured in dry air using a 90Sr source and a [300-430 nm] filter. The fluorescence yield in air is 4.23 $\pm$ 0.20 photons per meter when normalized to 760 mmHg, 15 degrees C and with an electron energy of 0.85 MeV. This result is consistent with previous experiments made at various energies, but with an accuracy improved by a factor of about 3. For the first time, the absolute continuous spectrum of nitrogen excited by 90Sr electrons has also been measured with a spectrometer. Details of this experiment are given in one of the author's PhD thesis [32].Comment: accepted for publication in NIM

Weak Pion Production off the Nucleon

We develop a model for the weak pion production off the nucleon, which besides the Delta pole mechanism (weak excitation of the $\Delta(1232)$ resonance and its subsequent decay into $N\pi$), includes also some background terms required by chiral symmetry. We re-fit the $C_5^A(q^2)$ form factor to the flux averaged $\nu_\mu p \to \mu^-p\pi^+$ ANL $q^2-$differential cross section data, finding a substantially smaller contribution of the Delta pole mechanism than traditionally assumed in the literature. Within this scheme, we calculate several differential and integrated cross sections, including pion angular distributions, induced by neutrinos and antineutrinos and driven both by charged and neutral currents. In all cases we find that the background terms produce quite significant effects and that they lead to an overall improved description of the data, as compared to the case where only the Delta pole mechanism is considered. We also show that the interference between the Delta pole and the background terms produces parity-violating contributions to the pion angular differential cross section, which are intimately linked to $T-$odd correlations in the contraction between the leptonic and hadronic tensors. However, these latter correlations do not imply a genuine violation of time reversal invariance because of the existence of strong final state interaction effects.Comment: Typos corrected; comments adde

Fisheries and trade of seahorses, Hippocampus spp., in southern India

Seahorses (Hippocampus spp.) are in much demand for traditional medicines and curios in dried form, and as aquarium fish when alive. Shallow seas abundant in sea grasses, sponges and corals characterise the natural habitats of the seahorses (Vincent 1994, 1995). All seahorses (Syngnathidae) belong to one genus Hippocampus. There are about 33 species of seahorses worldwide (Lourie, Vincent & Hall 1999; Lourie & Randall 2003). Seahorses are unique in their reproductive behaviour, in which the males become pregnant. The male fertilises and broods the eggs produced and deposited into its pouch by the female during courtship and mating, and in turn delivers the hatchling, after a long period of pregnancy and labour. Most species of seahorses studied so far show unique sexual fidelity and form faithful pair bonds (Vincent & Sadler 1995), in which case one male and one female mate repeatedly and exclusively giving up opportunities to interact with non-partners

Captive rearing of Hippocampus kuda and issues of seahorse conservation in India

Captive breeding and rearing of Hippocampus kuda, onc of the most dominant species of seahorscs was done to determine the optimum conditions of rearing, which would give the bighestsurvival, and growth of juveniles. A diet or enriched Artemia and mixed marine copepods was found to be the best feed combination during a rearing period 01'60 days. A stocking density 01'3 juveniles per litre was found to be the optimum, which gave the highest mean incrcment of growth in length and weight, as well as the highest mean production per litre

Socio-Economic support for good health in rural Malawi

Objective: To study the socio-economic support for good health among subsistence farmers in rural Malawi.Design: A cross-sectional survey.Setting: Lungwena, a rural area with 17000 inhabitants in southern Malawi.Participants: Seven hundred and ninety five pregnant women who attended the antenatal clinic at Lungwena Health Centre between June 1995 and September 1996. Interventions: Interviews about socio-economic conditions. Measurements of cultivated land areas and distances between home and the local health centre. Main outcome measures: Proportion of households lacking literate adults, adequate water source and sanitation, easy access to modern health care or food security.Results: Only 14% of the interviewed women could read and write and half of the households had no literate members. Every fifth household was lacking both an access to safe drinking water and a proper sanitary facility. The distance to the health centre was more than 5 kmamong half of the households and only 37% had enough land to grow food for all family members. When other potential means of obtaining food were taken into account, 27% of the households had no food security. Numerous households were lacking more than one socioeconomic prerequisites of good health: three or more were missing from a quarter of the families.Conclusions: Socio-economic prerequisites of health were commonly missing in Lungwena. Subsequent health interventions should strengthen the investments into general poverty alleviation

Energy resolution of alpha particles in a microbulk Micromegas detector at high pressure Argon and Xenon mixtures

The latest Micromesh Gas Amplification Structures (Micromegas) are achieving outstanding energy resolution for low energy photons, with values as low as 11% FWHM for the 5.9 keV line of $^{55}$Fe in argon/isobutane mixtures at atmospheric pressure. At higher energies (MeV scale), these measurements are more complicated due to the difficulty in confining the events in the chamber, although there is no fundamental reason why resolutions of 1% FWHM or below could not be reached. There is much motivation to demonstrate experimentally this fact in Xe mixtures due to the possible application of Micromegas readouts to the Double Beta Decay search of $^{136}$Xe, or in other experiments needing calorimetry and topology in the same detector. In this paper, we report on systematic measurements of energy resolution with state-of-the-art Micromegas using a 5.5 MeV alpha source in high pressure Ar/isobutane mixtures. Values as low as 1.8% FWHM have been obtained, with possible evidence that better resolutions are achievable. Similar measurements in Xe, of which a preliminary result is also shown here, are under progress.Comment: 16 pages, 19 figures, version after referees comments. Accepted for publication in Nuclear Instruments and Methods

Experimental and numerical investigations of flow structure and momentum transport in a turbulent buoyancy-driven flow inside a tilted tube.

Buoyancy-driven turbulent mixing of fluids of slightly different densities [At = Δρ/(2〈ρ〉) = 1.15×10−2] in a long circular tube tilted at an angle θ = 15° from the vertical is studied at the local scale, both experimentally from particle image velocimetry and laser induced fluorescence measurements in the vertical diametrical plane and numerically throughout the tube using direct numerical simulation. In a given cross section of the tube, the axial mean velocity and the mean concentration both vary linearly with the crosswise distance z from the tube axis in the central 70% of the diameter. A small crosswise velocity component is detected in the measurement plane and is found to result from a four-cell mean secondary flow associated with a nonzero streamwise component of the vorticity. In the central region of the tube cross section, the intensities of the three turbulent velocity fluctuations are found to be strongly different, that of the streamwise fluctuation being more than twice larger than that of the spanwise fluctuation which itself is about 50% larger than that of the crosswise fluctuation. This marked anisotropy indicates that the turbulent structure is close to that observed in homogeneous turbulent shear flows. Still in the central region, the turbulent shear stress dominates over the viscous stress and reaches a maximum on the tube axis. Its crosswise variation is approximately accounted for by a mixing length whose value is about one-tenth of the tube diameter. The momentum exchange in the core of the cross section takes place between its lower and higher density parts and there is no net momentum exchange between the core and the near-wall regions. A sizable part of this transfer is due both to the mean secondary flow and to the spanwise turbulent shear stress. Near-wall regions located beyond the location of the extrema of the axial velocity (|z|≳0.36 d) are dominated by viscous stresses which transfer momentum toward (from) the wall near the top (bottom) of the tube

Pattern of Reaction Diffusion Front in Laminar Flows

Autocatalytic reaction between reacted and unreacted species may propagate as solitary waves, namely at a constant front velocity and with a stationary concentration profile, resulting from a balance between molecular diffusion and chemical reaction. The effect of advective flow on the autocatalytic reaction between iodate and arsenous acid in cylindrical tubes and Hele-Shaw cells is analyzed experimentally and numerically using lattice BGK simulations. We do observe the existence of solitary waves with concentration profiles exhibiting a cusp and we delineate the eikonal and mixing regimes recently predicted.Comment: 4 pages, 3 figures. This paper report on experiments and simulations in different geometries which test the theory of Boyd Edwards on flow advection of chemical reaction front which just appears in PRL (PRL Vol 89,104501, sept2002

MEMPHYS:A large scale water Cerenkov detector at Fr\'ejus

A water \v{C}erenkov detector project, of megaton scale, to be installed in the Fr\'ejus underground site and dedicated to nucleon decay, neutrinos from supernovae, solar and atmospheric neutrinos, as well as neutrinos from a super-beam and/or a beta-beam coming from CERN, is presented and compared with competitor projects in Japan and in the USA. The performances of the European project are discussed, including the possibility to measure the mixing angle $\theta_{13}$ and the CP-violating phase $\delta$.Comment: 1+33 pages, 14 figures, Expression of Interest of MEMPHYS projec