Physical characteristics of Acidic Mining Lake 111

Measurements of physical properties have been conducted in Mining Lake 111 (ML111), located in Lusatia, Germany over the time period 1996- 2002. In the deepest area of the ML111, a monimolimnion was observed, that persisted for the years 1996-1999. It disappeared in 2000 and again formed in 2001. The definition of the main physical properties, such as the temperature compensation for electrical conductivity, in acidic mining lakes required a lake specific approach. The relation between conductivity, temperature and density was determined for the acidic ML111. The variation in dissolved substances affected these relationships such that conductivity varied with temperature even in different layers of the water column and the limitations for a lake wide correlation was evident. Variation in the conductivity of the epilimnion could be verified, and agreed with the estimates of evaporation from the lake surface during summer stratification. Calculations, following the gradient flux method, indicated vertical transport coefficients between 10-7 and 10-6m2/s throughout the hypolimnion. The heat budget indicated that heat was transferred into the lake bed or the ground during spring

Experimental investigation of the initial regime in fingering electrodeposition: dispersion relation and velocity measurements

Recently a fingering morphology, resembling the hydrodynamic Saffman-Taylor instability, was identified in the quasi-two-dimensional electrodeposition of copper. We present here measurements of the dispersion relation of the growing front. The instability is accompanied by gravity-driven convection rolls at the electrodes, which are examined using particle image velocimetry. While at the anode the theory presented by Chazalviel et al. describes the convection roll, the flow field at the cathode is more complicated because of the growing deposit. In particular, the analysis of the orientation of the velocity vectors reveals some lag of the development of the convection roll compared to the finger envelope.Comment: 11 pages, 15 figures, REVTEX 4; reference adde

Does ohmic heating influence the flow field in thin-layer electrodeposition?

In thin-layer electrodeposition the dissipated electrical energy leads to a substantial heating of the ion solution. We measured the resulting temperature field by means of an infrared camera. The properties of the temperature field correspond closely with the development of the concentration field. In particular we find, that the thermal gradients at the electrodes act like a weak additional driving force to the convection rolls driven by concentration gradients.Comment: minor changes: correct estimation of concentration at the anode, added Journal-re

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

Baroclinic, Kelvin and inertia-gravity waves in the barostrat instability experiment

International audienceThe differentially heated rotating annulus is a laboratory experiment historically designed for modelling large-scale features of the mid-latitude atmosphere. In the present study, we investigate a modified version of the classic baroclinic experiment in which a juxtaposition of convective and motionless stratified layers is created by introducing a vertical salt stratification. The thermal convective motions are suppressed in a central region at mid-depth of the rotating tank, therefore double-diffusive convection rolls can develop only in thin layers located at top and bottom, where the salt stratification is weakest. For high enough rotation rates, the baroclinic instability destabilises the flow in the top and the bottom shallow convective layers, generating cyclonic and anticyclonic eddies separated by the stable stratified layer. Thanks to this alternation of layers resembling the convective and radiative layers of stars, the planetary's atmospheric troposphere and stratosphere or turbulent layers at the sea surface above stratified waters, this new laboratory setup is of interest for both astrophysics and geophysical sciences. More specifically, it allows to study the exchange of momentum and energy between the layers, primarly by the propagation of internal gravity waves (IGW). PIV velocity maps are used to describe the wavy flow pattern at different heights. Using a co-rotating laser and camera, the wave field is well resolved and different wave types can be found: baroclinic waves, Kelvin, and Poincaré type waves. The signature of small-scale IGW can also be observed attached to the baroclinic jet. The baroclinic waves occur at the thin convectively active layer at the surface and the bottom of the tank, though decoupled they show different manifestation of nonlinear interactions. The inertial Kelvin and Poincaré waves seem to be mechanically forced. The small-scale wave trains attached to the meandering jet point to an imbalance of the large-scale flow. For the first time, the simultaneous occurrence of differentwave types is reported in detail for a differentially heated rotating annulus experiment

Absolute mass lower limit for the lightest neutralino of the MSSM from e+e−e^{+}e^{-} data at s\sqrt{s} up to 209 GeV

Charginos and neutralinos are searched for in the data collected by the ALEPH experiment at LEP for centre-of-mass energies up to 209 GeV. The negative result of these searches is combined with those from searches for sleptons and Higgs bosons to derive an absolute lower limit of 43.1 GeV/c(2) on the mass of the lightest supersymmetric particle (LSP), assumed to be the,lightest neutralino. This limit is obtained in the framework of the MSSM with R-parity conservation and with gaugino and sfermion mass unification at the GUT scale and assuming no mixing in the stau sector. The LSP limit degrades only slightly to 42.4 GeV/c(2) if stau mixing is considered. Within the more constrained framework of minimal supergravity, the limit is 50 GeV/c(2)

Search for charginos nearly mass degenerate with the lightest neutralino in e+e−e^+ e^- collisions at centre-of-mass energies up to 209 GeV

A search for charginos nearly mass degenerate with the lightest neutralino is performed with the data collected by the ALEPH detector at LEP, at centre-of-mass energies between 189 and 209 GeV, corresponding to an integrated luminosity of 628 pb-1. The analysis is based on the detection of isolated and energetic initial state radiation photons, produced in association with chargino pairs whose decay products have little visible energy. The number of candidate events observed is in agreement with that expected from Standard Model background sources. These results are combined with those of other direct searches for charginos, and a lower limit of 88 GeV/c2 at 95 % confidence level is derived for the chargino mass in the case of heavy sfermions, irrespective of the chargino-neutralino mass difference.A search for charginos nearly mass degenerate with the lightest neutralino is performed with the data collected by the ALEPH detector at LEP, at centre-of-mass energies between 189 and 209 GeV, corresponding to an integrated luminosity of 628 pb −1 . The analysis is based on the detection of isolated and energetic initial state radiation photons, produced in association with chargino pairs whose decay products have little visible energy. The number of candidate events observed is in agreement with that expected from Standard Model background sources. These results are combined with those of other direct searches for charginos, and a lower limit of 88 GeV/ c 2 at 95% confidence level is derived for the chargino mass in the case of heavy sfermions, irrespective of the chargino-neutralino mass difference.A search for charginos nearly mass degenerate with the lightest neutralino is performed with the data collected by the ALEPH detector at LEP, at centre-of-mass energies between 189 and 209 GeV, corresponding to an integrated luminosity of 628 pb-1. The analysis is based on the detection of isolated and energetic initial state radiation photons, produced in association with chargino pairs whose decay products have little visible energy. The number of candidate events observed is in agreement with that expected from Standard Model background sources. These results are combined with those of other direct searches for charginos, and a lower limit of 88 GeV/c2 at 95 % confidence level is derived for the chargino mass in the case of heavy sfermions, irrespective of the chargino-neutralino mass difference

Measurement of the tau lepton lifetime

The mean lifetime of the tau lepton is measured in a sample of 25700 tau pairs collected in 1992 with the ALEPH detector at LEP. A new analysis of the 1-1 topology events is introduced. In this analysis, the dependence of the impact parameter sum distribution on the daughter track momenta is taken into account, yielding improved precision compared to other impact parameter sum methods. Three other analyses of the one- and three-prong tau decays are updated with increased statistics. The measured lifetime is 293.5+/-3.1+/-1.7 fs. Including previous (1989-1991) ALEPH measurements, the combined tau lifetime is 293.7+/-2.7+/-1.6 fs