Cyanobacterial blooms were sampled at five locations in Lake Grand-Lieu on seven different occasions during May-October 1994. Strains of Microcystis aeruginosa and Anabaena circinalis were isolated ...from the samples. Microcystins were detected in freeze-dried field samples and the isolated strains by HPLC. The toxins were present in the blooms sampled between June and October. The microcystin content in the blooms varied with site and time, from undetectable concentrations to 0.23 mg g-1. The highest concentrations of microcystin were found in blooms sampled in September. Microcystin-LR and microcystins with retention times close to the retention time of${\rm Dha}^{7}\text{microcystin-}{\rm RR}$(probably varieties of microcystin-RR) were found in the field samples. Sixteen of the 98 isolated M. aeruginosa strains and 2 of the 24 A. circinalis strains produced microcystins. The total amount of microcystins varied from undetectable concentrations to 5.06 mg g-1in the M. aeruginosa isolates, and from undetectable concentrations to 1.86 mg g-1in the A. circinalis strains. Microcystin-LR was the main toxin found in strains of M. aeruginosa, but was not present in strains of A. circinalis. Both microcystin-producing strains and strains that did not produce microcystin coexisted in the bloom samples.
The full LEP-1 data set collected with the ALEPH detector at the
Z pole during 1991–1995 is analysed in order to measure the
τ
decay branching fractions. The analysis follows the global method used ...in the published study based on 1991–1993 data, but several improvements are introduced, especially concerning the treatment of photons and
π
0
's. Extensive systematic studies are performed, in order to match the large statistics of the data sample corresponding to over 300
000 measured and identified
τ
decays. Branching fractions are obtained for the two leptonic channels and 11 hadronic channels defined by their respective numbers of charged particles and
π
0
's. Using previously published ALEPH results on final states with charged and neutral kaons, corrections are applied to the hadronic channels to derive branching ratios for exclusive final states without kaons. Thus the analyses of the full LEP-1 ALEPH data are combined to yield a complete description of
τ
decays, encompassing 22 non-strange and 11 strange hadronic modes. Some physics implications of the results are given, in particular related to universality in the leptonic charged weak current, isospin invariance in
a
1
decays, and the separation of vector and axial-vector components of the total hadronic rate. Finally, spectral functions are determined for the dominant hadronic modes and updates are given for several analyses. These include: tests of isospin invariance between the weak charged and electromagnetic hadronic currents, fits of the
ρ
resonance lineshape, and a QCD analysis of the non-strange hadronic decays using spectral moments, yielding the value
α
s
(
m
τ
2
)
=
0.340
±
0
.
005
exp
±
0
.
014
th
. The evolution to the
Z mass scale yields
α
s
(
M
Z
2
)
=
0.1209
±
0.0018
. This value agrees well with the direct determination from the
Z width and provides the most accurate test to date of asymptotic freedom in the QCD gauge theory.
Exotic hadrons made of five quarks (pentaquarks) are searched for in hadronic Z decays collected by the ALEPH detector at LEP. No significant signal is observed. At 95% C.L., upper limits are set on ...the production rates N of such particles and their charge-conjugate state per Z decay: NΘ(1535)+⋅BR(Θ(1535)+→pKS0)<6.2×10−4,NΞ(1862)−−⋅BR(Ξ(1862)−−→Ξ−π−)<4.5×10−4,NΞ(1862)0⋅BR(Ξ(1862)0→Ξ−π+)<8.9×10−4,NΘc(3100)0⋅BR(Θc(3100)0→D*−p)<6.3×10−4,NΘc(3100)0⋅BR(Θc(3100)0→D−p)<31×10−4.
The CALICE collaboration is studying the design of high performance electromagneticand hadronic calorimeters for future International Linear Collider detectors. For the hadronic calorimeter, one ...option is a highly granular sampling calorimeter with steel as absorber and scintillator layers as active material. High granularity is obtained by segmenting the scintillator into small tiles individually read out via silicon photo-multipliers (SiPM). A prototype has been built, consisting of thirty-eight sensitive layers, segmented into about eight thousand channels. In 2007 the prototype was exposed to positrons and hadrons using the CERN SPS beam, covering a wide range of beam energies and angles of incidence. The challenge of cell equalization and calibration of such a large number of channels is best validated using electromagnetic processes. The response of the prototype steel-scintillator calorimeter, including linearity and uniformity, to electrons is investigated and described.
Lepton colliders are considered as options to complement and to extend the physics programme at the Large Hadron Collider. The Compact Linear Collider (CLIC) is an e super(+)e super(-) collider under ...development aiming at centre-of-mass energies of up to 3 TeV. For experiments at CLIC, a hadron sampling calorimeter with tungsten absorber is proposed. Such a calorimeter provides sufficient depth to contain high-energy showers, while allowing a compact size for the surrounding solenoid. A fine-grained calorimeter prototype with tungsten absorber plates and scintillator tiles read out by silicon photomultipliers was built and exposed to particle beams at CERN. Results obtained with electrons, pions and protons of momenta up to 10 GeV are presented in terms of energy resolution and shower shape studies. The results are compared with several GEANT4 simulation models in order to assess the reliability of the Monte Carlo predictions relevant for a future experiment at CLIC.
Understanding what controls the water vapor isotopic composition of
the sub-cloud layer (SCL) over tropical oceans (δD0) is
a first step towards understanding the water vapor isotopic composition
...everywhere in the troposphere. We propose an analytical model to predict
δD0 motivated by the hypothesis that the altitude from
which the free tropospheric air originates (zorig) is an important
factor: when the air mixing into the SCL is lower in altitude, it
is generally moister, and thus it depletes the SCL more efficiently.
We extend previous simple box models of the SCL by prescribing the
shape of δD vertical profiles as a function of humidity profiles
and by accounting for rain evaporation and horizontal advection effects.
The model relies on the assumption that δD profiles are steeper
than mixing lines, and that the SCL is at steady state, restricting
its applications to timescales longer than daily. In the model, δD0
is expressed as a function of zorig, humidity and temperature
profiles, surface conditions, a parameter describing the steepness
of the δD vertical gradient, and a few parameters describing
rain evaporation and horizontal advection effects. We show that δD0
does not depend on the intensity of entrainment, in contrast to several
previous studies that had hoped that δD0 measurements
could help estimate this quantity. Based on an isotope-enabled general circulation model simulation,
we show that δD0 variations are mainly controlled by mid-tropospheric
depletion and rain evaporation in ascending regions and by sea surface
temperature and zorig in subsiding regions. In turn, could δD0
measurements help estimate zorig and thus discriminate between
different mixing processes? For such isotope-based estimates of zorig
to be useful, we would need a precision of a few hundred meters in
deep convective regions and smaller than 20 m in stratocumulus regions.
To reach this target, we would need daily measurements of δD
in the mid-troposphere and accurate measurements of δD0
(accuracy down to 0.1 ‰ in the case of stratocumulus clouds,
which is currently difficult to obtain). We would also need information
on the horizontal distribution of δD to account for horizontal
advection effects, and full δD profiles to quantify the uncertainty
associated with the assumed shape for δD profiles. Finally,
rain evaporation is an issue in all regimes, even in stratocumulus
clouds. Innovative techniques would need to be developed to quantify
this effect from observations.
A highly granular electromagnetic calorimeter with scintillator strip readout is being developed for future linear collider experiments. A prototype of 21.5 X0 depth and 180×180mm2 transverse ...dimensions was constructed, consisting of 2160 individually read out 10×45×3mm3 scintillator strips. This prototype was tested using electrons of 2–32 GeV at the Fermilab Test Beam Facility in 2009. Deviations from linear energy response were less than 1.1%, and the intrinsic energy resolution was determined to be (12.5±0.1(stat.)±0.4(syst.))%∕EGeV⊕(1.2±0.1(stat.)−0.7+0.6(syst.))%, where the uncertainties correspond to statistical and systematic sources, respectively.
Bose-Einstein correlations are studied in pairs of charged pions from hadronic Z decays, collected by the ALEPH detector.The correlation function, measured using either the unlike-sign or the mixed ...reference sample, is studied in terms of the Lorentz-invariant four-momentum difference and its transverse, $Q_{\textrm{T}}$, and longitudinal, $Q_{\textrm{L}}$, components with respect to the longitudinal centre-of-mass system. Values for the correlation radii, $R_{\textrm{T}}$ and $R_{\textrm{L}}$, are obtained from the fit of the Goldhaber parametrisation.The results indicate that the correlation radii values depend on the chosen kind of reference sample and on the two-jet purity.
A prototype module for an International Linear Collider (ILC) detector was built, installed, and tested between 2006 and 2009 at CERN and Fermilab as part of the CALICE test beam program, in order to ...study the possibilities of extending energy sampling behind a hadronic calorimeter and to study the possibilities of providing muon tracking. The "tail catcher/muon tracker" (TCMT) is composed of 320 extruded scintillator strips (dimensions 1000 x 50 x 5 mm super(3)) packaged in 16 one-meter square planes interleaved between steel plates. The scintillator strips were read out with wavelength shifting fibers and silicon photomultipliers. The planes were arranged with alternating horizontal and vertical strip orientations. Data were collected for muons and pions in the energy range 6 GeV to 80 GeV. Utilizing data taken in 2006, this paper describes the design and construction of the TCMT, performance characteristics, and a beam-based evaluation of the ability of the TCMT to improve hadronic energy resolution in a prototype ILC detector. For a typical configuration of an ILC detector with a coil situated outside a calorimeter system with a thickness of 5.5 nuclear interaction lengths, a TCMT would improve relative energy resolution by 6-16% for pions between 20 and 80 GeV.
A first prototype of a scintillator strip-based electromagnetic calorimeter was built, consisting of 26 layers of tungsten absorber plates interleaved with planes of 45×10×3mm3 plastic scintillator ...strips. Data were collected using a positron test beam at DESY with momenta between 1 and 6GeV/c. The prototype׳s performance is presented in terms of the linearity and resolution of the energy measurement. These results represent an important milestone in the development of highly granular calorimeters using scintillator strip technology. A number of possible design improvements were identified, which should be implemented in a future detector of this type. This technology is being developed for a future linear collider experiment, aiming at the precise measurement of jet energies using particle flow techniques.
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