3,853 research outputs found
Personalities of Russian amateur botany, 3. Ivan M. Schvetzov and Theodor S. Nenukow, prominent experts in the flora of Nizhni Novgorod Region, and the taxonomic identity of plant species described by Nenukow
Ivan Schvetzov collected many specimens of vascular plants, fungi, mosses and lichens mostly from the western part of Nizhni Novgorod Region of Russia, including the original collections of Cytisus ruthenicus var. zingeri Nenukow. Theodor Nenukow was a prominent amateur botanist from Nizhni Novgorod. He studied the flora of Nizhni Novgorod Region, weed and meadow flora of Central Russia and vascular plants of Estonia. He described a few infraspecific taxa and two species of vascular plants, Valeriana estonica Nenukow (synonymised here with V. officinalis subsp. tenuifolia (Vahl) Schübl. & G.Martens) and Odontites estonicus Nenukow (a synonym of O. vulgaris Moench), and the basionym for Cytisus zingeri (Nenukow) V.I.Krecz. (a glabrous variety of C. ruthenicus Fisch. ex Otto). The places of valid publication are clarified for C. ruthenicus var. zingeri and Persicaria linicola, and the lectotype is designated for C. ruthenicus var. zingeri
Fast photoprocesses in a symmetric indotricarbocyanine dye (hitc) in solutions
Spectral-kinetic and photochemical properties of HITC dye with iodide and perchlorate counterions have been studied in environments where the dye molecules exist in different ionic forms. In ethanol, the dye molecules exist as free ions; in dichlorobenzene, as contact ion pairs. Superfast transformation of non-stationary spectra in an HITC dye bleaching band is found. The observed effects are interpreted within the framework of concepts on "burning out" a notch in the contour of a non-uniformly widened vibronic band of S0 → S1-absorption. Qualitative differences in recorded absorption spectra from the dye excited electronic states for weakly and highly polar solvents are found. It is shown that the observed differences are caused by superfast charge transfer in the contact ion pairs that results in the formation of free radicals
Moduli of mathematical instanton vector bundles with odd c_2 on projective space
The problem of irreducibility of the moduli space I_n of rank-2 mathematical
instanton vector bundles with arbitrary positive second Chern class n on the
projective 3-space is considered. The irreducibility of I_n was known for small
values of n: Barth 1977 (n=1), Hartshorne 1978 (n=2), Ellingsrud and Stromme
1981 (n=3), Barth 1981 (n=4), Coanda, Tikhomirov and Trautmann 2003 (n=5). In
this paper we prove the irreducibility of I_n for an arbitrary odd n.Comment: 62 page
Predictability in the large: an extension of the concept of Lyapunov exponent
We investigate the predictability problem in dynamical systems with many
degrees of freedom and a wide spectrum of temporal scales. In particular, we
study the case of turbulence at high Reynolds numbers by introducing a
finite-size Lyapunov exponent which measures the growth rate of finite-size
perturbations. For sufficiently small perturbations this quantity coincides
with the usual Lyapunov exponent. When the perturbation is still small compared
to large-scale fluctuations, but large compared to fluctuations at the smallest
dynamically active scales, the finite-size Lyapunov exponent is inversely
proportional to the square of the perturbation size. Our results are supported
by numerical experiments on shell models. We find that intermittency
corrections do not change the scaling law of predictability. We also discuss
the relation between finite-size Lyapunov exponent and information entropy.Comment: 4 pages, 2 Postscript figures (included), RevTeX 3.0, files packed
with uufile
Search for invisible decays of sub-GeV dark photons in missing-energy events at the CERN SPS
We report on a direct search for sub-GeV dark photons (A') which might be
produced in the reaction e^- Z \to e^- Z A' via kinetic mixing with photons by
100 GeV electrons incident on an active target in the NA64 experiment at the
CERN SPS. The A's would decay invisibly into dark matter particles resulting in
events with large missing energy. No evidence for such decays was found with
2.75\cdot 10^{9} electrons on target. We set new limits on the \gamma-A' mixing
strength and exclude the invisible A' with a mass < 100 MeV as an explanation
of the muon g_\mu-2 anomaly.Comment: 6 pages, 3 figures; Typos corrected, references adde
Strong Reduction of the Effective Radiation Length in an Axially Oriented Scintillator Crystal
We measured a considerable increase of the emitted radiation by 120 GeV/c electrons in an axially oriented lead tungstate scintillator crystal, if compared to the case in which the sample was not aligned with the beam direction. This enhancement resulted from the interaction of particles with the strong crystalline electromagnetic field. The data collected at the external lines of the CERN Super Proton Synchrotron were critically compared to Monte Carlo simulations based on the Baier-Katkov quasiclassical method, highlighting a reduction of the scintillator radiation length by a factor of 5 in the case of beam alignment with the [001] crystal axes. The observed effect opens the way to the realization of compact electromagnetic calorimeters or detectors based on oriented scintillator crystals in which the amount of material can be strongly reduced with respect to the state of the art. These devices could have relevant applications in fixed-target experiments, as well as in satellite-borne γ telescopes
A New 76Ge Double Beta Decay Experiment at LNGS
This Letter of Intent has been submitted to the Scientific Committee of the
INFN Laboratori Nazionali del Gran Sasso (LNGS) in March 2004. It describes a
novel facility at the LNGS to study the double beta decay of 76Ge using an
(optionally active) cryogenic fluid shield. The setup will allow to scrutinize
with high significance on a short time scale the current evidence for
neutrinoless double beta decay of 76Ge using the existing 76Ge diodes from the
previous Heidelberg-Moscow and IGEX experiments. An increase in the lifetime
limit can be achieved by adding more enriched detectors, remaining thereby
background-free up to a few 100 kg-years of exposure.Comment: 67 pages, 19 eps figures, 17 tables, gzipped tar fil
A concept of the transition radiation detector for a hadron separation in a forward direction of the LHC experiments
Studying of hadron production in forward direction at the LHC energy has a great interest both for understanding of the fundamental QCD processes and also in applied areas such as the description of ultra-high energy cosmic particle interactions. The energies of secondary hadrons in such studies almost reach the maximum energy available at the LHC of ∼6 TeV, which corresponds to a Lorentz γ-factor up to 104 and above. The only effective technique able to identify particles in this range is based on the transition radiation detectors (TRD). Prototypes of such kind of detector were built and tested at the CERN SPS accelerator. Some experimental results obtained in these tests are briefly presented here and compared with Monte Carlo (MC) simulations. MC model demonstrates a good agreement with the experiment. On this basis a concept of a full-scale TRD optimized for the hadron identification in the TeV energy region is proposed. Different particle identification techniques were considered and examined. The expected detector performance to reconstruct secondary hadrons produced in forward direction at the LHC is presented
First events from the CNGS neutrino beam detected in the OPERA experiment
The OPERA neutrino detector at the underground Gran Sasso Laboratory (LNGS)
was designed to perform the first detection of neutrino oscillations in
appearance mode, through the study of nu_mu to nu_tau oscillations. The
apparatus consists of a lead/emulsion-film target complemented by electronic
detectors. It is placed in the high-energy, long-baseline CERN to LNGS beam
(CNGS) 730 km away from the neutrino source. In August 2006 a first run with
CNGS neutrinos was successfully conducted. A first sample of neutrino events
was collected, statistically consistent with the integrated beam intensity.
After a brief description of the beam and of the various sub-detectors, we
report on the achievement of this milestone, presenting the first data and some
analysis results.Comment: Submitted to the New Journal of Physic
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