1,212 research outputs found
The ZEUS Forward Plug Calorimeter with Lead-Scintillator Plates and WLS Fiber Readout
A Forward Plug Calorimeter (FPC) for the ZEUS detector at HERA has been built
as a shashlik lead-scintillator calorimeter with wave length shifter fiber
readout. Before installation it was tested and calibrated using the X5 test
beam facility of the SPS accelerator at CERN. Electron, muon and pion beams in
the momentum range of 10 to 100 GeV/c were used. Results of these measurements
are presented as well as a calibration monitoring system based on a Co
source.Comment: 38 pages (Latex); 26 figures (ps
Observation of Scaling Violations in Scaled Momentum Distributions at HERA
Charged particle production has been measured in deep inelastic scattering
(DIS) events over a large range of and using the ZEUS detector. The
evolution of the scaled momentum, , with in the range 10 to 1280
, has been investigated in the current fragmentation region of the Breit
frame. The results show clear evidence, in a single experiment, for scaling
violations in scaled momenta as a function of .Comment: 21 pages including 4 figures, to be published in Physics Letters B.
Two references adde
Measurement of the open-charm contribution to the diffractive proton structure function
Production of D*+/-(2010) mesons in diffractive deep inelastic scattering has
been measured with the ZEUS detector at HERA using an integrated luminosity of
82 pb^{-1}. Diffractive events were identified by the presence of a large
rapidity gap in the final state. Differential cross sections have been measured
in the kinematic region 1.5 < Q^2 < 200 GeV^2, 0.02 < y < 0.7, x_{IP} < 0.035,
beta 1.5 GeV and |\eta(D*+/-)| < 1.5. The measured cross
sections are compared to theoretical predictions. The results are presented in
terms of the open-charm contribution to the diffractive proton structure
function. The data demonstrate a strong sensitivity to the diffractive parton
densities.Comment: 35 pages, 11 figures, 6 table
Isolated tau leptons in events with large missing transverse momentum at HERA
A search for events containing isolated tau leptons and large missing
transverse momentum, not originating from the tau decay, has been performed
with the ZEUS detector at the electron-proton collider HERA, using 130 pb^-1 of
integrated luminosity. A search was made for isolated tracks coming from
hadronic tau decays. Observables based on the internal jet structure were
exploited to discriminate between tau decays and quark- or gluon-induced jets.
Three tau candidates were found, while 0.40 +0.12 -0.13 were expected from
Standard Model processes, such as charged current deep inelastic scattering and
single W-boson production. To search for heavy-particle decays, a more
restrictive selection was applied to isolate tau leptons produced together with
a hadronic final state with high transverse momentum. Two candidate events
survive, while 0.20 +-0.05 events are expected from Standard Model processes.Comment: 28 pages, 4 figures, 3 tables, accepted by Phys. Lett. B. Updated
with minor changes to the text requested by the journal refere
Universality of Fedosov's Construction for Star Products of Wick Type on Pseudo-K\"ahler Manilfolds
In this paper we construct star products on a pseudo-K\"ahler manifold
using a modification of the Fedosov method based on a different
fibrewise product similar to the Wick product on . In a first step
we show that this construction is rich enough to obtain star products of every
equivalence class by computing Deligne's characteristic class of these
products. Among these products we uniquely characterize the ones which have the
additional property to be of Wick type which means that the bidifferential
operators describing the star products only differentiate with respect to
holomorphic directions in the first argument and anti-holomorphic directions in
the second argument. These star products are in fact strongly related to star
products with separation of variables introduced and studied by Karabegov. This
characterization gives rise to special conditions on the data that enter the
Fedosov procedure. Moreover, we compare our results that are based on an
obviously coordinate independent construction to those of Karabegov that were
obtained by local considerations and give an independent proof of the fact that
star products of Wick type are in bijection to formal series of closed
two-forms of type on . Using this result we finally succeed in
showing that the given Fedosov construction is universal in the sense that it
yields all star products of Wick type on a pseudo-K\"ahler manifold.Comment: terminology corrected, typos removed, appendix adde
Gene and genon concept: coding versus regulation: A conceptual and information-theoretic analysis of genetic storage and expression in the light of modern molecular biology
We analyse here the definition of the gene in order to distinguish, on the basis of modern insight in molecular biology, what the gene is coding for, namely a specific polypeptide, and how its expression is realized and controlled. Before the coding role of the DNA was discovered, a gene was identified with a specific phenotypic trait, from Mendel through Morgan up to Benzer. Subsequently, however, molecular biologists ventured to define a gene at the level of the DNA sequence in terms of coding. As is becoming ever more evident, the relations between information stored at DNA level and functional products are very intricate, and the regulatory aspects are as important and essential as the information coding for products. This approach led, thus, to a conceptual hybrid that confused coding, regulation and functional aspects. In this essay, we develop a definition of the gene that once again starts from the functional aspect. A cellular function can be represented by a polypeptide or an RNA. In the case of the polypeptide, its biochemical identity is determined by the mRNA prior to translation, and that is where we locate the gene. The steps from specific, but possibly separated sequence fragments at DNA level to that final mRNA then can be analysed in terms of regulation. For that purpose, we coin the new term “genon”. In that manner, we can clearly separate product and regulative information while keeping the fundamental relation between coding and function without the need to introduce a conceptual hybrid. In mRNA, the program regulating the expression of a gene is superimposed onto and added to the coding sequence in cis - we call it the genon. The complementary external control of a given mRNA by trans-acting factors is incorporated in its transgenon. A consequence of this definition is that, in eukaryotes, the gene is, in most cases, not yet present at DNA level. Rather, it is assembled by RNA processing, including differential splicing, from various pieces, as steered by the genon. It emerges finally as an uninterrupted nucleic acid sequence at mRNA level just prior to translation, in faithful correspondence with the amino acid sequence to be produced as a polypeptide. After translation, the genon has fulfilled its role and expires. The distinction between the protein coding information as materialised in the final polypeptide and the processing information represented by the genon allows us to set up a new information theoretic scheme. The standard sequence information determined by the genetic code expresses the relation between coding sequence and product. Backward analysis asks from which coding region in the DNA a given polypeptide originates. The (more interesting) forward analysis asks in how many polypeptides of how many different types a given DNA segment is expressed. This concerns the control of the expression process for which we have introduced the genon concept. Thus, the information theoretic analysis can capture the complementary aspects of coding and regulation, of gene and genon
Partial chord diagrams and matrix models
In this article, the enumeration of partial chord diagrams is discussed via
matrix model techniques. In addition to the basic data such as the number of
backbones and chords, we also consider the Euler characteristic, the backbone
spectrum, the boundary point spectrum, and the boundary length spectrum.
Furthermore, we consider the boundary length and point spectrum that unifies
the last two types of spectra. We introduce matrix models that encode
generating functions of partial chord diagrams filtered by each of these
spectra. Using these matrix models, we derive partial differential equations -
obtained independently by cut-and-join arguments in an earlier work - for the
corresponding generating functions.Comment: 42 pages, 14 figure
Higher order terms for the quantum evolution of a Wick observable within the Hepp method
The Hepp method is the coherent state approach to the mean field dynamics for
bosons or to the semiclassical propagation. A key point is the asymptotic
evolution of Wick observables under the evolution given by a time-dependent
quadratic Hamiltonian. This article provides a complete expansion with respect
to the small parameter \epsilon > 0 which makes sense within the
infinite-dimensional setting and fits with finite-dimensional formulae
Mycelium-enhanced bacterial degradation of organic pollutants under bioavailability restrictions
This work examines the role of mycelia in enhancing the degradation by attached bacteria of organic pollutants that have poor bioavailability. Two oomycetes, Pythium oligandrum and Pythium aphanidermatum, were selected as producers of mycelial networks, while Mycobacterium gilvum VM552 served as a model polycyclic aromatic hydrocarbon (PAH)-degrading bacterium. The experiments consisted of bacterial cultures exposed to a non-disturbed non-aqueous phase liquid (NAPL) layer containing a heavy fuel spiked with 14C-labeled phenanthrene that were incubated in the presence or absence of the mycelia of the oomycetes in both shaking and static conditions. At the end of the incubation, the changes in the total alkane and PAH contents in the NAPL residue were quantified. The results revealed that with shaking and the absence of mycelia, the strain VM552 grew by utilizing the bulk of alkanes and PAHs in the fuel; however, biofilm formation was incipient and phenanthrene was mineralized following zero-order kinetics, due to bioavailability limitation. The addition of mycelia favored biofilm formation and dramatically enhanced the mineralization of phenanthrene, up to 30 times greater than the rate without mycelia, possibly by providing a physical support to bacterial colonization and by supplying nutrients at the NAPL/water interface. The results in the static condition were very different because the bacterial strain alone degraded phenanthrene with sigmoidal kinetics but could not degrade alkanes or the bulk of PAHs. We suggest that bacteria/oomycete interactions should be considered not only in the design of new inoculants in bioremediation, but also in biodegradation assessments of chemicals present in natural environments
Radiation Damage and Recovery Properties of Common Plastics PEN (Polyethylene Naphthalate) and PET (Polyethylene Terephthalate) Using a 137Cs Gamma Ray Source Up To 1 MRad and 10 MRad
Polyethylene naphthalate (PEN) and polyethylene teraphthalate (PET) are cheap
and common polyester plastics used throughout the world in the manufacturing of
bottled drinks, containers for foodstuffs, and fibers used in clothing. These
plastics are also known organic scintillators with very good scintillation
properties. As particle physics experiments increase in energy and particle
flux density, so does radiation exposure to detector materials. It is therefore
important that scintillators be tested for radiation tolerance at these
generally unheard of doses. We tested samples of PEN and PET using laser
stimulated emission on separate tiles exposed to 1 MRad and 10 MRad gamma rays
with a 137Cs source. PEN exposed to 1 MRad and 10 MRad emit 71.4% and 46.7% of
the light of an undamaged tile, respectively, and maximally recover to 85.9%
and 79.5% after 5 and 9 days, respectively. PET exposed to 1 MRad and 10 MRad
emit 35.0% and 12.2% light, respectively, and maximally recover to 93.5% and
80.0% after 22 and 60 days, respectively
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