154 research outputs found
Quadrature-dependent Bogoliubov transformations and multiphoton squeezed states
We introduce a linear, canonical transformation of the fundamental
single--mode field operators and that generalizes the linear
Bogoliubov transformation familiar in the construction of the harmonic
oscillator squeezed states. This generalization is obtained by adding to the
linear transformation a nonlinear function of any of the fundamental quadrature
operators and , making the original Bogoliubov transformation
quadrature--dependent. Remarkably, the conditions of canonicity do not impose
any constraint on the form of the nonlinear function, and lead to a set of
nontrivial algebraic relations between the --number coefficients of the
transformation. We examine in detail the structure and the properties of the
new quantum states defined as eigenvectors of the transformed annihilation
operator . These eigenvectors define a class of multiphoton squeezed states.
The structure of the uncertainty products and of the quasiprobability
distributions in phase space shows that besides coherence properties, these
states exhibit a squeezing and a deformation (cooling) of the phase--space
trajectories, both of which strongly depend on the form of the nonlinear
function. The presence of the extra nonlinear term in the phase of the wave
functions has also relevant consequences on photon statistics and correlation
properties. The non quadratic structure of the associated Hamiltonians suggests
that these states be generated in connection with multiphoton processes in
media with higher nonlinearities.Comment: 16 pages, 15 figure
The neurotropic black yeast Exophiala dermatitidis has a possible origin in the tropical rain forest
The black yeast Exophiala dermatitidis is known as a rare
etiologic agent of neurotropic infections in humans, occurring particularly in
East and Southeast Asia. In search of its natural habitat, a large sampling
was undertaken in temperate as well as in tropical climates. Sampling sites
were selected on the basis of the origins of previously isolated strains, and
on the basis of physiological properties of the species, which also determined
a selective isolation protocol. The species was absent from outdoor
environments in the temperate climate, but present at low abundance in
comparable habitats in the tropics. Positive outdoor sites particularly
included faeces of frugivorous birds and bats, in urban as well as in natural
areas. Tropical fruits were found E. dermatitidis positive at low
incidence. Of the human-made environments sampled, railway ties contaminated
by human faeces and oily debris in the tropics were massively positive, while
the known abundance of the fungus in steam baths was confirmed. On the basis
of the species' oligotrophy, thermotolerance, acidotolerance, moderate
osmotolerance, melanization and capsular yeast cells a natural life cycle in
association with frugivorous animals in foci in the tropical rain forest,
involving passage of living cells through the intestinal tract was
hypothesized. The human-dominated environment may have become contaminated by
ingestion of wild berries carrying fungal propagule
Performance of ALICE pixel prototypes in high energy beams
The two innermost layers of the ALICE inner tracking system are instrumented
with silicon pixel detectors. Single chip assembly prototypes of the ALICE
pixels have been tested in high energy particle beams at the CERN SPS.
Detection efficiency and spatial precision have been studied as a function of
the threshold and the track incidence angle. The experimental method, data
analysis and main results are presented.Comment: 10 pages, 9 figures, contribution to PIX2005 Workshop, Bonn
(Germany), 5-8 September 200
Beam Test Performance and Simulation of Prototypes for the ALICE Silicon Pixel Detector
The silicon pixel detector (SPD) of the ALICE experiment in preparation at
the Large Hadron Collider (LHC) at CERN is designed to provide the precise
vertex reconstruction needed for measuring heavy flavor production in heavy ion
collisions at very high energies and high multiplicity. The SPD forms the
innermost part of the Inner Tracking System (ITS) which also includes silicon
drift and silicon strip detectors. Single assembly prototypes of the ALICE SPD
have been tested at the CERN SPS using high energy proton/pion beams in 2002
and 2003. We report on the experimental determination of the spatial precision.
We also report on the first combined beam test with prototypes of the other ITS
silicon detector technologies at the CERN SPS in November 2004. The issue of
SPD simulation is briefly discussed.Comment: 4 pages, 5 figures, prepared for proceedings of 7th International
Position Sensitive Detectors Conference, Liverpool, Sept. 200
Opportunistic, human-pathogenic species in the Herpotrichiellaceae are phenotypically similar to saprobic or phytopathogenic species in the Venturiaceae
Although morphologically similar, species of Cladophialophora
(Herpotrichiellaceae) were shown to be phylogenetically distinct from
Pseudocladosporium (Venturiaceae), which was revealed to be
synonymous with the older genus, Fusicladium. Other than being
associated with human disorders, species of Cladophialophora were
found to also be phytopathogenic, or to occur as saprobes on organic material,
or in water, fruit juices, or sports drinks, along with species of
Exophiala. Caproventuria and Metacoleroa were
confirmed to be synonyms of Venturia, which has Fusicladium
(= Pseudocladosporium) anamorphs. Apiosporina, based on
A. collinsii, clustered basal to the Venturia clade, and
appears to represent a further synonym. Several species with a
pseudocladosporium-like morphology in vitro represent a sister clade
to the Venturia clade, and are unrelated to Polyscytalum.
These taxa are newly described in Fusicladium, which is
morphologically close to Anungitea, a heterogeneous genus with
unknown phylogenetic affinity. In contrast to the
Herpotrichiellaceae, which were shown to produce numerous
synanamorphs in culture, species of the Venturiaceae were
morphologically and phylogenetically more uniform. Several new species and new
combinations were introduced in Cladophialophora, Cyphellophora
(Herpotrichiellaceae), Exophiala, Fusicladium, Venturia
(Venturiaceae), and Cylindrosympodium (incertae
sedis)
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