2,121 research outputs found
Global monitoring of tropospheric water vapor with GPS radio occultation aboard CHAMP
The paper deals with application of GPS radio occultation (RO) measurements
aboard CHAMP for the retrieval of tropospheric water vapor profiles. The GPS RO
technique provides a powerful tool for atmospheric sounding which requires no
calibration, is not affected by clouds, aerosols or precipitation, and provides
an almost uniform global coverage. We briefly overview data processing and
retrieval of vertical refractivity, temperature and water vapor profiles from
GPS RO observations. CHAMP RO data are available since 2001 with up to 200 high
resolution atmospheric profiles per day. Global validation of CHAMP water vapor
profiles with radiosonde data reveals a bias of about 0.2 g/kg and a standard
deviation of less than 1 g/kg specific humidity in the lower troposphere. We
demonstrate potentials of CHAMP RO retrievals for monitoring the mean
tropospheric water vapor distribution on a global scale.Comment: 7 pages, 4 figure
Nanoscale phase-engineering of thermal transport with a Josephson heat modulator
Macroscopic quantum phase coherence has one of its pivotal expressions in the
Josephson effect [1], which manifests itself both in charge [2] and energy
transport [3-5]. The ability to master the amount of heat transferred through
two tunnel-coupled superconductors by tuning their phase difference is the core
of coherent caloritronics [4-6], and is expected to be a key tool in a number
of nanoscience fields, including solid state cooling [7], thermal isolation [8,
9], radiation detection [7], quantum information [10, 11] and thermal logic
[12]. Here we show the realization of the first balanced Josephson heat
modulator [13] designed to offer full control at the nanoscale over the
phase-coherent component of thermal currents. Our device provides
magnetic-flux-dependent temperature modulations up to 40 mK in amplitude with a
maximum of the flux-to-temperature transfer coefficient reaching 200 mK per
flux quantum at a bath temperature of 25 mK. Foremost, it demonstrates the
exact correspondence in the phase-engineering of charge and heat currents,
breaking ground for advanced caloritronic nanodevices such as thermal splitters
[14], heat pumps [15] and time-dependent electronic engines [16-19].Comment: 6+ pages, 4 color figure
The relation between 13CO(2-1) line width in molecular clouds and bolometric luminosity of associated IRAS sources
We search for evidence of a relation between properties of young stellar
objects (YSOs) and their parent molecular clouds to understand the initial
conditions of high-mass star formation. A sample of 135 sources was selected
from the Infrared Astronomical Satellite (IRAS) Point Source Catalog, on the
basis of their red color to enhance the possibility of discovering young
sources. Using the Kolner Observatorium fur SubMillimeter Astronomie (KOSMA)
3-m telescope, a single-point survey in 13CO(2-1) was carried out for the
entire sample, and 14 sources were mapped further. Archival mid-infrared (MIR)
data were compared with the 13CO emissions to identify evolutionary stages of
the sources. A 13CO observed sample was assembled to investigate the
correlation between 13CO line width of the clouds and the luminosity of the
associated YSOs. We identified 98 sources suitable for star formation analyses
for which relevant parameters were calculated. We detected 18 cores from 14
mapped sources, which were identified with eight pre-UC HII regions and one UC
HII region, two high-mass cores earlier than pre-UC HII phase, four possible
star forming clusters, and three sourceless cores. By compiling a large (360
sources) 13CO observed sample, a good correlation was found between the 13CO
line width of the clouds and the bolometric luminosity of the associated YSOs,
which can be fitted as a power law: lg(dV13/km/s)=-0.023+0.135lg(Lbol/Lsolar).
Results show that luminous (>10^3Lsolar) YSOs tend to be associated with both
more massive and more turbulent (dV13>2km/s) molecular cloud structures.Comment: Accepted by Astronomy and Astrophysics; this version: sent to
publisher; 13 pages, 4 figures, 2 tables, 1 online appendi
Quantum critical states and phase transitions in the presence of non equilibrium noise
Quantum critical points are characterized by scale invariant correlations and
correspondingly long ranged entanglement. As such, they present fascinating
examples of quantum states of matter, the study of which has been an important
theme in modern physics. Nevertheless very little is known about the fate of
quantum criticality under non equilibrium conditions. In this paper we
investigate the effect of external noise sources on quantum critical points. It
is natural to expect that noise will have a similar effect to finite
temperature, destroying the subtle correlations underlying the quantum critical
behavior. Surprisingly we find that in many interesting situations the
ubiquitous 1/f noise preserves the critical correlations. The emergent states
show intriguing interplay of intrinsic quantum critical and external noise
driven fluctuations. We demonstrate this general phenomenon with specific
examples in solid state and ultracold atomic systems. Moreover our approach
shows that genuine quantum phase transitions can exist even under non
equilibrium conditions.Comment: 9 pages, 2 figure
Superinsulator Phase of Two-Dimensional Superconductors
Using path-integral Quantum Monte Carlo we study the low-temperature phase
diagram of a two-dimensional superconductor within a phenomenological model,
where vortices have a finite mass and move in a dissipative environment modeled
by a Caldeira-Leggett term. The quantum vortex liquid at high magnetic fields
exhibits superfluidity and thus corresponds to a {\em superinsulating} phase
which is characterized by a nonlinear voltage-current law for an infinite
system in the absence of pinning. This superinsulating phase is shifted to
higher magnetic fields in the presence of dissipation.Comment: 8 pages, 3 figures, to appear in Phys. Rev. Lett. (Oktober 1998
On CPT Symmetry: Cosmological, Quantum-Gravitational and other possible violations and their phenomenology
I discuss various ways in which CPT symmetry may be violated, and their
phenomenology in current or immediate future experimental facilities, both
terrestrial and astrophysical. Specifically, I discuss first violations of CPT
symmetry due to the impossibility of defining a scattering matrix as a
consequence of the existence of microscopic or macroscopic space-time
boundaries, such as Planck-scale Black-Hole (event) horizons, or cosmological
horizons due to the presence of a (positive) cosmological constant in the
Universe. Second, I discuss CPT violation due to breaking of Lorentz symmetry,
which may characterize certain approaches to quantum gravity, and third, I
describe models of CPT non invariance due to violations of locality of
interactions. In each of the above categories I discuss experimental
sensitivities. I argue that the majority of Lorentz-violating cases of CPT
breaking, with minimal (linear) suppression by the Planck-mass scale, are
already excluded by current experimental tests. There are however some
(stringy) models which can evade these constraints.Comment: 27 pages latex, Conference talk Beyond the Desert 200
Prevalence of Listeria species in camel sausages from retail markets in Aydin province in Turkey and RAPD analysis of Listeria monocytogenes isolates
Samples were taken from 100 camel sausages from the different retail markets in Aydin province in the south-west of Turkey and they were tested for the presence of Listeria spp by biochemical methods. Samples were enriched using Listeria Enrichment Broth and they were inoculated onto Listeria Selective Agar. Listeria monocytogenes was isolated from nine samples (9%), Listeria innocua from 14 samples (14%) and Listeria welshimeri from two samples(2%). A 701 bp fragment of listeriolysin O sequence for L. monocytogenes was amplified using specific primers by polymerase chain reaction (PCR) for confirmation of the identification. A random primer (OPA-11) was used in a random amplified polymorphic DNA (RAPD) assay. This detected five different band profiles amongst the L. monocytogenes isolates, indicating a relatively large amount of genetic heterogeneity amongst the nine isolates. The study has highlighted the need for improved strategies for food safety, in particular appropriate hygienic precautions to avoid contamination of sausage during the manufacturing process and appropriate preservation techniques during storage and transport, to prevent transmission of Listeria spp to consumers at home and abroad
Ultracold atomic gases in optical lattices: mimicking condensed matter physics and beyond
We review recent developments in the physics of ultracold atomic and
molecular gases in optical lattices. Such systems are nearly perfect
realisations of various kinds of Hubbard models, and as such may very well
serve to mimic condensed matter phenomena. We show how these systems may be
employed as quantum simulators to answer some challenging open questions of
condensed matter, and even high energy physics. After a short presentation of
the models and the methods of treatment of such systems, we discuss in detail,
which challenges of condensed matter physics can be addressed with (i)
disordered ultracold lattice gases, (ii) frustrated ultracold gases, (iii)
spinor lattice gases, (iv) lattice gases in "artificial" magnetic fields, and,
last but not least, (v) quantum information processing in lattice gases. For
completeness, also some recent progress related to the above topics with
trapped cold gases will be discussed.Comment: Review article. v2: published version, 135 pages, 34 figure
Scaling properties of protein family phylogenies
One of the classical questions in evolutionary biology is how evolutionary
processes are coupled at the gene and species level. With this motivation, we
compare the topological properties (mainly the depth scaling, as a
characterization of balance) of a large set of protein phylogenies with a set
of species phylogenies. The comparative analysis shows that both sets of
phylogenies share remarkably similar scaling behavior, suggesting the
universality of branching rules and of the evolutionary processes that drive
biological diversification from gene to species level. In order to explain such
generality, we propose a simple model which allows us to estimate the
proportion of evolvability/robustness needed to approximate the scaling
behavior observed in the phylogenies, highlighting the relevance of the
robustness of a biological system (species or protein) in the scaling
properties of the phylogenetic trees. Thus, the rules that govern the
incapability of a biological system to diversify are equally relevant both at
the gene and at the species level.Comment: Replaced with final published versio
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