1,146 research outputs found
Dynamics and optical absorption of electronic excitations under the influence of coloured noise
For a model dimer the influence of vibrational degrees of freedom on electronic excitations is described by a dichotomic Markov process with coloured noise. Within this model the energy transport between the two units of the dimer, especially the transition between coherent and incoherent motion is discussed. Furthermore the optical absorption line shape is evaluated for various values of the model parameters
ALMA detects a radial disk wind in DG Tauri
Astronomy and Astrophysics Letters, in press, 8 pagesAims. We aim to use the high spatial resolution of the Atacama Large Millimeter/submillimeter Array (ALMA) to map the flow pattern of molecular gas near DG Tauri and its disk, a young stellar object driving a jet and a molecular outflow. Methods. We use observations from ALMA in the J = 2-1 transition of 12CO, 13CO, and C 18O to study the Keplerian disk of DG Tauri and outflows that may be related to the disk and the jet. Results. We find a new wind component flowing radially at a steep angle (≈ 25° from the vertical) above the disk with a velocity of ≈ 3.1 km s -1. It continues the trend of decreasing velocity for increasing distance from the jet axis ("onion-like velocity structure"). Conclusions. The new component is located close to the protostellar disk surface and may be related to photoevaporative winds.Peer reviewe
Final Results from phase II of the Mainz Neutrino Mass Search in Tritium Decay
The paper reports on the improved Mainz experiment on tritum
spectroscopy which yields a 10 times' higher signal to background ratio than
before. The main experimental effects and systematic uncertainties have been
investigated in side experiments and possible error sources have been
eliminated. Extensive data taking took place in the years 1997 to 2001. A
residual analysis of the data sets yields for the square of the electron
antineutrino mass the final result of eV/c. We derive an upper limit of
eV/c at 95% confidence level for the mass itself.Comment: 22 pages, 22 figures submitted to EPJ
Applications of Radio-Frequency Heating in Environmental Technology
AbstractDirect dielectric heating with radio-frequency (RF) electromagnetic fields is used to optimize a variety of processes in environmental technology, namely soil remediation by soil vapor extraction or biodegradation, adsorptive-catalytic off-gas treatment, thermal regeneration of drying agents in biogas or natural gas treatment and decontamination and/or drying of brickwork
Operator entanglement of two-qubit joint unitary operations revisited: Schmidt number approach
Operator entanglement of two-qubit joint unitary operations is revisited.
Schmidt number is an important attribute of a two-qubit unitary operation, and
may have connection with the entanglement measure of the unitary operator. We
found the entanglement measure of two-qubit unitary operators is classified by
the Schmidt number of the unitary operators. The exact relation between the
operator entanglement and the parameters of the unitary operator is clarified
too.Comment: To appear in the Brazilian Journal of Physic
Quantum uniqueness
In the classical world one can construct two identical systems which have
identical behavior and give identical measurement results. We show this to be
impossible in the quantum domain. We prove that after the same quantum
measurement two different quantum systems cannot yield always identical
results, provided the possible measurement results belong to a non orthogonal
set. This is interpreted as quantum uniqueness - a quantum feature which has no
classical analog. Its tight relation with objective randomness of quantum
measurements is discussed.Comment: Presented at 4th Feynman festival, June 22-26, 2009, in Olomouc,
Czech Republic
The Role of Mass and Environment in Multiple Star Formation: A 2MASS Survey of Wide Multiplicity in Three Young Associations
We present the results of a search for wide binary systems among 783 members
of three nearby young associations: Taurus-Auriga, Chamaeleon I, and two
subgroups of Upper Scorpius. Near-infrared (JHK) imagery from 2MASS was
analyzed to search for wide (1-30"; ~150-4500 AU) companions to known
association members, using color-magnitude cuts to reject likely background
stars. We identify a total of 131 candidate binary companions with colors
consistent with physical association, of which 39 have not been identified
previously in the literature. Our results suggest that the wide binary
frequency is a function of both mass and environment, with significantly higher
frequencies among high-mass stars than lower-mass stars and in the T
associations than in the OB association. We discuss the implications for wide
binary formation and conclude that the environmental dependence is not a direct
result of stellar density or total association mass, but instead might depend
on another environmental parameter like the gas temperature. We also analyze
the mass ratio distribution as a function of mass and find that it agrees with
the distribution for field stars to within the statistical uncertainties. The
binary populations in these associations generally follow the empirical
mass-maximum separation relation observed for field binaries, but we have found
one candidate low-mass system (USco-160611.9-193532; Mtot~0.4 Msun) which has a
projected separation (10.8"; 1550 AU) much larger than the suggested limit for
its mass. (Abridged)Comment: Accepted to ApJ; 27 pages in emulateapj format. The full version of
table 2 can be downloaded via http://www.astro.caltech.edu/~alk/tab2.pdf
(PDF) or http://www.astro.caltech.edu/~alk/tab2.txt (text
Generalized quantum measurements. Part I: Information properties of soft quantum measurements
A special class of soft quantum measurements as a physical model of the fuzzy
measurements widely used in physics is introduced and its information
properties are studied in detail.Comment: 25 pages, 3 figures, 25 ref
Association of Fidaxomicin with C. difficile spores: Effects of Persistence on Subsequent Spore Recovery, Outgrowth and Toxin Production.
Background: We have previously shown that fidaxomicin instillation prevents spore recovery in an in-vitro gut model, whereas vancomycin does not. The reasons for this are unclear. Here, we have investigated persistence of fidaxomicin and vancomycin on C. difficile spores, and examined post-antibiotic exposure spore recovery, outgrowth and toxin production. Methods: Prevalent UK C. difficile ribotypes (n=10) were incubated with 200mg/L fidaxomicin, vancomycin or a non-antimicrobial containing control for 1 h in faecal filtrate or Phosphate Buffered Saline. Spores were washed three times with faecal filtrate or phosphate buffered saline, and residual spore-associated antimicrobial activity was determined by bioassay. For three ribotypes (027, 078, 015), antimicrobial-exposed, faecal filtrate-washed spores and controls were inoculated into broth. Viable vegetative and spore counts were enumerated on CCEYL agar. Percentage phase bright spores, phase dark spores and vegetative cells were enumerated by phase contrast microscopy at 0, 3, 6, 24 and 48 h post-inoculation. Toxin levels (24 and 48h) were determined by cell cytotoxicity assay. Results: Fidaxomicin, but not vancomycin persisted on spores of all ribotypes following washing in saline (mean=10.1mg/L; range= 4.0-14mg/L) and faecal filtrate (mean =17.4mg/L; 8.4-22.1mg/L). Outgrowth and proliferation rates of vancomycin-exposed spores were similar to controls, whereas fidaxomicin-exposed spores showed no vegetative cell growth after 24 and 48 h. At 48h, toxin levels averaged 3.7 and 3.3 relative units (RU) in control and vancomycin-exposed samples, respectively, but were undetectable in fidaxomicin-exposed samples. Conclusion: Fidaxomicin persists on C. difficile spores, whereas vancomycin does not. This persistence prevents subsequent growth and toxin production in vitro. This may have implications on spore viability, thereby impacting CDI recurrence and transmission rates
The Uncertainty Principle in the Presence of Quantum Memory
The uncertainty principle, originally formulated by Heisenberg, dramatically
illustrates the difference between classical and quantum mechanics. The
principle bounds the uncertainties about the outcomes of two incompatible
measurements, such as position and momentum, on a particle. It implies that one
cannot predict the outcomes for both possible choices of measurement to
arbitrary precision, even if information about the preparation of the particle
is available in a classical memory. However, if the particle is prepared
entangled with a quantum memory, a device which is likely to soon be available,
it is possible to predict the outcomes for both measurement choices precisely.
In this work we strengthen the uncertainty principle to incorporate this case,
providing a lower bound on the uncertainties which depends on the amount of
entanglement between the particle and the quantum memory. We detail the
application of our result to witnessing entanglement and to quantum key
distribution.Comment: 5 pages plus 12 of supplementary information. Updated to match the
journal versio
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