24,257 research outputs found
The dynamical Casimir effect in superconducting microwave circuits
We theoretically investigate the dynamical Casimir effect in electrical
circuits based on superconducting microfabricated waveguides with tunable
boundary conditions. We propose to implement a rapid modulation of the boundary
conditions by tuning the applied magnetic flux through superconducting quantum
interference devices (SQUIDs) that are embedded in the waveguide circuits. We
consider two circuits: (i) An open waveguide circuit that corresponds to a
single mirror in free space, and (ii) a resonator coupled to a microfabricated
waveguide, which corresponds to a single-sided cavity in free space. We analyze
the properties of the dynamical Casimir effect in these two setups by
calculating the generated photon-flux density, output-field correlation
functions, and the quadrature squeezing spectra. We show that these properties
of the output field exhibit signatures unique to the radiation due to the
dynamical Casimir effect, and could therefore be used for distinguishing the
dynamical Casimir effect from other types of radiation in these circuits. We
also discuss the similarities and differences between the dynamical Casimir
effect, in the resonator setup, and downconversion of pump photons in
parametric oscillators.Comment: 18 pages, 14 figure
X-band noise temperature effects of rain on DSN antenna feedhorns
Simulated rain tests were carried out to determine the noise temperature contribution of liquid water adhering to the aperture cover material on both a standard DSN X-band feedhorn and on an S/X-band common aperture feedhorn. It was found that for the particular common aperture feedhorn tested, system noise temperature increases were much greater when the plastic horn cover material was old and weathered than when it was new. The age and condition of the aperture cover material is believed to be a major factor in the amount of degradation experienced by a telecommunications system during rain events
Relations between entanglement and purity in non-Markovian dynamics
Knowledge of the relationships among different features of quantumness, like
entanglement and state purity, is important from both fundamental and practical
viewpoints. Yet, this issue remains little explored in dynamical contexts for
open quantum systems. We address this problem by studying the dynamics of
entanglement and purity for two-qubit systems using paradigmatic models of
radiation-matter interaction, with a qubit being isolated from the environment
(spectator configuration). We show the effects of the corresponding local
quantum channels on an initial two-qubit pure entangled state in the
concurrence-purity diagram and find the conditions which enable dynamical
closed formulas of concurrence, used to quantify entanglement, as a function of
purity. We finally discuss the usefulness of these relations in assessing
entanglement and purity thresholds which allow noisy quantum teleportation. Our
results provide new insights about how different properties of composite open
quantum systems behave and relate each other during quantum evolutions.Comment: 16 Pages, 10 Figures. One author added. Improved version with more
references and comment
Spin-dependent beating patterns in thermoelectric properties: Filtering the carriers of the heat flux in a Kondo adatom system
We theoretically investigate the thermoelectric properties of a
spin-polarized two-dimensional electron gas hosting a Kondo adatom hybridized
with an STM tip. Such a setup is treated within the single-impurity Anderson
model in combination with the atomic approach for the Green's functions. Due to
the spin dependence of the Fermi wavenumbers the electrical and thermal
conductances, together with thermopower and Lorenz number reveal beating
patterns as function of the STM tip position in the Kondo regime. In
particular, by tuning the lateral displacement of the tip with respect to the
adatom vicinity, the temperature and the position of the adatom level, one can
change the sign of the Seebeck coefficient through charge and spin. This opens
a possibility of the microscopic control of the heat flux analogously to that
established for the electrical current
Decoding Wheat Endosphere–Rhizosphere Microbiomes in Rhizoctonia solani–Infested Soils Challenged by Streptomyces Biocontrol Agents
The endosphere and the rhizosphere are pertinent milieus with microbial communities that perturb the agronomic traits of crop plants through beneficial or detrimental interactions. In this study, we challenged these communities by adding Streptomyces biocontrol strains to wheat seeds in soils with severe Rhizoctonia solani infestation. Wheat plants were grown in a glasshouse standardized system, and the bacterial and fungal microbiomes of 233 samples of wheat roots (endosphere) and rhizosphere soils were monitored for 20 weeks, from seed to mature plant stage. The results showed highly dynamic and diverse microbial communities that changed over time, with Sphingomonas bacteria and Aspergillus, Dipodascus, and Trichoderma fungi increasing over time. Application of biocontrol Streptomyces strains promoted plant growth and maturation of wheat heads and modulated the root microbiome, decreasing Paenibacillus and increasing other bacterial and fungal OTUs. The soils with the highest levels of R. solani had increased reads of Thanatephorus (Rhizoctonia anamorph) and increased root disease levels and increased Balneimonas, Massilia, Pseudomonas, and unclassified Micrococcaceae. As we enter the era of biologically sustainable agriculture, it may be possible to reduce and limit the effects of serious fungal infestations by promoting a beneficial microbiome through the application of biocontrol agents during different periods of plant development.RA was supported by an Endeavour Postdoctoral Fellowship. This study was financed by Grains Research and Development Corporation (GRDC) project no. UF00008
Isotopic replacement in ionic systems: the 4He2+ + 3He -> 3He4He+ + 4He reaction
Full quantum dynamics calculations have been carried out for the ionic
reaction 4He2+ + 3He and state-to-state reactive probabilities have been
obtained using both a time-dependent (TD) and a time-independent (TI) approach.
An accurate ab-initio potential energy surface has been employed for the
present quantum dynamics and the two sets of results are shown to be in
agreement with each other. The results for zero total angular momentum suggest
a marked presence of atom exchange (isotopic replacement) reaction with
probabilities as high as 60%. The reaction probabilities are only weakly
dependent on the initial vibrational state of the reactants while they are
slightly more sensitive to the degree of rotational excitation. A brief
discussion of the results for selected higher total angular momentum values is
also presented, while the l-shifting approximation [1] has been used to provide
estimates of the total reaction rates for the title process. Such rates are
found to be large enough to possibly become experimentally accessible
Recent tests for the statistical parton distributions
We compare some recent experimental results obtained at DESY, SLAC and
Jefferson Lab., with the predictions of the statistical model, we have
previously proposed. The result of this comparison is very satisfactory.Comment: 12 pages, 6 eps figures, version to appear in Mod. Phys. Lett.
Detection of bovine papillomavirus type 2 in the peripheral blood of cattle with urinary bladder tumours: possible biological role
Bovine papillomavirus type 2 (BPV-2) infection has been associated with urinary bladder tumours in adult cattle grazing on bracken fern-infested land. In this study, we investigated the
simultaneous presence of BPV-2 in whole blood and urinary bladder tumours of adult cattle in an attempt to better understand the biological role of circulating BPV-2. Peripheral blood samples were collected from 78 cattle clinically suffering from a severe chronic enzootic haematuria. Circulating BPV-2 DNA was detected in 61 of them and in two blood samples from healthy cows. Fifty of the affected animals were slaughtered at public slaughterhouses and neoplastic proliferations in the urinary bladder were detected in all of them. BPV-2 DNA was amplified and sequenced in 78% of urinary bladder tumour samples and in 38.9% of normal samples as a control. Circulating episomal BPV-2 DNA was detected in 78.2% of the blood samples. Simultaneous presence of BPV-2 DNA in neoplastic bladder and blood samples was detected in 37 animals. Specific viral E5 mRNA and E5 oncoprotein were also detected in blood by RT-PCR
and Western blot/immunocytochemistry, respectively. It is likely that BPV-2 can persist and be maintained in an active status in the bloodstream, in particular in the lymphocytes, as a reservoir of viral infection that, in the presence of co-carcinogens, may cause the development of urinary bladder tumours
Lower limit on the achievable temperature in resonator-based sideband cooling
A resonator can be effectively used as a cooler for another linear oscillator
with a much smaller frequency. A huge cooling effect, which could be used to
cool a mechanical oscillator below the energy of quantum fluctuations, has been
predicted by several authors. However, here we show that there is a lower limit
T* on the achievable temperature that was not considered in previous works and
can be higher than the quantum limit in realistic experimental realizations. We
also point out that the decay rate of the resonator, which previous studies
stress should be small, must be larger than the decay rate of the cooled
oscillator for effective cooling.Comment: 6 pages, 4 figures, uses psfra
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