14 research outputs found
Quantum superpositions of clockwise and counterclockwise supercurrent states in the dynamics of a rf-SQUID exposed to a quantized electromagnetic field
The dynamical behavior of a superconducting quantum interference device (a
rf-SQUID) irradiated by a single mode quantized electromagnetic field is
theoretically investigated. Treating the SQUID as a flux qubit, we analyze the
dynamics of the combined system within the low lying energy Hilbert subspace
both in the asymmetric and in the symmetric SQUID potential configurations. We
show that the temporal evolution of the system is dominated by an oscillatory
behavior characterized by more than one, generally speaking, incommensurable
Rabi frequencies whose expressions are explicitly given. We find that the
external parameters may fixed in such a way to realize a control on the
dynamical replay of the total system which, for instance, may be forced to
exhibit a periodic evolution accompanied by the occurrence of an oscillatory
disappearance of entanglement between the two subsystems. We demonstrate the
possibility of generating quantum maximally entangled superpositions of the two
macroscopically distinguishable states describing clockwise and
counterclockwise supercurrents in the loop. The experimental feasibility of our
proposal is briefly discussed.Comment: 16 pages, 7 figures, submitted to PR
An Assessment of the Systematic Uncertainty in Present and Future Tests of the Lense-Thirring Effect with Satellite Laser Ranging
We deal with the attempts to measure the Lense-Thirring effect with the
Satellite Laser Ranging (SLR) technique applied to the existing LAGEOS and
LAGEOS II terrestrial satellites and to the recently approved LARES
spacecraft.The first issue addressed here is: are the so far published
evaluations of the systematic uncertainty induced by the bad knowledge of the
even zonal harmonic coefficients J_L of the multipolar expansion of the Earth's
geopotential reliable and realistic?
Our answer is negative. Indeed, if the differences Delta J_L among the even
zonals estimated in different Earth's gravity field global solutions from the
dedicated GRACE mission are assumed for the uncertainties delta J_L instead of
using their covariance sigmas sigma_JL, it turns out that the systematic
uncertainty \delta\mu in the Lense-Thirring test with the nodes Omega of LAGEOS
and LAGEOS II may be up to 3 to 4 times larger than in the evaluations so far
published () based on the use of the sigmas of one model at a time
separately. The second issue consists of the possibility of using a different
approach in extracting the relativistic signature of interest from the
LAGEOS-type data. The third issue is the possibility of reaching a realistic
total accuracy of 1% with LAGEOS, LAGEOS II and LARES, which should be launched
in November 2009 with a VEGA rocket. While LAGEOS and LAGEOS II fly at
altitudes of about 6000 km, LARES will be likely placed at an altitude of 1450
km. Thus, it will be sensitive to much more even zonals than LAGEOS and LAGEOS
II. Their corrupting impact has been evaluated with the standard Kaula's
approach up to degree L=60 by using Delta J_L and sigma_JL; it turns out that
it may be as large as some tens percent.Comment: LaTex, 19 pages, 1 figure, 12 tables. Invited and refereed
contribution to The ISSI Workshop, 6-10 October 2008, on The Nature of
Gravity Confronting Theory and Experiment in Space To appear in Space Science
Review
Effects of sleep deprivation on neural functioning: an integrative review
Sleep deprivation has a broad variety of effects on human performance and neural functioning that manifest themselves at different levels of description. On a macroscopic level, sleep deprivation mainly affects executive functions, especially in novel tasks. Macroscopic and mesoscopic effects of sleep deprivation on brain activity include reduced cortical responsiveness to incoming stimuli, reflecting reduced attention. On a microscopic level, sleep deprivation is associated with increased levels of adenosine, a neuromodulator that has a general inhibitory effect on neural activity. The inhibition of cholinergic nuclei appears particularly relevant, as the associated decrease in cortical acetylcholine seems to cause effects of sleep deprivation on macroscopic brain activity. In general, however, the relationships between the neural effects of sleep deprivation across observation scales are poorly understood and uncovering these relationships should be a primary target in future research
Densidade e diversidade fenotípica de bactérias diazotróficas não simbióticas em solos da Reserva Biológica Serra dos Toledos, Itajubá (MG)
Bactérias diazotróficas não simbióticas (BDNS) atuam no desenvolvimento das plantas por meio da fixação biológica de nitrogênio e também pela produção e liberação de substâncias reguladoras do crescimento vegetal. Este estudo objetivou avaliar a densidade e diversidade fenotípica desse grupo de bactérias em fragmentos de solo da Reserva Biológica Serra dos Toledos e entorno, em Itajubá/MG. Essa reserva localiza-se na Área de Proteção Ambiental da Mantiqueira, constituindo-se em uma importante área de recarga e de abrigo à flora e fauna endêmicas. Amostras de solo superficial foram coletadas em áreas com diferentes declividades na reserva, em épocas representativas das estações de inverno (setembro/2006) e verão (abril/2007). A densidade, avaliada pelo número mais provável, utilizando os meios de cultura NFb, JNFb e Fam, para Azospirillum spp., Herbaspirillum spp. e A. amazonense, respectivamente, variou de 0,12 a 75,60 (NMP x 10(5)) bactérias g-1 solo seco. Foram obtidos 172 e 174 isolados, respectivamente para as amostras de inverno e verão, dos quais 30 e 55 % apresentaram similaridade igual ou superior a 70 % com as estirpes-tipo Azospirillum brasilense, A. amazonense, A. lipoferum, Herbaspirillum seropedicae e Burkholderia brasilensis. O resultado do comportamento dos isolados com base na tolerância à salinidade nem sempre foi semelhante ao obtido pelas características fenotípicas culturais a 70 % de similaridade, sendo indicado para estudos complementares de diversidade desses organismos. As BDNS apresentam potencial de utilização em estudos de avaliação da qualidade e sustentabilidade de ecossistemas. No entanto, apesar da alta densidade e diversidade fenotípica em solos da reserva, maiores valores foram obtidos no entorno, evidenciando o efeito positivo da cobertura vegetal do tipo gramíneas sobre elas, independentemente da variação climática
Multifocal renal cell carcinoma in sibs from a chromosome 9 linked (TSC1) tuberous sclerosis family.
New insights into the altered adhesive and mechanical properties of red blood cells parasitized by Babesia bovis
10.1111/j.1365-2958.2007.05850.xMolecular Microbiology6541092-1105MOMI