416 research outputs found
The coherent interaction between matter and radiation - A tutorial on the Jaynes-Cummings model
The Jaynes-Cummings (JC) model is a milestone in the theory of coherent
interaction between a two-level system and a single bosonic field mode. This
tutorial aims to give a complete description of the model, analyzing the
Hamiltonian of the system, its eigenvalues and eigestates, in order to
characterize the dynamics of system and subsystems. The Rabi oscillations,
together with the collapse and revival effects, are distinguishing features of
the JC model and are important for applications in Quantum Information theory.
The framework of cavity quantum electrodynamics (cQED) is chosen and two
fundamental experiments on the coherent interaction between Rydberg atoms and a
single cavity field mode are described.Comment: 22 pages, 7 figures. Tutorial. Submitted to a special issue of EPJ -
ST devoted to the memory of Federico Casagrand
Increased Physical Activity and Reduced Pain with Spinal Cord Stimulation: a 12-Month Study
International Journal of Exercise Science 13(3): 1583-1594, 2020. The purpose of this study was to assess changes in pain and physical activity after replacing a traditional spinal cord stimulation (SCS) implantable pulse generator with a next generation SCS in patients for whom traditional SCS was no longer providing adequate relief of low back and/or leg pain. Subjects (n = 19) who reported that they were no longer receiving adequate relief from traditional SCS were implanted with a next generation SCS. Eighteen additional patients who were receiving relief from traditional SCS were also followed as a control. Both groups (next generation, traditional) were assessed for low-back and limb pain (visual analog scale) and daily physical activity (wearable accelerometer) at baseline and three, six, nine and 12 months following the SCS implant. Relative to baseline, next generation SCS subjects exhibited reductions (p ≤ 0.05 for all) in low-back pain (average reduction of 22%) at every time point, in leg pain (average reduction of 23%) at every time point except six months and increased physical activity (average increase of 57%) at three, six and nine months. As expected, there were no changes in pain or physical activity in the traditional SCS subjects (p ≥ 0.1). In conclusion, pain decreased, and physical activity increased in patients receiving a next generation SCS. Physical activity may serve as an objectively measured marker of pain
Young Galaxy Candidates in the Hubble Frontier Fields - III. MACSJ0717.5+3745
In this paper we present the results of our search for and study of galaxy candidates behind the third Frontier Fields (FF) cluster,
MACSJ0717.5+3745, and its parallel field, combining data from Hubble and
Spitzer. We select 39 candidates using the Lyman Break technique, for which the
clear non-detection in optical make the extreme mid- interlopers hypothesis
unlikely. We also take benefit from samples selected using
previous Frontier Fields datasets of Abell 2744 and MACS0416 to improve the
constraints on the properties of very high-redshift objects. We compute the
redshift and the physical properties, such emission lines properties, star
formation rate, reddening, and stellar mass for all Frontier Fields objects
from their spectral energy distribution using templates including nebular
emission lines. We study the relationship between several physical properties
and confirm the trend already observed in previous surveys for evolution of
star formation rate with galaxy mass, and between the size and the UV
luminosity of our candidates. The analysis of the evolution of the UV
Luminosity Function with redshift seems more compatible with an evolution of
density. Moreover, no robust 8.5 object is selected behind the cluster
field, and few 9 candidates have been selected in the two previous
datasets from this legacy survey, suggesting a strong evolution in the number
density of galaxies between 8 and 9. Thanks to the use of the lensing
cluster, we study the evolution of the star formation rate density produced by
galaxies with L0.03L, and confirm the strong decrease observed
between 8 and 9.Comment: 21 pages - Accepted for publication in ApJ - v2: small correction
Vibrio cholerae vexH Encodes a Multiple Drug Efflux Pump That Contributes to the Production of Cholera Toxin and the Toxin Co-Regulated Pilus
The resistance-nodulation-division (RND) efflux systems are ubiquitous transporters that function in antimicrobial resistance. Recent studies showed that RND systems were required for virulence factor production in Vibrio cholerae. The V. cholerae genome encodes six RND efflux systems. Three of the RND systems (VexB, VexD, and VexK) were previously shown to be redundant for in vitro resistance to bile acids and detergents. A mutant lacking the VexB, VexD, and VexK RND pumps produced wild-type levels of cholera toxin (CT) and the toxin co-regulated pilus (TCP) and was moderately attenuated for intestinal colonization. In contrast, a RND negative mutant produced significantly reduced amounts of CT and TCP and displayed a severe colonization defect. This suggested that one or more of the three uncharacterized RND efflux systems (i.e. VexF, VexH, and VexM) were required for pathogenesis. In this study, a genetic approach was used to generate a panel of V. cholerae RND efflux pump mutants in order to determine the function of VexH in antimicrobial resistance, virulence factor production, and intestinal colonization. VexH contributed to in vitro antimicrobial resistance and exhibited a broad substrate specificity that was redundant with the VexB, VexD, and VexK RND efflux pumps. These four efflux pumps were responsible for in vitro antimicrobial resistance and were required for virulence factor production and intestinal colonization. Mutation of the VexF and/or VexM efflux pumps did not affect in vitro antimicrobial resistance, but did negatively affect CT and TCP production. Collectively, our results demonstrate that the V. cholerae RND efflux pumps have redundant functions in antimicrobial resistance and virulence factor production. This suggests that the RND efflux systems contribute to V. cholerae pathogenesis by providing the bacterium with protection against antimicrobial compounds that are present in the host and by contributing to the regulated expression of virulence factors
Synchronicity and rhythmicity of purkinje cell firing during generalized spike-and-wave discharges in a natural mouse model of absence epilepsy
Absence epilepsy is characterized by the occurrence of generalized spike and wave discharges (GSWDs) in electrocorticographical (ECoG) recordings representing oscillatory activity in thalamocortical networks. The oscillatory nature of GSWDs has been shown to be reflected in the simple spike activity of cerebellar Purkinje cells and in the activity of their target neurons in the cerebellar nuclei, but it is unclear to what extent complex spike activity is implicated in generalized epilepsy. Purkinje cell complex spike firing is elicited by climbing fiber activation and reflects action potential firing in the inferior olive. Here, we investigated to what extent modulation of complex spike firing is reflected in the temporal patterns of seizures. Extracellular single-unit recordings in awake, headrestrained homozygous tottering mice, which suffer from a mutation in the voltage-gated CaV2.1 calcium channel, revealed that a substantial proportion of Purkinje cells (26%) showed increased complex spike activity and rhythmicity during GSWDs. Moreover, Purkinje cells, recorded either electrophysiologically or by using Ca2+-imaging, showed a significant increase in complex spike synchronicity for both adjacent and remote Purkinje cells during ictal events. These seizure-related changes in firing frequency, rhythmicity and synchronicity were most prominent in the lateral cerebellum, a region known to receive cerebral input via the inferior olive. These data indicate profound and widespread changes in olivary firing that are most likely induced by seizure-related activity changes in the thalamocortical network, thereby highlighting the possibility that olivary neurons can compensate for pathological brain-state changes by dampening oscillations
In-situ characterization of the Hamamatsu R5912-HQE photomultiplier tubes used in the DEAP-3600 experiment
The Hamamatsu R5912-HQE photomultiplier-tube (PMT) is a novel high-quantum
efficiency PMT. It is currently used in the DEAP-3600 dark matter detector and
is of significant interest for future dark matter and neutrino experiments
where high signal yields are needed.
We report on the methods developed for in-situ characterization and
monitoring of DEAP's 255 R5912-HQE PMTs. This includes a detailed discussion of
typical measured single-photoelectron charge distributions, correlated noise
(afterpulsing), dark noise, double, and late pulsing characteristics. The
characterization is performed during the detector commissioning phase using
laser light injected through a light diffusing sphere and during normal
detector operation using LED light injected through optical fibres
Noncommutativity, generalized uncertainty principle and FRW cosmology
We consider the effects of noncommutativity and the generalized uncertainty
principle on the FRW cosmology with a scalar field. We show that, the
cosmological constant problem and removability of initial curvature singularity
find natural solutions in this scenarios.Comment: 8 pages, to appear in IJT
Exact results on decoherence and entanglement in a system of N driven atoms and a dissipative cavity mode
We solve the dynamics of an open quantum system where N strongly driven
two-level atoms are equally coupled on resonance to a dissipative cavity mode.
Analytical results are derived on decoherence, entanglement, purity, atomic
correlations and cavity field mean photon number. We predict decoherence-free
subspaces for the whole system and the N-qubit subsystem, the monitoring of
quantum coherence and purity decay by atomic populations measurements, the
conditional generation of atomic multi-partite entangled states and of cavity
cat-like states. We show that the dynamics of atoms prepared in states
invariant under permutation of any two components remains restricted within the
subspace spanned by the completely symmetric Dicke states. We discuss examples
and applications in the cases N=3,4.Comment: 7 pages, 4 figures, accepted in EPJ
Kangaroo mother care: a multi-country analysis of health system bottlenecks and potential solutions.
BACKGROUND: Preterm birth is now the leading cause of under-five child deaths worldwide with one million direct deaths plus approximately another million where preterm is a risk factor for neonatal deaths due to other causes. There is strong evidence that kangaroo mother care (KMC) reduces mortality among babies with birth weight <2000 g (mostly preterm). KMC involves continuous skin-to-skin contact, breastfeeding support, and promotion of early hospital discharge with follow-up. The World Health Organization has endorsed KMC for stabilised newborns in health facilities in both high-income and low-resource settings. The objectives of this paper are to: (1) use a 12-country analysis to explore health system bottlenecks affecting the scale-up of KMC; (2) propose solutions to the most significant bottlenecks; and (3) outline priority actions for scale-up. METHODS: The bottleneck analysis tool was applied in 12 countries in Africa and Asia as part of the Every Newborn Action Plan process. Country workshops involved technical experts to complete the survey tool, which is designed to synthesise and grade health system "bottlenecks", factors that hinder the scale-up, of maternal-newborn intervention packages. We used quantitative and qualitative methods to analyse the bottleneck data, combined with literature review, to present priority bottlenecks and actions relevant to different health system building blocks for KMC. RESULTS: Marked differences were found in the perceived severity of health system bottlenecks between Asian and African countries, with the former reporting more significant or very major bottlenecks for KMC with respect to all the health system building blocks. Community ownership and health financing bottlenecks were significant or very major bottlenecks for KMC in both low and high mortality contexts, particularly in South Asia. Significant bottlenecks were also reported for leadership and governance and health workforce building blocks. CONCLUSIONS: There are at least a dozen countries worldwide with national KMC programmes, and we identify three pathways to scale: (1) champion-led; (2) project-initiated; and (3) health systems designed. The combination of all three pathways may lead to more rapid scale-up. KMC has the potential to save lives, and change the face of facility-based newborn care, whilst empowering women to care for their preterm newborns
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