7,065 research outputs found
Transverse Entanglement of Biphotons
We measure the transverse entanglement of photon pairs on their propagation
from the near to the far field of spontaneous parametric downconversion (SPDC).
The Fedorov ratio, depending on the widths of conditional and unconditional
intensity measurements, is shown to be only able to characterize entanglement
in the near and far field zones of the source. Therefore we also follow a
different approach. By evaluating the first-order coherence of a subsystem of
the state we can quantify its entanglement. Unlike previous measurements, which
determine the Fedorov ratio via intensity correlations, our setup is sensitive
to both phase and modulus of the biphoton state and thus always grants
experimental access to the full transverse entanglement of the SPDC state. It
is shown theoretically that this scheme represents a direct measurement of the
Schmidt number.Comment: 11 pages, 6 figure
Compensation of anisotropy effects in the generation of two-photon light
We analyse a method to compensate for anisotropy effects in the spatial
distribution of parametric down-conversion (PDC) radiation in bulk crystals. In
this method, a single nonlinear crystal is replaced by two consecutive crystals
with opposite transverse walk-off directions. We implement a simple numerical
model to calculate the spatial distribution of intensity and correlations, as
well as the Schmidt mode structure, with an account for the anisotropy.
Experimental results are presented which prove the validity of both the model
and the method.Comment: 9 pages, 8 figure
Executive functions in insomnia disorder: a systematic review and exploratory meta-analysis
Background: Executive functions (EFs) are involved in the control of basic psychological processes such as attention and memory and also contribute to emotion regulation. Research on the presence of EFs impairments in insomnia yielded inconsistent results. Therefore, we performed a systematic review of the literature on three EFs: inhibitory control, working memory, and cognitive flexibility in adults with insomnia in order to investigate the presence and magnitude of insomnia-related EFs impairments.
Methods: PubMed, Scopus, Medline, and PsycINFO were searched. Risk of bias assessment of included studies was performed by two independent researchers. Findings were summarised using both a narrative approach and meta-analysis. Cohen’s d was calculated at 95% confidence interval (CI) as effect size of between groups differences.
Results: Twenty-eight studies comparing adult individuals with a diagnosis of insomnia and healthy controls on neuropsychological measures of EFs were included. Narrative synthesis revealed substantial variability across study findings. Factors that were primarily hypothesised to account for this variability are: objective sleep impairments and test sensitivity. Exploratory meta-analysis showed impaired performance of small to moderate magnitude in individuals with insomnia as compared to controls in reaction times, but not accuracy rates, of inhibitory control (d = −0.32, 95% CI: −0.52 to −0.13) and cognitive flexibility tasks (d = −0.30, 95% CI: −0.59 to −0.01). Performance in working memory tasks was also significantly impacted (d = −0.19, 95% CI: −0.38 to −0.00). Effects sizes were larger when insomnia was associated with objective sleep impairments, rather than normal sleep.
Conclusions: We gathered evidence supporting small to moderate deficits in EFs in individuals with insomnia. Due to the small sample size results should be considered preliminary and interpreted carefully
Nanoparticle-doped electrospun fiber random lasers with spatially extended light modes
Complex assemblies of light-emitting polymer nanofibers with molecular
materials exhibiting optical gain can lead to important advance to amorphous
photonics and to random laser science and devices. In disordered mats of
nanofibers, multiple scattering and waveguiding might interplay to determine
localization or spreading of optical modes as well as correlation effects. Here
we study electrospun fibers embedding a lasing fluorene-carbazole-fluorene
molecule and doped with titania nanoparticles, which exhibit random lasing with
sub-nm spectral width and threshold of about 9 mJ cm^-2 for the absorbed
excitation fluence. We focus on the spatial and spectral behavior of optical
modes in the disordered and non-woven networks, finding evidence for the
presence of modes with very large spatial extent, up to the 100
micrometer-scale. These findings suggest emission coupling into integrated
nanofiber transmission channels as effective mechanism for enhancing spectral
selectivity in random lasers and correlations of light modes in the complex and
disordered material.Comment: 22 pages, 6 figure
Regeneration of Ostrya carpinifolia Scop. forest after coppicing: modelling of changes in species diversity and composition
In temperate forest ecosystems, management is one of the most relevant factors that can drive the temporal pattern of
species. As species in an ecosystem show susceptibility
to stress and disturbance, it is useful to take into account the plant community "compositional dimension", which derives from
species behaviour and ecological attributes and provides information on the mechanisms underlying species assemblages. Taking into account the influence of environmental factors on species diversity and composition, in order to determine the most suitable ecological behaviour type of each species, the research aim was to generate
a model for Ostrya carpinifolia coppiced woods (central Italy) that describes forest ecosystem regeneration after coppicing by the assessment of change in the composition of ecological behaviour types. Vascular species cover percentage, field data, soil data, light intensity at the undergrowth, dominant
tree layer cover and time since last logging were recorded for 63 plots covering 400 m2 each (20 x 20 m), randomly selected within a set of homogeneous macro-environmental conditions. Low species richness is related to stressing factors
(acid soil, high soil skeleton percentage), while high species richness is linked to high light intensity at the undergrowth level due to scarce canopy cover soon after coppicing. The driving forces affecting floristic composition, highlighted through multi-response permutation procedures (MRPP)
were light intensity at the undergrowth, regenerative
phase, dominant tree layer cover, acidity, presence/absence of outcropping rock or rock fragments and total nitrogen content. Six species groups, each one characterized by homogeneous ecological behaviour, were defined by indicator
species analysis (ISA) and tested using bioindication values analysis. Floristic successional change, related to time since last coppicing, turned out to follow an ecological cycling process characterized by cyclical occurrence/disappearance of species belonging to the six groups
Diverse regimes of mode intensity correlation in nanofiber random lasers through nanoparticle doping
Random lasers are based on disordered materials with optical gain. These
devices can exhibit either intensity or resonant feedback, relying on diffusive
or interference behaviour of light, respectively, which leads to either
coupling or independent operation of lasing modes. We study for the first time
these regimes in complex, solid-state nanostructured materials. The number of
lasing modes and their intensity correlation features are found to be
tailorable in random lasers made of light-emitting, electrospun polymer fibers
upon nanoparticle doping. By material engineering, directional waveguiding
along the length of fibers is found to be relevant to enhance mode correlation
in both intensity feedback and resonant feedback random lasing. The here
reported findings can be used to establish new design rules for tuning the
emission of nano-lasers and correlation properties by means of the
compositional and morphological properties of complex nanostructured materials.Comment: 30 pages, 10 figure
Detection of non-classical space-time correlations with a novel type of single-photon camera
During the last decades, multi-pixel detectors have been developed capable of
registering single photons. The newly developed Hybrid Photon Detector camera
has a remarkable property that it has not only spatial but also temporal
resolution. In this work, we use this device for the detection of non-classical
light from spontaneous parametric down-conversion and use two-photon
correlations for the absolute calibration of its quantum efficiency
Reconstructing 2D spatial modes for classical and quantum light
We propose a method for finding 2D spatial modes of thermal field through a
direct measurement of the field intensity and an offline analysis of its
spatial fluctuations. Using this method, in a simple and efficient way we
reconstruct the modes of a multimode fiber and the spatial Schmidt modes of
squeezed vacuum generated via high-gain parametric down conversion. The
reconstructed shapes agree with the theoretical results
Differential Effects of Dabigatran and Warfarin on Bone Volume and Structure in Rats with Normal Renal Function
Background: Warfarin, a widely used anticoagulant, is a vitamin K antagonist impairing the activity of vitamin K-dependent Bone Gla Protein (BGP or Osteocalcin) and Matrix Gla Protein (MGP). Because dabigatran, a new anticoagulant, has no effect on vitamin K metabolism, the aim of this study was to compare the impact of warfarin and dabigatran administration on bone structure and vascular calcification.
Methods: Rats with normal renal function received for 6 weeks warfarin, dabigatran or placebo. Bone was evaluated immuno-histochemically and hystomorphometrically after double labelling with declomycin and calcein. Aorta and iliac arteries were examined histologically.
Results: Histomorphometric analysis of femur and vertebrae showed significantly decreased bone volume and increased trabecular separation in rats treated with warfarin. Vertebra analysis showed that the trabecular number was higher in dabigatran treated rats. Osteoblast activity and resorption parameters were similar among groups, except for maximum erosion depth, which was higher in warfarin treated rats, suggesting a higher osteoclastic activity. Therefore, warfarin treatment was also associated with higher bone formation rate/bone surface and activation frequency. Warfarin treatment may cause an increased bone turnover characterized by increased remodelling cycles, with stronger osteoclast activity compared to the other groups. There were no differences among experimental groups in calcium deposition either in aortic or iliac arteries.
Conclusions: These findings suggest for the first time that dabigatran has a better bone safety profile than warfarin, as warfarin treatment affects bone by reducing trabecular size and structure, increasing turnover and reducing mineralization. These differences could potentially result in a lower incidence of fractures in dabigatran treated patients.This study was supported by a grant form Boehringer-Ingelheim Pharma, Germany (manufacturer of Dabigatran). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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