182 research outputs found
Plasmonic terahertz detectors based on a high-electron mobility GaAs/AlGaAs heterostructure
In order to characterize magnetic-field (B) tunable THz plasmonic detectors,
spectroscopy experiments were carried out at liquid helium temperatures and
high magnetic fields on devices fabricated on a high electron mobility
GaAs/AlGaAs heterostructure. The samples were either gated (the gate of a
meander shape) or ungated. Spectra of a photovoltage generated by THz radiation
were obtained as a function of B at a fixed THz excitation from a THz laser or
as a function of THz photon frequency at a fixed B with a Fourier spectrometer.
In the first type of measurements, the wave vector of magnetoplasmons excited
was defined by geometrical features of samples. It was also found that the
magnetoplasmon spectrum depended on the gate geometry which gives an additional
parameter to control plasma excitations in THz detectors. Fourier spectra
showed a strong dependence of the cyclotron resonance amplitude on the
conduction-band electron filling factor which was explained within a model of
the electron gas heating with the THz radiation. The study allows to define
both the advantages and limitations of plasmonic devices based on high-mobility
GaAs/AlGaAs heterostructures for THz detection at low temperatures and high
magnetic fields.Comment: 8 pages, 11 figure
COVID-19 vaccine skeptics are persuaded by pro-vaccine expert consensus messaging
To further understand how to combat COVID-19 vaccination hesitancy, we examined the effects of pro-vaccine expert consensus messaging on lay attitudes about vaccine safety and intention to get a COVID-19 vaccine. We surveyed 729 unvaccinated individuals from four countries in the early stages of the pandemic and 472 unvaccinated individuals from two countries after 2 years of the pandemic. We found belief of vaccine safety strongly correlated with intention to vaccinate in the first sample and less strongly in the second. We also found that consensus messaging improved attitudes toward vaccination even for participants who did not believe the vaccine is safe nor intended to get it. The persuasiveness of expert consensus was unaffected by exposing participants’ lack of knowledge about vaccines. We conclude that highlighting expert consensus may be a way to increase support toward COVID-19 vaccination in those hesitant or skeptical.info:eu-repo/semantics/acceptedVersio
Measurement of Transverse Polarization of Electrons Emitted in Free Neutron Decay
The final analysis of the experiment determining both components of the
transverse polarization of electrons (, )
emitted in the -decay of polarized, free neutrons is presented. The
T-odd, P-odd correlation coefficient quantifying ,
perpendicular to the neutron polarization and electron momentum, was found to
be 0.0040.005. This value is consistent with time reversal
invariance, and significantly improves both earlier result and limits on the
relative strength of imaginary scalar couplings in the weak interaction. The
value obtained for the correlation coefficient associated with
, 0.0670.004, agrees with the Standard Model
expectation, providing an important sensitivity test of the experimental setup.
The present result sets constraints on the imaginary part of scalar and tensor
couplings in weak interaction. Implications for parameters of the leptoquark
exchange model and minimal supersymmetric model (MSSM) with R-parity violation
are discussed
Measurement of the Transverse Polarization of Electrons Emitted in Free Neutron Decay
Both components of the transverse polarization of electrons emitted in the
beta-decay of polarized, free neutrons have been measured. The T-odd, P-odd
correlation coefficient quantifying the component perpendicular to the decay
plane defined by neutron polarization and electron momentum, was found to be
R=0.008 +/- 0.015 +/-0.005. This value is consistent with time reversal
invariance, and significantly improves limits on the relative strength of
imaginary scalar couplings in the weak interaction. The value obtained for the
correlation coefficient associated with the electron polarization component
contained within the decay plane N=0.056 +/- 0.011 +/- 0.005, agrees with the
Standard Model expectation, providing an important sensitivity test of the
experimental setup.Comment: 4 pages, 4 figure
Endovascular treatment of long peripheral occlusions using a CTO-Crosser
W ostatnich latach obserwowuje się szybki rozwój metod wewnątrznaczyniowych w leczeniu niedokrwienia
obwodowego. Niestety długie i mocno uwapnione niedrożności wytyczają często granice dla
tych zabiegów. W poniższym artykule prezentujemy swoje pierwsze spostrzeżenia i uwagi dotyczące
użycia CTO-Crossera w długich i uwapnionych niedrożnościach.Although one can observe the quick development of less invasive techniques in the treatment of peripheral
ischemia, a long or heavily calcified stenosis still determines the limitation for such procedures. In
this article we present our first observations and remarks on the use of the CTO-Crosser in long and
calcified total occlusions
Free neutron decay and time reversal violation
Both components of the transverse electron polarization have been measured in free neutron decay. The T-odd, P-odd correlation coefficient associated with polarization component perpendicular to the neutron polarization
and electron momentum, was found to be R = 0:006 0:012 0:005. This value is consistent with time reversal invariance, and significantly improves limits on the relative strength of imaginary scalar couplings in the
weak interaction. The value obtained for the T-even, P-even correlation coefficient connected with the second transversal polarization component, N = 0:065 0:012 0:004, agrees with the Standard Model expectation
providing an important sensitivity test of the experimental setup
Magnon gap excitations in van der Waals antiferromagnet MnPSe
Magneto-spectroscopy methods have been employed to study the zero-wavevector
magnon excitations in MnPSe. Experiments carried out as a function of
temperature and the applied magnetic field show that two low-energy magnon
branches of MnPSe in its antiferromagnetic phase are gapped. The
observation of two low-energy magnon gaps (at 14 and 0.7 cm) implies
that MnPSe is a biaxial antiferromagnet. A relatively strong out-of-plane
anisotropy imposes the spin alignment to be in-plane whereas the spin
directionality within the plane is governed by a factor of 2.5
10 weaker in-plane anisotropy.Comment: 9 pages, 3 figure
Joint hypermobility in children with idiopathic scoliosis: SOSORT award 2011 winner
<p>Abstract</p> <p>Background</p> <p>Generalized joint hypermobility (JHM) refers to increased joint mobility with simultaneous absence of any other systemic disease. JHM involves proprioception impairment, increased frequency of pain within joints and tendency to injure soft tissues while performing physical activities. Children with idiopathic scoliosis (IS) often undergo intensive physiotherapy requiring good physical capacities. Further, some physiotherapy methods apply techniques that increase joint mobility and thus may be contraindicated.</p> <p>The aim of this paper was to assess JHM prevalence in children with idiopathic scoliosis and to analyze the relationship between JHM prevalence and the clinical and radiological parameters of scoliosis. The methods of assessment of generalized joint hypermobility were also described.</p> <p>Materials and methods</p> <p>This case-control study included 70 subjects with IS, aged 9-18 years (mean 13.2 ± 2.2), Cobb angle range 10°-53° (mean 24.3 ± 11.7), 34 presenting single curve thoracic scoliosis and 36 double curve thoracic and lumbar scoliosis. The control group included 58 children and adolescents aged 9-18 years (mean 12.6 ± 2.1) selected at random. The presence of JHM was determined using Beighton scale complemented with the questionnaire by Hakim and Grahame. The relationship between JHM and the following variables was evaluated: curve severity, axial rotation of the apical vertebra, number of curvatures (single versus double), number of vertebrae within the curvature (long versus short curves), treatment type (physiotherapy versus bracing) and age.</p> <p>Statistical analysis was performed with Statistica 8.1 (StatSoft, USA). The Kolmogorov-Smirnov test, U Mann-Whitney test, Chi<sup>2 </sup>test, Pearson and Spermann correlation rank were conducted. The value <it>p </it>= 0.05 was adopted as the level of significance.</p> <p>Results</p> <p>JHM was diagnosed in more than half of the subjects with idiopathic scoliosis (51.4%), whilst in the control group it was diagnosed in only 19% of cases (<it>p </it>= 0.00015). A significantly higher JHM prevalence was observed in both girls (<it>p </it>= 0.0054) and boys (<it>p </it>= 0.017) with IS in comparison with the corresponding controls. No significant relation was found between JHM prevalence and scoliosis angular value (<it>p </it>= 0.35), apical vertebra rotation (<it>p </it>= 0.86), the number of vertebrae within curvature (<it>p </it>= 0.8), the type of applied treatment (<it>p </it>= 0.55) and the age of subjects (<it>p </it>= 0.79). JHM prevalence was found to be higher in children with single curve scoliosis than in children with double curve scoliosis (<it>p </it>= 0.03).</p> <p>Conclusions</p> <p>JHM occurs more frequently in children with IS than in healthy sex and age matched controls. No relation of JHM with radiological parameters, treatment type and age was found. Systematically searched in IS children, JHM should be taken into account when physiotherapy is planned.</p
Testosterone Deficiency Accelerates Neuronal and Vascular Aging of SAMP8 Mice: Protective Role of eNOS and SIRT1
Oxidative stress and atherosclerosis-related vascular disorders are risk factors for cognitive decline with aging. In a small clinical study in men, testosterone improved cognitive function; however, it is unknown how testosterone ameliorates the pathogenesis of cognitive decline with aging. Here, we investigated whether the cognitive decline in senescence-accelerated mouse prone 8 (SAMP8), which exhibits cognitive impairment and hypogonadism, could be reversed by testosterone, and the mechanism by which testosterone inhibits cognitive decline. We found that treatment with testosterone ameliorated cognitive function and inhibited senescence of hippocampal vascular endothelial cells of SAMP8. Notably, SAMP8 showed enhancement of oxidative stress in the hippocampus. We observed that an NAD+-dependent deacetylase, SIRT1, played an important role in the protective effect of testosterone against oxidative stress-induced endothelial senescence. Testosterone increased eNOS activity and subsequently induced SIRT1 expression. SIRT1 inhibited endothelial senescence via up-regulation of eNOS. Finally, we showed, using co-culture system, that senescent endothelial cells promoted neuronal senescence through humoral factors. Our results suggest a critical role of testosterone and SIRT1 in the prevention of vascular and neuronal aging
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