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

Cavity-mediated coupling of antiferromagnetic spin waves

Coupling of space-separated oscillators is interesting for quantum and communication technologies. In this work, it is shown that two antiferromagnetic oscillators placed inside an electromagnetic cavity couple cooperatively to its terahertz modes and, in effect, hybridized magnon-polariton modes are formed. This is supported by a systematic study of reflection spectra from two parallel-plane slabs of hematite ($\alpha$-Fe$_2$O$_3$), measured as a function of their temperatures and separation distance, and modeled theoretically. The mediating cavity was formed by the crystals themselves and the experiment was performed in a practical distance range of a few millimetres and above room temperature. Cavity-mediated coupling allows for engineering of complex resonators controlled by their geometry and by sharing properties of their components

Antiferromagnetic resonance in α\alpha-Fe2_2O3_3 up to its N\'eel temperature

Hematite ($\alpha$-Fe$_2$O$_3$) is an antiferromagnetic material with a very low spin damping and high N\'eel temperature. The temperature dependence of the antiferromagnetic resonance in a bulk single crystal of hematite was characterized from room temperature up to the N\'eel temperature in the frequency range of 0.19-0.5 THz. From these data, the N\'eel temperature was estimated as 966 K

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

Conservative treatment of idiopathic scoliosis according to FITS concept: presentation of the method and preliminary, short term radiological and clinical results based on SOSORT and SRS criteria

<p>Abstract</p> <p>Background</p> <p>Conservative scoliosis therapy according to the FITS Concept is applied as a unique treatment or in combination with corrective bracing. The aim of the study was to present author's method of diagnosis and therapy for idiopathic scoliosis FITS-Functional Individual Therapy of Scoliosis and to analyze the early results of FITS therapy in a series of consecutive patients.</p> <p>Methods</p> <p>The analysis comprised separately: (1) single structural thoracic, thoracolumbar or lumbar curves and (2) double structural scoliosis-thoracic and thoracolumbar or lumbar curves. The Cobb angle and Risser sign were analyzed at the initial stage and at the 2.8-year follow-up. The percentage of patients improved (defined as decrease of Cobb angle of more than 5 degrees), stable (+/- 5 degrees), and progressed (increase of Cobb angle of more than 5 degrees) was calculated. The clinical assessment comprised: the Angle of Trunk Rotation (ATR) initial and follow-up value, the plumb line imbalance, the scapulae level and the distance from the apical spinous process of the primary curve to the plumb line.</p> <p>Results</p> <p>In the Group A: (1) in single structural scoliosis 50,0% of patients improved, 46,2% were stable and 3,8% progressed, while (2) in double scoliosis 50,0% of patients improved, 30,8% were stable and 19,2% progressed. In the Group B: (1) in single scoliosis 20,0% of patients improved, 80,0% were stable, no patient progressed, while (2) in double scoliosis 28,1% of patients improved, 46,9% were stable and 25,0% progressed.</p> <p>Conclusion</p> <p>Best results were obtained in 10-25 degrees scoliosis which is a good indication to start therapy before more structural changes within the spine establish.</p

Antagonistic Effects of Point Mutations on Charge Recombination and a New View of Primary Charge Separation in Photosynthetic Proteins

[Image: see text] Light-induced electron-transfer reactions were investigated in wild-type and three mutant Rhodobacter sphaeroides reaction centers with the secondary electron acceptor (ubiquinone Q(A)) either removed or permanently reduced. Under such conditions, charge separation between the primary electron donor (bacteriochlorophyll dimer, P) and the electron acceptor (bacteriopheophytin, H(A)) was followed by P(+)H(A)(–) → PH(A) charge recombination. Two reaction centers were used that had different single amino-acid mutations that brought about either a 3-fold acceleration in charge recombination compared to that in the wild-type protein, or a 3-fold deceleration. In a third mutant in which the two single amino-acid mutations were combined, charge recombination was similar to that in the wild type. In all cases, data from transient absorption measurements were analyzed using similar models. The modeling included the energetic relaxation of the charge-separated states caused by protein dynamics and evidenced the appearance of an intermediate charge-separated state, P(+)B(A)(–), with B(A) being the bacteriochlorophyll located between P and H(A). In all cases, mixing of the states P(+)B(A)(–) and P(+)H(A)(–) was observed and explained in terms of electron delocalization over B(A) and H(A). This delocalization, together with picosecond protein relaxation, underlies a new view of primary charge separation in photosynthesis

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

Magnon gap excitations in van der Waals antiferromagnet MnPSe3_3

Magneto-spectroscopy methods have been employed to study the zero-wavevector magnon excitations in MnPSe$_3$. Experiments carried out as a function of temperature and the applied magnetic field show that two low-energy magnon branches of MnPSe$_3$ in its antiferromagnetic phase are gapped. The observation of two low-energy magnon gaps (at 14 and 0.7 cm$^{-1}$) implies that MnPSe$_3$ 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 $\times$ 10$^{-3}$ weaker in-plane anisotropy.Comment: 9 pages, 3 figure