17 research outputs found
Characteristics of ferroelectric-ferroelastic domains in N{\'e}el-type skyrmion host GaVS
GaVS is a multiferroic semiconductor hosting N{\'e}el-type magnetic
skyrmions dressed with electric polarization. At T = 42K, the compound
undergoes a structural phase transition of weakly first-order, from a
non-centrosymmetric cubic phase at high temperatures to a polar rhombohedral
structure at low temperatures. Below T, ferroelectric domains are formed
with the electric polarization pointing along any of the four axes. Although in this material the size and the shape of the
ferroelectric-ferroelastic domains may act as important limiting factors in the
formation of the N{\'e}el-type skyrmion lattice emerging below T=13\:K, the
characteristics of polar domains in GaVS have not been studied yet.
Here, we report on the inspection of the local-scale ferroelectric domain
distribution in rhombohedral GaVS using low-temperature piezoresponse
force microscopy. We observed mechanically and electrically compatible lamellar
domain patterns, where the lamellae are aligned parallel to the (100)-type
planes with a typical spacing between 100 nm-1.2 m. We expect that the
control of ferroelectric domain size in polar skyrmion hosts can be exploited
for the spatial confinement and manupulation of N{\'e}el-type skyrmions
Relaxation dynamics of modulated magnetic phases in the skyrmion host GaV4S8: An ac magnetic susceptibility study
We report on the slow magnetization dynamics observed upon the magnetic phase
transitions of GaV4S8, a multiferroic compound featuring a long-ranged
cycloidal magnetic order and a N\'eel-type skyrmion lattice in a relatively
broad temperature range below its Curie temperature. The fundamental difference
between GaV4S8 and the chiral helimagnets, wherein the skyrmion phase was first
discovered, lies within the polar symmetry of GaV4S8, promoting a cycloidal
instead of a helical magnetic order and rendering the magnetic phase diagram
essentially different from that in the cubic helimagnets. Our ac magnetic
susceptibility study reveals slow relaxation dynamics at the field-driven phase
transitions between the cycloidal, skyrmion lattice and field-polarized states.
At each phase boundary, the characteristic relaxation times were found to
exhibit a strong temperature dependence, starting from the minute range at low
temperatures, decreasing to the micro- to millisecond range at higher
temperatures
Rapid and quantitative antimalarial drug efficacy testing via the magneto-optical detection of hemozoin
Emergence of resistant Plasmodium species makes drug efficacy testing a crucial part of malaria control. Here we describe a novel assay for sensitive, fast and simple drug screening via the magneto-optical detection of hemozoin, a natural biomarker formed during the hemoglobin metabolism of Plasmodium species. By quantifying hemozoin production over the intraerythrocytic cycle, we reveal that hemozoin formation is already initiated by ~ 6–12 h old ring-stage parasites. We demonstrate that the new assay is capable of drug efficacy testing with incubation times as short as 6–10 h, using synchronized P. falciparum 3D7 cultures incubated with chloroquine, piperaquine and dihydroartemisinin. The determined 50% inhibitory concentrations agree well with values established by standard assays requiring significantly longer testing time. Accordingly, we conclude that magneto-optical hemozoin detection provides a practical approach for the quick assessment of drug effect with short incubation times, which may also facilitate stage-specific assessment of drug inhibitory effects. © 2020, The Author(s)
Sensitive detection of Plasmodium vivax malaria by the rotating-crystal magneto-optical method in Thailand
The rotating-crystal magneto-optical detection (RMOD) method has been developed for the rapid and quantitative diagnosis of malaria and tested systematically on various malaria infection models. Very recently, an extended field trial in a high-transmission region of Papua New Guinea demonstrated its great potential for detecting malaria infections, in particular Plasmodium vivax. In the present small-scale field test, carried out in a low-transmission area of Thailand, RMOD confirmed malaria in all samples found to be infected with Plasmodium vivax by microscopy, our reference method. Moreover, the magneto-optical signal for this sample set was typically 1–3 orders of magnitude higher than the cut-off value of RMOD determined on uninfected samples. Based on the serial dilution of the original patient samples, we expect that the method can detect Plasmodium vivax malaria in blood samples with parasite densities as low as ∼5–10 parasites per microliter, a limit around the pyrogenic threshold of the infection. In addition, by investigating the correlation between the magnitude of the magneto-optical signal, the parasite density and the erythrocytic stage distribution, we estimate the relative hemozoin production rates of the ring and the trophozoite stages of in vivo Plasmodium vivax infections
Squeezing the periodicity of Néel-type magnetic modulations by enhanced Dzyaloshinskii-Moriya interaction of 4d electrons
In polar magnets, such as GaVS, GaVSe and VOSeO, modulated magnetic phases namely the cycloidal and the Néel-type skyrmion lattice states were identified over extended temperature ranges, even down to zero Kelvin. Our combined small-angle neutron scattering and magnetization study shows the robustness of the Néel-type magnetic modulations also against magnetic fields up to 2 T in the polar GaMoS. In addition to the large upper critical field, enhanced spin-orbit coupling stabilize cycloidal, Néel skyrmion lattice phases with sub-10 nm periodicity and a peculiar distribution of the magnetic modulation vectors. Moreover, we detected an additional single-q state not observed in any other polar magnets. Thus, our work demonstrates that non-centrosymmetric magnets with 4d and 5d electron systems may give rise to various highly compressed modulated states
aiMotive Dataset: A Multimodal Dataset for Robust Autonomous Driving with Long-Range Perception
Autonomous driving is a popular research area within the computer vision
research community. Since autonomous vehicles are highly safety-critical,
ensuring robustness is essential for real-world deployment. While several
public multimodal datasets are accessible, they mainly comprise two sensor
modalities (camera, LiDAR) which are not well suited for adverse weather. In
addition, they lack far-range annotations, making it harder to train neural
networks that are the base of a highway assistant function of an autonomous
vehicle. Therefore, we introduce a multimodal dataset for robust autonomous
driving with long-range perception. The dataset consists of 176 scenes with
synchronized and calibrated LiDAR, camera, and radar sensors covering a
360-degree field of view. The collected data was captured in highway, urban,
and suburban areas during daytime, night, and rain and is annotated with 3D
bounding boxes with consistent identifiers across frames. Furthermore, we
trained unimodal and multimodal baseline models for 3D object detection. Data
are available at \url{https://github.com/aimotive/aimotive_dataset}.Comment: The paper was accepted to ICLR 2023 Workshop Scene Representations
for Autonomous Drivin