PrBi, a sister member of the rare-earth monopnictide family, is an excellent candidate for studying extreme magnetoresistance and nontrivial topological electronic states. In this study, we perform ...angular magnetoresistance measurements as well as bulk and surface band structure calculations on this compound. PrBi's magnetoresistance is revealed to be significantly angle-dependent and shows a fourfold symmetry as always observed in the nonmagnetic isostructural counterparts, including LaSb, LaBi, and LuBi. Its angular magnetoresistance can be reproduced well using the semiclassical two-band model. The deduced parameters suggest that PrBi hosts an elongated electron pocket with a mobility anisotropy of 3.13 and is slightly uncompensated in its carrier concentration. Our bulk and surface band structure calculations confirm the anisotropic electronic features. Moreover, we reveal that a nodal-line-shaped surface state appears at the
X&cmb.macr;
point, and is associated with the quadratic dispersion along the
&z.Ggrm;
X&cmb.macr;
direction, and the linear type-I Dirac dispersion along the
X&cmb.macr;
M&cmb.macr;
direction. Owing to the type-I Dirac dispersion feature, PrBi could serve as a promising material platform for studying many unexpected physical properties, such as the highly anisotropic transport and valley polarization of electrons.
PrBi shows extreme and anisotropic magnetoresistance as well as nontrivial electronic band structures with a nodal-line-shaped surface state at the
X&cmb.macr;
point.
Aim To explore the altered spontaneous cerebral activity patterns and impaired functional regions in patients with diabetic retinopathy (DR) using resting-state functional magnetic resonance imaging ...(rs-fMRI) based on the amplitude of low-frequency fluctuations (ALFF) algorithm. Materials and methods Twenty-one patients with DR (mean age, 54.9±9.9 years; 11 females) and 17 healthy control subjects (54.8±5.7 years; 9 females) were prospectively studied. The DR patients underwent laboratory tests. All individuals underwent a neuropsychological test. The differences in the ALFF values between the two groups were compared. The relationships between ALFF values and clinical measurements were analysed using a multiple-factor analysis. Results Compared to the controls, the DR group showed significantly increased ALFF values in the bilateral occipital gyrus, right lingual gyrus, and precuneus, and decreased values in the right posterior/anterior cerebellar lobe and the parahippocampal, fusiform, superior temporal, inferior parietal, and angular gyrus. Furthermore, the Montreal Cognitive Assessment (MoCA) scores were negatively correlated with decreased ALFF values in the right occipital lobe of the DR group, while increased ALFF values in the right precuneus and lingual gyrus were found to be positively correlated with glycosylated haemoglobin (HbA1c) levels. Conclusions Patients with DR showed spontaneous cerebral activity abnormalities in many cerebral regions that were associated with cognitive impairments. HbA1c levels altered spontaneous cerebral activity in DR patients.
Fungal mitospores may function as dispersal units and/ or spermatia and thus play a role in distribution and/or mating of species that produce them. Mitospore production in ectomycorrhizal (EcM) ...Pezizales is rarely reported, but here we document mitospore production by a high diversity of EcM Pezizales on three continents, in both hemispheres. We sequenced the internal transcribed spacer (ITS) and partial large subunit (LSU) nuclear rDNA from 292 spore mats (visible mitospore clumps) collected in Argentina, Chile, China, Mexico and the USA between 2009 and 2012. We collated spore mat ITS sequences with 105 fruit body and 47 EcM root sequences to generate operational taxonomic units (OTUs). Phylogenetic inferences were made through analyses of both molecular data sets. A total of 48 OTUs from spore mats represented six independent EcM Pezizales lineages and included truffles and cup fungi. Three clades of seven OTUs have no known meiospore stage. Mitospores failed to germinate on sterile media, or form ectomycorrhizas on Quercus, Pinus and Populus seedlings, consistent with a hypothesized role of spermatia. The broad geographic range, high frequency and phylogenetic diversity of spore mats produced by EcM Pezizales suggests that a mitospore stage is important for many species in this group in terms of mating, reproduction and/or dispersal.
Asymptomatic patients, together with those with mild symptoms of coronavirus disease 2019 (COVID-19), may play an important role in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ...transmission. However, the dynamics of virus shedding during the various phases of the clinical course of COVID-19 remains unclear at this stage.
A total of 18 patients found to be positive for SARS-CoV-2 infection by real-time reverse transcription PCR (RT-PCR) assay and admitted to Chongqing University Central Hospital between 29 January and 5 February 2020 were enrolled into this study. Medical data, pulmonary computed tomographic (CT) scan images and RT-PCR results were periodically collected during the patients' hospital stay. All participants were actively followed up for 2 weeks after discharge.
A total of nine (50%) asymptomatic patients and nine (50%) patients with mild symptoms of COVID-19 were identified at admission. Six patients (66.7%) who were asymptomatic at admission developed subjective symptoms during hospitalization and were recategorized as being presymptomatic. The median duration of virus shedding was 11.5, 28 and 31 days for presymptomatic, asymptomatic and mildly symptomatic patients, separately. Seven patients (38.9%) continued to shed virus after hospital discharge. During the convalescent phase, detectable antibodies to SARS-CoV-2 and RNA were simultaneously observed in five patients (27.8%).
Long-term virus shedding was documented in patients with mild symptoms and in asymptomatic patients. Specific antibody production to SARS-CoV-2 may not guarantee virus clearance after discharge. These observations should be considered when making decisions regarding clinical and public health, and when considering strategies for the prevention and control of SARS-CoV-2 infection.
Forbidden hugs in pandemic times Cai, Y.-Z.; Pastorello, A.; Fraser, M. ...
Astronomy and astrophysics (Berlin),
11/2022, Letnik:
667
Journal Article
Recenzirano
Odprti dostop
We present an observational study of the luminous red nova (LRN) AT 2021biy in the nearby galaxy NGC 4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic ...surveys, but the transient was detected only at a few epochs from ∼231 days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT 2021biy shows a short-duration blue peak, with a bolometric luminosity of ∼1.6 × 10
41
erg s
−1
, followed by the longest plateau among LRNe to date, with a duration of 210 days. A late-time hump in the light curve was also observed, possibly produced by a shell-shell collision. AT 2021biy exhibits the typical spectral evolution of LRNe. Early-time spectra are characterised by a blue continuum and prominent H emission lines. Then, the continuum becomes redder, resembling that of a K-type star with a forest of metal absorption lines during the plateau phase. Finally, late-time spectra show a very red continuum (
T
BB
≈ 2050 K) with molecular features (e.g., TiO) resembling those of M-type stars. Spectropolarimetric analysis indicates that AT 2021biy has local dust properties similar to those of V838 Mon in the Milky Way Galaxy. Inspection of archival
Hubble
Space Telescope data taken on 2003 August 3 reveals a ∼20
M
⊙
progenitor candidate with log (
L
/
L
⊙
) = 5.0 dex and
T
eff
= 5900 K at solar metallicity. The above luminosity and colour match those of a luminous yellow supergiant. Most likely, this source is a close binary, with a 17–24
M
⊙
primary component.
The sequestrate (truffle-like) basidiomycete genera Rossbeevera, Chamonixia, and Octaviania are closely related to the epigeous mushroom genera Leccinum and Leccinellum. In order to elucidate the ...properties and placement of several undescribed sequestrate
taxa in the group and to reveal the evolutionary history of Rossbeevera and its allies, we conducted phylogenetic analyses based on three nuclear (ITS, nLSU, EF-1α) and two mitochondrial DNA loci (ATP6 and mtSSU) as well as precise morphological observations. Phylogenetic
analyses of three nuclear loci suggest a complex evolutionary history with sequestrate fruiting bodies present in several clades, including a previously unrecognized sister clade to Rossbeevera. Here we propose a new sequestrate genus, Turmalinea, with four new species and one
new subspecies as well as two new species of Rossbeevera. The three-locus nuclear phylogeny resolves species-level divergence within the Rossbeevera-Turmalinea lineage, whereas a separate phylogeny based on two mitochondrial genes corresponds to geographic distance within each
species-level lineage and suggests incomplete lineage sorting (ILS) and gene introgression within several intraspecific lineages of Rossbeevera. Furthermore, topological incongruence among the three nuclear single-locus phylogenies suggests that ancient speciation within Rossbeevera
probably involved considerable ILS. We also found an unusually long, minisatellite-like insertion within the ITS2 in all Rossbeevera and Turmalinea species. A barcode gap analysis demonstrates that the insertion is more informative for discrimination at various taxonomic levels
than the rest of the ITS region and could therefore serve as a unique molecular barcode for these genera.
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•Magnetron sputtering was used to fabricate Al films.•High coercivity and excellent corrosion resistance were obtained.•A weak ferromagnetic phase within intergranular phase was ...investigated.
Al film, which was coated in sintered Nd-Fe-B magnets prepared by magnetron sputtering, was employed for grain boundary diffusion source. Effects of the grain boundary diffusion processes (GBDP) on the microstructure evolution and properties were investigated in detail. Through grain boundary diffusion processes, the highest coercivity of 1184 kA/m and maximum energy product of 238 kJ/m3 could be obtained, increasing by 21.8% and 3.9%, respectively, compared with the initial magnet. Meanwhile, our results showed that fine, uniform and continuous intergranular phase induced by Al diffusion, was the main reason for properties improvement, while a weak ferromagnetic phase and the vague interface between main phase and RE-rich phase should be responsible to the deterioration of coercivity when the diffused temperature exceed 600 °C. Besides, the corrosion resistance of Al-diffused magnets was also greatly improved, owing to the fact that the Al element could promote the electrochemical potential of RE-rich phase and the more thin, continuous intergranular phase would also narrow the corrosion channel.
ABSTRACT
High time resolution and accuracy are of critical importance in the studies of timing analysis and time delay localization of gamma-ray bursts (GRBs), soft gamma-ray repeaters (SGRs) and ...pulsars. The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) consisting of two micro-satellites, GECAM-A and GECAM-B, launched on 2020 December 10, is aimed at monitoring and locating X-ray and GRBs all over the sky. To achieve its scientific goals, GECAM is designed to have the highest time resolution (0.1 $\mu {\rm s}$) among all GRB detectors ever flown. Here, we make a comprehensive time calibration campaign including both on-ground and on-orbit tests to derive not only the relative time accuracy of GECAM satellites and detectors, but also the absolute time accuracy of GECAM-B. Using the on-ground calibration with a $\rm ^{22}Na$ radioactive source, we find that the relative time accuracy between GECAM-A and GECAM-B is about 0.15 $\mu {\rm s}$ (1σ). To measure the relative time accuracy between all detectors of a single GECAM satellite, cosmic-ray events detected on orbit are utilized since they could produce many secondary particles simultaneously record by multiple detectors. We find that the relative time accuracy among all detectors onboard GECAM-B is about 0.12 $\mu {\rm s}$ (1σ). Finally, we use the novel Li-CCF method to perform the absolute time calibration with Crab pulsar and SGR J1935+2154, both of which were jointly observed by GECAM-B and Fermi/GBM, and obtain that the time difference between GECAM-B and Fermi/GBM is 3.06 ± 6.04 $\mu {\rm s}$ (1σ).
The usages of high-abundance rare-earth element Ce in the permanent magnet have drawn considerable interest from industrial and scientific societies. In this work, through PrCu addition combined with ...grain boundary diffusion process (GBDP), anisotropic hot deformed (HD) CeFeB magnets with Jr = 0.66 T, Hci = 514 kA/m, and (BH)max = 55 kJ/m3 can be acquired. The addition of intergranular phase PrCu in spark plasma sintering (SPS) is favorable to the improvement of the plastic deformation ability and the increase of the c-axis crystallographic texture of HDed magnet. Meanwhile, it can also act as a diffusion channel to increase the diffused efficiency during the subsequent GBDP. The observed three Curie temperatures on M-T curves, should be attributed to three various types of 2:14:1 phase, that is initial Ce2Fe14B phase and different (Pr, Ce)2Fe14B phases formed in the process of spark plasma sintering (SPS) and GBDP, respectively. Elemental metallurgical behavior revealed that, the intergranular phases are rich in Pr, Ce, and Cu but depleted in Fe. Intergranular phases analysis demonstrated that, Pr and Ce oxides including (Pr, Ce)O2, Pr12O22, and (Pr, Ce)2O3 can be identified, and amorphous phase is also observed. Through GBDP, magnetic properties, including the coercivity, remanence, and maximum energy product are all improved greatly, which is ascribed to the joint effects from the formation of (Pr, Ce)2Fe14B phase and intergranular phase.
Display omitted
•Anisotropic hot deformed CeFeB magnets were prepared.•The addition of PrCu alloy is favorable to the increase of c-axis texture.•Three Curie temperatures were observed.•Intergranular phase containing multiple different phases was revealed.
The maximum content of cation vacancies in perovskites determines the maximum adjustment to the physical properties. By using the classical criterion of the tolerance factor, we put forward a new ...method to obtain the maximum content of cation vacancies in perovskites. The effective ionic radius was calculated using the weighted average method, and the limit of tolerance factors was used to determine the maximum value of the cation vacancies. The calculated results of the La
1−
x
MnO
3
and La
0.75
Sr
0.25
Mn
1−
y
O
3
materials coincide with experimental results. For application, (A
1
)
1−
x
(A
2
)
x
1−
z
1
(B
1
B
2
)X
3
or (A
1
)
1−
x
(A
2
)
x
(B
1
B
2
)
1−
z
2
X
3
(X = O, F, Cl, Br, I) inorganic and hybrid organic-inorganic perovskite materials with vacancies at the A or B sites were predicted successfully, which provides a new method to improve the physical properties of perovskite materials.
Curves of the maximum or minimum values
versus
the different ratio of cation at the A sites for A
1−
h
1
PbX
3
hybrid perovskites.
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