551 research outputs found
Evidence for a preformed Cooper pair model in the pseudogap spectra of a Ca10(Pt4As8)(Fe2As2)5 single crystal with a nodal superconducting gap
For high-Tc superconductors, clarifying the role and origin of the pseudogap
is essential for understanding the pairing mechanism. Among the various models
describing the pseudogap, the preformed Cooper pair model is a potential
candidate. Therefore, we present experimental evidence for the preformed Cooper
pair model by studying the pseudogap spectrum observed in the optical
conductivity of a Ca10(Pt4As8)(Fe2As2)5 (Tc = 34.6 K) single crystal. We
observed a clear pseudogap structure in the optical conductivity and observed
its temperature dependence. In the superconducting (SC) state, one SC gap with
a gap size of {\Delta} = 26 cm-1, a scattering rate of 1/{\tau} = 360 cm-1 and
a low-frequency extra Drude component were observed. Spectral weight analysis
revealed that the SC gap and pseudogap are formed from the same Drude band.
This means that the pseudogap is a gap structure observed as a result of a
continuous temperature evolution of the SC gap observed below Tc. This provides
clear experimental evidence for the preformed Cooper pair model.Comment: 15 pages, 4 figure
Ballistic spin field-effect transistors: Multichannel effects
We study a ballistic spin field-effect transistor (SFET) with special
attention to the issue of multi-channel effects. The conductance modulation of
the SFET as a function of the Rashba spin-orbit coupling strength is
numerically examined for the number of channels ranging from a few to close to
100. Even with the ideal spin injector and collector, the conductance
modulation ratio, defined as the ratio between the maximum and minimum
conductances, decays rapidly and approaches one with the increase of the
channel number. It turns out that the decay is considerably faster when the
Rashba spin-orbit coupling is larger. Effects of the electronic coherence are
also examined in the multi-channel regime and it is found that the coherent
Fabry-Perot-like interference in the multi-channel regime gives rise to a
nested peak structure. For a nonideal spin injector/collector structure, which
consists of a conventional metallic ferromagnet-thin insulator-2DEG
heterostructure, the Rashba-coupling-induced conductance modulation is strongly
affected by large resonance peaks that arise from the electron confinement
effect of the insulators. Finally scattering effects are briefly addressed and
it is found that in the weakly diffusive regime, the positions of the resonance
peaks fluctuate, making the conductance modulation signal sample-dependent.Comment: 18 pages, 15 figure
Mobility-Induced Graph Learning for WiFi Positioning
A smartphone-based user mobility tracking could be effective in finding
his/her location, while the unpredictable error therein due to low
specification of built-in inertial measurement units (IMUs) rejects its
standalone usage but demands the integration to another positioning technique
like WiFi positioning. This paper aims to propose a novel integration technique
using a graph neural network called Mobility-INduced Graph LEarning (MINGLE),
which is designed based on two types of graphs made by capturing different user
mobility features. Specifically, considering sequential measurement points
(MPs) as nodes, a user's regular mobility pattern allows us to connect neighbor
MPs as edges, called time-driven mobility graph (TMG). Second, a user's
relatively straight transition at a constant pace when moving from one position
to another can be captured by connecting the nodes on each path, called a
direction-driven mobility graph (DMG). Then, we can design graph convolution
network (GCN)-based cross-graph learning, where two different GCN models for
TMG and DMG are jointly trained by feeding different input features created by
WiFi RTTs yet sharing their weights. Besides, the loss function includes a
mobility regularization term such that the differences between adjacent
location estimates should be less variant due to the user's stable moving pace.
Noting that the regularization term does not require ground-truth location,
MINGLE can be designed under semi- and self-supervised learning frameworks. The
proposed MINGLE's effectiveness is extensively verified through field
experiments, showing a better positioning accuracy than benchmarks, say root
mean square errors (RMSEs) being 1.398 (m) and 1.073 (m) for self- and
semi-supervised learning cases, respectively.Comment: submitted to a possible IEEE journa
Expression of PD-L1 in triple-negative breast cancer based on different immunohistochemical antibodies
Additional file 1. Additional Tables, Tables S1âS4
Atypical vitelliform macular dystrophy misdiagnosed as chronic central serous chorioretinopathy: case reports
BACKGROUND: To report two cases of atypical vitelliform macular dystrophy misdiagnosed as chronic central serous chorioretinopathy. CASE PRESENTATION: Two patients with incidentally discovered abnormalities of the retina without specific symptoms were referred to our hospital for consultation. Bilateral macula atrophic lesions were observed and optical coherence tomography revealed serous retinal detachment in the macula. Fluorescein angiography showed multiple leakages around the central hypofluorescent area and indocyanine green angiography showed partially dilated choroidal vessels. Fundus autofluorescence (FAF) showed a decreasing pattern of autofluorescence in the subretinal fluid area, and increasing autofluorescence at the border of the serous retinal detachment. Both patients were diagnosed with chronic central serous chorioretinopathy. Photodynamic therapy and intravitreal bevacizumab injection were administered for engorged choroidal vessels during follow-up, but neither patient showed improvement in symptoms or ophthalmologic findings. Based on re-evaluation by fundus photography, optical coherence tomography, fluorescein angiography, and comparison of the results of FAF with the first visit, vitelliform macular dystrophy was suspected and a definite diagnosis was made by electrooculography and genetic testing. CONCLUSION: In patients with continuous serous retinal detachment without response to photodynamic therapy or intravitreal bevacizumab injection, careful fundus exam and FAF can be used to diagnose atypical vitelliform macular dystrophy
Nasal Hemangiopericytoma Causing Oncogenic Osteomalacia
Oncogenic osteomalacia is a rare cause that makes abnormalities of bone metabolism. Our case arose in a 47-year-old woman presenting a nasal mass associated with osteomalacia. We excised the mass carefully. After surgery, it was diagnosed as hemangiopericytoma and her symptoms related with osteomalacia were relieved and biochemical abnormalities were restored to normal range. We report and review a rare case of nasal hemangiopericytoma that caused osteomalacia
Temperature dependence of the superconducting energy gaps in Ca9.35La0.65(Pt-3 As-8)(Fe2As2)(5) single crystal
We measured the optical reflectivity R(ω) for an underdoped (Ca0.935La0.065)10(Pt3As8)(Fe2As2)5 single crystal and obtained the optical conductivity σ1(ω) using the K-K transformation. The normal state σ1(ω) at 30 K is well fitted by a Drude-Lorentz model with two Drude components (ωp1 = 1446 cm-1 and ωp2 = 6322 cm-1) and seven Lorentz components. Relative reflectometry was used to accurately determine the temperature dependence of the superconducting gap at various temperatures below Tc. The results clearly show the opening of a superconducting gap with a weaker second gap structure; the magnitudes for the gaps are estimated from the generalized Mattis-Bardeen model to be Δ1 = 30 and Δ2 = 50 cm-1, respectively, at T = 8 K, which both decrease with increasing temperature. The temperature dependence of the gaps was not consistent with one-band BCS theory but was well described by a two-band (hence, two gap) BCS model with interband interactions. The temperature dependence of the superfluid density is flat at low temperatures, indicating an s-wave full-gap superconducting state. © The Author(s) 2018.1
Effect of proton irradiation on the fluctuation-induced magnetoconductivity of FeSe1−xTex thin films
The influence of proton irradiation on the fluctuation-induced magnetoconductivity of high quality
FeSe1−xTex (x=0.4, 0.55) (FST) thin films has been investigated. The measurements were performed
with magnetic fields up to 13 T applied in the two main crystal directions. The results were interpreted
in terms of the Ginzburg–Landau approach for three-dimensional materials under a total-energy
cutoff. The analysis shows that properly-tuned proton irradiation does not appreciably affect
fundamental superconducting parameters like the Tc value, the upper critical fields or the anisotropy.
This has important consequences from the point of view of possible applications due to the
enhancement of vortex pinning induced by irradiation.YSK was supported by the NRF grant funded by the Ministry of Science, ICT and Future Planning (No. NRF-2015M2B2A9028507 and NRF-2016R1A2B4012672). TP was supported by the NRF grant funded by the Ministry of Science, ICT and Future Planning of Korea (No. 2012R1A3A2048816). JM acknowledges support by project FIS2016-79109-P (AEI/FEDER, UE) and by the Xunta de Galicia (project AGRUP 2015/11). SL was supported by the Global Research Network program through the NRF funded by the Ministry of Science and ICT & Future Planning (NRF-2014S1A2A2028361)S
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