298 research outputs found
Work function of bulk-insulating topological insulator Bi2-xSbxTe3-ySey
Recent discovery of bulk insulating topological insulator (TI)
Bi2-xSbxTe3-ySey paved a pathway toward practical device application of TIs.
For realizing TI-based devices, it is necessary to contact TIs with a metal.
Since the band-bending at the interface dominates the character of devices,
knowledge of TIs' work function is of essential importance. We have determined
the compositional dependence of work function in Bi2-xSbxTe3-ySey by
high-resolution photoemission spectroscopy. The obtained work-function values
(4.95-5.20 eV) show a systematic variation with the composition, well tracking
the energy shift of the surface chemical potential seen by angle-resolved
photoemission spectroscopy. The present result serves as a useful guide for
developing TI-based electronic devices.Comment: 4pages, 2 figure
Direct Evidence for the Dirac-Cone Topological Surface States in Ternary Chalcogenide TlBiSe2
We have performed high-resolution angle-resolved photoemission spectroscopy
on TlBiSe2, which is a member of the ternary chalcogenides theoretically
proposed as candidates for a new class of three-dimensional topological
insulators. By measuring the energy band dispersions over the entire surface
Brillouin zone, we found a direct evidence for a non-trivial surface metallic
state showing a X-shaped energy dispersion within the bulk band gap. The
present result unambiguously establishes that TlBiSe2 is a strong topological
insulator with a single Dirac cone at the Brillouin-zone center. The observed
bulk band gap of 0.4 eV is the largest among known topological insulators,
making TlBiSe2 the most promising material for studying room-temperature
topological phenomena.Comment: 4 pages, 4 figure
Observation of band crossings protected by nonsymmorphic symmetry in the layered ternary telluride Ta3SiTe6
We have performed angle-resolved photoemission spectroscopy of layered
ternary telluride Ta3SiTe6 which is predicted to host nodal lines associated
with nonsymmorphic crystal symmetry. We found that the energy bands in the
valence-band region show Dirac-like dispersions which present a band degeneracy
at the R point of the bulk orthorhombic Brillouin zone. This band degeneracy
extends one-dimensionally along the whole SR high-symmetry line, forming the
nodal lines protected by the glide mirror symmetry of the crystal. We also
observed a small band splitting near EF which supports the existence of
hourglass-type dispersions predicted by the calculation. The present results
provide an excellent opportunity to investigate the interplay between exotic
nodal fermions and nonsymmorphic crystal symmetry.Comment: 6 pages, 4 figure
Plasticity of Repetitive DNA Sequences within a Bacterial (Type IV) Secretion System Component
DNA rearrangement permits bacteria to regulate gene content and expression. In Helicobacter pylori, cagY, which contains an extraordinary number of direct DNA repeats, encodes a surface-exposed subunit of a (type IV) bacterial secretory system. Examining potential DNA rearrangements involving the cagY repeats indicated that recombination events invariably yield in-frame open reading frames, producing alternatively expressed genes. In individual hosts, H. pylori cell populations include strains that produce CagY proteins that differ in size, due to the predicted in-frame deletions or duplications, and elicit minimal or no host antibody recognition. Using repetitive DNA, H. pylori rearrangements in a host-exposed subunit of a conserved bacterial secretion system may permit a novel form of antigenic evasion
Aberrant Methylation of p21 Gene in Lung Cancer and Malignant Pleural Mesothelioma
Suppression of p21 has been implicated in the genesis and progression of many human malignancies. DNA methylation is an important mechanism of gene silencing in human malignancies. In this study, we examined the expression status and aberrant methylaion of p21 in lung cancers and malignant pleural mesotheliomas (MPM). We used 12 small cell lung cancer (SCLC) cell lines, 13 non-small cell lung cancer (NSCLC) cell lines, 50 primary NSCLCs, 6 MPM cell lines and 10 primary MPMs. The expression and methylation of p21 was examined by reverse transcription-PCR (RT-PCR), Western blotting and methylation-specific PCR (MSP) assay. Loss of p21 protein expression was observed in 7 SCLC cell lines (58.3%), 5 NSCLC cell lines (38.5%) and 3 MPM cell lines (50%) while mRNA expression was lost in 2 SCLC cell lines (16.7%), 2 NSCLC cell lines (15.4%) and none of the MPM cell lines. Aberrant methylation of p21 was found in 8.3% of SCLC cell lines, 30.2% of NSCLCs and 6.3% of MPMs. Among primary NSCLCs, methylation in adenocarcinomas was significantly more frequent than in squamous cell carcinomas. Loss of p21 expression was frequently observed in lung cancers and MPMs and aberrant methylation was one of the mechanisms of suppression of p21, especially in NSCLCs
Unusual surface states associated with the PT-symmetry breaking and antiferromagnetic band folding in NdSb
We have performed micro-focused angle-resolved photoemission spectroscopy on
NdSb which exhibits the type-I antiferromagnetism below TN = 16 K. We succeeded
in selectively observing the band structure for all the three types of single-q
antiferromagnetic (AF) domains at the surface. We found that the two of three
surfaces whose AF-ordering vector lies within the surface plane commonly show
two-fold-symmetric surface states (SSs) around the bulk-band edges, whereas the
other surface with an out-of-plane AF-ordering vector displays
four-fold-symmetric shallow electronlike SS at the Brillouin-zone center. We
suggest that these SSs commonly originate from the combination of the PT
(space-inversion and time-reversal) symmetry breaking at the surface and the
band folding due to the AF order. The present results pave a pathway toward
understanding the relationship between the symmetry and the surface electronic
states in antiferromagnets.Comment: 20 pages, 5 figure
JASTRO IC/IS Guideline for Gynecologic Cancers
It has been postulated that the combination of intracavitary and interstitial brachytherapy (IC/IS) is effective and safe for large and irregularly shaped uterine cervical cancer patients. However, due to its invasiveness compared to conventional intracavitary brachytherapy (ICBT), it has to be said that the implementation speed of IC/IS is slow. Until now, there have been no guidelines for required equipment, human resources, and procedural guide focusing solely on IC/IS. The purpose of this guideline is to provide radiation oncologists and medical physicists who wish to start IC/IS with practical and comprehensive guidance for a safe IC/IS introduction and to help accelerate the spread of the utilization of IC/IS nationwide. This is the English translation of the Japanese IC/IS Guidelines, and it was created in an effort to share the Japanese approach to the management of locally advanced uterine cervical cancer worldwide
End-to-End Joint Target and Non-Target Speakers ASR
This paper proposes a novel automatic speech recognition (ASR) system that
can transcribe individual speaker's speech while identifying whether they are
target or non-target speakers from multi-talker overlapped speech.
Target-speaker ASR systems are a promising way to only transcribe a target
speaker's speech by enrolling the target speaker's information. However, in
conversational ASR applications, transcribing both the target speaker's speech
and non-target speakers' ones is often required to understand interactive
information. To naturally consider both target and non-target speakers in a
single ASR model, our idea is to extend autoregressive modeling-based
multi-talker ASR systems to utilize the enrollment speech of the target
speaker. Our proposed ASR is performed by recursively generating both textual
tokens and tokens that represent target or non-target speakers. Our experiments
demonstrate the effectiveness of our proposed method.Comment: Accepted at Interspeech 202
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