27 research outputs found
Anomalous T-dependence of phonon lifetimes in metallic VO2
We investigate phonon lifetimes in VO2 single crystals. We do so in the
metallic state above the metal-insulator transition (MIT), where strong
structural fluctuations are known to take place. By combining inelastic X-ray
scattering and Raman spectroscopy, we track the temperature dependence of
several acoustic and optical phonon modes up to 1000 K. Contrary to what is
commonly observed, we find that phonon lifetimes decrease with decreasing
temperature. Our results show that pre-transitional fluctuations in the
metallic state give rise to strong electron-phonon scattering that onsets
hundreds of degrees above the transition and increases as the MIT is
approached. Notably, this effect is not limited to specific points of
reciprocal space that could be associated with the structural transition
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Hemodynamic modeling of leukocyte and erythrocyte transport and interactions in intracranial aneurysms by a multiphase approach
Hemodynamics has been recognized as an important factor in the development, growth, and rupture of cerebral aneurysms, and investigated by computational fluid dynamics techniques using a single phase approach. However, flow-dependent cell transport and interactions are usually ignored in single phase models, in which blood is usually treated as a single phase Newtonian fluid. For getting better insight into the underlying pathology of intracranial aneurysm, cell transport and interactions should be covered in hemodynamic studies. In the present study, a multiphase hemodynamic model incorporating cell transport and interactions was developed, in which blood was modeled as multiphase fluid having a continuous phase (plasma) and two particulate phases (erythrocytes and leukocytes). The model showed good agreement with experimental data and observations in the literature, and was applied to four patient-specific aneurysms in a pulsatile manner. Leukocyte accumulations were predicted at locations with flow disturbance and low wall shear stress. The concentrations of leukocyte at accumulation sites were found to exceed 200 to 500% of normal physiological level on three unstable aneurysms, including two ruptured aneurysms and a growing aneurysm where accumulation was observed near a daughter sac and a secondary aneurysm. This suggested that aneurysms with complex secondary flow patterns could be prone to leukocyte accumulation on the wall. As this is the first study to characterize cell transport and interactions in aneurysm hemodynamics, our model can serve as a foundation for future intracranial aneurysm models.9 page(s
Protecting-group-free ortho-C–H borylation of anilines enabled by mesoionic carbene-Ir complex
We describe an iridium-catalyzed ortho-selective C–H borylation of unprotected anilines. The employing strong σ-donating cyclometalated mesoionic carbene as C^C bidentate ligand is crucial for the high ortho-selectivity. Computational studies support outer-sphere X–H···Oboryl hydrogen bond interactions, which are strengthened by bidentate C^C ligand introduction. The method shows broad substrate scope and high functional group tolerance
Whole-Exome Sequencing-Based Mutational Profiling of Hepatitis B Virus-Related Early-Stage Hepatocellular Carcinoma
Background. Hepatocellular carcinoma (HCC) ranks as the third leading cause of cancer-related mortality in China with increasing incidence. This study is designed to explore early genetic changes implicated in HCC tumorigenesis and progression by whole-exome sequencing. Methods. We firstly sequenced the whole exomes of 5 paired hepatitis B virus-related early-stage HCC and peripheral blood samples, followed by gene ontological analysis and pathway analysis of the single-nucleotide variants discovered. Then, the mutations of high frequency were further confirmed by Sanger sequencing. Results. We identified a mutational signature of dominant T:A>A:T transversion in early HCC and significantly enriched pathways including ECM-receptor interaction, axon guidance, and focal adhesion and enriched biological processes containing cell adhesion, axon guidance, and regulation of pH. Eight genes, including MUC16, UNC79, USH2A, DNAH17, PTPN13, TENM4, PCLO, and PDE1C, were frequently mutated. Conclusions. This study reveals a mutational profile and a distinct mutation signature of T:A>A:T transversion in early-stage HCC with HBV infection, which will enrich our understanding of genetic characteristics of the early-stage HCC
GAMMA Challenge:Glaucoma grAding from Multi-Modality imAges
Color fundus photography and Optical Coherence Tomography (OCT) are the two
most cost-effective tools for glaucoma screening. Both two modalities of images
have prominent biomarkers to indicate glaucoma suspected. Clinically, it is
often recommended to take both of the screenings for a more accurate and
reliable diagnosis. However, although numerous algorithms are proposed based on
fundus images or OCT volumes in computer-aided diagnosis, there are still few
methods leveraging both of the modalities for the glaucoma assessment. Inspired
by the success of Retinal Fundus Glaucoma Challenge (REFUGE) we held
previously, we set up the Glaucoma grAding from Multi-Modality imAges (GAMMA)
Challenge to encourage the development of fundus \& OCT-based glaucoma grading.
The primary task of the challenge is to grade glaucoma from both the 2D fundus
images and 3D OCT scanning volumes. As part of GAMMA, we have publicly released
a glaucoma annotated dataset with both 2D fundus color photography and 3D OCT
volumes, which is the first multi-modality dataset for glaucoma grading. In
addition, an evaluation framework is also established to evaluate the
performance of the submitted methods. During the challenge, 1272 results were
submitted, and finally, top-10 teams were selected to the final stage. We
analysis their results and summarize their methods in the paper. Since all
these teams submitted their source code in the challenge, a detailed ablation
study is also conducted to verify the effectiveness of the particular modules
proposed. We find many of the proposed techniques are practical for the
clinical diagnosis of glaucoma. As the first in-depth study of fundus \& OCT
multi-modality glaucoma grading, we believe the GAMMA Challenge will be an
essential starting point for future research