516 research outputs found
Non-Thermal Emergence of an Orbital-Selective Mott Phase in FeTeSe
Electronic correlation is of fundamental importance to high temperature
superconductivity. Iron-based superconductors are believed to possess moderate
correlation strength, which combined with their multi-orbital nature makes them
a fascinating platform for the emergence of exotic phenomena. A particularly
striking form is the emergence of an orbital selective Mott phase, where the
localization of a subset of orbitals leads to a drastically reconstructed Fermi
surface. Here, we report spectroscopic evidence of the reorganization of the
Fermi surface from FeSe to FeTe as Se is substituted by Te. We uncover a
particularly transparent way to visualize the localization of the
electron orbital through the suppression of its hybridization with the more
coherent electron orbitals, which leads to a redistribution of the
orbital-dependent spectral weight near the Fermi level. These noteworthy
features of the Fermi surface are accompanied by a divergent behavior of a band
renormalization in the orbital. All of our observations are further
supported by our theoretical calculations to be salient spectroscopic
signatures of such a non-thermal evolution from a strongly correlated metallic
phase towards an orbital-selective Mott phase in FeTeSe as Se
concentration is reduced.Comment: 11 pages, 5 figure
Mini-open anterior spine surgery for anterior lumbar diseases
Minimally invasive surgeries including endoscopic surgery and mini-open surgery are current trend of spine surgery, and its main advantages are shorter recovery time and cosmetic benefits, etc. However, mini-open surgery is easier and less technique demanding than endoscopic surgery. Besides, anterior spinal fusion is better than posterior spinal fusion while considering the physiological loading, back muscle function, etc. Therefore, we aimed to introduce the modified “mini-open anterior spine surgery” (MOASS) and to evaluate the feasibility, effectiveness and safety in the treatment of various anterior lumbar diseases with this technique. A total of 61 consecutive patients (46 female, 15 male; mean age 58.2 years) from 1997 to 2004 were included in this study, with an average follow-up of 24–52 (mean 43) months. The disease entities included vertebral fracture (20), failed back surgery (13), segmental instability or spondylolisthesis (10), infection (8), herniated disc (5), undetermined lesion for biopsy (4), and hemivertebra (1). Lesions involved 13 cases at T12–L1, 18 at L1–L2, 18 at L2–L3, 22 at L3–L4 and 11 at L4–L5 levels. All patients received a single stage anterior-only procedure for their anterior lumbar disease. We used the subjective clinical results, Oswestry disability index, fusion rate, and complications to evaluate our clinical outcome. Most patients (91.8%) were subjectively satisfied with the surgery and had good-to-excellent outcomes. Mean operation time was 85 (62–124) minutes, and mean blood loss was 136 (minimal-250) ml in the past 6 years. Hospital stay ranged from 4–26 (mean 10.6) days. Nearly all cases had improved back pain (87%), physical function (90%) and life quality (85%). Most cases (95%) achieved solid or probable solid bony fusion. There were no major complications. Therefore, MOASS is feasible, effective and safe for patients with various anterior lumbar diseases
Reversible Non-Volatile Electronic Switching in a Near Room Temperature van der Waals Ferromagnet
The ability to reversibly toggle between two distinct states in a
non-volatile method is important for information storage applications. Such
devices have been realized for phase-change materials, which utilizes local
heating methods to toggle between a crystalline and an amorphous state with
distinct electrical properties. To expand such kind of switching between two
topologically distinct phases requires non-volatile switching between two
crystalline phases with distinct symmetries. Here we report the observation of
reversible and non-volatile switching between two stable and closely-related
crystal structures with remarkably distinct electronic structures in the near
room temperature van der Waals ferromagnet FeGeTe. From a
combination of characterization techniques we show that the switching is
enabled by the ordering and disordering of an Fe site vacancy that results in
distinct crystalline symmetries of the two phases that can be controlled by a
thermal annealing and quenching method. Furthermore, from symmetry analysis as
well as first principle calculations, we provide understanding of the key
distinction in the observed electronic structures of the two phases:
topological nodal lines compatible with the preserved global inversion symmetry
in the site-disordered phase, and flat bands resulting from quantum destructive
interference on a bipartite crystaline lattice formed by the presence of the
site order as well as the lifting of the topological degeneracy due to the
broken inversion symmetry in the site-ordered phase. Our work not only reveals
a rich variety of quantum phases emergent in the metallic van der Waals
ferromagnets due to the presence of site ordering, but also demonstrates the
potential of these highly tunable two-dimensional magnets for memory and
spintronics applications
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Interdecadal seesaw of precipitation variability between North China and the Southwest US
This paper reports a consistent seesaw relationship between interdecadal precipitation variability over North China and the Southwest United States (US), which can be found in observations and simulations with several models. Idealized model simulations suggest the seesaw could be mainly driven by the Interdecadal Pacific Oscillation (IPO), through a large-scale circulation anomaly occupying the entire northern North Pacific, while the Atlantic Multidecadal Oscillation (AMO) contributes oppositely and less. Modulation of precipitation by the IPO tends to be intensified when the AMO is in the same phase. The warm IPO phase is associated with an anomalous cyclone over the northern North Pacific and consequently, anomalous southwesterly winds bring more moisture and rainfall to the southwest US, while northwesterly wind anomalies prevail over North China with negative rainfall anomalies. The east-west seesaw of rainfall anomalies reverses sign when the circulation anomaly becomes anticyclonic during the cold IPO phase. The IPO-related tropical SST anomalies affect the meridional temperature gradient over the North Pacific and adjacent regions and the mean meridional circulation. In the northern North Pacific, the atmospheric response to IPO forcing imposes an equivalent barotropic structure throughout the troposphere. An important impliciation from this study is the potential predictability of drought-related water stresses over these arid and semiarid regions, with the progress of our understanding and prediction of the IPO and AMO
Widespread Hypomethylation Occurs Early and Synergizes with Gene Amplification during Esophageal Carcinogenesis
Although a combination of genomic and epigenetic alterations are implicated in the multistep transformation of normal squamous esophageal epithelium to Barrett esophagus, dysplasia, and adenocarcinoma, the combinatorial effect of these changes is unknown. By integrating genome-wide DNA methylation, copy number, and transcriptomic datasets obtained from endoscopic biopsies of neoplastic progression within the same individual, we are uniquely able to define the molecular events associated progression of Barrett esophagus. We find that the previously reported global hypomethylation phenomenon in cancer has its origins at the earliest stages of epithelial carcinogenesis. Promoter hypomethylation synergizes with gene amplification and leads to significant upregulation of a chr4q21 chemokine cluster and other transcripts during Barrett neoplasia. In contrast, gene-specific hypermethylation is observed at a restricted number of loci and, in combination with hemi-allelic deletions, leads to downregulatation of selected transcripts during multistep progression. We also observe that epigenetic regulation during epithelial carcinogenesis is not restricted to traditionally defined “CpG islands,” but may also occur through a mechanism of differential methylation outside of these regions. Finally, validation of novel upregulated targets (CXCL1 and 3, GATA6, and DMBT1) in a larger independent panel of samples confirms the utility of integrative analysis in cancer biomarker discovery
Identification of miRs-143 and -145 that Is Associated with Bone Metastasis of Prostate Cancer and Involved in the Regulation of EMT
The principal problem arising from prostate cancer (PCa) is its propensity to metastasize to bone. MicroRNAs (miRNAs) play a crucial role in many tumor metastases. The importance of miRNAs in bone metastasis of PCa has not been elucidated to date. We investigated whether the expression of certain miRNAs was associated with bone metastasis of PCa. We examined the miRNA expression profiles of 6 primary and 7 bone metastatic PCa samples by miRNA microarray analysis. The expression of 5 miRNAs significantly decreased in bone metastasis compared with primary PCa, including miRs-508-5p, -145, -143, -33a and -100. We further examined other samples of 16 primary PCa and 13 bone metastases using real-time PCR analysis. The expressions of miRs-143 and -145 were verified to down-regulate significantly in metastasis samples. By investigating relationship of the levels of miRs-143 and -145 with clinicopathological features of PCa patients, we found down-regulations of miRs-143 and -145 were negatively correlated to bone metastasis, the Gleason score and level of free PSA in primary PCa. Over-expression miR-143 and -145 by retrovirus transfection reduced the ability of migration and invasion in vitro, and tumor development and bone invasion in vivo of PC-3 cells, a human PCa cell line originated from a bone metastatic PCa specimen. Their upregulation also increased E-cadherin expression and reduced fibronectin expression of PC-3 cells which revealed a less invasive morphologic phenotype. These findings indicate that miRs-143 and -145 are associated with bone metastasis of PCa and suggest that they may play important roles in the bone metastasis and be involved in the regulation of EMT Both of them may also be clinically used as novel biomarkers in discriminating different stages of human PCa and predicting bone metastasis
Contribution of Intrinsic Reactivity of the HIV-1 Envelope Glycoproteins to CD4-Independent Infection and Global Inhibitor Sensitivity
Human immunodeficiency virus (HIV-1) enters cells following sequential activation of the high-potential-energy viral envelope glycoprotein trimer by target cell CD4 and coreceptor. HIV-1 variants differ in their requirements for CD4; viruses that can infect coreceptor-expressing cells that lack CD4 have been generated in the laboratory. These CD4-independent HIV-1 variants are sensitive to neutralization by multiple antibodies that recognize different envelope glycoprotein epitopes. The mechanisms underlying CD4 independence, global sensitivity to neutralization and the association between them are still unclear. By studying HIV-1 variants that differ in requirements for CD4, we investigated the contribution of CD4 binding to virus entry. CD4 engagement exposes the coreceptor-binding site and increases the “intrinsic reactivity” of the envelope glycoproteins; intrinsic reactivity describes the propensity of the envelope glycoproteins to negotiate transitions to lower-energy states upon stimulation. Coreceptor-binding site exposure and increased intrinsic reactivity promote formation/exposure of the HR1 coiled coil on the gp41 transmembrane glycoprotein and allow virus entry upon coreceptor binding. Intrinsic reactivity also dictates the global sensitivity of HIV-1 to perturbations such as exposure to cold and the binding of antibodies and small molecules. Accordingly, CD4 independence of HIV-1 was accompanied by increased susceptibility to inactivation by these factors. We investigated the role of intrinsic reactivity in determining the sensitivity of primary HIV-1 isolates to inhibition. Relative to the more common neutralization-resistant (“Tier 2-like”) viruses, globally sensitive (“Tier 1”) viruses exhibited increased intrinsic reactivity, i.e., were inactivated more efficiently by cold exposure or by a given level of antibody binding to the envelope glycoprotein trimer. Virus sensitivity to neutralization was dictated both by the efficiency of inhibitor/antibody binding to the envelope glycoprotein trimer and by envelope glycoprotein reactivity to the inhibitor/antibody binding event. Quantitative differences in intrinsic reactivity contribute to HIV-1 strain variability in global susceptibility to neutralization and explain the long-observed relationship between increased inhibitor sensitivity and decreased entry requirements for target cell CD4
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