265 research outputs found
Chirality manipulation of ultrafast phase switchings in a correlated CDW-Weyl semimetal
A recently emerging concept for quantum phase discovery is the controlled
gapping of linear band crossings in topological semimetals. For example,
achieving topological superconducting and charge-density-wave (CDW) gapping
could introduce Majorana zero modes and axion electrodynamics, respectively.
Light engineering of correlation gaps in topological materials provides a new
avenue of achieving exotic topological phases inaccessible by conventional
tuning methods such as doping and straining. Here we demonstrate a light
control of correlation gaps and ultrafast phase switchings in a model CDW and
polaron insulator (TaSe)I recently predicted to be an axion insulator.
Our ultrafast terahertz photocurrent spectroscopy reveals a two-step,
non-thermal melting of polarons and electronic CDW gap via studying the fluence
dependence of a {\em longitudinal} circular photogalvanic current. The
helicity-dependent photocurrent observed along the propagation of light reveals
continuous ultrafast switchings from the polaronic state, to the CDW (axion)
phase, and finally to a hidden Weyl phase as the pump fluence increases. Other
distinguishing features corroborating with the light-induced switchings
include: mode-selective coupling of coherent phonons to polaron and CDW
modulation, and the emergence of a {\em non-thermal} chiral photocurrent above
pump threshold of CDW-related phonons. The ultrafast chirality control of
correlated topological states revealed here is important to realize axion
electrodynamics and quantum computing.Comment: 9 pages, 4 figure
Fe-assisted epitaxial growth of 4-inch single-crystal transition-metal dichalcogenides on c-plane sapphire without miscut angle
Epitaxial growth and controllable doping of wafer-scale single-crystal
transition-metal dichalcogenides (TMDCs) are two central tasks for extending
Moore's law beyond silicon. However, despite considerable efforts, addressing
such crucial issues simultaneously under two-dimensional (2D) confinement is
yet to be realized. Here we design an ingenious epitaxial strategy to
synthesize record-breaking 4-inch single-crystal Fe-doped TMDCs monolayers on
industry-compatible c-plane sapphire without miscut angle. In-depth
characterizations and theoretical calculations reveal that the introduction of
Fe significantly decreases the formation energy of parallel steps on sapphire
surfaces and contributes to the edge-nucleation of unidirectional TMDCs domains
(>99%). The ultrahigh electron mobility (~86 cm2 V -1 s-1) and remarkable
on/off current ratio (~108) are discovered on 4-inch single-crystal Fe-MoS2
monolayers due to the ultralow contact resistance and perfect Ohmic contact
with metal electrodes. This work represents a substantial leap in terms of
bridging the synthesis and doping of wafer-scale single-crystal 2D
semiconductors without the need for substrate miscut, which should promote the
further device downscaling and extension of Moore's law.Comment: 17 pages, 5 figure
Synthesis and anti-HIV activity of 2′-deoxy-2′-fluoro-4′-C-ethynyl nucleoside analogs
Based on the favorable antiviral profiles of 4′-substituted nucleosides, novel 1-(2′-deoxy-2′-fluoro-4′-C-ethynyl-β-D-arabinofuranosyl)-uracil (1a), -thymine (1b), and – cytosine (2) analogues were synthesized. Compounds 1b and 2 exhibited potent anti-HIV-1 activity with IC50 values of 86 and 1.34 nM, respectively, without significant cytotoxicity. Compound 2 was 35-fold more potent than AZT against wild-type virus, and also retained nanomolar antiviral activity against resistant strains, NL4-3(K101E) and RTMDR. Thus, 2 merits further development as a novel NRTI drug
Epidemic clones, oceanic gene pools and eco-LD in the free living marine pathogen Vibrio parahaemolyticus
We investigated global patterns of variation in 157 whole genome sequences of
Vibrio parahaemolyticus, a free-living and seafood associated marine bacterium.
Pandemic clones, responsible for recent outbreaks of gastroenteritis in humans
have spread globally. However, there are oceanic gene pools, one located in the
oceans surrounding Asia and another in the Mexican Gulf. Frequent recombination
means that most isolates have acquired the genetic profile of their current
location. We investigated the genetic structure in the Asian gene pool by
calculating the effective population size in two different ways. Under standard
neutral models, the two estimates should give similar answers but we found a
thirty fold difference. We propose that this discrepancy is caused by the
subdivision of the species into a hundred or more ecotypes which are maintained
stably in the population. To investigate the genetic factors involved, we used
51 unrelated isolates to conduct a genome-wide scan for epistatically
interacting loci. We found a single example of strong epistasis between distant
genome regions. A majority of strains had a type VI secretion system associated
with bacterial killing. The remaining strains had genes associated with biofilm
formation and regulated by c-di-GMP signaling. All strains had one or other of
the two systems and none of isolate had complete complements of both systems,
although several strains had remnants. Further top-down analysis of patterns of
linkage disequilibrium within frequently recombining species will allow a
detailed understanding of how selection acts to structure the pattern of
variation within natural bacterial populations
Isochorismatase domain-containing protein 1 (ISOC1) participates in DNA damage repair and inflammation-related pathways to promote lung cancer development
Background: The advent of novel molecular targets has dramatically changed the treatment landscape of lung cancer in recent years. Isochorismatase domain-containing protein 1 (ISOC1) has been reported as a potential biomarker in gastrointestinal cancer, while its function in lung cancer has not been determined.Methods: The expression levels and prognostic significance of ISOC1 were assessed using bioinformatic analysis. Overexpression of ISOC1 and miR-4633, and knockdown of ISOC1 in non-small cell lung cancer (NSCLC) cell lines were generated by lentiviral infection with overexpressed or shRNA plasmids. CRISPR/Cas9 system was applied to knockout ISOC1 in A549 cells. The functions of ISOC1 and miR-4633 in lung cancer development were investigated using cell proliferation, migration, and invasion assays. Xenograft tumor growth assays in nude mice were further assessed the effect of ISOC1 in the tumorigenesis of NSCLC in vivo. Cell cycle distribution analysis was performed to uncover the underlying mechanism of ISOC1 and miR-4633 in promoting NSCLC cell proliferation. Co-immunoprecipitation combined with mass spectrometry and RNA sequencing were performed to uncover the potential mechanism of ISOC1 in lung cancer development.Results: Our results found that ISOC1 expression was upregulated in NSCLC tissues and that increased expression of ISOC1 was significantly associated with worse disease-free survival in NSCLC patients. Overexpression of ISOC1 could increase the proliferation, viability, migration, and invasion of NSCLC cells. Furthermore, miR-4633, located in the first intron of ISOC1, could also promote tumor cell progression and metastasis. Mice xenograft tumor assay showed that knockout of ISOC1 could significantly inhibit tumor growth in vivo. Besides, co-immunoprecipitation combined with mass spectrometry assay revealed that ISOC1 interacted with the proteins of DNA damage repair pathways and that upregulated ISOC1 expression could significantly increase the number of DNA damage lesions. RNA sequencing analysis showed that the downstream signaling pathways mediated by ISOC1 were mainly inflammation-related.Conclusions: We demonstrated that ISOC1 and its intronic miR-4633, both of them could promote NSCLC cell proliferation, migration, invasion, and cell cycle progression. ISOC1 participates in DNA damage repair and inflammation to promote lung cancer development
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