1,334 research outputs found
2-(5-Amino-2H-tetrazol-2-yl)acetic acid
In the title molecule, C3H5N5O2, the tetrazole ring and carboxyl group form a dihedral angle of 82.25 (14)°. In the crystal, adjacent molecules are linked through O—H⋯N, N—H⋯O and N—H⋯N hydrogen bonds into layers parallel to the bc plane
Two-dimensional photonic crystal polarizer
A novel polarizer made from two-dimensional photonic bandgap materials was
demonstrated theoretically. This polarizer is fundamentally different from the
conventinal ones. It can function in a wide frequency range with high
performance and the size can be made very compact, which renders it useful as a
micropolarizer in microoptics.Comment: 8 pages, RevTex, 4 figure
Single ion-qubit exceeding one hour coherence time
Realizing a long coherence time quantum memory is a major challenge of
current quantum technology. Here, we report a single \Yb ion-qubit memory with
over one hour coherence time, an order of improvement compared to the
state-of-the-art record. The long coherence time memory is realized by
addressing various technical challenges such as ambient magnetic-field noise,
phase noise and leakage of the microwave oscillator. Moreover, systematically
study the decoherence process of our quantum memory by quantum process
tomography, which enables to apply the strict criteria of quantum coherence,
relative entropy of coherence. We also benchmark our quantum memory by its
ability in preserving quantum information, i.e., the robustness of quantum
memory, which clearly shows that over 6000 s, our quantum memory preserves
non-classical quantum information. Our results verify the stability of the
quantum memory in hours level and indicate its versatile applicability in
various scenarios.Comment: 7 pages, 7 figure
Generation of bottle beam using low-density channel in air
Cylindrical density depressions generated by femtosecond laser pulses
filamenting in air for different energy depositions is investigated
numerically, by using a set of hydrodynamic equations. The evolution of density
profile is calculated for different temperature elevations, the results
indicate that the gas density hole is getting shallower and wider with the
increasing temperature elevations. A simulation of the propagation inside
low-density channel implies a new way to generate a type of bottle beam.Comment: 4 pages,5 figure
Phylogeography of the Sino-Himalayan Fern Lepisorus clathratus on “The Roof of the World”
The Qinghai-Tibetan Plateau (QTP) and its southern and southeastern mountain ranges, Himalaya-Hengduan Mountains (HHM), are one of the most extensive habitats for alpine plants in the world. How ferns occurring in QTP and HHM changed their distribution ranges in response to Quaternary climatic oscillations remains almost unknown.We employed sequences of two chloroplast DNA regions, rps4-trnS and trnL-trnF, to reconstruct phylogeography of the Sino-Himalayan fern Lepisorus clathratus, occurring mainly in the QTP and HHM. Individuals of this species have either dehiscent or indehiscent sporangia with the latter evolved from the plesiomorphic dehiscent forms. Based on a range-wide sampling, we detected 27 cpDNA haplotypes that were divided into five groups by network analyses. Populations in the Hengduan Mountains possess the highest genetic diversity, while a single haplogroup is detected across the north-central region. A distinct phylogeographical subdivision was detected between the Hengduan Mountains and north-central region by AMOVA analysis. The haplogroup distribution pattern, coalescence and AMOVA analysis suggest that a long term survival area (refugia) of the species was located in the Hengduan Mountains during glaciations, with probable range expansions into north-central regions during interglacial periods. Populations with indehiscent sporangium can carry private haplotypes and are inclined to maintain genetic homogeneity. One group with indehiscent sporangia most likely survived in situ on the QTP during glaciations.This study for the first time sheds light on the response of alpine ferns in the QTP and HHM to the Quaternary climatic oscillations
Comparative transcriptomics analysis reveals difference of key gene expression between banana and plantain in response to cold stress
New Family of Robust 2D Topological Insulators in van der Waals Heterostructures
We predict a new family of robust two-dimensional (2D) topological insulators
in van der Waals heterostructures comprising graphene and chalcogenides BiTeX
(X=Cl, Br and I). The layered structures of both constituent materials produce
a naturally smooth interface that is conducive to proximity induced new
topological states. First principles calculations reveal intrinsic
topologically nontrivial bulk energy gaps as large as 70-80 meV, which can be
further enhanced up to 120 meV by compression. The strong spin-orbit coupling
in BiTeX has a significant influence on the graphene Dirac states, resulting in
the topologically nontrivial band structure, which is confirmed by calculated
nontrivial Z2 index and an explicit demonstration of metallic edge states. Such
heterostructures offer an unique Dirac transport system that combines the 2D
Dirac states from graphene and 1D Dirac edge states from the topological
insulator, and it offers new ideas for innovative device designs
The histone H3K9M mutation synergizes with H3K14 ubiquitylation to selectively sequester histone H3K9 methyltransferase Clr4 at heterochromatin
International audienceOncogenic histone lysine-to-methionine mutations block the methylation of their corresponding lysine residues on wild-type histones. One attractive model is that these mutations sequester histone methyltransferases, but genome-wide studies show that mutant histones and histone methyltransferases often do not colocalize. Using chromatin immunoprecipitation sequencing (ChIP-seq), here, we show that, in fission yeast, even though H3K9M-containing nucleosomes are broadly distributed across the genome, the histone H3K9 methyltransferase Clr4 is mainly sequestered at pericentric repeats. This selective sequestration of Clr4 depends not only on H3K9M but also on H3K14 ubiquitylation (H3K14ub), a modification deposited by a Clr4-associated E3 ubiquitin ligase complex. In vitro, H3K14ub synergizes with H3K9M to interact with Clr4 and potentiates the inhibitory effects of H3K9M on Clr4 enzymatic activity. Moreover, binding kinetics show that H3K14ub overcomes the Clr4 aversion to H3K9M and reduces its dissociation. The selective sequestration model reconciles previous discrepancies and demonstrates the importance of protein-interaction kinetics in regulating biological processes
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