233 research outputs found
(E)-3-[4-(Diphenylamino)phenyl]-1-(pyridin-2-yl)prop-2-en-1-one
The title compound, C26H20N2O, belongs to a new family of organic two-photon absorption materials with triphenylamine and pyridine units. In the molecule, the three benzene rings are arranged in a propeller-like fashion; the dihedral angles between the rings are 80.01 (14), 75.68 (13) and 56.93 (14)°. The pyridine ring is oriented at dihedral angles of 56.24 (14), 48.92 (15) and 22.02 (13)° with respect to the three benzene rings. Weak intermolecular C—H⋯O hydrogen bonding is present in the crystal structure
4-{2-[5-(3,5-Difluorophenyl)-2-methylthiophen-3-yl]-3,3,4,4,5,5-hexafluorocyclopent-1-en-1-yl}-1,5-dimethylpyrrole-2-carbonitrile
In the title compound, C23H14F8N2S, the dihedral angles between the pyrrole and thiophene groups and the almost planar C—C=C—C unit of the cyclopentene ring (r.m.s. deviation = 0.4193 Å) are 43.6 (5) and 50.1 (2)°, respectively. The distance of 3.612 (3) Å between the potentially reactive C atoms of the two heteroaryl substituents is short enough to enable a photocyclization reaction
1,2-Bis[5-(2,2′-dicyanovinyl)-2-n-pentyl-3-thienyl]-3,3,4,4,5,5-hexafluorocyclopent-1-ene: a new photochromic diarylethene compound
The title compound, C31H26F6N4S2, is a new photochromic dithienylethene with dicyanovinyl subsitituents. In the crystal structure, the molecule adopts a photoactive antiparallel conformation, with two n-pentyl groups located on opposite sides of the cyclopentene ring. The cyclopentene ring assumes an envelope conformation. The distance between the two reactive C atoms on the thiophene rings is 3.834 (7) Å. One of the n-pentyl groups is disordered over two positions; the site occupancy factors are ca 0.7 and 0.3
3-(4-{3,3,4,4,5,5-Hexafluoro-2-[5-(3-methoxyphenyl)-2-methyl-3-thienyl]cyclopent-1-enyl}-5-methyl-2-thienyl)benzonitrile
The title compound, C29H19F6NOS2, is a new unsymmetrical photochromic diarylethene derivative with different meta-phenyl substituents. The distance between the two reactive (i.e. can be irradiated to form a new chemical bond) C atoms is 3.501 (4) Å; the dihedral angles between the mean plane of the main central cyclopentene ring and the thiophene rings are 47.7 (5) and 45.1 (2)°, and those between the thiophene rings and the adjacent benzene rings are 29.4 (2) and 28.4 (3)°. The three C atoms and the F atoms of hexafuorocyclopentene ring are disordered over two positions, with site-occupancy factors of 0.751 (4) and 0.249 (4)
And\^o dilations for a pair of commuting contractions: two explicit constructions and functional models
One of the most important results in operator theory is And\^o's \cite{ando}
generalization of dilation theory for a single contraction to a pair of
commuting contractions acting on a Hilbert space. While there are two explicit
constructions (Sch\"affer \cite{sfr} and Douglas \cite{Doug-Dilation}) of the
minimal isometric dilation of a single contraction, there was no such explicit
construction of an And\^o dilation for a commuting pair of
contractions, except in some special cases \cite{A-M-Dist-Var, D-S, D-S-S}. In
this paper, we give two new proofs of And\^o's dilation theorem by giving both
Sch\"affer-type and Douglas-type explicit constructions of an And\^o dilation
with function-theoretic interpretation, for the general case. The results, in
particular, give a complete description of all possible factorizations of a
given contraction into the product of two commuting contractions. Unlike
the one-variable case, two minimal And\^o dilations need not be unitarily
equivalent. However, we show that the compressions of the two And\^o dilations
constructed in this paper to the minimal dilation spaces of the contraction
, are unitarily equivalent.
In the special case when the product is pure, i.e., if strongly, an And\^o dilation was constructed recently in \cite{D-S-S},
which, as this paper will show, is a corollary to the Douglas-type
construction.
We define a notion of characteristic triple for a pair of commuting
contractions and a notion of coincidence for such triples. We prove that two
pairs of commuting contractions with their products being pure contractions are
unitarily equivalent if and only if their characteristic triples coincide. We
also characterize triples which qualify as the characteristic triple for some
pair of commuting contractions such that is a pure
contraction.Comment: 24 page
(R)-N-{2-tert-Butyl-2-[(R)-tert-butylsulfonamido]ethylidene}-tert-butanesulfonamide
The title compound, C14H30N2O2S2, is the product of the monoaddition reaction of tert-butyl magnesium chloride with bis-[(R)-N-tert-butanesulfinyl]ethanediimine. There are two almost identical molecules in the asymmetric unit, the molecular conformation of which is stabilized by an intramolecular N—H⋯N hydrogen bond
Electron Fluxes in Biocathode Bioelectrochemical Systems Performing Dechlorination of Chlorinated Aliphatic Hydrocarbons
Bioelectrochemical systems (BESs) are regarded as a promising approach for the enhanced dechlorination of chlorinated aliphatic hydrocarbons (CAHs). However, the electron distribution and transfer considering dechlorination, methanogenesis, and other bioprocesses in these systems are little understood. This study investigated the electron fluxes in biocathode BES performing dechlorination of three typical CAHs, 1,1,2,2-tetrachloroethene (PCE), 1,1,2-trichloroethene (TCE) and 1,2-dichloroethane (1,2-DCA). Anaerobic sludge was inoculated to cathode and biocathode was acclimated by the direct acclimation and selection. The constructed biocathode at −0.26 V had significantly higher dechlorination efficiency (E24h > 99.0%) than the opened circuit (E24h of 17.2–27.5%) and abiotic cathode (E24h of 5.5–10.8%), respectively. Cyclic voltammetry analysis demonstrated the enhanced cathodic current and the positive shift of onset potential in the cathodic biofilm. Under autotrophic conditions with electrons from the cathode as sole energy source (columbic efficiencies of 80.4–90.0%) and bicarbonate as sole carbon source, CAHs dechlorination efficiencies were still maintained at 85.0 ± 2.0%, 91.4 ± 1.8%, and 84.9 ± 3.1% for PCE, TCE, and 1,2-DCA, respectively. Cis-1,2-dichloroethene was the final product for PCE and TCE, while 1,2-DCA went through a different dechlorination pathway with the non-toxic ethene as the final metabolite. Methane was the main by-product of the heterotrophic biocathode, and methane production could be enhanced to some extent by electrochemical stimulation. The various electron fluxes originating from the cathode and oxidation of organic substrates might be responsible for the enhanced CAHs dechlorination, while methane generation and bacterial growth would probably reduce the fraction of electrons provided for CAH dechlorination. The study deals with the dechlorination and competitive bioprocesses in CAH-dechlorinating biocathodes with a focus on electron fluxes
Probing the edge-related properties of atomically thin MoS2 at nanoscale
层状二维材料具有独特的物理化学性质,使其在光电器件、传感、能源和催化等领域得到了高度关注和广泛应用。二维材料在制备过程中不可避免引入结构缺陷,虽然这些缺陷尺度仅为数纳米甚至单原子,但是会极大地改变材料的结构和电子性质,从而影响其应用。化学化工学院任斌教授课题组在层状二维材料缺陷表征方面取得进展。该工作表明了TERS在原位、高空间分辨表征缺陷位的结构和电子性质方面具有独特的优势,可以进一步推广到其他二维材料,从而有效地指导缺陷设计和材料应用。
该工作通过校内外课题组紧密合作,在任斌教授、谭平恒研究员(中科院半导体研究所)和王翔博士共同指导下完成。实验部分主要由黄腾翔博士(第一作者,已毕业化学系博士生)完成,电子能带结构与光谱理论计算由谭平恒研究员课题组从鑫博士生(共同第一作者)完成,吴思思、林楷强、姚旭、何玉韩、吴江滨、包一凡、黄声超等参与了实验与讨论。【Abstract】Defects can induce drastic changes of the electronic properties of two-dimensional transition metal dichalcogenides and influence their applications. It is still a great challenge to characterize small defects and correlate their structures with properties. Here, we show that tipenhanced Raman spectroscopy (TERS) can obtain distinctly different Raman features of edge defects in atomically thin MoS2, which allows us to probe their unique electronic properties and identify defect types (e.g., armchair and zigzag edges) in ambient. We observed an edgeinduced Raman peak (396 cm−1) activated by the double resonance Raman scattering (DRRS) process and revealed electron–phonon interaction in edges. We further visualize the edge-induced band bending region by using this DRRS peak and electronic transition region using the electron density-sensitive Raman peak at 406 cm−1. The power of TERS demonstrated in MoS2 can also be extended to other 2D materials, which may guide the defect engineering for desired properties.The authors acknowledge the final supports from MOST of China (2016YFA0200601 and 2016YFA0301204), NSFC (21633005, 21790354, 21503181, 21711530704, 21621091, 11874350, 11474277, and 11434010), Natural Science Foundation of Fujian Province (2016J05046), and China Postdoctoral Science Foundation (2017M622062).
研究工作得到科技部、国家自然科学基金委员会、福建省自然科学基金和中国博士后基金资助
Synchrotron Radiation Dominates the Extremely Bright GRB 221009A
The brightest Gamma-ray burst, GRB 221009A, has spurred numerous theoretical
investigations, with particular attention paid to the origins of ultra-high
energy TeV photons during the prompt phase. However, analyzing the mechanism of
radiation of photons in the MeV range has been difficult because the high
flux causes pile-up and saturation effects in most GRB detectors. In this
letter, we present systematic modeling of the time-resolved spectra of the GRB
using unsaturated data obtained from Fermi/GBM (precursor) and
SATech-01/GECAM-C (main emission and flare). Our approach incorporates the
synchrotron radiation model, which assumes an expanding emission region with
relativistic speed and a global magnetic field that decays with radius, and
successfully fits such a model to the observational data. Our results indicate
that the spectra of the burst are fully in accordance with a synchrotron origin
from relativistic electrons accelerated at a large emission radius. The lack of
thermal emission in the prompt emission spectra supports a
Poynting-flux-dominated jet composition.Comment: 12 pages, 6 figures, 2 tables. Accepted for publication in ApJ
Calibration of the Timing Performance of GECAM-C
As a new member of the Gravitational wave high-energy Electromagnetic
Counterpart All-sky Monitor (GECAM) after GECAM-A and GECAM-B, GECAM-C
(originally called HEBS), which was launched on board the SATech-01 satellite
on July 27, 2022, aims to monitor and localize X-ray and gamma-ray transients
from 6 keV to 6 MeV. GECAM-C utilizes a similar design to GECAM but
operates in a more complex orbital environment. In this work, we utilize the
secondary particles simultaneously produced by the cosmic-ray events on orbit
and recorded by multiple detectors, to calibrate the relative timing accuracy
between all detectors of GECAM-C. We find the result is 0.1 , which
is the highest time resolution among all GRB detectors ever flown and very
helpful in timing analyses such as minimum variable timescale and spectral
lags, as well as in time delay localization. Besides, we calibrate the absolute
time accuracy using the one-year Crab pulsar data observed by GECAM-C and
Fermi/GBM, as well as GECAM-C and GECAM-B. The results are and , respectively. Finally, we investigate the
spectral lag between the different energy bands of Crab pulsar observed by
GECAM and GBM, which is .Comment: submitte
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