4,942 research outputs found
Development of a Robust PET-RAFT Polymerization Using Graphitic Carbon Nitride (g-C3N4)
The metal-free semiconductor, graphitic carbon nitride (g-C3N4), was introduced into RAFT polymerization for the first time. The production of linear polyacrylate and polyacrylamide has been achieved via PET-RAFT polymerization using g-C3N4 as a photoactive organocatalyst without prior deoxygenation. The resulting polymers display controlled molecular weights, narrow polymer dispersities, and high end-group fidelity as exemplified by 1H NMR analysis, MALDI-TOF-MS measurement, and chain extension experiment. Temporal control is illustrated by intermittent light and dark cycles, with polymer growth arrested in the absence of irradiation. The effects of changing RAFT agents (i.e., trithiocarbonates), solvents, catalyst concentrations, and degrees of polymerization in this system have been investigated. The successful polymerization of nonpurified monomer (i.e., still containing radical inhibitors) demonstrates the robust nature of the presented PET-RAFT system
Singular Effects of Spin-Flip Scattering on Gapped Dirac Fermions
We investigate the effects of spin-flip scattering on the Hall transport and
spectral properties of gapped Dirac fermions. We find that in the weak
scattering regime, the Berry curvature distribution is dramatically compressed
in the electronic energy spectrum, becoming singular at band edges. As a result
the Hall conductivity has a sudden jump (or drop) of when the Fermi
energy sweeps across the band edges, and otherwise is a constant quantized in
units of . In parallel, spectral properties such as the density of
states and spin polarization are also greatly enhanced at band edges. Possible
experimental methods to detect these effects are discussed
Magnetodielectric effect of Bi6Fe2Ti3O18 film under an ultra-low magnetic field
Good quality and fine grain Bi6Fe2Ti3O18 magnetic ferroelectric films with
single-phase layered perovskite structure have been successfully prepared via
metal organic decomposition (MOD) method. Results of low-temperature
magnetocapacitance measurements reveal that an ultra-low magnetic field of 10
Oe can produce a nontrivial magnetodielectric (MD) response in
zero-field-cooling condition, and the relative variation of dielectric
constants in magnetic field is positive, i.e., MD=0.05, when T<55K, but
negative with a maximum of MD=-0.14 when 55K<T<190K. The magnetodielectric
effect appears a sign change at 55K, which is due to transition from
antiferromagnetic to weak ferromagnetic; and vanishes abruptly around 190K,
which is thought to be associated with order-disorder transition of iron ion at
B site of perovskite structures. The ultra-low-field magnetodielectric
behaviour of Bi6Fe2Ti3O18 film has been discussed in the light of
quasi-two-dimension unique nature of local spin order in ferroelectric film.
Our results allow expectation on low-cost applications of detectors and
switches for extremely weak magnetic fields in a wide temperature range
55K-190K.Comment: 10 pages 4 figures, planned to submit to J. Phys.: Condensed Matte
Analysis of Y(4660) and related bound states with QCD sum rules
In this article, we take the vector charmonium-like state Y(4660) as a
bound state (irrespective of the hadro-charmonium and the
molecular state) tentatively, study its mass using the QCD sum rules, the
numerical value is consistent with the experimental
data. Considering the SU(3) symmetry of the light flavor quarks and the heavy
quark symmetry, we also study the bound states ,
and with the QCD sum rules,
and make reasonable predictions for their masses.Comment: 18 pages, 32 figures, revised versio
Spider-silk inspired polymeric networks by harnessing the mechanical potential of β-sheets through network guided assembly.
The high toughness of natural spider-silk is attributed to their unique β-sheet secondary structures. However, the preparation of mechanically strong β-sheet rich materials remains a significant challenge due to challenges involved in processing the polymers/proteins, and managing the assembly of the hydrophobic residues. Inspired by spider-silk, our approach effectively utilizes the superior mechanical toughness and stability afforded by localised β-sheet domains within an amorphous network. Using a grafting-from polymerisation approach within an amorphous hydrophilic network allows for spatially controlled growth of poly(valine) and poly(valine-r-glycine) as β-sheet forming polypeptides via N-carboxyanhydride ring opening polymerisation. The resulting continuous β-sheet nanocrystal network exhibits improved compressive strength and stiffness over the initial network lacking β-sheets of up to 30 MPa (300 times greater than the initial network) and 6 MPa (100 times greater than the initial network) respectively. The network demonstrates improved resistance to strong acid, base and protein denaturants over 28 days
Progress and Perspectives Beyond Traditional RAFT Polymerization.
The development of advanced materials based on well-defined polymeric architectures is proving to be a highly prosperous research direction across both industry and academia. Controlled radical polymerization techniques are receiving unprecedented attention, with reversible-deactivation chain growth procedures now routinely leveraged to prepare exquisitely precise polymer products. Reversible addition-fragmentation chain transfer (RAFT) polymerization is a powerful protocol within this domain, where the unique chemistry of thiocarbonylthio (TCT) compounds can be harnessed to control radical chain growth of vinyl polymers. With the intense recent focus on RAFT, new strategies for initiation and external control have emerged that are paving the way for preparing well-defined polymers for demanding applications. In this work, the cutting-edge innovations in RAFT that are opening up this technique to a broader suite of materials researchers are explored. Emerging strategies for activating TCTs are surveyed, which are providing access into traditionally challenging environments for reversible-deactivation radical polymerization. The latest advances and future perspectives in applying RAFT-derived polymers are also shared, with the goal to convey the rich potential of RAFT for an ever-expanding range of high-performance applications
Consistency of shared reference frames should be reexamined
In a recent Letter [G. Chiribella et al., Phys. Rev. Lett. 98, 120501
(2007)], four protocols were proposed to secretly transmit a reference frame.
Here We point out that in these protocols an eavesdropper can change the
transmitted reference frame without being detected, which means the consistency
of the shared reference frames should be reexamined. The way to check the above
consistency is discussed. It is shown that this problem is quite different from
that in previous protocols of quantum cryptography.Comment: 3 pages, 1 figure, comments are welcom
What Makes Theatrical Performances Successful in China's Tourism Industry?
This study aims to explore the factors affecting the success of a popular tourist product, namely, theatrical performance, within the context of China's tourism industry and develop a model based on previously successful productions. Using qualitative software, 22 Chinese-language articles on theatrical performances are analyzed to generate a list of success factors, classified as internal and external. The internal factors are storyline and performing, market positioning and marketing strategy, investment and financial support, operation and management, performing team, outdoor venue, indoor/outdoor stage supporting facilities, continuous improvement, and production team. The external factors are collaboration between cultural industries and local tourism, government support, privatization, and social and cultural effect. This study also provides suggestions for the future development of theatrical performances in China
Colposcopic accuracy in diagnosing squamous intraepithelial lesions: a systematic review and meta-analysis of the International Federation of Cervical Pathology and Colposcopy 2011 terminology
Background Colposcopy is an important tool in diagnosing cervical cancer, and the International Federation of Cervical Pathology and Colposcopy (IFCPC) issued the latest version of the guidelines in 2011. This study aims to systematically assess the accuracy of colposcopy in predicting low-grade squamous intraepithelial lesions or worse (LSIL+) / high-grade squamous intraepithelial lesions or worse (HSIL+) under the 2011 IFCPC terminology. Methods We performed a systematic review and meta-analysis, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched for studies about the performance of colposcopy in diagnosing cervical intraepithelial neoplasia under the new IFCPC colposcopy terminology from PubMed, Embase, Web of Science and the Cochrane database. Data were independently extracted by two authors and an overall diagnostic performance index was calculated under two colposcopic thresholds. Results In total, fifteen articles with 22,764 participants in compliance with the criteria were included in meta-analysis. When colposcopy was used to detect LSIL+, the combined sensitivity and specifcity were 0.92 (95% CI 0.88–0.95) and 0.51 (0.43–0.59), respectively. When colposcopy was used to detect HSIL+, the combined sensitivity and specifcity were 0.68 (0.58–0.76) and 0.93 (0.88–0.96), respectively. Conclusion In accordance with the 2011 IFCPC terminology, the accuracy of colposcopy has improved in terms of both sensitivity and specifcity. Colposcopy is now more sensitive with LSIL+ taken as the cut-of value and is more specifc to HSIL+. These fndings suggest we are avoiding under- or overdiagnosis both of which impact on patients’ well-being
Gluon fragmentation to ^3D_J quarkonia
We present a calculation of the leading order QCD fragmentation functions for
gluons to split into spin-triplet D-wave quarkonia. We apply them to evaluate
the gluon fragmentation contributions to inclusive ^3D_J quarkonium production
at large transverse momentum processes like the Tevatron and find that the
D-wave quarkonia, especially the charmonium 2^{--} state, could be observed
through color-octet mechanism with present luminosity. Since there are
distinctively large gaps between the contributions of two different (i.e,
color-singlet and color-octet) quarkonium production mechanisms, our results
may stand as a unique test to NRQCD color-octet quarkonium production
mechanism.Comment: 15 pages in LaTex (2 figures in PS-file
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