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Bilayer graphene with an AB-stacking sequence has emerged as one of the promising materials owing to its unique band-gap structure and the fascinating potential in electronic and photonic applications. However, the chemical vapor deposition growth of bilayer graphene on Cu substrates still suffers from limited bilayer coverage, poor uniformity, and random distribution of the stacking order. Herein, we demonstrated an efficient method to synthesize centimeter-sized graphene films with a bilayer ratio of over 80% on space-confined Cu substrates. Moreover, the stacking order of the as-obtained bilayer graphene films was proven to be 100% AB-stacking structure by transmission electron microscopy and Raman characterization. Band-gap tunability and uniform optical transmittance also confirmed the high quality of as-obtained bilayer graphene. This work provides a new insight into the growth of graphene with controlled layer thickness and a new choice for the production of AB-stacked bilayer graphene films.

Cellulose nanocrystals (CNC) possess a large aspect ratio, high crystallinity, good mechanical performance, and environmental friendliness. It can be used as a frame and spacer of two-dimensional conductive materials, which reduces the stacking effect and is conducive to enhancing the mechanical and electrochemical properties of two-dimensional materials. In this study, CNC-regulated MXene fibers with high electrical conductivity (344.67 S cm−1) were prepared by wet spinning. There is a strong bridging effect between CNC molecules rich in -OH and MXene molecules. This makes them have good compatibility and is good to the preparation of uniform dispersion solution. The prepared hybrid fibers exhibit superior electrochemical performance. In three-electrode system, the volumetric capacitance of the hybrid fibers reaches up to 885.6 F cm−3(0.38 A cm−3). The energy density of symmetric supercapacitors assembled from CNC/MXene hybrid fibers is 11.30 mWh cm−3, and the power density is 11.40 mW cm−3. Furthermore, after 9000 charge-discharge cycles, the capacitance maintains 93% of its initial capacity, demonstrating outstanding cycle stability. It is believed that this study can provide a simple and effective method for the preparation of portable and wearable energy storage devices.

Isolated attosecond pulses are useful to perform pump–probe experiments at a high temporal resolution, and provide a new tool for ultrafast metrology. However, it is still a challenging task to generate such pulses of high intensity, even for a few-cycle laser. Through particle-in-cell simulations, we show that it is possible to directly generate a giant isolated attosecond pulse in the transmission direction from relativistic laser-driven plasmas. Compared to attosecond pulse generation in the reflection direction, no further spectral filtering is needed. The underlying radiation mechanism is coherent synchrotron emission, and the transmitted isolated attosecond pulse can reach relativistic intensity. This provides a promising alternative to generate intense isolated attosecond pulses for ultrafast studies.

Two new cyano-bridged mixed-valence {FeIII2(μ-CN)4FeII2} clusters, {[(Tp)FeIII(CN)3]2[FeII(Py2N2)]2}·(ClO4)2·MeCN·Et2O (1·MeCN·Et2O), its solvent-free form (1), and {[(Tp)FeIII(CN)3]2[FeII(Me2Py2N2)]2}·(ClO4)2·5MeOH (2·5MeOH), were obtained [Tp = hydrotris(pyrazol-1-yl)borate; N,N′-bis(2-pyridylmethyl)-N,N′-bis(4-X-benzyl)-1,2-ethanediamine, Py2N2, X = H; Me2Py2N2, X = Me]. Complexes 1and 2·5MeOH exhibit gradual thermally induced two-step spin-crossover behavior (SCO) at two FeIImetal centers, and the transformation of high-spin (HS) to low-spin (LS) FeIIions with temperature was confirmed by a combination of X-ray crystallography, variable-temperature Fourier transform infrared, variable-temperature magnetic susceptibility, and 57Fe Mössbauer spectroscopy. Moreover, complexes 1·MeCN·Et2O and 1exhibit a reversible single-crystal-to-single-crystal transformation, and complex 1undergoes two-step SCO behavior with T1/2= 178 and 93 K accompanied by symmetry breaking in the structure.

Electron acceleration by the ponderomotive force of a laser pulse with duration less than the plasma wavelength in inhomogeneous underdense plasmas is studied by two-dimensional relativistic parallel particle-in-cell (PIC) code. Particular attention is paid to the mechanism of electron acceleration associated with the increasing group velocity of the laser pulse. In an underdense plasma layer with linearly descending density profile, the accelerated electrons move together with the laser pulse which propagates with increasing group velocity. In an inhomogeneous pre-plasma with linearly ramping density profile, as the incident laser propagates up the density gradient with decreasing group velocity, ponderomotive acceleration is reduced compared with the uniform pre-plasma. As the reflected laser propagates down the density gradient with increasing group velocity, the ponderomotive acceleration by the reflected laser is more effective due to increasing group velocity of the reflected light and the return currents induced by the incident laser light. Relativistic electrons with multi-tens-MeV energies are generated.

The core histone tail domains are “master control switches” that help define the structural and functional characteristics of chromatin at many levels. The tails modulate DNA accessibility within the nucleosome, are essential for stable folding of oligonucleosome arrays into condensed chromatin fibers, and are important for fiber–fiber interactions involved in higher order structures. Many nuclear signaling pathways impinge upon the tail domains, resulting in posttranslational modifications that are likely to alter the charge, structure, and/or interactions of the core histone tails or to serve as targets for the binding of ancillary proteins or other enzymatic functions. However, currently we have only a marginal understanding of the molecular details of core histone tail conformations and contacts. Here we review data related to the structures and interactions of the core histone tail domains and how these domains and posttranslational modifications therein may define the structure and function of chromatin. © 2003 Wiley Periodicals, Inc. Biopolymers 68: 539–546, 2003

ABSTRACTWe utilized a site-specific cross-linking technique to investigate the mechanism of nucleosome remodeling by hSWI/SNF. We found that a single cross-link between H2B and DNA virtually eliminates the accumulation of stably remodeled species as measured by restriction enzyme accessibility assays. However, cross-linking the histone octamer to nucleosomal DNA does not inhibit remodeling as monitored by DNase I digestion assays. Importantly, we found that the restriction enzyme-accessible species can be efficiently cross-linked after remodeling and that the accessible state does not require continued ATP hydrolysis. These results imply that the generation of stable remodeled states requires at least transient disruption of histone-DNA interactions throughout the nucleosome, while hSWI/SNF-catalyzed disruption of just local histone-DNA interactions yields less-stable remodeled states that still display an altered DNase I cleavage pattern. The implications of these results for models of the mechanism of SWI/SNF-catalyzed nucleosome remodeling are discussed.

We utilized a site-specific cross-linking technique to investigate the mechanism of nucleosome remodeling by hSWI/SNF. We found that a single cross-link between H2B and DNA virtually eliminates the accumulation of stably remodeled species as measured by restriction enzyme accessibility assays. However, cross-linking the histone octamer to nucleosomal DNA does not inhibit remodeling as monitored by DNase I digestion assays. Importantly, we found that the restriction enzyme-accessible species can be efficiently cross-linked after remodeling and that the accessible state does not require continued ATP hydrolysis. These results imply that the generation of stable remodeled states requires at least transient disruption of histone-DNA interactions throughout the nucleosome, while hSWI/SNF-catalyzed disruption of just local histone-DNA interactions yields less-stable remodeled states that still display an altered DNase I cleavage pattern. The implications of these results for models of the mechanism of SWI/SNF-catalyzed nucleosome remodeling are discussed.

We utilized a site-specific cross-linking technique to investigate the mechanism of nucleosome remodeling by hSWI/SNF. We found that a single cross-link between H2B and DNA virtually eliminates the accumulation of stably remodeled species as measured by restriction enzyme accessibility assays. However, cross-linking the histone octamer to nucleosomal DNA does not inhibit remodeling as monitored by DNase I digestion assays. Importantly, we found that the restriction enzyme-accessible species can be efficiently cross-linked after remodeling and that the accessible state does not require continued ATP hydrolysis. These results imply that the generation of stable remodeled states requires at least transient disruption of histone-DNA interactions throughout the nucleosome, while hSWI/SNF-catalyzed disruption of just local histone-DNA interactions yields less-stable remodeled states that still display an altered DNase I cleavage pattern. The implications of these results for models of the mechanism of SWI/SNF-catalyzed nucleosome remodeling are discussed.

A novel superplasticizer was synthesized by polycondensation of Alkyl phenol phosphate and toluene diisocyanate grafting with methoxy polyoxyethylene ether (MPEG). The chemical structure and molecular weight of polycondensates molecules were determined by 1H nuclear magnetic resonance (NMR) and gel permeation chromatography respectively. The experimental results indicated that the polycondensates of Alkyl phenol phosphate and toluene diisocyanate grafting with MPEG not only exhibited good water-reducing properties but also demonstrated effective anti-clay abilities alone. Furthermore, the polycondensates showed good fluidity maintaining abilities within 1-3 h and good workability of concrete. The results of T500 Time experiments show that lower plastic viscosity of the polycondensates leads to fresh concrete much "looser" than conventional PCEs in self-compacting concrete.

Macromolecules with pendant chlorine groups on their main chains were synthesized via free-radical copolymerization of 2-hydroxyethyl acrylate(HEA), TPEG and vinylbenzyl chloride(VBC) in the presence of intiator and chain transfer agent according to molecular structure design principle. The subsequent Arbuzov reaction between trimethoxyphosphine(TMP) and chlorine groups of macromolecules(PHVT) gave rise to new type of polycarboxylate superplaticizer with clay-inerting and high slump retention capability. The molecular structure of superplasticizer was determined by Fourier Transform Infrared Spectroscopy (FT-IR) and Gel Permeation Chromatography (GPC), respectively. The adaptability of clays, Zata potential, adsorption behavior and application performance in concrete were measured. The results shows that the polycarboxylate superplaticizer we prepared has good clay compatibility, excellent clay-inerting and high slump retention capability.

Two kinds of slump-retaining polycarboxylate superplasticizer with different molecular structures were synthesized via maleic anhydride(MAH), polyethylene glycol monoallyl ether(APEG) and hydroxyethyl acrylate (HEA)/ethyl acrylate (EA) according to molecular structure design principle. The comprehensive performances of each slump-retaining polycarboxylate superplasticizer were analyzed and compared with that of different molecular structure. The Gel Permeation Chromatography (GPC), surface tension, zeta potential, adsorption behavior, cement paste fluidity and application performance in concrete were measured. And the slump retention mechanism was analyzed. The results show that the polycarboxylate superplaticizer with hydroxyethyl group prepared in this study has good dispersing performance and high slump retention capability for concrete.

A new alkali-free liquid accelerator for shotcrete was prepared through normal temperature drop process by using the nano activated alumina and the modified alcohol amine as the main raw materials. The effect of alkali-free liquid accelerator on the cement setting time and the mechanical properties of mortar, the effect of the penetration strength on the shotcrete rebound were investigated. And the accelerating mechanism of the as-prepared alkali-free liquid accelerator was also analyzed via XRD and SEM characterization methods. The experimental results indicated that the hydration of C3A was accelerated by the polyamine complexation of accelerator, resulting in forming a large number of acicular ettringite and reducing the amount of Ca(OH)2 crystal, which would not affect the later hydration of cement. When the content of alkali-free liquid accelerator was 6%, the initial setting time and final setting time were less than 3min and 8min respectively, and 1d and 28d compressive strength ratios reached 207.6% and 114.2% respectively; beside that, the shotcrete rebound was very low because of the high penetration strength within 30min.

Slow-time-scale magnetic fields in an underdense plasma are investigated by two-dimensional particle simulation. An axis-symmetry slow-time-scale magnetic field is observed around the laser beam. The character of such a field is consistent with our theoretical model.