Directed Self-assembly of Vertical PS-b-PMMA Nanodomains Grown on Multilayered Polyelectrolyte Films

Layer-by-layer polyelectrolyte self-assembly, a common method for preparing high-quality ultra-thin films, was employed to direct the self-assembly behavior of polystyrene-block-poly(methyl methacrylate)(PS-b-PMMA) block copolymer for the first time. Differing from the previous neutral polymer brushes anchored to silicon substrates via chemical modification, polyelectrolyte multilayers(PEMs) were anchored by electrostatic interaction and provided a stable, smooth, and neutral interface. In the present study, PS-b-PMMA was deposited on poly(acrylamide hydrochloride)/poly(acrylic acid)(PAH/PAA) PEMs prepared by layer-by-layer self-assembly to successfully yield vertical nanodomains after thermal annealing. Seven layered PEMs revealed an excellent, smooth surface, with a low roughness of 0.6 nm. The periodic structure with interlamellar spacing of 47 nm was determined by grazing-incidence small-angle X-ray scattering(GISAXS). The morphology of the PS-b-PMMA nanodomains depended on the polyanion-to-polycation concentration ratio, which is related to the interaction between the block copolymer and the substrate. Our results demonstrate that layer-by-layer self-assembly is a helpful method for the phase separation of block polymers and the fabrication of vertical, ordered nanodomains.     

A density functional theory study on the atmospheric reaction of CH3O2 with HS: Mechanism and kinetics

The reaction mechanism of CH₃O₂ and HS was systematically investigated by density functional theory (DFT). Six singlet pathways and seven triplet ones are located on the potential surface (PES). The result indicates that the main products are CH₃O and HSO both on the singlet and triplet PES, different from the CH₃O₂ + OH reaction. Moreover, deformation density (ρ_def) and atoms in molecules (AIM) analyses were carried out to further uncover the nature of chemical bonding evolution in the primary pathways. Furthermore, reaction rate constants were calculated in the temperature range from 200 to 1000 K using the transition state theory with the Wigner and Eckart tunneling corrections. Our results can shed light on the title reaction and offer instructions for analogous atmospheric reactions, as well as experimental research in the future.     

Synthesis of a new ratiometric emission Ca2+ indicator for in vivo bioimaging

A novel fluorescent calcium indicator with a 490/582 nm ratiometric emission has been designed and synthesized.The indicator exhibits a highly selective ratiometric emission response to Ca²⁺ over other metal cations and a large Stokes shift of 202 nm.Moreover,its practical cell imaging capability for intracellular Ca²⁺ in the resting- and dynamic-state has been demonstrated in human umbilical vein endothelial cells using a confocal laser scanning microscope.     

3D Dendritic Nanostructure of Silver‐Array: Preparation,Growth Mechanism and Application in Nitrate Sensor

A 3D dendritic nanostructure of silver‐array (DSA) was prepared via electrodeposition on an interdigitated array (IDA) microelectrode. For preparation of this nanostructure, the optimal parameters such as deposition potential, deposition time, the electrode bandwidth and gap size were systematically investigated. It was found that the edge effect of the IDA microelectrode is a key factor for controlling the 3D dendritic growth of silver. Furthermore, the formation of the 3D dendritic morphology was discussed from the aspect of electrochemical nucleation theory and nonequilibrium growth dynamics to give a deep understanding of its growth mechanism. For its potential practical application, we showed that the as‐prepared 3D DSA nanomaterial exhibited high electrocatalytic reduction ability to nitrate in neutral solution and excellent performance for nitrate determination. An amperometric nitrate microsensor based on the 3D DSA was obtained.     

Development and application of a LC–MS/MS assay for the simultaneous quantification of edaravone and taurine in beagle plasma

An LC–MS/MS method was developed and validated for the simultaneous quantification of edaravone and taurine in beagle plasma. The plasma sample was deproteinized using acetonitrile containing formic acid. Chromatographic separations were achieved on an Agilent Zorbax SB‐Aq (100 × 2.1 mm, 3.5 μm) column, with a gradient of water (containing 0.03% formic acid) and methanol as the mobile phase at a flow rate of 0.3 mL/min. The analyte detection was carried out in multiple reaction monitoring mode and the optimized precursor‐to‐product transitions of m/z [M+H]⁺ 175.1 → 133.0 (edaravone), m/z [M+H]⁺ 189.1 → 147.0 (3‐methyl‐1‐p‐tolyl‐5‐pyrazolone, internal standard, IS), m/z [M–H]^? 124.1→80.0 (taurine), and m/z [M–H]^? 172.0 → 80.0 (sulfanilic acid, IS) were employed to quantify edaravone, taurine, and their corresponding ISs, respectively. The LOD and the lower LOQ were 0.01 and 0.05 μg/mL for edaravone and 0.66 and 2 μg/mL for taurine, respectively. The calibration curves of these two analytes demonstrated good linearity (r ＞ 0.99). All the validation data including the specificity, precision, recovery, and stability conformed to the acceptable requirements. This validated method has successfully been applied in the pharmacokinetic study of edaravone and taurine mixture in beagle dogs.     

Spectroscopic and voltammetric characterizations of the interaction of two local anesthetics with bovine serum albumin

The interactions of bovine serum albumin (BSA) with two local anesthetics, procaine hydrochloride (PCH) and tetracaine hydrochloride (TCH) were studied using spectroscopic methods such as fluorescence and ultraviolet visible (UV-vis), and electrochemical techniques including cyclic voltammetry (CV) and differential pulsed stripping voltammetry (DPSV). The results obtained from these techniques turned out that both PCH and TCH could bind to BSA. The binding constants (K_A) and the number of binding sites (n) of the two drugs with BSA at different temperatures were determined, respectively. At 291 K, K_A was found as 2.40×10⁴ and 1.42×10⁴ L mol⁻¹ and n was 1.03 and 0.99 for PCH-BSA and TCH-BSA, respectively. According to van’t Hoff equation, the thermodynamic parameters, ΔG, ΔH and ΔS, were obtained, showing the involvement of hydrophobic and electrostatic force in these interactions. Based on the theory of the Förster energy transference, the distance between the acceptor (PCH or TCH) and the donor (BSA) were determined as 2.32 and 3.62 nm for PCH and TCH, respectively. The effects of Fe³⁺, Cu²⁺, Mg²⁺, Mn²⁺, Zn²⁺ and Ca²⁺ on the binding of PCH or TCH to BSA were also evaluated.     

ηπ+ π- resonant structure around 1.8 GeV/c(2) and η(1405) in J/ψ → ωηπ+ π-

We present results of a study of the decay J/ψ → ωηπ+ π- using a sample of (225.2 ± 2.8) × 10(6) J/ψ events collected by the BESIII detector, and report the observation of a new process J/ψ → ωX(1870) with a statistical significance of 7.2σ, in which X(1870) decays to a(0)(±)(980)π±. Fitting to ηπ+ π- mass spectrum yields a mass M = 1877.3 ± 6.3(stat)(-7.4)(+3.4)(syst) MeV/c(2), a width Γ = 57 ± 12(stat)(-4)(+19)(syst) MeV/c(2), and a product branching fraction B(J/ψ → ωX) × B(X→a(0)(±)(980)π±) × B(a(0) (±)(980) → ηπ±) = [1.50 ± 0.26(stat)(-0.36)(+0.72) (syst)] × 10(-4). Signals for J/ψ → ωf(1)(1285) and J/ψ → ω η(1405) are also clearly observed and measured.     

Behaviors of cubic distortion product otoacoustic emissions evoked by amplitude modulated tones

Distortion product otoacoustic emissions (DPOAEs) were measured using sinusoidal amplitude modulation (AM) tones. When one of the primary stimuli (f(1) or f(2), f(1)?< f(2)) was amplitude modulated, a series of changes in the cubic difference tone (CDT) were observed. In the frequency domain, multiple sidebands were present around the CDT and their sizes grew with the modulation depth of the AM stimulus. In the time domain, the CDT showed different modulation patterns between two major signal conditions: the AM tone was used as the f(1) or the f(2). The CDT amplitude followed the AM tone when the f(1) was amplitude modulated. However, when the AM tone acted as the f(2), the CDT showed a more complex modulation pattern with a notch present at the AM tone peak. The relatively linear dependence of CDT on f(1) and the nonlinear relation with f(2) can be explained with a variable gain-control model representing hair cell functions at the DPOAE generation site. It is likely that processing of AM signals at a particular cochlear location depends on whether the hair cells are tuned to the frequency of the carrier. Nonlinear modulation is related to on-frequency carriers and off-frequency carriers are processed relatively linearly.     

Efficient homocoupling reactions of halide compounds catalyzed by manganese (II) chloride

A new efficient homocoupling reaction was reported in one pot by a combination of metallic magnesium and a catalytic amount of manganese (II) chloride. Various aromatic and alkyl halides underwent homocoupling smoothly, affording the corresponding symmetrical homocoupling compounds in moderate to good yields. The readily available MnCl₂, the mild reaction conditions and the operational simplicity and practicability allow for an easy and practical procedure for the purpose of carbon carbon bond formation. Copyright © 2007 John Wiley & Sons, Ltd.     

激光等离子体的声学诊断研究

提出了利用激光等离子体声波对高功率激光与材料相互作用过程进行了诊断的方法。实际测量了波长０．５３μｍ激光与几种金属材料相互作用的过程，其结果与采用春它方法得到的结果基本吻合。