一类非线性微分方程渐近概周期解的存在性

利用函数的遍历性和耗散型条件,研究一类非线性微分方程渐近概周期解的存在性．在某些特定的条件下,得到了这类方程渐近概周期解存在性和唯一性结论．从而得到的结果在一定程度上推广和改进了相关结果．     

PD3和PD3RE重轨钢的性能、组织等分布形貌及内耗

对PD3和中间包加少量稀土的PD3RE重轨钢的连铸坯和产品轨进行了硬度和组织的Profile观测.发现加稀土减小钢坯硬度分布的波动幅度,有效减消280mm×380 mm连铸坯心部的低性能区(在PD3RE铸坯上甚至未测出低硬度区);在仅含0.016%P的PD3钢坯里观测到Fe-P(C)共晶组织,而加稀土可完全抑制这种组织;还发现,PD3RE钢轨表层区出现很明显的硬化,这种硬化是珠光体细化引起的.测量轨腰样品的内耗表明,加稀土除了减小轨腰的内应力和增加铁素体中的固溶C之外,还增强了钢轨表层的渗氮倾向.     

Measurement of borneol based on infrared spectrometry

The infrared spectrometry contains multiple information of the sample, and it is easy to be applied to online measurement. To Chinese medicine, this technology can improve the standard of quality control and accelerate the modernization course. In this paper, we investigate the spectral characteristics of borneol,an effective ingredient in many Chinese medicines. The following results are achieved. In middle infrared (MIR) region, utilizing the linear relationship between absorption and concentration, the concentration of borneol with relative error within 4.30% in the strongest absorption region (2950-2970 cm-1) is measured;in near infrared (NIR) region, the predicted concentrations of borneol are calculated by using partial least squares (PLS) regression analysis, in which the wavelengths are selected by genetic algorithm (GA) from the absorption bands of borneol in NIR region. The predicted relative error of calibration model is less than 2%. This result shows that PLS regression analysis combining genetic algorithm is a good method to improve prediction and reduce data in NIR region.     

Study on the interactions between anti-tumor metal complexes and mononucleotides using trans-[en_2Os(η~2-H_2)(CF_3SO_3)](CF_3SO_3) as a ~1H NMR probe in a competitive mode

Trans-[en_2Os(η~2-H_2)]2 , the structure of which is shown in Scheme l, as described in an earlier paper[l] shows promise of being a useful and versatile probe for research on biomolecules. It has been shown to bind to a variety of biomolecules such as n…     

Polyethylene-supported poly(methyl methacrylate<Emphasis Type="Italic">-co-</Emphasis>butyl acrylate)-based novel gel polymer electrolyte for lithium ion battery

A new copolymer, poly(methyl methacrylate-co-butyl acrylate) (P(MMA-co-BA)), was synthesized by emulsion polymerization with different mass ratio of methyl methacrylate (MMA) and butyl acrylate (BA). The membranes were prepared by phase inversion and corresponding gel polymer electrolytes (GPEs) were obtained by immersing the membrane into a liquid electrolyte. In this design, the hard monomer MMA provided the copolymer with good electrolyte uptake, while the soft monomer BA provided the GPE with strong adhesion between the anode and cathode of lithium ion battery. The properties of the resulting product were investigated by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectra, scanning electron spectroscopy, linear sweep voltammetry, thermogravimetric analysis, cyclic voltammetry, electrochemical impedance spectroscopy and charge/discharge test. The results show that the obtained GPE based on P(MMA-co-BA) with the mass ratios of MMA and BA = 6:1 exhibits good conductivity (as high as 1.2 × 10^?3 S cm^?1) at room temperature and high electrochemical stability (up to 4.9 V vs. Li/Li⁺). With the application of the polyethylene (PE)-supported GPE in Li/Li(Li_0.13Ni_0.30Mn_0.57)O₂ battery, the battery presents good cyclic stability (maintaining 95.4 % of its initial discharge capacity after 50 cycles) at room temperature.     

Engineering of a monodisperse core-shell magnetic Ti-O-Si oxidation nanocatalyst

There has been limited development in catalyst carriers for magnetic separations where superparamagnetic nanoparticles of a high saturation magnetization with no coercivity are required to isolate expensive catalyst reagent that are subjected to repeated magnetic cycles. By using simple stepwise layer-by-layer nanochemistry techniques, we show that an fcc FePt nanomagnet can be created inside each silica particle with tailored dimensions to great precision. Subsequent engineering of the external surface with Ti-O-Si species in an optimum structure to create a unique interface gives high activity and excellent selectivity of the composite material for the trans-stilbene oxidation to the corresponding epoxide in the presence of tert-butyl hydroperoxide. Thus, a new magnetic separable epoxidation catalyst is described. This work clearly demonstrates the significance of nanoengineering of a single catalyst particle by a bottom-up construction approach in modern catalyst design, which could lead to new catalytic properties.     

Highly Twisted Conformation Thiopyrylium Photosensitizers for In Vivo Near Infrared-II Imaging and Rapid Inactivation of Coronavirus

Despite significant effort, a majority of heavy-atom-free photosensitizers have short excitation wavelengths, thereby hampering their biomedical applications. Here, we present a facile approach for developing efficient near-infrared (NIR) heavy-atom-free photosensitizers. Based on a series of thiopyrylium-based NIR-II (1000–1700 nm) dyads, we found that the star dyad HD with a sterically bulky and electron-rich moiety exhibited configuration torsion and significantly enhanced intersystem crossing (ISC) compared to the parent dyad. The electron excitation characteristics of HD changed from local excitation (LE) to charge transfer (CT)-domain, contributing to a ≈6-fold reduction in energy gap (ΔE_ST), a ≈10-fold accelerated ISC process, and a ≈31.49-fold elevated reactive oxygen species (ROS) quantum yield. The optimized SP@HD-PEG_2K lung-targeting dots enabled real-time NIR-II lung imaging, which precisely guided rapid pulmonary coronavirus inactivation.     

The enhanced catalytic degradation of SiO<Subscript>2</Subscript>/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/C@TiO<Subscript>2</Subscript> photo-Fenton system on p-nitrophenol

Heterogeneous photo-Fenton SiO₂/Fe₃O₄/C@TiO₂ (SFCT) catalyst with a core-multishell structure and a diameter of about 550 nm was successfully prepared and was characterized by scanning electron microscopy (SEM), TEM, XRD, Raman, and Fourier transform infrared (FT-IR). The results illustrated that anatase TiO₂ coexisted with rutile TiO₂, in which the anatase phase was the main crystal phase. In addition, the catalytic activity of SFCT catalyst had been evaluated in the catalytic degradation on p-nitrophenol (PNP). The influence factors on the PNP degradation, including SFCT component ratio (m _SFC/ m _TiO2), H₂O₂ dosage, solution pH, and PNP concentration, had been investigated. And the contrast experiments about the photo-Fenton catalytic mechanism revealed that the SFCT-2 catalyst possessed a superior activity in the neutral environment due to the optimal activity matching between Fe₃O₄ and TiO₂, and it exhibited the stable catalytic performance after five successive recycles. Therefore, the SFCT-2 catalyst had a promising application for the photo-Fenton degradation of organic contaminant.     

Recent advances of adsorbents in solid phase extraction for environmental samples

In recent years, some new and sensitive analytical instruments have been invented or existing instruments have been improved, which have resulted in many advanced achievements. However, sample pre-treatment techniques still play important and irreplaceable roles in the analysis of pollutants. Among the developed sample pre-treatment techniques, solid phase extraction is the most often used method and has been widely applied worldwide. In solid phase extraction, adsorbent is the key part to achieve high sensitivity and enrichment efficiency, which is the hot topic in analytical and environmental fields in recent years. In order to deeply understand the prospect of solid phase extraction, this review summarises the recent advances of adsorbents including ion imprinting materials, magnetic materials, core-shell materials, mesoporous materials, carbon nanotubes, TiO₂ nanotube arrays and some other new materials.