Synthesis of 2-(p-Aminophenyl)oxazoline and Its Cationic Polymerization Studies by Differential Scanning Calorimetry

Abstract

The monomer 2-(4-aminophenyl)oxazoline has been prepared in good yield and briefly investigated for cationic, homopolymerization and copolymerization characteristics, using 2-ethyloxazoline as a comonomer. Cationic polymerizations can be conducted to producesoluble poly[2-(4-aminophenyl)oxazoline] and poly[2-(4-aminophenyl)-oxazoline-co-2-ethyloxazoline].     

高效液相色谱法定量分析奥曲肽

建立奥曲肽的高效液相色谱定量分析方法。色谱柱为Eclipse plus C18柱(4.6 mm×250 mm,5 μm),流动相为乙腈-0.25%高氯酸水溶液(体积比为30∶70),流量为1.0 mL/min,检测波长为210 nm,柱温为25℃。奥曲肽的质量浓度在4.38~219 μg/mL范围内与色谱峰面积成良好的线性关系,相关系数为0.9999,检出限为1.1 ng,定量限为2.19 ng。测定结果的相对标准偏差为0.26%~0.46% (n=5),加标回收率为97.41%~100.26%。该方法简便、快速、准确,适用于奥曲肽原料药与制剂的定量分析。     

硬币为什么会漂浮在水面上

1问题的提出你注意过这种现象吗?将一枚硬币轻轻平 放于一杯清水中虽然硬币将液面压的明显凹陷,但它们却能漂浮在水面上.我们知道,金属的密度比水大,为什么硬币会浮在水面上?     

The Spectrum of Ne-Like Ar and the 4d-4p Transition of Kr7+ at 45 nm in Capillary Discharge Experiment

Capillary discharge soft X-ray laser, which is always called “table-top soft X-ray laser,” is one of the effective methods for miniaturization. The method is deemed to have experimental facility with practicable value. With capillary discharge mechanism, Ne-like Ar at 46.9 nm soft X-ray laser has been obtained, and the experimental results and the analyses are reported in this paper. Experimentally, a current pulse with the amplitude of 20 kA was used to excite three different gases: Ar, Kr, and N₂. The signals were detected by an X-ray diode (XRD), and the emission spectra were monitored with a Rowland spectrograph. The J = 0–1 line and one 3d-3p transition of Ne-like Ar were detected, with wavelengths of 46.9 nm and 48.5 nm, respectively. Adjusting the pure Ar to the appropriate pressure, the authors found that the J = 0–1 line gains amplification, while 3d-3p does not. When the Ar pressure was 26 Pa, the J = 0–1 line completely dominated the spectrum. N₂ and Kr were used as the materials of capillary discharge respectively. The spike signal was obtained by XRD, then the spectrum was detected by Rowland spectrograph, and the spectrum of Kr⁷⁺ was found.     

Thermoelastic damping in torsion microresonators with coupling effect between torsion and bending

Predicting thermoelastic damping (TED) is crucial in the design of high Q MEMS resonators. In the past, there have been few works on analytical modeling of thermoelastic damping in torsion microresonators. This could be related to the assumption of pure torsional mode for the supporting beams in the torsion devices. The pure torsional modes of rectangular supporting beams involve no local volume change, and therefore, they do not suffer any thermoelastic loss. However, the coupled motion of torsion and bending usually exists in the torsion microresonator when it is not excited by pure torque. The bending component of the coupled motion causes flexural vibrations of supporting beams which may result in significant thermoelastic damping for the microresonator. This paper presents an analytical model for thermoelastic damping in torsion microresonators with the coupling effect between torsion and bending. The theory derives a dynamic model for torsion microresonators considering the coupling effect, and approximates the thermoelastic damping by assuming the energy loss to occur only in supporting beams of flexural vibrations. The thermoelastic damping obtained by the present model is compared to the measured internal friction of single paddle oscillators. It is found that thermoelastic damping contributes significantly to internal friction for the case of the higher modes at room temperature. The present model is validated by comparing its results with the finite-element method (FEM) solutions. The effects of structural dimensions and other parameters on thermoelastic damping are investigated for the representative case of torsion microresonators.     

Intensity distribution of a capillary-discharge 46.9 nm soft X-ray laser

We realize a Ne-like Ar 46.9 nm soft X-ray laser pumped by a capillary discharge. The study of the laserpulse-intensity distribution is important for applications of soft X-ray lasers. The intensity distribution demonstrates the gain distribution, plasma radius, and axial plasma density that contribute to the study of the laser-pulse formation. To measure the intensity in different positions of the X-ray laser spot, we moved transversally an X-ray diode (XRD) assembled with a slit. We obtain the onedimensional intensity distribution. We find a laser divergence (FWHM) of 4.0 mrad. According to the gain-guided model, we calculate the intensity distribution. The measured divergence of 4.0 mrad roughly corresponds to a plasma radius a approximately equal to 230–250 μm and on-axis electron density n _e ≈ 8.0?10¹⁸ ?9.0?10¹⁸ cm ^?3. The results of calculations indicate that the divergence of the intensity distribution increases when the plasma radius decreases and the on-axis electron density increases.     

Effect of Temperature on the Composition and Properties of Poly[(alkylamino)borazine] Precursor to Boron Nitride

A novel poly[(alkylamino)borazine] (PPAB) precursor to boron nitride (BN) was synthesized and the effect of synthesis temperature (T_syn) on its composition and properties was investigated. The results showed that with elevation of temperature, the precursor turned from a colorless transparent liquid to a yellow foamed solid. The softening point (T_s) can be adjusted according to the equation T_s = 1.43T_syn – 125.7, in which the T_syn was between 130°C and 170°C. The PPAB was composed of B, C, N, and H elements and the C content in PPAB decreased gradually with an increase of T_syn. The soluble and fusible precursor, with a softening point of 95°C, provided good processability into polymer fibers. The weight loss of PPAB in N₂ can be divided into three ranges: below 240°C, 240～700°C, and 700～1200°C. The ceramic yield of PPAB was improved from 43 wt% to 55 wt%, when the T_syn was elevated from 110°C to 190°C. Furthermore, the residue from PPAB pyrolyzed under N₂ showed characteristic IR spectra of hexagonal BN.     

Electrically conductive pseudo IPNs of linear poly(carbonate-urethane) and crosslinked polychloroprene

A number of pseudo IPNs of poly(carbonate-urethane) (PCU) and crosslinked polychloroprene (CR) have been synthesized and characterized. The single phase morphology of these novel pseudo IPNs has been confirmed by DSC measurements and electron microscopy. The room temperature electrical conductives of homopolymers and pseudo IPNs have been investigated for both undoped and iodine-doped samples. © 1994 John Wiley & Sons, Inc.     

sp2 carbon-conjugated covalent organic frameworks for efficient photocatalytic degradation and visualized pH detection

The design and fabrication of versatile covalent organic frameworks (COFs) with multiple properties for diverse applications is highly desirable. Here, the difunctional COFs material g–C₁₈N₃–COF was prepared and modified to be applied for efficient photocatalytic degradation of Rhodamine B (RhB) and pH detection, respectively. Owing to the triazine unit which was suitable for photocatalyst construction, g–C₁₈N₃–COF was sensitive to visible light and exhibited excellent photocatalysis capability toward RhB. Specially, the photocatalytic degradation of RhB with a high concentration of 300 ppm using g–C₁₈N₃–COF reached equilibrium within 6 h. Moreover, g–C₁₈N₃–COF was further grown in-situ onto the filter paper to generate a novel composite material g–C₁₈N₃–COF@Paper with bright yellow fluorescence. g–C₁₈N₃–COF@Paper could visualize the pH detection by remarkable changes in its fluorescent intensity and color in the range of pH value from 1 to 5, on account of the protonation of the nitrogen atoms from the triazine ring in g–C₁₈N₃–COF. The triazine-based sp² carbon-conjugated g–C₁₈N₃–COF, respectively, used as photocatalyst and sensor in this work offers a new strategy to construct the versatile COFs material, facilitating the application of functional COFs in the environmental protection field.