ESR spectroscopics study of radicals formed from methoxycarbonylcholine picrate hemihydrate

Abstract

The electron spin resonance of γ-irradiated single crystals of methoxycarbonylcholine picrate hemihydrate, C₇H₁₆NO₃ ⁺ · C₆H₂N₃O₇ ^? · ½ H₂O has been observed and analyzed for different orientations of the crystal in the magnetic field. The crystals have been investigated between 70 and 350 K. The spectra were found to be temperature independent and the radiation damage centers are attributed to – ?[Obar]OCH₃ and –CH₂CH₂O? radicals. The g and hyperfine coupling constants were found to be almost isotropic with an average, g = 2.0060, a _H1 = 4.4G for –CH₂CH₂O?, g = 2.0050, a _H2 = 3.5G for –CH₂CH₂O? and g = 2.0045, a _H = 3.5 G for –?[Obar]OCH₃. These values indicate a long-range coupling between the unpaired electron and H protons.     

Effect of C60 fullerene additions on the thermal conductivity of low-density polyethylene films

The thermal conductivity of LDPE + C₆₀ nanocomposites with a fullerene concentration up to 10 wt % is studied in the temperature range 20–80°C. This conductivity is found to nonlinearly decrease with increasing fullerene concentration. The decrease in the thermal conductivity of the composites is considered to be caused by a decrease in the phonon mean free path as a result of an increase in the number of scattering centers. The temperature dependence of the thermal conductivity is found to have a maximum.     

III. Hyperfine splittings by gamma protons in ESR spectra of ketyl radicals

The interaction of γ-protons with the unpaired electron in alkyl 1-[2-(oxide anion)-, 5-mono-t-butyl-, or 3,5-di-i-propyl-, or 3,5-di-t-butyl-substituted]-phenyl ketyl radicals was observed. The values of γ-coupling constants are 0.5–0.7 G if the alkyl isn-propyl orn-butyl and zero if the alkyl is ethyl. The values of the, β- and γ-coupling constants depend on the type of solvent used.     

Investigation of free radicals induced by light ions in CR-39 using ESR spectroscopy

In previous investigations the formation of radicals induced by γ-irradiation in CR-39 samples has been studied by electron spin resonance (ESR) spectroscopy. On the other hand, all attempts fail to detect radicals in samples irradiated by particles (p, and neutrons). The present work succeeded in detection of radicals produced by charged particle radiation in CR-39 (TASTRAK). The detectors were irradiated with protons of 7 MeV and -particles of 3 MeV with fluences in the order of 10¹¹–10¹² particles/cm². The observed ESR signal is composed of at least four different resonance lines for each of which we determined the amplitudes, g-factors, lifetimes and the G-value. The amplitude of the total ESR signal decreases rapidly with a short and a longer lifetime. About 5 days after irradiation the ESR intensity decreased to an undetectable value. The lowest detectable dose (LDD) is of the order of 1 kGy.     

铜团簇束在硅上碰撞沉积的薄膜表面能谱分析

用一种新型磁控溅射气体凝聚团簇源产生Cu-n(n是团簇原子个数)团簇束 ,当团簇束分别在偏压为:0,1,3,5,10 kV的电场中加速后,在真空中,沉积在室温下的 P型Si(111)衬底上,获得Cu/P-Si(111)薄膜样品.用X射线光电子能谱(XPS)分析薄膜,结果表明:薄膜本身不含C和O等杂质;当Cu/P-Si(111)样品暴露在空气中时,样品表面会氧化和碳污染,铜的特征电子峰几乎被湮没.用能量3 keV流强为4～6 μA/cm2*!Ar+束, 预溅射处理样品表面后,用XPS分析,常规磁控溅射室温下得到的Cu/P-Si(111)样品和铜团簇束沉积,偏压分别为0,1,3,5,10 kV的样品XPS谱和块状Cu标样谱基本一样,Cu2P1、Cu2P3、 CuLMM特征峰位没有移动,反映不出原子结合能差异.     

卵黄低密度脂蛋白结构的红外光谱和激光拉曼光谱分析

低密度脂蛋白是把胆固醇运输到肝脏合成胆酸一种重要的脂蛋白。低密度脂蛋白结构的研究对弄清动脉硬化发病机理有着非常重要的意义。用硫酸铵分离法快速分离鸡蛋黄中各种蛋白成分,用Sephadex G-200柱层析分离、纯化获得纯度很高的低密度脂蛋白,对其进行SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)检测,结果显示低密度脂蛋白主要包含5种脱辅基蛋白。激光拉曼和红外光谱测定,检测出低密度脂蛋白中对称CH2以及不对称CH2的伸缩振动。红外光谱还检测到脂蛋白肽键中C=O伸缩振动、脂链中P=O的伸缩振动和磷脂中胆碱聚集体的N+(CH3)3的不对称振动。两种光谱分析为研究低密度脂蛋白的结构提供了有效信息。     

Simulation and analysis of the transverse spectrum in HIRFL-CSR

Particles in a storage ring oscillate in the longitudinal and transverse dimensions.Therefore,the signal that beam has generated can be analyzed in the frequency domain to extract many beam parameters,such as tune,momentum spread,emittance and their evolution with time and so on.In this paper,the transverse spectrum in HIRFI-CSR was simulated and analyzed under different conditions,including electron cooling,hollow electron beam,solenoid effect,the tune shift caused by power supply ripple and the misalignment between ion and electron beams.The result of the simulation shows that the longitudinal magnetic field of the electron cooling device should be compensated by a "compensation solenoid",and the power supply ripple must be controlled,otherwise the accumulation would be affected and the beam would be lost.     

Simulation and analysis of the transverse spectrum in HIRFL-CSR

Particles in a storage ring oscillate in the longitudinal and transverse dimensions. Therefore, the signal that beam has generated can be analyzed in the frequency domain to extract many beam parameters, such as tune, momentum spread, emittance and their evolution with time and so on. In this paper, the transverse spectrum in HIRFL-CSR was simulated and analyzed under different conditions, including electron cooling, hollow electron beam, solenoid effect, the tune shift caused by power supply ripple and the misalignment between ion and electron beams. The result of the simulation shows that the longitudinal magnetic field of the electron cooling device should be compensated by a “compensation solenoid”, and the power supply ripple must be controlled, otherwise the accumulation would be affected and the beam would be lost.     

Transformation kinetics of A-15 superconductors formed by solid state reactions

Various fabrication processes devised for making multifilamentary A-15 super-conductors are all based on solid state reactions, transforming the host metal into the binary A-15 phase. The kinetics of the growth process involved in the compound formation form the theme of this paper.     

Electron spin density distribution in the polymer phase of CsC60: assignment of the NMR spectrum

We present high resolution 133Cs-13C double resonance NMR data and 13C-13C NMR correlation spectra of 13C enriched samples of the polymeric phase of CsC60. These data lead to a partial assignment of the lines in the 13C NMR spectrum of CsC60 to the carbon positions on the C60 molecule. A plausible completion of the assignment can be made on the basis of an ab initio calculation. The data support the view that the conduction electron density is concentrated at the C60 "equator," away from the interfullerene bonds.     

Dynamic mechanical properties of interpenetrating polymer networks formed by UV curing processes

Two-component interpenetrating polymer networks (IPN) were made by stepwise synthesis by UV-irradiated polymerization and heat curing. The mechanical properties of normal IPN, inverse IPN and SIN (simultaneous interpenetrating networks) prepared with acrylate and epoxy were studied. Unique mechanical properties were found in each case. All of these iPN systems were composed of the individual preswollen networks. A homogeneous system is produced in the inverse IPN and SIN, while a heterogeneous system is brought about in the normal IPN. Glass transition temperatures for the inverse IPN and the SIN are lower than the normal IPN, and are attributed to molecular packing effects.     

Near-field 3D mapping of spiral light structures formed by a polymer nanocylinder

It is demonstrated that polymer nanocylinders can form spiral light structures. Spiral distributions of light intensity are observed at distances of 230–1100 nm above the nanocylinder with a diameter of 700 nm and a height of 1100 nm. The optical spirals are measured using a scanning near-field optical microscope that performs 3D scanning over planes when the nanocylinder is illuminated from the bottom with linearly polarized CW He-Ne-laser radiation at a wavelength of 632.8 nm. It is shown that the topology of the optical spirals significantly depends on the incident polarization.     

Dye laser probing of primary C2 radicals formed by IR intense field photolysis of ethylene

The C₂-radicals in the lower electronic statea ³ II _u have been studied by the method of laser-excited luminescence of products of ethylene IR photolysis. The dependence of C₂-radical concentration on IR field power density and its time evolution have been investigated. The threshold characteristics of C₂-radical occurrence and the ratio between excited and unexcited radicals have been determined. Different mechanisms for their formation are being discussed.     

Simulation of sintering of low-temperature ceramic products formed by additive technology

Computer simulation methods have been applied to study the processes of low-temperature ceramics synthesis corresponding to technological processes. The simulation is performed for micron- and nanosized powders with different morphology. The synthesized composite medium has the characteristics (microlayer thickness, pore volume fraction, etc.) that reflect imperfections in the initial dispersion. The developed model allows one to examine the governing factors of physical and chemical processes in low-temperature ceramics synthesis.     

The role played by the enthalpy of reactions in the disproportionation of free radicals

A semiempirical model of radical disproportionation was suggested. The reaction was modeled by an intersection of two potential curves describing stretching vibrations of interacting bonds. One of these curves was a parabola (stretching vibration of the attacked bond), and the other, a Morse curve (stretching vibration of the arising bond). Equations describing an increase in the interatomic distance in the reaction center of the transition state of such reactions as a function of the enthalpy of the reaction were obtained. A comparison of the calculation results and experimental data was performed to derive equations that described the rate constant for disproportionation as a function of bond elongation in the transition state and reaction enthalpy. A simple method for calculating interatomic distances in the reaction center of the reactions was suggested. Rate constants for several unstudied radical disproportionation reactions were calculated. The problem of the competition of disproportionation at various reaction centers was considered.     

线谱非平稳性分析和利用干涉谱测距

研究运动舰船辐射噪声线谱的非平稳性的规律并利用其来提高声呐的检测性能和实现目标测距测深功能是本研究的目的。线谱的非平稳性有3个方面来源,线谱声源的不稳定、传输途径和目标与接收点的相对运动。通过对大量的运动目标辐射噪声进行的时频分析,总结出运动目标辐射噪声线谱的非平稳性谱图的典型表现。对不同形态的线谱应用不同的处理和检测方法,对频率稳定的连续线谱可以用长积分的最佳检测方法进行,对多普勒变化的线谱可用Dopplerlet方法处理并用于目标测距和测速,对时断时有的线谱得可用卡尔曼跟踪对付断裂的特性。从理论上分析了钟型的“线谱群”的产生原因,证明了此现象是反射声和直达声之间的谱干涉引起的。利用谱干涉现象中的干涉谷之间的关系可实现目标测距测深的目的,最后给出某一实际海上运动目标距离和深度的测量结果。     

Identification of acoustic emission source mechanisms by energy spectrum spectrum analysis

The purpose of energy spectrum analysis is to calculate random signal parameters which, when considered statistically, may show characteristic differences between similar signals and hence indicate different source mechanisms generating the signals. A computer programme has been written to compute mean and median frequency, mean amplitude spectral density, mean energy spectral density and amplitude spectrum variance. Plots of amplitude spectra, normalized energy spectra and energy difference spectra (the difference between pairs of spectra) may also be selectively generated by the programme.The results obtained were from real data, from specially prepared reactor-grade zirconium test pieces.     

Low magnetic field DNP of diamagnetic products formed in reactions accompanied by electron hopping

DNP generation at diamagnetic products of electron transfer reactions accompanied by electron hopping in low magnetic fields has been investigated both experimentally and theoretically. A comparison of experimental and calculated DNP dependencies on reactant concentration and mw-field magnitude was made. The electron hopping rate constant for dimethylaniline radical-cation was evaluated. The value obtained corresponds to those reported in literature.