Improvement of electron capture efficiency by resonant excitation

A novel pulse sequence improving the efficiency for electron capture dissociation (ECD) of an unmodified Fourier transform ion cyclotron resonance (FTICR) mass spectrometer by more than an order of magnitude is presented. Commercially available FTICR instruments are usually equipped with a filament-based electron source producing an electron beam that has a rather small cross section. An ideal overlap between the rotating ion cloud and the electron beam appears to be a prerequisite for a high ECD efficiency. A reduced interception of the ion cloud and the electron beam is probably due to the contribution of the magnetron motion to the trajectory of the ions, resulting in a precession about the z-axis of the instrument. By increasing the kinetic energy and therefore increasing the cyclotron radii of the precursor ions by resonant excitation, the overlap of the rotating ion cloud with the electron beam is improved. By use of this protocol the efficiency of electron capture is substantially increased and consequently the acquisition time of ECD spectra is reduced significantly. The capability of resonant excitation of the precursor ions during the irradiation with electrons is demonstrated for standard peptides. This approach is particularly valuable for analysis and characterization of O-glycosylated peptides. In addition to amino acid sequence information, the attachment site of the labile glycan moiety is determined, and also radical-site-induced fragmentations of the glycosidic bonds are observed.     

Thermal degradation of iron polymethacrylate

Iron polymethacrylate was synthesized by free radical solution polymerization of methacrylic acid, followed by replacement of the carboxylic proton with iron. Thermal volatilization analysis and thermogravimetry were used to study its thermal stability from ambient temperature up to 500oC. The results reveal that ferric oxide is left as residue at the end of the thermal degradation experiments.The authors dedicate this paper to the memory of the late Dr. Mohammad Zulfiqar of Quaid i Azam University, Islamabad, Pakistan.     

纳米铁粉降解水中三硝基甲苯的条件优化与降解机理

研究了纳米铁粉降解水中三硝基甲苯(TNT)的影响因素;利用傅立叶变换红外光谱和紫外光谱分析了其降解机理.结果表明:将初始浓度为80.0mg/L、pH为4.00的TNT水溶液与5.0g/L的纳米铁粉在转速200r/min、温度40℃的振荡器中反应3h,水中TNT的浓度可降至0.1mg/L以下,降解率达到99%以上;就TNT的降解机理而言,其降解过程是纳米铁粉给出电子被氧化、TNT分子中的硝基接受电子被还原的过程.     

Synthesis and degradation of nucleic acid components by formamide and iron sulfur minerals

We describe the one-pot synthesis of a large panel of nucleic bases and related compounds from formamide in the presence of iron sulfur and iron-copper sulfur minerals as catalysts. The major products observed are purine, 1H-pyrimidinone, isocytosine, adenine, 2-aminopurine, carbodiimide, urea, and oxalic acid. Isocytosine and 2-aminopurine may recognize natural nucleobases by Watson-Crick and reverse Watson-Crick interactions, thus suggesting novel scenarios for the origin of primordial nucleic acids. Since the major problem in the origin of informational polymers is the instability of their precursors, we also investigate the effects of iron sulfur and iron-copper sulfur minerals on the stability of ribooligonucleotides in formamide and in water. All of the iron sulfur and iron-copper sulfur minerals stimulated degradation of RNA. The relevance of these findings with respect to the origin of informational polymers is discussed.     

Functionalization of silicon nanowires by iron oxide and copper for degradation of phenol

Research on Chemical Intermediates - Iron oxide (Fe3O4) and copper-functionalized silicon nanowires (SiNWs) from silicon powder mesh?<?500 with a spherical structure have been...     

Study on the radiation degradation of polyether-polyurethane induced by electron beam

Polyether-urethane samples were irradiated at the dose range from 10 to 2000 kGy by 2 MeV electron beams. Volatile species from the polymer degradation were analyzed quantitatively and qualitatively with GC/MS. Thermal properties and micro-phase separation of the samples were examined by TG and the morphology was studied by TEM and SEM. The results show that the irradiated polyether-polyurethane evolves CO₂, H₂, CH₄ and C₂H₆, etc. The thermal stabilities between the hard and soft segments in the irradiated samples are different. At high doses, the phase separation in the sample is predominant and the hard segment of sample is more stable. The dose rate affects the soft segment of the irradiated sample much more.     

Selective four electron reduction of O2 by an iron porphyrin electrocatalyst under fast and slow electron fluxes

An iron porphyrin catalyst with four electron donor groups is reported. The porphyrin ligand bears a distal hydrogen bonding pocket which inverts the normal axial ligand binding selectivity exhibited by porphyrins bearing sterically crowded distal structures. This catalyst specifically reduces O(2) by four electrons under both fast and slow electron fluxes at pH 7.     

Low-energy electron and X-ray degradation of biomedical plasma-fluoropolymer

Plasma-deposited thin films of fluoropolymer on metallic substrates were degraded by low-energy (1-100 eV) electrons and X-ray irradiation to simulate irradiation conditions of implanted coated stents in the human body during diagnostic procedures using high energy radiation. The desorption of anions and cations from the surface of the films induced by 1-100 eV electrons was recorded by mass spectrometry. The electron energy dependence of the emission of F⁻ exhibited a resonant peak at 12.9 ± 0.4 eV, showing the formation of a transient excited anion and a monotonic rise at higher energies, associated to dipolar dissociation. In the positive ion mode, the fragments F⁺, CF⁺, CF₂⁺, CF₃⁺, C₃F₃⁺, C₂F₄⁺ and C₂F₅⁺ were observed. Emission thresholds were measured and laid above 25 eV. The shape of the cation emission curves versus electron energy showed no resonant process. X-ray degradation was studied by X-ray photoelectron spectroscopy for different exposure times. Loss of fluorine in -CF₂ groups was observed and damage mechanisms were proposed.     

Transmission and fractionation of micro-sized particle suspensions

In processes aimed at the fractionation of a multi-component feed stream, transmission of particles through the membrane is at least as important as retention of larger particles. In this paper, we describe the mechanisms of transmission of mono-disperse latex particles through a polymer membrane. The effects of process parameters, such as transmembrane pressure, cross flow velocity and feed concentration were investigated. In dead end filtration mode, we found that, depending on the transmembrane pressure, four particle transmission regimes could be distinguished.

Particle deposition on polymer membranes and polymer microsieves was investigated in-line with confocal scanning laser microscopy (CSLM). It was observed that with the polymer membrane random depth deposition took place, while the microsieve exhibited in-pore fouling.

In addition, bi-disperse particle suspensions were fractionated with dead end and cross flow membrane filtration, and various effects were charted. Based on the phenomena observed, it is concluded that the design of a fractionation process starts with defining a stable transmission regime for small particles, and subsequently choosing the process conditions for minimal deposition of the larger particles.     

Characteristics and Kinetics of Nitrobenzene Reduction by Sucrose-modified Nanoiron

Sucrose-modified nanoscale zero-valent iron(SM-NZVI) was prepared with liquid phase reducing method, and characterized by transmission electron microscopy(TEM) and X-ray diffraction(XRD) for the shape and structure. The size of SM-NZVI particles was about 100―150 nm and they displayed better dispersity. The degradation of nitrobenzene(NB) in water by SM-NZVI was carried out in batch experiments. The results indicate that the efficiency of NB reduction via SM-NZVI increased by 44.24% compared with that via NZVI, and coexistent Ca²⁺, Mg²⁺, HCO₃^- and other ions showed little effect on NB reduction but negative influence on aniline(AN) production. Furthermore, the kinetic researches indicate that NB reduction with SM-NZVI could be described by pseudo first-order kinetic model at different initial pH values and iron dosage. The oxidation products of iron were mainly Fe₃O₄ and Fe₂O₃ with irregular shape.     

核桃壳生物炭负载铁催化降解亚甲基蓝性能研究

研究了以核桃壳生物炭负载铁催化剂和H2 O2组成类芬顿体系降解亚甲基蓝的性能.探究了催化剂中铁含量和反应条件对降解亚甲基蓝性能的影响,并确定反应动力学.由XRD结果可知铁物种是以Fe2 O3(Maghemite-C)形式存在于生物炭中.降解实验结果表明,当Fe2 O3负载量为5％,催化剂的投加量为100 mg,H2 O...     

高效毛细管电泳优化分离硝基甲苯类化合物的研究

采用正交设计法对胶束毛细管电泳中的优化分离条件进行了考察，研究了改性剂，十二烷基硫酸钠（SDS）及β－环糊精（β-CD）浓度和PH值几个参数对分离的影响，优化结果表明，在30min内，性质相近的邻，对、间－硝基甲苯及2，4－二硝基甲苯可得到较好的分离。     

The effects of axial ligands on electron distribution and spin states in iron complexes of octaethyloxophlorin, intermediates in heme degradation

The results presented here show that the nature of the axial ligand can alter the distribution of electrons between the metal and the porphyrin in complexes where there is an oxygen atom replacing one of the meso protons. The complexes (1-MeIm)(2)Fe(III)(OEPO) and (2,6-xylylNC)(2)Fe(II)(OEPO(*)) (where OEPO is the trianionic octaethyloxophlorin ligand and OEPO(*) is the dianionic octaethyloxophlorin radical) were prepared by addition of an excess of the appropriate axial ligand to a slurry of [Fe(III)(OEPO)](2) in chloroform under anaerobic conditions. The magnetic moment of (2,6-xylylNC)(2)Fe(II)(OEPO(*)) is temperature invariant and consistent with a simple S = (1)/(2) ground state. This complex with an EPR resonance at g = 2.004 may be considered as a model for the free-radical like EPR signal seen when the meso-hydroxylated heme/heme oxygenase complex is treated with carbon monoxide. In contrast, the magnetic moment of (1-MeIm)(2)Fe(III)(OEPO) drops with temperature and indicates a spin-state change from an S = (5)/(2) or an admixed S = (3)/(2),(5)/(2) state at high temperatures (near room temperature) to an S = (1)/(2) state at temperatures below 100 K. X-ray diffraction studies show that each complex crystallizes in centrosymmetric form with the expected six-coordinate geometry. The structure of (1-MeIm)(2)Fe(III)(OEPO) has been determined at 90, 129, and 296 K and shows a gradual and selective lengthening of the Fe-N(axial bond). This behavior is consistent with population of a higher spin state at elevated temperatures.     

离子注入修饰电极检测硝基苯

离子注入是一种新技术，可按人们的意愿和需要，将不同的离子注入不同的基本电极表面，制成具有催化活性强，稳定性高，重现性好等特点的修饰电极。作者研究了离子注入钴和注入镍的玻碳电极在０．１ｍｏｌ／ＬＨＡｃ－ＮａＡｃ缓冲溶液中硝基苯的行为及测定。     

Photocatalytic Reduction of Nitrobenzene by Titanium Dioxide Powder

The feasibility of photocatalytic reduction of nitrobenzene using titanium dioxide powder as photocatalyst, under the protection of nitrogen and presence of hole scavenger conditions, was studied. Effects of the illumination time, amount of catalyst and sorts of solvent on the photocatalytic reduction of nitrobenzene were investigated, respectively. The results showed that, for the photocatalytic reduction of nitrobenzene, aniline was the main product. When the illumination time was 6 h, 8.15×10^?4 mol/L of nitrobenzene could be photocatalytically reduced completely, with the yield of aniline being 88.5%. The optimum amount of TiO₂ used was 4.0 g/L, the optimum initial pH value of reaction solution was 4.0 and the best solvent was methanol. The kinetics and mechanisms of the photocatalytic reduction of nitrobenzene were also discussed.     

气相色谱法测定植株体内硝基苯

建立了气相色谱法测定植株样品体内硝基苯含量的方法。以苯-丙酮(50∶50,V/V)混合物作提取剂,高速匀浆后超声提取,硅镁型吸附剂净化,采用DB-1701石英毛细管色谱柱分离,GC-μECD检测。结果表明,3个水平添加时的回收率(n=5)分别为96.0%~107.0%、89.5%~99.5%和85.6%~97.8%;相对标准偏差均小于5%;方法检出限0.005μg/g;标准曲线相关系数r=0.9991。该方法可用于植株样品中硝基苯测定。     

Effect of dose rate on degradation of 2,6-dichlorophenol by electron beam irradiation

The effects of different dose rates on the degradation of 2,6-dichlorophenol (2,6-DCP) in aqueous solution were investigated at about 2?×?10⁴ Gy absorbed dose, using a 10 MeV electron beam accelerator. It was found that the removal efficiency decreased with increasing dose rate at all initial concentrations of 0.5, 1 and 2 g L^?1, and the effect was significantly diminished by addition of P25 TiO₂ nanoparticles. Alkaline medium were unfavorable for degradation of 2,6-DCP. Hydrogen peroxide (H₂O₂) could promote the removal efficiency at a lower dose rate rather than at a higher one.

     

壳聚糖季铵盐修饰电极对硝基苯的测定

通过共价键合的方法将壳聚糖季铵盐修饰在玻碳电极表面,制备了一种新型的壳聚糖季铵盐修饰电极,用循环伏安法和脉冲伏安法研究了修饰电极的电化学性能.实验结果表明,修饰电极的比表面积显著增大,用于硝基苯检测时,其峰电流明显增强,而且该电极在测试中表现出良好的稳定性和重复性.在pH 1.0的Britton-Robinson缓冲溶液中,硝基苯还原峰峰电流与其质量浓度在3.0 ～120 mg·L-1范围内呈良好的线性关系,检出限达0.7 mg·L-1.     

Mechanism of electron excitation energy degradation in solutions

The inductive-resonant mechanism of electronic energy degradation is proposed and proved for rare earth ions, transition metal ions and simple molecules (NO^?₂) in solutions. The interaction of two oscillators is considered, that is the vibronic interaction corresponding to the radiation spectrum of an excited ion or molecular and the vibrational spectrum corresponding to the excitation of high frequency vibrations of the solvent. The calculation of the energy degradation rare constant (k_degr.) by Förster's formula is shown to give k_degr. values of the same order as the experiment. Such a treatment can quantitatively explain all experimental regularities of the degradation process, for instance, the dependence of k_degr. on the distance from the electronic excitation centre to the nearest high frequency vibration gravity centre. It is shown that the suggested mechanism corretly explains the deuteration effect, the dependence of k_degr. on ΔE (energy gap) and the variation of this dependence for differenct classes of compounds. The possibility of proving the validity of the suggested model for the case of complex organic molecules is discussed.     

Scanning electron microscopy and roughness study of dental composite degradation

Our aim was to test the hypothesis that the use of mouthwashes, consumption of soft drinks, as well as the type of light curing unit (LCU), would change the surface roughness (Ra) and morphology of a nanofilled composite resin (Z350? 3M ESPE). Samples (80) were divided into eight groups: Halogen LCU, group 1, saliva (control); group 2, Pepsi Twist?; group 3, Listerine?; group 4, Colgate Plax?; LED LCU, group 5, saliva; group 6, Pepsi Twist?; group 7, Listerine?; group 8, Colgate Plax?. Ra values were measured at baseline, and after 7 and 14 days. One specimen of each group was prepared for scanning electron microscopy analysis after 14 days. The data were subjected to multifactor analysis of variance at a 95% confidence followed by Tukey's honestly significant difference post-hoc test. All the treatments resulted in morphological changes in composite resin surface, and the most significant change was in Pepsi Twist? groups. The samples of G6 had the greatest increase in Ra. The immersion of nanofilled resin in mouthwashes with alcohol and soft drink increases the surface roughness. Polymerization by halogen LCU (reduced light intensity) associated with alcohol contained mouthwash resulted in significant roughness on the composite.