Detection of PAH of molecular weight between 300 and 402 in airborne particulate matter by fused silica capillary GC and GC/MS

Gas chromatography (GC), low-voltage mass spectrometry (LV MS), and gas chromatography/mass spectrometry (GC/MS) have been used for detecting polycyclic aromatic hydrocarbons (PAH) of molecular weight between 300 and 402 in airborne particulate matter. Nearly 200 high molecular PAH separated by fused silica capillary columns could be characterized by their El mass spectra. The lack of reference substances precluded further structure elucidation.     

The preparation of carbon aerogels based upon the gelation of resorcinol-furfural in isopropanol with organic base catalyst

Carbon aerogels with high BET surface area were developed by sol-gel polycondensation of resorcinol and furfural in isopropanol using hexamethylenetetramine (HMTA) as a catalyst, and then directly drying the organic gels under isopropanol supercritical conditions, followed by carbonization under a nitrogen atmosphere. The preparation conditions of carbon aerogels were explored by changing the mole ratio of resorcinol to basic catalyst HMTA (R/C), the ratio of resorcinol to isopropanol (R/I), and the mole ratio of resorcinol to furfural (R/F). The effect of these preparation conditions on the porous structure of the carbon aerogels obtained was studied by nitrogen adsorption isotherms. According to the characterizations of TEM, SEM and nitrogen adsorption, the carbon aerogels obtained have a three-dimensional network that consists of carbon nano-particles with size from 20 to 30 nm, which define numerous micropores, mesopores and macropores. HMTA reacts not only as a catalyst but also as a reagent in the gelation polymerization. XRD characterization indicates that carbon aerogels have disordered nanocrystalline structures similar to activated carbon.     

Micro- and mesoporous silicas synthesized in acidic water-ethanol solution of equimolar catanionic surfactant

Porous silicas with combined micro- and mesoporosity are synthesized in acidic water-ethanol solution of equimolar catanionic mixture, where the mesopores are narrowly and uniformly distributed, and the micropores generate due to the addition of ethanol. To vary the pH value of the synthetic mixture can also change the ratio of micro-/mesopores volume in the resulting samples. Compared with other amorphous silica gels and ordered mesoporous silicas including MCM-41, MCM-48 and SBA-15, these micro- and mesoporous silicas show much improved adsorptive capacity for volatile nitrosamines.     

Structural and physical properties of cobalt nanocluster composite glasses

Composite systems with metallic nanoparticles embedded in dielectrics present peculiar physical properties which are attractive in several application fields. In the case of transition elements, the magnetic properties of the metal clusters embedded in a dielectric matrix mainly depend on the particle size and structure. In this work, silica films containing cobalt atoms were synthesized by RF magnetron co-sputtering deposition technique, with cobalt concentration of a few atomic percent. X-ray diffraction and transmission electron microscopy showed the presence of hcp cobalt nanoclusters in the as-deposited sample with the highest cobalt concentration. After deposition, thermal treatments were performed to promote cobalt compounds or nanoparticle formation. The thermal treatments were able to change the oxidation state of cobalt atoms, as well as the structure of metallic cobalt nanoclusters (from hcp to fcc), their final size depending on both the preparation parameters and the subsequent annealing atmospheres.     

Elastic scattering of electrons by benzene

Relative differential cross-sections for the elastic scattering of electrons from benzene have been measured at incident energies 300, 500, 700 and 900eV and for scattering angles between 30° and 120°. The results are discussed and compared with the independent atom model (IAM) calculations. Two different sets of scattering amplitudes for the constituent atoms of benzene were used in these calculations, one obtained from first Born approximation and the other from partial wave analysis of the Dirac equation. Only the static interaction was taken into account in the calculations. The higher the incident energy, the better is the observed agreement between experiment and theory. This indicates that at higher energies, absorption, exchange and polarization effects are not significant as compared to the static interaction and that the IAM satisfactorily predicts the interference of scattering from the individual atoms of C₆H₆.     

Pu300能量窗钚年龄算法

美国LLNL提出了采用钚材料γ谱的330—350keV(Pu300)能量窗计算钚年龄, 用此能量窗建立了相关钚年龄算法, 并对几个不同样品的谱数据进行了计算, 并将其结果与PC/FRAM的结果进行比较, 结果表明两者吻合得比较好.     

On Some Generalizations and Refinements of a Ky Fan Inequality

In this paper, a Ky Fan inequality and an inequality by Wu and Wang [10] will be generalized. Some new and improved refinements of the Ky Fan inequality will be put forward.AMS Subject Classification (2000) 26D15     

HL-2M 装置的 300MVA 发电机组保护装置

为保证 HL-2M 装置的 300MVA 立式发电机组的安全运行，需要对其设置保护装置。针对机组自身 特性，保护装置为发电机的多分支绕组采用了完全裂相横差保护、完全纵差保护和零序电流型横差保护。基于机 组脉冲工作模式，保护装置采用了快速频率跟踪算法实现频率变化时对发电机组的电压电流快速跟踪测量。实验 证明该保护装置满足机组的安全运行要求。      

Polyethylene Glycol (PEG 300) and Water–Ethanol as Benign Solvent Systems for the Synthesis of a Novel Series of 2-Hydroxynaphthalen-1(4H)-Ones

An improved, clean, simple, and efficient method for the synthesis of new series of 2-hydroxy-4-methylenenaphthalen-1(4H)-one is described. This new process involves a domino Michael addition of various methylene acid compounds with the sodium salt of 1,2-naphthoquinone-4-sulfonate either in basic (tBuOK) polyethylene glycol (PEG300) at room temperature or in a basic (NaOH) water–ethanol medium at 40 °C by a crushing in a mortar or a traditional heating.     

Sol-gel chemistry approach in the preparation of precursors for the substituted superconducting oxides

Sol-gel processing of ceramic materials for advanced applications involves several steps starting from precursor synthesis and ending up with multicomponent metal oxides. A simple sol-gel synthesis technique has been refined to prepare the precursors for the superconducting (Y_1−xSc_x)Ba₂Cu₄O₈ and (Y_1−xGa_x)Ba₂Cu₄O₈ compounds. The amorphous gel powders were characterized by powder X-ray diffraction, infrared spectroscopy, thermal analysis and elemental analysis. A systematic characterization of precursor gels led us to predict the approximate composition and the chemical reactions involved during gelation. The stability and high level of homogeneity obtained for the gels make them suitable as processable precursors to substituted (Y_1−xSc_x)Ba₂Cu₄O₈ and (Y_1−xGa_x)Ba₂Cu₄O₈ superconducting compounds.