用毛细管焦点法精确测量微量液体的折射率

介绍了用毛细管焦点法精确测最微量液体折射率的一种新技术.该技术基于共轴球面光学系统的成像原理,用LED(λ=580 nm,FWHM为32nm)为测量光源,用CCD为像接收装置.一次测量样品需要量小于0.002 mL.待测样品封闭在毛细管内测量,有利于对毒性、挥发性和吸湿性强的液体介质折射率的测量.用此技术对纯水、乙醇、乙二醇和丙三醇样品的折射率做了测量,测量精度分别为0.0001,0.0002,0.0003和0.0003.论文在分析实验装置的测量灵敏度和成像景深基础上,提出了进一步提高测最精度的方法.     

Nonlinear ion-acoustic waves in magnetized plasmas in presence of energetic electrons and positively charged dust

A theoretical investigation has been carried out for exploring different features of ion-acoustic solitary and shock waves in a three-component magnetized plasma containing a mixture of thermal and nonthermal (energetic) inertialess electrons, warm inertial ions, and positively charged stationary dust particles. The standard Korteweg-de Vries (Burgers) equation has been derived by employing the reductive perturbation method, and its solitary (shock) wave solution has been derived and examined analytically as well as numerically. The latter exhibits characteristic properties (amplitude, width, speed, and polarity) of the ion-acoustic solitary and shock waves. It has been shown that the ion-acoustic solitary and shock waves are significantly modified by different plasma parameters (viz. parameter measuring the ratio of dust charge density to ion charge density, parameter measuring the fraction of energetic electrons, parameter measuring ion or electron temperature, and the external magnetic field). The present investigation may help in understanding the physics of various nonlinear phenomena formed in many space plasma systems, (viz. earth's mesosphere, solar wind, and cometary tails) and laboratory devices (laboratory experiments of Samarian et al., Phys. rev. E. 64 , 056407 [2001] and of Fortov et al., New J. Physics 5 , 102 [2003]).     

Cone calorimeter analysis of flame retardant poly (methyl methacrylate)-silica nanocomposites

Nanocomposite is a promising method to reduce fire hazards of polymers. Specifically due to increased interfacial area between polymer and nanofillers, polymer nanocomposites have an advantage in reducing fire hazards efficiently even when the flame retardant additives are at a concentration of 5 mass% or less. In theory, crosslinking between the polymer chains can create a carbon-dense structure to enhance char formation, which can further promote the flame retardancy. However, little research has been done to explore the flammability of crosslinking polymer nanocomposites with a low concentration of nanosilica particles. In this study, crosslinked and non-crosslinked poly (methyl methacrylate) (PMMA) nanocomposites of a low concentration of nanosilica particles have been prepared via an in situ method. Their fire properties were tested by using the cone calorimeter at the heat flux of 50 kW m^?2. Although silica-containing flame retardants tend to negatively affect the ignitability and soot production especially at a high concentration, through the condensed phase mechanism, the samples of high loading rate of nanosilica particles show better fire retardancy performance in the aspect of flammability, including decreased heat release rate, mass loss rate, and total heat release. Additionally, crosslinking indeed attributes to the less intensive combustion of crosslinked PMMA samples, especially at a low concentration of nanosilica. The combination of nanosilica particles with the modification of the internal structure of the polymer nanocomposites might be a good strategy to improve fire retardancy.     

A sensor for acetaminophen in a blood medium using a Cu(II)-conducting polymer complex modified electrode

Complexation of Cu ions in a terthiophene carboxylic acid (TTCA) polymer film resulted an enhanced anodic current for acetaminophen oxidation when compared to polymer coated and bare glassy carbon electrodes in human blood and buffer media. Scanning electron microscopy (SEM) and ESCA experiments indicate the involvement of copper in the electrocatalytic oxidation of acetaminophen. No interference was observed from other biologically important and phenolic compounds used with this modified electrode. Especially, the non-interference from N-acetylcysteine, an antidote for the treatment of acetaminophen poisoning, reveals the proposed method’s superiority in medicinal applications. In addition, the present modified electrode avoids surface fouling at higher concentrations of acetaminophen. The calibration range obtained with CV was based between 2.0×10⁻⁵ and 5.0×10⁻³ M [r²=0.997 (n=5, R.S.D.=2.5%); DL=5.0×10⁻⁶ M (S/N=3)]. The analytical utility of the modified electrode was achieved by analyzing the content of acetaminophen in different drugs without pretreatment using CV and amperometric techniques.     

Evaluation of resazurin microtiter plate assay and HPLC- photodiode array analysis of the roots of Asparagus adscendens

Asparagus adscendens Roxb. (Asparagaceae), is native to the Himalayas. The present study, for the first time, was undertaken to explore the antimicrobial potential, to determine the minimum inhibitory concentration (MIC) values of the methanol extract of the roots of A. adscendens and its solid-phase extraction (SPE) fractions using resazurin microtitre assay against Gram-positive and negative bacterial-registered strains and to carry out HPLC-photodiode array analysis of the SPE fractions. The methanol extract and all SPE exhibited considerable level of antibacterial potential against Gram-positive bacteria (MIC: 2.5–0.009 mg/mL) than against Gram-negative bacteria (MIC: 1.25–2.5 mg/mL). The use of microtitre plates has the advantage of lower cost, fast and quantitative results. Like other Asparagus species, the presence of phenolic compounds in all SPE fractions was evident in the HPLC-PDA data.     

Enzyme Based Electrochemical Biosensor for Ethanolamine

Enzyme based electrochemical detection method developed for chemical toxicant ethanolamine (EA). Monoamine oxidase A (MAO‐A) enzyme was used for the oxidation of EA. A direct electron transfer from the electrode to EA without any mediator with the help of MAO‐A enzyme was attained and this confirms the application of this methodology for the development of third generation biosensor for EA sensing well below the IDLH (30 ppm) value of EA. Moreover, heterogeneous rate constant (0.021s^?1) and the number of electron involved (5.2) were deduced for EA in PBS buffer. The calibration plot showed linearity 2.02×10^?4 M to 10.10×10^?4 M of EA in PBS buffer with detection limit 4.1 ppm. The modified electrodes are characterized by Raman and Electrochemical impedance spectroscopy (EIS) techniques. The outcome of this work indicates about the utility of this methodology for the sensing of EA in the environment if it is present as well as to degrade EA into other compounds without using any indicator or mediator.     

Cylindrical and spherical electron-acoustic Gardner solitons and double layers in a two-electron-temperature plasma with nonthermal ions

Cylindrical and spherical Gardner solitons (GSs) and double layers (DLs) in a two-electron-temperature plasma system (containing cold electrons, hot electrons obeying a Boltzmann distribution, and hot ions obeying a nonthermal distribution) are studied by employing the reductive perturbation method. The modified Gardner equation describing the nonlinear propagation of the electron-acoustic (EA) waves is derived, and its nonplanar GS and DL solutions are numerically analyzed. The parametric regimes for the existence of GSs, which are associated with both positive and negative potential, and DLs which are associated with positive potential, are obtained. The basic features of nonplanar EA GSs, and DLs, which are found to be different from planar ones, are also identified. The implications of our results in space and laboratory plasmas are briefly discussed.     

Europium removal with a mineral mixtre

Natural mixture containing mostly minerals of iron, sillicon, magnesium, aluminium and calcium was exploited for the decontamination study of europium radionuclides from aqueous radioactive waste solutions. The physicochemical conditions, such as shaking and equilibration time, nature of hydrogen ions, pH, temperature, concentrations of adsorbate and adsorbent were experimentally determined. This study showed quantitative adsorption beyond pH 7 and under optimized conditions, up to 33 g of the adsorbate can be rapidly removed from radioactive effluents using only 1 kg of the mineral mixture (MM). Desorption study of the solidified radioactive waste product reveals no significant loss (< 0.01% month), indicating MM as an effective material for removal of radioactive europium and storing it in solid form over a long period of time.     

Mass spectrometry—II: The unimolecular decomposition of benzaldehyde azine in the gas phase induced by electron-impact

The mass spectra of benzaldehyde azine-α, αA-d² (III) and benzaldehyde azine-d¹⁰ (IV) reveal that both ring and α hydrogen are lost from the molecular ion of benzaldehyde azine (II) in forming the [M –1] ion. Data from the spectra of III and IV at 70 eV and reduced ionizing voltages are consistent with the existence of two competing pathways producing [M –1] ions. Rearrangement ions are observed in the spectra of II. Randomization is unimportant in the electron-impact-induced fragmentation reactions of II. The rearrangement-fragmentation reactions for II in general parallel those previously observed for acetophenone azine (I).