Practical aspects of ROESY experiments for identification of bound waters in the cyclic tetrasaccharide

ROESY pulse sequences are presented and evaluated to identify bound waters in the cyclic tetrasaccharide. The first experiment incorporated the double-pulsed field gradient spin-echo (DPFGSE) for selective water excitation at the initial portion of the pulse sequence. Although long, shaped pulses were used in DPFGSE to achieve the highly selective excitation of water resonance that is very close to resonances of the cyclic tetrasaccharide, the approach was not effective because of the loss of sensitivity. Concomitant use of long delays and moderate length of shaped pulses in the portion of DPFGSE gained more sensitivity. A simple approach incorporating spin-echo with long delays instead of DPFGSE also afforded a sensitive spectrum. Practical aspects of these ROESY experiments are illustrated using the cyclic tetrasaccharide cyclo-{-->6}-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->6)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->).     

On the use of actinometric emission spectroscopy in SF6-O2 radiofrequency discharges: Theoretical and experimental analysis

A comparison of the results obtained by solving the Boltzmann equation with the experimental results from optical emissions obtained in SF₆-O₂ radiofrequency discharges, when N₂, Ar, and He are also admitted as actinometers, has allowed us to explore the potentialities and limits of actinometry. The use of different actinometers also allowed us to monitor the evolution of the electron distribution functions as a function of the plasma parameters.     

The Dependence of Gliding Arc Gas Discharge Characteristics on Reactor Geometrical Configuration

The dependence of gliding arc gas discharge characteristics, including gas flow field, arc column motion and volatile organic compounds (VOCs) decomposition performance, on reactor configuration parameters was investigated based on numerical simulation and laboratory experimental findings. For a given supply voltage (10 kV) and a certain nozzle outlet diameter (1.5 mm), increasing the electrodes gap (1–4 mm) or decreasing vertical distance between electrode throat and nozzle outlet (25–10 mm) will increase the gas flow rate through the electrode throat, the gas velocity in the plasma region, the arc column velocity, the maximum attainable position of the arc column and the electrical power consumption, also, higher VOCs decomposition rate and lower specific energy requirement are observed according to the n-butane and toluene decomposition experiments.     

Efficient Degradation of Nitrobenzene Induced by Glow Discharge Plasma in Aqueous Solution

The oxidative degradation of nitrobenzene (NB) induced by gaseous glow discharge plasma in contact with aqueous solution was investigated. The experimental results indicated that NB removal obeyed first-order kinetics under certain applied currents. The major degradation byproducts such as nitrophenols, phenol, 1,3-dinitrobenzene and carboxylic acids have been detected. The distribution of nitrophenols follows the order o- > p- > m- and oxalic, formic and acetic acids are major carboxylic intermediates. The eventual products were nitrate ion and carbon dioxide. During the treatment, a large amount of hydrogen peroxide was produced. Addition of ferrous or ferric ions into the solution greatly enhanced the degradation rate due to Fenton’s reaction. The energy efficiencies of NB removal and hydrogen peroxide formation were compared with those of other discharges. Hydroxyl radicals were shown to be the most likely species responsible for NB degradation     

Simple and quick rotational temperature determination in N2-containing discharge plasma

A quick spectroscopic method of rotational temperature determination based on the low-resolution emission spectrum of the N₂ (v=2v=()) vibronic band profile of the second positive system iras developed. The new method of molecular gas temperature determination was used in an rf glow discharge excited in N₂ and N₂ + Ar + B₂ H₆ gas mixture at u pressure range 500–13011 Pa. This method of molecular gas temperature measurement is applicable to nonisothermic plasmas used in plasma-chemical reactors.     

Research on successive preparation of nano-FeNi alloy and its ethanol sol by pulsed laser ablation

Since Ogale et al.[1,2] firstly prepared metastable matter by pulsed laser ablation at the solid target sub-merged in liquid, there has been a great interest in it. Tokura et al.[3] prepared carbon films in the water by pulsed laser ablation. Zheng et al.[4—6] prepared nano and cluster matters with different shapes through pulsed laser ablation at interface of liquid and solid target. Yang et al.[7,8] prepared cube nano-nitride boron crystalloid and nano-diamond crystalloid with the same meth…     

Self-diffusion of polystyrene in solution 1. Experimental results of the NMR pulsed field gradient technique

We report self-diffusion measurements for polystyrene dissolved in benzene and chloroform using the NMR pulsed field gradient technique. The observed echo attenuations point to dynamic exchange processes or cluster formation in the semidilute solution. The experimental results are compared with theoretical predictions from the reptation mechanism and the blob theory. There is qualitative agreement, but a more comprehensive analysis of the data and results from experiments with polymer mixtures show that polymer self diffusion in semidilute solutions cannot be explained by the reptation mechanism in its simple form.     

Crystalline carbon nitrides: thin films and bulk samples

A new method was developed for the preparation of bulk samples of crystalline carbon nitride on exposure of an amorphous nitrogen- and carbon-containing material to high temperature and ultrahigh pressure in the presence of crystallization seeds. Amorphous carbon nitride whose composition was close to C₃N₄was used as a starting material. Thin films of crystalline carbon nitrides prepared by the laser-electric discharge method were used as crystallization seeds.     

Emission Characteristics of Jet Configurations for Jet-Boosted Glow Discharge Atomic Emission Spectrometry

Comparisons of emission characteristics and analytical performance have been made between three types of jet configuration. These include cone-jet configuration, six-jet configuration, and cylinder-jet configuration. The cone-jet configuration shows the highest emission intensity among all jet configurations. Regardless of the jet configuration, the Cu II 224.70 nm emission line was found to be the most dominant of all Cu emission lines. The intensity ratios of the resonance line Cu I 324.75 to a nonresonance line Cu I 282.44 nm was 1.3 for the six-jet configuration, 2.3 for the cylinder jet, and 2.8 for the cone jet. This may indicate that self-absorption was significant in six-jet configuration. The effects of main and auxiliary gas flow rates on the emission characteristics for the cone jet configuration were also investigated. The intensity of Cu I at 324.75 and 327.40 nm decreases about 30% when the gas flow rate increased from 0 to 150 ml/min, while the intensities of Cu II 224.70 nm and the UV–Visible Cu I 510.55-, 515.32-, and 521.82-nm lines increased by a factor of 2 to 3. The decrease in intensity of the resonance line relative to the Cu II and Cu I green lines may be caused by self-absorption. The cone-jet and six-jet configurations show comparable values of precision, linearity, and detection limits, while the cylinder-jet configuration provides the worst analytical performance among three types of jet configurations. The linearity of the calibration curve was the worst in the six-jet configuration due to self-absorption.     

Rapid evaluation of charge/discharge properties for lithium manganese oxide particles at elevated temperatures

A microelectrode technique was applied to investigate the electrochemical properties of LiMn₂O₄ particles at elevated temperatures. Cyclic voltammograms of LiMn₂O₄ were measured after the particles were exposed to the electrolytes. This technique results in rapid and precise evaluation of the redox behavior of the materials. A significant capacity fading was observed in 1 M LiPF₆/EC+PC electrolytic solution, which indicates that both LiMn₂O₄ and LiPF₆ participate in the reaction to produce an inert material on the particle surface. Next, the capacity fading for two different BET surface area particles were compared using 1 M LiPF₆/EC+PC at 50 °C. The reaction was found not to be controlled by the surface area. Finally, a Li_1.1Mn_1.9O₄ particle was employed. The fading in discharge was ca. 10% for 50 cycles even at 50 °C, which means that the partial substitution of Mn in LiMn₂O₄ by Li substantially enhanced the capacity stability. Electronic Publication