styrene is an important constituent of widely used organic solvents in industries for production of various synthetic materials. the use of solid-phase extraction (spe) has grown and is a fertile technique of sample preparation as it provides better results than those produced by liquidliquid extraction. in this study, spe has been optimized, regarding sample ph, sample concentration, sample fl...

phase sensitive detector described here has two principal applications: a- to produce a d.c out put proportional to- the amplitude of an incoming a,c signal and indicate, by the outut polarity, the phase of the signal with respect to an internal reference. b- to detect the presence of a signal of known phase and frequency which would otherwise be lost in «background noise» and to measure its am...

an experimental study of the phase inversion behavior of liquid-liquid dispersion has been conducted in a spray extraction column for systems of toluene / water, n-hexane/water, ccl4/water, toluene /water + glycerol (25 % wt), toluene + ccl4 (25 % wt) / water and toluene / acetic acid (5 % wt)/water. the effects of physical properties, mass transfer and column geometry on phase inversion have b...

in this paper, a new high dynamic range digitally-controlled oscillator (dco) for all-dpll systems is proposed. the proposed dco is based on using a δς modulator as a digital-to-analog converter. using δς dac can provide a very high resolution (18-bit) control on the dco. the δς dac output is a 2-level pulse signal that needs to be filtered for cancelling the out of band shaped noise. the used ...

the cycloaddition reaction of diphenylnitrilimine on the 1,5-benzodiazepines has been studied. new molecules of triazolobenzodiazepines type have been isolated and characterized.

background applying an appropriate method of analgesia in labor without alteration in its progression is of high importance. previous literature did not provide much information about the effect of various kinds of anesthesia on the duration of active phase of labor. objectives to assess the effect of painless labor methods on the duration of active phase of labor. patients and methods 80 pregn...

in this paper electrical conductivity measurements and optical investigations takes place in aot/ heptane/ (water or aqueous) systems. the water in oil system prepared with adding water in 50% by weight of aot/ heptane solution.  in other systems instead of water, aqueous solutions of 1) zinc acetate and water 2) potassium hydroxide and water were used. in each phase, the trend of the electrica...

the melt-phase synthesis of dioctyltin (iv) and triphenyltin (iv) benzoates were carried outusing stoichiometric amounts of benzoic acids and the corresponding organotin (iv) compounds.the reagents were ground together in a mortar and fed into a boiling glass tube. a cannula tubewas inserted into the boiling tube to discharge accumulated gaseous products. a syringe ensureda continuous flow of d...

background and objectives: analytical methods for volatile organic compounds (vocs) in different samples need extraction of compounds, by applying hazardous solvents. solid phase micro-extraction (spme) is a solvent-free equilibrium extraction method, in which proper calibration can allow quantitative determinations of vocs at a very good sensitivity without the use of any organic solvent. vocs...