Determination of trace amounts of antimony by spectrofluorimetry in hydrobromic acid medium at liquid nitrogen temperature

Trace amounts of antimony(III) may be determined in 6M hydrobromic acid by measurement of the red fluorescence of its bromide complex at -196 degrees , the optimum wavelengths of excitation and emission (360 and 586 nm respectively) being used. Calibration graphs are linear between 0.01 and 0.25 ppm. The effect of the presence of 50-fold molar amounts of 55 foreign ions has been studied. Of the ions studied, only iron(III) and tellurium(IV) interfere, and these may be tolerated at the 50- and 20-fold levels respectively. A 1000-fold molar amount of arsenic(III) causes no interference.     

(Z)-3-p-tolylsulfinylacrylonitrile as a chiral dienophile: diels-alder reactions with furan and acyclic dienes

The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles.     

Ion trapping and its effect on the conductivity of LISICON and other solid electrolytes

Conductivity data for the lithium ion conducting solid electrolyte, LISICON, Li_2+2xZn_1?xGeO₄ over a particularly wide composition range, 0.15 < x < 0.85, and over the temperature range ～25 to 150°C show that both the activation energy and preexponential factor pass through maxima around x ～ 0.4 to 0.5, at which the preexponential factor exhibits anomalously high values, ～10¹³ ohm^?1 cm^?1 K. An explanation is offered which involves the trapping of mobile Li⁺ ions by the immobile sublattice at lower temperatures. This model also accounts for ageing effects observed at lower temperatures in which the conductivity decreases slowly with time. In the isostructural Li⁺ electrolytes, Li_3+xSi_xY_1?xO₄ (Y = P, As, V), the compositional dependence of both the preexponential factor and activation energy is less marked and no evidence for ion trapping effects is observed.     

Preparation of 4-aryl-1,2,3,4-tetrahydro-3,3-dimethylisoquinolines and 1,2,3,4-tetrahydro-3,3-dimethyl-4-phenylbenz[h]isoquinolines

Synthetic procedures to prepare a number of 4-aryl-1,2,3,4-tetrahydro-3,3-dimethylisoquinolines and their benzo-homogues 3 through a series of intermediates are described. The condensation of α-(1-amino-1-methylethyl)arylmethanols 5 with arylaldehydes 6 gave imino derivatives 7 which on reduction with borohydride gave secondary amines 8 . The treatment of 8 with mineral acids gave the target compounds 3 . Biological activities of 3 are briefly discussed.     

Novel siloxane polymers as polymer electrolytes for high energy density lithium batteries

A variety of disubstituted (double-comb) polysiloxane polymers have been prepared containing linear, branched, and cyclic oligoethyleneoxide units, –(OCH₂CH₂)_n–, in the side chains and as part of the siloxane backbone. Copolymers, using mixtures of linear ethylene oxide side chains, were also synthesized. These polymers were doped with LiN(SO₂CF₃)₂ (LiTFSI, 1) and conductivities of the polymer-salt complexes were determined as a function of temperature and doping level. The maximum conductivity of these polymers at 25 ° C was 2.99 ×10^–4, for a copolymer containing equimolar amounts of side chains with n = 5 and 6.     

Copper(II) and nickel(II) complexes of 2-formylpyridine 3-piperidinyl-, 3-hexamethyleneiminyl- and 3-azabicyclo[3.2.2]nonylthiosemicarbazones

Summary Copper(II) and nickel(II) complexes of 2-formylpyridine 3-piperidinyl-, 3-hexamethyleneiminyl- and 3-azabicyclo-[3.2.2]nonylthiosemicarbazones were prepared and characterized spectroscopically. ¹H and ¹³C n.m.r. spectra of the thiosemicarbazones and a diamagnetic nickel(II) complex are reported, together with i.r., electronic and e.s.r. spectra of the metal complexes. The thiosemicarbazones and their copper(II) and nickel(II) complexes exhibit considerable growth inhibitory activity against Paecilomyces variotii, but show minimal activity against Aspergillus niger.     

The membrane free sonoelectroanalytical determination of trace levels of lead and cadmium in human saliva

In this paper, square wave anodic stripping voltammetry (SWASV), synergistically coupled with an ultrasonically enhanced preconcentration step has been shown to yield a quantitative determination of lead and cadmium in human saliva at a membrane free in situ plated mercury thin film glassy carbon electrode. The sensitivity was facilitated by acoustic streaming which promoted efficient mass transport to the electrode thus reducing sampling times. Cavitation was responsible for cleaning and activating the electrode surface, this was essential in order to obtain a reproducible and representative signal. In silent conditions electrode fouling leading to fluctuations in the baseline current and signal depression, precluded accurate quantitative analyses. The results presented herein provide an extension to the proof of concept given in the authors' earlier work, with the analysis of lead in human saliva as opposed to artificial saliva reported. We also address the hitherto unreported detection and determination of cadmium in this medium. Results for both were independently verified by inductively coupled plasma-mass spectroscopy (ICP-MS). Close agreement between lead concentration determined by sono-SWASV and independent and blind ICP-MS is reported for human saliva samples having a total lead content of 0.92 microg L(-1) and 5 microg L(-1) with a detection limit of 0.5 microg L(-1). Microaddition calibration data for cadmium additions of 0.0125 microg L(-1) to samples spiked with 2.5 microg L(-1) and 5.0 microg L(-1) (reflecting levels in workers occupationally exposed) exhibited close agreement with the known total cadmium in the samples. A detection limit of 1 microg L(-1) cadmium in saliva has been established.     

String vertices,overlap equations, τ functions and the Hirota equation

String vertices,V, are shown to satisfy a new type of overlap equation of the form as well as corresponding equations forA _n andB _n cycles. A special case of such an equation, when integrated, is shown to be the Hirota equation for the K–P hierarchy.