Lead determination in wine by potentiometric stripping analysis

Summary Computerized potentiometric stripping analysis (PSA) was used for lead determination in wine samples. In this method sample preparation before determination is limited to dilution with an appropriate supporting electrolyte (0.5 mol/l HCl and 40 mg/l Hg²⁺). Due to the very high sensitivity, the time needed for one determination can be reduced to 2 min. The method was tested by lead determination in different wines, different concentration ranges and in one European interlaboratory comparison organized by BCR. Using PSA it is possible to simultaneously determine cadmium, lead and copper in wine. For other elements such as Bi, Tl, Hg, Sn, As, Zn the determination procedures are under development. The PSA equipment is available on the market, small in size, relatively cheap and it does not require any special installation such as gas or cooling water.     

Real time task scheduling allowing fuzzy due dates

The paper deals with periodical task scheduling. The tasks are described by fuzzy due dates and fuzzy execution times. The goal of scheduling is to find an optimal assignment of priorities such that the satisfaction associated with due dates and execution times be minimized. The paper shows how the rules associated with task priorities improve the optimal assignment search.     

Strongly indecomposable finite groups

Motivated by examples in infinite group theory, we classify the finite groups whose subgroups can never be decomposed as direct products.     

The origin of embryonic laser cracks

The problem of the initial stage of crack formation in PMMA subjected to laser action is investigated. It is shown that the cracks develop from gas-filled cavities (centers). These centers have been experimentally investigated, and the center-crack transition carefully studied.Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 82–89, January–February, 1973.     

Longuet-Higgins groups of XeF6

A complete permutational analysis of the XeF₆ dynamics is presented. The Longuet-Higgins group for each mode of rearrangement is obtained. On the basis of the splitting scheme of rigid molecule levels and statistical weights and selection rules for the non rigid molecule levels, it appears that transverse digonal twists and turnstile mechanisms have the same spectroscopic effects as the BPR -6 mechanisms. Hence, the previous interpretation of IR and Raman spectra is consistent with tunneling through transverse digonal twists and turnstile mechanisms as well as through BPR -6.     

Inclusiveπ° production in 360 GeVpp interactions using the european hybrid spectrometer

The intermediate and forward gamma detectors of EHS are used to reconstructπ°'s produced by 360 GeV/cpp interactions in the Rapid Cycling Bubble Chamber (RCBC). Using thepp forwardbackward symmetry, the inclusiveπ° production cross section is obtainedσ _π°=(132±11) mb. The averageπ° multiplicity is determined as a function of the charged particle multiplicity. The (1?x) dependence is given for differentp _T regions.     

Thermal stability and the behaviour in organic solvents of some poly(ester-siloxane)urethanes

Three new chemically crosslinked polyurethanes were synthesized. Their behaviour in organic solvents and in dynamic heating conditions was studied. Predictions regarding the thermal stability have been made by using the isoconversion kinetic method.     

Generalized brownian motion in a double-well potential

The computational algorithm recently developed by Giordano, Grigolini and Marin makes it straightforward to investigate Kramers; theory of chemical kinetics. It is also possible to investigate a generalized version of this theory taking the non-white nature of noise into account.     

Polarization spectroscopy of atomic oxygen by dye and semiconductor diode lasers

Summary We used polarization spectroscopy to perform a high-resolution investigation of atomic oxygen in the visible and near-infrared spectral region by means of dye and semiconductor diode lasers. We measured the fine structure of the highly excited 4d ⁵ D level and resolved the hyperfine structure of the metastable 3s ⁵ S ₂ level of¹⁷O. Isotope shift values are also reported for several transitions of the three stable oxygen isotopes (¹⁶O,¹⁷O,¹⁸O). Polarization lineshapes are discussed and compared with those obtained in saturation techniques.