Determination of lead in the urine of exposed and unexposed adults by extraction and flow-injection/atomic absorption spectrometry

Lead is extracted from urine with ammonium pyrrolidien dithiocrbamate into methyl isobutyl ketone, and 20 μl of the extract is injected into a water carrier stream in a flow-injection/atomic absorption system. The procedure is simple, quick, accurate and reproducible. Recoveries are 96–105%. The mean urine lead contents of 20 unexposed and 20 printing-press lead exposed workers was found to be 39.0 ± 8.3 and 71.7 ± 26.3 μg Pb l^?1, respectively.     

A minimal multiconfigurational technique

A direct minimization method previously presented by the authors is applied here to biconfigurational wave functions. A very moderate increasing in the time by iteration with respect to the one-determinant calculation and good convergence properties have been found. So qualitatively correct studies on singlet systems with strong biradical character can be performed with a cost similar to that required by Hartree-Fock calculations.     

Synthesis of 4H-3,1-benzoxazines, quinazolin-2-ones, and quinoline-4-ones by palladium-catalyzed oxidative carbonylation of 2-ethynylaniline derivatives

An effective and straightforward approach to the synthesis of 4H-3,1-benzoxazines 3 and 4, quinazolin-2-ones 5, and quinoline-4-one derivatives 6 and 7 is provided by palladium-catalyzed cyclization-alkoxycarbonylation of variously substituted 2-(trimethylsilanyl)ethynylaniline amide or urea derivatives 2. Reactions are carried out in 7:1 MeCN/MeOH at 65 or 75 degrees C in the presence of catalytic amounts of 10% Pd/C in conjunction with Bu(4)NI and KF and under 2.4 MPa of a 3:1 mixture of CO and air. Anti and syn 6-exo-dig cyclization modes account for the formation of the two stereoisomers. Isomerization of the vinylpalladium intermediate may occur as well. Formation of a double carbonylation product 7r and of a gem-dimethoxycarbonylation product 6s, whose structures have been determined by X-ray diffraction analysis, is justified through an unusual type of rearrangement.     

Olive mill wastewater treatment by a pilot-scale subsurface horizontal flow (SSF-h) constructed wetland

Performances of a pilot-scale reed bed for the olive mill wastewater (OMW) treatment were investigated, by monitoring influent and effluent pH, total suspended solids (TSS), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), total phosphorus and polyphenols. In order to reduce the suspended matter concentration and to avoid clogging, OMW was pre-treated by adding lime putty, calcium hydroxide and hydraulic lime. The best results were obtained with 2 g/L of hydraulic lime. Pre-treated OMW was dosed in the reed bed at dilution ratios of 1/3 and 1/10 (v/v), pointing up that the latter only did not give rise to reed suffering and allowed to obtain good and durable removal efficiencies, above all for COD (74.1+/-17.6%) and polyphenols (83.4+/-17.8%). Recycling of the effluent was quite effective for the improvement of the wastewater quality, allowing a further removal of 26-70%, depending on the parameter taken into account. A post-dosage study, carried out by feeding the reed bed with the effluent of an activated sludge plant, pointed up a rapid decreasing of the outlet concentrations of the investigated parameters to values compatible with Italian regulations concerning wastewater discharge in surface water. Polyphenols were the exception, being their outlet concentration at the end of post-dosage study around 2 mg/L.     

Single electron traps at the surface of polycrystalline MgO: assignment of the main trapping sites

Paramagnetic centers at the surface of ionic oxides in the form of trapped electrons can be generated by exposure of the material to alkali metal or hydrogen atoms or of molecular hydrogen under UV irradiation. For many years, it has been assumed that the resulting paramagnetic centers consist of oxygen vacancies filled by one electron. High-resolution electron spin resonance spectra and ab initio quantum chemical calculations show that the paramagnetic centers consist of (H(+))(e(-)) electron pairs formed at morphological irregularities of the surface. At least three different kinds of (H(+))(e(-)) centers, [A], [B], and [C], have been identified with abundances of 80%, 10%, and 8%, respectively. In this work, we compare a wide set of measured and computed g-factors and hyperfine coupling constants of the unpaired electron with the surrounding (25)Mg, (17)O, and (1)H nuclei and we propose a general assignment of the centers. (H(+))(e(-)) pairs formed at Mg(4c) ions at steps and edges account for species [A], centers formed at Mg(4c) ions at reverse corners correspond to species [B], and species [C] originates from (H(+))(e(-)) pairs formed at Mg(3c) ions at corners and kinks.     

Shaping Solid-State Supramolecular Cavities: Chemically Induced Accordionlike Movement of gamma-Zirconium Phosphate Containing Polyethylenoxide Pillars

The hydrophilic oxygen atoms of polyethylenoxide chains inserted as pillars in gamma-zirconium phosphate form hydrogen bonds with the acid groups of the host. As a result the pillars are almost perpendicular to the gamma layers. Upon changing the pH level of the supernatant solution the hydrogen bonds are broken and the pillars become almost perpendicular to the layers (shown schematically). Thus there is a reversible enlargement-shortening of the interlayer space.     

Synthesis of some dibenzodiazepinone derivatives as potent and m2-selective antimuscarinic compounds

Two series of 5-[[4-[4-(dialkylamino)butyl]-l-cyclohexyl]acetyl], and 5-[(dialkylamino)acyl]-10,11-dihydro-5H- dibenzo[b,e][1,4]diazepin-11-ones were synthesized as potential m2-selective ligands 1,2. Their affinity and selectivity for the muscarinic cholinergic receptor m-AChR subtypes were determined. Replacing a nitrogen with CH in the piperidine ring of 5-[[4-[4-(dialkylamino)butyl]-l-piperidinyl]acetyl]-10,11-dihydro-5H-dibenzo-[b,e][1,4]diazepin-11-ones 3 significantly altered the affinity and selectivity to the muscarinic receptor subtypes.     

Optimization of culture medium and conditions for penicillin acylase production by Streptomyces lavendulae ATCC 13664

The culture medium for Streptomyces lavendulae ATCC 13664 was optimized on a shake-flask scale by using a statistical factorial design for enhanced production of penicillin acylase. This extracellular enzyme recently has been reported to be a penicillin K acylase, presenting also high hydrolytic activity against penicillin V and other natural aliphatic penicillins such as penicillin K, penicillin F, and penicillin dihydroF. The factorial design indicated that the main factors that positively affect penicillin acylase production by S. lavendulae were the concentration of yeast extract and the presence of oligoelements in the fermentation medium, whereas the presence of olive oil in the medium had no effect on enzyme production. An initial concentration of 2.5% (w/v) yeast extract and 3 microg/mL of CuSO4 x 5H2O was found to be best for acylase production. In such optimized culture medium, fermentation of the microorganism yielded 289 IU/L of enzyme in 72 h when employing a volume medium/volume flask ratio of 0.4 and a 300-rpm shaking speed. The presence of copper, alone and in combination with other metals, stimulated biomass as well as penicillin acylase production. The time course of penicillin acylase production was also studied in the optimized medium and conditions. Enzyme production showed catabolite repression by different carbon sources such as glucose, lactose, citrate, glycerol, and glycine.     

Integrated production of ethanol fuel and protein from Coastal Bermudagrass

The herbaceous crops that may provide fermentable carbohydrates for production of fuels and chemicals also contain 10–20% protein. Protein coproduction with biomass-derived fuels and chemicals has important advantages: (1) food and fuel production can be integrated, and (2) protein is a high-value product that may significantly improve overall process economics. We report the results of an integrated approach to producing protein and fermentable sugars from one herbaceous species, Coastal Bermudagrass (CBG). The ammonia fiber explosion (AFEX) process makes possible over 90% conversion of cellulose and hemicellulose to simple sugars (about 650 mg reducing sugars/g dry CBG) at 5 IU cellulase/g vs < 20% conversion for untreated CBG. The AFEX treatment also improves protein extraction from CBG; over 80% protein recovery is possible from AFEX-treated CBG vs about 30% recovery from untreated CBG.     

Use of a55Fe radioisotope for the determination of titanium in laterite samples via energy dispersive X-ray fluorescence

A rapid method for the determination of titanium in geochemical samples using a⁵⁵Fe radioisotope as the extraction source coupled to a Si(Li) detector and a PDP-11.05 computer is described. The relative standard deviation for a thin sample about 100 mg in weight is less than 4% and it is achieved in a fluorescent time of 100 sec. Data are given for the use of two different internal standards, KBrO₃ and K₂Cr₂O₇, the latter being more precise. The values for five international reference standards are in agreement for this method with the reported values. Finally, besides being rapid, no hydrofluoric acid dissolution of fusion is necessary as in atomic absorption and classical methods. This paper was presented at the XX Colloquium Spectroscopium Internationale, 8 Aug.–7. Sept. 1977, Prague, Czechoslovakia.