Efficient synthesis of diorganyl selenides via cleavage of Se-Se bond of diselenides by indium(III) catalyst and zinc

A simple and efficient procedure for the synthesis of unsymmetrical diorganyl selenides from an one-pot indium(III) catalyzed procedure, in the presence of zinc, has been developed. Various organic halides and even the unreactive organic chlorides underwent the reaction efficiently. Also diaryl and dialkyl diselenides underwent the coupling reaction.     

Seasonal variations of 222Rn and SGD fluxes to Ubatuba embayments, São Paulo

Summary We describe here an application of excess ²²²Rn to estimate submarine groundwater discharge in a series of small embayments of Ubatuba, S?o Paulo State, Brazil. Excess ²²²Rn inventories obtained in 11 vertical profiles varied from (3.3±1.1) ^. 10³ to (19±5) ^. 10³ dpm ^. m^-2. The estimated total fluxes required to support the inventories varied from (0.6±0.2) ^. 10³ to (3.4±0.9) ^. 10³ dpm ^. m^{-2 .} d^-1. Considering these results, the submarine groundwater discharge advective rates necessary to balance the sub-pycnocline fluxes calculated in Ubatuba embayments ranged from 0.06 to 1.9 cm ^. d^-1. During the period of this investigation (from March/03 to May/2004), the highest ²²²Rn in excess inventories were observed late in the summer season (March). Taking into account all vertical profiles established, the relative variability was 67%. Although, if we consider only the fluxes determined in both Flamengo and Fortaleza embayments, the relative variation was 21%.     

Monitoring the thermal efficiency of fouled heat exchangers: A simplified method

Fouling is a problem whether we are aware of it or not. In an industrial plant, it is important not only to be able to measure the buildup of unwanted deposits, but also to do it in the simplest and most economically possible way. This paper addresses the question of monitoring fouling in an oil refinery plant, where the high number of heat exchanger units and the variability of the feedstock charge pose additional problems in terms of the practicability of following the energetic performance of such equipment. In this case, the flow rates and quality of the fluids flowing through the heat exchangers do not usually correspond to the design conditions, because they change with time. Therefore, to assess the fouling level of the exchangers, the day-to-day measured thermal efficiency should not be compared with the efficiency predicted in the design calculations. The latter should be recalculated by introducing whenever necessary new values of flow rates, physical properties, and so forth, and by evaluating new heat transfer coefficients. However, the procedures are too time consuming to be applied frequently. The present work describes a simplified method for following heat exchanger performances, based on the assessment of the number of transfer units and thermal efficiencies, where the effects of changing the feedstock charge, particularly the flow rates of the fluids, are taken into account. The only data that need to be collected are the four inlet/outlet temperatures of the heat exchanger unit and one of the flow rates. Several heat exchanger units in an oil refinery were successfully monitored by means of this method, and it was found that the variations in the physical properties did not significantly affect the results obtained for the particular plant under study.     

Characterization,thermal properties and phase transitions of amazonian vegetable oils

Thermal profiles of buriti pulp oil (Mauritia flexuosa Mart.), tucumã pulp and kernel oils (Astrocarium vulgare Mart.), rubber seed oil (Hevea brasiliensis), passion fruit oil (Passiflora edulis) and ucuúba butter (Virola surinamensis) were analyzed by thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). Gas chromatography and calculated iodine values were performed to determine the fatty acid profile and to measure the degree of unsaturation in these oils, respectively. The TG curves showed three steps of mass loss, which can be attributed to the degradation of polyunsaturated, monounsaturated and saturated fatty acids. The DSC crystallization and melting curves are reported and depended on the fatty acid composition. Usually, oil samples with a high degree of saturation showed crystallization and melting profiles at higher temperatures than the oils with a high degree of unsaturation. The data obtained by physicochemical analysis of oil samples were analyzed by principal component analysis and hierarchical cluster analysis to increase understanding of the data set, examining the presence or absence of natural groupings between samples.     

Jacobson–Bourbaki Theory with Parameters

In this paper we generalize the classical Jacobson–Bourbaki correspondence for field extensions to K-vector space extensions (K a field). Namely, for such extensions, we state and prove a correspondence theorem – the Jacobson–Bourbaki correspondence with parameters. Some examples are provided.     

Particulate emission and element behaviours in a large coal power plant

Summary Particulate-matter release into the stack effluents of a large coal-fired power station was characterized. Particulate samplings were carried out in the chimney, downstream the electrostatic precipitation system, by means of an isokinetic probe. Concentration and size distribution of total particulate mattern as well elemental composition as a function of particle size were detemined. Concentrations of up to 24 elements were measured for whole filters by PIXE and AAS technique. Element enrichments in smaller particles and in emitted ashes and their behaviours in combustion are also studied. Work supported by ENEL-DSR.     

MR imaging findings of infectious cholangitis

The purpose of this study was to evaluate the appearance of infectious cholangitis on MRI. The MR images of 13 patients (9 women, 4 men; age range, 14-79 years) with clinically confirmed infectious cholangitis, who represent our complete 9.5 year experience with this entity, were retrospectively evaluated. All MR studies were performed at 1.5 T and included: in-phase and out-of-phase T(1)-weighted spoiled gradient echo (SGE), T(2)-weighted fat-suppressed echo train spin echo, single shot T(2)-weighted sequences, and serial postgadolinium T(1)-weighted SGE sequences without and with fat-suppression. The biliary ductal system was evaluated regarding presence of dilatation, stenosis, wall irregularities, wall thickening, and gadolinium enhancement of duct walls. The liver parenchyma was evaluated regarding focal signal abnormalities on precontrast and serial postgadolinium images. Biliary ductal dilatation was observed in 100% of patients. Mild to moderate thickening of bile duct walls combined with increased enhancement on postgadolinium images was observed in 92% of patients. The liver parenchyma showed periportal or wedge-shaped areas of hyperintense signal on T(2)-weighted images in 69% of patients. On T(1)-weighted images, 54% of patients showed areas of hypointense signal and 15% of patients showed wedge-shaped hyperintense areas. Areas with increased enhancement on immediate postgadolinium SGE were observed in 58% of patients, and in 42% of patients increased enhancement persisted on 2 min postgadolinium fat-suppressed images. Distinctive MRI findings on pre- and postgadolinium images are appreciated for infectious cholangitis.     

A study about the environmental impact of a large particulate matter source by means of a sampling station interactive with the environment

Summary The contribution of the particulate matter relapsed from a large oil-fired power plant into the surrounding environment was investigated by means of an automated sampling station interactive with the environment. This station performs real-time measurements of some meteorological parameters and of the concentrations of some gaseous pollutants, thus carrying out aerosol samplings only in situations of environmental interest such as fumigation or blank conditions. Elemental composition of the fractionated particulate matter and morphological observations on single particles were obtained using PIXE (particle-induced X-ray emission) and SEM (scanning electron microscopy) techniques.

---

Riassunto Il contributo all’inquinamento dovuto all’emissione di materiale particolato da una centrale termoelettrica ad olio combustibile è stato studiato utilizzando una stazione di prelievo funzionante in modo interattivo con l’ambiente. Questa stazione è in grado di effettuare prelievi di aerosol atmosferico pilotati da prefissati valori di parametri ambientali, sia di tipo meteorologico che di concentrazione di alcuni inquinanti gassosi, che permettono di discriminare situazioni di ricaduta del pennacchio da situazioni tipicamente di fondo. La composizione elementare del particolato, frazionato nelle diverse classi dimensionali, è stata ottenuta mediante la tecnica multielementare PIXE (emissione di raggi X indotte da particelle), mentre osservazioni morfologiche sulle particelle campionate sono state effettuate mediante SEM (microscopia elettronica a scansione).