Spectrophotometric determination of total vicinal diketones with isoniazide and a zirconium salt

Summary A method has been worked out for the spectrophotometric determination of total vicinal diketones.It is based on the distillation of diacetyl and/or 2,3-pentanedione, the subsequent condensation with isoniazide (yielding the corresponding hydrazones), the complexation with zirconium(IV) and the photometric measurement of the resulting yellow complexes at 410 nm. The two reactions were studied separately. Variables such as pH, heating time, and excess reactives are discussed. The method may be used for the determination of these compounds in foods.     

Regional Variations in Energy Consumption of Appliances: Conditional Demand Analysis Applied to Brazilian Households

Estimating the true consumption of appliances in use is important both for modeling and short term forecasting of electricity demand, as well as for planning and assessing Demand Side Management (DSM). This paper applies the new technique known as Conditional Demand Analysis (CDA) to estimate consumption of these appliances. This was made possible due to a major survey carried out for the Brazilian National Electricity Conservation Program by the Brazilian electric utility companies while they were still state owned. Results were checked against traditional appliance energy consumption figures, and investigations carried out to ascertain if differences were due to regional variations in consumption patterns from northern to southern Brazil.     

Interaction times in the19F+63Cu dissipative heavy ion reaction

Coherence energies extracted from excitation functions and angular distributions for the fragments emitted in the¹⁹F+⁶³Cu reaction, measured in the range θ_lab=10° to 120° at incident energies between 100 to 108 MeV (lab.), were compared to the Kun model of dissipative collisions. An overall agreement was found for the angular distributions at forward angles. The general behavior of coherence energies was also properly described and interaction times were deduced.     

Use of hydride generation-atomic absorption spectrometry to determine the effects of hard ions, iron salts and humic substances on arsenic sorption to sorghum biomass

At present, there is a great interest in studying new sorbent materials for the removal of arsenic from aqueous solutions because of its high toxicity and adverse effects on human health. In previous research, sorghum biomass was found to be an efficient and economic sorbent for the removal of arsenic from aqueous solutions. In this investigation, the effects of CaCl₂, MgCl₂, FeSO₄, MgSO₄, Fe(NO₃)₃, and humic substances (peat moss, humin and humic acids) on arsenic binding to sorghum biomass were evaluated. Among these compounds, only iron salts were found to positively increase the sorption of arsenic to sorghum biomass. In addition, the sorption equilibrium was reached faster when the reaction mixture contained iron salts. However, an overall reduction of 21% of arsenic sorption to sorghum biomass was observed in the presence of MgSO₄. This interference may be due to the presence of sulfate ions, instead of the hard cations, that could be in competition with As for the same interaction sites or ligands. Peat moss, humins and humic acid, extracted from sphagnum peat moss, significantly decreased the arsenic sorption to sorghum biomass.     

Rank 2 stable vector bundles on Fano 3-folds of index 2

Let X be a Fano 3-fold of the first kind with index 2. In this paper, we characterize the chern classes of rank 2 stable vector bundles on X and we find a bound for the least twist of a rank 2 reflexive sheaf on X which has a global section.     

Novel sesquiterpenoid esters from the nudibranch dendrodoris limbata

A novel sesquiterpenoid esterified by different fatty acids has been isolated from the digestive gland of the nudibranch $\text{Dendrodoris limbata}$.     

Some results on the Oberwolfach problem

Aequationes mathematicae -     

Intramolecular Diels-Alder reaction of 1-aminoisobenzofurans: Application to the synthesis of benzo[c]phenanthridines

Intramolecular Diels-Alder reactions of 1-aminoisobenzofurans give benzo[c]phenanthridines. The reactive intermediates are generated from o-(diazomethyl)benzamides.