On the asymptotic properties of the Rees powers of a module

Let R be a commutative ring and G a free R-module with finite rank e>0. For any R-submodule E⊂G one may consider the image of the symmetric algebra of E by the natural map to the symmetric algebra of G, and then the graded components E_n, n≥0, of the image, that we shall call the n-th Rees powers of E (with respect to the embedding E⊂G). In this work we prove some asymptotic properties of the R-modules E_n, n≥0, which extend well known similar ones for the case of ideals, among them Burch’s inequality for the analytic spread.     

Electroanalytical chemistry of cadmium complexes of amino acids at the ionic strength of seawater (0.70 M NaCLO4): Part II

The complexation of cadmium with naturally occurring amino acids was studied at the ionic strength of seawater (0.70 M in sodium perchlorate medium) and at 25±0.1°C by differential pulse polarography and potentiometry with a glass electrode.The Miniquad program was used to analyse and refine the results of the potentiometry.Although the stability of the complexes is very similar since the chelate groups of the ligands are the same, the rate of dissociation of the complexes can be different.The kinetic aspect has been studied by cyclic voltammetry which is under the influence of the type of adsorption. When this is strong the diffusion and adsorption peaks are well separated and, in principle the rate constant of dissociation of the complex can be determined. If there is weak adsorption the diffusion peak is distorted by adsorption and kinetic studies cannot be done. the adsorption of the ligands themselves has been studied by ac polarography at a 90° angle phase and it has been noticed that ligands with π bonds, sulphur groups or with long hydrocarbon chains are more adsorbed than those without.     

Optical studies on the red luminescence of InGaN epilayers

Photoluminescence, photoluminescence excitation and time-resolved photoluminescence studies were performed in a partially relaxed InGaN epilayer, and exhibiting a 3D growth mode at the surface. Two emission bands, a red (centred at 1.88 eV) and a blue (centred at 2.58 eV) were observed. In order to investigate their origin and their relation with the strain relaxation along the growth direction, the sample was etched. After etching, only an asymmetrical broad emission band centred at 2.15 eV was observed.The decrease of decay time and the increase of the band edge absorption energy with increasing monitored photon energy, along the red emission, are assigned to the effect of localization of excitons at potential minima, originated in compositional and strain inhomogeneities of the sample. Therefore, the blue shift observed on this band with an increase in temperature, is caused by the population of higher energy states. The large difference between the luminescence intensities, decay times and the thermal quenching of the red and blue (centred at 2.58 eV) band is also accounted for by the localization model. It is demonstrated that the luminescence observed after etching is a superposition of two bands, one originated from the InGaN film, and the other from the GaN underlayer. The large difference between absorption and emission energies, compared with those measured in the as-grown sample, within the same spectral region, indicates that this emission has a different origin. It is suggested that deep levels might be responsible for the luminescence observed after etching.     

Synthesis of indolizidines and pyrrolizidines through the [2 + 2]cycloaddition of five-membered endocyclic enecarbamates to alkyl ketenes. Unusual regioselectivity of Baeyer-Villiger ring expansions of alkyl aza-bicyclic cyclobutanones

The total syntheses of two indolizidine skeletons and of the necine base (+/-)-platynecine were accomplished in a concise manner with good overall yields starting from a common five-membered endocyclic enecarbamate. These syntheses feature a [2 + 2]cycloaddition of the five-membered endocyclic enecarbamate 5 to alkylketenes that proceeded in high yields and with high stereoselectivity to provide an endo alkyl cycloadduct as the major or only product. The minor exo alkyl cycloadducts, which can be observed in some [2 + 2]cycloadditions, seem to derive from the endo cycloadduct, the putative kinetic product, by epimerization. An unusual regioselectivity was observed for the Baeyer-Villiger oxidation of 7-alkyl-2-azabicyclic cyclobutanones. Endo-7-alkyl cycloadducts ring-expanded exclusively to a gamma-lactone in which oxygen is inserted into the C6-C7 bond in preference to the bridgehead C5-C6 bond. With the exo-7-alkyl cycloadduct the regioselectivity of the Baeyer-Villiger oxidation is drastically reduced, leading to mixtures of regioisomeric lactones in a ratio of approximately 1.5 to 1. It is hypothesized that the steric strain built into the Criegee cyclobutane intermediate is the regioselective controlling factor in these oxidations, overriding any stereoelectronic bias for ring expansion. A rationale for the mechanism of the [2 + 2]cycloaddition involving enecarbamates and ketenes is presented, which seems to involve the participation of an N-acyliminium-enolate intermediate.     

Calibration of the LNMRI Secondary Standard Ionization Chamber for 131I capsules used in nuclear medicine

The radionuclide ¹³¹I has been increasingly used in nuclear medicine therapy procedures. Nowadays, the ¹³¹I source administered to the patient is manufactured in two different geometries: solution and capsules. The purpose of this study is the accurate measurement of the activity present in a ¹³¹I capsule without destroys it. The methodology to determine the capsules activity is to obtain the calibration factor of an IG12 secondary standard activity measurement system based on the IG12 well-type ionization chamber set up at Brazilian national metrology laboratory for ionizing radiation (LNMRI) of institute of radiation protection and dosimetry (IRD).The result obtained, 6.4670?±?0.0381?×?10^?18?A?Bq^?1, is quite similar to the calibration factor of the ¹³¹I solution contained in the standard ampoule geometry, 6.4515?±?0.0368?×?10^?18?A?Bq^?1. After obtaining the calibration factor it was used to measure ¹³¹I therapy capsules in order to check the performance of radionuclide calibrators of some Brazilian nuclear medicine centers.     

Herbal medicine physical quality evaluation by thermal analysis using adapted Ozawa method

Journal of Thermal Analysis and Calorimetry - The aim of this study was to evaluate the physical quality of Tabebuia caraiba (Mart.) Bur. powder, separately in three batches of different particle...     

New In Vitro-In Silico Approach for the Prediction of In Vivo Performance of Drug Combinations

Pharmacokinetic (PK) studies improve the design of dosing regimens in preclinical and clinical settings. In complex diseases like cancer, single-agent approaches are often insufficient for an effective treatment, and drug combination therapies can be implemented. In this work, in silico PK models were developed based on in vitro assays results, with the goal of predicting the in vivo performance of drug combinations in the context of cancer therapy. Combinations of reference drugs for cancer treatment, gemcitabine and 5-fluorouracil (5-FU), and repurposed drugs itraconazole, verapamil or tacrine, were evaluated in vitro. Then, two-compartment PK models were developed based on the previous in vitro studies and on the PK profile reported in the literature for human patients. Considering the quantification parameter area under the dose-response-time curve (AUC_effect) for the combinations effect, itraconazole was the most effective in combination with either reference anticancer drugs. In addition, cell growth inhibition was itraconazole-dose dependent and an increase in effect was predicted if itraconazole administration was continued (24-h dosing interval). This work demonstrates that in silico methods and AUC_effect are powerful tools to study relationships between tissue drug concentration and the percentage of cell growth inhibition over time.     

Thermodynamics of uptake of cadmium by Chlorella marina

From voltammetric titration curves of living Chlorella marina cells with cadmium ion, at constant pH, the surface binding capacity of the alga was determined and interpreted in terms of average conditional equilibrium constants and of differential equilibrium function. Since the alga can live in estuaries, the influence of ionic strength and competition of alkaline and alkaline earth cations has been considered. Cadmium complexation with dead algae killed by heat or using formaldehyde has also been studied for comparison.