Niobium to alcohol mol ratio control of the concurring esterification and etherification reactions promoted by NbCl5 and Al2O3 catalysts under microwave irradiation

Alcohols and acids can be switched to produce ethers or esters by varying the alcohol to catalyst mol ratio, in a new etherification and esterification method using NbCl5/Al2O3 catalyst under "solvent free" conditions and promoted by MW (microwave) irradiation. A "two sites" mechanism for the reaction is proposed, in an attempt to clarify the tendency of the catalyst to be dependent on the alcohol alone during the esterification process. (c) 2008 Elsevier B.V. All rights reserved.

Monitoring the process mean and variance using a synthetic control chart with two-stage testing

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Size distribution and sex ratio in the spider crab Epialtus brasiliensis (Dana 1852) associated with seaweed on a rocky shore in southeastern Brazil (Crustacea, Decapoda, Brachyura, Majoidea, Epialtidae).

This study analyzed a population of the spider crab Epialtus brasiliensis, in regard to its size distribution, sex ratio and Sexual maturity. The study was conducted on a rocky shore in the Ubatuba region, state of Silo Paulo, Brazil, where a wide strip of algae covers the intertidal zone. A total of 378 specimens were obtained: 200 males (128 juvenile and 72 adult crabs) and 178 females (46 juveniles and 132 adults). Their Sizes ranged from 3.4 to 16.7 mm carapace length (CL). Taking into account that the pubertal and terminal molts are coincident in majid crabs, the maximum sizes attained by males and females are especially dependent on the factors that influence sexual maturity, mainly food resources, temperature and intraspecific competition. Males of E. brasiliensis occurred in all size classes, whereas females occurred only as far the 10th size class (12-13 min CL). file total sex ratio did not differ statistically from 1 : 1, but when the juvenile and adult specimens were analyzed separately the differences between sexes were significantly different, with higher proportions of immature males and mature females. The CL50 calculated for males and females was 10.4, and 6.9 min CL, respectively. Thus, males reach their sexual maturity at a larger size than females. This feature may be important for the reproductive strategy of this species, because larger males probably have greater reproductive Success.

A single statistic for monitoring the covariance matrix of bivariate processes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The use of landforms to predict the variability of soil and orange attributes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Growth and home range size of the gracile mouse opossum Gracilinanus microtarsus (Marsupialia: Didelphidae) in Brazilian cerrado

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Use of the Normalized Absorbance Ratio as an Internal Standardization Approach To Minimize Measurement Error in Enzyme-Linked Immunosorbent Assays for Diagnosis of Human Papillomavirus Infection

The serological detection of antibodies against human papillomavirus (HPV) antigens is a useful tool to determine exposure to genital HPV infection and in predicting the risk of infection persistence and associated lesions. Enzyme-linked immunosorbent assays (ELISAs) are commonly used for seroepidemiological studies of HPV infection but are not standardized. Intra-and interassay performance variation is difficult to control, especially in cohort studies that require the testing of specimens over extended periods. We propose the use of normalized absorbance ratios (NARs) as a standardization procedure to control for such variations and minimize measurement error. We compared NAR and ELISA optical density (OD) values for the strength of the correlation between serological results for paired visits 4 months apart and HPV-16 DNA positivity in cervical specimens from a cohort investigation of 2,048 women tested with an ELISA using HPV-16 virus-like particles. NARs were calculated by dividing the mean blank-subtracted (net) ODs by the equivalent values of a control serum pool included in the same plate in triplicate, using different dilutions. Stronger correlations were observed with NAR values than with net ODs at every dilution, with an overall reduction in nonexplained regression variability of 39%. Using logistic regression, the ranges of odds ratios of HPV-16 DNA positivity contrasting upper and lower quintiles at different dilutions and their averages were 4.73 to 5.47 for NARs and 2.78 to 3.28 for net ODs, with corresponding significant improvements in seroreactivity-risk trends across quintiles when NARs were used. The NAR standardization is a simple procedure to reduce measurement error in seroepidemiological studies of HPV infection.

Multivariated variance analysis applied to biological experiments: An analysis with curves of rats teeth growth as influenced by colchicine

The evaluation of the growth of incisor teeth of rats as influenced by colchicine (doses of 25, 50, 100 and 200 μg/kg) injected during 10 and 18 days is performed using a multivariated variance analysis, which allowed a global view of the results, showing that: there are differences in the growth of teeth of control group (untreated rats) and those treated with colchicine, in the measurements made at the 4th, 7th and 10th days of experiment); there is no difference in the growth of the teeth between the groups treated during 10 and 18 days, except in the measurements made at the 7th day; there is no influence of the doses of colchicine in the group treated during 10 days and in the group treated during 18 days - only at the 7th day is observed an influence of the doses used; and there was no significant interaction between treatment and days of measurement, showing the similarity of the groups during the experiment.

The variance of the index (R) of aggregation of Clark and Evans

The exact formula for the variance of the Index (R) of aggregation of Clark and Evans is derived. Due to the fact that R is a dimensionless number, its variance is independent of population density, being only a function of the sample size and so can be manipulated. © 1985 Springer-Verlag.

Influence of barium and strontium addition on the ratio c/a of PZT obtained by the polymeric precursor method

Lead zirconate titanate powder, with Zr/Ti ratio of 50/50 was prepared by Pechini method after adding up to 10,0 mol% of Ba +2 and Sr +2 ions. Tetragonal phase is favored by the increase of barium and strontium concentration in the LiNbO 3 crystal lattice. The ratio c/a for tetragonal phase increases with the content of Ba +2 and Sr +2.

Free diet selection by broilers as influenced by dietary macronutrient ratio and corticosterone supplementation. 1. Diet selection, organ weights, and plasma metabolites

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Structural study of aged saturated silica gels obtained from tetramethoxysilane sonohydrolysis with different water/tetramethoxysilane molar ratio

The structural characteristics of saturated silica sonogels were studied by means of small-angle x-ray scattering (SAXS) and thermogravimetric analysis (TG), after a long time of aging in saturated conditions. The sonogels were obtained by a sol-gel routine from ultrasound stimulated tetramethoxysilane (TMOS) hydrolysis carried out with the initial water/TMOS molar ratio (r) ranging from 2 to 10. The saturated sonogel structure can be described as composed by mass fractal-like aggregates (clusters) of primary silica particles, all imbibed in a liquid phase. The values of the mass fractal dimension (D) of the clusters was found all around 2.5, while the characteristic size of the clusters (ξ) was found generally increasing with r, going from approximately 2.3 nm (r = 2) to 4.5 nm (r = 10). The volume fraction of the clusters was estimated from the SAXS data. The results were compared to the values of weight loss fraction at the inflection point that has been found in the derivative of the TG curve, which should accounts for the instant in which the meniscus of the liquid phase penetrates into the clusters under a rapid evaporation process as in a TG test.

Variance heterogeneity for milk yield in Brazilian and Colombian Holstein herds

Heterogeneity of variances for milk yield (MY) was determined for Brazilian and Colombian herds. The herds were grouped as high or low variability within each country, using as criterion the phenotypic standard deviation (PSD) of MY in the contemporary groups of cows, from the first to the sixth calving. Brazilian and Colombian herds with PSD greater than 1,168 kg or 1,012 kg, respectively, were classified as high variability while the herd groups with values lower than those were classified as low variability. The genetic parameters for MY within each herd group were estimated using bivariate analysis in an animal model and the restricted maximum likelihood method with a derivative free algorithm, using 72,280 first lactations of cows, daughters of 1,880 sires. Heterogeneous variances were found, and Brazilian herds with high PSD had the greatest additive and residual genetic variances and heritability coefficients for MY. MY genetic correlation coefficients between herds of high and low variability within each country were 0.96 and 0.93 while between countries they varied from 0.72 to 0.81, suggesting that there was a reclassification of animals in the two countries and also heterogeneity of variances. This phenomenon leads to the questioning of the strategy of imported semen usage and the need to do genetic evaluations to identify sires with greater genetic potential for (sub) tropical environmental conditions.