A fast permutation-based algorithm for block clustering

A stepwise divisive procedure for the clustering of numerical data recorded in matrix form into homogeneous groups is introduced. The methodology relates to those proposed by Hartigan (1972) and Duffy and Quiroz (1991). As the latter, the proposed methodology uses the permutation distribution of the data in a block as the reference distribution to make inferences about the presence of clustering structure. A local (within block) criteria and Bayesian sequential decision methodology are used to evaluate the significance of potential partitions of blocks, resulting in an algorithm which is faster than those considered by Duffy and Quiroz (1991). The class of possible clustering structures that our procedure can discover is also larger than those previously considered in the literature.     

Infection by Toxoplasma gondii in children with infantile cerebral palsy

An analytic relationship between positivity of the indirect immunofluorescent test (IIFT) for toxoplasmosis and clinical findings in a population of 328 children with cerebral infantile palsy (CIP) was performed. Children were distributed by age in one of four groups: I (0-2 years); II (3-6 years); III (7-12 years) and IV (13-18 years). One control group of 168 children with no PCI clinical findings was included. 125 sera were positive at 1:64 dilutions. The study of the binomial mother-child of 40 cases rendered 26 mothers with significant titer values. The majority of positive mothers to IIFT correlated with the youngest children (Groups I, II and III), mainly with group I (70.0%), which showed the highest titer ranges. Correlation between positive IIFT and clinical features was as high as 100.0%.     

Effects of the type and concentration of alkylaluminum cocatalysts on the molar mass of polypropylene made with in situ supported metallocene catalysts

Propylene homopolymerizations were carried out with rac‐dimethylsilylenebis(indenyl)zirconium dichloride, methylaluminoxane‐modified silica, and common alkylaluminum cocatalysts. Supported catalysts were prepared by the in situ immobilization technique. The effects of the type and concentration (Al/Zr = 40–1000) of alkylaluminum on the propylene polymerization were evaluated with triethylaluminum (TEA), isoprenylaluminum (IPRA), and triisobutylaluminum (TIBA) as cocatalysts. The polymers were analyzed by gel permeation chromatography, differential scanning calorimetry, and ¹³C‐NMR. The polypropylene molar mass varied according to the nature of the alkylaluminum in the following order: TIBA > IPRA > TEA > no alkylaluminum. The polymers made with an in situ supported catalyst had lower crystallinities and melting points than the ones produced by homogeneous polymerization. The isotacticity was not affected by the polymerization conditions examined in this investigation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1050–1055, 2005     

A three-step metal fractionation scheme for fly ashes collected in an Argentine thermal power plant

A new three-step fractionation scheme was applied to study the distribution of Al, As, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, S, Sb, Ti, V and Zn in fly ashes collected in the electrostatic precipitator of a thermal power plant in the city of San Nicolás (Argentina). Seven samples were collected during one week of operation in 2005. For the fractionation, the scheme applied consisted of extracting the elements in three fractions: (i) soluble and exchangeable elements, (ii) carbonates, oxides and reducible elements and (iii) residual elements. Metals and metalloids at μg g⁻¹ level were determined in each fraction by plasma based techniques namely, inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry (ICP-MS). For validation, a certified reference materials NIST SRM 2711 (Montana soil) was subject to the same chemical sequential extraction procedure. X-ray diffraction powder (XRD) analysis and scanning electron microscopy (SEM) were used to characterize the major minerals present in the matrix. The predominant phases found in the total samples were mullite, quartz, iron oxides and lime. Total analyte concentration varied (in μg g⁻¹) from 1.54 for Cd to 30 600 for Al. The leachability of the 15 elements under study proved to be different. All the elements (except Cd and Pb) were detected in the soluble fraction in the order: Cu (0.10%) ∼ Mn (0.13%) < Ni (0.17%) ∼ Ti (0.19%) ∼ Fe (0.20%) ∼ As (0.21%) < Zn (0.86%) < Al (1.3%) < Cr (2.9%) < V (3.9%) < Sb (6.9%) < Mo (45.1%) < S (58.0%). Percentages higher than 20% of S (24.1%) < V (27.5%) < Mn (29.0%) were detected in the second fraction. Al, As, Cr, Cd, Cu, Fe, Ni, Pb, Sb and Zn were mostly associated to the residual fraction. Recoveries of the overall procedure varied between 106% (Mo) and 72% (Cr).     

Synthesis,physicochemical characterisation and biological activity of anandamide/ɛ‐polycaprolactone nanoparticles obtained by electrospraying

Drug encapsulation in nanocarriers such as polymeric nanoparticles (Nps) may help to overcome the limitations associated with cannabinoids. In this study, the authors’ work aimed to highlight the use of electrospraying techniques for the development of carrier Nps of anandamide (AEA), an endocannabinoid with attractive pharmacological effects but underestimated due to its unfavourable physicochemical and pharmacokinetic properties added to its undesirable effects at the level of the central nervous system. The authors characterised physicochemically and evaluated in vitro biological activity of anandamide/ɛ‐polycaprolactone nanoparticles (Nps‐AEA/PCL) obtained by electrospraying in epithelial cells of the human proximal tubule (HK2), to prove the utility of this method and to validate the biological effect of Nps‐AEA/PCL. They obtained particles from 100 to 900 nm of diameter with a predominance of 200–400 nm. Their zeta potential was −20 ± 1.86 mV. They demonstrated the stable encapsulation of AEA in Nps‐AEA/PCL, as well as its dose‐dependent capacity to induce the expression of iNOS and NO levels and to decrease the Na⁺ /K⁺ ATPase activity in HK2 cells. Obtaining Nps‐AEA/PCL by electrospraying would represent a promising methodology for a novel AEA pharmaceutical formulation development with optimal physicochemical properties, physical stability and biological activity on HK2 cells.Inspec keywords: cellular biophysics, molecular biophysics, nanoparticles, nanofabrication, biochemistry, encapsulation, drugs, neurophysiology, electrokinetic effects, enzymes, biomedical materials, nanomedicine, polymers, sprayingOther keywords: electrospraying techniques, pharmacological effects, pharmacokinetic properties, in vitro biological activity, biological effect, HK2 cells, optimal physicochemical properties, polymeric nanoparticles, AEA pharmaceutical formulation development, anandamide‐ε‐polycaprolactone nanoparticles, drug encapsulation, nanocarriers, endocannabinoid, central nervous system, epithelial cells, human proximal tubule, zeta potential, stable encapsulation, dose‐dependent capacity, Na⁺ ‐K⁺ ATPase activity, physical stability, size 100.0 nm to 900.0 nm, NO, Na⁺ ‐K⁺      

Polymerization of ethylene by (α‐Diimine) nickel catalyst and statistical analysis of the effects of reaction conditions

This article regards the ethylene polymerization catalyzed by a nickel catalyst and activated by ethylaluminum sesquichloride (EASC). The effects of the reaction conditions [polymerization temperature, cocatalyst (EASC) concentration, and ethylene concentration] on the average molecular weights of the final polymers and reaction yields were evaluated with the help of empirical statistical models. It is shown that reaction temperature and cocatalyst (EASC) concentration exert the most important effects on average molecular weights and catalyst activity. The polydispersities of the obtained polyethylenes are larger than the polydispersities of polyethylenes obtained with typical Brookhart catalysts. The analysis of polymer branching frequencies shows new types of short branching and significant amounts of long branches, which may explain the relatively large polydispersities of the obtained polymer samples. POLYM. ENG. SCI., 50:1797–1808, 2010. © 2010 Society of Plastics Engineers     

Quadratic forms of the empirical processes for the two-sample problem for functional data

The use of quadratic forms of the empirical process for the two-sample problem in the context of functional data is considered. The convergence of the family of statistics proposed to a Chi-squared limit is established under metric entropy conditions for smooth functional data. The applicability of the proposed methodology is evaluated in simulations and real data examples.     

Fabrication and application of Nafion®-modified boron-doped diamond electrode as sensor for detecting caffeine

The surface of boron-doped diamond (BDD) electrodes has been modified by Nafion^®. The polymer film was applied onto the BDD electrode surface by solvent evaporation. Nafion^®-BDD electrode was used as a sensor for caffeine detection in e.g. cola beverage samples. In cyclic voltammetric measurements, favorable ionic interaction between the Nafion^® film and caffeine enhances the current response, and thus the sensitivity, compared to that at the bare electrode. The modified electrode exhibits a stable and sensitive response to caffeine and may represent a new analytical tool, offering a significant improvement over other electroanalytical methods (e.g.: Nafion^®-modified glassy carbon electrode) and the accepted method for caffeine analysis (HPLC-MS). The analysis of residuals from the linear regression proved that a linear response exists from 2.0 × 10^? 7 to 1.2 × 10^? 5 M, obtaining a limit of detection of about 1.0 × 10^? 7 M. The findings presented in this study are described and discussed in the light of the existing literature.     

Winter host component reduces colonization by bird-cherry-oat aphid,Rhopalosiphum padi (L.) (homoptera,aphididae), and other aphids in cereal fields

Methyl salicylate, a volatile component ofPrunus padus, the winter host ofRhopalosiphum padi, was found to reduce colonization of the summer host by this aphid. The compound was identified by gas chromatographic analysis coupled with recordings from cells in the primary rhinarium on the sixth antennal segment of the aphid. Methyl salicylate eliminated the attractancy of oat leaves to spring migrants in olfactometer tests. In Sweden, this compound significantly decreased colonization of field grown cereals byR. padi and in the U.K., populations ofSitobion avenae andMetopolophium dirhodum were significantly lower on treated plots.     

2D 1H and 13C NMR evidence for stereoselective formation of a new bond C-N, C-S or C-C in the reaction of ivalin acetate with substituted pyrimidines

OBJECTIVE: This review examines the evidence supporting the proposition that a threshold clozapine plasma level can predict clinical response. In addition, it provides a brief overview of the pharmacokinetics, side effects, drug interactions and assay methodology of clozapine. METHOD: A comprehensive search of relevant literature was made with respect to the above criteria. The findings were collated and analysed to produce an overview of the usefulness of using clozapine levels in clinical practice. RESULTS: Most researchers find that, although the correlation between dose of clozapine and clinical effect is not high, a threshold plasma level of 350-420 ng mL-1 of clozapine is associated with an increased probability of a good clinical response to the drug. Results vary, however, with the study design. CONCLUSIONS: The data reviewed present a case for increasing the dose of clozapine in non-responsive patients to achieve a plasma level of at least 350-420 ng mL-1. Non-response at these levels, however, should not preclude a further upward titration of dose. This should occur unless (i) clinical response is obtained at a lower dose, (ii) intolerable side effects occur, or (iii) a daily dose of 900 mg is reached.