Synthesis and characterization of functional gradient copolymers of glycidyl methacrylate and butyl acrylate

Epoxy-functional spontaneous gradient copolymers of glycidyl methacrylate (G) and n-butyl acrylate (B) were synthesized via atom transfer radical polymerization (ATRP). The copolymerization reactions were carried out in toluene solution at 70 °C, using methyl 2-bromopropionate (MBrP) as initiator and copper chloride with N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) as the catalyst system. The kinetic behaviour of the statistical copolymerizations was studied in a wide composition interval with molar fractions of G ranging from 0.10 to 0.75. The synthesized copolymers were characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. ¹H NMR was employed to determine the copolymer composition, demonstrating the gradient character of the copolymers along the main chain in the whole monomer conversion interval. Apart from this, the sequence distribution and stereoregularity were analyzed. These microstructural experimental data agreed well with those calculated from Mayo-Lewis terminal model (MLTM) and a Bernoullian statistic with an isotacticity parameter of σ_G = 0.28 and a coisotacticity parameter of σ = 0.30.     

A p‐version,first order shear deformation,finite element for geometrically non‐linear vibration of curved beams

A p‐version, hierarchical finite element for curved, moderately thick, elastic and isotropic beams is introduced. The convergence properties of the element are analysed and some results are compared with results published elsewhere or calculated using a commercial finite element package. It is verified that, with the proposed element, shear locking does not affect the computation of the natural frequencies and that low dimensional, accurate models are obtainable. Geometrically non‐linear vibrations due to finite deformations, which occur for harmonic excitations with frequencies close to the first three natural frequencies of vibration, are investigated using Newmark's method. The influence of the thickness, longitudinal inertia and curvature radius on the dynamic behaviour of curved beams are studied. Copyright © 2004 John Wiley & Sons, Ltd.     

Structural characterization of the cyanelle peptidoglycan of Cyanophora paradoxa by 252Cf plasma desorption mass spectrometry and fast atom bombardment/tandem mass spectrometry

A strategy for the structural characterization of the four major NaBH4-reduced peptidoglycan monomers derived from muramidase-digested peptidoglycan from the cyanelles of the flagellate Cyanophora paradoxa Korschikoff is described. Initial molecular weight determination of these glycopeptides was performed by positive and negative ion plasma desorption mass spectrometry. Due to the presence of two pairs of disaccharide tripeptide and disaccharide tetrapeptide monomers differing in mass by 112 units, respectively, an as yet unknown peptidoglycan modification either at the carbohydrate or at the peptide moiety was assumed. beta-Elimination of the disaccharide unit from the unreduced peptidoglycan monomers yielded the corresponding (modified) N1-lactyltripeptides and -tetrapeptides, respectively. These peptides, N-terminally blocked with lactic acid, unambiguously showed the modification to be located on the peptide moiety. By positive ion fast atom bombardment/hybrid tandem mass spectrometry of the reduced peptidoglycan monomers as well as of the corresponding deglycosylated monomers (= N1-lactylpeptides) the modification was determined to be linked to the glutamic acid moiety. Based on combined data from plasma desorption mass spectrometry, tandem mass spectrometry, accurate mass measurement and amino acid analysis of the acid hydrolysate after derivatization with o-phthaldialdehyde by high-performance liquid chromatography we could establish the structure of the modification as N-acetylputrescine. Finally, the confirmation of the linkage of the glutamic acid to diaminopimelic acid via the gamma-COOH was based on the presence of a-type peptide backbone fragment ions in the positive ion plasma desorption mass spectra of the modified N1-lactylpeptides.     

Learning Recursive Bayesian Multinets for Data Clustering by Means of Constructive Induction

This paper introduces and evaluates a new class of knowledge model, the recursive Bayesian multinet (RBMN), which encodes the joint probability distribution of a given database. RBMNs extend Bayesian networks (BNs) as well as partitional clustering systems. Briefly, a RBMN is a decision tree with component BNs at the leaves. A RBMN is learnt using a greedy, heuristic approach akin to that used by many supervised decision tree learners, but where BNs are learnt at leaves using constructive induction. A key idea is to treat expected data as real data. This allows us to complete the database and to take advantage of a closed form for the marginal likelihood of the expected complete data that factorizes into separate marginal likelihoods for each family (a node and its parents). Our approach is evaluated on synthetic and real-world databases.     

Environmental Problems in Sao Paulo: The Challenge for Co-Responsibility and Innovative Crisis Management

This article describes and analyzes the main environmental problems that affect the city of Sao Paulo. The article views the impacts of the local dynamics of urbanization and its effects on daily life. The discussion is centered on the complexity of the environmental management processes and the implementation of conventional and non-conventional policies and programmes to prevent environmental degradation. Possible solutions to alleviate the effects of floods and climate factors on households are debated as well as the possibilities of formulating more participatory oriented policies to engage citizens in the knowledge of environmental risks. These issues represent a very complex challenge to the urban government of Sao Paulo.     

The risk of seroconversion in surgeons of the hepatitis B, hepatitis C and human immunodeficiency viruses (in a specific surgical population)

The prevalence of hepatitis B surface antigen (HBs Ag) and antibody to hepatitis C virus (HCV) and human immunodeficiency virus (HIV) was determined in the serum specimens of 288 patients treated surgically in the orthopaedic department of an urban public teaching hospital. The cumulative risk of HBV, HCV and HIV seroconversion for an orthopaedic surgeon during the surgical career span was calculated. We found that 1.4%, 3.1% and 1.7% of patients were seropositive for HBsAg, HCV antibody and HIV antibody, respectively. Seropositivity was neither associated with age nor with trauma, whereas male patients had a greater likelihood of seropositivity. Risk factor assessment did not prove to be discriminating in identifying which patients may pose a potential exposure risk. This study supports the concept of universal infection control precautions for orthopaedic surgeons regardless of the patients' risk factor or serologic status.     

Screening of supports for the immobilization of pectinmethylesterase from acerola (Malpighia glabra L)

A partially purified extract of pectinmethylesterase (PME) from acerola fruit was immobilized on various supports: glass, celite, chrysotile, agarose, concanavalin A Sepharose 4B, egg shell, polyacrylamide and gelatin. In addition, reticulation with glutaraldehyde was assessed, as well as the use of gelatin in the presence of celite, glass and silica. The highest immobilization yields were obtained when the pectinmethylesterase was immobilized in concanavalin A Sepharose 4B (81.7%) and in gelatin‐water (78.0%). Copyright © 2004 Society of Chemical Industry     

Electrical Conductivity Measurement Through the Loaded Q Factor of a Resonant Cavity

We present a method for measuring the electrical conductivity of metallic materials that relies on the ratio of two loaded Q factors, Q_R/Q_X, with Q_R corresponding to a TE₀₁₁-mode reference cavity made of aluminum, and Q_X the Q that results upon replacing the aluminum plate with the one fabricated from the material to be examined. Electrical conductivity is mathematically inferred from the ratio Q_R/Q_X where the loaded Q factors are measured by using the transmission-type method. Within a 3.0 percent accuracy, conductivities determined at 8.7 GHz for electrolytic copper (5.6 times 10⁷ S/m) and brass (1.6 times 10⁷ S/m) show to be in good agreement with those reported in the literature.     

MODELING WATER LOSS DURING FRYING OF POTATO STRIPS: EFFECT OF SOLUTE IMPREGNATION

The effect of solute impregnation on water loss and oil uptake during potato strip frying was studied. Blanched potato strips were impregnated at 25°C by soaking in a solution of sucrose-NaCl-water, 20-5-75% by weight. After rinsing and air drying, strips were deep fried in sunflower oil at 160, 170 and 180°C. A control treatment, consisting of potato strips blanched but not soaked and later air dried was also conducted. Solute impregnation provided a decrease of the oil uptake. Two models, based on Fick's law were used to describe water loss during frying. The first one is the classic model with an effective moisture diffusion coefficient assumed a constant value. The second model considers that diffusion coefficient varies during the frying process. For a given frying temperature, constant diffusion coefficient for control potatoes resulted in lower values than the impregnated ones. The variable diffusivity model showed a two-stage behavior: during the first stage of frying, diffusion coefficient increased with frying temperatures, but from a given time on an inverse behavior began. This last fact was found to be related to an increase of the measured peak force needed to penetrate the potato crust.