Microbiological and chemical characterization of honeys from central Argentina

The characterization of some honey samples from southern Córdoba (Argentina) was carried out on the basis of their microbiological (Clostridium, fungi and yeasts), physical (colour) and chemical (carbohydrates, HMF, water and free acidity) analysis. The results showed that honeys produced in this region are of good quality. HMF content and free acidity values were mostly low, indicating honey freshness. Most of the samples contained less than 20% water. Glucose and fructose accounted for more than 60% of the weight. The amount of yeast and fungi found in the honey samples was less than 1 × 10² CFU/g. Low quantities of vegetative cells and spores of Clostridia were found in some honey samples. A standardization and a rationalization of beekeeping techniques throughout southern Córdoba may further improve honey quality, and ensure it over the years.     

A comparison between the physico-chemical properties of tuber and cereal starches

Biofilms based on waxy maize and cassava starches (cereal and tuber starch, respectively), plasticized with glycerol were characterized through their crystallinity, dynamic-mechanical behavior (DMA), thermal degradation (TGA), moisture content and water vapor permeability (WVP). X-ray diffraction experiments show that both materials were mainly amorphous, with the waxy starch presenting a discreetly A-type X-ray pattern. Microscopic investigation of the cryo-fractured surfaces supported this observation. The glass transition of the glycerol-rich phase (measured by DMA) occurs at higher temperatures for cassava than for waxy maize starch, suggesting that the dispersion level of glycerol is higher in the former. TGA showed that maize starch has a slightly higher thermal stability than cassava starch, while glycerol interacts more strongly with the last one. The WVP was 18% higher in the case of the cassava starch film.     

Composites from PMMA modified thermosets and chemically treated woodflour

The mechanical behavior of composites made from woodflour and a modified thermoset unsaturated polyester resin has been examined. Polymethylmethacrylate (PMMA), a common low profile additive (LPA), was used as the matrix modifier. Woodflour, the reinforcing filler, was used ‘as received’ and was also modified with a commercial alkenyl succinic anhydride (ASA), in order to enhance the compatibility with the resin. The composites exhibited higher flexural and compressive modulus and compressive yield stress than the neat resin, while flexural strength and ultimate strain were reduced. The addition of PMMA to the unfilled thermoset led to a LPA morphology and decreased the flexural modulus, but produced an increment in flexural strain at break, impact energy and toughness of the UP resin. No enhancement in the mechanical behavior of the composites was found when treated woodflour instead of unmodified woodflour was used.     

In hemodialysis, adiponectin, and pro-brain natriuretic peptide levels may be subjected to variations in body mass index

Adiponectin exerts cardiovascular protective actions, although some studies have shown the opposite. In hemodialysis, obese subjects display lower mortality rates despite hypoadiponectinemia, while higher adiponectin concentrations correlate with an elevated cardiovascular risk in nonobese subjects. The aim of the study is to suggest that adiponectin level variations are associated with differences in the body mass index (BMI). The interplay between adiponectin and pro-brain natriuretic peptide (Pro-BNP) levels may vary according to body fat mass. Fifty-two chronic hemodialysis patients were divided into three groups. Group A, BMI<25 (n=20); Group B, BMI 25 to 30 (n=21), and Group C, BMI>30 (n=11). Diabetics: Group A 10%; Group B 6 29%; Group C 55%, P=0.027. Determinations: Adiponectin, Pro-BNP, insulin, insulin resistance (HOMA), troponin T, nutritional status, ultrafiltration rates, C-reactive protein (CRP), vascular accesses, and echocardiography. Group A: adiponectinemia positively and significantly correlated with Pro-BNP, CRP, and troponin T. As BMI increased, adiponectin, Pro-BNP, and malnutrition significantly decreased, while insulin, HOMA, and ultrafiltration rates significantly increased. Cardiac restriction was significantly higher in obese patients. In all groups, Pro-BNP and troponin T displayed a strong positive correlation. In low-BMI subjects, high Pro-BNP and adiponectin, low myocardial restriction, and worse nutritional status were prevalent. In obesity, hypoadiponectinemia stimulates cardiac remodeling, cardiac hypertrophy, and decreased stretching, rendering Pro-BNP levels low despite high ultrafiltration rates. Thus, adiponectin correlates inversely with BMI, probably playing different cardiovascular roles as BMI changes.     

Chitosan interaction with iron from yoghurt using an in vitro digestive model: comparative study with plant dietary fibers

The objective of this work was to investigate the interaction of chitosan with iron from yoghurt by an in vitro gastrointestinal tract model. Taking into account that chitosan is a polysaccharide included in fiber definition by Codex Alimentarius; chitosan behavior was studied and compared with different plant fiber (wheat, bamboo, apple, psyllium and inulin) behaviors, in the same in vitro conditions. Ferrous sulfate was added to yoghurts with each type of fiber. The gastric environment was simulated with HCl (pH 1.0-2.0). The duodenal environment was simulated with NaHCO(3) (pH 6.8-7.2) and a dialysis tubing cellulose membrane. Results showed that chitosan had the highest iron retention percentages (53.2% at 30 min; 56.8% at 60 min) interacting in a more pronounced manner with iron than the plant fibers used in this work.     

The Minimum Number of Errors in the N-Parity and its Solution with an Incremental Neural Network

The N-dimensional parity problem is frequently a difficult classification task for Neural Networks. We found an expression for the minimum number of errors f as function of N for this problem, performed by a perceptron. We verified this quantity experimentally for N=1,...,15 using an optimal train perceptron. With a constructive approach we solved the full N-dimensional parity problem using a minimal feedforward neural network with a single hidden layer of h=N units.     

Short-wavelength near-infrared spectra of sucrose, glucose, and fructose with respect to sugar concentration and temperature

Short-wavelength near-infrared (SW-NIR) (700-1100 nm) spectra of aqueous solutions of sucrose, D-glucose, and D-fructose were monitored with respect to change in temperature and sugar concentration. Sugar OH and CH related vibrations were identified by analysis of the spectra of sugar solutions in deuterium oxide (D2O), and of sucrose-d8 solutions in D2O. Absorption spectra were explained in terms of the second and third overtones of OH stretching vibrations and the third overtone of CH2 and CH stretchings. In deuterated solutions, CH and CH2 higher overtone vibration bands became apparent. The major spectral effect of decreased temperature or increased sugar concentration was a decrease in absorbance at 960 nm and an increase in absorbance at 984 nm, interpreted as an increase in the degree of H bonding. Partial least-squares (PLS) calibrations on sugar concentrations (with spectra collected at several sample temperatures) relied strongly on the 910 nm sugar CH related bands, whereas calibrations on temperature depended equally on all OH associated vibrations (750, 840, 960, and 985 nm).     

Curing kinetics of divinyl ester resins with styrene

The curing reaction of a divinyl ester resin with different proportions of styrene—4, 20, and 40% by weight—was investigated by differential scanning calorimetry (DSC) using isothermal and dynamic modes. The different constraints on the reaction rate was globally considered, taken the reaction as divided in two regimens: below the vitrification regimen and during the vitrification regimen. Below the vitrification regimen, the autocatalytic model developed by Kamal was used to perform the analysis of the curing kinetics of divinyl ester resin with styrene. Experimental data from dynamic and isothermic runs, at a fixed composition, were simultaneously considered, while the actual temperature records (measured during the DSC runs) were also taken into account. The adjusted kinetic parameters took into account the gel effect on the radicals' termination rate and the structure constraints on the reactivity of pendant vinyls groups, present during this stage. During the vitrification stage, the diffusion control due to the low mobility of the reactive groups and molecules was incorporated into the overall rate constant according to the Rabinowitch model, which considers the two regimen contributions to the overall reaction rate kinetic. The Vogel–Fulcher relationship was adopted to express the temperature dependence of the rate constant during the vitrification stage. The method presented here has been satisfactorily applied to dynamic and isothermal curing reactions, allowing a simple and general kinetic expression useful in the design, optimization, and control of the processing of composites based on these thermoset polymers to be obtained. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1044–1053, 1999     

Toxicity assessment of heavy metal mixtures by Lemna minor L

The discharge of untreated electroplating wastewaters directly into the environment is a certain source of heavy metals in surface waters. Even though heavy metal discharge is regulated by environmental laws many small-scale electroplating facilities do not apply adequate protective measures. Electroplating wastewaters contain large amounts of various heavy metals (the composition depending on the facility) and the pH value often bellow 2. Such pollution diminishes the biodiversity of aquatic ecosystems and also endangers human health. The aim of our study was to observe/measure the toxic effects induced by a mixture of seven heavy metals on a bioindicator species Lemna minor L. Since artificial laboratory metal mixtures cannot entirely predict behaviour of metal mixtures nor provide us with informations relating to the specific conditions in the realistic environment we have used an actual electroplating wastewater sample discharged from a small electroplating facility. In order to obtain three more samples with the same composition of heavy metals but at different concentrations, the original electroplating wastewater sample has undergone a purification process. The purification process used was developed by Orescanin et al. [Orescanin V, Mikeli? L, Luli? S, Nad K, Rubci? M, Pavlovi? G. Purification of electroplating wastewaters utilizing waste by-product ferrous sulphate and wood fly ash. J Environ Sci Health A 2004; 39 (9): 2437-2446.] in order to remove the heavy metals and adjust the pH value to acceptable values for discharge into the environment. Studies involving plants and multielemental waters are very rare because of the difficulty in explaining interactions of the combined toxicities. Regardless of the complexity in interpretation, Lemna bioassay can be efficiently used to assess combined effects of multimetal samples. Such realistic samples should not be avoided because they can provide us with a wide range of information which can help explain many different interactions of metals on plant growth and metabolism. In this study we have primarily evaluated classical toxicity endpoints (relative growth rate, Nfronds/Ncolonies ratio, dry to fresh weight ratio and frond area) and measured guaiacol peroxidase (GPX) activity as early indicator of oxidative stress. Also, we have measured metal accumulation in plants treated with waste ash water sample with EDXRF analysis and have used toxic unit (TU) approach to predict which metal will contribute the most to the general toxicity of the tested samples.     

Composite resins based on novel and highly reactive bisglycidyl methacrylate monomers

Three new bisglycidyl monomers; 1,4‐bis((2‐hydroxy‐3‐methacryloxypropoxy) methyl)benzene (MB‐Phe‐OH), 1,4‐bis(2‐hydroxy‐3‐methacryloxypropoxy)2‐cis‐butene (MB‐Cis‐OH), and 1,7‐bis(2‐hydroxy‐3‐methacryloxypropoxy)heptane (MB‐1,7‐OH); were synthesized and used as Bis‐GMA/TEGDMA (bisphenolglycidyl methacrylate/triethylene glycol dimethacrylate) composite resin additives. Flexural properties and double bond conversion of the dental resins composed of silanizated inorganic filler and organic matrices containing new monomers were evaluated. The composite resins formulated, using the monomers MB‐Cis‐OH and MB‐1,7‐OH, have mechanical properties and double bond conversion comparable with those of Bis‐GMA/TEGDMA composite resin used as control. The composite containing the new monomer MB‐Phe‐OH has better flexural properties (flexural strength 65.01 MPa and flexural modulus 5675.91 MPa) than the control composite resin (flexural strength 52.85 MPa and flexural modulus 4879.72 MPa); this could be attributed to the molecular structure of the monomer and its high double bond conversion level of 74.19%. The new bisglycidyl methacrylate monomer MB‐Phe‐OH could be potentially useful in the development of new organic matrices for dental composite resins with high double bond conversion and enhanced mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40971.