Characterization by tin-specific size exclusion chromatography of the free radical copolymerization of tributyltin methacrylate and methyl methacrylate

Copolymers of tributyltin methacrylate (TBTM) and methyl methacrylate (MMA) comprise an important class of biocidal slow-release organometallic polymers (OMPs). Little is known of the kinetics and mechanism of copolymerization. TBTM and MMA were copolymerized in the presence of a free radical initiator (benzoyl peroxide) at 80.1°C. Aliquots, taken at preselected intervals from 0 to 1440 min, were fractionated by size exclusion chromatography (SEC) coupled with ultraviolet (UV) and tin-specific graphite furnace atomic absorption (GFAA) detectors. A UV absorbance observed at 254 nm was associated with low-molecular-weight species, decreasing in concentration continuously with time of reaction. Tin-specific GFAA indicated a decrease in low-molecular-weight species (ca. 350 daltons) with concurrent increases in high-molecular-weight species (ca. 40,000 daltons). The fraction of high molecular-weight increased as a linear function of the logarithm of the time of reaction. SEC–UV–GFAA thus provides a tool of major importance for characterizing the time dependence and continuity of the process by which monomers of TBTM are converted to a useful bioactive slow-release coating material.     

The thin dielectric film capacitive displacement transducer tonanometer

The paper deals with the new capacitive transducer for small displacements (from a few micrometers to a few millimeters), denoted the Thin Dielectric Film Capacitive Displacement Transducer (TFCDT). This principle is based on the properties of a very thin dielectric film between the faced electrodes. The film may be applied by a dielectric, such as alumina. The transducers are designed in a differential form. Their electrodes have to be constructed by either photo-chemical- or laser etching. A few implementation prototypes (IPs) of the TFCDT have been designed and constructed. The first of the IPs (TO IF) has been constructed in two forms, for linear and rotary displacement by a dielectric spray varnish with thickness of about 2 μm. The second of the IPs (II°IP) has been designed and constructed only in the form for linear displacement, with different techniques for achieving lower thickness of the alumina dielectric film. The test results on both the I°IP and II°IP are critically analyzed. The sensitivity and linearity obtained, respectively, are about: 5 pF/mm, 0.6 pF/°, 25×10^-6, 2 nF/mm, and 7 nm/μV, nearly in the absence of nonlinearities. A feature for improving the sensitivity and linearity, respectively, to about 40 μV/nm and to a few×10^-8 is also illustrated. A variable absolute scale of capacitance and capacitive voltage divider based on the TFCDT is also proposed     

Effect of the lentil flour and hydrocolloids on baking characteristics of wholemeal durum wheat bread

In this study, the characterisation of functional bread based on wholemeal durum wheat flour enriched with lentil flour was investigated to find a good balance between the nutritional and organoleptic properties of the final product. In particular, the effect of different percentage of lentil flour (10%, 20% and 25%) and the type and amount of structuring agents (carboxymethyl cellulose, guar seed flour, pectin and tapioca starch) were studied by assessing the sensorial, textural and nutritional properties of the functional bread. Results showed that the increase in the lentil flour at 20% and 25% negatively affected the dough texture and the sensorial quality of the bread. The screening of different hydrocolloids on the bread sample enriched with 25% of legume flour highlighted that the guar seed flour at concentration of 2% allowed obtaining the best results in terms of sensory properties. The nutritional analysis of the optimised functional bread showed an increase in proteins and dietary fibre (total, soluble and insoluble), suggesting its high functional value and the possibility to propose it on a market that is constantly changing and attentive to health benefit of foods.     

Optimisation of Glucose Biosensors Based on Sol–Gel Entrapment and Prussian Blue-Modified Screen-Printed Electrodes for Real Food Analysis

In this study, we report the construction of amperometric screen-printed glucose biosensors for food analysis by using two procedures for Prussian Blue (PB) deposition and different membranes for enzymatic immobilisation. The comparison between the screen-printed electrodes modified with PB by electrochemical and chemical deposition showed higher analytical performance (detection limit of 1 μM, linear range from 0.5 to 500 μM and a sensitivity of 823 μA mM^?1 cm^?2) when the latter was employed. Then, the immobilisation of glucose oxidase (GOD) by silica sol–gel and polyvinyl alcohol (PVA) hydrogel was performed on electrochemically modified PB electrodes. The electrochemical response of two glucose biosensors was evaluated by flow injection analysis. Biosensors constructed by silica sol–gel entrapment showed a wider linear range (0.005–1 mM) and a detection limit (0.02 mM) that was 10-fold lower than using entrapped GOD in PVA. The selected glucose biosensor showed negligible interference from ascorbic acid when the Nafion membrane was used to cover the PB-modified electrode surface. Additionally, it exhibited an operating lifetime of 8 h under continuous glucose injections ranging from 0.01 to 2 mM. Finally, the biosensor was applied for specific determination of glucose in red and white wines, juices and dried fruit.     

Impact of oleuropein on rheology and breadmaking performance of wheat doughs,and functional features of bread

Oleuropein (OP) is a polyphenol present in drupes and leaves of olive tree with health benefits and, as antioxidant, potentiality to alter gluten functionality. Effects of OP inclusion to wheat flour (0.01% and 0.02% on flour weight basis) on dough rheology and breadmaking performance, and bread features were investigated. Farinograph, uniaxial extension and shear rheometry (oscillatory and creep-recovery) were applied. Doughs containing OP were stronger, more elastic, and less sticky indicating the ability of OP to act as flour improver. The strengthening effect of OP on gluten led to the increase in bread volume and softer crumb compared to control. A lower crumb density of bread with the addition of OP was related to a higher in vitro glycaemic response. An increase in the antioxidant capacity of bread made with the phenolic compound was also found.     

Alginate-based coatings charged with hydroxyapatite and quercetin for fresh-cut papaya shelf life

In this study, the effect of alginate-based coatings charged with quercetin glycoside compounds and hydroxyapatite/quercetin glycoside compounds (HA/QUE) on the microbiological quality, and on bioactive compounds of fresh-cut papaya, was evaluated for 14 days at 6 °C. Alginate coatings with hydroxyapatite/quercetin showed a high capability to slow down the growth of all microbiological parameters investigated. At the end of cold storage, the total bacteria count in papaya samples covered with HA/QUE alginate coating was 4.8 log CFU g⁻¹ which is significantly lower (P < 0.05) than 8.3 log CFU g⁻¹ for uncoated samples. Total carotenoids’ percentage decrease, at the end of storage, was about 20% in papaya with active coatings, with respect to the losses of 39 and 35%, registered in uncoated and alginate-coated samples respectively. Vitamin C content and the antioxidant activity measured in papaya coated with HA/QUE alginate showed significantly higher values (P < 0.05) for each storage day than those detected for control- and alginate-coated samples. Based on the sensory evaluation, active-coated fresh-cut papaya reached, at the end of the storage period, suitable values for commercial purposes.     

Numerical Study of Scale Effects on the Stiffness Modulus of Rock Masses

The purpose of this paper is to contribute to the study of scale effects on the stiffness modulus of discontinuous rock masses from a mechanical point of view. The study has been conducted on the basis of the observation that the length and density of the natural discontinuities (cracks) in rock masses increase with the volume of the mass. Compressive tests on specimens containing open and closed flat cracks have been simulated through a numerical procedure that is based on the displacement discontinuity method and the fictitious stress method. Cracks have been generated, through a random process, with dips in the 0°–180° range. Both open and closed cracks have been considered. The numerical results obtained for specimens containing open cracks are found to approach the values obtained through an analytical solution. Then, the numerical method has been applied to the study of scale effects on the stiffness modulus of specimens with closed cracks. The numerical results show a decrease in the stiffness modulus with an increase in the size of the rock volume.