Skin nanostructural features determine suture biomechanics

The stress state surrounding wounds in the skin plays an important role in the healing process; it affects the tissue strength, its aesthetic, and its resistance to infections. In this paper, the collagen fibril and elastin matrix damage mechanics following suture point application is investigated at the nanoscale; to this purpose, a model has been developed, which accounts for the architectural and mechanical features of the tissue components. Results indicate that the force displacement caused by the suture point application curve initially stiffens and subsequently softens. Softening occurs due at first to the enlargement of the elastin matrix damaged area and second to the collagen fibril disruption. Three regions may be identified: the first one, (0-0.38 N) refers to skin withstanding the force both in the collagen and elastin components; the second one (0.38-0.75 N) concerns the mechanism of elastin matrix damage; in the last one (>0.75 N), the collagen fibrils also fail. Accordingly, by properly choosing the number of suture points, it is possible to define the optimal suture points number for a given wound closure force.     

Simulation of multistage extraction of antioxidants from Chilean hazelnut (<Emphasis Type="Italic">Gevuina avellana</Emphasis>) hulls

The objective of this study was to analyze the factors affecting the ethanol extraction of Chilean hazelnut (Gevuina avellana) hulls to obtain antioxidant compounds. The effects of temperature on the kinetics of polyphenolics extraction and on the antioxidant activities of the extracts were assessed. The radical-scavenging activities of the extracts were comparable with that of BHA when used at the same concentration. The optimal temperature for the antioxidant activities of the extracts was 40°C. A four-stage cross-flow extraction was carried out and a four-stage countercurrent extraction was simulated, where each stage lasted 30 min. Best results were obtained with countercurrent extraction, which produced an extract that showed 94.4% α,α-diphenyl-β-picrylhydazyl radical inhibition, compared with 86.2% obtained in the first stage of cross-flow extraction and 92.62% in a batch extraction that lasted 100 h. UV-vis and NIR spectra of extracts from cross-flow and from the simulated countercurrent extraction revealed that the composition of extracts varied along the stages and was affected by the operational strategy.     

Dietary fiber potential in Iberian-American countries: food,products and residues

The reduced intake of dietary fiber (DF) has been associated with the increase in the incidence of several non-transmissible chronic diseases. Recently many researchers from Iberian-American countries have been studying DF of food and industrial residues in order to improve technological knowledge about concentrates production as well as the development and test of enriched products originated from regional food. The present study aimed to evaluate the regional DF potential based on compilation of data about this nutrient. There is great availability of regional and traditional food with considerable DF amounts as we may find in fruits, vegetables and cereals and legumes. Concentrated sources of DF obtained from different industrial residues were characterized and evaluated making possible their utilization in food enrichment. Cookies added to corn residues (16.8% DF in integral weight) in Colombia, and pasta added to lupine fiber in Chile (11.2%) are examples of tested enriched products. Products like bread with whole wheat (12%), products for especial uses as well as pills of citric DF (55%) and food for enteral diets (1-1.9%) are already available on Cuba market. The dietary fiber contents presented in this work allow us to have an idea of the potential of such nutrient in Iberian-American countries. Such potential has been proved to be considerably representative. It is worth to inform that the complete DF database is available on the CYTED X1.6/CNPq Project Web site (http://www.fcf.usp.br/cytedxi16). It provides data on 817 regional, traditional and not conventional foods, that can be searched and utilized by professional from different areas.     

Integrated ambient ozone evaluation by passive samplers and clover biomonitoring mini-stations

An ozone monitoring network was set up using passive samplers and biological mini-stations of two clones of white clover (Trifolium repens L. cv. Regal), NC-R (O(3)-resistant) and NC-S (O(3)-sensitive). This paper reports on a pilot study performed in the period June-October 1999 in the Rome municipal area by using five biomonitoring mini-stations and ozone passive samplers with a new nitrite based design. This combined methodology can be used to obtain information on the biological implications of the injury due to tropospheric ozone. The two techniques can integrate data for the short-medium period and can be placed in different urban and rural sites, proving to be a very useful tool for ozone concentration mapping.     

Distributed Belief Revision

In this paper, a distributed approach to belief revision is presented. It is conceived as a collective activity of a group of interacting agents, in which each component contributes with its own local beliefs. The integration of the different opinions is performed not by an external supervisor, but by the entire group through an election mechanism. Each agent exchanges information with the other components and uses a local belief revision mechanism to maintain its cognitive state consistent. We propose a model for local belief revision/integration based on what we called: Principle of Recoverability. Computationally, our way to belief revision consists of three steps acting on the symbolic part of the information, so as to deal with consistency and derivation, and two other steps working with the numerical weight of the information, so as to deal with uncertainty. In order to evaluate and compare the characteristics and performance of the centralized and of the distributed approaches, we made five different experiments simulating a simple society in which each agent is characterized by a degree of competence, communicates with some others, and revise its cognitive state. The results of these experiments are presented in the paper.     

Influence of lactic acid bacteria on survival of Escherichia coli O157:H7 in inoculated Minas cheese during storage at 8.5 degrees C

Minas cheese is a typical Brazilian fresh cheese, manufactured by addition of rennin and CaCl2 to milk, followed by draining the curd. The intrinsic characteristics of this product make it favorable for growth of pathogens, including Escherichia coli O157:H7. The influence of the addition of a commercial mesophilic type O lactic culture to this product on the growth of this pathogen during storage at 8.5 degrees C was evaluated. Eight different formulations of Minas cheese were manufactured using raw or pasteurized milk and with or without salt and lactic culture. Individual portions of each formulation were transferred to sterile plastic bags and inoculated with E. coli O157:H7 to yield ca. 10(3) or 10(6) CFU/g. After blending by hand massaging the bags, samples were stored at 8.5 degrees C for up to 14 days. E. coli O157:H7 was counted after 1, 2, 7, and 14 days of storage using 3M Petrifilm Test Kit-HEC. Counts in samples without added lactic culture showed a 2-log increase in the first 24 h and remained constant during the following 14 days. Counts in samples with added lactic culture showed a 0.5-log increase in the first 24 h, followed by a decrease. These variations were statistically significant (P < 0.05). No significant variations (P > 0.05) were obtained for cheese samples manufactured with pasteurized or raw milk, with or without salt. Results indicate that the addition of type O lactic culture may be an additional safeguard to well-established good manufacturing practices and hazard analysis and critical control point programs in the control of growth of E. coli O157:H7 in Minas cheese.     

A minimum-time control strategy for torque tracking in permanent magnet AC motor drives

A minimum-time torque control strategy for permanent-magnet AC motor drives is presented. The proposed technique neither requires the solution of a HJB-type equation, which would be practically unfeasible, nor uses Pontryagin's maximum principle. Instead, the solution is obtained by an ad hoc procedure based on the computation of reachability and controllability sets. In principle, the optimal control strategy can be carried out by iteratively solving a fourth-degree polynomial equation. For its efficient implementation, an algorithm based on Sturm sequences is suggested. The sequence of online operations required by the algorithm for a given tolerance on the optimal time is illustrated. The method has been tested on a laboratory prototype. Experimental results show the effectiveness of the technique.     

Predicting Oil Ring Self-Lubricated Sleeve Bearing Temperature Rise and its Effect on Shaft Criticals

Several steps are involved in predicting the temperature rise within the babbitt/oil film of sleeve bearings. Initially, the viscous friction loss developed in the oil film is determined. This loss depends on the speed, length, and diameter of the journal, oil viscosity, and diametral clearance. A heat balance study then compares heat loss generation and dissipation rates. The final consideration is the ability of the oil rings to deliver the necessary oil flow rate. An approach for predicting sleeve bearing temperature rise and the adequacy of oil ring lubrication is described. It is shown that some of the design variables affecting the bearing temperature rise also influence the bearing oil film stiffness. The value of this stiffness plays a vital role in determining the shaft critical speed.     

Dissimilar Resistance Spot Welding of Q&P and TWIP Steel Sheets

Dissimilar resistance spot welding of twinning induced plasticity (TWIP) and quenching and partitioning (Q&P) steel grades has been investigated by evaluating the effects of clamping force, welding current, and welding time on the microstructure, shear tension strength, and fracture of welded samples. The spot welding of TWIP and Q&P steels promotes the occurrence of an asymmetrical weld nugget with a greater dilution of TWIP steel because of its lower melting temperature and thermal conductivity. As a result, weld nuggets exhibit an austenitic microstructure. TWIP steel undergoes a grain coarsening in the HAZ, whereas Q&P steel undergoes some phase transformations. Welded samples tend to exhibit higher shear tension strength as they are joined at the highest welding current, even though an improper clamping force can promote excessive metal expulsion, thereby reducing the mechanical strength of the welded joints. Shear tension welded samples failed through interfacial fracture with partial thickness fracture mode for a low welding current, while partial thickness with button pull fractures were observed when a high welding current was used. The weld spots predominantly failed at the TWIP side. However, as TWIP steel can work harden significantly in the more resistant welded joints, the failures occur, instead, at the Q&P side.     

A new route to graphene starting from heavily ozonized fullerenes: Part 3 – an electron spin resonance study

It is shown that graphite oxide (GO) and both heavily ozonized C₆₀ and C₇₀ fullerenes, known as “fullerene ozopolymers,” are paramagnetic materials with a very strong electron spin resonance (ESR) signal at room temperature. When thermally annealed, the paramagnetic centers are gradually lost in large part. This occurs at 350°C in the case of GO, while for fullerene ozopolymers, a higher temperature is required, reaching the same results in the end. The half-width of ESR signal is linked to the distribution of paramagnetic centers. Once again, striking analogies were found in the half-width of the ESR signal measured on GO and fullerene ozopolymers, at least in the temperature range of 25–450°C. Similarly, the same g-factor values, which are diagnostic for understanding the chemical nature of paramagnetic centers, were found on both GO and fullerene ozopolymers in all ranges of temperature considered.