Analysis of shearing stress in the limited durability of bovine pericardium used as a biomaterial

The objective of the study was to determine the shearing stress exerted by the suture thread under conditions of normal working stress. Thirty-six samples of calf pericardium, similar to that employed in the manufacture of bioprosthetic cardiac valve leaflets, were subjected to tensile testing. Prior to the trial, a continuous suture was sewn in the central zone of each sample, at a 45° angle to the longest axis of the sample, using commercially-available threads (silk, Gore-Tex, Surgilene and nylon). Application of the Mohr circle for combined wear revealed that the shearing stress ranged between 2.68-fold greater (for samples sewn with silk) and 5.48-fold greater (for samples sewn with nylon) than the working tensile stress in the region of the suture. It is concluded that the shearing stress is responsible for the limited durability of sutured samples of calf pericardium prepared to simulate bioprosthetic cardiac valve leaflets. © 1998 Chapman & Hall     

Out of the picture? How incompatible knowledge and distant visual stimuli may foster idea generation

Visual stimuli such as pictures, sketches or prototypes play a major role in idea generation. Companies today often promote the use of these non‐verbal tools during creativity sessions, at the early stages of design. However, recent studies tend to show that these tools do not systematically enhance idea generation. Our research project therefore aims to better understand the contribution of visual stimuli during creativity sessions, and especially the contribution of distant stimuli which present knowledge that appears to be incompatible with the design topic. This study is based on an exploration led at the automotive company Renault by a team working on new services for charging electric vehicles. During idea generation sessions, a set of pictures was used by a meeting facilitator to inspire the team with new ideas. We show that the effects produced by the different pictures are varied: they do not always promote radical expansion, and when they do, expansion is not always of the same nature. Moreover, represented knowledge appears to have a major influence on idea generation, as the most original ideas came from pictures that not only expanded initial knowledge, but also helped to reorder the team's knowledge base and introduce new design rules.     

A statistical trust system in wireless mesh networks

Most trust and reputation solutions in wireless mesh networks (WMNs) rely on the intrusion detection system (IDS) Watchdog. Nevertheless, Watchdog does not consider packet loss on wireless links and may generate false positives. Consequently, a node that suffers from packet loss on one of its links may be accused wrongly, by Watchdog, of misbehaving. To deal with this issue, we propose in this paper a novel trust system which considers packet loss of links. Our trust system is based on a statistical detection method (SDM) implemented on each node of the network. Firstly, the SDM, via CUSUM test, analyzes the behavior of the packets loss in order to detect a dropping attack. Secondly, the SDM, through the Kolmogorov-Smirnov test, compares the behavior of the total packets loss with that of the control packets in order to identify the attack type. Our system allows every WMN’s node to assign to each of its neighbors, a trust value which reflects its real behavior. We have validated the proposed SDM method via extensive simulations on ns2 and have compared our trust system with an existing solution. The results display that our SDM solution offers better performance.     

Transition metal catalysis in fluorous media: application of a new immobilization principle to rhodium-catalyzed hydrogenation of alkenes

Biphase systems were generated by combining toluene solutions of alkenes (2-cyclohexen-1-one, 1-dodecene, cyclododecene, 4-bromostyrene) and CF₃C₆F₁₁ solutions of the pre-catalyst ClRh[P(CH₂CH₂(CF₂)₅CF₃)₃]₃ ((1); 1.1–0.8 mol%) and placed under 1 atm of H₂. The perfluoroalkyl segments in (1) confer high affinities for fluorocarbons. After 8–26 h at 45°C, the CF₃C₆F₁₁ phases were separated, and extracted with an equal volume of toluene. GLC analyses of the toluene solutions showed 98–87% yields of the hydrogenation products cyclohexanone, dodecane, cyclododecane, and 4-bromoethylbenzene (turnover numbers 120–87). The CF₃C₆F₁₁ phases were charged with new toluene solutions of 2-cyclohexen-1-one or 1-dodecene, and similarly treated with H₂. There was no significant loss of catalyst activity over three cycles. A preparative reaction gave cyclohexanone in 89% yield. Some C=C isomerization could be detected during the course of 1-dodecene hydrogenation, and (1) gave a dihydride complex in the absence of alkene.     

ADAPTIVE PREDICTIVE CONTROL: LIMITS OF STABILITY

This paper summarizes the stability results already derived for predictive and adaptive predictive control, discusses them from an intuitive and practical implementation perspective and, from the same perspective, illustrates them by means of two simulated examples. In this way it recalls the limits of stability when applying predictive control and how they are related to the modelling errors, which may change as the process dynamics changes. Also it recalls how, by adding adaptation to the predictive scheme, this source of instability may be compensated for. Already within the adaptive predictive formulation it considers the limits of stability for different scenarios, particularly when a reduced-order adaptive predictive model cannot account for unmodelled process dynamics. © 1997 John Wiley & Sons, Ltd.     

Analysis of a 35·6 kb Region on the Right Arm of Saccharomyces cerevisiae Chromosome XV

We report the sequence of a 35 600 bp fragment covering the PET123 region on the right arm of chromosome XV from Saccharomyces cerevisiae. This region contains 19 possible open reading frames (ORFs) of which 16 are non-overlapping ORFs. Eight ORFs correspond to the SPP2, SMP3, RPB2, PDR5, NFI1, PUP1, PET123 and MTR10 loci, described previously. Two ORFs correspond to yeast homologues of genes from other organisms: O3530 is a member of the large ribosomal subunit protein L13 family and O3560 (SME1 gene) is a 94-codon ORF and is a homologue of the mammalian SmE spliceosomal core protein. Three ORFs (O3513, O3521, O3548) present significant similarities to proteins of unknown function and three ORFs (O3510, O3536, O3545) lack homology to sequences within the databases screened. The sequence has been deposited in the GenBank database under Accession Number U55020. © 1997 by John Wiley & Sons, Ltd.     

EFFECT OF ULTRASONIC TREATMENTS ON THERMOACIDOPHILIC ALICYCLOBACILLUS ACIDOTERRESTRIS IN APPLE JUICE

The effect of ultrasonic treatments on Alicyclobacillus acidoterrestris in apple juice was investigated. In general, inactivation of the cells was more pronounced at an elevated power level and as the processing time increased. Approximately 60% of the cells were inactivated after treating the apple juice with 300-W ultrasound for 30 min. The reduction reached more than 80% when the juice was processed for 60 min. The linear inactivation rates ( D values) of ultrasound on A. acidoterrestris were both process- and strain-dependent. The lowest D value at 36.18 min was found when using 600-W ultrasound to treat the A30 strain isolated from the air of a commercial apple juice processing plant, whereas the strain isolated from apple juice concentrate was found most resistant against ultrasound. Changes of sugar content, acidity, haze and juice browning were noted after ultrasonic treatments but did not adversely alter the juice quality.

PRACTICAL APPLICATIONS

Characterization of the effects of ultrasonic treatments on thermoacidophilic Alicyclobacillus acidoterrestris provides better understanding of how ultrasound technology could assist in alleviating the hard-to-detect spoilage caused by this spore former. Although ultrasonic technology might not be suitable as a standalone unit operation to inactivate high cell loads, the process could be integrated with other thermal or nonthermal technologies to enhance processing efficiencies, consequently preventing microbial spoilage caused by A. acidoterrestris .     

The effects of skewness and kurtosis of processing times in unpaced lines

Numerous empirical studies have shown that, in unpaced lines, the stations' processing times have a variety of shapes (i.e., skewness and kurtosis))65. Thispaper investigates how the line's utilization factor is affected by these skewness and kurtosis measures. We found that positive skewness has a significant negative effect on utilization, and that the magnitude of this effect is greater if the line has more stations or less buffer capacity, or if the processing-times' cv is larger. Kurtosis also affects utilization significantly, but the effect may be negative or positive, depending upon the processing-times' skewness and the number of stations in the line. Our findings imply that when simulating long lines with small buffer capacities, it may be necessary to model more accurately the actual processing times. Also, the common practice of using normal distributions to approximate the typically positively-skewed processing times often leads to an overestimation of the actual utilization rate.     

Coordination Chemistry in Mineral Processing

Abstract

In mineral processing industry, achieving an optimal extraction of valuable mineral components is an extremely important goal. The processes of leaching, solvent extraction and flotation are major methods of processing minerals under aqueous conditions in which coordination chemistry may play an important role, and in facilitating the realization of this goal. The success of some of these processes is ascribed to the ability of the chemical reagents to form stable coordination complexes with metal ions in the aqueous solution or on the surfaces of the mineral lattice. Leaching processes which involve complex formation usually result in increased dissolution of mineral values in aqueous solution, and may include cyanide, basic and chloride leaching. In solvent extraction, the extractant and masking reagents react with metal ions to form principally coordination complexes, which are either selectively extracted into the organic phase or retained in the aqueous raffinate. This is the basis underlying the concentration and purification of metal values by this process. Flotation processes, which employ collectors and depressants whose interactions with metal ions in aqueous solution lead to complex formation through coordinate bonding are believed to be more efficient than other analogous processes. In an effort to contribute to the understanding of the chemistry of these processes, the authors have attempted to review the role of coordination chemistry in mineral processing by flotation, leaching and solvent extraction.     

Aloysia triphylla infusion protects rats against dextran sulfate sodium-induced colonic damage

BACKGROUND: Inflammatory bowel diseases consist of uncontrolled intestinal inflammation leading to mucosal disruption. Polyphenols are micronutrients with antioxidant and anti‐inflammatory properties and may play an interesting role in the prevention of intestinal inflammation. Lemon verbena (Aloysia triphylla (L'Herit.) Britton, Verbenaceae) infusion is a popular herbal drink rich in polyphenols. This study evaluated the protective effects of lemon verbena infusion consumption on the development of dextran sulfate sodium (DSS)‐induced colitis in rats. The infusion was given to rats as a drink providing 82 µmol polyphenols day^?1 for 21 days. Colitis was induced with 40 g l^?1 DSS in the drink for the last 7 days. RESULTS: Lemon verbena infusion treatment restored body weight gain and prevented colonic shortening. Despite no protective effect on myeloperoxidase activity, A. triphylla infusion limited histological colonic alterations. CONCLUSION: The results suggest that lemon verbena infusion partially protects rats against DSS‐induced inflammation. Copyright © 2011 Society of Chemical Industry