Investigation of polymerizability of ω-alkenyldioxolanes with α-olefins and alkyl vinyl ethers by modified ziegler-natta catalysts

Results are presented of an investigation on the polymerizability of functional olefins, such as allylisopropylidene glycerol (AIPG) and undecenylisopropylidene glycerol (UIPG), in the presence of conventional and modified Ziegler-Natta catalysts based on TiCl₄ or MgCl₂-supported titanium and triisobutylaluminum, hexaisobutyltetraalumoxane, or bisdiethyl-aluminum sulfate. Homopolymerization experiments were performed on AIGP at temperatures of -78, 25, and 50°C; only these at 50°C provided appreciable amounts of polymeric materials insoluble in methanol, whose structures comprise monomeric units derived from opening both dioxolane rings and vinyl double bonds. In spite of all attempts and precautions, polymerization experiments carried out on mixtures of the functional olefins AIPG and UIPG with either 4-methyl-1-pentene or isopropyl vinyl ether gave rise to the homopolymers of the nonfunctional α-olefin and of the vinyl ether, without any appreciable amount of either copolymers or homopolymers of the dioxolane containing monomers. © 1996 John Wiley & Sons, Inc.     

A strategy for the efficient full-wave description of complex waveguide networks

The mode-matching analysis of rectangular waveguide networks requires a complex segmentation of the structure into simple elements. The way these elements are connected has a strong influence on the computing performance of the code. Moreover, for complex structures the size of the coefficient matrix of the main system can easily reach unaffordable dimensions, so that the use of an efficient solving strategy becomes indispensable. A new approach to the optimum automatic choice of the interconnections is presented, leading to a highly stable and outperforming method of analysis. A Butler 4 × 4 matrix, with six branch guide couplers and four phase shifters, containing 336 uniform waveguide sections and bifurcations, has been studied, and the presented strategy has allowed a performance increase up to two orders of magnitude. © 1996 John Wiley & Sons, Inc.     

DTG combustion behaviour of charcoals

In this paper, data are reported for the behaviour of some charcoals during combustion and devolatilization in a thermal analyser.     

Experimental validation of a geographical information systems-based procedure for predicting pesticide exposure in surface water

A GIS-based procedure for predicting pesticide exposure in surface waters has been applied on a pilot river basin characterized by intensive agricultural activity. The predictive approach has been validated through experimental monitoring, performed by collecting manual and automatic water samples during the productive season. Five active ingredients (terbuthylazine, metolachlor, alachlor, linuron, fenitrothion) were selected for analysis to validate the predictive approach. Comparison between predicted and experimental values showed good agreement for terbuthylazine and metolachlor (used in large volumes within the basin), demonstrating the reliability of the approach. However, some anomalous results were obtained for some of the other chemicals, which serve to highlight the difficulties in getting reliable input data, in particular on application patterns (rate and time). Furthermore, the value of mapping pesticide exposure on the medium-large scale is described, and the limitations of the reported predictive approach are discussed.     

Characterization of a deswapped triple mutant bovine odorant binding protein

The stability and functionality of GCC-bOBP, a monomeric triple mutant of bovine odorant binding protein, was investigated, in the presence of denaturant and in acidic pH conditions, by both protein and 1-aminoanthracene ligand fluorescence measurements, and compared to that of both bovine and porcine wild type homologues. Complete reversibility of unfolding was observed, though refolding was characterized by hysteresis. Molecular dynamics simulations, performed to detect possible structural changes of the monomeric scaffold related to the presence of the ligand, pointed out the stability of the β-barrel lipocalin scaffold.     

Biodiesel production from Stichococcus strains at laboratory scale

BACKGROUND: This paper reports the results of an experimental campaign of autotrophic cultures of Stichococcus strains aiming at selecting the most promising strain for biofuel production. The strain selected—S. bacillaris 158/11—was cultivated in 1 L lab‐scale bubble column photobioreactors under fed‐batch and semi‐continuous conditions. A Bold basal medium supplemented with NaNO₃ as nitrogen source was adopted. Tests were carried out at 23 °C, 140 µE m^?2 s^?1, and air flow rate ranging between 0.4 and 4 vvm. Cultures were characterized in terms of pH, concentration of total nitrogen, total organic carbon, total inorganic carbon, biomass, lipid fraction and methyl‐ester distribution of transesterified lipids. RESULTS: S. bacillaris 158/11 proved to be the best strain to produce biodiesel. Methyl‐ester distribution was characterized by a large fraction of methyl palmitate, methyl linolenate, methyl linoleate, and methyl oleate along with phytol. The process photosynthetic efficiency—fraction of available light stored as chemical energy ‐ was about 1.5%. Specific biomass productivity was ～60 mg_DM L^?1 day^?1 under the semi‐continuous conditions tested. Total lipid productivity was 14 mg L^?1 day^?1 at a dilution rate of 0.050 L day^?1. CONCLUSION: S. bacillaris 158/11 is a potential strain for massive microalgae cultures for biofuel production. Higher biomass/total‐lipid productivity could be obtained in sunlight. Copyright © 2011 Society of Chemical Industry     

Nanostructured Polymer Blends: From Core/Shell Nanoobjects to Continuous Three‐Phase Morphologies

A PS‐b‐PIP‐b‐PMMA copolymer has been melt‐blended with homo‐PMMA with a similar molecular weight as the PMMA block. For a 50:50 wt.‐% mixture, the components form 3D bicontinuous lamellae. Upon annealing at 190 °C, a more regular network is observed, which consists of PMMA and 55 nm‐thick bilayered lamellae of triblock copolymer, both being continuous. This co‐continuity persists even when $\overline {M} _{{\rm n}} $ of the homo‐PMMA is twice that of the PMMA block in the copolymer. For 30:70 and 20:80 wt.‐% copolymer/homopolymer pair, the copolymer forms cylindrical and spherical phases, respectively. Blends have also been prepared by solvent casting. Large domains of copolymer interconnected by few lamellae are observed in the 50:50 blend that reorganize into a bicontinuous network upon annealing.

     

Failure Analysis of Modern Silicon Dice

Although the utilization of silicon dice in electronic devices has been in place for approximately 50 years, its widespread application has occurred more recently with the rapid expansion of the consumer markets for digital devices such as cameras, personal computers, video players, and smart phones. In particular, due to the recent market drive in the miniaturization and cost reduction of electronic products, silicon dice are often utilized without encapsulation and mounted directly to the substrate by means of conductive adhesives or BGA mounting. Silicon die often need to be thinned to a few hundred micrometers thickness to fit into compact devices and to reduce parasitics. The intrinsic brittle nature of silicon in combination with the lack of mechanical protection such as encapsulation has made fracture of bare dice a typical failure mechanism in handheld electronic devices. In the current work, we tested to failure {100} silicon dice and obtained mirror–mist boundary measurements for correlation to the fracture strengths of the parts. This work will also present various practical examples of how to reliably conduct failure analysis of fractured silicon dice. The intrinsic brittle nature of silicon in combination with the lack of mechanical protection such as encapsulation has made fracture of bare dice a typical failure mechanism in handheld electronic devices such as cameras, portable computers, tablets, media players, and smart phones. In these products, silicon dice are often utilized without encapsulation and are attached directly to the substrate by means of conductive adhesives or ball grid array mounting. Modern silicon dice used in these products typically have small dimensions and higher flexural strength compared to their predecessors. Prior silicon fractographic findings have investigated low strength failures. In the current work, we extend the quantitative fractography of silicon to the high failure stress regime. We have mechanically tested modern silicon dice to failure by four‐point bending and obtained mirror–mist boundary measurements for correlation to the fracture strengths of the specimens. Two key areas are addressed which improve the practical application of quantitative fractography to modern silicon dice: (1) application of silicon fractography to high flexural strength regimes and (2) development of a systematic means of reliably measuring fracture surface features.