Role of fibers in controlling unrestrained expansion and arresting cracking in Portland cement concrete undergoing alkali-silica reaction

An experimental study was undertaken to investigate the role of polypropylene or brass-coated steel fibers in controlling unrestrained expansions and delaying and arresting cracking in Portland cement concrete due to alkali-silica reaction. Portland cement concrete and fiber-reinforced concrete (FRC) mixtures were prepared at a w/c ratio of 0.40 using modified Type I cement, reactive fine particles, and coarse limestone aggregates. Prism (5×5×30 cm) and plate (13.5×13.5×3 cm) specimens were prepared and cured for 7 or 28 days before exposure to a special treatment to accelerate ASR. Expansion, time of cracking, and ultrasonic pulse velocity were determined over a treatment period of 65 days using prism specimens. Ultimate cracking pattern and extent were determined after a treatment period of 85 days using plate specimens. The results showed that while fibers did not contribute significantly to controlling pre-cracking and post-cracking expansions, they played a significant role in delaying cracks formation and limiting their extent. Considering its lower cost and content, the performance of polypropylene fibers was superior to that of brass-coated steel ones. The potential of brass-coated fibers in arresting ASR cracking was significantly affected by age of concrete when subjected to treatment.     

Comparative modelling of major house dust mite allergen Der p I: structure validation using an extended environmental amino acid propensity table

A model of the 3-D structure of a major house dust mite allergenDer p I associated with hypersensitivity reactions in humanswas built from its amino acid sequence and its homology to threeknown structures, papain, actinidin and papaya proteinase flof the cysteine proteinase family. Comparative modelling usingCOMPOSER was used to arrive at an initial model. This was refinedusing interactive graphics and energy minimization with theAMBER force field incorporated in SYBYL (Tripos Associates).Compatibility of the Der p I amino add sequence with the cysteineproteinase fold was checked using an environment-dependent aminoadd propensity table incorporated into a new program HARMONYwith a variable length windowing facility. A fiveresidue windowwas used to probe local conformational integrity. Propensitieswere derived from a structural alignment database of homologousproteins using a robust entropy-driven smoothing procedure.Der p I shares essential structural and mechanistic featureswith other papain-like cysteine proteinases, including cathepsinB. The active-site t iolate-imidazolium ion pair comprises theside chains of Cys34 and Hisl70. A cystine disulfide not presentin other known structures bridges residue 4 of an N-terminalextension and the core residue 117. Two conserved disulfidebridges are formed by residues 31 and 71 and residues 65 and103. Model building of peptide substrate analogue complexessuggests a preference for phenylalanyl or bask residues at theP₂ position, whilst selectivity may be of minor importance atthe S₁ subsite. The electrostatic influences on the Der p Iactive-site ion pair and extended peptide binding region aremarkedly different from those in known structures. A highlyimmunogenic surface exposed region (residues 107–131),comprising several overlapping T cell epitope sites, has noshared sequence identity with human liver cathepsin B and containsthree insertion-deletion sites. The structure provides a basisfor testing the substrate specificity of Der p I and the potentialrole of proteinase activity in hypersensitivity reactions. Thesestudies may offer a new treatment strategy by hyposensitizationwith inactive mutants or mutants with significantly alteredproteinase activity, either alone or complexed with antibody.     

13C nuclear magnetic resonance spectroscopic analysis of the triacylglycerol composition ofBiota orientalis and carrot seed oil

¹³C nuclear magnetic resonance (NMR) spectroscopic analysis of the whole oil (triacylglycerols) ofBiota orientalis seeds confirms the presence of oleate [18:1(9Z)], linoleate [18:2(9Z, 12Z)], linolenate [18:3((9Z, 12Z, 15Z)], 20:3 (5Z, 11Z, 14Z), 20:4(5Z, 11Z, 14Z, 17Z), and saturated fatty acids in the acyl groups by comparing the observed carbon shifts with previously established shift data for model triacylglycerols. This technique shows that the saturated, 20:3 and 20:4 fatty acids are distributed mainly in the α-acyl positions, whereas oleate, linoleate, and linolenate are randomly acylated to the α- and β-positions of the glycerol “backbone”. Stereospecific hydrolysis of theBiota oil with pancreatic lipase, followed by chromatographic analysis of fatty esters, reveals the presence of trace amounts of 16:0(0.7%), 18:0(0.5%), 20:3 (0.4%), and 20:4 (1.3%) in the β-position of the glycerol “backbone”, which are undetectable by¹³C NMR technique on the whole oil. Semiquantitative assessment of the¹³C NMR signal intensities gives the relative percentages of the fatty acid distribution as: saturated 16:0, 18:0 (12.0% α-acyl), oleate (7.7% α-acyl 8.7% β-acyl), total linoleate and linolenate (31.7% α-acyl; 24.2% βacyl), total 20:3 and 20:4 (15.7% α-acyl). The¹³C NMR spectroscopic analysis of carrot seed oil identifies the presence of saturated (18:0), 18:1(6Z), 18:1(9Z), and 18:2(9Z, 12Z). The saturated fatty acid is found in the α-acyl positions. Semi-quantitative assessment of the signal intensities gives the relative percentages of the fatty acids as: 18:0 (4.5% α-acyl), 18:1(6Z) (49.6% α-acyl; 19.7% β-acyl), oleate (6.5% α-acyl; 8.6% β-acyl) and linoleate (5.2% α-acyl; 6.9% β-acyl).     

A hybrid mobile object tracker based on the modified Cuckoo Search algorithm and the Kalman Filter

Most revolutionary algorithms are inspired from the behavior of natural species. This inspiration can be drawn from their reproductive behavior, flying mode, or even their ways of communication. One of the most efficient metaheuristics in a discrete search space is the Cuckoo Search algorithm, inspired by the Cuckoo?s reproductive behavior and combined with the Lévy flight pattern adopted by many animals and insects. In this paper, we present a new tracking approach, the Hybrid Kalman Cuckoo Search tracker, using a modified version of the Cuckoo Search algorithm combined with the well-known Kalman Filter. The Cuckoo Search algorithm is combined with the prediction step adopted by the Kalman Filter to enhance the initial population?s quality. Using the Hybrid Kalman Cuckoo Search tracker, we can efficiently explore the search space in order to locate an object?s position from one frame to the next. The Lévy flight model is also modified in order to re-adapt the Lévy step size as the algorithm approaches the desired solution. The Hybrid Kalman Cuckoo Search tracker is tested on a variety of datasets including one where we incorporated different situations, as well as some videos from the CAVIAR, SPEVI, and other datasets. The comparative study results show that the proposed algorithm outperforms the Particle Swarm Optimization based tracker, especially in terms of computation time.     

Advantages of an Emulsion‐Produced Ziegler‐Natta Catalyst Over a Conventional Ziegler‐Natta Catalyst

Summary: Self‐supported and MgCl₂‐supported Ziegler‐Natta catalysts, produced by two catalyst synthesis methods are compared. Borealis Polymers OY (Finland), who supplied the catalysts, developed the catalyst synthesis methods. The first method (Method One) is based on an emulsion system and consists of an in situ single step preparation. The second method (Method Two) consists mainly of two steps: formation of the catalyst carrier particles, and their subsequent impregnation with the active material. The results showed that Method One produced catalysts of compact, spherical particles with good intra‐particle homogeneity and a narrow particle size distribution. On the other hand, Method Two produced catalyst particles whose properties depended directly on that of the catalyst carrier: they were spherical but very porous, with a broad particle size distribution. Polymer particles produced with the two catalyst systems are perfect replicas of the catalyst particles. Fines formed either during catalyst preparation or during polymerization were observed only with the catalyst prepared using Method Two. The particles of the catalysts produced using Methods One and Two had similar activities, independent of the initial particle size. Fragmentation of catalyst particles was very fast for both catalyst systems and was only observed to be 100% completed using the catalyst produced with Method One. Studies of the thermal properties showed that the catalyst prepared using Method One produced poly(propylene) of higher crystallinity and with a narrower melting peak.

SEM images of polymer particles produced by (A) Method One and (B) Method Two.     

Pitting corrosion of lead in sodium carbonate solutions containing NO3 ions

Pitting corrosion of Pb in Na₂CO₃ solutions (pH=10.8) containing NaNO₃ as a pitting corrosion agent has been studied using potentiodynamic anodic polarization, cyclic voltammetry and chronoamperometry techniques, complemented with scanning electron microscopy (SEM) examinations of the electrode surface. In the absence of NO₃⁻, the anodic voltammetric response exhibits three anodic peaks prior to oxygen evolution. The first anodic peak A₁ corresponds to the formation of PbCO₃ layer and soluble Pb²⁺ species in solution. The second anodic peak A₂ is due to the formation of PbO beneath the carbonate layer. Peak A₂ is followed by a wide passive region which extends up to the appearance of the third anodic peak A₃. The later is related to the formation of PbO₂. Addition of NO₃⁻ to the carbonate solution stimulates the anodic dissolution through peaks A₁ and A₂ and breaks down the dual passive layer prior to peak A₃. The breakdown potential decreases with an increase in nitrate concentration, temperature and electrode rotation rate, but increases with an increase in carbonate concentration and potential scan rate. Successive cycling leads to a progressive increase in breakdown potential. The current/time transients show that the incubation time for passivity breakdown decreases with increasing the applied anodic potential, nitrate concentration and temperature.     

MICROWAVE VACUUM DRYING OF BANANA SLICES

Vacuum drying of banana slices was studied in a domestic microwave oven. The results show that banana temperature rises uniformly and rapidly to the saturation water vapor temperature corresponding to the vacuum used then rises slowly until most of the free moisture is lost. The thermal and drying efficiencies were found to drop from almost 100% at the beginning of the drying (high moisture content) to as low as 40% and 30% respectively at the end of drying. Both efficiencies were found to increase with the use of vacuum, especially at low moisture content.     

Preparation and characterization of cyclic polyesters from ring‐chain reactions of poly(oxyepichlorhydrin oxymaloyl)

In this article, the synthesis and characterization of cyclic polyesters of poly(oxyepichlorhydrin oxymaloyl) from a ring‐chain reaction induced by “Maghnite,” an acid‐exchanged montmorillonite as acid solid ecocatalyst (Mag‐H⁺), is described. Maghnite is already used as catalyst for polymerization of many vinylic and heterocyclic monomers [Belbachir, U.S. Pat. 066969.0101 (2001)]. The reactions were monitored by gel permeation chromatography and ¹H‐NMR spectroscopy and the existence of cyclic species was proven. The effect of the amount of catalyst on yield and molecular weight of polymer was studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1240–1243, 2006     

Kinetic investigation of the radical polymerization of N-acryloylpiperidine in solution

The kinetics of free radical polymerizations of N-acryloylpiperidine (NAPi) were studied in benzene (Bz) using 2,2′-azobisisobutyronitrile (AIBN) as initiator. The activation energy was determined to be 111.7 kJ mol^?1. The overall rate of polymerization of the NAPi-AIBN-Bz system at 60°C was investigated as a function of monomer and initiator concentrations. Deviation from normal kinetics was observed with an order of 1.48 with respect to the monomer. The observed dependence of the rate constants k_p/k on monomer concentration could not be explained by the diffusion theory or the theory of electron donor-acceptor (EDA) complexes. The observed data have, however, been satisfactorily interpreted by the ‘hot’ radical theory.     

2D grid architectures for the DFT and the 2D DFT

New algorithms for the DFT and the 2-dimensional DFT are presented. The DFT and the 2-dimensional DFT matrices can be expressed as the Kronecker product of DFT matrices of smaller dimension. These algorithms are synthesized by combining the efficient factorization of the Kronecker product of matrices with the highly hardware efficient recursive implementation of the smaller DFT matrices, to yield these algorithms. The architectures of the processors implementing these algorithms consist of 2-dimensional grid of processing elements, have temporal and spatial locality of connections. For computing the DFT of sizeN or for the 2D DFT of sizeN=N ₁ byN ₁, these algorithms require 2N multipliers and adders, take approximately computational steps for computing a transform vector, and take approximately computation steps between the computation of two successive transform vectors.