Cure kinetics of a low epoxide/hydroxyl group-ratio bisphenol a epoxy resin–anhydride system by infrared absorption spectroscopy

An infrared absorption spectroscopy study of the curing kinetics of a low (1.12) epoxide/hydroxyl-group ratio bisphenol A epoxy resin—phthalic anhydride system is reported. A full infrared peak assignment to molecular vibrational modes is given for the range 400 to 4000 cm^?1, and the optical density behavior of all peaks during reaction is discussed in detail. Proposed rival reaction mechanisms are considered and their respective kinetic behavior discussed. The reaction was found to follow consecutive-step addition esterification and simultaneous addition etherification, and epoxide—hydroxyl group and carboxylic acid dimer hydrogen bonding was found to occur. The reaction behavior supports a proposed hydroxyl group-limited inhomogeneous bulk reaction mechanism of a colloid type.     

The effect of platinum and silver deposits in the photocatalytic oxidation of resorcinol

The effects of platinum (Pt) and silver (Ag) metallisation in the photocatalytic oxidation of resorcinol at pH 3 ± 0.5 have been investigated. The photocatalytic degradation of resorcinol was significantly improved by Pt/TiO₂, while the presence of Ag/TiO₂ enhanced the initial photocatalytic degradation rate of resorcinol slightly. Likewise, the photocatalytic mineralisation of resorcinol continued to be enhanced by Pt/TiO₂, but it was retarded when Ag/TiO₂ was used.

The function of Pt and Ag deposits on the surface of TiO₂ has been found to be markedly influenced by the interaction of resorcinol and its degradation products with the metal deposits. The presence of Pt or Ag on the surface of TiO₂ altered the distribution of degradation products of resorcinol as well as the production of photoactive species for the photocatalytic oxidation of resorcinol. The X-ray photoelectron spectroscopy (XPS), zeta potential and transmission electron microscopy (TEM) analyses have indicated that the contrasting effect of Pt and Ag deposits were governed by the oxidation states and the catalytic property of metal deposits. In addition to that, it has been found that the roles of metal deposits are specific and should not be generalised.     

HOW LIQUIDS SPREAD ON SOLIDS

A theory of the wetting of solids by liquids is put forward. The theory accounts for capillary pressure gradient, gravitational potential gradient, surface tension gradient, disjoining pressure gradient driving forces of flow in thick thin-films and of surface diffusion in thin thin-films. Disjoining pressure stems from the way intermolecular forces aggregate in submicroscopically thin films. For thick thin-films of slowly varying thickness the lubrication approximation to velocity distributions is appropriate. With this approximation the spontaneous, unsteady, two-dimensional spreading of liquid is shown to be governed by a nonlinear convective-diffusion equation for the evolution of the film thickness profile. The predictions of the theory agree with Marmur and Lelah's (1980, 1981) observations of water drops spreading on glass and with Bascom, Cottington and Singleterry's (1964) and Ludviksson and Lightfoot's (1971) observations of oils spreading on high energy surfaces. The theory is used to analyze Derjaguin and co-workers' (1944, 1957, 1970) blowing-off experiments designed to measure thin-film rheology. The theory is also used to buttress the proposition that much contact angle hysteresis is due simply to slow attainment of equilibrium.     

In situ, noninvasive characterization of superhydrophobic coatings

Light scattering was used to measure the time-dependent loss of air entrapped within a submerged microporous hydrophobic surface subjected to different environmental conditions. The loss of trapped air resulted in a measurable decrease in surface reflectivity and the kinetics of the process was determined in real time and compared to surface properties, such as porosity and morphology. The light-scattering results were compared with measurements of skin-friction drag, static contact angle, and contact-angle hysteresis. The in situ, noninvasive optical technique was shown to correlate well with the more conventional methods for quantifying surface hydrophobicity, such as flow slip and contact angle.     

Optimisation of four-sensor probes for measuring bubble velocity components in bubbly air-water and oil-water flows

In a previous paper Lucas and Mishra (2005) [3] a local four-sensor conductance probe was introduced to measure the velocity vectors of dispersed bubbles in bubbly two-phase flow in which the continuous phase is water. There are a very limited number of alternative methods available for bubble velocity vector measurement with which results from, for example, computational fluid dynamic models can be compared and so the four-sensor probe technique is of interest to the multiphase flow community. In the previous paper [3] a mathematical model was presented to calculate the velocity vector of each gas bubble from seven time intervals which were measured using the output signals from each of four ‘needle’ conductance sensors located within the probe. In the present paper, a new technique for making the local four-sensor probe is introduced to minimise interference with the measured bubbles. A new signal processing method is presented using criteria to ensure that (i) the group of sensor signals from which the bubble velocity vector is to be determined are all produced by the same bubble and (ii) bubbles which contact the local four-sensor probe in an ambiguous manner are ignored. The accuracy with which the locations of each of the rear sensors in the probe relative to the lead sensor can be measured influences the accuracy with which the bubble velocity vector can be measured. However, the degree to which the accuracy of the measured velocity vector is affected by errors in the measured probe dimensions is dependent upon the geometrical arrangement of the four sensors within the probe. Experimental results and an error analysis are presented which show that the susceptibility of the velocity vector measurement technique to errors in the measured probe dimensions is reduced if the geometrical arrangement of the four sensors is optimised. As a result of this initial work, an optimised probe, known as the P30 probe, was designed and built and results obtained from the P30 probe in swirling oil-in-water bubbly flow are presented. A probe calibration factor is defined in this paper which can be interpreted as a measure of the interference of a probe with the motion of the bubbles with which it interacts. For the probes described in this paper the calibration factor was found to be much closer to unity than for previous four-sensor probes described in the literature (e.g. [3]) suggesting that these new probes have a much smaller effect on the bubbles’ motion than previous probes.     

Silver Bullet Talks with Jeremiah Grossman

Silver Bullet Security Podcast host Gary McGraw interviews Jeremiah Grossman, founder and CTO of WhiteHat Security, who is well known for his work in Web application security.     

Magnetic quadrupole doublet focusing system for high energy ions

A high energy focused ion beam microprobe using a doublet arrangement of short magnetic quadrupole lenses was used to focus 1-3 MeV protons to spot sizes of 1x1 microm2 and 1-4.5 MeV carbon and silicon ion beams to spot sizes of 1.5x1.5 microm2. The results presented clearly demonstrate that this simple doublet configuration can provide high energy microbeams for microanalysis and microfabrication applications.     

CLUSTEREASY: A program for lattice simulations of scalar fields in an expanding universe on parallel computing clusters

We describe an MPI C++ program that we have written and made available for calculating the evolution of interacting scalar fields in an expanding universe on parallel clusters. The program is a parallel programming extension of the simulation program LATTICEEASY. The ability to run these simulations on parallel clusters, however, greatly extends the range of scales and times that can be simulated. The program is particularly useful for the study of reheating and thermalization after inflation. The program and its full documentation are available on the Web at http://www.science.smith.edu/departments/Physics/fstaff/gfelder/latticeeasy/. In this paper we provide a brief overview of what the program does and what it is useful for.

Program summary

Program title: CLUSTEREASYCatalogue identifier: AEBJ_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEBJ_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 7469No. of bytes in distributed program, including test data, etc.: 613 334Distribution format: tar.gzProgramming language: C++/MPIComputer: Cluster. Must have the library FFTW installedOperating system: AnyRAM: Typically 4 MB to 1 GB per processorClassification: 1.9External routines: A single-precision version of the FFTW library (http://www.fftw.org/) must be available on the target machine.Nature of problem: After inflation the universe consisted of interacting fields in a high energy, nonthermal state [1]. The evolution of these fields cannot be described with standard approximation techniques such as linearization, kinetic theory, or Hartree expansion, and must thus be simulated numerically. Fortunately, the fields rapidly acquire large occupation numbers over a range of frequencies, so their evolution can be accurately modeled with classical field theory [2]. The specific fields and interactions relevant at these high energies are not known, so different models must be tested phenomenologically. In many cases, e.g., those involving symmetry breaking, the wide range of physical time and length scales in the problem requires parallel computing.Solution method: CLUSTEREASY solves the equations of motion for interacting scalar fields in an expanding universe. The user describes a particular theory by entering the field potential and its derivatives in a model file and the program then uses a staggered leapfrog method to evolve the field equations and Friedmann equation for the fields and the expansion of the universe. Different processors compute the evolution on subgrids defined by block decomposition, and the processors exchange edge data after each time step to allow for calculation of spatial derivatives.Restrictions: In its current form CLUSTEREASY only includes scalar fields and does not include metric perturbations. For 2D and 3D simulations the cluster must already have the (free) libraries FFTW installed.Additional comments: CLUSTEREASY is the parallel form of the program LATTICEEASY (AEAW_v1_0), Comp. Phys. Comm. 178 (2008) 929.Note: The default installation type for FFTW is double-precision so care must be taken to specify single-precision when running the “configure” file associated with the FFTW software package installation.Running time: The running time can range from minutes to weeks.References:[1] A.D. Linde, Particle Physics and Inflationary Cosmology, Harwood, Chur, Switzerland, 1990.[2] S. Khlebnikov, I. Tkachev, Phys. Rev. Lett. 77 (1996) 219, hep-ph/9603378.     

"Evaluation of child witnesses for confrontation by criminal defendants": Erratum.

Reports an error in the original article by M. A. Small and G. B. Melton (Professional Psychology: Research and Practice, 1994[August], Vol 25[3], 228–233). Footnote 1 incorrectly indicates that the Craig brief was written without the aid of private legal counsel. Though the brief in question was written with more APA member involvement than has been the case for other briefs, private legal counsel participated and was listed as a coauthor. (The following abstract of this article originally appeared in record 1994-43476-001.) States have passed legislation governing the procedures by which children may testify in cases of child abuse. In Maryland v. Craig (1990), the US Supreme Court reviewed the constitutionality of these procedures. As a result, psychologists may be asked to perform evaluations regarding the potential trauma a child faces in confronting a defendant in a criminal case. Specifically, opinions of psychologists may be sought as to the potential trauma a child may endure as a result of a face-to-face confrontation with a defendant. Research relevant to this assessment is reviewed, and it is suggested that psychologists may be of most help in preparing children to testify.… (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Engineering linear F(ab')2 fragments for efficient production in Escherichia coli and enhanced antiproliferative activity

We developed a novel bivalent antibody fragment, the linear(L-) F(ab')₂, comprising tandem repeats of a heavy chain fragmentV_H–C_H1–V_H–C_H1 cosecreted with a light chain.Functional humanized L-F(ab')₂ directed against p185^HER2 wassecreted from Escherichia coli at high titer (100 mg/l) andpurified to homogeneity. The L-F(ab')₂ binds two equivalentsof antigen with an apparent affinity (K_d = 0.46 nM) that iswithin 3-fold of the corresponding thioether-linked F(ab')₂fragment The N-terminal site binds antigen with an affinity(K_d = 1.2 nM) that is 4-fold greater than that for the C-terminalsite, as shown by the comparison of L-F(ab')₂ variants containinga single functional binding site. L-F(ab')₂ has greater antiproliferativeactivity than the thioether-linked F(ab')₂ against the p185^HER2-overexpressingtumor cell line BT474. Linear and thioether-linked F(ab')₂ havevery similar pharmacokinetic properties in normal mice, andtheir serum permanence times are respectively 7- and 8-foldlonger than the corresponding Fab fragment L-F(ab')₂ offersa facile route to bivalent antibody fragments that are potentiallysuitable for clinical applications, and that may have improvedbiological activity compared with thioether-linked F(ab')₂ fragments.