bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymerization of acrylates and bulky methacrylates with the use of zirconocene precursors: Block copolymers with methyl methacrylate
Authors: Kostakis Konstantinos , Mourmouris Stylianos , Pitsikalis Marinos , Hadjichristidis Nikos
Published: June 2005

The polymerization behavior of cyclohexyl methacrylate and trimethylsilyloxyethyl methacrylate with the catalytic system Cp2ZrMe2/B(C6F5)3/ZnEt2 was examined. Block copolymers of these bulky methacrylates with methyl methacrylate (MMA), having high molecular weights and relatively narrow molecular weight distributions, were prepared. n‐Butyl acrylate and tert‐butyl acrylate were polymerized with various catalytic systems based on zirconocene complexes. These polymerizations seemed to proceed to a nonquantitative yield, producing polymers with high molecular weights and relatively low polydispersities. This behavior indicated the presence of termination reactions in the initiation step, which appeared to be faster than the propagation step. Block copolymers of these acrylates with MMA were synthesized with the catalytic system rac‐Et(Ind)2ZrMe2/[B(C6F5)4]−[Me2NHPh]+/ZnEt2, starting from the polymerization of MMA. The block copolymers produced were well defined in most cases, as indicated by size exclusion chromatography, NMR, and differential scanning calorimetry measurements. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3337–3348, 2005
Electrical Conduction Mechanisms of Nitrogenated Amorphous Carbon Films Deposited by High‐Density Plasma Chemical Vapor Deposition
Authors: Guerino Marciel , Mousinho Ana P. , Massi Marcos , Mansano Ronaldo D.
Published: June 2005

Summary: In this work, we study the electrical conduction mechanisms of nitrogenated amorphous carbon (a‐C:H:N) films, which were deposited by a high‐density plasma chemical vapor deposition (HDP‐CVD) technique. The plasma was inductively coupled by an external planar coil. Mixtures of methane and nitrogen at different concentrations were used in the depositions. The working pressure process was 15 mTorr and the RF power was 250 W. An analysis focused on the influence of the precursor gases and plasma parameters on the conduction mechanisms of the a‐C:H:N films is reported. Current‐voltage (I‐V) curves were used to study the conduction mechanisms of the a‐C:H:N films. As a result of these studies we observed that the main electrical conduction mechanism found in the I‐V characteristics of our a‐C:H:N films was the Poole‐Frenkel emission. I‐V curves were also obtained in the range of 0–100 V and they were used to determine the electrical resistivity of the films.

Current‐voltage characteristics of the a‐C:H:N films deposited with various N2 content in the discharge.

magnified image

Current‐voltage characteristics of the a‐C:H:N films deposited with various N2 content in the discharge.
Characterizing the Structure of Abrasive Fineparticles
Authors: Kaye Brian H. , Clark Garry G. , Liu Ying
Published: June 2005

A new computer‐aided image analysis procedure for characterizing the number and sharpness of potential cutting facets on the profiles of the image of an abrasive fineparticle is described. In the method, the digitized profile is explored by a running chord generating procedure which generates what is described as the facet signature of the profile. This signature can be processed at different threshold levels to recognize facets of the profile having different levels of sharpness as defined by the acute angle of the facet. Several different ways in which data from the procedure could be used to describe a population of polishing powder fineparticles are outlined. The potential use of the new descriptive characterization procedures for following the physical changes in the powder corresponding to the degeneration in performance of a polishing powder during use is outlined. The possible use of the new methodology to describe the health hazards of angular shaped dust fineparticles and flake type fillers (such as mica) in composite material technology is outlined.
Data Scatter in Richardson Plots
Authors: Clark Nigel N. , Maeder Anthony J. , Reilly Stephanie
Published: June 2005

Two dimensional images are often used as a basic for calculating shape descriptors of particles. An edge roughness descriptor, the fractal dimension, can be found from a Richardson plot of measured perimeter versus the measuring step length. Data Scatter on these plots is shown to be related to the incipient formation of polygonal harmonics, which are regular polygons formed during a structured walk around the image edge. This relationship was verified using both computer generated fractal images and real particle outlines.
Characterization of the Structure of Agglomerate Particles
Authors: Rogak Steven N. , Flagan Richard C.
Published: June 2005

Agglomerates of uniformly sized primary spheres are found in many aerosol and colloidal systems. Such particles have been described as fractal although they possess selfsimilarity over only a narrow range of length scales. Previous work suggests that, for such objects, ideal fractal scaling laws may require substantial corrections. The problem is particularly acute for measurements of particle structure from 2d images. The relation between the structure of an agglomerate and the characteristics of its projection is investigated using simple analytical models and clusters generated by a modified cluster cluster aggregation simulation. The morphology of the simulated clusters is varied by changing the ratio of masses of the colliding clusters. The fractal dimensions Df3 of the simulated clusters were typically 10–20% higher than those measured for the projections, Df2, even though Df3 > 2. This difference decreases as the cluster size increases. It was found that the fraction of primary particles visible in the 2d image is more sensitive to cluster size than to fractal dimension for clusters with less than several thousand primary particles.
The Aggregation Probability in Random Coagulation and Breakup Processes
Authors: Cohen Ruben D.
Published: June 2005

A single parameter, denoted as the "aggregation probability", is introduced to represent the average potential of clustering in a suspension in which the aggregates are undergoing random and simultaneous coagulation and breakup by means of mechanical stirring. The parameter may be useful for obtaining quick estimates of the equilibrium cluster size distributions in such systems.
Transport and Deposition of Wear Particles in Computer Disk Drives
Authors: Tsai Chuen‐Jinn , Pui David Y. H. , Liu Benjamin Y. H.
Published: June 2005

To understand the roles that wear particles play in disk crashes, analytical and numerical approaches have been used to study three dimensional fluid flow and wear particle transport and deposition in computer disk drives. The study shows that wear particles are flying very close to the disk surface. They can deposit on the disk surface and cause damage to disk drives. Cooling air flow through the disk hub of corotating disks has been found to play important roles in removing wear particles from disk drives. Parametric study has shown that the optimum cooling air flow rate is 12 slpm for 8″ disk with the Reynolds number of 150,000.
Operation Characteristics of Vibrating‐Orifice Generators: The coherence length
Authors: Anders Klaus , Roth Norbert , Frohn Arnold
Published: June 2005

The use of monosized droplet streams for the calibration and testing of optical particle sizing methods and their application to the study of basic phenomena in two‐phase systems are discussed. Owing to their coherent structure–all the droplets have the same size and spacing–such droplet streams are very useful tools for these applications. The droplets streams have been produced with a vibrating‐orifice generator. Limitations and problems that occur during the operation of these generators are described. Special emphasis is laid on the problem of the loss of coherence with increasing distance from the exit of the generator, which sometimes restricts the application of the generator for certain purposes.
Evaluation of the Dual‐Cylindrical Wave Laser Technique for sizing of liquid droplets
Authors: Naqwi Amir A. , Liu Xiao‐Z. , Durst Franz
Published: June 2005

The newly developed dual‐cylindrical wave laser system is an alternative to the phase Doppler technique. It requires only frequency measurements for particle sizing and velocimetry, and hence prevents the difficulties associated with the phase measurements. This technique was evaluated experimentally using monosize liquid droplets of water and diethyl phthalate. The experimental results are compared with the theoretical predictions of the system response, based on geometrical optics and the electromagnetic theory of light, under certain simplifying assumptions. Although the measurements generally agree with the theory, some minor oscillations in the measured response are only roughly represented by the theory. Also, the experimental data indicate a large deviation from the theory if the particle is within a distance of three diameters from the origin of the cylindrical waves, hence defining the boundary of the region in which the theory is applicable. This work indicates that a properly laid out dual‐cylindrical wave laser system can be employed for sizing of small droplets in liquid sprays.
Monte Carlo Simulation of Multiple Scattering in arbitrary 3‐D geometry
Authors: Briton Jean‐Philippe , Maheu Bruno , Gréhan Gérard , Gouesbet Gérard
Published: June 2005

MUSCAT is a Monte Carlo code for numerical simulation of Multiple Scattering. Only the general restrictive assumptions of the steady‐state, scalar radiative transfer equation are required, hence the MUSCAT code can deal with a broad field of applications. The algorithm follows the physical phenomena as closely as possible and realistic 3‐D problems can be handled without geometric simplifications. Special care has been devoted to the analysis and validation of the pseudo‐random generator subroutine. Global validations of the code in 1‐D and 2‐D geometries have been successfully carried out. An example of application is reported concerning 3‐D studies of visibility in foggy weather.
A Droplet Vaporization Model for Spray Calculations
Authors: Renksizbulut Metin , Bussmann Markus , Li Xianguo
Published: June 2005

A semi‐analytical model of multi‐component droplet vaporization in a convective environment is formulated. The model includes many important physical effects such as variable properties, non‐unity Lewis number, transient liquid phase heat and mass transport, and the blowing effect of evaporation on heat, mass and momentum transfer. The liquid phase heating is calculated from a Nusselt number model which incorporate heat transfer enhancement due to internal circulation. The model predictions are in good agreement with detailed numerical results for droplets vaporizing in various ambient conditions. The behavior of droplets in simultaneously changing concentration, temperature and velocity fields, is also examined.
Light Scattering Applied to LDA and PDA Measurements part 2: Computational results and their discussion
Authors: Naqwi Amir A. , Durst Franz
Published: June 2005

A general procedure for the design of a phase Doppler system is presented, which includes computations based on the computer codes described previously. The utility of Mie computations is demonstrated through six examples pertaining to sizing of large particles; in particular, new considerations in bubble sizing are pointed out. Through additional examples, it is shown that the phase Doppler technique may be used for sizing of submicron particles as well as large particles. Recognition of particle material, in addition to the measurement of diameter, is also made possible.
Monte Carlo Studies of the Effect of Spatial Coincidence Errors on the accuracy of the size characterization of respirable dust
Authors: Kaye Brian H. , Clark Garry G.
Published: June 2005

The effect of coincidence errors on the accuracy of fineparticle profile characterization of respirable dust hazard by Image Analysis procedures is discussed. Monte Carlo routines are used to characterize the level of clustering that can occur in a field of view from random chance. The effectiveness of some image processing strategies used to separate touching components of visible clusters are discussed. Monte Carlo routines are also used to explore at what level of space occupancy a monosized population of dust fineparticles being deposited at random has no significant level of stochastic clustering. These studies demonstrate that if reliable information on dust hazards is to be forthcoming from image analysis studies of the deposited dust deposition, measurement routines must change radically from those in current use. It is also pointed out that interpretive uncertainties associated with many previous studies of dust levels to which industrial workers have been exposed may invalidate experimental data reported from the workplace.
A Comparison of Image Analysis With Other Methods of particle size measurement for general purpose PVC resins
Authors: Davidson John A. , Etter A. A. , Thomas M. , Butler R. S.
Published: June 2005

Of all methods of particle size analysis determination only microscopy and subsequent image analysis enables accurate, geometrically determined size parameters to be measured. For this reason image analysis is a convenient referee or umpire method against which to compare other techniques.

In this study, a series of seven poly(vinyl) chloride (PVC) resins were characterized by optical microscopy and image analysis, sieves, HIAC and Coulter counter. It was not found possible to perform the image analysis measurements without operator intervention with a light pen to separate agglomerates. The PVC particles were far too irregular to enable this task to be performed by erosion and dialation techniques. The errors at 90% confidence associated with the image analysis study were: calibration ± 1.7%, counting statistics ± 1% (max) with a focus and algorithms error which ranged from ½‐3% depending upon the quantity being measured. These numbers gave a total error of ± 2% (ca. one pixel) for equivalent circular diameter (ECD) and ± 4% (ca. two pixels) for object breadth. In general the agreement between the various techniques was quite good suggesting that the object breadth (OB) as measured by sieves was nearly identical to equivalent spherical diameter (ECD) as measured by the HIAC and Coulter counter for the samples investigates.

A study of the image analysis data alone confirmed that OB and ECD were nearly identical with ECD running about 6.1 m̈m above OB.

Mass resin samples, which are prone to electrostatic charging effects, tended to give slightly higher results in those methods which measured the resin in the dry state (HIAC and sieves). Finally, it should be suggested that many of the classical concepts of resolution and depth of focus which are used to place limits upon the performance of the optical microscope do not necessarily apply to particle size determination by image analysis. If the chord through the particle which describes its diameter can be considered an approximation to a square wave then it is the fundamental frequency of the Fourier components of that square wave that contains the size information. This should be true for microscopic objects which are absorbing of light and non‐retarding in nature.

Once this fundamental frequency can be identified then sizing accuracy is dependent chiefly on the signal to noise ratio of the system.
The electromagnetic scattering problem of Laser‐Doppler Anemometry. Part I: Fluid investigation
Authors: Raszillier Hans , Durst Franz
Published: June 2005

Light scattering by moving particles as used in laser‐Doppler anemometry (LDA) is reviewed. This first part of the review describes the situation where the scattering particles play the role of tracers of fluid flow. In this situation only general properties of the scattering process are of relevance. No special knowledge of the specific scattering mechanism is needed, provided that a detectable signal intensity is obtained. The velocity of the particle in a direction determined by the two laser beams of an LDA measuring device can be derived exclusively from the modulation frequency of the signal. In the second part of the review a description of specific properties of the scattering process will be given with the purpose of gaining information on the particles themselves.
Interaction Between the Motion of particles and their turbulent carrier fluid flow
Authors: Ebert Fritz
Published: June 2005

The turbulence occurring in the flow of the carrier fluid exerts a substantial influence on the motion of suspended particles or droplets. This influence is obvious, e.g. if fine particles are dispersed in free flows or deposited on free surfaces, bluff obstacles or channel walls. With application in aerosol science in mind, the interaction between dispersed phase and carrier fluid is described in terms of turbulence intensities, energy spectra, turbulence time scales and eddy diffusivities. Experimental results obtained for different important flow types are reviewed and compared with theoretical predictions. With regard to the latter, the different methods of treating theoretically turbulent two‐phase flows of low concentration are discussed.
Particle Sizing by Photon Correlation Spectroscopy. Part III: Mono and bimodal distributions and data analysis
Authors: Finsy Robert , de Jaeger Nicolas , Sneyers Rik , Geladé Eric
Published: June 2005

The possibilities and limitations of photon correlation spectroscopy (PCS) as a practical tool for particle sizing are reviewed. In this part the most frequently used methods of data analysis are briefly surveyed. The practical performances for the determination of particle size distributions were evaluated by a comparative study with different kinds of users (industrial and academic research groups and manufacturers). The PCS results were also compared with electron microscopy (EM) and static light scattering (SLS) results. Thereby it was confirmed that the amount of reliable information that can be obtained by PCS about particle size distributions with measuring times of the order of minutes is limited by the ill‐conditioning of the data inversion procedure, among other factors. Nevertheless, the information obtained from the PCS measurements agrees essentially with the EM and SLS results.
Relevance of Light Scattering Theory in Photon correlation spectroscopic experiments
Authors: van der Meeren Paul , Bogaert Herwig , Vanderdeelen Jan , Baert Leon
Published: June 2005

Since photon correlation spectroscopy (PCS) is essentially a light scattering technique, it estimates the intensity‐weighted particle size distribution. Using the Mie theory, some consequences were demonstrated. First, argon ion lasers were shown to be superior for particle sizing of very small particles. In addition, multiple scattering was shown to be largely dependent on the scattering angle and the state of polarization of the light source. Owing to this disturbing phenomenon, sizing of supermicron particles becomes troublesome. The estimated intensity distribution of polydisperse samples could be greatly influenced by the observation angle. The use of simplified light scattering theories such as the Rayleigh and the Debye‐Gans theory was shown to be limited to small particles, especially in the case of high refractive indices. Finally, it was shown that the smoothing effect of PCS data analysis software may give rise to artificial bimodal number‐ or weight distributions, even when the Mie theory is considered.
Localized Approximation of Generalized Lorenz‐Mie Theory: Faster algorithm for computations of beam shape coefficients, g
Authors: Ren Kuan F. , Gréhan Gérard , Gouesbet Gérard
Published: June 2005

Beam shape coefficients, g, are at the core of the generalized Lorenz‐Mie theory describing the scattering of a shaped beam by spheres. A decrease in computation times is essential for systematic applications of the theory. This paper introduces a new formulation to compute beam shape coefficients, g, in the framework of the localized approximation and discusses symmetry relations between the coefficients. The new formulation permits computation times to be decreased by one to two orders of magnitude.
Characteristics of Particle Sizes produced by suspension polymerization of styrene
Authors: Stamatoudis Michael , Apostolidou Christina
Published: June 2005

Experiments on the suspension polymerization of styrene were conducted at various stabilizer concentrations, dispersed phase hold‐up fractions, impeller types and impeller speeds. The experimental final particle size distributions obtained were almost always described by the upper limit number distribution. Plots of the maximum diameter, amax, and the mean diameters, a21 and a10, vs. the Sauter mean diameter, a32, gave straight lines with slopes of 1.24, 0.99 and 0.97, respectively.
Computer Aided Image Analysis Procedures for Characterizing the stochastic structure of chaotically assembled pigmented coatings
Authors: Kaye Brian H. , Clark Garry G.
Published: June 2005

New techniques for studying stochastic (random) clustering in paint films and composite materials are discussed. The interpretation of measured levels of clustering from the perspective of percolation theory of fractal systems is discussed. The possibility of increasing the optical efficiency of pigments by interfering with stochastic clustering by means of extender pigment and/or microencapsulation is discussed. The use of intertrack measurements on a section through a paint film to study pigment dispersion efficiency is explored by Monte Carlo Routines and illustrative measurements made on a section through a carbonblack dispersion. The design of an intelligent machine to monitor pigment dispersion in real films is discussed.
The Effect of Suspension Medium Refractive index on the particle size analysis of quartz by laser diffraction
Authors: Hitchen Christopher J.
Published: June 2005

The size distributions of four samples of quartz dust, suspended in liquids of different refractive index (RI), were determined using a Malvern 2600 laser particle sizing instrument. As the relative RI, between particle and suspension media, approached unity the instrument over‐estimated the mean particle size for the three finest quartz samples. An under‐estimated mean particle size was recorded for the largest quartz sample indicating the complex nature of light scattering by small particles under conditions of low relative RI.

A regime of relative refractive index is determined within which particle size analysis using laser diffraction, invoking anomalous diffraction theory, becomes prone to large errors and this range is compared with the van de Hulst criterion.
Phase‐Doppler Sizing of Optically Absorbing Liquid Droplets: Comparison between mie theory and experiment
Authors: Manasse Uwe , Wriedt Thomas , Bauckhage Klaus
Published: June 2005

Phase‐Doppler experiments applied to optically absorbent (homogeneous and inhomogeneous) liquids are described. Simultaneous size and velocity measurements of single droplets were executed at three off‐axis angles ψ. These angles were found to be suitable for the evaluation of the phase‐Doppler technique by Mie theory. Both the sizes of the monodisperse droplets and their absorption properties were varied. At least with respect to homogeneous liquids, comparison of the droplet diameters obtained by phase‐Doppler measurement and by photography (reference technique) showed good agreement. Concerning the optical properties of inhomogeneous liquids, additional phase‐Doppler measurements were carried out using an alternative device based on a laser diode and photodiodes. The longer wavelength λ (830 nm instead of 488 nm) reduced the influence of the inhomogeneities on the droplets' scattering behaviour and thereby improved significantly the phase‐Doppler results. It is concluded that phase‐Doppler anemometry is suitable for the sizing of optically absorbent droplets of real process fluids. Such droplets result from atomization processes often used in various branches, such as the chemical, pharmaceutical and food industries (production of powders and granules, "spray drying"), automotive engineering (dispersing fuels for combustion) and agriculture (crop spraying). Mie scattering theory is a powerful aid for describing the scattering behaviour of dispersed droplets of real process fluids with more complicated optical properties compared with water, i.e. the behaviour of optically absorbent homogeneous liquids, and for determining the necessary parameters of the optical set‐up.
The electromagnetic scattering problem of Laser‐Doppler Anemometry. Part II: Particle investigation
Authors: Raszillier Hans , Durst Franz
Published: June 2005

The second part of this review concentrates on the situation where the moving particles that scatter light are themselves an essential part of the flow under investigation. In order to obtain information also on their nature und their shape, their quantitative characterization by light scattering is needed. This characterization is codified in the magnitude which describes scattering, the scattering amplitude. It becomes transparent for very small and very large particles, because their scattering mechanisms can be interpreted in terms of electromagnetic multipoles and of geometrical optics, respectively. Scatterers of the simplest composition and shape, homogeneous spheres, are considered in detail; they are characterized optically by their radius and index of refraction. It is shown that phase measurements of the modulated scattering signal (phase Doppler anemometry, PDA) can provide, with suitably located detectors, information on these quantities.
On the Prediction of Droplet Size and Velocity distributions in sprays through maximum entropy principle
Authors: Li Xianguo , Tankin Richard S.
Published: June 2005

Based on the conservation laws of mass, momentum and energy, the droplet size and velocity distributions in liquid sprays are formulated through the maximum entropy principle, without taking into account the details of liquid atomization processes such as the characteristics of disturbances and behavior of liquid bulk preceding the droplet formation. The joint probability distribution function in size and velocity of the droplets can be predicted from the atomization conditions which are represented by the Weber number and the source terms in the formulation. The model prediction agrees well with the experimental data measured by a phase Doppler particle analyzer.
Thermal Conductivity as a Method to Assess Powder Compacts
Authors: Osborne N. D.
Published: June 2005

The porosity of pentaerythirtol tetraacetate, tar granulated carbon and spray dried lactose compacts were determined using mercury intrusion porosimetry. These results were compared to data from thermal conductivity experiments which showed correlations to mercury intrusion volume and median pore size.
Characterizing the Fractal Structure of Fineparticle Profiles using the concepts of geometrical probability
Authors: Kaye Brian H. , Trottier Remi A. , Clark Garry G.
Published: June 2005

Several theorems exist in the subject of geometrical probability with regard to the intersection frequency in two‐dimensional space of stochastic sets of Euclidean line systems of various length and structure. When some of the intersecting lines are fractal in nature, these theories can be modified to deduce the fractal dimensions of the line system, including fineparticle profiles, from observed intersection frequency of the stochastically distributed line system using search grids of known length Analytical procedures based upon such measurements are particulary useful for quality control measurements of a product in which structural changes lie within a relatively restricted range. The theory of the procedures are presented along with experimental data demonstrating the usefulness and efficiency of the procedures.
Sizing Particles by Optical Microscopy through criteria developed by the analysis of image profiles
Authors: Davidson John A. , Butler R. S.
Published: June 2005

Modern image analysis equipment has now made it possible to obtain detailed intensity profile information about objects imaged under the optical microscope. If the object contrast is generated by light absorption alone then the image profile of the object is a square wave and the size information is contained in the fundamental frequency of the Fourier components of that square wave. The period of the fundamental frequency lies very close to the intensity midpoint of the image profile. As long as the microscope objective numerical aperture (NA) is high enough to pass this fundamental the object can be sized to an accuracy which is chiefly dependent upon the signal to noise ratio of the system and independent of classical notions of microscope resolution.

Thus for latex particle metal replicas it was possible to determine the diameter to a precision which was typically on the order of 13% of the classical Sparrow limit of resolution for the objective employed.

By sizing the same particle replica with objectives of different NA it was demonstrated that the size obtained was independent of the objective NA used as long as the replica diameter was above the Sparrow limit. This is in accordance with optical theory.

About mid‐summer the Goldstein "Zernike" program became available to us through the kindness of Dr. Goldstein. With this program it was possible to model the effect of optical path difference. Unlike particle replicas, most real objects generate object profiles that are a function of refractive index difference and thickness or path difference in addition to object size and transmittance. Although the "Zernike" program can accommodate path differences, it assumes that the object has negligible thickness‐an assumption not merited by most real microscopic objects.

Although exact quantitative agreement could not always be obtained with reasonable assumptions, the predictions of the "Zernike" program nevertheless could help to define sample preparation conditions which enabled high accuracy sizing to be performed.

This work thus demonstrates that an extremely high degree of accuracy and precision in particle sizing is available from the optical microscope which is independent of classical notions of microscope "resolution". The major requirements are that the objective NA be sufficiently high enough to pass the Fourier components which contain the size information and that features in the image can be identified which contain the size information.
The Effect of Particle Shape on the Amplitude of scattered light for a sizing instrument
Authors: Orfanoudakis Nicholas G. , Taylor Alexander M. K. P.
Published: June 2005

The relationship between size and intensity of laser light scattered from coal particles, glass beads and calibration pinholes in the size ranges 10–140 m̈m, 17–240 m̈m and 5–200 m̈m respectively has been measured. The purposes were to determine the effect of shape of non‐spherical particles and beads by varying three parameters in the collection optics.

These were: the angle, θc, between the axis of the collection optics and that of the incident laser beam; the aperture of the f/3.66 collection lens; and the diameter of the spatial filter on the photodetector. A spatial filter diameter of 0.5 mm was used on the detector as a compromise between image vignetting and reducing the size of the effective measuring volume of the instrument. Due to refraction, and particularly for diameters larger than about 80 m̈m, the beads scattered more light than the pinholes or the coal particles. A mask, introduced to limit the collection lens aperture to angles less than 5.3°, reduced the intensity collected from the beads, while the response curves for the pinholes and coal particles were unaffected. Non‐spherical beads larger than about 60 m̈m with aspect ratios up to 1.8 resulted in departure from the response curve, established from the calibration pinholes, by up to a factor of two. The aspect ratio was defined by the maximum and minimum projected lengths of the image of the scatterer. The response curves for beads and coal particles approached that of the pinholes as θc was changed from 2.5° to 1.4° and as the angular position of the mask limiting the aperture of the collection lens nearest to the incident beam axis, θi, was reduced from 2.9° to 0.9°. The best results were obtained for θi and θc equal to 0.9° and 1.4° respectively, for which the precision and accuracy were 9 m̈m and + 5 m̈m for nominally spherical glass beads and 5 m̈m and −1 m̈m for the coal particles for diameters up to 60 m̈m and aspect ratio up to 2.5.
Information Potential of the Method of pulsed recording of light‐scattering particles
Authors: Oshchepkov Sergey L.
Published: June 2005

The topical problem of pulsed recording of light‐scattering particles in a flux has been studied. Along with the determination of the sizes of particles, this problem involves the simultaneous evaluation of their material composition. Such a task arises in analysing multi‐component disperse systems. It is shown that it can easily be realized if the particle materials differ appreciably in absorption coefficients and closeness of their refractive indices to that of the dispersion medium. This is connected with the significant difference of the spatial distribution of the scattered light. A simple method for solving such a problem has been designed with regard to the peculiarities of recording weak light fluxes and the necessity for real‐time optical measurement processing.
Data Analysis of Multi‐Angle Photon Correlation measurements without and with prior knowledge
Authors: Finsy Robert , de Groen Pieter , Deriemaeker Luc , Geladé Eric , Joosten Jacques
Published: June 2005

The application of the singular value analysis and reconstruction method (SVR) and of the Contin method for the collective analysis of multi‐angle noisy photon correlation data sets was investigated. Provided the data are sampled equidistant in time and by proper tuning of the sampling time to the scattering angle, a collective multi‐angle SVR analysis is feasible. For homogeneous spherical particles such an analysis does not require any prior knowledge of the angular dependence of particle scattering power (e.g. Mie scattering). SVR allows the information content to be separated from noisy intensity autocorrelation data. It is illustrated that the multi‐angle SVR analysis enhances the recovery of the information content. Moreover, SVR can be used as a fast and accurate preprocessor for extracting the field autocorrelation function for a subsequent Contin analysis whereby prior knowledge of particle scattering power as a function of scattering angle is used as a constraint. Compared with the data analysis of multi‐angle time‐averaged scattered intensity measurements, the information that can be extracted from multi‐angle PCS data in comparable accumulation times is poorer.
Application of Precision Transparent Sieves to the determination of low number concentrations of oversize particles in powders
Authors: Allen Terry
Published: June 2005

Powders are often added to film coatings in order to improve handling or end‐use properties. The presence of oversize particles at the level of less than one in a trillion can lead to substandard or reject products. Using current methods of testing it is difficult to detect such low levels of oversize particles until after the final product is made. Sieving techniques have been tried but these are generally unreliable due to the difficulty of controlling cross contamination. A filtration technique is described here for determining low levels of oversize particle in powders and suspensions, in which cross‐contamination is minimized by using a single container for the particle separation and the subsequent number concentration measurement. Precision Transparent Sieves are used in a holder, specially designed to minimize contamination, for use with a Coulter Counter. The method permits the determination of number concentration (oversize particles per gram or ml) with reasonable accuracy at levels not previously possible.
Outlaw locked particles – 3rd order locking criteria
Authors: Meloy Thomas P. , Preti Ugo
Published: June 2005

An unexpectedly large additional three phase locking region, the outlaw area has been found where three phase, locked particle may be formed. This implies that in some ores, the number of three phase locked particles may be an order of magnitude larger than expected. The size of this outlaw region is sensitive to the angle at which the three phases meet. Since these higher order locked particles behave differently in separation circuits, it is proposed that in characterizing a solid or ore rock, these angles between the interfacial planes be both measured and included in a Textural Transform.
Structure and energy landscape of a photoswitchable peptide: A replica exchange molecular dynamics study
Authors: Nguyen Phuong H. , Mu Yuguang , Stock Gerhard
Published: June 2005

A replica exchange molecular dynamics (REMD) simulation of a bicyclic azobenzene peptide in explicit dimethyl sulfoxide solution is presented in order to characterize the conformational structures and energy landscape of a photoswitchable peptide. It is shown that an enhanced‐sampling technique such as the REMD method is essential to obtain a converged conformational sampling of the peptide at room temperature. This is because conventional MD simulations of less than ∼100‐ns length are either trapped in local minima (at 295 K) or—if run at high temperature—do not resemble the room‐temperature REMD results. Calculating various nuclear Overhauser effects (NOEs) and 3J‐couplings, a good overall agreement between the REMD simulations and the NMR experiments of Renner et al. (Biopolymers 2000;54:501–514) is found. In particular, the REMD study confirms the general picture drawn by Renner et al. that the trans‐isomer of the azobenzene peptide exhibits a well‐defined structure, while the cis‐isomer is a conformational heterogeneous system; that is, the trans‐isomer occurs in 2 well‐defined conformers, while the cis‐isomer represents an energetically frustrated system that leads to an ensemble of conformational structures. Employing a principal component analysis of the REMD data, the free energy landscape of the systems is studied at various temperatures. The implications for the folding and unfolding pathways of the system are discussed. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Ligand‐induced fit in mycobacterial MabA: The sequence‐specific C‐terminus locks the conformational change
Authors: Cohen‐Gonsaud Martin , Ducasse‐Cabanot Stéphanie , Quemard Annaïk , Labesse Gilles
Published: June 2005

The protein MabA of Mycobacterium tuberculosis is a β‐ketoacyl reductase (KAR) and catalyses one of the four steps of the fatty acid elongation system FAS‐II. The crystal structures of different KARs revealed a significant rearrangements of the active site between a “closed” inactive conformation and an “open” and active form in presence of the cofactor. MabA is a potential therapeutic target. However, only the structure of the “closed” form was obtained and rational drug design requires the structure of the active form. Here we described the sequences and structures analysis of the KARs to stabilize the “open form” in MabA. The crystal structure of a mutated MabA protein was then solved in both inactive and active form. The crystal structure of the wild‐type MabA in the presence of NADP was also solved and showing a mixture of the two mutually exclusive conformations. This new structure of MabA is analyzed in view of its distinctive enzymatic and structural properties and those of related enzymes. Proteins 2005. © 2005 Wiley‐Liss, Inc.
Data‐driven docking: HADDOCK's adventures in CAPRI
Authors: van Dijk A. D. J. , de Vries S. J. , Dominguez C. , Chen H. , Zhou H.‐X. , Bonvin A. M. J. J.
Published: June 2005

We have shown previously that given high‐resolution structures of the unbound molecules, structure determination of protein complexes is possible by including biochemical and/or biophysical data as highly ambiguous distance restraints in a docking approach. We applied this method, implemented in the HADDOCK (High Ambiguity Driven DOCKing) package (Dominguez et al., J Am Chem Soc 2003;125:1731–1737), to the targets in the fourth and fifth rounds of CAPRI. Here we describe our results and analyze them in detail. Special attention is given to the role of flexibility in our docking method and the way in which this improves the docking results. We describe extensions to our approach that were developed as a direct result of our participation in CAPRI. In addition to experimental information, we also included interface residue predictions from PPISP (Protein–Protein Interaction Site Predictor; Zhou and Shan, Proteins 2001;44:336–343), a neural network method. Using HADDOCK we were able to generate acceptable structures for 6 of the 8 targets, and to submit at least 1 acceptable structure for 5 of them. Of these 5 submissions, 3 were of medium quality (Targets 10, 11, and 15) and 2 of high quality (Targets 13 and 14). In all cases, predictions were obtained containing at least 40% of the correct epitope at the interface for both ligand and receptor simultaneously. Proteins 2005;60:232–238. © 2005 Wiley‐Liss, Inc.
Searching for protein–protein interaction sites and docking by the methods of molecular dynamics, grid scoring, and the pairwise interaction potential of amino acid residues
Authors: Terashi Genki , Takeda‐Shitaka Mayuko , Takaya Daisuke , Komatsu Katsuichiro , Umeyama Hideaki
Published: June 2005

In CAPRI Rounds 1 and 2, we assumed that because there are many ionic charges that weaken electrostatic interaction forces in living cells, the hydrophobic interaction force might be important entropically. As a result of Rounds 1 and 2, the predictions for binding sites and geometric centers were acceptable, but those of the binding axes were poor, because only the largest benzene cluster was used for generating the initial docking structures. These were generated by fitting of benzene clusters formed on the surface of receptor and ligand. In CAPRI Rounds 3–5, the grid‐scoring sum on the protein–protein interaction surface and the pairwise potential of the amino acid residues, which were indicated as coming easily into the protein–protein interaction regions, were used as the calculation methods, along with the smaller benzene clusters that participated in benzene cluster fitting. Good predicted models were obtained for Targets 11 and 12. When the modeled receptor proteins were superimposed on the experimental structures, the smallest ligand root‐mean‐square deviation (RMSD) values corresponding to the RMSD between the model and experimental structures were 6.2 Å and 7.3 Å, respectively. Proteins 2005;60:289–295. © 2005 Wiley‐Liss, Inc.
Research on historic structures in seismic areas in Italy
Authors: Binda Luigia , Saisi Antonella
Published: June 2005

The paper analyses the most recent research carried out in Italy concerning the seismic behaviour of historic buildings. The last Umbria (Italy) earthquake in 1997 was an interesting on site test for the evaluation of the repair and prevention techniques applied to masonry building of historic centres in seismic areas, but also of the structural modelling. Most of the situations examined made important contributions to a general re‐thinking of masonry evaluation and strengthening. The great importance in the mechanical behaviour of a building of building rules and of structural details, as well as transformation phases has been demonstrated.
Luminescent characteristics of pure and Ce doped K2LaCl5 phase in KCl host
Authors: Voloshinovskii A. , Stryganyuk G. , Zimmerer G. , Rodnyi P. , Antonyak O. , Myagkota S. , Savchyn P.
Published: June 2005

The formation of Ce3+ doped K2LaCl5 microphase has been revealed for the KCl–LaCl3–CeCl3 system. Luminescent characteristics of pure and Ce3+ doped K2LaCl5 microcrystals, embedded in KCl matrix, are studied in comparison with those of bulk K2LaCl5:Ce(0.1%) crystal. For both the micro‐ and bulk K2LaCl5:Ce crystals the bands peaked at 344 and 373 nm are attributed to Ce3+ emission revealing a 24 ns time constant for the main decay component upon the excitation within the Ce3+ f–d absorption range. The method elaborated for the synthesis of the activated K2LaCl5 microphase in the KCl–LaCl3–CeCl3 system provides the possibility of producing large‐size homogeneous scintillation elements possessing efficient emission of rare earth doped A2LaX5 micro‐ and nano‐phases embedded in AX matrices (A = Cs, K, Rb; X = F, Cl, Br, I). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electric field gradients at indium sites in spinels measured by perturbed angular correlations
Authors: Pasquevich A. F.
Published: June 2005

The Electric Field Gradient (EFG) at 111Cd isotope (produced by the Electron Capture (EC) decay of 111In) has been measured using Perturbed Angular Correlations (PAC) technique in many spinels. In the present work, data arising from such experiments were collected. The experimental EFG values, obtained at room temperature, at the B site of normal spinels are compared with those calculated considering the monopole moment of the ions and the dipole polarization of the anions. This comparison allows the determination of the u‐parameter, which gives the anion position in the lattice. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of PZT (54/46) ferroelectric ceramics under the influence of a ‘soft’ double modification with La and Nb
Authors: Suárez‐Gómez A. , Calderón‐Piñar F. , Durruthy M. D. , Peláiz‐Barranco A. , Saniger‐Blesa J. , de Frutos J.
Published: June 2005

In the present work, a ‘soft‐doped’ PZT ceramic system with a near MPB Zr/Ti ratio of about 54/46, is characterized when simultaneously modified with Lanthanum (La) and Niobium (Nb) at the same doping level, x = 0.4, 1.0 and 1.4 mol%. X‐rays diffraction patterns showed the rombohedral/tetragonal perovskite phase coexistence as reported for Zr/Ti ratios near the Morphotropic Phase Boundary (MPB). Scanning Electron Microscopy (SEM) showed a decrease of the mean grain size when increasing the doping level. On the other hand, permittivity and AC conductivity were analysed in the ferro‐ and paraelectric phases. Samples showed a lower Curie temperature for higher doping levels as well as normal ferroelectric/paraelectric transitions. The piezoelectric response of thin polarized cylinder‐shaped samples was measured for a near‐saturation poling field. The behaviour of some electromechanical parameters and possible applications for these materials are also discussed herein. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Density of electronic states in impurity‐doped quantum well wires
Authors: Betancur F. J. , Orozco E. A. , Gonzalez J. D. , Mikhailov I. D.
Published: June 2005

We analyze the effect of the mixing of the 1s and 2px,y subbands on the ground state binding energy of the off‐axis donors in cylindrical nanotubes by using the recently developed fractal dimension method. Curves of the D0 ground state binding energies as a function of the donor distance from axis are presented and compared with those obtained previously without consideration of the effect of the subband mixing. Also, we analyze the density impurity states in nanotubes with randomly distributed donors. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)