bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dry Mechanical Dispersion of Submicron Particles
Authors: Leschonski Kurt , Benker Bernd , Bauer Ulrich 
Published: May 2005

AbstractConcerning the use of air classifiers with cut sizes in the micron range and lower, it is necessary to disperse the feed material properly in an air flow to avoid agglomerates larger than the desired cut size. Commonly used dispersing devices such as injectors use large amounts of air. To reduce the size and costs of the subsequent air classifiers, two new types of dispersing systems were developed, one design being related to a brush feeder and the other to a pin mill. Both apply mechanical rather than fluid mechanical forces in the dispersion process. The brush disperser achieves the same size distributions as the pin mill disperser with much less machinery. Its properties as a feeding and dispersing system are shown and its ability to disperse particles in the submicron range is confirmed by two independent particle size analysis systems: a new diffraction spectrometer and an impactor.
On Measuring and Modeling Local Average Particle Velocities for particle ensembles in classifying systems
Authors: Riehle Claus 
Published: May 2005

AbstractIn most multi‐phase flow problems, the particulate phase is exposed to an external field which causes dispersion. Therefore, local velocity measurements of the disperse phase are no longer equivalent with respect to averaging in time and averaging in volume. While the local time‐averaged velocity still characterizes the transport of the ensemble in the Eulerian sense, one has to be be careful in modeling this velocity average by considering the ensemble's composition. It is shown for different particle ensembles that the conventional particle velocity average M1,0 calculated with respect to the dispersion relationship and a particle size number density distribution is far below the measured ensemble average; the deviation depends on the width of the particle size distribution. It is deduced that Eulerian particle velocity values referring to a certain time interval can be modeled by a ratio of velocity moments M2,0/M1,0 calculated with particle size number distributions referring to a certain probe volume. This relationship was confirmed by measurements.
Particle Size Determination by Laser Reflection: Methodology and problems
Authors: Monnier Olivier , Klein Jean‐Paul , Ratsimba Berthe , Hoff Christian 
Published: May 2005

AbstractThe particle size distribution of crystalline solids has progressively become a key parameter in manufacturing processes, as important as chemical purity. Among the particle size determination and counting systems available on the market, very few offer the possibility of continuous in situ monitoring of the particle size evolution during crystallization. For this reason, much interest has been aroused by the appearance of the Par Tec 100, patented by Laser Sensor Technology [1, 2]. A study has been carried out in a stirred vessel to verify the precision and reproducibility of particle size measurement and elucidate the influence of experimental parameters on data accessible with this instrument. Optimum reproducibility has logically been achieved by fixing the highest possible cycle time and taking the mean of several cycles. Determinations with the Par Tec 100 are influenced variously, according to whether they relate to the total number of particles counted or to the mean size. Thus, the number of counts measured by a particle size probe largely depends on the operating conditions and more particularly on the hydrodynamic conditions, solvent, temperature and focal point position. Its dependence relative to the concentration of the solid in suspension is normal and linear for a solid and for a given monodisperse sample. To establish the relationship between the number of counts and the population density would therefore necessitate delicate calibration on a case‐by‐case basis. The mean size determined does not depend on suspension homogeneity, provided that the stirring speed is sufficient for a statistically significant total count. On the other hand, for a given sample, a displacement of the focal point can lead to considerable variations in the size determined. The optimal focal point position for small sizes is in fact highly sensitive. Lastly, the optimal position of the focal point is considerably dependent on the true size of the particles, which means that this counter is unsuitable for the precise analysis of a dispersed sample since each particle size class would require a different setting of the focal point. In addition, the sizes determined, irrespective of the products studied, appear to be underestimated for large particles and over estimated for small particles.
Experimental Studies of Electrically Active Fibrous Filter Loading
Authors: Walsh Declan , Stenhouse Ian 
Published: May 2005

AbstractElectrically active fibrous filters, that is fibrous filters whose fibres carry a permanent electric charge, are an increasingly popular alternative to conventional fibrous filters in applications where low pressure drop and high collection efficiencies are critical. The advantage of these materials is the additional collection efficiency, due to electrostatic mechanisms, that can be achieved without pressure drop increase. The efficiency of these materials can fall as they are loaded with aerosol particles, so it is necessary that proper account be taken of this process during use. A complete understanding of the mechanisms responsible for this reduction in efficiency has not yet been reached. An experimental study has been undertaken at Loughborough University of Technology investigating the loading behaviour of a mixed fibre type electrically active material. The experimental techniques used in this work and experimental findings with a range of aerosol particle sizes are reported here.
Phase‐Doppler Anemometry with the Dual Burst Technique for measurement of refractive index and absorption coefficient simultaneously with size and velocity
Authors: Onofri Fabrice , Girasole Thierry , Gréhan Gérard , Gouesbet Gérard , Brenn Günter , Domnick Joachim , Xu Tian‐Hua , Tropea Cameron 
Published: May 2005

AbstractThe principle of the dual burst technique (DBT) based on phase‐Doppler anemometry (PDA) is proposed for simultaneous particle refractive index, size and velocity measurements. This technique used the trajectory effects in PDA systems to separate the two contributions of the different scattering processes. In the case of forward scattering and refracting particles, it is shown that from the phase of the reflected contribution, the particle diameter can be deduced, whereas from the refracted contribution the particle refractive index and velocity can be obtained. Furthermore, the intensity ratio of these two scattering processes can be used for absorption measurements. Simulations based on generalized Lorenz‐Mie theory and experimental tests using monodispersed droplets of different refractive indices and absorption coefficients have validated this technique.
Simultaneous Measurement of Velocity and Equivalent Diameter of Particles with arbitrary shape
Authors: Terhaag Ulrich , Renz Ulrich 
Published: May 2005

AbstractOnly a few optical techniques are available to measure simultaneously the velocity and size of coarse particles dispersed in a fluid. Since particles are randomly shaped with a rough surface and inhomogeneous with respect to the refractive index, phase‐based sizing techniques are not reliable. The applied optical sizing technique is based on light intensity measurement of a scattering particle crossing a top‐hat laser beam. This optical set‐up was first described by Gréhan et al. In the range of geometrical optics, the sampled light at the receiving system is proportional to the square of the equivalent particle diameter within the diameter range 20–700 μmVelocity information is obtained by using a smaller concentric laser Doppler probe volume. Coincidence of the signals is guaranteed by the optical set‐up, since the smaller probe volume diameter defines the triggering event. To demonstrate the performance of the system, some diameter distributions measured with the top‐hat beam system are compared with results for a commercial laser diffraction system for different materials. The system is applied to obtain size‐correlated velocity information of a particle‐laden two‐phase flow at a single‐sided backward‐facing step.
On the measurements of particles by imaging methods: Theoretical and Experimental Aspects
Authors: Ren Kuan Fang , Gouesbet Gérard , Géhan Gérad , Lebrun Denis , Özkul Cafer , Kleitz Alain 
Published: May 2005

AbstractImaging techniques in particle sizing have always been important. Nevertheless, owing to the progress in CCD cameras, these techniques have found new potential which strongly depends on the capability to describe the image formation. Based on a combination of the generalized Lorenz‐Mie theory and the diffraction theory, the image characteristics are described, taking into account the beam size, particle location, direction of observation and collecting optics characteristics. In the case of forward detection, a finite coherence is introduced and the results are compared with those obtained by a convolution approach, with the point spread function assumed to be Gaussian. Then some experimental results are displayed which underline the improvement achieved in particle size measurement.
Image‐Sedimentation technique for practical size analysis
Authors: Ma Xinghua , Wan Mingrui 
Published: May 2005

AbstractA method called “image‐sedimentation”, based on the application of Stokes' law to suspension and image techniques, is proposed for the rapid analysis of particle size distributions. A parallel beam of optical light, after passing through a cell containing particles, is measured with a linear image sensor with 2048 photodetectors to determine the attenuated light intensity displayed on a monitor screen. The settling height between any given point and the liquid surface can be measured accurately by use of this image technique without any additional mechanical device to move either the light beam or the glass cell containing the suspension. Consequently, the total time required for the determination of the particle size distribution, typically of a carborundum powder having a median diameter of 5 μm, takes only 5 min as compared with more than 20 min by using other instruments based on the sedimentation principle.
A modified high‐output, size‐selective aerosol generator
Authors: Chein Hungmin , Chou Charles C.‐K. 
Published: May 2005

AbstractA compact and commercial aerosol generator capable of generating narrowly size‐distributed aerosols with high mass concentrations was designed, fabricated and tested. The aerosol generator, consisting of a Delavan simplex nozzle (Model 30610‐4), an L‐shaped settling chamber and a virtual impactor with a clean air core, was modified and improved from Chein and Lundgren's work [20] to be more compact and readily commercial. The performance of the aerosol generator was evaluated using corn‐oil, sodium chloride and uranine solutions. The results indicated that the cornoil droplets produced by the generator had a mass medium aerodynamic diameter (MMAD) of 7.20 ± 0.32 μm with a geometric standard deviation (GSD) of 1.48 ± 0.01 and the aerosol generation rate was 13.8 ± 1.3 mg/min. Solid aerosols generated from NaCl solution were found to have an MMAD in the range 1.39–4.88 μm with a GSD of 1.34–1.47 with the volumetric solution concentration varying from 0.1% to 9%. At the same time, the aerosol generation rate varied from 0.27 ± 0.05 to 15.8 ± 1.8 mg/min. depending on the solution concentration and the particle size produced. In addition, a 0.01% uraniane solution was tested to generate a submicron aerosol with an MMAD of 0.93 μm and a GSD of 1.48.
pH Dependence of 2,3‐diphosphoglycerate binding to human hemoglobin Ao at 21.5°C
Authors: Hobish Mitchell K. , Powers Dennis A. 
Published: May 2005

AbstractRate equilibrium dialysis was used to measure the binding of 2,3‐diphosphoglycerate (DPG) to human oxy‐ and deoxyhemoglobin AO over the range pH 5–9, at 21.5°C. This approach yielded an accurate, precise, and self‐consistent set of model‐independent association constants. These data were successfully fitted to a thermodynamic model which is fuctionally similar to a Hill equation. The isotherms generated by this fitting procedure appear to intersect at low pH and converge at high pH. This apparent convergence at high pH is consistent with results obtained by oxygen equilibria studies performed under conditions of saturating DPG. These calculated isotherms were used to determine the enhancement of the Bohr effect as a function of pH. These results are consistent with data obtained by pH stat measurements by other investigators.This paper presents the first in a series of studies that will provide a systematic characterization of the interaction between hemoglobin and DPG.
Kinetic characterization of early intermediates in the folding of E. coli tryptophan‐synthase β2 subunit
Authors: Blond Sylvie , Goldberg Michel E. 
Published: May 2005

AbstractThis report describes the use of fluorescence energy transfer between an intrinsic energy donor (tryptophan 177) and two chemically added acceptors to study intermediates in the folding of the β2 subunit of E. coli tryptophan‐synthase. Two early folding steps are thus identified and characterized. One is very rapid (its rate constant at 12°C is 0.02 sec−1) and corresponds to the folding of the N‐terminal domain into a structure whose overall features approximate well those of the native domain. The second step is somewhat slower (its rate constant at 12°C is 0.008 sec−1) and involves a conformational rearrangement of the N‐terminal domain brought about by the interactions between the N‐and C‐terminal domains within a monomeric β chain. This brings to five the number of intermediates which have been identified and ordered on the folding pathway of the dimeric β2 subunit.
Proteolytic dissection of a hapten binding site
Authors: Sen Jyoti , Beychok Sherman 
Published: May 2005

AbstractIgG Gar, a human myeloma protein that binds riboflavin with a high affinity, was used to derive variable region fragments from the heavy chain and the light chain. Riboflavin binding ability of the active site generated by V(H) and light chain and the active site generated by V(H) and V(L) was compared to riboflavin binding by the F(ab) fragment. The riboflavin binding ability of the F(ab) fragment is the same as the intact molecule, while the binding ability of the active site formed by V(H) and light chain is lowered by two to three orders of magnitude, indicating that the removal of C(H1) domain decreases the interaction between riboflavin and the amino acids that is important in tight binding of riboflavin. Removal of the third hypervariable region and the constant region domain from the light chain further lowers the binding constant by one order of magnitude. The results indicate that the V(H) and V(L) segments of IgG Gar can reconstitute a riboflavin binding site. The decrease in affinity probably reflects a decrease in the rigidity with which the hypervariable loops are held together to place the contact amino acid residues in optimal contact with the hapten.
Affinity of nonhomologous amphiphilic peptides toward a monoclonal antibody raised against apolipoprotein A‐I
Authors: Khalil Adli , Bramson Neal , Kezdy Ferenc J. , Kaiser Emil Thomas , Scanu Angelo M. 
Published: May 2005

AbstractMonoclonal antibodies against human apolipoprotein A‐I (apoA‐I) were generated by the hybridoma technique. Clone G‐10 was selected on the basis of its highest titer. The affinity of this antibody toward a series of synthetic peptides differing in length, amino acid composition, and amphiphilicity was tested by using both the indirect and the competitive enzyme‐linked immunosorbent techniques (ELISA). From these measurements we calculated dissociation constants of the complexes of the antibody with apoA‐I bound to the surface of the microtiter plate, apoA‐I in solution, and any of the several peptides in solution. The dissociation constant (Kd) of the immobilized apoA‐I/anti‐apoA‐I‐complex, Kd = 2 × 10−9 M, was significantly lower than that of the complex resulting from the interaction between anti‐apoA‐I and either apoA‐I in solution or any of the several amphiphilic helical peptides in solution. Peptides devoid of amphiphilic secondary structure were inert. These data are consistent with the proposal that monoclonal G‐10 recognizes in antigenic peptides an α‐helical secondary structure of defined hydrophilic‐lipophilic balance and comparatively less the specific amino acid side chains. We propose that the highest contribution to the free energy of binding (8 Kcal/mole) is derived from the docking of the helix to the antibody. It follows that in probing the specificity of a monoclonal antibody the conformation and the physical environment of the interacting antigen must be taken into account.
Sequence conservation and region shuffling in an endoglucanase and an exoglucanase from Cellulomonas fimi
Authors: Warren R. A. J. , Beck C. F. , Gilkes N. R. , Kilburn D. G. , Langsford M. L. , Miller R. C. , O'Neill G. P. , Scheufens M. , Wong W. K. R. 
Published: May 2005

AbstractCellulomonas fimi produces an endoglucanase and an exoglucanase which bind strongly to cellulose. Each enzyme contains three distinct regions: a short sequence of about 20 amino acids containing only proline and threonine (the ProThr box); an irregular region, rich in hydroxyamino acids, of low charge density, and which is predicted to have little secondary structure; and an ordered region of higher charge density which contains a potential active site, and which is predicted to have secondary structure; and an ordered region of higher charge density which contains a potential active site, and which is predicted to have secondary structure. The Pro‐Thr box is conserved almost perfectly in the two enzymes. The irregular regions are 50% conserved, and the conserved sequences include four Asn‐Xaa‐Ser/Thr sites. The ordered regions appear not to be conserved, but the potential active sites both have the sequence Glu‐Xaa7‐Asn‐Xaa6‐Thr; they occur at widely separated sites in the two regions. The order of the regions is reversed in the two enzymes: irregular‐Pro‐Thr box‐ordered in the endoglucanase; ordered‐Pro‐Thr box irregular in the exoglucanase. The genes for the two enzymes appear to have arisen by shuffling of two conserved sequences and either one or two other sequences.
Ion pairs in alpha helices
Authors: Sundaralingam M. , Sekharudu Y.C. , Yathindra N. , Ravichandran V. 
Published: May 2005

AbstractA survey of 47 globular proteins was made to determine the probability of occurrence of ion pairs separated by 1, 2, 3, … and 8 residues in the alpha helices. As a control, the probability of occurrence of like charged pairs was also determined. The survey showed that ion pairs of the type i, i±3 and i, i±4 are the most predominant. Such a preference was not observed for like charged pairs. The observed frequency of ion pairs is significantly greater than their expected frequency. The normalized frequencies of occurrence of the ion pairs were also found to increase generally with the helix length. These results indicate that the ion pairs may contribute to the stability of solvent‐exposed alpha helices. Since the stabilization of protein secondary structure, these results may throw light on the mechanism of protein folding.
Three‐dimensional structure of neuraminidase of subtype N9 from an avian influenza virus
Authors: Baker A.T. , Varghese J.N. , Laver W.G. , Air G.M. , Colman P.M. 
Published: May 2005

AbstractNeuraminidases from different subtypes of influenza virus are characterized by the absence of serlogical cross‐reactivity and an amino acid sequence homology of approximately 50%. The three‐dimensional structure of the neuraminidase antigen of subtype N9 from an avian influenza virus (A/tern/Australia/G70c/75) has been determined by X‐ray crystallography and shown to be folded similarly to neuraminidase of subtype N2 isolated from a human influenza virus. This result demontrates that absence of immunological cross‐reactivity is no measure of dissimilarity of polypeptide chain folding. Small differences in the way in which the subunits are organized around the molecular fourfold axis are observed. Insertions and deletions with respect to subtype N2 neuraminidase occur in four regions, only one of which is located within the major antigenic determinants around the enzyme active site.
Modeling the biochemical differences between rabbit muscle and human liver phosphorylase
Authors: Rath Virginia L. , Newgard Christopher B. , Sprang Stephen R. , Goldsmith Elizabeth J. , Fletterick Robert J. 
Published: May 2005

AbstractGlycogen phosphorylases catalzye the regulated breakdown of glycogen to glucose‐1‐phosphate. In mammals, glycogen phosphorylase occurs in three different isozymes called liver, muscle and brain after the tissues in which they are prefer entially expressed. The muscle isozyme binds and is activated cooperatively by AMP. In contrast, the liver enzyme binds AMP noncooperatively and is poorly activated. The amino acid sequence of human liver phosphorylase is 80% identical with rabbit muscle phosphorylase, and those residues which contact AMP are conserved. Using computer graphics software, we replaced side chains of the known rabbit muscle structure with those of human liver phosphorylase and interpreted the effects of these changes in order to account for the biochemical differences between them. We have identified two substitutions in liver phosphorylase potentially important in altering the cooperative binding and activation of this isozyme by AMP.
Pattern descriptors and the unidentified reading frame 6 human mtDNA dinucleotide‐binding site
Authors: Webster Teresa A. , Lathrop Richard H. , Smith Temple F. 
Published: May 2005

AbstractIn an effort to identify the structural elements essential to a given protein function a new pattern‐directed inference system has been developed. It has been employed to identify a potential dinucleotide‐binding domain within the human mitochondrial unidentified reading frame 6 product, thereby supporting an earlier study that this gene may encode a NADH dehydrogenase subunit.
Site‐directed mutations altering methyl‐accepting residues of a sensory transducer protein
Authors: Nowlin Dawn M. , Bollinger John , Hazelbauer Gerald L. 
Published: May 2005

AbstractThe Trg protein is one of a family of transducer proteins that mediate chemotactic response in Escherichia coli. Transducers are methylaccepting proteins that gain or lose methyl esters on specific glutamyl residues during sensory adaptation. In this study, the significance of multiple sites of methylation on transducer proteins was addressed by using oligonucleotide‐directed, site‐specific mutagenesis to substitute an alanyl residue at each of the five methyl‐accepting sites in Trg. The resulting collection of five mutations, each inactivating a single site, was analyzed for effects on covalent modification at the remaining sites on Trg and for the ability of the altered proteins to mediate sensory adaptation. Most of the alanyl substitutions had substantial biochemical effects, enhancing or reducing methyl‐accepting activity of other sites, including one case of activation of a site not methylated in wild‐type protein. Analysis of the altered proteins provided explanations for many features of the complex pattern of electrophoretic forms exhibited by Trg. The mutant proteins were less efficient than normal Trg in mediating adaptation. Correlation of biochemical and behavioral data indicated that reduction in the number of methyl‐accepting sites on the transducer lengthened the time required to reach an adapted state.