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Roller compaction followed by milling of the generated ribbons is a typical dry granulation route. It is desirable to be able to predict the size distribution of the granules exiting the mill based on the ribbon properties and mill operational conditions. Two DEM-PBM approaches for predicting this size distribution are compared; a direct approach where the size distribution is experimentally determined, and an indirect approach where the successive change in size distribution due to each stressing event is determined mathematically by the PBM. The experimental component of the direct approach assumes shear deformation to be the dominant breakage mechanism. This approach provides a reasonable agreement to experimental data, though the influence of mill parameters is not experimentally tested. When considering breakage to be driven by impact, the indirect approach predicts the correct magnitude of fines generation, though incorrectly predicts the fine fraction to increase with impeller speed. When abrasion is assumed to be the dominant breakage mechanism, the indirect approach suggests the same trend, though with a less pronounced effect of impeller speed and a closer agreement to experimental data. Prediction accuracy is expected to improve by considering distributions of stressing conditions and material strength, the latter being explicitly captured in the experimental component of the direct approach. Furthermore, the direct approach accounts for the variable loading conditions of the fragments in the mill. [Display omitted] • Direct and indirect DEM-PBM ribbon milling size prediction approaches are described. • The two approaches are compared and contrasted. • A critique is given on the important features of ribbon milling prediction models. [ABSTRACT FROM AUTHOR]

In this paper, we introduce the notion of HvBE-algebra and investigate the some properties of it. Also some types of HvBE-algebras are studied and the relationship between them are stated. We try to show that these notions are independent, by some examples. In addition we show that HvBE-algebra is an extension of hyper BE-algebra and compute the number of HvBE-algebras in cases |H| = 2 and 3. Furthermore, we study several kinds of homomorphisms on HvBE-algebras. [ABSTRACT FROM AUTHOR]

In this study, nonlinear dynamics and vibrations of a mass, spring and damper system with constant and variable velocities have been investigated. One end of the large-sag cable is fixed and the other one can be varied using different heights with respect to the first end. The oscillator can be accelerated by the tangential component of the weight force. The governing equations of motion are derived with regard to the mutual influence of the cable movement and vertical motion of attached mass. The Galerkin's method is employed in the displacement field in conjunction with the average acceleration method in the time domain to solve the governing equations. The parametric study is performed on the vertical movement of the oscillator, the displacement of the cable and the velocity of the moving oscillator. [ABSTRACT FROM AUTHOR]

Triboelectric charging of powders causes nuisance and electrostatic discharge hazards. It is highly desirable to develop a simple method for assessing the triboelectric charging tendency of powders using a very small quantity. We explore the use of aerodynamic dispersion by a pulse of pressurised air using the disperser of Morphologi G3 as a novel application. In this device particles are dispersed by injection of a pulse of pressurised air, the dispersed particles are then analysed for size and shape analysis. The high transient air velocity inside the disperser causes collisions of sample particles with the walls, resulting in dispersion, but at the same time it could cause triboelectric charging of the particles. In this study, we analyse this process by evaluating the influence of the transient turbulent pulsed-air flow on particle impact on the walls and the resulting charge transfer. Computational Fluid Dynamics is used to calculate particle trajectory and impact velocity as a function of the inlet air pressure and particle size. Particle tracking is done using the Lagrangian approach and transient conditions. The charge transfer to particles is predicted as a function of impact velocity and number of collisions based on a charge transfer model established previously for several model particle materials. Particles experience around ten collisions at different velocities as they are dispersed and thereby acquire charges, the value of which approaches the equilibrium charge level. The number of collisions is found to be rather insensitive to particle size and pressure pulse, except for fine particles, smaller than about 30 µm. As the particle size is increased, the impact velocity decreases, but the average charge transfer per particle increases, both very rapidly. Aerodynamic dispersion by a gas pressure pulse provides an easy and quick assessment of triboelectric charging tendency of powders. [ABSTRACT FROM AUTHOR]

Although thioacids have been proposed as acylating agents and energy carriers in the context of prebiotic chemical evolution, there has been little exploration of their synthesis in an aqueous, abiotic setting. Here we report that α-amino thioacids are generated from α-amino acids in water in the presence of carbonyl sulfide (COS), a component of volcanic and deep sea vent emissions. Traces of thioacid are formed when amino acids react with COS alone in water, with the required sulfide presumably originating from COS decomposition. Higher yields of thioacid are observed when sulfide ions are added exogenously to the reactions. The proposed mechanism involves activation of the amino acid to an N-carboxyanhydride (NCA) mediated by COS. Our data shows that COS also catalyzes the hydrolysis of α-amino thioacids, so the observed yields are a net of thioacid synthesis and breakdown. Although the NCA has been a topic of research for decades, this is the first report to our knowledge of NCA-mediated thioacid formation in water. These findings broaden the scope of reactions mediated by COS, suggesting a mechanism by which peptide formation, phosphate activation and phosphorylation, and the syntheses of aminoacyl thioacids, could have shared a common pathway on the prebiotic Earth. [ABSTRACT FROM AUTHOR]

In this article, the equation of motion for a rotating nanocantilever has been developed based on the Euler–Bernoulli beam model, which includes the effect of temperature, small scale effect, and centrifugal force. A power series method has been employed to obtain the exact solution of the natural frequencies. The results also compared with other solutions of exact and approximate differential quadrature method. The effects of temperature, angular velocity, and small scale in the vibration characteristics of a rotating nanocantilever beam are investigated. It is shown that the effect of temperature plays a significant role in the behavior of the vibration of a rotating nanocantilever. Nondimensional frequency increases in the first mode with increasing the nonlocal parameter while it is inverse for the second and third modes of vibration. [ABSTRACT FROM PUBLISHER]

The coalescence of a water drop in a dieletric oil phase at a water layer interface in the presence of an electric field is simulated by solving the Navier–Stokes and charge conservation equations with the finite element method. The proprietary software Comsol Multiphysics is used for this purpose. The interface between the oil and water phases is tracked by implementing a Level Set approach. The sensitivity of the model with respect to some input parameters are reported. In particular, the calculations are sensitive to the size of the computational grid elements, interface thickness and re-initialization parameter. The ratio between the volume of secondary droplets and the initial drop volume is calculated as a function of the initial drop size and compared with experiments available in the literature. A good quantitative agreement can be obtained if the parameters are suitably tuned. The model also predicts a strong role played by the water phase conductivity in the formation of progeny droplets. [ABSTRACT FROM AUTHOR]

Fine cohesive powders are often dry granulated to improve their flowability. Roller compaction is commonly used to produce dense ribbons which are then milled. The material properties of the powder and the conditions in the roller compactor affect the strength of the ribbons, however there is no method in the literature to predict the size distribution of the product of ribbon milling. Here we introduce a method, by using the Distinct Element Method (DEM) to determine the prevailing impact velocities and stresses in the mill, with bonded spheres representing the ribbons. The bond strength is calibrated by matching experimental results of three point bend measurements and predictions from numerical simulations. The ribbons are then exposed to the dynamic conditions predicted by the DEM, by dropping them from a controlled height to cause fragmentation, and subsequently stressing them in a shear cell under the conditions again predicted by the DEM. The fragments are sheared under these conditions to represent repeated passage of bars over the fragments at the mill base. Sieve analysis is used here to determine the particle size distribution under given mill conditions. The predicted size distribution of the mill product compares well with the plant data. It is found that the mill speed and length of ribbons fed to the mill have no significant influence on the product size distribution for the range tested. [ABSTRACT FROM AUTHOR]

Particles are frequently exposed to shear stresses during manufacturing, which leads to breakage. This is particularly relevant to weak active pharmaceutical ingredients and is prevalent in pharmaceutical and food industries. The attrition of paracetamol and aspirin caused by shear deformation at very low stresses is investigated here. The extent of breakage of these particles is related to the prevailing shear stresses and strains. In contrast to the expected trend, smaller particles exhibited increased breakage rates. At the onset of shearing at low stresses aspirin particles experienced slightly more breakage than the paracetamol, however prolonged shearing resulted in greater breakage of paracetamol. Breakage occurred initially through chipping with some fragmentation, particularly more noticeable for aspirin, with an increase in abrasion after extensive shear strain for paracetamol. Empirical breakage relationships are proposed and when combined with process stresses and strain analyses the extent of breakage occurring in process equipment can be estimated. [ABSTRACT FROM AUTHOR]

Electric fields are commonly used to enhance the coalescence of water drops in oils. However, this process could cause some undesirable phenomena such as secondary droplets formation, reducing the separation efficiency. Here the effect of pulsatile electric fields (PEF) on the secondary droplets formation has been investigated. In the presence of a very low frequency PEF or DC electric field three distinct drop–drop and drop–interface interaction patterns are observed: complete coalescence, partial coalescence and rebound without coalescence. The first is the ideal pattern not leaving any secondary droplets. It has previously been shown that an increase in the electric field strength and/or a decrease in the interfacial tension result in non-ideal patterns in drop–interface coalescence. The application of PEF shifts the coalescence pattern from a non-ideal to an ideal one in both drop–drop and drop–interface coalescences. Three waveform types, i.e. square, half-sinusoidal and sawtooth waves have been applied to the coalescence process. It is shown that the sawtooth waveform is the most effective in reducing the secondary droplets formation in drop–interface coalescence, followed closely by the half-sinusoidal one. The observation of videos sequences suggests that a threshold frequency exists above which a non-ideal pattern switches to an ideal one. For drop–drop coalescence this threshold frequency depends on the PEF amplitude and the size of primary drop pairs, as for bigger primary drop pairs and larger amplitudes of PEF the threshold frequency would be higher. When using pulsatile electric fields higher field strengths can be applied for systems having high water content without causing field breakdown, as compared to the constant DC field. This is useful in optimizing the electro-coalescence process. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cortical spreading depression (CSD) plays an important role in migraine with aura. [•] The caudate has interactions with brain regions that are important in migraine. [•] CSD inhibited the neuronal activity in the caudate. [•] Reduced activity in the caudate may contribute to pain in migraine. [ABSTRACT FROM AUTHOR]

The antiplane stress analysis of two anisotropic finite wedges with arbitrary radii and apex angles that are bonded together along a common edge is investigated. The wedge radial boundaries can be subjected to displacement-displacement boundary conditions, and the circular boundary of the wedge is free from any traction. The new finite complex transforms are employed to solve the problem. These finite complex transforms have complex analogies to both kinds of standard finite Mellin transforms. The traction free condition on the crack faces is expressed as a singular integral equation by using the exact analytical method. The explicit terms for the strength of singularity are extracted, showing the dependence of the order of the stress singularity on the wedge angle, material constants, and boundary conditions. A numerical method is used for solving the resultant singular integral equations. The displacement boundary condition may be a general term of the Taylor series expansion for the displacement prescribed on the radial edge of the wedge. Thus, the analysis of every kind of displacement boundary conditions can be obtained by the achieved results from the foregoing general displacement boundary condition. The obtained stress intensity factors (SIFs) at the crack tips are plotted and compared with those obtained by the finite element analysis (FEA). [ABSTRACT FROM AUTHOR]

The numerical solutions to the singular integral equations obtained by the fracture mechanical analyses of a cracked wedge under three different conditions are considered. The three considered conditions are: (i) a radial crack on a wedge with a non-finite radius under the traction-traction boundary condition, (ii) a radial crack on a wedge with a finite radius under the traction-traction boundary condition, and (iii) a radial crack on a finite radius wedge under the traction-displacement boundary condition. According to the boundary conditions, the extracted singular integral equations have different forms. Numerical methods are used to solve the obtained coupled singular integral equations, where the Gauss-Legendre and the Gauss-Chebyshev polynomials are used to approximate the responses of the singular integral equations. The results are presented in figures and compared with those obtained by the analytical response. The results show that the obtained Gauss-Chebyshev polynomial response is closer to the analytical response. [ABSTRACT FROM AUTHOR]

Abstract: Powder processing operations can give rise to tribo-electrification of particles. The resulting electrostatic force can cause segregation/agglomeration of particles as well as their adhesion to the walls of the processing equipment, adversely affecting process operations and the end quality of the product. Current methods for evaluation of the tribo-electric charging of powders are unsuitable for testing small quantities of sample. Moreover, limited work has been reported on the tribo-electrification of powders due to aerodynamic dispersion, which is an area of great interest, e.g. in particle characterisation processes and dry powder inhalers. A simple methodology is reported here using a commercially available dispersion unit to investigate the tribo-electric charging of powders. A small quantity of powder, typically a few milligrammes, is sandwiched between two thin metal foils in the dispersion unit. An air pressure pulse is applied to burst the foils and the rapid penetration of air through the packed bed of powder disperses it. The unit is mounted on a conventional Faraday cup, connected to an electrometer to measure the net charge transfer following powder dispersion. Tribo-electric charging of model particles (glass beads) is reported here. The results show that the tribo-electric charging of glass beads is independent of the pressure used within the range tested, i.e. 150–600kPa (0.5–5barg) for a single thickness of aluminium foil (6μm) and the charge transfer is linearly proportional to the surface area of the beads. The surface materials of the dispersion device and the bursting foils used to sandwich the powder affect the transferred charge. The methodology developed in this work has the potential to be used to characterise tribo-electric charging of small quantities of powders. The operating procedure is less time consuming as compared to other current charge characterisation devices. The methodology is potentially suitable for testing active pharmaceutical ingredients (APIs), which are sparse in the early development stages. [Copyright &y& Elsevier]

Abstract: Combining clay minerals containing silica with polymers can improve the performance of polymers in biomedical applications by the synergistic combination of physico-chemical and biological properties of both phases. In this study, Laponite® — a synthetic biocompatible and biodegradable silicate clay mineral, was combined with alginate to improve alginate mechanical and biological characteristics. The physico-chemical properties (porosity, degradation, swelling, crystalline structure, compressive strength, and injectability) and biological responses (cytotoxicity and cell morphology) of the Laponite/alginate nanocomposites were investigated in the study. The results showed that the incorporation of Laponite into alginate significantly enhanced alginate compression strength without hindering its injectability when the percentage of clay mineral was below 50%. The prepared clay polymer nanocomposites (CPN) were not toxic and the viability of cells cultured in its extract was indeed higher than alginate alone. However, these prepared CPN poorly supported cell adhesion, probably due to the high degradation rate of the materials. [Copyright &y& Elsevier]

The article discusses the relationship of socio-economical status of people and society groups in Tehran City, Iran, and their vulnerability degree to natural hazards. It outlines the three main concepts in determining the socio-spatial differences of vulnerability based on the social structure view including socio-economic status, neighborhood, and socio-spatial segregation.

Modeling and simulation of membrane-based solvent extraction is conducted by computational fluid dynamics (CFD). The process is used for removal of priority organic pollutants from aqueous waste streams in nanoporous membranes. The pollutants include phenol, nitrobenzene, and acrylonitrile extracted by organic solvents. The mathematical model commonly applied to predict the performance of membrane-based solvent extraction is the conventional resistance-in-series model. Here, a comprehensive mathematical model is developed to predict the transport of pollutants through nanoporous media. In order to predict the performance of the separation process, conservation equations for pollutants in the membrane module are derived and solved numerically. The model is then validated through comparing with experimental data reported in the literature. The simulation results were in good agreement with the experimental data for different values of feed flow rates. [ABSTRACT FROM AUTHOR]

Abstract: During agitated drying and mixing processes, particle beds are exposed to shear deformation. This leads to particle attrition, the extent of which is dependent on the prevailing stresses and strains in the bed. The distributions of shear stresses and strain rates within the bed are highly non-uniform, requiring attention to localised conditions. Therefore a narrow angular sector of the bed is divided radially and vertically into a number of measurement cells, within which the stresses and strain rates are calculated throughout one rotation by the Distinct Element Method. These are then used in an empirical relationship of material breakage to predict the extent of attrition due to agitation. Here we investigate the influence of the measurement cell size on the estimated stresses and strain rates, and the subsequent effect on the predicted attrition. The measurement cell size is altered by varying the measurement sector size and the number of radial and vertical divisions within it. The median particle size is also varied to establish its influence on the predicted attrition. An increase in the average number of particles in a given cell, by varying the particle size or measurement cell dimensions, leads to a reduction in the estimated stresses and strain rates, and therefore a reduction in the predicted attrition. Comparison of the predicted attrition with the experimental breakage in the agitated vessel shows that the prediction method is accurate when the cell dimensions are comparable to the width of a naturally occurring shear band. [Copyright &y& Elsevier]

The extraction of gold in membrane extractors was theoretically investigated. Extraction of gold in the form of $ {\rm Au(CN)}_2^- $ in a solution of n-heptane and synergistic extractants of LIX79+TOPO was studied. The membrane extractor consists of three sections: the tube side, the membrane, and the shell side. Conservation equations were derived for $ {\rm Au(CN)}_2^- $ in the membrane module and were numerically solved based on finite element method. Simulations were conducted through solving the momentum and mass transfer equations simultaneously. It was indicated that as the feed flows within the tube side, it moves into the membrane due to the concentration difference, and then gets swept by the moving extractants within the shell side. The distribution of solute concentration in the membrane contactor was obtained. Simulation results showed increasing the feed flow rate reduces the extraction efficiency, while doing the same for the organic phase flow rate does not change the extraction efficiency. [ABSTRACT FROM AUTHOR]

Abstract: The majority of pharmaceutical powders produced through crystallisation are dried in agitated dryers. The rotation of the impeller causes shear deformation of the bed, which enhances the drying rate, but also leads to particle breakage. A method of predicting the extent of breakage occurring due to agitation is described and applied for Paracetamol in a small-scale dryer. The distributions of stresses and strains in the bed are estimated using the Distinct Element Method (DEM). The information obtained here is then coupled with the measured attrition of Paracetamol in an annular shear cell in order to predict the attrition in the agitated bed. The experiments are carried out on dry material so as to establish purely the effect of stresses and strains on attrition, whilst keeping moisture content and temperature constant. The shear cell provides uniform condition for stresses and strains so that the breakage taking place under relatively well-defined conditions is quantified. In contrast, the prevailing shear stresses and strains in the agitated bed have wide distributions, as little shearing takes place near the impeller shaft, whilst there are considerable shearing stresses near the impeller tip. Therefore, the bed is divided into a number of segments for which the extent of attrition can be evaluated for each segment, based on the shear cell data. A good quantitative agreement is found between the predictions and experimental results obtained for the attrition of Paracetamol in the small scale dryer. The resulting prediction also suggests that, for a given number of impeller rotations, the extent of breakage is independent of impeller speed in the range tested (20–78rpm). This is expected as the prevailing strain rates are too low for the inertial effects to be dominating and the shear stresses are independent of shear rates within the range investigated. The attrition prediction suggest that over half of the attrition occurs in the bottom third of the bed, with increased attrition at greater radial distances. The attrition is also predicted to occur predominantly within the region extending from 30° in front of to 30° behind the impeller. [Copyright &y& Elsevier]

Abstract: The coalescence of an aqueous droplet at an oil–water interface under an electric field has been investigated, with a view to quantify conditions that give rise to secondary droplet formation. Two patterns of drop-interface coalescence may occur: complete coalescence and partial coalescence. The former is obviously the desirable pattern for industrial coalescers. However in practice, the process of coalescence could actually produce smaller droplets, which become more difficult to remove, and hence undesirable. This is caused by either necking, due to extensive elongation of the droplet, or reaction to a fast and energetic coalescence and is referred to as partial coalescence. The volume of the droplets formed in this way has been analyzed as a function of the initial droplet size, electric field strength and the distance between the droplet and the interface. The expansion speed of the neck connecting the droplet and interface at the beginning of the pumping process has also been quantified. These results are useful in optimizing the electro-coalescence process. [Copyright &y& Elsevier]

Abstract: A novel method for manufacturing granules with a large particle at their core, referred to as seeded granules, is presented. As an example, calcium carbonate powders (Durcal) of different grades are used as primary particles and polyethylene glycol (PEG) as liquid binder in high shear granulators of different scales (Cyclomix, manufactured by Hosokawa Micron B.V., The Netherlands). The conditions giving rise to seeded granulations are specified in the form of an operational regime map. It is found that the seeded structure is strongly dependent on the impeller speed and the primary particles size distribution. It is shown that a Stokes number of around 0.1 represents the optimal dynamic conditions in the given example for producing seeded granules, regardless of the scale of the granulator. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the anti-plane shear deformation of an anisotropic sector with a radial crack is investigated. The traction–traction boundary conditions are imposed on the radial edges and the traction-free condition is considered on the circular segment of the sector. A novel mathematical technique is employed for the solution of the problem. This technique consists of the use of some recently proposed finite complex transforms (), which have complex analogies to the standard finite Mellin transforms of the first and second kinds. However, it is essential to state the traction-free condition of the crack faces in the form of a singular integral equation which is done in this paper by describing an exact analytical method. The resultant dual integral equations are solved numerically to determine the stress intensity factors at the crack tips. In the special cases, the obtained results coincide with those cited in the literature. [Copyright &y& Elsevier]

Abstract: Results of a study of the influence of impeller speed on the strength, structure and morphology of granules produced in a type of high shear mixer granulators are reported. Calcium carbonate particles (Durcal 65) have been granulated in a Cyclomix with a capacity of 5 L. An aqueous solution of polyethylene glycol was used as the binder. The granules produced have been dried and their structure visualized using X-ray micro-tomography equipment, Nanotom, with a resolution of less than 1 μm. It is shown that the operation of the granulator at high impeller tip speeds produces granules with a higher strength and lower porosity than those produced at medium and low impeller speeds. Two different granule micro-structures and morphologies are produced at high and low impeller speeds. Structure descriptors such as phase volume fraction (as representative of porosity), chord length distribution and auto-correlation function (as indices of homogeneity of structure) are used to quantify the internal structure of granules in 3D, which in turn affects the granule strength. [Copyright &y& Elsevier]

Abstract: Dispersion is the desired disintegration of particle clusters down to their primary constituents through the application of external forces, which overcome the interparticle attraction forces. This method is beneficial for many processes but especially for the characterisation of particulate systems and therapeutic drug delivery via the lungs from dry powder inhalers (DPIs). Dry powder dispersion is becoming increasingly popular as a method of sample preparation for a range of instruments such as a laser diffraction measurement device. There are many advantages for dry dispersion compared to wet methods. However, complete dispersion of fine cohesive powders is difficult due to the relatively large interparticle attraction forces compared to separating forces arising from fluid energy. This review identifies the current state of theoretical and experimental understanding of powder dispersing in a gaseous medium. The approaches to relate bulk powder properties to dispersion, the stresses produced on a particulate structure due to aerodynamic forces and possible approaches for linking the two are discussed. Furthermore, the available dispersion technology is reviewed with a discussion of individual dispersers and commercial devices used for dispersing bulk powder. Also, the review highlights the research needed in this field to gain a better understanding of how bulk powders interact with a dispersing fluid. [Copyright &y& Elsevier]

Abstract: Results of a study on the influence of operation scale and impeller speed of high shear mixer granulators on the strength of granlues are reported in this paper. Calcium carbonate particles have been granulated in four scales of a geometrically similar high shear granulator (Cyclomix) with 1, 5, 50 and 250L capacities. For the smallest scale, the effect of a small deviation from geometric similarity was also investigated. An aqueous solution of polyethylene glycol was used as the binder. Three scaling rules of constant tip speed, constant shear stress and constant Froude number have been used to determine the impeller speed for the different scales of the granulators. The granules produced in these experiments have been dried and tested for strength using side crushing test method. The data have then been analysed and compared. Operation of granulators according to the constant tip speed rule produces granules with a similar strength for all four scales, followed by a similar trend for the constant shear stress rule, albeit to the less extent. The constant Froude number rule produces a heterogeneous strength distribution and is not a suitable criterion for scaling-up of high shear granulators. The distribution of granule strength has been fitted to the normal, log-normal and Weibull distributions. Weibull distribution fits the data well for the constant tip speed operations. [Copyright &y& Elsevier]

In the detergent industry, enzymes are used to catalyze the breakdown of tough stains such as oils and fats, which cannot be easily removed with surfactants and bleaches. In the 1960s, a number of plant workers developed respiratory allergies from inhaling enzyme dust over long periods. The response from the enzyme manufacturing companies was to encapsulate the enzymes by granulation, fluid bed coating, extrusion and other techniques. The end users of encapsulated enzymes such as the detergent industry concentrated on the installation of engineering containment and dust extraction systems. These were combined with other safe systems of work, including airborne monitoring and health surveillance. The result was a significant decrease in the concentration of airborne enzyme dust in the working environment and virtually eliminated the incidence of respiratory allergy. However, enzyme dust generation has not been eliminated completely and the integrity of the enzyme encapsulates remains a key control point. In 2000, the Enzyme Dust Consortium was formed with the objective to design a validated test method with a protocol (for granule qualification and quality control) to correlate with dust levels in plant. Current test methods for dust formation do not replicate the mechanical stresses in the detergent plant and limit the enzyme manufacturer's ability to develop better granules. Our efforts are focused on evaluating the prevailing mechanical stresses in detergent manufacturing plants and their effect on enzyme granule attrition. Dust sampling of the factory ventilation ductwork show a large variation in enzyme dust levels. This may be attributed to the presence of some weak granules. Nevertheless, the likely sources and mechanisms of enzyme dust need to be identified. Once a new testing procedure is established, enzyme manufacturers will be able to design and produce improved products that will result in a further reduction of enzyme exposure in detergent manufacturing facilities. [ABSTRACT FROM AUTHOR]

Abstract: Agglomerates are ubiquitous as intermediate or manufactured products in chemical, pharmaceutical and food industries. During handling and processing they may suffer breakage if they are weak. On the other hand, if they are too strong, their dispersion and disintegration could be difficult. The control of their mechanical strength is therefore highly desirable. However, the analysis of agglomerate strength is complex due to the large number of parameters that influence agglomerate behaviour, such as the primary particle size, density and elastic modulus, and the interparticle bond strength. A simple mechanistic model is presented here which relates the number of broken contacts in agglomerate due to impact velocity, interparticle adhesion energy and the particle properties of the particles forming the agglomerate. The model is based on the hypothesis that the energy used to break contacts during impact is proportional to the incident kinetic energy of the agglomerate. The damage ratio defined as the ratio of broken contacts to the initial number of bonds is shown to depend on the dimensionless group, , in the form , where V is the impact velocity, E the elastic modulus, D the particle diameter, the particle density and the interface energy. This dimensionless group, , incorporates the Weber number, , which was previously shown to be influential in agglomerate breakage, and may be presented in the form, , where . The predicted dependency of the damage ratio on the surface energy has been tested using distinct element method (DEM). Four different agglomerates have been formed and impacted against a target for three different values of the surface energy of the primary particles. The simulation results show that the effect of surface energy is better described by the above mechanistic model than by the Weber number alone, as previously used to characterise the impact strength of agglomerates. [Copyright &y& Elsevier]

Abstract: When bulk particulate solids are subjected to an electric field, a remarkable phenomenon occurs as manifested, e.g. in the electro rheological fluids and in a device developed for controlling the flow of granular materials, the electromechanical valve for solids (EVS). It has generally been established that the resistance to shear deformation is enhanced by the application of an electric field. However, no satisfactory description has yet been given for the microscopic mechanisms that are involved in the process. For the EVS it has been found that it is essential to maintain continuous inter-particle contacts for the satisfactory operation of the device. The flow of current through the bed of particles, albeit very small, is considered to be the key to the mechanism involved. In this paper, the measurements of the electrical clamping force across a contact between a resistive sphere and a conductive plate are reviewed. The results are shown to be consistent with the measurements of the macroscopic bulk shear strength under the influence of an electric field. However, they are in disagreement with the predictions of the models of the electrical clamping force available in the literature. For the latter it is considered that the cause of the discrepancy is due to the shortcoming in assuming that the contact deformation follows a Hertzian pattern. An analysis is presented based on the sphere resistance model, which clearly demonstrates the shortcomings in the models of the electrical clamping force. [Copyright &y& Elsevier]

Abstract: Copper(II) complexes with 2,2′-bipyridine(bpy) and 1,8-dibenzyl-1,3,6,8,10,13-hexaazacyclotetradecane (macrocycle) immobilized between silicate layers of montmorillonite and nanoreactors of MCM-41 successfully catalyze the epoxidation of norbornene and trans-2-hexene-1-ol with good to excellent reactivity and 48–100% selectivity toward the formation of the corresponding epoxides. [Copyright &y& Elsevier]

In a number of powder processing operations such as dosing, compaction and tabletting, the behaviour of bulk powders subjected to compression is of great interest. Single particle mechanical properties obviously affect the bulk behaviour and there have been a number of attempts to establish relationships between the two scales of single particle and bulk deformation. A widely used approach, particularly in the pharmaceutical industries, is the Heckel analysis where the applied load and bulk deformation are used to infer the yield stress of individual particles. However, it is difficult to analyse this process rigorously and to ascribe any significance to the parameters quantified in the Heckel analysis because the individual particles are not loaded uniformly in the bed. It is therefore of great interest to elucidate what exactly the Heckel analysis does provide. The most appropriate approach for this purpose is the use of the Distinct Element Method (DEM) to simulate the bulk deformation based on single particle properties. Our analysis shows that there is a critical ratio of Young''s modulus to the yield stress of individual particles (E/σy)c, above which the Heckel analysis does reflect the effect of the yield stress, but below which it in fact reflects the effect of Young''s modulus. Heckel''s parameter is numerically equal to the yield stress of particles only for a certain value of E/σy. For ratios higher than this value, Heckel''s parameter can even exceed the yield stress of the individual particles. Therefore the Heckel analysis does not have general validity and should be used with caution. [Copyright &y& Elsevier]

Single particles as well as assemblies of particles of α-lactose monohydrate have been subjected to compressive loads at different temperatures with a view to investigate the effect of temperature on the crushing behaviour. The results show a significant decrease in the extent of breakage of both single and bulk particles when the temperature is decreased, presumably due to an increase in fracture toughness. The energy utilisation in the bulk compression, expressed in terms of specific surface area created per unit of input energy has also been quantified. It is found to be relatively constant for different levels of input energy, but surprisingly it decreases with a decrease in temperature. [Copyright &y& Elsevier]

Simultaneous determination of sulfite and thiosulfate at sub-ppm levels in petroleum and its distillates was investigated using a convenient, accurate and sensitive procedure. This method involved preliminary extraction of the sample followed by detection via differential pulse polarography (DPP) at a dropping mercury electrode. In this procedure, an appropriate amount of sample was shaken with a recommended volume of 0.25% (w/w) sodium acetate solution. The mixture was filtered in two steps and was then ready for DPP. The method was free from interferences from hydrogen sulfide, elemental sulfur, organic sulfides, and thiophene. Various instrumental factors such as scan rate, pulse height, initial and final potential, and purge time were optimized. The 3σ detection limits were 410 and 125 ng g−1 for sulfite and thiosulfate, respectively. At 5 μg g−1 level in samples, the relative standard deviations (n=4) were 2.51 and 1.15% for sulfite and thiosulfate, respectively. The proposed method was applied to real samples containing input feeds, distillates and fuel oils from Abadan Petroleum Refinery in the south of Iran. [Copyright &y& Elsevier]

Man's preoccupation with potency, or the lack thereof, has been present through the ages. Several documents still exist from which the clinical approaches of erectile dysfunction (ED) in medieval Persia can be ascertained. The medieval physicians described definitions and apparent causes of ED. They also noted hygienic and dietary rules as well as long lists of natural substances used in the treatment of ED. Many of the approaches of practitioners in medieval Persia are accurate and accepted even today; however, still more of them could be of use to modern medicine. The present review provides an overview of the knowledge of ED at the time.International Journal of Impotence Research (2004) 16, 80-83. doi:10.1038/sj.ijir.3901153 [ABSTRACT FROM AUTHOR]

Cryogenic milling could reduce the ductility in the milling operations of semi-brittle and relatively ductile pharmaceutical particles. However, to achieve a better application of this technology, it is necessary to establish the relationship between the influence of temperature on the mechanical properties and breakage characteristics of the single particle and the bulk crushing behavior of these types of material. The focus of this paper is on the analysis of bulk crushing behavior of α-lactose monohydrate particles in response to temperature variations, based on single particle mechanical properties and side crushing strength at different temperatures and the use of distinct element analysis. The effect of temperature on the side crushing strength of the particles has been quantified by quasistatic side crushing tests. The experimental results show a significant increase in the strength of the single particles by decreasing the temperature. These results are used in the distinct element analysis to simulate the bulk crushing behavior of pharmaceutical particles as affected by the temperature. The predictions are compared with the experimental results, for which a reasonable agreement is found for the ambient temperature case. There are some differences for the case of -20°C, due to lack of reliable data for Young's modulus. [ABSTRACT FROM AUTHOR]

The study of agglomerate strength is of vital importance in several industrial applications such as pharmaceutical, detergent and food manufacturing. Agglomerates could experience a size reduction during the production and handling processes due to collisions with other agglomerates or with the moving components and walls as well as during bulk flow due to shear deformation. In this analysis, we focus on the agglomerate damage due to oblique impact on walls, as this is a common damage process during, for example, pneumatic conveying and size reduction in pin mills.Computer simulations have been carried out using Distinct Element Analysis, where the breakage characteristics of oblique impacts and the effect of the interparticle bond strength have been analysed. The procedure adopted here provides an isotropic and spherical agglomerate (uniform mass distribution and coordination number within radial segments of the agglomerate). The results indicate that the damage ratio (i.e. the number fraction of the broken bonds) depends on the normal component of the impact velocity only, i.e. the tangential component has little effect. However, the position of the clusters produced on impact does depend on the impact angle, which influences the pattern of breakage and in turn the size distribution of the large clusters. [Copyright &y& Elsevier]

The mechanical properties and evolved structure of agglomerates depend strongly on the manufacturing method. There is a great interest in finding a simple way of establishing a rank order in their processing behaviour, e.g., the ease with which they could be dispersed in fluids. For this reason, the breakage propensity of two types of detergent agglomerates produced by different processes but with the same formulation has been evaluated under different conditions by impact testing with a view to diagnose differences in mechanical properties and structure arising from their manufacturing method. The effects of impact velocity, agglomerate size, impact angle, fatigue, humidity, and temperature have been analysed. Both samples show extensive plastic deformation due to the elongation and eventual rupture of the interparticle bridges, especially for the humidified samples. Reducing the temperature increases the extent of breakage substantially. The impact test results of samples kept at −20 °C show brittle failure mode, whilst those of oblique impacts at 45° and ambient conditions show a semi-brittle failure mode by shear deformation. Drying strengthens the agglomerates presumably due to the solidification of bridges. In contrast, humidifying the granules decreases their strength. A general comparison of the impact test results of both samples for different feed sizes shows that, due to the structural differences, the breakage trend of these two types of agglomerate varies with increasing agglomerate size. [Copyright &y& Elsevier]

Single particle impact testing has been carried out to evaluate the attrition by chipping of ionic single crystals of MgO, NaCl and KCl, used as model materials having a semi-brittle failure mode. The results have verified the theoretical predictions presented in Part 1. The dimensionless attrition propensity parameter, η=ρv2lH/K2c, is shown to account for the dependence of the material loss per impact on the material properties, impact velocity and particle size. The ‘chipping’ mechanism of impact attrition is further confirmed by the observations of the impact damage by the use of scanning electron microscopy. In addition, the influence of rigidity of target materials on attrition rate is also addressed. [Copyright &y& Elsevier]

A mechanistic model of impact attrition of particulate solids, having a semi-brittle failure mode, has been developed. The model describes the chipping mechanism, where the material loss from the particle is due to the formation of the subsurface lateral cracks. Indentation fracture mechanics is used to analyse the propagation of these cracks in order to provide a base to estimate the rate of attrition. A dimensionless attrition propensity parameter is derived from the above approach, whereby the extent of breakage is related to the material properties and impact conditions. It has the form:η=ρv2lH/Kc2,where ρ is the particle density, v is the impact velocity, l is a characteristic particle size, H is the hardness and Kc is the fracture toughness. The experimental evaluation of the above model is presented in Part 2, where the impact attrition of three materials has been quantified and compared to the model predictions. [Copyright &y& Elsevier]

Analyzes the nature of stress distribution experienced by large particles in a dense granular media subjected to slow shearing, using the distinct element method. Evolution of stress distribution in the submerged particle during shearing; Evaluation of the hydrostatic and deviatoric stress states of the submerged particle; Critical size ratio at which the nature of stress distribution in a submerged particle is dominant.

The largest class of multivalued systems satisfying the module-like axioms is the H[subv]-module. H[subv]-modules first were introduced by Vougiouklis. In this paper we define weak equality between two subsets of an H[subv]-module and introduced the notion of exact sequences of H[subv]-modules. Also some results on the weak equality and exact sequences are given. [ABSTRACT FROM AUTHOR]

Examines cyclic peptides as part of the search for a class of adapters more versatile than cyclodextrins. Alteration of unitary conductance and ion selectivity; Ability of positively charged peptides to act as binding sites for various small polyanions; Modulation of single-channel currents through pores containing cyclic peptide adapters.

Presents a strategy for the design of artificial membrane ion channels based on a self-assembled cylindrical peptide architecture. Naturally occurring membrane channels; Formidable task of designing artificial biological systems.

Discusses the design, synthesis and characterization of organic nanotubes based on rationally designed cyclic polypeptides. Crystallization into tubular structures upon protonation; Electron microscopy; Electron diffraction; Fourier-transform infrared spectroscopy; Molecular modelling; Application.

Describes an approach for the construction of diffusion-limited size-selective ion biosensors. Analysis of the structural properties of monolayer-supported peptide nanotubes; Performance of grazing angle fourier transform infrared spectroscopy; Incorporation of cyclic peptide into monolayers of dodecanethiol and octadecyl sulfide.

Describes an alternative masking method for high-voltage ion implantation masking of compound semiconductors. Description of ion implantation; Data on the scanning electron micrograph cross-section image of the sample.

The article provides information on a study which evaluated the spatial location of the urban parks of Noor-Abad in Iran. Topics covered include the use of the descriptive analytical methodology, the methods of data analyzing and test hypothesis applied and the indicators used to investigate the suitability of number and spatial distribution of parks to provision good access and status of Noor-Abad city's parks.

This article presents a study on a boolean logic functions of a synthetic peptide network. Researchers have adapted nucleic acids and proteins to the design of molecular logic gates and computational systems, while other works have affected computation in living cells via biochemical pathway engineering. Here is present a designed synthetic peptide networks which can also mimic some of the basic logic functions of the more complex biological networks. It shows that segments of a small network whose graph structure is composed of five nodes and 15 directed edges can express OR, NOR, and NOTIF logic.