Low Angle Laser Light Scattering Research Articles

PHYSICOCHEMICAL PROPERTIES AND BIOLOGICAL ACTIVITY OF THE NEW ANTIVIRAL SUBSTANCE

Objective: To develop a set of quality control procedures for the promising antiviral pharmaceutical substance L-histidyl-1-adamantylethylamine dihydrochloride monohydrate, a derivative of rimantadine.
 Methods: Substances and solvents: synthesized in laboratory L-histidyl-1-adamantylethylamine dihydrochloride monohydrate (H-His-Rim•2HCl•H2O), rimantadine hydrochloride (Rim•HCl), 99%, ethanol 96%, N, N-dimethylformamide (DMF) anhydrous, 99.8% and n-hexane anhydrous, 95%, deionized high-resistance water (18.2 MΩ•cm at 25 °C, Milli-Q system), silver nitrate. Infrared (IR) Spectroscopy–Cary 630 Fourier Transform IR Spectrometer, elemental analysis–elemental composition analyzer CHNS-O EuroEA3000, ultraviolet (UV) spectrometry–Cary-60 spectrophotometer, polarimetry–POL-1/2 polarimeter with an external Peltier module, granulometric analysis by optical microscopy (Altami BIO 2 microscope) and low-angle laser light scattering (LALLS)–Master Sizer 3600, measurement of potential for hydrogen–potentiometer PB-11, Spirotox method–the study of temperature dependences of Spirostomum ambiguum lifetime to characterize the biological activity of the studied compounds.
 Results: The substance H-His-Rim•2HCl•H2O is an amorphous yellowish powder, slightly soluble in water, soluble in ethanol, freely soluble in N, N-dimethylformamide, and practically insoluble in n-hexane. A study of the elemental composition has confirmed the authenticity of H-His-Rim•2HCl•H2O. Comparison of the spectral characteristics of H-His-Rim•2HCl•H2O and Rim•HCl by IR spectroscopy and UV spectrometry confirmed the authenticity of the substance. The racemic form of the substance Rim•HCl with an insignificant amount of impurity of the levorotatory enantiomer was proved polarimetrically: α =-0.0126±0.0003 (1% aqueous solution, 20±0.5 °С). The specific optical rotation of 1% aqueous solution H-His-Rim•2HCl•H2O . In 1% ethanol solution -10.32±0.12. Using the method of laser light diffraction for a substance H-His-Rim•2HCl•H2O, the dimensional spectra «fraction of particles, %-d, μm» were characterized, the maximum of which in hexane is in the region of 40–50 μm. Arrhenius’s kinetics on the Spirotox model established statistically significant differences in ligand-receptor interactions, which are characterized by values of observed apparent activation energy °bsEa, kJ/mol: 132.36±1.55 for H-His-Rim•2HCl•H2O and 176.15±0.48 for Rim•HCl.
 Conclusion: The developed set of methods for assessment of physical and chemical properties and biological activity of a new antiviral substance H-His-Rim•2HCl•H2O is the basis for establish of regulatory documentation.

Complexes of end-functionalized polystyrenes carrying amine end-group with transition metals: association effects in organic solvents

Linear end-functionalized polystyrenes of different molecular weights bearing amino end-group (NPS) were synthesized by anionic polymerization high vacuum techniques. The polymers were exposed to copper and iron salts (CuCl2.2H2O and FeCl3.6H2O) to form complexes with specific metal/amino molar ratios. The thermal stability of these complexes was studied by Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG), whereas their solution behavior was studied by Low Angle Laser Light Scattering (LALLS), Dynamic Light Scattering (DLS) and dilute solution Viscometry. Extended aggregation phenomena of these complexes were observed in organic solvents. The association behavior was influenced by the molecular weight of the polymer chain, the metal/amine group molar ratio, the chemical nature of the metal and the polarity of the solvent. A complex situation was revealed by DLS showing the existence of equilibrium between aggregates and clusters. Under the influence of shear forces applied in the capillary tube of the viscometer the clusters are disrupted.

LIGHT SCATTERING IN RESEARCH AND QUALITY CONTROL OF DEUTERIUM DEPLETED WATER FOR PHARMACEUTICAL APPLICATION

Objective: Development of a methodology for measuring the deuterium content in water for pharmaceutical purposes by laser light scattering based on ideas about the cluster structure of water.
 Methods: Samples of industrially manufactured drinking water from different manufacturers with varying deuterium content from 10 ppm to 115 ppm. For the titration of laboratory samples of deuterium depleted water in increments of 5 ppm the following reagents were used: Water, deuterium-depleted (≤1 ppm (D2O, Aldrich, USA); Deuterium oxide/Heavy water/Water-d2 (99.9 atom % D, Aldrich, USA); water Milli-Q (specific resistance 18.2 µS·sm at 25 оС, ТОС ≤ 5 ppb, Merck Millipore). The determination of deuterium content in samples of industrially manufactured water and water obtained in a laboratory manner was carried out by the method of low-angle laser light scattering (LALLS) at the Mastersizer (Malvern Instruments) analyzer and using a working measuring tool–laser dispersion meter/MDL («Cluster-1», Russia/Ukraine). The statistical methods–packages OriginPro®9.
 Results: It was found that the content of isotopologies in water leads to physicochemical water’s properties changes and morphology changes of giant heterogeneous clusters (GHC). The results of low-angle laser light scattering (LALLS) in the water samples under investigation showed the dependence of the water GHC "dispersibility" expressed in the differentiation of curves of the volume size distribution ("size spectra"), the volume concentration, w%, the laser obscuration values (I ‒I0) as the function of the water isotopic composition variations. The laser diffraction method results correlate with two-dimensional (2D) multi-descriptor mathematical analysis.
 Conclusion: When identifying deuterium depleted water, it should be considered not only the indicators that determine its pharmacopoeial quality, but also the D/H ratio, because even small changes in the natural isotopic composition of water lead to significant biological effects. Our proposed approach using laser diffraction in combination with mathematical apparatus of (2D) multi-descriptor laser scattering analysis makes possible the exact calculation of individual signs of deuterium depleted water as the pharmaceutical object of study.

MECHANOCHEMICAL ACTIVATION OF PHARMACEUTICAL SUBSTANCES AS A FACTOR FOR MODIFICATION OF THEIR PHYSICAL, CHEMICAL AND BIOLOGICAL PROPERTIES

Objective: Study the influence of the mechanical preparation methods (grinding, fluidization) of solid pharmaceutical substances (PS) and herbal raw material on their physicochemical properties and biological activities.
 Methods: Test substances and solvents-Lactose monohydrate (DFE Pharma, Germany). Sodium chloride, bendazol hydrochloride (all Sigma-Aldrich, USA) and herbal raw material (Callisia fragrans). The dispersity and native structure of pharmaceutical substances were analyzed by several methods: optical microscopy–Altami BIO 2 microscope (Russia); low angle laser light scattering (LALLS) method (Malvern Instruments, UK); Spirotox method–Quasichemical kinetic of cell transition of cellular biosensor Spirostomum ambiguum; Fourier-transform infrared spectroscopy–the analysis in the middle IR region was carried out using an IR Cary 630 Fourier spectrometer (Agilent Technologies, USA). The analysis of dried leaves of C. fragrans before and after mechanical activation was performed using Shimadzu EDX-7000 X-ray fluorescence spectrophotometer without mineralization (Shimadzu, Japan).
 Results: It was established that the mechanical change, such as dispersion and drying, alters the biological activity of PS and herbal raw materials. The observed increase in the influence of the dispersed substance on the biosensor S. ambiguum is quantitatively estimated from the values of the activation energy (obsEa), which turns to be valued 1,5 (P≤0,05) times more than for the native form substance. In the study of the dependence of the availability of chemical elements K, Ca, Zn on the degree of dispersion of herbal raw materials was established a quantitative 4-fold (P≤0,05) increase in the concentration of elements in mechano-activated raw materials.
 Conclusion: By the example of the biological model of Spirotox (single-celled biosensor S. ambiguum) and herbal raw materials obtained from C. fragrans, the increase of biological activity of PS at the dispersion of initial preparations was proved.

СУЧАСНІ МЕТОДИ ЕКСПЕРТИЗИ СОНЯШНИКОВОЇ ОЛІЇ В ТЕХНОЛОГІЧНОМУ ПРОЦЕСІ ВІНТЕРИЗАЦІЇ

Метою даного дослідження є аналіз існуючих методів та засобів контролю розмірних фракцій воскоподібних сполук соняшникової олії в технологічному процесі вінтеризації з застосуванням методики дифракційної фотометрії. Метод лазерної дифракції, або відхилення випромінювання під малим кутом (Low Angle Laser Light Scattering – LALLS), використовується для визначення розподілу частинок за розміром та заснований на аналізі профілю розсіювання світла, що виникає при освітленні частки лазерним опроміненням. У методі лазерної дифракції (Particle size analysis, PSD – Laser diffraction methods) використовується апроксимація Фраунгофера, а також обернене розсіювання світла. Даний метод є фармакопейним (USP24, EРh 6.0).

Droplet Size Distribution in Water-Crude Oil Emulsions by Low-Field NMR

This paper reports the droplet size distribution (DSD) measurements in 28 W/O (water/oil) crude oil emulsions prepared with two Brazilian oils (medium and heavy) under different shear conditions using both 10 g L-1 NaCl solution and water production by low field nuclear magnetic resonance (NMR, 2.2 MHz). The PFGSTE (pulsed-field gradient-stimulated echo) pulse sequence applied was able to separate the crude oil emulsion signal for both medium and heavy oil even for low dispersed phase content (1.51 wt.%) and took into account only the aqueous phase signal. All emulsions exhibited an average diameter smaller than 5.5 µm because of the severe shear conditions. Despite the difficult processing of the S24 (6.48 wt.%) emulsion signal, good agreement was achieved between low field NMR and low-angle laser light scattering (LALLS) results. Finally, the paramagnetic ions in the water production did not affect the NMR measurements, demonstrating its applicability for analyzing real emulsions.

POLARIMETRIC RESEARCH OF PHARMACEUTICAL SUBSTANCES IN AQUEOUS SOLUTIONS WITH DIFFERENT WATER ISOTOPOLOGUES RATIO

Objective: Methodology development for quality control of optically active pharmaceutical substances based on water isotopologues.Methods: Solutions of L-ascorbic acid, glucose, galactose and valine stereoisomers were prepared using deuterium depleted water (DDW-«light» water, D/H=4 ppm), natural deionized high-ohmic water (BD, D/H=140 ppm), heavy water (99.9% D2O). The optical rotation was observed using an automatic polarimeter Atago POL-1/2. The size distribution of giant heterogeneous clusters (GHC) of water was recorded by low angle laser light scattering (LALLS) method.Results: The infringement of Biot’s Law was found for solutions of ascorbic acid, expressed in the absence of a constant value of the specific optical rotation at a concentration of below 0.1%, depends on the D/H ratio. The inequality was established in absolute values of optical rotation for L-and D-isomers of valine in solutions with different ratios of hydrogen isotopologues. The mutarotation of glucose confirmed the first-order kinetics, and the activation energies were statistically distinguishable for BD and DDW. The mutarotation of the natural galactose D-isomer proceeded with a lower energy consumption compared to the L-isomer. In heavy water, the mutarotation of monosaccharides had different kinetic mechanisms. Polarimetric results correlated with the number and size of GHC, which confirmed the possibility of chiral solvent structures induction by optically active pharmaceutical substances.Conclusion: In the optically active pharmaceutical substances quality control there should be considered the contribution of induced chiral GHC of water to the optical rotation value that depends on the isotopic D/H ratio, the substance nature and the form of its existence at a given pH.

Synthesis and Physicochemical Properties of Nd‐, Sm‐, Eu‐Based Cuprate High‐Temperature Superconductors

The aim of the research is to create new high‐temperature superconductors (HTS) NdBa2Cu3O7−x, SmBa2Cu3O7−x, EuBa2Cu3O7−x, and Nd1/3Sm1/3Eu1/3Ba2Cu3O7−x based on light rare earth (LRE) metals. The superconducting materials are investigated for microstructural and physicochemical properties. The paper describes the preparation process of substrate powders and the granulation results of the raw material mixtures before the first calcination, as well as after the first and the second calcination. The granulation analysis of the raw materials are performed using a low‐angle laser light scattering (LALLS) method. Qualitative and quantitative phase analysis of the superconducting materials after the first and the second calcination and after annealing in oxygen atmosphere have been performed by X‐Ray diffraction (XRD) technique. A detailed structural investigations mainly shows the orthorhombic phase with small amounts of BaCuO2 and CuO compounds detected in all samples. A microstructural analysis of materials are carried out by using Raman spectroscopy and scanning electron microscopy (SEM), respectively. The magnetic properties of the superconducting materials are characterized by AC magnetic susceptibility as a function of temperature. The critical current densities at liquid nitrogen temperatures were also measured.

Chemical Composition and Particle Size Analysis of Kaolin

The mineral and elemental composition, crystal structure and particle size distribution of kaolin clays have been determined to ascertain its industrial significance. The mineral composition is evaluated by X- Ray Fluorescence (XRF), crystalline structure by X-Ray Diffraction (XRD) and particle size distribution using low angle laser light scattering (LALLS) technique. The results shows the presence of eight elements expressed in percentages in form of their oxides as: SiO 2, Al 2 O 3, Fe 2 O 3, MgO, CaO, K 2 O, TiO 2 and P 2 O 5. Five crystalline structures are revealed by XRD result. The particle size distribution shows that kaolin particles are mainly in the range of 25–35 µm, while few particles have size distribution varied between 0.4–0.75 μm. The report is found to be in agreement with other researchers.

Accurate particle speed prediction by improved particle speed measurement and 3-dimensional particle size and shape characterization technique

Accurate particle mass and velocity measurement is needed for interpreting test results in erosion tests of materials and coatings. The impact and damage of a surface is influenced by the kinetic energy of a particle, i.e. particle mass and velocity. Particle mass is usually determined with optical methods, e.g. laser light scattering, and velocity by the double disk (DD) method. In this article we present two novel techniques, which allow a more accurate measurement of mass, velocity and shape, and we later compare the experimentally obtained flow velocities of particles with a simulation that also includes the particle's shape parameter, known as sphericity. Mass and sphericity are obtained from 3-dimensional data with an industrial X-ray computed tomography (CT) scanner. CT data can be used to accurately determine the volume-basis median of the particles (using the volume-equivalent particle diameter). Velocity is measured with a fast 2-dimensional particle imaging method using a pulsed LED. Good agreement of the measured and simulated particle velocity was found when including the sphericity from CT results. 2-dimensional optical particle size measurements in the jet of an erosion rig are compared with detailed 3-dimensional CT measurements and a low angle laser light scattering (LALLS) measurement system for six different samples of particles. It is shown that the particle volume or mass is usually overestimated by 16–22% when using 2-dimensional methods or LALLS. For CT allows additionally the surface-equivalent diameter to be calculated by using 2-dimensional projections of each particle, these results can be used to correct particle diameters measured with the particle imaging method using a pulsed LED.

Effect of colloidal silica on rheological properties of common pharmaceutical excipients

In pharmaceutical industry, the use of lubricants is mostly based on historical experiences or trial and error methods even these days. It may be demanding in terms of the material consumption and may result in sub-optimal drug composition. Powder rheology enables more accurate monitoring of the flow properties and because the measurements need only a small sample it is perfectly suitable for the rare or expensive substances. In this work, rheological properties of four common excipients (pregelatinized maize starch, microcrystalline cellulose, croscarmellose sodium and magnesium stearate) were studied by the FT4 Powder Rheometer, which was used for measuring the compressibility index by a piston and flow properties of the powders by a rotational shear cell. After an initial set of measurements, two excipients (pregelatinized maize starch and microcrystalline cellulose) were chosen and mixed, in varying amounts, with anhydrous colloidal silicon dioxide (Aerosil 200) used as a glidant. The bulk (conditioned and compressed densities, compressibility index), dynamic (basic flowability energy) and shear (friction coefficient, flow factor) properties were determined to find an optimum ratio of the glidant. Simultaneously, the particle size data were obtained using a low-angle laser light scattering (LALLS) system and scanning electron microscopy was performed in order to examine the relationship between the rheological properties and the inner structure of the materials. The optimum of flowability for the mixture composition was found, to correspond to empirical findings known from general literature. In addition the mechanism of colloidal silicone dioxide action to improve flowability was suggested and the hypothesis was confirmed by independent test. New findings represent a progress towards future application of determining the optimum concentration of glidant from the basic characteristics of the powder in the pharmaceutical research and development.

Particle size composition of Holocene–Pleistocene deposits of the Laptev Sea (Buor-Khaya Bay)

New data on the particle size composition of the Laptev Sea shelf deposits were obtained on the basis of results of low-angle laser light-scattering of core samples from the columns studied. It was revealed that the sand fraction dominates. The results of comparative analysis of the particle size composition of deposits show that the Laptev Sea shelf zone was characterized by highly variable spatial–temporal conditions and settings of sedimentation in the Quaternary, a polygenic character of deposits, and a pulsating influence of fluvial and slope processes on the conditions of sedimentation. A tendency of coarsening in the vertical sequence that contributes to thawing of the permafrost was revealed in the Ivashkina lagoon.

Influence of Grinding and Sonication on the Crystal Structure of Talc

AbstractTalc is an important industrial mineral with a broad range of applications. Particle size and crystal structure have a significant influence on the potential uses. The present study examined the influence of grinding and ultrasound treatment on talc from a new deposit, Gemerská Poloma, in Slovakia. The general knowledge that grinding produces progressive structural disorder leading to amorphization, whereas sonication has a negligible effect on the talc crystal structure, was confirmed by X-ray diffraction (XRD), infrared (IR) spectroscopy, and transmission electron microscopy (TEM). Partial reduction of particle size along with delamination was observed by XRD after sonication, low-angle laser light scattering (LALLS), scanning electron microscopy (SEM), and TEM. The specific surface area (SSA) increased slightly after prolonged sonication, but grinding initially caused a rapid increase in SSA followed by a drastic decrease after prolonged grinding time of up to 120 min which was attributed to the aggregation of amorphized talc. Sonication and grinding had different influences on the thermal behavior of the talc studied. Sonication decreased slightly the dehydroxylation temperature, whereas grinding added a significant mass loss at low temperature, arising from the dehydration of hydrated Mg cations released from the talc structure during amorphization. The initial high whiteness value of talc decreased slightly after grinding or sonication. Thermogravimetry was suggested as a useful tool to track and predict changes in the talc structure upon sonication and grinding.

The effect of magnetic field on ion hydration and sulfate scale formation

Abstract Scale is one of the most common and costly problems in industrial water treatment and petroleum industry. In this study, 0.5 M Ba(NO 3 ) 2 , 0.5 M Sr(NO 3 ) 2 , 0.5 M Ca(NO 3 ) 2 , 0.5 M AgNO 3 , 0.5 M Na 2 (SO 4 ) and 0.5 M NaCl solutions flowed with a flow rate of 25 L/h under magnetic flux of 1.0 T. After magnetic treatment, BaSO 4 , SrSO 4 , CaSO 4 and AgCl salts were precipitated using equivalent volumes of cation and anion scalant. The colloidal dispersions were characterized by means of sedimentation rate measurements and low angle laser light scattering (LALLS). The effect of the magnetic treatment was more evident in the case of SrSO 4 , scales, which led to considerably smaller particles and more stable dispersions. This effect remained for two days after treating the pristine solutions. The “memory” effect was destroyed upon heating at 60 °C for 20 min. The crystallinity of insoluble particles was weakly affected by the external magnetic field. The kinematic viscosity values of 0.5 M Ba(NO 3 ) 2 , 0.5 M Sr(NO 3 ) 2 and 0.5 M Ca(NO 3 ) 2 solutions treated with a magnetic field were larger than those of untreated solutions. However, no effects could be observed for 0.5 M AgNO 3 , 0.5 M Na 2 (SO 4 ) and 0.5 M NaCl solutions treated with magnetic field. A model based on the effect of magnetic field on the ion hydration and orientation at air/water interface was proposed to explain the experimental observations.

Polymer Characterization by Static Laser Light Scattering

Low angle laser light scattering (LALLS) and multi-angle laser light scattering (MALLS) methods have become valuable, if not indispensable, tools for the chemist and biochemist, since they can be used to determine the absolute molecular weight and size of molecules in solution. When linked to a gel permeation chromatography system, they become even more powerful tools, providing information on molecular weight averages and their distributions (polydispersity). LALLS has essenttially been superseded by the development of on-line MALLS and size-exclusion chromatography (SEC)/MALLS systems, which have facilitated the greater application of light scattering theory in structure elucidation. For example, the determination of root mean square radii, molecular conformation and structure, branching ratios etc., are now readily achievable. This paper reviews the “theoretical backbone” of light scattering methods and the technology available for use in this particular aspect of macromolecular characterisation. Particular emphasis is placed on the use of SEC/MALLS and SEC/LALLS for the molecular weight elucidation of polysaccharides (such as carrageenans, starch, hyaluronic acid and dextrans), proteins, and the examination of branching in large macromolecular structures

Effect of both grafting and blending modifications on the performance of lignosulphonate-modified sulphanilic acid–phenol–formaldehyde condensates

Modifying sulphanilic acid–phenol–formaldehyde condensates (SPF) with sodium lignosulphonate (LS) allows for both the grafting (GSPF) and blending (BSPF) of a series of products from SPF and LS with different LS content. The grafted macromolecule SPF-g-LS was confirmed to exist in GSPF by low-angle laser light scattering (LALLS) and Fourier-Transform infrared (FTIR) spectroscopy. GSPF formed different adsorption configurations on cement particles than BSPF, which ultimately affected their dispersive properties, because of the high charge density and large steric hindrance of the SPF-g-LS macromolecule. Both the absolute value of the ζ potential and the paste fluidity of the cement particles were greater for GSPF than BSPF at identical LS contents. GSPF and BSPF both significantly inhibited cement bleeding relative to SPF; however, this inhibition was greater for GSPF than BSPF at identical LS contents.

GPC-低角度光散乱測定法による非線状ブロック共重合体の絶対分子特性化

低角度光散乱光度計付きGPC (GPC-LALLS)を用いて，新たに導出した解析式により非線状ブロック共重合体の絶対分子特性化を行った．ブロック共重合体の二つの組成分布を考慮してこの解析式を求めた．一つ目は異なった分子量におけるそれであり，二つ目は同じ分子量内でのそれである．スチレン基を片末端にもつポリスチレンマクロモノマーとポリイソプレンマクロモノマーを逐次リビングアニオン重合して(PSt)n-star-(PIs)mヘテロアーム星型共重合体を合成した．PSt-graft-ポリ(n-ヘキシルイソシアナート)グラフト共重合体を逐次分解して，グラフト鎖数が異なるグラフト共重合体を合成した．これら非線状ブロック共重合体の絶対分子量をGPC-LALLSにより決定し，組成分布をRIとUV検出器の併用により決定した．(PSt)n-star-(PIs)mの三次元分子量分布や腕鎖数分布も決定した．

Manufacturing pellets with different binders: Effect on water stability and feeding response in juvenile Cherax albidus

In this study, we used natural polysaccharides (pectin, alginate and chitosan) as binders to generate pellets for crayfish feeding. Pellets were produced by cold extrusion in order to preserve nutrients from degradation and reduce energy consumption. Thereafter, pellets were submitted to a coating procedure, with the aim of improving pellet stability in water. Pellet water stability was analyzed by monitoring the diameter of the released particles in water over progressive time intervals up to 24 h, employing a Low Angle Laser Light Scattering Technique. Alginate containing pellets released particles with a smaller diameter than chitosan and pectin containing pellets, indicating that alginate containing pellets disaggregated more and therefore were less stable in water than the other pellet types. The effects of the different polysaccharide containing pellets were evaluated on crayfish feeding response employing juvenile Cherax albidus. The feeding experiment was carried out for 12 weeks, at the end of which growth parameters and the activity of amylase, lipases and proteases in the gastric juice, hepatopancreas and intestine were recorded. Crayfish fed pectin containing pellets exhibited a significant weight gain. Digestive enzyme activities did not statistically show significant differences in the digestive tract except for amylase that was significantly higher in the intestine of animals fed pectin containing pellets. Our data indicate that pectin and chitosan pellets showed the best water stability performances, moreover pectin pellets brought about the highest body weight gain and affected the amylase profile in the intestine of juvenile Cherax albidus.

Investigation of low-angle laser light scattering patterns using the modified Twomey iterative method for particle sizing

We first applied the Twomey iteration method to the low-angle laser light scattering (LALLS) method. The Twomey method is known by the simple iteration algorithm for Fredholm integral equation. However, the algorithm is not applied to the LALLS result itself because the kernel function pattern is not stable. We solved the unstable kernel issue by modifying the Twomey algorithm to fit the LALLS data in this study. The performance of inversion was studied by computer simulation and experimental results from detectors containing 24 elements from angle 0.0005 to 2.5 rad. The computer simulation was carried out for particles of mean sizes from 0.1 to 1000 μm with mono-dispersion and log-normal distributions. A conventional algorithm is also carried out to compare the performance of the Twomey method. The noise effect of the inverse problem was tested by computer simulation. Experimental results were measured with standard polystyrene latex from 0.081 to 1007 μm. All the tests were performed under conditions in which the light from a linearly polarized laser at 633 nm was scattered by a diluted aqueous suspension. The modified Twomey (MT) method and conventional method show good reproduction results for particles with log-normal distributions. However, narrow distribution particles indicate that the MT method shows excellent reproduction results when compared with the conventional method.

Microencapsulation of PCMs with a styrene-methyl methacrylate copolymer shell by suspension-like polymerisation

The microencapsulation of phase change materials (PCMs) by a suspension copolymerisation of styrene (St) and methyl methacrylate (MMA) has been studied. The influence of the monomers/paraffin and the MMA/St mass ratio on the encapsulation process and the physical properties of the resulting microcapsules has been studied. The thermal properties, morphology, chemical composition and particle size distribution of the microcapsules were characterised by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), environmental scanning electron microscopy (ESEM), optical microscopy (OM), Fourier transform infrared spectroscopy (FT-IR) and low angle laser light scattering (LALLS). It was found that the MMA/St mass ratio has a marked influence on the polymerisation rate, affecting the con