Optical Probe for the In-Line Determination of Particle Shape, Size, and Velocity

A laboratory optical probe was developed to simultaneously determine the following particle characteristics: circularity, particle projection area, equivalent diameter of a circle, length of the particle outline or perimeter, maximum chord length, aspect ratio, and particle velocity. Using the projection area and the perimeter, the particle shape factor circularity can be determined. The aspect ratio was approximated by the ratio of the equivalent diameter to the maximum chord length. The basic measuring principle is multi-point scanning of the particle shadow image by a line of optical fibers. In addition, the particle velocity can be measured by a differential spatial filter of optical fibers. These fibers are step index fibers with a core diameter of 64 µm and cladding of 70 µm. The shadow image of a single particle was generated by a parallel laser beam. The uncertainty of the measured circularity and aspect ratio was investigated by using metal wires with diameters of 0.12 to 0.5 mm as test particles with known circularity and aspect ratio. The standard deviations were 1.9% for the circularity and 15.5% for the approximated aspect ratio. In addition, the optical probe system was investigated by measurements of solid particles with different shapes. As an example, the results of sand, marjoram seed, and metallic oxide particles are shown. Using 1000 sand particles, the correlation between equivalent diameter and particle velocity could be demonstrated. The presented configuration of the optical probe is applicable in the size range of 0.1 to 0.9 mm and up to a particle velocity of 5 m/s.     

PARTICLE CONCENTRATION MEASUREMENTS BY LASER IMAGING FOR A TURBULENT DISPERSION

A laser imaging system has been developed which can be used for investigating the particle concentration variation in explosive test apparatus such as the Ciba-Geigi and Hartmann Bomb during turbulent dispersions of air-particle mixtures. The pulsed UV (337 nm) laser imaging system using a 500X optical and electronic magnification system has a measurement volume of 900 µm by 675 µm and an in-focus depth of field of 780 µm for a 32 µm diameter particle. Particles in the measurement control volume are imaged every 33 ms during the dispersion process and viewed in real time but stored for later analysis on a video tape system.

This paper presents the results of investigating the lycopodium particle concentration variations during the dispersion process of 0.200 grams of lycopodium particles in the Hartmann Bomb explosive test apparatus. Data were taken at the center line and at a radius ratio of 0.5 at a height of 0.102 m (4 inches) above the base of the Hartmann lucite tube. Twenty-five separate dispersions were made at each radius ratio and were based on a reservoir pressure of 103 kPa (15 psig) and 0.200 g of lycopodium powder. The average number of lycopodium particles based upon 25 dispersions at 33 ms intervals in the 473.9 × 10⁶ m³ control volume are reported for a total elapsed time of 15 seconds. The maximum average particle concentration observed was 6.4 particles at 133 ms for r/R = 0.0 and 6.5 particles in 333 ms for r/R = 0.5. Based upon uniform dispersion model for 0.200 g of lycopodium powder, 6.8 particles per control volume, would be expected. The time averaged data followed a Poisson Distribution for each time increment after 0.73 s for both radius ratios of r/R = 0.0 and 0.5 (based upon 95% confidence interval and Kolmogorov-Smirnov test). Data from 0 to 0.73 seconds could not be assigned confidence levels as the data did not follow a Poisson Distribution or any other known statistical distribution. No significant particle agglomeration was observed for the dispersion of lycopodium particles. In any one dispersion the number of lycopodium particles in the control volume was observed to vary widely during each 033 second measurement cycle.

To further investigate the particle dispersion, the flow pattern characteristics in the Hartmann dispersion apparatus were studied using flow visualization techniques based upon a matched Reynolds number (3.13 × 10⁶) dispersion of fluorescent dye by turbulent water injection. The matched Reynolds number flow visualization work further indicated the Hartmann Bomb dispersion method produces local pockets of nonuniformly-mixed mixtures during initial stages of the dispersion process, and this work further points out the shortcomings of integrating optical probes.     

Comparison of three pharmaceutical products obtained from Mexico and the United States: a case study

In recent years, there has been much debate concerning the relative pros and cons of purchasing medications from foreign markets such as Mexico and Canada. The following study compares the content uniformity and weight variation for three medicinal products, acquired from pharmacies in both Mexico and the United States: amoxicillin capsules (500 mg), amoxicillin/clavulanic acid suspension (400 mg and 57 mg/5 mL, respectively), and furosemide tablets (40 mg). Twenty capsules/tablets were individually weighed and a designated aliquot was taken. Following dissolution in an appropriate solvent and sonication, a sample was taken and analyzed via high performance liquid chromatography (HPLC). The suspensions were prepared according to directions on the label. Five samples of the suspensions were then taken and analyzed via an appropriate HPLC method. The content uniformity for the amoxicillin capsules was found to be 15.4 ± 2.4% and 99.4 ± 9.3%, for Mexican and U.S. capsules, respectively. The percent relative standard deviation (% RSD) for weight variation was found to be 8.7% and 1.5% for capsules obtained from Mexico and the United States, respectively. Content uniformity analysis for the Mexican suspension product resulted in an average of 85.5 ± 1.2% for amoxicillin and 98.6 ± 1.9% for the clavulanic acid content, while the results for the U.S. suspension product were 104.4 ± 3.1% and 117.8 ± 3.6% for amoxicillin and clavulanic acid, respectively. Content uniformity for the furosemide tablets was found to be 90.3 ± 4.8% and 95.6 ± 2.1% for Mexican and U.S. tablets, respectively. The % RSD of weight variation for the Mexican tablets was 2.1%, while the % RSD for the U.S. tablets was found to be 1.0%. From the three products tested, content analysis revealed that the amount of active ingredients for two of the products acquired in Mexico were appreciably less than the concentrations for their U.S. counterparts.     

Preceramic polymer derived cellular ceramics

Ceramic foams were prepared by a self-blowing process of a poly(silsesquioxane) melt at 270 °C. The cell size, the interconnectivity density and the shape of the foam cells were adjusted by a thermal pre-curing procedure of the polymer at 200 °C. Inorganic fillers were used to modify processing behaviour and properties of the pyrolysed ceramic foam. After pyrolysis in inert atmosphere at 1200 °C ceramic composite foams with a total porosity up to 87% were obtained. The open cell ceramic foams had a mean cell diameter of 1.2 mm and a mean strut thickness of 0.2 mm. Interpenetrating phase composites (IPCs) were fabricated by infiltrating the open cellular ceramic preform with Mg alloy melt at 680 °C and a pressure of 86 MPa. The mechanical properties were found to depend on the reactions between the metal and the ceramic forming MgO, Mg₂Si and Al₁₂Mg₁₇ as the major reaction products. The IPCs showed a significantly higher creep resistance at 135 °C, compression strength and elastic modulus compared to the unreinforced magnesium alloys.     

Aqueous Sol-Gel Coating of Pitch-Based Graphite Fibers for Inclusion in Aluminum Matrix Composites

A coating on graphite is required to provide a wettable surface and prevent reaction between the graphite and the molten metal during the fabrication of high thermal conductivity metal matrix composites. An aqueous sol-gel procedure using zirconium acetate precursors to form continuous, crack-free, bridge-free zirconia coatings approximately 0.1 µm thick on graphite fibers 10 µm in diameter is described. Parameters were determined for dip-coating the fibers as a tow in an aqueous zirconium acetate solution and developing the coating structure by thermal desiccation, pyrolysis, and crystallization in a controlled environment.     

Stability-indicating spectrophotometric and densitometric methods for determination of aceclofenac

Three methods were developed for the determination of aceclofenac in the presence of its degradation product, diclofenac. In the first method, third-derivative spectrophotometry (D₃) is used. The D₃ absorbance is measured at 283 nm where its hydrolytic degradation product diclofenac does not interfere. The suggested method shows a linear relationship in the range of 4-24 µg mL^-1 with mean percentage accuracy of 100.05±0.88. This method determines the intact drug in the presence of up to 70% degradation product with mean percentage recovery of 100.42±0.94. The second method depends on ratio-spectra first-derivative (RSD₁) spectrophotometry at 252 nm for aceclofenac and at 248 nm for determination of degradation product over concentration ranges of 4-32 µg mL^-1 for both aceclofenac and diclofenac with mean percentage accuracy of 99.81±0.84 and 100.19±0.72 for pure drugs and 100.17±0.94 and 99.73±0.74 for laboratory-prepared mixtures, respectively. The third method depends on the quantitative evaluation of thin-layer chromatography of aceclofenac using chloroform:methanol: ammonia (48:11.5:0.5 v/v/v) as a mobile phase. Chromatograms were scanned at 274 and 283 nm for aceclofenac and diclofenac, respectively. The method determined aceclofenac and diclofenac in concentration ranges of 2-10 and 1-9 µg spot^-1 with mean percentage accuracy of 100.20±1.03 and 100.14±0.98 for pure drugs and 99.77±0.74 and 100.07±0.78 for laboratory-prepared mixtures, respectively. This method retains its accuracy in the presence of up to 80% degradation product for the studied drug.

The suggested procedures were checked using laboratory-prepared mixtures and were successfully applied for the analysis of their pharmaceutical preparation. The validity of the proposed methods was further assessed by applying a standard addition technique. The obtained results agreed statistically with those obtained by the reported method.     

PREDICTION OF HEAT TRANSFER IN A TURBULENT GAS-SOLID PIPE FLOW USING A TWO-FLUID MODEL

The dynamic and thermal behaviour of a turbulent gas-solid flow in a vertical pipe has been numerically studied by means of an original two-fluid approach which includes the effects of particle-particle and particle-wall collisions as well as particle-turbulence interactions. A k-ε-k_p model for the flow dynamics has been combined with the energy balances of each phase. Comparisons have been carried out with available experimental data, first for the dynamic validation, and then for the thermal portion of the problem, in the case of rather large panicles (200 to 500 µm). Heat transfer from wall to suspension is seen to be strongly affected by particles. As a consequence, a suspension Nusselt number decrease of 20% may be observed at loading ratio smaller than two. Further increase is possible if more panicles are injected. Predictions had excellent agreement with experimental data for 500 µm particles. Slight discrepancies appear for smaller particles, probably due to more complex, partially understood panicle-turbulence interactions.     

Piroxicam benzoate--synthesis,HPLC determination,and hydrolysis

An improved method of piroxicam benzoate synthesis was described, and an isocratic reversed-phase high-performance liquid chromatography method for its determination was developed and fully validated. The method was found to be specific, precise (relative standard deviation 0.3%), accurate (mean recovery 99.9%), and robust. Limit of detection was estimated at 0.055 µg mL^-1 and limit of quantification at 0.185 µg mL^-1. The kinetics of piroxicam benzoate hydrolysis in aqueous buffer solutions (pH 1.1 and 10), simulated gastric and intestinal fluids was studied. The hydrolysis followed first-order kinetics. The following rate constants were obtained at pH 10: k = 1.8 × 10^-3 hr^-1 at 37°C and k = 3.4 × 10^-2 hr^-1 at 60°C. In acidic media, no significant hydrolysis was observed after 24 hr. During the 24-hr period in simulated intestinal fluid, only 10.9% of the starting ester was hydrolyzed.     

Effect of Erodent Particle Hardness on Velocity Exponent in Erosion of Steels and Cast Irons

This article reports the effect of hardness of erodent particles on velocity exponent of some weld deposited alloys. Three steels and two alloy cast irons were selected for the present investigation. The bulk hardness of the alloys was in the range of 300 to 800 HV, whereas erodnet particles were having hardness in the range of 400 to 1875 HV. Erosion tests were conducted with 125-150 µm cement clinker, 125-150 µm blast furnace sinter, 100-150 µm silica sand, and 125-150 µm alumina particles and at impingement angles of 30° and 90° and with impingement velocities in the range of 25 to 120 m sec^-1. The erosion rate showed power-law dependence on impingement velocity, E = kVⁿ, where kis a constant and nis the velocity exponent. The velocity exponents obtained in the present work were in the range of 1.91 to 2.52. The velocity exponent showed an increasing trend with increasing hardness of the alloys irrespective of the hardness of the erodent particles and the impingement angle. The velocity exponent increased with increasing hardness of erodent particles, irrespective of the impingement angle and hardness of the alloys. The velocity exponents obtained in the present work were rationalized with respect to erodent particle properties, material properties and erosion mechanisms.     

MASS TRANSFER OF SULFUR DIOXIDE TO CONDENSING AQUEOUS AEROSOLS

Sodium chloride aerosols were generated from a 1.0 percent solution and passed through a tubular furnace, then recondensed at 29°C in a cooling section in the presence of SO₂. The dry particles ranged from 0.711 to 0.843 µm and the condensed droplets were in the 1.66 to 2.88 µm range. Final droplet size was varied by controlling the temperature of the nebulizer solution between 17 and 50°C. The SO₂ concentration in the gas phase of the condensing cloud was varied between 0.5x10 - ³ and 2.5 xl0 - ³ atm.

Cloud droplets were separated from the gas stream in a point-to-plane electrostatic precipitator and the droplets analyzed colorimetrically for total sulfur content.

Concentrations of SO₂ in the aqueous phase were about one order of magnitude greater than values obtained from equilibrium constants. The collection rate of SO₂ at 29°C appeared to be first order in SO₂ gas phase concentrations.

A model for this process was constructed, based on the hydrate formation in the gas-water interface[SO₂]_g + n[H₂O]ℓ ⇋ [SO₂ · n(H₂O)]ℓ

The order of the hydrate n was estimated to be 4.0.     

SPINNING FIBERS FROM POWDER SUSPENSIONS

Green ceramic fibers from Al₂O₃, Si₃N₄, Ce-ZrO₂, SiC, and other ceramics can be prepared by dry spinning of powder-loaded suspensions. The green fibers contain 54 to 64 vol. % ceramic powder in an ethyl methacrylate polymer base. Continuous fibers with an average diameter of 60 to 175 µm were spun at rates of 10 to 40 meters/minute. Spinnable dope compositions are defined for simple ternary powder + polymer + solvent systems, and are compared for several powders in MEK-based solvents. Spinnability is related to extrusion pressure, and drying conditions, and the shear rheological behavior of the dope. Fiber preparation by suspension dry spinning is compared with melt spinning of powder-loaded thermoplastics.     

Thermolysis and Photolysis of C60 Diozonides

Ozonation of C₆₀ in o-xylene produced three C₆₀(O₃)₂ diozonides that were separated from one another and from two C₆₀(O₃)₃ triozonides by High Performance Liquid Chromatography (HPLC). Upon thermolysis at 10, 15, and 16.6°C, each of the diozonides dissociated sequentially, first to a C₆₀O(O₃) oxyozonide, then to a C₆₀O₂ diepoxide. The three diepoxides were stable in solution for at least 3 weeks. The mean lifetimes of the three diozonides were 52 ± 5, 62 ± 6, and 17.3 ± 1.8 min, respectively (all at 15°C). The mean lifetimes of the three oxyozonides were 69.7 ± 0.7 and 58 ± 6 min at 16.6°C, respectively and about 240 min at 10°C. Photolysis of the diozonides yielded two dioxidoannulenes with UV-Vis adsorption maxima at 333 and 332 nm, and what appeared to be an epoxide-oxidoannulene with UV-Vis adsorption maximum at 327 nm. These annulenes were observed to form dimers. We have synthesized and characterized six C₆₀O₂ dioxides, at least three and possibly four of which were hitherto unknown. We report the discovery of oxyozonides that form during the dissociation of diozonides.     

CONTRIBUTIONS OF ROAD DUST RESUSPENSION TO THE AIRBORNE PARTICLE CONCENTRATIONS IN TAIPEI

The high concentrations of airborne particles have been one of the main air pollution problems in Taipei, Taiwan. In this study, the possible sources of airborne particles were investigated using concentration profile and chemical composition. The vertical concentration profile of TSP was measured at 1.5 m, 11 m, and 38 m above ground. The concentrations of TSP at 1.5 m above ground are always greater than 300 µg/m³; and even up to 1230 µg/m³, while those at 11 m above ground are only half of these values. The concentrations at 38 m above ground are only about half of those at 11 m above ground. Similar concentration profiles are found for Mg, Ca, Pb, Fe, and Zn measured and the enrichment factors with respect to the composition of road dust are generally less than 3. Therefore, there is a not upward flux of airborne particles from ground. The net upward fluxes are estimated to be about 100 ton/yr/km¹ from the vertical concentrations profiles and particle size distributions. The particle resuspension rates due to wind flow from a Teflon filter were also determined at the same time. The resuspension rates of particles by wind were found to be on the order of 10^-6 to 10^-5sec^-1. These particle resuspension fluxes are much smaller than those calculated by concentration profile. Other mechanisms, e.g. traffic-induced resuspension, are needed to be included in further study.     

PREDICTION OF PRESSURE DROP IN PNEUMATIC TRANSPORT SYSTEMS AT VARIOUS PIPE ORIENTATIONS USING AN EMPIRICAL CORRELATION FOR THE PARTICLE VELOCITY

A new empirical correlation for the particle velocity which incorporates the angle of inclination is proposed here. This correlation coupled with the expression for the solids friction factor obtained from the force balance on the particle was used to predict the pressure drops in the 0.0266 m and 0.0504 m systems held at various angles of inclination. Particles used in these systems included glass particles of 67, 450, and 900 µm weight mean diameter. The existence of minimum points in the predicted pressure drop curves as a function of gas velocity was corroborated by these two expressions.     

Stability indicating HPTLC determination of linezolid as bulk drug and in pharmaceutical dosage form

A simple, selective, precise, and stability-indicating high-performance thin layer chromatographic method of analysis of Linezolid both as a bulk drug and in formulations was developed and validated in pharmaceutical dosage form. The method employed TLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of toluene-acetone (5:5, v/v). This system was found to give compact spots for Linezolid (R_f value of 0.29 ± 0.01). Linezolid was subjected to acidic, alkali hydrolysis, oxidation, and photodegradation. The degraded products also were well separated from the pure drug. Densitometric analysis of Linezolid was conducted in the absorbance mode at 254 nm. The linear regression data for the calibration plots showed good linear relationship with r² = 0.997 ± 0.001 in the concentration range of 300-800 ng/spot. The mean value of correlation coefficient, slope, and intercept were 0.998 ± 0.003, 0.15 ± 0.009, and 19.52 ± 1.66 respectively. The method was validated for precision, accuracy, ruggedness, and recovery. The limits of detection and quantification were 20 ng/spot and 50 ng/spot, respectively. The drug undergoes degradation under acidic and basic conditions, oxidation and photo degradation. All the peaks of degraded product were resolved from the standard drug with significantly different R_f values. This indicates that the drug is susceptible to acid-base hydrolysis, oxidation, and photo degradation. Statistical analysis proves that the method is reproducible and selective for the estimation of the said drug. Because the method could effectively separate the drug from its degradation products, it can be used as a stability indicating one.     

Bimodal Size Distribution and Shape Anisotropy in Ball-Milled Nano-Sized α-Al2O3

-Al₂O₃ prepared by combustion technique was ball-billed in a planetary mill in toluene medium at 300 rpm in ZrO₂ pot with a ball to powder ratio 10:1 for 1, 5, 10, 15, and 20 hours. X-ray diffraction pattern from the milled materials showed super-Lorentzian peak shapes for -Al₂O₃ peak profiles. The super-Lorentzian peak shape has been attributed to the bimodal size distribution of the -Al₂O₃ particles. Rietveld analysis using two different phase fractions of -Al₂O₃ with different microstructural features yielded a low goodness-of-fit of the x-ray data indicating the suitability of the assumed model. The phase fraction of -Al₂O₃ particles with smaller size increases with the milling time. Further the particles shapes were observed to be cylindrical in this case with the cylinder axis along the crystallographic c-axis. The cylinder diameter and the length were obtained to be 86  and 140  respectively after 20 hrs of milling. The -Al₂O₃ particles of larger size are isotropic. It is, thus, proposed that milling induces bimodal size distribution in the initial hours of milling.     

Acrylate-based transdermal therapeutic system of nitrendipine

The objective of the present research investigation was to fabricate an acrylate-based transdermal therapeutic system (TTS) of nitrendipine, which could deliver drug at maximum input rate so as to deliver drug in minimum patch size. Transdermal patches were fabricated using synthesized acrylate pressure-sensitive adhesives (PSAs): PSA1, PSA2, and commercially available PSA3 and PSA4 using d-limonene as permeation enhancer. Effect of concentration of d-limonene on permeation kinetics of nitrendipine in PSAs was studied. Fabricated TTS in mentioned PSAs were evaluated for in-vitro release and permeation kinetics through guinea-pig skin. Cumulative release of drug in PSA1, PSA2, PSA3, and PSA4 was observed to be 45%, 40%, 25%, and 25%, respectively, upto 24 hr. Flux of drug through guinea-pig skin calculated at 48 hr in PSA1, PSA2, PSA3, and PSA4, with and without d-limonene, was observed to be 0.346 ± 0.10, 0.435 ± 0.17, 0.410 ± 0.17, and 0.162 ± 0.06, and 0.625 ± 0.19, 1.161 ± 0.46, 0.506 ± 0.17, and 0.520 ± 0.18 (µg/cm²/hr), respectively. The TTS in PSA2 showed comparatively high flux and could deliver drug at high input rate through transdermal route. PSA2 was found to have good rate-controlling property and could be successfully employed in transdermal delivery of nitrendipine.     

Development of a topical suspension containing three active ingredients

The objective of this study was to develop a topical suspension that contains sarafloxacin hydrochloride (1 mg/mL), triamcinolone acetonide (1 mg/mL), and clotrimazole (10 mg/mL), and is stable at room temperature (15-28°C) for clinical usage. Due to the difference in the physicochemical properties and chemical stability profiles of these three active ingredients, it is a challenge to develop a stable suspension formulation containing these three drugs. In this study, the stability of these drugs in different buffer solutions was determined under different accelerated isothermal conditions. The Arrhenius equation was subsequently utilized to predict the room-temperature stability of these three drugs in these buffer solutions. By knowing the room-temperature solubility of the drugs in the buffer solution, the stability of the drugs in suspension was predicted. As a result, a 0.02 M phosphate buffer (pH 7.0) containing 0.02% (w/v)polysorbate 20, 1% (w/v) NaCl, and 0.1% (w/v) EDTA was determined to be an acceptable medium. In addition, 0.35% (w/v) high-viscosity carboxymethylcellulose (HV-CMC) was first selected as the suspending agent to enhance the redispersibility of the suspension. Stability data further supported that all three drugs were stable in the suspension containing HV-CMC with less than 5% potency loss for at least 6 months at 40°C and 12 months at 25°C. However, the viscosity drop of this HV-CMC formulation at 25°C and 40°C became a product stability concern. To improve the viscosity stability of the suspension, the medium-viscosity carboxymethylcellulose (MV-CMC) was selected to replace the HV-CMC as the suspending agent. The optimal combination of MV-CMC and sodium chloride in achieving the most desirable dispersion properties for the formulation was determined through the use of a 3² factorial design. The optimal formulation containing 1% MV-CMC and 1% sodium chloride has shown improved viscosity stability during storage and has been used for clinical studies.     

RE-ENTRAINMENT OF DUSTS FROM THE DUST LAYER ON THE THE DEPOSITED DUSTS IN THE CYCLONE DUST COLLECTORS

There were many papers concerning the experimental results of the collection efficiency, but up to this time there are a few papers concerning the experimental results of the re-entrainment or dispersion of the dust particles from the dust layer by the turbulent rotational air flow in the dust bunker for the cyclone dust collector. Then in this paper, the author described the experimental results of the re-entrainment of the test dust ( talc X_R50 = 8.O µm ) for the four kinds of the throat diameter D₃ = 50, 80, 100 and 150 mm. Especially it is very importance to take into consideration of flow rate Qb into the dust bunker which is a function of D₃ and cyclone diameter D₁ and the maximum tangential velocity Vet in the dust bunker which depends on D₁,D₃ and Qb.     

Morphological Study of Cavity and Worthington Jet Formations for Newtonian and Non-Newtonian Liquids

In this article a morphological study of the cavity formation and the liquid column formation of the Worthington jet with lapse of time for the Newtonian liquids of water and glycerine wt 70% solution and for non-Newtonian liquids of acrylic copolymer solution of ACA-wt1%, ACA-wt2%, and ACA-wt3% by a droplet falling to the free surface of the target liquid in the cylindrical container from a height of H = 100, 200, 300, 400, and 500 mm is described. The calculated results by the energy equation for the maximum cavity radius Rmax/d and for the morphological size D · h/d² of the Worthington jet are in agreement with the experimental results. In order to take photographs of the cavity formation and the Worthington jet formation with lapse of time, a CCD camera was used. The falling droplet and the target liquid are the same material. Here d is the mean diameter of the droplet and D and h are the mean diameter and maximum height of the liquid column of the Worthington jet.