Influence of Process Parameters on Tablet Bed Microenvironmental Factors During Pan Coating

Recent studies have shown the importance of monitoring microenvironmental conditions (temperature, relative humidity) experienced by the tablet bed during a pan coating process, thereby necessitating the need to understand how various process parameters influence these microenvironmental conditions. The process parameters studied in this work include exhaust air temperature, spray rate, inlet airflow rate, gun-to-bed distance, coating suspension percent solids, and atomization and pattern air pressure. Each of these process parameters was found to have an impact on the tablet bed relative humidity (RH), as measured using PyroButton data logging devices. A higher tablet bed RH was obtained with an increase in spray rate and atomization air pressure and with a decrease in exhaust air temperature, inlet airflow rate, gun-to-bed distance, suspension percent solids, and pattern air pressure. Based on this work, it can be concluded that the tablet bed thermodynamic conditions are a cumulative effect of the various process conditions. A strong correlation between the tablet bed RH and the frequency of tablet coating defect (logo bridging) was established, with increasing RH resulting in a higher percent of logo bridging events.     

The effect of air support on droplet characteristics and spray drift

Air assistance on field sprayers creates a forced airstream under the spray boom which blows the spray droplets into the crop. The advantages of this relative new technique are less drift of spray droplets and the possibility to reduce the amount of pesticides and spray Liquid. The purpose of this work was to investigate the effect of air assistance on the characteristics of spray droplets and their driftability. Based on air velocity measurements on an air assisted field sprayer, a system of air assistance was developed in addition to a laser-based measuring set-up for the characterisation of spray droplets. With this set-up, the effect of air support on the droplet characteristics was investigated for different settings of the air assistance. The effect on spray drift was quantified based on field drift measurements. A reducing effect on the total amount of spray drift was demonstrated for the Hardi ISO F 110 02, F 110 03 and LD 110 02 nozzles with drift reduction factors a(d) of, respectively, 2.08, 1.77 and 1.53. The use of air support had no significant effect for the LD 110 03 nozzles on the total amount of spray drift. Comparing droplet size and drift results, it was found that air support has the highest impact on the amount of spray drift for the finer sprays by increasing droplet velocities. The effect of air support on droplet sizes is rather limited.     

Comparison of the performance between a spray gun and a spray boom in ornamentals

Flemish greenhouse growers predominantly use handheld spray guns and spray lances for their crop protection purposes although these techniques are known for their heavy workload and their high operator exposure risks. Moreover, when these techniques are compared with spray boom equipment, they are often found to be less effective. On the other hand, handheld spraying techniques are less expensive and more flexible to use. Additionally, many Flemish growers are convinced that a high spray volume and spray pressure is needed to assure a good plant protection. The aim of this work was to evaluate and compare the spray deposition, penetration and uniformity between a manually pulled horizontal spray boom and a spray gun under controlled laboratory conditions. In total, six different spray application techniques were evaluated. In general, the total deposition results were comparable between the spray boom and the spray gun applications but the boom applications resulted in a more uniform spray distribution over the crop. On a plant level, the spray distribution was not uniform for the different techniques with highest deposits on the upper side of the top leaves. Using spray guns at a higher spray pressure did not improve spray penetration and deposition on the bottom side of the leaves. From the different nozzle types, the XR 80 03 gave the best results. Plant density clearly affected crop penetration and deposition on the bottom side of the leaves.     

Scale-up of a pan-coating process

The purpose of this work was to develop a practical scale-up model for a solvent-based pan-coating process. Practical scale-up rules to determine the key parameters (pan load, pan speed, spray rate, air flow) required to control the process are proposed. The proposed scale-up rules are based on a macroscopic evaluation of the coating process. Implementation of these rules does not require complex experimentation or prediction of model parameters. The proposed scale-up rules were tested by conducting coating scale-up and scale-down experiments on 24-inch and 52-inch Vector Hi-coaters. The data demonstrate that using these rules led to similar cumulative drug release profiles (f2≫50; and P Analysis of Variance [P _ANOVA]≫0.05 for cumulative percentage of drug released after 12 hours [Cum 12] from tablets made at 24- and 52-inch scales. Membrane characteristics such as opacity and roughness were also similar across the 2 scales. The effects of the key process variables on coat weight uniformity and membrane characteristics were also studied. Pan speed was found to be the most significant factor related to coating uniformity. Spray droplet size was found to affect the membrane roughness significantly, whereas opacity was affected by the drying capacity.     

Investigation on Side-Spray Fluidized Bed Granulation with Swirling Airflow

Top-spray fluidized bed granulation with axial fluidization airflow from the bottom of the granulator is well-established in the pharmaceutical industry. The application of swirling airflow for fluidized bed granulation was more recently introduced. This study examined the effects of various process parameters on the granules produced by side-spray fluidized bed with swirling airflow using the central composite and Box–Behnken design of experiment. Influence of the amount of binder solution, spray rate, and distance between spray nozzle and powder bed were initially studied to establish operationally viable values for these parameters. This was followed by an in-depth investigation on the effects of inlet airflow rate, atomizing air pressure and distance between spray nozzle and powder bed on granule properties. It was found that the amount of binder solution had a positive correlation with granule size and percentage of lumps but a negative correlation with size distribution and Hausner ratio of the granules. Binder solution spray rate was also found to affect the granules size. High drug content uniformity was observed in all the batches of granules produced. Both inlet airflow rate and atomizing air pressure were found to correlate negatively with granule size and percentage of lumps but correlate positively with the size distribution of the granule produced. Percentage of fines was found to be significantly affected by inlet airflow rate. Distance between spray nozzle and powder bed generally affected the percentage of lumps.     

Modeling weight variability in a pan coating process using Monte Carlo simulations

The primary objective of the current study was to investigate process variables affecting weight gain mass coating variability (CV _m) in pan coating devices using novel video-imaging techniques and Monte Carlo simulations. Experimental information such as the tablet location, circulation time distribution, velocity distribution, projected surface area, and spray dynamics was the main input to the simulations. The data on the dynamics of tablet movement were obtained using novel video-imaging methods. The effects of pan speed, pan loading, tablet size, coating time, spray flux distribution, and spray area and shape were investigated. CV _m was found to be inversely proportional to the square root of coating time. The spray shape was not found to affect the CV _m of the process significantly, but an increase in the spray area led to lower CV _ms. Coating experiments were conducted to verify the predictions from the Monte Carlo simulations, and the trends predicted from the model were in good agreement. It was observed that the Monte Carlo simulations underpredicted CV _ms in comparison to the experiments. The model developed can provide a basis for adjustments in process parameters required during scale-up operations and can be useful in predicting the process changes that are needed to achieve the same CV _m when a variable is altered.     

Measuring Spray Droplet Size from Agricultural Nozzles Using Laser Diffraction

When making an application of any crop protection material such as an herbicide or pesticide, the applicator uses a variety of skills and information to make an application so that the material reaches the target site (i.e., plant). Information critical in this process is the droplet size that a particular spray nozzle, spray pressure, and spray solution combination generates, as droplet size greatly influences product efficacy and how the spray moves through the environment. Researchers and product manufacturers commonly use laser diffraction equipment to measure the spray droplet size in laboratory wind tunnels. The work presented here describes methods used in making spray droplet size measurements with laser diffraction equipment for both ground and aerial application scenarios that can be used to ensure inter- and intra-laboratory precision while minimizing sampling bias associated with laser diffraction systems. Maintaining critical measurement distances and concurrent airflow throughout the testing process is key to this precision. Real time data quality analysis is also critical to preventing excess variation in the data or extraneous inclusion of erroneous data. Some limitations of this method include atypical spray nozzles, spray solutions or application conditions that result in spray streams that do not fully atomize within the measurement distances discussed. Successful adaption of this method can provide a highly efficient method for evaluation of the performance of agrochemical spray application nozzles under a variety of operational settings. Also discussed are potential experimental design considerations that can be included to enhance functionality of the data collected.     

Computer modelling of the meteorological and spraying parameters that influence the aerial dispersion of agrochemical sprays

 An insight into the nature of prevailing meteorological conditions and the manner in which they interact with spraying parameters is an important prerequisite in the analysis of the dynamics of agrochemical sprays. Usually, when these sprays are projected from hydraulic nozzles, their initial velocity is greater than that of the ambient wind speed. The flowfield therefore experiences changes in speed and direction which are felt upstream as well as downstream of the spray droplets. The pattern of the droplet flow, i.e. the shape of the streamlines marking typical trajectories, will be determined by a balance of viscous forces related to wind speed, inertial forces resulting from the acceleration of the airstream and pressure forces which can be viewed in terms of the drag forces exerted on the spray droplets themselves. At a certain distance in the ensuing motion, when the initial velocity of the spray droplets has decreased sufficiently for there to be no acceleration, their trajectories will be controlled entirely by the random effects of turbulence. These two transport processes in the atmosphere can be modelled mathematically using computers. This paper presents a model that considers the velocity of spray droplets to consist of a ballistic velocity component superimposed by a random-walk velocity component. The model is used to study the influence of meteorological and spraying parameters on the three-dimensional dynamics of spray droplets projected in specified directions in neutral and unstable weather conditions. The ballistic and random-walk velocity components are scaled by factors of (1–ξ) and ξ respectively, where ξ is the ratio of the sedimentation velocity and the relative velocity between the spray droplets and the surrounding airstream. This ratio increases progressively as the initial velocity of the spray droplet decreases with air resistance and attains a maximum when the sedimentation velocity has been reached. As soon as this occurs, the random-walk process predominates. The computed effects of the release height of spray droplets, atmospheric turbulence intensity, evaporation, drop size spectrum, wind velocity and wind direction on the transport process have been studied and an analysis of spray drift is provided. Received: 5 March 1997 / Accepted: 17 December 1997     

Trajectory of aerosol droplets from a sprayed bacterial suspension

Simulated droplet trajectories of a polydispersed microbial aerosol in a laminar air flow regimen were compared with observed dispersal patterns of aerosolized Bacillus subtilis subsp. niger spores in quasilaminar airflow. Simulated dispersal patterns could be explained in terms of initial droplet sizes and whether the droplets evaporated to residual aeroplanktonic size before settling to the ground. For droplets that evaporated prior to settling out, a vertical downwind size fractionation is predicted in which the microbial residue of the smallest droplets settles the least, and is found in the airstream at about sprayer height, and progressively larger droplet residues settle to progressively lower heights. Observations of spore particle size distributions downwind from a spray source support the simulation. Droplet and particle size distributions near the source had three size fractions: one containing large, presumably nonevaporated droplets of greater than or equal to 7 microns in diameter, and two smaller fractions, with diameters of 2 to 3 microns (probably the residue of droplets containing more than one spore) and 1 to 2 microns (probably the residue from single-spore droplets). As predicted by the simulation, the aerosol settled and progressed downwind, with the number of small droplets and particles increasing in proportion to the height and distance downwind.     

Trajectory of aerosol droplets from a sprayed bacterial suspension.

Simulated droplet trajectories of a polydispersed microbial aerosol in a laminar air flow regimen were compared with observed dispersal patterns of aerosolized Bacillus subtilis subsp. niger spores in quasilaminar airflow. Simulated dispersal patterns could be explained in terms of initial droplet sizes and whether the droplets evaporated to residual aeroplanktonic size before settling to the ground. For droplets that evaporated prior to settling out, a vertical downwind size fractionation is predicted in which the microbial residue of the smallest droplets settles the least, and is found in the airstream at about sprayer height, and progressively larger droplet residues settle to progressively lower heights. Observations of spore particle size distributions downwind from a spray source support the simulation. Droplet and particle size distributions near the source had three size fractions: one containing large, presumably nonevaporated droplets of greater than or equal to 7 microns in diameter, and two smaller fractions, with diameters of 2 to 3 microns (probably the residue of droplets containing more than one spore) and 1 to 2 microns (probably the residue from single-spore droplets). As predicted by the simulation, the aerosol settled and progressed downwind, with the number of small droplets and particles increasing in proportion to the height and distance downwind.     

Entrapment of an air gun pellet between the thyroid cartilage and the lining mucosa in a patient with a penetrating neck injury: a case report

ABSTRACT: INTRODUCTION: Air guns, either modern or traditional models, are powerful weapons that are capable ofcausing serious or life-threatening injuries. CASE PRESENTATION: Here, we present a case of an air gun pellet injury, with the pellet trapped between the thyroidcartilage and the lining mucosa of a 58-year-old Iranian man. CONCLUSION: Entrapment of air gun pellet between thyroid cartilage and the lining mucosa, as presented inour case, may cause diagnostic challenges through the clinical presentation of slightodynophagia.     

Serious childhood injuries caused by air guns.

OBJECTIVE: To determine the severity of nonfatal injuries to children caused by air guns and pellet guns. DESIGN: Case series (hospital chart review). SETTING: Inpatient wards of the Children''s Hospital of Eastern Ontario. PATIENTS: All children under 18 years of age admitted to the hospital from Jan. 1, 1979, to Dec. 31, 1989, under ICD code E917, E922, E955, E965, E970 or E985 who had suffered air gun injuries. MAIN OUTCOME MEASURES: Personal data, circumstances of event and clinical data. RESULTS: The 43 children (37 boys) had a median age of 12 years. The circumstances of the accident were known in 20 cases: 17 children were playing and 3 were cleaning the gun when it went off. Four children thought the gun was unloaded. In five cases the bullet ricocheted into the eye. Nine injuries were self-inflicted. Injury was to the extremities in 21 (49%), the eyes in 15 (35%) and the head and neck in 7 (16%). The median length of hospital stay was 4 days. Six children had long-term disabilities, all the result of eye injuries; two had cataract surgery, and four required enucleation of the eye. CONCLUSIONS: Air guns can cause serious injury to children. Their sale needs to be banned or at least carefully regulated.     

Assessment of the Influence Factors on Nasal Spray Droplet Velocity Using Phase-Doppler Anemometry (PDA)

Droplet velocity is an important parameter that can be used to characterize nasal spray products. In this study, a phase-Doppler anemometry (PDA) system was used to measure the droplet velocities of nasal sprays. A survey of seven commercial nasal spray products showed a range of droplet velocities from 6.7 to 19.2 m/s, all significantly different from each other. A three-level, four-factor Box–Behnken design of experiments (DOE) methodology were applied to investigate the influences of actuation parameters and formulation properties on nasal spray droplet velocity using a set of placebo formulations. The DOE study shows that all four input factors (stroke length, actuation velocity, concentration of the gelling agent, and concentration of the surfactant) have significant influence on droplet velocity. An optimized quadratic model generated from the DOE results describes the inherent relationships between the input factors and droplet velocity thus providing a better understanding of the input factor influences. Overall, PDA provides a new in vitro characterization method for the evaluation of inhalation drugs through assessment of spray velocity and may assist in product development to meet drug delivery equivalency requirements.     

Water guns affect abundance and behavior of bigheaded carp and native fish differently

Water guns have shown the potential to repel nuisance aquatic organisms. This study examines the effects of exposure to a 1966.4 cm³ seismic water gun array (two guns) on the abundance and behavior of Bighead Carp Hypophthalmichthys nobilis, Silver Carp H. molitrix (collectively referred to as bigheaded carp) and native fishes (e.g., Smallmouth Buffalo Ictiobus bubalus). Water guns were deployed in a channel that connects the Illinois River to backwater quarry pits that contained a large transient population of bigheaded carp. To evaluate the effect of water guns, mobile side-looking split-beam hydroacoustic surveys were conducted before, during and between replicated water gun firing periods. Water guns did not affect abundance of bigheaded carp, but abundance of native fish detected during the firing treatment was 43 and 34% lower than the control and water guns off treatments, respectively. The proximity of bigheaded carp to the water gun array was similar between the water guns on and water guns off treatments. In contrast, the closest detected native fish were detected farther from the water guns during the water guns on treatment (mean ± SE, 32.38 ± 3.32 m) than during the water guns off treatment (15.04 ± 1.59 m). The water gun array had a greater impact on native fish species than on bigheaded carp. Caution should be taken to the extrapolation of these results to other fish species and to fish exposed to water guns in different environments (e.g., reduced shoreline interaction) or exposure to a larger array of water guns, or for use of water guns for purposes other than a barrier.     

Modern plant cultivation technologies in agriculture under controlled environment: a review on aeroponics

This review paper describes a novel approach to plant cultivation under soil-less culture. At present, global climate change is expected to raise the risk of frequent drought. Agriculture is in a phase of major change around the world and dealing with serious problems. In future, it would be difficult task to provide a fresh and clean food supply for the fast-growing population using traditional agriculture. Under such circumstances, the soil-less cultivation is the alternative technology to adapt effectively. The soil-less system associated with the Hydroponic and Aeroponics system. In the aeroponics system, plant roots are hanging in the artificially provided plastic holder and foam material replacement of the soil under controlled conditions. The roots are allowed to dangle freely and openly in the air. However, the nutrient rich-water deliver with atomization nozzles. The nozzles create a fine spray mist of different droplet size at intermittently or continuously. This review concludes that aeroponics system is considered the best plant growing method for food security and sustainable development. The system has shown some promising returns in various countries and recommended as the most efficient, useful, significant, economical and convenient plant growing system then soil and other soil-less methods.     

Development and Application of a Process Window for Achieving High-Quality Coating in a Fluidized Bed Coating Process

Next to the coating formulation, process conditions play important roles in determining coating quality. This study aims to develop an operational window that separates layering from agglomeration regimes and, furthermore, the one that leads to the best coating quality in a fluidized bed coater. The bed relative humidity and the droplet size of the coating aerosol were predicted using a set of engineering models. The coating quality was characterized using a quantitative image analysis method, which measures the coating thickness distribution, the total porosity, and the pore size in the coating. The layering regime can be achieved by performing the coating process at a certain excess of the viscous Stokes number (ΔSt _v). This excess is dependent on the given bed relative humidity and droplet size. The higher the bed relative humidity, the higher is the ΔSt _v required to keep the process in the layering regime. Further, it is shown that using bed relative humidity and droplet size alone is not enough to obtain constant coating quality. The changes in bed relative humidity and droplet size have been identified to correlate to the fractional area of particles sprayed per unit of time. This parameter can effectively serve as an additional parameter to be considered for a better control on the coating quality. High coating quality is shown to be achieved by performing the process close to saturation and spraying droplets small enough to obtain high spraying rate, but not too small to cause incomplete coverage of the core particles.     

The influence of process parameters in production of lipopeptide iturin A using aerated packed bed bioreactors in solid-state fermentation

The strain Bacillus iso 1 co-produces the lipopeptide iturin A and biopolymer poly-γ-glutamic acid (γ-PGA) in solid-state fermentation of substrate consisting of soybean meal, wheat bran with rice husks as an inert support. The effects of pressure drop, oxygen consumption, medium permeability and temperature profile were studied in an aerated packed bed bioreactor to produce iturin A, diameter of which was 50 mm and bed height 300 mm. The highest concentrations of iturin A and γ-PGA were 5.58 and 3.58 g/kg-dry substrate, respectively, at 0.4 L/min after 96 h of fermentation. The low oxygen uptake rates, being 23.34 and 22.56 mg O₂/kg-dry solid substrate for each air flow rate tested generated 5.75 W/kg-dry substrate that increased the fermentation temperature at 3.7 °C. The highest pressure drop was 561 Pa/m at 0.8 L/min in 24 h. This is the highest concentration of iturin A produced to date in an aerated packed bed bioreactor in solid-state fermentation. The results can be useful to design strategies to scale-up process of iturin A in aerated packed bed bioreactors. Low concentration of γ-PGA affected seriously pressure drop, decreasing the viability of the process due to generation of huge pressure gradients with volumetric air flow rates. Also, the low oxygenation favored the iturin A production due to the reduction of free void by γ-PGA production, and finally, the low oxygen consumption generated low metabolic heat. The results show that it must control the pressure gradients to scale-up the process of iturin A production.     

Mechanical aids to improve the speed and sensitivity of plant virus diagnosis by the biological test method

Modifications to a Pollahne leaf sap press are described which allow it to be used for bioassay purposes without risk of cross contamination. Constructional details are given for manual and automatic versions which utilise hot and cold water to sterilise and cool the working parts of the press. Two compressed air guns which are used together to inoculate indicator plants, are also described. The first incorporates carborundum powder into a jet of air and causes controlled wounding of plant epidermal cells to permit virus entry. The other applies sap inoculum as a finely divided spray to the wounded plants. The variables affecting the use of these guns are discussed. Improvements in sensitivity of 64 fold, compared to manual methods were obtained and potential to develop this to 500fold demonstrated.     

Gas–liquid dispersion in a fibrous fixed bed biofilm reactor at growth and non-growth conditions

There is limited data on gas dispersion characteristics of fixed bed biofilm reactors under growth and non-growth conditions. In this paper, the gas–liquid dispersion of a bubble bed packed with a fibrous structured packing for biofilm application is studied. The reactor is operated with Pseudomonas putida aimed at aniline degradation in wastewater. Gas hold-up and bubble size distribution are determined. Running gas–liquid reaction conditions as well as non-reactive flow gas hold-up and bubble size distribution in the presence of surface-active and viscous components were measured. The properties of the gas dispersion proved to be stabilized by the fibrous bed presence and showed improvement of the dispersion parameter by the packing. Gas hold-up was found to increase monotonously with the rise of gas superficial velocity and viscosity and with surface tension fall. Liquid superficial velocity showed marginal effect. Apart from showing high gas hold-up and low bubble size due to surface-active and viscous dissolved elements, the biochemical reaction did not pose any significant additional effect. In agreement with the expected lack of bubble coalescence and break-up in the highly ionic solution practiced, the population size distribution and average bubble size were found to vary with the major operation factors opposite to their gas hold-up contribution. Gas hold-up was correlated with the specific bubble-to-channel size ratio and further with the variables considered. An empirical equation is proposed that relates gas hold-up with all studied variables. Assuming geometric similarity of the prototype and the real vessels, the equation as well as its corresponding range of fluid velocities can be used for bioreactor design and scale-up. The results concerning the gas hold-up are shown to be comparable with previous studies of mesh wire packing.     

Modelling a solid-state fluidized bed fermenter for Ethanol production with S. cerevisiae

A model is proposed to describe the performance of a new type of fermenter for ethanol production, the fluidized bed gas-solid fermenter, with respect to scaling-up effects. Based on the fact that in the fluid bed the substrate is not supplied continuously to each particle, two scale-up parameters are derived, circulation time τ and specific substrate supply Δm _G,P , which are shown to influence reactor efficiency significantly. The validity of the model is checked by comparing the calculated yield coefficients for ethanol, cell mass and carbon dioxide to the results of fermentation experiments performed under aerobic conditions in a laboratory-scale reactor and a semi-technical fermenter.