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PubMedDate not supplied

Effects of fabrication conditions on the characteristics of etanidazole spray-dried microspheres.

Etanidazole, a hypoxic radiosensitizer, has potential applications in radiotherapy. Due to its high solubility in water, common methods to encapsulate etanidazole into microspheres are not feasible. In this study, a spray-drying technique was employed to encapsulate etanidazole into the biodegradable polymer, PLGA65:35. Different fabrication conditions, such as polymer concentration, inlet temperature, feed rate, compressed air flow rate, aspirator ratio, as well as drug-loading were investigated to understand their effects on the particle size and distribution, encapsulation efficiency, and release behaviour. The effect on the morphologies of microspheres were also observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was demonstrated that most of these fabrication conditions influence either the droplet formation process or its subsequent evaporation and particle shrinking process, thereby determining the properties of the microspheres obtained. In many cases, temperature seems to be more important among all the factors considered. The present study demonstrates good fabrication conditions for producing the etanidazole-PLGA65:35-microspheres by using DCM as a solvent. The release of etanidazole from the spray dried PLGA65:35 microspheres was very fast, with an initial burst of 47% within the first 30 min and a cumulative release of over 80% within the first 5.5 h. The encapsulation efficiency of the drug in the microspheres varied with operating conditions from 69-96%.

Calorimetry, Differential Scanning↗
PubMed2006

Effect of manufacturing parameters on the characteristics of vitamin C encapsulated tripolyphosphate-chitosan microspheres prepared by spray-drying.

To prepare the sustained release vitamin C carriers, vitamin C was successfully encapsulated in tripolyphosphate (TPP) cross-linked chitosan (TPP-chitosan) microspheres by the spray-drying method at different manufacturing conditions. Manufacturing parameters (inlet temperature, liquid flow rate, chitosan concentration and volume of 1% w/v TPP solution) had a significant influence on the characteristics of thus prepared microspheres. The optimum spray-drying conditions such as inlet temperature, liquid flow rate and compressed air flow rate for the encapsulation of vitamin C in TPP-chitosan microspheres was found to be 170 degrees C, 2 ml min(-1) and 101 min(-1), respectively. The size and yield of the TPP-chitosan microspheres ranged from 3.9-7.3 microm and 54.5-67.5%, respectively. The encapsulation efficiency of TPP-chitosan microspheres ranged from 45.72-68.7% and it decreased with the increasing volume of 1% w/v TPP solution. At the same cross-linking extent, the encapsulation efficiency of TPP-chitosan microspheres increased when the concentration of chitosan was increased from 0.5-1% w/v. Effect of volume of 1% w/v TPP solution on the surface morphology of chitosan microspheres was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These studies revealed that chitosan solution (250 ml) cross-linked with 15 ml 1% w/v TPP solution produced more porous microspheres than that cross-linked with 5 and 10 ml TPP solution. The release rate of vitamin C from TPP-chitosan microspheres decreased when the concentration of chitosan was increased from 0.5-1.0% w/v. Vitamin C release rate was also modulated by varying the volume of 1% w/v TPP solution. The release rate of vitamin C from TPP-chitosan microspheres decreased with increasing volume (5-15 ml) of 1% w/v TPP solution.

Ascorbic Acid↗
PubMed2002

Laboratory and clinical tests of a prototype pressure sensor for clincial assessment of prosthetic socket fit.

Lower limb prosthetic socket fabrication is a highly refined process relying on the prosthetist's skill and experience. Despite their best efforts, patients often return with complications. Additionally, clinical application of technological advances for the quantification of biomechanical factors at the socket interface has not changed in practice. Measuring pressure levels at the stump/socket interface could provide valuable information in the process of prosthetic socket fabrication, fit and modification. This paper presents findings on the performance of a prototype capacitance pressure sensor designed for prosthetic socket use. Bench tests using compressed air were performed to measure accuracy, hysteresis and drift responses in both a flatbed chamber and a custom-modified pressure vessel. For the contoured testing, the sensors were placed on nine sites on a positive trans-tibial stump mould and enveloped with a silicone liner. Additionally, a preliminary clinical evaluation was performed with two trans-tibial amputee subjects at the nine sites during normal ambulation. Bench test results showed that the prototype capacitance sensor performed well in all categories, exhibiting a 2.42% (flatbed) and 9.96% (contoured) accuracy error, a 12.93% (flatbed) and 12.95% (contoured) hysteresis error, and a 4.40% (flatbed) and 6.20% (contoured) drift error. The clinical study showed that after three hours of continual use, no noticeable sensor drift occurred between pre and post-test calibration values. The results from this study were encouraging and the authors hope to conduct further laboratory and clinical trials to assess the influence of shear force and dynamic loading on sensor response.

Ambulatory Care Facilities↗
PubMed2004

A novel method to aerosolize powder for short inhalation exposures at high concentrations: isolated rat lungs exposed to respirable diesel soot.

More efficient methods are needed to aerosolize dry powders for short-duration inhalation exposures at high concentrations. There is an increasing need to reach the peripheral lung with dry powder medications as well as with collected ambient aerosol particulates in environmental research projects. In a novel aerosol generator, a fixed volume of compressed air was used to create a short burst of a highly concentrated aerosol in a 300-ml holding chamber. Collected diesel soot was deagglomerated to a fine aerosol with a mass median aerodynamic diameter (MMAD) of 0.55 microm, not much larger than the 0.25 microm MMAD of diesel exhaust particles measured in air. A fine powder such as 3-microm silica particles was completely deagglomerated to an aerosol with a MMAD of 3.5 microm. Immediately after generation, the aerosol was available for exposure at a chosen flow rate by the use of an automated valve system. Tritium-labeled diesel soot was thus used to expose the isolated perfused rat lung at an air concentration of approximately 3 mg/L and a flow rate of 370 ml/min in a 1-min-long exposure. The lungs were ventilated at 75 breaths/min and a tidal volume of 1.13 +/- 0.11 ml (SD, n = 3). Results showed that 19.8 +/- 1.1 microg (SD, n = 3) soot was deposited in the lungs. This amount constitutes 9.5% of the amount inhaled and is close to literature data on deposition of similar sized particles in the rat lung. More than 97% of the deposited soot was located distal to the extrapulmonary bronchi, indicating that the system delivers a highly respirable aerosol. The aerosol system is particularly useful for peripheral lung delivery of collected ambient aerosols or dry powder pharmaceuticals following a minimal effort in formulation of the powder.

Administration, Inhalation↗
PubMed2005

Single-pass environmental chamber for quantifying human responses to airborne chemicals.

Despite increasing interest in the short-term effects of airborne environmental contaminants, experimental findings are generated at a very slow pace. This is due in part to the expense and complexity of most environmental chambers, which are needed for quantifying effects of wholebody exposures. We lessened this obstacle by designing, constructing, and testing a single-pass, 10-m3 stainless-steel chamber. Compressed air is purified before being sent to an air dilution olfactometer, which supplies 1000 L (1 m3) per minute (referenced to STP) while maintaining 40% relative humidity (RH) and 22.6 degrees C. Precise control of all stimulus parameters is greatly simplified since air is not recirculated. Vapor-phase odorant concentrations are achieved by varying the proportion of total airflow passing through one or more saturators, and are verified in real time by an infrared (IR) spectrometer. An adjoining 5-m3 anteroom is used for introducing known intensities of more chemically complex vapor and/or particulate stimuli into the chamber. Prior to the point that air is exhausted from the chamber, all components are made of stainless steel, Teflon, or glass. A LabView program contains feedback loops that achieve document chamber conditions and document performance. Additional instrumentation and computer systems provide for the automated collection of perceptual, respiratory, eye blink, heart rate, blood pressure, psychological state, and cognitive data. These endpoints are now being recorded, using this facility, in response to ranges of concentrations of propionic acid and environmental tobacco smoke.

Air Pollutants↗
PubMed2000

The indigenous fisherman divers of Thailand: diving-related mortality and morbidity.

The Urak Lawoi are indigenous fishermen on Thailand's west coast. The population includes an estimated 400 divers who dive using surface-supplied compressed air. In a cross-sectional survey conducted among the 6 major communities of Urak Lawoi, questionnaire-based interviews were administered to active divers, ex-divers, and families or colleagues of divers who had died in the previous 5 years. Six deaths resulting from diving-related accidents were identified, indicating a diving-related mortality rate of approximately 300 per 100,000 person-years, while in the same 5-year period 11 divers had been disabled owing to diving-related events, indicating a diving-related disabling event rate of approximately 550 per 100,000 person-years. Among 342 active divers interviewed, one third reported having suffered from decompression illness, although based on reported current symptoms over 50% were classified as suffering from recurring non-disabling decompression illness. Physical examination conducted on a subset of 98 active divers revealed the presence of spinal injury (clonus, raised muscle tone, and heightened reflexes) and of joint damage (pain in one or more joint, crepitus, or restricted movement) in 24 and 30% respectively. Improved primary prevention and medical treatment are needed to reduce mortality and morbidity among this population.

Accidents, Occupational↗
PubMed2006

Laboratory study on the immobilization of bacterial spores in arid environments.

In this study, two effective, non-toxic, wind erosion palliative materials were analyzed for their efficacy in preventing the spread of bacterial spores. Desert sand was employed in a laboratory setting with a non-toxic simulant bacterium in an attempt to accurately represent the spreadability of the hantavirus. Spore simulants were used instead of viruses due to availability, decreased susceptibility to desiccation and detection ability without involving tissue cultures. The simulant was used to contaminate sand in a controlled environment, and an artificial turbulence was introduced using compressed air to generate airflow that could be expected in a desert environment. The airborne spores were identified both qualitatively and quantitatively through microscopy, Gram staining, plating, and incubation to monitor effectiveness. A water-based polysaccharide product, Surtac, was found to be most effective for the immobilization of bacteria on sand and greatly reduced the amount of contaminant that becomes airborne. The results suggest that the two wind erosion products used in this study may be successfully employed to reduce the ability of bacterial spores to spread in arid regions.

Air Microbiology↗
PubMedDate not supplied

Lead exposure among workers renovating a previously deleaded bridge: comparison of trades, work tasks.

Airborne and surface lead exposures were evaluated for construction trade groups at a previously deleaded bridge renovation site in the midwestern United States. Although all lead-based paint should have been removed, old layers of leaded paint were still present on some sections of the bridge. Ironworkers performing metal torch cutting had the highest exposures (188 microg/m3), followed by workers engaged in clean-up operations and paint removal (p < 0.001). Respirators were most frequently worn by workers with the greatest lead exposures; however, laborers performing clean-up operations had exposures to lead dust of 43 microg/m3 and often wore no respiratory protection. Wipe samples revealed that almost all contractor vehicles were contaminated with lead. Heavy equipment operators with low airborne lead exposure had the highest levels of surface contamination in personal vehicles (3,600 microg/m2). Laborers cleaning structural steel with compressed air and ironworkers exposed to lead fumes from cutting had the highest concentrations of lead dust on clothing (mean 4,766 microg/m2). Handwashing facilities were provided, but were infrequently used. No separate clothes changing facility was available at the site. The potential for "take-home" contamination was high, even though this site was thought to be relatively free of lead. Construction contractors and their workers need to be aware that previous deleading of a site may not preclude exposure to significant amounts of lead.

Air Pollutants, Occupational↗
PubMedDate not supplied

Inhalable dust exposures, tasks, and use of ventilation in small woodworking shops: a pilot study.

Measures of workers' inhalable dust exposures, tasks, and ventilation use were made in five small woodworking shops prior to the start of an intervention effectiveness study aimed at lowering personal wood dust exposures. The data were used to (1) design a sampling protocol for an intervention success measure, (2) identify targets for intervention among the tasks and activities responsible for high dust levels, and (3) develop shop-level measures as tools for tailoring intervention activities. Geometric mean dust concentrations ranged from 1.6 to 9.9 mg/m3 in the five shops, with the highest levels occurring in a cabinet shop. All shops had centralized dust collection systems and workers generally used dust control on stationary tools (60-100% of the time) when it was available. Sanding with both stationary and handheld powered tools, cleaning with methods that can disperse dust (e.g., brushes, compressed air), and miscellaneous tasks were all responsible for significant personal exposures. The positive association between miscellaneous tasks and exposures probably reflects the high background levels generated by nearby processes. Sanding with both stationary tools and handheld powered tools represents the most significant influence on personal exposures in small woodworking shops. The authors conclude that pilot studies are useful tools for designing occupational health and safety intervention effectiveness studies.

Dust↗
PubMed1980

Laboratory production of ammonium and ferric sulfate aerosols.

Since sulfate aerosol particles are an environmental factor of possible concern, laboratory studies are being conducted to determine their health effects. It is important in such studies that aerosols be controlled and monitored. Submicron sulfate aerosols at high (greater than 80%) and low (30-40%) relative humidities were generated and characterized in support of animal inhalation experiments. Aqueous solutions of ammonium sulfate and ferric sulfate were aerosolized with a compressed air nebulizer, dried, discharged and passed into an aerosol chamber. Aerosol characterization was performed using cascade impactors, electron microscopy, filter samples and an electrical mobility analyzer. Parameters measured included particle size distribution and mass concentration. Instruments used for sizing the aerosols were compared. The electrical mobility analyzer provided useful information on the time stability of the particle size and the mass concentration, but agreement between this instrument and electron microscopy or cascade impaction was poor.

Aerosols↗
PubMed1980

Generation of fume aerosols of zinc oxide.

Fume aerosols of zinc oxide were generated by nebulization of aqueous solutions of zinc acetate (30 milligrams zinc acetate per milliliter water), with subsequent thermal vaporization and chemical degradation to the oxide. A Retec nebulizer operated with compressed air was used to generate the zinc acetate mists which were passed through a quartz tube furnace (1150 degrees C) to dry the droplets and degrade the acetate to the oxide form. Ultrafine particles were formed in this process, demonstrating that zinc acetate was vaporized as aerosol entered the heated tube prior to thermolysis. The few larger particles probably represent those larger droplets which do not completely vaporize prior to thermolysis. Cascade impactor samples indicated a mass median aerodynamic diameter (MMADar) of 0.8 +/- 0.1 (SD) microns with geometric standard deviation (sigma g) of 2.9 +/- 0.5 (SD). About 25% of the zinc was associated with particles smaller than 0.3 microns in aerodynamic diameter, equivalent to spherical particles smaller than 0.09 microns in geometric diameter.

Aerosols↗
PubMed1980

Improved methodology for generating controlled test atmospheres.

Improved methodology has been developed for generating controlled test atmospheres. Vaporization of volatile liquids is accomplished in a 28 mm (O.D.) glass J-tube in conjunction with a compressed air flameless heat torch, a pressure-sensitive switch, and a positive displacement piston pump. The vaporization system has been very reliable with a variety of test materials in studies ranging from a few days to several months. The J-tube vaporization assembly minimizes the possibility of thermal decomposition of the test material and affords a better margin of safety when vaporizing potentially explosive materials.

Environment, Controlled↗
PubMed1983

Do pressure-demand breathing systems safeguard against inward leakage?

Rescue operations conducted in toxic atmospheres require respiratory protective equipment capable of providing a very high degree of protection. A slight positive pressure in the facepiece throughout the breathing cycle is used in the pressure-demand, compressed-air breathing apparatus to eliminate any inward leakage. In the present work an inward leakage test with sulphur hexafluoride (SF6) was used to measure facepiece penetration in a pressure-demand system at different work loads. During the test, inspiratory-flow pressure variations within the facepiece and heart rate were also measured. Tests were performed on a dummy head and on two subjects. In some tests a poor face seal was introduced by putting an open tubing with an inner diameter of 2 mm and outer diameter of 3 mm under the sealing edge of the mask. It was found that inward leakage was less than 0.0001% under all conditions as long as facepiece pressure was positive. When facepiece pressure fell below zero, which occurred at inhalation peak flows about 300 L/min, an inward leakage was detected. One subject achieved, at extreme work load, an inhalation peak flow around 450 L/min. These results show that pressure-demand systems should be tested with a breathing machine giving peak flows of at least 300 L/min to ascertain the capability of these systems to maintain positive pressure in the facepiece during hard rescue work.

Adult↗
PubMed1992

Use of fluidizing bed aerosol generators to establish a dust mixture of two substances at a fixed ratio for inhalation toxicity studies.

A method was developed to use two fluidizing bed generators to deliver a mixture of 1 mg cobalt + 15 mg tungsten carbide/m3 to an inhalation exposure chamber with the output from the cobalt generator split to provide the same cobalt concentration to a cobalt-only chamber. To provide a more uniform delivery of material and to minimize the amount of starting dust needed, a subsystem that produced timed bursts of compressed air was used to prevent the accumulation of dust along the aerosol transport tubes. The addition of an electrostatic precipitator placed in the exhaust lines reduced the amount of dust delivered to the high-efficiency particulate air filters, thereby reducing the number of filter changes.

Aerosols↗
PubMed1995

Lead, chromium, and cadmium emission factors during abrasive blasting operations by bridge painters.

Work space airborne concentrations of lead, chromium, and cadmium were measured during abrasive blasting by bridge painters for the determination of emission rates. The operation used compressed air to blast steel grit at steel or metal surfaces, removing lead-based paint. It was enclosed with plastic tarpaulins to prevent the release of lead- and chromium-laden dust. Consequently, workers were at increased risk from exposure by inhalation or ingestion. Area samples were collected in 13 contained work areas on a 4-leaf bridge and adjacent viaduct while blasting was performed. Enclosure volume and exhaust air flow rate were measured for each containment area. Work space airborne concentrations ranged from 196-31,410 micrograms/m3 for lead, 1-657 micrograms/m3 for chromium, and 1-19 micrograms/m3 for cadmium. Mass balance models were used to calculate emission rates and emission factors using the measured area concentrations. Average emission factors on the bridge were 20,400 mg/m2 for lead, 75 mg/m2 for chromium, and 16 mg/m2 for cadmium; and on the viaduct were 8790 mg/m2 for lead, 568 mg/m2 for chromium, and 2.0 mg/m2 for cadmium. These values were validated using estimates of total paint volume and composition on the structure and total waste generation. All estimates were within 50% of each other except chromium estimates for the bridge. The emission factors allow prediction of work space airborne concentrations during similar operations and are a first step in the design and implementation of control measures.

Air Pollutants, Occupational↗
PubMed2003

Textile dyeing wastewater treatment in a sequencing batch reactor system.

This study was undertaken to examine the feasibility of treating biologically textile wastewater for organic carbon removal. The study was conducted over a lab scale SBR equipped with an in-house developed data acquisition and control software. From monitored operation of SBR and dissolved oxygen values, together with a simple compressed air ON/OFF control scheme, on-line Oxygen Uptake Rate (OUR) profiles during aerobic reaction periods were obtained. Due to the high variability of wastewater characteristics, periodical analyses of textile wastewater were conducted and thus characterized for pH, conductivity, total and volatile solids, COD, ammonia, and TKN. After an initial period of activated sludge adaptation to textile wastewater, the SBR was operated at step-feed strategy to reduce the effluent biodegradable matter presents in the wastewater by SBR water change ratio modification and feeding strategy.

Automation↗
PubMed2002

Mouthpiece versus facemask for delivery of nebulized salbutamol in exacerbated childhood asthma.

We compared the bronchodilator response to salbutamol (albuterol) delivered by a compressed air nebulizer through a mouthpiece and via a facemask in 18 asthmatic children, to determine the most appropriate delivery method. Patients using a mouthpiece had significantly better mean percent increases in forced expiratory volume in 1 sec (FEV1) and in forced vital capacity (FVC) than those using a facemask 30 min after inhalation (FEV1, 56.4 +/- 32.6% vs. 28.9 +/- 19.1%, FVC: 34.4 +/- 26.4% vs. 7.5 +/- 14.9%, respectively). Nebulized therapy plays an important role in the management of bronchial asthma in children and should be delivered by a mouthpiece whenever possible in cases of exacerbated asthma.

Administration, Inhalation↗
PubMed2004

Foraging by deep-diving birds is not constrained by an aerobic diving limit: a model of avian depth-dependent diving metabolic rate.

The theoretical aerobic diving limit (tADL) specifies the duration of a dive after which oxygen reserves available for diving are depleted. The tADL has been calculated by dividing the available oxygen stores by the diving metabolic rate (DMR). Contrary to diving mammals, most diving birds examined to date exceed the tADL by a large margin. This discrepancy between observation and theory has engendered two alternative explanations suggesting that dive duration is extended either anaerobically or by depressing aerobic metabolism. Current formulations of tADL uncritically assume that DMR is independent of depth. However, diving birds differ from other vertebrate divers by having a larger respiratory system volume and by retaining air in their plumage while diving, thereby elevating buoyancy. Because air compresses with depth, diving power requirement decreases with depth. Following this principle, we modeled DMR to depth for Adelie and little penguins and reformulated the tADL accordingly. The model's results suggest that < approximately 5% of natural dives by Adelie penguins exceed the reformulated tADL(d), or maximal aerobic depth, and none in the more buoyant little penguin. These data suggest that, for both small and large species, deep diving birds rarely if ever exceed tADL(d).

Animals↗