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PubMed1998

Negative pressure ventilation vs. spontaneous assisted ventilation during rigid bronchoscopy. A controlled randomised trial.

BACKGROUND: Ventilation during interventional rigid bronchoscopy (IRB) under general anaesthesia (jet ventilation, positive pressure ventilation and spontaneous assisted ventilation) may offer some difficulties. This study compares the effectiveness during IRB of intermittent negative pressure ventilation (INPV) and spontaneous assisted ventilation (SAV). METHODS: Thirty-eight patients submitted to IRB were randomised into two groups: SAV or INPV. All patients received a total intravenous anaesthesia; INPV patients were paralysed. Pre- and intra-operative arterial blood gases and O2 flow through a rigid bronchoscope were assessed. The endoscopist applying a subjective score evaluated the operating conditions. RESULTS: Patients of the INPV group, as compared to the SAV group, required a lower dosage of fentanyl (2.6 +/- 1.8 micrograms.kg-1.h-1 vs. 6.6 +/- 4.8 micrograms.kg-1.h-1), a lower O2 supply (3.3 +/- 2.8 l/min vs. 11.6 +/- 3.4 l/min), a shorter recovery time (5.4 +/- 2.9 min vs. 9.8 +/- 7.1 min) and no manually assisted ventilation (0 +/- 0 vs. 1 +/- 1.1 n degree/procedure). Intraoperative PaCO2 was higher in the SAV (8.1 +/- 1.3 kPa) than in the INPV group (5.0 +/- 1.6 kPa) and intraoperative pH differed in the two groups (7.26 +/- 0.05, SAV vs. 7.47 +/- 0.08, INPV). Operating conditions, as assessed by a subjective score, were considered better with INPV than with SAV (4.9 vs. 4.3). CONCLUSIONS: As compared to SAV, INPV in paralysed patients during IRB reduces administration of opioids, shortens recovery time, prevents respiratory acidosis, excludes the need for manually assisted ventilation, reduces O2 need and affords optimal surgical conditions. INPV appears a safe, non-invasive and effective ventilatory management during IRB.

Adult↗

PubMedDate not supplied

Anesthesia for carbon dioxide laser microsurgery of the larynx.

Jet ventilation via the Sanders injector during intravenous general anesthesia provides excellent operative conditions for CO2 laser microsurgery of the larynx. This technique, which includes complete muscle relaxation, is superior to traditional methods of anesthesia because the endotracheal tube is eliminated, thus improving the surgical field and reducing burn hazards owing to ignition of the tube. The laryngoscope has been modified to carry multiple ports into which a 14-gauge needle is inserted and the tip advanced just distal to the vocal cords. This needle is securely attached to the injector and pressure from the oxygen source is adjusted according to the patient's build and total compliance. Satisfactory arterial blood gases, superb operating conditions, safety, and rapid awakening make this the method of choice for most patients.

Adolescent↗

PubMed2004

Resistance in series model for micellar enhanced ultrafiltration of eosin dye.

A study has been performed to quantify the extent of flux decline during micellar enhanced ultrafiltration (MEUF) of an acid dye (eosin red) using hexadecyl (cetyl) pyridinium chloride as the cationic surfactant. Effects of the operating conditions, e.g., transmembrane pressure drop and feed-surfactant-to-dye ratio, on the permeate flux profile and observed retention have been investigated in an unstirred batch ultrafiltration (UF) cell. A simple resistance-in-series model has been used to quantify the flux decline. From the flux decline history, it has been found that the membrane permeability decreases rapidly due to reversible pore blocking and further flux decline is caused by the growth of a gel-type layer over the membrane surface. The different resistances and growth kinetics of the gel layer have been investigated as functions of the operating conditions.

Journal Article↗

PubMed2004

Scale-up methodologies for Escherichia coli and yeast fermentation processes.

Scale-up techniques from the literature have been compiled and reviewed for applicability to Escherichia coli and yeast processes. The consistency of design and operating parameters for the pilot scale vessels in an existing fermentation pilot plant, ranging in nominal volume from 100 l to 19,000 l, was established and compared favorably with approaches found in the literature. Differences were noted as a function of parameters such as fermentor scale, vessel geometry, agitator type/size and ungassed/gassed power input. Further analysis was conducted using actual fermentation data for historical and recent development processes collected over a 10-year-period, focussing on operating conditions at peak culture oxygen uptake rates. Scale-up estimates were performed based on geometric similarity, agitator tip speed, gassed power per unit volume and mixing time. Generally, scale-up calculations from the 280 l scale were most similar to the parameters of installed equipment. Scale-up from the 30 l laboratory scale typically underpredicted parameters with scale-up from the 280 l scale being most appropriate. The 19,000 l fermentor installation was notably different in geometric similarity from the 280 l-1900 l scales since its design was meant to accommodate a wide range of operating volumes. Analysis of historical and recent processing performance was conducted for single cell bacterial or yeast fermentations which challenged peak operating conditions of the fermentors. Identification of key issues associated with scale-up for these specific pilot plant vessels was believed to be critical to efficient process development, clinical material production, and expected process transfer to a manufacturing facility.

Journal Article↗

PubMed2003

Life cycle assessment of gasoline blending options.

A life cycle assessment has been done to compare the potential environmental impacts of various gasoline blends that meet octane and vapor pressure specifications. The main blending components of alkylate, cracked gasoline, and reformate have different octane and vapor pressure values as well as different potential environmental impacts. Because the octane and vapor pressure values are nonlinearly related to impacts, the results of this study show that some blends are better for the environment than others. To determine blending component compositions, simulations of a reformer were done at various operating conditions. The reformate products of these simulations had a wide range of octane values and potential environmental impacts. Results of the study indicate that for low-octane gasoline (95 Research Octane Number), lower reformer temperatures and pressures generally decrease the potential environmental impacts. However, different results are obtained for high-octane gasoline (98 RON), where increasing reformer temperatures and pressures increase the reformate octane values faster than the potential environmental impacts. The higher octane values for reformate allow blends to have less reformate, and therefore high-octane gasoline can have lower potential environmental impacts when the reformer is operated at higher temperatures and pressures. In the blends studied, reformate and cracked gasoline have the highest total impacts, of which photochemical ozone creation is the largest contributor (assuming all impact categories are equally weighted). Alkylate has a much lower total potential environmental impact but does have higher impact values for human toxicity by ingestion, aquatic toxicity, terrestrial toxicity, and acidification. Therefore, depending on environmental priorities, different gasoline blends and operating conditions should be chosen to meet octane and vapor pressure specifications.

Gasoline↗

PubMed2005

Movement of different-shaped particles in a pan-coating device using novel video-imaging techniques.

The purpose of this study was to investigate the effects of particle shape on the movement of particles in a pan-coating device using novel video-imaging techniques. An area scan CCD camera was installed inside a 24-in pan coater at the same location as that of a spray nozzle, and the movement of particles was tracked using machine vision. A white tracer particle was introduced inside a bed of black-coated particles. The effects of pan loading, pan speed, and particle shape on the movement of particles was studied. The response variables were circulation time, surface time, projected area of particle per pass, dynamic angle of repose, cascading velocity, and dispersion coefficient. Experiments were conducted at 3 different pan speeds, 6, 9, and 12 rpm, and 2 fill levels (ratio of bed depth to pan diameter), one eighth and one quarter, and data were collected over a 30-minute time period. The differences in circulation times of spheres and tablets, with similar volume equivalent diameter as that of the sphere, were found to be insignificant at the 95% confidence interval. The circulation time ranged from 2.8 to 10.8 seconds depending on the operating condition and increased with increasing pan load and decreasing pan speed. The distributions of circulation time, surface time, and projected surface area were found to be nonnormal. The dynamic angle of repose for tablets was higher than for spheres. Also, the bed surface for spheres was much flatter in comparison with tablets where the bed shape attained a "wave-like" form. The average velocity of tablets in the cascading layer was found to be significantly higher than spheres. A linear model (R(2) > 0.98) best described the variation of velocity as a function of pan speed for all of the operating conditions.

Motion↗

PubMed1969

Effect of shaking speed and type of closure on shake flask cultures.

Growth of microorganisms and biosynthesis of microbial products in shake flasks may be limited by operating conditions which provide inadequate supplies of oxygen. Methods are described for meeting the oxygen requirements of test organisms by using standard baffled flasks with pad-type closures and shaking at relatively high speeds. Growth of Escherichia coli B in a rich medium and production of candidin by Streptomyces viridoflavus were the test systems used. Flasks shaken at 230 to 385 rev/min gave sulfite oxidation rates of 1 to 8 mmoles of oxygen per liter per min over a useful working volume range (40 to 150 ml in 300-ml flasks). These rates are as high as those obtained in agitated fermentors under usual operating conditions.

Anti-Bacterial Agents↗

PubMed2001

Graphical method for the calculation of chromatographic performance in representing the trade-off between purity and recovery.

A simple engineering framework that enables the rapid representation of the performance of liquid chromatographic separations is provided in this paper. The fractionation diagram and its associated maximum purification factor versus product yield, and contamination index versus product yield diagrams, may be derived directly from chromatographic data. The fractionation diagram plots the relative change in the cumulative fractional mass of product eluted with the corresponding fractional total mass eluted, while the maximum purification factor versus yield diagram shows the degree of trade-off between the levels of purity and recovery achieved in the chromatographic step. The minimum contamination index versus yield plot is especially suitable for cases where the product and impurity are expressed in different units and shows how the extent of contaminant removal changes relative to product yield. These diagrams are more straightforward and easily interpretable compared to the basic conventional chromatograms and enable investigation of the degree of trade-off between purity and recovery for any set of operating conditions to be made. The approach is demonstrated for two different chromatographic systems. In the first, a set of simulation results from a verified size exclusion model is used to demonstrate the approach for product recovery. In the second, a set of experimental results for the removal of endotoxin from DNA is used. This demonstrates a problem where the product and impurity content are measured by different assay techniques and are expressed in different units, and also where the quality of process information is limited by the small number of fractions collected. The studies show how such an approach can help to identify the optimal operating conditions, in terms of acceptable yield and desired level of contaminant removal, and to redefine the location of product fractions needed to achieve these specifications.

Algorithms↗

PubMed2003

Optimization of accelerated solvent extraction for polyhalogenated dibenzo-p-dioxins and benzo-p-furans in mineral and environmental matrixes using experimental designs.

This paper deals with the optimization of accelerated solvent extraction (ASE) for the analysis of the polychlorinated dibenzo-p-dioxins, benzo-p-furans (PCDD/Fs), mixed bromine/chlorine-dibenzo-p-dioxins, and benzo-p-furans (so-called MXDD/Fs) in solid samples. Previous theoretical studies have shown that these compounds exhibit similar electronic properties. It is reasonable to assume that there is little difference in the behavior, formation, and toxicity of PCDD/Fs and MXDD/Fs. Indeed, for most of the cases, the affinity is defined by these weak interactions. Only eight native standards are available for the MXDD/Fs; hence, the use of similar compounds (native and (13)C(12)-labeled), such as PCDD/Fs, is required to optimize and to validate experimental methods. This would allow conclusions to be applied for the MXDD/Fs without extended studies involving complex synthesis methods. Experimental design methodology was used to evaluate the influence of five parameters (temperature, pressure, static time, number of cycles, and solvent nature) on the polyhalogenated dibenzodioxin and -furan (PXDD/Fs) extractions in different materials. The extraction profiles and the optimal operating conditions were determined for each matrix from the modeling of extraction performance. The two following effects, the relative peak area and the co-extracted matrix (CEM), were screened in this study. The temperature of extraction was found to be the most important parameter. ASE offers automation and appears to be as efficient as Soxhlet or Soxtet; however, a major benefit was that a 4-fold decrease in extraction time was obtained. Results suggest that extraction efficiency was quantitative with extraction times as low as 15 min for all congeners at 130 degrees C with a mixed solvent (n-hexane/acetone (1/1)). Under these operating conditions, the CEM and the degradation of the highly brominated compounds were minimized. The analysis of some real life samples from municipal solid waste incinerators showed significant amounts of PXDD/Fs.

Journal Article↗

PubMed1985

Mobile phase effects in reversed-phase chromatography. VII. Dependence of retention on mobile phase composition and column temperature.

The relationship between logarithmic retention factor, kappa, in reversed-phase chromatography and operating conditions including mobile phase composition and column temperature is still controversial. Earlier, the following analytical relationship was proposed for use with alkyl benzenes: kappa = A1 phi (1 - Tc/T) + A2/T + A3 where phi is volume fraction organic co-solvent of the hydro-organic mobile phase, T is absolute temperature and A1-A3 are parameters appropriate to the eluite and stationary phase. Insofar as its use had not been tested with polar eluites that are retained by only one mechanism, its description of the retention of 54 polar and apolar eluites was examined and compared to equations with other, usually more complex, relationships between retention and operating conditions. The following four-parameter equation described best most data: kappa = A1 phi (1 - Tc/T) + A2/T + A3 + A4 phi. But neither this nor any other four-parameter equation under examination here emerged solely as the best expression for the dependence of retention on the eluent composition and temperature. The average relative errors were 7.8% and 6% with use of the three- and the four-parameter equations which were found to be best for a given eluite, respectively. In view of the small decrease in error but significant increase in complexity and in data points with the use of the four-parameter equation, the three-parameter equation is recommended for general use.

Chemical Phenomena↗

PubMedDate not supplied

Multi-center trial with an in vitro NMR protocol. EEC Concerted Research Project.

The EEC Protocol for in vitro measurement of T1 and T2 presented in paper II of this series was tested in 15 centers on a variety of instruments. This article discusses the results of this protocol trial using biological samples (rat liver and thigh muscle) and two reference gel samples. Each reference gel was prepared as a single batch, dispensed into appropriate sample tubes and sent to all participants. Details of instrument types and operating conditions are given, along with measurement frequencies and temperatures and the results of precision testing. The relaxation time measurements from the gels for the trial are compared with temperature and frequency effects examined in independent centers under similar conditions. The relaxation time values for biological tissues are examined in the light of the scatter of such values in the general literature. To check the effects of data analysis methods on relaxation times, full relaxation data for one reference sample was provided by each group. This was re-analyzed in three centers using different methods; these results are compared with the values calculated by each group using its own method. In general, the results from different groups show good consistency with the reference values. The use of this Protocol has helped reduce scatter in results from biological samples and has provided information for improvement of individual operating conditions and improvement of the protocol to its final form.

Animals↗

PubMed2006

Ultrasound assisted supercritical fluid extraction of oil and coixenolide from adlay seed.

Oil and coixenolide are important components of adlay seed (Coix lachrymal-jobi L. var. Adlay) with many beneficial functions to human health. In this work, a novel extraction technique--ultrasound assisted supercritical fluid extraction (USFE)--was studied. Effects of operating conditions on the extraction, including extraction temperature (T), pressure (P), time (t), CO(2) flow rate (F) and ultrasonic power (I) were investigated. There are optimum temperatures which gives the maximum extraction yields (EYs) for the supercritical fluid extractions with and without ultrasound. The effect of pressure on EYs for is similar to that of pressure on CO(2) density. Based on the yield of extraction, the favorable conditions for supercritical fluid extraction (SFE) were: T at 45 degrees C, P at 25 MPa, t at 4.0 h and F at 3.5L/h. While ultrasound was applied as in USFE, the following parameters were preferred: T at 40 degrees C, P at 20 MPa, t at 3.5h and F at 3.0 L/h, respectively. The results show that supercritical fluid extraction with the assistance of ultrasound could reduce the temperature, pressure, CO(2) flow rate, as well as time used in the process. Compared with SFE, USFE could give a 14% increase in the yield for extracting oil and coixenolide from adlay seed with less severe operating conditions.

Chromatography, Supercritical Fluid↗

PubMed2005

Scale-up of high shear granulation based on the internal stress measurement.

Scale-up of wet granulation in a vertical high shear mixer was conducted. Pharmaceutical excipient powders composed of lactose, cornstarch and micro-crystallinecellulose, and hydroxypropylcellulose as a binder were mixed together and then granulated with purified water under various operating conditions and vessel scales. A novel internal stress measurement system was developed and stress of normal and tangential directions that granules received from the agitator blade during the granulation was continuously measured. The results indicated that granules received stress mainly from the tangential direction, which also showed the largest value near at the vessel wall. The effects of the agitator tip speed and the centrifugal acceleration on the measured stress was investigated. It was found that the tip speed of the agitator blade could be the main factor for the granule growth. The physical properties such as strength, size distribution and compressibility of granules prepared by changing the operating conditions and the vessel scales were evaluated and the scale-up characteristics of high shear granulation were investigated experimentally. The results showed that these physical properties had linear correlations with the tip speed. It was finally concluded that the scale-up of high shear granulation could be well conducted by means of the tip speed of the agitator blade.

Algorithms↗

PubMed2006

Kinetic modelling of phenol co-oxidation using horseradish peroxidase.

Phenol is an industrial pollutant and its removal from industrial wastewaters is of great importance. In order to design optimised phenol removal procedures by using horseradish peroxidase-based systems, there are some points that have to be dealt with. One of the most important issues is the need for reliable kinetics as this is one of the difficulties found during process scale-up. Although simplified kinetics can be used for limited ranges of operating conditions, they are not usually reliable for the description of varying process conditions. The present work describes the implementation of a kinetic model, based on a mechanism, for the co-oxidation of phenol and 4-aminoantipyrine (Am-NH2), which is used as a chromogen agent, with hydrogen peroxide as the oxidant. The model covers not only the variation of the concentrations of all the species involved, but also the effect of temperature in the reaction. The estimation of kinetic rate constants and activation energies for the various steps in the mechanism is performed with a single optimisation procedure, and all the experimental results are described using a unique set of parameters, which, thus, is valid over an extended range of operating conditions. The mechanism allowed the determination of a reliable kinetic model which is appropriate for the range of experimental conditions used. The computational model was also tested with an independent set of experiments with different conditions from the ones for which the parameters were estimated.

Ampyrone↗

PubMed2007

Neural network prediction of thermophilic (65 degrees C) sulfidogenic fluidized-bed reactor performance for the treatment of metal-containing wastewater.

The performance of a fluidized-bed reactor (FBR) based sulfate reducing bioprocess was predicted using artificial neural network (ANN). The FBR was operated at high (65 degrees C) temperature and it was fed with iron (40-90 mg/L) and sulfate (1,000-1,500 mg/L) containing acidic (pH = 3.5-6) synthetic wastewater. Ethanol was supplemented as carbon and electron source for sulfate reducing bacteria (SRB). The wastewater pH of 4.3-4.4 was neutralized by the alkalinity produced in acetate oxidation and the average effluent pH was 7.8 +/- 0.8. The oxidation of acetate is the rate-limiting step in the sulfidogenic ethanol oxidation by thermophilic SRB, which resulted in acetate accumulation. Sulfate reduction and acetate oxidation rates showed variation depending on the operational conditions with the maximum rates of 1 g/L/d (0.2 g/g volatile solids (VS)/d) and 0.3 g/L/d (0.06 g/g VS/d), respectively. This study presents an ANN model predicting the performance of the reactor and determining the optimal architecture of this model; such as best back-propagation (BP) algorithm and neuron numbers. The Levenberg-Marquardt algorithm was selected as the best of 12 BP algorithms and optimal neuron number was determined as 20. The developed ANN model predicted acetate (R=0.91), sulfate (R=0.95), sulfide (R=0.97), and alkalinity (R=0.94) in the FBR effluent. Hence, the ANN based model can be used to predict the FBR performance, to control the operational conditions for improved process performance.

Acetates↗

PubMedDate not supplied

Intracellular pH monitoring as a tool for the study of hybridoma cell behavior in batch and continuous bioreactor cultures.

We show in this paper the results obtained when studying the behavior of hybridoma cells by monitoring of the pHi during batch and continuous bioreactor cultures. A first set of experiments, consisting of a batch culture and a continuous culture at variable dilution rate, was set up under normal physiological operating conditions. Significant pHi variations were measured during these cultures. For the batch culture, maximal pHi values around 7.60 were associated with the middle of the growth phase, while lower values were found in the culture beginning and during the decay phase, respectively 7.47 and 7.40. For the continuous culture, pHi increased with increasing dilution rate, ranging between 7.40 and 7. 60 for dilution rates between 0.010 and 0.040 h-1. These pHi variations were found for both cultures to be linked to variations of the specific growth rate of the cells. The observed link between pHi and cell growth provided us a general framework for the study of the effect of suboptimal operating conditions on cell behavior, all having a particular interest in animal cell culture technology. First, our results indicate that a decrease of the medium pH of its normal value of 7.00 to 6.70 did not necessarily result in cytoplasmic acidification, at least not after prolonged exposition times in continuous culture, and this despite a pronounced growth inhibitory effect. This effect can therefore rather be explained by the combination of the increased demand for maintenance energy associated with the higher DeltapH gradient maintained across the cell membrane and the decreased supply of energy, in particular via the glucose metabolism. Second, our results indicate that also increased ammonium ion concentrations do not lower pHi. This observation, together with the results of batch cultures carried out at a more alkaline pH, indicates that the form NH3, and not the form NH4+, has a negative effect on cell growth of our hybridoma cell line. Third, in the case of an osmolality increase, a significant pHi increase was observed, with mean values of 7.35 at the lower osmolalities 335 and 370 mOsm/kg and 7.45 at the higher osmolalities of 400, 425, and 450 mOsm/kg. This higher pHi might account at least partially for the increased monoclonal antibody production observed at hyperosmolality and coincided furthermore with a faster glutamine consumption rate.

Animals↗

PubMed2005

Chemical pathway and kinetics of phenol oxidation by Fenton's reagent.

Phenol oxidation by Fenton's reagent (H2O2 + Fe2+) in aqueous solution has been studied in depth for the purpose of learning more about the reactions involved and the extent of the oxidation process, under various operating conditions. An initial phenol concentration of 100 mg/L was used as representative of a phenolic industrial wastewater. Working temperatures of 25 and 50 degrees C were tested, and the initial pH was set at 3. The H2O2 and the Fe2+ doses were varied in the range of 500-5000 and 1-100 mg/L, respectively, corresponding to 1-10 times the stoichiometric ratio. A series of intermediates were identified, corresponding mainly to ring compounds and short-chain organic acids. Most significant among the former were catechol, hydroquinone, and p-benzoquinone; the main organic acids were maleic, acetic, oxalic, and formic, with substantially lower amounts of muconic, fumaric, and malonic acids. Under milder operating conditions (H2O2 and Fe2+ at lower concentrations), a great difference was found between the measured total organic carbon (TOC) and the amount of carbon in all analyzed species in the reaction medium. This difference decreased as the doses of H2O2 and Fe2+ increased, indicating that the unidentified compounds must correspond to oxidation intermediates between phenol and the organic acids. To establish a complete oxidation pathway, experiments were carried out using each of the identified intermediates as starting compounds. Dihydroxybenzenes were identified in the earlier oxidation stages. Muconic acid was detected in catechol but not in the hydroquinone and p-benzoquinone oxidation runs; the last two compounds were oxidized to maleic acid. Oxalic and acetic acid appeared to be fairly refractory to this oxidation treatment. A detailed knowledge of the time evolution of the oxidation intermediates is of environmental interest particularly in the case of hydroquinone and p-benzoquinone because their toxicities are several orders of magnitudes higher than that of phenol itself. The time evolution of the intermediates and TOC was fitted to a simple second-order kinetic equation, and the values of the kinetic constants were determined. This provides a simplified approach useful for design purposes.

Acids↗

PubMed1998

Pre-operative and per-operative factors conditioning long-term facial nerve function in vestibular schwannoma surgery through translabyrinthine approach.

Facial nerve function was evaluated in 103 patients, after vestibular schwannoma removal through the translabyrinthine approach. The mean follow-up was 43 months (minimum six months). Grade I facial function was achieved in 100 per cent of stage I schwannomata compared with 36 per cent of stage IV schwannomata. Grade I or II facial function was found in 78 per cent of homogeneous schwannomata, compared with 48 per cent of heterogeneous schwannomata. Facial function was preserved in 89 per cent of cases, if the angle between the internal auditory canal and the schwannoma was > 66 degrees, compared with 54 per cent if the angle was < 66 degrees. There was 82 per cent of normal facial function when the nerve appeared normal after tumour removal, compared with 18 per cent when the nerve was traumatized. When the ratio (stimulation threshold at the internal auditory canal/stimulation threshold at brainstem) was < 2, post-operative facial function was preserved in 87 per cent of cases, compared with 13 per cent when the ratio was > 2.

Adolescent↗