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PubMed1998

Ethene removal from gas by recycling a water-immiscible solvent through a packed absorber and a bioreactor.

Hydrophobic pollutants in waste gases are difficult to remove with the conventional biological treatment techniques because of the slow gas/water mass transfer rate. A two-stage system with a water-immiscible solvent as intermediate liquid was developed. This system consisted of a packed absorber for transfer of the model pollutant, ethene, from gas to solvent and a stirred-tank reactor (mixer) for solvent/water transfer and subsequent degradation by Mycobacterium parafortuitum. The solvent FC40, a perfluorocarbon, was recycled between these two compartments. The stability of the system was shown during a run of 10 days. The elimination efficiency was found to be a function of the solvent flow: 9% and 15% elimination were obtained at solvent flows of 6 x 10(-8) m3.s-1 and 11.3 x 10(-8) m3.s-1, respectively. Ethene removal remained constant at increasing solvent hold-ups up to 50% (v/v). In spite of the low elimination efficiencies caused by an inefficient use of the column, the feasibility of the system to remove ethene has been demonstrated. The system's performance was described by a steady-state mathematical model. Simulated ethene removal efficiencies agreed well with the experimental data. Based on this, the model was used to optimise the dimensions and operating conditions. Furthermore, the model was used to compare the performance of the combined system (PA/MS) with the performance of a similar system without solvent. It was found that the use of solvent as intermediate liquid can improve substantially the removal efficiency of hydrophobic gaseous pollutants compared with the system without solvent. This is dependent however, on the solubility of the pollutant in the solvent, on the dimensions of the system and on the operating conditions.

Absorption↗

PubMed1993

[Integrated health promotion in business: starting problems and proposed solutions].

Integrated worksite health promotion takes into account as well the demands of employees as those of the enterprises and at the same time applies to both, health behaviour and operational conditions of the companies. It is not restricted to a singular action but makes a continuous effort to promote the health of employees as an integrated part of employers' planning and politics. Apprehension between employers and employees seems to be one of the key obstacles of worksite health promotion. Therefore both sides have to keep negotiating to what extent health promotion has to improve efficiency of employees in respect to enterprises or how far operational conditions have to be adjusted to suit the well-being of personnel. A possible solution to solve this dilemma would be a widening of the conception of efficiency and incorporating of long-term thinking.

Health Behavior↗

PubMedDate not supplied

Variables that affect xylitol production from sugarcane bagasse hydrolysate in a zeolite fluidized bed reactor.

The operational conditions for xylitol production by fermentation of sugarcane bagasse hydrolysate in a fluidized bed reactor with cells immobilized on zeolite were evaluated. Fermentations were carried out under different conditions of air flowrate (0.0125-0.0375 vvm), zeolite mass (100-200 g), initial pH (4-6), and xylose concentration (40-60 g/L), according to a 2(4) full factorial design. The air flowrate increase resulted in a metabolic deviation from product to biomass formation. On the other hand, the pH increase favored both the xylitol yield (Y(P/S)) and volumetric productivity (Q(P)), and the xylose concentration increase positively influenced the xylitol concentration. The best operational conditions evaluated were based on the use of an air flowrate of 0.0125 vvm, 100 g of zeolite, pH 6, and xylose concentration of 60 g/L. Under these conditions, 38.5 g/L of xylitol were obtained, with a Y(P/S) of 0.72 g/g, Q(P) of 0.32 g/L.h, and cell retention of 25.9%.

Bioreactors↗

PubMed2004

Degradation of polycyclic aromatic hydrocarbons in aqueous solutions by ultrasonic irradiation.

The effect of various operating conditions (initial concentration, liquid phase temperature, applied power, ultrasound frequency) and of the presence of matrix components (1-butanol, NaCl and FeSO(4)) on the sonochemical degradation of naphthalene, acenaphthylene and phenanthrene in water has been studied. A horn-type sonicator was used to deliver the ultrasound energy, while immersion sampling solid-phase microextraction (SPME) coupled with GC-MS was employed to follow concentration-time profiles of the chosen PAHs. At the operating conditions in question (initial concentrations of 150, 300 and 450 microg/l, temperatures of 20 and 40 degrees C, applied power of 45, 75 and 150 W and ultrasound frequencies of 24 and 80 kHz), all PAHs were susceptible to sonochemical treatment and, in most cases, complete degradation could be achieved in up to 120 min of treatment. Conversion was found to decrease with increasing initial concentration and temperature and decreasing power and frequency as well as in the presence of an excess of dissolved salts. Addition of 1-butanol, a known hydroxyl radical scavenger, substantially suppressed degradation throughout the course of the reaction, thus highlighting the role of oxidation reactions in PAHs degradation. In contrast, addition of Fe(2+) ions at a low concentration enhanced degradation through a Fenton-like reaction.

Gas Chromatography-Mass Spectrometry↗

PubMed1997

Microbial biodegradation of organic wastes containing surfactants in a continuous-flow reactor.

In a continuous flow bioreactor seeded with microbes from municipal activated sludge, complete organic carbon oxidation of simulated graywater (wastewater produced in human residences, excluding toilet wastes) was achieved at dilution rates up to 0.36 h-1 in the presence of 64.1 microM linear alkylbenzenesulfonate (LAS) L-1. At LAS concentrations of 187 microM, the system functioned only at dilution rates up to 0.23 h-1, and the biomass yield was two-fold lower. There were physiological changes in the microbial communities under different operating conditions, as measured by specific contents of ATP and extracellular hydrolases as well as the respiratory potential of the biomass. LAS inhibited the activity of LAS-degrading microbes at >150 microM LAS, and the activity of other microbes at >75 microM LAS. Chemical analysis of graywater indicated that samples consisted primarily of biological polymers (proteins and polysaccharides) and lower concentrations of surfactants. Biological remediation of graywater is possible, although treatment efficiency is influenced by the operating conditions and wastestream composition.

Alkanesulfonates↗

PubMed2002

The role of the kneading paddle and the effects of screw revolution speed and water content on the preparation of solid dispersions using a twin-screw extruder.

The twin-screw hot-melt extrusion process is useful for preparing solid dispersions which can improve the dissolution and absorption of drugs. The kneading paddle elements of the screws play an important role in changing the crystallinity and dissolution properties of a solid dispersion of kneaded nifedipine-hydroxypropylmethylcellulose phthalate (NP-HPMCP). After operating the machine, a small amount of kneaded material adhering to the screws was collected and its physicochemical properties examined. Samples from the kneading paddle with a twist angle of 60 degrees were transparent and exhibited super-saturation on dissolution testing. When the kneading paddle elements were detached from the screws and only the feed screw elements were operated, the physicochemical properties of the extruded material were significantly influenced by the operating conditions of the machine e.g. revolution rate of screws, and the amount of water added to the feed materials. Slow revolution of the screws and the addition of a suitable amount of water to the mixture increased the rate of drug dissolution, although no super-saturation occurred. As the kneading paddle elements can retain the mixture in the machine for a longer period under intense shear, desired solid dispersions can be prepared routinely irrespective of the operating conditions. Moreover, a capillary rheometer can be useful to predetermine the amount of water added and the temperature for the preparation of solid dispersions using a twin-screw extruder.

Calcium Channel Blockers↗

PubMed2003

Entrained phase adsorption of PCDD/F from incinerator flue gases.

The emission abatement of polychlorinated dioxins and furans (PCDD/F) issued from municipal solid waste incineration (MSWI) is growing in importance because of more stringent emission standards and general health concern. These substances cannot be separated by conventional gas cleanup processes. They are successfully removed through adsorption onto carbonaceous materials, and the entrained-phase injection of pulverized adsorbents in the flue gas, followed by high-efficiency separation, is widely applied. Operating conditions and results obtained in Flemish MSWIs are given. The results illustrate the excellent overall removal efficiency: the regulation limit of 0.1 ng TEO/Nm3 dry gas at 11% O2 can be achieved. Furans are adsorbed to a slightly higher extent than the dioxins. The PCDD/F removal by carbonaceous adsorbents is thereafter modeled from first principles for the contribution of both entrained-phase (eta1) and cake filtration (eta2) to the overall efficiency (etaT), with dominant parameters being the operating temperature, the dosage and activity of adsorbent, and the fraction of adsorbent in the filter cake. Application of the model equations and comparison of measured and predicted overall efficiencies for the Flemish MSWIs demonstrate the validity of the model, which enables the MSWI operators both to predict the adsorption efficiencies for combinations of major operating parameters and to assess the sensitivity of the process to varying operating conditions. Finally, some practical difficulties encountered with the entrained-phase adsorption are discussed.

Adsorption↗

PubMed2004

Thermal elevation in the human eye and head due to the operation of a retinal prosthesis.

An explicit finite-difference time-domain formulation of the bio-heat equation is employed with a three-dimensional head eye model to evaluate the temperature increase in the eye and surrounding head tissues due to the operation of the implanted stimulator IC chip of a retinal prosthesis designed to restore partial vision to the blind. As a first step, a validation of the thermal model and method used is carried out by comparison with in vivo measurements of intraocular heating performed in the eyes of dogs. Induced temperature increase in the eye and surrounding tissues is then estimated for several different operational conditions of the implanted chip. In the vitreous cavity, temperature elevation of 0.26 degrees C is observed after 26 min for a chip dissipating 12.4 mW when positioned in the mid-vitreous cavity while it is 0.16 degrees C when the chip is positioned in the anterior portion between the eye's ciliary muscles. Corresponding temperature rises observed on chip are 0.82 degrees C for both the positions of the chip. A comprehensive account of temperature elevations in different tissues under different operational conditions is presented.

Adult↗

PubMed2004

Effects of feeding strategies on the performance of an anaerobic discontinuous reactor containing immobilized biomass with circulation system for liquid-phase mixing.

Data on the influence of feeding strategy on the performance of a fed-batch anaerobic sequencing reactor containing biomass immobilized on polyurethane foam and subjected to liquid phase circulation are presented and discussed. Six-hour cycles, temperature of 30 degrees C and circulation flow rate of 6 L/h were used. During each cycle 890 mL of synthetic domestic wastewater, with organic matter concentration of 500 mgCOD/L were fed to the reactor. The feeding strategies were implemented using fill times of 6 min (batch mode), 60, 120, 240 (fed-batch/batch mode) and 360 min (fed-batch mode). The system attained high efficiency and stability for all the operating conditions, and the substrate removal efficiency based on filtered samples presented a slight decrease from 85% to 81% when fill time was increased from 6 min to 360 min. A model considering a first-order kinetic equation was fitted to the experimental data. The apparent kinetic parameters for both batch and fed-batch phases were estimated, thus permitting evaluation of the influence of the feeding strategy on the reactor performance. The current system may be considered flexible in terms of the operating conditions it is subjected to.

Bacteria, Anaerobic↗

PubMed2000

Single injection peribulbar anaesthesia. Total upper eyelid drop as an end-point marker.

A prospective, observer blinded study on 51 patients undergoing cataract surgery was conducted to assess Total Upper Eyelid Drop as a new end-point marker to single injection peribulbar block. At present, no such clinical marker exists to stop clinicians injecting more than necessary volumes of local anaesthetic and therefore to prevent dangerous increases in intra-ocular pressure. Using this technique, satisfactory ocular akinesia was achieved in 90% of eyes 10 min after injection. Operating conditions were satisfactory in 98% of cases. The mean (range) volume injected was 9.1 (4-15) ml. The mean increase in intra-ocular pressure immediately after injection was 6.9 mmHg, decreasing to 0.7 mmHg after 5 min without the application of ocular compression. We found a negative correlation between the increase in intra-ocular pressure and the volume of injection (p < 0.002), which has never previously been reported. We conclude that Total Upper Eyelid Drop is a reliable endpoint marker for producing satisfactory operating conditions for cataract surgery while minimising increases in intra-ocular pressure and its use may therefore avoid the risks associated with ocular compression.

Aged↗

PubMed1995

Therapeutic potential of drugs with mixed 5-HT4 agonist/5-HT3 antagonist action in the control of emesis.

Drugs interacting with serotonin (5-hydroxytryptamine, 5-HT) receptors are of value in the treatment of several gastrointestinal disturbances. Selective 5-HT3 receptor antagonists (ondansetron, granisetron, tropisetron) are widely utilized to control emesis induced by chemotherapy and radiation, while agonists at 5-HT4 receptors (cisapride, renzapride, BIMU compounds) are endowed with gastrointestinal prokinetic action. Here we overview the therapeutic potential of drugs with potent mixed 5-HT4 agonist/5-HT3 antagonist properties (i.e. BIMU 1) in the management of anticancer therapy-induced emesis and of intestinal adynamic post-operative conditions associated with vomiting. In the former situation, the agonism at 5-HT4 receptors is expected to be of benefit via two possible mechanism: (i) inhibition of 5-HT release from enterochromaffin cells; (ii) restoration of anally driven peristaltic waves in the upper gastrointestinal tract. Moreover, 5-HT4 receptor-induced prokinetic activity may counteract colonic constipation, an unwanted effect which occurs in a number of patients treated with pure 5-HT3 receptor antagonists. Additionally, the above mentioned drugs might be of value in post-operative conditions associated with intestinal adynamia and emesis sensitive to 5-HT3 receptor blockade.

Animals↗

PubMed2000

Mechanochemical solid-state polymerization (X): the influence of copolymer structure in copolymeric prodrugs on the nature of drug release.

From the standpoint of the mechanism of mechanochemical polymerization, two kinds of copolymeric prodrug, whose monomer sequence distribution (MSD) is different from each other, can be prepared by this polymerization under appropriate operational conditions: one is a random copolymer abundant in the longer block consisting of the same repeating units (multi-block copolymer), and the other is a block copolymer. To confirm the difference of MSD, the 13C-NMR spectra of poly(acrylamide-co-sodium acrylate) prepared by mechanochemical polymerization were measured and compared with the spectrum of that synthesized by a conventional radical-initiated solution polymerization, which produces the random copolymer normally. The results show that MSD in copolymers depends on the polymerization method (operational condition). We prepared three kinds of copolymeric prodrug consisting of acrylamide and vinyl monomer of 5-fluorouracil, whose MSD is different from one another. These copolymeric prodrugs had almost the same number average molecular weight, particle diameter and composition, and differed only in MSD. We compared the rate of drug release of these copolymeric prodrugs. The rate of drug release was the highest with the random copolymer, followed by the mechanochemically produced multi-block copolymer and the block copolymer. This result suggests that the rate of drug release depends on MSD of copolymeric prodrugs. These results are useful as they give a fundamental insight into the synthesis of copolymeric prodrugs having the desired rate of drug release.

Antimetabolites↗

PubMed1992

Fumaric acid production from hydrolysates of starch-based substrates.

Fumaric acid production by Rhizopus arrhizus from commercial hydrolysates of corn starch (i.e. glucose molasses) was studied at different initial concentrations of glucose (S) and C:N ratios (R) by performing a 3(2) factorial experiment. By using the response surface methodology and statistical analysis, fumaric acid (YF) and mycelial biomass (YX) yields, as referred to the initial concentration of glucose and fumaric acid productivity (PF), were fitted to the only significant first-order effects of S and R with mean percentage errors ranging from 11 to 15%. The resulting empiric models were used to determine the optimal values of S (100-130 g dm-3) and R (150-210 g-atom C per g-atom N) associated with YF and PF varying in the ranges 40-49% and 7-8.5 g dm-3 day-1, respectively. After establishing the validity of these data at the 95% confidence level, an optimal operating condition (S = 120 g dm-3 and R = 150) was further tested using other substrates (i.e. glucose and acid or enzymatic hydrolysates of cassava, corn and potato flours). Statistically significant improvements in the fumaric acid yield and productivity were determined with respect to the predicted values. Since the highest values of YF and PF were obtained from the acid hydrolysates of the starch-based materials and such values were also found to be insensitive to the substrate used (at a probability level of 0.05), the above operating condition might be further employed to minimise fumaric acid production costs as a function of the feedstock used.

Culture Media↗

PubMed1991

Spinal anaesthesia for inguinal hernia repair in high-risk neonates.

To avoid the high incidence of respiratory complications associated with general anaesthesia in premature neonates, 44 spinal anaesthetics for inguinal hernia repair in very low birthweight infants were administered in 47 attempts. Hyperbaric tetracaine with epinephrine 1:200,000 was administered in a dose range of 0.27-1.10 mg.kg-1. Attempted lumbar puncture failed in three infants. In 24 procedures, spinal anaesthesia alone provided satisfactory operating conditions; in 20, supplementary inhalational general anaesthesia or iv ketamine was necessary. Perioperative apnoeic episodes requiring bag/mask assisted ventilation occurred in six infants. In five infants, apnoeic spells occurred in the postoperative period. No infant required tracheal intubation; there was no haemodynamic instability. Twenty-four infants required no postoperative analgesia. Our experience suggests that spinal anaesthesia for inguinal hernia repair in very low birth weight infants reduces but does not eliminate the risk of respiratory instability, and that supplementary anaesthesia is often necessary to provide satisfactory operating conditions.

Anesthesia, Inhalation↗

PubMed2002

Removal of PCDD/F from incinerator flue gases by entrained-phase adsorption.

The emission abatement of polychlorinated dioxins and furans (PCDD/F) Issued from municipal solid waste incineration is growing in importance because of more stringent emission standards and general concern about their toxic characteristics. These substances cannot be separated by conventional gas cleanup processes but are successfully removed through adsorption onto carbonaceous materials. The simplest technique is the entrained-phase injection of pulverized adsorbents in the flue gas, followed by fabric filter separation. The various related techniques are briefly reviewed here. Operating conditions and results obtained from Flemish MSWIs are given. The results illustrate the excellent overall removal efficiency. Furans are adsorbed to a slightly higher extent than dioxins. PCDD/F removal by carbonaceous adsorbents is thereafter modeled from first principles for the contribution of both entrained-phase (eta1) and cake filtration (eta2) to the overall efficiency (etaT). Application of the model equations and comparison of measured and predicted overall efficiencies for the Flemish municipal solid waste incinerators (MSWIs) demonstrate that the approach is meaningful and that the dominant parameters are the operating temperature, the dosage and activity of adsorbent, and the fraction of adsorbent in the filter cake. The model equations enable the MSWI operators to predict the adsorption efficiencies for any combination of operating parameters and to assess the sensitivity of the process to varying operating conditions.

Adsorption↗

PubMed2001

Experimental design methodology applied to adsorption of metallic ions onto fly ash.

The objective of this study was to define operating conditions which would conciliate a high removal of the five metallic cations (Cu2+, Ni2+, Zn2+, Cd2+, Pb2+) and a low desorption of these metal ions from the contaminated sorbents. To achieve this goal the strategy relied on the use of experimental design methodology. The influence of four parameters (fly ash/lime mass ratio, type of fly ash/lime sorbent, solution temperature, and sorbent concentration) on the removal at pH = 5 and the stabilization of the five metallic ions was studied. In the first step, the influence of three parameters on the removal of Cu2+ ions was studied (R2 = fly ash/lime mass ratio, type of sorbent, temperature). It was found that the same set of parameter values would produce both the highest removal and the lowest desorption for this cation: R2 = 9 g g(-1), sorbent B (made by mixing fly ash and lime in water, then drying this paste at 105 degrees C for 24 h), temperature of suspension equal to 60 degrees C. The formation of calcium silicate hydrate (CSH), resulting from the pozzolanic activity of fly ash, is assumed to be partially responsible for these mechanisms. In the second step, simplex methodology and Doehlert matrix were used to find the conditions in a 2D space (sorbent concentration, temperature of solution) that would give the highest removal from a solution containing five metallic cations and the lowest desorption of these five cations adsorbed on the contaminated sorbents. Then, the system response that had to be optimized was the total metallic ions concentration (TMIC, mol L(-1)). A TMIC was measured both for adsorption and leaching experiments. These responses were modelized using a second-order polynomial and the surface responses were plotted for adsorption and desorption results. A difference was observed between operating conditions reaching the highest adsorption from those that gave the lowest desorption. However, an adsorbent concentration around 122 g L(-1) and a solution temperature of 66 degrees C would lead simultaneously to a high adsorption and a low desorption.

Adsorption↗

PubMed2000

The effect of chronic food and water restriction on open-field behaviour and serum corticosterone levels in rats.

In operant conditioning experiments, two methods are commonly used to motivate laboratory rats to perform designated tasks. The first is restricting food so that rats are forced to lose 20% of body weight within one week, followed by maintenance at 80% of the baseline weight for the remainder of the experiment. The second is restricting access to water to 15 min in each 24 h period. These methods are effective in motivating the animals. There is, however, little information available on the effects on performance in tests of behaviour that are not related to operant conditioning. In addition, it is not clear if these commonly used methods of food and water restriction will lead to physiological stress as indicated by an elevation of serum corticosterone. Male rats were either food-restricted to reduce and maintain their weight at 80% of baseline weight, or were restricted to 15 min access to water every 24 h. Activity in the open field was significantly greater in food-restricted rats than in water-restricted or control rats, but freezing behaviour was similar in all experimental groups. Food-restricted rats had a higher mean serum corticosterone level than water-restricted and control rats 37 days after the start of the experimental period. These data suggested that chronically restricting food and maintenance of body weight at 80% of baseline body weight led to significant behavioural changes and physiological stress. In contrast, water restriction did not lead to changes in behaviour or corticosterone levels. A second experiment was conducted to compare the effects of food restriction to 80% of baseline body weight, as described above, with a less stringent protocol in which test rats were initially reduced to 80% of baseline weight, but were then maintained at 80% of an ad libitum fed control rat's weight. Serum corticosterone levels and adrenal gland weights were measured after the initial week of forced weight loss and after maintenance for 21 days. Forced loss of 20% of body weight in the first week led to significantly increased serum corticosterone levels and adrenal gland weights compared to ad libitum fed controls. Serum corticosterone levels and adrenal gland weights in rats maintained at 80% of their initial body weight for 21 days remained higher than ad libitum fed control rats. However, rats maintained at 80% of an ad libitum fed control rat's weight did not differ from control rats in serum corticosterone levels or adrenal gland weights at the end of the 21-day study period. Adjustment of the feeding regimen in this manner eliminated physiological evidence of chronic stress.

Adrenal Glands↗

PubMed1999

A comparison of patient comfort during cataract surgery with topical anesthesia versus topical anesthesia and intracameral lidocaine.

OBJECTIVE: To determine whether intraocular lidocaine increases patient comfort during cataract surgery while under topical anesthesia. DESIGN: Prospective, randomized, double-masked, placebo-controlled clinical trial. PARTICIPANTS: Both men and women between 45 and 85 years of age who were scheduled for elective cataract surgery while under topical anesthesia participated. Sixty-eight patients were randomized to each group. INTERVENTION: Patients were randomized to receive either topical anesthesia plus intracameral 1% preservative-free lidocaine or intracameral balanced salt solution. MAIN OUTCOME MEASURES: Patient assessment of pain during delivery of the anesthesia, surgery, and after surgery using a visual analog pain scale was measured. Patients also recorded the degree to which they were bothered by tissue manipulation and the microscope light. Surgeon assessments of operative conditions, patient cooperation, and intraoperative complications were recorded. The attending anesthesiologist recorded any required supplemental intravenous sedation and any increase in pulse or increase in blood pressure. RESULTS: There was no significant difference in patient-reported pain scores for delivery of anesthesia (P = 0.902), surgery (P = 0.170), or after surgery (P = 0.680). Patients in the lidocaine group reported being less bothered by tissue manipulation (P = 0.021). The surgeon assessment showed more patient cooperation in the lidocaine group (P = 0.043). CONCLUSIONS: Both topical anesthesia alone and topical anesthesia plus intracameral lidocaine provide good operative conditions for the surgeon and comfortable surgical circumstances for the patient. Injection of intraocular lidocaine increases patient cooperation and decreases the degree to which patients are bothered by tissue manipulation, two outcomes that justify its use.

Administration, Topical↗