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PubMed2003

A mathematical model of lateral flow bioreactions applied to sandwich assays.

Lateral flow (LF) biodetectors facilitate low-cost, rapid identification of various analytes at the point of care. The LF cell consists of a porous membrane containing immobilized ligands at various locations. Through the action of capillary forces, samples and reporter particles are transported to the ligand sites. The LF membrane is then scanned or probed, and the concentration of reporter particles is measured. A mathematical model for sandwich assays is constructed and used to study the performance of the LF device under various operating conditions. The model provides insights into certain experimental observations including the reduction in the level of the detected signal at high target analyte concentrations. Furthermore, the model can be used to test rapidly and inexpensively various operating conditions, assist in the device's design, and optimize the performance of the LF device.

Biosensing Techniques↗

PubMed2006

Outpatient arthroscopic knee surgery under combined local and intravenous propofol anesthesia in children and adolescents.

BACKGROUND: This prospective observational study included a case series of children and adolescents receiving light intravenous propofol anesthesia combined with local anesthesia (LA) for arthroscopic knee procedures. The aim was to examine the merits of anesthesia, to discuss the indications for the procedure and to analyze recovery/discharge times from the postanesthesia care unit (PACU). METHODS: A cohort of 147 children and adolescents (ASA 1 and 2) aged 12-18 years admitted for outpatient arthroscopic knee procedures between January 2004 and May 2005 were studied. After IV access in the operating theater, the patients received propofol (10 mg.ml(-1)). Arthroscopy was performed approximately 15 min after injecting local anesthetic (15 ml 2% lidocaine with epinephrine 1:200,000) partly at the site of insertion of the arthroscope and other instruments (5 ml), and the rest intra-articular. The following parameters were assessed: airway patency, propofol requirement, vital signs, procedure time, surgical operating conditions, patient satisfaction score, time to discharge, postoperative analgesia and adverse events. RESULTS: Of 147 patients, 133 patients (90.5%) underwent arthroscopic knee surgery, whereas knee arthroscopy alone was performed in 14 patients (9.5%) without indication for operative treatment. The arthroscopy was well tolerated in 96.6% patients (no pain, movement or discomfort during the procedure) and only five patients required conversion to general anesthesia. Pain experienced during the injection of lidocaine was more severe than pain experienced during the surgical procedure itself (P < 0.001). The surgical evaluation of operative conditions (visualization and access to intra-articular structures) was generally satisfactory and completely acceptable. Almost 94% (138/147) of patients said they would have the same procedure again under the same type of anesthesia. The mean propfol induction dose was 1.4 mg.kg(-1) (range: 0.9-3.8) and mean propofol infusion rate 167 microg.kg(-1).min(-1) (range: 130-250). Movement was more likely at lower infusion rates (mean: 151 microg.kg(-1).min(-1)). The maximal decrease in respiratory rate was 5.9 +/- 5.1 br.min(-1) (27.2 +/- 21%) and no patient became hypoxic. Patients recovered to preoperative values at 9.8 +/- 7.5 min following infusion discontinuation. There were no respiratory or cardiovascular complications. The mean stay in PACU was 47 min (range: 32-150). As many as 71% (105/147) of patients required no analgesics during the first two postoperative hours. CONCLUSIONS: The combination of light intravenous propofol anesthesia combined with local anesthesia for arthroscopic knee procedures provided effective sedation, good preservation of upper airway patency, rapid recovery and pain relief without major side effects and offers a good alternative to the methods already available. The majority of patients did not require postoperative analgesia.

Adolescent↗

PubMed1997

A comparison of the nasal mask and the nasopharyngeal airway in paediatric chair dental anaesthesia.

This study compared the quality of anaesthesia and surgical access afforded by two techniques for the administration of anaesthesia during paediatric chair dental procedures. A total of 50 ASA 1 paediatric day case patients were randomly assigned to receive anaesthesia through either the traditional Goldman nasal mask or through a nasopharyngeal airway. Patients in the nasal mask group were judged to have significantly worse airway patency (p = 0.0001) and significantly more episodes of airway obstruction (14 vs. 4; p = 0.0032) than those in the nasopharyngeal airway group. Anaesthetic, surgical and oxygen saturation data did not differ significantly between the two groups. Operating conditions were universally graded as excellent in the nasopharyngeal airway group, while those in the nasal mask group were graded as excellent/good in only 79% of cases (p < 0.0001). These results suggest that better quality anaesthesia and operating conditions can be achieved by using a nasopharyngeal airway rather than the traditional nasal mask for the administration of anaesthesia to paediatric chair dental patients.

Adolescent↗

PubMed1982

[The risk of anaesthesia. Investigations based on 153,660 anaesthetic procedures (author's transl)].

153,660 protocols of general and local anaesthesias were evaluated according to the complications observed during anaesthesia. The complications recorded were analysed with respect to the following criteria: type of anaesthetic procedure, experience of the anaesthesiologist, urgency of the operation and pre-operative condition (risk group) of the patient. The study shows that under the requirements of anaesthetic treatment at a university clinic, the degree of risk connected with anaesthesia is only slightly dependent on the type of the anaesthetic procedure and the experience of the physician performing the anaesthesia. Distinct differences in the complications recorded are found to be dependent on the urgency of the operation (cardiovascular and technical complications) and on the pre-operative condition of the patient (cardiovascular complications). A further decrease of the anaesthetic risk is only possible if all measures for optimal preparation before an operation are fully met and compromises are avoided to the utmost. However, spectacular improvement must not be expected with these measures.

Anesthesia↗

PubMed2005

Comparison of cellulose solubilisation rates in rumen and landfill leachate inoculated reactors.

The aim of this study was to conduct a number of controlled digestions to obtain easily comparable cellulose solubilisation rates and to compare these rates to those found in the literature to see which operational differences were significant in affecting cellulose degradation during anaerobic digestion. The results suggested that differences in volumetric cellulose solubilisation rates were not indicative of the true performance of cellulose digestion systems. When cellulose solubilisation rates were normalised by the mass of cellulose in the reactor at each time step, the comparison of the rates became more meaningful. Cellulose solubilisation was surface area limited. Therefore, changes in the loading rate of cellulose to the reactor altered the volumetric solubilisation rate without changing the mass normalised rate. Comparison of mass normalised solubilisation rates from this study and the literature demonstrated that differences in reactor configuration and operational conditions did not significantly impact on the solubilisation rate whereas the difference in composition of the microbial communities showed a marked effect. This work highlights the importance of using appropriately normalised data when making comparisons between systems with differing operational conditions.

Animals↗

PubMed2004

Membrane gas transfer under conditions of creeping flow: modeling gas composition effects.

A computational model was developed to predict gas transfer and gas composition changes in membrane modules designed for addition of gases to groundwater. The model was verified using pilot-scale gas transfer experiments. The modeling and experimental results suggest that back diffusion of dissolved gases into the membrane has a significant effect on gas transfer via hollow-fiber membrane. In the experimental study, N(2) back-diffusion reduced the partial pressure of O(2) within the membrane and decreased the concentration gradient for gas transfer. The model was able to simulate both the dynamic and steady-state gas transfer behavior of the membranes under a variety of operating conditions. This model can be used to estimate gas transfer as a function of different membrane module design and operating conditions.

Equipment Design↗

PubMed2004

Investigation of biological and fouling characteristics of submerged membrane bioreactor process for wastewater treatment by model sensitivity analysis.

In this study, a mathematical model for the submerged membrane bioreactor (SMBR) was developed. The activated sludge model No. 1 (ASM1) was modified to be suitable for describing the characteristics of the SMBR, and the resistance-in-series model was integrated into the ASM1 to describe membrane fouling. Using the newly developed model, the biological and fouling characteristics of the submerged membrane bioreactor process for wastewater treatment was investigated by sensitivity analysis. The sensitivity of effluent COD and nitrogen, TSS in the reactor and membrane flux with respect to each parameter (K(h), mu(H), K(S), K(NHH), K(NOH), b(H), Y(H), mu(A), K(NHA), b(A), Y(A), K(m) and alpha) was investigated by model simulation. As a result, the most important factors affecting membrane fouling were hydrolysis rate constant (K(h)) and cross-flow effect coefficient (K(m)). Heterotrophic yield coefficient (Y(H)) had a great influence on effluent quality. Effluent quality was also somewhat sensitive to K(h). Peculiar operating conditions of the SMBR such as long solids retention time (SRT), absolute retention of solids by membrane and high biomass concentration in bioreactor could explain these model simulation results. The model developed in this study would be very helpful to optimize operating conditions as well as design parameters for a SMBR system.

Biofilms↗

PubMed2002

Optimisation of the coagulation-flocculation process of raw water by optimal design method.

In the present paper, a systematic study of the influence of raw water quality and operating conditions on the effectiveness of the coagulation-flocculation process using aluminium sulphate (AS) is presented. The influence of raw water composition is studied at two levels, fractional factorial designs and a Doehlert uniform shell design to determine the influence of the operating conditions. The analysis of the experimental responses (residual turbidity and minimally AS dose are denoted as (Tu(m)) and (AS(m)), respectively) shows that the parameters which have the greatest influence change depending on the response. It is not always possible, for a given water composition, to obtain simultaneously low residual turbidity and minimally AS dose. However, under the conditions of this study, the search for a criterion of optimisation must bear the minimisation of residual turbidity, because it remains the principal criterion of effectiveness of the process, even, if in a few cases, it results in an increase in the cost of treatment.

Alum Compounds↗

PubMed2004

Patient-controlled sedation with propofol in minor oral surgery.

PURPOSE: We sought to evaluate the benefits of patient-controlled sedation with propofol for minor oral surgery. PATIENTS AND METHODS: After instructions were given on how to use the technique, 28 male and 24 female patients sedated themselves during minor oral surgery with titrating 18-mg bolus doses of propofol with a lockout period of 1 minute. RESULTS: Surgery lasted from 5 to 29 minutes; 28 patients were moderately and 17 were deeply sedated. Seven patients were oversedated. All of those who were oversedated responded to commands within 1 minute of being unresponsive and continued to obtain increments of propofol. Vital signs were stable in all patients even during oversedation. Eighteen patients were talkative, and 17 complained of pain along the vein. Operating conditions were good in 38, fair in 12, and poor in 2. The majority, 48 patients, were relaxed, and 47 were willing to undergo the sedation technique again. Ten had total, 22 had partial, and 20 had no amnesia. CONCLUSIONS: Relaxed patients, good operating conditions, and quick recovery of oversedated patients without unstable vital signs provide evidence that propofol has favorable pharmacokinetic and pharmacodynamic properties for patient-controlled sedation. This study also highlights the importance of close monitoring of patients during patient-controlled sedation.

Adolescent↗

PubMed2005

Optimisation and robustness analysis of a hydrophobic interaction chromatography step.

Process development, optimisation and robustness analysis for chromatography separations are often entirely based on experimental work and generic knowledge. The present study proposes a method of gaining process knowledge and assisting in the robustness analysis and optimisation of a hydrophobic interaction chromatography step using a model-based approach. Factorial experimental design is common practice in industry today for robustness analysis. The method presented in this study can be used to find the critical parameter variations and serve as a basis for reducing the experimental work. In addition, the calibrated model obtained with this approach is used to find the optimal operating conditions for the chromatography column. The methodology consists of three consecutive steps. Firstly, screening experiments are performed using a factorial design. Secondly, a kinetic-dispersive model is calibrated using gradient elution and column load experiments. Finally, the model is used to find optimal operating conditions and a robustness analysis is conducted at the optimal point. The process studied in this work is the separation of polyclonal IgG from BSA using hydrophobic interaction chromatography.

Adsorption↗

PubMed1999

Sophorolipid production by Candida bombicola: medium composition and culture methods.

Candida bombicola is able to produce sophorolipid molecules with surfactant properties when grown in a medium composed of two different carbon sources (usually sugar and oil) and a nitrogen source (frequently yeast extract). In this work, the composition of the medium and the culture method employed have been studied. The influences of glucose concentration, properties of oil and yeast extract concentration have been taken into account. Accordingly, a production medium composition is proposed (100 g/l glucose, 100 g/l sunflower oil and 1 g/l yeast extract). The most frequent culture methods reported in literature, i.e. batch, medium pulse mode and resting-cell methods, have been tested. The resting-cell method was found to produce the highest final concentration of sophorolipid, obtaining a good yield of carbon sources in a relatively short time. Under the best operational conditions and using the resting-cell method, 120 g/l sophorolipid was obtained in 8 d, with a carbon source yield of 0.60. Product distribution has also been investigated and the sophorolipid molecular structure of opened or cycled molecules has been determined under different operational conditions. Low yeast extract concentration and long fermentation time enhance the production of cycled structures by all the production methods studied.

Journal Article↗

PubMed2002

The effect of C/N ratio on ammonia oxidising bacteria community structure in a laboratory nitrification-denitrification reactor.

A laboratory scale reactor operated as a single sludge, denitrification-nitrification bioreactor (DNB), was fed a synthetic wastewater. The effect of the C/N ratio of the influent on the structure of beta-proteobacterial autotrophic ammonia-oxidizing bacterial (AOB) communities was determined by DGGE analysis of 16S rRNA gene fragments amplified using a range of AOB-selective primers. Fluorescence in situ hybridisation (FISH) was used to determine quantitative changes in the AOB communities. When operated at a C/N ratio of 2 the DNB was effective in nitrogen removal and nitrification was measured at approximately 1.0 mg NH4+-N/g dry wt/h. Altering the C/N ratio to 5 resulted in a 50% reduction in nitrification rates. Nitrification was restored to its original level when the C/N ratio was returned to 2. AOB were detected by DGGE analysis of samples from the DNB under all operating conditions but the changes in C/N ratio and nitrification rates were accompanied by changes in the community structure of the AOB. However, quantitative FISH analysis indicated that beta-proteobacterial AOB were only present in high numbers (ca. 10(8) cells/ml) under the original operating conditions with a C/N ratio of 2. Beta-proteobacterial AOB could not be detected by FISH when the C/N ratio was 5. When nitrification activity was restored by returning the C/N ratio to 2, beta-proteobacterial AOB were still not detected and it is likely that either beta-proteobacterial AOB were not responsible for ammonia oxidation or that beta-proteobacterial AOB that did not contain the target sites for the range of 4 AOB selective probes used, were present in the reactor.

Ammonia↗

PubMedDate not supplied

Pretreatment of swine wastewater using anaerobic filter.

Efforts were made to assess the efficiency of an anaerobic filter packed with porous floating ceramic media and to identify the optimum operational condition of anaerobic filter as a pretreatment of swine wastewater for the subsequent biological removal of nitrogen and phosphorus. A stepwise decrease in hydraulic retention time (HRT) and an increase in organic loading rate (OLR) were utilized in an anaerobic filter reactor at mesophilic temperature (35 degrees C). The optimum operating condition of the anaerobic filter was found to be at an HRT of 1 d. A soluble chemical oxygen demand (COD) removal efficiency of 62% and a total suspended solids removal efficiency of 39% at an HRT of 1 d were achieved with an OLR of 16.0 kg total COD/(m3.d), respectively. The maximum methane production rate approached 1.70 vol of biogas produced per volume of reactor per day at an HRT of 1 d. It was likely that the effluent COD/total Kjeldahl nitrogen ratio of 22, the COD/total phosphorous ratio of 47, and the high effluent alkalinity >2500 mg/L as CaCO3 of the anaerobic filter operated at an HRT of 1 d was adequate for the subsequent biological removal of nitrogen and phosphorus.

Animals↗

PubMed2006

Mass transfer within electrostatic precipitators: trace gas adsorption by sorbent-covered plate electrodes.

Varying degrees of mercury (Hg) capture have been reported within the electrostatic precipitators (ESPs) of coal-fired electric utility boilers. There has been some speculation that the adsorption takes place on the particulate-covered plate electrodes. This convective mass transfer analysis of laminar and turbulent channel flows provides the maximum potential for Hg adsorption by the plate electrodes within an ESP under those conditions. Mass transfer calculations, neglecting electrohydrodynamic (EHD) effects, reveal 65% removal of elemental Hg for a laminar flow within a 15-m-long channel of 0.2-m spacing and 42% removal for turbulent flow within a similar configuration. Both configurations represent specific collection areas (SCAs) that are significantly larger than conventional ESPs in use. Results reflecting more representative SCA values generally returned removal efficiencies of <20%. EHD effects, although potentially substantial at low Reynolds numbers, diminish rapidly with increasing Reynolds number and become negligible at typical ESP operating conditions. The present results indicate maximum Hg removal efficiencies for ESPs that are much less than those observed in practice for comparable ESP operating conditions. Considering Hg adsorption kinetics and finite sorbent capacity in addition to the present mass transfer analyses would yield even lower adsorption efficiencies than the present results. In a subsequent paper, the author addresses the mass transfer potential presented by the charged, suspended particulates during their collection within an ESP and the role they potentially play in Hg capture within ESPs.

Adsorption↗

PubMed2006

Baeyer-Villiger oxidation of cyclohexanone to epsilon-caprolactone in airlift sonochemical reactor.

Baeyer-Villiger oxidation of cyclohexanone to epsilon-caprolactone was studied in a new type reactor--the airlift loop sonochemical reactor. The reactor plays a synergistic effect of sonochemsity and higher oxygen transfer rate. The influences of ultrasound intensity, reaction temperature, the molar ratio of benzaldehyde to cyclohexanone and oxygen gas flow rate on the conversion and selectivity of cyclohexanone were investigated and discussed. Under ultrasound, the amount of benzaldehyde can be reduced from 75% to 67%. Ultrasound not only intensified the rates of reactions but also increased the yield of product. The optimized operation conditions are listed as follows: the reaction temperature is 30 degrees C, the molar ratio of cyclohexanone to benzaldehyde is 1:2, the oxygen gas flow rate is 1.15 cm s(-1), and ultrasonic irradiations 2h at 40 kHz, 2.25 W cm(-2). Under the optimum operation conditions, the average molar yield of epsilon-caprolactone comes up to 87.7%.

Journal Article↗

PubMed2001

Modeling of copper biosorption by Arthrobacter sp. in a UF/MF membrane reactor.

Copper biosorption by Arthrobacter sp. has been studied in this work. The process has been realized inside of a ultrafiltration/microfiltration (UF/MF) reactor in order to confine cells. A mathematical model has been developed that is able to predict experimental data under different operating conditions. The model takes into account different phenomena, which might occur during the process, such as a dependence of equilibrium parameters on pH, a partial cell disruption, and a change in the membrane retention properties at high biomass concentrations. Experimental tests have been performed under different operating conditions: a full factorial design has been implemented with pH (levels: 4, 5, and 6 units) and biomass concentration (levels: 1 and 5 g/L) as factors. A simple mathematical model based on metal mass balance taking into account the effect of pH on the Langmuir equilibrium adsorption parameters well fitted experimental data at low pH values and biomass concentrations. A more complex mathematical model, which considers a partial cell disruption during the biosorption trial, was proposed to understand and analyze the anomalous system behavior at pH = 6 and biomass concentration equal to 5 g/L. The effect of mechanical stress on biomass performances was also examined by using a discontinuous system (test tube trials) simulating the membrane reactor apparatus. In this alternative system biosorption trials were carried out in test tubes in such a way to avoid or at least minimize the disruption due to mechanical stress. Experimental results obtained by using this system can be modeled up to pH = 5 without considering cell disruption phenomenon, while at pH = 6 possible chemical reactions of biomass constituents could happen.

Adsorption↗

PubMed1990

Production of 5'-ribonucleotides by enzymatic hydrolysis of RNA.

Study of optimal operational conditions for RNA enzymatic hydrolysis to obtain 5'-ribonucleotides has been carried out. RNA from brewer's yeasts, obtained by ammonium extraction, was hydrolysed by a partially purified 5'-phosphodiesterase from barley rootlets. Temperature of 60 degrees C and pH 7 have been determined as the best operational conditions. Low RNA initial concentration (approximately 0.1%) and reaction time (approximately 1 h) have been identified as necessary to obtain a good yield of 5'-ribonucleotides.

Hydrolysis↗

PubMed2006

Estimation of respiratory gas exchange: a comparative study of linear and nonlinear model-based estimation techniques.

Monitoring of respiratory gas exchange in humans is an important task in order to establish the physical condition of the patient and to control important physiological indices. In a previous work, we proposed an approximated linear dynamical model of gas exchange within a controlled volume, to be used as a basis for Kalman filtering technique in order to improve the accuracy of the estimates. In this paper, we propose an alternative nonlinear dynamical model of the same phenomenon and suggest the use of a nonlinear estimation technique. A simulation study demonstrates that operative conditions exist where the latter results are more accurate than the estimates based on the linear model. A set of controlled experiments are also designed in order to create situations in which the above difference is significant. In the paper it is evidenced that, in different operative conditions, the analysis both of simulated and experimental data, give systematically the same indications about the choice of the filtering method. The conclusive result of this paper is that a nonlinear model, and the corresponding nonlinear estimation technique, turn out to be convenient when the operative volume and the accuracy of the instrumentation of the experimental set up are both low (operative volumes of about ten liters and flows measurements errors with variances not less than 1 [liter/min]2). It should be also remarked that the proposed model-based estimation techniques, both linear and nonlinear, are highly superior to conventional methods used in medical practice. The present study provides insights and guidelines that can also be useful when dealing with similar gas exchange estimation problems in many other different application areas.

Algorithms↗