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At least 649 records · Page 36Linked to original sources
PubMed1991

On-line immunoaffinity sample pre-treatment for column liquid chromatography: evaluation of desorption techniques and operating conditions using an anti-estrogen immuno-precolumn as a model system.

An immunoaffinity precolumn (immuno-precolumn) containing an immobilized antibody directed against estrogen steroids, was used as a model system for the evaluation of different desorbing techniques, suitable for on-line coupling to column liquid chromatography (LC). Desorption of estrogen analytes from the immuno-precolumn proved to be impossible with the buffers and chaotropic solutions frequently used in affinity desorption. Micellar solutions are effective in obstructing the antibody-antigen reaction, but their use as desorbing solutions was not found to be practical because of the large interferences introduced into the chromatograms. Desorption with aqueous solutions at elevated temperature, created by microwave action or conventional heating, although effective is not practical in this instance, because the agarose used in this study as the stationary phase for the immuno-precolumn is prone to heat decomposition. The most effective and practical approach is desorption with a methanol-water mixture (95 + 5 v/v). On-line dilution of the eluate allows the concentration of the desorbed analytes using a reversed-phase LC system with subsequent separation and ultraviolet detection. The performance of the system with spiked urine and plasma samples, which were introduced directly into the system, was evaluated and the results were compared with immunoselective desorption.

Antibodies↗
PubMed1983

Separation of glycosylated haemoglobins using immobilized phenylboronic acid. Effect of ligand concentration, column operating conditions, and comparison with ion-exchange and isoelectric-focusing.

Haemoglobins from diabetic and non-diabetic individuals have been separated by affinity chromatography using immobilized phenylboronate, which interacts specifically with diol-containing compounds such as glycosylated haemoglobin. The effects of ligand concentration, flow rate, column geometry, preincubation of sample, buffer composition and temperature have been investigated. Significant correlation was found between results from affinity-chromatography and ion-exchange and isoelectric-focusing methods. Isoelectric-focusing of the haemoglobin fractions obtained from affinity chromatography indicate that, in addition to haemoglobin A1c, some haemoglobin A is also bound to immobilized phenylboronic acid. Assays of haemolysates obtained from red blood cells incubated in glucose solutions suggest that unstable pre-(haemoglobin A1c) does not interfere. The assay is not affected by the presence of haemoglobin F.

Boronic Acids↗
PubMed2003

[Ultrasound-guided interventions using magnetic field navigation. First experiences with Ultra-Guide 2000 under operative conditions].

AIM: Ultrasound-guided interventions are presently performed as free-hand-type procedures or using biopsy transducers. In this article we report on our experience with a new navigation-system for sonographically guided interventional procedures under OR-conditions. METHODS: The US-Guide 2000 trade mark is an electromagnetic guidance system that assists physicians in ultrasound-guided interventional procedures. This system accommodates both in-plane and out-of-plane needle placement. We evaluated this system for the first time under OR-conditions. Overall, for 39 interventional procedures (23 thermoablations of malignant liver lesions, 16 diagnostic punctures) were performed. RESULTS: All targets were reached successfully without any complications. No interactions with other OR-devices were seen. CONCLUSION: The US-Guide 2000 trade mark as a virtual needle-guiding system allows a safe and accurate sonographically assisted intervention. The major advantage is the possibility of out-of-plane needle placement and the combination of flexibility of free-hand-type procedures with the accuracy of a biopsy transducer. This increases the safety of punctures especially when lesions are difficult to reach and/or are situated next to vulnerable structures. It also reduces the interventional trauma.

Biopsy, Needle↗
PubMed2004

Experimental assessment of the operative conditions of copper extraction from three contaminated soils.

Column experiments of EDTA extraction of copper from a sandy, a calcareous, and a highly organic soil, were performed. The influence of EDTA concentration, pH, and the flow rate of a flushing solution on copper extraction yield was investigated. Extraction yields of 84.8%, 93.0% and 96.9% were achieved respectively for sandy soil, calcareous soil and highly organic soil, after the injection of a volume of flushing solution equal to 15 pore volumes. TOC measurements performed on the extracted solution showed that, after the extraction phase, the percolation of an equal volume of water was necessary to ensure complete EDTA removal from the treated soils. In addition, results showed that the simultaneous dissolution of calcite consumed approximately 93.6% of the chelant agent when EDTA concentration in the flushing solution was 0.05 M.

Chelating Agents↗
PubMed2005

Evaluation of trickle-bed air biofilter performance under periodic stressed operating conditions as a function of styrene loading.

Trickle-bed air biofilters (TBABs) are suitable for treating volatile organic compounds (VOCs) at a significantly high practical loading because of their controlled environmental conditions. The application of TBAB for treating styrene-contaminated air under periodic backwashing and cyclical nonuse periods at a styrene loading of 0.64-3.17 kg chemical oxygen demand (COD)/m3 x day was the main focus of this study. Consistent long-term efficient performance of TBAB strongly depended on biomass control. A periodic in situ upflow with nutrient solution under media fluidization, that is, backwashing, was approached in this study. Two different nonuse periods were employed to simulate a shutdown for equipment repair or during weekends and holidays. The first is a starvation period without styrene loading, and the second is a stagnant period, which reflects no flow passing through the biofilter. For styrene loadings up to 1.9 kg COD/m3 x day, removal efficiencies consistently above 99% were achieved by conducting a coordinated biomass control strategy, that is, backwashing for 1 hr once per week. Under cyclical nonuse periods for styrene loadings up to 1.27 kg COD/m3 x day, stable long-term performance of the biofilter was maintained at more than 99% removal without employing backwashing. No substantial impact of nonuse periods on the biofilter performance was revealed. However, a coordinated biomass control by backwashing subsequently was unavoidable for attaining consistently high removal efficiency at a styrene loading of 3.17 kg COD/m3 x day. As styrene loading was increased, reacclimation of the biofilter to reach the 99% removal efficiency following backwashing or the nonuse periods was delayed. After the non-use periods, the response of the biofilter was a strong function of the biomass in the bed. No significant difference between the effects of the two different nonuse periods on TBAB performance was observed during the study period.

Air Movements↗
PubMed2002

Effect of operating conditions on the separation of ammonium and nitrate ions with nanofiltration and reverse osmosis membranes.

This paper presents the pilot scale membrane separation studies on the Elmali Lake raw water in Istanbul, which is highly polluted by discharging of sewage waters. Low pressure nanofiltration (NF) and reverse osmosis (LPRO) membranes having the surface area of 2 m2 have been used during the experimental runs. Experiments were conducted at different pressures, temperature and pH ranges. Feed flow rate was about 300 L/h. As a result, flux values increased linearly with increasing pressure. Ammonia and nitrate ion rejections also increased with increasing pressure and characteristics of rejection were similar for the both types of membranes. Permeate flux value increased proportionally with the temperature. The temperature changing has also influenced the rejection rate of ammonia and nitrate ions. Both ammonia and nitrate ion rejections at neutral pH values were very high. Therefore, neutral pH value is suitable for TFC-S and TFC-HR membranes to remove ammonia and nitrate ions.

Filtration↗
PubMed1994

Nitrous oxide does not influence operating conditions or postoperative course in colonic surgery.

We studied 150 patients undergoing elective colonic surgery; they were allocated randomly to undergo artificial ventilation with either air-oxygen or nitrous oxide-oxygen during surgery. Eleven patients were excluded. Preoperative management, surgery and postoperative analgesia were similar in both groups. Anaesthesia included propofol by infusion, pancuronium and fentanyl 3 micrograms kg-1 h-1. The air-oxygen group required a continuous infusion of propofol of 4-6 mg kg-1 h-1 whereas the nitrous oxide-oxygen group required only 1-2 mg kg-1 h-1. There were no differences between the groups in duration of anaesthesia, distension of the bowel and postoperative bowel function. The postoperative hospital stay was similar for both groups.

Adult↗
PubMed2004

Fluid dynamic analysis of the 50 cc Penn State artificial heart under physiological operating conditions using particle image velocimetry.

In order to bridge the gap of existing artificial heart technology to the diverse needs of the patient population, we have been investigating the viability of a scaled-down design of the current 70 cc Penn State artificial heart. The issues of clot formation and hemolysis may become magnified within a 50 cc chamber compared to the existing 70 cc one. Particle image velocimetry (PIV) was employed to map the entire 50 cc Penn State artificial heart chamber. Flow fields constructed from PIV data indicate a rotational flow pattern that provides washout during diastole. In addition, shear rate maps were constructed for the inner walls of the heart chamber The lateral walls of the mitral and aortic ports experience high shear rates while the upper and bottom walls undergo low shear rates, with sufficiently long exposure times to potentially induce platelet activation or thrombus formation. In this study, we have demonstrated that PIV may adequately map the flow fields accurately in a reasonable amount of time. Therefore, the potential exists of employing PIV as a design tool.

Blood Flow Velocity↗
PubMed2006

The role of gas dynamics in operation conditions of a Pulsed Microplasma Cluster Source for nanostructured thin films deposition.

This study intends to explain the fluid dynamic characteristics of a Pulsed Microplasma Cluster Source (PMCS). An axially symmetric steady state simulation is performed for modeling the real-life three-dimensional unsteady flow of hypersonic helium inside our PMCS. Hypersonic helium flow is simulated using Realizable k-epsilon turbulent model. We obtained the jet velocity, density, and pressure field inside our PMCS for the conditions considered and discussed them with respect to our experimental observations. We also presented a qualitative discussion on the formation-termination process of this hypersonic jet. In particular, simulation, in agreement with the experiment, indicates that the middle stage of the injection process, where the Mach disk stands close to the ablation target and at the same time the mass flow rate is relatively high, is almost the appropriate time for firing the electric discharge. We simulated the jet-electrode impingement and tracked the trajectory of the ablated carbon clusters, considered as rigid spheres, inside the PMCS. We noticed that the spatial distribution of the clusters inside PMCS is highly conserved during the free expansion of the cluster beam out of the nozzle (in the vacuum chambers) and is recognizable in the deposited carbon film. This indicates that the geometry of PMCS plays a significant role in the uniformity of the deposited film.

Computer Simulation↗