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At least 1,171 records · Page 65Linked to original sources

PubMed2003

Three-component competitive adsorption model for flow-through PAC systems. 1. Model development and verification with a PAC/membrane system.

Natural organic matter (NOM) interferes with the adsorption of trace organic compounds on porous adsorbents such as powdered activated carbon (PAC) by pore blockage and direct competition for adsorption sites. The competitive effect of NOM in flow-through systems in which the retention time of the PAC is greater than the hydraulic retention time of the system can be magnified because NOM from the influent water can continue to adsorb on the PAC retained in the system. As a result, the adsorption capacity and the diffusion coefficient of trace compounds can decrease as NOM from the influent water accumulates. In this study, a dynamic three-component adsorption model was developed to quantitatively describe the removal of a trace compound from water in flow-through PAC processes. The system was simplified by using p-dichlorobenzene (p-DCB) to represent the NOM fraction that competes directly with the target trace organic atrazine for adsorption sites and by using poly(styrene sulfonate) (PSS-1.8k) to represent large, pore-blocking NOM. The model was based on the homogeneous surface diffusion assumption with the adsorption capacity of atrazine being gradually adjusted using a simplified version of the ideal adsorbed solution theory model developed in this study. The surface diffusion coefficients of atrazine and p-DCB were modeled as a function of the surface concentration of the pore-blocking compound, PSS-1.8k. The model was verified experimentally with a PAC/microfiltration (MF) system. The use of single-solute adsorption parameters obtained from batch isotherm and kinetic tests resulted in good model predictions for the adsorption of atrazine and the two model compounds under operating conditions typical of PAC/MF systems. The model will be applied to study various operating conditions and other system parameters of PAC/membrane systems in part 2 of this study.

Adsorption↗

PubMed2004

Mice lacking 5-HT receptors show specific impairments in contextual learning.

Using 5-HT(7) receptor knockout mice it has been shown that the 5-HT(7) receptor is the main mediator of serotonin-induced hypothermia but very little is known about the relevance of 5-HT(7) receptors in behaviour. We here report that lack of 5-HT(7) receptors leads to a specific learning deficit that is not due to general sensory or behavioural deficits. The knockout mice show impaired contextual fear conditioning but no significant deficits in motor and spatial learning or cued and operant conditioning. In addition, we demonstrate that 5-HT(7) receptor knockout mice display decreased long-term synaptic plasticity within the CA1 region of the hippocampus. The results indicate an important role for the 5-HT(7) receptor in contextual hippocampal-dependent learning and suggest a possible neuronal correlate for such a role is present within the CA1 region of the hippocampus.

Adaptation, Ocular↗

PubMed2004

Patient maintained propofol sedation for dental surgery.

AIM: This study evaluated a system for patients to operate a target-controlled infusion (TCI) of propofol for sedation. PARTICIPANTS: 50 healthy adults, undergoing minor oral surgical procedures under local anaesthesia. METHODS: Following instructions, patients were allowed to control their own sedation to comfortably undergo surgery. OUTCOME MEASURES: Operating conditions, degree of sedation, vital signs and patients' assessment of the technique. RESULTS: Operating conditions were described as good in 47 patients and fair in 3. Optimal sedation was provided at a median target blood concentration of 2 mcg/ml (range1-3mcg/ml). 30 were sedated moderately, 16 deeply and 4 mildly. None were oversedated. The vital signs were stable in all patients. 30% of patients had injection pain and 28% became talkative. Patient satisfaction was high with 86% feeling adequately relaxed and 92% willing to use it again. 14 patients had complete and 22 had partial amnesia for the procedure. CONCLUSIONS: This technique combines the benefits of target-controlled infusion with patient-controlled feedback and produces safe dental sedation.

Adult↗

PubMed2003

Appropriate conditions or maximizing catalytic reduction efficiency of nitrate into nitrogen gas in groundwater.

This study focused on the appropriate catalyst preparation and operating conditions for maximizing catalytic reduction efficiency of nitrate into nitrogen gas from groundwater. Batch experiments were conducted with prepared Pd and/or Cu catalysts with hydrogen gas supplied under specific operating conditions. It has been found that Pd-Cu combined catalysts prepared at a mass ratio of 4:1 can maximize the nitrate reduction into nitrogen gas. With an increase in the quantity of the catalysts, both nitrite intermediates and ammonia can be kept at a low level. It has also been found that the catalytic activity is mainly affected by the mass ratio of hydrogen gas to nitrate nitrogen, and hydrogen gas gauge pressure. Appropriate operating values of H(2)/NO(3)-N ratio, hydrogen gas gauge pressure, pH, and initial nitrate concentration have been determined to be 44.6g H(2)/g N, 0.15 atm, 5.2 (-), 100 mg x L(-1) for maximizing the catalytic reduction of nitrate from groundwater.

Ammonia↗

PubMed1984

Hearing in children.

The hearing tests for neonates, babies and young children must be adapted to the age of the patient. Neonates and young babies (under 9 months of age) are best examined with non-conditioned reflexes. For young children operant conditioning is the most suited technique. Preventive medicine is very much interested in hearing screening. We insist on a thorough history taking of the parents and on the importance of the high risk register for the early detection of congenital sensorineural hearing loss. We suspect that tympanometric screening of otitis serosa still is in an experimental stage.

Acoustic Stimulation↗

PubMed2005

Tramadol premedication in operative extraction of the mandibular third molar: a placebo-controlled crossover study.

Anxiolytic drugs are widely used for premedication in oral surgery. Since anxiety is usually associated with the fear of pain, we tested the effects of the analgesic tramadol in premedication before operative extraction of the mandibular third molar under local anesthesia. In a double-blind crossover study, 20 patients were randomized to receive 100 mg oral tramadol or placebo 1 h before operation. Anxiety, nausea, dryness of the mouth, pain and discomfort were recorded before administration of the drug, immediately before and after operation, and 0.5, 1, and 2 h postoperatively using ungraded 0-100 mm VAS scales. Blood pressure and heart rate were measured at the same times; vigilance was tested using the Maddox Wing Test and sensorimotor performance using the Trieger Dot Test; hemoglobin oxygen saturation (SpO2) was measured using a pulse oximeter. In addition, SpO2 and heart rate were recorded continuously in nine patients using a pulse oximeter connected to a computer. The surgeon assessed the quality of operating conditions on the VAS scale. Tramadol delayed and decreased the need of analgesics on the day of operation (p < 0.05). The operating conditions were better in patients on tramadol premedication than in those on placebo during the first operation (p < 0.05), but no differences were seen in patient well-being between treatments. The second operation was less stressful than the first. Tramadol is recommended only with special indications for premedication of patients undergoing third molar extraction under local anesthesia.

Adult↗

PubMed2006

Repeated cocaine effects on learning, memory and extinction in the pond snail Lymnaea stagnalis.

The persistence of drug addiction suggests that drugs of abuse enhance learning and/or impair extinction of the drug memory. We studied the effects of repeated cocaine on learning, memory and reinstatement in the pond snail, Lymnaea stagnalis. Respiratory behavior can be operantly conditioned and extinguished in Lymnaea, and this behavior is dependent on a critical dopamine neuron. We tested the hypothesis that repeated cocaine exposure promotes learning and memory or attenuates the ability to extinguish the memory of respiratory behavior that relies on this dopaminergic neuron. Rotating disk electrode voltammetry revealed a K(m) and V(max) of dopamine uptake in snail brain of 0.9 micromol l(-1) and 558 pmol s(-1) g(-1) respectively, and the IC(50) of cocaine for dopamine was approximately 0.03 micromol l(-1). For operant conditioning, snails were given 5 days of 1 h day(-1) immersion in water (control) or 0.1 micromol l(-1) cocaine, which was the lowest dose that maximally inhibited dopamine uptake, and snails were trained 3 days later. No changes were found between the two groups for learning or memory of the operant behavior. However, snails treated with 0.1 micromol l(-1) cocaine demonstrated impairment of extinction memory during reinstatement of the behavior compared with controls. Our findings suggest that repeated exposure to cocaine modifies the interaction between the original memory trace and active inhibition of this trace through extinction training. An understanding of these basic processes in a simple model system may have important implications for treatment strategies in cocaine addiction.

Animals↗

PubMed2005

Biodiversity analysis of microbial community in the chem-bioflocculation treatment process.

Total DNA was directly extracted from environmental samples and amplified with polymerase chain reaction (PCR) technique. The PCR products were fingerprinted via denaturing gradient gel electrophoresis (DGGE). Significant differences were observed in the microbial community structures between traditional treatment process and chem-bioflocculation process. The microbial community structure shift at different sampling locations in chem-bioflocculation process and on two typical operational conditions was studied. 16S rDNA V3 regions of some dominant species were sequenced and the species were identified. The microbial communities were stable in both the chem-bioflocculation process and the activated sludge process under various experimental conditions presented in this work. The attached growth treatment process was less stable when operational conditions changed.

Bacteria↗

PubMed2004

Dual column capillary gas chromatographic system for the in situ analysis of volatile organic compounds on a cometary nucleus.

Two Wall Coated Open Tubular capillary columns, coated with poly(cyanopropylphenyl-dimethyl)siloxane and poly(diphenyl-dimethyl)siloxane stationary phases, have been selected for use in the COmetary SAmpling and Composition space experiment for the separation and identification of the wide range of volatile organic compounds which could be present in cometary nuclei. This article presents the main characteristics of the tandem column system for the analysis of solutes of cometary interest within the constraints of space instrumental operating conditions. The high efficiency of the columns is demonstrated and the influence of the operating conditions on their separation properties are investigated. The studied columns exhibit complementary retention pattern: their use in a dual column system makes it possible to achieve the separation and the identification of the compounds of interest. Finally, the good analytical behavior of the columns when analyzing samples which include large amounts of water, the main presumed volatile in comets, is demonstrated. The presented results thus show the suitability of the selected tandem columns system for the desired analyses, and their performance on adaptation to in-situ cometary chemical investigation.

Chromatography, Gas↗

PubMed2005

Sequencing batch reactor performance treating PAH contaminated lagoon sediments.

The applicability of sediment slurry sequencing batch reactors (SBR) to treat Venice lagoon sediments contaminated by polycyclic aromatic hydrocarbons (PAHs) was investigated, carrying out experimental tests. The slurry, obtained mixing tap water and contaminated sediments with 17.1 mg kg(-1) TS total PAHs content, was loaded to a 8l lab-scale completely stirred reactor, operated as a sequencing batch reactor. Oxygen uptake rate exerted by the slurry, measured by means of a DO-stat titrator, was used to monitor the in-reactor biological activity and to select the optimal operating conditions for the sediment slurry SBR. The PAHs removal efficiency was evaluated in different operating conditions, obtained changing the hydraulic retention time (HRT) of the lab-scale reactor and adding an external carbon source to the slurry. HRT values used during the experiments are 98, 70 and 35 days, whereas the carbon source was added in order to evaluate its effect on the biological activity. The results have shown a stable degradation of PAHs, with a removal efficiency close to 55%, not dependent on the addition of carbon source and the tested HRTs.

Biodegradation, Environmental↗

PubMed2006

Simulation of the flue gas cleaning system of an RDF incineration power plant.

Because of the stringent pollutant emission standards introduced with the European Union guidelines for waste incineration, it is very important to optimize the flue gas cleaning systems which are able to result in a low environmental impact according to the emission limits. In this paper a thermochemical model has been proposed for the simulation of the flue gas cleaning system of an RDF incineration plant. The model simulates the operation of the flue-gas treatment section and the combustion section by using a simplified approach. The combustion includes the grate incinerator and the post-combustion chamber, while the cleaning section includes the NO(x) reduction process (urea injection) and the scrubbing of SO(2) and HCl (Ca(OH)(2) as sorbent). The modelling has been conducted by means of ASPEN PLUS code. The simulation results have been validated with the operating data. The model proposed by the authors can be a useful tool in both evaluating the efficiency of the gas cleaning system by verifying the environmental pollution of an incinerator power plant in nominal operating conditions and in forecasting the efficiency of the cleaning system in off-design operating conditions.

Computer Simulation↗

PubMed1981

Axial changes of blood and plasma flow, pressure, and cellular deposition in capillary plasma filters.

The ability to separate plasma on-line from whole blood by membranes has generated interest in applying this process to source plasma collection and to the therapeutic treatment of various disease states. The availability of capillary membrane devices in particular has prompted investigations in these areas. The deposition of blood cellular elements has required the investigation of those parameters related to fluid and mass flux. Analytical solutions relating blood flow rate, filtration rate, and pressure and deposition with respect to axial distance have been obtained. Comparison of these solutions with preliminary experimental results have been made. Results indicate that the deposition parameter versus distance from the inlet is a very sensitive function of capillary membrane properties and operating conditions. Plasma fluxes are also highly dependent on blood, membrane, and filter properties and operating conditions.

Blood↗

PubMedDate not supplied

[Functional role of the red nucleus in the cerebral cortex-cerebellum-spinal cord communication system].

Unilateral transection of the rubrospinal tract before lesion of the red nucleus or the ventrolateral thalamic nucleus has been shown to facilitate recovery of operantly conditioned reflexes and compensatory processes in rats. Such strengthening of the recovery plasticity and operantly conditioned was found when transection of the bulbar pyramide performed before ablation of the sensorimotor cortex. These influences are explained by activation of the rubroolivary projection, which is switching of descending cortico-rubrospinal system on the corticospinal system, and on the contrary. The general property of this phenomenon is that preliminary lesion of the peripheral part of the descending spinal projection to acquire a signal forestalling significance for mibilization of compensatory brain capacity in order to recovery the deficit of central link of the system.

Animals↗

PubMed1990

Impact of heating and air conditioning system operation and leakage on ventilation and intercompartment transport: studies in unoccupied and occupied Tennessee Valley homes.

Forced-air heating and air conditioning (HAC) systems caused an average and maximum increase in air infiltration rates of 1.8- and 4.3-fold, respectively, during brief whole-house studies of tracer gas decay in 39 occupied houses. An average increase in air infiltration rate of 0.33 +/- 0.37 h-1 corresponded to an incremental air leak of 240 m3/h, based on approximate house volume. More detailed tracer gas decay studies were performed in basement, kitchen and bedroom locations of six homes with low air infiltration rates (i.e., less than 0.25 h-1). The HAC mixed the indoor air efficiently between measurement sites. HAC operation also caused 1.1- to 3.6-fold increases in air infiltration rates, corresponding to absolute increases of 0.02 to 0.1 h-1. In an unoccupied research house, three-fold increases in average air infiltration rate with HAC operation (i.e., from 0.13 to 0.36 h-1) were reduced to two-fold (i.e., from 0.10 to 0.18 h-1) by sealing the external HAC unit and crawlspace ductwork system. This sealing also resulted in a 30 percent reduction in crawlspace-to-indoor transport rates with the HAC turned on. Blower door tests indicated a less than 20 percent reduction in house leakage area.

Air Conditioning↗

PubMed1985

[Conditions for the standardization of the process of cephalosporin biosynthesis].

Dependence of the final results of cephalosporin biosynthesis on the parameters of the operating conditions and the design of fermentors was shown. The value of the specific power input for agitation had a significant effect on the biosynthetic process. An equation for estimating the final results of the biosynthetic process by the values of the operating conditions and the fermentor design parameters is presented.

Acremonium↗

PubMed2003

Conditioned H-reflex increase persists after transection of the main corticospinal tract in rats.

The brain shapes spinal cord function throughout life. Operant conditioning of the H-reflex, the electrical analog of the spinal stretch reflex (SSR), is a relatively simple model for exploring the spinal cord plasticity underlying this functional change and may provide a new method for modifying spinal cord reflexes after spinal cord injury. In response to an operant conditioning protocol, rats can gradually increase (i.e., up-training mode) or decrease (i.e., down-training mode) the soleus H-reflex. This study explored the effects of midthoracic transection of the ipsilateral lateral column (LC) (rubrospinal, vestibulospinal, and reticulospinal tracts), the dorsal column corticospinal tract (CST), or the dorsal column ascending tract (DA) on maintenance of an H-reflex increase that has already occurred. Rats were implanted with EMG electrodes in the right soleus muscle and a nerve-stimulating cuff on the right posterior tibial nerve. After initial (i.e., control) H-reflex size was determined, the rats were exposed for 50 days to the up-training mode, in which reward was given when the H-reflex was above a criterion value. H-reflex size gradually rose to 168 +/- 12% (mean +/- SE) of its initial value. Each rat then received an LC, CST, or DA transection and continued under the up-training mode for 50 more days. None of the transections abolished the H-reflex increase. H-reflex size increased further to 197 +/- 19% of its initial value and did not differ significantly among LC, CST, and DA rats (P > 0.78 by ANOVA). Although earlier studies show that the main CST is needed for acquisition of H-reflex up-training and down-training and for maintenance of down-training, this study shows that it is not needed for maintenance of up-training. It adds to the evidence that H-reflex conditioning changes the spinal cord and that the spinal cord plasticity associated with up-training is different from that associated with down-training.

Animals↗

PubMed2002

Directivity pattern of neurosurgical endoscopic ultrasonic probes.

The objective of this paper is to present recent investigations in characteristics of the sound field generated by neurosurgical endoscopic ultrasonic probes (NEUPs) for minimally invasive surgery. The importance of this information has been investigated and discussed taking into account following facts: 1. According to the International Standard IEC 61847:1998 basic acoustical output characteristics of ultrasonic surgical equipment is declared for and measured in an acoustical free field. The standard generally treats the ultrasonic probe as an omnidirectional point source of the zero order (monopole source). 2. In real conditions, operations with NEUPs are performed within the acoustical near field. Having in mind that the cavitational and hydrodynamic effects are dominant, two theoretical boundary conditions can be present. The first one takes place when operations are performed near the "soft" acoustical boundary (tissue/air), and the second one is near the "rigid" acoustical boundary (tissue/bone). Reflections of sound waves from boundaries have influence on the characteristics of the ultrasonic probe (transducer) and on the sound field. In such cases spherical waves of the first and second order are generated. Directivity of sound sources takes shape in the far field and is easier to measure there. On the basis of measured directivity patterns, the influence of different operational conditions (immersion depth of the probe tip, boundary type, acoustical impedance of the medium etc.) on the radiated sound power and spatial distribution of the sound pressure can be estimated.

Endosonography↗

PubMed1990

Pain relief for outpatient colonoscopy: a comparison of alfentanil with fentanyl.

Alfentanil was used as an adjuvant to midazolam for analgesia in thirty outpatients undergoing colonoscopy. A similar group of thirty outpatients received fentanyl. The operating conditions and recovery times of the two groups were compared. Alfentanil usage resulted in better operating conditions. Recovery time was similar. Patient acceptance was high. No patient suffered respiratory depression during or after the procedure.

Adult↗