PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Conditioning, Operant”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,387 records · Page 77Linked to original sources
PubMed2002

Comparison of polysulfone and ceramic membranes for the separation of phenol in micellar-enhanced ultrafiltration.

Micellar-enhanced ultrafiltration (MEUF) of phenol and a cationic surfactant, cetylpyridinium chloride (CPC), is studied using two polysulfone membranes of 5- and 50-kDa molecular weight cutoff (MWCO) and two ceramic membranes of 15- and 50-kDa MWCO. Filtrations are run under laminar cross-flow and steady-state conditions. The effect of operation variables (pressure and retentate flux) and membrane properties (nature and MWCO) on permeate flux, surfactant, and phenol rejections is analyzed. The permeate flux depends, among other variables, on the fouling favored by membrane-micelle interactions, which are strongest in the 50-kDa MWCO ceramic membrane. On the other hand, surfactant rejection is mainly determined by the pore size and influenced by the pressure for both 50-kDa MWCO membranes. An equilibrium distribution constant, K(s), of phenol between surfactant micelles and water is calculated. Its value is not significantly affected by operation conditions and membrane type. K(s) is also approximately 20% lower than the value determined in a previous work with batch dead-end ultrafiltration.

Journal Article↗
PubMed1985

Spectral sensitivity of the African cichlid fish, Haplochromis burtoni.

Spectral sensitivity of the cichlid fish Haplochromis burtoni was measured under both scotopic and photopic conditions using a two-choice, food reward, operant conditioning paradigm. The highest absolute sensitivity (scotopic) is one quantum for every 5 to 50 rods measured at 475 nm (equivalent to a corneal irradiance of 3.8 x 10(6) Q s-1 cm-2). A P500(1) photopigment apparently mediates spectral sensitivity over most of the visible spectrum; microspectrophotometric studies of rods had previously shown them to contain this photopigment. However, the scotopic behavioral action spectrum shows a sensitivity to short wavelength light higher than is consistent with a P500(1) photopigment alone mediating the scotopic visual process. Determinations made under photopic conditions reveal a behavioral action spectrum broader than that found under scotopic conditions and consistent with mediation by interaction of the three known cone types in an opponent processing manner. The calculated photopic threshold value of approximately 10(4) Q s-1 (receptor)-1 is in agreement with results from other species and corresponds to a corneal irradiance of about 7 x 10(10) Q s-1 cm-2.

Animals↗
PubMed1996

Parametric analysis of the inductively coupled plasma.

A systematic parametric study of an LTE (local thermodynamic equilibrium) mathematical model of pure inductively coupled argon plasma (ICAP) used for spectrochemical purposes was performed by means of computer simulations. The spatial distributions of temperature, gas velocity, magnetic field and energy losses were investigated under typical plasma operating conditions as function of the ICAP geometrical dimensions and dynamic parameters. These theoretical calculations can be used to predict the properties of the applied plasma in the course of practical work, to choose the optimal conditions by changing the operating parameters and to interpret existing analytical results.

Journal Article↗
PubMed1995

Adaptive predictive control of dissolved oxygen concentration in a laboratory-scale bioreactor.

We present an algorithm for the adaptive control of dissolved oxygen concentration in a bioreactor, based on the agitation rate. The dynamics are represented by an incremental first-order model with variable dead-time and parameters. These are estimated on-line by a recursive least-squares identification method with a forgetting factor and a constant sensitivity. The model is employed to predict the behaviour of the dissolved oxygen concentration over a finite horizon, using an original method which requires little computation. Then, a Generalized Predictive Control optimisation strategy computes the agitation rate from the predictions and the desired set point, while gradually updating the controller smoothness. This algorithm, which requires little preliminary knowledge, has been implemented on a laboratory-scale fed-batch bioreactor for which the use of conventional controllers showed limited performance, due to the unpredictable and evolutive nature of the dynamics. The new controller proved to be robust and effective over a wide range of operating conditions, while requiring no operator adjustments.

Algorithms↗
PubMed1981

6-Hydroxydopamine and radiofrequency lesions of the lateral entorhinal cortex facilitate an operant appetitive conditioning task in mice.

The entorhinal cortex seems heterogeneous as dopaminergic terminals are present only in the anterior part of the lateral entorhinal cortex. In order to clarify the interaction of this cortex with the hippocampus in memory processes, the effects of either 6-hydroxydopamine or radiofrequency bilateral lesions were compared. Both lesions enhance the retention of a Skinner task with continuous reinforcement schedule. Involvement of dopamine in memory processes is discussed.

Animals↗
PubMed2006

Preparation and application of granular ZnO/Al2O3 catalyst for the removal of hazardous trichloroethylene.

Trichloroethylene (TCE) is a volatile and nerve-toxic liquid, which is widely used in many industries as an organic solvent. Without proper treatment, it will be volatilized into the atmosphere easily and hazardous to the human health and the environment. This study tries to prepare granular ZnO/Al(2)O(3) catalyst by a modified oil-drop sol-gel process incorporated the incipient wetness impregnation method and estimates its performance on the catalytic decomposition of TCE. The effects of different preparation and operation conditions are also investigated. Experimental results show that the granular ZnO/Al(2)O(3) catalyst has good catalytic performance on TCE decomposition and the conversion of TCE is 98%. ZnO/Al(2)O(3)(N) catalyst has better performance than ZnO/Al(2)O(3)(O) at high temperature. Five percent of active metal concentration and 550 degrees C calcination temperature are the better and economic preparation conditions, and the optimum operation temperature and space velocity are 450 degrees C and 18,000 h(-1), respectively. The conversions of TCE are similar and all higher than 90% as the oxygen concentration in feed gas is higher than 5%. By Fourier transform infrared spectrography (FT-IR) analyses, the major reaction products in the catalytic decomposition of TCE are HCl and CO(2). The Brunauer-Emmett-Teller (BET) surface areas of catalysts are significantly decreased as the calcination temperature is higher than 550 degrees C due to the sintering of catalyst materials, as well as the reaction temperature is higher than 150 degrees C due to the accumulations of reaction residues on the surfaces of catalysts. These results are also demonstrated by the results of scanning electron micrography (SEM) and energy disperse spectrography (EDS).

Aluminum Oxide↗
PubMed2005

Anterolateral thigh flaps for reconstruction of head and neck defects.

PURPOSE: This article presents our clinical experience with head and neck reconstruction using a free anterolateral thigh (ALT) flap and describes the morbidity of the donor site. MATERIALS AND METHODS: From October 2001 to October 2003, 20 free ALT flaps were transferred for reconstructing soft tissue defects of the head and neck. The age and gender of the patients, the site of the primary tumor, tumor stage, previous operative condition, types of associated operation, results of flap transfer, donor site morbidity, and clinical course were analyzed. RESULTS: Of 20 cases, 19 free flaps were successfully performed. The success rate was 95%. The size of the ALT flaps ranged from 6 to 10 cm in width and 9 to 20 cm in length (54 to 200 cm2 in area). Sixteen of the 20 donor sites were closed primarily, whereas 4 cases required a split-thickness skin graft to cover the donor site. Complications and morbidity of the donor site were minimal. CONCLUSION: The ALT flap has some advantages over other free flaps, including a long pedicle with a suitable diameter for anastomoses, the availability of different tissues with large amounts of skin, the ease of closing the donor site, and the ability for 2 teams to simultaneously perform the operation.

Adult↗
PubMed1989

Idiotypic networks incorporating T-B cell co-operation. The conditions for percolation.

Previous work was concerned with symmetric immune networks of idiotypic interactions amongst B cell clones. The behaviour of these networks was contrary to expectations. This was caused by an extensive percolation of idiotypic signals. Idiotypic activation was thus expected to affect almost all (greater than 10(7] B cell clones. We here analyse whether the incorporation of helper T cells (Th) into these B cell models could cause a reduction in the percolation. Empirical work on idiotypic interactions between Th and B cells however, would suggest that two different idiotypic Th models should be developed: (1) a Th which recognises native B cell idiotypes, i.e. a non-MHC-restricted "ThId" model, and (2) a "classical" MHC-restricted helper T cell model. In the ThId model, the Th-B cell interaction is symmetric. A 2-D model of a Th and a B cell clone that interact idiotypically with each other accounts for various equilibria (i.e. one virgin and two immune states). Introduction of antigen does indeed lead to a state switch from the virgin to the immune state; such a system is thus able to "remember" its exposure to antigen. Idiotypic signals do however, percolate in ThId models via these "B-Th-B-Th" pathways: proliferating Th and B cell clones that interact idiotypically, will always activate each other reciprocally. In the MHC-restricted Th model, Th-B interactions are asymmetric. Because the B cell idiotypes are processed and subsequently presented by MHC molecules, the Th receptor and the native B cell receptor are not expected to be complementary. Thus the Th and the B cells are unable to activate each other reciprocally, and a 2-D Th-B cell model cannot account for idiotypic memory. In contrast to the ThId model, idiotypic activation cannot percolate via "B-Th-B-Th" interactions. Due to the assymmetry idiotypic activation stops at the first Th level. A Th clone cannot activate a subsequent B cell clone: if the B cells recognise the Th cells, they see idiotype but get no help; if the Th cells see the B cells, the B cells are helped but see no idiotype. The percolation along "B-B-B" pathways in these two models is next analysed. Two B cells clones, each helped by one Th clone, are connected by a symmetric idiotypic interaction. It turns out that in both models the second (i.e. anti-idiotypic) B cells (B2) never proliferate.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2001

Predicting peak shape in capillary zone electrophoresis: a generic approach to parametrizing peaks using the Haarhoff-Van der Linde (HVL) function.

We have found that the Haarhoff-Van der Linde (HVL) peak function provides excellent fitting to the shapes of CZE peaks. Initially designed for overloaded peaks in gas chromatography, this function describes a Gaussian peak when there is no peak distortion, and a triangular peak when there is no diffusional peak broadening. As such, it is ideal for CZE peaks distorted by electromigration dispersion (EMD). Fitting peaks with this function gives four parameters: three of them can be related to the Gaussian peak that would have been obtained in case of no EMD; the last one is a measure of the peak distortion. Using moving boundary theory, this peak distortion parameter may readily be expressed in terms of analyte and background electrolyte mobilities and concentrations, electric field, and sample injection length. The variance of an HVL peak is shown to be described by a universal function, and a master equation is presented. The region where EMD adds less than 10% to the Gaussian variance is shown to be very narrowly spread around the mobility matching condition. Under typical CZE operating conditions with an analyte at 1% of the BGE concentration, significant peak distortion is always present. Because the total peak variance is not an addition of the Gaussian and triangular contributions, the HVL model and the methodology introduced here should always be used to correctly combine variances.

Journal Article↗
PubMed2005

Accelerated solvent extraction of ochratoxin a from rice samples.

In this paper, accelerated solvent extraction (ASE) for the analysis of ochratoxin A (OTA) is applied for the first time. Optimization of the method is given for the extraction of OTA from rice samples. Several parameters such as type of solvent, temperature, pressure, static time, and cell size were investigated thoroughly to find the optimal extraction conditions. The optimum ASE operating conditions were methanol as extraction solvent, 1500 psi, 40 degrees C, 5 min of static time, 50% flush volume, 60 s of purge, 1 cycle, and 11 mL cell size. The total extraction time was approximately 15 min. OTA was determined by liquid chromatography coupled with a fluorescence detector and confirmed by methyl ester derivatization. The analytical performance of the method was monitored with quality control parameters. Finally, the optimized method was used to evaluate 12 rice samples, 1 of which was positive with an OTA content of 4.17 ng/g. The proposed method offers the possibility of a fast and simple process to obtain a quantitative extraction of OTA.

Chromatography, High Pressure Liquid↗
PubMed1996

Nicotinic autoreceptors mediating enhancement of acetylcholine release become operative in conditions of "impaired" cholinergic presynaptic function.

The existence in the mammalian CNS of release-inhibiting muscarinic autoreceptors is well established. In contrast, few reports have focused on nicotinic autoreceptors mediating enhancement of acetylcholine (ACh) release. Moreover, it is unclear under what conditions the function of one type of autoreceptor prevails over that of the other. Rat cerebrocortex slices, prelabeled with [3H]choline, were stimulated electrically at 3 or 0.1 Hz. The release of [3H]ACh evoked at both frequencies was inhibited by oxotremorine, a muscarinic receptor agonist, and stimulated by atropine, a muscarinic antagonist. Nicotine, ineffective at 3 Hz, enhanced [3H]ACh release at 0.1 Hz; mecamylamine, a nicotinic antagonist, had no effect at 3 Hz but inhibited [3H]ACh release at 0.1 Hz. The cholinesterase inhibitor neostigmine decreased [3H]ACh release at 3 Hz but not at 0.1 Hz; in the presence of atropine, neostigmine potentiated [3H]ACh release, an effect blocked by mecamylamine. In synaptosomes depolarized with 15 mM KCl, ACh inhibited [3H]ACh release; this inhibition was reversed to an enhancement when the external [Ca2+] was lowered. The same occurred when, at 1.2 mM Ca2+, external [K+] was decreased. Oxotremorine still inhibited [3H]ACh release at 0.1 mM Ca2+. When muscarinic receptors were inactivated with atropine, the K+ (15 mM)-evoked release of [3H]ACh (at 0.1 mM Ca2+) was potently enhanced by ACh acting at nicotinic receptors (EC50 approximately 0.6 microM). In conclusion, synaptic ACh concentration does not seem to determine whether muscarinic or nicotinic autoreceptors are activated. Although muscarinic autoreceptors prevail under normal conditions, nicotinic autoreceptors appear to become responsive to endogenous ACh and to exogenous nicotinic agents under conditions mimicking impairment of ACh release. Our data may explain in part the reported efficacy of cholinesterase inhibitors (and nicotinic agonists) in Alzheimer's disease.

Acetylcholine↗
PubMed1977

Comparison of thiopentone, Althesin and ketamine in anaesthesia for otolaryngological surgery in children.

Thiopentone 4 mg/kg, Althesin 0.055 ml/kg and ketamine 2 mg/kg were compared in 157 children undergoing minor otolaryngological surgery, mostly adenotonsillectomy. Premedication was with pethidine and atropine and anaesthesia was maintained with nitrous oxide in oxygen and halothane. Tracheal intubation was facilitated with suxamethonium. In each group half of the children received pethidine 0.7 mg/kg after intubation and the remainder received saline. Ketamine increased arterial pressure after induction. The cardiovascular responses to intubation were more obvious after thiopentone and Althesin than after ketamine. Operating conditions, cardiovascular changes during operation and the course of extubation were similar in all groups. The recovery after ketamine was longer than after thiopentone and Althesin. Thiopentone was associated with significantly less vomiting immediately after operation than was Althesin and ketamine. In the period immediately after operation Althesin was associated with a higher need for analgesics compared with thiopentone and ketamine. Pethidine prolonged the recovery after thiopentone, decreased the incidence of vomiting immediately after operation associated with Althesin and increased that associated with ketamine.

Alfaxalone Alfadolone Mixture↗
PubMed1995

Effect of intrathecal saline injection and Valsalva maneuver on cerebral perfusion pressure during transsphenoidal surgery for pituitary macroadenoma.

Cerebrospinal fluid pressure (CSFP) was monitored through a lumbar intrathecal catheter in 32 patients undergoing transsphenoidal excision of pituitary macroadenomas. In the first 20 patients, standardized intermittent Valsalva maneuvers were followed by intrathecal saline injections in 2.5-ml increments. Their effects on CSFP, mean arterial pressure (MAP), and therefore, cerebral perfusion pressure (CPP) were compared. The increase in CSFP produced by one Valsalva maneuver (4 +/- 2 mm Hg) was similar to that produced by a single increment of intrathecal saline (4 +/- 2 mm Hg), but the effect of saline was more sustained. With Valsalva maneuvers, the maximum CSFP produced was 13 +/- 4 mm Hg, and the CPP decreased to 50 +/- 14 mm Hg, whereas with saline, the maximum CSFP was 25 +/- 7 mm Hg, and the CPP decreased to 59 +/- 13 mm Hg. Because the increase in CSFP was greater and better sustained with intrathecal saline, Valsalva maneuvers were omitted in the next 12 patients. Peroperative data, including surgical conditions, and post-operative morbidity, with special reference to low-pressure headache and meningeal infection, were analyzed in all 32 patients. Operative conditions produced with intrathecal saline were judged excellent or good in 75% of patients. However, because this technique can decrease the CPP excessively, we recommend that it be used only with continuous CSFP monitoring.

Adenoma↗