Bibliografías temáticas / Deactivation

Literatura académica sobre el tema "Deactivation"

Autor: Grafiati
Publicado: 4 de junio de 2021
Última modificación: 13 de julio de 2024

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Artículos de revistas sobre el tema "Deactivation"

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Persson, Jonas, Cindy Lustig, James K. Nelson y Patricia A. Reuter-Lorenz. "Age Differences in Deactivation: A Link to Cognitive Control?" Journal of Cognitive Neuroscience 19, n.º 6 (junio de 2007): 1021–32. http://dx.doi.org/10.1162/jocn.2007.19.6.1021.

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The network of regions shown by functional imaging studies to be deactivated by experimental tasks relative to nominally more passive baselines (task < baseline) may reflect processes engaged during the resting state or “default mode.” Deactivation may result when attention and resources are diverted from default-mode processes toward task processes. Aging is associated with altered patterns of deactivation which may be related to declining resources, difficulties with resource allocation, or both. These possibilities predict that greater task demand, which increases deactivation levels in younger adults, should exacerbate age-related declines in allocating resources away from the default mode. The present study investigated the magnitude and temporal properties of deactivations in young and older adults during tasks that varied in their demand for cognitive control. Two versions of a verb generation task that varied in their demand for selection among competing alternatives were compared to word reading and a fixation baseline condition. Consistent with our hypothesis, greater deactivations were found with increasing demand. Young and older adults showed equivalent deactivations in the minimal selection condition. By contrast, age differences in both the magnitude and time course of deactivation increased with selection demand: Compared to young adults', older adults' deactivation response showed less sensitivity to demand. Demand-related changes in deactivation magnitude correlated with performance changes, suggesting that individual and group differences in deactivation have functional significance.
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2

Serdyukov, D. V., O. V. Kanunnikov, V. A. Akselrod y N. G. Loyko. "Antimicrobial Properties of a Biocide Based on Quaternary Ammonium Compounds plus Polyhexamethylene Guanidine and Possible Methods of Its Deactivation". Biotekhnologiya 36, n.º 6 (2020): 115–26. http://dx.doi.org/10.21519/0234-2758-2020-36-6-115-126.

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Biocidal agents (BA) are widely used in environmentally safe toilet complexes (ESTC) of passenger railcars to suppress microbial activity in fаecal sludge (FS). Subsequent disposal of BA-containing FS at municipal sewage treatment facilities adversely affects their work due to the loss of activated sludge. The antimicrobial properties of BA, based on quaternary ammonium compounds (QAC) and polyhexamethylene guanidine (PHMG), as well as methods for its neutralization, have been studied. It was confirmed that BA based on QAC and PHMG has an antimicrobial effect on various groups of bacteria, reducing their number by 10-100 or more times. It was found that FS contains two groups of microorganisms with different sensitivity to BA. Methods for deactivation of the BA antimicrobial action in FS were tested using: (1), a deactivating agent; (2), incubation with thermophilically digested wastewater sludge as a source of the microbial methanogenic community; and (3), chemical deactivation by acidification or alkalization. The highest efficiency was shown by the method of deactivation of BA via thermophilic anaerobic digestion with pretreatment of FS with a strong acid biocide, fаecal sludge of ESTC of passenger railcars, antimicrobial activity, quaternary ammonium compounds, polyhexamethylene guanidine, deactivator, methanogenic microbial community This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation.
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3

Garner, Daniel, Matthew Blackburn, David J. Wright y Archana Rao. "Improving guideline-mandated care of patients with implantable cardiac defibrillators". British Journal of Hospital Medicine 81, n.º 8 (2 de agosto de 2020): 1–10. http://dx.doi.org/10.12968/hmed.2020.0259.

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Background/Aims Implantable cardiac defibrillators reduce the risk of sudden cardiac death in selected patients. The value of an implantable cardiac defibrillator declines as the patient's disease progresses. Guidelines suggest that the appropriateness of maintaining implantable cardiac defibrillator therapy be regularly reviewed as part of monitoring of the patient's disease trajectory. It is recommended that implantable cardiac defibrillators are deactivated as patients approach the end of life. Patients with a better understanding of their current state of health and the role that the implantable cardiac defibrillator plays within it are more likely to make informed decisions about the timing of deactivation. Methods: A quality improvement project was undertaken on appropriate deactivation of implantable cardiac defibrillators within a large tertiary cardiac centre. This was driven by audit data showing inadequate patient communication and documentation around deactivation. Drivers for change included the introduction of electronic data records, clinical review of comorbid patients approaching elective battery change and an ongoing forum for patient and carer education. Measured outcomes included the number of deactivations performed, evidence of patient discussion and consent, and timing of deactivation of the implantable cardiac defibrillator. Results There were increased numbers of timely device deactivations undertaken following the interventions with improved documented evidence of patient discussion and consent. The educational forum was received favourably. Conclusions Focused multidisciplinary interventions can impact favourably on appropriate implantable cardiac defibrillator deactivation and improve patient engagement.
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4

Malhotra, Shveta y Stephen G. Lomber. "Sound Localization During Homotopic and Heterotopic Bilateral Cooling Deactivation of Primary and Nonprimary Auditory Cortical Areas in the Cat". Journal of Neurophysiology 97, n.º 1 (enero de 2007): 26–43. http://dx.doi.org/10.1152/jn.00720.2006.

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Although the contributions of primary auditory cortex (AI) to sound localization have been extensively studied in a large number of mammals, little is known of the contributions of nonprimary auditory cortex to sound localization. Therefore the purpose of this study was to examine the contributions of both primary and all the recognized regions of acoustically responsive nonprimary auditory cortex to sound localization during both bilateral and unilateral reversible deactivation. The cats learned to make an orienting response (head movement and approach) to a 100-ms broad-band noise stimulus emitted from a central speaker or one of 12 peripheral sites (located in front of the animal, from left 90° to right 90°, at 15° intervals) along the horizontal plane after attending to a central visual stimulus. Twenty-one cats had one or two bilateral pairs of cryoloops chronically implanted over one of ten regions of auditory cortex. We examined AI [which included the dorsal zone (DZ)], the three other tonotopic fields [anterior auditory field (AAF), posterior auditory field (PAF), ventral posterior auditory field (VPAF)], as well as six nontonotopic regions that included second auditory cortex (AII), the anterior ectosylvian sulcus (AES), the insular (IN) region, the temporal (T) region [which included the ventral auditory field (VAF)], the dorsal posterior ectosylvian (dPE) gyrus [which included the intermediate posterior ectosylvian (iPE) gyrus], and the ventral posterior ectosylvian (vPE) gyrus. In accord with earlier studies, unilateral deactivation of AI/DZ caused sound localization deficits in the contralateral field. Bilateral deactivation of AI/DZ resulted in bilateral sound localization deficits throughout the 180° field examined. Of the three other tonotopically organized fields, only deactivation of PAF resulted in sound localization deficits. These deficits were virtually identical to the unilateral and bilateral deactivation results obtained during AI/DZ deactivation. Of the six nontonotopic regions examined, only deactivation of AES resulted in sound localization deficits in the contralateral hemifield during unilateral deactivation. Although bilateral deactivation of AI/DZ, PAF, or AES resulted in profound sound localization deficits throughout the entire field, the cats were generally able to orient toward the hemifield that contained the acoustic stimulus, but not accurately identify the location of the stimulus. Neither unilateral nor bilateral deactivation of areas AAF, VPAF, AII, IN, T, dPE, nor vPE had any effect on the sound localization task. Finally, bilateral heterotopic deactivations of AI/DZ, PAF, or AES yielded deficits that were as profound as bilateral homotopic cooling of any of these sites. The fact that deactivation of any one region (AI/DZ, PAF, or AES) was sufficient to produce a deficit indicated that normal function of all three regions was necessary for normal sound localization. Neither unilateral nor bilateral deactivation of AI/DZ, PAF, or AES affected the accurate localization of a visual target. The results suggest that hemispheric deactivations contribute independently to sound localization deficits.
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5

Jaklová, Karolína Dlasková, Lucie Šindelářová, Jan Kohout, Ivana Hradecká, Nikita Sharkov y Aleš Vráblík. "Comparison of the Accelerated and Spontaneous Deactivation of the HDS Catalyst". Processes 9, n.º 12 (14 de diciembre de 2021): 2258. http://dx.doi.org/10.3390/pr9122258.

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Owing to the increased use of secondary materials for diesel production, refineries must confront bad quality parameters. Therefore, catalysts with certain capabilities (to remove heteroatoms and improve quality parameters at low hydrogen consumption) and their lifetimes are required. An important parameter that influences the quality of the products and the economy of the unit is the activity of the catalyst. Prior to industrial use, the catalyst is typically tested in a pilot unit. This is necessary to obtain a considerable amount of data on the lifetime of the catalyst in the shortest feasible time. Here, deactivation steps were used to test the catalyst. Two experiments were performed to evaluate the effect of two types of accelerated deactivations on the catalyst activity and product properties. The first type of deactivation proceeded for 6 h and comprised a tripling of the amount of incoming feedstock, and the second type proceeded for 18 h without an increase in the amount of feedstock. For both cases, the pressure and hydrogen flow were minimised. Both types of accelerated deactivations had similar effects on the quality of the final products and catalyst. The only difference was in the duration of catalyst recovery after deactivation. The results were compared with those of a test in which the spontaneous deactivation of the catalyst was studied.
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Madre, M., E. Pomarol-Clotet, P. McKenna, J. Radua, J. Ortiz-Gil, F. Panicali, J. M. Goikolea et al. "Brain functional abnormality in schizo-affective disorder: an fMRI study". Psychological Medicine 43, n.º 1 (15 de mayo de 2012): 143–53. http://dx.doi.org/10.1017/s0033291712000943.

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BackgroundSchizo-affective disorder has not been studied to any significant extent using functional imaging. The aim of this study was to examine patterns of brain activation and deactivation in patients meeting strict diagnostic criteria for the disorder.MethodThirty-two patients meeting Research Diagnostic Criteria (RDC) for schizo-affective disorder (16 schizomanic and 16 schizodepressive) and 32 matched healthy controls underwent functional magnetic resonance imaging (fMRI) during performance of the n-back task. Linear models were used to obtain maps of activations and deactivations in the groups.ResultsControls showed activation in a network of frontal and other areas and also deactivation in the medial frontal cortex, the precuneus and the parietal cortex. Schizo-affective patients activated significantly less in prefrontal, parietal and temporal regions than the controls, and also showed failure of deactivation in the medial frontal cortex. When task performance was controlled for, the reduced activation in the dorsolateral prefrontal cortex (DLPFC) and the failure of deactivation of the medial frontal cortex remained significant.ConclusionsSchizo-affective disorder shows a similar pattern of reduced frontal activation to schizophrenia. The disorder is also characterized by failure of deactivation suggestive of default mode network dysfunction.
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7

Wöhrl, Katharina, Yash Kotak, Christian Geisbauer, Sönke Barra, Gudrun Wilhelm, Gerhard Schneider y Hans-Georg Schweiger. "Analysis of Deactivation of 18,650 Lithium-Ion Cells in CaCl2, Tap Water and Demineralized Water for Different Insertion Times". Sensors 23, n.º 8 (11 de abril de 2023): 3901. http://dx.doi.org/10.3390/s23083901.

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The deployment of battery-powered electric vehicles in the market has created a naturally increasing need for the safe deactivation and recycling of batteries. Various deactivating methods for lithium-ion cells include electrical discharging or deactivation with liquids. Such methods are also useful for cases where the cell tabs are not accessible. In the literature analyses, different deactivation media are used, but none include the use of calcium chloride (CaCl2) salt. As compared to other media, the major advantage of this salt is that it can capture the highly reactive and hazardous molecules of Hydrofluoric acid. To analyse the actual performance of this salt in terms of practicability and safety, this experimental research aims to compare it against regular Tap Water and Demineralized Water. This will be accomplished by performing nail penetration tests on deactivated cells and comparing their residual energy against each other. Moreover, these three different media and respective cells are analysed after deactivation, i.e., based on conductivity measurements, cell mass, flame photometry, fluoride content, computer tomography and pH value. It was found that the cells deactivated in the CaCl2 solution did not show any signs of Fluoride ions, whereas cells deactivated in TW showed the emergence of Fluoride ions in the 10th week of the insertion. However, with the addition of CaCl2 in TW, the deactivation process > 48 h for TW declines to 0.5–2 h, which could be an optimal solution for real-world situations where deactivating cells at a high pace is essential.
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8

Barker, Virgil M. "Deactivation of Pacemakers at the End of Life". Ethics & Medics 44, n.º 9 (2019): 1–2. http://dx.doi.org/10.5840/em201944912.

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The liceity of deactivating pacemakers and implantable cardio-defibrillators at the end of life has been considered only recently. The current discussion divides into two main camps: those who view deactivation as the moral equivalent of the withdrawal of other life-sustaining interventions, and those who hold deactivation as the equivalent of physician-assisted suicide. Some authors contend that similar to a transplanted organ, the pacemaker establishes an organic unity with the human body. Hence, its deactivation is equivalent to the removal or disabling of an organ. On the contrary, the relationship of a pacemaker to the human body is similar to other supportive mechanical devices. There are burdens associated with the presence of these devices. In the face of a terminal diagnosis, the deactivation of a cardio-pacemaker is morally similar to the withdrawal of other extraordinary measures currently accepted within the Catholic moral teachings.
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9

Broering, J. M. y A. S. Bommarius. "Cation and strong co-solute effects on protein kinetic stability". Biochemical Society Transactions 35, n.º 6 (23 de noviembre de 2007): 1602–5. http://dx.doi.org/10.1042/bst0351602.

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Degradation of proteins is important for the operating life of biocatalysts and the shelf life of protein pharmaceuticals. We have previously found that the deactivating effects of salts on proteins can be correlated to an indicator of ion hydration, the B-viscosity coefficient of the anion in solution. Here, we test the influence of cations on protein kinetic stability by observing deactivation of mRFP (monomeric red fluorescent protein) in ammonium, caesium and chloride salt solutions, and we find that mRFP deactivation does not depend on cation hydration. We also measure mRFP deactivation in solutions containing denaturants (guanidinium chloride or urea) or stabilizing co-solutes (glycerol or sucrose) frequently encountered in many protein formulations to test whether hydration of these co-solutes can be used to indicate their relative effects on protein kinetic stability. We find that mRFP deactivation in solutions containing kosmotropic salts or stabilizers reaches a limiting rate and that hydration of denaturants is not an indicator of their denaturing strength.
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Harrisson, Simon. "The Chain Length Distribution of an Ideal Reversible Deactivation Radical Polymerization". Polymers 10, n.º 8 (8 de agosto de 2018): 887. http://dx.doi.org/10.3390/polym10080887.

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The chain length distribution (CLD) of a reversible deactivation radical polymerization at full conversion is shown to be a negative binomial distribution with parameters that are simple functions of the number-average degree of polymerization and either the chain transfer constant (in the case of polymerizations that incorporate a reversible chain transfer step) or the concentrations of dormant polymer chains and deactivating agent and the rate constants of propagation and deactivation (other types of RDRP). Expressions for the CLD at intermediate conversions are also derived, and shown to be consistent with known expressions for the number-average degree of polymerization and dispersity. It is further demonstrated that these CLDs are well-approximated by negative binomial distributions with appropriate choice of parameters. The negative binomial distribution is thus a useful model for CLDs of reversible deactivation radical polymerizations.
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Tesis sobre el tema "Deactivation"

1

Azzu, Vian. "Deactivation of mitochondrial uncoupling proteins". Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/252159.

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Devadas, P. "Catalyst deactivation in propane aromatization". Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1997. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3145.

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O'Toole, Ann Marie. "Thermal deactivation of Pseudomonas aeruginosa biofilms". Thesis, University of Iowa, 2015. https://ir.uiowa.edu/etd/1715.

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Bacterial biofilm infection is a common (~ 2 to 4%) complication for recipients of surgically implanted medical devices. Due to the tremendous increase in antibiotic resistance when these bacteria enter the biofilm phenotype, present treatment requires explantation and replacement of the device, often with multiple surgeries and always with much longer patient recovery time. The specific objective of this study was to quantify the degree of biofilm deactivation from exposure to thermal shock for varying temperature and time durations. While extreme temperature (>150˚C) is routinely used to sterilize (e.g. autoclaves), such temperatures have a severe cost within the body. Despite extensive studies on thermal deactivation of bacteria in the planktonic phenotype over a wide range of temperatures (e.g., pasteurization protocols), surprisingly little is known about the thermal deactivation of biofilms except under extreme conditions. Here, the deactivation of Pseudomonas aeruginosa biofilms is reported. These biofilms were cultured at 37°C for 24 hours in a drip-flow reactor and subjected to heat shocks on the range of 50°C to 80°C for durations of 1 to 30 minutes. Heat shocks were delivered by immersion in thermostatted media for the prescribed time and the resulting concentration of colony forming units (CFU/mL) were quantified using direct enumeration. Up to 6.6 orders of magnitude reduction in CFU concentration was observed, indicating that thermal deactivation is a reasonable approach to biofilm mitigation. Integrating this approach with a magnetic nanoparticle implant coating will result in an innovative treatment for implant infections in situ without explantation or device replacement.
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Arteaga, Colina Geomar Daniel. "Deactivation of Pt/(gamma)-A12O3 during hydrocarbon reactions : mechanism of initial deactivation stages and carbonaceous residue characterisation". Thesis, University of Aberdeen, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521157.

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Deactivation of a 0.53 wt% Pt/γ-Al2­O3 catalyst due to strongly adsorbed carbonaceous residue was investigated.  The role of the carbonaceous residue formed during hydrocarbon conversion reactions of 1-octene, toluene and 1:1 volume mixture of 1-octene/toluene at 300, 400 and 450°C was established and a model developed to account for the activity and selectivity changes at the very start of the reaction, just as the hydrocarbon residue begins to form on the surface of the catalyst.  CO pulse chemisorption was used to determine the extent of Pt surface blocked by the hydrocarbon residue by titrating the Pt sites that remained exposed.  The efficiency of catalyst regeneration with H2 at 400°C was investigated and hydrocarbon reactions were performed on the regenerated catalyst to assess the catalytic activity and selectivity on a Pt surface covered with carbonaceous residue.  Characterisation of the carbonaceous residue deposited on the catalyst during hydrocarbon conversion reactions was carried out using TPO, TGA-MS and Raman microspectroscopy.  The amount, composition, reactivity and chemical structure of the carbonaceous residue in relation to reaction time and temperature was investigated. Increasing the reaction temperature accelerated the formation of coke.  The H:C ratio of the carbonaceous residue played an important role in the selectivity of the hydrocarbon reaction.  In addition, two batches of the 0.53 wt% Pt/γ-Al2O3 catalyst spent six months in an industrial Pyrolysis gasoline (Pygas) Hydrotreatment reactor.  The catalyst batches were strategically placed at the inlet and outlet of the reactor.  Raman microspectroscopy revealed that the coke accumulated on the individually coked samples consisted of a mixture of disordered and ordered pre-graphitic polycrystalline coke.  The reactivity and type of the coke varied between the samples placed near the inlet or the outlet of the industrial reactor.
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Steiner, Petr. "Kinetic and Deactivation Studies of Hydrodesulfurization Catalysts". Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-94.

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Hydrodesulfurization is an important part of the hydrotreating process. More stringent regulations on the quality of fuels bring new requirements to the catalytic processes. The removal of sulfur has become a key issue in the oil refining and this work aims to address several aspects of the process.

Kinetic studies of the hydrodesulfurization reaction over conventional (molybdenum-based) and new (Pt/Y-zeolite) catalysts are reported. The hydrodesulfurization of both the real oil (light gas oil from Statoil Mongstad refinery) and model compounds (thiophene and dibenzothiophene) over a NiMo/γ-Al2O3 catalyst were studied. In a high-pressure study of the light gas oil, substituted alkyl-DBTs were found to be the most difficult to desulfurize and the order of reactivity was found to be DBT > 4-MDBT > 4,6-DMDBT. Steric hindrance together with electronic effects were identified as possible reasons for this behavior. The difference in reactivities of the individual compounds was found to decrease with the increasing reaction temperature. A gas chromatograph equipped with the atomic emission detector (GC-AED) was used for the analysis of the individual components of the oil.

The initial deactivation and the steady-state kinetics were studied during the HDS of thiophene at atmospheric pressure. Unpromoted Mo/γ-Al2O3, CoMo/γ-Al2O3, NiMo/γ-Al2O3, and phosphorus modified NiMo/γ-Al2O3 were used for the deactivation study, while NiMo/γ-Al2O3,CoMo/γ-Al2O3, and Pt/Y-zeolite (with three different pretreatments) were used for the steadystate study. Several experiments related to the deactivation of Mo/γ-Al2O3 and NiMo/γ-Al2O3 catalysts prepared with the chelating agent (NTA) were also performed and NTA was found to have no significant effect on the activity of the catalysts.

In the deactivation study, a fast initial decrease in the activity was observed on all the catalysts. However, nickel promoted catalysts were found to be more resistant to deactivation than unpromoted ones. The presence of phosphorus slightly increased the activity of the catalyst towards the thiophene HDS, but had no effect on the deactivation behavior. Several methods to regenerate the catalyst were investigated. During the resulfiding experiments, a difference between Mo/γ-Al2O3 and NiMo/γ-Al2O3 was observed. Deactivation of the Mo catalyst was more severe with increasing temperature, while for the NiMo catalyst the opposite behavior was observed. Carbon deposition on catalysts followed the similar trend: More carbon was observed on the Mo catalyst at higher temperatures, while the opposite is true for NiMo. The restoration of the activity of NiMo was complete, while the reactivation of the Mo catalyst was only partial. The results from the reactivation experiments with pure H2 and inert gas (helium) suggest that several mechanisms of the restoration of activity exist: Resulfiding of the desulfided active sites, hydrogenation and removal of the deposited carbonaceous species, and the desorption of the reactants and products from the active sites of the catalyst. Based on the observed results, the higher hydrogenation activity of nickel is assumed to be the reason for the behavior. Hydrogenation causes the faster removal of the deposited carbonaceous species and this leads to the conclusion that the desulfiding of the active sites and the adsorption of the reaction species is significantly less pronounced on the NiMo/γ-Al2O3 catalyst.

Characterization studies show differences between standard and NTA-based catalysts. The higher amount of carbon on the NTA catalysts is attributed to the presence of the carboncontaining precursor - NTA. The changes in the surface area and the pore volume were observed only during the sulfiding process. In the case of standard catalysts the surface area and the pore volume decreased, while for the NTA-based catalysts the opposite is true. No change in the surface area and the pore volume with the increasing time on stream indicates that the deactivation is not due to structural changes of the catalyst. The amount of sulfur was found to be constant during the time on stream for all the catalysts.

In the steady-state study of the HDS of thiophene, CoMo and NiMo catalysts were found to be equally active. The activity of the Pt/Y-zeolite catalyst was found to be comparable to conventional catalysts when based on the amount of active material, but a fast deactivation was observed. The product selectivities during the HDS of thiophene were found to be the same for all standard catalysts, but slightly different for the Pt/Y-zeolite catalyst. This was attributed to a higher hydrogenation activity of the Pt/Y-zeolite catalyst.

The inhibition effect of other sulfur compounds and aromatics on the high-pressure hydrodesulfurization of dibenzothiophene (DBT), the so-called “matrix effect” was studied. Thiophene and DMDS have the same inhibiting effect on the total conversion of DBT, but differences exist in the effect on the selectivities of the products at low concentrations. The results indicate that the inhibiting effect of H2S on the direct desulfurization route is stronger than the effect of thiophene on the hydrogenation pathway. In the study of aromatics, both toluene and naphthalene affect the total conversion of DBT. Naphthalene was found to be a much stronger inhibitor and inhibits mainly the direct desulfurization pathway, while the hydrogenation route is more affected by the presence of toluene.

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Rashchi, Fereshteh. "Deactivation of Pb-contaminated sphalerite by polyphosphate". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36828.

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Activation of sphalerite by lead ions in the presence of ethyl xanthate was investigated by microflotation, zeta potential measurements, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and extraction by ethylenediaminetetraacetate (EDTA). The source of lead, either from solution or contact with galena particles, proved immaterial. From EDTA extraction data flotation response was determined as a function of surface concentration of Pb ([Pb]surf, mg/cm2). A critical [Pb]surf ≃ 0.5 x 10-4 mg/cm2 causing activation was estimated. By combining with a Pb ion production model from the literature, the possibility of Pb activation for an ore of given Pb grade was explored. Ores with as little as 0.1% Pb are candidates for accidental activation.
A mechanism of lead interaction is proposed: at weakly acidic to mildly alkaline conditions Pb2+ and PbOH+ adsorb on sphalerite and react with xanthate to form PbX2 and Pb(OH)X; at high pH, hydrophilic Pb(OH)2(s) precipitates depress flotation.
Various candidate deactivators were compared using microflotation. The reagents were diethylenetriamine (DETA), sodium bicarbonate (NaHCO3), silica sol (SS), sodium phosphate (Na3PO4·12H 2O) and sodium polyphosphate (NaPO3)n. The latter had the strongest effect and was selected for detailed study. The mechanism of polyphosphate action was investigated by SEM and XPS. The results show that polyphosphate acted to remove Pb ("clean") from the sphalerite by forming soluble complexes.
The polyphosphate (PP) to lead (Pb) ratio in the complexes was determined from conductometric titration of lead nitrate vs. polyphosphate. It was found that initially a precipitate formed with PP/Pb of 1/3. The precipitate dissolved in excess polyphosphate, resulting in a variety of complexes with PP/Pb of 1/2, 1/1, 3/2, 2/1, and 3/1. Knowing the amount of Pb to be removed and taking the lowest PP/Pb ratio, 1/2, the quantity of polyphosphate required to solubilize the Pb can be calculated.
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McQueen, Paul. "Catalysis deactivation in staged direct coal liquefaction". Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/746.

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Mandani, Faisal Mohammad. "Kinetic and deactivation studies during catalytic dehydrogenation". Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305913.

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Paweewan, Boontham. "Coking and deactivation of zeolite-based catalysts". Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624350.

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Hu, Ing-Feng. "Activation and deactivation of glassy carbon electrodes /". The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726339902366.

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Libros sobre el tema "Deactivation"

1

1924-, Petersen Eugene E., Bell Alexis T. 1942- y International Symposium on Catalysis Deactivation and Poisoning (3rd : 1985 : Lawrence Berkeley Laboratory), eds. Catalyst deactivation. New York: M. Dekker, 1987.

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Illinois State Board of Education (1973- ). Deactivation at a glance. Springfield, Ill: Illinois State Board of Education, 2005.

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3

Kumbilieva, Krassimira. Kinetic Aspects of Catalyst Deactivation. Sofia: Prof. Marin Drinov Academic Publishing House, 2012.

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Jacques, Oudar y Wise Henry 1919-, eds. Deactivation and poisoning of catalysts. New York: M. Dekker, 1985.

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Butt, John B. Activation, deactivation, and poisoningof catalysts. Orlando: Academic Press, 1988.

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6

Sadana, Ajit. Biocatalysis: Fundamentals of enzyme deactivation kinetics. Englewood Cliffs, N.J: Prentice Hall, 1991.

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Butt, John B. Activation, deactivation, and poisoning of catalysts. San Diego: Academic Press, 1988.

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8

Matyjaszewski, Krzysztof, Haifeng Gao, Brent S. Sumerlin y Nicolay V. Tsarevsky, eds. Reversible Deactivation Radical Polymerization: Materials and Applications. Washington, DC: American Chemical Society, 2018. http://dx.doi.org/10.1021/bk-2018-1285.

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O'Connor, Paul, Toru Takatsuka y Geoffrey L. Woolery, eds. Deactivation and Testing of Hydrocarbon-Processing Catalysts. Washington, DC: American Chemical Society, 1996. http://dx.doi.org/10.1021/bk-1996-0634.

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Rashchi, Fereshteh. Deactivation of Pb-contaminated sphalerite by polyphosphate. Montréal, Qué: McGill University, 2000.

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Capítulos de libros sobre el tema "Deactivation"

1

Weik, Martin H. "deactivation". En Computer Science and Communications Dictionary, 366. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/1-4020-0613-6_4457.

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Richardson, James T. "Catalyst Deactivation". En Principles of Catalyst Development, 185–222. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4899-3725-4_8.

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Figueiredo, J. L. y F. Ramôa Ribeiro. "Catalyst Deactivation". En Combinatorial Catalysis and High Throughput Catalyst Design and Testing, 145–73. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4329-5_5.

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Boskovic, Goran y Manfred Baerns. "Catalyst Deactivation". En Basic Principles in Applied Catalysis, 477–503. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-662-05981-4_14.

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Schmal, Martin y José Carlos Pinto. "Catalyst deactivation". En Chemical Reaction Engineering, 511–32. 2a ed. London: CRC Press, 2021. http://dx.doi.org/10.1201/9781003046608-19.

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Guisnet, M. y P. Magnoux. "Deactivation of Zeolites by Coking. Prevention of Deactivation and Regeneration". En Zeolite Microporous Solids: Synthesis, Structure, and Reactivity, 457–74. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2604-5_20.

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Ganczarski, Artur, Halina Egner y Marcin Cegielski. "Deactivation of Damage Effects". En Encyclopedia of Continuum Mechanics, 1–9. Berlin, Heidelberg: Springer Berlin Heidelberg, 2019. http://dx.doi.org/10.1007/978-3-662-53605-6_256-1.

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Dell, P., M. Bonvallet y A. Hugelin. "Mechanisms of Reticular Deactivation". En Ciba Foundation Symposium - The Nature of Sleep, 86–107. Chichester, UK: John Wiley & Sons, Ltd., 2008. http://dx.doi.org/10.1002/9780470719220.ch5.

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Nielsen, P. E. Højlund. "Deactivation of Synthesis Catalyst". En Catalytic Ammonia Synthesis, 285–301. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4757-9592-9_8.

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Janssens, J. P., A. D. van Langeveld, S. T. Sie y J. A. Moulijn. "Catalyst Deactivation in Hydrodemetallization". En ACS Symposium Series, 238–52. Washington, DC: American Chemical Society, 1996. http://dx.doi.org/10.1021/bk-1996-0634.ch018.

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Actas de conferencias sobre el tema "Deactivation"

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Strange, Dakota B. y Pingen Chen. "A Cylinder Deactivation Control Framework for Gasoline Engines without Valve Deactivation". En 2020 American Control Conference (ACC). IEEE, 2020. http://dx.doi.org/10.23919/acc45564.2020.9147316.

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Vinodh, B. "Technology for Cylinder Deactivation". En SAE 2005 World Congress & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2005. http://dx.doi.org/10.4271/2005-01-0077.

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NAGASAWA, YUTAKA, SATORU NAKASHIMA, CHIHIRO EGAMI, TADASHI OKADA, TAKAMITU KOHZUMA, RAN MATUKURA y SACHIKO YANAGISAWA. "COHERENT DEACTIVATION PROCESS OF PSEUDOAZURIN". En With Foreword by Prof A H Zewail, Nobel Laureate in Chemistry, 1999. WORLD SCIENTIFIC, 2002. http://dx.doi.org/10.1142/9789812777980_0080.

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Xu, Zhiwen, Yuxin Li, Yungang Wang, Hao Wang y Qinxin Zhao. "Deactivation Characteristics of SCR Catalyst at Different Stages in Coal-Fired Flue Gas". En ASME 2018 12th International Conference on Energy Sustainability collocated with the ASME 2018 Power Conference and the ASME 2018 Nuclear Forum. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/es2018-7352.

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Through analyzing the impact of the factors of catalyst deactivation, different factors are classified according to timeliness characteristics. In this research, experiments were made under the condition of coal combustion flue gas on a coal-fired boiler to study the characteristics of the early deactivation of the SCR catalyst. Analysis shows that the main cause of early deactivation of catalyst is chemical poisoning (mainly alkali metal) and pores clogging on the surface of the catalyst. While the main cause of long-term deactivation is deeper chemical poisoning, pores clogging and the chemical form changes of elements on the surface of the catalyst. Through analyzing the influence of the factors of catalyst deactivation, separate factors are classified according to timeliness characteristics. This research provides a strong fundamental support to clear the deactivation mechanism of the SCR catalyst.
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Dou, Danan y Owen H. Bailey. "Investigation of NOx Adsorber Catalyst Deactivation". En International Fall Fuels and Lubricants Meeting and Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1998. http://dx.doi.org/10.4271/982594.

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Uy, Dairene y Ann E. O'Neill. "Raman Studies of Automotive Catalyst Deactivation". En SAE 2006 World Congress & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2006. http://dx.doi.org/10.4271/2006-01-0409.

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Bemman, Ya-Juan, Tom Frei, Chris Jones y Mathias Keck. "Passive Exhaust System With Cylinder Deactivation". En SAE 2005 Noise and Vibration Conference and Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2005. http://dx.doi.org/10.4271/2005-01-2351.

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Bartley, Gordon J. y Theodore Kostek. "SCR Deactivation Study for OBD Applications". En SAE 2012 World Congress & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2012. http://dx.doi.org/10.4271/2012-01-1076.

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Giroire, Frédéric, Nicolas Nisse, Kostiantyn Ohulchanskyi, Małgorzata Sulkowska y Thibaud Trolliet. "Preferential Attachment Hypergraph with Vertex Deactivation". En 2023 31st International Symposium on Modeling, Analysis, and Simulation of Computer and Telecommunication Systems (MASCOTS). IEEE, 2023. http://dx.doi.org/10.1109/mascots59514.2023.10387624.

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Ku¨hnel, Janpeter y Reza S. Abhari. "Part Load Behavior Optimization of Hybrid Coal and Gas Fired Combined Cycles Including Deactivation of Components". En ASME Turbo Expo 2002: Power for Land, Sea, and Air. ASMEDC, 2002. http://dx.doi.org/10.1115/gt2002-30136.

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This paper presents a methodology to optimize the part load behavior of complex power plant cycles. As free optimization parameters the traditional continuous control parameter and the activation/deactivation of defined plant components are considered resulting in a mixed integer non-linear programming problems (MINLP). The procedure starts with a continuous process on either side of the non-linearity in part load, while refining the steps as it approaches the discontinuity. It is shown that good convergence around the non-linearity can be found with the present scheme. For part load operation a number of continuous and binary free optimization parameters are available creating a challenging optimization problem. The developed procedure is applied to a conventional steam cycle power plant, which is parallel repowered with a modern gas turbine. The resulting power plant layout is a hybrid coal and gas fired combined cycle. As objective function the maximized overall thermal efficiency and the minimized fuel costs are two examples chosen. Investigating the minimized fuel costs as the objective function the optimized operation strategy is found to be an unique function of the fuel price ratio between coal and gas for the chosen layout. Finally we show, that the operation strategy can be notably improved by considering the deactivation of cycle components for minimizing the fuel costs and for maximizing the cycle efficiency. For example the cycle efficiency can be improved up to 2% by deactivating the high pressure feed water preheating. The fuel costs are reduced by 20% for a particular load point by deactivating the gas turbine.
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Informes sobre el tema "Deactivation"

1

Szilagyi, Andrew. Deactivation implementation guide. Office of Scientific and Technical Information (OSTI), septiembre de 1999. http://dx.doi.org/10.2172/1491067.

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Yook, H. R., J. R. Barnett y T. L. Collins. Deactivation of Building 7602. Office of Scientific and Technical Information (OSTI), octubre de 1995. http://dx.doi.org/10.2172/204212.

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Smalley, Vinyard y Evans. L51511 Deactivating Power Cylinders under Reduced Load on Two-Cycle Engines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), septiembre de 1986. http://dx.doi.org/10.55274/r0010517.

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Investigates potential and procedures for selective deactivation of one or more power cylinders in two-cycle engines under reduced load to effect fuel savings while avoiding possible engine derangement. The objectives were to identify any major problems with cylinder deactivation, to quantify likely benefits, to determine potential increases in load or stress, and to generate guidelines from the project results. This study showed that economic benefits are possible with the careful use of cylinder deactivation; however, several operational problems were encountered, such as spark plug fouling, oil pumping, increased noise due to a mismatched muffler cutoff frequency, and increased wear in the deactivated cylinders.
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Bogen, D. M. PFP deactivation project management plan. Office of Scientific and Technical Information (OSTI), julio de 1997. http://dx.doi.org/10.2172/312807.

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Stefanski, L. D. UO3 deactivation end point criteria. Office of Scientific and Technical Information (OSTI), octubre de 1994. http://dx.doi.org/10.2172/10186476.

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Lund, D. P. y 309 Building Working Group. 309 Building deactivation function analysis report. Office of Scientific and Technical Information (OSTI), septiembre de 1995. http://dx.doi.org/10.2172/447988.

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Stordeur, R. T. ,. Westinghouse Hanford. 340 Waste handling facility deactivation plan. Office of Scientific and Technical Information (OSTI), diciembre de 1996. http://dx.doi.org/10.2172/325070.

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Peterson, David Shane y Frank Laverne Webber. Deactivation, Decontamination and Decommissioning Project Summaries. Office of Scientific and Technical Information (OSTI), julio de 2001. http://dx.doi.org/10.2172/910753.

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Lund, D. P. y 308 Building Working Group. 308 Building deactivation function analysis report. Office of Scientific and Technical Information (OSTI), septiembre de 1995. http://dx.doi.org/10.2172/450042.

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Lund, D. P. y PUREX Working Group. PUREX Plant deactivation function analysis report. Office of Scientific and Technical Information (OSTI), septiembre de 1995. http://dx.doi.org/10.2172/450051.

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