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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Engineering Characteristics of Sensitive Marine Clays - Examples of Clays in Eastern Canada

Nader, Athir 28 February 2014 (has links)
Sensitive marine clay in Ottawa is a challenging soil for geotechnical engineers. This type of clay behaves differently than other soils in Canada or other parts of the world. They also have different engineering characteristic values in comparison to other clays. Cone penetration testing in sensitive marine clays is also different from that carried out in other soils. The misestimation of engineering characteristics from cone penetration testing can result. Temperature effects have been suspected as the reason for negative readings and erroneous estimations of engineering characteristics from cone penetration testing. Furthermore, the applicability of correlations between cone penetration test (CPT) results and engineering characteristics is ambiguous. Moreover, it is important that geotechnical engineers who need to work with these clays have background information on their engineering characteristics. This thesis provides comprehensive information on the engineering characteristics and behaviour of sensitive marine clays in Ottawa. This information will give key information to geotechnical engineers who are working with these clays on their behaviour. For the purpose of this research, fifteen sites in the Ottawa area are taken into consideration. These sites included alternative technical data from cone and standard penetration tests, undisturbed samples, field vanes, and shear wave velocity measurements. Laboratory testing carried out for these sites has resulted in acquiring engineering parameters of the marine clay, such as preconsolidation pressure, overconsolidation ratio, compression and recompression indexes, secondary compression index, coefficient of consolidation, hydraulic conductivity, clay fraction, porewater chemistry, specific gravity, plasticity, moisture content, unit weight, void ratio, and porosity. This thesis also discusses other characteristics of sensitive marine clays in Ottawa, such as their activity, sensitivity, structure, interface shear behaviour, and origin and sedimentation. Furthermore, for the purpose of increasing local experience with the use of cone and ball penetrometers in sensitive marine clays in Ottawa, three types of penetrometer tips are used in the Canadian Geotechnical Research Site No. 1 located in south-west Ottawa: 36 mm cone tip, and 40 mm and 113 mm ball tips. The differences in their response in sensitive marine clays will be discussed. The temperature effects on the penetrometer equipment are also studied. The differences in the effect of temperature on these tips are discussed. Correlations between the penetrometer results and engineering characteristics of Ottawa's clays are verified. The applicability of correlations between the testing results and engineering characteristics of sensitive marine clays in Ottawa is also presented in this thesis. Two correlations from the Canadian Foundation Engineering Manual are examined. One of these correlations is between the N60 values from standard penetration testing and undrained shear strength. The other correlation is between the shear wave velocity measurement and site class. Temperature corrections are suggested and discussed for penetrometer equipment according to laboratory calibrations. The significance of the effects due to radical temperature changes in Canada and Ottawa is discussed. Some of the main findings from this research are as follows. • The Canadian Foundation Engineering Manual presents a correlation between standard penetration tests (SPTs) and the undrained shear strength of soils. This relationship may not be applicable to sensitive marine clays in Ottawa. • Another correlation between the site class, shear wave velocity, and undrained shear strength is presented by this same manual which may not be applicable to sensitive marine clays in Ottawa. • The rotation rate for field vane testing as recommended by ASTM D2573 is slow for sensitive marine clays in Ottawa. • Correction factors applied to undrained shear strength from laboratory vane tests may not result in comparable values with the undrained shear strength obtained by using field vane tests. • Loading schemes in consolidation or oedometer testing may affect the quality of the targeted results. • Temperature corrections should be applied to penetrometer recordings to compensate for the drift in the results of these recordings due to temperature changes. • The secondary compression index to compression index ratio presented in the literature may not be the value obtained from this research.
92

Estimation of Pile Capacity by Optimizing Dynamic Pile Driving Formulae

Rauf, Awais January 2012 (has links)
Piles have been used since prehistoric times in areas with weak subsurface conditions either to reinforce existing ground, create new ground for habitation or trade, and support bridges and buildings. Originally piles were composed of timber and driven with drop hammers using very heavy ram weights. As technology improved so did the materials that piles are composed of as well as the equipment itself. Currently, piling is a multibillion dollar a year industry, thus the need to develop more accurate prediction methods can potentially represent a significant savings in cost, material, and man power. Multiple predictive methods have been developed to estimate developed pile capacity. These range from static theoretical formulae based on geotechnical investigation prior to pile driving even occurring using specific pile and hammer types to semi empirically based dynamic formulae used during actual driving operations to more recently developed computer modeling and signal matching programs which are calibrated with site condition during initial geotechnical investigations or test piling to full scale static load tests where piles are loaded to some predetermined value or failure condition. In this thesis, dynamic formulae are used to predict pile capacity from those installed by drop and diesel hammers and are compared to the results from pile load tests, which are taken as the true measure of developed bearing capacity. The dynamic formulae examined are the Engineering News Record (ENR), Gates, Federal Highway Administration (FHWA) modified Gates, Hiley, and Ontario Ministry of Transportation (MTO) modified Hiley formulae. Methods of investigation include calculating pile capacities from the formulae as they are, omitting the factors of safety, revising the formulae with averaged coefficients and conducting multi regression analysis to solve for one or two coefficients simultaneously and revising the dynamic formula to determine if more accurate bearing capacity prediction are possible. To objectively determine which formulae provide the most accurate bearing capacities, the predicted capacities will be compared to results obtained from static pile load tests and simple statistics on the resulting data set will be calculated including regression analysis, standard deviations, coefficients of variation, coefficients of determination, and correlation values.
93

Caminhos da Reforma Agrária: o processo histórico da Reforma Agrária no alto sertão paraibano, da luta pela terra à luta na terra (1985-2012).

Oliveira, Giordan Silva de 29 August 2013 (has links)
Made available in DSpace on 2015-05-14T12:23:08Z (GMT). No. of bitstreams: 1 ArquivoTotalGiordan.pdf: 3155029 bytes, checksum: d30fd7482a1c6ce8eb108c7e608a8c49 (MD5) Previous issue date: 2013-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study investigated the historical process of Agrarian Reform in High Hinterland of Paraíba in the period 1985-2012, showing the process of occupation of the backcountry, highlighting the importance of cotton activity not only for the economy, but also for maintenance of working relationships not typically capitalist, serving as a damper for conflicts between landowners and peasants in this region. As it is located in a region full semiarid Paraiba this research has its area of concentration of study in Brazil Regional History. The work shows the first phase of the fights in public areas and the process of formation of the Pastoral Land Commission (CPT) in High Hinterland of Paraíba. Another aspect studied is the second phase of the struggles that took place in private areas and the creation and operation of the Central Associations of Paraiba backwoods settlements of Upper (CAAASP), identifying the major changes that have occurred in the lives of peasants as well as the impacts of these changes in the region. The story of this journey was systematized, bringing an overview of the processes, facts and achievements of the people in the struggle for land and the land in this region in search of better living conditions . To rescue the history of the struggle for land in High Hinterland of Paraíba this work becomes an invitation to the academic community for further research, both on the topic of Agrarian Question and the Field of Social Movements, how about a multitude of issues relevant to life rural communities in the region. / Este trabalho investigou o processo histórico de Reforma Agrária no Alto Sertão da Paraíba no período entre 1985 a 2012, mostrando o processo de ocupação do espaço sertanejo, destacando a importância da atividade algodoeira não só para a economia, como também para manutenção das relações de trabalho não tipicamente capitalistas, servindo de amortecedor para os conflitos entre os latifundiários e os camponeses nessa região. Como se trata de uma região localizada em pleno Semiárido paraibano esta pesquisa tem sua área de concentração de estudo na História Regional do Brasil. O trabalho mostra a primeira fase das lutas em áreas públicas e o processo de formação da Comissão da Pastoral da Terra (CPT) no Alto Sertão paraibano. Outro aspecto pesquisado é a segunda fase das lutas que se deu em áreas privadas e a criação e atuação da Central das Associações dos Assentamentos do Alto Sertão Paraibano (CAAASP), identificando-se as principais mudanças que ocorreram na vida dos camponeses, bem como, os impactos dessas mudanças na região. A história desse percurso foi sistematizada, trazendo uma visão geral dos processos, fatos e conquistas do povo na luta pela terra e na terra, nessa região, na busca de melhoria das condições de vida. Ao resgatar a história da luta pela terra no Alto Sertão Paraibano, este trabalho torna-se um convite à comunidade acadêmica para novas investigações, tanto sobre o tema da Questão Agrária e dos Movimentos Sociais do Campo, como sobre uma infinidade de questões pertinentes à vida das comunidades rurais nessa região.
94

Engineering Characteristics of Sensitive Marine Clays - Examples of Clays in Eastern Canada

Nader, Athir January 2014 (has links)
Sensitive marine clay in Ottawa is a challenging soil for geotechnical engineers. This type of clay behaves differently than other soils in Canada or other parts of the world. They also have different engineering characteristic values in comparison to other clays. Cone penetration testing in sensitive marine clays is also different from that carried out in other soils. The misestimation of engineering characteristics from cone penetration testing can result. Temperature effects have been suspected as the reason for negative readings and erroneous estimations of engineering characteristics from cone penetration testing. Furthermore, the applicability of correlations between cone penetration test (CPT) results and engineering characteristics is ambiguous. Moreover, it is important that geotechnical engineers who need to work with these clays have background information on their engineering characteristics. This thesis provides comprehensive information on the engineering characteristics and behaviour of sensitive marine clays in Ottawa. This information will give key information to geotechnical engineers who are working with these clays on their behaviour. For the purpose of this research, fifteen sites in the Ottawa area are taken into consideration. These sites included alternative technical data from cone and standard penetration tests, undisturbed samples, field vanes, and shear wave velocity measurements. Laboratory testing carried out for these sites has resulted in acquiring engineering parameters of the marine clay, such as preconsolidation pressure, overconsolidation ratio, compression and recompression indexes, secondary compression index, coefficient of consolidation, hydraulic conductivity, clay fraction, porewater chemistry, specific gravity, plasticity, moisture content, unit weight, void ratio, and porosity. This thesis also discusses other characteristics of sensitive marine clays in Ottawa, such as their activity, sensitivity, structure, interface shear behaviour, and origin and sedimentation. Furthermore, for the purpose of increasing local experience with the use of cone and ball penetrometers in sensitive marine clays in Ottawa, three types of penetrometer tips are used in the Canadian Geotechnical Research Site No. 1 located in south-west Ottawa: 36 mm cone tip, and 40 mm and 113 mm ball tips. The differences in their response in sensitive marine clays will be discussed. The temperature effects on the penetrometer equipment are also studied. The differences in the effect of temperature on these tips are discussed. Correlations between the penetrometer results and engineering characteristics of Ottawa's clays are verified. The applicability of correlations between the testing results and engineering characteristics of sensitive marine clays in Ottawa is also presented in this thesis. Two correlations from the Canadian Foundation Engineering Manual are examined. One of these correlations is between the N60 values from standard penetration testing and undrained shear strength. The other correlation is between the shear wave velocity measurement and site class. Temperature corrections are suggested and discussed for penetrometer equipment according to laboratory calibrations. The significance of the effects due to radical temperature changes in Canada and Ottawa is discussed. Some of the main findings from this research are as follows. • The Canadian Foundation Engineering Manual presents a correlation between standard penetration tests (SPTs) and the undrained shear strength of soils. This relationship may not be applicable to sensitive marine clays in Ottawa. • Another correlation between the site class, shear wave velocity, and undrained shear strength is presented by this same manual which may not be applicable to sensitive marine clays in Ottawa. • The rotation rate for field vane testing as recommended by ASTM D2573 is slow for sensitive marine clays in Ottawa. • Correction factors applied to undrained shear strength from laboratory vane tests may not result in comparable values with the undrained shear strength obtained by using field vane tests. • Loading schemes in consolidation or oedometer testing may affect the quality of the targeted results. • Temperature corrections should be applied to penetrometer recordings to compensate for the drift in the results of these recordings due to temperature changes. • The secondary compression index to compression index ratio presented in the literature may not be the value obtained from this research.
95

Zeitabhängige Verfestigungseffekte im Sand

Conzen, Philipp 20 May 2021 (has links)
Gegenstand dieser Arbeit ist die Untersuchung von zeitabhängigen Verfestigungseffekten in Sandböden. Dies geschieht im Rahmen des Leitthemas „Modifizierung und Optimierung von Baugrund zur Ressourcenschonung“ bei der G²-Gruppe Geotechnik. Die bereits in Feld- und Laborversuchen beobachtete und untersuchte Zunahme von Festigkeits- und Steifigkeitsparametern in grobkörnigen Böden über Zeit, die nicht auf die Setzung zurückzuführen ist, wird anhand von zwei Versuchsmethoden unter Laborbedingungen untersucht. Die Versuche werden unter Betrachtung verschiedener Einflussfaktoren durchgeführt. Die verwendeten Methoden sind eine Labor-Drucksondierung und eine Ultraschalluntersuchung, deren Prüfgeräte für die Untersuchung der zeitabhängigen Verfestigungseffekte entwickelt wurden. Die Kontrolle der Geeignetheit für den Nachweis der zu untersuchenden Effekte und die damit verbundenen Anpassungen der Prüfgeräte sollen die Erstellung und Optimierung eines Versuchsprogramms ermöglichen.:Einleitung 1 Überblick 1.1 Hinweis zum Ultraschallversuch 2 Ziele 3 Grundlagen und Stand der Wissenschaft 3.1 Beschreibung des Effekts 3.2 Abgrenzung zu zeitabhängigen Verfestigungseffekten in bindigen Böden 3.3 Sand in der Geotechnik 3.3.1 Makroskopische Betrachtung geotechnischer Eigenschaften 3.3.2 Mikroskopische Betrachtung geotechnischer Eigenschaften 3.4 Kenntnisstand der Wissenschaft zum Aging-Effekt in grobkörnigen Böden 3.5 Labor- und Feldversuche zur Untersuchung von Aging-Effekten in Sandböden 4 Versuchsmethodik 4.1 Einführung 4.2 Untersuchung des Versuchsmaterials 4.2.1 Bodenkenngrößen 4.2.2 Mikroskopische Bodenuntersuchung 4.3 Labor-Drucksondierung 4.3.1 Versuchsaufbau 4.3.2 Übersicht der Versuchsreihen 4.3.3 Versuchsauswertung 5 Ergebniszusammenstellung und Auswertung 6 Fazit und Ausblick 7 Literaturverzeichnis Erklärung / The subject is the investigation of time-dependent consolidation effects in sandy soils. This takes place within the framework of the main theme 'Modification and optimization of subsoil to conserve resources' at the G²-Gruppe Geotechnik. The increase in strength and stiffness parameters in granular soils over time, which has already been observed and investigated in field and laboratory tests, and which is not due to settlement, is investigated using two testing methods under laboratory conditions. The tests are carried out considering various parameters. The methods used are a Mini-CPT and an ultrasonic examination, the test equipment of which was developed for the examination of the Aging-effect of soils. The control of the suitability for the verification of the effects to be examined and the related adaptations of the test devices should enable the designing of a test routine.:Einleitung 1 Überblick 1.1 Hinweis zum Ultraschallversuch 2 Ziele 3 Grundlagen und Stand der Wissenschaft 3.1 Beschreibung des Effekts 3.2 Abgrenzung zu zeitabhängigen Verfestigungseffekten in bindigen Böden 3.3 Sand in der Geotechnik 3.3.1 Makroskopische Betrachtung geotechnischer Eigenschaften 3.3.2 Mikroskopische Betrachtung geotechnischer Eigenschaften 3.4 Kenntnisstand der Wissenschaft zum Aging-Effekt in grobkörnigen Böden 3.5 Labor- und Feldversuche zur Untersuchung von Aging-Effekten in Sandböden 4 Versuchsmethodik 4.1 Einführung 4.2 Untersuchung des Versuchsmaterials 4.2.1 Bodenkenngrößen 4.2.2 Mikroskopische Bodenuntersuchung 4.3 Labor-Drucksondierung 4.3.1 Versuchsaufbau 4.3.2 Übersicht der Versuchsreihen 4.3.3 Versuchsauswertung 5 Ergebniszusammenstellung und Auswertung 6 Fazit und Ausblick 7 Literaturverzeichnis Erklärung
96

Blast-Induced Liquefaction and Downdrag Development on a Micropile Foundation

Lusvardi, Cameron Mark 14 December 2020 (has links)
Frequently, deep foundations extend through potentially liquefiable soils. When liquefaction occurs in cohesionless soils surrounding a deep foundation, the skin-friction in the liquefied layer is compromised. After cyclical forces suspend and pore pressures dissipate, effective stress rebuilds and the liquefied soil consolidates. When the settlement of the soil exceeds the downward movement of the foundation, downdrag develops. To investigate the loss and redevelopment of skin-friction, strain was measured on an instrumented micropile during a blast-induced liquefaction test in Mirabello, Italy. The soil profile where the micropile was installed consisted of clay to a depth of 6m underlain by a medium to dense sand. The 25cm diameter steel reinforced concrete micropile was bored to a depth of 17m. Pore pressure transducers were placed around the pile at various depths to observe excess pore pressure generation and dissipation. Soil strain was monitored with profilometers in a linear arrangement from the center of the 10m diameter ring of buried explosives out to a 12m radius. Immediately following the blast, liquefaction developed between 6m and 12m below ground. The liquefied layer settled 14cm (~2.4% volumetric strain) while the pile toe settled 1.24cm under elastic displacement. The static neutral plane in the pile occurred at a depth of 12m. From 6m to 12m below ground, the incremental skin-friction was 50% compared to pre-liquefaction measurements. The decrease in residual skin-friction is consistent with measurements observed by Dr. Kyle Rollins from previous full-scale tests in Vancouver, BC, Canada, Christchurch, New Zealand, and Turrel, Arkansas.
97

Promoting the implementation of collaborative tuberculosis and human immunodefiency virus activities in Addis Ababa, Ethiopia

Amenu Wesen Denegetu 11 1900 (has links)
This study assessed implementation status of collaborative TB/HIV services in Addis Ababa City Administration aiming to promote better implementation strategies. The study employed mixed research methods and was descriptive. The study design used both quantitative and qualitative data using structured questionnaires and semi-structured interview guides, respectively. The study population for the quantitative design included 1,683 TB/HIV patients from 10 conveniently selected health facilities: Zewditu and Menelik Hospitals, health centres of Lideta, Yeka, Kazanchis, NifaSilk-Lafto-No1, Woreda-7, Kality, Bole and Gulele. All the patients who were on their follow-up cares during the data collection period were interviewed. Participants for qualitative design were 1,650 TB/HIV patients for short answered questions; 8 FGDs among patients; interview of 10 TB/HIV care facility coordinators/health workers and one regional TB/HIV care coordinator, all purposively selected. Quantitative data was analysed using SPSS 15.0, while qualitative data were thematically analysed manually. Majority of HIV patients (92.8%) self-reported that they had been screened for TB; of which, 11.2% were diagnosed for active TB during their follow-up cares. Whereas, 87.1% of TB patients had been offered for HIV test; 79.8% tested; 20.2% tested positive. Knowledge on TB and HIV diseases, transmission and prevention was found to be low. However, participants appreciated the support of the healthcare delivery system in improving their health. Collaborative TB/HIV activities brought additional on-the-job training for healthcare workers; improved flow of logistics and re-arrangement of infrastructures of facilities. The study revealed that, implementation of collaborative TB/HIV activities in Addis Ababa need boosting. The study recommends the need for coordinated efforts of all stakeholders for improving implementation of collaborative TB/HIV care services, as identified by this study. The contribution of this study developed pocket-guide for healthcare workers on collaborative TB/HIV care services, which provides guidance in promoting better TB/HIV care / Health Studies / D. Litt. et Phil. (Health Studies)
98

TITRATING COGNITIVE CONTROL: TRIAL-LEVEL DYNAMIC USE OF PROACTIVE AND REACTIVE COGNITIVE CONTROL

Elizabeth A Wiemers (9182093) 29 July 2020 (has links)
<p>Cognitive control is accomplished by a set of higher-order cognitive processes that are recruited to aid in the completion of various tasks. A popular proposed mechanism is the Dual Mechanisms of Control (Braver, Gray, & Burgess, 2007), proposing proactive and reactive mechanisms. While neuroscience studies provide evidence that these are two distinct processes, it remains unclear whether the processes are competing, or whether they can be used together. That is, are the two processes able to both be enacted to some degree? Further, whether these mechanisms can be titrated to produce a gradient-like use of control on a trial-level basis is unknown. These are the two primary pursuits of this dissertation. Experiment 1 shows the titrated pattern of control use, indicating (a) sensitivity to task demands, and (b) dynamic use of proactive and reactive control at the trial level, in a new task. Further, a novel contribution is the observation of ability to titrate the use of control. Additional experiments relate performance on this task to working memory (Experiment 2), replicate the findings in an online format (Experiment 3), and differentiate performance from distance effects commonly seen in relative judgment tasks (Experiment 4). This work has implications for the understanding of how cognitive control functions and how dynamically the use of these mechanisms can be adjusted.</p>
99

Blast-Induced Liquefaction and Downdrag Development on a Micropile Foundation

Lusvardi, Cameron Mark 14 December 2020 (has links)
Frequently, deep foundations extend through potentially liquefiable soils. When liquefaction occurs in cohesionless soils surrounding a deep foundation, the skin-friction in the liquefied layer is compromised. After cyclical forces suspend and pore pressures dissipate, effective stress rebuilds and the liquefied soil consolidates. When the settlement of the soil exceeds the downward movement of the foundation, downdrag develops. To investigate the loss and redevelopment of skin-friction, strain was measured on an instrumented micropile during a blast-induced liquefaction test in Mirabello, Italy. The soil profile where the micropile was installed consisted of clay to a depth of 6m underlain by a medium to dense sand. The 25cm diameter steel reinforced concrete micropile was bored to a depth of 17m. Pore pressure transducers were placed around the pile at various depths to observe excess pore pressure generation and dissipation. Soil strain was monitored with profilometers in a linear arrangement from the center of the 10m diameter ring of buried explosives out to a 12m radius. Immediately following the blast, liquefaction developed between 6m and 12m below ground. The liquefied layer settled 14cm (~2.4% volumetric strain) while the pile toe settled 1.24cm under elastic displacement. The static neutral plane in the pile occurred at a depth of 12m. From 6m to 12m below ground, the incremental skin-friction was 50% compared to pre-liquefaction measurements. The decrease in residual skin-friction is consistent with measurements observed by Dr. Kyle Rollins from previous full-scale tests in Vancouver, BC, Canada, Christchurch, New Zealand, and Turrel, Arkansas.
100

Cognitive dysfunction and schizophrenia : Modelling attentional impairment with psychotomimetics. Investigating attentional impairment and structural brain abnormalities following phencyclidine administration: Enhancing translatability between preclinical and clinical tests of attention utilising the modified 5-choice task in rats - the 5-Choice Continuous Performance Test.

Barnes, Samuel January 2011 (has links)
This thesis consisted of experiments designed to explore the construct of attention and investigate the disruptive effects of psychotomimetics, with a specific focus on NMDA antagonists. Phencyclidine (PCP) was administered through a variety of treatment regimens in order to to determine the ability of inducing cognitive-specific disruptions in attentional functioning. The hypothesis that sub-chronic exposure to PCP would result in persistent attentional impairment was tested, using the 5-choice serial reaction time task (5-CSRTT). The 5-CSRTT assesses not only visuospatial attention, but also components of impulsivity, compulsivity, speed of processing and motivation. It was determined that an additional task-related intervention that increased the attentional load was required to elucidate attentional impairment following sub-chronic PCP treatment. The ability of rats to perform the modified version of the 5-CSRTT, known as the 5-choice continuous performance test (5C-CPT), was investigated. The 5C-CPT was implemented to provide a task that may have greater analogy to the human CPT, than the original 5-CSRTT. The consequence of dopaminergic D1 system activation was investigated. It was revealed that D1 partial agonism improved attentional performance in a baseline-dependent manner. Following successful acquisition of the task, it was shown that repeated PCP treatment induced cognitive disruption that was cognitive-specific, and not confounded by generalised response disruption. Furthermore, a partial attenuation of the PCP-induced performance disruption was achieved following administration of the D1 partial agonist, SKF 38393. Moreover, sub-chronic PCP treatment was shown to impair 5C-CPT performance in the drug-free state. However, an additional challenge that further increased the attentional load was needed to elucidate a performance deficit. This highlighted that sustained attention/vigilance is sensitive to persistent impairment following sub-chronic PCP administration in a manner consistent with deficits observed in schizophrenia patients. This prompted the investigation that tested the hypothesis that sub-chronic PCP treatment could induce enduring structural deficits in regions associated with attentional performance. Magnetic resonance imaging (MRI) was conducted, in conjunction with 5-CSRTT and pre-pulse inhibition (PPI). It was revealed that sub-chronic PCP treatment resulted in morphological brain abnormalities in brain regions associated with 5-CSRTT performance. This was coupled with deficits in sustained attentional performance following an increase in attentional load, yet PPI was unaffected. Taken together, these findings suggested sub-chronic PCP treatment impairs attentional functionality, an effect that dissociates between effortful and passive attentional processes.

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