An initial evaluation of gellan gum as a material for tissue engineering applications

Alpha-modified minimum essential medium (αMEM) has been found to cross-link a 1% gellan gum solution, resulting in the formation of a self-supporting hydrogel in 1:1 and 5:1 ratios of polysaccharide: αMEM. Rheological data from temperature sweeps confirm that in addition to orders of magnitude differences in G' between 1% gellan and 1% gellan with αMEM, there is also a 20°C increase in the temperature at which the onset of gelation takes place when αMEM is present. Frequency sweeps confirm the formation of a true gel; mechanical spectra for mixtures of gellan and αMEM clearly demonstrate G' to be independent of frequency. It is possible to immobilize cells within a three-dimensional (3D) gellan matrix that remain viable for up to 21 days in culture by adding a suspension of rat bone marrow cells (rBMC) in αMEM to 1% gellan solution. This extremely simple approach to cell immobilization within 3D constructs, made possible by the fact that gellan solutions cross-link in the presence of millimolar concentrations of cations, poses a very low risk to a cell population immobilized within a gellan matrix and thus indicates the potential of gellan for use as a tissue engineering scaffold. © 2007 Sage Publications.

Oxidised LDL-lipids increase beta amyloid production by SH-SY5Y cells through glutathione depletion and lipid raft formation

Elevated total cholesterol in midlife has been associated with increased risk of dementia in later life. We have previously shown that low-density lipoprotein (LDL) is more oxidized in the plasma of dementia patients, although total cholesterol levels are not different from those of age-matched controls. β-Amyloid (Aβ) peptide, which accumulates in Alzheimer disease (AD), arises from the initial cleavage of amyloid precursor protein by β-secretase-1 (BACE1). BACE1 activity is regulated by membrane lipids and raft formation. Given the evidence for altered lipid metabolism in AD, we have investigated a mechanism for enhanced Aβ production by SH-SY5Y neuronal-like cells exposed to oxidized LDL (oxLDL). The viability of SH-SY5Y cells exposed to 4 μg oxLDL and 25 μM 27-hydroxycholesterol (27OH-C) was decreased significantly. Lipids, but not proteins, extracted from oxLDL were more cytotoxic than oxLDL. In parallel, the ratio of reduced glutathione (GSH) to oxidized glutathione was decreased at sublethal concentrations of lipids extracted from native and oxLDL. GSH loss was associated with an increase in acid sphingomyelinase (ASMase) activity and lipid raft formation, which could be inhibited by the ASMase inhibitor desipramine. 27OH-C and total lipids from LDL and oxLDL independently increased Aβ production by SH-SY5Y cells, and Aβ accumulation could be inhibited by desipramine and by N-acetylcysteine. These data suggest a mechanism whereby oxLDL lipids and 27OH-C can drive Aβ production by GSH depletion, ASMase-driven membrane remodeling, and BACE1 activation in neuronal cells. © 2014 The Authors.

Formation and precise geometry control of SNAP microresonators by external electrostatic fields

In SNAP (Surface nanoscale axial photonics) resonators propagation of a slow whispering gallery mode along an optical fiber is controlled by nanoscale variation of the effective radius of the fiber [1]. Similar behavior can be realized in so - called nanobump microresonators in which the introduced variation of the effective radius is asymmetric, i.e. depends on the axial coordinate [2]. The possibilities of realization of such structures “on the fly” in an optical fiber by applying external electrostatic fields to it is discussed in this work. It is shown that local variations in effective radius of the fiber and in its refractive index caused by external electric fields can be large enough to observe SNAP structure - like behavior in an originally flat optical fiber. Theoretical estimations of the introduced refractive index and effective radius changes and results of finite element calculations are presented. Various effects are taken into account: electromechanical (piezoelectricity and electrostriction), electro-optical (Pockels and Kerr effects) and elasto-optical effect. Different initial fibre cross-sections are studied. The aspects of use of linear isotropic (such as silica) and non-linear anisotropic (such as lithium niobate) materials of the fiber are discussed. REFERENCES [1] M. Sumetsky, J. M. Fini, Opt. Exp. 19, 26470 (2011). [2] L. A. Kochkurov, M. Sumetsky, Opt. Lett. 40, 1430 (2015).

Coke formation in the oxidative dehydrogenation of ethylbenzene to styrene by TEOM

A packed bed microbalance reactor setup (TEOM-GC) is used to investigate the formation of coke as a function of time-on-stream on γ-Al2O3 and 3P/SiO2 catalyst samples under different conditions for the ODH reaction of ethylbenzene to styrene. All samples show a linear correlation of the styrene selectivity and yield with the initial coverage of coke. The COX production increases with the coverage of coke. On the 3 wt% P/SiO2 sample, the initial coke build-up is slow and the coke deposition rate increases with time. On alumina-based catalyst samples, a fast initial coke build-up takes place, decreasing with time-on-stream, but the amount of coke does not stabilize. A higher O2 : EB feed ratio results in more coke, and a higher temperature results in less coke. This coking behaviour of Al2O3 can be described by existing "monolayer-multilayer" models. Further, the coverage of coke on the catalyst varies with the position in the bed. For maximal styrene selectivity, the optimal coverage of coke should be sufficient to convert all O2, but as low as possible to prevent selectivity loss by COX production. This is in favour of high temperature and low O2 : EB feed ratios. The optimal coke coverage depends in a complex way on all the parameters: temperature, the O2 : EB feed ratio, reactant concentrations, and the type of starting material. This journal is

A qualitative study of the impact of an educational intervention on older parents of adults with disabilities engaged in the phenomenon of future-care planning

This phenomenological study describes the impact of an educational intervention on the day-to-day experiences of older parent caregivers of adults with developmental disabilities who were engaged in the process of future-care planning. Qualitative strategies of individual and focus group interviewing were used with a purposive sample of older caregivers. Participants were members of an existing parent support group. Twenty-three caregivers representing 18 families were queried before and after the education program. The disabilities represented were mental retardation, cerebral palsy and autism. Parents whose children live at or away from home were included. The intervention was conducted on five Saturdays over a two month period; the duration of the study was five months. Findings used typical words of the respondents from their individual and focus group interviews to describe feelings, attitudes and experiences in making future-care plans. Data from verbatim transcriptions and researcher's field notes were coded, analyzed, sorted into themes, and subjected to interpretive analysis. Respondents showed a positive change in attitudes and actions after participating in the education program, regardless of their initial stage in care planning. Fears were replaced by hope and determination; hesitation and ineptitude by feelings of competence and confidence; and procrastination and delay by purposeful actions. Other key findings: use of a planning document greatly aided caregivers; barriers to planning were often intrinsic and amenable to education; residential plans were the most difficult aspect of planning; listening to the experiences of other parent caregivers was helpful; and making burial plans for their offspring was one aspect of planning parents wished to do themselves. ^

Inter-subjective and transnational racial effects: The role of the United States in the formation and evolution of the collective perception and racial relations in Cuba, 1898–1902

Since the arrival of the first African slaves to Cuba in 1524, the issue of race has had a long-lived presence in the Cuban national discourse. However, despite Cuba’s colonial history, it has often been maintained by some historians that race relations in Cuba were congenial with racism and racial discrimination never existing as deep or widespread in Cuba as in the United States (Cannon, 1983, p. 113). In fact, it has been argued that institutionalized racism was introduced into Cuban society with the first U.S. occupation, during 1898–1902 (Cannon, 1983, p. 113). This study of Cuba investigates the influence of the United States on the development of race relations and racial perceptions in post-independent Cuba, specifically from 1898-1902. These years comprise the time period immediately following the final fight for Cuban Independence, culminating with the Cuban-Spanish-American War and the first U.S. occupation of Cuba. By this time, the Cuban population comprised Africans as well as descendants of Africans, White Spanish people, indigenous Cubans, and offspring of the intermixing of the groups. This research studies whether the United States’ own race relations and racial perceptions influenced the initial conflicting race relations and racial perceptions in early and post-U.S. occupation Cuba. This study uses a collective interpretative framework that incorporates a national level of analysis with a race relations and racial perceptions focus. This framework reaches beyond the traditionally utilized perspectives when interpreting the impact of the United States during and following its intervention in Cuba. Attention is given to the role of the existing social, political climate within the United States as a driving influence of the United States’ involvement with Cuba. This study reveals that emphasis on the role of the United States as critical to the development of Cuba’s race relations and racial perceptions is credible given the extensive involvement of the U.S. in the building of the early Cuban Republic and U.S. structures serving as models for reconstruction. U.S. government formation in Cuba aligned with a governing system reflecting the existing governing codes of the U.S. during that time period.

Formation of Polycyclic Aromatic Hydrocarbons and Nitrogen Containing Polycyclic Aromatic Compounds in Titan's Atmosphere, the Interstellar Medium and Combustion

Several different mechanisms leading to the formation of (substituted) naphthalene and azanaphthalenes were examined using theoretical quantum chemical calculations. As a result, a series of novel synthetic routes to Polycyclic Aromatic Hydrocarbons (PAHs) and Nitrogen Containing Polycyclic Aromatic Compounds (N-PACs) have been proposed. On Earth, these aromatic compounds originate from incomplete combustion and are released into our environment, where they are known to be major pollutants, often with carcinogenic properties. In the atmosphere of a Saturn's moon Titan, these PAH and N-PACs are believed to play a critical role in organic haze formation, as well as acting as chemical precursors to biologically relevant molecules. The theoretical calculations were performed by employing the ab initio G3(MP2,CC)/B3LYP/6-311G** method to effectively probe the Potential Energy Surfaces (PES) relevant to the PAH and N-PAC formation. Following the construction of the PES, Rice-Ramsperger-Kassel-Markus (RRKM) theory was used to evaluate all unimolecular rate constants as a function of collision energy under single-collision conditions. Branching ratios were then evaluated by solving phenomenological rate expressions for the various product concentrations. The most viable pathways to PAH and N-PAC formation were found to be those where the initial attack by the ethynyl (C2H) or cyano (CN) radical toward a unsaturated hydrocarbon molecule led to the formation of an intermediate which could not effectively lose a hydrogen atom. It is not until ring cyclization has occurred, that hydrogen elimination leads to a closed shell product. By quenching the possibility of the initial hydrogen atom elimination, one of the most competitive processes preventing the PAH or N-PAC formation was avoided, and the PAH or N-PAC formation was allowed to proceed. It is concluded that these considerations should be taken into account when attempting to explore any other potential routes towards aromatic compounds in cold environments, such as on Titan or in the interstellar medium.

Química em cena: uma proposta para formação inicial de professores de química

In educational observed difficulty in train teachers to meet the medium and higher education needs, and one reason for this is the different experiences in the training of educators in relation to those found in the classroom. So often arise criticisms related to relevance and efficiency of degree courses, as regards the performance of its natural mission, which weakens the teacher training. Thus, improving the quality of education is very dependent on the initiatives of teachers, creating teaching alternatives to strengthen their performance in school. From this reflection, it is concluded that teacher training needs new educational proposals that qualify, and so can promote the formation of his students more adequately. Among the educational proposals as alternatives to initial teacher training may use the scientific theater (TC). Considering this possibility, this work has been proposed as investigate and discuss the influence of TC combined with experimentation in the initial training of future teachers in Chemistry who participate in the Groups Fanatics chemistry Theatre (UERN) and Chemistry on Stage (UFRN). Therefore, there was, in a first stage, theatrical essays based on the theater of the oppressed, and written dramaturgical scripts, a collaborative proposal. To incorporate experimentation in chemistry to theater rehearsals, there was a systematic literature search and after content analysis, were selected categories, materials and reagents easily accessible, easy procedures and implementation with low risk of accidents and easy care chemical waste. In the second part we identified: a) the beliefs of student teachers in the use of TC ally trial for initial training of chemistry teachers; b) the influence of TC ally to trial on learning of chemical concepts of high school students who attended the shows; c) the reasons for using or not TC ally to trial by chemistry teachers who participated in the TC group and currently work in the classroom. In this study, questionnaires and interviews were used, compounds, respectively, by a Likert scale and open questions. Quantitative data were analyzed by classical statistics the media, using as centrality measures the average, the concordance argument and the average deviation. Qualitative data were discussed according to content analysis, with categories that emerged from reading the answers. These analyzes concluded that the licensees have a positive view on the use of scientific theater for disclosure of the chemical for use in the learning of chemical concepts, pedagogical and disciplinary knowledge, and to form promotion strategy for research and extension at the University. They credit improvements in their initial training on the use of scientific theater combined with experimentation. The TC provides motivation for the construction of conceptual thinking in an informal way of chemical communication, allowing the student to expand their knowledge, not only favoring the phenomenological approach, but also the construction of chemical knowledge and the internalization of scientific concepts.

Política de formação de professores: variação do locus de formação e a experiência do CEFET-RN

The present article discusses the directives of the policies of the initial teachers’ formation introduced in Brazil in the 1990’s. These directives have brought new directions and demands, both to the formation institutions and to teachers’ formation. This work analyzes the enlargement and the variation of the formation locus, a topic criticized by the teaching educators for enabling different and flexible models which have taken to a more technical and instrumental formation to the detriment of a theoretical and practical solid formation. In a general way, the study reveals that the CEFET’s use as a space of teachers’ formation has given priority to the quantitative aspects, the optimization of the resources and the instrumentation of the educators’ formation, even though under the speech of the quality of the educational process. Differently, the operationalization of this policy at CEFET-RN has favored a formative model, which has joined research, extension and teaching, guaranteeing the specificity of a solid formation, as well as the articulation between theory and practice and the sense of investigation, necessary characteristics to the formation of a devoted educator with the quality of public education.

Volume averaging of multiphase flows with hydrate formation in subsea pipelines

In oil and gas pipeline operations, the gas, oil, and water phases simultaneously move through pipe systems. The mixture cools as it flows through subsea pipelines, and forms a hydrate formation region, where the hydrate crystals start to grow and may eventually block the pipeline. The potential of pipe blockage due to hydrate formation is one of the most significant flow-assurance problems in deep-water subsea operations. Due to the catastrophic safety and economic implications of hydrate blockage, it is important to accurately predict the simultaneous flow of gas, water, and hydrate particles in flowlines. Currently, there are few or no studies that account for the simultaneous effects of hydrate growth and heat transfer on flow characteristics within pipelines. This thesis presents new and more accurate predictive models of multiphase flows in undersea pipelines to describe the simultaneous flow of gas, water, and hydrate particles through a pipeline. A growth rate model for the hydrate phase is presented and then used in the development of a new three-phase model. The conservation equations of mass, momentum, and energy are formulated to describe the physical phenomena of momentum and heat transfer between the fluid and the wall. The governing equations are solved based on an analytical-numerical approach using a Newton-Raphson method for the nonlinear equations. An algorithm was developed in Matlab software to solve the equations from the inlet to the outlet of the pipeline. The developed models are validated against a single-phase model with mixture properties, and the results of comparative studies show close agreement. The new model predicts the volume fraction and velocity of each phase, as well as the mixture pressure and temperature profiles along the length of the pipeline. The results from the hydrate growth model reveal the growth rate and location where the initial hydrates start to form. Finally, to assess the impact of certain parameters on the flow characteristics, parametric studies have been conducted. The results show the effect of a variation in the pipe diameter, mass flow rate, inlet pressure, and inlet temperature on the flow characteristics and hydrate growth rates.

Caminhos da professoralidade no Curso de Dança da UFU: impasses e desafios na construção da identidade profissional

Teacher identity is a subject of study and discussion in the academic world whichhas become an object of attention of researchaddressing teaching and teacher formation. Life history, initial and continuing formation, the meaning of teaching to the teacher, and also pedagogical practice are all contributing factors to teachers’ professional identity. The present study is a proposal developed in the research field of Educational Knowledge and Practice, and its main focus lies in university teaching. Higher education teaching in the context of a dance course, and the issues and challenges of constructing teachers’ professional identity are presented. Thus, my main questions were: what is the teaching path followed by newly hired dance teachers in the Federal University of Uberlândia? How is teaching identity developed in these new teachers’ professional socialization process? What kind of educational knowledge is (re)produced and mobilized by teachers when they join university teaching? In order to answer these questions, my objectives are: to analyze the teaching path of the newly hired dance teachers of the Federal University of Uberlândia; to investigate how their teaching identity is built within their professional socialization process; and identify the kinds of educational knowledge they (re)produce and mobilize as soon as they become university teachers. The present research comprises a qualitative data analysis from previous studies on the subject, having as starting point relevant bibliographic research, followed by an identification questionnaire and an interview conducted with the newly hired dance teachers. The construction of teaching identity is related to objective and subjective conditions involving a teaching job and how the teacher perceives this identity as constantly evolving. Hence I understand the importance of personal and institutional incentives to prepare studies which raise or problematize issues specific to this area, contributing to extend the debate over higher education professionals’ formation, in particular that of dance course teachers on national scope.

O PIBID - Programa Institucional de Bolsas de Iniciação à Docência e a crise das Licenciaturas: o caso de um Curso de Pedagogia a Distância

Tendo em vista a atual crise das licenciaturas, especialmente em termos da pouca atratividade que a formação para a docência vem apresentando em nosso contexto educacional e, considerando, ainda, as críticas sobre a fragilidade da formação inicial de professores ocorrer na modalidade a distância (no caso, o curso de Pedagogia), o PIBID - Programa Institucional de Bolsas de Iniciação à Docência surge como uma política de incentivo e valorização do magistério com o propósito de contribuir para uma formação mais sólida e articulada em termos da relação teoria-prática, especialmente pela proximidade que favorece aos alunos bolsistas, com o cotidiano escolar – este é o foco desta investigação que teve por objetivos: refletir sobre o histórico da formação docente em interface com a desvalorização do magistério que, consequentemente, levou à crise das licenciaturas e, a partir disso, analisar a proposição do PIBID como uma política pública para o enfrentamento desta crise; analisar as representações de bolsistas do PIBID, de um curso de Pedagogia a distância, sobre a experiência que estão tendo, e se ela contribui, no caso dos licenciandos, para o fortalecimento da escolha pela carreira docente; verificar as contribuições do programa para a formação dos licenciandos, dos supervisores (professores das escolas públicas parceiras) e do coordenador de área e se este oportuniza uma complementação na preparação para o exercício da docência. A pesquisa realizou uma revisão da literatura sobre a crise das licenciaturas e o contexto do aparecimento do PIBID, bem como sobre a formação de professores ocorrer na modalidade a distância, tendo como referencial teórico autores como Libâneo (1998), Gatti e Barreto (2009), Bahia e Duran (2011), Scheibe (2006), Sommer (2010), FCC (2009), Tardif (2005). Realizou, também, uma pesquisa de campo que teve como sujeitos sete bolsistas do PIBID de um curso de Pedagogia a distância (de uma instituição de ensino superior, particular, de São Paulo), sendo: quatro licenciandas, duas supervisoras e uma coordenadora de área do subprojeto. Foram aplicados dois instrumentos para a coleta de dados: um questionário para o delineamento do perfil dos sujeitos e a realização de entrevistas de aprofundamento. As reflexões realizadas a partir da revisão da literatura e das análises dos dados coletados junto aos sujeitos indicam que: em relação à proposição da formação inicial de professores a distância, esta denota maiores críticas, diferentemente da formação continuada de professores a distância, que apresenta uma maior aceitabilidade; em relação ao PIBID, os estudos vêm apontando a positividade das diversas experiências que vêm se desenvolvendo no território nacional e que denotam um trabalho articulado entre teoria e prática, bem como no resgate da identidade docente, com uma ênfase na valorização, inserção e permanência dos licenciandos nos seus cursos; as representações dos sujeitos investigados sobre a experiência que estão tendo com o PIBID apontam para: o reconhecimento de que o Programa garante, efetivamente, a reflexão e vivência entre a teoria e prática; a contribuição para a aquisição de maior segurança na relação com os alunos das escolas parceiras e também no desenvolvimento das atividades práticas; a certeza e/ou convicção de que realmente querem ser professoras.

Examining current provision, practice and experience of initial teacher training providers in Ireland preparing pre service teachers for the inclusion of students with special education needs in physical education classes.

Research from an international perspective in relation to the preparation of pre service teachers in physical education and special educational needs indicates that initial teacher training providers are inconsistent in the amount of time spent addressing the issue and the nature of curricular content (Vickerman, 2007). In Ireland, research of Meegan and MacPhail (2005) and Crawford (2011) indicates that physical education teachers do not feel adequately prepared to accommodate students with Special Educational Needs (SEN) in physical education classes. This study examined initial teacher training provision in Ireland in the training of pre service physical education teachers in SEN. The methodology used was qualitative and included questionnaires and interviews (n=4). Findings indicated that time allocation (semester long modules), working with children with disabilities in mainstream settings (school or leisure centre based), lack of collaboration with other PETE providers (n=4) and a need for continued professional development were themes in need of address. Using a combined approach where the recently designed European Inclusive Physical Education Training (Kudlácěk, Jesina, & Flanagan, 2010) model is infused through the undergraduate degree programme is proposed. Further, the accommodation of hands on experience for undergraduates in mainstream settings and the establishment of inter institutional communities of practice, with a national disability research initiative, is essential to ensure quality adapted physical activity training can be accommodated throughout Ireland.

Citizenship formation for a new millennium in Sweden : a prognosis of our time

The aim of this article is to forecast the present situation of citizenship formation in the field of Swedish education. In highlighting trends and tendencies in the educational assignment to provide for democratic citizenship in the first decade of the 21st century, which can be characterised as lacking collective visions for change, three depictions of citizenship are prevailing: citizenship formation for deliberation, for entrepreneurship and for therapeutic intervention. These depictions are analysed in terms of the direction for action taking and attention that they stress and produce as concerns citizenship in the making. The first one, citizenship formation for deliberation, stresses an inward-looking and inward-feeling citizenship. The second one, citizenship formation for entrepreneurship, stresses an inward-looking and outward-making citizenship, and the third one, citizenship formation for therapeutic intervention, stresses an inward-looking and outward-making citizenship. Taking on this forecast, which actualises democracy as something that is already achieved as a consequence of an assumedly post political situation, we argue that citizenship as well as society itself risks being pictured as apolitical and democratically “saturated.” This situation is hazardous, we argue, as it does not open up for change to come into question as desirable or even possible. Put differently, it leaves us with the notion that things have to be as they are, as we are living in the best of worlds. 

Transformer les pratiques professionnelles vis-à-vis des personnes prestataires de l’aide sociale : développement participatif et évaluation d’une formation continue en cabinet dentaire

L’objectif de la présente thèse est de générer des connaissances sur les contributions possibles d’une formation continue à l’évolution des perspectives et pratiques des professionnels de la santé buccodentaire. Prônant une approche centrée sur le patient, la formation vise à sensibiliser les professionnels à la pauvreté et à encourager des pratiques qui se veulent inclusives et qui tiennent compte du contexte social des patients. L’évaluation de la formation s’inscrit dans le contexte d’une recherche-action participative de développement d’outils éducatifs et de transfert des connaissances sur la pauvreté. Cette recherche-action aspire à contribuer à la lutte contre les iniquités sociales de santé et d’accès aux soins au Québec; elle reflète une préoccupation pour une plus grande justice sociale ainsi qu’une prise de position pour une santé publique critique fondée sur une « science des solutions » (Potvin, 2013). Quatre articles scientifiques, ancrés dans une philosophie constructiviste et dans les concepts et principes de l’apprentissage transformationnel (Mezirow, 1991), constituent le cœur de cette thèse. Le premier article présente une revue critique de la littérature portant sur l’enseignement de l’approche de soins centrés sur le patient. Prenant appui sur le concept d’une « épistémologie partagée », des principes éducatifs porteurs d’une transformation de perspective à l’égard de la relation professionnel-patient ont été identifiés et analysés. Le deuxième article de thèse s’inscrit dans le cadre du développement participatif d’outils de formation sur la pauvreté et illustre le processus de co-construction d’un scénario de court-métrage social réaliste portant sur la pauvreté et l’accès aux soins. L’article décrit et apporte une réflexion, notamment sur la dimension de co-formation entre les différents acteurs des milieux académique, professionnel et citoyen qui ont constitué le collectif À l’écoute les uns des autres. Nous y découvrons la force du croisement des savoirs pour générer des prises de conscience sur soi et sur ses préjugés. Les outils développés par le collectif ont été intégrés à une formation continue axée sur la réflexion critique et l’apprentissage transformationnel, et conçue pour être livrée en cabinet dentaire privé. Les deux derniers articles de thèse présentent les résultats d’une étude de cas instrumentale évaluative centrée sur cette formation continue et visant donc à répondre à l’objectif premier de cette thèse. Le premier consiste en une analyse des transformations de perspectives et d’action au sein d’une équipe de 15 professionnels dentaires ayant participé à la formation continue sur une période de trois mois. L’article décrit, entre autres, une plus grande ouverture, chez certains participants, sur les causes structurelles de la pauvreté et une plus grande sensibilité au vécu au quotidien des personnes prestataires de l’aide sociale. L’article comprend également une exploration des effets paradoxaux dans l’apprentissage, notamment le renforcement, chez certains, de perceptions négatives à l’égard des personnes prestataires de l’aide sociale. Le quatrième article fait état de barrières idéologiques contraignant la transformation des pratiques professionnelles : 1) l’identification à l’idéologie du marché privé comme véhicule d’organisation des soins; 2) l’attachement au concept d’égalité dans les pratiques, au détriment de l’équité; 3) la prédominance du modèle biomédical, contraignant l’adoption de pratiques centrées sur la personne et 4) la catégorisation sociale des personnes prestataires de l’aide sociale. L’analyse des perceptions, mais aussi de l’expérience vécue de ces barrières démontre comment des facteurs systémiques et sociaux influent sur le rapport entre professionnel dentaire et personne prestataire de l’aide sociale. Les conséquences pour la recherche, l’éducation dentaire, le transfert des connaissances, ainsi que pour la régulation professionnelle et les politiques de santé buccodentaire, sont examinées à partir de cette perspective.