963 resultados para Construct Development
Resumo:
The present study sought to develop and validate an interview version of the Native American Cultural Involvement and Detachment Anxiety Questionnaire (CIDAQ; McNeil, Porter, Zvolensky, Chaney, & Kee, 2000) in an effort to construct a more culturally appropriate means of obtaining anxiety-related information from a tribally homogenous sample of Native Americans. Five pilot subjects (60% women; M age = 35.8 years) and 50 Native American participants (46% women; M age = 40.32 years) residing on a Northern Plains reservation were administered the CIDAQ - Interview, designed specifically for this study, the Worry Domains Questionnaire (WDQ; Tallis, Eysenck, & Mathews, 1992), a measure of non-pathological worry, the CIDAQ (McNeil et al., 2000), a self-report measure of culturally-related anxiety, and a demographics form. Using a mixed design method of analysis, interviews were audio taped and data was both qualitatively and quantitatively compared for convergence and discrepancies across measures. As hypothesized, CIDAQ-Interview subscales corresponded with subscales from the CIDAQ self-report and included worries and anxiety in three content areas: (1) social involvement with Native Americans and cultural knowledge, (2) economic issues, and (3) social involvement with the majority culture. Results further revealed similarities between CIDAQ-Interview items and those on the CIDAQ self-report, indicating reliability for the Interview. Findings also confirmed the Interview's validity (r 's range = .349-.754), as well as a high level of internal consistency for the CIDAQ self-report (Cronbach alpha = .931). Data suggest the CIDAQ-Interview is a more culturally appropriate method of assessment and may be capable of assessing anxiety at a higher level of specificity then the self-report version. Results of the study are discussed in relation to the assessment of anxiety for homogenous reservation Native Americans, study limitations and directions for future research with the CIDAQ-Interview are also discussed.
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Objectives: The aim of the present study was to investigate the construct validity of the Assessment of Countertransference Scale (ACS) in the context of the trauma care, through the identification of the underlying latent constructs of the measured items and their homogeneity. Methods: ACS assesses 23 feelings of CT in three factors: closeness, rejection and indifference. ACS was applied to 50 residents in psychiatry after the first appointment with 131 victims of trauma consecutively selected during 4 years. ACS was analyzed by exploratory (EFA) and confirmatory (CFA) factor analysis, internal consistence and convergent-discriminant validity. Results: In spite of the fact that closeness items obtained the highest scores, the EFA showed that the factor rejection (24% of variance, alpha = 0.88) presented a more consistent intercorrelation of the items, followed by closeness (15% of variance, alpha = 0.82) and, a distinct factor, sadness (9% of variance, alpha = 0.72). Thus, a modified version was proposed. In the comparison between the original and the proposed version, CFA detected better goodness-of-fit indexes for the proposed version (GFI = 0.797, TLI = 0.867, CFI = 0.885 vs. GFI = 0.824, TLI = 0.904, CFI = 0.918). Conclusions: ACS is a promising instrument for assessing CT feelings, making it valid to access during the care of trauma victims.
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Die TGFbeta/BMP Signaltransduktionskaskade ist wichtig für viele Entwicklungsprozesse fast aller embryonaler sowie extraembryonaler Gewebe und sie ist ebenso essentiell bei der Aufrechterhaltung der Homöostase im adulten Organismus. In vielen Mausmodellen und Zellkulturversuchen wurde gezeigt, dass Liganden dieses Signalweges in verschiedene Stadien der Knorpel- und Knochenentwicklung involviert sind. BMPs sind beispielsweise maßgeblich an der frühen Kondensation und Bildung des Knorpels und später an Proliferation und Hypertrophie der Chondrozyten beteiligt. BMPs können ektopisch Knochenbildung auslösen und das Expressionsmuster der Liganden und spezifischen Rezeptoren in der Wachstumsfuge lässt auf eine wichtige Rolle der BMPs in der Wachstumsfuge schließen. Der gezielte knock out der BMP-Rezeptoren Bmpr1a und Bmpr1b in proliferierenden Chondrozyten führt zur Ausbildung einer generellen Chondrodysplasie. Smad1, Smad5 und Smad8 sind die Mediatoren der BMP-Signalkaskade. Im Rahmen der vorliegenden Arbeit sollte die Rolle und Funktion der Smad1- und Smad5-Proteine in der Wachstumsfuge untersucht werden. Hierzu wurden konditionale Smad1-knock out-Mäuse mit einer transgenen Mauslinie gekreuzt, die die Cre-Rekombinase spezifisch in proliferierenden Chondrozyten exprimiert. Diese Mäuse wurden mit und ohne heterozygotem Smad5-Hintergrund charakterisiert. Bei einem knock out von Smad1 allein konnte ein leichte Verkürzung der Wachstumsfuge beobachtet werden, wobei prähypertrophe und hypertrophe Zone gleichermaßen betroffen waren. Dieser Phänotyp war verstärkt in Mäusen mit zusätzlichem heterozygotem Smad5-Hintergrund. Eine Verringerung der Proliferationsrate konnte zusammen mit einer verminderten Ihh-Expression nachgewiesen werden. Zusätzlich konnte anhand von Röntgenaufnahmen eine Dysorganisation der nasalen Region und ein fehlendes nasales Septum beobachtet werden. Produktion und Mineralisation der extrazellulären Matrix waren nicht beeinträchtigt. Um die Rolle der BMP- und TGFbeta-Signalkaskaden während der endochondralen Ossifikation zu vergleichen, wurden transgene Mäuse generiert, in denen die TGFbeta-Signalkaskade spezifisch in proliferierenden Chondrozyten gestört war. Zwei Mauslinien, die ähnliche Phänotypen zeigten, wurden untersucht. Esl1 ist ein TGFbeta-bindendes Protein, von dem man annimmt, dass es die TGFbeta-Signalkaskade inhibieren kann. Esl1-knock out-Mäuse sind kleiner als Wildtypmäuse und die Überexpression von Esl1 in proliferierenden Chondrozyten führt zu einer Verlängerung der Wachstumsfuge und einer verstärkten Proliferationsrate. Knorpelmarker, wie Col2a1 und Sox9 sind in diesen Mäusen herunterreguliert, während Col10a1 und Ihh als Marker für die hypertrophe und prähypertrophe Zone herunterreguliert waren. Dies führt zu der Annahme, dass mehr Zellen in die terminale Differenzierung eintreten. Bei transgenen Mäusen, in denen ein dominant-negativer (dn) TGFbeta-Rezeptor in proliferierenden Chondrozyten überexprimiert wurde, konnte eine verlängerte prähypertrophe Zone, eine erhöhte Ihh-Expression, sowie eine verstärkte Proliferationsrate beobachtet werden. Zusätzlich konnte in homozygoten Tieren ein craniofacialer Phänotyp beschrieben werden, der zu Problemen bei der Nahrungsaufnahme und damit zu einer starken Wachstumsbeeinträchtigung führte. Die BMP- und TGFbeta-Signalkaskaden haben möglicherweise antagonistische Effekte in der Wachstumsfuge. Während der Ausfall von BMP in proliferierenden Chondrozyten aufgrund einer gesunkenen Proliferationsrate zu einer Verkürzung der Wachstumsfuge führte, kann man in Mäusen mit einer Störung der TGFbeta-Signalkaskade eine verstärkte Proliferation in einer daher verlängerten Wachstumsfuge beobachten. Ein weiteres Ziel dieser Arbeit war die Generation einer transgenen Mauslinie, die die Cre-Rekombinase spezifisch in hypertrophen Chondrozyten exprimiert. Promoterstudien mit transgenen Mäusen weisen darauf hin, dass ein putatives AP1-Element, etwa 4 kb vor dem ersten Exon des Col10a1 gelegen, wichtig für die spezifische Expression in hypertrophen Chondrozyten ist. Ein Konstrukt, dass vier Kopien dieses Elements und den basalen Promoter enthält, wurde benutzt, um die Cre-Rekombinase spezifisch zu exprimieren. Diese Mauslinie befindet sich in der Testphase und erste Daten deuten auf eine spezifische Expression der Cre-Rekombinase in hypertrophen Chondrozyten hin.
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The evaluation of the farmers’ communities’ approach to the Slow Food vision, their perception of the Slow Food role in supporting their activity and their appreciation and expectations from participating in the event of Mother Earth were studied. The Unified Theory of Acceptance and Use of Technology (UTAUT) model was adopted in an agro-food sector context. A survey was conducted, 120 questionnaires from farmers attending the Mother Earth in Turin in 2010 were collected. The descriptive statistical analysis showed that both Slow Food membership and participation to Mother Earth Meeting were much appreciated for the support provided to their business and the contribution to a more sustainable and fair development. A positive social, environmental and psychological impact on farmers also resulted. Results showed also an interesting perspective on the possible universality of the Slow Food and Mother Earth values. Farmers declared that Slow Food is supporting them by preserving the biodiversity and orienting them to the use of local resources and reducing the chemical inputs. Many farmers mentioned the language/culture and administration/bureaucratic issues as an obstacle to be a member in the movement and to participate to the event. Participation to Mother Earth gives an opportunity to exchange information with other farmers’ communities and to participate to seminars and debates, helpful for their business development. The absolute majority of positive answers associated to the farmers’ willingness to relate to Slow Food and participate to the next Mother Earth editions negatively influenced the UTAUT model results. A factor analysis showed that the variables associated to the UTAUT model constructs Performance Expectancy and Effort Expectancy were consistent, able to explain the construct variability, and their measurement reliable. Their inclusion in a simplest Technology Acceptance Model could be considered in future researches.
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Mainstream hardware is becoming parallel, heterogeneous, and distributed on every desk, every home and in every pocket. As a consequence, in the last years software is having an epochal turn toward concurrency, distribution, interaction which is pushed by the evolution of hardware architectures and the growing of network availability. This calls for introducing further abstraction layers on top of those provided by classical mainstream programming paradigms, to tackle more effectively the new complexities that developers have to face in everyday programming. A convergence it is recognizable in the mainstream toward the adoption of the actor paradigm as a mean to unite object-oriented programming and concurrency. Nevertheless, we argue that the actor paradigm can only be considered a good starting point to provide a more comprehensive response to such a fundamental and radical change in software development. Accordingly, the main objective of this thesis is to propose Agent-Oriented Programming (AOP) as a high-level general purpose programming paradigm, natural evolution of actors and objects, introducing a further level of human-inspired concepts for programming software systems, meant to simplify the design and programming of concurrent, distributed, reactive/interactive programs. To this end, in the dissertation first we construct the required background by studying the state-of-the-art of both actor-oriented and agent-oriented programming, and then we focus on the engineering of integrated programming technologies for developing agent-based systems in their classical application domains: artificial intelligence and distributed artificial intelligence. Then, we shift the perspective moving from the development of intelligent software systems, toward general purpose software development. Using the expertise maturated during the phase of background construction, we introduce a general-purpose programming language named simpAL, which founds its roots on general principles and practices of software development, and at the same time provides an agent-oriented level of abstraction for the engineering of general purpose software systems.
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The present study describes the development of and results obtained from the first version of a new mindfulness scale: the Comprehensive Inventory of Mindfulness Experiences beta (CHIME-β). The aim of the present analysis was to investigate two relevant open questions in mindfulness assessment: (1) the coverage of aspects of mindfulness and (2) the type of interrelationships among these aspects. A review of the aspects of mindfulness assessed by eight currently available mindfulness questionnaires led to the identification of nine aspects of mindfulness. The CHIME-β was constructed in order to cover each of these aspects in a balanced way. Initially, principal component and confirmatory factor analyses, as well as reliability and validity analyses, were performed in the entire sample (n = 313) of individuals from the general population and mindfulness-based stress reduction (MBSR) groups. The factor structure that emerged from this analysis was further investigated in meditation-trained individuals (n = 144) who had just completed an MBSR intervention. Results suggested a four-factor structure underlying the nine aspects proposed. The relationship between these mindfulness factors appears to be influenced by the degree of meditation experience. In fact, the mindfulness factors showed a greater interconnectedness among mediation-trained participants. Finally, data suggest that a non-avoidant stance plays a central role in mindfulness, while the capacity to put inner experiences into words may be related to mindfulness rather than a component of the construct.
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During the last decades, the narcissistic personality inventory (npi) was the most widely used questionnaire to measure narcissism as a personality trait. But the npi assesses grandiose narcissism only, while recent discussions emphasize the existence of vulnerable narcissism. The pathological narcissism inventory (pni, pincus et al., 2009) is a new questionnaire assessing these different aspects of narcissism. However, with 54 items on seven subscales, the pni is quite long to serve as a screening tool for narcissistic traits. We therefore developed a short form to facilitate its application in research and practice. Even though the pni covers different symptoms of narcissism, they are all expressions of the same underlying construct. We therefore used the rasch model to guide the item selection. Method and results: a sample of 1837 participants (67.5% female, mean age 26.8 years) was used to choose the items for the short form. Two criteria were adopted: all aspects, represented by the seven subscales in the original, should be retained, and items should be rasch homogenous. In a step-by-step procedure we excluded items successively until reaching a homogenous pool of 22 items. All remaining items had satisfactory fit indices and fitstatistics for the model were good. characteristics of the resulting short form were tested using a new independent validation sample (n=104, mean age = 32.8, 45% female). Correlations of the short pni with different validation measures were comparable to the correlations obtained with the original form, indicating that the two forms were equivalent. Conclusion: the resulting one-dimensional measure can be used as a screening questionnaire for pathological narcissism. The rasch homogeneity facilitates the comparison of narcissism scores among a variety of samples.
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Plasmodium parasites express a potent inhibitor of cysteine proteases (ICP) throughout their life cycle. To analyze the role of ICP in different life cycle stages, we generated a stage-specific knockout of the Plasmodium berghei ICP (PbICP). Excision of the pbicb gene occurred in infective sporozoites and resulted in impaired sporozoite invasion of hepatocytes, despite residual PbICP protein being detectable in sporozoites. The vast majority of these parasites invading a cultured hepatocyte cell line did not develop to mature liver stages, but the few that successfully developed hepatic merozoites were able to initiate a blood stage infection in mice. These blood stage parasites, now completely lacking PbICP, exhibited an attenuated phenotype but were able to infect mosquitoes and develop to the oocyst stage. However, PbICP-negative sporozoites liberated from oocysts exhibited defective motility and invaded mosquito salivary glands in low numbers. They were also unable to invade hepatocytes, confirming that control of cysteine protease activity is of critical importance for sporozoites. Importantly, transfection of PbICP-knockout parasites with a pbicp-gfp construct fully reversed these defects. Taken together, in P. berghei this inhibitor of the ICP family is essential for sporozoite motility but also appears to play a role during parasite development in hepatocytes and erythrocytes.
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Objective: Since 2011, the new national final examination in human medicine has been implemented in Switzerland, with a structured clinical-practical part in the OSCE format. From the perspective of the national Working Group, the current article describes the essential steps in the development, implementation and evaluation of the Federal Licensing Examination Clinical Skills (FLE CS) as well as the applied quality assurance measures. Finally, central insights gained from the last years are presented. Methods: Based on the principles of action research, the FLE CS is in a constant state of further development. On the foundation of systematically documented experiences from previous years, in the Working Group, unresolved questions are discussed and resulting solution approaches are substantiated (planning), implemented in the examination (implementation) and subsequently evaluated (reflection). The presented results are the product of this iterative procedure. Results: The FLE CS is created by experts from all faculties and subject areas in a multistage process. The examination is administered in German and French on a decentralised basis and consists of twelve interdisciplinary stations per candidate. As important quality assurance measures, the national Review Board (content validation) and the meetings of the standardised patient trainers (standardisation) have proven worthwhile. The statistical analyses show good measurement reliability and support the construct validity of the examination. Among the central insights of the past years, it has been established that the consistent implementation of the principles of action research contributes to the successful further development of the examination. Conclusion: The centrally coordinated, collaborative-iterative process, incorporating experts from all faculties, makes a fundamental contribution to the quality of the FLE CS. The processes and insights presented here can be useful for others planning a similar undertaking. Keywords: national final examination, licensing examination, summative assessment, OSCE, action research
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Introduction. Tissue engineering techniques offer a potential means to develop a tissue engineered construct (TEC) for the treatment of tissue and organ deficiencies. However, a lack of adequate vascularization is a limiting factor in the development of most viable engineered tissues. Vascular endothelial growth factor (VEGF) could aid in the development of a viable vascular network within TECs. The long-term goals of this research are to develop clinically relevant, appropriately vascularized TECs for use in humans. This project tested the hypothesis that the delivery of VEGF via controlled release from biodegradable microspheres would increase the vascular density and rate of angiogenesis within a model TEC. ^ Materials and methods. Biodegradable VEGF-encapsulated microspheres were manufactured using a novel method entitled the Solid Encapsulation/Single Emulsion/Solvent Extraction technique. Using a PLGA/PEG polymer blend, microspheres were manufactured and characterized in vitro. A model TEC using fibrin was designed for in vivo tissue engineering experimentation. At the appropriate timepoint, the TECs were explanted, and stained and quantified for CD31 using a novel semi-automated thresholding technique. ^ Results. In vitro results show the microspheres could be manufactured, stored, degrade, and release biologically active VEGF. The in vivo investigations revealed that skeletal muscle was the optimal implantation site as compared to dermis. In addition, the TECs containing fibrin with VEGF demonstrated significantly more angiogenesis than the controls. The TECs containing VEGF microspheres displayed a significant increase in vascular density by day 10. Furthermore, TECs containing VEGF microspheres had a significantly increased relative rate of angiogenesis from implantation day 5 to day 10. ^ Conclusions. A novel technique for producing microspheres loaded with biologically active proteins was developed. A defined concentration of microspheres can deliver a quantifiable level of VEGF with known release kinetics. A novel model TEC for in vivo tissue engineering investigations was developed. VEGF and VEGF microspheres stimulate angiogenesis within the model TEC. This investigation determined that biodegradable rhVEGF 165-encapsulated microspheres increased the vascular density and relative rate of angiogenesis within a model TEC. Future applications could include the incorporation of microvascular fragments into the model TEC and the incorporation of specific tissues, such as fat or bone. ^
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Ras genes are mutated in 15% of human cancers. Ras GTPases operate as molecular switches regulating cellular processes including proliferation, differentiation, and apoptosis. The three main isoforms of Ras – H-Ras, K-Ras, and N-Ras – inhabit distinct nanodomains of the plasma membrane and intracellular compartments including the Golgi. However, the role of single endogenous Ras isoforms on these compartments remains unclear as most studies have utilized ectopically expressed and mutant forms of Ras proteins. In an effort to develop novel tools that will allow us to abrogate individual endogenous Ras isoforms, we targeted the catalytic domain of p120RasGAP to the plasma membrane with the hypervariable region (HVR) of H-Ras (GAP-CTH) or K-Ras (GAP-CTK) and to the Golgi using the HVR of H-Ras with insertion of a point mutation (GAP-CTH181S). We performed GST-RBD pull-downs on cells expressing each GAP construct and stimulated with epidermal growth factor (EGF). We found that GAP-CTH and GAP-CTK specifically inhibited H-Ras or K-Ras, respectively. However, we did not detect any effect of GAP-CTH181S on Ras activation. Additionally, we used confocal microscopy to verify the ability of GAP constructs to abrogate Ras activation in distinct sub-cellular compartments. We found that GAP-CTH inhibits H-Ras activation on the plasma membrane, while GAP-CTK inhibits K-Ras activation on the plasma membrane. On the contrary, GAP-CTH181S inhibited H-Ras activation on the Golgi. We also analyzed the effects of these GAP constructs on the activation of ERK and Akt in response to EGF stimulation. We found that EGF stimulation of the MAPK pathway was inhibited by GAP-CTK but none of the other GAP constructs, while Akt activation was not inhibited by any GAP construct. Finally, we assayed cellular proliferation and differentiation. We found that GAP-CTK and GAP-CTH were equipotent inhibitors of cellular growth, whereas GAP-CTH181S was less potent. We also found that GAP-CTK and GAP-CTH inhibited differentiation with similar potency, while GAP-CTH181S was more potent. This approach may be adapted to investigate any Ras-dependent signaling pathway. Therefore, it has the potential to become a powerful tool for studying Ras isoform-specific signaling outputs.
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Polyelectrolyte multilayers (PEM) built by layer-by-layer technique have been extensively studied over the last years, resulting in a wide variety of current and potential applications. This technique can be used to construct thin films with different functionalities, or to functionalize surfaces with substantial different properties of those of the underlying substrates. The multilayering process is achieved by the alternate adsorption of oppositely charged polyelectrolytes. In this work we get advantage of the protein resistant property of the Poly (l-lysine)-graft-(polyethyleneglycol) to create protein patterns. Proteins can be immobilized on a surface by unspecific physical adsorption, covalent binding or through specific interactions. The first protein used in this work was laccase, a copper-containing redox enzyme that catalyse the oxidation of a broad range of polyphenols and aromatic substrates, coupled to the reduction of O2 to H2O without need of cofactors. Applications of laccases have been reported in food, pulp, paper, and textile industry, and also in biosensor development. Some uses require the immobilization of the enzyme on solid supports by adsorption, covalent attachment, entrapment, etc, on several substrates. Especially for biosensor development, highly active, stable and reproducible immobilization of laccase is required.
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La ecología no solamente ha puesto de manifiesto problemas ambientales, sino que ha confirmado la necesidad de una nueva armonía entre los propios seres humanos y de éstos con la naturaleza y con todos los seres que la habitan. Es necesario un nuevo contrato que determine nuestras relaciones con la Naturaleza (Serrs1), y una nueva Ética para nuestras vidas (Guattari2). La ética medioambiental nos ha dado una visión universal y supra-generacional de la gestión de la naturaleza y como consecuencia, una nueva forma de construir nuestra ‘segunda’ Naturaleza, que es la arquitectura. ¿Qué es lo esencial que esta nueva ética exige para la arquitectura? Este es un momento crucial para reconsiderar los objetivos de la arquitectura, porque lo ‘eco’ está produciendo grandes cambios. ¿Implica esta era post-ecológica una particular ética, es decir, referida a sus fines y medios? ¿Porqué, para qué, para quién, cómo debemos hacer la arquitectura de nuestro tiempo? Es momento de afrontar críticamente el discurso de la eco-arquitectura, e incluso de repensar los propios límites de la arquitectura. El desarrollo actual del conocimiento medioambiental es esencialmente técnico y utilitario, pero ¿es el reto solamente técnico?¿Es suficiente la suma de lo medioambiental-social-económico-cultural para definirla? ¿Hay claves que nos puedan dar la dimensión ética de esta aproximación técnica-empírica? ¿Sabemos lo que estamos haciendo cuando aplicamos este conocimiento? Y, sobre todo, ¿cuál es el sentido de lo que estamos haciendo? La tesis que se propone puede resumirse: De acuerdo con el actual conocimiento que tenemos de la Naturaleza, la Arquitectura de nuestro tiempo deber reconsiderar sus fines y medios, puesto que la ética medioambiental está definiendo nuevos objetivos. Para fundamentar y profundizar en esta afirmación la tesis analiza cómo son hoy día las relaciones entre Ética-Naturaleza-Arquitectura (Fig.1), lo que facilitará las claves de cuáles son los criterios éticos (en cuanto a fines y medios) que deben definir la arquitectura del tiempo de la ecología. ABSTRACT Ecology shows us not only environmental problems; it shows that we need a new balance and harmony between individuals, beings, communities and Nature. We need a new contract with Nature according to Serres576, and a new Ethics for our lives according to Guattari577. Environmental ethics have given us a universal and supra-generational vision of the management of our Nature and, as a consequence, a new way to construct our ‘second’ nature, which is architecture. What is essential for this new architecture that the new ethics demand? This is a critical moment to reconsider the object of architecture, because the ‘eco’ is making significant changes in it. Are there any specifically ethical concerns (ends and means) in the post-ecological era? Why, for what, for whom, how should we make architecture in our times? This is the time to approach the eco-architectural discourse critically and to question the current boundaries of architecture itself: Where is eco-architecture going? The current development of environmental knowledge is essentially technical and utilitarian, but it is its technical aspect the only challenge? Is the sum of environmental-social-economic aspects enough to define it? Are there any clues which can give an ethical sense to this technical-empirical approach? Do we know what we are doing when we apply this knowledge? And overall, what is the meaning of what we are doing? Exploring this subject, this thesis makes a statement: In accordance with the actual knowledge of Nature, Architecture of our time must reconsider its ends and means, since the environmental ethics is defining new objectives. To support that, the thesis analyzes what the relationships between Ethics –Nature- Architecture (Fig. 53) are like nowadays, this will provide the clues of which ethical criteria (ends and means) must architecture of an ecological era define.
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The experiments presented in this report were designed to specifically examine the role of CD4–major histocompatibility complex (MHC) class II interactions during T cell development in vivo. We have generated transgenic mice expressing class II molecules that cannot interact with CD4 but that are otherwise competent to present peptides to the T cell receptor. MHC class II expression was reconstituted in Aβ gene knock-out mice by injection of a transgenic construct encoding either the wild-type I-Aβb protein or a construct encoding a mutation designed to specifically disrupt binding to the CD4 molecule. We demonstrate that the mutation, EA137 and VA142 in the β2 domain of I-Ab, is sufficient to disrupt CD4–MHC class II interactions in vivo. Furthermore, we show that this interaction is critical for the efficient selection of a complete repertoire of mature CD4+ T helper cells as evidenced by drastically reduced numbers of conventional CD4+ T cells in animals expressing the EA137/VA142 mutant I-Ab and by the failure to positively select the transgenic AND T cell receptor on the mutated I-Ab. These results underscore the importance of the CD4–class II interaction in the development of mature peripheral CD4+ T cells.
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Control of cell identity during development is specified in large part by the unique expression patterns of multiple homeobox-containing (Hox) genes in specific segments of an embryo. Trithorax and Polycomb-group (Trx-G and Pc-G) proteins in Drosophila maintain Hox expression or repression, respectively. Mixed lineage leukemia (MLL) is frequently involved in chromosomal translocations associated with acute leukemia and is the one established mammalian homologue of Trx. Bmi-1 was first identified as a collaborator in c-myc-induced murine lymphomagenesis and is homologous to the Drosophila Pc-G member Posterior sex combs. Here, we note the axial-skeletal transformations and altered Hox expression patterns of Mll-deficient and Bmi-1-deficient mice were normalized when both Mll and Bmi-1 were deleted, demonstrating their antagonistic role in determining segmental identity. Embryonic fibroblasts from Mll-deficient compared with Bmi-1-deficient mice demonstrate reciprocal regulation of Hox genes as well as an integrated Hoxc8-lacZ reporter construct. Reexpression of MLL was able to overcome repression, rescuing expression of Hoxc8-lacZ in Mll-deficient cells. Consistent with this, MLL and BMI-I display discrete subnuclear colocalization. Although Drosophila Pc-G and Trx-G members have been shown to maintain a previously established transcriptional pattern, we demonstrate that MLL can also dynamically regulate a target Hox gene.