994 resultados para Modelo atômico nuclear
Huntingtin interacting protein 1 modulates the transcriptional activity of nuclear hormone receptors
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Internalization of activated receptors regulates signaling, and endocytic adaptor proteins are well-characterized in clathrin-mediated uptake. One of these adaptor proteins, huntingtin interacting protein 1 (HIP1), induces cellular transformation and is overexpressed in some prostate cancers. We have discovered that HIP1 associates with the androgen receptor through a central coiled coil domain and is recruited to DNA response elements upon androgen stimulation. HIP1 is a novel androgen receptor regulator, significantly repressing transcription when knocked down using a silencing RNA approach and activating transcription when overexpressed. We have also identified a functional nuclear localization signal at the COOH terminus of HIP1, which contributes to the nuclear translocation of the protein. In conclusion, we have discovered that HIP1 is a nucleocytoplasmic protein capable of associating with membranes and DNA response elements and regulating transcription.
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If there is one uncontroversial point in nuclear weapons politics it is that uninventing nuclear weapons is impossible. This article seeks to make this claim controversial by showing that it is premised on attenuated understandings of invention and the status of objects operative through familiar but problematic conceptual dualisms. The claimed impossibility of uninvention is an assertion that invention is irreversible. Drawing on “new materialism” this article produces a different understanding of invention, reinvention, and uninvention as ontologically similar practices of techno-political invention. On the basis of empirical material on the invention and re-invention of nuclear weapons, and an in-depth ethnography of laboratories inventing a portable radiation detector, both the process of invention and the “objects” themselves (weapons and detectors) are shown to be fragile and not wholly irreversible processes of assembling diverse actors (human and non-human) and provisionally stabilizing their relations. Nuclear weapons cannot be uninvented! Why not?
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One of the main challenges faced by the nuclear industry is the long-term confinement of nuclear waste. Because it is inexpensive and easy to manufacture, cement is the material of choice to store large volumes of radioactive materials, in particular the low-level medium-lived fission products. It is therefore of utmost importance to assess the chemical and structural stability of cement containing radioactive species. Here, we use ab initio calculations based on density functional theory (DFT) to study the effects of 90Sr insertion and decay in C-S-H (calcium-silicate-hydrate) in order to test the ability of cement to trap and hold this radioactive fission product and to investigate the consequences of its β-decay on the cement paste structure. We show that 90Sr is stable when it substitutes the Ca2+ ions in C-S-H, and so is its daughter nucleus 90Y after β-decay. Interestingly, 90Zr, daughter of 90Y and final product in the decay sequence, is found to be unstable compared to the bulk phase of the element at zero K but stable when compared to the solvated ion in water. Therefore, cement appears as a suitable waste form for 90Sr storage.
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The calcineurin/nuclear factor of activated T-cell (NFAT) pathway represents a crucial transducer of cellular function. There is increasing evidence placing the sarcolemmal calcium pump, or plasma membrane calcium/calmodulin ATPase pump (PMCA), as a potential modulator of signal transduction pathways. We demonstrate a novel interaction between PMCA and the calcium/calmodulin-dependent phosphatase, calcineurin, in mammalian cells. The interaction domains were located to the catalytic domain of PMCA4b and the catalytic domain of the calcineurin A subunit. Endogenous calcineurin activity, assessed by measuring the transcriptional activity of its best characterized substrate, NFAT, was significantly inhibited by 60% in the presence of ectopic PMCA4b. This inhibition was notably reversed by the co-expression of the PMCA4b interaction domain, demonstrating the functional significance of this interaction. PMCA4b was, however, unable to confer its inhibitory effect in the presence of a calcium/calmodulin-independent constitutively active mutant calcineurin A suggesting a calcium/calmodulin-dependent mechanism. The modulatory function of PMCA4b is further supported by the observation that endogenous calcineurin moves from the cytoplasm to the plasma membrane when PMCA4b is overexpressed. We suggest recruitment by PMCA4b of calcineurin to a low calcium environment as a possible explanation for these findings. In summary, our results offer strong evidence for a novel functional interaction between PMCA and calcineurin, suggesting a role for PMCA as a negative modulator of calcineurin-mediated signaling pathways in mammalian cells. This study reinforces the emerging role of PMCA as a molecular organizer and regulator of signaling transduction pathways.
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BACKGROUND: Dyslipidemia has been linked to vascular complications of Type 1 diabetes (T1DM). We investigated the prospective associations of nuclear magnetic resonance-determined lipoprotein subclass profiles (NMR-LSP) and conventional lipid profiles with carotid intima-media thickness (IMT) in T1DM.
METHODS: NMR-LSP and conventional lipids were measured in a subset of Diabetes Control and Complications Trial (DCCT) participants (n = 455) at study entry ('baseline', 1983-89), and were related to carotid IMT determined by ultrasonography during the observational follow-up of the DCCT, the Epidemiology of Diabetes Interventions and Complications (EDIC) study, at EDIC Year 12 (2004-2006). Associations were defined using multiple linear regression stratified by gender, and following adjustment for HbA1c, diabetes duration, body mass index, albuminuria, DCCT randomization group, smoking status, statin use, and ultrasound devices.
RESULTS: In men, significant positive associations were observed between some baseline NMR-subclasses of LDL (total IDL/LDL and large LDL) and common and/or internal carotid IMT, and between conventional total- and LDL-cholesterol and non-HDL-cholesterol and common carotid IMT, at EDIC Year 12; these persisted in adjusted analyses (p < 0.05). Large LDL particles and conventional triglycerides were positively associated with common carotid IMT changes over 12 years (p < 0.05). Inverse associations of mean HDL diameter and large HDL concentrations, and positive associations of small LDL with common and/or internal carotid IMT (all p < 0.05) were found, but did not persist in adjusted analyses. No significant associations were observed in women.
CONCLUSION: NMR-LSP-derived LDL particles, in addition to conventional lipid profiles, may help in identifying men with T1DM at highest risk for vascular disease.
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PURPOSE: To quantify the association between siblings in age-related nuclear cataract, after adjusting for known environmental and personal risk factors. METHODS: All participants (probands) in the Salisbury Eye Evaluation (SEE) project and their locally resident siblings underwent digital slit lamp photography and were administered a questionnaire to assess risk factors for cataract including: age, gender, lifetime sun exposure, smoking and diabetes history, and use of alcohol and medications such as estrogens and steroids. In addition, blood pressure, body mass index, and serum antioxidants were measured in all participants. Lens photographs were graded by trained observers masked to the subjects' identity, using the Wilmer Cataract Grading System. The odds ratio for siblings for affectedness with nuclear cataract and the sibling correlation of nuclear cataract grade, after adjusting for covariates, were estimated with generalized estimating equations. RESULTS: Among 307 probands (mean age, 77.6 +/- 4.5 years) and 434 full siblings (mean age, 72.4 +/- 7.4 years), the average sibship size was 2.7 per family. After adjustment for covariates, the probability of development of nuclear cataract was significantly increased (odds ratio [OR] = 2.07, 95% confidence interval [CI], 1.30-3.30) among individuals with a sibling with nuclear cataract (nuclear grade > or = 3.0). The final fitted model indicated a magnitude of heritability for nuclear cataract of 35.6% (95% CI: 21.0%-50.3%) after adjustment for the covariates. CONCLUSIONS: Findings in this study are consistent with a genetic effect for age-related nuclear cataract, a common and clinically significant form of lens opacity.
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High power lasers have proven being capable to produce high energy γ-rays, charged particles and neutrons, and to induce all kinds of nuclear reactions. At ELI, the studies with high power lasers will enter for the first time into new domains of power and intensities: 10 PW and 10^23 W/cm^2. While the development of laser based radiation sources is the main focus at the ELI-Beamlines pillar of ELI, at ELI-NP the studies that will benefit from High Power Laser System pulses will focus on Laser Driven Nuclear Physics (this TDR, acronym LDNP, associated to the E1 experimental area), High Field Physics and QED (associated to the E6 area) and fundamental research opened by the unique combination of the two 10 PW laser pulses with a gamma beam provided by the Gamma Beam System (associated to E7 area). The scientific case of the LDNP TDR encompasses studies of laser induced nuclear reactions, aiming for a better understanding of nuclear properties, of nuclear reaction rates in laser-plasmas, as well as on the development of radiation source characterization methods based on nuclear techniques. As an example of proposed studies: the promise of achieving solid-state density bunches of (very) heavy ions accelerated to about 10 MeV/nucleon through the RPA mechanism will be exploited to produce highly astrophysical relevant neutron rich nuclei around the N~126 waiting point, using the sequential fission-fusion scheme, complementary to any other existing or planned method of producing radioactive nuclei.
The studies will be implemented predominantly in the E1 area of ELI-NP. However, many of them can be, in a first stage, performed in the E5 and/or E4 areas, where higher repetition laser pulses are available, while the harsh X-ray and electromagnetic pulse (EMP) environments are less damaging compared to E1.
A number of options are discussed through the document, having an important impact on the budget and needed resources. Depending on the TDR review and subsequent project decisions, they may be taken into account for space reservation, while their detailed design and implementation will be postponed.
The present TDR is the result of contributions from several institutions engaged in nuclear physics and high power laser research. A significant part of the proposed equipment can be designed, and afterwards can be built, only in close collaboration with (or subcontracting to) some of these institutions. A Memorandum of Understanding (MOU) is currently under preparation with each of these key partners as well as with others that are interested to participate in the design or in the future experimental program.
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Dissertação, Mestrado, Marketing, Instituto Politécnico de Santarém, Escola Superior de Gestão e Tecnologia, 2014
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Dissertação, Mestrado, Gestão Pública, Instituto Politécnico de Santarém, Escola Superior de Gestão e Tecnologia, 2014
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Dissertação, Mestrado, Contabilidade e Finanças, Instituto Politécnico de Santarém, Escola Superior de Gestão e Tecnologia, 2014
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Nos meados da década de 60, o Nobel da Medicina Sidney Brenner propôs a utilização do nemátode bacteriófago, do solo, Caenorhabditis elegans, também conhecido como C. elegans, para estudos de genética e desenvolvimento, dado possuir um conjunto de características que o tornavam o ideal para modelo biológico, nomeadamente a sua pequena dimensão (ca. de 1 mm), facilidade de observação, facilidade de cultivo e manutenção em laboratório, curto ciclo de vida com uma capacidade reprodutiva notável, presença de hermafroditas e machos (5%). O seu artigo seminal de 1974, “The genetics of C. elegans” abriu o caminho para a investigação nesta área. Hoje em dia, revistas como a Nature, Science, Genes and Development, etc… publicam frequentemente os resultados da investigação com recurso a este modelo. É de notar, no entanto, que os nemátodes têm sido utilizados há muito tempo como modelo de estudo, tais como van Beneden, em finais do século XIX, que observando células de Ascaris equorum, descobriu o fenómeno da meiose. O fenómeno da fertilização foi igualmente descoberto num nemátode. Desde a década de setenta até aos nossos dias, o C. elegans tem sido intensamente utilizado para estudos de anatomia interna e sua correlação com linhagens celulares e desenvolvimento. Assim, Sulston e Horvitz elucidaram a origem e desenvolvimento das 959 células somáticas que, de uma forma constante, se produzem nesta espécie (eutelia). Um dos primeiros sistemas a ser estudado foi o sistema nervoso, sendo este nemátode o primeiro animal de que se conhece perfeitamente a identidade de todos os neurónios, a sua linhagem e o circuito nervoso global. Para além de modelo de biologia do desenvolvimento, o C. elegans tem sido alvo de estudo do fenómeno do envelhecimento celular, tendo sido possível identificar os respectivos genes. Kennyon, nos anos 90, e mais recentemente Arantes e Oliveira, têm demonstrado ser possível “prolongar” a vida deste animal de 21 para mais de 180 dias, o que corresponde a 675 anos em vida humana, através de manipulações diversas, tais como agentes mutagénicos, ablação com raio laser, etc.. Também o mecanismo de morte celular programada ou “apoptose” tem sido estudado neste modelo. Em 2002, o Comité Nobel entendeu atribuir o prémio Nobel da Medicina a Brenner, Sulston e Horvitz “for their discoveries concerning genetic regulation of organ development and programmed cell death”. É interessante notar pela leitura de “The common thread”, de John Sulston, a importância decisiva da sequenciação do genoma de C. elegans, em 1998, para o avanço na sequenciação do genoma humano efectuada em 2000, e de cuja mega-equipa Sulston participou de forma decisiva. Finalmente, e como modelo pedagógico, o nemátode C. elegans constitui a escolha ideal para diversas disciplinas dos cursos de Biologia, tais como Biologia celular, Histologia, Biologia do Desenvolvimento, Genética, Etologia, etc….
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Portugal apresenta uma actividade sísmica que resulta em grande parte da sua proximidade à fronteira entre as placas tectónicas Euro-asiática (EA) e Nubia (NU), numa faixa que se estende desde Gibraltar até ao arquipélago dos Açores. A fractura litosférica contida nessa faixa é habitualmente designada por Fractura Açores-Gibraltar. A forte interacção entre os dois blocos, manifesta-se por um aumento da sismicidade nesta faixa, fortemente influenciada pela interacção entre os dois blocos tectónicos. No prolongamento para Ocidente deste acidente atinge-se a Crista Média Atlântica (CMA) num ponto localizado a noroeste do arquipélago dos Açores, e que constitui a fronteira entre a placa Americana (AM) e as placas EA e NU. Este ponto também é conhecido por Junção Tripla dos Açores. A interacção entre os três limites de placas confere à região dos Açores a actividade sísmica que se lhe conhece, uma das mais significativas no contexto nacional. Toda esta zona, devido ao potencial e efectivo risco sísmico testemunhado pelos eventos sísmicos recentes e pelos grandes terremotos historicamente documentados, é alvo de um elevado esforço que nos últimos anos resultou, de forma integrada, em avanços como: 1) melhoria da capacidade de observação do fenómeno sísmico –a existência dos meios mínimos de monitorização sísmica é hoje uma realidade que reconhecemos, salientando contudo, o muito que há a fazer em domínios como: a instalação de estações sísmicas submarinas (OBS) capazes de suprir as lacunas verificadas; a compatibilização de dados e o livre acesso aos mesmos; a criação de uma rede de acelerómetros capaz de registar os movimentos fortes; 2) aumento da capacidade de investigação – o recrutamento de novos investigadores através de projectos multi-disciplinares em domínios como a sismicidade, fonte sísmica e mecanismos focais, geomagnetismo, gravimetria, geodesia e análise estrutural....
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A intervenção psicológica em contextos educativos tem sido pautada por abordagens e modelos centrados num paradigma médico-psicológico, baseado nos pressupostos médicos de doença e causalidade interna dos problemas de aprendizagem da criança — se a criança não aprendia era porque havia algo de errado dentro dela (Bairrão, 1985, 1995; Loxley, 1980). O foco no indivíduo levou a uma ênfase nas diferenças individuais e a uma tendência para ignorar o papel das variáveis sociais e ambientais no desenvolvimento, bem como à concepção de que a criança é responsável pelos seus problemas de aprendizagem (Siegel & Cole, 2003). O falhanço das intervenções baseadas nestes pressupostos levou, gradualmente, à implementação de novas modalidades de intervenção, baseadas na ideia de que a pessoa e o seu ambiente não formam entidades separadas, de que a pessoa é uma parte activa e intencional do ambiente em que interage. Os ambientes directos em que a pessoa interage estão embebidos num ambiente mais amplo, com as suas propriedades físicas, sociais e culturais, que operam directa e indirectamente em todos os níveis da interacção pessoaambiente (Bronfenbrenner, 1979, 1995, 1999, 2005). O desenvolvimento humano poderá, então, ser entendido como um processo cultural — as pessoas desenvolvem-se como participantes nas suas comunidades culturais (Rogoff, 2003). Esta reconstrução da psicologia da educação implica que o psicólogo adopte novos papéis de intervenção, que lhe permitam actuar, não com problemas individuais descontextualizados, mas dentro de um sistema (do qual ele é também parte interveniente) com todos os seus participantes, tendo em conta que a mudança num elemento do contexto vai influenciar todos os outros elementos. A intervenção será, assim, fundamentalmente através de projectos centrados na escola, mas num contexto de relação de feed-back com a comunidade e envolvendo os vários elementos que participam nos contextos mais relevantes. Isto não implica a recusa de serviços directos e de intervenções individuais; antes significa que qualquer intervenção requer a participação do sistema social da criança e de todos os seus elementos significativos (Reynolds & Miller, 2003). Esta comunicação pretende apresentar uma experiência de intervenção psicológica em contexto escolar baseada nestes pressupostos e reflectir sobre as potencialidades de um modelo ecológico – desenvolvimental na prática da psicologia da educação.