999 resultados para RNase III
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The a-globin major genes from diploid and tetraploid Odontophrynus americanus were studied using PCR-based technology. The cloned and sequenced amplified fragments were shown to contain most of the exon II sequences as well as the whole exon III sequence of the a-globin gene. Unexpectedly, intron 2 was entirely absent in the amplified fragments of both 2n and 4n origin. High conservation was observed among the obtained sequences when compared to corresponding sequences from human and Xenopus laevis origin. The possibility that these sequences might be pseudogenes is raised
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Julkaisussa: Accuratissima orbis antiqui delineatio, sive, geographia vetus, sacra & profana
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Carbon monoxide diffusing capacity (DLCO) or transfer factor (TLCO) is a particularly useful test of the appropriateness of gas exchange across the lung alveolocapillary membrane. With the purpose of establishing predictive equations for DLCO using a non-smoking sample of the adult Brazilian population, we prospectively evaluated 100 subjects (50 males and 50 females aged 20 to 80 years), randomly selected from more than 8,000 individuals. Gender-specific linear prediction equations were developed by multiple regression analysis with single breath (SB) absolute and volume-corrected (VA) DLCO values as dependent variables. In the prediction equations, age (years) and height (cm) had opposite effects on DLCOSB (ml min-1 mmHg-1), independent of gender (-0.13 (age) + 0.32 (height) - 13.07 in males and -0.075 (age) + 0.18 (height) + 0.20 in females). On the other hand, height had a positive effect on DLCOSB but a negative one on DLCOSB/VA (P<0.01). We found that the predictive values from the most cited studies using predominantly Caucasian samples were significantly different from the actually measured values (P<0.05). Furthermore, oxygen uptake at maximal exercise (VO2max) correlated highly to DLCOSB (R = 0.71, P<0.001); this variable, however, did not maintain an independent role to explain the VO2max variability in the multiple regression analysis (P>0.05). Our results therefore provide an original frame of reference for either DLCOSB or DLCOSB/VA in Brazilian males and females aged 20 to 80 years, obtained from the standardized single-breath technique.
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The Ca2+-modulated, dimeric proteins of the EF-hand (helix-loop-helix) type, S100A1 and S100B, that have been shown to inhibit microtubule (MT) protein assembly and to promote MT disassembly, interact with the type III intermediate filament (IF) subunits, desmin and glial fibrillary acidic protein (GFAP), with a stoichiometry of 2 mol of IF subunit/mol of S100A1 or S100B dimer and an affinity of 0.5-1.0 µM in the presence of a few micromolar concentrations of Ca2+. Binding of S100A1 and S100B results in inhibition of desmin and GFAP assemblies into IFs and stimulation of the disassembly of preformed desmin and GFAP IFs. S100A1 and S100B interact with a stretch of residues in the N-terminal (head) domain of desmin and GFAP, thereby blocking the head-to-tail process of IF elongation. The C-terminal extension of S100A1 (and, likely, S100B) represents a critical part of the site that recognizes desmin and GFAP. S100B is localized to IFs within cells, suggesting that it might have a role in remodeling IFs upon elevation of cytosolic Ca2+ concentration by avoiding excess IF assembly and/or promoting IF disassembly in vivo. S100A1, that is not localized to IFs, might also play a role in the regulation of IF dynamics by binding to and sequestering unassembled IF subunits. Together, these observations suggest that S100A1 and S100B may be regarded as Ca2+-dependent regulators of the state of assembly of two important elements of the cytoskeleton, IFs and MTs, and, potentially, of MT- and IF-based activities.
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This article is a transcription of an electronic symposium in which active researchers were invited by the Brazilian Society of Neuroscience and Behavior (SBNeC) to discuss the advances of the last decade in the neurobiology of emotion. Four basic questions were debated: 1) What are the most critical issues/questions in the neurobiology of emotion? 2) What do we know for certain about brain processes involved in emotion and what is controversial? 3) What kinds of research are needed to resolve these controversial issues? 4) What is the relationship between learning, memory and emotion? The focus was on the existence of different neural systems for different emotions and the nature of the neural coding for the emotional states. Is emotion the result of the interaction of different brain regions such as the amygdala, the nucleus accumbens, or the periaqueductal gray matter or is it an emergent property of the whole brain neural network? The relationship between unlearned and learned emotions was also discussed. Are the circuits of the former the underpinnings of the latter? It was pointed out that much of what we know about emotions refers to aversively motivated behaviors, like fear and anxiety. Appetitive emotions should attract much interest in the future. The learning and memory relationship with emotions was also discussed in terms of conditioned and unconditioned stimuli, innate and learned fear, contextual cues inducing emotional states, implicit memory and the property of using this term for animal memories. In a general way it could be said that learning modifies the neural circuits through which emotional responses are expressed.
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Defects in semiconductor crystals and at their interfaces usually impair the properties and the performance of devices. These defects include, for example, vacancies (i.e., missing crystal atoms), interstitials (i.e., extra atoms between the host crystal sites), and impurities such as oxygen atoms. The defects can decrease (i) the rate of the radiative electron transition from the conduction band to the valence band, (ii) the amount of charge carriers, and (iii) the mobility of the electrons in the conduction band. It is a common situation that the presence of crystal defects can be readily concluded as a decrease in the luminescence intensity or in the current flow for example. However, the identification of the harmful defects is not straightforward at all because it is challenging to characterize local defects with atomic resolution and identification. Such atomic-scale knowledge is however essential to find methods for reducing the amount of defects in energy-efficient semiconductor devices. The defects formed in thin interface layers of semiconductors are particularly difficult to characterize due to their buried and amorphous structures. Characterization methods which are sensitive to defects often require well-defined samples with long range order. Photoelectron spectroscopy (PES) combined with photoluminescence (PL) or electrical measurements is a potential approach to elucidate the structure and defects of the interface. It is essential to combine the PES with complementary measurements of similar samples to relate the PES changes to changes in the interface defect density. Understanding of the nature of defects related to III-V materials is relevant to developing for example field-effect transistors which include a III-V channel, but research is still far from complete. In this thesis, PES measurements are utilized in studies of various III-V compound semiconductor materials. PES is combined with photoluminescence measurements to study the SiO2/GaAs, SiNx/GaAs and BaO/GaAs interfaces. Also the formation of novel materials InN and photoluminescent GaAs nanoparticles are studied. Finally, the formation of Ga interstitial defects in GaAsN is elucidated by combining calculational results with PES measurements.
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Kartta kuuluu A. E. Nordenskiöldin kokoelmaan
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Kartta kuuluu A. E. Nordenskiöldin kokoelmaan
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Kartta kuuluu A. E. Nordenskiöldin kokoelmaan
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Kartta kuuluu A. E. Nordenskiöldin kokoelmaan
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Koodeksiin sisältyy kolme tekstikokonaisuutta. Ydinosan muodostavat suomalainen kirkkokäsikirja ja messu eli jumalanpalvelusjärjestys, joilla on oma, alkuperäinen sivunumerointinsa. Kolmas kokonaisuus on suomennos saksalaisen Urbanus Rhegiuksen laatimasta sielunhoidon opaskirjasta Sieluin vahvistus, lohutos ja lääkitys.
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This thesis constitutes an interdisciplinary approach to the Polish Romanticism combining literature studies with memory studies, nationalism research and psychoanalysis. This phenomenon-based study attempts to answer the question, how the Polish national poet Adam Mickiewicz (1798–1855) – or more exactly the implied authors in his works – perceived the role of poetry in mnemonic terms and how it changes in course of time. Consequently, ‘memory in literature’ (Astrin Erll and Ansger Nünning) is discussed here. Two pieces of writing by Mickiewicz – Konrad Wallenrod [1828] and the third part of Forefathers [1832], where a bard respectively a poetic genius appears – are seen as meta-texts defining goals of poets in time of the political non-existence of a state. Poetry is supposed to keep memory of the glorious past alive, kindle the love for the motherland, support the collective identity of a group and initiate a liberation movement. Poets function as memory guards, leaders of the nation and prophets. Thus, literature is a medium of collective memory – it stores crucial contents, transmits them and acts as a cue. Nevertheless, shifting the focus from the community towards well-being of individuals, which is consistent with the postmodern thinking, the impact that poetry has on members of a given memory culture (Jan Assmann) can be described in ‘vampiric’ terms (Maria Janion). Poetry embodying collective memory may be compared to ‘poison’, ‘infecting’ people with a nationalistic way of thinking to their disadvantage as far as their personal lives are concerned.
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Iron is one of the most common elements in the earth’s crust and thus its availability and economic viability far exceed that of metals commonly used in catalysis. Also the toxicity of iron is miniscule, compared to the likes of platinum and nickel, making it very desirable as a catalyst. Despite this, prior to the 21st century, the applicability of iron in catalysis was not thoroughly investigated, as it was considered to be inefficient and unselective in desired transformations. In this doctoral thesis, the application of iron catalysis in combination with organosilicon reagents for transformations of carbonyl compounds has been investigated together with insights into iron catalyzed chlorination of silanes and silanols. In the first part of the thesis, the synthetic application of iron(III)-catalyzed chlorination of silanes (Si-H) and the monochlorination of silanes (SiH2) using acetyl chloride as the chlorine source is described. The reactions proceed under ambient conditions, although some compounds need to be protected from excess moisture. In addition, the mechanism and kinetics of the chlorination reaction are briefly adressed. In the second part of this thesis a versatile methodology for transformation of carbonyl compounds into three different compound classes by changing the conditions and amounts of reagents is discussed. One pot reductive benzylation, reductive halogenation and reductive etherification of ketones and aldehydes using silanes as the reducing agent, halide source or cocatalyst, were investigated. Also the reaction kinetics and mechanism of the reductive halogenation of acetophenone are briefly discussed.