997 resultados para LIGHT-ELEMENTS


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Quantum Chemical calculations for group 14 elements of Periodic Table (C, Si, Ge, Sn, Pb) and their functional groups have been carried out using Density Functional Theory (DFT) based reactivity descriptors such as group electronegativities, hardness and softness. DFT calculations were performed for a large series of tetracoordinated Sn compounds of the CH3SnRR'X type, where X is a halogen and R and R' are alkyl, halogenated alkyl, alkoxy, or alkyl thio groups. The results were interpreted in terms of calculated electronegativity and hardness of the SnRR'X groups, applying a methodology previously developed by Geerlings and coworkers (J. Phys. Chem. 1993, 97, 1826). These calculations allowed to see the regularities concerning the influence of the nature of organic groups RR' and inorganic group X on electronegativities and hardness of the SnRR'X groups; in this case, it was found a very good correlation between the electronegativity of the fragment and experimental 119Sn chemical shifts, a property that sensitively reflects the change in the valence electronic structure of molecules. This work was complemented with the study of some compounds of the EX and ER types, where E= C, Si, Ge, Sn and R= CH3, H, which was performed to study the influence that the central atom has on the electronegativity and hardness of molecules, or whether these properties are mainly affected for the type of ligand bound to the central atom. All these calculations were performed using the B3PW91 functional together with the 6-311++G** basis set level for H, C, Si, Ge, F, Cl and Br atoms and the 3-21G for Sn and I atoms.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The present paper deals with Saint Thomas's commentary to Aristotle's De Anima III, in wich we find the famous analogy of light. It is sustained that due to the limitations of the analogy, Saint Thomas is forced to introduce a series of Neo-platonic elements incompatible with Aristotle's philosophy. The author means to explain this "betrayal" to Aristotle's philosophy by one of his most credited commentators. It is concluded that in order to reconcile the pagan world with the Catholic theology, Thomas Aquinas needs to redirect Aristotle through a less economical argument; that is, the introduction of the Intellectus Agens

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Visual art practice has generally been described as a lonely affair, thinking about what an artist has experienced in the outside world. This study is an inquiry into a visual art practice of another kind: the relational one. The research purpose is twofold. The first purpose is to shed light on a visual artist’s conceptions of art, education and scholarship. The second purpose is to by reasoning on imagination and a rhizomatic formation interpret the relations created between art, multimodality and literacy learning as an aesthetic approach to education. By inquiry into a specific collaborated long-term art practice, the study conveys how the meaning making elements of an arts based learning practice gradually transform an artist’s and a teacher’s concepts of art education to an aesthetic approach to education. In the art practice examined the typical Finnish rye bread and a poem have represented a cultural theme that has been elaborated through art conventions. The poem and the rye bread have in the art practice been articulated as cultural representations of as well as symbolic projections on the Swedishspeaking minority culture in Finland. The study connects art informed inquiry to a hermeneutic research rationale where the research reasoning is generated through a rhizomatic alliance between empiric data and theories. The reasoning is constructed as an interpretation pattern that expands throughout the study. The study arguments that the rhizome as an aesthetic formation can be appropriate to refer to when articulating arts based meaning making and when creating arts based educational strategies, dialogues, aesthetic learning and multimodal literacy in education. The study investigates an aesthetic approach to research in education, which means that the art practice surveyed is interpreted through articulation appropriate to poetic aspects of art, education and research.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Fungi require special substrates for their isolation, vegetative growth and sporulation. In experiments conducted in the laboratory, the influence of substrates, light, filter paper and pH on the sporulation of Cercospora sojina conidia, the causal agent of soybean frogeye leaf spot, was assessed. The media potato sucrose agar, V-8 agar, tomato extract agar, soybean leaf extract agar, soybean seed extract agar, soybean meal agar, soybean flour agar and wheat flour agar were tested, added on the surface, with and without filter paper and under two light regimes, with 12 h light at 25°± 2°C and in the dark. A triple factorial 8x2x2 (substrates x light/dark x with/without filter paper) design with four replicates was used. V-8 agar medium was employed and the pH was adjusted with HCl 0.1N or NaOH 0.1N before autoclaving to the values: 3, 4, 5, 6, 7 and 8, and the pH of V-8 agar medium is 6.7. The evaluation was done on the seventh day of incubation. Data underwent regression analysis. Sporulation was maximized on the agar media V-8, seed extract, oat flour, tomato extract, and potato sucrose in the presence of filter paper and 12h light. On V-8 medium, maximal sporulation was obtained with pH 6.7.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Four levels of shading (full sunlight (0%), 30, 50, 70% of solar radiation interception on growth, chlorophyll concentration and photosynthetic rate were studied in Croton urucurana Baill., a pioneer plant species. This species seedlings are of potential interest for reforestation projects and recovery of degraded areas. The seedlings were grown in pots containing soil and sand (2:1) and later transferred to plastic bags of 3 dm³ and submitted to different levels of shading (30, 50, 70%) of solar radiation and full sunlight, as control. The experimental design was completely randomized with five replicates and each experimental unit was composed of five plants. The results suggest that plants submitted to 70% shading showed higher dry weight accumulation in leaf and root, and higher plant height and leaf area. However, the seedlings root system showed higher dry biomass under full sunlight. It was observed a tendency to increase chlorophyll concentration and to decrease photosynthetic rate with the increase of the shading level.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This thesis studies the various forms and layers of representations of the past that can be found in the Disney comics of Don Rosa. To stay true to the legacy of renowned comic book artist Carl Barks, Rosa has stopped time in the duck universe to the 1950’s: the decade when Barks created his most noted stories. There is a special feel of historicalness in Rosa’s duck stories, as his characters recall events that occurred in both Rosa’s own stories as well as Barks’. Rosa has shed new light to the past of the characters by writing and illustrating the history of Scrooge McDuck, one of the most beloved Disney characters. Rosa is also adamant that the historical facts used in his stories are always correct and based on thorough research. The methodological tools used in the analysis of the comics come from the fields of comic book studies, film theory, and history culture. Film and comics are recognized by many scholars as very similar media, which share elements that make them comparable in many ways. This thesis utilizes studies on historical film, narrative and genre, which provide valuable insight and comparisons for analysis. The thesis consists of three main chapters, the first of which deconstructs the duck universe in the stories in order to understand how the historicalness in them is created,and which outside elements might affect them, including the genre of Disney comics, publishers, and the legacy of Barks. The next chapter focuses on The Life and Times of Scrooge McDuck series, i.e. the stories which are located in the past. Such stories feature similar representations of history as for example Westerns. They also compress and alter history to meet the restrictions of the medium of comics. The last part focuses on the adventure stories which draw inspiration from for example mythology, and take the characters to strange and mystical, but yet historical worlds. Such treasure-hunting stories show similarity to the action-adventure genre in film and for example their stereotypical representations of foreign cultures. Finally, the chapter addresses the problematic of historical fiction and its capability to write history.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Cordia curassavica (Jacq.) Roem. & Schult. (Boraginaceae), also referred to as Cordia verbenacea DC, has been traditionally used for medicinal purposes. This study was driven to verify the behavior of the species in similar conditions to its natural environment, such as high light intensity and sandbank soil, and in conditions of low light intensity and fertilized substratum (dystroferric red nitosoil plus earthworm humus). The growth of the plant, the income of leaf crude extracts and, in the alcoholic extract, the number of substances found in thin layer cromatography and the toxicity of the substratum was observed. The results indicated that the growth of the root biomass, stem and leaves in discharge or lower light intensity was similar, but smaller in sandbank soil than in fertilized soil. The relative income of extracts in ether of petroleum and alcohol was larger in high light intensity and fertilized substratum. The light intensity and the substratum type didn't affect the number of substances detected in the alcoholic extract or the toxicity of this extract. Stains corresponding to the rosmarinic acid were only evidenced in some samples of the alcoholic extract, not allowing the verification of the effect of the treatments about its production.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The aim of the present study was to demonstrate the wide applicability of the novel photoluminescent labels called upconverting phosphors (UCPs) in proximity-based bioanalytical assays. The exceptional features of the lanthanide-doped inorganic UCP compounds stem from their capability for photon upconversion resulting in anti-Stokes photoluminescence at visible wavelengths under near-infrared (NIR) excitation. Major limitations related to conventional photoluminescent labels are avoided, rendering the UCPs a competitive next-generation label technology. First, the background luminescence is minimized due to total elimination of autofluorescence. Consequently, improvements in detectability are expected. Second, at the long wavelengths (>600 nm) used for exciting and detecting the UCPs, the transmittance of sample matrixes is significantly greater in comparison with shorter wavelengths. Colored samples are no longer an obstacle to the luminescence measurement, and more flexibility is allowed even in homogeneous assay concepts, where the sample matrix remains present during the entire analysis procedure, including label detection. To transform a UCP particle into a biocompatible label suitable for bioanalytical assays, it must be colloidal in an aqueous environment and covered with biomolecules capable of recognizing the analyte molecule. At the beginning of this study, only UCP bulk material was available, and it was necessary to process the material to submicrometer-sized particles prior to use. Later, the ground UCPs, with irregular shape, wide size-distribution and heterogeneous luminescence properties, were substituted by a smaller-sized spherical UCP material. The surface functionalization of the UCPs was realized by producing a thin hydrophilic coating. Polymer adsorption on the UCP surface is a simple way to introduce functional groups for bioconjugation purposes, but possible stability issues encouraged us to optimize an optional silica-encapsulation method which produces a coating that is not detached in storage or assay conditions. An extremely thin monolayer around the UCPs was pursued due to their intended use as short-distance energy donors, and much attention was paid to controlling the thickness of the coating. The performance of the UCP technology was evaluated in three different homogeneous resonance energy transfer-based bioanalytical assays: a competitive ligand binding assay, a hybridization assay for nucleic acid detection and an enzyme activity assay. To complete the list, a competitive immunoassay has been published previously. Our systematic investigation showed that a nonradiative energy transfer mechanism is indeed involved, when a UCP and an acceptor fluorophore are brought into close proximity in aqueous suspension. This process is the basis for the above-mentioned homogeneous assays, in which the distance between the fluorescent species depends on a specific biomolecular binding event. According to the studies, the submicrometer-sized UCP labels allow versatile proximity-based bioanalysis with low detection limits (a low-nanomolar concentration for biotin, 0.01 U for benzonase enzyme, 0.35 nM for target DNA sequence).

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The theme of this thesis is the learning process that occurs when teachers become professional voice users. The aim is to explore what it (really) means to become a professional voice user in a teaching profession; thereby developing an understanding of how future education in this field can be arranged so as to both effectively prevent vocal problems and to develop oral didactical competence among teachers. The ambition is to describe, interpret, and understand the learning process through a combination of emic and ethic research perspectives. The theoretical frame of reference reflects the cross disciplinary character of the thesis. Voice problems are common among both student teachers and inservice teachers and adversely affect professional competence, identity and quality of life. Additionally, vocal problems are proven to have a negative impact on pupils´ learning. The individual elements of learning are explored in the light of experiential learning theory and transformative learning theory. The social elements of learning are explored in relation to the theory of situated learning. In addition, theories of teacher professionalisation in terms of competence and identity are outlined. The empirical study has a longitudinal and multi method character. It is anchored in a phenomenological hermeneutical tradition, more specifically in narrative inquiry. The point of departure is the learning experiences of ten student teachers, who attended a ten week long course on voice production as part of their teacher training at Åbo Akademi University, in the autumn of 2002 and the spring of 2003. Four interviews in the form of conversations were conducted with each participant. These were crystallised with a process diary, a Swedish Voice Handicap Index, a voice observation, and a video observation. A fifth interview was conducted with each participant five years post teacher training, in the spring of 2008. Participant observation was also conducted throughout the course. The research materials have been analysed and interpreted narratively using a phenomenological hermeneutical method. The results are presented descriptively as individual narratives, which are reflected in logopedic research materials. Learning is here understood as emergent awareness. This is followed by a meta narrative concerning learning as experiences in the four dimensions body, thought, feeling, and relation. Finally, interpretation is expressed with respect to the theory of relational education. Learning is here understood as a movement in the field between the actual and the possible voice. It is also viewed as fundamentally rooted in inter-human relationships, in moments of presence and coexistence. As a tentative answer to the call for an existential space for learning in order to be a professional voice user, I suggest the concept of a learning refuge as a locus for a learning process built on trust, mutuality and openness.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Bauhinia variegata and B. variegata var. candida, commonly known as orchid trees, are small sized trees widely used for urban forestry and landscaping. Adult plants grow under full sun; in Brazil, however, seedlings are generally cultivated in commercial nurseries under natural half-shading. The objective of this study was to evaluate the influence of different colored shade nets and light conditions on the initial growth of B. variegata and B. variegata var. candida. The influence of six light conditions (red net with 50% shading; blue net with 50% shading; black net with 70% shading; black net with 50% shading; black net with 30% shading; and full sun) on the initial growth of B. variegata and B. variegata var. candida were evaluated along 160 days, and growth relationships were calculated. Seedlings showed more efficiency on the use of photoassimilated compounds when grown under full sun. Such condition is the most appropriate for seedling production of B. variegata and B. variegata var. candida, contradicting what has been performed in practice.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Den viktigaste råvaran i papperstillverkning är pappersmassa. Massan innehåller (ved)fibrer men också finmaterial och andra typers (ved)celler, så som kärlceller. Hur dessa komponenter beter sig under arkformationen i pappersmaskinen eller hur de bidrar till egenskaperna hos det färdiga pappret avgörs till stor del av massakomponenternas ytkemiska sammansättning, fysiska struktur och mängden joniserbara grupper på ytan. I denna avhandling studerades ytegenskaperna hos fraktionerade kemiska massor och returfibermassor med avancerade analystekniker. Rester av avfärgningskemikalier identifierades på både returfibrer och på kärlceller. Dessa kan påverka arkformationen och arkstyrkan på returfiberpapper. Kärlcellernas cellväggsstruktur visade sig skilja sig från fibrernas. Resultaten kan främja utvecklingen av returfiberprosessen och användningen av kärlcellsrika lövvedsmassor.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Currently, the standards that deal with the determination of the properties of rigidity and strength for structural round timber elements do not take in consideration in their calculations and mathematical models the influence of the existing irregularities in the geometry of these elements. This study has as objective to determine the effective value of the modulus of longitudinal elasticity for structural round timber pieces of the Eucalyptus citriodora genus by a technique of optimization allied to the Inverse Analysis Method, to the Finite Element Method and the Least Square Method.