934 resultados para GEOMETRIA PLANA
Resumo:
Em meados do século XX através da importação de sementes de gramíneas forrageiras, surgiu nos campos do sul do Brasil uma das mais graves invasões biológicas dessa região: o Campim Annoni (Eragrostis plana Ness)
Resumo:
The autoxidation of conjugated linoleic acid (CLA) is poorly understood in spite of increasing interest in the beneficial biological properties of CLA and growing consumption of CLA-rich foods. In this thesis, the autoxidation reactions of the two major CLA isomers, 9-cis,11-trans-octadecadienoic acid and 10-trans,12-cis-octadecadienoic acid, are investigated. The results contribute to an understanding of the early stages of the autoxidation of CLA methyl ester, and provide for the first time a means of producing and separating intact CLA methyl ester hydroperoxides as well as basic knowledge on lipid hydroperoxides and their hydroxy derivatives. Conjugated diene allylic monohydroperoxides were discovered as primary autoxidation products formed during autoxidation of CLA methyl esters in the presence and absence of α-tocopherol. This established that one of the autoxidation pathways of CLA methyl ester is the hydroperoxide pathway. Hydroperoxides were produced from the two major CLA methyl esters by taking advantage of the effect of α-tocopherol to promote hydroperoxide formation. The hydroperoxides were analysed and separated first as methyl hydroxyoctadecadienoates and then as intact hydroperoxides by HPLC. The isolated products were characterized by UV, GC-MS, and NMR techniques. In the presence of a high amount of α-tocopherol, the autoxidation of CLA methyl ester yields six kinetically-controlled conjugated diene monohydroperoxides and is diastereoselective in favour of one particular geometric isomer as a pair of enantiomers. The primary autoxidation products produced from the two major CLA isomers include new positional isomers of conjugated diene monohydroperoxides, the 8-, 10-, 12-, and 14-hydroperoxyoctadecadienoates. Furthermore, two of these new positional isomers have an unusual structure for a cis,trans lipid hydroperoxide where the allylic methine carbon is adjacent to the cis instead of the usual trans double bond. The 1H and 13C NMR spectra of nine isomeric methyl hydroxyoctadecadienoates and of ten isomeric methyl hydroperoxyoctadecadienoates including the unusual cis,trans hydroperoxides, i.e. Me 8-OOH-9c,11t and Me 14-OOH-10t,12c, were fully assigned with the aid of 2D NMR spectroscopy. The assigned NMR data enabled determination of the effects of the hydroxyl and hydroperoxyl groups on the carbon chemical shifts of CLA isomers, identification of diagnostic signals, and determination of chemical shift differences of the olefinic resonances that may help with the assignment of structure to as yet unknown lipid hydroperoxides either as hydroxy derivatives or as intact hydroperoxides. A mechanism for the hydroperoxide pathway of CLA autoxidation in the presence of a high amount of α-tocopherol was proposed based on the characterized primary products, their relative distribution, and theoretical calculations. This is an important step forward in CLA research, where exact mechanisms for the autoxidation of CLA have not been presented before. Knowledge of these hydroperoxide formation steps is of crucial importance for understanding the subsequent steps and the different pathways of the autoxidation of CLA. Moreover, a deeper understanding of the autoxidation mechanisms is required for ensuring the safety of CLA-rich foods. Knowledge of CLA oxidation and how it differs from the oxidation of nonconjugated polyunsaturated fatty acids may also be the key to understanding the biological mechanisms of CLA activity.
Resumo:
Head and neck squamous cell cancer (HNSCC) is the sixth most common cancer worldwide. Despite advances in combined modality therapy (surgery, radiotherapy, chemotherapy) the 5-year survival rate in stage III and IV disease remains at 40% - 60%. Short-range Auger-electron emitters, such as In-111 and In-114m, tagged with a drug, molecule, peptide, protein or nanoparticles brought in close proximity to nuclear DNA represent a fascinating alternative for treating cancer. In this thesis, we studied the usefulness of Indium-111-bleomycin complex (In-111-BLMC) in the diagnostics and potential therapy of HNSCC using in vitro HNSCC cell lines, in vivo nude mice, and in vivo HNSCC patients. In in vitro experiments with HNSCC cell lines, the sensitivity to external beam radiation, BLM, In-111-BLMC, and In-111-Cl3 was studied using the 96-well plate clonogenic assay. The influence of BLM and In-111-BLMC on the cell cycle was measured with flow cytometry. In in vivo nude mice xenograft studies, the activity ratios of In-111-BLMC were obtained in gamma camera images. The effect of In-111-BLMC in HNSCC xenografts was studied. In in vivo patient studies, we determined the tumor uptake of In-111-BLMC with gamma camera and the radioactivity from tumor samples using In-111-BLMC with specific activity of 75, 175, or 375 MBq/mg BLM. The S values, i.e. absorbed dose in a target organ per cumulated activity in a source organ, were simulated for In-111 and In-114m. In vitro studies showed the variation of sensitivity for external beam radiation, BLM, and In-111-BLMC between HNSCC cell lines. IC50 values for BLM were 1.6-, 1.8-, and 2.1-fold higher than In-111-BLMC (40 MBq/mg BLM) in three HNSCC cell lines. Specific In-111 activity of 40 MBq/mgBLM was more effective in killing cells than specific In-111 activity of 195MBq/mgBLM (p=0.0023). In-111-Cl3 alone had no killing effect. The percentage of cells in the G2/M phase increased after exposure to BLM and especially to In-111-BLMC in the three cell lines studied, indicating a G2/M block. The tumor-seeking behavior was shown in the in vivo imaging study of xenografted mice. BLM and In-111-BLMC were more effective than NaCl in reducing xenografted tumor size in HNSCC. The uptake ratios received from gamma images in the in vivo patient study varied from 1.2 to 2.8 in malignant tumors. However, the uptake of In-111-BLMC was unaffected by increasing the injected activity. A positive correlation existed between In-111-BLMC uptake, Ki-67/MIB activity, and number of mitoses. Regarding the S values, In-114m delivered a 4-fold absorbed radiation dose into the tumor compared with In-111, and thus, In-114m-BLMC might be more effective than In-111-BLMC at the DNA level. Auger-electron emitters, such as In-111 and In-114m, might have potential in the treatment of HNSCC. Further studies are needed to develop a radiopharmaceutical agent with appropriate physical properties of the radionuclide and a suitable carrier to bring it to the targeted tissue.
Resumo:
Tässä väitöskirjassa perehdytään magneettisen rekonnektion ilmenemismuotoihin ja vaikutuksiin Maan magnetosfäärissä. Keskeisenä tutkimusvälineenä käytetään magnetohydrodynaamista (MHD) Gumics-magnetosfäärisimulaatiota. Työssä kehitetään myös uusia menetelmiä simulaatiossa ilmenevän rekonnektion tunnistamiseksi ja mittaamiseksi. MHD-simulaatio sopii suuren mittakaavan ilmiöiden tarkasteluun, joten kuvaa rekonnektiosta täydennetään pienen mittakaavan piirteiden osalta Cluster-satelliittien avulla. Tärkein tutkimuksen tuoma edistysaskel menetelmien saralla on rekonnektioviivan paikallistaminen topologisesti erityyppisten magneettikenttäviivojen alueiden liitoskohdassa olevana erottajaviivana neljän kentän tienoon menetelmää käyttäen. Tämä topologinen lähestymistapa on hyödyllinen erityisesti magnetopausilla, jonka monimutkainen geometria tekee magneettikentän paikalliseen käyttäytymiseen perustuvien rekonnektioviivan etsintätapojen soveltamisen hankalaksi. Topologisesti määritelty rekonnektioviiva on myös helppo tunnistaa magnetosfäärin globaalin konvektion solmukohdaksi. Magnetopausin rekonnektioviivan käyttäytyminen Gumicsissa noudattaa komponenttirekonnektio-olettamaan pohjautuvia teoreettisia ennusteita. Rekonnektion kvantitatiivinen tarkastelu Gumics-simulaatiossa perustuu energian muuntumiseen, joka lasketaan Poyntingin vektorin divergenssinä tai Poyntingin vuona valitun umpinaisen pinnan läpi. Rekonnektioon liittyvän energian muuntumisen jakautumista magnetopausilla tarkastellaan energian muuntumisen pintatiheyden avulla ja rekonnektion kokonaismäärää rekonnektiotehon avulla. Magnetopausin ja pyrstön rekonnektiotehot ovat simulaatiossa samaa suuruusluokkaa. Tärkeimmät magnetopausin rekonnektiotehoa säätelevät parametrit ovat aurinkotuulen nopeus ja aurinkotuulen magneettikentän suunta. Magnetopausin rekonnektio puolestaan säätelee energian ja aineen pääsyä magnetosfääriin, joskaan magnetopausin läpäisevät vuot eivät ole aivan suoraan verrannollisia rekonnektiotehoon. Pyrstön rekonnektioteho sen sijaan on suoraan verrannollinen magnetopausilta tulevaan energiavuohon; pyrstörekonnektio Gumicsissa on siis ulkoista pakotetta seuraava passiivinen energian käsittelijä. Simulaation tuottama rekonnektio on realistinen magnetosfäärin globaalissa mittakaavassa tarkasteltuna, mutta satelliittihavainnot paljastavat rekonnektiosta simulaation erottelukykyä pienimittakaavaisempia piirteitä. Havaintopuolella tämän väitöstutkimuksen tärkein löytö on protonien diffuusioalueen rakenteeseen kuuluvien Hallin kenttien kääntyminen pyrstön virtalevyn aaltoilun mukana.
Resumo:
Nucleation is the first step in the formation of a new phase inside a mother phase. Two main forms of nucleation can be distinguished. In homogeneous nucleation, the new phase is formed in a uniform substance. In heterogeneous nucleation, on the other hand, the new phase emerges on a pre-existing surface (nucleation site). Nucleation is the source of about 30% of all atmospheric aerosol which in turn has noticeable health effects and a significant impact on climate. Nucleation can be observed in the atmosphere, studied experimentally in the laboratory and is the subject of ongoing theoretical research. This thesis attempts to be a link between experiment and theory. By comparing simulation results to experimental data, the aim is to (i) better understand the experiments and (ii) determine where the theory needs improvement. Computational fluid dynamics (CFD) tools were used to simulate homogeneous onecomponent nucleation of n-alcohols in argon and helium as carrier gases, homogeneous nucleation in the water-sulfuric acid-system, and heterogeneous nucleation of water vapor on silver particles. In the nucleation of n-alcohols, vapor depletion, carrier gas effect and carrier gas pressure effect were evaluated, with a special focus on the pressure effect whose dependence on vapor and carrier gas properties could be specified. The investigation of nucleation in the water-sulfuric acid-system included a thorough analysis of the experimental setup, determining flow conditions, vapor losses, and nucleation zone. Experimental nucleation rates were compared to various theoretical approaches. We found that none of the considered theoretical descriptions of nucleation captured the role of water in the process at all relative humidities. Heterogeneous nucleation was studied in the activation of silver particles in a TSI 3785 particle counter which uses water as its working fluid. The role of the contact angle was investigated and the influence of incoming particle concentrations and homogeneous nucleation on counting efficiency determined.
Resumo:
A new deterministic three-dimensional neutral and charged particle transport code, MultiTrans, has been developed. In the novel approach, the adaptive tree multigrid technique is used in conjunction with simplified spherical harmonics approximation of the Boltzmann transport equation. The development of the new radiation transport code started in the framework of the Finnish boron neutron capture therapy (BNCT) project. Since the application of the MultiTrans code to BNCT dose planning problems, the testing and development of the MultiTrans code has continued in conventional radiotherapy and reactor physics applications. In this thesis, an overview of different numerical radiation transport methods is first given. Special features of the simplified spherical harmonics method and the adaptive tree multigrid technique are then reviewed. The usefulness of the new MultiTrans code has been indicated by verifying and validating the code performance for different types of neutral and charged particle transport problems, reported in separate publications.
Resumo:
In this thesis acceleration of energetic particles at collisionless shock waves in space plasmas is studied using numerical simulations, with an emphasis on physical conditions applicable to the solar corona. The thesis consists of four research articles and an introductory part that summarises the main findings reached in the articles and discusses them with respect to theory of diffusive shock acceleration and observations. This thesis gives a brief review of observational properties of solar energetic particles and discusses a few open questions that are currently under active research. For example, in a few large gradual solar energetic particle events the heavy ion abundance ratios and average charge states show characteristics at high energies that are typically associated with flare-accelerated particles, i.e. impulsive events. The role of flare-accelerated particles in these and other gradual events has been discussed a lot in the scientific community, and it has been questioned if and how the observed features can be explained in terms of diffusive shock acceleration at shock waves driven by coronal mass ejections. The most extreme solar energetic particle events are the so-called ground level enhancements where particle receive so high energies that they can penetrate all the way through Earth's atmosphere and increase radiation levels at the surface. It is not known what conditions are required for acceleration into GeV/nuc energies, and the presence of both very fast coronal mass ejections and X-class solar flares makes it difficult to determine what is the role of these two accelerators in ground level enhancements. The theory of diffusive shock acceleration is reviewed and its predictions discussed with respect to the observed particle characteristics. We discuss how shock waves can be modeled and describe in detail the numerical model developed by the author. The main part of this thesis consists of the four scientific articles that are based on results of the numerical shock acceleration model developed by the author. The novel feature of this model is that it can handle complex magnetic geometries which are found, for example, near active regions in the solar corona. We show that, according to our simulations, diffusive shock acceleration can explain the observed variations in abundance ratios and average charge states, provided that suitable seed particles and magnetic geometry are available for the acceleration process in the solar corona. We also derive an injection threshold for diffusive shock acceleration that agrees with our simulation results very well, and which is valid under weakly turbulent conditions. Finally, we show that diffusive shock acceleration can produce GeV/nuc energies under suitable coronal conditions, which include the presence of energetic seed particles, a favourable magnetic geometry, and an enhanced level of ambient turbulence.
Resumo:
The magnetically induced currents in organic monoring and multiring molecules, in Möbius shaped molecules and in inorganic all-metal molecules have been investigated by means of the Gauge-including magnetically induced currents (GIMIC) method. With the GIMIC method, the ring-current strengths and the ring-current density distributions can be calculated. For open-shell molecules, also the spin current can be obtained. The ring-current pathways and ring-current strengths can be used to understand the magnetic resonance properties of the molecules, to indirectly identify the effect of non-bonded interactions on NMR chemical shifts, to design new molecules with tailored properties and to discuss molecular aromaticity. In the thesis, the magnetic criterion for aromaticity has been adopted. According to this, a molecule which has a net diatropic ring current might be aromatic. Similarly, a molecule which has a net paratropic current might be antiaromatic. If the net current is zero, the molecule is nonaromatic. The electronic structure of the investigated molecules has been resolved by quantum chemical methods. The magnetically induced currents have been calculated with the GIMIC method at the density-functional theory (DFT) level, as well as at the self-consistent field Hartree-Fock (SCF-HF), at the Møller-Plesset perturbation theory of the second order (MP2) and at the coupled-cluster singles and doubles (CCSD) levels of theory. For closed-shell molecules, accurate ring-current strengths can be obtained with a reasonable computational cost at the DFT level and with rather small basis sets. For open-shell molecules, it is shown that correlated methods such as MP2 and CCSD might be needed to obtain reliable charge and spin currents. The basis set convergence has to be checked for open-shell molecules by performing calculations with large enough basis sets. The results discussed in the thesis have been published in eight papers. In addition, some previously unpublished results on the ring currents in the endohedral fullerene Sc3C2@C80 and in coronene are presented. It is shown that dynamical effects should be taken into account when modelling magnetic resonance parameters of endohedral metallofullerenes such as Sc3C2@C80. The ring-current strengths in a series of nano-sized hydrocarbon rings are related to static polarizabilities and to H-1 nuclear magnetic resonance (NMR) shieldings. In a case study on the possible aromaticity of a Möbius-shaped [16]annulene we found that, according to the magnetic criterion, the molecule is nonaromatic. The applicability of the GIMIC method to assign the aromatic character of molecules was confirmed in a study on the ring currents in simple monocylic aromatic, homoaromatic, antiaromatic, and nonaromatic hydrocarbons. Case studies on nanorings, hexaphyrins and [n]cycloparaphenylenes show that explicit calculations are needed to unravel the ring-current delocalization pathways in complex multiring molecules. The open-shell implementation of GIMIC was applied in studies on the charge currents and the spin currents in single-ring and bi-ring molecules with open shells. The aromaticity predictions that are made based on the GIMIC results are compared to other aromaticity criteria such as H-1 NMR shieldings and shifts, electric polarizabilities, bond-length alternation, as well as to predictions provided by the traditional Hückel (4n+2) rule and its more recent extensions that account for Möbius twisted molecules and for molecules with open shells.
Resumo:
Con la finalidad de analizar la influencia de tres diferentes niveles de nitrógeno (0, 50 y 100 kg/ha de nitrógeno), tres diferentes fraccionamientos (25-25-50; 25-50-25 y 33-33-33 por ciento del fertilizante aplicado a cada momento) y dos diferentes momentos de aplicación (0 - 16 -32 y 0 -32 -48 días después de la siembra) sobre el crecimiento, desarrollo y rendimiento del maíz (Zea mays L.) variedad NB-12, se estableció en experimiento trifactorial montado en un diseño de bloques completos al azar, más un testigo absoluto con cinco repeticiones en la Hacienda Las Mercedes, Managua, cuyos suelos son de topolofía plana, textura franco arcillosa a franca y medios en materia orgánica. Para el crecimiento y desarrollo se encotró el mejor comportamiento con el nivel de 100 kg/ha de nitrógeno fraccionados en un 25-50-25 o en tres aplicaciones iguales y aplicados a la siembra, 32 y 48 y a la siembra, 16 y 32 días después respectivamente. Por otro lado se observó de manera general que el rendimiento y sus componetes principales tienden a aumentar con el nivel de 100 kg/ha de nitrógeno, divididos en tres aplicaciones iguales y sumunistrados a la siembra, 16 y 32 días después.
Resumo:
Con la finalidad de estudiar el comportamiento del crecimiento, desarrollo y rendimiento de los cultivos de sorgo (Sorghum bicolor. L. Moench) híbrido D-55 y maíz (Zea mays L) variedad NB-30, bajo los efectos de diferentes cultivos leguminosos: Maní (Arachis hypogaea L. ), caupí (Vigna unguiculata L. Walp), soya (Glycine max L. Merril) y frijol común ( Phaseolus vulgaris L.) como cultivos antecesores, se realizó un experimento de campo, utilizando un diseño de Bloques Completos al Azar con doce tratamientos y cuatro repeticiones realizados durante la siembra de primera y postrera de 1991, en el Centro Experimental La Compañía; Carazo, cuyo suelos son de topografía plana, textura media, franco limoso ( Typic Durandept ). De los resultados obtenidos se llegó a la conclusión que los diferentes cultivos leguminosos influyeron sobre el crecimiento, desarrollo y rendimiento de los cultivos de sorgo y maíz, ya que estos fueron afectados de manera significativa por los cultivos antecesores. Por otro lado se comprobó que el sorgo y el maíz, cuando tienen como cultivo antecesor a las leguminosas, sus rendimientos fueron superiores que cuando se tiene al sorgo y al maíz como cultivo antecesor. De las leguminosas, el cultivo de maní tuvo un mayor efecto sobre el rendimiento del sorgo y maíz. (4,391 y 1,675 kg/ha respectivamente). Se comprobó cuantitativamente el efecto negativo de utilizar a los cultivos de sorgo y maíz como cultivos antecesores a su mismo cultivo, ya que los rendimientos disminuyen considerablemente, siendo estos los siguientes: sorgo-sorgo obtuvo 2,170 kg/ha., maíz-sorgo dio un rendimiento de 2,373 kg/ha, maíz-maíz presentó 762 kg/ha, y finalmente el tratamiento sorgo-maíz rindió 674 kg/ha.
Resumo:
Resumen: El presente estudio tuvo por objeto explorar el desarrollo de las habilidades narrativas de niños de 5 años de nivel socioeconómico (NSE) bajo y medio. A principio del año escolar, se les solicitó a los niños que seleccionaran un libro de cuentos y lo “leyeran”. Los niños de NSE bajo no respondieron a la consigna, por lo que se analizó su desempeño narrativo luego de la implementación de una propuesta de alfabetización temprana que incluía la lectura diaria y repetida de cuentos. El análisis de los relatos infantiles permitió identificar diferencias entre los grupos de distinto NSE. Mientras que los niños de NSE medio recuperaban la historia o “hacían que leían” apelando a recursos lingüísticos característicos de historias de ficción, los relatos de los niños de NSE bajo, aún después de la intervención, mantenían marcas de oralidad y estaban ligados a guiones y experiencias personales.
Resumo:
Contenido: El tratamiento de la providencia general de Dios en Santo Tomás de Aquino / Gabriel Delgado – Sobre el ente posible y necesario en Tomás de Aquino / Alberto Berro – El apogeo del nominalismo escolástico y la imposibilidad de la metafísica / Mario Enrique Sacchi – La psicologia de Nietzsche e il suo influsso nella Psicoanalisi / Martín F. Echavarría – Ernst Cassirer: de la tragedia a la ambivalencia de la cultura (parte II) / Amán Rosales Rodríguez – Conocimiento y respuesta al valor. Enfoque fenomenológico axiológico de von Hildebrand / Elizabeth Da Dalt de Mangione -- Heidegger, Aristóteles y la Escolástica / Silvana Filippi – Los “juicios directos” y la probabilidad. Introducción al concepto de probabilidad según John Maynard Keynes / Marcelo Luis Imperiale – Generalis Relativitatis Theoria: geometria et philosophia / Ramiro Délio Borges de Meneses – El arte de gobernar. Nota sobre Michel Foucault a 20 años de su muerte -- Bibliografía
Resumo:
Con el Objetivo de estudiar la influencia de tres diferentes nieves de nitrógeno (0.70 y 140 kilogramos por hectárea), cuatro diferentes espaciamientos (40,60 80 y 120 cm) y tres diferentes densidades de población (41 500.62 500 y 83 250 plantas por Hectárea) sobre el crecimiento, desarrollo y rendimiento de maíz (Zea mays L.) var. NB-6, se estableció un experimento, utilizando el diseño de parcelas Divididas con cuatro repeticiones, en la Estación Experimental La Compañía, Carazo, cuyos suelos son de topografía plana, textura media, altos en materia orgánica, Clase II pertenecientes a la serie Masatepe. Los resultados obtenidos indican que la aplicación de nitrógeno y los diferentes espaciamientos entre surcos no produjeron efecto significativo sobre el rendimiento y sus componentes, asimismo no se determinó efecto significativo de las intersecciones cobre el rendimiento y sus componentes, La densidad de población mostró un efecto altamente significativo sobre el rendimiento en grano obteniéndose 7,470 kilogramos por hectárea. Se determinó que el mayor rendimiento se produjo utilizando 140 kilogramos de nitrógeno por hectárea, espaciamientos de 40 cm y una densidad de población de 83.250 plantas por hectárea, al cual corresponde un ingreso Neto de $756,743 córdobas equivalente a una tasa de retorno Marginal de 6.58.
Resumo:
[EUS] Matematikaren irakaskuntzaren helburuenetako bat hezkuntza maila guztietan ikasleen ahalmen intelektualen garapena da. Ahalmen espazialaren trataera eskolan urria izan da, bereziki zenbakizko ahalmenak edota arrazonamenduzko ahalmenak izan duten trataerarekin konparatzen badugu. Hezkuntza Matematikoan egindako berrikusketek ahalmen espazialaren azterketaren garrantzia azpimarratzen dute nahiz eta erreferentzi marko baten ezak sakabanatzen eta zailtzen dituen emaitzen lorpena, behin betikoak izateko erreplikagarriak izan behar dutela jakinik. Ondoren proposatzen den ikerketa-lerroak ahalmen espaziala alderdi hirukoitz batetik abiaturik aztertu nahi du: egitura, garapena eta hobetze-proposamenak kontutan harturik. Hiru arlo horietan proposaturiko ereduek bermatuko dute diagnostiko zuzen bat, ikasleen ahalmen espaziala hobetuko duena.
Resumo:
IX,481 p.