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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The Study and Fabrication of Quasi-phase-matched LiNbO3 Crystal Fiber for Wavelength Conversion

Cho, Yu-Chieh 25 June 2003 (has links)
All-optical wavelength conversion is necessary for efficient managing and routing optical signals in a complex all-optical network model. With the bit-rate increases as time evolves, all-optical conversion will become more promising due to its high transparency for data rate and format and the low cost penalty compared with O/E/O method. Periodically poled LiNbO3 crystal fiber (PPLNCF) for wavelength conversion is successfully grown by LHPG method with in situ electric field bias. The pitch depends on the frequency of applied external electric field. Domain period of 9.76 microms and crystal length over 160 mm are demonstrated in this thesis. Electrically induced micro-swing during growth is managed to assist poling process. After the optical test, 0.27% peak offset shows the accuracy of our fabrication. The wavelength and temperature bandwidths were measured to be 17.2 nm and 42.8oC. With the improvement of uniformity, broadband design, and the implementation of guiding structure, high quality PPLNCF will be widely promoted for its superior performance.
2

QPM Devices in KTA and RKTP

Zukauskas, Andrius January 2014 (has links)
Even though KTiOPO4 (KTP) is considered to be one of the best nonlinear materials for quasi phase matched (QPM) frequency conversion in the visible and the near-infrared spectral regions, its use is often limited by poor material homogeneity, high ionic conductivity, a considerable linear absorption and photochromatic damage. On the other hand, the improved material homogeneity and the lower ionic conductivity of bulk Rb-doped KTP (RKTP) make this material an ideal alternative for fabrication of fine-pitch QPM gratings, while the arsenate isomorph KTiOAsO4 (KTA) promises a better performance in the green spectral region and adds the advantage of a wider transparency window in the infrared. Unfortunately, the available studies on these materials are limited and unable to answer the question whether RKTP and KTA are feasible alternatives to KTP in terms of periodic poling and optical performance. The optical performance of the QPM devices depends on the periodic poling quality, therefore, a detailed comprehension of domain-grating formation in the KTP isomorphs is highly desired. The goals of this thesis were to gain a better understanding of the periodic poling process in the KTP isomorphs, in order to study the specifics of ferroelectric domain engineering in KTA and RKTP, and to evaluate the optical performance of these isomorphs. Fine-pitch periodically poled structures were engineered both in KTA and RKTP crystals. It was demonstrated that QPM gratings with excellent quality and with periods as short as 8.49 μm can be fabricated in KTA crystals. Comparative transmission studies have shown that periodically poled KTA (PPKTA) crystals can be superior to KTP for QPM second harmonic generation in the visible spectral region due to lower linear absorption. It was also demonstrated that RKTP is a superior alternative to KTP for high-quality QPM grating fabrication. A consistent room-temperature periodic poling of 5 mm thick RKTP crystals with a period of 38.86 μm has been achieved. The obtained large aperture periodically poled RKTP (PPRKTP) crystals showed an outstanding QPM grating uniformity and excellent optical performance in optical parametric oscillator (OPO) applications. Moreover, it was shown that RKTP is less susceptible to blue-induced infrared absorption than KTP. Finally, a novel and a relatively simple method for self-assembling quasi-periodic sub-μm scale ferroelectric domain structure in RKTP crystals has been presented. It was shown that, after treatment in aqueous KOH/KNO3 solution, periodic poling of RKTP with planar electrodes resulted in one-dimensional ferroelectric domain structure with an average periodicity of 650±200 nm, extending over the whole 1 mm thick crystal. Such self-assembled structures in RKTP were used to demonstrate 5th order non-collinear QPM backward second harmonic generation. / <p>QC 20140114</p>
3

Second-order nonlinear optical interactions and cascading effects in thinorganic films

Ksianzou, Viachaslau January 2010 (has links)
The presented work describes new concepts of fast switching elements based on principles of photonics. The waveguides working in visible and infra-red ranges are put in a basis of these elements. And as materials for manufacturing of waveguides the transparent polymers, dopped by molecules of the dyes possessing second order nonlinear-optical properties are proposed. The work shows how nonlinear-optical processes in such structures can be implemented by electro-optical and opto-optical control circuit signals. In this paper we consider the complete cycle of fabrication of several types of integral photonic elements. The theoretical analysis of high-intensity beam propagation in media with second-order optical nonlinearity is performed. Quantitative estimations of necessary conditions of occurrence of the nonlinear-optical phenomena of the second order taking into account properties of used materials are made. The paper describes the various stages of manufacture of the basic structure of the integrated photonics: a planar waveguide. Using the finite element method the structure of the electromagnetic field inside the waveguide in different modes was analysed. A separate part of the work deals with the creation of composite organic materials with high optical nonlinearity. Using the methods of quantum chemistry, the dependence of nonlinear properties of dye molecules from its structure were investigated in details. In addition, the paper discusses various methods of inducing of an optical nonlinearity in dye-doping of polymer films. In the work, for the first time is proposed the use of spatial modulation of nonlinear properties of waveguide according Fibonacci law. This allows involving several different nonlinear optical processes simultaneously. The final part of the work describes various designs of integrated optical modulators and switches constructed of organic nonlinear optical waveguides. A practical design of the optical modulator based on Mach-Zehnder interferometer made by a photolithography on polymer film is presented. / Die vorliegende Arbeit beschreibt neue Konzepte für schnelle photonische Schaltelemente. Diese Elemente basieren auf optischer Wellenleitung im sichtbaren und nahen infraroten Spektralbereich. Die Arbeit ist auf organische Wellenleiter aus transparenten, farbstoffdotierten Polymeren fokussiert, welche Chromophore mit besonders großen optischen Nichtlinearitäten zweiter Ordnung enthalten. Insbesondere wird dargestellt, wie nichtlineare optische Prozesse in derartigen Bauelementen genutzt werden können, wenn man elektrische oder optische Steuersignale einsetzt. Es wird der gesamte Her-stellungszyklus verschiedener integrierter photonischer Bauelemente betrachtet. Die Arbeit umfasst weiterhin eine detaillierte theoretische Analyse der Wellenausbreitung in Medien mit großer nichtlinearer optischer Suszeptibilität zweiter Ordnung bei hoher Lichtintensität. Unter Annahme optischer Materialkonstanten, welche den experimentell ermittelten Werten entsprechen, erfolgte eine quantitative Abschätzung für das Auftreten von Szenarien, bei denen messbare Abwei-chungen der Strahlausbreitung vom linearen Regime auftreten, z:B. das Auftreten von zeitlichen, räumlichen und spektralen Satteliten zu den im Material propagierenden Laserpulsen. Es gelang, we-sentliche Aspekte der Strahlpropagationsprozesse durch Anwendung von Jacobi-Integralfunktionen in geschlossener mathematischer Form darzustellen. Darüber hinausgehende theoretische Untersuchungen nutzten die Finite-Elemente-Methode, um die Verteilung des elektromagnetischen Feldes im Inneren optischer Wellenleiter für verschiedene Pro-pagationsmoden zu analysieren. Ein weiterer Teil der Arbeit beschäftigt sich mit organischen Kompositmaterialen, welche große opti-sche Nichtlinearitäten aufweisen. Mittels quantenchemischer Verfahren erfolgte eine detaillierte Un-tersuchung der Zusammenhänge zwischen der molekularen Struktur und den linearen sowie den nichtlinearen optischen Eigenschaften der untersuchten Farbstoffmoleküle und Polymere. In Bezug auf die Probenpräparation sind unterschiedliche Verfahren zur Schichtbildung und zur molekularen Orientierung miteinander verglichen und bewertet worden, da letztere eine Voraussetzung für das Auftreten nichtlinearer optischer Prozesse zweiter Ordnung bildet. Die Untersuchungen erstreckten sich auf Vakuumaufdampfschichten aus niedermolekularen Chromophoren und auf Polymerschich-ten, welche durch Vakuumabscheidung sowie durch Spincoating oder andere Flüssigphasenabschei-dungsverfahren hergestellt worden sind. Auf orientierenden Substraten (z.B. geriebene Schichten aus Polytetrafluoräthylen) konnte eine spontane Orientierung der deponierten Chromophore nachgewie-sen werden. Die Chromophore in Polymerschichten wurden durch Coronapolung orientiert. In der Arbeit ist zum ersten Mal vorgeschlagen worden, eine räumliche Modulation der nichtlinearen optischen Eigenschaften durch gezielte lokale Coronapolung oder andere Orientierungstechniken derart zu generieren, dass die Abfolge gepolter Domänen dem Bildungsgesetz einer modifizierten Fibonacci-Reihe mit gebrochen rationalen Zahlen gehorcht. Der Vorteil von optischen Wellenleitern mit dieser Struktur darin, dass diese mehrere unterschiedli-che nichtlineare optische Prozesse gleichzeitig unterstützen und somit eine Vielzahl neuartiger Phä-nomene auftreten kann, welche man in neuartigen photonischen Bauelementen, z.B. für die optische Informations- und Kommunikationstechnik nutzen kann. Der letzte Teil der Arbeit beschreibt den Aufbau verschiedener integrierter optischer Modulatoren und Schalter, die sich mit Hilfe das neu entwickelten Verfahrens herstellen lassen. Zukünftige Entwicklungen in der Photonik, insbesondere der optischen Informations- und Kommuni-kationstechnik werden im abschließenden Teil der Arbeit diskutiert.
4

Wavelength Conversion Using Periodically Poled Lithium Niobate Crystal fiber

Chiu, Po-Chun 14 July 2005 (has links)
All-optical wavelength conversion will be one of the most key technologies in all-optical network. Wavelngth converter using nonlinear effect can resolve wavelength contentions with its high transparency and subcarrier-multiplexed channels in a complex all-optical network model which is more beneficial than O/E/O method. Periodically poled LiNbO3 crystal fiber for wavelength conversion is successfully grown by LHPG method with high-electric-field bias. It does not require conducting the metallic electrode to define domain period. The pitch depends on the frequency of applied external electric field and the growth speed. Domain period of 18.9 £gm for C-band wavelength converter and domain period of 15.45 £gm for tunable blue/green laser are demonstrated in this thesis. Micro-swing during growth is managed to assist poling process. More than 40 nm wavelength range of blue/green laser was generated and 10% internal SHG conversion efficiency was achieved. A simulation shows that maximum tuning range using a graded-period qusai-phase-matching structure can be as large as 33 nm. With the improvement of uniformity, broadband design for cascaded processes, and waveguide structure, superior performance of periodically poled LiNbO3 crystal fiber can be achieved.
5

Investigating Periodically Poled Ferroelectric Crystal Fiber with Second Harmonic Microscopy

Wang, Sheng-yi 15 July 2007 (has links)
Lithium niobate (LiNbO3) and Lithium tantalate (LiTaO3) are high-performance nonlinear optical materials that have been popularly used in electro-optical modulation and nonlinear optics. Second-harmonic generation (SHG) microscope is applied to get SH images, as compared to etching method. SH image method has the advantage of faster and non-invasive inspection. Our system can rapid and non-destructive mapping of the detailed features of the crystal fibers in three dimensions. By simulation, we can explain that in the interface of +Z and ¡VZ domain, because the Li ions can stay in positive and negative two stable energy valleys. It may induce stronger SH intensity by QPM than +Z and -Z domain.
6

Acceptance, perceptions and willingness to pay for Quality Protein Maize (QPM) by rural consumers in Tanzania

Kiria, Christine Gacheri 17 November 2011 (has links)
Malnutrition remains a persistent and increasing problem in Sub-Saharan Africa (SSA). Food production has not kept pace with population growth, and many people have poor access to adequate, nutritious diet. In many areas of the developing world, maize is a vital staple and a main source of dietary protein. In Eastern and Southern Africa, maize is the basic food for the subsistence farmers. Per capita consumption of maize in Malawi, Zambia and Zimbabwe is 100 kg per year, while in Tanzania, per capita consumption is estimated at 73 kg per year. Unfortunately, the nutritional value of conventional maize is poor, partly due to the low biological value of its protein. To ensure sufficient protein intake, conventional maize should therefore be consumed with complementary protein sources, such as legumes or animal proteins. The complementary proteins sources however, tend to be expensive, or take a lot of time and fuel to cook, for instance beans. The main aim of this study was to evaluate the sensory characteristics and consumer acceptance of quality protein maize (QPM) in rural Tanzania. QPM is a maize cultivar which has almost double the amount of tryptophan and lysine. QPM has been adopted in several countries of SSA, but very few studies have been undertaken on its acceptance by consumers. In Tanzania, no study has been undertaken to elicit consumers‟ acceptability for this maize variety. The sensory characteristics of food products affect consumers‟ immediate consumption gratification. This study makes a unique contribution to the literature by exploring the roles that sensory evaluation and nutritional information play in shaping consumers‟ QPM flour purchasing behaviour through economic experiments in rural Tanzania. A triangle test was undertaken to find out whether there is a difference between QPM and conventional maize. Additionally, a rural household survey was undertaken which collected consumers‟ demographic, farming and individual characteristics. This was done using structured questionnaires administered by trained enumerators. Moreover, modified home use sensory testing and central location sensory testing were also undertaken to determine sensory characteristics of QPM and conventional maize. Stiff porridge, a major maize product in East and South Africa, was used to undertake this experiment. Finally, acceptability of QPM was tested using experimental auctions with the Becker-DeGroot-Marschak (BDM) procedure, and maize flour was used to undertake this experiment. The sensory evaluation findings of the study indicated that consumer characteristics of QPM stiff porridge were highly appreciated than those of conventional maize stiff porridge. This was observed both in the modified home use testing and central location testing. Likewise, consumers were willing to pay more for QPM than for conventional maize in all evaluation criteria used. Triangle test showed a significant difference between QPM and conventional maize. Sensory evaluation however needs to be repeated with other QPM varieties to ensure that it is not only a specific QPM variety that has favourable consumer characteristics. This study further revealed that providing QPM nutritional information to consumers increases their willingness to pay for QPM. Subjects who were provided with QPM nutritional information had higher WTP for QPM than those who were not. This shows that creating awareness of the nutritional contents, especially of the new varieties, would increase the appreciation by consumers hence help in fighting malnutrition in SSA. Providing QPM nutritional information, on the other hand, decreased consumers‟ WTP for conventional maize. This was unexpected because the information provided only concerned QPM. The study recommends that another study be carried out to find out the cause of decrease in WTP for conventional maize when QPM nutritional information is provided. This study clearly reveals that QPM is acceptable by rural consumers in Tanzania. This information can help policy makers in Africa to better understand consumers' food behaviour and make initiatives to improve diet and health, which can be important in reducing malnutrition in Sub Saharan Africa. / Dissertation (MSc(Agric))--University of Pretoria, 2011. / Agricultural Economics, Extension and Rural Development / unrestricted
7

Avaliação da qualidade de alimentos biofortificados produzidos em sistemas agroecológicos do trópico úmido / Evaluation of the quality of biofortified food produced in agroecological systems in the humid tropics

Silva, Aline Gomes de Moura e [UNESP] 18 February 2016 (has links)
Submitted by ALINE GOMES DE MOURA E SILVA null (aline.gms@gmail.com) on 2016-03-11T13:44:41Z No. of bitstreams: 1 TESE VERSÃO FINAL CORRIGIDA.pdf: 1163303 bytes, checksum: a526bf08995bae194a0b248c489531cc (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-03-14T18:09:14Z (GMT) No. of bitstreams: 1 silva_agm_dr_sjrp.pdf: 1163303 bytes, checksum: a526bf08995bae194a0b248c489531cc (MD5) / Made available in DSpace on 2016-03-14T18:09:14Z (GMT). No. of bitstreams: 1 silva_agm_dr_sjrp.pdf: 1163303 bytes, checksum: a526bf08995bae194a0b248c489531cc (MD5) Previous issue date: 2016-02-18 / O sistema de cultivo em aleias é uma forma de agricultura sustentável que melhora a qualidade do solo do trópico úmido. O objetivo deste trabalho foi avaliar a influência do sistema de cultivo em aleias na produtividade e na qualidade nutricional das culturas biofortificadas de milho e mandioca. O milho QPM (Quality Protein Maize) BR 473 foi cultivado em Chapadinha (MA). Foram utilizadas as combinações de leguminosas: GA (Gliricídia + Acácia), GS (Gliricídia + Sombreiro), LA (Leucena + Acácia), LS (Leucena + Sombreiro) e sem leguminosas (SL), com ou sem adição de 80-80 kg/ha de cloreto de potássio e ureia. As análises realizadas foram: massa de 100 grãos, número de grãos/espiga, massa da espiga, produtividade de grãos, composição centesimal, carotenoides totais, teores de minerais, perfil de ácidos graxos e de tocoferóis. O plantio com resíduos de leguminosas e a adição de cloreto de potássio e ureia aumentaram a produtividade do milho. Com relação à proteína, a ureia teve maior influência que os resíduos de leguminosas. As combinações sem adubação com ureia e cloreto de potássio obtiveram os maiores teores de tocoferóis. O plantio da mandioca BRS Dourada foi realizado em São Luís (MA). Foram utilizadas as combinações de leguminosas: GA (Gliricídia + Acácia), GS (Gliricídia + Sombreiro), GL (Gliricídia + Leucena), LA (Leucena + Acácia), LS (Leucena + Sombreiro) e sem leguminosas (SL), com ou sem adição de 100 kg/ha de ureia. As análises realizadas foram: produtividade de parte aérea, número de raízes por pé, massa de raiz, produtividade de raízes, composição centesimal, teor de amido, minerais, tempo de cocção, perfil de carotenoides e teor de pró- vitamina A. A produtividade foi maior em GL. A adição de ureia ao solo aumentou os teores de proteína e amido. Para a pró-vitamina A, GS com ureia se destacou com 12,4 RAE (Equivalente de atividade retinol) /100 g. A escolha da combinação de leguminosas está relacionada à cultura a ser plantada e ao atributo de qualidade desejado. O sistema de cultivo em aleias foi capaz de aumentar a produção de milho e de mandioca biofortificados e influenciar diferentemente cada nutriente. / No-tillage alley cropping is a form of sustainable agriculture that improves soil quality of the humid tropics. The aim of this study was to evaluate the influence of the alley cropping system in the productivity and nutritional quality of biofortified maize and cassava. The highquality protein maize (QPM) BR 473 was grown in Chapadinha (MA). The combinations of legumes were: GA (Gliricidia + Acacia), GS (Gliricidia + Sombreiro), LA (Leucena + Acacia), LS (Leucena + Sombreiro) and the bare soil, with or without addition of 80-80 kg/ha of potassium chloride and urea. The analysis were: 100-grain weight (g), grain/ear, weight of ear, grain yield, proximate composition, mineral content, carotenoids, fatty acid profile and tocopherols. The planting with legume residues and addition of potassium chloride and urea increased corn yield. Regarding protein, urea had greater influence than residues. The combinations of trees without fertilization with urea and potassium chloride had the highest levels of tocopherols. The BRS Dourada cassava was grown in São Luís (MA). The combinations of legumes were: GA (Gliricidia + Acacia), GS (Gliricidia + Sombreiro), LA (Leucena + Acacia), LS (Leucena + Sombreiro), GL (Gliricidia + Leucena) and the bare soil, with or without addition of 100 kg/ha of urea. The analysis were: shoot production, number of roots/plant, root weight, root production, proximate composition, starch, minerals, cooking time, carotenoids profile and pro-vitamin A contents. The yield was greater in GL. The addition of urea to the soil increased the protein and starch contents. For pro-vitamin A, the GS with ureia stood out with 12.4 RAE (Retinol Activity Equivalent) /100 g. The choice of combination of pulses is related to the crop to be planted and the desired quality attribute. The cropping system in alleys was able to increase the production of corn and biofortified cassava and to influence differently each nutrient.
8

Fabrication and characterization of periodically poled KTB and RB-doped KTB for applications in the visible and UV

Wang, Shunhua January 2005 (has links)
This thesis deals with the fabrication and the characterization of periodically-poled crystals for use in lasers to generate visible and UV radiation by second-harmonic generation (SHG) through quasi-phasematching (QPM). Such lasers are of practical importance in many applications like high-density optical storage, biomedical instrumentation, colour printing, and for laser displays. The main goals of this work were: (1) to develop effective monitoring methods for poling of crystals from the KTiOPO4 (KTP) family, (2) to develop useful non-destructive domain characterization techniques, (3) to try to find alternative crystals to KTP for easier, periodic poling, (4) to investigate the physical mechanisms responsible for optical damage in KTP. The work shows that the in-situ SHG technique used together with electro-optic monitoring, makes it possible to obtain reliable, real-time information regarding the poling quality over the whole crystal aperture during the electric-field poling process. Using this combined monitoring method, both KTP and Rb-doped KTP (RKTP) crystals were successfully poled. By comparing these two crystals, we found that a low-doped KTP has a substantially reduced ionic conductivity and, thus, a high-quality periodic poling can be obtained without otherwise affecting the properties of the crystal. RKTP is a good alternative candidate to KTP for poling purpose. We have also shown that Atomic Force Microscopy (AFM) is an informative tool for investigating domain nucleation, growth, and merging. Furthermore, we have demonstrated a simple technique for 3D characterization of QPM samples. It utilizes a group-velocity mismatched, type-II SHG of femtosecond pulses for layer-by-layer monitoring of the effective nonlinearity along the propagation direction of the beam. The quality of these crystals was finally reflected in a number of SHG experiments with a variety of laser sources. High energies and high efficiencies were thus demonstrated using CW, mode-locked and Q-switched lasers. Gratings with pitches smaller than 3 µm, were demonstrated for first-order UV generation. Type-II QPM SHG was demonstrated as a technique for reducing the fabrication constraints. High intensity light in the visible and the UV leads to modification of the material properties and, eventually, to optical damage. In KTP and its isomorphs, the first sign of material change is an optically-induced absorption. We have used thermal-lens spectroscopy with a common-path interferometer for high-sensitivity measurements of green light-induced infrared absorption dynamics in single-domain and periodically-poled KTP (PPKTP). The saturated, green light-induced absorption has been shown to be consistently higher in periodically-poled crystals, and is attributed to the creation of stoichiometric and interstitial defects in the crystals during the poling process. Finally, irreversible bulk damage thresholds in PPKTP have been determined for pulsed frequency converters. As the characteristics of optical damage are closely related to the material quality, this investigation can provide useful information for crystal manufactures and will help to optimise the crystal growth conditions.
9

Fabrication and characterization of periodically poled KTB and RB-doped KTB for applications in the visible and UV

Wang, Shunhua January 2005 (has links)
<p>This thesis deals with the fabrication and the characterization of periodically-poled crystals for use in lasers to generate visible and UV radiation by second-harmonic generation (SHG) through quasi-phasematching (QPM). Such lasers are of practical importance in many applications like high-density optical storage, biomedical instrumentation, colour printing, and for laser displays.</p><p>The main goals of this work were: (1) to develop effective monitoring methods for poling of crystals from the KTiOPO<sub>4</sub> (KTP) family, (2) to develop useful non-destructive domain characterization techniques, (3) to try to find alternative crystals to KTP for easier, periodic poling, (4) to investigate the physical mechanisms responsible for optical damage in KTP. The work shows that the in-situ SHG technique used together with electro-optic monitoring, makes it possible to obtain reliable, real-time information regarding the poling quality over the whole crystal aperture during the electric-field poling process. Using this combined monitoring method, both KTP and Rb-doped KTP (RKTP) crystals were successfully poled. By comparing these two crystals, we found that a low-doped KTP has a substantially reduced ionic conductivity and, thus, a high-quality periodic poling can be obtained without otherwise affecting the properties of the crystal. RKTP is a good alternative candidate to KTP for poling purpose. We have also shown that Atomic Force Microscopy (AFM) is an informative tool for investigating domain nucleation, growth, and merging. Furthermore, we have demonstrated a simple technique for 3D characterization of QPM samples. It utilizes a group-velocity mismatched, type-II SHG of femtosecond pulses for layer-by-layer monitoring of the effective nonlinearity along the propagation direction of the beam. The quality of these crystals was finally reflected in a number of SHG experiments with a variety of laser sources. High energies and high efficiencies were thus demonstrated using CW, mode-locked and Q-switched lasers. Gratings with pitches smaller than 3 µm, were demonstrated for first-order UV generation. Type-II QPM SHG was demonstrated as a technique for reducing the fabrication constraints.</p><p>High intensity light in the visible and the UV leads to modification of the material properties and, eventually, to optical damage. In KTP and its isomorphs, the first sign of material change is an optically-induced absorption. We have used thermal-lens spectroscopy with a common-path interferometer for high-sensitivity measurements of green light-induced infrared absorption dynamics in single-domain and periodically-poled KTP (PPKTP). The saturated, green light-induced absorption has been shown to be consistently higher in periodically-poled crystals, and is attributed to the creation of stoichiometric and interstitial defects in the crystals during the poling process. Finally, irreversible bulk damage thresholds in PPKTP have been determined for pulsed frequency converters. As the characteristics of optical damage are closely related to the material quality, this investigation can provide useful information for crystal manufactures and will help to optimise the crystal growth conditions.</p>
10

Rendimento industrial e valor nutricional de grãos de milho QPM e de grãos de gérmem de milho comum / Industrial yield and nutritional value of a qpm corn grain and the grain and germ of common maize

CASTRO, Maiza Vieira Leão de 14 July 2008 (has links)
Made available in DSpace on 2014-07-29T15:22:58Z (GMT). No. of bitstreams: 1 Maiza.pdf: 418262 bytes, checksum: def50a68e6b9cd3076fdcccbf779fb64 (MD5) Previous issue date: 2008-07-14 / Endosperm hardness is an essential attribute for producers and industries that using corn as a raw material. Kernel texture alterations, however, hamper the commercial use of Quality Protein Maize (QPM). In this experiment, industrial yield was compared in kernel degerming and endosperm splitting and the nutritional value of a QPM variety and common corn genotypes. One QPM variety and three commercial corn hybrids cultived in Goiás were studied. The QPM and the common corn hybrids were processed using the dry degerming method and the resulting yield was expressed as the ratio of the weight of the fractions obtained to the initial weight of the whole corn. The chemical composition and the amino acid profile of QPM, common corn and common corn germ were determined and an experiment with recently weaned Wistar rats was carried out. Four 7 %-protein and one nonprotein diet were prepared. Protein utilization was estimated using the DCF (Dietary Conversion Factor), NPR (Net Protein Ratio), True Digestibility, and the PDCAAS (Protein Digestibility- Corrected Amino Acid Score). In comparison with common corn, QPM presented lower endosperm yield, higher germ and fine fractions (< 0.5 mm) yield, and the same yield for hominy in endosperm splitting. QPM presented similar levels of proteins, lipids and ash, and higher levels of lysine, dietary fiber and iron in the germ in relation to common corn hybrids. NPR values for QPM diets and corn germ diets were similar, lower than the reference and above the NPR values of common corn. The DCF of the QPM diet was higher than that of the casein diet, but it was the same as that of common corn germ and lower than the value obtained for common corn. QPM and common corn germ presented a protein value (NPR) that was 72 % of the value for casein, while that of common corn was 60 % of the casein value. QPM and the germ fraction of common corn are good quality protein sources when compared to common corn protein, and they present a satisfactory yield for use in the food industry as raw materials which add nutritional value to the products generated / A dureza do endosperma do milho é atributo essencial para produtores e indústrias que utilizam este cereal como matéria-prima. Porém, os milhos de alta qualidade protéica (QPM) apresentam alterações na textura do grão, dificultando seu uso comercial. Este trabalho investigou o rendimento industrial, na degerminação do grão e no fracionamento do endosperma, e o valor nutricional, de uma variedade de milho QPM em relação a genótipos de milho comum comercializados em Goiás. Foi estudada uma variedade de milho QPM e três híbridos comerciais de milho comum, cultivados em Goiás. O milho QPM e os híbridos de milho comum foram processados utilizando método de degerminação a seco, e o rendimento resultante foi dado pela relação entre o peso das frações obtidas e o peso inicial do milho inteiro. Foi determinada a composição química e o perfil de aminoácidos do milho QPM, milho comum e do gérmen de milho comum, e realizado um experimento com ratos Wistar, recém-desmamados. Foram elaborados quatro dietas com 7 % de proteína e uma aprotéica. Estimou-se a utilização protéica mediante os índices: NPR (Net Protein Ratio), FCA (Fator de Conversão Alimentar), Digestibilidade Verdadeira, e PDCAAS (Protein Digestibility-Corrected Amino Acid Score). Em comparação ao milho comum, o milho QPM apresentou menor rendimento de endosperma, maior rendimento de gérmen e de frações finas (< 0,5 mm), e mesmo rendimento de canjica no fracionamento do endosperma. O milho QPM apresentou teores similares de proteínas, lipídios e cinzas, e maiores teores de fibra alimentar, de lisina, e de zinco e ferro (gérmen) em relação aos híbridos de milho comum. Os valores de NPR para as dietas com milho QPM e gérmen de milho comum foram semelhantes entre si, inferiores ao padrão, e superiores ao milho comum. A dieta QPM apresentou FCA maior que a dieta de caseína, porém foi menor que o milho comum, e igual ao gérmen de milho comum. O milho QPM e o gérmen de milho comum apresentaram valor protéico (em relação à caseína) de 72 %, enquanto que o milho comum apresentou valor de 60 %. O milho QPM e a fração gérmen de milho comum são fontes de proteína de melhor qualidade quando comparados ao milho comum e apresentam rendimento satisfatório para serem usados na indústria de alimentos como matérias-primas que agregam valor nutricional aos produtos gerados

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