Whole-plant corn silage (WPCS) is a major source of forage for lactating dairy cattle in Brazil. Improved kernel processing may be especially advantageous when feeding corn hybrids with vitreous endosperm, which are more difficult to be broken. Two experiments were conducted to evaluate the effects of theoretical length of cut (TLOC) and ensiling time on whole-plant corn silage (WPCS) particle size and kernel processing with two types of forage harvesters. The same vitreous corn hybrid DKB 177 VT PRO 2 was used in both experiments. In the first experiment, the whole-plant corn was harvested by a pull-type forage harvester (PTFH) at TLOC of 3, 6 and 9-mm. In the second experiment, the harvesting was performed by a self-propelled forage harvester (SPFH) at the following TLOC settings: 6, 12 and 18-mm with a roll gap of 3-mm. The WPCS were stored for 0, 35 and 140 d. Vitreousness, measured by dissection in unfermented kernels, averaged 65.6%. Data from both trials were analyzed as a split-plot design using the procedure MIXED of SAS (SAS Institute Inc., Cary, NC). The model included the fixed effects of TLOC, ensiling time and the interaction TLOC × ensiling time. In PTFH, the TLOC of 3 and 6-mm did not differ WPCS particle size distribution and mean particle length (MPL). However, the TLOC of 9-mm increased particles above the top 2 sieves and, as a consequence, the MPL. The rise of TLOC in SPFH led to a higher MPL and percentage of long particles (< 19-mm). The ensiling time increased MPL and long particles only for WPCS harvested by SPFH. The strategy of reducing TLOC in SPFH increased the percentage of kernels smaller than 4.75-mm. Furthermore, The TLOC of 6-mm led to the best kernel processing for SPFH. The ensiling time reduced the particle size of kernel fraction for both forage harvesters. The corn silage processing score only improved with 140 d of ensiling for SPFH samples. In the third experiment the objective was to evaluate the impact of two types of forage harvesters and two TLOC settings on the physical characteristics of WPCS. A vitreous corn silage hybrid (BM 709, Sementes Biomatrix) was cultivated and harvested when whole-corn plant DM achieved 34.8%. The whole-plant was harvested with a conventional pull-type forage harvester (PTFH) without kernel processor (KP) at 6 and 10 of theoretical lengths of cut (TLOC) or by a new PTFH with KP at same TLOC settings. Whole-plant corn silage (WPCS) samples were stored for 35 d. Vitreousness, measured by dissection in unfermented kernels, averaged 62.4%. Data were analyzed as completely randomized design in a factorial arrangement: 2 harvesters × 2 TLOC using the procedure MIXED of SAS (SAS Institute Inc., Cary, NC). The model included the fixed effects of harvester, TLOC and the interaction harvester × TLOC. The major differences occurred only in TLOC of 10-mm. KP reduced the material above the 19-mm sieve from 4.7 to 1.8% which, in turn, increased the percentage of particles below 8-mm sieve while MPL was decreased. This TLOC displayed the highest value of material retained in the 8-mm and the lowest values in the 4-mm sieve for unprocessed WPCS. Kernel processing and short TLOC led to a rise in particles retained in a 4-mm sieve. KP increased the percentage of kernels smaller than 4.75-mm from 56.4 to 80.0% and the starch content below 8-mm sieve. The short TLOC and kernel processing, together, led to a reduction of kernel geometrical mean particle size (GMPS) followed by an increase of surface area. The new PTFH with KP promoted more extensive and effective kernel breakage. The impact of this harvester in WPCS particle size distribution was pronounced in the TLOC of 10-mm which led to a drop in MPL. The reduction of TLOC for both forage harvesters may be a good strategy to fracture corn kernels for WPCS at 34.8% of DM. In the fourth experiment, the objectives of this study were: 1) to evaluate the effect of kernel processing on a Brazilian vitreous endosperm corn hybrid and 2) the increment of particle size in WPCS on intake, lactation performance, total-tract nutrient digestibility, feeding behavior and milk fatty acids profile. The following treatments were performed during the harvest: 1) pull-type forage harvester (without kernel processor, JF AT 1600) set for a 6-mm theoretical length of cut (TLOC) - PT6; 2) self-propelled forage harvester (New Holland, FR 9050) set for a 6-mm TLOC - SP6; 3) self-propelled forage harvester set for a 12-mm TLOC - SP12; and 4) self-propelled forage harvester set for a 18- mm TLOC - SP18. The WPCS of treatments were storaged for 9 months. The CSPS of the WPCS were: 32.1% (PT6), 53.9% (SP6), 49.0% (SP12) and 40.1% (SP18). Holstein cows (n = 24; 139 ± 63 DIM) were blocked and assigned to six 4 × 4 Latin squares, with 24-d period (18 d of adaptation). Diets were formulated to contain (% DM) 48.5% WPCS, 9.5% soybean meal, 6.9% soybean meal non- enzymatic browned, 15.1% dry ground corn, 15.5% citrus pulp, 1.7% minerals and vitamins mix, 1.8% calcium soap of palm fatty acids, and 1% urea. Nutrient composition of the diets (% DM) was: 16.5% CP, 28.9% NDF and 25.4% starch. Three orthogonal contrasts were used to compare treatments: C1 = PT6 vs. SP6 (effect of kernel processing), C2 = SP6 vs. SP12 (effect of particle size) and C3 = SP12 vs. SP18 (effect of particle size). Cows fed SP6 WPCS had greater 1.2 kg/d milk yield with no changes in DMI, resulting in greater feed efficiency when compared with PT6. The total-tract starch digestibility (TTSD) and plasma glucose was also improved when cows were fed SP6. Moreover, the higher milk protein (+ 36 g/d), lactose (+ 61 g/d) and solids (+ 94 g/d) secretions were a result of the improvement in milk yield for SP6. In addition, the mechanism apparently involved a better nutrient digestibility and glucose availability for the synthesis of lactose by the mammary gland. There was no evidence for differences in DMI (kg/d) among self-propelled treatments. The SP12 cows achieved the same milk yield of SP6; however they tended to reduce plasma D-lactate and serum amiloyd A (SAA) while maximizing chewing time and selecting for fine particles. In SP6, cows selected against fine particles and tended to show higher levels of SAA than PT6. The SP18 reduced TTSD and tended to reduce milk production, and plasma glucose. The SP6 raised milk linear-odd chain fatty acids content in comparison with PT6. Nonetheless, a reduction of these same fatty acids occurred in SP12 in relation to SP6. SP6 cows had higher content of some monounsaturated fatty acids (C14:1 and C16:1), however the opposite occurred for SP12. Kernel processing at TLOC settings of 6 and 12-mm enhanced nutrient digestibility, plasma glucose and milk yield, whereas the 18-mm TLOC impaired lactation performance and TTSD. The TLOC of 12-mm improved chewing time and reduced blood sub- acute acidotic markers. The findings of this set of studies suggest that ensiling time and low TLOC in SPFH (6-mm) may be strategies to increase kernel damage and thus starch digestibility in WPCS. Despite 6-mm TLOC has improved kernel processing, the TLOC of 12-mm appeared to be the best setting to harvest whole-corn plant to feed dairy cows. / Silagem de milho (SM) é a principal fonte de forragem para vacas leiteiras em sistemas intensificados de produção no Brasil. O processamento adequado dos grãos é crucial principalmente quando SM são oriundas de híbridos com endosperma vítreo, os quais são mais difíceis de serem quebrados. Nesse sentindo dois experimentos foram conduzidos para avaliar os efeitos do tamanho teórico de corte (TTC) e do tempo de estocagem sobre o tamanho de partículas e o processamento dos grãos em SM colhida com diferentes tipos de colhedoras. O mesmo híbrido de milho vítreo DKB 177 VT PRO 2 foi usado em ambos os experimentos. A média do teor de matéria seca da planta no momento da colheita foi de 34,2%. No primeiro experimento, a lavoura de milho foi colhida por uma colhedora de forragem tracionada por trator (CFTT; JF AT 1600, sem processador de grãos) nos TTC de 3, 6 e 9-mm. No segundo experimento, a colheita foi realizada por uma colhedora de forragem auto propelida (CFAP; New Holland, FR 9050) nos seguintes TTC: 6, 12 e 18-mm com distância entre os rolos de 3-mm. As SM foram armazenadas em mini-silos (4 repetições por tratamento) por 0, 35 e 140 dias. A vitreosidade foi medida por dissecação em grãos não fermentados e foi de 65,6%. Os dados de ambos os ensaios foram analisados como arranjo em parcelas subdivididas usando o procedimento MIXED do SAS (SAS Institute Inc., Cary, NC). O modelo incluiu os efeitos fixos do TTC, tempo de estocagem e a interação entre os mesmos. Na CFTT, os TTC de 3 e 6-mm não impactaram na distribuição das partículas e no tamanho médio de partículas (TMP). No entanto, o TTC de 9-mm aumentou a porcentagem de partículas acima das 2 peneiras superiores do separador de partículas da Penn State e consequentemente, o TMP. O aumento do TTC na CFAP levou a aumento da porcentagem de partículas longas (< 19-mm) e do TMP. O tempo de estocagem também aumentou porcentagem de partículas longas e TMP apenas para SM colhida por CFAP. A estratégia de redução de TTC na CFAP melhorou a porcentagem de grãos menores que 4,75-mm. Além disso, o TTC de 6-mm proporcionou o melhor processamento de grãos nesta mesma colhedora. O tempo de estocagem reduziu o tamanho de partículas da fração grãos para ambas as colhedoras. O corn silage processing score (CSPS) aumentou apenas após 140 dias de estocagem somente para as amostras colhidas por CFAP. No terceiro experimento, o objetivo foi avaliar o efeito de uma CFTT equipada com processador de grãos (PG) regulado em diferentes tamanhos de corte sobre características físicas de SM. Um híbrido de endosperma vítreo (BM 709, Sementes Biomatrix) foi cultivado e colhido quando a MS da planta de milho atingiu 34,8%. A plantação foi colhida com uma CFTP sem PG regulada para TTC de 6 e 10-mm ou por uma CFTP com PG ajustada para os mesmos TTC. As amostras de SM foram armazenadas por 35 dias. A vitreosidade foi de 62,4%. Os dados foram analisados em delineamento inteiramente casualizado em arranjo fatorial: 2 tipos de colhedoras × 2 TTC utilizando o procedimento MIXED da SAS (SAS Institute Inc., Cary, NC). O modelo incluiu os efeitos fixos de colhedora, do TTC e da interação dos mesmos. As seguintes diferenças ocorreram apenas no TTC de 10-mm. O PG reduziu o material retido acima da peneira de crivo de 19 mm de 4,7 para 1,8%, o que por sua vez aumentou a percentagem de partículas abaixo da peneira de crivo de 8-mm e diminuiu o TMP. Este TTC exibiu o valor mais alto de material retido na peneira de 8-mm e os valores mais baixos na peneira de 4 mm para SM não processada. Tanto o processamento de grãos e como a redução do TTC levaram a um aumento de partículas retidas na peneira de 4 mm. O PG aumentou a porcentagem de grãos menores que 4,75 mm de 56,4 para 80,0% e o teor de amido abaixo da peneira de 8-mm. O TTC de 6-mm e o PG levaram a uma redução do tamanho geométrico dos grãos, com subsequente aumento da área superficial. A nova CFTT com PG promoveu um processamento mais intenso nos grãos. No quarto experimento, os objetivos do estudo foram: 1) avaliar o efeito do processamento de grãos em um híbrido brasileiro de endosperma vítreo e 2) aumento no tamanho de partículas da SM no consumo, desempenho, digestibilidade dos nutrientes, comportamento alimentar e perfil de ácidos graxos no leite de vacas leiteiras. Os seguintes tratamentos foram realizados durante a colheita: 1) CFTT (sem PG, JF AT 1600) ajustada para um TTC de 6-mm - PT6; 2) CFAP (New Holland, FR 9050) ajustada para um TTC de 6-mm - SP6; 3) CFAP ajustada para um TTC de 12-mm - SP12; e 4) CFAP ajustada para um TTC de 18-mm -SP18. As SM foram estocadas por 9 meses. Os CSPS das SM dos tratamentos foram: 32,1% (PT6), 53,9% (SP6), 49,0% (SP12) e 40,1 (SP18). Vinte e quatro vacas da raça Holandesa (139 ± 63 DEL) foram blocadas e distribuídas em seis quadrados latinos 4 × 4, com período de 24 dias (18 dias de adaptação). As dietas foram formuladas para conter (% MS) 48,5% SM, 9,5% farelo de soja, 6,9% farelo de soja protegido, 15,1% milho moído seco, 15,5% polpa cítrica, 1,7% de minerais e vitaminas, 1,8% de sabão de cálcio de ácidos graxos de palma e 1% de ureia. A composição nutricional das dietas (% MS) foi: 16,5% PB, 28,9% FDN e 25,4% amido. Três contrastes ortogonais foram usados para comparar os tratamentos: C1 = PT6 vs. SP6 (efeito do processamento de grãos), C2 = SP6 vs. SP12 (efeito do tamanho de partículas) e C3 = SP12 vs. SP18 (efeito do tamanho de partículas). Vacas alimentadas com SP6 apresentaram maior produção de leite de 1,2 kg / d, sem alterações no consumo de matéria seca, resultando em maior eficiência alimentar quando comparadas com PT6. A digestibilidade do amido no trato total e a glicose plasmática também foram maiores para as vacas alimentas com SP6. Além disso, as maiores secreções de proteína (+ 36 g/d), lactose (+ 61 g/d) e sólidos do leite (+ 94 g/d) foram resultado da melhora na produção de leite para as vacas do SP6. O mecanismo envolve uma melhor digestibilidade dos nutrientes e disponibilidade de glicose para a síntese de lactose pela glândula mamária. Não houve evidência de diferenças no consumo de matéria seca (kg/d) entre os tratamentos colhidos por SPFH. As vacas do SP12 alcançaram a mesma produção de leite em relação ao SP6; no entanto, elas tenderam a reduzir a concentração plasmática de D-lactato e o amiloide sérico A (SAA), maximizando o tempo de mastigação e selecionando a favor de partículas finas. No SP6, vacas selecionaram contra partículas finas e tenderam a aumentar SAA em relação a PT6. O SP18 reduziu a digestibilidade do amido no trato total e tendeu a reduzir a produção de leite e a glicose plasmática. O SP6 elevou o teor de ácidos graxos da cadeia linear ímpar do leite em comparação ao PT6. No entanto, uma redução desses mesmos ácidos graxos ocorreu no SP12 em relação ao SP6. As vacas SP6 apresentaram maior teor de alguns ácidos graxos monoinsaturados (C14:1 e C16:1), porém o oposto ocorreu para SP12. O processamento de grãos nos TTC de 6 e 12-mm aumentou a digestibilidade de amido, glicose plasmática e produção de leite, enquanto o TTC de 18-mm prejudicou o desempenho e a digestibilidade de amido. O TTC de 12-mm melhorou o tempo de mastigação e reduziu os marcadores de acidose subclínica no sangue. Estes resultados sugerem que o tempo de estocagem de pelo menos 140 dias e TTC curto (6-mm) para SPFH podem ser estratégias para maximizar o processamento de grãos e, assim, a digestibilidade do amido em SM. Porém, para promover desempenho e saúde de vacas leiteiras, o TTC de 12-mm é o indicado para colheita de híbridos de milho endosperma vítreo para SM.

Nous présentons une étude in situ du verre de silice v-SiO2 sous pression hydrostatique de gaz rares par spectroscopie Brillouin et Raman. Les échantillons sont pressurisés avec de l'hélium, du néon et de l'argon dans une cellule à enclume de diamant, dans la gamme 0 - 8 GPa. Les atomes d'hélium et de néon pénètrent dans la structure du verre sous pression. On estime qu'environ un atome d'hélium par tétraèdre SiO4 et qu'environ deux fois moins dans le cas du néon sont adsorbés à 6 GPa. Les modules de compression et de cisaillement en fonction de la pression de fluide sont obtenus à partir des mesures des vitesses acoustiques longitudinales et transverses. L'anomalie de comportement du module de compression de v-SiO2 (minimum à 2 GPa) est supprimée par l'adsorption de He et de Ne, les réarrangements structuraux liés à cette anomalie étant empêchés parl'occupation des sites interstitiels par les atomes d'hélium et de néon. En présence d'hélium et de néon, l'équation d'état V (P) ne permet pas de retrouver le module de compression car la silice se comporte comme un milieu poreux ouvert. La simulation Monte-Carlo des isothermes d'adsorption combinée à la théorie généralisée de la poromécanique permet de décrire les déformations volumiques et les quantités de fluide adsorbées en accord avec les résultats expérimentaux. Dans le cas du néon, la cinétique d'adsorption-désorption est observée par spectroscopie Brillouin. Les spectres Raman VV et VH de v-SiO2 ont été mesurés en fonction de la pression de fluide. La réduction de la distribution des angles Si–O–Si est empêchée par l'insertion d'hélium. / We present an in situ study of vitreous silica v-SiO2 under hydrostatic noble gases pressure by Brillouin and Raman spectroscopy. Samples are pressurized in helium, neon and argon in a diamond anvil cell, in the range 0 - 8 GPa. Helium and neon atoms penetrate in the pressurized glass structure. We estimate that about one atom of helium per SiO4 tetrahedron and about half in the neon case are adsorbed at 6 GPa. Bulk and shear moduli as a function of fluid pressure are obtained from measurements of the longitudinal and transverse acoustic velocities. The behaviour anomaly of the bulk modulus of v-SiO2 (minimum at 2 GPa) is suppressed by He and Ne adsorption, structural rearrangements associated with this anomaly being prevented by the occupation of interstitial sites by helium and neon atoms. In the presence of helium and neon, the V(P) equation of state does not allow to recover bulk modulus because silica behaves like an open porous medium. Monte-Carlo simulation of adsorption isotherms combined with the generalized theory of poromechanics allows to describe volume deformations and adsorbed fluid amount in agreement with experimental results. In the neon case, adsorption-desorption kinetics is observed by Brillouin spectroscopy. Measurements of VV and VH Raman spectra of v-SiO2 are made as function of fluid pressure. The reduction of Si–O–Si angles distribution is prevented by the insertion of helium.

A obtenção da sílica vítrea pelo processo de sinterização por plasma pulsado (SPS), a partir de matérias-primas de diferentes estruturas (cristalina e amorfa) e diferentes granulometrias, foi investigada. Análises de difração de raios X, transmitância óptica, microscopia óptica e eletrônica de varredura, e medições de densidade foram realizadas nas amostras sinterizadas. Sílicas vítreas transparentes foram fabricadas a partir de pós de quartzo atingindo-se temperaturas finais entre 1450 e 1600°C, enquanto que nanopó e pó amorfo de sílica formaram consolidados transparentes com temperaturas máximas próximas de 1200° C. Taxas de aquecimento entre 40 e 150°C/min. foram utilizadas nas sinterizações, com tempos de processo menores que 40 minutos. As maiores taxas de aquecimento exigiram uma maior temperatura final para a fusão completa do material cristalino e causaram, de forma indireta, a presença de aglomerações de micro-bolhas nas amostras obtidas com o nanopó. Um gradiente radial de temperatura (decrescente do centro para as bordas) foi observado nos consolidados fabricados com os pós cristalinos, facilitando o processo de fechamento da porosidade aberta. A presença ou ausência de material não fundido e de bolhas nas amostras foram analisadas por difratogramas de raios X, microscopia óptica e medidas de densidade. A análise da transmitância indicou uma quantidade praticamente nula de grupos OH nos compactos sinterizados com os pós cristalinos e em torno de 20 ppm no caso dos sólidos fabricados com matéria-prima sol-gel. Amostras de nanopós de sílica dopada com titânia (~6% em massa) foram processadas com temperaturas finais de 1200 e 1400°C apresentando coloração azulada e negra, respectivamente, e aumento dos clusters de titânia para a temperatura mais elevada. A sinterização a uma temperatura em torno 1200°C mantida por apenas 4 minutos resultou na conversão completa da fase anatase para a fase rutilo da titânia. / The production of vitreous silica by the spark plasma sintering (SPS) process, starting from raw materials of different structures (crystalline and amorphous) and granulometry were investigated. Analysis of X-ray diffraction, optical transmittance, optical and scanning electron microscopy, and density measurements were performed on the sintered compacts. Transparent vitreous silica was fabricated from quartz powder at final temperatures ranging from 1450 and 1600°C while silica nanopowder and silica powder formed transparent compacts at temperatures around 1200°C. Heating rates between 40 and 150° C/min. were used in processes with durations smaller than 40 minutes. Higher heating rates demanded higher final temperatures to complete the fusion process and caused, indirectly, the formation of micro-bubbles agglomerations in the samples produced from the nanopowder. A radial gradient of temperature (decreasing from the center to the border) was observed at the compacts fabricated with the crystalline powders favoring the closure of the open porosity. The presence or the absence of non-fused material and bubbles in the samples was analyzed by X-ray diffraction, optical microscopy and density measurements. The transmittance analysis indicated an almost zero quantity of OH groups in the compacts sintered from crystalline powders and about 20 ppm in the solids fabricated from the sol-gel raw material. Nanopowder samples of silica titania (~6 wt % of titania) were processed with final temperatures of 1200°C and 1400°C presenting blue and black coloration, respectively, and an increase of the titania clusters for the highest temperature. The sintering at temperatures near 1200°C with a holding time of just 4 minutes caused the complete anatase-rutile conversion in titania.

The transport in oxides is studied by the use of gas phase analysis (GPA). An experimental method to identify transported species of gases and their contribution to the overall transport of gases in oxides and an experimental method to evaluate the parameters diffusivity, concentration, permeability of gases in oxides and effective pore size in oxides are developed, respectively. Pt has two effects on the thermal oxidation of metals. One is to enhance the oxidation of metals which takes place at the oxide-metal interface by promoting a high concentration gradient of dissociated oxygen across the oxide layer. The other effect is to suppress the oxidation of metals by decreasing the contact area between metal and oxygen. The overall effect of Pt on the oxidation of metals depends on the mechanism of oxide growth in the absence of Pt. It is suggested that an appropriate amount of Pt coating induces a balanced oxide growth resulting from stoichimetrical inward oxygen flux to outward metal flux, which leads to a reduced oxidation rate. The diffusion of diatomic gases in oxides such as vitreous silica and yttria stabilized zirconia (YSZ) takes place in both molecular and dissociated (atomic or/and ionic) form. The fraction of transport of molecular species decreases with temperatures, and the fraction of transport of dissociated species increases with temperatures. Measured permeabilities of diatomic gases in vitreous silica are higher than the expected permeabilities of their molecules, which are explained by diffusion of molecules combined with a retardation of dissociated species in reversible traps. The diffusion of hydrogen in vitreous silica is concentration dependent and increases with local concentration. Transport paths are shared among transported species and gases at all temperatures in YSZ. Helium shares transport path with molecular oxygen and nitrogen at low temperatures; whereas helium shares transport path with dissociated oxygen and also dissociated nitrogen at high temperatures. / QC 20100705

Myopia is a refractive defect of the eye in which collimated light produces images focused in front of the retina. Myopia can be artificially induced in animal models by form deprivation (form deprivation myopia, FDM) or by application of negative lenses (lens induced myopia, LIM). In this study myopia was induced using diffusers. The project had two main aims: 1. To determine if there is an interaction between the GABAergic system and dopaminergic system in the retina in terms of myopia? 2. To determine if there is an interaction between the GABAergic system and cholinergic system in the retina in terms of myopia? Firstly, an experiment focusing on the interaction between dopaminergic receptors antagonists and GABAC receptor antagonist was developed. Comparison of the different drug treated eye with the control was found and the effects of combination injections were compared to individual drug injections. Use of different blockers for various subtype of receptors simplified the understandings the underlying pharmacological interventions for GABAC receptor antagonist TPMPA. The D1 subtype of receptors was found to be involved in transmission of signals from GABAC receptors. Our results showed that D1 receptor antagonist SCH-23390 antagonizes the actions of TPMPA. In addition to this it was also found that possibly 5HT receptor may also play an important role in modulation of signaling from GABA receptor to dopaminergic receptors in the retina. These results were consistent with the drug combination effects for agonists. GABA A/C receptor agonist muscimol negativate the efficacy of D1 receptor agonist SKF-38393 but the activity of D2/4 receptor agonist quinpirole was not affected by muscimol. Although dopaminergic receptors are found to interact with GABAergic signaling, but an alternative interaction with anticholinergic (most widely studied antimyopic agents) could not be ruled out. This problem led to a follow-up experiment, in which GABA receptors intervention in anticholinergic agents was studied. The GABAergic receptor agonist muscimol when injected with anticholinergics (atropine and pirenzepine) showed a moderate interaction. As muscimol interacted with atropine to a lesser extent a more specific M1/5 receptor antagonist pirenzepine (earlier found to inhibit myopia) was used under these circumstances. The second aim to study the interaction between muscimol and pirenzepine showed more interaction with GABAA/C receptor agonist. There were data suggesting that there is a muscarinic and GABAergic interaction in retina, such that each modulation of each receptor had an effect on FDM. However, a drug combination treatment helped in understanding the underlying mechanism. Several previous studies have indicated that there exist a strong interaction between excitatory neurotransmitter acetylcholine and inhibitory transmitter GABA in retina. The results of this study indicate a similar finding. Thus results of this study may be summarized as: 1. D1 antagonists and not D2 antagonists blocks the antimyopic effects of GABAC antagonist TPMPA 2. GABA A/C agonist muscimol partially blocks the antimyopic activity of anticholinergics (e.g. atropine and pirenzepine).

Diss. (sammanfattning) Linköping : Univ., 2004. / Härtill 4 uppsatser.

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A remoção de íons Cu²+ de soluções ácidas diluídas é investigada utilizando eletrodos de Pt recobertos com polipirrol previamente reduzido (PPl) e eletrodos de carbono vítreo reticulado (CVR). O estudo tem por objetivo a redução de Cu²+ sobre ppl via reação espontânea e eletroredução a -0,40 V vs. eletrodo de calomelano saturado (ECS), e a eletroredução sobre CVR. Nestes experimentos, a concentração de íons Cu²+ remanescentes na solução é monitorada por voltametria de varredura linear ou por voltametria potenciodinâmica em um ultramicroeletrodo de platina (UME). Também o monitoramento por espectrometria de absorção atômica (EAA) foi realizado nos processos de remoção por eletrodeposição. Foi mostrado que o CVR é o material mais adequado para este fim. O cobre depositado sobre platina em meio sulfúrico exibe uma, duas ou três ondas de redissolução anódica, que correspondem respectivamente à oxidação de uma camada de cobre adsorvida sobre a platina, à oxidação de um filme fino depositado sobre a camada adsorvida e à oxidação do depósito de cobre denso que cresce sobre o filme fino. Este comportamento foi evidenciado por ciclos potenciodinâmicos impostos a um UME de disco de Pt na faixa de concentrações de Cu²+ entre 10-5 e 10-4 M em meio sulfúrico. / The removal of CU²+ ions from dilute acidic solutions is studied at Pt electrodes recovered with electrically neutral polypyrrole and at reticulated vitreous carbon electrodes, in the presence of dissolved oxygen. The aim is to remove Cu²+ ions by reduction on neutra I polypyrrole both through the spontaneous reaction and by its electroreduction at -0.40 V vs. a saturated calomel electrode, and by electroreduction on reticulated vitreous carbono In these experiments the concentration of the Cu²+ ions remaining in the solution is monitored by linear scan voltammetry or by potentiodynamic voltammetry at a Pt ultramicroelectrode. Monitoring of Cu²+ ions by atomic absorption spectrometry was also performed in the electroreduction processes at neutral polypyrrole and reticulated vitreous carbono It has been shown that the best efficiency results were found for reticulated vitreous carbono Copper electrodeposited on Pt in sulphuric medium may exhibit one, two or three anodic stripping waves, which correspond respectively to the oxidation of a bulk copper deposit, a thin copper film and a copper monolayer adsorbed on pt. This behaviour has been evidenced by potentiodynamic cycles imposed to a Pt disk ultramicroelectrode in the 10-5 to 10-4 M Cu²+ concentration range in sulfuric media.

A remoção de íons Cu²+ de soluções ácidas diluídas é investigada utilizando eletrodos de Pt recobertos com polipirrol previamente reduzido (PPl) e eletrodos de carbono vítreo reticulado (CVR). O estudo tem por objetivo a redução de Cu²+ sobre ppl via reação espontânea e eletroredução a -0,40 V vs. eletrodo de calomelano saturado (ECS), e a eletroredução sobre CVR. Nestes experimentos, a concentração de íons Cu²+ remanescentes na solução é monitorada por voltametria de varredura linear ou por voltametria potenciodinâmica em um ultramicroeletrodo de platina (UME). Também o monitoramento por espectrometria de absorção atômica (EAA) foi realizado nos processos de remoção por eletrodeposição. Foi mostrado que o CVR é o material mais adequado para este fim. O cobre depositado sobre platina em meio sulfúrico exibe uma, duas ou três ondas de redissolução anódica, que correspondem respectivamente à oxidação de uma camada de cobre adsorvida sobre a platina, à oxidação de um filme fino depositado sobre a camada adsorvida e à oxidação do depósito de cobre denso que cresce sobre o filme fino. Este comportamento foi evidenciado por ciclos potenciodinâmicos impostos a um UME de disco de Pt na faixa de concentrações de Cu²+ entre 10-5 e 10-4 M em meio sulfúrico. / The removal of CU²+ ions from dilute acidic solutions is studied at Pt electrodes recovered with electrically neutral polypyrrole and at reticulated vitreous carbon electrodes, in the presence of dissolved oxygen. The aim is to remove Cu²+ ions by reduction on neutra I polypyrrole both through the spontaneous reaction and by its electroreduction at -0.40 V vs. a saturated calomel electrode, and by electroreduction on reticulated vitreous carbono In these experiments the concentration of the Cu²+ ions remaining in the solution is monitored by linear scan voltammetry or by potentiodynamic voltammetry at a Pt ultramicroelectrode. Monitoring of Cu²+ ions by atomic absorption spectrometry was also performed in the electroreduction processes at neutral polypyrrole and reticulated vitreous carbono It has been shown that the best efficiency results were found for reticulated vitreous carbono Copper electrodeposited on Pt in sulphuric medium may exhibit one, two or three anodic stripping waves, which correspond respectively to the oxidation of a bulk copper deposit, a thin copper film and a copper monolayer adsorbed on pt. This behaviour has been evidenced by potentiodynamic cycles imposed to a Pt disk ultramicroelectrode in the 10-5 to 10-4 M Cu²+ concentration range in sulfuric media.

Au cours de ce travail, essentiellement expérimental, nous nous sommes intéressés à la relaxation structurale dans un verre silicaté que nous avons analysé et interprété en terme de dynamique hétérogène. Expérimentalement, nous avons couplé les informations obtenues par différentes spectroscopies qui sondent des échelles spatiales allant du nm (Raman, Infrarouge) à une centaine de nanomètres (Brillouin). Numériquement, nous avons décomposé les fonctions de relaxation obtenues par les différentes spectroscopies et nous avons mis en évidence l’existence de plusieurs échelles temporelles ainsi existantes. A longue distance, les expériences in situ Brillouin effectuées le long d’une rampe de chauffage et des isothermes montrent que (i) les phonons acoustiques sont affectés par le recuit et (ii) la dynamique de relaxation est hétérogène à l’approche de la transition vitreuse. Ainsi, contre toute attente cette hétérogénéité est très fortement dépendante du parcours suivi en température. A courte et moyenne distance, les mesures in situ Raman à hautes température sur des rampes de chauffe et des isothermes, montrent que la relaxation structurale affecte l’ordre spatiale du réseau silicaté. Le couplage des analyses en composantes individuelles et principales a permis d’identifier deux processus de relaxation attribués respectivement à la relaxation du fond continu et des entités Qn. Par des mesures in situ d’Emissivité Infrarouge dans le liquide et grâce à un modèle proche du modèle binaire l’abondance des espèces Qn lors des processus de relaxation et cristallisation a été obtenue. Un mécanisme d’activation de la relaxation à grande distance par une re-polymérisation locale est mis en évidence. Ce même mécanisme est un précurseur de la cristallisation. / Résumé en cours de rédaction