Submitted by Danielle Karla Martins Silva (danielle.martins@ufpe.br) on 2015-03-13T15:19:57Z No. of bitstreams: 2 TESE Victor Holanda Rusu.pdf: 9721565 bytes, checksum: 063e96f770d05cfa859b3846c87a33f5 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-13T15:19:57Z (GMT). No. of bitstreams: 2 TESE Victor Holanda Rusu.pdf: 9721565 bytes, checksum: 063e96f770d05cfa859b3846c87a33f5 (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2014 / CAPES / Desenvolvimento de um campo de força “coarse-grain” para carboidratos. Doutorado em Química, orientador prof. Dr. Roberto Dias Lins Neto, Departamento de Química Fundamental, Universidade Federal de Pernambuco, Recife, Pernambuco, Brasil, 2014. Na natureza, os carboidratos são geralmente encontrados na forma polimérica e/ou complexados com outras biomoléculas, tais como proteínas, lipídeos, etc. A descrição teórica do comportamento destes sistemas biomoleculares requer simulações relativamente longas e consequentemente, computacionalmente custosas. Uma maneira de diminuir os requerimentos computacionais é através do uso de campos de força “coarse-grain” (CG). Nesta abordagem, grupos de átomos são mapeados em esferas diminuindo o número total de partículas no sistema, mas com o custo da perda de detalhes químicos. Neste trabalho desenvolvemos uma nova maneira de expressar carboidratos de forma mais aproximada e combinando com o modelo de água SPC CG GROMOS. O novo campo de força, denominado PITOMBA, corretamente mapeia as conformações barco e cadeira, bem como, os anômeros alfa e beta. A validação dos parâmetros são mostrados para as amilose V e A e α-, β- and γ-ciclodextrinas (CD). Nosso trabalho abre a possibilidade de simular sistemas contendo carboidratos e a termodinâmica de formação de complexos com CDs com um ganho de tempo computacional de 1-2 ordens de grandeza em comparação aos campo de força atomísticos.

Weens die unieke eiesoortigheid van die mens is sy behoeftes vanselfsprekend uiters divers. Wat vir die een persoon prioriteit is, mag vir sy buurman geensins belangrik wees nie. Dit is egter ook ’n gegewe, dat die mens heelwat gemeenskaplike ervarings, emosies en behoeftes deel. Een hiervan is die behoefte wat hy het om te weet dat die besluit wat hy gaan of wil neem die regte een binne die konteks van sy keuse mag wees. Die woord ‘behoefte’ kan waarskynlik in hierdie geval vervang word met die begrip ‘genade’. Sonder om 'n platvorm vir debat te skep, word die stelling gehandhaaf dat ‘genade’ slegs van die Skepper afkomstig is. Met hierdie stelling as agtergrond was dit 'n minder aangename ervaring om vir feitlik twintig jaar te moes toekyk hoe koringboere hul besluite, veral met betrekking tot die samestelling van wisselboustelsels, moes neem, klaarblyklik in totale gebrek aan die gawe van ‘genade’. Nodeloos om te sê, met gepaardgaande negatiewe gevolge. Die meer gemaklike verontskuldiging is om te redeneer dat ons Skepper relatief suinig is met die uitdeel van sy ‘genade’. Alvorens die begrip van Prediker 10:10 nog nie ten volle begryp is nie, kan so 'n stelling dalk makliker gemaak word. Hierdie gedeelte uit die Skrif sê in werklikheid die teenoorgestelde – dat God baie vrygewig is met Sy ‘genade’, maar dat die mens sy gesonde verstand moet gebruik om dit ten volle te benut. Die wens is dat hierdie studie, 'n deel sal uitmaak van die proses om die byl skerp te maak om sodoende die houtkap-proses effektief uit te voer.

Laboratory maintained Sitobion avenae of all developmental stages had a mean inherent supercooling ability below -20°C. Acclimation alone, or in conjunction with starvation had no significant effect on supercooling. Surface moisture on the aphid cuticle during cooling resulted in a significant loss in supercooling. Repeat coolings to temperatures markedly above the mean supercooling point resulted in increasing levels of mortality. Field collected ~ avenae showed a seasonal variation in supercooling with a higher mean supercooling point in the winter than in the remainder of the year. Field populations showed a dramatic decline in December when environmental temperatures were well above mean and individual supercooling points. It was concluded that the aphids were dying before they froze and that the supercooling point was not a reliable indicator of the lower lethal temperature. The development and reproduction of s.avenae in the field over winter were directly and positively related to temperature whilst mortality increased with decreasing temperature. The development of a multi-channel micro-bead thermistor unit allowed the study of a previously unrecorded thermal event (exotherm) during the cooling of aphids. The cause of the exotherm is unknown and warrants further investigation. Laboratory experiments on ~ avenae and the lupin aphid, Macrosiphum albifrons revealed that the adults of the two species had lower lethal temperatures (LT50) of approximately -7.5°C and -7.0°C respectively. Nymphs of ~. ayenae were significantly more cold hardy than adults in terms of LT50 values. Acclimation prior to experimentation significantly improved the cold hardiness (LT50) of s.avenae. It is concluded that in the case of s.avenae and other aphids supercooling points are ecologically irrelevant if aphids are already dead before they freeze. An experimental protocol is suggested for future experiments on insect cold hardiness.

Field trials were conducted in 2010/11, 2012 and 2013 at the Royal Agricultural University’s Soil Association certified organic Harnhill Manor Farm, Gloucestershire, UK (NGR SP 075 006), to investigate suitable cultivation techniques and legume cover crops for winter and spring wheat production. Cultivation treatments included conventional tillage (CT), low residue non-inversion tillage (LRNiT) and high residue non-inversion tillage (HRNiT) as main plots while undersowing white clover (WC), black medic (BM) or no undersowing (Nus) as subplots. Wheat establishment, growth, grain yield and weeds infestation were assessed to determine the feasibility of these husbandry techniques. For winter wheat in 2010/11, LRNiT seems to be an acceptable alternative for CT. However, for spring wheat in 2012 and 2013, CT seems to be more reliable management option. The performance of undersown legumes was highly weather reliant and inconsistent in the seasons studied. Plant establishment and the succeeding yield parameters were positively related to grain yield. CT had significantly higher plant establishment than LRNiT or HRNiT in each season. For winter wheat, the competition and compensation on shoot density among CT and LRNiT did potentially outweighed cultivation-induced effects on plant establishment. This condition resulted in statistically equivalent crop growth and yields with LRNiT to that of CT. In contrast, for spring wheat in 2012 and 2013, CT that had significantly higher plant establishment also resulted in better crop growth and greater grain yields than other cultivation treatments. In all seasons, HRNiT had significantly lower plant establishment and also reduced grain yields, compared with LRNiT or CT. More soil cultivation also significantly reduced total weeds than less tilled soil such as HRNiT. On the basis of weed species, significantly higher broadleaf weeds were present under CT and significantly higher grass weeds were present under HRNiT. Out of three investigated years, legume cover crops effects were clearly observed only in 2012 with spring wheat. More vigorous growth of WC showed a significantly inverse relationship with broadleaf weeds and total weeds, compared with slow growing BM. This situation, resulted in non-significant yield components or grain yield reduction, compared with non-undersown spring wheat. In this context, white clover seems to be more suitable legume cover crop than black medic.

Grain boundaries form the basis of an important Josephson junction technology in the cuprates and also limit the superconducting critical currents attainable in practical, polycrystalline materials. An improved understanding of these defects is therefore important for applications. The status of the current understanding of cuprate grain boundaries is summarised and experimental investigations are presented, focusing on the less well understood high angle boundaries. Measurements of the capacitance of grain boundaries in the overdoped superconductor Y1-xCaxBa2Cu3O7-8, were performed as a function of the calcium content, using the Josephson coupling across the boundaries. Particular care was taken to eliminate the effects of heating and stray capacitance due to the substrate. The effect of thermal noise was also assessed. These measurements provide important information about the area and the width of the grain boundaries, that highlights their inhomogeneous nature. A new technique was applied to measure the normal state properties of YBa2Cu3O7-8 grain boundaries above the critical temperature. Since the resistance of the adjacent material at high temperatures is comparable to, or greater than, that of the grain boundary a compensating Wheatstonebridge structure was used. The errors involved in this technique are carefully assessed and quantified. The normal state resistance of a number of different grain boundary orientations was measured from room temperature to the critical temperature. Detailed characterisation of the grain boundaries, including measurements of the critical current and the current voltage characteristics at low temperatures, was performed. The results obtained are used to assess the validity of the various theories for the grain boundary electrical structure. A tunneling model that accounts for the band structure of the material is developed and applied to potential barriers consistent with a band bending model. This theory is shown to provide a convincing account of the experimental results presented in this thesis.

Critical currents in the latest biaxially textured 'coated conductors' are now limited by 2D networks of low angle grain boundaries (LAGBs) with misorientation θm = 1 - 10°. In order to understand and optimise current transfer in these materials it is essential to elucidate the electromagnetic behaviour of the LAGB. This work presents an investigation into the transport properties of [001]-tilt LAGBs formed by the thin film deposition of YBa2Cu3O7 onto bicrystalline substrates. Through the use of a precision two-axis goniometer, measurements of the V-I characteristic and critical current density were made as magnetic field was rotated in angles θ and φ relative to the LAGB defect. It is found that for fields applied parallel to the LAGB defect plane, dissipation is dominated by the viscous flux flow of vortices along the boundary. Clear evidence for this is found in the V-I characteristic, which displays an increased linearity indicative of the viscous regime. It is shown that the number of vortex rows involved in the flow process can discontinuously switch, leading to a V-I characteristic made up of straight segments of different gradient. For fields applied away from the LAGB defect plane a kinked vortex structure develops and the boundary critical current density, JcGB, is determined by the channelling of vortex segments still lying within the LAGB. The channelling regime is seen in angular measurements as a marked decrease in JcGB(θ,φ) as field becomes aligned to within critical angles φK or θK of the LAGB. The aligned vortices experience a reduction in dimensionality that is manifest in a reduced temperature dependence of JcGB(T). For fields applied at a sufficiently large angle from the defect plane the deleterious effects of the LAGB on current transport are mitigated considerably. In this regime a collinear vortex structure is regained and transport is controlled by the intragranular (IG) sections of the LAGB track; JcGB = δJcIG where δ ~ 0.8, a result that is independent of field, temperature and angle for a 4.9° LAGB. For rotation of the applied field within the LAGB defect plane, the presence of a pinning peak in JcGB for field aligned to the dislocation array is confirmed and modelled. The peak is found to be absent in IG track measurements and increases relative to the intrinsic peak with both increasing field and temperature. In addition, a pronounced angular hysteresis is presented, which is directly linked to a corresponding 'static' hysteresis in JcGB(B) with field. Magneto-optic measurements confirm that this effect is controlled by the flux density profile in the IG regions of the LAGB track. Finally, above a temperature, angle and sample dependent merging field, B*, the LAGB is found to be effectively transparent, as δ ~ 1. This is due to the irreversibility line, above which dissipation occurs across the whole LAGB track.

High-moisture barley, preserved either anaerobically, chemically or by drying, was evaluated in a series of digestibility and nitrogen utilization trials with monogastrics and ruminants. In the first of 3 phases, high-moisture barley HMB (17% moisture) from the Peace River region was preserved in experimental silos by: (1) airtight storage, (2) alkali - 3.2 g NaOH/kg HMB (air dry basis) in a 32% w/w solution, (3) acid - 1% mixture of 60:40 acetic-propionic acids and (4) drying - 8 tonnes per hour at 82°C. After 9 months of storage, these treatments were evaluated in a digestibility trial with pigs and a nitrogen balance trial with rats. In the pigs there was no treatment effect on dry matter digestibility, but neutral detergent fibre digestibility was reduced (P < 0.001) in the dried barley. True nitrogen digestibility, with both pigs and rats, was significantly (P < 0.001) reduced by alkali treatment. In the rat trial, alkali-treated barley depressed net protein utilization (NPU) by over 20%. Differences between the non-alkali treatments were small. Digestibility studies with sheep were not carried out on these treatments due to poor palatability results. In the second phase, barley from Lacombe was harvested at 33 and 12% moisture. The HMB (33% moisture) was either stored airtight or artificially dried (ADB) to 88% DM and the field-dried barley (FDB) (12% moisture) was either stored aerobically or reconstituted (RB) to 70% DM and stored airtight. These treatments were evaluated in a nitrogen balance trial with rats and a digestibility, nitrogen-retention trial with sheep. In the rat trial, true nitrogen digestibility was highest (P < 0.001) for HMB while biological valve was higher (P < 0.001) for both of the dry treatments. NPL) tended to be the same for all treatments. In the sheep trial, dry matter digestibility of RB was improved above ADB, but organic matter digestibility of both HMB and RB were greater than that of ADB (P < 0.01). Acid detergent fibre digestibility of HMB was highest (P < 0.001) followed by FDB and RB and then ADB. There was no treatment effect for either nitrogen digestibility or nitrogen retention. Straw from both HMB and FDB was also evaluated in sheep. Apparent dry matter, organic matter and nitrogen digestibility were all significantly (P < 0.001) greater for straw from HMB. The final phase of the study was conducted with barley of an unknown origin. Dry barley was reconstituted to 30% moisture (RB) and portions were treated with 3% NaOH (NaOH-RB) or 1% and 3% anhydrous ammonia (NH3-RB) on a w/w air dry basis. These treatments were again evaluated in a nitrogen balance trial with rats and a digestibility, nitrogen-retention trial with sheep. In the rat trial, true nitrogen digestibility for NaOH-RB was approximately 20% lower than the other treatments. Biological value and NPU were also depressed below all other treatments by NaOH-RB (P < 0.001). NPU for both 1 and 3% NH₃-RB were lower (P < 0.001) than RB after most of the NH₃ was allowed to evaporate for several days. However, there appeared to be no residual effect on protein utilization after the NH₃ was removed completely from the treated barley, as NPU for both 1 and 3% NH₃-RB were not different from RB. Dry matter digestibility was improved by all alkali-treatments (P < 0.001). In the sheep trial, both apparent dry matter digestibility and organic matter digestibility were significantly (P < 0.01) better for only the 3% NH₃-RB as compared to the other treatments. Acid detergent fibre digestibility was lower for 1 and 3% NH₃-RB than RB or NaOH-RB, between which treatments there were no significant differences. NaOH treatment reduced nitrogen digestibility by approximately 20 percentage units, but nitrogen-retention was unchanged between treatments with sheep. / Land and Food Systems, Faculty of / Graduate

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