Conselho Nacional de Desenvolvimento Científico e Tecnológico / The effect of level of forage intake on blood flow and oxygen consumption (Experiment 1), and mesenteric infusion of ammonium bicarbonate (NH4HCO3), L-alanine or L-arginine on oxygen consumption and net flux of metabolites (Experiment 2) through the splanchnic (portal-drained viscera [PDV] plus liver (ST)) tissues were evaluated in sheep surgically implanted with chronic indwelling catheters into the mesenteric, portal and hepatic veins. In both experiments, blood flow was estimated by downstream dilution of p-aminohippurate. In experiment 1, three adult male Polwarth wethers (42±4.4 kg body weight (BW)), housed in metabolism cages and offered Tifton (Cynodon sp.) hay were used in a 3 x 3 Latin Square design. Treatments consisted of hay allowances of 7, 14 or 21 g dry matter (DM)/kg BW/day, offered in four equal daily meals, every 6 h. Blood flow across PDV was linearly (P<0.05) related to OM intake, whereas the hepatic-arterial and total ST blood flow were no affected. Oxygen expenditure by PDV was directly (P<0.05) related to OM intake, while oxygen consumption by the liver was not affected. Oxygen expenditure was linearly (P<0.05) related to blood flow across tissues for PDV, liver and total ST. The proportion of metabolizable energy (ME) intake spent as heat by PDV and total ST reduced when ME intake increased. In addition, this reduction occurred in a curvilinear manner as the difference between PDV and ST heat production reduced at increased ME intake. In experiment 2, four multicatheterized Polwarth wethers (40 ± 3.8 kg BW) fed 14 g DM of oat (Avena sativa) plus ryegrass (Lolium multiflorum Lam) hay/kg BW/day of Tifton hay were used in a 4 x 4 Latin Square design. Treatments were mesenteric vein infusion of 500 μL/min of saline solution (control) or a solution containing NH4HCO3, L-alanine or L-arginine. The net flux of glucose and urea through PDV and ST were not affected by treatments. Portal appearance and liver removal of N-NH3 were higher (P<0.05) with the NH4HCO3 infusion. The PDV and ST net flux of oxygen were not affected by treatments, whereas the hepatic oxygen consumption was higher in control treatment (P<0.05). The hypothesis that ureagenesis and/or gluconeogenesis increases hepatic energy spenditure was not observed in the present study. Methodological aspects are included in results discussion. / Foi avaliado o efeito do nível de consumo de forragem sobre o fluxo de sangue e utilização de O2 (Experimento 1), e da infusão mesentérica de bicarbonato de amônio (NH4HCO3), L-alanina ou L-arginina (Experimento 2) sobre a utilização de O2 e fluxo de metabólitos pelo sistema visceral (tecidos drenados pela veia porta (TDVP) e o fígado) em ovinos implantados cirurgicamente com catéteres permanentes nas veias mesentérica, porta e hepática. Em ambos experimentos o fluxo de sangue foi estimado pela técnica de diluição de p-aminohipurato. No experimento 1, três ovinos machos da raça Polwarth (42±4.4 kg de peso corporal (PC), alojados em gaiolas de metabolismo e alimentados com feno de Tifton (Cynodon sp.) foram utilizados em um delineamento Quadrado Latino 3 x 3. O feno foi oferecido nas quantidades de 7, 14 ou 21 g matéria seca (MS)/dia/kg de PC em quatro porções diárias iguais, a cada 6 h. O fluxo de sangue nos TDVP aumentou linearmente (P<0,05), mas o fluxo de sangue hepático-arterial e visceral total não foram afetados pelo aumento no consumo de forragem. O gasto de O2 pelos TDVP foi positivamente (P<0,05) relacionado com o consumo de matéria orgânica (MO). O gasto de O2 relacionou-se linearmente com o fluxo de sangue (P<0,05) nos TDVP, fígado e sistema visceral. A proporção de energia metabolizável (EM) consumida gasta como calor pelos TDVP e fígado diminuiu com o aumento no consumo de EM de forma curvilinear, sendo que a diferença entre a produção de calor visceral e dos TDVP reduziu com o aumento no consumo de EM. No experimento 2, quatro ovinos Corriedale (40 ± 3.8 kg PC), implantados com catéteres permanentes nas veias mesentérica, porta e hepática, alimentados com 14 g MS de feno de aveia (Avena sativa) e azevém (Lolium multiflorum Lam)/dia/kg de PC, foram utilizados em um delineamento Quadrado Latino 4 x 4. Os tratamentos consistiram da infusão na veia mesentérica de 500 μL/min de solução salina (controle) ou de uma solução contendo NH4HCO3, L-alanina ou L-arginina. Os fluxos portal e visceral total líquido de glicose e N-uréia não foram afetados significativamente pelos tratamentos. O fluxo de O2 pelos TDVP não diferiu entre tratamentos. Contudo, houve maior (P<0,05) gasto de O2 pelo fígado no tratamento controle. A hipótese de que a ureagênese e/ou a neoglicogênese impactam o gasto de energia pelo fígado não foi comprovada no presente estudo. Aspectos metodológicos são considerados na discussão destes resultados.

Light-harvesting in nature is known to work differently than conventional man-made solar cells. Recent studies found electronic excitations, delocalised over several chromophores, and a soft, vibrating structural environment to be key schemes that might protect and direct energy transfer yielding increased harvest efficiencies even under adversary conditions. Unfortunately, testing realistic models of noise assisted transport at the quantum level is challenging due to the intractable size of the environmental wave function. I developed a powerful tree tensor network states (TTNS) method that finds an optimally compressed explicit representation of the combined electronic and vibrational quantum state. With TTNS it is possible to simulate exciton-phonon quantum dynamics from small molecules to larger complexes, modelled as an open quantum system with multiple bosonic environments. After benchmarking the method on the minimal spin-boson model by reproducing ground state properties and dynamics that have been reported using other methods, the vibrational quantum state is harnessed to investigate environmental dynamics and its correlation with the spin system. To enable simulations of realistic non-Born-Oppenheimer molecular quantum dynamics, a clustering algorithm and novel entanglement renormalisation tensors are employed to interface TTNS with ab initio density functional theory (DFT). A thereby generated model of a pentacene dimer containing 252 vibrational normal modes was simulated with TTNS reproducing exciton dynamics in agreement with experimental results. Based on the environmental state, the (potential) energy surfaces, underlying the observed singlet fission dynamics, were calculated yielding unprecedented insight into the super-exchange mediated avoided crossing mechanism that produces ultrafast and high yield singlet fission. This combination of DFT and TTNS is a step towards large scale material exploration that can accurately predict excited states properties and dynamics. Furthermore, application to biomolecular systems, such as photosynthetic complexes, may give valuable insights into novel environmental engineering principles for the design of artificial light-harvesting systems.