Ice-sheet contributions to future sea-level change

Accurate simulation of ice-sheet surface mass balance requires higher spatial resolution than is afforded by typical atmosphere-ocean general circulation models (AOGCMs), owing, in particular, to the need to resolve the narrow and steep margins where the majority of precipitation and ablation occurs. We have developed a method for calculating mass-balance changes by combining ice-sheet average time-series from AOGCM projections for future centuries, both with information from high-resolution climate models run for short periods and with a 20 km ice-sheet mass-balance model. Antarctica contributes negatively to sea level on account of increased accumulation, while Greenland contributes positively because ablation increases more rapidly. The uncertainty in the results is about 20% for Antarctica and 35% for Greenland. Changes in ice-sheet topography and dynamics are not included, but we discuss their possible effects. For an annual- and area-average warming exceeding 4.5 +/- 0.9 K in Greenland and 3.1 +/- 0.8 K in the global average, the net surface mass balance of the Greenland ice sheet becomes negative, in which case it is likely that the ice sheet would eventually be eliminated, raising global-average sea level by 7 m.

Recent Glacier Retreat Exceeds Internal Variability

Glacier fluctuations exclusively due to internal variations in the climate system are simulated using downscaled integrations of the ECHAM4/OPYC coupled general circulation model (GCM). A process-based modeling approach using a mass balance model of intermediate complexity and a dynamic ice flow model considering simple shearing flow and sliding are applied. Multimillennia records of glacier length fluctuations for Nigardsbreen (Norway) and Rhonegletscher (Switzerland) are simulated using autoregressive processes determined by statistically downscaled GCM experiments. Return periods and probabilities of specific glacier length changes using GCM integrations excluding external forcings such as solar irradiation changes, volcanic, or anthropogenic effects are analyzed and compared to historical glacier length records. Preindustrial fluctuations of the glaciers as far as observed or reconstructed, including their advance during the “Little Ice Age,” can be explained by internal variability in the climate system as represented by a GCM. However, fluctuations comparable to the present-day glacier retreat exceed any variation simulated by the GCM control experiments and must be caused by external forcing, with anthropogenic forcing being a likely candidate.

Chaotic mixing and transport in Rossby-wave critical layers

A simple, dynamically consistent model of mixing and transport in Rossby-wave critical layers is obtained from the well-known Stewartson–Warn–Warn (SWW) solution of Rossby-wave critical-layer theory. The SWW solution is thought to be a useful conceptual model of Rossby-wave breaking in the stratosphere. Chaotic advection in the model is a consequence of the interaction between a stationary and a transient Rossby wave. Mixing and transport are characterized separately with a number of quantitative diagnostics (e.g. mean-square dispersion, lobe dynamics, and spectral moments), and with particular emphasis on the dynamics of the tracer field itself. The parameter dependences of the diagnostics are examined: transport tends to increase monotonically with increasing perturbation amplitude whereas mixing does not. The robustness of the results is investigated by stochastically perturbing the transient-wave phase speed. The two-wave chaotic advection model is contrasted with a stochastic single-wave model. It is shown that the effects of chaotic advection cannot be captured by stochasticity alone.

Os efeitos sistêmicos de uma reestruturação produtiva

A presente dissertação tem como objetivo estudar o caso da empresa Lupatech CSL no que se refere, fundamentalmente, ao seu processo produtivo. Busca-se também discutir a possibilidade de se promoverem melhorias e mudanças que possam oferecer saídas que oportunizem, através de uma reestruturação produtiva, diferenciações competitivas ao negócio da empresa. Nesse sentido, considerando a análise sistêmica do ambiente, propõe-se a adoção de alguns princípios de gestão do M odelo Toyota de Produção, cujo um dos princípios preconiza uma relação de efetiva parceria com os fornecedores. Para tanto, considerando a permanente necessidade de as empresas buscarem seu equilíbrio e distinção no mercado, procurou-se fazer uma análise do pensamento sistêmico e outras fundamentações de convergência teórica com este trabalho. Além disso, a fim de melhor entender os prós e contras do pensamento toyotista de administração, buscou-se traçar uma investigação desde o antecessor modelo de produção em massa taylorista-fordista até os últimos acontecimentos que abalaram mundialmente a imagem da montadora Toyota. Acredita-se, ao final, que a análise dissertativa do caso da Lupatech poderá fortalecer e auxiliar a empresa em sua tomada de decisão, tanto no campo operacional como na definição de uma proposta estratégica de gestão.

Resistência e performance na arte de João Cota

Researching about the art of tell and the tales told by João Cota is somehow revisiting the oral tradition and social practice in the story-telling art. It takes into consideration the resistance this art still exerts, mainly by using the performance of oral transmission and receptiveness to tales. The study of this practice contributes to the vivacious and dynamcis permanence of this authentic and traditional storyteller of his repertory and of his form to tellin our culture. Story-telling is part of the humankind living heritage communicated by means of popular wisdom. Despite the risk of vanishing into thin air, along with their narrators, the tales still manage to resist the contemporary mass culture model. How long further will stories like the ones narrated by João Cota be able to resist to strong and stronger structures dictated by writing and other communication means? João Cota s practice in story-telling will be studied not only as a proposal to identify the presence of this practice and the oral cultural resistance but also, through the performance prospective, to identify the oral transmission and receptiveness to the tales that are part of this storyteller s repertoire. In other words: what he tells, how he tells it, and why he tells it. The advent of new technologies such as internet, through which people can easily communicate with others in different parts of the world, and the greater and greater expansion in the writing skill concept interfere the maintenance of the oral tradition elements present in João Cota s narratives and inserted in the Brazilian culture. This has become more visible in the latest decades although we still notice the living tradition and permanence of the story-telling practice in several parts of the country through their wise storytellers. Our research target will require - in each of its study stages reference to works by several theoreticians namely Paul Zumthor, Mikhail Bakhtin, Câmara Cascudo, theoreticians from the receptiveness aesthetic, from the written culture history, from oral cultures and reading practices, from tradition and the Brazilian Culture of oral story-telling. In order to get to know and draw a profile of this storyteller, we ve chosen to use the comprehensive interview method by French Sociologist Jean Claude Kaufmann. The originality in the method consists of the qualitative data put together in situ , concentrated on the storyteller s narratives/speeches recorded on tape, which will be the focal point of this study. Our analysis method is based on tireless sessions of listening to interviews out of which we gathered information related to the storyteller, his practice in telling the tales, and his repertoire

Energy and angular momentum of the gravitational field in the teleparallel geometry

The Hamiltonian formulation of the teleparallel equivalent of general relativity is considered. Definitions of energy, momentum and angular momentum of the gravitational field arise from the integral form of the constraint equations of the theory. In particular, the gravitational energy-momentum is given by the integral of scalar densities over a three-dimensional spacelike hypersurface. The definition for the gravitational energy is investigated in the context of the Kerr black hole. In the evaluation of the energy contained within the external event horizon of the Kerr black hole, we obtain a value strikingly close to the irreducible mass of the latter. The gravitational angular momentum is evaluated for the gravitational field of a thin, slowly rotating mass shell. © 2002 The American Physical Society.

Estimativa da radiação solar ultravioleta em Botucatu/SP Brasil utilizando técnicas de aprendizado de máquina

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Estudo das propriedades ópticas de poços quânticos de InGaAsN/GaAs para aplicação em dispositivos optoeletrônicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo de sistemas quânticos não-hermitianos com espectro real

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação da dinâmica temporal da evaporação no reservatório de Itumbiara, GO, utilizando dados obtidos por sensoriamento remoto

The object of this work was to study the dynamics of evaporation in the Itumbiara reservoir, located in Central Brazil, using MODIS-derived water surface temperature (product MOD11A1) and meteorological data acquired over the water surface. The evaporation rates were derived from latent heat flux, estimated through a mass transfer model. The estimates were carried out for the period between 1/1/2010 and 31/12/2010. The results showed that evaporation rate tends to increase from January to September and then decrease from September to December. The evaporation rate reached values near 20 mm day-1 in Itumbiara reservoir during the dry season in 2010. The mean evaporation rate for the wet season was 3.66 mm day-1 and 8.25 mm day-1 for the dry season. The total water volume evaporated from Itumbiara reservoir during 2010 was estimated at about 1.7 billion m³ (2,300 mm) which represents 10% of total reservoir volume. The results suggest that advection is the main transport mechanism which drives the evaporation in Itumbiara. The convective processes contribute secondarily to evaporation in Itumbiara reservoir.

Um estudo da recente transformação na estrutura social do Brasil: nova classe média?

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ecological carrying capacity for intensive tilapia (Oreochromis niloticus) cage aquaculture in a large hydroelectrical reservoir in Southeastern Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Models of the Distribution of Persistent Organic Pollutants in the Marine Environment

Persistent organic pollutants (POPs) is a group of chemicals that are toxic, undergo long-range transport and accumulate in biota. Due to their persistency the distribution and recirculation in the environment often continues for a long period of time. Thereby they appear virtually everywhere within the biosphere, and poses a toxic stress to living organisms. In this thesis, attempts are made to contribute to the understanding of factors that influence the distribution of POPs with focus on processes in the marine environment. The bioavailability and the spatial distribution are central topics for the environmental risk management of POPs. In order to study these topics, various field studies were undertaken. To determine the bioavailable fraction of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated naphthalenes (PCNs), and polychlorinated biphenyls (PCBs) the aqueous dissolved phase were sampled and analysed. In the same samples, we also measured how much of these POPs were associated with suspended particles. Different models, which predicted the phase distribution of these POPs, were then evaluated. It was found that important water characteristics, which influenced the solid-water phase distribution of POPs, were particulate organic matter (POM), particulate soot (PSC), and dissolved organic matter (DOM). The bioavailable dissolved POP-phase in the water was lower when these sorbing phases were present. Furthermore, sediments were sampled and the spatial distribution of the POPs was examined. The results showed that the concentration of PCDD/Fs, and PCNs were better described using PSC- than using POM-content of the sediment. In parallel with these field studies, we synthesized knowledge of the processes affecting the distribution of POPs in a multimedia mass balance model. This model predicted concentrations of PCDD/Fs throughout our study area, the Grenlandsfjords in Norway, within factors of ten. This makes the model capable to validate the effect of suitable remedial actions in order to decrease the exposure of these POPs to biota in the Grenlandsfjords which was the aim of the project. Also, to evaluate the influence of eutrophication on the marine occurrence PCB data from the US Musselwatch and Benthic Surveillance Programs are examined in this thesis. The dry weight based concentrations of PCB in bivalves were found to correlate positively to the organic matter content of nearby sediments, and organic matter based concentrations of PCB in sediments were negatively correlated to the organic matter content of the sediment.

The incomplete ionization of substitutional dopants in Silicon Carbide

This thesis analyzes theoretically and computationally the phenomenon of partial ionization of the substitutional dopants in Silicon Carbide at thermal equilibrium. It is based on the solution of the charge neutrality equation and takes into account the following phenomena: several energy levels in the bandgap; Fermi-Dirac statistics for free carriers; screening effects on the dopant ionization energies; the formation of impurity bands. A self-consistent model and a corresponding simulation software have been realized. A preliminary comparison of our calculations with existing experimental results is carried out.

Modeling contaminant behavior in Lake Superior : a comparison of PCBs, PBDEs, and mercury

A mass‐balance model for Lake Superior was applied to polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and mercury to determine the major routes of entry and the major mechanisms of loss from this ecosystem as well as the time required for each contaminant class to approach steady state. A two‐box model (water column, surface sediments) incorporating seasonally adjusted environmental parameters was used. Both numerical (forward Euler) and analytical solutions were employed and compared. For validation, the model was compared with current and historical concentrations and fluxes in the lake and sediments. Results for PCBs were similar to prior work showing that air‐water exchange is the most rapid input and loss process. The model indicates that mercury behaves similarly to a moderately‐chlorinated PCB, with air‐water exchange being a relatively rapid input and loss process. Modeled accumulation fluxes of PBDEs in sediments agreed with measured values reported in the literature. Wet deposition rates were about three times greater than dry particulate deposition rates for PBDEs. Gas deposition was an important process for tri‐ and tetra‐BDEs (BDEs 28 and 47), but not for higher‐brominated BDEs. Sediment burial was the dominant loss mechanism for most of the PBDE congeners while volatilization was still significant for tri‐ and tetra‐BDEs. Because volatilization is a relatively rapid loss process for both mercury and the most abundant PCBs (tri‐ through penta‐), the model predicts that similar times (from 2 ‐ 10 yr) are required for the compounds to approach steady state in the lake. The model predicts that if inputs of Hg(II) to the lake decrease in the future then concentrations of mercury in the lake will decrease at a rate similar to the historical decline in PCB concentrations following the ban on production and most uses in the U.S. In contrast, PBDEs are likely to respond more slowly if atmospheric concentrations are reduced in the future because loss by volatilization is a much slower process for PBDEs, leading to lesser overall loss rates for PBDEs in comparison to PCBs and mercury. Uncertainties in the chemical degradation rates and partitioning constants of PBDEs are the largest source of uncertainty in the modeled times to steady‐state for this class of chemicals. The modeled organic PBT loading rates are sensitive to uncertainties in scavenging efficiencies by rain and snow, dry deposition velocity, watershed runoff concentrations, and uncertainties in air‐water exchange such as the effect of atmospheric stability.