Importance of mixed energy in the Pliocene development Orinoco Delta lobes, and the impact of large volumes of Amazon fluid mud

This research focuses on how river-, wave- and tidal current energy is interpreted to have mixed and been preserved in well-exposed Pliocene strata of both wave-dominated and tide-dominated Orinoco delta lobes. A new method of process facies analysis has been adopted, allowing a more quantitative interpretation. In addition, the very large volumes of Amazon-derived mud that impact the front of the Orinoco Delta today are followed back through the Pliocene Orinoco record, and documented here for the first time. The detection of mixed energies and the additional impact of large mud volumes on the delta front are important because most previous studies on ancient systems have commonly attempted to focus on the dominant process and tended to overlook the complexity of process mixing. The research was carried out in the Pliocene Orinoco Delta on Trinidad using four datasets: an outcrop dataset of 1190 m of measured sections from the topset segments of shelf margin clinoforms of the Moruga Formation; a 260 m outcrop segment from the outer shelf to upper slope environments of the Moruga Formation; a 125 m thick outcrop segment from a tide-dominated delta lobe of the Manzanilla Formation; and three selected outcrop examples (15-80 m thick) from the Morne L’Enfer, Manazanilla and Mayaro formations. The results demonstrate how fluvial and wave signals have mixed as the shelf margin clinoform developed in a strong storm wave-dominated setting. The data suggest that the fluvial signals (including parts of distributary channel-fills and delta fronts) were preserved because of unusually high subsidence rates (averaging >1 km/My on the topsets) and rapid sediment burial probably with a sheltered coastal morphology on this early Atlantic shelf margin, preventing some of the fluvial deposits from being completely reworked by storm waves. Some of the tide-dominated segments of the Pliocene Orinoco Delta are shown to have had a compound deltaic clinoform that reveals detailed interaction of river, wave, and tide processes with the impinging fluid mud. This part of the research suggests that the abundant fluid mud caused wave damping and the preferred preservation of river and tidal signals on the subaqueous delta platform due to the reduced wave action. The Amazon-derived mud tended to accumulate on the subaqueous platform in tide-dominated delta lobes, whereas it was more likely to be eroded and re-deposited into a deeper setting on storm wave-dominated delta lobes.Geological Science

Development of new membranes for proton exchange membrane and direct methanol fuel cells

textProton exchange membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC) are drawing much attention as alternative power sources for transportation, stationary, and portable applications. Nafion membranes are presently used in both PEMFC and DMFC as electrolytes, but are confronted with a few difficulties: (i) high cost, (ii) limited operating temperature of 140 °C and water is not needed for proton conduction. However, it is found that CsHSO₄ decomposes to Cs₂SO₄ and H₂S at 150 °C in H₂ atmosphere in contact with the Pt/C catalyst. Thus, new catalyst materials need to be explored for CsHSO₄ to be used in practical high temperature PEMFC. Thin self-humidifying Nafion membranes with dispersed Pt/C catalyst powder are prepared and tested in PEMFC with dry H₂ and O₂. The Pt/C particles provide sites for catalytic recombination of H₂ and O₂ permeating from the anode and cathode, and the water produced at these sites directly humidifies the membrane. The performance of the cell with the self-humidifying membrane operated with dry reactants is ~ 90 % of that obtained with well humidified H₂ and O₂.Materials Science and Engineerin

Research on Texas savannas : fractional woody cover mapping, potential woody cover modelling, and woody plant encroachment analysis

Tested in Texas savannas of a wide rainfall gradient, this dissertation endeavors to (1) map fractional woody cover at Landsat scale, for close and continuous woody plant encroachment monitoring, (2) model the pattern of potential woody cover over the present rainfall gradient, for implication of the end-point of woody plant encroachment, (3) analyze the rate and effect factors of woody plant encroachment under the regional context, for pertinent savanna management strategy. Web-Enabled Landsat Data (WELD) was used to calibrate the Salford Systems’ Classification and Regression Trees (CART) against training data of fractional woody cover derived from 1m resolution digital orthophotos. The CART model output was verified against an independent test data. This study provides a way to accurately monitor woody plant encroachment across savanna ecosystems at a fine spatial scale, and sets up a protocol for landscape components mapping at sub-pixel level in other ecosystems. The pattern of potential woody cover was modelled over the wide rainfall gradient at Landsat scale (30m) and MODIS scale (500m) respectively. While a positive linear relationship between potential woody cover and mean annual precipitation (MAP) was revealed at Landsat scale, a prominent three-segment relationship was observed at MODIS scale. This discrepancy corroborates the scale dependency of the primary determinants of savanna woody plant density. According to the three-segment pattern at MODIS scale, Texas savannas are divided into arid savanna (MAP 735mm). Analysis of the encroachment of Ashe juniper at its early life stage (initial ~20 years) at local (hectare) scale suggests that water availability has a significant positive effect on the encroachment rate in semi-arid savanna, but not in mesic savanna. In addition, a quadratic relationship was revealed between the encroachment rate and woody plant density in mesic savanna. That is, the encroachment rate increases with woody plant density by a threshold density, then starts decreasing with woody plant density. These results demonstrate that regional context such as rainfall and biological traits of woody species is critical to understand the trend of woody plant encroachment.Geography and the Environmen

Spatial imaging of Zn and other elements in Huanglongbing-affected grapefruit by synchrotron-based micro X-ray fluorescence investigation

Huanglongbing (HLB) is a highly destructive, fast-spreading disease of citrus, causing substantial economic losses to the citrus industry worldwide. Nutrient levels and their cellular distribution patterns in stems and leaves of grapefruit were analysed after graft-inoculation with lemon scions containing 'Candidatus Liberibacter asiaticus' (Las), the heat-tolerant Asian type of the HLB bacterium. After 12 months, affected plants showed typical HLB symptoms and significantly reduced Zn concentrations in leaves. Micro-XRF imaging of Zn and other nutrients showed that preferential localization of Zn to phloem tissues was observed in the stems and leaves collected from healthy grapefruit plants, but was absent from HLB-affected samples. Quantitative analysis by using standard references revealed that Zn concentration in the phloem of veins in healthy leaves was more than 10 times higher than that in HLB-affected leaves. No significant variation was observed in the distribution patterns of other elements such as Ca in stems and leaves of grapefruit plants with or without graft-inoculation of infected lemon scions. These results suggest that reduced phloem transport of Zn is an important factor contributing to HLB-induced Zn deficiency in grapefruit. Our report provides the first in situ, cellular level visualization of elemental variations within the tissues of HLB-affected citrus. © 2014 © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology

Rasta Resin-TBD-Catalyzed γ-Selective Morita–Baylis–Hillman Reactions of α,γ-Disubstituted Allenones

postprin

Technology entrepreneurship and value creation on open innovation platforms

This dissertation studies how entrepreneurial firms create economic value from open source technology platforms, interfaces on which firms disclose knowledge and distribute innovation for free without retaining any proprietary rights. Despite their increasing importance in innovation and growing popularity among profit-seeking new ventures, open source platforms present a major challenge for value creation, as they lack price signals to guide ventures’ transactions and forfeit ventures’ control over key resources and knowledge for innovation. Those features are in contrast with the fundamental assumption about price and revenue in economics. They also run counter to the central tenet in strategy research that private knowledge and rare resources are central to competitive advantage and profiting from innovation. To address this puzzle about value creation from free technologies base on free knowledge and resources, this dissertation specifically focus on the economic implications of strategies ventures can leverage within and across open source development communities. Chapter I reviews the literature relevant to entrepreneurship in an open and inter-dependent innovation environment. Exploring research opportunities emerged from the literature review, Chapter II explores the possibility that multihoming, a critical growth strategy of ventures as open source complementors in platform competition, allows ventures to reinforce their existing user base – a prerequisite of value creation from open source. Chapter III directly addresses value creation by investigating how collaborating with external contributors, another critical open source strategy, influences venture capital investment. Both essays highlight how platform network effects unfold without price signals and proprietary rights of the technologies in shaping the outcome for ventures’ strategies. They also emphasize those strategies’ demand side implications on users, participants on another side of open source platforms. The empirical analyses of this dissertation are based on multiple open source technologies platforms, with data obtained from on GitHub, the worlds’ largest open source software storage provider, containing 5 Terabytes of information on 2.1 million ventures, 96 million technologies and over 2 billion development activities, under research designs for deriving causal references. Overall, the dissertation seeks to advance the understanding of value creation in entrepreneurship through open source platforms, an increasingly important phenomenon in contemporary economy.Managemen

An adaptive interpolating MLS based response surface model applied to design optimizations of electromagnetic devices

Author name used in this publication: S. L. HoAuthor name used in this publication: S. Y. Yang2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A combined wavelet-FE method for transient electromagnetic-field computations

Author name used in this publication: S. Y. YangAuthor name used in this publication: S. L. HoAuthor name used in this publication: G. Z. Ni2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Which group velocity of light in a dispersive medium?

The interaction between a light pulse, traveling in air, and a generic linear, non-absorbing and dispersive structure is analyzed. It is shown that energy conservation imposes a constraint between the group velocities of the transmitted and reflected light pulses. It follows that the two fields propagate with group velocities depending on the dispersive properties of the environment (air) and on the transmission properties of the optical structure, and are one faster and the other slower than the incident field. In other words, the group velocity of a light pulse in a dispersive medium is reminiscent of previous interactions. One example is discussed in detail.Comment: To be submitted on PR