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Temporal dilemma, time preferences and natural resource extraction
No full textThis dissertation sheds lights on two important questions related to temporal dilemma with respect to natural resource (fisheries) extraction:
(i) How does the presence of temporal dilemma impact resource users´ extraction behavior?
(ii) What is the relationship between individual time preferences and resource extraction behavior?
For both cases I consider two different aspects of extraction behavior: (i) effort level decision, and (ii) extraction method choice.
Chapter 2 looks at the impact of temporal dilemma on the distinct but inter-related problems of over-extraction and destructive extraction in natural resource use settings. I employ standard CPR experiments without time delay (control groups) and CPR experiments with time delay (time treatment groups) in conservation earnings to investigate whether or not participants were likely to extract greater amount of resource in the presence of temporal dilemma.
Our results suggest that delaying the benefits of conservation – an experimental feature which brings the experiment closer to reality, as conservation benefits always occur with a time delay – mainly impacts participants’ extraction decision by making them more likely to try out destructive extraction methods. I find that the number of people, who do not opt for destructive extraction method even once during gear choice rounds, was significantly less in the time treatment groups as compared to control groups. On the other hand, I do not find any evidence of difference in effort level between time treatment groups and control groups when participants could not chose their extraction method.
Chapter 3 combines experimental methods and questionnaire data to understand the relationship between individual time preferences and natural resource (fisheries) extraction. I elicit individual time preference with incentivized choice experiments and link the resulting time preference measures to extraction data from questionnaires and CPR experiment.
Our findings s
Trace Element and Isotope Geochemistry of Particle-Reactive Elements in River Waters of the Amazon River Basin
No full textRivers transport large amounts of dissolved and suspended particulate material from their catchment area to the oceans and are a major source of trace metals to seawater. The Amazon River is the world’s largest river and supplies approximately 15% of the global freshwater flux to the oceans. However, the behavior of trace elements, especially particle-reactive elements such as the rare earth elements, within this river as well as in the estuary is not well constrained and rather little is known about their transport mechanisms. This thesis presents major and trace element distributions as well as Nd and Hf isotope data of river water samples from the Amazon Basin. The Amazon River and most of its major tributaries were sampled during seasons of high and low discharge. Samples were separated into suspended particulate and dissolved load prior to analysis to investigate transport properties of particle-reactive elements along the sampled river transect. Ultrafiltration techniques were applied to selected samples to investigate specific transport mechanisms of particle-reactive elements in the colloidal – truly dissolved load.
The geochemistry of the Amazon River is mainly controlled by its tributaries draining the Andes, whereas tributaries draining the Precambrian shields and Amazonian lowlands only have a minor influence. The Andean tributaries supply large amounts of inorganic (nano-) particles and colloids that significantly influence the geochemistry of the Amazon River. Large differences in composition of the particulate, nanoparticulate and truly dissolved load could be traced by major and trace element chemistry in the Amazon River and its major Andean tributary, the Rio Solimões. In contrast, the geochemistry of tributaries that drain the Amazonian lowlands and Precambrian shields is dominated by the presence of organic (nano-) particles and colloids. In these rivers, a constant exchange between the truly dissolved, nanoparticulate and particulate load occ
Interference Alignment and DOF Analysis of Interference and Interference Broadcast Channels
No full textMulti-user wireless communication is interference limited. Information theoretically, even the capacity region of a two-user Gaussian interference channel (IC) is an open problem. Recently a new cooperative interference management technique, called the interference alignment (IA), is proposed and proved to achieve the optimum degrees of freedom (DOF) in any interference networks.
IA is a technique in which all the interfering signals observed from different transmitters are aligned onto the same direction or a common subspace while maintaining independence with the desired signal in a particular receiver.
One of the main drawbacks of IA is the requirement of instantaneous channel state information at the transmitter (CSIT) and a robust generalized IA algorithm for any interference network still remains an open problem.
In this thesis, we address these existing challenges and provide following three fold contributions:
1.Improvement of existing IA algorithms: Using cooperation among the receivers, it is shown that a proper precoding and zero-forcing matrix can be designed iteratively by minimizing the interference power and maximizing the desired signal power simultaneously. Simulation results show that such precoding matrices improve the system capacity.
2.Relaxation of the requirement of CSIT: A space-time transmission scheme is proposed that requires only the knowledge of delayed CSIT and is proved to achieve greater than one DOF in any multiple input single output interference broadcast channels (MISO-IBC).
3.Proposition of a new alignment technique: A new grouping based IA technique is proposed where the receivers within a group cooperatively align the interference from a common source onto an overlapping space. By doing so, they take benefit from the unused spatial dimensions. By determining the optimal overlapping between any two adjacent receivers, a chain based DOF analysis technique, called receiver chain alignment (RCA) is proposed
The role of anode buffer layers in P3HT-PCBM based bulk heterojunction organic solar cells
No full textRealizing cheap-end cost-effective electronics has been the principle motivation behind the research in organic photovoltaic (OPV) field. The promise of low cost relies on using semiconducting polymers which can be cheaply synthesized with electronic properties tailored according to need. These cheaper organic semiconductors can be wet-chemically processed at room temperature on flexible substrates. This entire process can be scaled up to large scale roll-to-roll process which opens the door to a new field of “plastic electronics”. OPV has been considered to be the next generation of photovoltaics. However, among other challenges, the understanding of efficient charge carrier extraction with the use of optimized buffer layer has been one of the major drawbacks in these OPV systems.
In this PhD work, PEDOT:PSS has been used as a model anode buffer layer for a P3HT-PCBM based bulk heterojunction solar cells, used here as a standard organic solar cells. Although PEDOT:PSS is the most common buffer layer used in P3HT-PCBM based organic solar cells, it is not the most optimized anode buffer layer available. This thesis creates a path toward the understanding of buffer layers in organic solar cells based on P3HT-PCBM systems with a primary focus on the anode buffer layer. PEDOT:PSS has been used in the majority of this work as the standard buffer layer system for P3HT-PCBM active layer. It has been modified and treated with various additives and solvents in order to understand
the mechanisms for device performance enhancement. A novel electropolymerization method for depositing the polythiophene anode buffer layer, namely the timedependent cyclic-potential-sweep method, was developed and successfully applied for enhanced performance of the organic solar cells. Similarly, the area dependence seen in OSCs while treating PEDOT:PSS with some additives and solvents has been systematically studied and explained with simple models
Computational study of Excitation Energy Transfer Dynamics in Light-Harvesting Systems
No full textPhotosynthesis is one of the key processes to sustain life on earth. The initial step of photosynthesis involves capturing the sunlight by pigments in so-called light-harvesting complexes and transferring the excitation energy towards the reaction center where charge separation processes take place. In subsequent steps, the respective energy is used for the production of ATP. The transfer efficiency of the excitation energy to the reaction center might be enhanced by quantum effects. The detailed mechanism of this quantum effects is still under debate. In addition, this kind of quantum coherence effects might also help to improve the efficiency of (organic) solar cells. Sun light is not only used by plants as primary source of energy production but also bacteria and algae. In this thesis light-harvesting complexes from bacteria and algae are investigated theoretically. To this end, a multi-scale approach is employed using classical molecular dynamics simulation with subsequent electronic structure calculations and quantum dynamics. The Fenna-Matthews-Olson (FMO) complex of green sulfur bacteria and the Phycoerythrin 545 (PE545) antenna of marine algae are studied in detail. To be able to perform molecular dynamics simulations, one needs to obtain the respective force fields. Thus, here comparison between two different force fields for a bacteriochlorophyll molecule
is carried out. As a test the so-called spectral density was determined, which describes the energy-dependent coupling between pigment and environment. Furthermore by calculating
the excitonic coupling among the pigments, the population dynamics was determined using an ensemble-averaged wave packet formalism. In additon, a new parametrization of the
bacteriochlorophyll a molecule was performed using the CGENFF formalism. Finally, the
light-havesting complex PE555 has been simulated and compared to similar PE545 aggregate
Power Optimization in Wireless Communication Systems
No full textMobile wireless communication is undoubtedly one of the main drivers of industrial development and economic growth in modern societies. Its ability to incorporate cutting-edge technologies and deliver the successful value proposition to end-users has made it an essential part of human lives. Regardless of the technology used, any system would like to achieve optimal interference management or maximize its efficiency. And interestingly, the underlying element that characterizes such parameters is the transmission power. From a network efficiency viewpoint or the quality services provided to the users, the transmission power plays an important role in achieving the optimality in either of the cases. With an objective to address the power optimization in wireless systems, in this thesis, different types of network architectures are considered, with an objective to improve the spectrum and energy efficiency.
In particular, starting with the conventional multi-antenna system, this thesis addresses the long-standing problem of dependency on channel state information in network optimization. In doing so, a simple solution to introducing robustness in imperfect channel estimates based on classical transmit power minimization metric is considered. Furthermore, the energy efficiency issue in a hybrid network topology with the macro base station co-existing with small cell networks is also investigated. We show the key idea in achieving energy efficient network with a higher level of granularity is the strategical selection of base stations. With an insight into the millimeter wave systems, a lucrative solution in estimating channel parameters compared to the state-of-the-art is provided, thus reducing the energy cost at the transmitter and/or receiver. In addition, transmit power optimization in millimeter wave systems is also considered thereby revisiting the key transmission strategies with a low complexity analog and digital beamforming/precoding design
Methods for characterization of bacterial channel using electrophysiology
No full textThis thesis emphasizes an interdisciplinary approach to comprehend the mechanisms of antibiotic translocation across the cell membrane. The single channel electrophysiology experiments were employed to obtain durable artificial lipid bilayer even at high voltages and molecular detail of antibiotic permeation through the outer membrane protein channels. The interactions of antibiotics with the outer membrane protein channels from Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa which have been studied investigation of three different subjects: the first study is carried out with a capillary-integrated compact microfluidic chip. The system is not only enabling the solvent-free bilayer experiments on a chip but also allows single protein detection and its antibiotic permeability through their channels with the low sample consumption. In the second study, we mainly investigate the interaction of phosphonic acid class of antibiotics with OprO and OprP porins from Pseudomonas aeruginosa at a single molecular level. In the third study, we demonstrate a possible stabilization approach for lipid bilayers using polydopamine deposition from dopamine containing solution. In addition to that, the study allows us to control translocation of antibiotic molecules through bacterial nanopores and use it as a biosensor for future applications
Invariant graphs, tilings, and iterated monodromy groups
No full textThe past three decades have shown that lots of questions in holomorphic dynamics can be reduced to tractable combinatorial problems. One of the main objectives of this thesis is to gain better understanding of dynamics of the iteration of rational maps via developing good combinatorial models. The first such models, given by finite invariant graphs, were constructed for postcritically-finite polynomial maps and were used to classify these maps. However, the case of general rational maps is much more complicated and still draws lots of attention.
In this work we construct combinatorial models for the family of expanding Thurston maps, which include all postcritically-finite rational maps with Julia sets given by the entire Riemann sphere. We show that each sufficiently large iterate of an expanding Thurston map has an invariant planar embedded tree containing the postcritical set. The latter result can be extended to the case of postcritically-finite rational maps with Sierpinski carpet Julia sets. In the thesis, we also provide a complete classification of critically fixed rational maps. The main tool is, again, a certain planar embedded invariant graph, called the Tischler graph, associated to each such map. We show that these graphs are always connected, answering a question raised by Pilgrim.
We use the combinatorial models given by invariant graphs to study properties of the iterated monodromy groups (IMG's) of different classes of Thurston maps. In particular, we show that, in the presence of an invariant tree, the IMG's can be described in a very simple combinatorial way. This allows us to describe the IMG's that arise from critically fixed rational maps and conclude that these maps have amenable IMG's of exponential growth. Finally, in a joint work with Daniel Meyer, we construct conceptually new examples of rational maps with the IMG's of exponential growth
Synthesis and Analysis of Chlorogenic Acid Derivatives from Food Processing
No full textChlorogenic acids (CGAs) are known as common secondary plant metabolites and coffee, tea, potatoes as well as many vegetables and fruits are known to display particularly high contents of such esters. Food processing (roasting, cooking, baking, frying, steaming, microwaving, fermenting) of many dietary plants enriches the profile of the CGAs and their derivatives in a given food, which are then available to human consumption and potentially human metabolism. Even the simple exposure of phenolics to hot water at slightly acidic pH results in an astonishing number of transformation products.
These newly formed CGA derivatives contribute to the desired taste, flavor, aroma and color of the foods and beverages. A series of mono-, di- and triacylated chlorogenic acids and derivatives were synthesized in the current project; the chosen cinnamoyl substituents were caffeoyl, feruloyl and dimethoxycinnamoyl. Efficient orthogonal protecting group strategies were developed and employed for the alcohols and carboxylic acid of the quinic acid moiety, and for the phenols of the hydroxycinnamate moiety.
In food processing, water does not simply act as a solvent and innocent bystander but as a reactive reagent resulting in significant chemical changes of the dietary material. It was documented in the current study that water addition to the olefinic moiety of the cinnamoyl residues of CGAs, caffeoylglucoses, methyl quinates and γ-quinides takes place in a regiospecific manner. The water addition derivatives were found not only in compound model brews but also in the coffee beverage and the maté tea brew. Other transformation products were detected to form in hot water at slightly acidic pH from CGAs, including trans-cis isomerization and acyl migration products. Liquid chromatography coupled to powerful mass spectrometry techniques and authentic or synthesized standards were used for the identification and characterization of these chemical transformation products
Unconventional Information Processing Systems, Novel Hardware: A Tour d'Horizon
No full textThis report provides a wide-angle survey on computational paradigms which have a possible bearing on the development of unconventional computational substrates and hardware devices. Such unconvential substrates and devices have some prop- erties that alienate them from the classical Turing model of computation. Among other challenging characteristics, they are non-digital, unclocked, low-precision, exhibit static and dynamic parameter drift, and may have limited lifetime. Such properties are shared with biological computing systems – brains, but not only brains – , so this survey includes ideas and insights from neuroscience and the natural computing field