Electroosmotic pumping in rectangular microchannels: A numerical treatment by the finite element method

In this work, the analysis of electroosmotic pumping mechanisms in microchannels is performed through the solution of Poisson-Boltzmann and Navier Stokes equations by the Finite Element Method. This approach is combined with a Newton-Raphson iterative scheme, allowing a full treatment of the non-linear Poisson-Boltzmann source term which is normally approximated by linearizations in other methods.

Spin coherence generation in negatively charged self-assembled (In,Ga)As quantum dots by pumping excited trion states

Spin coherence generation in an ensemble of negatively charged (In,Ga)As/GaAs quantum dots was investigated by picosecond time-resolved pump-probe spectroscopy measuring ellipticity. Robust coherence of the ground-state electron spins is generated by pumping excited charged exciton (trion) states. The phase of the coherent state, as evidenced by the spin ensemble precession about an external magnetic field, varies relative to spin coherence generation resonant with the ground state. The phase variation depends on the pump photon energy. It is determined by (a) pumping dominantly either singlet or triplet excited states, leading to a phase inversion, and (b) the subsequent carrier relaxation into the ground states. From the dependence of the precession phase and the measured g factors, information about the quantum dot shell splitting and the exchange energy splitting between triplet and singlet states can be extracted in the ensemble.

Viabilidade técnica da fabricação de cimento com mistura de escória de aciaria LD e resíduo de granito

Esse trabalho estuda a viabilidade técnica da fabricação de cimento com uma mistura de resíduo proveniente da serragem de blocos de granito e escória de aciaria LD. Para isso, foi preparada uma mistura desses materiais de modo que a relação %CaO / %SiO2 fosse 1,2. Essa mistura foi fundida e resfriada rapidamente em água. A amostra foi caracterizada e o difratograma de raios X mostrou um material amorfo e a presença das fases mineralógicas Akermanita e Gehlenita, as quais são consideradas como as fases mineralógicas ideais para a atividade hidráulica. Essa mistura foi adicionada ao clínquer para a fabricação de cimento. Com o cimento fabricado, foram feitos ensaios cujos resultados são apresentados e comparados com os valores obtidos para o cimento de alto-forno. Esses resultados indicam a viabilidade técnica da utilização da mistura na fabricação de cimento.

A new double laser pulse pumping scheme for transient collisionally excited plasma soft X-ray lasers

Within this thesis a new double laser pulse pumping scheme for plasma-based, transient collisionally excited soft x-ray lasers (SXRL) was developed, characterized and utilized for applications. SXRL operations from ~50 up to ~200 electron volt were demonstrated applying this concept. As a central technical tool, a special Mach-Zehnder interferometer in the chirped pulse amplification (CPA) laser front-end was developed for the generation of fully controllable double-pulses to optimally pump SXRLs.rnThis Mach-Zehnder device is fully controllable and enables the creation of two CPA pulses of different pulse duration and variable energy balance with an adjustable time delay. Besides the SXRL pumping, the double-pulse configuration was applied to determine the B-integral in the CPA laser system by amplifying short pulse replica in the system, followed by an analysis in the time domain. The measurement of B-integral values in the 0.1 to 1.5 radian range, only limited by the reachable laser parameters, proved to be a promising tool to characterize nonlinear effects in the CPA laser systems.rnContributing to the issue of SXRL pumping, the double-pulse was configured to optimally produce the gain medium of the SXRL amplification. The focusing geometry of the two collinear pulses under the same grazing incidence angle on the target, significantly improved the generation of the active plasma medium. On one hand the effect was induced by the intrinsically guaranteed exact overlap of the two pulses on the target, and on the other hand by the grazing incidence pre-pulse plasma generation, which allows for a SXRL operation at higher electron densities, enabling higher gain in longer wavelength SXRLs and higher efficiency at shorter wavelength SXRLs. The observation of gain enhancement was confirmed by plasma hydrodynamic simulations.rnThe first introduction of double short-pulse single-beam grazing incidence pumping for SXRL pumping below 20 nanometer at the laser facility PHELIX in Darmstadt (Germany), resulted in a reliable operation of a nickel-like palladium SXRL at 14.7 nanometer with a pump energy threshold strongly reduced to less than 500 millijoule. With the adaptation of the concept, namely double-pulse single-beam grazing incidence pumping (DGRIP) and the transfer of this technology to the laser facility LASERIX in Palaiseau (France), improved efficiency and stability of table-top high-repetition soft x-ray lasers in the wavelength region below 20 nanometer was demonstrated. With a total pump laser energy below 1 joule the target, 2 mircojoule of nickel-like molybdenum soft x-ray laser emission at 18.9 nanometer was obtained at 10 hertz repetition rate, proving the attractiveness for high average power operation. An easy and rapid alignment procedure fulfilled the requirements for a sophisticated installation, and the highly stable output satisfied the need for a reliable strong SXRL source. The qualities of the DGRIP scheme were confirmed in an irradiation operation on user samples with over 50.000 shots corresponding to a deposited energy of ~ 50 millijoule.rnThe generation of double-pulses with high energies up to ~120 joule enabled the transfer to shorter wavelength SXRL operation at the laser facility PHELIX. The application of DGRIP proved to be a simple and efficient method for the generation of soft x-ray lasers below 10 nanometer. Nickel-like samarium soft x-ray lasing at 7.3 nanometer was achieved at a low total pump energy threshold of 36 joule, which confirmed the suitability of the applied pumping scheme. A reliable and stable SXRL operation was demonstrated, due to the single-beam pumping geometry despite the large optical apertures. The soft x-ray lasing of nickel-like samarium was an important milestone for the feasibility of applying the pumping scheme also for higher pumping pulse energies, which are necessary to obtain soft x-ray laser wavelengths in the water window. The reduction of the total pump energy below 40 joule for 7.3 nanometer short wavelength lasing now fulfilled the requirement for the installation at the high-repetition rate operation laser facility LASERIX.rn

Metastability exchange optical pumping in 3 He gas up to 30 mT: Efficiency measurements and evidence of laser-induced nuclear relaxation

Advances in metastability exchange optical pumping (MEOP) of 3He at high laser powers, with its various applications, but also at high gas pressures p3 and high magnetic field strengths B, have provided strong motivation for revisiting the understanding and for investigating the limitations of this powerful technique. For this purpose, we present systematic experimental and theoretical studies of efficiency and of relaxation mechanisms in B≤30 mT and p3=0.63−2.45 mbar. 3He nuclear polarisation is measured by light absorption in longitudinal configuration where weak light beams at 1083 nm parallel to magnetic field and cell axis with opposite circular polarisations are used to probe the distribution of populations in the metastable state. This method is systematically tested to evaluate potential systematic biases and is shown to be reliable for the study of OP dynamics despite the redistribution of populations by OP light. Nuclear polarisation loss associated to the emission of polarised light by the plasma discharge used for MEOP is found to decrease above 10 mT, as expected, due to hyperfine decoupling in highly excited states. However, this does not lead to improved MEOP efficiency at high laser power. We find clear evidence of additional laser-induced relaxation instead. The strong OP-enhanced polarisation losses, currently limiting MEOP performances, are quantitatively investigated using an angular momentum budget approach and a recently developed comprehensive model that describes the combined effects of OP, ME and relaxation, validated by comparison to experimental results.

Manual pumping test method for characterizing the productivity of drilled wells equipped with rope pumps

Since the introduction of the rope-pump in Nicaragua in the 1990s, the dependence on wells in rural areas has grown steadily. However, little or no attention is paid to rope-pump well performance after installation. Due to financial restraints, groundwater resource monitoring using conventional testing methods is too costly and out of reach of rural municipalities. Nonetheless, there is widespread agreement that without a way to quantify the changes in well performance over time, prioritizing regulatory actions is impossible. A manual pumping test method is presented, which at a fraction of the cost of a conventional pumping test, measures the specific capacity of rope-pump wells. The method requires only sight modifcations to the well and reasonable limitations on well useage prior to testing. The pumping test was performed a minimum of 33 times in three wells over an eight-month period in a small rural community in Chontales, Nicaragua. Data was used to measure seasonal variations in specific well capacity for three rope-pump wells completed in fractured crystalline basalt. Data collected from the tests were analyzed using four methods (equilibrium approximation, time-drawdown during pumping, time-drawdown during recovery, and time-drawdown during late-time recovery) to determine the best data-analyzing method. One conventional pumping test was performed to aid in evaluating the manual method. The equilibrim approximation can be performed while in the field with only a calculator and is the most technologically appropriate method for analyzing data. Results from this method overestimate specific capacity by 41% when compared to results from the conventional pumping test. The other analyes methods, requiring more sophisticated tools and higher-level interpretation skills, yielded results that agree to within 14% (pumping phase), 31% (recovery phase) and 133% (late-time recovery) of the conventional test productivity value. The wide variability in accuracy results principally from difficulties in achieving equilibrated pumping level and casing storage effects in the puping/recovery data. Decreases in well productivity resulting from naturally occuring seasonal water-table drops varied from insignificant in two wells to 80% in the third. Despite practical and theoretical limitations on the method, the collected data may be useful for municipal institutions to track changes in well behavior, eventually developing a database for planning future ground water development projects. Furthermore, the data could improve well-users’ abilities to self regulate well usage without expensive aquifer characterization.

The effect of demand, tank parameters, and pumping stations on energy use in municipal drinking water distribution systems

Two of the indicators of the UN Millennium Development Goals ensuring environmental sustainability are energy use and per capita carbon dioxide emissions. The increasing urbanization and increasing world population may require increased energy use in order to transport enough safe drinking water to communities. In addition, the increase in water use would result in increased energy consumption, thereby resulting in increased green-house gas emissions that promote global climate change. The study of multiple Municipal Drinking Water Distribution Systems (MDWDSs) that relates various MDWDS aspects--system components and properties--to energy use is strongly desirable. The understanding of the relationship between system aspects and energy use aids in energy-efficient design. In this study, components of a MDWDS, and/or the characteristics associated with the component are termed as MDWDS aspects (hereafter--system aspects). There are many aspects of MDWDSs that affect the energy usage. Three system aspects (1) system-wide water demand, (2) storage tank parameters, and (3) pumping stations were analyzed in this study. The study involved seven MDWDSs to understand the relationship between the above-mentioned system aspects in relation with energy use. A MDWDSs model, EPANET 2.0, was utilized to analyze the seven systems. Six of the systems were real and one was a hypothetical system. The study presented here is unique in its statistical approach using seven municipal water distribution systems. The first system aspect studied was system-wide water demand. The analysis involved analyzing seven systems for the variation of water demand and its impact on energy use. To quantify the effects of water use reduction on energy use in a municipal water distribution system, the seven systems were modeled and the energy usage quantified for various amounts of water conservation. It was found that the effect of water conservation on energy use was linear for all seven systems and that all the average values of all the systems' energy use plotted on the same line with a high R 2 value. From this relationship, it can be ascertained that a 20% reduction in water demand results in approximately a 13% savings in energy use for all seven systems analyzed. This figure might hold true for many similar systems that are dominated by pumping and not gravity driven. The second system aspect analyzed was storage tank(s) parameters. Various tank parameters: (1) tank maximum water levels, (2) tank elevation, and (3) tank diameter were considered in this part of the study. MDWDSs use a significant amount of electrical energy for the pumping of water from low elevations (usually a source) to higher ones (usually storage tanks). The use of electrical energy has an effect on pollution emissions and, therefore, potential global climate change as well. Various values of these tank parameters were modeled on seven MDWDSs of various sizes using a network solver and the energy usage recorded. It was found that when averaged over all seven analyzed systems (1) the reduction of maximum tank water level by 50% results in a 2% energy reduction, (2) energy use for a change in tank elevation is system specific, and (2) a reduction of tank diameter of 50% results in approximately a 7% energy savings. The third system aspect analyzed in this study was pumping station parameters. A pumping station consists of one or more pumps. The seven systems were analyzed to understand the effect of the variation of pump horsepower and the number of booster stations on energy use. It was found that adding booster stations could save energy depending upon the system characteristics. For systems with flat topography, a single main pumping station was found to use less energy. In systems with a higher-elevation neighborhood, however, one or more booster pumps with a reduced main pumping station capacity used less energy. The energy savings for the seven systems was dependent on the number of boosters and ranged from 5% to 66% for the analyzed five systems with higher elevation neighborhoods (S3, S4, S5, S6, and S7). No energy savings was realized for the remaining two flat topography systems, S1, and S2. The present study analyzed and established the relationship between various system aspects and energy use in seven MDWDSs. This aids in estimating the amount of energy savings in MDWDSs. This energy savings would ultimately help reduce Greenhouse gases (GHGs) emissions including per capita CO 2 emissions thereby potentially lowering the global climate change effect. This will in turn contribute to meeting the MDG of ensuring environmental sustainability.

IMPROVING FLOW DISTRIBUTION IN SMALL-SCALE WATER-SUPPLY SYSTEMS THROUGH THE USE OF FLOW-REDUCING DISCS AND METHODS FOR ANALYZING THE EFFECTIVENESS OF SOLAR POWERED PUMPING FOR A DRINKING WATER SUPPLY IN RURAL PANAMA

As continued global funding and coordination are allocated toward the improvement of access to safe sources of drinking water, alternative solutions may be necessary to expand implementation to remote communities. This report evaluates two technologies used in a small water distribution system in a mountainous region of Panama; solar powered pumping and flow-reducing discs. The two parts of the system function independently, but were both chosen for their ability to mitigate unique issues in the community. The design program NeatWork and flow-reducing discs were evaluated because they are tools taught to Peace Corps Volunteers in Panama. Even when ample water is available, mountainous terrains affect the pressure available throughout a water distribution system. Since the static head in the system only varies with the height of water in the tank, frictional losses from pipes and fittings must be exploited to balance out the inequalities caused by the uneven terrain. Reducing the maximum allowable flow to connections through the installation of flow-reducing discs can help to retain enough residual pressure in the main distribution lines to provide reliable service to all connections. NeatWork was calibrated to measured flow rates by changing the orifice coefficient (θ), resulting in a value of 0.68, which is 10-15% higher than typical values for manufactured flow-reducing discs. NeatWork was used to model various system configurations to determine if a single-sized flow-reducing disc could provide equitable flow rates throughout an entire system. There is a strong correlation between the optimum single-sized flow- reducing disc and the average elevation change throughout a water distribution system; the larger the elevation change across the system, the smaller the recommended uniform orifice size. Renewable energy can jump the infrastructure gap and provide basic services at a fraction of the cost and time required to install transmission lines. Methods for the assessment of solar powered pumping systems as a means for rural water supply are presented and assessed. It was determined that manufacturer provided product specifications can be used to appropriately design a solar pumping system, but care must be taken to ensure that sufficient water can be provided to the system despite variations in solar intensity.

Assessing and mapping LD and SLM to directly support the planning and scaling up of SLM interventions to combat desertification

Global investment in Sustainable Land Management (SLM) has been substantial, but knowledge gaps remain. Overviews of where land degradation (LD) is taking place and how land users are addressing the problem using SLM are still lacking for most individual countries and regions. Relevant maps focus more on LD than SLM, and they have been compiled using different methods. This makes it impossible to compare the benefits of SLM interventions and prevents informed decision-making on how best to invest in land. To fill this knowledge gap, a standardised mapping method has been collaboratively developed by the World Overview of Conservation Approaches and Technologies (WOCAT), FAO’s Land Degradation Assessment in Drylands (LADA) project, and the EU’s Mitigating Desertification and Remediating Degraded Land (DESIRE) project. The method generates information on the distribution and characteristics of LD and SLM activities and can be applied at the village, national, or regional level. It is based on participatory expert assessment, documents, and surveys. These data sources are spatially displayed across a land-use systems base map. By enabling mapping of the DPSIR framework (Driving Forces-Pressures-State-Impacts-Responses) for degradation and conservation, the method provides key information for decision-making. It may also be used to monitor LD and conservation following project implementation. This contribution explains the mapping method, highlighting findings made at different levels (national and local) in South Africa and the Mediterranean region. Keywords: Mapping, Decision Support, Land Degradation, Sustainable Land Management, Ecosystem Services, Participatory Expert Assessment

Functional and motor neuronal analysis of defensive siphon responses in {\it Aplysia californica}

One of the central goals of neuroscience research is to determine how networks of neurons control and modify behavior. One of the most influential model systems for this kind of analysis is the siphon and gill withdrawal reflex of the marine mollusc A. californica. In response to tactile stimulation, the siphon displays 3 different responses: (1) a posterior pointing and leveling (flaring) of the siphon in response to tail stimulation (the siphon T response), (2) constriction and anterior pointing to head stimulation (the siphon H response) and (3) constriction and withdrawal between the animal's parapodia (the siphon S response). The siphon S response is pseudoconditioned by a noxious tail stimulus to resemble the siphon T response. Behavioral and combined behavioral/intracellular studies were conducted to determine the motor neuronal control of these behaviors and to search for mechanisms of siphon response transformation following pseudoconditioning. The present studies have found that the flaring component of pseudoconditioned siphon S responses occurs during mantle pumping (MP) triggered by noxious tail stimulation. Siphon stimulation also triggers MP, as recorded in neurons of the Interneuron II pattern generator which commands MP. The 4 LF$\rm\sb{SB}$ siphon motor neurons (SMNs) were found necessary and sufficient for the siphon T response, while SMNs RD$\rm\sb S$ and LD$\rm\sb{S1}$ were found necessary and sufficient for the siphon H response. Following pseudoconditioning, there is an increase in the number of evoked spikes to the test stimulus for the LF$\rm\sb{SB}$ cells and a decreased number for RD$\rm\sb S.$ Siphon flaring occurring during the pseudoconditioned response correlates with increased LF$\rm\sb{SB}$ activity during triggered MP cycles. This suggests that psuedoconditioning is in part due to reconfiguration of the motor outputs of the Interneuron II network. These results suggest that these defensive responses are controlled and patterned by a well-defined, finite set of motor neurons and interneurons (Interneuron II) that are dedicated to specific behavioral functions, but also have parallel distributed properties. ^