Advancing C1 catalysis by spatiotemporal analysis and dynamic operation

La química del C1, reaccions en les que participen molècules d’un carboni com CO, CH2 i CO2, s’espera que jugui un paper més important en la indústria química i la protecció mediambiental. Aquesta tesis descriu nous conceptes de reactors i metodologies analítiques operando per a entendre i innovar tres reaccions de la química del C1: l’acoblament oxidatiu de metà (OCM), la captura de CO2 i la seva reducció (CCR) a metà, i el reformat sec de metà (DRM). Per al OCM, la investigació espai temporal de gradients fisicoquímics de la concentració gasosa, la temperatura del catalitzador i el comportament del coc present al reactor catalític sota condicions extremes (fins a 1000 ºC) clarifiquen diferents mecanismes de reacció regits per la naturalesa del catalitzador utilitzat. S’observa que reaccions homogènies no selectives que tenen lloc en la fase gasosa són induïdes per l’oxidació explosiva de l’hidrogen produïda mitjançant l’oxidació parcial del CH4. Aquests camins desfavorables de la reacció es poden suprimir utilitzant promotors que modifiquen la superfície del catalitzador, millorant així dràsticament la selectivitat del producte a età i etilè en lloc de CO i CO2. En segon lloc, es desenvolupa una nova estratègia CCR per a la metanació de CO2 basada en una operació d’estat no estacionari utilitzant catalitzadors de Ni. Els efectes de dos promotors, K i La, en la capacitat de capturar CO2, el rati de reducció i els mecanismes de reacció són desvelats utilitzant mesures operando i espai temporals de DRIFTS. Finalment, s’explora el potencial d’operacions en estat no estacionari i el concepte de looping per al DRM fent ús de catalitzadors de Ni, aclarint així els rols que tenen el suports, els promotors i la temperatura de la reacció en la descomposició de CH4, així com la formació de coc i la seva oxidació per CO2.La química del C1, reacciones en las que participan moléculas de un carbono como CO, CH4 y CO2, se espera que juegue un papel más importante en la industria química y protección medioambiental. Esta tesis doctoral describe nuevos conceptos de reactores y metodologías analíticas operando para entender e innovar tres reacciones de la química del C1: el acoplamiento oxidativo de metano (OCM), la captura de CO2 y su reducción (CCR) a metano, y el reformado seco de metano (DRM). Para el OCM, la investigación espaciotemporal de gradientes fisicoquímicos de la concentración gaseosa, la temperatura del catalizador y el comportamiento del coque presente en el reactor catalítico bajo condiciones extremas (hasta 1000 ºC) clarifican distintos mecanismos de reacción regidos por la naturaleza del catalizador empleado. Se observa que reacciones homogéneas no selectivas que tienen lugar en la fase gaseosa son inducidas por la oxidación explosiva del hidrógeno producida mediante la oxidación parcial del CH4. Estos caminos desfavorables de la reacción se pueden suprimir utilizando promotores que modifican la superficie del catalizador, mejorando así drásticamente la selectividad del producto hacia etano y etileno en lugar de CO y CO2. En segundo lugar, se desarrolla una nueva estrategia CCR para la metanación de CO2 basada en una operación de estado no estacionario utilizando catalizadores de Ni. Los efectos de dos promotores, K y La, en la capacidad de capturar CO2, la ratio de reducción y los mecanismos de reacción son desvelados mediante medidas operando y espaciotemporales de DRIFTS. Finalmente, se explora el potencial de operaciones en estado no estacionario y el concepto de looping para el DRM utilizando catalizadores de Ni, aclarando los roles que tienen los soportes, los promotores y la temperatura de la reacción en la descomposición de CH4, así como la formación de coque y su oxidación por CO2.C1 chemistry, reactions involving one-carbon containing molecules such as CO, CH4 and CO2, is expected to play even more vital roles for future chemical industries and environmental protection. This doctoral thesis describes novel reactor concepts and operando analytical methodologies to understand and innovate three C1 chemistry of future importance, namely oxidative coupling of methane (OCM), CO2 capture and reduction (CCR) to methane, and dry reforming of methane (DRM). For OCM, spatiotemporal investigation of physicochemical gradients of gaseous concentration, catalyst temperature and coking behavior present in the catalytic reactor under harsh conditions (up to ca. 1000 °C) clarifies distinct reaction mechanisms ruled by the nature of the catalyst materials used. Strikingly, unselective homogeneous reactions taking place in the gas phase are shown to be induced by the explosive oxidation of hydrogen produced via partial oxidation of CH4. Such unfavorable reaction paths can be suppressed by the use of promoters which modify the catalyst surface, thereby drastically improving the product selectivity towards C2 molecules (ethane and ethylene) against CO and CO2. Secondly, a novel CCR strategy for CO2 methanation based on unsteady-state operation is developed using Ni-based catalysts. The effects of two promoters, K and La, on CO2 capture capacity, reduction rate and reaction mechanisms are unraveled by means of spatiotemporal operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Finally, the potential of unsteady-state operation and looping concept are explored for DRM using Ni-based catalysts, clarifying the critical roles of support materials, promoters and reaction temperature on CH4 decomposition, coke formation and coke oxidation by CO2

Microscopic Clustering in Light Nuclei

We review recent experimental and theoretical progress in understanding the microscopic details of clustering in light nuclei. We discuss recent experimental results on $\alpha$-conjugate systems, molecular structures in neutron-rich nuclei, and constraints for ab initio theory. We then examine nuclear clustering in a wide range of theoretical methods, including the resonating group and generator coordinate methods, antisymmetrized molecular dynamics, Tohsaki-Horiuchi-Schuck-R\"opke wave function and container model, no-core shell model methods, continuum quantum Monte Carlo, and lattice effective field theory.Comment: Accepted for publication in Review of Modern Physics, 50 pages, 28 figures, minor change to titl

The Drought Risk Analysis, Forecasting, and Assessment under Climate Change

This Special Issue is a platform to fill the gaps in drought risk analysis with field experience and expertise. It covers (1) robust index development for effective drought monitoring; (2) risk analysis framework development and early warning systems; (3) impact investigations on hydrological and agricultural sectors; (4) environmental change impact analyses. The articles in the Special Issue cover a wide geographic range, across China, Taiwan, Korea, and the Indo-China peninsula, which covers many contrasting climate conditions. Hence, the results have global implications: the data, analysis/modeling, methodologies, and conclusions lay a solid foundation for enhancing our scientific knowledge of drought mechanisms and relationships to various environmental conditions

Temperature Variation Aware Energy Optimization in Heterogeneous MPSoCs

Thermal effects are rapidly gaining importance in nanometer heterogeneous integrated systems. Increased power density, coupled with spatio-temporal variability of chip workload, cause lateral and vertical temperature non-uniformities (variations) in the chip structure. The assumption of an uniform temperature for a large circuit leads to inaccurate determination of key design parameters. To improve design quality, we need precise estimation of temperature at detailed spatial resolution which is very computationally intensive. Consequently, thermal analysis of the designs needs to be done at multiple levels of granularity. To further investigate the flow of chip/package thermal analysis we exploit the Intel Single Chip Cloud Computer (SCC) and propose a methodology for calibration of SCC on-die temperature sensors. We also develop an infrastructure for online monitoring of SCC temperature sensor readings and SCC power consumption. Having the thermal simulation tool in hand, we propose MiMAPT, an approach for analyzing delay, power and temperature in digital integrated circuits. MiMAPT integrates seamlessly into industrial Front-end and Back-end chip design flows. It accounts for temperature non-uniformities and self-heating while performing analysis. Furthermore, we extend the temperature variation aware analysis of designs to 3D MPSoCs with Wide-I/O DRAM. We improve the DRAM refresh power by considering the lateral and vertical temperature variations in the 3D structure and adapting the per-DRAM-bank refresh period accordingly. We develop an advanced virtual platform which models the performance, power, and thermal behavior of a 3D-integrated MPSoC with Wide-I/O DRAMs in detail. Moving towards real-world multi-core heterogeneous SoC designs, a reconfigurable heterogeneous platform (ZYNQ) is exploited to further study the performance and energy efficiency of various CPU-accelerator data sharing methods in heterogeneous hardware architectures. A complete hardware accelerator featuring clusters of OpenRISC CPUs, with dynamic address remapping capability is built and verified on a real hardware

Annual report of the town officers of Merrimack, New Hampshire for the fiscal year ending December 31, 1995.

This is an annual report containing vital statistics for a town/city in the state of New Hampshire

Production of valuable hydrocarbons by catalytic hydrodechlorination of chloromethanes

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Física Aplicada. Fecha de lectura: 16-07-2020La realización de este trabajo ha sido posible gracias al apoyo económico del Ministerio de Economía y Competitividad (MINECO) a través de los proyectos CTM2014-53008-R y CTM2017-85498-R, y gracias a la concesión de una beca de Formación de Personal Investigador (FPI) del MINECO (Referencia BES-2015- 075219

Stimulated emission depletion microscopy with optical fibers

Imaging at the nanoscale and/or at remote locations holds great promise for studies in fields as disparate as the life sciences and materials sciences. One such microscopy technique, stimulated emission depletion (STED) microscopy, is one of several fluorescence based imaging techniques that offers resolution beyond the diffraction-limit. All current implementations of STED microscopy, however, involve the use of free-space beam shaping devices to achieve the Gaussian- and donut-shaped Orbital Angular Momentum (OAM) carrying beams at the desired colors –-- a challenging prospect from the standpoint of device assembly and mechanical stability during operation. A fiber-based solution could address these engineering challenges, and perhaps more interestingly, it may facilitate endoscopic implementation of in vivo STED imaging, a prospect that has thus far not been realized because optical fibers were previously considered to be incapable of transmitting the OAM beams that are necessary for STED. In this thesis, we investigate fiber-based STED systems to enable endoscopic nanoscale imaging. We discuss the design and characteristics of a novel class of fibers supporting and stably propagating Gaussian and OAM modes. Optimization of the design parameters leads to stable excitation and depletion beams propagating in the same fiber in the visible spectral range, for the first time, with high efficiency (>99%) and mode purity (>98%). Using the fabricated vortex fiber, we demonstrate an all-fiber STED system with modes that are tolerant to perturbations, and we obtain naturally self-aligned PSFs for the excitation and depletion beams. Initial experiments of STED imaging using our device yields a 4-fold improvement in lateral resolution compared to confocal imaging. In an experiment in parallel, we show the means of using q-plates as free-space mode converters that yield alignment tolerant STED microscopy systems at wavelengths covering the entire visible spectrum, and hence dyes of interest in such imaging schematics. Our study indicates that the vortex fiber is capable of providing an all-fiber platform for STED systems, and for other imaging systems where the exploitation of spatio-spectral beam shaping is required

Integrated System Architectures for High-Performance Internet Servers

Ph.D.Computer Science and EngineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/90845/1/binkert-thesis.pd

Radiation Induced Processes in Biomolecules and Clusters in Controlled Beams

The fundamental nanoscale processes that initiate radiation damage in biological material have not yet been fully elucidated. This represents a significant barrier to developing multidimensional simulations of radiation effects that can lead to advances in radiotherapy and radioprotection. This thesis explores UV- and electron-induced processes in DNA and RNA bases. Pure and hydrated clusters are studied in order to better understand the effects of the chemical environment on the radiation response of these important biomolecules. Although extensive research has been carried out on the relaxation pathways of UV-excited nucleobases, no previous experiments have investigated bond breaking in neutral electronic excited states. This thesis reveals a new fragment ion from uracil (C3H4N2O+) that can be accessed by multi-photon ionization (MPI) but not by electron impact ionization (ElI). This provides the first experimental demonstration that neutral excited state dynamics in a nucleobase can lead to bond breaking in the aromatic ring, as predicted in recent theoretical studies. The specific excited state dynamics have not yet been identified definitively and are the subject of on-going ultrafast pump-probe experiments in collaboration with Townsend and co-workers (Heriot-Watt University). The time-resolved measurements provide new evidence supporting a theoretically predicted relaxation pathway into long-lived triplet states. Dissociative ionization of hydrated nucleobases and uracil-adenine clusters has been studied experimentally for the first time. Evidence for deamination reactions is observed in hydrated adenine complexes. The production of C3H4N2O+ fragments from uracil is strongly suppressed by clustering with water whereas the channel remains open in uracil-adenine complexes. To unravel the specific cluster-mediated dynamics and reactions responsible for these effects, further experiments are required with greater control over the cluster targets. Indeed the range of monomers and cluster configurations in neutral beams currently limits interpretations and direct comparisons with calculations. In response to this challenge, a new experiment has been built that enables radiation effects to be studied on molecules and clusters in Stark-deflected beams (MPI, ElI, and future electron attachment measurements). Early results on nitromethane beams include a demonstration that studying ElI as a function of the Stark deflector voltage can be used to deduce whether certain product ions came from monomers or from clusters