Relaxometry Models Compared with Bayesian Technique: Ganglioside Micelle Example

In this work a methodology to perform Bayesian model-comparison is developed and exemplified in the analysis of magnetic relaxation dispersion (NMRD) experiments of water in Ganglioside micelle system. The NMRD powerful probe of slow dynamics in complex liquids is obtained. There are many interesting systems to study with NMRD, such as ionic and Lyotropic liquids or electrolytes. However, to progress in the understanding of the physical chemistry of studied systems relatively detailed theoretical NMRD-models are required. To improve the models they need to be carefully compared, in addition to physico-chemical considerations of molecular and spin dynamics. The comparison is performed by computing the Bayesian evidence in terms of a thermodynamic integral solved with Markov chain Monte Carlo. The result leads to a conclusion of two micelle water sites, and rules out lower and higher complexity level, i.e., one and three sites. In contrast, and provided only with the quality of best fit, suggest a three site model. The two approximate selection tools, Akaike and Baysian information criterions, may lead to wrong conclusions compared to the the full integration. The methodology is expected to be one of several important tools in NMRD model development, however, is completely general and should find awakened use in many research areas. </div

Simulering av Relaxationsprocesser inom Fluoresens, EPR och NMR Spektroskopi

Relaxation models are developed using numerical solutions of the Stochastic Liouville Equation of motion. Simplified descriptions such as the stochastic master equation is described in the context of fluorescence depolarisation experiments. Redfield theory is used in order to describe NMR relaxation in bicontinuous phases. The stochastic fluctuations in the relaxation models are accounted for using Brownian Dynamics simulation technique. A novel approach to quantitatively analyse fluorescence depolarisation experiments and to determine intramolecular distances is presented. A new Brownian Dynamics simulation technique is developed in order to characterize translational diffusion along the water lipid interface of bicontinuous cubic phases

Relaxometry models compared with Bayesian techniques:ganglioside micelle example

Abstract In this work a methodology to perform Bayesian model-comparison is developed and exemplified in the analysis of nuclear magnetic relaxation dispersion (NMRD) experiments of water in a ganglioside micelle system. NMRD is a powerful tool to probe slow dynamics in complex liquids. There are many interesting systems that can be studied with NMRD, such as ionic and lyotropic liquids or electrolytes. However, to progress in the understanding of the studied systems, relatively detailed theoretical NMRD-models are required. To improve the models, they need to be carefully compared, in addition to physico-chemical considerations of molecular and spin dynamics. The comparison is performed by computing the Bayesian evidence in terms of a thermodynamic integral solved with Markov chain Monte Carlo. The result leads to a conclusion of two micelle water-pools, and rules out both less and more parameters, i.e., one and three pools. On the other hand, if only the quality of the fits is considered (i.e., mean square deviation or χ²) a three water-pool model is the best. The latter can be expected since with more adjustable parameters a better fit is more likely. Bayesian evidence is needed to rank the uncertainty of the models, and in order to explain the outcome a notation of Ockham-entropy is defined. The two approximate selection tools, Akaike and Baysian information criterions, may lead to wrong conclusions compared to the full integration. This methodology is expected to be one of several important tools in NMRD model development; however, it is completely general and should find awakened use in many research areas

Prediction of low-field nuclear singlet lifetimes with molecular dynamics and quantum-chemical property surface

Abstract Molecular dynamics and quantum chemistry methods are implemented to quantify nuclear spin-1/2 pair singlet-state relaxation rates for three molecular systems at low magnetic field and room temperature. Computational methodology is developed for weak interactions, particularly important for singlet states at low field. These include spin-rotation and spin-internal-motion effects, which describe the coupling of the spin-carrying nuclei to fluctuating local magnetic fields induced by the overall and internal molecular fluctuations, respectively. A high-dimensional tensor property surface using Kriging interpolation is developed to circumvent costly quantum-chemical calculations. Together with the intramolecular dipolar relaxation, all the simulated relaxation mechanisms are accounted for with a common theoretical framework. Comparison with experiment indicates that quantitative accuracy is obtained, sufficient to enable guidance in the molecular design of molecules with long-lived singlet order

Evaluation of an FPGA for space applications

A new FPGA suitable for space applications has just reached the market. To investigate whether there are any possible flaws or limitations similar to those previously seen on FPGAs, an evaluation has to be done. This master thesis contains the evaluation of this new radhard FPGA with focus on possible design limitations and package related electrical phenomena.Areas evaluated: Ground-/VDD bounce, Cross talk, Rise time sensitivit, Power cycling, Power consumption, Place and route tool, Radiation hardnessThis report contains all steps in the evaluation. From method to measurements, comparisons, theory, results and conclusions. In the evaluation work, special effort has been made to develop designs that really stress the FPGA to find potential problems. All problems found are dealt with in this report.Results: Ground-/VDD bounce measurements showed that devices using a fast slew rate resulted in TTL-level violation. However, by separating sensitive signals and SSOs in different I/O banks it is possible to work around the problem. Cross talk measurements has shown that the phenomena causes problems when using a long rise time input with toggling outputs placed next to the signal. Power cycling did not result in any alarming inrush currents. Regular power up showed an unwanted behaviour with pulses on all I/Os right before power on reset kicked in. When comparing the tool value with measurements regarding power consumption it was clear that it differed as much as 40-50%. The FPGA consumes 40-50% more power than what the power calculator tool estimates

Implementing a receiver in a fast data transfer system : A feasibility study

This report is an outcome of a master degree project at Linköpings University in co-operation with Micronic Laser Systems AB. The purpose with this master degree project was to investigate how to implement a receiver in a data transfer system. The system consists of several data channels, where every channel consists of three parts: driver, transmission lines and receiver. The driver send low amplitude differential signals via the transmission lines to the receiver that amplifies and converts it to a single-ended signal. The receiver has to be fast and be able to feed an output signal with high voltage swing. It is also needed for the receivers to have low power consumption since they are close to the load, which is sensitive to heat. Different amplifier architectures were investigated to find a suitable circuit for the given prerequisites. In this report the advantages and disadvantages of voltage and current feedback are discussed. The conclusions of this work are that in a system with an amplifier as a receiver with differential transmission lines, a single operational amplifier cannot be used. An input stage is needed to isolate the feedback net from the inputs of the operational amplifier. When fast rise time and large output swing are wanted the best amplifier architecture is current feedback amplifiers. A current feedback amplifier in CMOS with the required high voltages and slew rate is hard to realize without very high power consumption

Implicit numerical schemes for the stochastic Liouville equation in Langevin form

We present and numerically test implicit as well as explicit numerical schemes for solving the Stochastic Liouville Equation in Langevin form. It is found that implicit schemes provide significant gain in robustness, for example, when nonsecular Hamiltonian terms cannot be ignored in electron and nuclear spin resonance. Implicit schemes open up several spectroscopic relaxation problems for direct interpretation using the Stochastic Liouville Equation. To illustrate the proposed numerical schemes, studies are presented for an electron paramagnetic resonance problem involving a coordinated copper complex and a fluorescence problem

Gender and Violence against Political Candidates: Lessons from Sri Lanka

A nascent body of literature has highlighted the violence (broadly defined) that women sometimes face as they enter politics. Some interpretations depict this violence as primarily gender motivated: women politicians are targeted because they are women. Another interpretation is that violence in some contexts is an everyday political practice targeting men and women alike. However, because we lack large-scale, systematic comparisons of men's and women's exposure to election violence, we know little about the extent to which—and how—candidate sex shapes this form of violence. We address this research gap by using original survey data on 197 men and women political candidates in the 2018 Sri Lankan local elections. Sri Lanka is a suitable case for analysis because it is a postconflict country in which political violence has been endemic and the number of women candidates has increased rapidly due to gender quota adoption. Overall, we find large similarities in men's and women's exposure to violence, suggesting that violence sometimes is part of a larger political practice. However, we find that women are exposed to forms of intimidation of a sexual nature more often than men. This finding demonstrates the need for gender-sensitive analyses of election violence

A Frequency Triplexer for Ultra-wideband Systems Utilizing Combined Broadside- and Edge-coupled Filters

A fully integrated triplexer for multiband ultra-wideband radio is presented. The triplexer utilizes a microstrip network and three combined broadside- and edge-coupled filters. It is fully integrated in a printed circuit board with low requirements on the printed circuit board process tolerance. Three flat subbands in the frequency band 3.1-4.8 GHz have been achieved. The group delay variation within each 500-MHz subband was measured to be around 1 ns. A good agreement between simulation and measurement was obtained.©2009 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. Magnus Karlsson, Pär Håkansson and Shaofang Gong, A Frequency Triplexer for Ultra-wideband Systems Utilizing Combined Broadside- and Edge-coupled Filters, 2008, IEEE Transactions on Advanced Packaging, (31), 4, 794-801.http://dx.doi.org/10.1109/TADVP.2008.2004415microstrip components, multiplexing equipment , ultra wideband communicatio