Compression Theorems for Periodic Tilings and Consequences

We consider a weighted square-and-domino tiling model obtained by assigning real number weights to the cells and boundaries of an n-board. An important special case apparently arises when these weights form periodic sequences. When the weights of an nm-tiling form sequences having period m, it is shown that such a tiling may be regarded as a meta-tiling of length n whose weights have period 1 except for the first cell (i.e., are constant). We term such a contraction of the period in going from the longer to the shorter tiling as period compression . It turns out that period compression allows one to provide combinatorial interpretations for certain identities involving continued fractions as well as for several identities involving Fibonacci and Lucas numbers (and their generalizations)

Rock fracture under static stress conditions

A knowledge of the strength of a material is an essential prerequisite to the successful design of a structure in that material. Consequently, in designing deep level mining excavations and large civil engineering structures, an understanding of the mechanics of rock fracture, particularly under compressive stress conditions, is of fundamental importance. This thesis contains details of an investigation into the applicability of Griffith's brittle fracture theory, modified to account for the effects of crack closure in compression, to the prediction of rock fracture behaviour. It is shown that this theory provides a reliable basis for the analysis of hard rock fracture under static stress conditions. The application of the Griffith's theory to the prediction of rock fracture initiation and propagation in a complex stress field is illustrated by means of a detailed analysis of the behaviour of the rock around a circular hole in a biaxial stress field. While this study is primarily concerned with rock fracture problems associated with deep level mining, it is believed that the general principles are equally useful in the analysis of rock and concrete fracture problems encountered in civil engineering

Chemical Symmetry Breaking

This book entitled “Chemical Symmetry Breaking” is a collective volume of state-of-the-art reports on unique nonlinear chemical and physical symmetry-breaking phenomena that were experimentally observed upon a thermally or photochemically induced phase transition in various organic condensed phases, such as metastable liquid crystals, crystals, amorphous solids, and colloidal polymer materials, only under nonequilibrium conditions. Each author summarizes the introductory section in simple terms but in detail for beginners in this field. We wish that many readers familiarize themselves with the general concepts and features of nonlinear and nonequilibrium (or out of equilibrium) complexity theory, which govern a variety of unique dynamic behaviors observed in chemistry, physics, life science and other fields, so that they may discover novel symmetry-breaking phenomena in their own research areas

Modelling of fluid flow through packed beds and application in water treatment processes

Filtration is a process for the removal of solid particles from a suspension (a two-phase system containing particles in a fluid) by the passage of the suspension through a porous medium, yet comprehensive analysis of the microscale fluid dynamics during the process is still incomplete. In this study, a combined Lattice Boltzmann Method (LBM) and Discrete Element Method (DEM) based on spherical and elliptical particles are developed to conduct microscale investigations of the fluid dynamics during the filtration processes. Firstly, the developed LBM-DEM model is used to describe fluid flow over the spherical sand particles surface in the sand filtration process. Critical flow velocity is introduced as the balance between hydrodynamic and adhesive torques acting on the sand particle surface. Furthermore, effective filter surface (EFS), is defined as the area where the velocity near sand particles surface is less than the critical flow velocity. Then the LBM-DEM model simulates the dynamic membrane spherical particles deposition and resuspension on the microfiltration (MF) membrane surface. For the DM particles deposition process, a critical and a threshold particle mass proportion (PMP) and fluid inlet velocity (V) are identified under the given conditions. For the DM particles resuspension process, the time (T) required for the DM resuspension at 100% as a function of DM thickness (L) and backwash velocity (Vf,b) is derived. Moreover, the LBM-DEM is further developed to simulate the fluid flow through elliptical particle beds. Firstly, the LBM-DEM model studied the fluid flow through mono-size elliptical particle packings, where a set of drag force correlations are proposed. Then the LBM-DEM model simulated fluid flow through binary-sized elliptical particle packings, where a generalized hydraulic tortuosity correlation is proposed. Lastly, the LBM-DEM model was applied in simulating the fluid flow through an asymmetric ceramic microfiltration membrane, where the asymmetric structure was represented by DEM simulated elliptical particles packed beds. A new asymmetric ceramic MF membrane intrinsic permeability correlation as a function of pore size, porosity and layer thickness is derived. The developed LBM-DEM model provides a useful tool for microscale understanding of the fluid dynamics, such as fluid velocity profile, drag force, hydraulic tortuosity and permeability of the filtration process

Plant phenolics and absorption features in vegetation reflectance spectra near 1.66μm

AbstractPast laboratory and field studies have quantified phenolic substances in vegetative matter from reflectance measurements for understanding plant response to herbivores and insect predation. Past remote sensing studies on phenolics have evaluated crop quality and vegetation patterns caused by bedrock geology and associated variations in soil geochemistry. We examined spectra of pure phenolic compounds, common plant biochemical constituents, dry leaves, fresh leaves, and plant canopies for direct evidence of absorption features attributable to plant phenolics. Using spectral feature analysis with continuum removal, we observed that a narrow feature at 1.66μm is persistent in spectra of manzanita, sumac, red maple, sugar maple, tea, and other species. This feature was consistent with absorption caused by aromatic CH bonds in the chemical structure of phenolic compounds and non-hydroxylated aromatics. Because of overlapping absorption by water, the feature was weaker in fresh leaf and canopy spectra compared to dry leaf measurements. Simple linear regressions of feature depth and feature area with polyphenol concentration in tea resulted in high correlations and low errors (% phenol by dry weight) at the dry leaf (r2=0.95, RMSE=1.0%, n=56), fresh leaf (r2=0.79, RMSE=2.1%, n=56), and canopy (r2=0.78, RMSE=1.0%, n=13) levels of measurement. Spectra of leaves, needles, and canopies of big sagebrush and evergreens exhibited a weak absorption feature centered near 1.63μm, short ward of the phenolic compounds, possibly consistent with terpenes. This study demonstrates that subtle variation in vegetation spectra in the shortwave infrared can directly indicate biochemical constituents and be used to quantify them. Phenolics are of lesser abundance compared to the major plant constituents but, nonetheless, have important plant functions and ecological significance. Additional research is needed to advance our understanding of the spectral influences of plant phenolics and terpenes relative to dominant leaf biochemistry (water, chlorophyll, protein/nitrogen, cellulose, and lignin)

Validation of Nanosecond Pulse Cancellation Using a Quadrupole Exposure System

Nanosecond pulsed electric fields (nsPEFs) offer a plethora of opportunities for developing integrative technologies as complements or alternatives to traditional medicine. Studies on the biological effects of nsPEFs in vitro and in vivo have revealed unique characteristics that suggest the potential for minimized risk of complications in patients, such as the ability of unipolar nsEPs to create permanent or transient pores in cell membranes that trigger localized lethal or non-lethal outcomes without consequential heating. A more recent finding was that such responses could be diminished by applying a bipolar pulse instead, a phenomenon dubbed bipolar cancellation, paving the way for greater flexibility in nsPEF application design. Transitioning nsPEFs into practical use, however, has been hampered by both device design optimization and the intricacies of mammalian biology. Generating electric fields capable of beneficially manipulating human physiology requires high-voltage electrical pulses of nanosecond duration (nsEPs) with high repetition rates, but pulse generator and electrode design in addition to the complex electrical properties of biological fluids and tissues dictate the strength range and distribution of the resulting electric field. Faced with both promising and challenging aspects to producing a biomedically viable option for inducing a desired nsPEF response that is both focused and minimally invasive, the question becomes: how can the distinct features of unipolar and bipolar nsPEF bioeffects be exploited in a complex electrode exposure system to spatially modulate cell permeabilization? This dissertation presents a systematic study of an efficient coplanar quadrupole electrode nsPEF delivery system that exploits unique differences between unipolar and bipolar nsPEF effects to validate its ability to control cell responses to nsPEFs in space. Four specific aims were established to answer the research question, with specific attention to the roles played by pulse polarity, grounding configuration and electric field magnitude in influencing nsPEF stimulation of electropermeabilization in space. Using a prototype wire electrode applicator charged by a custom-built multimodal pulse generator, the aims were to spatially quantifyelectropermeabilization due (1) unipolar and (2) bipolar nsPEF exposure, to (3) apply synchronized pulses with a view to canceling bipolar cancellation (CANCAN) through superposition that could shift the effective nsPEF response, and to (4) evaluate the ability of the quadrupole system to facilitate remote nsPEF electropermeabilization. Numerical simulations were employed to approximate the nsPEF distribution for a two-dimensional (2-D) area resulting from unipolar, bipolar or CANCAN exposure in a varied-pulse quadrupole electrode configuration. For all experiments, the independent variables were fixed for pulse width (600 ns), pulse number (50) and repetition rate (10 Hz). Electropermeabilization served as the biological endpoint, with green fluorescence due to cell uptake of the nuclear dye YO-PRO-1® (YP1) tracer molecule serving the response variable. An agarose-based 3-D tissue model was used to acquire, quantify and compare fluorescence intensity data in vitro, which was measured by stereomicroscopy to enable macro versus micro level 2-D visualization. Results of this investigation showed that increasing the magnitude of the applied voltage shifts unipolar responses from localization at the anodal to cathodal electrode, and that adding a second proximal ground electrode increases the response area. Bipolar nsPEF responses were generally less intense than unipolar, but these depended on both the inter-electrode location measured and amplitude of the second phase. CANCAN preliminary indicated some ability to decrease strong uptake at electrodes, but evaluation across experimental and published data indicate that greater differences between unipolar and bipolar responses are needed to improve possibilities for distal stimulation. Overall, this work demonstrated the potential for more complex pulser-electrode configurations to successfully modulate nsPEF electropermeabilization in space by controlling unipolar and bipolar pulse delivery and contributed to a deeper understanding of bipolar cancellation. By providing a set of metrics for test and evaluation, the data provided herein may serve to inform model development to support prediction of nsPEF outcomes and help to more acutely define spatial-intensity relationships between nsPEFs and cell permeabilization as well as delineate requirements for future non-invasive nsPEF therapies

Development of a suite of bioinformatics tools for the analysis and prection of membrane protein structure.

This thesis describes the development of a novel approach for prediction of the three-dimensional structure of transmembrane regions of membrane proteins directly from amino acid sequence and basic transmembrane region topology.The development rationale employed involved a knowledge-based approach. Based on determined membrane protein structures, 20x20 association matrices were generated to summarise the distance associations between amino acid side chains on different alpha helical transmembrane regions of membrane proteins. Using these association matrices, combined with a knowledge-based scale for propensity for residue orientation in transmembrane segments (kPROT) (Pilpel et al., 1999), the software predicts the optimal orientations and associations of transmembrane regions and generates a 3D structural model of a given membrane protein, based on the amino acid sequence composition of its transmembrane regions. During the development, several structural and biostatistical analyses of determined membrane protein structures were undertaken with the aim of ensuring a consistent and reliable association matrix upon which to base the predictions. Evaluation of the model structures obtained for the protein sequences of a dataset of 17 membrane proteins of determined structure based on cross-validated leave-one-out testing revealed general1y high accuracy of prediction, with over 80% of associations between transmembrane regions being correctly predicted. These results provide a promising basis for future development and refinement of the algorithm, and to this end, work is underway using evolutionary computing approaches. As it stands, the approach gives scope for significant immediate benefit to researchers as a valuable starting point in the prediction of structure for membrane proteins of hitherto unknown structure.Tese (Doutorado em Filosofia) - University of Bedfordshire