The effect of structure directing agents on the ordering of fluoride ions in pure silica MFI zeolites

The authors would like to thank Keele University and the University of St Andrews for providing a PhD studentship for SLB. PW would like to thank the EPSRC for funding (EP/E041825/1). RJD would like to thank Prof. Colin Fyfe of the University of British Columbia for useful discussions and for providing NMR spectrometer time for initial results.The effect of different sizes of structure directing agents on the ordering of the fluoride ions in pure silica MFI zeolites has been determined using magic angle spinning solid state NMR. By synthesizing fluoride containing pure silica MFI zeolites using methyltributylammonium cations as the structure directing agent, it has been possible to change the type of ordering seen for the fluoride ions at room temperature from the previously reported dynamic to static disorder. An initial mechanism for how this fluoride ordering occurs is suggested based upon the coulombic interaction between the positive charge on the nitrogen and the negative fluoride ion, within the zeolite framework, with different sizes of tetraalkylammonium cations.Publisher PDFPeer reviewe

An algorithm for counting circuits: application to real-world and random graphs

We introduce an algorithm which estimates the number of circuits in a graph as a function of their length. This approach provides analytical results for the typical entropy of circuits in sparse random graphs. When applied to real-world networks, it allows to estimate exponentially large numbers of circuits in polynomial time. We illustrate the method by studying a graph of the Internet structure.Comment: 7 pages, 3 figures, minor corrections, accepted versio

Numerical techniques in digital microscopic holographic particle image velocimetry

Digital microscopic holographic particle image velocimetry (DµHPIV) is a technique which records scattered coherent light and uses it to measure displacement of particles in a fluid flow. The work in this thesis begins with the construction of a digital holographic microscope and explores the different possible methods of recording and holographic reconstruction, finding an off-axis forward-scatter geometry to be most suitable for the task. A comparison follows of methods to measure displacement in a sparsely seeded environment by performing a simple experiment. It finds that complex amplitude correlation performs significantly better than both intensity correlation and nearest neighbour analysis; the two other possible methods of displacement tracking. Later, an experiment is performed to investigate the behaviour of a microfluidic blood separator. The separator is intended to remove blood plasma from whole blood without other contaminants such as red blood cells and without the need for expensive laboratory equipment. In this chapter a new technique, higher order correlation, is introduced which can be used to strengthen the peaks in correlations of three or more particle images in a flow, and a potential flow CFD model of the separator is built from scratch to predict whether the separator will work, and against which the results can be compared. Finally, there is an experiment carried out which for the first time allows aberration free imaging within objects with irregular, highly curved surfaces; in this case optical fibres and inkjet droplets, by numerically reconstructing the droplet surface.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Ising Model on Networks with an Arbitrary Distribution of Connections

We find the exact critical temperature $T_c$ of the nearest-neighbor ferromagnetic Ising model on an `equilibrium' random graph with an arbitrary degree distribution $P(k)$. We observe an anomalous behavior of the magnetization, magnetic susceptibility and specific heat, when $P(k)$ is fat-tailed, or, loosely speaking, when the fourth moment of the distribution diverges in infinite networks. When the second moment becomes divergent, $T_c$ approaches infinity, the phase transition is of infinite order, and size effect is anomalously strong.Comment: 5 page

Self-organization of collaboration networks

We study collaboration networks in terms of evolving, self-organizing bipartite graph models. We propose a model of a growing network, which combines preferential edge attachment with the bipartite structure, generic for collaboration networks. The model depends exclusively on basic properties of the network, such as the total number of collaborators and acts of collaboration, the mean size of collaborations, etc. The simplest model defined within this framework already allows us to describe many of the main topological characteristics (degree distribution, clustering coefficient, etc.) of one-mode projections of several real collaboration networks, without parameter fitting. We explain the observed dependence of the local clustering on degree and the degree--degree correlations in terms of the ``aging'' of collaborators and their physical impossibility to participate in an unlimited number of collaborations.Comment: 10 pages, 8 figure

Introducing the student designer to the role of emotion in design

Products satisfy needs beyond the functional. These needs may include aspirations, emotions, cultural and social needs. It is crucial that designers are equipped to deal with the emotional domain of products and users. Carlson (1997) considered emotion to be short term waves of feeling arising without conscious effort, whereas mood, is defined as a longer termed state with less intensity. The authors’ working definition of the ‘emotional domain’ is the range of states of mind (which may influence the body) and which are influenced by internal and external stimuli. These effects tend to be transient although an individual will have a tendency towards a particular state, such as melancholy, happiness, calmness and so on. But even here various stimuli can cause a significant swing in state of mind. But this is a highly individual effect for example, one person may find the new iMac computer delightful and cheerful, where as others, may find it irritating and repulsive

The role of electronic triplets and high-lying singlet states in the deactivation mechanism of the parent BODIPY: An ADC(2) and CASPT2 study

The potential tunability of the spectroscopic properties of the BODIPY parent dye by suitable functionalization makes it attractive for a number of applications. Unfortunately, its strong fluorescence against minor intersystem crossing to the triplet states prevents its application in photodynamic therapy. With the perspective of designing BODIPY derivatives with enhanced intersystem crossing, the goal of this work is two-fold: (i) investigate the main deactivation channels of the parent BODIPY following irradiation, paying particular attention to the accessibility of the triplet state potential energy surfaces, as well as the non-radiative pathways involving the second brightest more stable singlet electronic state, S2, and (ii) evaluate the performance of the computationally efficient second order algebraic-diagrammatic construction scheme for the polarization propagator, (ADC(2)) against the complete active space second-order perturbation theory (CASPT2) method. Three singlet/triplet crossings were found, all of them with small spin-orbit couplings, being the S1/T2 crossing the most plausible for the observed intersystem crossing yield. Methodologically, it is found that the ADC(2) method qualitatively reproduces the landscape of the potential energy profiles for the photophysical processes investigated; however, it systematically underestimates the energies of the stationary points and crossings of the same and different multiplicity, with the largest discrepancies found at S1/S0 crossing points. Our CASPT2 results provide a comprehensive picture of the landscape of the excited state potential energy surfaces of the parent BODIPY that might serve as a basis for the rational design of photosensitizers with a particular photophysical profileThis work has been supported by the Project CTQ2015-63997- C2 of the Ministerio de Economía y Competitividad of Spain. I.C. gratefully acknowledges the “Ramón y Cajal” program of the Ministerio de Economía y Competitividad of Spain. M.D.V. thanks the Marie Curie Actions, within the Innovative Training Network-European Join Doctorate in Theoretical Chemistry and Computational Modelling TCCM-ITN-EJD-642294, for financial suppor

Finding long cycles in graphs

We analyze the problem of discovering long cycles inside a graph. We propose and test two algorithms for this task. The first one is based on recent advances in statistical mechanics and relies on a message passing procedure. The second follows a more standard Monte Carlo Markov Chain strategy. Special attention is devoted to Hamiltonian cycles of (non-regular) random graphs of minimal connectivity equal to three

6-Deoxyhexoses froml-Rhamnose in the Search for Inducers of the Rhamnose Operon: Synergy of Chemistry and Biotechnology

In the search for alternative non‐metabolizable inducers in the l ‐rhamnose promoter system, the synthesis of fifteen 6‐deoxyhexoses from l ‐rhamnose demonstrates the value of synergy between biotechnology and chemistry. The readily available 2,3‐acetonide of rhamnonolactone allows inversion of configuration at C4 and/or C5 of rhamnose to give 6‐deoxy‐d ‐allose, 6‐deoxy‐d ‐gulose and 6‐deoxy‐l ‐talose. Highly crystalline 3,5‐benzylidene rhamnonolactone gives easy access to l ‐quinovose (6‐deoxy‐l ‐glucose), l ‐olivose and rhamnose analogue with C2 azido, amino and acetamido substituents. Electrophilic fluorination of rhamnal gives a mixture of 2‐deoxy‐2‐fluoro‐l ‐rhamnose and 2‐deoxy‐2‐fluoro‐l ‐quinovose. Biotechnology provides access to 6‐deoxy‐l ‐altrose and 1‐deoxy‐l ‐fructose

Statistical Mechanics of maximal independent sets

The graph theoretic concept of maximal independent set arises in several practical problems in computer science as well as in game theory. A maximal independent set is defined by the set of occupied nodes that satisfy some packing and covering constraints. It is known that finding minimum and maximum-density maximal independent sets are hard optimization problems. In this paper, we use cavity method of statistical physics and Monte Carlo simulations to study the corresponding constraint satisfaction problem on random graphs. We obtain the entropy of maximal independent sets within the replica symmetric and one-step replica symmetry breaking frameworks, shedding light on the metric structure of the landscape of solutions and suggesting a class of possible algorithms. This is of particular relevance for the application to the study of strategic interactions in social and economic networks, where maximal independent sets correspond to pure Nash equilibria of a graphical game of public goods allocation