Stretched Non-negative Matrix Factorization

An algorithm is described and tested that carries out a non negative matrix factorization (NMF) ignoring any stretching of the signal along the axis of the independent variable. This extended NMF model is called StretchedNMF. Variability in a set of signals due to this stretching is then ignored in the decomposition. This can be used, for example, to study sets of powder diffraction data collected at different temperatures where the materials are undergoing thermal expansion. It gives a more meaningful decomposition in this case where the component signals resemble signals from chemical components in the sample. The StretchedNMF model introduces a new variable, the stretching factor, to describe any expansion of the signal. To solve StretchedNMF, we discretize it and employ Block Coordinate Descent framework algorithms. The initial experimental results indicate that StretchedNMF model outperforms the conventional NMF for sets of data with such an expansion. A further enhancement to StretchedNMF for the case of powder diffraction data from crystalline materials called Sparse-StretchedNMF, which makes use of the sparsity of the powder diffraction signals, allows correct extractions even for very small stretches where StretchedNMF struggles. As well as demonstrating the model performance on simulated PXRD patterns and atomic pair distribution functions (PDFs), it also proved successful when applied to real data taken from an in situ chemical reaction experiment.Comment: 39 pages, 16 figure

Trace CO2 capture by an ultramicroporous physisorbent with low water affinity.

CO2 accumulation in confined spaces represents an increasing environmental and health problem. Trace CO2 capture remains an unmet challenge because human health risks can occur at 1000 parts per million (ppm), a level that challenges current generations of chemisorbents (high energy footprint and slow kinetics) and physisorbents (poor selectivity for CO2, especially versus water vapor, and/or poor hydrolytic stability). Here, dynamic breakthrough gas experiments conducted upon the ultramicroporous material SIFSIX-18-Ni-β reveal trace (1000 to 10,000 ppm) CO2 removal from humid air. We attribute the performance of SIFSIX-18-Ni-β to two factors that are usually mutually exclusive: a new type of strong CO2 binding site and hydrophobicity similar to ZIF-8. SIFSIX-18-Ni-β also offers fast sorption kinetics to enable selective capture of CO2 over both N2 (S CN) and H2O (S CW), making it prototypal for a previously unknown class of physisorbents that exhibit effective trace CO2 capture under both dry and humid conditions

Human-animal chimeras for vaccine development: an endangered species or opportunity for the developing world?

<p>Abstract</p> <p>Background</p> <p>In recent years, the field of vaccines for diseases such as Human Immunodeficiency Virus (HIV) which take a heavy toll in developing countries has faced major failures. This has led to a call for more basic science research, and development as well as evaluation of new vaccine candidates. Human-animal chimeras, developed with a 'humanized' immune system could be useful to study infectious diseases, including many neglected diseases. These would also serve as an important tool for the efficient testing of new vaccine candidates to streamline promising candidates for further trials in humans. However, developing human-animal chimeras has proved to be controversial.</p> <p>Discussion</p> <p>Development of human-animal chimeras for vaccine development has been slowed down because of opposition by some philosophers, ethicists and policy makers in the west-they question the moral status of such animals, and also express discomfort about transgression of species barriers. Such opposition often uses a contemporary western world view as a reference point. Human-animal chimeras are often being created for diseases which cause significantly higher morbidity and mortality in the developing world as compared to the developed world. We argue in our commentary that given this high disease burden, we should look at socio-cultural perspectives on human-animal chimera like beings in the developing world. On examination, it's clear that such beings have been part of mythology and cultural descriptions in many countries in the developing world.</p> <p>Summary</p> <p>To ensure that important research on diseases afflicting millions like malaria, HIV, Hepatitis-C and dengue continues to progress, we recommend supporting human-animal chimera research for vaccine development in developing countries (especially China and India which have growing technical expertise in the area). The negative perceptions in some parts of the west about human-animal chimeras can be used as an opportunity for nurturing important vaccine development research in the developing world.</p

The social life of a strategy document

Strategy documents are curious artefacts of the modern organisation. They represent formal strategic planning processes that have come under criticism, in part for not representing the emergent strategy path that organisations follow in practice. This criticism of formal planning’s efficacy has coincided with a marked decline of research output in this field. This is at odds with the practice world of strategy, where formal strategic planning has become a hallmark of good governance. A Strategy-as-Practice (S-a-P) stream of research has emerged over the last fifteen years to counter this divide between theory and practice and has largely focused on the micro-practices of strategy making. This study is firmly rooted in this tradition of looking at the micro-practices of strategy work to offer novel explication on new ways of organising. This study follows the social life of a strategy document in an institute of higher education from its initial conception, writing, consultation and use, to understand the role these curious documents play in organisational life. Philosophically, this work is inductive, phenomenological, and interpretive. As a process, it presents an ethnography of strategy making, an autoethnography of strategy consultations, a deconstruction of the strategy text produced as an output, and interviews with all those in and around the strategy document’s life in the organisation. Themes of power and dramaturgy emerged in the exploration of strategy making that are further developed by reflecting on how the strategy interacts with organisational life. The tightly controlled and somewhat inauthentic strategy-making, reveals a surprising emancipatory aspiration that is reflected through the strategy in use. These findings question the the lack of focus on the concept of power in the strategy research agenda. The work follows a single strategy document’s life and therefore has a limited claim to generalisability, however, in presenting an all-encompassing view of strategy work through the strategy document, the work presents a totalising account of the role of this document in an organisation. This is a coherent account of the social life of a strategy document from in inception to its life in the organisation. The work adds to an emerging critical perspective on strategy practices and is of interest to managers and strategists alike in considering the process of writing, consulting and calling upon their strategy documents. The study adds a new perspective to the meaning of strategy work in the modern ideal of the university. Keywords: Strategy-as-Practice, Open Strategy, Higher Education Strategy, Ethnograph

Interpenetrated hybrid ultramicroporous materials: insight into structure-property relationships

Crystal Engineering is the field of chemistry that studies the design, properties, and application of crystalline materials. An aspect of crystal engineering is the design of coordination networks using linker ligands that cross-link transition metal nodes. Coordination networks that can exhibit permanent porosity have attracted attention for their potential application in gas storage, separation, and catalysis. In the context of separations, 15% of global energy costs are associated with separation of chemical commodities. That some coordination networks are inherently modular through node/linker substitution enables crystal engineering studies that can provide insight into structure-function relationships. Square lattice (sql) coordination networks were perhaps the first class of coordination networks to undergo systematic study; thanks mainly to their propensity to form from many nodes and linkers. Further, some sql coordination networks can be pillared to afford primitive cubic (pcu) coordination networks, offering modularity that, in principle, has at least four variables: node, linker, pillar, interpenetration. A class of pillared sql coordination networks known as Hybrid Ultramicroporous Materials (HUMs) has recently set new benchmarks for several important gas separations thanks to their ultramicropores (≤0.7 nm) which are lined by inorganic pillars that can act as molecular traps for small gas molecules. For example, ethylene (C2H4) is the highest volume chemical feedstock and contains ca. 1% acetylene (C2H2) impurities that must be removed. The goal herein is to conduct crystal engineering studies of interpenetrated HUMs in the context of C2H2/C2H4 gas separations and hydrolytic stability. The insight found herein may afford better design principles for future porous coordination networks in terms of performance and stability. Chapter 1 introduces crystal engineering, coordination networks, and HUMs. Chapter 2 addresses the C2H2/C2H4 separation performance of the two-fold interpenetrated pcu (pcu-c) HUM, SIFSIX-14-Cu-i ([Cu(1,2-bis(4- pyridyl)diazene)2(SiF6)]n). Sorption-based gas separation/purification is hindered by a general inverse relationship between selectivity and uptake capacity in porous materials. Ideal molecular sieves could be a compromise with pores that block larger gas molecules and adsorb high quantities of smaller gas molecules. SIFSIX-14-Cu-i has ultramicropores (3.4 Å) that effectively exclude C2H4 molecules but is constructed from SiF6 2- pillars yielding benchmark C2H2 uptake (58 cm3 cm-3 at 0.01 bar) and selectivity at 298 K (>6000 vs 44 for the previous benchmark, SIFSIX-2-Cu-i ([Cu(1,2-bis(4- pyridyl)acetylene)2(SiF6)]n)). Dynamic gas breakthrough studies further confirm separation performance with an effluent C2H4 production of 87.5 mmol/g (99.9999% pure) and capturing 1.18 mmol/g C2H2 per cycle. Chapter 3 reports on the rare and poorly understood phenomenon of partial interpenetration and its potential relevance to gas separations as it could, in principle, enable an increase in uptake capacity without reducing selectivity. Systematic synthesis afforded solid solutions of SIFSIX-14-Cu-i and its non-interpenetrated pcu polymorph SIFSIX-14-Cu. Solid solutions exhibited proportions of two-fold interpenetration ranging from 70-99%. C2H2/C2H4 gas separation studies reveal that partial interpenetration negatively affects separation performance and is attributed to a reduction in the bulk density of C2H2 molecular traps. Chapter 4 details the study of linker and pillar substitution, enabling greater understanding of how subtle differences in structure may affect properties. The pcu-c HUMs TIFSIX-2-Cu-i ([Cu(1,2-bis(4-pyridyl)acetylene)2(TiF6)]n) and TIFSIX-4-Cu-i ([Cu(1,4-bis(4-pyridyl)benzene)2(TiF6)]n) demonstrate that variations in linkers and pillars can affect C2H2/C2H4 separation performances. Whereas TiF6 2- pillars impart stronger electrostatics and improved performance in TIFSIX-2-Cu-i (compared with SIFSIX-2-Cu-i), the longer ligand in TIFSIX-4-Cu-i leads to larger pores and weaker sorbent-sorbate interactions. Indeed, TIFSIX-4-Cu-i exhibits offset interpenetration resulting in two types of pores. Gas sorption studies of TIFSIX-4-Cu-i exhibited a stepped isotherm as a result of sequential pore filling. Chapter 5 continues the study of linker/pillar substitution, with TIFSIX-14-Cu-i ([Cu(1,2-bis(4-pyridyl)diazene)2(TiF6)]n) and NbOFFIVE-2-Cu-i ([Cu(1,2-bis(4- pyridyl)acetylene)2(NbOF5)]n), and its effect on C2H2/C2H4 gas separations. Although these pillars would be expected to afford the strongest electrostatics, an evaluation of bond lengths reveals that subtle pore size effects can be more influential. This observation leads to the conclusion that there is an optimal balance between pore size and pore chemistry that yields benchmark performances. Chapter 6 reports water vapour sorption in four hybrid materials; benchmarks for C2H2 capture (SIFSIX-14-Cu-i, SIFSIX-2-Cu-i, and SIFSIX-1-Cu) and CO2 capture (SIFSIX-3-Ni). The effects of water vapour on performance and stability remain understudied, despite practical relevance. Three materials exhibit a negative-water vapour-sorption phenomenon wherein adsorbed vapour uptake decreases as pressure increases and is attributed to a water-vapour-induced phase transformation, where initial structures convert to sql or interpenetrated square lattices (sql-c*). Although studied, the mechanisms by which coordination networks change degrees and modes of interpenetration are not understood. SIFSIX-2-Cu-i retained its structure leading to an understanding of the interactions controlling hydrolytic stability. Chapter 7 extends the study of water vapour sorption with SIFSIX-7-Cu, TIFSIX-7-Cu, and GEFSIX-7-Cu ([Cu(1,2-bis(4-pyridyl)ethylene)2(MF6)]n; M = Si, Ti, Ge). Water vapour adsorption is observed to lead each compound to undergo the pcu to sql-c* phase transformation at different relative humidity levels, underlining the different interaction strengths imparted by each pillar. Further, a structural analysis suggests that the close packing of the sql-c* phase may inhibit structures with longer ligands from undergoing this irreversible phase transformation. Chapter 8 offers a conclusion to the crystal engineering of interpenetrated HUMs reported herein and looks towards possible future directions. The synthesis of solid solutions and substitution of linkers and pillars provide an understanding of structure-property relationships in C2H2/C2H4 gas separations and water vapour sorption with a view to designing future porous coordination networks with improved performance and stability

An economic analysis of public versus private provision of health services in Ireland

Governments everywhere are under pressure to deliver service to the community in a situation where the expectation of the population is growing and the public finances are static or falling. To address this problem many regimes seek to increase their financial base by encouraging the private sector to become involved in areas of service delivery which had previously been the preserve of the public sector. The advent of the Private Finance Initiative in the United Kingdom in the early 1990s, which morphed into the Public Private Partnership, was one method of selling to the public the idea of private involvement in public service delivery. Many believed this was a positive development. Others thought this was the private sector putting its hand into the public purse with no other motive than to enrich itself. This thesis asks: Does it matter who owns the means of delivery? The most efficient method of delivery is surely the one which costs the taxpayer the least and conveys the best product to the public in terms of quality. Delivery of health services is not simple. Indeed to speak of a ‘health service’ as one homogeneous product is to misunderstand the nature of the service. It is a range of services delivered to a range of people in a range of different settings, some of which are appropriate and some of which are not. Each individual service to each individual patient is a unique transaction. Countries such as the United Kingdom, Sweden and New Zealand have all made efforts to dramatically change the public service delivery of health care. Most have found changes to be problematic and some have returned to the public service model. In this thesis we test the issue of ownership in cases where the comparison can be made and look at the occasions where attempts were made to introduce the private sector into the public delivery of health, and assess whether or not the experiments were for the good or to the detriment of the stakeholders in the Irish context. We look first at the international situation to put the subject in context. Then we lay out our theoretical framework. We contemplate the infusion of private sector involvement in public service delivery. This is followed by our cases of comparison between the public and private sectors. Today Ireland’s spending on health as a percentage of Gross Domestic Product is such that we could expect a world class service. Our findings suggest that a cautious approach should be taken by policy makers but the expectation of the public and the diminishing nature of public finances means that innovative, tailored and sector specific solutions to the many difficulties in the services will need to be crafted. This thesis is a unique examination of the public and private delivery of health care in Ireland and contributes the first analysis of the current situation

Sexual violence and restorative practices in Belgium, Ireland and Norway: a thematic analysis of country variations

The article compares and contrasts the provision of some restorative practices in cases of sexual violence in three European countries: Belgium, Ireland and Norway. It begins by briefly outlining efforts to address the ‘justice gap’ experienced by victims of sexual violence within conventional justice systems. The article points to calls for the development of alternative or complementary innovative justice responses to sexual violence. It suggests that restorative justice advocates believe they can deliver a participatory, empowering and flexible form of restorative justice, which can run in tandem with conventional criminal justice processes. However, it is noted that the application of restorative approaches to cases of sexual violence has engendered some controversy. The article points to considerable inter-country divergence in the extent to which restorative justice is accessible to victims of sexual crimes and to the emergence of country-specific patterns in the provision of restorative justice in cases of sexual violence