1,782 research outputs found
Gordon Campbell Talking
No full textG. Campbell talking to faculty in Education House. Left to right: unidentified, W. Schulz, G. Campbell, Miss G.D. Pentland, Mrs. E.M. Flood.
Photograph SC-085 - SC-094 are of a tour of the College by the Principal and charter faculty of the College taken by an unidentified photographer. Faculty in these pictures are:
Gordon Campbell is/was Principal
Mrs. E.M. Flood is/was French instructor
Miss G.D. Pentland is/was Chairman, Biology Dept.
W. Schulz is/was Chairman, Physics Dept
High pressure behaviour of AIP04-5 in penetrating/ non penetrating pressure medium
No full textAluminophosphate are objects of a growing research interest due to their potential technologieal and industriaI applications [e.g 1,2]. Their large channels serve as ideaI host for organie compounds and small polymers. Among those, AIP0-5 is a synthetic zeolite characterized by an open-framework of (P,AI)O4 tetrahedra. The tetrahedra are connected to form six-and twelve-membered rings, in such a way that a large channel (0~7.3À), parallel to the [001] direction, occurs. Klap et al. [3] underlines that every crystal of AIP0-5 is built up by three different microdomains, in which the positions of the framework oxygen atoms are slightly different; the main effect of the structural disorder is the very large anisotropie displacement parameters of the framework oxygens. We performed two in situ single-crystal synchrotron X-ray diffraction experiments using both penetrating (methanol:ethanol:H20 mix, m:e:w) and non-penetrating (silicon oil) pressure media [4]. The structure refinements showed that: 1) for compression in m:e:w mix, H20 molecules are absorbed at low-P regime, forming a H20-network by H-bonding interaction; 2) the elastic parameters of the super-hydrated AIP04 5 are different if compared to the one compressed in silicon oil; 3) the structural deformation mechanisms of super-hydrated and regular AIP04 -5 are different; 4) evidence of a incommensurately modulated structure occur (according to [3]), and there is an evolution of the non-Bragg reflections with pressure.
The author acknowledges the ltalian Ministry of Education, MIUR-Project: "Futuro in Ricerca 2012 -ImPACT-RBFR12CLQD".
[lJ Tang Z.K. et al. Applied Physies Letters 1998; 73, 2287-2289.
[2] Yang W.S. et al. Microporous and mesoporous materials 20i6; 219,87-92. [3J Klap G.J. et al. Mieroporous and mesoporous materials 2000; 38,403-412. [4J Gatta, G.D. Mieroporous and Mesoporous Material 2010; 128, 78-84
F.C. Hawthorne, Landmark papers : structure topology
No full textIn this second volume of the Mineralogical Society’s ‘Landmark’ series, Prof. Frank Hawthorne has selected a number of key papers, some of which are true milestones of mineralogy and crystallography, showing the acceleration of research and the increase in knowledge in the field of crystal-chemistry. The papers follow in chronological sequence, allowing the reader to see how crystallography and, particularly, mineralogy have evolved during the last 80 years. He has chosen the papers on the basis of three related aspects: (a) the nature of chemical bonds, and (b) their relation to bond topology, leading to (c) the prediction of bond topologies and their hierarchical organization. His commentaries on the selected papers provided a coherent narrative thread running through the volume. In the first chapter ‘Bond topology and Minerals’, Hawthorne reviews the long history of the mineralogy and crystallography, reporting the evolution of the knowledge and the experimental findings in the last 2,000 years. The author introduces the mathematical concept of topology and how to use this tool for the description of the structural configuration in crystals. In addition, he discusses the motivation of mineralogists for understanding and developing principles of bond topology. In chapter 2, two milestone papers by Linus Pauling (both published in 1929) on the structure of complex ionic crystals are reported and enriched with comments. Chapter 3 is devoted to a further milestone paper for mineralogy written by W.L. Bragg (1930), on the structure classification of the silicate minerals, the isomorphous replacement in silicates and on the application of the Pauling’s rules to this class of minerals. In Chapter 4, we jump to the 1970s with the paper of P.B. Moore (1970) on the stereoisomerism among octahedral and tetrahedral chains. Moore based his study not on a specific mineral structure, but examined the different ways in which polyhedra could link via vertices to form chains. He defines the concept of ‘‘structural hierarchy’’ as a general scheme that ties together a certain number of arrangements. An extension of the structural analysis of Moore is found in chapter 6, which is devoted to his systematic study of edge-sharing clusters, deriving the possible arrangements based solely on topological and geometrical principles according to the notions of energy minima and stability (Moore 1974). Chapter 5 deals with the paper by Brown and Shannon (1973), on the empirical bond-valence/ bond-length curves for oxides. A further refinement of the Brown and Shannon approach, into a comprehensive theory that addresses many aspects of the chemical bonding, was developed by Brown (1981), and is presented in chapter 8. Bond-valence analysis of inorganic crystal structures is an essential check on the validity of any structure determination. In his commentary on chapter 8, Hawthorne outlines the critical points introduced by Brown in the bond-valence theory, with interesting application in mineralogy, and presents the bond-valence theory as a molecular orbital theory and as an ionic theory. Chapter 7 is devoted to the paper by L.S. Dent Glasser (1979) on non-existent silicates, emphasizing that the observed arrangements in silicates represent only a small fraction of those topologically possible. Chapter 9 deals with the paper of Hawthorne (1983) on the graphical enumeration of polyhedral clusters. The author developed a ‘‘structural hierarchy’’ hypothesis which has an energetic basis and relates to paragenetic sequences. An example is Bowen’s reaction series shown as a function of the polymerization characteristic of the structure involved. A related topic is covered in chapter 10, which discusses the energetic content of bond topology with reference to the paper by Burdett et al. (1984). The last paper of this collection constituting chapter 11 is devoted to the role of OH and H2O in oxide and oxysalt minerals, based on Hawthorne (1992). The author analysed the roleplayed by (OH) , (H2O)0, (H3O)+ and (H5O2)2+ in controlling bonding topology, topological dimensionality and the role of H2O as a bond-valence transformer, which bears on the, often highly selective, uptake of interstitial cations by environmentally significant minerals. Chapter 12 is the coda, focusing on the prediction of bond topology and of the stoichiometry of stable compounds in a given chemical system. I think that the re-publication of these landmark papers, accompanied by the commentaries of Prof. Hawthorne, will be useful not only for undergraduate or PhD students, but for all structural mineralogists. This collection provides valuable insights into the evolution of structural mineralogy and its wider application to the petrology. As several of the milestone papers collected in this book are published in German journals (Zeitschrift fu ̈r Kristallographie, Neues Jahrbuch fu ̈r Mineralogie Monatshefte), I did a little inquiry and I found that these journals are often not readily available in departmental libraries, and so this is another good reason to have this book in your own library. In conclusion, I warmly recommend this volume to all mineralogists and to Earth sciences libraries.
G. DIEGO GATT
High-brilliance X-ray system for high-pressure in-house research: applications for studies of superhard materials
No full textNewly installed, at Bayerisches Geoinstitut, X-ray system consists of three major components:
RIGAKU FR-D high-brilliance source, Osmic’s Confocal Max-Flux optics, and SMART APEX 4K
CCD area detector. We tested the system for single-crystal structural studies on example of garnet,
Co3Al2Si3O12, for powder diffraction analysis on example of a small sample of boron carbide, B4C,
recovered after treatment in a multi-anvil apparatus, and for in situ experiments at high pressure
on example of FeO compressed in a diamond anvil cell to >100 GPa. In all the cases, the system
demonstrated its reliability and provided results comparable with those obtained using the best currently
available instruments. Using a new X-ray system, we measured the compressibility of superhard
nanocrystalline diamond at pressures up to 26 GPa and found it to be extremely incompressible with
KT = 488(4) GPa, K' = 3.1(2), and V0 = 3.401(6) cm3/mol
Ultra-fast escape of a deformable jet-propelled body
No full textIn this work a cephalopod-like deformable body that fills an internal cavity with fluid and expels it to propel an escape manoeuvre, while undergoing a drastic external shape change through shrinking, is shown to employ viscous as well as mainly inviscid hydrodynamic mechanisms to power an impressively fast start. First, we show that recovery of added-mass energy enables a shrinking rocket in a dense inviscid flow to achieve greater escape speed than an identical rocket in a vacuum. Next, we extend the shrinking body results of Weymouth & Triantafyllou (J. Fluid Mech., vol. 702, 2012, pp. 470–487) to three-dimensional bodies and show that three hydrodynamic mechanisms must be combined to achieve rapid escape performance in a viscous fluid: added-mass energy recovery; flow separation elimination; and an optimized energy storage and recovery. In particular, we show that the mechanism of separation elimination achieved through rapid body shrinking, coordinated with the mechanism of recovering the initially imparted added-mass energy, is critical to achieving a high escape speed. Hence a flexible, collapsing body can be vastly superior to a rigid-shell jet-propelled body
Compressional behaviour of paulingite -A sub-nanosponge?
No full textIntroduction
Paulingite is a rare zeolite, found in vesicles in basalt flows, with ideal chemical formula: (K,Na,Ca0.5,Ba0.5,)10(Al10Si32O84)30H2O (Z = 16). Its crystal structure was solved and refined by Gordon et al. (1966) in the space group Im3m, showing the complex framework topology of this zeolite designated with the IZA-code “PAU”. A structural re-investigation was carried out later by Lengauer et al. (1997). The tetrahedral framework topology of paulingite is characterized by a connecting double 8-ring (D8R), which links alternatively the -cage (truncated cuboctahedron) and the -cage (gmelinite-type cage). The D8R, the -cage and the -cage represent the building-block units of the PAU framework. The main voids systems of the PAU framework are represented by two parallel (and independent) sets of a three-dimensional channel systems oriented along the principal axes and shifted 1⁄2, 1⁄2, 1⁄2 against each other. Along the threefold axis of the PAU framework, a second type of a channel system exists, which is built up by the -cage and a modified form of the levyne-cage only observed in the paulingite topology (i.e., -cage) (Lengauer et al. 1997). The PAU framework type is considered as one of the most complex in the mineral world. In all the structure refinements so far reported, the Si/Al-distribution was modelled as completely disordered. A series of extra-framework sites were located. The long “free diameters” of the channel systems make this zeolite a good candidate to explore the P-induced penetration of external molecular species in response to hydrostatic compression (e.g., Gatta 2008, 2010).
Experimental Methods
A sample of paulingite from Vinařická hora Hill near Kladno (Czech Republic) was used for our experiments. A sample from the same locality was previously used by Lengauer et al. (1997) for their chemical and crystallographic study. Electron microprobe analysis (in wavelength dispersive mode) along with thermo-gravimetric data yielded the following chemical formula: (Ca2.57K2.28Ba1.39Na0.38)(Alll.55Si30.59O84)x 27H2O (Lengauer et al. 1997).
A single-crystal of paulingite, free of defects under polarized microscope, was selected for the in-situ diffraction experiment with a diamond anvil cell (DAC). Intensity diffraction data were first collected at room-conditions with a Stoe StadiVari diffractometer with an high-brilliance Incoatec Mo Iμs X-ray-source and a Dectris Pilatus 300K pixel detector. The structure refinement was performed in the space group Im3m using the structural model of Lengauer et al. (1997) to a R1 = 0.0802 for 2477 Fo > 4(Fo) and 255 refined parameters. The same crystal was used for the high-pressure (HP) experiment performed using an ETH-type DAC. The experiment was conducted using a mixture of methanol:ethanol = 4:1 as hydrostatic P-transmitting medium, along with a few ruby chips serving as P-calibrant. Unit-cell parameters were measured between 0.0001 (crystal in the DAC with no pressure medium) and 3.3(1) GPa.
Two further in-situ HP synchrotron X-ray powder diffraction experiments were performed at the X7A beamline at the national synchrotron light source (NSLS) at Brookhaven National Laboratory (BNL). A gas-proportional position-sensitive detector was used. The wavelength of the incident beam was 0.60046(1) Å as determined from a CeO2 standard. A modified Merrill–Bassett DAC was used to generate HP-conditions. Two compression experiments with two different P-fluids were performed, i.e., with silicon-oil and a mix of methanol:ethanol:water = 16:3:1. The evolution of the cell parameters with P for all three pressure-transmitting media is shown in Fig. 1.
Results and Discussion
The evolution of the unit-cell parameters of paulingite with P based on our experiments with different P-media show a dramatic role played by the compression-fluid on the behavior of this zeolite (Figure 1). Due to its polymeric nature, silicon-oil can be unambiguously considered as a “non-penetrating” P-medium. The compressional pattern obtained with silicon-oil describes the actual elastic behavior of paulingite (i.e., without any interference of the P-fluid). The Birch-Murnaghan equation of state truncated to the second-order was used to fit the experimental P-V data within the P-range investigated (i.e. 0.0001-2.5(1) GPa), giving the following isothermal bulk modulus: K0 = 0-1 = V0(P/V) = 18(1) GPa (0 = 0.055(3) GPa-1). Paulingite appears to be one of the softest crystalline inorganic materials reported so far. The HP-data obtained using the mix methanol:ethanol = 4:1 and methanol:ethanol:water = 16:3:1 suggest that these molecules act as “penetrating” media in response to the applied pressure. The P-induced penetration of external molecules through the cavities leads to a lower bulk compressibility of paulingite. The different compressibility of paulingite in methanol:ethanol = 4:1 and methanol:ethanol:water = 16:3:1 mix reflects the different penetrability of the media. Water is clearly the most penetrating molecule in response to the applied pressure, and so in general an hydrous medium tends to decrease significantly the compressional pattern of a porous material (Gatta 2008, 2010). Interestingly, the P-induced penetration of external molecules in paulingite structure does not lead to spectacular expansion (with a drastic discontinuity in the P-V behaviour), as observed for example in natrolite (Lee et al. 2002).
The complexity of the paulingite structure did not allow to perform structure refinement at high pressure, hindering a description of the penetration mechanisms at the atomic scale. A series of further experiments are in progress in order to explore: 1) the reversibility of the P-induced penetration of aforementioned molecules and 2) the behavior of this zeolite as a “sub-nanosponge” for other small molecules in response to hydrostatic pressure.
Acknowledgment
GDG acknowledges the Italian Ministry of Education, MIUR-Project: “Futuro in Ricerca 2012 - ImPACT- RBFR12CLQD”.
References
Gatta, G.D. (2008) Does porous mean soft? On the elastic behaviour and structural evolution of zeolites under pressure. Zeitschrift für Kristallographie, 223, 160–170.
Gatta, G.D. (2010) Extreme deformation mechanisms in open-framework silicates at high-pressure: Evidence of anomalous inter-tetrahedral angles. Microporous and Mesoporous Materials, 128, 78–84.
Gordon, E.K., Samson, S. and Kamb, W.B. (1966). Crystal structure of the zeolite paulingite. Science, 154, 1004-1007.
Lee, Y., Vogt, T., Hriljac, J.A., Parise, J.B., and Artioli, G. (2002) Pressure-Induced Volume Expansion of Zeolites in the Natrolite Family. Journal of the American Chemical Society, 124, 5466-5475.
Lengauer, C.L., Giester, G., and Tillmanns, E. (1997). Mineralogical characterization of paulingite from Vinarická Hora, Czech Republic. Mineralogical Magazine, 61, 591-606
A Letter from Sir Charles G.D. Roberts (A Personal Memoir)
No full textSkala recounts her first and subsequent meetings with Charles G.D. Roberts whom she met when he was in his late seventies, and she in her teens. Roberts was a man of paradox, an author of emotionally-distanced verse yet a man of strong sentiment. He was a chameleon, a person who was everything to everybody; he played the role of gentle poet, mentor, and editor; he was a husband, father, and friend. He wrote about unique characters, animal or human, and he was quite naturally an elitist, though his "elite" could have been chosen from all ranks of society, and, indeed, from all societies. Also discussed are some of the critical views on Roberts' work, praiseworthy and not, as well as Roberts' own critical assessment of Skala's early verse
Sunitinib treatment exacerbates intratumoral heterogeneity in metastatic renal cancer
No full textThis work was supported by the Chief Scientist Office, Scotland (ETM37; to G.D. Stewart, A.C.P. Riddick, M. Aitchison, and D.J. Harrison), Cancer Research UK (Experimental Cancer Medicine Centre; to T. Powles, London and D.J. Harrison, Edinburgh), Medical Research Council (to A. Laird and D.J. Harrison), Royal College of Surgeons of Edinburgh (to A. Laird), Melville Trust (to A. Laird), Medical Research Council (MC_UU_12018/25; to I.M. Overton), Royal Society of Edinburgh Scottish Government Fellowship cofunded by Marie Curie Actions (to I.M. Overton), Renal Cancer Research Fund (to G.D. Stewart), Kidney Cancer Scotland (to G.D. Stewart) and an educational grant from Pfizer (to T. Powles).Purpose: The aim of this study was to investigate the effect of VEGF targeted therapy (sunitinib) on molecular intratumoral heterogeneity (ITH) in metastatic clear cell renal cancer (mccRCC). Experimental design: Multiple tumor samples (n=187 samples) were taken from the primary renal tumors of mccRCC patients who were sunitinib treated (n=23, SuMR clinical trial) or untreated (n=23, SCOTRRCC study). ITH of pathological grade, DNA (aCGH), mRNA (Illumina Beadarray) and candidate proteins (reverse phase protein array) were evaluated using unsupervised and supervised analyses (driver mutations, hypoxia and stromal related genes). ITH was analysed using intratumoral protein variance distributions and distribution of individual patient aCGH and gene expression clustering. Results: Tumor grade heterogeneity was greater in treated compared to untreated tumors (P=0.002). In unsupervised analysis, sunitinib therapy was not associated with increased ITH in DNA or mRNA. However, there was an increase in ITH for the driver mutation gene signature (DNA and mRNA) as well as increasing variability of protein expression with treatment (p<0.05). Despite this variability, significant chromosomal and transcript changes to key targets of sunitinib, such as VHL, PBRM1 and CAIX, occurred in the treated samples. Conclusions: These findings suggest that sunitinib treatment has significant effects on the expression and ITH of key tumor and treatment specific genes/proteins in mccRCC. The results, based on primary tumor analysis, do not support the hypothesis that resistant clones are selected and predominate following targeted therapy.Peer reviewe
Perturbed conformal field theory, nonlinear integral equations and spectral problems
No full textThis thesis is concerned with various aspects of perturbed conformal field theory and the methods used to calculate finite-size effects of integrable quantum field theories. Nonlinear integral equations are the main tools to find the exact ground-state energy of a quantum field theory. The thermodyamic Bethe ansatz (TBA) equations are a set of examples and are known for a large number of models. However, it is also an interesting question to find exact equations describing the excited states of integrable models. The first part of this thesis uses analytical continuation in a continuous parameter to find TBA like equations describing the spin-zero excited states of the sine-Gordon model at coupling β(^2) = 16π/3. Comparisons are then made with a further type of nonlinear integral equation which also predicts the excited state energies. Relations between the two types of equation are studied using a set of functional relations recently introduced in integrable quantum field theory. A relevant perturbation of a conformal field theory results in either a massive quantum field theory such as the sine-Gordon model, or a different massless conformal field theory. The second part of this thesis investigates flows between conformal field theories using a nonlinear integral equation. New families of flows are found which exhibit a rather unexpected behaviour. The final part of this thesis begins with a review of a connection between integrable quantum field theory and properties of certain ordinary differential equations of second- and third-order. The connection is based on functional relations which appear on both sides of the correspondence; for the second-order case these are exactly the functional relations mentioned above. The results are extended to include a correspondence between n(^th) order differential equations and Bethe ansatz system of SU(n) type. A set of nonlinear integral equations are derived to check the results
Corruption and behaviour change tracking social norms and values in South Africa
No full textCommissioned by the German Agency for International Cooperation (GIZ), MarchThe National Anti-Corruption Strategy (NACS) 2020-2030 is an inclusive plan to eliminate corruption in South Africa. It aims to promote and encourage active citizenry, whistleblowing, integrity and transparency in all spheres of society. Amongst the goals of the NACS is the creation of a culture of zero-tolerance for corruption, calling on members of the public to report corruption if they witness it. The primary aim of the present study is to support the goals of the NACS by trying to understand how we can create a culture of zero-tolerance for corruption amongst the mass public in the country. In order to achieve this aim, it focuses on the social norms and values that inform both anti-corruption and corruption attitudes as well as behaviours in post-apartheid society. The multi-year study is being conducted by the Human Sciences Research Council (HSRC) with the support of the German Agency for International Cooperation (GIZ).N/
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