753 research outputs found
Editorial note - On the aims and scope and priority areas in Materials and Design
No full textAlexander M. Korsunsky, A. Geoffrey Gibson, Giang D. Nguyen, Marco Sebastiani, Xu Song, Tan Su
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
Bias in effect size of systemic lupus erythematosus susceptibility loci across Europe: a case-control study
No full textThis work was supported by Fondo de Investigacion Sanitaria of the Instituto de Salud Carlos III(Spain) grant 08/0744 and by RETICS Program RD08/0075 that are partially financed by the European Regional Development Fund of the European Union, and by grants from the Xunta de Galicia and BMBF KN Rheuma (C2.12 to TW).Alonso-Perez, E., Suarez-Gestal, M., Calaza, M., Sebastiani, G.D., Pullmann, R., Papasteriades, C., Kovacs, A., Skopouli, F.N., Bijl, M., Suarez, A., Marchini, M., Migliaresi, S., Carreira, P., Ordi-Ros, J., Witte, T., Ruzickova, S., Santos, M.J., Barizzone, N., Blanco, F.J., Lauwerys, B.R., Gomez-Reino, J.J., Gonzalez, A
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
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
Association of systemic lupus erythematosus clinical features with european population genetic substructure
No full textAlonso-Perez, E., Suarez-Gestal, M., Calaza, M., Witte, T., Papasteriades, C., Marchini, M., Migliaresi, S., Kovacs, A., Ordi-Ros, J., Bijl, M., Santos, M.J., Ruzickova, S., Pullmann, R., Carreira, P., Skopouli, F.N., D'Alfonso, S., Sebastiani, G.D., Suarez, A., Blanco, F.J., Gomez-Reino, J.J., Gonzalez, A
Persistence of bDMARD therapy in Rheumatoid Arthritis after first-line TNF-inhibitor failure: the RECORD study of the Italian Society for Rheumatology
No full textObjective: The optimal choice of a second biological disease-modifying anti-rheumatic drug (bDMARD) after failure with first line tumour necrosis factor inhibitor (TNFi) represents a critical therapeutic challenge. This study aims to evaluate the persistence with treatment using second line bDMARDs with different mechanisms of action in rheumatoid arthritis (RA) patients with inadequate response to first line TNFi. Method: A retrospective cohort study on administrative healthcare databases was conducted. We analysed the relationship between different bDMARDs and persistence with treatment in RA patients who started second line bDMARD therapy according to two different strategies: cycling (second TNFi) or switching [change in mechanism of action: abatacept (ABA), tocilizumab (TCZ), and rituximab (RTX)] with or without concomitant conventional synthetic (cs) DMARDs. Results: The cohort comprised 1434 patients. The mean age was 53.8 years and 1142 (79.6%) were women. Among second line bDMARDs, 969 patients (67.6%) started TNFi, 204 (14.2%) ABA, 145 (10.1%) RTX, and 116 (8.1%) TCZ. A bDMARD was prescribed as monotherapy in 359 patients (25.0%). The switching strategy showed a lower overall discontinuation rate [hazard ratio (HR) 0.72], while switching compared to cycling showed significantly better survival for ABA (HR 0.61) and RTX (HR 0.76), but no significant difference for TCZ (HR 0.82). A lower impact of better drug survival in the switching strategy occurred in patients with concurrent methotrexate. Conclusions: Among RA patients failing a first TNFi, switching is associated with marginally better persistence, in particular for ABA and RTX, with only marginal differences in patients on concurrent csDMARDs
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
Mineralogical application of nanoindentation testing
No full textThe study of elastic properties of rocks and minerals had a significant development because these data are crucial for the interpretation of the propagation of seismic waves on which all models of Earth's internal structure are based. In addition, these properties are essential for determining the equation of state of geological materials [1,2]. Other physical properties related to elasticity, such as hardness, fracture toughness, contact stiffness, creep resistance, can be used to understand the mechanisms of ductile deformation of rocks at the level of the mantle or deep crust, and of the brittle behaviour of rocks at the level of upper crust. Finally, since the elastic properties are closely related to the crystal-chemistry of minerals, they can be used to probe the structural deformations induced by phase transitions and/or ionic substitutions [3,4]. The measurement of the elastic properties of minerals is essentially based on three methods: 1) direct mechanical methods; 2) sound wave velocity measurements and 3) electromagnetic wave scattering methods (Brillouin, inelastic X-ray/neutron). All of these methods are now well established, mature and widely used however they have an inherent limitation: they do not allows the measurement of elastic properties of materials at micro to nano scale [5].
Nanoindentation testing (introduced by Oliver and Pharr in 1992 [6]) has been widely adopted in the last two decades for the surface mechanical characterization of bulk materials and coatings. The method involves the controlled penetration of a diamond pyramidal indenter into the material: by measuring the load and displacement during the loading and unloading parts of the test, hardness (i.e. resistance to plastic deformation) and elastic modulus can be calculated [6-7]. In this way, a very accurate characterisation of the elastic properties at material’s surface can be achieved, with a depth resolution and a lateral spatial resolution of the order of few nanometres.
Three factors motivate the use of nanoindentation for the study of the mechanical properties of minerals. Firstly, in such tests the load and displacement of the indenter tip, are continuously monitored thus the method is ideal for probing local gradients and heterogeneities in samples. Second, no extensive sample preparation is required prior to mechanical testing. Third, most nanoindentation instruments provide experimental control that allows for a variety of different deformation modes. The data so far published are scarse and cover a limited number of minerals (some phyllosilicate, kyanite, K-feldspar, periclase, garnet, quartz and the first nine minerals of the Mohs scale) [8,9,10,11]. However, the results show the possibility of very interesting developments in the field of mineralogy, applied mineralogy and gemmology.
[1] J. Schreuer, S. Huassühl, EMU Notes in Mineralogy 7 (2005) 95-116.
[2] G.D. Price, Mineral Physics: Treatise On Geophysics. Elsevier (2009) 656 pp.
[3] M.A. Carpenter, E.K.H. Salje, Eur. J. Mineral. 10 (1998) 693-812.
[4] W. van Westrenen, J. Blundy, B. Wood, Am. Mineral. 84 (1999) 838-847.
[5] R.J. Angel, J.M. Jackson, H.J. Reichmann, S. Speziale, Eur. J. Mineral. 21 (2009) 525-550.
[6] W.C. Oliver, G.M. Pharr, J. Mater. Res. 7 (1992) 1564-1583.
[7] C.A. Schuh, Materials Today 9 (2006) 32-40.
[8] M.E. Broz, R.F. Cook, D.L. Whitney, Am. Mineral. 91 (2006) 135-142.
[9] D.L. Whitney, M.E. Broz, R.F. Cook, Am. Mineral. 92 (2007) 281-288.
[10] A. Mikowski, P. Soares, F. Wypych, C.M. Lepienski, Am. Mineral. 93 (2008) 844-852.
[11] G. Zhang, Z. Wei, R.E. Ferrell, S. Guggenheim, R.T. Cygan, J. Luo, Am. Mineral. 95 (2010) 863-869
Efficacy and safety of anti-TNF-alpha therapy combined with cyclosporine A in patients with rheumatoid arthritis and concomitant hepatitis C virus infection
No full textThis study further expands our previous observation demonstrating the usefulness of combination therapy of anti-TNF-alpha and Cyclosporine A in the treatment of rheumatoid arthritis and concurrent hepatitis C virus infection, as well its efficacy and safety in controlling HCV viremia and liver toxicity. Seven patients were included in the study; transaminase levels remained unchanged, HCV RNA serum levels decreased significantly and DAS 28 significantly improved after twelve month follow-up. No side effects were registered
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