3,129 research outputs found
Improving the altimetric rain record from Jason-1 & Jason-2
No full textDual-frequency rain-flagging has long been a standard part of altimetric data analysis, both for quality control of the data and for the study of rain itself, because altimeters can provide a finer spatial sampling of rain than can passive microwave instruments. However, there have been many varied implementations, using different records of the surface backscatter and different thresholds. This paper compares four different measures available for the recently-launched Jason-2. The evaluation compares these measures against clearly desired properties, finding that in most cases the adjusted backscatter and that from the ice retracker perform much better than that recommended in the users' handbook. The adjusted backscatter measure also provides a much better link to observations from Jason-1, opening up a much longer period for consistent rain investigations, and enabling greatly improved analysis of the short-scale variability of precipitation. Initial analysis shows that although the spatial and temporal gradients of backscatter increase at very low winds, the spatial gradients in rain attenuation are concentrated where rainfall is greatest, whilst the temporal changes have a simple broad latitudinal pattern
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
Preparation of highly visible-light active N-doped TiO<sub>2</sub> photocatalyst
No full textA series of N-doped anatase TiO2 samples have been prepared using a solvothermal method in an organic amine/ethanol–water reaction system. The effects of different starting N:Ti atomic ratios on the catalysts structure, surface property and catalytic activity have been investigated. The photocatalytic activity and stability of the N-doped TiO2 samples were evaluated through using the decomposition of Methylene blue (MB) and Methyl orange (MO) as model reaction under visible light irradiation. Characterization results show that the nitrogen dopant has a significant effect on the crystallite size and optical absorption of TiO2. It was found that the N-doped TiO2 catalysts have enhanced absorption in the visible light region, and exhibit higher activity for photocatalytic degradation of model dyes (e.g. MB and MO). The catalyst with the highest performance was the one prepared using N:Ti molar ratio of 1.0. Electron paramagnetic resonance (EPR) measurement suggests the materials contain Ti3+ ions, with both the degree of N doping and oxygen vacancies make contributions to the visible light absorption of TON. The presence of superoxide radicals (O•-) and hydroxyl radicals (•OH) on the surface of TON were found to be responsible for MB and MO solution decoloration under visible light. Based on the results of the present study, a visible light induced photocatalytic mechanism has been proposed for N-doped anatase TiO2
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
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
The hydrothermal synthesis of BiOBr flakes for visible-light-responsive photocatalytic degradation of methyl orange
No full textFlake-like BiOBr semiconductors have been prepared using hydrothermal synthesis with meticulous control of synthesis parameters and used for photocatalytic degradation of methyl orange. XRD, SEM and UV–vis characterizations have been performed to study the obtained BiOBr materials. The results indicate that the morphology and crystallite size of BiOBr depend significantly on the temperature and duration of the hydrothermal syntheses. Diffuse UV–vis spectra show the BiOBr materials to be indirect semiconductors with an optical bandgap of approximately 2.92 eV, which is essentially unaffected by the synthesis parameters. The hydrothermal-synthesized BiOBr flakes exhibit noticeable activity for photo-degradation of methyl orange under visible light (>400 nm) illumination, with the BiOBr synthesized by hydrothermal treatment at 120 °C for 6 h exhibiting superior photocatalytic performance in these flakes. The excellent activity and photo-stability reveal that BiOBr is a promising visible-light-responsive photocatalyst
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
Photon and dilepton production in supersymmetric Yang-Mills plasma
No full textBy weakly gauging one of the U(1) subgroups of the R-symmetry group, = 4 super-Yang-Mills theory can be coupled to electromagnetism, thus allowing a computation of photon production and related phenomena in a QCD-like non-Abelian plasma at both weak and strong coupling. We compute photon and dilepton emission rates from finite temperature = 4 supersymmetric Yang-Mills plasma both perturbatively at weak coupling to leading order, and non-perturbatively at strong coupling using the AdS/CFT duality conjecture. Comparison of the photo-emission spectra for = 4 plasma at weak coupling, = 4 plasma at strong coupling, and QCD at weak coupling reveals several systematic trends which we discuss. We also evaluate the electric conductivity of = 4 plasma in the strong coupling limit, and to leading-log order at weak coupling. Current-current spectral functions in the strongly coupled theory exhibit hydrodynamic peaks at small frequency, but otherwise show no structure which could be interpreted as well-defined thermal resonances in the high-temperature phase
Stenothemus septimus Y. Yang et X. Yang, sp. nov.
No full textStenothemus septimus Y. Yang et X. Yang, sp. nov. Figs. 6, 18, 33 ‒35, 43 Type material. Holotype ♂ (MHBU): CHINA: Xizang: Mêdog, Hanmi, 2380m, 9.VIII. 2003, leg. G.D. Ren. Paratypes: 22 ♂♂, 10 ♀♀ (MHBU): same data as holotype; 6 ♂♂, 4 ♀♀ (MHBU): same locality, 28.VII. 2013, leg. X.L. Bai & J.S. Shan. [all transliterated from Chinese labels]. Distribution. China (Xizang). Description. Male (Fig. 6). Head black, light brown on middle line of vertex, mouthparts light yellow, more or less darkened at maxillary and labial palpi, dark brown at apices of mandibles, antennae black, light yellow at apex of each antennomere, pronotum light yellow, with a large dark brown marking on disc, scutellum light yellow, elytra light yellow and mottled with irregular black brown markings, legs light yellow, black at bases of coxae and tibiae and apices of femora and tarsomeres, more or less darkened at outer sides of femora and outer and dorsal sides of tibiae, prosternum light yellow, meso- and metasterna and abdominal ventrites dark brown, light yellow at posterior margin of abdominal ventrites and the whole terminal ventrite. Body densely covered with light brown pubescence, mixed with slightly long, semirecumbent light brown pubescence and erect black brown setae on elytra. Head subquadrate, temples straight and slightly converging posteriorly, dorsum moderately convex in central part, surface semilustrous, densely and finely punctate, each side with a smooth and rectangular impression behind antennal socket; eyes strongly protruding, head width across eyes distinctly narrower than pronotum; terminal maxillary palpomeres long-triangular, widest at basal one-third, with apical parts of inner margins arcuate and sharp, acute at apices; antennae extending to basal two-thirds length of elytra, antennomeres II about twice longer than wide at apices, III slightly longer than II, IV longest, from V to XI gradually shortened, XI pointed at apex. Pronotum about 1.25 times as wide as long, widest nearly in middle, anterior margin together with anterior angles and lateral margins rounded, posterior margin arcuate and narrowly bordered, posterior angles moderately sharp, protruding, disc distinctly convex on posterolateral parts, surface lustrous, finely and sparsely punctate. Elytral length about 4 times length of pronotum, 3 times as long as humeral width, with lateral margins slightly diverging posteriorly, surface semilustrous, rugulose-lacunose and finely punctate. Aedeagus (Figs. 33‒35): ventral process of each paramere bent ventrally about 60 degrees, with the bent portion at apical part distinctly longer than the basal portion, not thickened terminally, circular at apex in lateral view, dorsal plate distinctly shorter than ventral process, abruptly narrowed apically, acute at apex (Fig. 33 a); laterophyse hooked at apex. Female. Similar to male, but head slightly convex on dorsum, antennae shorter and extending to elytral midlength, pronotum moderately convex on posterolateral parts of disc, elytra with lateral margins distinctly diverging posteriorly, abdominal sternite VIII (Fig. 18) abruptly narrowed posteriorly, nearly flat on middle sclerotized part, with lateral margins strongly sclerotized at anterior part and nearly membranous at posterior part, posterior margin triangularly emarginated in middle, lateroapical angles subrectangular, anterior margin triangularly emarginated in middle, the lobe slightly sclerotized and triangular, sternite VII triangularly protuberant in middle of posterior margin. Body length: 7.5 ‒9.0 mm; width: 1.5 ‒2.0 mm. Diagnosis. This species can be easily distinguished from others by the abdominal sternite VII of female triangularly protuberant in middle of posterior margin; aedeagus: ventral process of each paramere not thickened terminally, laterophyse hooked at apex. Etymology. This specific name is derived from the Latin septimus (seventh), referring to its characteristic abdominal sternite VII of female, which is triangularly protuberant in middle of posterior margin.Published as part of Yang, Yuxia, Su, Junyan & Yang, Xingke, 2014, Review of the Stenothemus harmandi species-group (Coleoptera, Cantharidae), with description of six new species from China, pp. 203-220 in Zootaxa 3847 (2) on pages 214-216, DOI: 10.11646/zootaxa.3847.2.2, http://zenodo.org/record/22578
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