HOLOGRAPHIC IMAGES OF IODINE ATOMS ON A SILVER SURFACE FROM ELECTRON-EMISSION PATTERNS

BARTON 1 has suggested that photoelectron interference patterns may be used directly as holograms to obtain atomic-resolution images of surface structures. Bulk structures have been obtained previously by this means from experimental patterns of high-energy Kikuchi(quasi-elastically scattered) and Auger electrons 2,3. Here we test the feasibility of this technique for determination of surface structures using Auger intensity patterns obtained 4,5 from iodine chemisorbed on a pseudomorphic silver monolayer on Pt{111}. By direct numerical holographic inversion, we obtain three-dimensional images which show that iodine adatoms are located in hollows of 3-fold symmetry on the surface. The images yield the site symmetry with good atomic resolution in the surface plane, but suffer from poor resolution along the Ag-I axis. We anticipate that data with better angular resolution obtained at low temperatures would improve the spatial resolution of such images.

Simple preparation of positively charged silver nanoparticles for detection of anions by surface-enhanced Raman spectroscopy

Modification of citrate and hydroxylamine reduced Ag colloids with thiocholine bromide, a thiol functionalized quaternary ammonium salt, creates particles where the zeta potential is switched from the normal values of ca. -50 mV to ca. + 50 mV. These colloids are stable but can be aggregated with metal salts in much the same way as the parent colloids. They are excellent SERS substrates for detection of anionic targets since their positive zeta potentials promote adsorption of negatively charged ions. This is important because the vast majority of published SERS studies involve cationic or neutral targets. Moreover, the fact that the modifier is a quaternary ammonium ion means that the negative surface charge is maintained even at alkaline pH. The modified colloids can be used to detect compounds which cannot be detected using conventional negatively-charged citrate or hydroxylamine reduced metal nanoparticles, for example the detection limit was 5.0 x 10(-5) M for perchlorate and

Silicon, the silver bullet for mitigating biotic and abiotic stress, and improving grain quality, in rice?

Adequate silicon fertilization greatly boosts rice yield and mitigates biotic and abiotic stress, and improves grain quality through lowering the content of cadmium and inorganic arsenic. This review on silicon dynamics in rice considers recent advances in our understanding of the role of silicon in rice, and the challenges of maintaining adequate silicon fertility within rice paddy systems. Silicon is increasingly considered as an element required for optimal plant performance, particularly in rice. Plants can survive with very low silicon under laboratory/glasshouse conditions, but this is highly artificial and, thus, silicon can be considered as essential for proper plant function in its environment. Silicon is incorporated into structural components of rice cell walls were it increases cell and tissue rigidity in the plant. Structural silicon provides physical protection to plants against microbial infection and insect attack as well as reducing the quality of the tissue to the predating organisms. The abiotic benefits are due to silicon's effect on overall organ strength. This helps protect against lodging, drought stress, high temperature (through efficient maintenance of transpiration), and photosynthesis by protecting against high UV. Furthermore, silicon also protects the plant from saline stress and against a range of toxic metal stresses (arsenic, cadmium, chromium, copper, nickel and zinc). Added to this, silicon application decreases grain concentrations of various human carcinogens, in particular arsenic, antimony and cadmium. As rice is efficient at stripping bioavailable silicon from the soil, recycling of silicon rich rice straw biomass or addition of inorganic silicon fertilizer, primarily obtained from iron and steel slag, needs careful management. Silicon in the soil may be lost if the silicon-cycle, traditionally achieved via composting of rice straw and returning it to the land, is being broken. As composting of rice straw and incorporation of composted or non-composted straw back to land are resource intensive activities, these activities are declining due to population shifts from the countryside to cities. Processes that accelerate rice straw composting, therefore, need to be identified to aid more efficient use of this resource. In addition, rice genetics may help address declining available silicon in paddy soils: for example by selecting for characteristics during breeding that lead to an increased ability of roots to access recalcitrant silicon sources from soil and/or via selection for traits that aid the maintenance of a high silicon status in shoots. Recent advances in understanding the genetic regulation of silicon uptake and transport by rice plants will aid these goals.

Performance of sustainable SCC mixes with mineral additions for use in precast concrete industry

The aim of this research was to study the impact that different mineral powders have on the properties of self-compacting concrete (SCC) in order to obtain relations that make it possible to optimize their dosages for being used in precast concrete applications. Different combinations and contents of cement, mineral additions (active and inert), superplasticizers, and aggregates are considered. A new approach for determining the saturation point of superplasticizers is introduced. The fresh state performance was assessed by means of the following tests: slump flow, V-funnel, and J-ring. Concrete compressive strength values at different ages up to 56 days have been retained as representative of the materials’ performance in its hardened state. All these properties have been correlated with SCC proportioning. As a result, a number of recommendations for the precast concrete industry arise to design more stable SCC mixes with a reduced carbon footprint.

The effect of niobium and tantalum on physicochemical and catalytic properties of silver and platinum catalysts based on MCF mesoporous cellular foams

MCF, NbMCF and TaMCF Mesostructured Cellular Foams were used as supports for platinum and silver (1 wt%). Metallic and bimetallic catalysts were prepared by grafting of metal species on APTMS (3-aminopropyltrimethoxysilane) and MPTMS (2-mercaptopropyltrimethoxysilane) functionalized supports. Characterizations by X-ray diffraction (XRD), ultraviolet–visible (UV–Vis) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF) spectroscopy, and in situ Fourier Transform Infrared (FTIR) spectroscopy allowed to monitor the oxidation state of metals and surface properties of the catalysts, in particular the formation of bimetallic phases and the strong metal–support interactions. It was evidenced that the functionalization agent (APTMS or MPTMS) influenced the metals dispersion, the type of bimetallic species and Nb/Ta interaction with Pt/Ag. Strong Nb–Ag interaction led to the reduction of niobium in the support and oxidation of silver. MPTMS interacted at first with Pt to form Pt–Ag ensembles highly active in CH3OH oxidation. The effect of Pt particle size and platinum–silver interaction on methanol oxidation was also considered. The nature of the functionalization agent strongly influenced the species formed on the surface during reaction with methanol and determined the catalytic activity and selectivity.

Silver nanoparticles flow in an aquatic trophic chain

Silver nanoparticles (AgNP) have been produced and applied in a variety of products ranging from personal care products to food package containers, clothing and medicine utilities. The antimicrobial function of AgNP makes it very useful to be applied for such purposes. Silver (Ag) is a non-essential metal for organisms, and it has been historically present in the environment at low concentrations. Those concentrations of silver increased in the last century due to the use of Ag in the photographic industry and lately are expected to increase due to the use of AgNPs in consumer products. The presence of AgNP in the aquatic environment may pose a risk for aquatic species, and the effects can vary from lethal to sublethal effects. Moreover, the contact of aquatic organisms with AgNP may not cause immediately the death of individuals but it can be accumulated inside the animals and consequently transferred within the food chain. Considering this, the objective of this work was to study the transfer of silver nanoparticles in comparison to silver ions, which was used as silver nitrate, within an aquatic food chain model. To achieve this goal, this study was divided into four steps: the toxicity assessment of AgNP and AgNO3 to aquatic test-species, the bioaccumulation assessment of AgNP and AgNO3 by Pseudokirchneriella subcapitata and Daphnia magna under different exposure scenarios, and finally the evaluation of the trophic transfer of Ag through an experimental design that included the goldfish Carassius auratus in a model trophic chain in which all the species were exposed to the worse-case scenario. We observed that the bioconcentration of Ag by P. subcapitata is mainly driven by ionic silver, and that algae cannot internalize these AgNPs, but it does internalizes dissolved Ag. Daphnia magna was exposed to AgNP and AgNO3 through different exposure routes: water, food and both water and food. The worse-case scenario for Daphnia Ag bioaccumulation was by the joint exposure of contaminated water and food, showing that Ag body burdens were higher for AgNPs than for AgNO3. Finally, by exposing C. auratus for 10 days through contaminated water and food (supplied as D. magna), with another 7 days of depuration phase, it was concluded that the 10 days of exposure were not enough for fish to reach a plateau on Ag internal concentration, and neither the 7 days of elimination were sufficient to cause total depuration of the accumulated Ag. Moreover, a higher concentration of Ag was found in the intestine of fish when compared with other organs, and the elimination rate constant of AgNP in the intestine was very low. Although a potential for trophic transfer of AgNP cannot be suggested based in the data acquired in this study, there is still a potential environmental risk for aquatic species.

Containing precious metals: hallmarking, minting and the materiality of gold and silver in medieval and modern England.

This book chapter extends the argument constructed by Oakley in his conference paper ‘Containing gold: Institutional attempts to define and constrict the values of precious metal objects’ presented at ‘Itineraries of the Material’, a conference held at Goethe Universitaet, Frankfurt am Main in 2011. Oakley’s chapter investigates the social forces that define the identities, social pathways and physical movement of objects made of precious metal. It presents a case study in which constitutive substance rather than the conceptual object is the key driver behind the social trajectories of numerous artefacts and their reception by contemporary audiences. This supports the main contention of the book as a whole: the need to reconsider, and when necessary challenge, the dominance of the social biography of objects in the study of material culture. Oakley’s research used historical and ethnographic approaches, including three years’ of ethnographic field research in the jewellery industry. This included training as a precious metal assayer at the Birmingham Assay Office and observing the industry and public response to government proposals to abolish the hallmarking legislation. This fieldwork was augmented by archive, library and object collection research on the histories of assaying and goldsmithing. Oakley presents an analysis of the historical development and contemporary social relevance of hallmarking, a technological process that has never previously been subject to ethnographic study, yet is fundamental to one of the UK’s creative industries.

Some additions and other records new to the ornithology of South Carolina

This document contains notes on several species of birds observed by Arthur T. Wayne in South Carolina including the Sooty Shearwater, the Harlequin Duck, the Snow Goose, the Blue Goose, the Egret, the Yellow-crowned Night Heron, the Hudsonian Curlew, the Turnstone, the Pigeon Hawk, the Crested Flycatcher, the Bronzed Grackle, the Carolina Grackle, the Ipswich Sparrow, Leconte’s Sparrow, the Mountain Solitary Vireo, Bachman’s Warbler, the Magnolia Warbler, the Black-throated Green Warbler, and the Connecticut Warbler.

Free coinage of silver : speech of Hon. William Elliott, of South Carolina, in the House of Representatives, Thursday, February 13, 1896 [Pamphlet]

This speech is given to the United States House of Representatives. Hon. William Elliot gives a persuasive argument for why he will be voting against the senate amendment for free coinage of silver. He defines free coinage of silver and he describes fifty-cent dollar. He discusses the fall in the price of products and provides causation.

Registre F de Philippe Auguste. Écrit vers 1247, avec additions.

Entré à la Bibliothèque du roi en 1732 parmi les mss. de Jean-Baptiste Colbert; cf. Delisle, Cab. des mss., I, 439-547; Omont, Concordances des mss. latins, 48-77; — décrit dans le catalogue de la bibliothèque des Carmes de Clermont "[G] Vol. in quo est registrum Philippi regis Francorum. Literae aliquorum pontificum ad reges Francorum. Chartae abbatiarum et aliarum ecclesiarum de feudis"; cf. Delisle, Cab. des mss, I, 476 et 480-482; Montfaucon, Bibl. bibl., II, col. 1278 et ss.

Formulaire manuel à l'usage d'un officier des Monnaies, probablement d'un essayeur général, du règne de François I, écrit en 1529, avec additions jusqu'en 1577.

Contient : Comptes faits pour le paiement des gages ; Renseignements sur le calendrier et spécialement la date de Pâques ; Évaluation du marc d'argent, et renseignements sur la fabrication et les essais des gros testons et autres pièces ; « Ensuyvent les noms des monnoyes [ateliers monétaires] de ce royaulme, pays et seigneuries du roy de France » ; Renseignements sur l'organisation et le personnel des monnaies ; « Lettres de maistre de monnoye », acte de François premier, concernant la monnaie de La Rochelle, 1528 ; « Serment des maistres des monnoyes » ; Déclaration des généraux maîtres des monnaies sur le fait et gouvernement des monnaies, maîtres particuliers, gardes, essayeurs et autres officiers des monnaies, sur les changeurs, affineurs et orfèvres du royaume, vers 1423 [cf. ms. franç. 18500, f. 18] ; « Gros testons. Ce qui a esté de nouvel advisé en la Chambre des Monnoyes pour le bien et (de) la continuation de l'ouvraige de gros testons », décembre 1521 (f. 57) ; « C'est le pris que l'en a donné en or et en argent au marc et à la value des monnoyes du royaume de France, depuis l'an M IIIe et VI » jusqu'au 21 juillet 1519 [cf. ms. français 18500, f. 4] ; « Cy s'ensuivent les pris que l'on a donné au marc d'argent de Paris et les monnoyes blanches et noires faictes au royaulme de France, depuis... mil IIe IIIIxx XIII » jusqu'en 1418/9 ; « S'ensuit le pris que a valu le marc d'argent, selon la Chambre des Monnoyes estant à Bourges, depuis le vingt-septiesme jour d'avril, l'an mil quatre cens et dix-huit » jusqu'en 1436 ; Valeur de la « forte monnoye », et analyse de pièces concernant le cours et la fabrication des monnaies, 1422-1521 ; « Lettres d'atache des généraulx des monnoyes pour ung office de changeur donné par le Roy », 21 mai 1529 ; Tableaux des valeurs des divisions du marc d'or fin, règles pour savoir le poids et le titre du marc d'or, etc ; Addition de la même main que ce qui précède : « Lettres d'office d'essayeur », acte de François premier, 25 septembre 1529 ; Addition d'une autre main : Lettre de Charles VI, sur les ouvrages des orfèvres de Paris, et règlement sur le métier d'orfèvrerie, 11 juillet 1379 ; Additions d'une autre main : Recueil d'actes royaux, baux, ordonnances, etc., concernant les finances. Actes de Charles VII dauphin, 1419 (f. 138 v), — et de Charles VI, 1420-1421 (f. 145 et suiv.), — et analyses d'actes de Louis XII, 1513 (f. 176), — François premier, 1532-1540 (f. 168), et 1519-1543 (f. 176), — Henri II, 1549/1550 (f. 169 v et 178 v), — Charles IX, 1561-1573 (f. 170 et 179 v), — et Henri III, 1574-1577 (f. 174 et 182)