The United States has a National Oil Reserve but no food reserve. Just as the oil reserve is designed to buffer unforeseen disruptions in the critical supply, the nation should also have a food reserve for at least the same purpose. The United States and other developed nations have little or no food reserve beyond the typical demands between growing seasons. Marvelous production achievements in agriculture beginning in the early 1960s and known as the “Green Revolution” are now leveling off. Food production, suffering from such negative side effects as reduced water tables, is being outstripped by population growth (Bourne, 2009). In 2006 through 2008 the US and world drawdown of wheat and other grain stocks, together with agricultural events such as droughts in various parts of the world, caused grain reserves to hit historically low levels. The resulting lack of supply created significant disruptions, including record high prices (Figure 1) (Good and Li, 2010, USDA - Foreign Agricultural Service, 2011), countries refusing to export, riots, and famine (CNN.com, 2008). The need for higher world grain stocks seems clear. Higher grain stocks should result in lower price volatility and higher food security in Utah, the US, the UK, and internationally.

Depuis plusieurs décennies, la catalyse par les métaux de transition est devenue un outil incontournable pour la synthèse organique. Chaque année, des milliers de publications décrivent le développement de nouvelles réactions effectuées en présence de complexes organométalliques. Le premier chapitre de ce manuscrit présente une comparaison générale de la réactivité des métaux du groupe 11 (Cu, Ag, Au), avec une attention particulière sur leur capacité à réaliser des réactions d’activation électrophile (Au) ou des transferts de nucléophiles (Cu). Des exemples représentatifs sont donnés pour illustrer ces concepts. Dans la seconde partie, la synthèse d’allènes et d’énones trifluorométhylés par catalyse à l’or(I) est détaillée. Une méthode générale de préparation d’allènes-CF3 a été développée par un transfert d’hydrure-1,5 induit par un complexe d’or(I). Les limites de la méthode ainsi que certaines applications des produits sont décrites. Dans la même idée, un réarrangement-[3,3] d’acétates propargylique catalysé par l’or(I) a été appliqué à la synthèse d’énones-CF3. L’incorporation de cette méthode dans un processus monotope avec une réaction de Diels-Alder est également présentée. La troisième partie est centrée sur les réactions de borofonctionnalisation d’allènes catalysées par le cuivre(I). Les récents développements de ce domaine sont passés en revue, et notre contribution à ce sujet est détaillée. Enfin, un travail préliminaire sur l’élaboration d’un processus monotope impliquant une catalyse coopérative cuivre(I)/or(I) est présenté. / During the last decades, transition metal catalysis has become an essential tool in organic synthesis. Each year, thousands of publications report the development of new reactions mediated by metal complexes. This manuscript depicts our contribution to this field. The first chapter presents a general comparison of the reactivity of coinage metals (Cu, Ag, Au) complexes in catalysis, with a special focus on their ability to perform electrophilic activation (Au) or nucleophilic transfer (Cu) reactions. Representative examples are given to illustrate these concepts. In the second part of the manuscript, the synthesis of trifluoromethylated allenes and enones by gold(I) catalysis is reported. A general method for the preparation of CF3-allenes has been developed based on a gold(I)-mediated 1,5-hydride shift. The scope and limitations of the method, as well as some subsequent transformations of the products are described. Using similar substrates, a gold(I)-catalyzed [3,3]-acetate rearrangement was applied to the preparation of CF3-enones. The employment of this method into a one-pot procedure involving a subsequent Diels-Alder reaction is also reported. The third part focuses on the copper(I)-catalyzed borofunctionalization of allenes. The recent reports from the literature are reviewed, and our contributions to this area of research are described through the study of a new copper(I)-catalyzed allene boroacylation method. Finally, preliminary results on the elaboration of a copper(I)/gold(I) catalytic one-pot process are presented.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements of the degree of Master of Science. November 1995. / The preparation of supported cobalt and gold catalysts by the technique of electroless plating, and the establishment of the influence of synthesis variables on the physical properties of the supported catalyst, forms the basis of this dissertation. In both the cases of cobalt and gold supported on extruded cylindrical alumina pellets, the penetration profile of the metal into the support showed dependence on the pH of the activation solution, while the metal loading onto the same support showed no dependence on pH of the activation solution at all. The variables involved in the plating process of the activated pellets, namely: i) the concentration of the activation solution, ii) pH and temperature of the plating bath, iii) plating time, and Iv) variation of the concentrations of components of the plating bath all influenced the mass of metal loaded onto the support, but not the penetration characteristics. It is therefore possible to prepare a supported catalyst with very specific , properties using the above information. Under similar conditions, with extruded alumina pellets as support and with the specific plating formulations used, gold showed higher metal loadings at lower gold concentrations than cobalt.

Thesis (M.Com. (Accounting))--University of the Witwatersrand, Faculty of Commerce, Law and Management, School of Accountancy, 2012. / The recent spate of strikes in the mining sector in South Africa has created a perceived nervousness amongst shareholders. Within the mining sector in South Africa, gold mining is of significance historically and economically. This study aims to assess the impact of strikes on shareholder value in the gold mining industry during the period beginning January 2007 and December 2012, and uses the popular event study methodology developed by Ball and Brown (1968). The effect of the announcement and duration of the strike on the share price was tested. Significant negative cumulative abnormal returns were observed during the announcement of the strike. The impact of the announcement of protected strikes compared to unprotected strikes on the share price was compared. Although both types of strikes had a negative impact on shareholder value, an unprotected strike had less of an impact on shareholder value compared to a protected strike. This observation is of particular significance given the recent increase in unprotected strikes. Strikes with a duration of 15 days or longer resulted in smaller negative cumulative abnormal returns as opposed to strikes which lasted for less than 15 days.

Multicomponent ligand interactions are involved in essentially all nanoparticle (NP) applications. However, the ligand conformation and ligand binding mechanisms on NPs are highly controversial. The research reported here is focused on deepening the fundamental understanding of multicomponent ligand interactions with gold and silver nanoparticles (AuNPs and AgNPs) in water. We demonstrated that AuNPs passivated by saturated layer of poly(ethylene glycol) (PEG-SH) have large fractions of AuNP surface area available for ligand adsorption and exchange. The fraction of AuNP surface area passivated by PEG-SH with molecular weights of 2000, 5000, and 30000 g/mol was calculated to be ~ 25%, ~20%, and ~9% using 2-mercaptobenzimidazole and adenine as model ligands. The effect of both reduced and oxidized protein cysteine residues on protein interactions with AgNPs was investigated. The model proteins included wild-type and mutated GB3 variants with 0, 1, or 2 reduced cysteine residues. Bovine serum albumin containing 34 oxidized (disulfide-linked) and 1 reduced cysteine residues was also included. Protein cysteine content that were found to have no detectable effect on kinetics of protein/AgNP binding. However, only proteins that contain reduced cysteine induced significant AgNP dissolution. We further demonstrated that organothiols can induce both AgNP disintegration and formation under ambient conditions by simply mixing organothiols with AgNPs or AgNO3, respectively. Surface plasmon- and fluorescence-active AgNPs formed by changing the concentration ratio between Ag+ and organothiol. Organothiols also induced AuNP formation by mixing HAuCl4 with organothiols, but no AuNP disintegration occured. Finally, we proposed that multicomponent ligand binding to AuNPs can be highly dependent on the sequence of ligand mixing with AuNPs. Quantitative studies revealed that competitive adenine and glutathione adsorption onto both as-synthesized and PEG-SH functionalized AuNPs is predominantly a kinetically controlled process. Besides providing new insights on multicomponent ligand interactions with colloidal AuNPs and AgNPs, this study opens a new avenue for fabrication of novel nanomaterials in biological/biomedical applications.

No description available.

>Magister Scientiae - MSc / Different nanoparticles have the ability to improve plant tolerance to drought stress. In the study we report for the first time novel morpholin-4-ium 4-methoxyphenyl (morpholino) phosphinodithioate capped- gold nanoparticles (GYY4137-capped AuNPs). The GYY4137 is a slow releasing hydrogen sulfide (H2S) donor. The GYY4137 AuNPs compared to preliminary experiments of L-serine and L-threonine gold nanoparticles. The nanoparticles were prepared using a simple reflux reduction method in a rolling boil flask at 80 oC. The uncapped GYY4137-AuNPs were relatively stable and had surface plasmon resonance at 562 nm compared to 524 nm and 560 nm of serine-AuNPs and threonine-AuNPs. The nanoparticles were capped with different concentrations (0.1-5 %) of water-soluble poly (ethylene) glycol (PEG) (Mw300) and 0.2% chitosan. The PEG did not fully encapsulate the gold nanoparticles, while the chitosan successfully produced positively charged gold nanoparticles. The formation of chitosan capped GYY4137-AuNPs were verified with UV-Visible spectroscopy (UV-Vis), High Resolution Transmission electron microscopy (HRTEM), Dynamic Light scattering (DLS) and the Zetasizer. The UV-Vis, HRTEM and STEM verified chitosan capped nanoparticles had a surface plasmon resonance peak at 560 nm, with icosahedral, tetrahedron and spherical shaped nanoparticles as the serine-AuNPs that absorb at 560 nm. The agglomerated threonine-AuNPs had a maximum absorbance peak at 524 nm. The chitosan GYY4137-AuNPs had hydrodynamic size of 347.9 nm and zeta potential of + 47 mV, while serine-AuNPs and threonine-AuNPs had hydrodynamic size of 110 nm, zeta potential of -2.9 mV and -230 mV respectively. The polydispersity index (PDI) of the chitosan capped gold nanoparticles was 0.357 compared to 0.406 of both the amino acid gold nanoparticles. The polydispersity index (PDI) showed that the nanoparticles were polydispersed nanoparticles with broad size range as confirmed by the HRTEM and STEM results/ of chitosan capped GYY4137-AuNPs. The sizes of the nanoparticles were 100 nm and 60 nm for GYY4137-AuNPs while the size serine-AuNPs were 60 nm. The gold nanoparticles structural compositions were further confirmed by energy-dispersive X-ray spectrometry (EDX) and Attenuated total reflection infrared spectroscopy (ATR-IR). EDX results proved successful gold nanoparticles synthesis by presence of the element Au in all three nanoparticles and the chitosan GYY4137-AuNPs had 48. 56 wt. % of gold. The FTIR-ATR new bands formation shows that new chemical bonds are formed between the reducing agents, the precursor gold salt solution and capping agents. The shifts showed successful encapsulation with chitosan in GYY4137-AuNPs. The chitosan encapsulation improved surface charge and reactivity of the gold nanoparticles to improve delivery of the hydrogen sulfide donor GYY4137 for later applications to plants.

No description available.

No / Gold on polydimethylsiloxane (PDMS) stretchable conductors were prepared using a novel approach by interlacing an hydrogenated amorphous carbon (a-C : H) layer between the deposited metal layer and the elastomer. AFM analysis of the a-C : H film surface before gold deposition shows nanoscale buckling, the corresponding increase in specific surface area corresponds to a strain compensation for the first 4–6% of bi-axial tensile loading. Without this interlayer, the deposited gold films show much smaller and uni-directional ripples as well as more cracks and delaminations. With a-C : H interlayer, the initial electrical resistivity of the metal film decreases markedly (280-fold decrease to 8 × 10−6 Ω cm). This is not due to conduction within the carbon interlayer; both a-C : H/PDMS and PDMS substrates are electrically insulating. Upon cyclic tensile loading, both films become more resistive, but return to their initial state after 20 tensile cycles up to 60% strain. Profiling experiments using secondary ion mass spectroscopy and x-ray photoelectron spectroscopy indicate that the a-C : H layer intermixes with the PDMS, resulting in a graded layer of decreasing stiffness. We believe that both this graded layer and the surface buckling contribute to the observed improvement in the electrical performance of these stretchable conductors.

No / This paper presents a novel method to prepare stretchable conductors and pressure sensors based on the gold/polydimethylsiloxane (PDMS) system. The gold films were sputtered onto structured PDMS surfaces produced with a photolithographic surface treatment with the aim of reducing tensile strains in the gold film. Scanning electron microscopy (SEM) and atomic force microscopy analyses showed that these 3D patterns reduce cracks and delaminations in the gold film. Electrical measurements indicate that the patterns also protect the films against repeated tensile cycling, although the un-patterned samples remained conducting as well after the completion of 120 cycles. The extrapolated resistivity value of the patterned sample (4.5 × 10−5 Ωcm) compares well with previously published data. SEM micrographs indicate that the pattern features deflect the cracks and therefore toughen the gold film. However, x-ray photoelectron spectroscopy and contact angle analyses indicate that the patterning process also slightly modifies the surface chemistry. This patterning method was used to prepare capacitive strain gauges with pressure sensitivity (ΔZ/Z)/P of 0.14 kPa−1 in the sub-kPa regime. Such stretchable and potentially conformal low-pressure sensors have not been produced before and could prove advantageous for many smart fabric applications.