33,407 research outputs found
Jack Baird and Henry R. Clay
No full textL-R Jack Baird, in Scottish uniform, and Henry R. Clay standing in front of a house. Image displayed (72 dpi JPEG), Master image (600 dpi TIFF)
Clay minerals in South Australian Holocene basaltic volcanogenic soils and implications for halloysite genesis and structure
No full textThe clay mineralogical composition was determined of 8 soils formed from pyroclastic ejecta (tephra) from adjacent 5000-year old basaltic volcanoes at Mounts Gambier and Schank in South Australia. Both nanocrystalline (short-range order) and crystalline aluminosilicates and also Fe oxides and hydroxides were identified in the soils. Allophane generally occurred to a greater extent in the 4 soils derived from glass-rich Mt Schank tephra than in most of those from glass-poor Mt Gambier tephra. Ferrihydrite occurred along with allophane. Smectite, kaolinite, illite, and an interstratified kaolinite-smectite comprised the crystalline minerals in these soils. There was no evidence for halloysite. Unlike in New Zealand, decreased leaching resulted in Si-rich allophane, rather than halloysite, forming in place of the Al-rich form of the same mineral. This result may indicate that ferrous iron is an essential impurity in halloysite. It was likely absent from these soils because their high pH due to underlying calcareous rocks precludes its occurrence. The probable requirement of Fe(II) as an essential component of halloysites may have been overlooked because of oxidation consequent upon the inevitable drying of samples prior to analyses
Polymer-clay Nanocomposites
No full textPhDPolymer-clay nanocomposites are attracting global interest principally because
property enhancements are obtained at low clay particle loadings (1-5 wt%).
However there is lack of fundamental understanding of such composites. The aim
of this work is to provide an insight into the interaction between polymer and clay.
This includes the driving force for intercalation, the reinforcement mechanisms and
property-volume fraction relationships.
Functionalised poly(ethylene glycol)-clay, poly(c-caprolactone)-clay and
thermoplastic starch-clay nanocomposites with a range of polymer molecular
weights, clay volume fractions and with different clays were prepared using
solution methods, melt-processing methods, and in situ polymerisation. A reliable
X-ray diffraction technique for low angle basal plane spacing of clay, the essential
parameter for structure determination, was established obtaining ±0.005 Mn
between three diffractometers. The basal plane spacing was found to be unaffected
by polymer molecular weight and preparation method but was affected by the
nature of the polymer and clay. Increasing clay loading could lead to a lower
spacing. As a cautionary observation, poly(ethylene glycol) with high molecular
weight (2: 10,000) was found to undergo degradation readily during preparation of
nanocomposites with and without clay.
Competitive sorption experiments for molecular weight showed that high
molecular weight fractions of polymer intercalate preferentially into clay during
solution preparation. Thermodynamic studies on the intercalation process found
that significant enthalpic change occurred during intercalation, which is coincident
with the observation that heat-treated clays without interlayer water can intercalate
polymer. The calculation of true volume fraction against nominal volume fraction
provided reasonable explanation of property enhancement and helps understand the
relation between nanocomposites and conventional composites. At a given clay
loading, nanocomposites with better dispersion gave more property enhancement
than those with lower dispersion or conventional composites. The crystallinity of
semicrystalline polymer was also affected by varying extents of dispersion of clay.
The use of X-ray diffraction with an internal standard was explored for quantitative
analysis of intercalation and exfoliation
Henry R. Clay in Oxford, Endland
No full textHenry Clay, sitting left in sports clothing, while at Oxford, England in 1917. Image displayed. (72 dpi JPEG), Master image (600 dpi TIFF)
A ‘putty-practically-clay’ vintage model with R&D driven biases in energy-saving technical change
Get PDFThis paper deals with the problem of tackling the adverse effect of output growth on environmental quality. For this purpose we use an intermediate sector that builds ‘putty-practically-clay’ capital consisting of an energy-raw capital amalgam used for final goods production. The putty-practically-clay model is a strongly simplified version of a full putty-clay model, that mimics all the relevant behaviour of a full putty-clay model, but that does not entail the administrative hassle of a full putty-clay vintage model. In addition to this, we introduce an R&D sector that develops renewable- and conventional energy-based technologies. The allocation of R&D activities over these two uses of R&D gives rise to an induced bias in technical change very much as in Kennedy (1964). In the context of our model, this implies that technological progress is primarily driven by the desire to counteract the upward pressure on production cost implied by a continuing price increase of conventional energy resources. Hotelling’s rule suggests that this price rise is unavoidable in the face of the ongoing depletion of conventional energy reserves. By means of some illustrative model simulations we study the effects of energy policy on the dynamics of the model for alternative policy options aimed at achieving GHG emission reductions. We identify the conditions under which energy policy might partly backfire and present some non-standard policy implications.macroeconomics ;
Mineral acquisition from clay by Budongo Forest chimpanzees
Get PDFDate of Acceptance: 06/07/2015Chimpanzees of the Sonso community, Budongo Forest, Uganda were observed eating clay and drinking clay-water from waterholes. We show that clay, clay-rich water, and clay obtained with leaf sponges, provide a range of minerals in different concentrations. The presence of aluminium in the clay consumed indicates that it takes the form of kaolinite. We discuss the contribution of clay geophagy to the mineral intake of the Sonso chimpanzees and show that clay eaten using leaf sponges is particularly rich in minerals. We show that termite mound soil, also regularly consumed, is rich in minerals. We discuss the frequency of clay and termite soil geophagy in the context of the disappearance from Budongo Forest of a formerly rich source of minerals, the decaying pith of Raphia farinifera palms.Peer reviewe
Prefferred orientations and anisottropy in shales: Callovo-oxfordian shale (France) and opalinus clay (Switzerland)
No full textAnisotropy in clay-rich sedimentary rocks is receiving increasing attention. Seismic anisotropy is essential in the prospecting for petroleum deposits. Anisotropy of diffusion has become relevant for environmental contaminants, including nuclear waste. In both cases, the orientation of component minerals is a critical ingredient and, largely because of small grain size and poor crystallinity, the orientation distribution of clay minerals has been difficult to quantify. A method is demonstrated that relies on hard synchrotron X-rays to obtain diffraction images of shales and applies the crystallographic Rietveld method to deconvolute the images and extract quantitative information about phase fractions and preferred orientation that can then be used to model macroscopic physical properties. The method is applied to shales from European studies which investigate the suitability of shales as potential nuclear waste repositories (Meuse/Haute-Marne Underground Research Laboratory near Bure, France, and Benken borehole and Mont Terri Rock Laboratory, Switzerland). A Callovo-Oxfordian shale from Meuse/Haute-Marne shows a relatively weak alignment of clay minerals and a random distribution for calcite. Opalinus shales from Benken and Mont Terri show strong alignment of illite-smectite, kaolinite, chlorite, and calcite. This intrinsic contribution to anisotropy is consistent with macroscopic physical properties where anisotropy is caused both by the orientation distribution of crystallites and high-aspect-ratio pores. Polycrystal elastic properties are obtained by averaging single crystal properties over the orientation distribution and polyphase properties by averaging over all phases. From elastic properties we obtain anisotropies for p waves ranging from 7 to 22%
Guide to the nature and methods of analysis of the clay fraction of tephras from the South Auckland region, New Zealand.
No full textThe manual outlines some of the more common laboratory procedures available for qualitatively and quantitatively analysing the composition of the tephric clays, many of which are difficult to determine because of their short range order or 'amorphous' nature. Techniques described and assessed in terms of their rapidity and quantitativeness include XRD, IR, DTA, TEM and SEM, sodium fluoride reactivity, chemical dissolution analyses, and surface area measurements. No one technique alone produces a definitive clay fraction analysis of tephric deposits. -from Author
Reactivity of the Clay Mineral Montmorillonite: A First Principles Study
No full textPhDThe recent development of clay-polymer nanocomposite materials has led to ail
increased interest in the structure and properties of clay minerals. In this thesis the
reactivity of the clay mineral montmorillonite is explored by means of density
functional theory based calculations. In particular three aspects are considered:
catalytic properties, cation migration and dehydroxylation.
The origin of the catalytic properties of the clay mineral is investigated in the
context of the synthesis of clay-polymer nanocomposite materials, by in sttu,
intercalative polymerisation. It is found that catalysis is most likely to occur at the
clay mineral lattice-edge where exposed aluminium atoms act as Lewis acid sites.
Migration of lithium cations into the clay mineral lattice is explored by
means of first principles molecular dynamics. Comparison of calculated hvdrox-vl
stretching frequencies, with those from experiment indicates that cations migrate to
vacant octahedral sites, as oppose to the ditrigonal cavities.
Dehydroxylation of the clay mineral is examined by consideration of a cis-vacant
pyrophyllite structure. It is shown that dehydroxylation leads to formation of a
tyan8-vacant structure, with aluminium in trigonal bipyramidal coordination and a
highly distorted tetrahedral layer. Differences in the dehydroxylation behaviour of
cm and tran8-vacant pyrophyllite are shown to be due to the fact that in the
former adjacent hydroxyl groups bridge different pairs of aluminium atoms,
while in the latter they are both bonded to the same pair.
Overall density functional theory based calculations are shown to be
a powerful tool for the studly of the structure and reactivity of clay minerals.Queen Mary University of London
W.R. Grace & Co
Capital accumulation, unemployment, and the putty-clay
Get PDFThis note studies the dynamics of labor markets in a putty-clay framework. It analyzes the evolution of job creation and job destruction in an economy without market frictions. Unemployment and labor market flows emerge under putty-clay technologies because low productive jobs become unused factors. As capital accumulates, firms destruct low productive jobs by obsolescence. Simultaneously, the use of capital intensive technologies s new jobs by the low substitution between capital and labor.
- …
