Dating of Old Lime Based Mixtures with the "Pure Lime Lumps" Technique

A number of studies carried out over the last forty years describe the application of radiocarbon dating of lime mixtures such as mortars, plasters and renders. Despite the fact that this method is very simple in principle, several studies have highlighted various practical challenges and factors that must be considered. These arise mainly from the contamination of samples with carbonaceous substances such as incompletely burnt limestone and aggregates of fossil origin including limestone sand. However, recently studies have shown that accurate sample processing allow a significant reduction of these error sources and moreover adoption of a special sampling procedure based on the careful selection of lumps of incompletely mixed lime, provides an interesting alternative that avoids problems associated with contamination. The founding principle underlying this technique is the use of the pure lime lumps. These are thought to originate from imperfect mixing and are most prevalent in mortars, renders and plasters predating mechanical mixing. Previous sampling methods for radiocarbon dating did not discriminate between pure and contaminated lime lumps. As pure lumps contain the same lime as that used in other parts of the mixtures but importantly are free of contaminants such as sand grains or under burned pieces of limestone, they can dramatically reduce the errors in the radiocarbon dating

EFFECTIVE COSTS AND CHEMICAL USE IN U.S. AGRICULTURAL PRODUCTION: BENEFITS AND COSTS OF USING THE ENVIRONMENT AS A "FREE" INPUT

This study uses a cost-function-based model of production processes in U.S. agriculture to represent producers' input and output decisions, and the implied costs of reductions in risk associated with leaching and runoff from agricultural chemical use. The model facilitates evaluation of the statistical significance of measured shadow values for "bad" outputs, and their input- and output-specific components, with a focus on the impacts on pesticide demand and its quality and quantity aspects. The shadow values of risk reduction are statistically significant, and imply increased demand for effective pesticides over time that stem largely from improvements in quality due to embodied technology, and that vary substantively by region.Environmental Economics and Policy, Farm Management,

Photocatalytic Properties of Commercially Available TiO2 Powders for Pollution Control

The photocatalytic properties of titanium dioxide have been widely studied over recent decades since the discovery of water photolysis by TiO2 electrodes in 1972. Titanium dioxide has three main crystal polymorphs; anatase, rutile and brookite and rutile is the most common as the metastable polymorph. Each polymorph has different band gap positions. Anatase’s band gap is 3.2 eV, higher than rutile’s which is 3.0 eV. This difference in the band gap will determine their optimum UV wavelength range to promote a photocatalytic process. There are different methods to assess the photocatalytic activity of a material. The most commonly used method is the degradation of a dye in aqueous solution under UV light, due to its simplicity. Under these conditions the decomposition rate of a suitable organic dye is used as a measure of activity. Physical properties such as particle size and surface area will determine the effective area that will interact and absorb the dye prior to degradation. The physical mechanisms involved in such aqueous based methods differ from gas phase reactions. More advanced techniques use mass spectrometers to evaluate photocatalytic activity of titanium dioxide in the gas phase. An effective photocatalyst for heterogeneous reactions in the gas phase is one which is efficient at creating radicals as a result of an absorbed photon

An α-disconnected space has no proper monic preimage

AbstractAll spaces are compact Hausdorff. α is an uncountable cardinal or the symbol ∞. A continuous map τ:X→Y is called an α-SpFi morphism if τ-1(G) is dense in X whenever G is a dense α-cozero set of Y. We thus have a category α-SpFi (spaces with the α-filter) which, like any category, has its monomorphisms; these need not be one-to-one. For general α, we cannot say what the α-SpFi monics are, but we show, and R.G. Woods showed, that ∞-SpFi monic means range-irreducible. The main theorem here is: X has no proper α-SpFi monic preimage if and only if X is α-disconnected. This generalizes (by putting in α = ∞) the well-known fact: X has no proper irreducible preimage if and only if X is extremally disconnected. If, in our theorem, we restrict to Boolean spaces and apply Stone duality, we have the theorem of R. Lagrange, that in Boolean α-algebras, epimorphisms are surjective.The theory of spaces with filters has a lot of connections with ordered algebra—Boolean algebras of course, but also lattice-ordered groups and frames. This paper is a contribution to the development of this topological theory

Effect of fibre loading on the microstructural, electrical, and mechanical properties of carbon fibre incorporated smart cement-based composites

Carbon fibre incorporated smart cement-based composite has great potential for the multifunctional health monitoring of concrete structures. This paper presents the microstructural, electrical, and mechanical properties of smart cement-based composites incorporating chopped carbon fibres from low dosages at 0–0.1% by volume (vol%) with detailed intervals, to high dosages up to 2.4 vol%. In comparison to a plain mortar, smart cement-based composites at all fibre contents had higher flexural strength. A 95% improvement in flexural strength was obtained at a fibre content of 0.3 vol%, whereas compressive strength increased up to a fibre content of 1.0 vol%, with the highest improvement, 105%, at 0.2 vol%. The bulk conductivity of smart cement-based composites underwent a double percolation process where the percolation zone of the fibres was identified at fibre contents of 0–0.1 vol% and the percolation zone of the capillary pores resided at fibre contents of 2.1–2.4 vol% indicating an extremely low durability. This study presents the laboratory characterization on smart cement-based composites where the fundamentals of the transitional behaviours of the mechanical properties and the percolation in electrical property through fibre loading were studied, which is a necessary step prior to the assessment of the self-sensing performance. The impact of this study will enable the physical properties of carbon fibre incorporated smart cement-based composites to be optimized through the design and manufacturing process. This will lead to robust performance and superior in-situ multi-functional health monitoring of concrete structures.</p

Towards the development of sustainable concrete incorporating waste tyre rubbers:A long-term study of physical, mechanical &amp; durability properties and environmental impact

The dramatic increase in the demand for vehicle tyres and consequently the rapid rise in associated waste rubber has been a concern for several decades. Rubber disposal has adverse effects on the environment, human health and a detrimental effect on sustainable development across the world. This paper investigates the effectiveness of a sodium hydroxide treatment method for waste rubber in addition to the utilisation of silica fume to improve the interfacial transition zone between the rubber and cement matrix. This has been shown to have important implication for the long-term development of physical and mechanical properties of concrete aged for 2 years. This study emphasises that while satisfactory improvements are attained through the rubber treatment alone, the actual performance of rubberized concrete containing silica fume could only be investigated over the long term owing to the slow pozzolanic reaction and its dependency on the formation of calcium hydroxide. The pre-treatment of rubber and more specifically the utilisation of silica fume improved the durability of concrete over rubber replacement levels from ∼20% to 40%. Long-term thermal conductivity and sound permeability of concrete containing tyre rubber were shown to have important consequences in energy conservation and social sustainability in construction practice. Results reported on the cost efficiency and consequently the CO2 emissions of concrete containing rubber do not only enhance awareness of the development of sustainable construction materials but also lead a cleaner alternative waste management route for tyre rubber

The vortex state in geologic materials: a micromagnetic perspective

A wide variety of Earth and planetary materials are very good recorders of paleomagnetic information. However, most magnetic grains in these materials are not in the stable single domain grain size range but are larger and in nonuniform vortex magnetization states. We provide a detailed account of vortex phenomena in geologic materials by simulating first‐order reversal curves (FORCs) via finite‐element micromagnetic modeling of magnetite nanoparticles with realistic morphologies. The particles have been reconstructed from focused ion beam nanotomography of magnetite‐bearing obsidian and accommodate single and multiple vortex structures. Single vortex (SV) grains have fingerprints with contributions to both the transient and transient‐free zones of FORC diagrams. A fundamental feature of the SV fingerprint is a central ridge, representing a distribution of negative saturation vortex annihilation fields. SV irreversible events at multiple field values along different FORC branches determine the asymmetry in the upper and lower lobes of generic bulk FORC diagrams of natural materials with grains predominantly in the vortex state. Multivortex (MV) FORC signatures are modeled here for the first time. MV grains contribute mostly to the transient‐free zone of a FORC diagram, averaging out to create a broad central peak. The intensity of the central peak is higher than that of the lobes, implying that MV particles are more abundant than SV particles in geologic materials with vortex state fingerprints. The abundance of MV particles, as well as their single domain‐like properties point to MV grains being the main natural remanent magnetization carriers in geologic materials

An updated analysis of NN elastic scattering data to 1.6 GeV

An energy-dependent and set of single-energy partial-wave analyses of $NN$ elastic scattering data have been completed. The fit to 1.6~GeV has been supplemented with a low-energy analysis to 400 MeV. Using the low-energy fit, we study the sensitivity of our analysis to the choice of $\pi NN$ coupling constant. We also comment on the possibility of fitting $np$ data alone. These results are compared with those found in the recent Nijmegen analyses. (Figures may be obtained from the authors upon request.)Comment: 17 pages of text, VPI-CAPS-7/

Sudakov Resummation for Subleading SCET Currents and Heavy-to-Light Form Factors

The hard-scattering contributions to heavy-to-light form factors at large recoil are studied systematically in soft-collinear effective theory (SCET). Large logarithms arising from multiple energy scales are resummed by matching QCD onto SCET in two stages via an intermediate effective theory. Anomalous dimensions in the intermediate theory are computed, and their form is shown to be constrained by conformal symmetry. Renormalization-group evolution equations are solved to give a complete leading-order analysis of the hard-scattering contributions, in which all single and double logarithms are resummed. In two cases, spin-symmetry relations for the soft-overlap contributions to form factors are shown not to be broken at any order in perturbation theory by hard-scattering corrections. One-loop matching calculations in the two effective theories are performed in sample cases, for which the relative importance of renormalization-group evolution and matching corrections is investigated. The asymptotic behavior of Sudakov logarithms appearing in the coefficient functions of the soft-overlap and hard-scattering contributions to form factors is analyzed.Comment: 50 pages, 10 figures; minor corrections, version to appear in JHE