Lime Based Materials in Construction: Experimental investigations for the development and validation of atomic models

Recent advances in computing power make atomistic modelling a viable approach for the study of complex chemical processes in a variety of applications. Atomistic modelling has, thus, the potential to explain some of the mechanisms of the most complex reactions occurring in construction materials such as carbonation of hydrates and the decomposition of carbonates. The research described in this paper seeks to highlight the potential of atomistic modelling applied to the materials used in the construction industry by investigating the decomposition process of dolomite. The paper, in particular, describes the results of experimental investigations that will be used to design and validate computational models. Studies undertaken using thermal gravimetric analysis, X-ray diffraction and Raman spectroscopy suggest that dolomite decomposes through the formation of Mg-rich calcite phases that, in turn, decompose forming lime and periclase. Results suggest that the view held by some researchers which describe the decomposition of dolomite through the formation of both, Ca and Mg carbonates as intermediate compounds may not be completely accurate and consequently, this process can be disregarded in developing the computational models

Metropolitan Centers: Evaluating Local Implementation of Regional Plans and Policies

The Denver and Salt Lake City Metropolitan Planning Organizations (MPOs) have embarked upon regional visioning strategies that promote development around higher density, mixed use centers with current or future access to transit. This study examines the programs and policies in the Salt Lake City and Denver regions to examine regional vision influence on local planning and the opportunities and constraints facing centers. The research team analyzed local plans over the past several decades, interviewed planners, and examined demographic, land use and transportation characteristics in select centers across the region. We found that the regional vision had a moderate influence on local planning, due to vague definitions and criteria. However, light rail investment and market forces have had a more substantial influence—resulting in cities developing supportive transit oriented development policies. While over 100 centers have been designated, many face significant challenges to support regional goals, particularly because many light rail lines were located along rail and freeway alignments. A limited number of “tipping point centers” already contain the necessary elements to be successful with city and private investment. Many “greenfield centers” offer significant future opportunity for development, but their suburban location and infrastructure needs present significant costs and challenges. Many other “redevelopment centers” are dominated by industrial, commercial or office development, and the land use and transportation patterns within these centers present substantial hurdles that may limit their potential to achieve regional goals

Carbonation of Hydrous Materials at the Molecular Level: A Time of Flight-Secondary Ion Mass Spectrometry, Raman and Density Functional Theory Study

Carbonation of hydrous minerals such as calcium hydroxide (Ca(OH)2) is an important process in environmental and industrial applications for the construction industry, geological disposal repositories for nuclear waste, and green technologies for carbon capture. Although the role of ions during the carbonation mechanism of Ca(OH)2 is still unclear, we identified the exchange of ions during the dissolution and precipitation process, by determining the change in isotopic composition of carbonation products using time-of-flight-secondary ion mass spectrometry. Our samples of pure Ca(18OH)2 carbonated in air were characterized using scanning electron microscopy and Raman spectroscopy, aided by density functional theory calculations. Our results show that the carbonation process at high pH is a two-stage mechanism. The first stage occurs in a short time after Ca(18OH)2 is exposed to air and involved the dissolution of surface Ca ions and hydroxyl 18OH groups, which reacts directly with dissolved CO2, leading to 1/3 of 18O in the oxygen content of carbonate phases. The second stage occurs within 24 h of exposure allowing a rebalance of the oxygen isotopic composition of the carbonate phases with a higher content of 16O

Atomistic modelling for the construction industry

Advances in computing power now make atomistic modelling a viable approach for the study of complex chemical processes in a number of applications including construction. We aim to apply these methods to processes such as the carbonation of lime mortars. The current research highlights the potential for studying construction materials using atomistic modelling. Computational models of different oxide structures simulating products of the thermal decomposition of dolomite support the view of some authors that suggest formation of phase separated calcium and magnesium minerals

Polynomial-time proofs that groups are hyperbolic

Funding: UK EPSRC grant number EP/I03582X/1.It is undecidable in general whether a given finitely presented group is word hyperbolic. We use the concept of pregroups, introduced by Stallings (1971), to define a new class of van Kampen diagrams, which represent groups as quotients of virtually free groups. We then present a polynomial-time procedure that analyses these diagrams, and either returns an explicit linear Dehn function for the presentation, or returns fail, together with its reasons for failure. Furthermore, if our procedure succeeds we are often able to produce in polynomial time a word problem solver for the presentation that runs in linear time. Our algorithms have been implemented, and when successful they are many orders of magnitude faster than KBMAG, the only comparable publicly available software.PostprintPeer reviewe

ElAM: A computer program for the analysis and representation of anisotropic elastic properties

Copyright © 2010 Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in Computer Physics Communications. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Computer Physics Communications, Volume 181, Issue 12 (2010), DOI: 10.1016/j.cpc.2010.08.033The continuum theory of elasticity has been used for more than a century and has applications in many fields of science and engineering. It is very robust, well understood and mathematically elegant. In the isotropic case elastic properties are easily represented, but for non-isotropic materials, even in the simple cubic symmetry, it can be difficult to visualise how properties such as Young's modulus or Poisson's ratio vary with stress/strain orientation. The ElAM (Elastic Anisotropy Measures) code carries out the required tensorial operations (inversion, rotation, diagonalisation) and creates 3D models of an elastic property's anisotropy. It can also produce 2D cuts in any given plane, compute averages following diverse schemes and query a database of elastic constants to support meta-analyses. Program summary Program title: ElAM1.0 Catalogue identifier: AEHB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 43 848 No. of bytes in distributed program, including test data, etc.: 2 498 882 Distribution format: tar.gz Programming language: Fortran90 Computer: Any Operating system: Linux, Windows (XP, Vista) RAM: Depends chiefly on the size of the arrays representing elastic properties in 3D Classification: 7.7 Nature of problem: Representation of elastic moduli and ratios, and of wave velocities, in 3D; automatic discovery of unusual elastic properties. Solution method: Stiffness matrix (6×6)(6×6) inversion and conversion to compliance tensor (3×3×3×3)(3×3×3×3), tensor rotation, dynamic matrix diagonalisation, simple optimisation, postscript and VRML output preparation. Running time: Dependent on angular accuracy and size of elastic constant database (from a few seconds to a few hours). The tests provided take from a few seconds for test0 to approximately 1 hour for test4

Atomistic modelling for low-carbon cement and concrete technologies

In recent years, a number of theoretical methods and computational techniques have been applied to construction materials to investigate processes such as water transport in nano-pores and hydration processes in cement. This approach has proved to be extremely useful and beneficial to understanding the chemical and physical processes. These methods and techniques are generally referred to as “atomistic modelling”. The main limitation to a more widespread use of atomistic modelling has been the computing power. However, recent advances in the speed at which computers can now process data make these methods and techniques a viable approach for the study of complex chemical processes in construction materials. This contribution seeks to highlight the potential of atomistic modelling applied to the development of low carbon building materials. In our research we investigated different processes involved in the production and use of lime by combining atomistic modelling and applied research. Experimental data from manufactured samples were used to inform atomistic models which, in turn, can guide the development of materials with optimised performance

Role of the Fractalkine Receptor in CNS Autoimmune Inflammation: New Approach Utilizing a Mouse Model Expressing the Human CX3CR1

Multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system (CNS) is the leading cause of non-traumatic neurological disability in young adults. Immune mediated destruction of myelin and oligodendrocytes is considered the primary pathology of MS, but progressive axonal loss is the major cause of neurological disability. In an effort to understand microglia function during CNS inflammation, our laboratory focuses on the fractalkine/CX3CR1 signaling as a regulator of microglia neurotoxicity in various models of neurodegeneration. Fractalkine (FKN) is a transmembrane chemokine expressed in the CNS by neurons and signals through its unique receptor CX3CR1 present in microglia. During experimental autoimmune encephalomyelitis (EAE), CX3CR1 deficiency confers exacerbated disease defined by severe inflammation and neuronal loss. The CX3CR1 human polymorphism I249/M280 present in ∼20% of the population exhibits reduced adhesion for FKN conferring defective signaling whose role in microglia function and influence on neurons during MS remains unsolved. The aim of this study is to assess the effect of weaker signaling through hCX3CR1I249/M280 during EAE. We hypothesize that dysregulated microglial responses due to impaired CX3CR1 signaling enhance neuronal/axonal damage. We generated an animal model replacing the mouse CX3CR1 locus for the hCX3CR1I249/M280 variant. Upon EAE induction, these mice exhibited exacerbated EAE correlating with severe inflammation and neuronal loss. We also observed that mice with aberrant CX3CR1 signaling are unable to produce FKN and ciliary neurotrophic factor during EAE in contrast to wild type mice. Our results provide validation of defective function of the hCX3CR1I249/M280 variant and the foundation to broaden the understanding of microglia dysfunction during neuroinflammation. © 2018 Cardona et al