Influence of age on masonry bond strength and mortar microstructureThis article is one of a selection of papers published in this Special Issue on Masonry.

2007 ◽  
Vol 34 (11) ◽  
pp. 1433-1442 ◽  
Author(s):  
Heber Sugo ◽  
Adrian W. Page ◽  
Stephen Lawrence
Keyword(s):  
Bond Strength ◽  
Microstructural Change ◽  
Small Scale ◽  
Initial Increase ◽  
Special Issue ◽  
X Ray Diffraction ◽  
X Ray ◽  
The University ◽  
Effect Of Age ◽  
Selection Of

The effect of age on bond strength and mortar microstructure was investigated as part of an ongoing masonry bond strength research program at The University of Newcastle. Previous work has shown that both strength losses and strength gains occur with age. The potential loss of bond strength with time has structural implications as the design of masonry using the Australian masonry standard AS 3700–2001 is based on the 7 d bond strength. In this investigation, a single mortar-and-unit combination (dry pressed clay and 1:1:6 mortar) cured under ambient laboratory conditions was studied. Bond strength was determined at ages ranging from 3 to 365 d using a small-scale uniaxial tension test. Maximum bond strength was observed to occur at 180 d with strength minima occurring at 90 and 365 d. Scanning electron microscopy and X-ray diffraction techniques were used to further identify the mortar constituents and hydration levels. Changes in the density of the paste microstructure were observed up to 28 d, which correlated with the initial increase in bond strength. No other microstructural change to account for the strength variations between 28 and 365 d could be observed using these techniques.

Dalnegroite, Tl5–xPb2x(As,Sb)2l–xS34, a new thallium sulphosalt from Lengenbach quarry, Binntal, Switzerland

2009 ◽  
Vol 73 (6) ◽  
pp. 1027-1032 ◽  
Author(s):  
F. Nestola ◽  
A. Guastoni ◽  
L. Bindi ◽  
L. Secco
Keyword(s):  
Polarized Light ◽  
New Mineral ◽  
X Ray Diffraction ◽  
X Ray ◽  
Elemental Concentrations ◽  
Reflected Light ◽  
Mohs Hardness ◽  
The Mean ◽  
The University ◽  
Probable Space

AbstractDalnegroite, ideally Tl4Pb2(As12Sb8)Σ20S34, is a new mineral from Lengenbach, Binntal, Switzerland. It occurs as anhedral to subhedral grains up to 200 μm across, closely associated with realgar, pyrite, Sb-rich seligmanite in a gangue of dolomite. Dalnegroite is opaque with a submetallic lustre and shows a brownish-red streak. It is brittle; the Vickers hardness (VHN25) is 87 kg mm-2(range: 69—101) (Mohs hardness ∼3—3½). In reflected light, dalnegroite is highly bireflectant and weakly pleochroic, from white to a slightly greenish-grey. In cross-polarized light, it is highly anisotropic with bluish to green rotation tints and red internal reflections.According to chemical and X-ray diffraction data, dalnegroite appears to be isotypic with chabournéite, Tl5-xPb2x(Sb,As)21-xS34. It is triclinic, probable space groupP1, witha= 16.217(7) Å,b= 42.544(9) Å,c= 8.557(4) Å, α = 95.72(4)°, β = 90.25(4)°, γ = 96.78(4)°,V= 5832(4) Å3,Z= 4.The nine strongest powder-diffraction lines [d(Å) (I/I0) (hkl)] are: 3.927 (100) (10 0); 3.775 (45) (22); 3.685 (45) (60); 3.620 (50) (440); 3.124 (50) (2); 2.929 (60) (42); 2.850 (70) (42); 2.579 (45) (02); 2.097 (60) (024). The mean of 11 electron microprobe analyses gave elemental concentrations as follows: Pb 10.09(1) wt.%, Tl 20.36(1), Sb 23.95(1), As 21.33(8), S 26.16(8), totalling 101.95 wt.%, corresponding to Tl4.15Pb2.03(As11.86Sb8.20)S34. The new mineral is named for Alberto Dal Negro, Professor in Mineralogy and Crystallography at the University of Padova since 1976.

Solid-state Thermoelectric Characteristics of NiII, FeII, CoII, and CuII Borohydrides

2021 ◽  
Author(s):  
Isam M. Arafa ◽  
Mazin Y. Shatnawi ◽  
Yousef N. Obeidallah ◽  
Ahmed K. Hijazi ◽  
Yaser A . Yousef
Keyword(s):  
Energy Transport ◽  
Waste Heat ◽  
Mixed Valence ◽  
Small Scale ◽  
X Ray Diffraction ◽  
Promising Candidate ◽  
X Ray ◽  
Cold Pressed ◽  
Thermal Energy Transport ◽  
Body Heat

Abstract Four transition metal borohydrides (MTBHs, MT = Ni, Fe, Co, and Cu) were prepared by sonicating a mixture of the desired MT salt with excess NaBH4 in a nonaqueous DMF/CH3OH media. The process afforded bimetallic (Ni-BH4), trimetallic (Fe-BH4, Co-BH4), and mixed-valence (Cu-H, Cu-BH4) amorphous, ferromagnetic nanoparticles as identified by thermal, ATR-IR, X-Ray diffraction, and magnetic susceptibility techniques. The electrical conductivity (σ) of cold-pressed discs of these MTBHs shows a nonlinear increase while their thermal conductivity (κ) decreases in the temperature range of 303 ≤ T ≤ 373 K. The thermal energy transport occurs through phonon lattice dynamics rather than electronic. The σ/κ ratio shows a nonlinear steep increase from 9.4 to 270 KV-2 in Ni-BH4, while a moderate-weak increase is observed for Fe-BH4, Co-BH4, and Cu-BH4. Accordingly, the corresponding thermoelectric (TE) parameters S, PF, ZT, and η were evaluated. All TE data shows that the bimetallic Ni-BH4 (S, 80 μVK-1; PF, 259 μWm-1K-2; ZT 0.64; η, 2.56%) is a better TE semiconductor than the other three MT-BHs investigated in this study. Our findings show that Ni-BH4 is a promising candidate to exploit low-temperature waste heat from body heat, sunshine, and small domestic devices for small-scale TE applications.

scholarly journals Solidified Fillings of Nanopores

2005 ◽  
Vol 876 ◽  
Author(s):  
Patrick Huber ◽  
Klaus Knorr
Keyword(s):  
Pore Diameter ◽  
Stacking Faults ◽  
Pore Geometry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Medium Length ◽  
Close Packed Structure ◽  
Packed Structure ◽  
Diffraction Patterns ◽  
Selection Of

AbstractWe present a selection of x-ray diffraction patterns of spherical (He, Ar), dumbbell- (N2, CO), and chain-like molecules (n-C9H20, n-C19H40) solidified in nanopores of silica glass (mean pore diameter 7nm). These patterns allow us to demonstrate how key principles governing crystallization have to be adapted in order to accomplish solidification in restricted geometries. 4He, Ar, and the spherical close packed phases of CO and N2 adjust to the pore geometry by introducing a sizeable amount of stacking faults. For the pore solidified, medium-length chainlike n-C19H40 we observe a close packed structure without lamellar ordering, whereas for the short-chain C9H20 the layering principle survives, albeit in a modified fashion compared to the bulk phase.

Evolution of texture and internal stresses within polycrystalline rock salt using in situ 3D synchrotron computed tomography and 3D X-ray diffraction

2021 ◽  
Vol 54 (5) ◽  
pp. 1379-1393
Author(s):  
Amirsalar Moslehy ◽  
Khalid A. Alshibli ◽  
Timothy J. Truster ◽  
Peter Kenesei ◽  
Wadi H. Imseeh ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Slip System ◽  
Rock Salt ◽  
Small Scale ◽  
Internal Stresses ◽  
X Ray Diffraction ◽  
Crack Network ◽  
X Ray ◽  
Fully Connected

Rock salt caverns have been extensively used as reliable repositories for hazardous waste such as nuclear waste, oil or compressed gases. Undisturbed rock salt deposits in nature are usually impermeable and have very low porosity. However, rock salt formations under excavation stresses can develop crack networks, which increase their porosities; and in the case of a connected crack network within the media, rock salt may become permeable. Although the relationship between the permeability of rock salt and the applied stresses has been reported in the literature, a microscopic study that investigates the properties influencing this relationship, such as the evolution of texture and internal stresses, has yet to be conducted. This study employs in situ 3D synchrotron micro-computed tomography and 3D X-ray diffraction (3DXRD) on two small-scale polycrystalline rock salt specimens to investigate the evolution of the texture and internal stresses within the specimens. The 3DXRD technique measures the 3D crystal structure and lattice strains within rock salt grains. The specimens were prepared under 1D compression conditions and have shown an initial {111} preferred texture, a dominant {110}〈110〉 slip system and no fully connected crack network. The {111} preferred texture under the unconfined compression experiment became stronger, while the {111}〈110〉 slip system became more prominent. The specimens did not have a fully connected crack network until applied axial stresses reached about 30 MPa, at a point where the impermeability of the material becomes compromised due to the development of multiple major cracks.

Editorial

2018 ◽  
pp. 1-4
Author(s):  
Daniele Checci ◽  
Janet Gornick
Keyword(s):  
Income Distribution ◽  
Data Center ◽  
Research Community ◽  
Final Outcome ◽  
Special Issue ◽  
National Data ◽  
Blind Review ◽  
The University ◽  
Selection Of ◽  
Cross National

The articles included in this special issue of the Journal of Income Distribution are a selection of papers originally presented at the first LIS-LWS Users Conference, hosted by LIS, the cross-national data center in Luxembourg. The conference took place at the University of Luxembourg in Belval, Luxembourg, on April 27- 28, 2017. The submitted papers underwent a process of blind review, and this collection of five articles is the final outcome. Taken as a whole, these articles constitute an interesting overview of the ways in which the research community uses the LIS-LWS Databases, which provide researchers access to microdata on income and wealth, respectively.

The Colonial Experience in Education: Historical Issues and Perspectives. Edited by ANTONIO NÓVOA, MARC DEPAEPE, ERWIN V. JOHANNINGMEIER. (Pedagogica Historica: Supplementary Series, Vol. 1.) Gent: CSHP, 1995. Pp. 382. Belg. Fr. 1200 (ISSN 0030-9230; ISBN 90-800947-3-6).

1997 ◽  
Vol 38 (1) ◽  
pp. 123-177
Author(s):  
JOHN D. HARGREAVES
Keyword(s):  
History Of Education ◽  
Special Issue ◽  
International Conference ◽  
Supplementary Series ◽  
Colonial Experience ◽  
History Of ◽  
The University ◽  
Historical Issues ◽  
Selection Of

This special issue of Pedagogica Historica, a journal published from the University of Gent, presents a selection of eighteen papers from an international conference on the history of education held in Lisbon in 1993. The texts are in English and French, although there are no contributors from France or Britain. The contributions deal with general themes and European backgrounds as well as colonial experience. Six which relate to Africa will be briefly described here.

scholarly journals Kinetic Control of Parallel versus Antiparallel Amyloid Aggregation via Shape of the Growing Aggregate

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ali Asghar Hakami Zanjani ◽  
Nicholas P. Reynolds ◽  
Afang Zhang ◽  
Tanja Schilling ◽  
Raffaele Mezzenga ◽  
...  
Keyword(s):  
Self Assembly ◽  
Small Scale ◽  
Kinetic Control ◽  
Amyloid Aggregation ◽  
X Ray Diffraction ◽  
Human Lysozyme ◽  
X Ray ◽  
Contact Topology ◽  
Future Design ◽  
Assembly Pathways

Abstract By combining atomistic and higher-level modelling with solution X-ray diffraction we analyse self-assembly pathways for the IFQINS hexapeptide, a bio-relevant amyloid former derived from human lysozyme. We verify that (at least) two metastable polymorphic structures exist for this system which are substantially different at the atomistic scale, and compare the conditions under which they are kinetically accessible. We further examine the higher-level polymorphism for these systems at the nanometre to micrometre scales, which is manifested in kinetic differences and in shape differences between structures instead of or as well as differences in the small-scale contact topology. Any future design of structure based inhibitors of the IFQINS steric zipper, or of close homologues such as TFQINS which are likely to have similar structures, should take account of this polymorphic assembly.

Innovative seismic design of a post-tensioned concrete masonry houseThis article is one of a selection of papers published in this Special Issue on Masonry.

2007 ◽  
Vol 34 (11) ◽  
pp. 1393-1402 ◽  
Author(s):  
Gavin D. Wight ◽  
Jason M. Ingham ◽  
Andrew R. Wilton
Keyword(s):  
Seismic Design ◽  
Masonry Walls ◽  
Special Issue ◽  
Innovative Design ◽  
Concrete Masonry ◽  
Limited Application ◽  
House Design ◽  
The University ◽  
Selection Of ◽  
Post Tensioned

Post-tensioned concrete masonry walls provide improved seismic performance, but have had limited application in seismic regions because of a lack of research pertaining to their in-plane response. Following focused research over recent years, a consortium of product suppliers has collaborated with the University of Auckland to construct New Zealand’s first post-tensioned concrete masonry house. A feature of this innovative design was that all incorporated products were commercially available, with no proprietary products being specifically developed for the prestressed masonry system used. Consequently, it is hoped that this house will be a showcase, and provide exposure for the technology in New Zealand and elsewhere. This paper provides a brief review of previous post-tensioned concrete masonry research applications, then discusses post-tensioning details and their application to house design and construction.

Experiments using a light gas gun to investigate the impact melting of gunshot residue analogues

2019 ◽  
Author(s):  
V. Spathis ◽  
M. C. Price
Keyword(s):  
Physical State ◽  
Gunshot Residue ◽  
Ignition Process ◽  
X Ray ◽  
Gas Gun ◽  
High Purity Silicon ◽  
The University ◽  
The Impact ◽  
Insight Into ◽  
Selection Of

Abstract In this set of experiments, the versatility of the University of Kent's light gas gun was utilised to obtain a selection of corroborative data regarding the formation and impact of metallic gunshot residues onto high purity silicon wafers. The results from the two experiments are presented. The first experiment investigated how the formation of metallic residues varied as gunshot residue analogues traversed through air under a range of pressures from 0.056 millibar (5.6 Pa) to 1 bar (100 kPa), using solely the energy released during primer ignition; the second involved firing a metallic powder mix of pre-determined composition (via a split-sabot) under vacuum at two velocities- 500 ms-1 and 2000 ms-1. This ensured that there was no ignition or heating of the powders, unlike the first experiment, and so the morphology of the particles collected would be solely due to impact. The residues on the substrates were then analysed using a cold Field Emission Gun Scanning Electron Microscope (FEG) and Energy Dispersive X-ray (EDX) detector. By separating the ignition process of the primers from the residue impacts, it allows for a closer look into the formation of these particles and helps determine whether their varied morphologies are due to the heating caused during the activation and combustion of the primer or whether its due to impact melting. This information can aid in the understanding of metallic particle formation in different pressure environments and give insight into the physical state of firearm residues when they impact a surface. Hydrocode modelling was also incorporated to corroborate the results observed during these experiments and gave results which mimicked the experimental data.

scholarly journals Petrographic and Chemical–Mineralogical Characterization of Mortars from the Cistern at Amaiur Castle (Navarre, Spain)

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 311 ◽  
Author(s):  
Graciela Ponce-Antón ◽  
Maria Cruz Zuluaga ◽  
Luis Angel Ortega ◽  
Juantxo Agirre Mauleon
Keyword(s):  
Organic Additive ◽  
X Ray Diffraction ◽  
Mineralogical Characterization ◽  
X Ray ◽  
Rock Fragments ◽  
Application Techniques ◽  
Aggregate Nature ◽  
Specific Construction ◽  
Selection Of

Mortars from the cistern in Amaiur Castle (Navarre, Spain) were analysed to assess the mortar manufacturing process and application techniques. To this end, optical microscopy, scanning electron microscopy (SEM), thermogravimetric analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), Raman microspectroscopy, and Fourier transform infrared spectroscopy (FTIR) were performed. The study of both structural and plaster mortars from Amaiur Castle cistern show patterns/rules in the mortar manufacture according to the specific construction requirements. A multilayer application technique was used for the construction of the cistern tank. Deliberate selection of the aggregate nature and grading contributed to mortar impermeability. Ceramic and silico-aluminous rock fragments were used as aggregates in the cistern tank to confer hydraulicity to the mortars, instead of carbonated aggregates as used in the vault. Aluminosilicated phases present in the aggregates led to the formation of amesite, which is a magnesium aluminosilicate hydrate (M-A-S-H) phase conferring hydraulicity to the mortar. Two types of additives were identified in the outer pigmented layer of plaster. Beeswax was the identified organic additive used to improve the impermeability of mortar, while hematite was the identified inorganic additive giving rise to the reddish colour of the layer.

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