Bronwyn Lowe

Thermal and moisture transfer properties of sock fabrics differing in fiber type, yarn, and fabric structure

This study aimed to determine the relative effects of fiber type (fine wool, mid-micron wool, acrylic), yarn type (high-twist, low-twist, single), and fabric structure (single jersey, half-terry, terry) on thermal resistance, water vapor resistance, thermal conductance, water vapor permeability, liquid absorption capacity, and regain of sock fabrics. Fabric structure had the greatest effect on thermal resistance, water vapor resistance, water vapor permeability, liquid absorption capacity, and thermal conductance. Terry fabrics were the most thermal and water vapor resistant, most absorbent, and most conductive. Results were consistent with current understanding of the effect of fabric thickness on thermal and moisture transfer properties when measured under static conditions: However, the effects of yarn type and/or fabric structure of sock fabrics have not previously been explained.

The Effect of Ultrasonic Instruments on the Quality of Preparation Margins and Bonding to Dentin

STATEMENT OF THE PROBLEM Ultrasonic instruments have recently been developed for finishing crown preparations. They are successful in accessing difficult areas on the preparation margin, but their effects on the dentin surface and on bond strength are contradictory. PURPOSE The aim was to evaluate the condition of crown preparation margins finished using new ultrasonic instruments and to assess their effects on dentin bond strength. METHODS Characteristics of tooth surfaces prepared using two different ultrasonic protocols were compared; Perfect Margin Shoulder (PMS) (PMS 3, Satelec, Merignac, France) 1, 2, and 3 (complete finishing) versus PMS 1 and 2 (partial finishing). They were assessed using scanning electron microscopy (SEM) and surface roughness analysis. Bonding of composite resin to dentin surfaces prepared with the complete PMS kit was compared with dentin surfaces prepared with finishing diamond burs, using micro-tensile testing. RESULTS SEM images revealed a clear difference between the two preparation sequences (PMS 1, 2 versus PMS 1, 2, and 3). Surfaces finished using the PMS tips 1, 2, and 3 appeared continuous, even, and smooth compared with PMS tips 1 and 2 only. The additional use of the PMS 3 uncoated tip enhanced smear layer removal. There was no significant difference when comparing the surface roughness obtained with the PMS 1, 2, and 3 protocol with the PMS 1 and 2 only (p > 0.05). Micro-tensile bond strength was not significantly different between the surfaces prepared with the ultrasonic instruments and the surfaces prepared with the diamond burs (p > 0.05). CONCLUSION The use of the complete PMS finishing kit (PMS 1, 2, and 3) produced better quality finishing lines than PMS 1 and 2. The use of ultrasonic instruments to prepare dentin resulted in comparable bond strengths to the use of diamond burs. CLINICAL SIGNIFICANCE The extremely precise preparation margin possible with ultrasonic instruments improves the quality and accuracy of crown preparations, which may lead to better impressions and closer adaptation of restorations. The complete set of three Perfect Margin Shoulder instruments is recommended, which can produce comparable bond strengths to preparations with rotary instruments.

Understanding the variability of vegetable fibres: a case study of harakeke (Phormium tenax)

Fibre properties may be an important source of information to identify, conserve and protect intraspecific diversity within culturally significant fibre plants such as harakeke (Phormium tenax, New Zealand flax). Māori weavers recognise differences in whītau * (fibre aggregate prepared using traditional practices) extracted from leaves of different harakeke cultivars. However, tensile properties of fibre aggregates are reportedly highly variable. The aim of this study was to investigate variation in fibre aggregate physical and mechanical properties among leaves harvested from different fans within two bushes representing different cultivars of harakeke. Tenacity, extension to maximum load, specific modulus and specific energy to maximum load of fibre aggregates differed between the bushes, and also among leaves within each bush. Leaf width and thickness were weakly correlated with fibre aggregate properties suggesting that wider, thicker leaves yield tougher and more pliable fibre aggregates. Variability among leaves differed according to the property measured, and was highest for fibre aggregate length and lowest for specific energy to maximum load. Although fibre aggregate tenacity (or strength) is commonly used to compare intra and interspecific fibre properties, specific modulus, extension at maximum load and specific energy to maximum load were all more appropriate for identifying intraspecific differences in harakeke fibre properties.

The effect of fiber type, yarn structure and fabric structure on the frictional characteristics of sock fabrics

The objective of this study was to measure the combined effects of fiber type (fine wool, mid-micron wool, acrylic), yarn type (high twist, low twist, single) and fabric structure (single jersey, half-terry, terry) on friction between sock fabrics and a synthetic skin using the horizontal platform method. The effect of weight of a hypothetical wearer and moisture content of a sock fabric were also investigated. Differences among fabrics were analyzed using frictional force traces. Data compared included the static and dynamic friction and coefficients of friction, as well as three new descriptive parameters. All variables investigated affected the frictional characteristics between a sock fabric and a synthetic skin. Single jersey fabrics had the lowest coefficient of static and dynamic friction. Friction between fabric and a synthetic skin was affected most by the applied weight, with the simulated adult weight resulting in a greater frictional force, and higher coefficients of static and dynamic friction. The most important effect of fiber was on the static frictional force and coefficient of static friction of damp fabrics, with fabrics composed of fine wool exhibiting lowest friction, and acrylic fabrics the highest.

Consolidation of Black-dyed Māori Textile Artefacts: Evaluating the Efficacy of Sodium Alginate

ABSTRACT Black-dyed artefacts are found in museums worldwide, many produced using an iron-tannate compound. Deterioration of iron-tannate dyed artefacts is an international preservation issue: in New Zealand the deterioration of paru (iron-tannate) dyed Māori textiles is widespread. This article reports experimental work testing the efficacy of sodium alginate, a consolidant developed for deteriorated paru-dyed muka (fibre from harakeke; Phormium tenax). The colour stability, strength retention, and acidity of paru-dyed muka consolidated with sodium alginate (0.25, 0.5, and 1% w/v in water) was tested pre- and post-artificial light ageing. This study found that sodium alginate had no negative effect on paru-dyed muka and in some cases provided benefit. Interestingly, the colour of paru-dyed muka is substantially more stable in UV-filtered light than previously recognised. Also microfading results were in agreement with visual assessments of colour change at 1 Mlux hour exposure, providing confidence in this relatively new technique to assess colour change.

Sock fabrics: relevance of fiber type, yarn, fabric structure and moisture on cyclic compression

The objective of this study was to subject dry and damp sock fabrics to repeated compression cycles in order to determine the relative effects of fiber type (fine wool, mid-micron wool, acrylic), yarn type (high twist, low twist, single) and fabric structure (single jersey, half-terry, terry) on fabric compression and recovery from compression. Changes in fabric thickness were measured using a tensile tester and a number of parameters identified and analyzed: retained thickness, recovered thickness, compression to recovery ratio, energy absorption and energy absorption standardized for fabric thickness. The dominant factor was the number of compression cycles, with most change in the thickness retained and recovered evident within the first 10 cycles. The pattern of response of dry and damp fabrics was quite different with, the dry fabrics having a better compression to recovery ratio. Energy absorption was affected strongly by fabric structure, however this was closely related to initial fabric thickness. When fabrics were made damp, fabrics composed of acrylic fibers had a better compression to recovery ratio than fabrics composed of wool.

Tensile Properties of Silk from Endemic New Zealand Spiders

Differences in tensile properties were measured among individuals from four species of endemic New Zealand spiders that occupy different positions on the phylogenetic tree. The lowest load, stiffness, and work, but highest strain was measured for Porrhothele antipodiana, an ancestral Mygalomorph. In comparison, the highest load, stiffness, and work, and lowest strain were measured for a modern day Theridiid Cambridgea foliata. The gauge length of the specimen and the speed of the test significantly affected the tensile property data values measured.

Oblique accretion and riverbank plant survival on a regulated lowland river

This study examines the relationship between sedimentation (oblique accretion) and riverbank plant survival on the lower Murrumbidgee River, sourheast Australia. Oblique accretion is the lateral accumulation of fine-grained sediment on the prograding convex bank of a meandering river channel. Although this process is considered uncommon compared to point bar, overbank and counterpoint accretion (NANSON & CROKE 1992), recent work on Australian lowland rivers indicates that oblique accretion may be the dominant process in floodplain formation (WOODYER et al. 1979, GIBLING et al. 1998, PAGE et al. 1998).

Identification of historical plant material using micro-computed tomography

Abstract This work investigates the use of micro-computed tomography (micro-CT) for identification of New Zealand plant leaf material from artefacts. Micro-CT was explored as a result of difficulties in preparing transverse sections from aged plant material artefacts to compare with reference slides for microscopic identification of plant species. Plant names in te reo Māori (Māori language) are followed by the English name and botanic name, and are subsequently referred to by Māori names. The three plants investigated (harakeke, New Zealand flax, Phormium tenax, J. R. Forst & G. Forst; tī kōuka, cabbage tree, Cordyline australis, (Forst.f.) Endl,; kiekie, Frecinetia banksii A.Cunn.) were/are commonly used by Māori for the manufacture of objects often found in cultural institutions. Contemporary and historical specimens (from artefacts) of plant leaf material were investigated. Contemporary specimens were viewed using micro-CT and showed identifiable features compared with micrographs of transverse sections from reference material. Diagnostic features of each plant species were then named and measured, providing the basis for development of an identification key using both visual and objective criteria. Positive identification of historical specimens using this key varied across plant species and according to level of ageing and processing. Despite this, micro-CT had several advantages over traditional transverse sections: samples were not prepared for, or altered by, analysis, and numerous cross sections across the entire sample could be easily viewed to locate identifiable characteristics. Although measurable criteria supplied apply only to the three named New Zealand plant species, this paper provides methods that could be applied to the identification of other aged plant leaf material. Knowledge of plant anatomy at the level of major cell and tissue types (e.g. mesophyll, sclerenchyma, vascular tissue, and epidermis) is sufficient for the level of analysis carried out in this study.

The effect of different geometric shapes and angles on the fracture strength of IPS e.max computer-aided designed ceramic onlays: An in vitro study

Statement of Problem: The current ceramic onlay preparation techniques for cuspal areas involve the reduction of cusps following the cuspal anatomy and the removal of all sharp angulations. However, there is little research literature studying the effect of occlusal preparation angles. Furthermore, there is no recent literature on the effect of angulations on IPS e.max computer-aided designed (CAD) (e.max) ceramic onlays. Purpose: The purpose of this study is to investigate the effect of geometric cuspal angulation and different internal preparation angles on the fracture strength of e.max CAD ceramic onlays. Materials and Methods: Sharp (33° and 22°) and round (33° and 22°) preparations were tested, each group having 10 specimens. e.max ceramic onlays were milled, sintered, glazed, and then bonded onto geometric tooth models. Fracture strength was measured at the initial fracture with a universal testing machine. The load was applied laterally to the central fossa (2-point contact) and vertically to the cusp peak (1-point contact). Results: A reduced cuspal angulation of 22° resulted in a stronger ceramic onlay than a 33° angulation when laterally loaded (P = 0.001). The presence of sharp angles weakened the ceramic significantly for both the 22° preparation (P = 0.0013) and 33° preparation (P = 0.0304). Conclusion: This in vitro study found that preparation angles of 22° resulted in superior fracture strength during central fossa loading and that rounding the preparation resulted in significantly higher fracture strength when a cusp peak load was applied. When the cusp tip loading is applied, the preparation angle does not appear to influence the fracture strength.