Opiate Prescription Practices and VPMS Use: Impacts of the Vermont Prescription Monitoring System

Introduction. Our project assessed prescriber use of the Vermont Prescription Monitoring System (VPMS) and collected suggestions for its improvement, and for reducing opiate diversion.https://scholarworks.uvm.edu/comphp_gallery/1083/thumbnail.jp

Characterisation of lead pipes used in the water industry: extrusion processing, alloy microstructure and their role in service failures

The issue of leakage within the water distribution system is one of importance not only at an economic level for the industry, but also as a result of an environmental agenda addressing issues of water sustainability. The present work is concerned with leakage from lead based assets, in particular distribution pipes. Very little is known about the failure mechanisms within lead based assets. The present paper presents the findings from a study in which lead samples from intact and failed pipes, sourced from the Thames Water area, have been examined. The failure mechanisms have been identified at the macroscopic level and the pipe microstructure has been characterised -aspects of the microstructure control particular properties of the pipe (e.g. strength, creep and fatigue behaviour) and so may contribute to the potential failure modes. The present study is the first stage in a programme of work designed to develop a better understanding of the failure modes in lead assets, leading to the formulation of a more effective condition assessment model

WEIBULL BASED METHODOLOGY FOR CONDITION ASSESSMENT OF CAST IRON WATER MAINS AND ITS APPLICATION

Abstract A qualitative and quantitative understanding of how cast iron water distribution pipes fail in service would facilitate a targeted approach to the management of rehabilitation in the water industry. This paper proposes a technique for assessing the condition of pipes, based on strength characteristics obtained from small samples; this offers an alternative way of estimating the likelihood of failure to current methodologies based on pit-depth measurements. Examination of recovered pipe samples indicates that the strength of the cast iron pipe reduces over time as a result of corrosion, although other time-dependent processes, such as fatigue, may also contribute to this degradation. Taken with previous work, this paper suggests that the variation in strength of small samples removed from cast iron water distribution pipes can be characterised using Weibull methods. It is argued that the Weibull modulus provides a useful indicator of the condition of the pipe. Using scaling arguments, inherent in the Weibull methodology, it is then possible to use data from small samples to predict the likely strength characteristics of water distribution pipes in the ground, which is reasoned to be a good measure of the potential performance of the pipe in service. The Weibull approach is applied to a number of different data sets obtained from testing samples extracted from a range of pipes, which have seen service at various locations in the Thames Water region. One of these data sets was from locations where failure had occurred in service. It is shown that the use of Weibull analysis can identify pipes in the network that have degraded the most significantly. A methodology is suggested whereby this information taken with other performance indicators can be used to identify the local regions where rehabilitation is required most urgently. Alternatively it can be used to identify those regions of the network which are in good condition and unlikely to need repair or replacement work

Equipment for tensile testing of fresh concrete

The development of equipment suitable for measuring tensile stress-strain curves on fresh concrete is described. With such weak materials, it is essential to eliminate friction effects and this is achieved by the use of air-bearing plates. The objective of the new equipment is to enable data to be obtained to define the rapidly changing tensile stress-strain performance in the first 6 h after water is added at the mixer. This information is important for understanding plastic shrinkage cracking. The equipment is also being used to investigate early-age internal cracking problems which have been observed with high-strength concrete and which are related to the internal tensile failure strain of the cement paste. Some typical tensile stress-strain curves obtained ruing the equipment are shown for two types of concrete

Factors affecting the plastic shrinkage cracking of high-strength concrete

Tests were developed to quantify parameters affecting the plastic shrinkage cracking of high-strength concrete of 28-day cube strength in excess of 70 MPa. The parameters measured were tensile stress-strain performance during the first 5 h after mixing and negative pore pressure development and free shrinkage during the first 24 h. Eight high-strength mixes were used containing a variety of supplementary cementing materials such as microsilica, pulverised fuel ash, granulated slag and metakaolin. Two types of superplasticers were included. Plastic shrinkage cracking was assessed using restrained ring tests in which measurements were taken using sealed samples and samples exposed to wind. The research has shown that there is no simple relationship between early age stress-strain curves, negative pore pressure, early age shrinkage and macrocracking in adverse conditions but two factors were always present when plastic cracking was observed, these being microsilica and wind

A unilateral NMR magnet for sub-structure analysis in the built environment: The Surface GARField

A new, portable NMR magnet with a tailored magnetic field profile and a complementary radio frequency sensor have been designed and constructed for the purpose of probing in situ the sub-surface porosity of cement based materials in the built environment. The magnet is a one sided device akin to a large NMR-MOUSE with the additional design specification of planes of constant field strength vertical bar B(0)vertical bar parallel to the surface. There is a strong gradient G in the field strength perpendicular to these planes. As with earlier GARField magnets, the ratio G/vertical bar B(0)vertical bar is a system constant although the method of achieving this condition is substantially different. The new magnet as constructed is able to detect signals 50 mm ((1)H NMR at 3.2 MHz) away from the surface of the magnet and can profile the surface layers of large samples to a depth of 35-40 mm by moving the magnet, and hence the resonant plane of the polarising field, relative to the sample surface. The matching radio frequency excitation/detector coil has been designed to complement the static magnetic field such that the polarising B(0) and sensing B(1) fields are, in principal, everywhere orthogonal. Preliminary spatially resolved measurements are presented of cement based materials, including two-dimensional T(1)-T(2) relaxation correlation spectra. (c) 2007 Published by Elsevier Inc

The effects of fibres on the plastic shrinkage cracking of high strength concrete

Plastic shrinkage cracking in concrete usually occurs during the first 5 hours after placing and therefore the mechanics of fibre reinforcement were studied during this period. Two types of polypropylene fibres were mixed at 0.1% by volume. The development of bond strengths and the stresses which the fibres could sustain across cracks were measured by uniaxial tensile tests during the first 5 hours after mixing. Fibre stresses up to 130 MPa at 5 hours were achieved which were equivalent to a composite post-crack strength of 65 kPa. Restrained ring tests were used to assess the amount of cracking which occurred during the first 24 hours in a different high strength mix and, although the results were very variable, the fibres were found to reduce the crack area by between 40% and 85% compared with plain concrete, depending on fibre type

Two-dimensional correlation relaxation studies of cement pastes

Two-dimensional nuclear magnetic resonance relaxation correlation studies of cement pastes have been performed on a unilateral magnet, the Surface GARField. Through these measurements, the hydration process can be observed by monitoring the evolution of porosity. Characteristic relaxation time distributions have been observed in different cement pastes: fresh white cement, prehydrated white cement and ordinary Portland cement. The observed T-1/T-2 ratio in these cements has been shown to agree with expectations based on high field values. (C)) 2007 Elsevier Inc. All rights reserved

Two-dimensional correlation relaxometry studies of cement pastes performed using a new one-sided NMR magnet

We present preliminary results of the first NMR T(1)-T(2) two-dimensional relaxation Correlation experiments performed using a one-sided NMR system in cement based materials. Two-dimensional correlation relaxometry has itself only recently been demonstrated in cement paste where it proved to be a particularly sensitive probe of pore-water dynamics providing direct information on exchange of water between the gel and capillary pore networks. Further to this we have observed differences in the structural development of a selection of cement pastes throughout the early stages of hydration and verified the theoretical frequency dependence of the ratio T(1)/ T(2). When coupled with instrumentation developments in one-sided NMR magnets the way is opened to detailed, spatially resolved studies of the development of hydration and porosity in the surface layers (top 50 mm) of cementitious materials. A new magnet, suitable for such applications, is discussed. (C) 2006 Elsevier Ltd. All rights reserved