Reflection Photoelastic Stress Analysis of a Dental Bridge

The stress distribution on the surface of a four unit gold bridge was determined by reflection photoelasticity. The highest stress concentration was at the soldered joints. The distribution of stress was a function of the support of the abutment teeth. Good support caused the bridge to function as one that was fixed at both ends, whereas poor support caused it to function as a cantilever beam.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68063/2/10.1177_00220345710500052701.pd

Apparent Modulus of Elasticity of Dental Amalgams

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66932/2/10.1177_00220345750540043301.pd

Left ear advantage in speech-related dichotic listening is not specific to auditory processing disorder in children: A machine-learning fMRI and DTI study

AbstractDichotic listening (DL) tests are among the most frequently included in batteries for the diagnosis of auditory processing disorders (APD) in children. A finding of atypical left ear advantage (LEA) for speech-related stimuli is often taken by clinical audiologists as an indicator for APD. However, the precise etiology of ear advantage in DL tests has been a source of debate for decades. It is uncertain whether a finding of LEA is truly indicative of a sensory processing deficit such as APD, or whether attentional or other supramodal factors may also influence ear advantage. Multivariate machine learning was used on diffusion tensor imaging (DTI) and functional MRI (fMRI) data from a cohort of children ages 7–14 referred for APD testing with LEA, and typical controls with right-ear advantage (REA). LEA was predicted by: increased axial diffusivity in the left internal capsule (sublenticular region), and decreased functional activation in the left frontal eye fields (BA 8) during words presented diotically as compared to words presented dichotically, compared to children with right-ear advantage (REA). These results indicate that both sensory and attentional deficits may be predictive of LEA, and thus a finding of LEA, while possibly due to sensory factors, is not a specific indicator of APD as it may stem from a supramodal etiology

Effects of Cement Bases on the Stresses in Amalgam Restorations

A computerized dental model was used to study the stress induced in a Class 1 amalgam restoration when supported by bases of varying materials and thicknesses. Under the same load, the maximum tensile stresses and deftections in the amalgam restoration increased at least threefold with a zinc oxideeugenol base as compared with a ZnPO 4 cement base.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67330/2/10.1177_00220345750540010101.pd

Stress Distribution in Photoelastic Models of Transverse Sections of Porcelain-Fused-to-Gold Crowns and Preparations

The stress distribution in composite photoelastic models of transverse sections of porcelain-fused-to-gold restorations and preparations was determined. The optimum design was one in which the porcelain-gold junction was on the lingual side of contact points that represented the contact of adjacent teeth.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68216/2/10.1177_00220345730520051201.pd

Stress distribution within circumferential clasp arms

An analysis of stress distributions within circumferential clasp arms with various tapers, was undertaken in an effort to (1) determine the area of maximum stress concentration in both tapered and non-tapered clasps, and (2) to compare this point of maximum stress concentration with the area of frequent clasp breakage. The non-tapered clasp showed better distribution of stresses than the tapered clasps. The less favourable stress concentrations could result in eventual failure of the clasp when coupled with other factors such as porosities. The maximum shear stresses in the non-tapered clasp also were lower than those in the tapered clasps. As the taper of the clasp became more accentuated, the magnitude of the stresses increased and shifted towards the tip of the clasp. The maximum tensile stress calculated in a replica of a chromium–cobalt–nickel clasp was in the order of 34 MN/m 2 which is well below the ultimate tensile strength of the alloy. This observation leads to the proposal that failure of clasps is a function not only of design but also of other variables, such as porosities, surface irregularities, and fatigue.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71998/1/j.1365-2842.1976.tb01453.x.pd

High frequency surface acoustic wave resonator-based sensor for particulate matter detection

This paper describes the characterization of high frequency Surface Acoustic Wave Resonator-based (SAWR) sensors, for the detection of micron and sub-micron sized particles. The sensor comprises two 262 MHz ST-cut quartz based Rayleigh wave SAWRs where one is used for particle detection and the other as a reference. Electro-acoustic detection of different sized particles shows a strong relationship between mass sensitivity (Δf/Δm) and particle diameter (Dp). This enables frequency-dependent SAWR sensitivity to be tailored to the size of particles, thus making these types of sensors good candidates for PM10, PM2.5 and ultrafine particle (UFP) detection. Our initial characterisation demonstrated a typical SAWR frequency shift of 60 Hz in response to a deposition of ca. 0.21 ng of 0.75 μm-sized gold particles (∼50 particles) on sensor’s surface. Sensor responses to different size particles, such as ∼30 μm diameter silicon, gold (diameters of ∼0.75 μm and ∼20 μm), ∼8 μm fine sugar, PTFE (∼1 μm and ∼15 μm), ∼4 μm talcum powder, and ∼2 μm molybdenum powder were evaluated, and an average mass sensitivity of 275 Hz/ng was obtained. Based on the results obtained in this study we believe that acoustic wave technology has great potential for application in airborne particle detection. Moreover, acoustic resonator devices can be integrated with CMOS interface circuitry to obtain sensitive, robust, low-power and low-cost particle detectors for variety of applications including outdoor environmental monitoring

Effects of Cement Bases on the Stresses and Deflections in Composite Restorations

A model was used to show that tensile and shear stresses can occur in sufficient magnitude to cause failure in a cement base supporting a composite material in a posterior Class I restoration. Highest values of stress were observed when lining materials with a low modulus were used.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68080/2/10.1177_00220345760550010301.pd

The UTMOST pulsar timing programme I: overview and first results

We present an overview and the first results from a large-scale pulsar timing programme that is part of the UTMOST project at the refurbished Molonglo Observatory Synthesis Radio Telescope (MOST) near Canberra, Australia. We currently observe more than 400 mainly bright southern radio pulsars with up to daily cadences. For 205 (8 in binaries, 4 millisecond pulsars) we publish updated timing models, together with their flux densities, flux density variability, and pulse widths at 843 MHz, derived from observations spanning between 1.4 and 3 yr. In comparison with the ATNF pulsar catalogue, we improve the precision of the rotational and astrometric parameters for 123 pulsars, for 47 by at least an order of magnitude. The time spans between our measurements and those in the literature are up to 48 yr, which allows us to investigate their long-term spin-down history and to estimate proper motions for 60 pulsars, of which 24 are newly determined and most are major improvements. The results are consistent with interferometric measurements from the literature. A model with two Gaussian components centred at 139 and $463~\text{km} \: \text{s}^{-1}$ fits the transverse velocity distribution best. The pulse duty cycle distributions at 50 and 10 per cent maximum are best described by log-normal distributions with medians of 2.3 and 4.4 per cent, respectively. We discuss two pulsars that exhibit spin-down rate changes and drifting subpulses. Finally, we describe the autonomous observing system and the dynamic scheduler that has increased the observing efficiency by a factor of 2-3 in comparison with static scheduling.Comment: 31 pages, 14 figures, 6 tables, accepted for publication in MNRA