Anthropomorphic cardiac ultrasound phantom

A new phantom is described which simulates the human cardiac anatomy for applications in ultrasound imaging, ultrasound Doppler, and color-flow Doppler imaging. The phantom consists of a polymer left ventricle which includes a prosthetic mitral and aortic valve and is connected to a mock circulatory loop. Aerated tap water serves as a blood simulating fluid and ultrasound contrast medium within the circulatory loop. The left ventricle is housed in a Lexan ultrasound visualization chamber which includes ultrasound viewing ports and acoustic absorbers. A piston pump connected to the visualization chamber by a single port pumps degassed water within the chamber which in turn pumps the left ventricle. Real-time ultrasound images and Doppler studies measure flow patterns through the valves and within the left ventricle.     

Effect of Methionine Supplementation on Nitrogen Balance in Infants Fed a Low-Cost Soy-Oats Formula

A nitrogen balance study, comparing a low-cost soy-oats infant formula with and without supplemental methionine, was carried out with infants of ages 3 - 26 months at a single equivalent level of nitrogen intake (approximately 850 mg/kg/day). Nitrogen retention was found to be unaffected by methionine supplementation. Com- parison of data obtained in this study with previous research re- vealed that a critical value for intake of total L-sulfur amino acids apparently exists in infants 3 - 26 months of age, below which methionine supplementation will increase nitrogen retention, but above which it will not. This value appears to coincide with that of 49 mg/kg/day recommended for infants by the FNB.     

Influence of weld misalignment and weld metal overmatch on the prediction of fracture in pipeline girth welds

$\text{J-}\text{integral}$ estimates using elastic-plastic finite element calculations, are shown to compare well with experimental results from single edge-notch bend (SENB) specimens made of X483 grade line pipe steel.The influence of weld misalignment and weld metal overmatch on fracture of cracked girth welds is predicted, also using elastic-plastic finite element calculations. Weld metal overmatch reduces plastic strain levels in the weld and appears beneficial in reducing $\text{J-}\text{integral}$ magnitudes. Predicted values of $\text{J-}\text{integral}$ are shown to increase with weld misalignment. However, $\text{J-}\text{integral}$ magnitudes near the critical value for crack growth initiation were only attained after considerable plastic straining at or near limit load. This result suggests that limit load calculations may be more appropriate for prediction of failure of cracked girth welds than conventional fracture techniques.     

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Evaluating the solar resource: a review of problems resulting from temporal, spatial and angular variations

Accurate assessment of the availability of solar energy at the Earth's surface is hampered by difficulties associated with the variability of solar radiation in space and time and with the angular position in the sky hemisphere. This paper assesses each of these problem areas by highlighting the difficulties and the attempts to offset them. Major emphasis is placed on extrapolation and interpolation procedures, the sensitivity of inclined surfaces to variations in the solar input, numerical models for calculating the irradiance of inclined surfaces and the time scales for which these computations are valid.Finally, the reader is urged to consider the significance of these difficulties in light of both radiation measurement errors and the sensitivity of the application to imprecise determinations of the radiation environment.     

Preliminary Assessment of Contaminants in Soft Sediments of the Detroit River

Soft sediments from the Detroit River were analyzed for the USEPA priority pollutants to generally characterize contaminant distribution. Forty-three were detected. Highest heavy metal concentrations were found in the Trenton Channel and immediately downstream of Grosse Ile. They ranged from an area mean (N = 2) of 0.19 mg/kg mercury to 338.7 mg/kg zinc (dry weight). Polynuclear aromatic hydrocarbons ranged from 0.1 mg/kg to 38.8 mg/kg (mean, N = 2) with the highest levels near Grosse Ile. PCBs ranged from 0.015 mg/kg to 1.7 mg/kg (mean, N = 2). Organochlorine pesticides were not detected except for a trace of heptachlor in one sample. Sediment contamination in the Detroit River is widespread with higher concentrations on the U.S. side downstream of the Rouge River and in the Trenton Channel. The significance of these in-place pollutants to biota and as a source to Lake Erie is still unknown.     

The effects of stress and crack morphology on time-of-flight diffraction signals

A model based on the theory of infinite contacting surfaces is used to analyse the transmission and reflection of ultrasound at tight fatigue cracks under compressive stress. The model developed is valid for both compression and shear (SV) waves incident at arbitrary angles on a fatigue crack and includes mode conversion effects. In discussing diffraction of ultrasound by the tips of finite length fatigue cracks, we associate the amplitude of the diffracted signal with the strength of the signal reflected from cracks of infinite extent. Thus we allow all the energy transmitted by the tight crack to play no part in the diffraction process. Comparison is made with experiments carried out at Harwell and we conclude that, for these particular experiments, the cracks are fully open when subjected to about 88 MPa of tension, and that the experimental results are consistent with a root mean square deviation from flatness of the crack faces of about 1·5 μm. This is in broad agreement with the actual crack profile when a sampling length of about 30 μm is used. Using these values the theory and experiment show excellent agreement to within 2 dB over the whole applied stress range. The results show, for example, a diffraction signal decreased by a maximum of about 13 dB when the applied compressive load corresponds to 70% of the maximum load used during crack growth. Similar conclusions are also drawn for conventional pulse-echo inspection, whereas Tandem suffers a greater reduction in signal strength due to the usually lower frequency.