A method for evaluating the acceptability of light sources for clinical visual evaluation of cyanosis

The accurate identification of cyanosis depends on a number of factors including the quality and quantity of the lighting used. Requirements framed in terms of permissible limits on correlated colour temperature and colour-rendering indices worked satisfactorily for many years. However, the demise of halophosphate fluorescent lamp technology and its replacement with triphosphor technology has led to a need to reevaluate the former methods and acceptance criteria. The experimental methods of assessing previous light sources were long and involved. It is impractical to replicate them as each new light source or new lighting technology is developed. There is a need, therefore, for a colorimetric method of assessing light sources for this purpose. In this study, the spectral reflectance characteristics of blood with oxygen saturation levels from 95.6–0.7% are used to calculate colour changes with respect to a reference illuminant and correlated with the results of an extensive study, some years ago, of the influence of light sources in the detection of cyanosis. The results lead to a method of evaluation with a single value criterion for acceptability. The method lends itself to simple modeling techniques for phosphor mixtures and should simplify the design of appropriate fluorescent tube sources for clinical visual evaluation of cyanosis. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23, 4–17, 1998.     

Cutting temperatures when ball nose end milling γ-TiAl intermetallic alloys

Experimental results are presented for Ti–45Al–2Mn–2Nb + 0.8 vol% TiB₂XD and Ti–45Al–8Nb–0.2C alloys. Three approaches were employed involving a constantan-workpiece thermocouple arrangement, implanted K-type thermocouples and IR thermography. New and worn (~300 μm flank wear) coated carbide tools were used under dry conditions when down milling at 50–345 m/min, with workpieces mounted horizontally and at 45°. Despite slight variation in ancillary finishing parameters there was generally good agreement between data sets for the different evaluation techniques employed and for both alloys. Higher temperatures were measured with the workpiece at 45°, with constantan-workpiece thermocouple temperatures of 375 °C and 413 °C for new and worn tools respectively at 345 m/min.     

A development in rock cutting technology

This paper describes a novel method of rock cutting — oscillating disc cutting (ODC) — in which the forces acting on the cutting tools, and hence on the excavation machine supporting these tools, are extremely low. Four different techniques are incorporated in the cutting method to achieve this result. The importance of this novel method is that it allows very strong and/or abrasive rock to be machined easily and rapidly without suffering the high rates of tool wear and/or tool failure that are experienced by conventional cutting machines operating in these types of rock. Also the fact that the ODC method requires very low machine reaction forces means that lightweight, and therefore manoeuvrable, mining and tunnelling machines can be employed in the excavation process. In the initial sections of this paper we discuss the physics of the process of rock breakage caused by mechanical cutting tools and the wear and failure mechanisms of these tools. The arguments are given in order to introduce the thinking behind the ODC method.     

Use of mass loading to operate a thin film ultrasonic transducer in the 300 kHz–10 MHz frequency range

Thin film ultrasonic transducers have been designed which operate over an important frequency range, 300 kHz to 10 MHz. The transducers were made using piezoelectric aluminium nitride films a few microns thick. The films would have a fundamental thickness mode resonance at 1–3 GHz if fabricated as an unsupported film, however operation at much lower frequencies has been demonstrated when the transducers are fabricated on bulk substrates. This would enables them to be used in ultrasonic non-destructive testing in circumstances where the film can be deposited directly onto the object under test. We have found that the major factors influencing the below-resonance operation of the thin film transducers are the device impedance, the spectrum of the excitation pulse, and any mechanical (mass) loading applied to the back face of the transducer. Results are presented showing that the evolution of device impedance as a function of device area could be predicted using a PSpice model of the thin film transducer. The ability of the transducer to generate longitudinal mode pulses rather than shear wave pulses was found to depend on increasing the mechanical loading at the back face of the transducer. This mechanism for pulse generation was confirmed by Finite Element Modelling using PZFlex.     

Extraordinarily high plastic deformation in polyurethane/silica nanoparticle nanocomposites with low filler concentrations

We have synthesized segmented polyurethane (SPU)/silica nanoparticle (SiNP) nanocomposites with extraordinarily high tensile strength and strain-at-break using an in-situ polymerization method with low SiNP concentrations. A 20-fold increase in strain-at-break compared with the pristine polymer has been achieved for the 0.5 wt% SiNP nanocomposites. A suite of characterization tools including transmission electron microscopy, ultra-small angle X-ray scattering, X-ray diffraction, differential scanning calorimetry and thermogravimetric analysis has been used to correlate the phase morphology, crystallization, and mechanical properties. The location of SiNP in the phase separated SPU is believed to be the main reason for the mechanical property enhancement.     

Cell-cell interaction in prostate gene regulation and cytodifferentiation

To examine the role of intercellular interaction on cell differentiation and gene expression in human prostate, we separated the two major epithelial cell populations and studied them in isolation and in combination with stromal cells. The epithelial cells were separated by flow cytometry using antibodies against differentially expressed cell-surface markers CD44 and CD57. Basal epithelial cells express CD44, and luminal epithelial cells express CD57. The CD57+ luminal cells are the terminally differentiated secretory cells of the gland that synthesize prostate-specific antigen (PSA). Expression of PSA is regulated by androgen, and PSA mRNA is one of the abundant messages in these cells. We show that PSA expression by the CD57+ cells is abolished after prostate tissue is dispersed by collagenase into single cells. Expression is restored when CD57+ cells are reconstituted with stromal cells. The CD44+ basal cells possess characteristics of stem cells and are the candidate progenitors of luminal cells. Differentiation, as reflected by PSA production, can be detected when CD44+ cells are cocultured with stromal cells. Our studies show that cell-cell interaction plays an important role in prostatic cytodifferentiation and the maintenance of the differentiated state.     

Feature-based image reconstruction in three dimensions for electron microscopy Part 2: Image reconstruction

The three-dimensional reconstruction of an electron microscopy specimen from a feature-based representation of the images taken from it is described. The method involves the assembling of the features, their correlation, and the measurement of the disparities between the original images.     

The enhanced S cone syndrome: an analysis of receptoral and post-receptoral changes

The purpose of the study was to test the hypothesis that the retinae of patients with enhanced S cone syndrome (ESCS) have more S cones than the normal retina and these cones have replaced some of the L and M cones. Standard and spectral full-field electroretinograms, measurements of L, M, and S cone system sensitivities and S cone acuity were obtained from three patients with ESCS. The results were qualitatively consistent with the presence of more S cones and more S cone ganglion cells. To test this hypothesis further, a model of the receptoral and post-receptoral components of the S cone system was used in conjunction with psychophysical measurements of S cone system sensitivity under flashed and steady-state adaptation conditions. Within the context of the model, the data were consistent with an increase in the number of S cones and S - (L + M) ganglion cells and with a decrease in the total L + M cone input to each S - (L + M) ganglion cell.