A portable reflectance instrument for the rapid quantification of cutaneous haemoglobin and melanin is presented. Light emitting diodes (LEDS) are used to illuminate the skin and a silicon photodiode to detect the light diffusely reflected from the surface. Reflectance measurements are made at only three wavelengths and the problems of pigment quantification consequent upon this are discussed. In addition to quantification of haemoglobin and melanin, qualitative information on the redox state of the blood may also be obtained. Measurements made on a port wine stain, which had been treated with 576 nm CW laser radiation at times between 1 and 6 months previously, provided information on the vascular response to this thermal injury. Despite the treated area visually appearing normal at 6 months post-treatment the measured levels of deoxygenated and total haemoglobin were still markedly higher than those in the adjacent uninvolved skin. The cutaneous pigment indices are insensitive to skin movement and almost all body sites are suitable for measurement.

A portable rapid scan reflectance spectrometer (400-700 nm in 2.8 s) has been developed for the measurement of cutaneous pigments. The instrument incorporates a tungsten halogen lamp light source, light transmission by fibre optics and wavelength selection by a circular variable wavelength interference filter. A microcomputer controls the instrument and processes the data. The performance of the instrument was evaluated by undertaking in vitro measurements of the reflectance spectra of blood. An index of the haemoglobin content of the sample based on the gradients of the log inverse reflectance spectrum between isobestic points at 527.5, 544 and 573 nm was devised and shown to be independent of the oxygenation of the haemoglobin. The haemoglobin index was combined with measurements at 558.5 nm, a wavelength at which absorbance is sensitive to the oxygenation of haemoglobin, to give a measure of oxygen saturation. The parameter was validated by determining the oxygen dissociation curve of red cells in plasma in vitro at pH 7.33, 37 degrees C and under a partial pressure of 40 mmHg of CO2.

Wrist injuries have been reported to account for 35%–45% of snowboarding injuries. Snowboarding wrist protectors are designed to limit impact forces and prevent wrist hyperextension. The absence of a standard for snowboarding wrist protectors makes it hard to identify models offering an adequate level of protection. Wrist surrogates are well suited for testing and benchmarking wrist protectors. This study investigated the effect of introducing a soft tissue simulant onto an otherwise stiff wrist surrogate on the bending stiffness of snowboarding wrist protectors. A compliant surrogate (stiff core and 3 mm thick silicone layer) and a comparable stiff surrogate were fabricated. Two snowboarding wrist protectors were tested on each surrogate, under three strapping conditions, following a bend test to ~80° wrist extension. The introduction of a compliant layer to the wrist surrogate gave higher torque values for a given wrist extension angle, increasing protector effective stiffness, relative to a rigid surrogate.

Auxetic foam can have higher indentation resistance, better protection under impact and higher vibration damping than conventional foam. Unlike auxetic open cell foam, with established, commercially viable options for manufacturing, methods for making auxetic closed cell foam are not established. We revisited pressure-vessel methods, proposed in 1996, for making auxetic closed cell foam. We processed low-density polyethylene foam for six hours at 400 to 700 kPa and 100 °C, causing foams to shrink by a factor of two to five. The volumetric compression kinked cell walls, producing negative Poisson’s ratios as low as -0.2 and Young’s moduli from 0.2 to 1.2 MPa. Trends between applied volumetric compression and Poisson’s ratio agree with those for open cell foam – initially decreasing to negative values as volume reduced by a factor of two after processing, then plateauing or slightly increasing as volume decreased by a factor of two to five. Foams of different sizes and shapes (15 to 75 mm sides) processed in the same conditions (700 kPa, 6 hours, 100 °C) shrank evenly in all three axes and had similar final volume ratios. We noticed a long settling period, of up to three months, where foams slowly shrank. Placing foam in a vacuum after processing reduced the settling period to within 24 hours.

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