Ultrasonic displacement measurements from local absorption of ultrasound in thermochromic liquid crystal sensors.

Wavefield imaging can be used for measuring the wavefield produced by an ultrasound transducer for medical and industrial applications, or for the detection and monitoring of defects in non-destructive testing. Typical wavefield imaging methods include interferometry/vibrometry, and the use of microphones and hydrophones. These involve scanning, making them time consuming, and microphones have limited resolution. An alternative method presented here uses thermochromic liquid crystal sensors which react to heat generated due to absorption of ultrasonic waves. The result is a colour scale that varies with temperature, with the temperature change dependent on ultrasonic displacement. Measurements of the resonant modes of a flexural ultrasonic transducer were taken between 320 kHz and 6.77 MHz. Temperature maps were obtained from photographs of the TLC sensor using the true-colour image processing method. The obtained temperature change across the transducer face was compared with displacement measurements taken using interferometry, showing excellent agreement in the position of the mode features and good resolution at lower frequencies. Thermal measurements were also taken to directly observe the heating of the transducer cap, showing the effect of the thermal conductivity of the transducer along with confirming the increased heat generated by the ultrasound absorption when a backing layer is used. The sensors show promise for fast transducer characterisation, with further potential applications in structural health monitoring and defect detection.

Estrus detection using radiotelemetry or visual observation and tail painting for dairy cows on pasture.

The efficiency and accuracy of estrus detection using HeatWatch (DDx Inc., Denver, CO) or visual observation were compared in an autumn-calving Friesian herd (n = 48 per group) and a spring-calving Jersey herd (n = 50 per group) grazing on pasture. Cows in the group monitored by the HeatWatch system were fitted with a pressure-sensitive transmitter that signaled mounting activities associated with estrus. Visual observation was carried out for about 20 min before the morning and afternoon milkings and was aided by a strip of paint applied over the tailhead. Ovarian cyclicity was monitored with progesterone concentrations in milk samples collected twice a week. The efficiency and accuracy of estrus detection were, respectively, 98.4 and 97.6% for visual observation and 91.7 and 100% for HeatWatch detection. Autumn-calving herds differed from spring-calving herds in duration of estrus (9.7 vs. 7.3 h), number of mounts (13.6 vs. 8.5), total duration of mounts (36.8 vs. 19.9 s), and mean duration of a mount (2.6 vs. 2.3 s). There was no significant variation in the distribution of the time of onset of estrus or mounting activities at different hours of the day. Conception rate was similar for AI after estrus detection with HeatWatch (65.8%) or after visual observation (65.0%). The highest conception rate was obtained when AI was carried out between 12 and 18 h after the first mount. Both the HeatWatch system and visual observation plus tail painting can be used for estrus detection of dairy cows on pasture.

Hyperglycemia during normothermic cardiopulmonary bypass: the role of the kidney.

BACKGROUND: Hyperglycemia commonly occurs during cardiopulmonary bypass. We studied the quantitative impact of glucose input and its renal excretion on hyperglycemia during cardiopulmonary bypass. METHODS: The quantity of glucose infused and metabolite and hormone concentrations in plasma, as well as oxygen consumption, carbon dioxide production, and renal glucose excretion, were determined before, during, and after cardiopulmonary bypass in 8 patients. RESULTS: Hyperglycemia (14 to 29 mmol/L) was accompanied by an increase in plasma insulin levels. The degree of hyperglycemia was directly related to the amount of glucose infused. The rate of oxygen consumption did not decrease and the rate of urea appearance (gluconeogenesis) did not rise. Despite a very high filtered load of glucose, there was very little glucosuria, indicating a markedly enhanced renal absorption of glucose. CONCLUSIONS: Hormonal and metabolic factors permit the development of hyperglycemia during cardiopulmonary bypass but its severity depends on the quantity of glucose infused and, what appears to be a new finding, a markedly enhanced renal reabsorption of filtered glucose. Thus the kidney plays an important role in the development of severe hyperglycemia during cardiopulmonary bypass.

Miniature liquid-crystal-on-silicon display assembly.

A novel integrated assembly process for miniature liquid-crystal-on-silicon displays using photodefinable benzocyclobutene resin is presented. Spin coating speed defines the cell gap, photolithography defines the cell perimeter and spacers, and thermocompression bonding provides the adhesion. The photodefined adhesive spacers provide thin liquid-crystal cell gap control (<2.5 microm) with excellent uniformity (+/-100 nm) for glass-on-glass and glass-on-silicon assemblies. The resin is compatible with common liquid-crystal alignment films and exhibits a bonding shear strength of 22+/-3.2 MPa The assembly process flow and characterization of demonstration devices are described.

Spin-cast planarization of liquid-crystal-on-silicon microdisplays.

A simplified method for planarizing liquid-crystal-on-silicon (LCOS) backplanes is presented. The method relies on the planarizing capability of spin-cast benzocyclobutene (BCB) polymeric resin. BCB planarization shows a sixfold reduction in step height on the surface of a typical LCOS backplane. Contact with the underlying pixel circuitry is made by dry etching through openings in the BCB layer. Reflective metal (87% reflectivity) is deposited over the planarized surface and patterned to form high-aperture-ratio pixel mirrors (84%). An average resistance of 0.75 Omega per via was achieved with 3.6-microm-diameter vias in 2-microm-thick BCB. The method and the results of this LCOS backplane planarization and postprocessing are described.

Smart-pixel spatial light modulator for incorporation in an optoelectronic neural network.

We present the design, fabrication, and testing of a novel liquid-crystal-on-silicon optically addressed spatial light modulator for use as a weight matrix in an ART-1 optoelectronic neural processor. Each pixel in the 50 x 83 element array occupies 75 microm x 75 microm and consists of a photodetector, a threshold circuit, a 1-bit (flip-flop) memory element, and a liquid-crystal modulating mirror. The array is designed to switch all the pixels initially to the ON state. Subsequently each pixel is independently switched to the OFF state if a superthreshold amount of light falls upon the pixel's photodetector. The device has a contrast ratio of 20:1, a switch-on time (10-90% rise time) of 500 micros, and a switch-off time of ~500 micros (depending on the externally set threshold). Measured device uniformities and interpixel coupling are also described.

High-speed liquid-crystal-on-silicon spatial light modulators using high-voltage circuitry.

Two high-speed liquid-crystal-on-silicon spatial light modulators that use high-voltage circuitry are described. The high-voltage circuits used can provide 30 and 15 V for switching chiral smectic liquid-crystal spatial light modulators with 10-90% switching times of 30 and 50 micros, respectively. The ON/OFF contrast ratios are 13:1 and 15:1.

Analog distorted helix ferroelectric liquid-crystal-on-silicon spatial light modulator.

We report what are to our knowledge the first results from a liquid-crystal-on-silicon spatial light modulator that uses the distorted helix ferroelectric mode to perform analog light modulation. The spatial light modulator is an electronically addressed analog 128 x 128 pixel device with which we have demonstrated 16 gray levels and contrast ratios of 33:1 in the zeroth diffracted order and 6:1 when imaged. The liquid-crystal switching speed in this device is approximately 235 micros, which when added to the data load time of 100 micros gives a maximum frame rate of approximately 3 kHz.

Optoelectronic hit/miss transform for screening cervical smear slides.

An optoelectronic morphological processor for detecting regions of interest (abnormal cells) on a cervical smear slide using the hit/miss transform is presented. Computer simulation of the algorithm tested on 184 Papsmear images provided 95% detection and 5% false alarm. An optoelectronic implementation of the hit /miss transform is presented, along with preliminary experimental results.

Continuous view of dc-balanced images on a ferroelectric liquid-crystal spatial light modulator.

A scheme is presented that permits a continuous view of an image displayed on a dc-balanced ferroelectric liquid-crystal-on-silicon spatial light modulator. I develop the theory and present experimental results, using a 256 x 256 ferroelectric liquid-crystal-on-silicon spatial light modulator. It is shown that both halves of the dc-balanced cycle can be made to produce identical outputs even when the illumination is polychromatic and the spatial light modulator liquid-crystal layer thickness is not an ideal half-wave plate and for an arbitrary liquid-crystal switching angle.

256 × 256 liquid-crystal-on-silicon spatial light modulator.

A 256 × 256 pixel spatial light modulator (SLM) is designed and constructed by the use of liquid-crystalon-silicon technology. The device is a binary electrically addressed SLM with a measured zero-order contrast ratio of 70:1 and an imaged contrast ratio of 10:1. The pixel pitch is 21.6 µm, which gives an array size of 5.53 mm. The electronic load time is 43 µs, and the 10%-90% switching time of the liquid crystal is ~75-80 µs at room temperature, which implies a maximum frame rate of ~8.3 kHz. We discuss the design trade-offs that are intrinsic to this type of device and describe how the primary application for the device in an optical correlator influenced the final design.

Development of a spatial light modulator: a randomly addressed liquid-crystal-over-nMOS array.

The construction of a 50- x 50-pixel spatial light modulator based on an active silicon backplane and using the hybrid field effect in nematic liquid crystals as the light modulating process is described. The design and electrical evaluation of the pixel array, which is fabricated in 1.5-microm nMOS and has an individual memory cell within each pixel, are discussed. The performances of a 16 x 16 prototype SLM and the new 50- x 50-pixel device are compared to provide an indication of progress toward high performance spatial light modulators with onboard pixel memory.

Catamenial pneumothorax and malignant hyperthermia.

This paper presents a patient showing both the unusual syndrome of catamenial pneumothorax and a strong family history of malignant hyperthermia. The anaesthetic management is described and discussed.