Medical Library

Optofluidic variable aperture.

A variable aperture has been fabricated and demonstrated using polydimethylsiloxane-based optofluidic technology. The device consists of a deformable membrane, an air pressure chamber, a cavity filled with light-absorbing liquid, and a rigid transparent upper plate. The working principle of the device is based on the deformable capability of the thin membrane structure and its resultant contact with the rigid plate. The contact area can be easily controlled by varying the air volume introduced and hence can serve as a light transmission aperture. Experimental results show that aperture diameter can be continuously changed from zero to 6.35 mm.

Hongbin Y, Guangya Z, Siong CF, Feiwen L.

Near-infrared metamaterial films with reconfigurable transmissive/reflective properties.

A near-infrared metamaterial design that is reconfigurable between almost completely transmissive and reflective states is presented. The reconfiguration is enabled by tuning the anisotropic nematic liquid crystals used as a spacer layer between two silver nanoplates in a planar doubly periodic metamaterial. The design is optimized for maximum difference in transmittance between the two states by using a genetic algorithm. For a linearly polarized illumination at normal incidence, full-wave electromagnetic analysis predicts that the optimized metamaterial film can change the transmittance between 98.7% and 0.1% at a wavelength of 1.1 mum.

Kwon DH, Wang X, Bayraktar Z, Weiner B, Werner DH.

Multiple-image hiding by information prechoosing.

The information inevitably lost in multiple-image hiding is discarded in advance by the operation of prechoosing information before the hiding process; thus both fidelity and multiplexing capacity can be improved significantly. Various characters of each image provide a great many possibilities for information prechoosing. The ideal low-pass filter presented with the matched encoding and hiding procedure may be one of the simplest examples of information prechoosing for generally used images. Computer simulations demonstrate its good performance, and the security is analyzed as well.

Shi Y, Situ G, Zhang J.

Femto-Newton light force measurement at the thermal noise limit.

The measurement of very small light forces has wide applications in many fields of physics. A common measurement method for small force detection is the determination of changes in the dynamic behavior of mechanical oscillators, either in amplitude or in frequency. The detection of slowly varying forces mostly requires long period oscillators, such as a torsion pendulum. We demonstrate the application of a macroscopic, low-noise, torsion balance oscillator for the detection of radiation pressure forces at the femto-Newton level. The system is \”precooled\” (removing excess seimic noise) to be only thermal noise limited. The demonstrated force sensitivity reaches the thermal limit.

Mueller F, Heugel S, Wang LJ.

Miniaturized fiber inline Fabry-Perot interferometer fabricated with a femtosecond laser.

We report a miniaturized inline Fabry-Perot interferometer directly fabricated on a single-mode optical fiber with a femtosecond laser. The device had a loss of 16 dB and an interference visibility exceeding 14 dB. The device was tested and survived in high temperatures up to 1100 degrees C. With an accessible cavity and all-glass structure, the new device is attractive for sensing applications in high-temperature harsh environments.

Wei T, Han Y, Tsai HL, Xiao H.

Dynamic modulation transfer function: a method to characterize the temporal performance of liquid-crystal displays.

A method to measure the dynamic modulation transfer function (DMTF) of a liquid-crystal display (LCD) is proposed to characterize its performance when rendering motion images. The method includes a measurement system to capture the temporal luminance variation of a LCD while using a well-designed input data sequence and a simulation model based on smooth pursuit eye tracking and temporal light integration at the human retina. It predicts the perceived performance of a moving sine wave pattern on a LCD and subsequently calculates the DMTF. With this approach, several technologies to reduce motion blur were evaluated and discussed.

Zhang Y, Teunissen K, Song W, Li X.

Children\’s thermoregulation during exercise in the heat - a revisit.

The review revisits some child-adult differences relevant to thermoregulation and offers alternatives to accepted interpretations. Morphologically, children have a higher body surface area to mass ratio - a major factor in “dry” heat dissipation and effective sweat evaporation. Locomotion-wise, children are less economical than adults, producing more heat per unit body mass. Additionally, children need to divert a greater proportion of their cardiac output to the skin under heat stress. Thus, a larger proportion of their cardiac output is shunted away from the body\’s core and working muscles - particularly in hot conditions. Finally, under all environmental conditions and allometric comparisons, children's sweating rates are lower than those of adults. The differences appear to suggest thermoregulatory inferiority, but no epidemiological data show higher heat-injury rates in children, even during heat waves. We suggest that children employ a different thermoregulatory strategy. In extreme temperatures, they may indeed be more vulnerable, but under most ambient conditions they are not necessarily inferior to adults. Children rely more on dry heat dissipation by their larger relative skin surface area than on evaporative heat loss. This also enables them to evaporate sweat more efficiently with the added bonus of conserving water better than adults.

Falk B, Dotan R.

A pediatric perspective on inflammation and oxidative stress in response to exercise.

Dr. Oded Bar-Or was a giant in the area of pediatric exercise science and made numerous contributions to the health of children around the world. He also had a significant impact on a relatively new area of pediatric exercise science - pediatric exercise immunology. Under his supervision, some aspects of the immunobiology of exercise have been unravelled from a pediatric perspective. In general, healthy children experience less inflammatory stress in response to standardized exercise, while demonstrating an exercise-induced elevation in the anabolic cytokine IL-8. Mechanisms for the maturity- and age-dependent changes in cytokine responses to exercise are unknown, but may involve oxidative stress. Studies of oxidative stress and exercise in children are scant, but preliminary data suggests that, like the inflammatory cytokine response to exercise, children may experience less oxidative stress in response to intense exercise. We propose that the links between exercise, inflammatory and oxidative stress, and growth factors will be important to understand in the context of how exercise contributes to optimal growth and development during childhood. This understanding will be particularly relevant for childhood diseases that restrict growth.

Timmons BW, Raha S.

Non-invasive methods in paediatric exercise physiology.

Oded Bar-Or\’s hypothesis that children may be “metabolic non-specialists”, even when engaging in specialized sports, has stimulated the study of paediatric exercise metabolism since the publication of his classic text Pediatric sports medicine for the practitioner in 1983. Evidence drawn from several methodologies indicates an interplay of anaerobic and aerobic exercise metabolism in which children have a relatively higher metabolic contribution from oxidative energy pathways than adolescents or adults, whereas there is a progressive increase in glycolytic support of exercise with age, at least into adolescence and possibly into young adulthood. The picture is generally consistent but incomplete, as research with young people has been limited by both ethical and methodological constraints. The recent rigorous introduction of non-invasive techniques such as breath-by-breath respiratory gas analysis and magnetic resonance spectroscopy into paediatric exercise physiology promises to open up new avenues of research and generate unique insights into the metabolism of the exercising muscle during growth and maturation. It therefore appears that we might have available the tools necessary to answer some of the elegant questions raised by Professor Bar-Or over 25 years ago.

Armstrong N, Fawkner SG.

Children’s Health and Exercise Research Centre, University of Exeter, Exeter, UK.

Acute physical activity and sports injuries in children.

An increase in the physical activity of individuals has many health benefits, but a drawback of an increase in physical activity is the risk of related injuries. To reduce the short- and long-term effects in terms of social and economic consequences, prevention of physical activity injuries is an important challenge. A sequence of prevention model has been proposed that aims to prevent physical activity injuries in different steps. The model includes (i) identification of the problem in terms of incidence and severity of physical activity injuries, (ii) identification of the risk factors and injury mechanisms that play a role in the occurrence of physical activity injuries, (iii) introduction of measures that are likely to reduce the future risk and (or) severity of physical activity injuries, and (iv) evaluation of the effectiveness of the measures by conducting a randomized controlled trial (RCT). This review describes what is currently known about all of the various aspects of the sequence of prevention in children (steps i-iv).

Collard DC, Verhagen EA, Chin A Paw MJ, van Mechelen W.

EMGO Institute and Department of Public and Occupational Health, Amsterdam, The Netherlands and Research Centre TNO Vumc. Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands.