A new eicosapentaenoic acid formed from arachidonic acid in the coralline red algaeBossiella orbigniana

Aqueous extracts of the coralline red algaeBossiella orbigniana have been shown to catalyze the enzymatic oxidation of arachidonic acid to a previously unreported ω6 eicosapentaenoic acid product. This unique fatty acid contains a conjugated tetraene with absorption maxima at 293, 306, and 321 nm, and was identified by spectral methods as 5(Z),8(Z),10(E),12(E),14(Z)-eicosapentaenoic acid. The compound was given the trivial name bosseopentaenoic acid. Under experimental conditions, production of bosseopentaenoic acid was linear up to 2 hr and dioxygen was consumed. Bosseopentaenoic acid, along with several other conjugated tetraenes, was also present in the algae endogenously as revealed by a comparison of the ultraviolet (UV) spectra and the high-performance liquid chromatographic (HPLC) pattern of the purified product and the organic extract ofBossiella.     

School attendance and daily respiratory symptoms in children: influence of moisture damage

We investigated the effect of weekends and school holidays on the daily frequency and severity of respiratory and other symptoms among children attending schools with (index) or without (reference) moisture damage in Spain, the Netherlands, and Finland. Throughout 1 year, parents of 419 children with a respiratory condition attending index (n=15) or reference (n=10) primary schools completed three symptom diaries. We assessed associations between lower respiratory tract, upper respiratory tract or allergy, and other symptom scores and school day, weekend, or summer holiday using mixed regression models stratified by country and moisture damage. We evaluated interactions between moisture damage and type of day. We combined country‐specific estimates (incidence rate ratios [IRRs] and 95% confidence interval [CI]) in meta‐analyses. Symptom scores were lower during weekends and holiday. Lower respiratory tract symptoms were statistically significantly less common during holiday with strongest effect in index schools (IRR=0.7; CI=0.6–0.8). Reporting of other symptoms was more reduced during holiday in index (IRR=0.6; CI=0.4–0.9) than in reference (IRR=0.95; CI=0.8–1.2) schools (interaction P<.01). In conclusion, symptoms were less frequent and/or severe during summer holiday and weekends. This pattern was stronger among children attending moisture‐damaged schools, suggesting potential improvement in moisture damage‐related symptoms during school breaks.     

Classification of Illumination Methods for Mixed Reality

A mixed reality (MR) represents an environment composed both by real and virtual objects. MR applications are used more and more, for instance in surgery, architecture, cultural heritage, entertainment, etc. For some of these applications it is important to merge the real and virtual elements using consistent illumination. This paper proposes a classification of illumination methods for MR applications that aim at generating a merged environment in which illumination and shadows are consistent. Three different illumination methods can be identified: common illumination, relighting and methods based on inverse illumination. In this paper a classification of the illumination methods for MR is given based on their input requirements: the amount of geometry and radiance known of the real environment. This led us to define four categories of methods that vary depending on the type of geometric model used for representing the real scene, and the sdifferent radiance information available for each point of the real scene. Various methods are described within their category. The classification points out that in general the quality of the illumination interactions increases with the amount of input information available. On the other hand, the accessibility of the method decreases since its pre‐processing time increases to gather the extra information. Recent developed techniques managed to compensate unknown data with clever techniques using an iterative algorithm, hardware illumination or recent progress in stereovision. Finally, a review of illumination techniques for MR is given with a discussion on important properties such as the possibility of interactivity or the amount of complexity in the simulated illumination.     

High-energy (59 pJ) and low-jitter (250 fs) picosecond pulses from gain-switching of a tapered-stripe laser diode via resonant driving

High-energy (59 pJ), low-jitter (250 fs), high-extinction ratio (800), and short (14.5 ps FWHM) pulses were generated by gain-switching of a tapered stripe gain-guided laser diode (LD) via resonant driving. These characteristics are attributed to a stable single-mode near-field pattern, a single-lobe far-field pattern, and multilongitudinal modes associated with the tapered stripe LD under high driving current pulses. These pulses from a comb generator were enhanced mainly from reflection at the LD-transmission line impedance mismatch; the line length was adjusted for resonance with the reflection from the step recovery diode, further increasing the driving current.     

Analysis of the clover-shaped geometry for a Hall generator

The influence of the contact size on the Hall voltage and its nonlinear behaviour has been investigated for the clover-shaped geometry. The potential problem has been solved by an expansion and an integral-equation technique.     

A developmental approach AIDS motor learning

Bernstein (1967) suggested that people attempting to learn to perform a difficult motor task try to ameliorate the degrees-of-freedom problem through the use of a developmental progression. Early in training, people maintain a subset of their control parameters (e.g., joint positions) at constant settings and attempt to learn to perform the task by varying the values of the remaining parameters. With practice, people refine and improve this early-learned control strategy by also varying those parameters that were initially held constant. We evaluated Bernstein's proposed developmental progression using six neural network systems and found that a network whose training included developmental progressions of both its trajectory and its feedback gains outperformed all other systems. These progressions, however, yielded performance benefits only on motor tasks that were relatively difficult to learn. We conclude that development can indeed aid motor learning.     

Tilted-wing-induced stress distribution in epitaxial lateral overgrown GaN

Epitaxial lateral overgrowth (ELO) is one of the most extensively studied techniques used to improve the mismatched heteroepitaxy of GaN on sapphire (-Al₂O₃) substrates. In this method, a mask is first deposited over the GaN seed layer and parallel windows are opened along a specific direction in the mask. GaN is grown vertically at the window position and then grows laterally along the mask surface (wing region). The adjacent GaN regions will coalesce to form a continuous film if enough growth time is used. The impact of the ELO of GaN on sapphire substrates using a SiO₂ mask is measured with the white beam synchrotron X-ray topography technique. The topography results show that the crystal planes in the laterally overgrown regions (wings) are tilted. The maximum wing tilt is about 0.36° at a fill factor of 0.5 (fill factor measures the window width relative to the window width plus SiO₂ mask width). High-resolution micro-Raman spectroscopy stress-mapping measurements, using Ar⁺ 488-nm laser excitation, indicate that the GaN epilayer is under compressive stress, as is expected from the growth conditions. The measured average compressive stress is about 460 MPa. Furthermore, a wave-like stress field is observed in the ELO GaN epilayer. The wave valley (low compressive stress region) is usually located at the coalesced region between two adjacent wings. In general, these coalesced regions exhibit about 60 MPa lower compressive stress than the average stress in the ELO epilayer. Voids formed by the tilted wings at the coalesced region are regarded as a possible reason for the lower compressive stress in the coalesced region.     

Characterization of ultrasonic Rayleigh surface waves in asphaltic concrete

This research examines the application of ultrasonic Rayleigh surface waves to the non-destructive evaluation (NDE) of asphaltic concrete in the frequency range 40–100 kHz. Two ultrasonic parameters, the phase velocity and amplitude attenuation, are considered to be sensitive to local compositional and structural variations and are measured. A wedge technique is used to generate Rayleigh surface waves in an asphaltic concrete beam with uniformly distributed aggregate, and this technique is shown to be effective in launching Rayleigh waves in this highly viscoelastic (absorptive) and heterogeneous medium. Three different ultrasonic detection setups using contact and non-contact transducers as receivers are examined and their results are compared. The experimental results show that the wedge generation technique along with an air-coupled receiving transducer with a finite-size aperture is the most reliable for characterizing Rayleigh waves in asphaltic concrete. It is also experimentally demonstrated that the proposed setup may be used to detect aggregate segregation in asphaltic concrete.