Wireless Microfluidic Systems for Programmed,Functional Transformation of Transient Electronic Devices

Electronic systems that enable programmable transformation of functional behaviors by remote control or by autonomous responses to user‐defined circumstances create unusual engineering opportunities, where physical changes in the hardware induce desired changes in operation. This paper presents materials and device architectures for technologies of this type, in which localized microfluidic chemical etching of targeted constituent components in the electronics occurs in a sequential, selective manner. Custom circuits that include reconfigurable radio‐powered thermal actuators with analog amplifiers and square waveform generators illustrate the concepts.     

Liquid water flow in Pinus radiata during drying

End-sealed 60×60×250?mm³ Pinus radiata pieces were dried at 65/37 °C (dry bulb/wet bulb temperature) and 4 ms^-1 air speed to study various drying phenomena above fibre saturation point. While drying, an X-ray computed tomography (CT) scanner captured a cross-cut density image every ten minutes. The density data was used to determine moisture content, rate of moisture loss from the core, wetline (boundary line of the free water region) depth and cross-cut area of the wood pieces. Repeating patterns were observed, which indicated that the cavity-size distribution of the wood pieces dictated fluctuations in the rate of moisture loss from the core and cross-cut area shrinkage during drying in the free water phase. It is hypothesised that, while drying an interconnected capillary network in the free water phase, the largest meniscus penetrates a wood piece through the largest cavities, thus also allowing air into the capillary network. The largest meniscus would always get smaller as it penetrates the wood piece until it is not the largest meniscus in the network anymore. Then the new largest meniscus would start penetrating the capillary network, etc. The largest meniscus would also determine the liquid tension in the capillary network. When the largest meniscus gets small enough, and the liquid tension strong enough, deformation and collapse of the remaining liquid-filled cavities can occur. A large liquid-filled interconnected capillary network would eventually fragment into a number of smaller liquid-filled interconnected networks, at which point a receding wetline could be observed.     

Pyroglutamins?ure in Bohnenkaffee

Zusammenfassung Die Identifizierung von Pyroglutaminsäure in Kaffee durch GC/MS des Di-trimethylsilylderivats wird beschrieben. Pyroglutaminsäure findet sich im Röstkaffee zu 0,5 bis 1,5 g/kg und im Kaffee-Extrakt zu ca. 5 g/kg.

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Pyroglutamic acid in coffee

Summary The identification of pyroglutamic acid in coffee by means of gas chromatography/mass spectrometry is described. The contents of this acid are 0.5 to 1,5 g/kg in roast coffee and about 5 g/kg in coffee extracts.

     

Frequency-domain optical tomographic imaging of arthritic finger joints

We are presenting data from the largest clinical trial on optical tomographic imaging of finger joints to date. Overall we evaluated 99 fingers of patients affected by rheumatoid arthritis (RA) and 120 fingers from healthy volunteers. Using frequency-domain imaging techniques we show that sensitivities and specificities of 0.85 and higher can be achieved in detecting RA. This is accomplished by deriving multiple optical parameters from the optical tomographic images and combining them for the statistical analysis. Parameters derived from the scattering coefficient perform slightly better than absorption derived parameters. Furthermore we found that data obtained at 600 MHz leads to better classification results than data obtained at 0 or 300 MHz.     

Vibrational properties of the LiNbO3 z-surfaces

The existence of localized vibrational modes both at the positive and at the negative LiNbO3 (0001) surface is demonstrated by means of first-principles calculations and Raman spectroscopy measurements. First, the phonon modes of the crystal bulk and of the (0001) surface are calculated within the density functional theory. In a second step, the Raman spectra of LiNbO(3) bulk and of the two surfaces are measured. The phonon modes localized at the two surfaces are found to be substantially different, and are also found to differ from the bulk modes. The calculated and measured frequencies are in agreement within the error of the method. Raman spectroscopy is shown to be sensitive to differences between bulk and surface and between positive and negative surface. It represents therefore an alternative method to determine the surface polarity, which does not exploit the pyroelectric or piezoelectric properties of the material.     

Photocatalytic TiO2 films deposited by different methods

Photocatalytic TiO₂ layers are deposited with different methods available within the Fraunhofer Photocatalysis Alliance. These are: Magnetron sputtering, evaporation, sol‐gel, laquer coating, and CVD. The photocatalytic activity under UV illumination is determined by decomposition of stearic acid. The optical properties of the films are compared and discussed.     

Short wavelength emission of AlGaInP quantum dots grown on GaP substrate

We report on the growth of AlGaInP quantum dots (QDs) with Al contents between 0% and 10% on GaP substrate by gas-source molecular beam epitaxy and the investigation of their morphological and low temperature photoluminescence properties. These high areal density QDs show short wavelength emission between 575 and 612 nm depending on their composition. The authors interpret the QD emission as originating from indirect type-II transitions. This interpretation is supported by a single-band effective-mass model, which allows us to describe the role of differing barrier composition in the QD emission. Time-resolved photoluminescence measurements are performed and discussed with respect to the calculations.     

Re-evaluation of correction factors of a primary standard graphite calorimeter in 60Co gamma ray beams as a basis for the appointment of the BEV absorbed dose rate to water reference value

The graphite calorimeter of the Federal Office of Metrology and Surveying (BEV-Bundesamt für Eich- und Vermessungswesen) was established in the 1980s as the primary standard for the absorbed dose to water for (60)Co gamma ray beams. To maintain the primary standard at an international level the graphite calorimeter and its corresponding components had to undergo a refurbishment and modernisation process. The correction factors of the graphite calorimeter were re-evaluated with Monte Carlo and experimental methods to obtain improved values. These are the correction for the effect of the gaps (1.0061), the scaling correction (0.9998), the correction for the difference in air attenuation (0.9971) and the corrections for the effective measurement depths in the graphite phantom for the graphite calorimeter (0.9886) and the CC01-105 ionisation chamber (0.9913). Consequently, it was necessary to change the reference value for the absorbed dose rate to water of the (60)Co teletherapy unit used for the calibration of secondary standard dosemeters.