Time-resolved monitoring of cavitation activity in megasonic cleaning systems

The occurrence of acoustic cavitation in the cleaning liquid is a crucial precondition for the performance of megasonic cleaning systems. Hence, a fundamental understanding of the impact of different parameters of the megasonic process on cavitation activity is necessary. A setup capable of synchronously measuring sonoluminescence and acoustic emission originating from acoustically active bubbles is presented. The system also includes a high-speed-stroboscopic Schlieren imaging system to directly visualize the influence of cavitation activity on the Schlieren contrast and resolvable bubbles. This allows a thorough characterization of the mutual interaction of cavitation bubbles with the sound field and with each other. Results obtained during continuous sonication of argon-saturated water at various nominal power densities indicate that acoustic cavitation occurs in a cyclic manner, during which periods of stable and inertial cavitation activity alternate. The occurrence of higher and ultraharmonics in the acoustic emission spectra is characteristic for the stable cavitation state. The inertial cavitation state is characterized by a strong attenuation of the sound field, the explosive growth of bubbles and the occurrence of broadband components in the acoustic spectra. Both states can only be sustained at sufficiently high intensities of the sound field. At lower intensities, their occurrences are limited to short, random bursts. Cleaning activity can be linked to the cavitation activity through the measurement of particle removal on standard 200 mm silicon wafers. It is found that the particle removal efficiency is reduced, when a continuous state of cavitation activity ceases to exist.     

Functional Properties of Pork Liver Protein Fractions

The functional (emulsifying, gelling and foaming) properties of liver protein fractions as well as their molecular weight distribution and surface hydrophobicity were investigated and compared to commercial proteins. Two protein fractions were characterized: water soluble (WSLP) and WSLP combined with salt soluble liver proteins (W?+?SSLP). The effect of salt concentrations was also investigated (0, 1.8 and 3.4 % NaCl). Both WSLP and W?+?SSLP displayed good emulsifying properties and foam stability. However, their gelling properties were rather poor. An increase in salt concentration decreased the emulsifying properties of WSLP while the effect on W?+?SSLP was less pronounced. Addition of 1.8 % NaCl increased foaming ability of WSLP and W?+?SSLP while foam stability was not affected. Further increase of NaCl (3.4 %) decreased both foaming ability and foam stability and is probably attributed to refolding of the protein molecules because of the higher level of hydrophobic groups with 3.4 % NaCl. Gel forming ability of WSLP and W?+?SSLP containing 0 % was higher compared to high salt concentrations. However, higher salt concentrations shifted onset gelation temperature of WSLP and W?+?SSLP to lower temperatures probably due to partial unfolding of the proteins as indicated by an increase of the surface hydrophobicity.     

In-game assessment and training of nonverbal cognitive skills using TagTiles

We present a field study with a game for children called ‘Tap the little hedgehog’, which is played on the TagTiles console, a tangible electronic interface. The game was developed to train and assess cognitive skills and includes tasks which, in isolation, exhibit a high correlation with a number of subtests from the Wechsler Intelligence Scale for Children (WISC-III-NL). The tasks address a range of nonverbal skills by requiring children to perform different operations on abstract patterns such as copying, reproducing sequences from memory and mirroring patterns. In the current study, we tested whether these tasks kept their ability to address these skills if included in a gaming context, whether children are able to play the game independently and whether they are motivated to play the game. The results of the study support the hypothesis that nonverbal IQ-scores, as measured by the Wechsler Intelligence Scale for Children, can improve by training with a game. Hence, games like ‘Tap the little hedgehog’ can be used to train specific skills and serve as a screening tool for these skills. The results also confirm that children can play the game independently and that they enjoy it. We further found that children quickly learn how to play the game and use the interface.     

Investigation of “Thermal Touch” Response of Coated Steel Plates Employing Square-Wave-Excited Photothermal Infrared Radiometry

When a person is touching an object, which is at a different temperature than the person??s body, heat starts to flow from the body to the object (or in the other direction), and as a result, the temperature of the skin starts to decrease (increase), leading to a cold (warm) perception of the object??s temperature. It is well accepted that the degree of thermal impact of touching the free surface of a bulk material is determined by the thermal effusivity of that material. In this study, the more complicated situation of touching a coating covering a substrate with different thermal properties is studied. Insight in the involved heat transport effects and their effect on the thermal touch is gained by a photothermal model experiment in which the effect of touching on the measured surface temperature, and from there, the calculated heat flux is mimicked by the effect of illumination by laser light.     

On the Feasibility of Shearographic Imaging of Acoustic Cross‐Modulation

Abstract: The detectability of defects as well as their detection contrast have significantly increased in recent years because of the use of nonlinear variants of the classical non‐destructive acoustic methods. The non‐uniformity of stiffness and hysteresis around the area of a defect results in strong non‐classical acoustic nonlinearity, which can be used to effectively distinguish the presence of defects. Motivated by the latest advances in nonlinear laser Doppler vibrometry and nonlinear ultrasonics, we investigated the potential of shearography to detect the so‐called cross‐modulation effect. This effect arises when a strong, low‐frequency pump wave dynamically changes the elastic response of a defect, so that the amplitude of a weak, high‐frequency probing wave passing through the defect is modulated. As a result, the frequency spectrum of the response contains mixed frequency components, which are directly attributed to the underlying defect.     

Study on the Implementation of Optical Transparent Transport Networks in the European Environment—Results of the Research Project COST 239

Photonic Network Communications -     

Basic Measurements in a Rail Type Plasma Gun

The rail-type plasma-gun is a well suited laboratory set-up for the experimental determination of the physical properties of short lived plasmas. The ONERA plasma-gun is the most conventional rail type gun, with two cylindrical electrodes; an electrical discharge between two auxiliary electrodes generates the plasma whenever a puff of argon is injected into the plasma gun. Measurements on the set-up are devised to give the following data: - mass flow rate through the injection nozzle or amount of argon corresponding to each puff; - current and voltage during a discharge; - self induction of the rails; - shape and displacement of the plasma column (magnetic coil probe and photo-cell recordings). Though not necessarily an efficient space propulsion device, the parallel rail plasma-gun allows the development and improvement of many experimental techniques, which can be used for the study of more efficient electric thrustors.     

Developmental pathways leading to externalizing behaviors in 5 year olds born before 29 weeks of gestation

Recent studies have improved our understanding of the cytogenesis, biology, and therapy of chronic lymphocytic leukemia (CLL). This review highlights this recent progress reported over the past year. We have improved our understanding of the cytogenetic abnormalities in CLL and soon may see identification of new tumor suppressor genes that may be deleted in the leukemia cells of a large number of patients with this disease. We have achieved a better understanding of the surface antigens that help govern the pattern of tissue-infiltration of leukemia cells in vivo. Studies on the immune pathophysiology of CLL are providing clues to potential mechanisms leading to the immunodeficiency associated with this disease. Combination chemotherapy with purine analogues is showing promise for improved efficacy in CLL. Finally, new therapies incorporating bone marrow transplantation, and possibly gene therapy, increasingly are being considered for the therapy of patients with this disease.     

Extreme prematurity in healthy 5-year-old children: a re-analysis of sex effects on event-related brain activity

A male disadvantage has been reported in several outcome studies of children born preterm. Twenty-two healthy premature children (10 girls, 12 boys) born between 25 and 28 weeks of gestation and 20 controls born full-term (10 boys, 10 girls) were matched on socioeconomical status and age. Event-related potentials (ERPs) were recorded by using 14 electrodes in a visual oddball task, with 75% frequent and 25% rare stimuli. This task elicited a larger P3 to the rare than to the frequent stimuli, with a prominent parietocentral localization. However, the amplitude was larger in full-term boys than in full-term girls, a difference that was not observed between preterm boys and preterm girls, especially to targets and on the central electrodes. In addition, the preterm group was characterized by a frontal slow wave larger in boys than in girls. In these prematures, the lack of the sex-related difference may be accounted by differences in the strength of the neuronal generators in males, as they might have been affected by the high level of androgens by the fetal testis under the control of placental gonadotropes during the first two thirds of gestation.