Carrier medium exchange through ultrasonic particle switching in microfluidic channels

This paper describes a method, utilizing acoustic force manipulation of suspended particles, in which particles in a laminar flow microchannel are continuously translated from one medium to another with virtually no mixing of the two media. During the study, 5-microm polyamide spheres suspended in distilled water, spiked (contaminated) with Evans blue, were switched over to clean distilled water. More than 95% of the polyamide spheres could be collected in the clean medium while removing up to 95% of the contaminant. Preliminary experiments to use this method to wash blood were performed. Red blood cells were switched from blood, spiked with Evans blue, to clean blood plasma. At least 95% of the red blood cells (bovine blood) could be collected in clean blood plasma while up to 98% of the contaminant was removed. The obtained results indicate that the presented method can be used as a generic method for particle washing and, more specifically, be applied for both intraoperative and postoperative blood washing.     

Assessing reproducibility of a protein dynamics study using in vivo labeling and liquid chromatography tandem mass spectrometry

Measuring dynamics of proteins abundance in cells in response to stimuli such as growth factors or drugs requires analysis of more than one time point. Proteomic approaches have traditionally been used to measure only one state at a time because quantitation is difficult, especially when mass spectrometry is used as a readout. Isotopically labeled reagents have recently been introduced that allow comparison of two or three different states by mass spectrometry. Here, we evaluate the reproducibility of an experiment that measures three states simultaneously through stable isotope labeling of cells with amino acids in cell culture (SILAC) using light, medium, and heavy versions of amino acids. The major goal of this study was to assess the reproducibility of such experiments in combination with liquid chromatography tandem mass spectrometry (LC-MS/MS). Our results show that it is possible to obtain reproducible quantitative data to study protein dynamics based on our analysis of more than 220 peptide sets derived from 20 proteins from 3 different LC-MS/MS runs.     

Cross Layer Considerations for an Adaptive OFDM-Based Wireless Communication System

Future applications require high, but variable data rates and different quality of services (QoS) which is a real challenge for the communication system design. Additionally, the broadband radio channel can be assumed to be frequency selective and time variant, which means the transmission performance varies over time and frequency. The OFDM transmission technique is very flexible in adapting the transmission parameters to the current channel situation and to the application-specific requirements. This kind of flexibility will be applied to solve the technical tasks in the design procedures of future communication systems.Prof. Hermann Rohling received the Diplom Mathematiker degree from the Technical University Stuttgart, Germany in 1977 and the PhD from the Faculty of Electrical Engineering, Rheinisch-Westfälischen Technischen Hochschule (RWTH) Aachen, Germany in 1984. From 1977 to 1988 he was with the AEG Research Institute, Ulm as a researcher working in the area of digital signal processing for radar and communications applications. From 1988 to 1999 he was a Professor of Communications Engineering at the Technical University Braunschweig (TUBS). Since 1999, Professor Rohling is with the Technical University in Hamburg-Harburg (TUHH), Germany. His research interests include Wideband Mobile Communications especially based on Multicarrier Transmission Techniques (OFDM) for future broadband systems (4G), Wireless Local Loops, Multiple Access and channel coding schemes, Digital Radar Signal Processing especially for automotive radar applications, differential GPS for high precision navigation. Prof. Rohling is a member of ITG, DGON and a senior member of IEEE.Dr. RainerGrünheid studied Electrical Engineering at theTechnical University Braunschweig (TUBS), Germany, from 1989–1994. After receiving his Diploma degree, he pursued his Ph.D. at the Technical University Hamburg-Harburg (TUHH), Germany, until 2000. Currently, he is working as a research assistant at the Department of Telecommunications at TUHH. His research interests include mobile communications and multicarrier systems (OFDM), with a special emphasis on multiple access schemes, MAC protocols, link adaptation techniques and cross-layer design.     

Transparent and flexible carbon nanotube transistors

We report the fabrication of transparent and flexible transistors where both the bottom gate and the conducting channel are carbon nanotube networks of different densities and Parylene N is the gate insulator. Device mobilities of 1 cm(2) V(-1) s(-1) and on/off ratios of 100 are obtained, with the latter influenced by the properties of the insulating layer. Repetitive bending has minor influence on the characteristics, with full recovery after repeated bending. The operation is insensitive to visible light and the gating does not influence the transmission in the visible spectral range.     

Electrodialytic remediation of copper mine tailings

Mining activities in Chile have generated large amounts of solid waste, which have been deposited in mine tailing impoundments. These impoundments cause concern to the communities due to dam failures or natural leaching to groundwater and rivers. This work shows the laboratory results of nine electrodialytic remediation experiments on copper mine tailings. The results show that electric current could remove copper from watery tailing if the potential gradient was higher than 2 V/cm during 21 days. With addition of sulphuric acid, the process was enhanced because the pH decreased to around 4, and the copper by this reason was released in the solution. Furthermore, with acidic tailing the potential gradient was less than 2 V/cm. The maximum copper removal reached in the anode side was 53% with addition of sulphuric acid in 21 days experiment at 20 V using approximately 1.8 kg mine tailing on dry basis. In addition, experiments with acidic tailing show that the copper removal is proportional with time.     

The influence of previous substrate heat treatment on the epitaxial growth of silver on mica

The growth of silver films prepared by evaporation in ultrahigh vacuum onto mica cleaved in air and previously heat treated at various temperatures T_H for 24 h was studied by reflection high energy electron diffraction. It was found that for T_H < 250 °C the silver films are well oriented from the initial stages of growth. At higher T_H the initial stages are characterized by crystallites with random orientation and with two main orientations (each with double positioning). With increasing thickness, first the randomly oriented crystallites disappear and then those with one of the main orientations; finally a single-crystal film is obtained (T_H < 320 °C. For films with a certain thickness it is found that, the higher T_H is, the higher is the fraction of randomly oriented crystallites. The results are explained by the decrease in water vapour concentration on the mica surface as T_H is increased, which in turn causes the reduction in the orientation of the initial nuclei as well as in their density.     

Induction of a specific olfactory memory leads to a long-lasting activation of protein kinase C in the antennal lobe of the honeybee

In this study we investigated the role of protein kinase C (PKC) in associative learning of Apis mellifera. Changes in PKC activity induced by olfactory conditioning were measured in the antennal lobes, a brain structure involved in associative learning. Multiple conditioning trials inducing a memory different from that induced by a single conditioning trial specifically cause an increase in PKC activity. This increase begins 1 hr after conditioning, lasts up to 3 d, and is attributable to an increased level of constitutive PKC. The increased level of constitutive PKC consists of an early proteolysis-dependent phase and a late phase that requires RNA and protein synthesis. Inhibition of the pathways resulting in constitutive PKC selectively impairs distinct phases of multiple-trial induced memory. The inhibition of the proteolytic mechanism has an instant effect on an early phase of multiple-trial induced memory but does not affect acquisition and the late phase of memory. Blocking of the transient PKC activation during conditioning does not affect the induction of memory formation. Thus, the constitutive PKC in the antennal lobe seems to contribute to the early phase of memory that is induced by multiple-trial conditioning.     

Influence of precursors on the morphology and performance of TiO2 photoanodes

The preparation of TiO₂ photoanodes for dye-sensitized electrochemical devices was investigated. TiO₂ precursors with different rates of hydrolysis were used to modify the microstructures of the resulting TiO₂ photoanodes. The photoelectrochemical quantum yield for electrodes prepared from citrate remained low. Acetate precursors gave rise to electrodes with high fill factors and high open circuit voltages. Titanium isopropoxide hydrolysed very rapidly, leaving a powderous, poorly compacted deposit. Photoanodes from TiCl₄ precursors exhibit high surface roughness, which is necessary for a high degree of dye adsorption. With high hydrolysis rates, isopropoxide precursors produced powdery, poorly coherent films. A composite electrode with an acetate-based substrate and TiCl₄-based surface layers appears to be a suitable compromise.     

Studies of photon induced gas desorption using synchrotron radiation

In view of finalizing the design of the vacuum system of the Large Electron and Positron Storage Ring (LEP) we have studied synchrotron radiation induced neutral gas desorption. A 3 m section of an aluminum vacuum chamber has been exposed to the photon beam emerging from the electron storage ring DCI in Orsay, under conditions closely simulating the environment in a particle acceletor. In order of importance the gases desorbed were H₂, CO₂, CO and CH₄ with H₂O practically absent. Under the experimental conditions of an unbaked chamber and 11 mrad glancing incidence of the photons, the initial molecular desorption yields for these gases were typically 0.5, 8 × 10^?2, 2 × 10^?2 and 8 × 10^?3 molecules per photon respectively. These values could be reduced by about 1 to 2 orders of magnitude during continued photon exposure and most cases without evidence that this ‘beam cleaning action’ would be limited. After exposure to air and pumpdown of the previously cleaned chamber, we observe a significant memory effect. The dependence of the photon desorption on the angle of incidence has been studied down to a glancing angle of 11 mrad showing a definite deviation from the previously assumed 1/sin ø scaling. The implications of the results in terms of the expected beam-gas lifetime in LEP are discussed.     

Identification of different imperfections by measurement of thermal resistivity in high purity copper

Low temperature measurements of thermal resistivity of high purity copper foils with different concentrations of iron impurities in the ppm range are carried out after internal oxidation. By comparison with samples containing different contents of oxidized iron impurities and samples with point defects produced by mechanical deformation, it can be shown that the deviations from Matthiessen' rule for thermal resistivities are characteristic for the kind of ‘extra’ point defects in the lowest concentration range.