Showing papers by "Fraunhofer Society published in 1994"
TL;DR: In this article, an atomic force microscope was constructed enabling one to image the topography of a sample, and to monitor simultaneously ultrasonic surface vibrations in the MHz range, where a part of the position sensing light beam reflected from the cantilever is directed to an external knife-edge detector.
Abstract: We have constructed an atomic force microscope enabling one to image the topography of a sample, and to monitor simultaneously ultrasonic surface vibrations in the MHz range. For detection of the distribution of the ultrasonic vibration amplitude, a part of the position‐sensing light beam reflected from the cantilever is directed to an external knife‐edge detector. Acoustic images taken on the surface of a wafer show a lateral resolution of about 100 nm at an ultrasonic frequency of 20 MHz.
339 citations
TL;DR: In this article, six starches of different amylose content were studied by static light scattering from very dilute aqueous solutions at 20°C and their angular dependences were obtained after submitting the solutions to a controlled autoclaving step where the solutions were heated up to 135-155°C.
Abstract: Six starches of different amylose content were studied by static light scattering from very dilute aqueous solutions at 20°C. Reproducible results were obtained after submitting the solutions to a controlled autoclaving step where the solutions were heated up to 135-155°C. Amylose rich starches exhibited significantly different angular dependences from those with low amylose content. The high experimental accuracy of the angular dependences allowed separate determination of the molar masses Mw and radii of gyration Rg for both components in the mixture. Molar masses of 60-106 to 110- 106 and radii around 220nm were found for the amylopectins from the various starches. Unexpectedly high molar masses between 450-103 and 2.5-106 were found for the amylose components but only low radii of gyration. Comparison with synthetic amyloses indicate strong intra and intermolecular aggregation in the form of laterally (side-by-side) aligned chains which could contain up to 35 amylose chains. The possibility of a quantitative determination of the degree of branching via the shrinking factor g (=Rg2Ap/Rg2Am I at the same molar mass) is discussed at some length.
203 citations
TL;DR: In this article, the influence of both compressive and tensile strain on semiconductor lasers and optical amplifiers is reevaluated in the light of recent experimental and theoretical work, which appears to adequately explain the TE and TM gain in compressive-and tensile structures, including polarizationindependent amplifiers, the behavior of visible lasers and the improved frequency characteristics of InGaAs/GaAs lasers.
Abstract: The influence of both compressive and tensile strain on semiconductor lasers and optical amplifiers is reevaluated in the light of recent experimental and theoretical work. Strain reduces the three-dimensional symmetry of the lattice and helps match the wave functions of the holes to the one-dimensional symmetry of the laser beam. It can also decrease the density of states at the valence band maximum and so reduce the carrier density required to reach threshold. These two effects appear to adequately explain the TE and TM gain in compressive and tensile structures, including polarization-independent amplifiers, the behavior of visible lasers and the improved frequency characteristics of InGaAs/GaAs lasers. In 1.5 /spl mu/m InGaAsP/InP lasers phonon-assisted Auger recombination appears to remain the dominant current path and can explain why the temperature sensitivity parameter to remains >
192 citations
Journal Article•
TL;DR: It is found that LPS-induced macrophages activation also involves the Raf-1 kinase, a key component in mitogenic signal transduction, and data argue that Raf- 1 functions downstream of tyrosine kinases in L PS-mediated macrophage activation and cytokine production.
Abstract: Bacterial LPS is a potent macrophage activator. The early steps in LPS signal transduction involve the tyrosine phosphorylation and activation of a number of kinases of the src family, and inhibition of this pathway causes a severe impairment in the production of the cytokines TNF-alpha and IL-1 beta. We find that LPS-induced macrophages activation also involves the Raf-1 kinase, a key component in mitogenic signal transduction. Treatment of BAC-1.2F5 macrophages with LPS causes phosphorylation and activation of Raf-1. This is paralleled by the stimulation of MEK-1 and MAP-kinase activity and by the phosphorylation of the transcription factor Elk-1, a nuclear target of MAP-kinase. Activation of the Raf/MAP-kinase pathway was inhibited upon pretreatment of the cells with genistein, a tyrosine kinase inhibitor. Raf-1 must thus lie downstream of tyrosine kinase in LPS signal transduction. However, Raf-1 is not a direct substrate of a LPS-induced tyrosine kinase, because Raf-1 immunoisolated from LPS-induced cells contains only phosphoserine. This resembles the situation after CSF-1-stimulation of macrophages, in which Raf-1 clearly transduces a signal generated by the CSF-1 receptor kinase, but is phosphorylated exclusively in serine. Phosphopeptide maps of Raf-1 immunoprecipitated from LPS- or CSF-1-treated cells are indistinguishable, suggesting that these agents activate Raf-1 by similar mechanisms. Finally, v-raf-infected BAC-1.2F5 macrophages were found to constitutively express low levels of IL-1 beta and TNF-alpha. These data argue that Raf-1 functions downstream of tyrosine kinases in LPS-mediated macrophage activation and cytokine production.
149 citations
TL;DR: Net uptake of sulphate by the roots, and its transport to the shoot was inhibited in intact tobacco plants by 1 h exposure of its roots to 0.1 or 1.0 mM GSH, and apparently, sulphate uptake, but not xylem loading of sulphates was inhibited by GSH.
Abstract: Net uptake of sulphate by the roots, and its transport to the shoot was inhibited in intact tobacco plants by 1 h exposure of its roots to 0.1 or 1.0 mM GSH. The relative amount of sulphate taken up that was transported to the shoot was not affected by this treatment. Apparently, sulphate uptake, but not xylem loading of sulphate, was inhibited by GSH. Similar results were obtained when L-cysteine was used instead of GSH. As L-cysteine, mediated inhibition of sulphate, net uptake was counteracted by exposure of the roots to BSO, GSH synthesis seems to be required for inhibition of sulphate uptake by L-cysteine. However, exposure to 0.1 or 1.0 mM GSH did not result in an enhanced GSH level in roots or shoots. Also the cysteine contents remained unchanged
137 citations
120 citations
TL;DR: This paper introduces an incremental approach to software process management based on a net-based software process modeling language called FUNSOFT nets and model software processes by means of different views onto a software process model.
Abstract: Software processes are usually described by guidelines and advices. These guidelines are claimed to be valid for many projects. This understanding leads to software processes which deviate from initial plans and which frequently yield insufficient results. System-atic management of software processes can help to overcome these shortcomings. In this paper, we introduce an incremental approach to software process management. This approach covers the complete life-cycle of software process models, i.e., it deals with software process modeling, software process model analysis, and software process model enaction. It is based on a net-based software process modeling language called FUNSOFT nets. FUNSOFT nets are high-level Petri nets adapted to the application domain of software process management. We model software processes by means of different views onto a software process model. Our approach is implemented in a software process management environment called MELMAC.
118 citations
TL;DR: In this paper, the substituent pattern of carboxymethyl cellulose (CMC) was determined by means of high-performance liquid chromatography, where the hydrolysates of CMC were separated on a polystyrene-based strong cation-exchange resin into glucose, 2,3,6-tri-O-carboxyldimethyl glucose and groups of 2, 3,and 6-mono-O -carboxylated and unsubstituted units.
Abstract: A rapid and convenient procedure was developed for the determination of the substituent pattern of carboxymethyl cellulose (CMC) by means of high-performance liquid chromatography. The hydrolysates of CMC are separated on a polystyrene-based strong cation-exchange resin into glucose, 2,3,6-tri-O-carboxymethyl glucose and groups of 2-, 3-and 6-mono-O- and 2,3-, 2,6-, and 3,6-di-O-carboxymethyl glucoses. By this method the determination of the average degree of substitution as well as the substituent pattern is possible. In this way we found that CMC samples which were synthesized in LiCl/N,N-dimethylacetamide as a cellulose solvent, contain a significantly higher amount of both tricarboxymethylated and unsubstituted units than those obtained in a slurry of cellulose in isopropanol/water at comparable DS values. The substituent pattern of heterogeneously synthesized CMC is mainly determined by statistics.
114 citations
24 Oct 1994
TL;DR: A new approach for estimating the orientation field of oriented textures based on the covariance matrix of the grey value changes in an image is described, which is used in the unsupervised road segmentation in the initial phase as well as in the supervised road segmentsation in subsequent phases.
Abstract: The extraction of road boundaries is one of the basic requirements for an autonomous navigation system to guide a vehicle on a road. The existent road detection approaches have some difficulties with the roads that have neither marked lanes nor different colors between their surface and the environment. Instead of gray value or color, texture can be an important feature in such images. Taking this as motivation, the authors developed a texture-based road segmentation approach. The textures in road images are usually strongly anisotropic with a dominant orientation. Such oriented textures can be described by their orientation field that consists of orientation and strength of texture anisotropy. The authors describe a new approach for estimating the orientation field of oriented textures based on the covariance matrix of the grey value changes in an image. As an image feature, the strength of texture anisotropy is then used in the unsupervised road segmentation in the initial phase as well as in the supervised road segmentation in subsequent phases. The authors' algorithm has been tested with real road image sequences.
111 citations
TL;DR: In this article, a new type of patent indicator is introduced replacing direct technology measures more adequately than most of the established indicators, which can be used in terms of both individual enterprises or research institutions and the national economy.
110 citations
TL;DR: The presented flowthrough system allows the testing of volatile and instable chemicals, problematic in static test systems, and the EPR parameter is suitable for the early characterization of chemicals acting as specific inhibitors of the photosynthetic electron transport chain.
TL;DR: In this paper, the authors investigate a specific aspect of the science and technology interface: inventor-author relations and find evidence for the claim that references in patents to non-patent literature (NPL references, mostly scientific publications) indicate "science intensity".
01 Dec 1994
TL;DR: In this article metadata for mulimedia documents are classified in conformity with their nature, and the different kinds of metadata are brought into relation with the different purposes intended.
Abstract: In this article metadata for mulimedia documents are classified in conformity with their nature, and the different kinds of metadata are brought into relation with the different purposes intended. We describe how metadata may be organized in accordance with the ISO standards SGML, which facilitates the handling of structured documents, and DFR, which supports the storage of collections of documents. Finally, we outline the impact of our observations on future developments.
TL;DR: It is concluded that flow cytometric routine diagnostics of CGD can easily enhance the reliability of recognition and the yield of information about this disease compared to conventional methods.
Abstract: Neutrophils from 50 pediatric patients with normal phagocyte functions, from 150 healthy adults, from 10 chronic granulomatous disease (CGD)-patients (4 CGD+), and from 18 X-linked carriers for CGD have been tested for their production of H2O2 using staining with dihydrorhodamine 123 and subsequent flow cytometry. Additionally, neutrophils from three patients with myeloperoxidase deficiency were assessed. Cells were activated to produce H2O2 by the phorbol ester phorbol-myristate-acetate (PMA) and by phagocytosis of Escherichia coli bacteria. To evaluate the sensitivity of the method, H2O2-production by neutrophils which was inhibited by different concentrations of diphenyljodonium (DPI) was measured. The results were compared to those from other methods (NBT-testing, cytochrome c-reduction, and especially chemiluminescence). Normal values and ranges of scatter profile were evaluated in terms of peak channel fluorescence: 97% > 700, X = 840 ± 59 (S.D.), 97% 485, 97% < 680, peak channel fluorescence. We conclude that flow cytometric routine diagnostics of CGD can easily enhance the reliability of recognition and the yield of information about this disease compared to conventional methods. © 1994 Wiley-Liss, Inc.
TL;DR: In this article, the authors developed a method for estimating the cutting forces in 3-axis milling so that the NC programmer can "optimize" the machining parameters and establish the best rough milling strategy to reduce machining time and cost.
Abstract: The use of CAD/CAM systems and NC machine tools for die and mold manufacturing offers considerable advantages over conventional methods, such as reduction in machining time and costs, and improvements in accuracy and reproducibility. However, the selection of cutting tools and machining strategy and parameters, which have a significant impact on overall machining efficiency and process reliability, still depends on the experience of the machinist or the NC programmer. Based on these considerations, this study had two major objectives: (a) develop a method for estimating the cutting forces in 3-axis milling so that the NC programmer can “optimize” the machining parameters; and (b) establish the “best” rough milling strategy to reduce machining time and cost. This paper concentrates on the first objective, namely on optimizing the feed rate to improve machining efficiency in end milling. By simulating the end milling process and predicting the cutting force in 3-axis milling of sculptured surfaces, an approach and the associated computer program have been developed to optimize the feed rate, already at the NC programming stage. The calculated cutting force, which includes the overall net effect of all process variables, is used as a feedback variable to adjust the feed rate. The method also allows the NC programmer to visualize cutting forces in a CATIA CAD/CAM environment.
TL;DR: In this paper, a single chip pressure and tenperature sensor system with on chip electronics is presented, where the capacitive pressure sensor is fabricated using a CMOS process with additional surface micromachining steps to form a membranes.
Abstract: In this paper a single chip pressure and tenperature sensor system with on chip electronics is presented. The capacitive pressure sensor is fabricated using a CMOS process with additional surface micromachining steps to form a membranes. The membrane dimensions have been optimized for a pressure range of 2, 3.5, 10 and 35 bars, respectively. The temperature sensor shows a straight linear output signal in a temperature range of 0 to 70 °C. For the signal processing switched capacitor circuits are used. The sensor signals are converted to a pulse width modulated output signal. The silicon chip has an active area of 3.5 mm 2 . Between 0 and 80 °C a temperature dependence of the pressure segnal of less than 200 ppm/°C referring to full scale was found.
TL;DR: The integrated optical configuration of a Young interferometer is proposed for refractometry and chemical sensing by fixing a laser diode directly at the input of the optical device, resulting in visibility modulation of the interference fringes caused by the low coherence length of the emitted light.
Abstract: The integrated optical configuration of a Young interferometer is proposed for refractometry and chemical sensing. We coupled light into an integrated optical Y branch by fixing a laser diode directly at the input of the optical device. We solved the problem of ambiguity in the interference order by operating the laser diode at currents below threshold, resulting in visibility modulation of the interference fringes caused by the low coherence length of the emitted light. A very compact device results that measures the refractive index of liquids or gases. An electronic scanning technique by means of a CCD array provides a fast readout without the need for moving parts.
TL;DR: In this article, a new isolation method has been developed for the determination of pesticides in environmental water samples using solid-phase microextraction (SPME), which can be used to identify even unknown compounds in environmental samples.
TL;DR: The on-line multicomponent analysis software is based on line-by-line retrieval and least-squares fitting procedures, including the effects of multiple aerosol scattering and cloud and rain influences.
Abstract: Fourier transform infrared spectroscopy is an efficient technique for the detection and quantification of molecules in gas mixtures. Measurement results from a mobile laboratory for ambient air analysis and for remote sensing of plume emission with the commercially available K300 spectrometer are reported. CO, CO(2), NO, NO(2), N(2)O, NH(3), CH(4), SO(2), H(2)O, HCl, and HCHO concentrations have been determined with good agreement with in situ results. The on-line multicomponent analysis software is based on line-by-line retrieval and least-squares fitting procedures, including the effects of multiple aerosol scattering and cloud and rain influences.
TL;DR: In this article, a high-current pulsed arc (HCA) was developed to increase the deposition rate by several times in comparison with conventional arc evaporation units, which can work with an average arc current as high as 1000 A. This represents an increase of more than five times over the d.c. currents of 100-200 A usually used.
Abstract: A new type of arc evaporator, the so-called HCA (high-current pulsed arc), was developed to increase the deposition rate by several times in comparison with conventional arc evaporation units. This device makes use of pulsed arc discharges with nearly sinusoidal current shapes (duration 0.1–1 ms, peak current > 5 kA), which are ignited repeatedly (0–300 s-1) in the centre of a circular cathode. The high pulse current drives the cathode spots radially at high velocity, but before touching the cathode border the arc is switched off and another cycle is started in the centre. The new arc evaporator can work with an average arc current as high as 1000 A. This represents an increase of more than five times over the d.c. currents of 100–200 A usually used. The controllable arc duration and repetition frequency mean that only a well defined circular area of erosion is affected by the arc evaporation. Besides the high rate, there are some other advantages: the deposition rate can easily be controlled and adjusted in a range from zero to a maximum value. The pulsed arc operates with peak deposition rates about 20 times higher than an ordinary arc evaporation unit. Using this method a modified film structure and/or composition can be expected. The number of droplets will be strongly diminished. Using two or more evaporation units, films with a well defined modulated composition and structure (e.g. multilayer films with single film densities of some nanometres) can be produced effectively and with high reproducibility. All the advantages of vacuum arc deposition (high degree of ionisation, ion energies of about 20–50 eV, option for reactive deposition) are enhanced or preserved.
TL;DR: In this paper, a monolithic single-chip sensor array for measuring chemical and biochemical parameters has been developed and fabricated in a modified standard CMOS process, which is used for amperometric or potentiometric measurements in order to get a concentration-dependent spatial profile of the detected analyte.
Abstract: A monolithic single-chip sensor array for measuring chemical and biochemical parameters has been developed and fabricated in a modified standard CMOS process. The array can be used for amperometric or potentiometric measurements in order to get a concentration-dependent spatial profile of the detected analyte. In addition to 400 working electrodes and two reference electrodes, the chip contains integrated read-out amplifiers, digital circuits for addressing the individual components and test circuits. The on-chip signal processing allows detection of chemical or biochemical analytes without any interference by the external measurement equipment. High electrode impedances and low power consumption have been achieved by using CMOS technology. Chemical modification of the electrodes is possible by applying an external voltage to the electrodes. In advantage to non-integrated solutions, the system can be used in a wide field of applications, especially for measurements in narrow passages because of the total chip size of only 14×14 mm.
TL;DR: In this article, a series of images which were progressively weighted by transverse relaxation have been acquired by application of a spin-echo back-projection technique, and the relaxation was analyzed pixel by pixel using a single chain model for the molecular dynamics of the polymer network.
Abstract: Spatially resolved investigations of molecular properties in polymer materials are shown to be possible by means of parameter-selective NMR imaging. The transformation of NMR parameters into material properties can be performed using a suitable theoretical description of the molecular mobility in the polymer under investigation. Rubber samples consisting of three pieces of rubber with different crosslink densities have been investigated in a first experiment. A series of images which were progressively weighted by transverse relaxation have been acquired by application of a spin-echo back-projection technique. The relaxation was analyzed pixel by pixel using a single chain model for the molecular dynamics of the polymer network
TL;DR: In this article, an LC separation in combination with postcolumn addition of a volatile salt solution was developed, which permits the analysis of 95 pesticides with a single LC-MS method using reversed phase gradient caution.
TL;DR: Using porous silicon as a sacrificial layer, a surface micromachining (SMM) process with a large distance from the structure to the substrate is realized in this article, where the application of this process for making free standing structures of polysilicon and flow channels is described.
Abstract: Using porous silicon as a sacrificial layer a surface micromachining (SMM) process with a large distance from the structure to the substrate is realized. The application of this process for making free standing structures of polysilicon and flow channels is described.
TL;DR: In this article, the authors derived theoretical expressions for the impedance of quantum-well lasers below and above threshold based on a simple rate equation model, which is dominated by purely electrical parameters related to carrier capture/transport and carrier re-emission.
Abstract: We derive theoretical expressions for the impedance of quantum-well lasers below and above threshold based on a simple rate equation model. These electrical laser characteristics are shown to be dominated by purely electrical parameters related to carrier capture/transport and carrier re-emission. The results of on-wafer measurements of the impedance of high-speed In/sub 0.35/Ga/sub 0.65/As/GaAs multiple-quantum-well lasers are shown to be in good agreement with this simple model, allowing us to extract the effective carrier escape time and the effective carrier lifetime, and to estimate the effective carrier capture/transport time. >
TL;DR: With this analytical system antibodies specific against the HIV have been detected in human serum samples within a few minutes and with a selectivity and sensitivity comparable to a licensed HIV ELISA.
Abstract: An immunosensing system for the detection of human immunodeficiency virus (HIV) specific antibodies comprising a piezoelectric immunosensor integrated in a flow through system is presented. The fundamental sensor effect is based on the linear dependence of the resonance frequency of an oscillating quartz crystal upon the mass accumulation on the surface during the measurement. An immunospecific detector was realized by immobilizing synthetic peptides or recombinant proteins with major diagnostic epitopes of HIV on the surface of the transducer. With this analytical system antibodies specific against the HIV have been detected in human serum samples within a few minutes and with a selectivity and sensitivity comparable to a licensed HIV ELISA.
TL;DR: A transputer-based platform has been developed which allows control of most relevant parameters of a diode- laser spectrometer and a signal-processing concept with novel aspects for tunable-diode-laser spectroscopy is presented and discussed.
Abstract: Tunable-diode-laser absorption spectroscopy fulfills the major requirements for trace-gas analysis: sensitivity, specifity, high detection speed, and the possibility of simultaneous in situ measurements The well-known limitations for low-concentration measurements become more and more dominant at sub-part-per-billion levels, where sensitive spectrometers are often influenced by noise, drift effects, and changes in the spectral background structure While many improvements in instrument development focus on optimizing electronics and optical components, much less effort has been put into postdetection signal processing and adaptive control Therefore, a transputer-based platform has been developed which allows control of most relevant parameters of a diode-laser spectrometer Fluctuations in the signal amplitude as well as drift and jitter effects in the frequency domain can cause a significant degradation of system performance and therefore determine the ultimate detection limit A signal-processing concept with novel aspects for tunable-diode-laser spectroscopy is presented and discussed
25 Jan 1994
TL;DR: In this article, the buckling effect of a heated pure silicon bridge structure was used for thermally driven micro-valve design with high flow rate of more than 700 ml/min.
Abstract: The paper presents theoretical and experimental results of a new thermally driven microvalve. In contrast to earlier reported devices with bimorph composition this valve is based on the buckling effect of a heated pure silicon bridge structure. Simulation, fabrication and experimental results are presented. Analytical and finite-element calculations of the thermomechanical behaviour are performed. Prototypes of this first valve design operate with inlet pressures up to 1.0 bar showing flow rates of more than 700 ml/min. The measured switching time is about 15 ms which is extremely low for thermal principles. The power consumption of this valve is between 1 and 4 W.
TL;DR: In this paper, thin-film SnO 2 gas sensors have been constructed on Si substrates and shown to be temperature stable at 900°C in synthetic air for 48 h. No significant outdiffusion of the sensor layers can be observed after annealing.
Abstract: Thin-film SnO 2 gas sensors have been structured on Si substrates. The sensors are temperature stable at 900°C in synthetic air for 48 h. No significant outdiffusion of the sensor layers can be observed after annealing. Pt catalysts lead to CO sensors without cross sensitivity to CO 2 . Pt/Ca catalyst combinations also lead to CO 2 gas response. CO 2 sensitivity between 1000 and 10 000 ppm has been demonstrated at 270°C. CO 2 might be indirectly detected via humidity exchange between CO 2 and the heated Ca-catalysed SnO 2 surface.
TL;DR: The carbon monoxide (CO) reference scale created by the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL) is used to quantify measurements of CO in the atmosphere, calibrate standards of other laboratories and to provide reference gases to the community measuring atmospheric CO as discussed by the authors.
Abstract: The carbon monoxide (CO) reference scale created by the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL) is used to quantify measurements of CO in the atmosphere, calibrate standards of other laboratories and to otherwise provide reference gases to the community measuring atmospheric CO. This reference scale was created based upon a set of primary standards prepared by gravimetric methods at CMDL and has been propagated to a set of working standards. In this paper we compare CO mixing ratios assigned to the working standards by three approaches: (1) calibration against the original gravimetric standards, (2) calibration using only working standards as the reference gas, and (3) calibration against three new gravimetric standards prepared to CMDL. The agreement between these values was typically better than 1%. The calibration histories of CMDL working standards are reviewed with respect to expected rates of CO change in the atmosphere. Using a Monte Carlo approach to simulate the effect of drifting standards on calculated mixing ratios, we conclude that the error solely associated with the maintenance of standards will limit the ability to detect small CO changes in the atmosphere. We also report results of intercalibration experiments conducted between CMDL and the Diode Laser Sensor Group (DACOM) at the NASA Langley Research Center (Hampton, Virginia), and CMDL and the Fraunhofer-Institut (Garmisch-Partenkirchen, Germany). Each laboratory calibrated several working standards for CO using their reference gases, and these results were compared to calibrations conducted by CMDL. The intercomparison of eight standards (CO concentrations between approximately 100 and approximately 165 ppb) by CMDL and NASA agreed to better than +/- 2%. The calibration of six standards (CO concentrations between approximately 50 and approximately 210 ppb) by CMDL and the Fraunhofer-Institut agreed to within +/- 2% for four standards, and to within +/- 5% for all six standards.