Showing papers by "Fraunhofer Society published in 1991"

Current-induced light emission from a porous silicon device

Abstract: Experiments with light-emitting porous silicon (LEPOS) are described. The porous silicon was made from n-type silicon by anodization in an electrolytic cell by HF with an applied electrical current. Visible light emission was achieved by irradiation with ultraviolet light. Visible electroluminescence (EL) was achieved by applying a DC or AC voltage to a solid-state contact on top of the porous layer. Optical spectra from both experiments are shown. >

A micromachined electrohydrodynamic (EHD) pump

Abstract: A new micromachined electrohydrodynamic (EHD) injection pump is presented. The pump mainly consists of two facing grids, which are micromachined from s

High-frequency equivalent circuit of GaAs FETs for large-signal applications

Abstract: The application of GaAs field effect transistors in digital circuits requires a valid description by an equivalent circuit at all possible gate and drain bias voltages for all frequencies from DC up to the gigahertz range. An equivalent circuit is presented which takes into account the gate current of positively biased transistors as well as the symmetrical nature of the devices at low drain voltages. A fast method of determining the elements of the equivalent circuit at all bias points without frequency limitations is presented. Direct computation from analytical expressions, without iteration, allows this parameter extraction procedure to be used for real-time on-wafer parameter extraction. Large-signal calculations are possible by inserting the voltage dependences evaluation for the elements into suitable simulation programs, such as SPICE. >

TMAHW etchants for silicon micromachining

Abstract: Etching solutions based on tetramethyl ammonium hydroxide and water (TMAHW) are proposed for etching monocrystalline silicon. The nature of TMAHW solutions is discussed with respect to anisotropy, selectivity, and IC-process compatibility. At a solution temperature of 80 degrees C and 2 wt.% TMAH, a maximum

Microfabricated actuator with moving permanent magnet

Abstract: A microactuator is presented which uses electromagnetic force generation within micromachined silicon devices. A rare-earth permanent magnet is bonded on a movable micromachined silicon plate suspended by thin silicon beams. A monolithically integrated planar coil is used to generate a magnetic field which forces the magnet to move vertically. Using a magnet with a dimension of 1.5*1.5*1.0 mm/sup 3/ and a 17-turn coil driven with 300 mA, a static elevation of 70 mu m has been achieved. The actuator concept offers a variety of application-specific design possibilities. The use of a moving permanent magnet allows a magnetic coupling of the actuator force to the environment. By integrating a magnetic field sensor and signal processing, an active, controlled microsystem can be realized. High, long-range forces can be generated in order to realize devices with large deflections. >

Midlatitude lidar backscatter to mass, area, and extinction conversion model based on in situ aerosol measurements from 1980 to 1987.

Abstract: Balloonborne particle counter data from Laramie, WY are used to define a seasonally averaged stratospheric sulfuric acid aerosol size distribution in three altitude intervals from 15 to 30 km for the 1980–1987 period. This period includes the volcanic eruptions of Mt. St. Helens, Alaid, Nyamuragira, El Chichon, and Nevado del Ruiz and begins and ends at what are believed to be periods of near background (nonvolcanic) stratospheric conditions. The size distributions are used to calculate lidar backscatter to extinction, mass, and area ratios for an appropriate range of particle indices of refraction. These ratios may then be used to infer particle extinction, mass, and area from midlatitude lidar data for this time period.

Absorption of atmospheric NO2 by spruce (Picea abies L. Karst.) trees

Abstract: summary When spruce (Picea abies L., Karst.) branches were exposed to 5.2–18.7 nl NO2 l−1the flux to the shoots increased linearly with increasing NO2 concentrations. At NO2 concentrations below 2.6 nl l−1uptake of NO2 by the shoots was not observed. The measured flux of NO2 to the shoots was found to be lower than the NO2 flux predicted from the shoot conductance to diffusion of H2O. These results are consistent with the existence of internal resistances for NO2 influx, e.g. production and emission of NO2 by the leaves. However, emission of NO2 was not observed. When the NO2 flux to the shoots was plotted versus transpiration rate, a linear increase was found with an y-axis intercept. The intercept may be interpreted as the NO2 flux to the cuticle and the bark; its value increased with increasing atmospheric NO2 concentrations. The flux of NO2 to the shoots showed diurnal variation with high levels in the light and low levels during darkness. NO2 flux to the branches was dependent on light intensity. This dependency can largely be explained by light dependent changes in shoot conductance. Daytime light intensity determined also the night-time shoot conductance and, hence, the NO2 flux to the branches during the night. The ratio of NO2 flux to transpiration rate was higher in the dark than in the light. Whether this observation can be explained by a light dependency of internal resistances remains to be elucidated. The absorption of NO2 by the shoots enhanced the in vitro NR activity of the needles, while NiR and GS activities were not increased significantly. One day after exposure to NO2 concentrations of 60 nl l−1, nitrate reductase (NR) activity was three times higher than that of untreated controls. However, after three days of NO2 exposure the NR activity declined to the level of untreated controls. Apparently, the increased in vitro NR activity upon NO2 fumigation is a transient phenomenon in spruce needles. The regulatory events that may modulate NR activity of the needles, when exposed to atmospheric NO2, are discussed.

Electrohydrodynamic pumping and flow measurement

Abstract: A micromachined electrohydrodynamic (EHD) injection pump with improved characteristics and a novel method for flow measurement with the same structure are presented. Based on the structure of the EHD injection pump, an improved design with grid distances in the range between 10 mu m and 60 mu m was achieved, yielding a reduction in the required driving voltage. Grid areas of 2.5*2.5 mm/sup 2/ and 1*1 mm/sup 2/ were accomplished. The outer dimensions of the smallest pumps are 3*3*1.0 mm/sup 3/. One of the grids is etched back from the frontside and mounted upside down on the lower grid in order to reduce the grid distance. The two grids are bounded together by anodic bonding. The pump is mounted in a ceramic housing with two fluid ports. Based on this structure, a novel method for the measurement of fluid flow and velocity was developed. This technique is well suited for small flow rates below 100 mL/min down to some mu L/min. Volumetric flow rates down to 8 mu L/min were measured with a 2.5*2.5 mm/sup 2/ grid area. >

Diagnosis of chronic granulomatous disease and of its mode of inheritance by dihydrorhodamine 123 and flow microcytofluorometry.

Abstract: Dihydrorhodamine 123 (DHR) attached to membranes of granulocytes (PMN) and monocytes is caused to fluoresce by reactive oxygen intermediates (ROI) indicating the ability of phagocytes to produce these microbicide metabolites in a flow microcytofluorimeter. Whole blood samples from five boys with known chronic granulomatous disease (CGD) and from their mothers (and from one father and one grandmother), were examined following erythrocyte lysis in order to test this new method. An incubation period of 10 min with phorbol-myristate-acetate, followed by another 15 min incubation period with DHR before flow microcytofluorimetric analysis of 5 or 10×103 phagocytes, was sufficient to obtain the following results. PMN and monocytes from four patients with CGD could clearly not produce any ROI whereas cells from one patient displayed decreased activity in ROI production as compared to cells from a healthy donor. The X-linked mode of inheritance was detected in six carriers by the presence of two different cell populations (one normal ROI-producing and one negative or less active population). All the phagocytes from one mother produced ROI in normal amounts suggesting an autosomal mode of inheritance. All in all, the method presented provides a fast and most simple tool to diagnose CGD, to determine a decrease or total lack of ROI production and to establish the mode of inheritance of the disease.

Improved control of TiN coating properties using cathodic arc evaporation with a pulsed bias

Abstract: A combined d.c.-pulse bias voltage was used in combination with a cathodic arc evaporation process for the deposition of TiN on planar plates and drilling tools at substrate temperatures T between 330 and 500 °C. This new pulse technique appeared to be a powerful tool to achieve independent control of the substrate temperature, coating adhesion and uniformity of deposition. As a result, high coating adhesion can be obtained at low substrate temperatures. The adhesion uniformity across large-area samples is considerably improved. Unpolished rough substrate parts can be coated without cauliflower-like growth defects. Because of intensive ion bombardment in the pulse period, smoother TiN coatings with a reduced droplet size were obtained.

Estimation of heat transfer in SOI-MOSFETs

Abstract: Heat flow in MOSFETs built on separation by implantation of oxygen (SIMOX) wafers is described and quantified. Silicon-on-insulator (SOI) structures are examined numerically to show the influence of connection lines and different materials on the heat transport. Correct boundary conditions for device simulation and analytical expressions for compact models are derived. Designers of short- and narrow-channel devices should be aware of an error in the range of 10% due to neglecting the influence of the interconnection lines. Test devices may not be typical for a device in VLSI circuits, as their thermal resistances may be significantly lower. Device parameters should be extracted from pulsed measurements and at raised ambient temperature. Pads should be kept at least 100 mu m away from the test devices. Thermal resistances of SOI devices are not significantly larger than the resistances of bulk devices under VLSI conditions and will be about one order of magnitude larger under test conditions. The absolute value can be calculated from a simple formula that is verified by numerical simulations. Bulk and SOI technologies are compared. >

Signal-to-noise ratio analysis in laser absorption spectrometers using optical multipass cells

Abstract: In high resolution absorption spectrometers with conventional light sources, the signal-to-noise ratio (SNR) is usually limited by the thermal noise level of the detector-preamplifier combination, which is independent of the light source power. However, the noise in many laser absorption spectrometers is dominated by the excess or shot noise which is dependent on the transmitted laser power, and which in turn is dependent on the number of reflections in a multipass cell. The optimum absorption path length for a high frequency modulated (FM) and a conventional wavelength modulated (WM) diode laser absorption spectrometer is investigated in this paper. The major result is that, due to the power attenuation by the multipass cell, the best SNR of a shot noise limited FM spectrometer is achieved at substantially shorter absorption paths, when compared with the excess noise limited WM spectrometer. This finding implies that the implementation of the FM technique in absorption spectrometers with multipasscells can improve the SNR only by 1 order of magnitude. Although desirable, this is substantially less than the improvement of 2 orders of magnitude expected in quantum limited conditions with a single pass cell.

Robot calibration—Method and results

Abstract: For many applications, robots are needed which have an absolute Cartesian pose accuracy of the same order of magnitude as their repeatability. Calibration procedures must be applied to reach this aim. In this paper, a calibration procedure is presented which allows the automatic determination of all kinematic parameters, gear parameters, and static elasticity effects. With the aid of these results it is possible to increase pose accuracy up to the robot's system limit as determined by its repeatability. Moreover, information can be acquired which suggests improvements in robot design, thereby also improving repeatability.

Tumours by the Intraperitoneal and Intrapleural Routes and their Significance for the Classification of Mineral Fibres

Abstract: In 1967, the first author of this paper started intraperitoneal studies on the carcinogenicity of asbestos. Later Wagner and coworkers (1974) published their large inhalation experiment with five asbestos types and this provided the incentive to perform similar inhalation studies with man-made mineral fibres. This aim was achieved in 1983 after some years of planning and the construction of the facilities for inhalation toxicology at the Fraunhofer Institute in Hannover. It was a great disappointment that Muhle and coworkers (1987) at the new facilities could not even find a clear carcinogenic effect in the groups exposed to chrysotile or crocidolite. Even in a parallel injection study with about 109 chrysotile fibres there was no clear carcinogenic effect. In these experiments Californian chrysotile was used as a positive control following the recommendation of NIOSH. The crocidolite sample used gave an unequivocally positive result after intraperitoneal injection of a relatively low number of fibres but no significant carcinogenic effect could be detected in the inhalation study. This compares with the work of Wagner and others (1985, 1987) who also failed to reproduce the high tumour rates observed with crocidolite in their previous inhalation study.

Multi-Gb/s silicon bipolar clock recovery IC

Abstract: A novel clock recovery IC for optical fiber communication systems with data rates up to several Gb/s is presented. It combines nonlinear signal preprocessing directly with a regenerative frequency divider scheme and an external filter in the divider loop. Hence, the center frequency of the filter and the working frequency of the amplifier are halved. The extracted clock frequency corresponds to half the bit rate, as required for many clocked circuit components within fiber optic lines. Two versions of the same IC design, scheduled for two bit rate ranges between 0.3-4 Gb/s, are realized with a conventional Si bipolar process. Clock recovery is demonstrated at 2.2 and 3.52 Gb/s, using both cavity and surface acoustic wave (SAW) filters. >

Negative-U, off-center OAS in GaAs and its relation to the EL3 level

Abstract: Using comparative local-vibrational-mode and deep-level transient spectroscopy, we have studied the off-center ${\mathrm{O}}_{\mathrm{As}}$ defect in high-resistivity, undoped GaAs and neutron-transmutation-doped, n-type samples from the same starting material. The results fully support that this defect has a negative-U character. They also reveal that its deeper, two-electron level corresponds to the chemically unidentified EL3-defect level in GaAs at ${\mathit{E}}_{\mathit{c}}$-0.58 eV.

Expansion and high proliferative potential of the macrophage system throughout life time of lupus-prone NZB/W and MRL lpr/lpr mice. Lack of down-regulation of extramedullar macrophage proliferation in the postnatal period.

Abstract: Systemic lupus erythematosus is an autoimmune disease, characterized by high titers of autoantibodies against many cell-membrane and intracellular antigens. Polyclonal B cell activation and alterations in the T cell compartment have been described. The present report deals with the organ-associated macrophage (M phi) system of two lupus-prone mouse strains (NZB/W and MRL lpr/lpr) and demonstrates that in both mouse strains the M phi compartment of liver and spleen is clearly expanded. In the liver the number of F 4/80+ M phi is strongly elevated. In addition, presence of early M phi precursors and of extramedullary organ-associated monocyte proliferation in response to colony-stimulating factor (CSF) is documented in liver and spleen of these mice. Further, in normal animals during the first two weeks of life extramedullar monocytopoiesis is present in liver and spleen, which is then down-regulated in the third week of life. In the two lupus-prone mouse strains down-regulation does not occur but extramedullar monocyte proliferation is sustained at high level throughout life time. As possible correlates for the expansion of the M phi system elevated CSF-1 mRNA levels are demonstrated in kidney, spleen and liver of NZB/W mice and elevated CSF serum levels are documented in MRL lpr/lpr mice. The possible contribution of the expanded M phi system to B and T cell dysregulation is discussed.

A programmable CORDIC chip for digital signal processing applications

Abstract: A chip implementing the coordinate rotation digital computer (CORDIC) algorithm is described. It contains a 10-MHz 16-b fixed-point CORDIC arithmetic unit, 2-kb RAM, a controller, and input/output (I/O) registers. A modified data-path architecture allows cross-wire free data flow. The chip design involved development of optimized carry-select adders and a modified programmable-logic-array (PLA) cell layout, which allows speed increase in single-layer metal technology. The authors designed, fabricated, and tested a general-purpose fully parallel programmable CORDIC chip in CMOS technology and developed optimal iteration sequences. >

Immunotherapy of murine visceral leishmaniasis with murine recombinant interferon-γ and MTP-PE encapsulated in liposomes

Abstract: The efficiency of immunotherapy with murine recombinant interferon-γ (rIFN-γ) in mouse visceral leishmaniasis caused by Leishmania donovani was examined. To avoid the side effects encounte...

Thiol Accumulation and Cysteine Desulfhydrase Activity in H2S-Fumigated Leaves and Leaf Homogenates of Cucurbit Plants

Abstract: Fumigation of both, cucurbit plants and cucurbit leaf homogenates with hydrogen sulfide (H2S) resulted in an increase in soluble thiol, mainly glutathione and cysteine. In leaf homogenates this increase was counteracted or prevented by the addition at 1 mM of inhibitors of pyridoxalphosphate dependent enzymes or of products of the cysteine desulfhydrase reaction. These compounds inhibited cysteine desulfhydrase activity, but did not severely affect O-acetylserine sulfhydrylase activity at this concentration. These results provide circumstantial evidence that cysteine desulfhydrase in its reverse reaction, but not O-acetylserine sulfhydrylase participates in the assimilation of atmospheric H2S.

Electromagnetic microactuators with multiple degrees of freedom

Abstract: Various types of actuators have been fabricated which make use of electromagnetic forces within micromachined silicon devices. A Nd-Fe-B permanent magnet is bonded to a movable silicon plate suspended by thin silicon beams. Planar coils are integrated monolithically on the chip to generate the driving magnetic field. Different actuators for torsional motion, with two degrees of freedom and with three degrees of freedom, are investigated theoretically and experimentally. Torsional angles up to 8 degrees and vertical displacements up to 40 mu m have been achieved. >

Corner compensation techniques in anisotropic etching of

Abstract: Various compensation structures preventing the undercutting of convex corners of

A CMOS readout amplifier for instrumentation applications

Abstract: An integrated readout amplifier for instrumentation applications in smart sensor systems is presented. A fully integrated CMOS version of such an amplifier has been developed using switched-capacitor techniques. The amplifier system provides differential input capability, programmable amplification, clock generation, and low-pass filtering on the chip. The output signal is continuous in time and the system can be used without any of the special precautions necessary for sampled-data circuits. Emphasis was put on high PSRR (-63 dB at DC), low noise (10- mu V/sub rms/ input equivalent wideband noise) and offset, low harmonic distortion, and small amplification error ( >