Search

In this paper the application of modern DOA algorithms to an existing 8-element Adcock antenna array in the VHF frequency range is investigated. With simulations and measurements it is shown that without changing the antenna hardware an improvement in means of direction finding errors can be accomplished. Furthermore, with a minimal antenna hardware change, sensitivity and bandwidth can be increased and the super resolution algorithm MUSIC can be applied.

Down-regulation of receptor tyrosine kinases such as the epidermal growth factor receptor (EGFR) is achieved by endocytosis of the receptor followed by degradation or recycling. We demonstrated that in the absence of ligand, increased phosphatidylinositol 3,4,5-trisphosphate (PIP3) concentrations induced clathrin- and dynamin-mediated endocytosis of EGFR but not that of transferrin or G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptors. Endocytosis of the receptor in response to binding of EGF resulted in a decrease in the abundance of the EGFR, but PIP3-induced internalization decreased receptor ubiquitination and phosphorylation and resulted in recycling of the receptor to the plasma membrane. An RNA interference (RNAi) screen directed against lipid-binding domain-containing proteins identified polarity complex proteins, including PARD3 (partitioning defective 3), as essential for PIP3-induced receptor tyrosine kinase recycling. Thus, PIP3 and polarity complex proteins regulate receptor tyrosine kinase trafficking, which may enhance cellular responsiveness to growth factors.

Down-regulation of receptor tyrosine kinases such as the epidermal growth factor receptor (EGFR) is achieved by endocytosis of the receptor followed by degradation or recycling. We demonstrated that in the absence of ligand, increased phosphatidylinositol 3,4,5-trisphosphate (PIP3) concentrations induced clathrin- and dynamin-mediated endocytosis of EGFR but not that of transferrin or G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptors. Endocytosis of the receptor in response to binding of EGF resulted in a decrease in the abundance of the EGFR, but PIP3-induced internalization decreased receptor ubiquitination and phosphorylation and resulted in recycling of the receptor to the plasma membrane. An RNA interference (RNAi) screen directed against lipid-binding domain-containing proteins identified polarity complex proteins, including PARD3 (partitioning defective 3), as essential for PIP3-induced receptor tyrosine kinase recycling. Thus, PIP3 and polarity complex proteins regulate receptor tyrosine kinase trafficking, which may enhance cellular responsiveness to growth factors.

Background Glycosylation is an important posttranslational modification of proteins influencing protein folding, stability and regulation of the biological activity. The sialyl mojety (sialic acid, 5-N-acetylneuramic acid) is usually exposed at the terminal position of N-glycosylation and therefore, a major contributor to biological recognition and ligand function, e.g. IgG featuring terminal sialic acids were shown to induce less inflammatory response and increased serum half-life. The biosynthesis of sialyl conjugates is controlled by a set of sugar-active enzymes including sialyltransferases which are classified as ST3, ST6 and ST8 based on the hydroxyl position of the glycosyl acceptor the Neu5Ac is transferred to [1]. The ST6 family consists of 2 subfamilies, ST6Gal and ST6GalNAc. ST6Gal catalyzes the transfer of Neu5Ac residues to the hydroxyl group in C6 of a terminal galactose residue of type 2 disaccharide (Galb1-4GlcNAc). To our knowledge, the access to recombinant ST6GalI for therapeutic applications is still limited due to low expression and/or poor activity in various hosts (Pichia pastoris, Spodoptera frugiperda and E. coli). The present study describes the high-yield expression of two variants of human beta-galactoside alpha-2,6 sialyltransferase 1 (ST6Gal-I, EC 2.4.99.1; data base entry P15907) by transient gene expression in HEK293 cells with yields >100 mg/L featuring distinct mono(G2 +1SA) as well as bi(G2+2SA) sialylation activity. Materials and methods Two N-terminally truncated fragments of human ST6Gal-I (delta89, residues 89-406, and delta108, residues 109-406) were designed for transient gene expression (TGE): Instead of the natural leader sequence and N-terminal residues, both ST6Gal-I coding regions harbor the Erythropoietin (EPO) signal sequence in order to ensure correct processing of the polypeptides by the secretion machinery. Following cloning into pM1MT, expression of the ST6Gal-I coding sequences is under control of a hCMV promoter followed by an intron A. Sialyltransferase assays: 1. Asialofetuin was used as acceptor and CMP-9F-NANA as donor substrate. Enzymatic activity was determined by measuring the transfer of 9F-NANA to asialofetuin. 2. Recombinant humanized IgG1 and IgG4 monoclonal antibodies (mabs), characterized as G2+0SA, as well as desialylated EPO were used as targets in sialylation experiments (30 μg enzyme/300 μg target protein). Both enzyme variants of ST6Gal-I (delta89 and delta108) were used under identical reaction conditions and the sialylation status was analyzed by mass spectrometry.

In this paper the design of a direction finding antenna array for the application on airborne platforms especially for helicopters covering the frequency range starting at 800 MHz up to 2200 MHz is presented. Measured results of a first prototype are shown and an estimation of the installed performance is given, considering different mounting positions on the platform.

We discuss the relevance of quantum gravitational corrections to the functional Schr\"odinger equation for the information loss paradox in black hole evaporation. These corrections are found from the Wheeler-DeWitt equation through a semiclassical expansion scheme. The dominant contribution in the final evaporation stage, when the black hole approaches the Planck regime, is a term which explicitly violates unitarity in the non-gravitational sector. While pure states remain pure, there is an increase in the degree of purity for non-pure states in this sector. This result holds irrespective of whether full quantum gravity respects unitarity or not., Comment: 6 pages, Latex, ZU-TH 25/93

Substantial recovery of function following peripheral and central nervous system (CNS) injury critically depends on longitudinally directed axon regeneration across the injury site, which requires a mechanical guidance providing scaffold. We have previously shown that anisotropic alginate-based hydrogels with a defined capillary diameter (25 μm), which form via a self-organizing process driven by unidirectional diffusion of divalent cations into sodium alginate sols, promoted longitudinally oriented elongation of CNS axons in vitro and in vivo. In the present study the influence of various capillary diameters and the incorporation of gelatin to promote directed axon outgrowth and Schwann cell migration were assessed in a dorsal root ganglion outgrowth assay in vitro. Superimposing an alginate sol with Cu2+, Sr2+, or Zn2+ ion containing solutions allowed the creation of hydrogels with capillaries 18, 25 and 55 μm in diameter, respectively. Axon outgrowth and Schwann cell migration were analyzed in terms of axon length/density and Schwann cell density within the capillary structures. Axon ingrowth into capillary hydrogels, which was always accompanied by Schwann cells, was enhanced with increasing capillary diameter. The incorporation of gelatin did not influence overall axon density, but promoted the length of axon outgrowth within the hydrogels. The longitudinal orientation of axons decreased in wider capillaries, which suggests that medium-sized capillaries are the optimal substrate to elicit substantial axon growth and longitudinal orientation after axon injury.

A modern state of the art direction finder system consists of several direction finding (DF) antennas and the direction finder electronics. In order to achieve most accurate results for all azimuth directions the direction finder antenna system is often built using a circular antenna array. The need for light weight mobile DF systems leads to smaller DF antenna designs using less frequency bands to cover the whole frequency range. In this paper, an ultrabroadband DF antenna array covering the whole UHF frequency range from 0.3 GHz to 3GHz is introduced. Unlike the common antenna designs using dipols [1, 2] the new design consists of ten vivaldi-type antenna elements to cover the UHF frequency range fully.

The presented UHF DF slot antenna design shows no degradation of the DF error and expected 3 dB (typical) in sensitivity only when compared to the DF antenna design in [1]. This shows that the broadband slot antenna design, introduced in this paper, can be used for conformal direction finding antennas. This conformal DF antennas are integrated into the structure of modern platforms, which have an optimized low radar cross section.

This study aims at ranking various luting systems according to their susceptibility to adhering Streptococcus mutans and at evaluating the influence of incongruent mixing ratios on adhesion quantities.Circular specimens measuring 8 mm in diameter were made of nine widely used dental cements -- three of them mixed in different ratios -- and then incubated with S. mutans. Adhering streptococci were quantified using a biofluorometric assay in combination with an automated plate reader for cell quantification. Surface roughness (R(a)) was determined by perthometer measurements.Meron plus revealed the highest R(a) (0.90 microm) and glass the lowest R(a) (0.01 microm). In regular cement mixtures, the highest mean fluorescence intensities indicated the presence of many viable bacteria [Meron Plus (35,533 relative fluorescence units (rfu)), Maxcem (13,374 rfu), and Panavia F 2.0 (11,701 rfu)]. Moderate fluorescence intensities were found in Harvard (4,171 rfu), Ketac cem (3,766 rfu), Durelon (3,276 rfu), Calibra (3,259), Rely X Unicem (4,358 rfu), and Bifix SE (3,102 rfu). A medium correlation between R(a) and S. mutans adhesion was found. Changes in regular cement proportions (powder/liquid and base/catalyst, respectively) had a significant influence on relative fluorescence intensities, which linearly increased with a higher proportion of liquid in Harvard and with a higher proportion of catalyst in Calibra and Maxcem.Various luting systems revealed considerable differences in their potential to adhere S. mutans. Variations from recommended cement proportions led to significant changes in the amount of adhering streptococci.

The presented results show that the simulation with a modern simulation tool using methods of moments agree very well with the measurements of a prototype. Furthermore it is shown that the monostatic RCS of a UHF DF antenna can be successfully reduced without degrading the DF performance

In R. Mueller et. al. (2006) the design of a UHF direction finding antenna with optimised radar cross section (RCS) was introduced. In the present paper the monostatic RCS of the antenna is characterised up to 18 GHz. Measured results of the RCS are compared to simulated results which are obtained using the new commercially available multilevel fast multipole method (MLFMM) ( U. Jakobus and J. van Tonder, 2005).

Insulin is the blood glucose-lowering hormone essential for glucose homeostasis. β-Cells secrete insulin in pulses in response to glucose. Loss of the oscillatory nature of insulin secretion is associated with the development of type II diabetes. Calcium is the most important trigger of insulin release even though the exact mechanism of insulin secretion regulation by calcium is elusive. Arachidonic acid (AA) is an essential signalling molecule involved in regulation of physiological functions of many cell types. In insulin secreting pancreatic β-cells AA was shown to modulate calcium levels and as result to trigger insulin secretion. However, the exact interplay between AA signalling and insulin secretion is still a matter of speculation. In the present work we investigated the difference of AA action at the internal membranes (IMs) and the plasma membrane (PM) of β-cells. To perform this study, we developed a caging group which permits localization, visualization and quantitative photorelease of AA exclusively on the PM of living cells. We applied it in combination with a previously reported caging group used to release AA on the IMs. We found that the release of AA on the PM and the IMs leads to a significantly different modulation of intracellular calcium dynamics. Uncaging of AA on the PM induces calcium oscillations in non-oscillating cells and increases the duration of calcium transients in oscillating cells, leading to overall higher calcium levels. Release of AA on the IM results in transiently or permanently diminished calcium oscillations in β-cells and lower average calcium levels. We attribute the observed effects to direct action of AA on Arachidonic acid Regulated Calcium (ARC) channels localized on the PM and potentially a negative feedback mechanism triggered by higher levels of AA at the internal membranes.

We have doped the core of Ytterbium (Yb) laser fibers additionally with Neodymium (Nd) to exploit wavelength-multiplexed high-power pump systems, which are commercially available. By pumping such a Nd:Yb-codoped fiber with the 808/940/978 nm-diode system, we could demonstrate CW output powers of more than 1 kW with high laser slope efficiency. In order to get a better understanding of this laser medium, we studied the fluorescence and the laser behavior of Nd:Yb fibers with different rare earth concentrations in comparison to a fiber doped solely with Nd. A theoretical model for the calculation of the fluorescence decay curve and spectrum as well as the laser characteristic and wavelength was developed, that takes the energy transfer process from Nd to Yb ions into account. Comparing the experimental and theoretical results, the behavior of the Nd:Yb high power fiber laser is understood as a collective emission of both ion types within the same wavelength region. These investigations contribute to the optimization of high power fiber lasers under the viewpoint of thermal load.

A new type of multi-clad rare-earth doped silica fiber was designed, prepared and tested for the power scaling of high power fiber lasers in the 1 .1 tm wavelength region. By means of a dedicated laboratory setup a maximum output power of more than 1 .300 watts with excellent spectral and beam behavior was achieved. The fundamental investigation of the energy transfer processes and of the fluorescence lifetimes of different Nd:Yb co-doped has been studied. Such fiber-lasers were tested in the laboratory at several materials (plastics, metals, glass) in the fields of material processing and micro-marking, respectively.

The inscription of fiber Bragg gratings during the drawing process is shown to be a very useful method to realize sensor arrays with high numbers of gratings and excellent mechanical strength and also type two gratings with high temperature stability. Results of single pulse grating arrays with numbers between ten and >100 and definite wavelengths and positions for sensor applications were achieved at 1550nm and 830nm using new photosensitive fibers developed in IPHT. Single pulse type-1 gratings at 1550 nm with more than 30% Reflectivity were shown first time to our knowledge. The mechanical strength of this fiber with an Ormocer coating with those single pulse gratings is the same like standard telecomm fibers. Weibull plots of fiber tests will be shown. At 830 nm we reach more than 10% reflectivity with single pulse writing during the fiber drawing in photosensitive fibers with less than 16 dB transmission loss. These gratings are useful for stress and vibration sensing applications. Type two gratings with reflectivity near 100% and smooth spectral shape and spectral width of about 1 nm reach temperature stability above 1200 K. They are also realized in the fiber drawing process. These Gratings are useful for temperature sensor applications.

The availability of extreme ultraviolet (EUV) light sources, measurement tools and integrated test systems is of major importance for the development of EUV lithography for use in high volume chip manufacturing which is expected to start in 2009. The estimates of cost of an EUV exposure tool in combination with sophisticated throughput models leads to a throughput of 120 wafers per hour necessary for economic use of EUV lithography. Concluding from that light sources are necessary which deliver an EUV output power of 115 W at 13.5 nm at the entrance of the illuminator system. The power requirement in combination with the required lifetimes of source components and collector optics make the source technology the most critical issue to be solved when developing EUV lithography. The present paper gives an update of the development status of EUV light sources at XTREME technologies, a joint venture of Lambda Physik AG, Goettingen, and Jenoptik LOS GmbH, Jena, Germany. Results on both laser produced plasma (LPP) and gas discharge produced plasma (GDPP), the two major technologies in EUV sources, are given. The LPP EUV sources use xenon-jet target systems and pulsed lasers with 500 W average power at up to 10 kHz developed at XTREME technologies. The maximum conversion efficiency from laser power into EUV in-band power is 1.0% into 2π solid angle. 2.0 W EUV radiation is generated at 13.5 nm in 2π sr solid angle. The small source volume of < 0.3 mm diameter will allow large collection angles of 5 sr. The intermediate focus power is estimated to 1 W. Collector mirror lifetime tests showed 5 million pulses lifetime without debris mitigation. With debris mitigation in place lifetimes of more than 1 billion pulses are estimated. For the next generation of higher power EUV LPP sources a laser driver has been tested at 1.3 kW average laser power. This will lead to 5 W EUV power in intermediate focus. The GDPP EUV sources use the Z-pinch principle with efficient sliding discharge pre-ionization. Prototype commercial gas discharge sources with an EUV power of 35W in 2π sr were already delivered for integration into EUV microsteppers. These sources are equipped with a debris-filter which results in an optics lifetime exceeding 100 million discharges at 1 kHz repetition frequency. The same lifetime was achieved for the components of the discharge system itself. The progress in the development of high-power discharge sources resulted in an EUV power of 150 W in continuous operation at 4.5 kHz repetition rate by implementation of porous metal cooling technology. The EUV plasma has a FWHM-diameter of 0.5 mm and a FWHM-length of 1.5 mm. The intermediate focus power is calculated to be in the range of 15 W - 20 W, depending somewhat on the transmission of the optical path to the intermediate focus and on the etendue specification. The typical fluctuations of the EUV energy are standard deviation σ

Semiconductor chip manufacturers are expecting to use extreme ultraviolet (EUV) lithography for high volume manufacturing of DRAMs and ICs starting by the end of this decade. Among all the technologies and modules which have to be developed EUV sources at 13.5 nm are considered to be the most critical issue. Specifically the required output power of 115 W at the entrance of the illuminator system in combination with the required lifetimes of source components and collector optics make the source technology critical for EUV lithography. The present paper gives an update of the development status of EUV light sources at XTREME technologies, a joint venture of Lambda Physik AG, Goettingen, and Jenoptik LOS GmbH, Jena, Germany. Results on both laser produced plasma (LPP) and gas discharge produced plasma (GDPP), the two major technologies in EUV sources, are given. The LPP EUV sources use xenon-jet target systems and pulsed lasers with 500 W average power at up to 10 kHz developed at XTREME technologies. The maximum conversion efficiency from laser power into EUV in-band power is 1.0 % into 2p solid angle. 2.0 W EUV radiation is generated at 13.5 nm in 2p sr solid angle. The small source volume of < 0.3 mm diameter will allow large collection angles of 5 sr. The intermediate focus power is estimated to 1 W. Collector mirror lifetime tests showed 5 million pulses lifetime without debris mitigation. With debris mitigation in place lifetimes of more than 1 billion pulses are estimated. For the next generation of higher power EUV LPP sources a laser driver has been tested at 1.3 kW average laser power. This will lead to 5 W EUV power in intermediate focus. The GDPP EUV sources use the Z-pinch principle with efficient sliding discharge pre-ionization. Prototype commercial gas discharge sources with an EUV power of 35W in 2p sr were already delivered for integration into EUV microsteppers. These sources are equipped with a debris-filter which results in an optics lifetime exceeding 100 million discharges at 1 kHz repetition frequency. The same lifetime was achieved for the components of the discharge system itself. The progress in the development of high-power discharge sources resulted in an EUV power of 150 W in continuous operation at 4.5 kHz repetition rate by implementation of porous metal cooling technology. The EUV plasma has a FWHM-diameter of 0.5 mm and a FWHM-length of 1.5 mm. The intermediate focus power is calculated to be in the range of 15 W - 20 W, depending somewhat on the transmission of the optical path to the intermediate focus and on the etendue specification. The typical fluctuations of the EUV energy are standard deviation s

In this paper a very compact device of a very efficient high- power fiber-laser based on a specially designed Ytterbium (Yb)-doped double-clad D-Shape silica fiber with an output power of more than 8 watts will be described. The development, preparation and characterization of rare-earth doped double- clad optical fibers based on silica for the application in high-power fiber-lasers were done at the Optics Division of the Institute for Physical High-Technology e.V. Jena (IPHT) in the last few years. The doping with Ytterbium as the laseractive component was one of the most important questions which were investigated. Many samples had to be made for the optimum concentration of Yb, the optimum codoping and geometry, respectively. As a result of these experiments we realized a double-clad fiber with D-shape geometry of the pump-core. This D-shape resulted from ray-tracing calculations performed at the Lasercentre Hannover e.V. (LZH) as an optimal solution for the high conversion efficiency of the pump-power. Considering these numerical results, such fibers were realized at IPHT by drawing a sidepolished preform by preserving the cross section of the preform. After some basic investigations on the optimum wavelength for the pump-light and the resonator length, respectively, a compact device with a launched pump- power of approx. 13 W and an output-power of more than 8 watts was developed and realized. The maximum output-power was only limited by the pump-power available at our laboratory at the chosen wavelength. Main advantages of the setup are the short length of the laseractive fiber (less than 10 m), the high efficiency (greater than 60%) and the compactness of the device. Additionally, the diameter of the pump-core was reduced to 125 micrometer. These kinds of fibers were tested with a specially designed pump-source of the Fraunhofer Institute for Applied Optics and Precision Engineering in Jena. The first result with a double-clad Yb-doped fiber of only 4 meter length was a fiber-laser with an output-power of about 4 Watts. Last but not least, some basic experiments with Fiber-Bragg-Gratings (FBG) as one of the resonator mirrors were done. A fiber-laser with a FBG for the laser-wavelength had an output-power of about 700 mW with a FWHM of about 0.1 nm.

In this paper the results of the systematical investigation of the basic effects in Nd-doped silica fibers and their application in high-power fiber-lasers will be presented. The development and manufacturing of rare-earth doped double-clad optical fibers based on silica was done at the department 'Moderne Optik' of the Institut fur Physikalische Hochtechnologie e.V. Jena (IPHT). In the last few years at the IPHT Jena rare-earth doped double-clad fibers based on silica for the application in high-power fiber-lasers were developed and characterized. The doping with Neodymium as the laseractive component was one of the most important questions which were investigated. Many samples had to be made for the determination of the optimum concentration of Nd, the optimum codoping and geometry, respectively. As a result we realized a double-clad fiber with D-shape geometry of the pump-core. This D-shape resulted from ray-tracing calculations performed at the Laserzentrum Hannover e.V. (LZH) as an optimal solution for the high conversion efficiency of the pump power. Considering these numerical results, such double-clad fibers with different diameters of the Nd-doped laser-core (multimode or single-mode) was realized at IPHT by drawing of sidepolished preforms with different compositions and geometries by preserving the cross section of the preform. In a tight cooperation with the LZH cw-output powers of more than 30 W (multimode fiber-laser) and approx. 14 W (single-mode fiber-laser), respectively, were realized in the lab. First compact and transportable 19'-devices of high-power fiber- laser with a pumping power of approx. 10 W and an output power of more than two watts were developed and realized.

For a small system the coupling to a reservoir causes energy shifts as well as transitions between the system's energy levels. We show for a general stationary situation that the energy shifts can essentially be reduced to the relaxation rates. The effects of reservoir fluctuations and self reaction are treated separately. We apply the results to a two-level atom coupled to a reservoir which may be the vacuum of a radiation field., Comment: 6 pages, Latex, to appear in Phys. Lett. A

We study the spontaneous de-excitation and excitation of accelerated atoms on arbitrary stationary trajectories (``generalized Unruh effect''). We consider the effects of vacuum fluctuations and radiation reaction separately. We show that radiation reaction is generally not altered by stationary acceleration, whereas the contribution of vacuum fluctuations differs for all stationary accelerated trajectories from its inertial value. Spontaneous excitation from the ground state occurs for all { accelerated stationary} trajectories and is therefore the ``normal case''. We furthermore show that the radiative energy shift (``Lamb shift'') of a two-level atom is modified by acceleration for all stationary trajectories. Again only vacuum fluctuations give rise to the shift. Our results are illustrated for the special case of an atom in circular motion, which may be experimentally relevant., Comment: 12 pages, LaTeX, 1 figure, to be published in Classical and Quantum Gravity

Automatic recording of live lectures and presentations has been explored and evaluated by various research projects since the mid-1990s and has meanwhile been adapted by a number of commercial systems. With these tools, teachers can automatically capture their live lectures and presentations in classrooms and lecture halls, make them available as e-lectures in a variety of output formats for access over the internet, and use them as kernels of web-based learning modules. One special incarnation of this idea is 'Authoring on the Fly' (AOF) which is the focus of this paper. We give an overview of the whole concept of lecture recording with AOF describing all necessary steps involved in the production process. We summarise the basic idea of this approach, highlight its relevance for RIA generation, and report on evaluations and field studies describing the usage of the produced e-lectures and their influence on teaching and learning.

Fiber Bragg gratings (FBG) were manufactured during the fiber drawing process [draw tower grating (DTG)] with excellent reflectivity values. This was done in the region of 1550 nm by single pulses of a 248-nm excimer laser applied during the fiber drawing process of single mode fibers. An improved setup for the writing process and special photosensitive fibers enable the manufacture of type I DTG arrays with a reflectivity of up to 40% and type II DTGs with a reflectivity near 100%. Details of the setup and results of the DTG arrays and DTGs of type II are reported.