Low temperature TLP bonding of Al2O3-ceramics using eutectic Au-(Ge, Si) alloys

In this study, Al2O3-ceramics were joined via TLP bonding using interlayers of eutectic Au-12Ge (wt%) and Au-3Si (wt%) solder alloys, respectively, with a melting temperature of 361 and 363°C and Ni wetting layers. The Ni layers were part of a metallic multilayer coating (Ti/W/Ni) applied on the ceramic surface to ensure wetting and adhesion during the joining process. For comparison, a soldering process was performed as well by changing the multilayer structure to Ti/W/Au. With respect to the different joining processes the influence of the variation in wetting layers on the interface reactions, mechanical properties and re-melting temperature was analyzed by scanning electron microscopy, shear testing, and differential scanning calorimetry. It is shown that sound joint can be produced at a joining temperature of 400°C, achieving reasonable shear strength and re-melting temperatures more than 550°C above the initial melting temperature of the filler meta

Achieving Efficient and Realistic Full-Radar Simulations and Automatic Data Annotation by exploiting Ray Meta Data of a Radar Ray Tracing Simulator

In this work a novel radar simulation concept is introduced that allows to simulate realistic radar data for Range, Doppler, and for arbitrary antenna positions in an efficient way. Further, it makes it possible to automatically annotate the simulated radar signal by allowing to decompose it into different parts. This approach allows not only almost perfect annotations possible, but also allows the annotation of exotic effects, such as multi-path effects or to label signal parts originating from different parts of an object. This is possible by adapting the computation process of a Monte Carlo shooting and bouncing rays (SBR) simulator. By considering the hits of each simulated ray, various meta data can be stored such as hit position, mesh pointer, object IDs, and many more. This collected meta data can then be utilized to predict the change of path lengths introduced by object motion to obtain Doppler information or to apply specific ray filter rules in order obtain radar signals that only fulfil specific conditions, such as multiple bounces or containing specific object IDs. Using this approach, perfect and otherwise almost impossible annotations schemes can be realized.Comment: Accepted for IEEE RadarConf 202

Joining of Cu, Ni, and Ti Using Au-Ge-Based High-Temperature Solder Alloys

Au-Ge-based solder alloys are promising alternatives to lead containing solders due to the fact that they offer a combination of interesting properties such as good thermal and electrical conductivity and high corrosion resistance in addition to a relatively low melting temperature (361°C for eutectic Au-28Ge at.%). By adding a third element to the eutectic Au-28Ge alloy not only the Au content could be reduced but also the melting temperatures could be further decreased. In this study, in addition to the eutectic Au-28Ge (at.%) two ternary alloys were chosen from the Au-Ge-Sb and Au-Ge-Sn system, respectively. The soldering behavior of these alloys in combination with the frequently used metals Cu, Ni, and Ti was investigated. The interface reactions and microstructures of the joints were characterized in detail by SEM and EDX analysis. For the determination of the mechanical properties, shear tests were conducted. Mean shear strength values up to 104MPa could be achieved

PhotoApp: Photorealistic Appearance Editing of Head Portraits

Photorealistic editing of head portraits is a challenging task as humans are very sensitive to inconsistencies in faces. We present an approach for high-quality intuitive editing of the camera viewpoint and scene illumination (parameterised with an environment map) in a portrait image. This requires our method to capture and control the full reflectance field of the person in the image. Most editing approaches rely on supervised learning using training data captured with setups such as light and camera stages. Such datasets are expensive to acquire, not readily available and do not capture all the rich variations of in-the-wild portrait images. In addition, most supervised approaches only focus on relighting, and do not allow camera viewpoint editing. Thus, they only capture and control a subset of the reflectance field. Recently, portrait editing has been demonstrated by operating in the generative model space of StyleGAN. While such approaches do not require direct supervision, there is a significant loss of quality when compared to the supervised approaches. In this paper, we present a method which learns from limited supervised training data. The training images only include people in a fixed neutral expression with eyes closed, without much hair or background variations. Each person is captured under 150 one-light-at-a-time conditions and under 8 camera poses. Instead of training directly in the image space, we design a supervised problem which learns transformations in the latent space of StyleGAN. This combines the best of supervised learning and generative adversarial modeling. We show that the StyleGAN prior allows for generalisation to different expressions, hairstyles and backgrounds. This produces high-quality photorealistic results for in-the-wild images and significantly outperforms existing methods. Our approach can edit the illumination and pose simultaneously, and runs at interactive rates

PhotoApp: Photorealistic Appearance Editing of Head Portraits

Photorealistic editing of portraits is a challenging task as humans are very sensitive to inconsistencies in faces. We present an approach for high-quality intuitive editing of the camera viewpoint and scene illumination in a portrait image. This requires our method to capture and control the full reflectance field of the person in the image. Most editing approaches rely on supervised learning using training data captured with setups such as light and camera stages. Such datasets are expensive to acquire, not readily available and do not capture all the rich variations of in-the-wild portrait images. In addition, most supervised approaches only focus on relighting, and do not allow camera viewpoint editing. Thus, they only capture and control a subset of the reflectance field. Recently, portrait editing has been demonstrated by operating in the generative model space of StyleGAN. While such approaches do not require direct supervision, there is a significant loss of quality when compared to the supervised approaches. In this paper, we present a method which learns from limited supervised training data. The training images only include people in a fixed neutral expression with eyes closed, without much hair or background variations. Each person is captured under 150 one-light-at-a-time conditions and under 8 camera poses. Instead of training directly in the image space, we design a supervised problem which learns transformations in the latent space of StyleGAN. This combines the best of supervised learning and generative adversarial modeling. We show that the StyleGAN prior allows for generalisation to different expressions, hairstyles and backgrounds. This produces high-quality photorealistic results for in-the-wild images and significantly outperforms existing methods. Our approach can edit the illumination and pose simultaneously, and runs at interactive rates.Comment: http://gvv.mpi-inf.mpg.de/projects/PhotoApp

Activated Polymorphonuclear Leukocytes Rapidly Synthesize Retinoic Acid Receptor-α: A Mechanism for Translational Control of Transcriptional Events

In addition to releasing preformed granular proteins, polymorphonuclear leukocytes (PMNs) synthesize chemokines and other factors under transcriptional control. Here we demonstrate that PMNs express an inducible transcriptional modulator by signal-dependent activation of specialized mechanisms that regulate messenger RNA (mRNA) translation. HL-60 myelocytic cells differentiated to surrogate PMNs respond to activation by platelet activating factor by initiating translation and with appearance of specific mRNA transcripts in polyribosomes. cDNA array analysis of the polyribosome fraction demonstrated that retinoic acid receptor (RAR)-α, a transcription factor that controls the expression of multiple genes, is one of the polyribosome-associated transcripts. Quiescent surrogate HL60 PMNs and primary human PMNs contain constitutive message for RAR-α but little or no protein. RAR-α protein is rapidly synthesized in response to platelet activating factor under the control of a specialized translational regulator, mammalian target of rapamycin, and is blocked by the therapeutic macrolide rapamycin, events consistent with features of the 5′ untranslated region of the transcript. Newly synthesized RAR-α modulates production of interleukin-8. Rapid expression of a transcription factor under translational control is a previously unrecognized mechanism in human PMNs that indicates unexpected diversity in gene regulation in this critical innate immune effector cell

Nanoscale Near-Field Tomography of Surface States on (Bi(0.5)b(0.5))(2)Te-3

Three-dimensional topological insulators (TIs) have attracted tremendous interest for their possibility to host massless Dirac Fermions in topologically protected surface states (TSSs), which may enable new kinds of high-speed electronics. However, recent reports have outlined the importance of band bending effects within these materials, which results in an additional two-dimensional electron gas (2DEG) with finite mass at the surface. TI surfaces are also known to be highly inhomogeneous on the nanoscale, which is masked in conventional far-field studies. Here, we use near-field microscopy in the mid infrared spectral range to probe the local surface properties of customtailored (Bi0.5Sb0.5)(2)Te-3 structures with nanometer precision in all three spatial dimensions. Applying nanotomography and nanospectroscopy, we reveal a few-nanometer-thick layer of high surface conductivity and retrieve its local dielectric function without assuming any model for the spectral response. This allows us to directly distinguish between different types of surface states. An intersubband transition within the massive 2DEG formed by quantum confinement in the bent conduction band manifests itself as a sharp, surface-bound, Lorentzian-shaped resonance. An additional broadband background in the imaginary part of the dielectric function may be caused by the TSS. Tracing the intersubband resonance with nanometer spatial precision, we observe changes of its frequency, likely originating from local variations of doping or/and the mixing ratio between Bi and Sb. Our results highlight the importance of studying the surfaces of these novel materials on the nanoscale to directly access the local optical and electronic properties via the dielectric function

Novel Anti-bacterial Activities of β-defensin 1 in Human Platelets: Suppression of Pathogen Growth and Signaling of Neutrophil Extracellular Trap Formation

Human β-defensins (hBD) are antimicrobial peptides that curb microbial activity. Although hBD's are primarily expressed by epithelial cells, we show that human platelets express hBD-1 that has both predicted and novel antibacterial activities. We observed that activated platelets surround Staphylococcus aureus (S. aureus), forcing the pathogens into clusters that have a reduced growth rate compared to S. aureus alone. Given the microbicidal activity of β-defensins, we determined whether hBD family members were present in platelets and found mRNA and protein for hBD-1. We also established that hBD-1 protein resided in extragranular cytoplasmic compartments of platelets. Consistent with this localization pattern, agonists that elicit granular secretion by platelets did not readily induce hBD-1 release. Nevertheless, platelets released hBD-1 when they were stimulated by α-toxin, a S. aureus product that permeabilizes target cells. Platelet-derived hBD-1 significantly impaired the growth of clinical strains of S. aureus. hBD-1 also induced robust neutrophil extracellular trap (NET) formation by target polymorphonuclear leukocytes (PMNs), which is a novel antimicrobial function of β-defensins that was not previously identified. Taken together, these data demonstrate that hBD-1 is a previously-unrecognized component of platelets that displays classic antimicrobial activity and, in addition, signals PMNs to extrude DNA lattices that capture and kill bacteria

Electrical Transport and Magnetoresistance in MBE-grown 3D Topological Insulator Thin Films and Nanostructures

The main focus of this thesis are the 3D topological insulators bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3), which have been known for several decades as narrow band gap insulators (about 150 meV) and for their thermoelectric properties. Since they were found to be topological insulators, scientific interest in the search for topologically protected surface states has increased and the electronic properties of these states have been studied widely using angle-resolved photoemission spectroscopy. These measurements confirmed the presence of metallic states within the band gap with almost linear dispersion relations and a Dirac point. Also, surface magneto-electric properties measured by scanning tunnelling microscopy have shown that the protected surface states in Sb2Te3 thin films are less sensitive to intrinsic defects. This promises charge carriers with a high mobility at the surface of these materials. However, all properties mentioned above are solely restricted to the topological protected surface states and thus require the bulk to be insulating in order to observe these effects in electrical transport. Otherwise they will be masked by the bulk conductance. This has proven to be a difficult task, since all the binary materials tend to be intrinsically doped due to the formation of crystal defects during growth. Therefore, the effort has concentrated on controlling the sample fabrication, carrier compensation doping, or alloying of intrinsic chalcogenide materials, in order to shift the Fermi level into the energy bandgap and closer to the Dirac zero gap point of the surface energy spectra. In this work, we analyze thin films grown by molecular beam epitaxy on Si(111)-substrates. First, the binary materials are introduced in terms of crystal structure, growth parameters, electronic structure and elemental distribution via investigations done by transmission electron spectroscopy, angle-resolved photoemission spectroscopy and atom probe tomography. This illustrates the intrinsic doping of Bi2Te3 and Sb2Te3 and the presence of different crystal domains due to the growth mechanism of the layered films. We also compare films grown on 100 mm wafers with samples of selectively grown films on pre-patterned substrates. These samples are precursors to the nanostructures that will be discussed in the last chapter. Next, two different approaches to engineer the Fermi level are presented. Films of (Bi{1-x}Sb{x})}2Te3 with different compositions x, measured by Raman spectroscopy, and heterostructures with increasing Sb2Te3 thicknesses on top of a Bi2Te3 layer with fixed height are investigated. Both reveal a transition between opposite types of doping in angle-resolved photoemission spectroscopy. After this, the methods of sample preparation are presented, including two different approaches for preparing nanostructures using selective area growth. The last chapter is divided into two main parts. The first part begins by summarizing our measurements and characterizations of Bi2Te3 and Sb2Te3 films with regards to their transport properties like doping, mobility and parameters of phase coherent transport. We also extract these parameters from (Bi{1-x}Sb{x})}2Te3 with different compositions and the Sb2Te3/Bi2Te3 heterostructures with varying layer thicknesses. We search for hints of topologically protected surface states in field dependent measurements at low temperatures and analyse the influence of electrical gates. The second part contains the results from measurements on Bi2Te3 nanostructures. We present nanoribbons prepared by the two different approaches for selective area growth, show their respective idiosyncrasies and compare transport parameters obtained from wider ribbons with those from the films in the previous part. Next, nanodots are investigated to check for transport anisotropies with regards to the crystalorientation. In both cases we also analyse the corresponding magnetoresistance measurements for effects of phase coherent transport and influences of the surface states. Finally, we demonstrate our first attempts on suspended films of Bi2Te3

Electrical transport and magnetoresistance in MBE-grown 3D topological insulator thin films and nanostructures

The main focus of this thesis are the 3D topological insulators bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3), which have been known for several decades as narrow band gap insulators (about 150 meV) and for their thermoelectric properties. Since they were found to be topological insulators, scientific interest in the search for topologically protected surface states has increased and the electronic properties of these states have been studied widely using angle-resolved photoemission spectroscopy. These measurements confirmed the presence of metallic states within the band gap with almost linear dispersion relations and a Dirac point. Also, surface magneto-electric properties measured by scanning tunnelling microscopy have shown that the protected surface states in Sb2Te3 thin films are less sensitive to intrinsic defects. This promises charge carriers with a high mobility at the surface of these materials. However, all properties mentioned above are solely restricted to the topological protected surface states and thus require the bulk to be insulating in order to observe these effects in electrical transport. Otherwise they will be masked by the bulk conductance. This has proven to be a difficult task, since all the binary materials tend to be intrinsically doped due to the formation of crystal defects during growth. Therefore, the effort has concentrated on controlling the sample fabrication, carrier compensation doping, or alloying of intrinsic chalcogenide materials, in order to shift the Fermi level into the energy bandgap and closer to the Dirac zero gap point of the surface energy spectra. In this work, we analyze thin films grown by molecular beam epitaxy on Si(111)-substrates. First, the binary materials are introduced in terms of crystal structure, growth parameters, electronic structure and elemental distribution via investigations done by transmission electron spectroscopy, angle-resolved photoemission spectroscopy and atom probe tomography. This illustrates the intrinsic doping of Bi2Te3 and Sb2Te3 and the presence of different crystal domains due to the growth mechanism of the layered films. We also compare films grown on 100 mm wafers with samples of selectively grown films on pre-patterned substrates. These samples are precursors to the nanostructures that will be discussed in the last chapter. Next, two different approaches to engineer the Fermi level are presented. Films of (Bi{1-x}Sb{x})}2Te3 with different compositions x, measured by Raman spectroscopy, and heterostructures with increasing Sb2Te3 thicknesses on top of a Bi2Te3 layer with fixed height are investigated. Both reveal a transition between opposite types of doping in angle-resolved photoemission spectroscopy. After this, the methods of sample preparation are presented, including two different approaches for preparing nanostructures using selective area growth. The last chapter is divided into two main parts. The first part begins by summarizing our measurements and characterizations of Bi2Te3 and Sb2Te3 films with regards to their transport properties like doping, mobility and parameters of phase coherent transport. We also extract these parameters from (Bi{1-x}Sb{x})}2Te3 with different compositions and the Sb2Te3/Bi2Te3 heterostructures with varying layer thicknesses. We search for hints of topologically protected surface states in field dependent measurements at low temperatures and analyse the influence of electrical gates. The second part contains the results from measurements on Bi2Te3 nanostructures. We present nanoribbons prepared by the two different approaches for selective area growth, show their respective idiosyncrasies and compare transport parameters obtained from wider ribbons with those from the films in the previous part. Next, nanodots are investigated to check for transport anisotropies with regards to the crystalorientation. In both cases we also analyse the corresponding magnetoresistance measurements for effects of phase coherent transport and influences of the surface states. Finally, we demonstrate our first attempts on suspended films of Bi2Te3