Time-Resolved Studies of a Rolled-Up Semiconductor Microtube Laser

We report on lasing in rolled-up microtube resonators. Time-resolved studies on these semiconductor lasers containing GaAs quantum wells as optical gain material reveal particularly fast turn-on-times and short pulse emissions above the threshold. We observe a strong red-shift of the laser mode during the pulse emission which is compared to the time evolution of the charge-carrier density calculated by rate equations

Quantized Dispersion of Two-Dimensional Magnetoplasmons Detected by Photoconductivity Spectroscopy

We find that the long-wavelength magnetoplasmon, resistively detected by photoconductivity spectroscopy in high-mobility two-dimensional electron systems, deviates from its well-known semiclassical nature as uncovered in conventional absorption experiments. A clear filling-factor dependent plateau-type dispersion is observed that reveals a so far unknown relation between the magnetoplasmon and the quantum Hall effect.Comment: 5 pages, 3 figure

Three-Dimensionally Confined Optical Modes in Quantum Well Microtube Ring Resonators

We report on microtube ring resonators with quantum wells embedded as an optically active material. Optical modes are observed over a broad energy range. Their properties strongly depend on the exact geometry of the microtube along its axis. In particular we observe (i) preferential emission of light on the inside edge of the microtube and (ii) confinement of light also in direction of the tube axis by an axially varying geometry which is explained in an expanded waveguide model.Comment: 5 pages, 4 figure

miR-124a and miR-155 enhance differentiation of regulatory T cells in patients with neuropathic pain

Background: Accumulating evidence indicates that neuropathic pain is a neuro-immune disorder with enhanced activation of the immune system. Recent data provided proof that neuropathic pain patients exhibit increased numbers of immunosuppressive regulatory T cells (Tregs), which may represent an endogenous attempt to limit inflammation and to reduce pain levels. We here investigate the molecular mechanisms underlying these alterations. Methods: Our experimental approach includes functional analyses of primary human T cells, 3'-UTR reporter assays, and expression analyses of neuropathic pain patients' samples. Results: We demonstrate that microRNAs (miRNAs) are involved in the differentiation of Tregs in neuropathic pain. We identify miR-124a and miR-155 as direct repressors of the histone deacetylase sirtuin1 (SIRT1) in primary human CD4+ cells. Targeting of SIRT1 by either specific siRNA or by these two miRNAs results in an increase of Foxp3 expression and, consecutively, of anti-inflammatory Tregs (siRNA: 1.7 +/- 0.4;miR-124a: 1.5 +/- 0.4;miR-155: 1.6 +/- 0.4;p < 0.01). As compared to healthy volunteers, neuropathic pain patients exhibited an increased expression of miR124a (2.5 +/- 0.7, p < 0.05) and miR-155 (1.3 +/- 0.3;p < 0.05) as well as a reduced expression of SIRT1 (0.5 +/- 0.2;p < 0.01). Moreover, the expression of these two miRNAs was inversely correlated with SIRT1 transcript levels. Conclusions: Our findings suggest that in neuropathic pain, enhanced targeting of SIRT1 by miR-124a and miR-155 induces a bias of CD4(+) T cell differentiation towards Tregs, thereby limiting pain-evoking inflammation. Deciphering miRNA-target interactions that influence inflammatory pathways in neuropathic pain may contribute to the discovery of new roads towards pain amelioration

Optical Properties of GaAs Quantum Dots Fabricated by Filling of Self-Assembled Nanoholes

Experimental results of the local droplet etching technique for the self-assembled formation of nanoholes and quantum rings on semiconductor surfaces are discussed. Dependent on the sample design and the process parameters, filling of nanoholes in AlGaAs generates strain-free GaAs quantum dots with either broadband optical emission or sharp photoluminescence (PL) lines. Broadband emission is found for samples with completely filled flat holes, which have a very broad depth distribution. On the other hand, partly filling of deep holes yield highly uniform quantum dots with very sharp PL lines

Influence of freedom of movement on the health of people with demnetia:A systematic review

Background and Objectives To protect residents with dementia from harm, nursing homes (NHs) often have closed-door policies. However, current research suggests a positive influence of freedom of movement, that is, the right to (decide to) independently move from one place to another, on the health of NH residents with dementia. This systematic review aims to collate, summarize, and synthesize the scientific evidence published to date on the influence of freedom of movement on health among NH residents with dementia. Research Design and Methods Multiple databases were searched up until March 2021. Peer-reviewed qualitative, quantitative, and mixed methods studies were included. Health was operationalized using the Positive Health framework, encompassing 6 dimensions: bodily functions, mental functions and perception, existential dimension, quality of life, social and societal participation, and daily functioning. The quality of included studies was assessed using the Mixed Methods Appraisal Tool. Results Sixteen studies were included of good to excellent quality. Compared to closed NHs, freedom of movement in semiopen and open NHs may have a positive influence on bodily functions, mental functions and perception, quality of life, and social and societal participation. The influence on daily functioning and on the existential dimension remains unclear. Discussion and Implications Freedom of movement of NH residents with dementia is often studied as part of a larger context in which other factors may contribute to health benefits. More research is therefore needed to unravel the underlying mechanisms of the positive influence of freedom of movement on health

Far-Infrared Excitations below the Kohn Mode: Internal Motion in a Quantum Dot

We have investigated the far-infrared response of quantum dots in modulation doped GaAs heterostructures. We observe novel modes at frequencies below the center-of-mass Kohn mode. Comparison with Hartree-RPA calculations show that these modes arise from the flattened potential in our field-effect confined quantum dots. They reflect pronounced relative motion of the charge density with respect to the center-of-mass.Comment: 8 pages, LaTeX with integrated 6 PostScript figure

Automation concepts and gripping solutions for bonding with reactive multilayer systems

Reactive multilayer systems (RMS) represent an innovative heat source for the establishment of solder joints. They offer fast bonding processes that introduce very little thermal input and internal stress on the bonded parts. The current application process of RMS is predominantly manual labor. There are a couple of challenges to be overcome to automate this process, a requirement for its introduction into industrial production. In this paper we evaluate the requirements for an automated joining process with RMS and devise a concept of a modular assembly system for different product structures. Furthermore we show our results in gently and reliably gripping and handling of RMS.Federal Ministry of Economic and Technology (BMWi)InnoJoin GmbH & Co. KG, Breme

Guided Neuronal Growth on Arrays of Biofunctionalized GaAs/InGaAs Semiconductor Microtubes

We demonstrate embedded growth of cortical mouse neurons in dense arrays of semiconductor microtubes. The microtubes, fabricated from a strained GaAs/InGaAs heterostructure, guide axon growth through them and enable electrical and optical probing of propagating action potentials. The coaxial nature of the microtubes -- similar to myelin -- is expected to enhance the signal transduction along the axon. We present a technique of suppressing arsenic toxicity and prove the success of this technique by overgrowing neuronal mouse cells.Comment: 3 pages, 4 figure