1,162 research outputs found
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
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