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Microglia-Derived Insulin-like Growth Factor 1 Is Critical for Neurodevelopment
No full textInsulin-like growth factor 1 (IGF-1) is a peptide hormone essential for the proper development and growth of the organism, as a complete knockout of Igf1 in mice is lethal, causing microcephaly, growth retardation and the defective development of organs. In the central nervous system, neurons and glia have been reported to express Igf1, but their relative importance for postnatal development has not yet been fully defined. In order to address this, here, we obtained mice with a microglia-specific inducible conditional knockout of Igf1. We show that the deficiency in microglial Igf1, starting in the first postnatal week, leads to body and brain growth retardation, severely impaired myelination, changes in microglia numbers, and behavioral abnormalities. These results emphasize the importance of microglial-derived Igf1 for brain development and function and open new perspectives for the investigation of the role of microglial-Igf1 in neurological diseases
Die Sächsische Gartenakademie: Informations- und Weiterbildungsangebot 2020
No full textDie Gartenakademie des Sächsischen Landesamtes für Umwelt, Landwirtschaft und Geologie wendet sich mit einem vielfältigen Weiterbildungsangebot an alle Freizeitgärtnerinnen und Freizeitgärtner. Der Flyer bietet einen Überblick über das gesamte Angebot der Gartenakademie im Jahr 2020.
Redaktionsschluss: 31.8.201
Die Sächsische Gartenakademie: Aktiv für den Freizeitgartenbau 2023
No full textDie Gartenakademie des Sächsischen Landesamtes für Umwelt, Landwirtschaft und Geologie wendet sich mit einem vielfältigen Weiterbildungsangebot an alle Freizeitgärtnerinnen und Freizeitgärtner. Der Flyer bietet einen Überblick über das gesamte Angebot der Gartenakademie im Jahr 2023.
Redaktionsschluss: 04.11.202
Mechanical cell interactions in bioengineered 3D microenvironments
No full textCells are surrounded by a microenvironment that sends constant biochemical and mechanical cues. In a tumor, this microenvironment is altered and the signals to the resident cancer cells are corrupted. Since cells are sensitive to such biochemical and mechanical cues, this affects their biophysical properties. The biophysical properties of cells are important in influencing their behavior and are tightly regulated. Additionally, during cancer progression as cells proliferate and eventually invade, their biophysical properties dynamically adapt. Thus, both the microenvironment and cancer progression influence the biophysical properties of cells. Previous studies exploring this question have mainly employed artificial 2D cell culture systems and only a few have used physiologically relevant 3D models. This thesis aimed to bridge that knowledge gap by using mechanically tunable 3D PEG-heparin hydrogels with defined biochemical properties. This system allowed for the methodical study of the impact of microenvironment stiffness and degradability on cells. By employing Brillouin microscopy, a non-contact method for mechanical characterization, the BFS (Brillouin frequency shift) was measured as a proxy for the longitudinal modulus of the cells. It was observed that single cells had a higher BFS in stiffer gels. Microenvironment stiffness also led to lower cell volume and an increased percentage of cells in the G1 phase of the cell cycle. Once the single cells started to proliferate and form spheroids, changes in cells’ biophysical properties were observed. With the formation of spheroids, cells had a higher BFS and became smaller. These adaptations were due to water efflux and changes in cell cycle distribution. This effect of multicellularity was also studied in the context of invasion from spheroids in 3D. As expected, single invading cells out of the spheroid had lower BFS and became larger. Since tumors are multicellular, it was relevant to study the effect of microenvironment mechanics on spheroids and not just single cells. So, tumor spheroids were formed in gels of varying stiffness and degradability. Spheroids in stiffer gels had (i) a higher BFS, (ii) were smaller in size with increased number density and (iii) inhibited invasion. The compressive stress of the microenvironment correlated with the BFS of the spheroids. This thesis highlighted the effect of microenvironment stiffness and degradability on the biophysical properties and behavior of single cells and spheroids. It also emphasized the effect of cell-cell interactions on biophysical properties during proliferation and invasion. Thus, starting from proliferation in a tumor microenvironment, to invasion, until a few ‘single’ cells metastasize to a new microenvironment, cells are constantly adapting their biophysical properties
Yaron Z. Eliav: A Jew in the Roman Bathhouse: Cultural Interaction in the Ancient Mediterranean
No full textIonization dynamics in relativistic laser plasma
No full textThis work presents a novel resonance X-ray diagnostic method for hot dense plasma with femtosecond temporal resolution. In particular, I was able to show that the Cu 21+ ionization state in relativistic laser-matter interaction with 1021 W/cm2 intensity is strongly localized in depth to less than a micrometer. This precision allows to reveal disagreements with state-of-the-art particle-in-cell simulations. Experimentally, I employed the combination of a relativistic femtosecond laser and a free-electron X-ray laser (XFEL), enabling synchronous excitation and probing of the plasma. Emission spectroscopy and X-ray imaging were employed for the selective study of the temporal and spatial evolution of ionization states.
My results will allow to improve the understanding of these laser-matter-interactions and implementation of currently lacking processes into simulations.:1 Introduction
1.1 Background and Motivation
1.2 Objectives of the Thesis
1.3 Structure of the Thesis
2 European XFEL and Relativistic Laser
2.1 European XFEL
2.1.1 Synchrotron Radiation
2.1.2 Undulator
2.1.3 X-FELs
2.1.4 European XFEL
2.2 ReLaX – Relativistic Laser at XFEL
2.2.1 Chirped-Pulse Amplification
2.2.2 ReLaX – Details and parameters
2.3 Synchronization of XFEL X-ray Pulses and ReLaX Laser Pulses
2.3.1 Challenges in Temporal Synchronization
2.3.2 The RF Master Timer System
2.3.3 The Cross-Correlation Method, Photon Arrival Monitor, Zero-Timing
3 Fundamental Aspects of Laser-Induced Plasma in Femtosecond Laser–Matter Interaction
3.1 Plasma theory – Hot and Dense plasma regime
3.1.1 Essential Plasma Parameters
3.1.2 Dense Plasma Regimes: Hot Dense Plasma and Warm Dense Plasma
3.2 Femtosecond laser plasma
3.2.1 Structure of a Femtosecond Laser Pulse
3.2.2 Dielectric Permittivity of Plasma and Critical Density
3.2.3 Interaction of laser prepulse with target. Preplasma
3.2.4 Laser Field Ionization
3.2.5 Absorption Mechanisms for Laser Pulses
3.2.6 Hot Electrons Generation
3.2.7 Stages of Femtosecond Plasma Generation
3.3 X-Ray Emission Generation in Laser Plasma, Ionization Distribution
3.3.1 Bremsstrahlung Radiation
3.3.2 Characteristic X-Ray generation
3.4 Relaxation and Recombination
3.4.1 Collisional Relaxation
3.4.2 Heat Transfer Processes
3.4.3 Adiabatic Expansion
3.4.4 Plasma Recombination
3.5 X-Ray Methods in Plasma Research
3.5.1 X-ray Emission Spectroscopy (XES)
3.5.2 Resonant Inelastic X-ray Scattering (RIXS)
3.5.3 X-ray Absorption Spectroscopy (XAS)
3.5.4 Small-Angle X-ray Scattering (SAXS)
3.5.5 X-ray Diffraction (XRD)
3.5.6 X-ray Thomson Scattering (XRTS)
4 Resonant X-Ray Emission Spectroscopy of Specific Ionization States
4.1 X-ray Resonant Probing
4.1.1 Principle of X-ray Resonant Probing
4.1.2 Efficiency of Resonant Absorption
4.2 Targets
4.3 High-Resolution X-ray Spectroscopy for HED Instrument
4.3.1 Bragg Spectroscopy: Von Hámos Geometry
4.3.2 Jungfrau detectors
4.3.3 Technical concept
4.4 Experimental setup
4.5 Spectrum processing and Results
4.6 Conclusions
5 Absorption Imaging of X-Ray Resonant Pumping
5.1 X-Ray Imaging with XFEL
5.1.1 Using XFEL for X-ray Imaging
5.1.2 Phase Contrast Imaging
5.1.3 The Complex Refractive Index in X-ray Optics
5.1.4 Implementation of Phase Contrast Imaging
5.1.5 Propagation-Based Imaging Scheme
5.2 Compound Refractive Lenses
5.3 Experimental Setup
5.4 Image processing and results
5.5 Conclusions
6 Simulations of X-Ray Resonant Probing and Results Discussion
6.1 Methods for Modeling the Interaction of Laser Radiation with Matter
6.1.1 Static models
6.1.2 Hydrodynamics Models
6.1.3 Kinetic Models
6.1.4 Particle-In-Cell (PIC) method
6.1.5 Atomic Codes
6.1.6 Hybrid Codes
6.2 Opacity spectra calculated with FLYCHK
6.3 PIC-simulations of Laser-Plasma Interaction
6.4 Imaging Calculations with Simulated Resonant Opacities
6.5 Results discussion
7 Summary and Outlook
7.1 Summary
7.2 Outlook
Bibliography
Acknowledgment
Amplified photomodulation of a bis(dithienylethene)-substituted phosphine
No full textPhosphine ligands play a crucial role in homogeneous catalysis, allowing fine-tuning of the catalytic activity of various metals by modifying their structure. An ultimate challenge in this field is to reach controlled modulation of catalysis in situ, for which the development of phosphines capable of photoswitching between states with differential electronic properties has been proposed. To magnify this light-induced behavior, in this work we describe a novel phosphine ligand incorporating two dithienylethene photoswitchable moieties tethered to the same phosphorus atom. Double photoisomerization was observed for this ligand, which remains unhindered upon gold(I) complexation. As a result, the preparation of a fully ring-closed phosphine isomer was accomplished, for which amplified variation of phosphorus electron density was verified both experimentally and by computational calculations. Accordingly, the presented molecular design based on multiphotochromic phosphines could open new ways for preparing enhanced photoswitchable catalytic systems
Improving Early Optics Instruction Using a Phenomenological Approach: A Field Study
No full textPrevious research has shown that phenomenological approaches in early optics education
might be superior to traditional model-based instruction based on the light ray realm with regards
to fostering students’ conceptual understanding of basic optics topics. However, it remains open
to date which learning difficulties students encounter when being introduced to optics following
a phenomenological approach—in particular, in comparison to the learning difficulties that are
widespread among students introduced to optics via traditional model-based instruction. With
this article, we contribute to closing this gap: We report the results of a quasi-experimental field
study with N = 189 secondary school students. We used ten items adapted from the literature in
a pre-posttest design for an in-depth exploration of the conceptions of introductory optics topics
acquired by N = 89 students introduced to optics following a phenomenological teaching-learning
sequence and compare these students’ conceptions to the ones acquired by N = 100 peers who
participated in traditional model-based instruction covering the same content topics. The results of
this study substantiate earlier findings according to which phenomenological teaching might be a
fruitful endeavour for early optics education, in particular, when it comes to teaching and learning
about image formation by converging lenses
Traversing Cognitive Spaces. Material Samples for Harnessing Tacit Knowledge: Workshop on Experimental Negotiation Methods
No full textSOCIAL INNOVATION AND DESIGN CHALLENGE