Der Berg-Karabach-Konflikt als Herausforderung im Kontext des russischen Krieges gegen die Ukraine | Լեռնային Ղարաբաղի հակամարտությունը որպես մարտահրավեր Ուկրաինայի դեմ ռուսական պատերազմի համատեքստում: Eine Stellungnahme aus außenpolitischer Perspektive | Մի դիրքորոշում արտաքին քաղաքականության տեսանկյունից

Der Artikel stellt einen kurzen Abriß der Entwicklung des Konflikts um Arzach seit der Perestroika Gorbatschows dar. Der kritisiert die Vernachlässigung dieses Konflikts durch den Westen, der ihn unter die ›eingefrorenen Konflikte‹ zählt, obwohl er über die Jahre immer wieder Todesopfer forderte. Man verschloss die Augen vor der lange andauernden Aufrüstung Aserbaidschans. Nach dem Krieg 2020 übernahm Russland die Rolle eines Moderators für den Frieden – füllt diese jedoch nicht aus. Die EU sieht mit dem Krieg Russlands gegen die Ukraine und den damit verbundenen Problemen der Energieversorgung die Priorität in Aserbaidschan als Quelle von Energie. Erste Ansätze der EU, Armenien zu schützen, Aserbaidschan in die Pflicht zu nehmen und auf seine Verantwortung für die armenische Bevölkerung einschließlich der Bewahrung seiner Kultur in Arzach zu verweisen, müssen verstärkt werden. Es braucht Initiativen, die Weltöffentlichkeit auf die tragische Situation Armeniens und Arzachs aufmerksam zu machen.The article presents a brief outline of the development of the conflict over Artsakh since Gorbachev’s perestroika. It criticizes the neglect of this conflict by the West, which counts it among the ›frozen conflicts‹, although it has repeatedly claimed lives over the years. People turned a blind eye to Azerbaijan’s long-lasting rearmament. After the war in 2020, Russia took on the role of a mediator for peace – but is not filling it. With Russia’s war against Ukraine and the related problems of energy supply, the EU sees Azerbaijan as a priority source of energy. Initial EU approaches to protect Armenia, to hold Azerbaijan to account and to point to its responsibility for the Armenian people, including the preservation of its culture in Artsakh, need to be strengthened. Initiatives are needed to draw the world’s attention to the tragic situation of Armenia and Artsakh

Chemical Gradients in Polymer-Modified Paper Sheets — Towards Single-Layer Biomimetic Soft Robots

Biomimetic actuators are typically constructed as functional bi- or multilayers, where actuating and resistance layers together dictate bending responses upon triggering by environmental stimuli. Inspired by motile plant structures, like the stems of the false rose of Jericho (Selaginella lepidophylla), we introduce polymer-modified paper sheets that can act as soft robotic single-layer actuators capable of hygro-responsive bending reactions. A tailored gradient modification of the paper sheet along its thickness entails increased dry and wet tensile strength and allows at the same time for hygro-responsiveness. For the fabrication of such single-layer paper devices, the adsorption behavior of a cross-linkable polymer to cellulose fiber networks was first evaluated. By using different concentrations and drying procedures fine-tuned polymer gradients throughout the thickness can be achieved. Due to the covalent cross-linking of polymer with fibers, these paper samples possess significantly increased dry and wet tensile strength properties. We furthermore investigated these gradient papers with respect to a mechanical deflection during humidity cycling. The highest humidity sensitivity is achieved using eucalyptus paper with a grammage of 150 g m⁻² modified with the polymer dissolved in IPA (~13 wt%) possessing a polymer gradient. Our study presents a straightforward approach for the design of novel hygroscopic, paper-based single-layer actuators, which have a high potential for diverse soft robotic and sensor applications

Humidity Influence on Mechanics and Failure of Paper Materials: Joint Numerical and Experimental Study on Fiber and Fiber Network Scale

Paper materials are natural composite materials and well-known to be hydrophilic unless chemical and mechanical processing treatments are undertaken. The relative humidity impacts the fiber elasticity, the fiber-fiber bonds and the failure mechanism. In this work, we present a comprehensive experimental and computational study on the mechanical and failure behaviour of the fiber and the fiber network under humidity influence. The manually extracted cellulose fiber is exposed to different levels of humidity, and then mechanically characterized using Atomic Force Microscopy, which delivers the humidity dependent longitudinal Young's modulus. The obtained relationship allows calculation of fiber elastic modulus at any humidity level. Moreover, by using Confoncal Laser Scanning Microscopy, the coefficient of hygroscopic expansion of the fibers is determined. On the other hand, we present a finite element model to simulate the deformation and the failure of the fiber network. The model includes the fiber anisotropy and the hygroscopic expansion using the experimentally determined constants. In addition, it regards the fiber-fiber bonding and damage by using a humidity dependent cohesive zone interface model. Finite element simulations on exemplary fiber network samples are performed to demonstrate the influence of different aspects including relative humidity and fiber-fiber bonding parameters on the mechanical features such as force-elongation curves, wet strength, extensiability and the local fiber-fiber debonding. In meantime, fiber network failure in a locally wetted region is revealed by tracking of individually stained fibers using in-situ imaging techniques. Both the experimental data and the cohesive finite element simulations demonstrate the pull-out of fibers and imply the significant role of the fiber-fiber debonding in the failure process of the wet paper.Comment: 21 pages,10 figure

Mechanistic Understanding and Three‐Dimensional Tuning of Fluid Imbibition in Silica‐Coated Cotton Linter Paper Sheets

Paper‐based microfluidic devices are used in point of care diagnostic, sensor technology or lab‐on‐a‐chip devices. Although a number of studies has been reported, only relatively few paper‐based diagnostic tools are available on the market. A remaining challenge is the mechanistic understanding and precise design of capillary flow in paper. Here, silica coatings are applied to control paper wettability, fiber swelling, and thus fluid transport in all three dimensions of a paper sheet via a simple dip‐coating and post‐treatment process. By adjusting the three‐dimensional silica coating distribution, a three‐dimensional asymmetric wettability gradient within the paper sheet is obtained which controls the fluid distribution and imbibition. The correlation between silica coating amount and silica distribution with the resulting fluid behavior is systematically elaborated by analyzing the interaction between fiber and fluid as well as the fiber swelling by applying confocal microscopy. Three different silica‐amount dependent fluid distribution states are demonstrated. These new insights into the mechanism of fluid imbibition using simple silica coatings enable the specific design of different imbibition mechanisms and thus the adjustment of the microfluidic properties in paper‐based microfluidic devices with control over all three spatial dimensions of a paper sheet in one fabrication step

Humidity influence on mechanics of paper materials: joint numerical and experimental study on fiber and fiber network scale

Paper materials are well-known to be hydrophilic unless chemical and mechanical processing treatments are undertaken. The relative humidity impacts the fiber elasticity, the interfiber joint behavior and the failure mechanism. In this work, we present a comprehensive experimental and computational study on mechanical properties of the fiber and the fiber network under humidity influence. The manually extracted cellulose fiber is exposed to different levels of humidity, and then mechanically characterized using atomic force microscopy, which delivers the humidity dependent longitudinal Young’s modulus. We describe the relation and calibrate the data into an exponential function, and the obtained relationship allows calculation of fiber elastic modulus at any humidity level. Moreover, by using confoncal laser scanning microscopy, the coefficient of hygroscopic expansion of the fibers is determined. We further present a finite element model to simulate the deformation and the failure of the fiber network. The model includes the fiber anisotropy and the hygroscopic expansion using the experimentally determined constants, and further considers interfiber behavior and debonding by using a humidity dependent cohesive zone interface model. Simulations on exemplary fiber network samples are performed to demonstrate the influence of different aspects including relative humidity and fiber-fiber bonding parameters on the mechanical features, such as force-elongation curve, strength and extensibility. Finally, we provide computational insights for interfiber bond damage pattern with respect to different humidity level as further outlook

Fluid Flow Programming in Paper-Derived Silica–Polymer Hybrids

In paper-based devices, capillary fluid flow is based on length-scale selective functional control within a hierarchical porous system. The fluid flow can be tuned by altering the paper preparation process, which controls parameters such as the paper grammage. Interestingly, the fiber morphology and nanoporosity are often neglected. In this work, porous voids are incorporated into paper by the combination of dense or mesoporous ceramic silica coatings with hierarchically porous cotton linter paper. Varying the silica coating leads to significant changes in the fluid flow characteristics, up to the complete water exclusion without any further fiber surface hydrophobization, providing new approaches to control fluid flow. Additionally, functionalization with redox-responsive polymers leads to reversible, dynamic gating of fluid flow in these hybrid paper materials, demonstrating the potential of length scale specific, dynamic, and external transport control