Coherent Phonon-Induced Modulation of Charge Transfer in 2D Hybrid Perovskites

Electron–phonon interactions play an essential role in charge transport and transfer processes in semiconductors. For most structures, tailoring electron–phonon interactions for specific functionality remains elusive. Here, it is shown that, in hybrid perovskites, coherent phonon modes can be used to manipulate charge transfer. In the 2D double perovskite, (AE2T)₂AgBiI₈ (AE2T: 5,5“-diylbis(amino-ethyl)-(2,2”-(2)thiophene)), the valence band maximum derived from the [Ag_0.5Bi_0.5I₄]^2– framework lies in close proximity to the AE2T-derived HOMO level, thereby forming a type-II heterostructure. During transient absorption spectroscopy, pulsed excitation creates sustained coherent phonon modes, which periodically modulate the associated electronic levels. Thus, the energy offset at the organic–inorganic interface also oscillates periodically, providing a unique opportunity for modulation of interfacial charge transfer. Density-functional theory corroborates the mechanism and identifies specific phonon modes as likely drivers of the coherent charge transfer. These observations are a striking example of how electron–phonon interactions can be used to manipulate fundamentally important charge and energy transfer processes in hybrid perovskites.     

Photocatalytic Valorization of Plastic Waste over Zinc Oxide Encapsulated in a Metal–Organic Framework

The conversion of waste plastic into high-value-added chemicals is regarded as a promising approach for relieving global plastic pollution and contributing to the circular economy. Herein, a partial calcination strategy is developed to fabricate a zinc oxide/UiO66-NH₂ (ZnO/UiO66-NH₂) heterojunction, in which ZnO is encapsulated in porous UiO66-NH₂ for the photocatalytic valorization of plastic. This strategy preserves the framework structure of UiO66-NH₂, thus enabling the formation of ZnO with ultra-small size distributed inside the skeleton. The synergistic effect of the obtained ZnO/UiO66-NH₂ heterojunction facilitates providing an efficient channel for carrier/mass transfer and guarantees structural stability. As a result, ZnO/UiO66-NH₂ exhibits high activity for converting polylactic acid (PLA) and polyvinyl chloride (PVC) into acetic acid, coupled with H₂ production. This work provides a feasible strategy for rationally designing heterojunction photocatalysts, as well as an insight into understanding the process of photocatalytic valorization of plastic.     

Long‐term effects of angiotensin II blockade with irbesartan on inflammatory markers in hemodialysis patients: A randomized double blind placebo controlled trial (SAFIR study)

Introduction: Low‐grade chronic inflammation is common in hemodialysis (HD) patients. Previous studies suggest an anti‐inflammatory effect of angiotensin II receptor blocker (ARB) treatment. The aim of this study was to compare the effect of ARB vs. placebo on plasma concentrations of inflammatory markers in HD patients. Methods: Adult HD patients were randomized for double‐blind treatment with the ARB irbesartan 150–300 mg/day or placebo. At baseline, 1 week, 3, 6, 9, and 12 months plasma high sensitivity C‐reactive protein (hsCRP), interleukin (IL)?1β, IL‐6, IL‐8, IL‐18, and transforming growth factor‐β (TGF‐β) were measured using Luminex and enzyme‐linked immunosorbent assay (ELISA) technology. Findings: Eighty‐two patients were randomized (placebo/ARB: 41/41). The groups did not differ in initial levels of any of the inflammatory markers (placebo/ARB median(range)): hsCRP 3.3(0.2–23.4)/2.7(0.2–29.6) μg/mL; IL‐1β 1.1(0.0–45.9)/1.1(0.0‐7.2) pg/mL; IL‐6 10(1–90)/12(1–84) pg/mL; IL‐8 31(9–134)/34(5–192) pg/mL; IL‐18 364(188–1343)/377(213–832) pg/mL; TGF‐β 3.2(0.8–13.9)/3.6(1.3–3.8) ng/mL. Overall, there was no significant difference in hsCRP, IL‐6, IL‐8, and TGF‐β between placebo and ARB‐treated patients during the study period, and hsCRP, IL‐6, IL‐8, and TGF‐β were relatively stable during the study period (P ≥ 0.18 in all tests for parallel curves, equal levels, and constant levels). The IL‐1β level was slightly different in the two groups over time, but not significantly (P = 0.09 in test for parallel curves) and it was also relatively stable during the study period (P ≥ 0.49 in tests for equal levels and constant level). IL‐18 was the only inflammatory marker which was not constant during the study period (P = 0.001 in test for constant level), but there was no significant difference between placebo and ARB‐treated (P ≥ 0.51 in tests for parallel curves and equal levels). Discussion: Inflammatory biomarkers were neither acutely, nor in the long‐term significantly affected by the ARB irbesartan. Our findings suggest that ARB treatment in HD patients does not offer protective anti‐inflammatory effects.     

Relaxing high-dimensional constraints in the direct solution space method for early phase development

Early phase distributed system design can be accomplished using solution spaces that provide an interval of permissible values for each functional parameter. The feasibility property guarantees fulfillment of all design requirements for all possible realizations. Flexibility denotes the size measure of the intervals, with higher flexibility benefiting the design process. Two methods are available for solution space identification. The direct method solves a computationally cheap optimization problem. The indirect method employs a sampling approach that requires a relaxation of the feasibility property through re-formulation as a chance constraint. Even for high probabilities of fulfillment, \(P>0.99\), this results in substantial increases in flexibility, which offsets the risk of infeasibility. This work implements the chance constraint formulation into the direct method for linear constraints by showing that its problem statement can be understood as a linear robust optimization problem. Approximations of chance constraints from the literature are transferred into the context of solution spaces. From this, we derive a theoretical value for the safety parameter \(\varOmega\). A further modification is presented for use cases, where some intervals are already predetermined. A problem from vehicle safety is used to compare the modified direct and indirect methods and discuss suitable choices of \(\varOmega\). We find that the modified direct method is able to identify solution spaces with similar flexibility, while maintaining its cost advantage.     

Challenges of Diffusion Bonding of Different Classes of Stainless Steels

Solid state diffusion bonding is used to produce monolithic parts exhibiting mechanical properties comparable to those of the bulk material. This requires diffusion of atoms across mating surfaces at high temperatures, accompanied by grain growth. In case of steel, polymorphy helps to limit the grain size, since the microstructure is transformed twice. The diffusion coefficient differs extremely for ferritic and austenitic phases. Alloying elements may shift or suppress phase transformation until the melting range. In this paper, diffusion bonding experiments are reported for austenitic, ferritic, and martensitic stainless steels possessing varying alloying elements and contents. Passivation layers of different compositions are formed, thus affecting the local diffusion coefficient and impeding diffusion across faying surfaces. As a consequence, different bonding temperatures are needed to obtain good bonding results, making it difficult to control the deformation of parts, since strong nonlinearities exist between temperature, bonding time, and bearing pressure. For martensitic stainless steel, it is shown that it is very easy to obtain good bonding results at low deformation, whereas ferritic and austenitic stainless steels require much more extreme bonding parameters.

     

Responses of the reflectance indices PRI and NDVI to experimental warming and drought in European shrublands along a north-south climatic gradient

The aim of this study was to evaluate the use of ground-based canopy reflectance measurements to detect changes in physiology and structure of vegetation in response to experimental warming and drought treatment at six European shrublands located along a North-South climatic gradient. We measured canopy reflectance, effective green leaf area index (green LAIe) and chlorophyll fluorescence of dominant species. The treatment effects on green LAIe varied among sites. We calculated three reflectance indices: photochemical reflectance index PRI [531 nm; 570 nm], normalized difference vegetation index NDVI₆₈₀ [780 nm; 680 nm] using red spectral region, and NDVI₅₇₀ [780 nm; 570 nm] using the same green spectral region as PRI. All three reflectance indices were significantly related to green LAIe and were able to detect changes in shrubland vegetation among treatments. In general warming treatment increased PRI and drought treatment reduced NDVI values. The significant treatment effect on photochemical efficiency of plants detected with PRI could not be detected by fluorescence measurements. However, we found canopy level measured PRI to be very sensitive to soil reflectance properties especially in vegetation areas with low green LAIe. As both soil reflectance and LAI varied between northern and southern sites it is problematic to draw universal conclusions of climate-derived changes in all vegetation types based merely on PRI measurements. We propose that canopy level PRI measurements can be more useful in areas of dense vegetation and dark soils.     

Locating computer clubs in multicultural neighborhoods: How collaborative project work fosters integration processes

Located in socially and culturally diverse neighborhoods, we have built a network of intercultural computer clubs, called come_IN. These clubs offer a place to share practices among children and adults of diverse ethnical backgrounds. We show how this initiative ties into the striving for the integration of migrant communities and host society in Germany. In this paper, we analyze how collaborative project work and the use of mobile media and technologies contribute to integration processes in multicultural neighborhoods. Qualitative data gathered from interviews with club participants, participative observation in the computer clubs, as well as the analysis of artifacts created during project work provides the background needed to match local needs and peculiarities with (mobile) technologies. Based on these findings we present two approaches to add to the technological infrastructure: (1) a mesh-network extending the clubs into the neighborhood and (2) a project management tool, which supports projects and stimulates the sharing of ideas among projects.     

Exploring the benefits of the combination of a software architecture analysis and a usability evaluation of a mobile application

Designing easy to use mobile applications is a difficult task. In order to optimize the development of a usable mobile application, it is necessary to consider the mobile usage context for the design and the evaluation of the user-system interaction of a mobile application. In our research we designed a method that aligns the inspection method “Software ArchitecTure analysis of Usability Requirements realizatioN” SATURN and a mobile usability evaluation in the form of a user test. We propose to use mobile context factors and thus requirements as a common basis for both inspection and user test. After conducting both analysis and user test, the results described as usability problems are mapped and discussed. The mobile context factors identified define and describe the usage context of a mobile application. We exemplify and apply our approach in a case study. This allows us to show how our method can be used to identify more usability problems than with each method separately. Additionally, we could confirm the validity and identified the severity of usability problems found by both methods. Our work presents how a combination of both methods allows to address usability issues in a more holistic way. We argue that the increased quantity and quality of results can lead to a reduction of the number of iterations required in early stages of an iterative software development process.     

Ceramic micro parts produced by micro injection molding: latest developments

Powder injection molding is a preferred technology for the production of micro parts or microstructured parts. Derived from the well known thermoplastic injection molding technique it is suitable for a large-scale production of ceramic and metallic parts without final machining. To achieve good surface quality and control the part size and distortions is an important goal to allow mass production. This means that all process steps like part design adjusted for MIM/CIM-technology, appropriate choice of powder and binder components and injection molding simulation to design the sprue are required. Concerning the injection molding itself high quality mold inserts, high-precision injection molding with suitable molding machines like Battenfeld Microsystem50 or standard machine with special equipment like variotherm or evacuation of the molding tool and an adjusted debinding and sintering process have to be available. Results of producing micro parts by powder injection molding of ceramic feedstock will be presented.