Rethinking how external pressure can suppress dendrites in lithium metal batteries

We offer an explanation for how dendrite growth can be inhibited when Li metal pouch cells are subjected to external loads, even for cells using soft, thin separators. We develop a contact mechanics model for tracking Li surface and sub-surface stresses where electrodes have realistically (micron-scale) rough surfaces. Existing models examine a single, micron-scale Li metal protrusion under a fixed local current density that presses more or less conformally against a separator or stiff electrolyte. At the larger, sub-mm scales studied here, contact between the Li metal and the separator is heterogeneous and far from conformal for surfaces with realistic roughness: the load is carried at just the tallest asperities, where stresses reach tens of MPa, while most of the Li surface feels no force at all. Yet, dendrite growth is suppressed over the entire Li surface. To explain this dendrite suppression, our electrochemical/mechanics model suggests that Li avoids plating at the tips of growing Li dendrites if there is sufficient local stress; that local contact stresses there may be high enough to close separator pores so that incremental Li+ ions plate elsewhere; and that creep ensures that Li protrusions are gradually flattened. These mechanisms cannot be captured by single-dendrite-scale analyses

Graphen der Lernverlaufsdiagnostik interpretieren und anwenden - Leseförderung mit der Onlineverlaufsmessung Levumi

Viele Schüler mit sonderpädagogischem Förderbedarf entwickeln Schwierigkeiten im sprachlichen Bereich. Dies hat zur Folge, dass insbesondere der Leseerwerb einer pädagogischen Aufbereitung bedarf. In dieser pädagogischen Arbeit bietet der problemlösende Ansatz der Lernverlaufsdiagnostik (engl. Curriculum- Based Measurement) Lehrkrä%en eine Unterstützung bei der Überprüfung der Effektivität ihres Unterrichts durch kurze und leicht handhabbare Tests. Diese Unterstützung kann durch weiterführende Materialien (z. B. Interpretationshilfen, Fördermaterialien) bestärkt werden. Für eine erfolgreiche Etablierung der Lernverlaufsdiagnostik und der damit verbundenen computergestützten Testsysteme in der Praxis müssen die aus dem Schulsystem bedingten Anforderungen berücksichtigt werden. Dieser Beitrag thematisiert literaturbasiert die Chancen und Grenzen bei der Implementation der Lernverlaufsdiagnostik in der pädagogischen Praxis. Dafür werden digitale Testsysteme, die Perspektive der Lehrkrä%e sowie Schwierigkeiten bei der Interpretation von Lernverlaufsgraphen fokussiert betrachtet. Als Praxisbeispiel wird das Angebot der kostenlosen Onlineplattform Levumi (www.levumi.de), ihre Lernverlaufstests im Bereich Lesen, die Interpretation der Klassen- und Individualgraphen und Fördermaterialien vorgestellt. Damit sich der Ansatz der Lernverlaufsdiagnostik in Deutschland im inklusiven Schulsystem etablieren kann, müssen Barrieren durch Kosten oder einen fehlenden technischen Support abgebaut werden. Zusätzlich können adaptive Testsysteme die Leseförderung durch automatisierte Empfehlungen von Fördermaterialien, schülergerechte Rückmeldungen und Analysen der Kompetenzpro+le der Schüler den Unterricht bereichern

Correlation of pre-operative cancer imaging techniques with post-operative gross and microscopic pathology images

In this paper, different algorithms for volume reconstruction from tomographic cross-sectional pathology slices are described and tested. A tissue-mimicking phantom made with a mixture of agar and aluminium oxide was sliced at different thickness as per pathological standard guidelines. Phantom model was also virtually sliced and reconstructed in software. Results showed that shape-based spline interpolation method was the most precise, but generated a volume underestimation of 0.5%

Adding Spin Functionality to Traditional Optoelectronics via Chiral Perovskite

Spin polarized current generation and injection into semiconductors at room temperature are key to enable a broader range of opto-spintronic functionalities, yet the inherent efficiency of spin injection across commonly used semiconductor-ferromagnet interfaces is limited. Here, we demonstrate efficient spin injection into commercially viable III-V light emitting diodes (LED) by integrating chiral halide perovskite layers with (AlxGa1-x)0.5In0.5P multiple quantum wells (MQW). Spin polarized current is injected via chirality induced spin selectivity (CISS) and the spin accumulation in the III-V semiconductor is detected via the emission of circularly polarized light with a degree of circular polarization of up to ~ 15%. X-ray photoemission spectroscopy (XPS) and transmission electron microscopy (TEM) cross sectional imaging indicate a pristine perovskite/III-V interface. These findings demonstrate chiral perovskite semiconductors transform well-developed semiconductor platforms to enable control over spin, charge, and light

Catalysing sustainable fuel and chemical synthesis

Concerns over the economics of proven fossil fuel reserves, in concert with government and public acceptance of the anthropogenic origin of rising CO2 emissions and associated climate change from such combustible carbon, are driving academic and commercial research into new sustainable routes to fuel and chemicals. The quest for such sustainable resources to meet the demands of a rapidly rising global population represents one of this century’s grand challenges. Here, we discuss catalytic solutions to the clean synthesis of biodiesel, the most readily implemented and low cost, alternative source of transportation fuels, and oxygenated organic molecules for the manufacture of fine and speciality chemicals to meet future societal demands

Levumi: A Web-Based Curriculum-Based Measruement to Monitor Learning Progress in Inclusive Classrooms

Our paper introduces and assesses the Levumi platform’s web-based assessment of reading fluency. One challenges of inclusive education is meeting the needs of the learners with special education needs (SEN). Children with SEN and other risk factors face an increased risk of failing in schools and manifesting academic and social problems over the time. Web-based curriculum-based measurement (CBM) can provide an effective tool to track progress of learners and limit such risks. In particular, it can ease the challenges of test administration in inclusive classrooms through automation and providing multiple difficulty levels without the need of different paper-forms. Furthermore, Levumi can help educators track children and thus provide support for learners. Levumi takes advantage of the strengths of web-based CBM to assess reading fluency in primary school students. We confirmed the reading fluency test’s test-retest reliability (n = 334), its ability to measure learning over time in individual learners with SEN (n = 8, across 14 MPs), and its applicability to learners with SEN (n = 300, including n = 46 with SEN). We evaluate Levumi’s overall usefulness in assessing different types of learners, and discuss its contributions to CBM research

In situ liquid-cell electron microscopy of silver–palladium galvanic replacement reactions on silver nanoparticles

International audienceGalvanic replacement reactions provide an elegant way of transforming solid nanoparticles into complex hollow morphologies. Conventionally, galvanic replacement is studied by stopping the reaction at different stages and characterizing the products ex situ. In situ observations by liquid-cell electron microscopy can provide insight into mechanisms, rates and possible modifications of galvanic replacement reactions in the native solution environment. Here we use liquid-cell electron microscopy to investigate galvanic replacement reactions between silver nanoparticle templates and aqueous palladium salt solutions. Our in situ observations follow the transformation of the silver nanoparticles into hollow silver-palladium nanostructures. While the silver-palladium nanocages have morphologies similar to those obtained in ex situ control experiments the reaction rates are much higher, indicating that the electron beam strongly affects the galvanic-type process in the liquid-cell. By using scavengers added to the aqueous solution we identify the role of radicals generated via radiolysis by high-energy electrons in modifying galvanic reactions