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In Situ X-ray Scattering of Tin Oxide Nanoparticles during Chemical Vapor Synthesis
No full textGas phase production processes of nanoparticles (NPs) such as Chemical Vapor Synthesis (CVS) enable the generation of NPs with high purity, crystallinity, narrow size distribution, and a low degree of hard agglomeration. The design of materials with desired properties is enabled by a control of CVS process parameters, which demands a fundamental understanding of CVS. Ex situ investigation of the CVS process may suffer from artifacts due to particle collection, oxidation, or aging. This may be circumvented by in situ studies. Such studies are described here using small- and wide-angle X-ray scattering of tin oxide NPs as a model system. We demonstrate the formation of crystalline order as well as variation of morphology, size, and agglomeration as a function of process temperature and pressure. Results are compiled in a size-temperature pseudo-phase diagram of the CVS process
Revisiting NaCoO: A renewed magnetic phase diagram based on electrochemical reaction synthesis
No full textThe assertion of intrinsic material properties based on measured experimental data is being challenged by emerging sample synthesis protocols, which opens new avenues for discovering novel functionalities. In this study, we revisit one of the most widely studied strongly correlated materials of the early 2000s, Na_CoO (NCO). Leveraging the sensitivity of muon spin rotation and relaxation (SR) measurements, we discern significant differences between NCO samples synthesized via conventional solid-state reaction (SSR) and our electrochemical reaction (ECR) approach. Contrary to SSR-synthesized NaCoO, which exhibits a nonmagnetic ground state, our ECR-derived sample showcases an antiferromagnetic (AF) order from ≥0.7, challenging established phase boundaries. We attribute the observed magnetic phenomena in ECR-NCO to long-range order of Na-ions and/or vacancies, as well as the inherent flexibility of the crystal framework. Our study holds implications for tailoring and optimization of next-generation devices based on layered materials
Evidence for longitudinally polarized bosons in the electroweak production of same-sign boson pairs in association with two jets in pp collisions at TeV with the ATLAS detector
No full textThis Letter reports the first evidence of production of same-sign boson pairs where at least one of the bosons is longitudinally polarized and the most stringent constraint to date for the production of two longitudinally polarized same-sign bosons. The data set used corresponds to an integrated luminosity of 140 fb of proton-proton collisions at a center-of-mass energy of 13 TeV, collected with the ATLAS detector during Run 2 of the Large Hadron Collider. The study is performed in final states including two same-sign leptons (electrons or muons), missing transverse momentum, and at least two jets with a large invariant mass and a large rapidity difference. Two independent fits are performed targeting the production of same-sign bosons with at least one, or two longitudinally polarized bosons. The observed (expected) significance of the production with at least one longitudinally polarized boson is 3.3 (4.0) standard deviations. An observed (expected) 95% confidence level upper limit of 0.45 (0.70) fb is reported on the fiducial production cross section of two longitudinally polarized same-sign bosons
Measurements of the production cross-sections of a Higgs boson in association with a vector boson and decaying into with the ATLAS detector at TeV
No full textMeasurements of the total and differential Higgs boson production cross-sections, via and associated production using and decays, are presented. The analysis uses proton-proton events delivered by the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector between 2015 and 2018. The data correspond to an integrated luminosity of 140 fb. The sum of the and cross-sections times the branching fraction is measured to be (stat.) (syst.) pb, in agreement with the Standard Model prediction. Higgs boson production is further characterised through measurements of the differential cross-section as a function of the transverse momentum of the vector boson and in the framework of Simplified Template Cross-Sections
Search for resonant leptoquark production via lepton-jet signatures in collisions at TeV and TeV with the ATLAS detector
No full textThis paper presents a search for physics beyond the Standard Model targeting a heavy resonance visible in the invariant mass of the lepton-jet system. The analysis focuses on final states with a high-energy lepton and jet, and is optimised for the resonant production of leptoquarks-a novel production mode mediated by the lepton content of the proton originating from quantum fluctuations. Four distinct and orthogonal final states are considered: +light jet, +light jet, +-jet, and +-jet, constituting the first search at the Large Hadron Collider for resonantly produced leptoquarks with couplings to electrons and muons. Events with an additional same-flavour lepton, as expected from higher-order diagrams in the signal process, are also included in each channel. The search uses proton-proton collision data from the full Run 2, corresponding to an integrated luminosity of 140 fb at a centre-of-mass energy of TeV, and from a part of Run 3 (2022-2023), corresponding to 55 fb at TeV. No significant excess over Standard Model predictions is observed. The results are interpreted as exclusion limits on scalar leptoquark () production, substantially improving upon previous ATLAS constraints from leptoquark pair production for large coupling values. The excluded mass ranges depend on the coupling strength, reaching up to 3.4 TeV for quark-lepton couplings , and up to 4.3 TeV, 3.1 TeV, and 2.8 TeV for , , and couplings set to 3.5, respectively
Continuous structure modification of metal-organic framework glasses via halide salts
No full textMelting and glass formation of metal-organic frameworks (MOFs) allow them to be processed into bulk materials. However, two major challenges remain: only a small fraction of MOF crystals undergo melting and glass-formation, and no well-established strategies exist for tuning MOF glass structures and properties. Here, we address both challenges through co-melting of zeolitic imidazole frameworks (ZIFs), a subset of MOFs, with heterocycle-based halide salts. The salt acts as a chemical “modifier”, akin to the role of alkali modifiers in traditional silicate glasses, e.g., allowing the melting of ZIF-8 that otherwise decomposes prior to melting. Through experimental and computational analyses, we show that the salts depolymerize the ZIFs, enabling continuous tuning of the fraction of bridging to non-bridging imidazolate linkers and, thereby, the thermal and mechanical properties. The proposed strategy enables diversification of MOF glass chemistry, tunable structures and properties, and ultimately an increased number of glass-forming MOFs with improved functionalities
Search for heavy neutral Higgs bosons A and H in the Z channel in proton-proton collisions at 13 TeV
No full textA direct search for new heavy neutral Higgs bosons A and H in the Z channel is presented, targeting the process pp A ZH with H . For the first time, the channel with decays of the Z boson to muons or electrons in association with all-hadronic decays of the system is targeted. The analysis uses proton-proton collision data collected at the CERN LHC with the CMS experiment at = 13 TeV, which correspond to an integrated luminosity of 138 fb. No signal is observed. Upper limits on the product of the cross section and branching fractions are derived for narrow resonances A and H with masses up to 2100 and 2000 GeV, respectively, assuming A boson production through gluon fusion. The results are also interpreted within two-Higgs-doublet models, complementing and substantially extending the reach of previous searches
Search for jet quenching with dijets from high-multiplicity pPb collisions at = 8.16 TeV
No full textThe first measurement of the dijet transverse momentum balance x in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy of = 8.16 TeV is presented. The x observable, defined as the ratio of the subleading over leading jet transverse momentum in a dijet pair, is used to search for jet quenching effects. The data, corresponding to an integrated luminosity of 174.6 nb, were collected with the CMS detector in 2016. The x distributions and their average values are studied as functions of the charged-particle multiplicity of the events and for various dijet rapidity selections. The latter enables probing hard scattering of partons carrying distinct nucleon momentum fractions x in the proton- and lead-going directions. The former, aided by the high-multiplicity triggers, allows probing for potential jet quenching effects in high-multiplicity events (with up to 400 charged particles), for which collective phenomena consistent with quark-gluon plasma (QGP) droplet formation were previously observed. The ratios of x distributions for high- to low-multiplicity events are used to quantify the possible medium effects. These ratios are consistent with simulations of the hard-scattering process that do not include QGP production. These measurements set an upper limit on medium-induced energy loss of the subleading jet of 1.26% of its transverse momentum at the 90% confidence level in high multiplicity pPb events.[graphic not available: see fulltext
Wimmelbild: Mathematik im Kita-Alltag entdecken, 2. Aufl.
No full textWimmelbild für die Fortbildung "Spielen, Bauen und Sortieren - Mathematik im Kita-Alltag entdecken und begleiten" von Neugier ahoi! MINT mit Kindern entdecken (www.neugier-ahoi.de). Hidden object picture for the professional development programme "Playing, Building and Sorting - Discovering and Facilitating Mathematics in the Everyday Life of Early Childhood Education Centers" by Neugier ahoi! MINT mit Kindern entdecken (www.neugier-ahoi.de
Global 3D-gradient-structured steel sheets with superior strength-ductility combination
No full textGlobal gradient structures (GGS) from core to surface processed by twisting have been reported to possess exceptional strength-ductility combinations. However, it is hard to apply this technique to sheet (plate) samples because of their lower axial symmetry. Here, we report a novel 3D-GGS produced in a 304 stainless steel (304ss) sheet using cyclic twisting. The 3D-GGS 304ss sheets exhibited much better strength-ductility combinations than GGS 304ss rods due to their more pronounced heterostructural effects. During the tensile testing, a unique transformation-induced plasticity (TRIP) effect was activated in which reverse martensitic transformation (α′ → γ) was first activated, then transited to forward martensitic transformation (γ → α′) after some strain. Both the reverse and forward TRIP effects contributed to higher ductility. In addition, the 3D-structures also produced hetero-deformation induced (HDI) work hardening to retain ductility. This work developed a practical approach to constructing 3D-GGS to enhance integrated performances of metal sheets and components without changing their geometries