Siamese Basis Function Networks for Data-Efficient Defect Classification in Technical Domains

Training deep learning models in technical domains is often accompanied by the challenge that although the task is clear, insufficient data for training is available. In this work, we propose a novel approach based on the combination of Siamese networks and radial basis function networks to perform data-efficient classification without pretraining by measuring the distance between images in semantic space in a data-efficient manner. We develop the models using three technical datasets, the NEU dataset, the BSD dataset, and the TEX dataset. In addition to the technical domain, we show the general applicability to classical datasets (cifar10 and MNIST) as well. The approach is tested against state-of-the-art models (Resnet50 and Resnet101) by stepwise reduction of the number of samples available for training. The authors show that the proposed approach outperforms the state-of-the-art models in the low data regime

Low temperature fatigue crack propagation in toughened epoxy resins aimed for filament winding of type V composite pressure vessels

In this study, application relevant toughened epoxy-amine formulations were investigated regarding their mechanical behavior at low temperatures and compared to a non-toughened reference. The application-oriented resins are based on reactive diluent-modified diglycidylether of bisphenol A (DGEBA) which were tested at 22 °C and −50 °C in regard to their fracture toughness (KIC) and fatigue crack propagation (da/dN) behavior. The E′ and E’’ moduli and the corresponding glass transition temperatures Tg were determined via dynamic mechanical thermal analyses (DMTA) which also described the influence of the block copolymeric toughener on the epoxy resin network. The plastic zone size, calculated during crack propagation, reveals the temperature dependent toughener-matrix interaction. The prevailing energy dissipation mechanisms were correlated with the changes of E’. SEM micrographs confirm the superior performance of the toughened system at −50 °C by the decrease of the fatigue cack propagation slopes and highlight the trends of the materials low temperature behavior

Glutathione reductase-catalyzed cascade of redox reactions to bioactivate potent antimalarial 1,4-naphthoquinones--a new strategy to combat malarial parasites.

Our work on targeting redox equilibria of malarial parasites propagating in red blood cells has led to the selection of six 1,4-naphthoquinones, which are active at nanomolar concentrations against the human pathogen Plasmodium falciparum in culture and against Plasmodium berghei in infected mice. With respect to safety, the compounds do not trigger hemolysis or other signs of toxicity in mice. Concerning the antimalarial mode of action, we propose that the lead benzyl naphthoquinones are initially oxidized at the benzylic chain to benzoyl naphthoquinones in a heme-catalyzed reaction within the digestive acidic vesicles of the parasite. The major putative benzoyl metabolites were then found to function as redox cyclers: (i) in their oxidized form, the benzoyl metabolites are reduced by NADPH in glutathione reductase-catalyzed reactions within the cytosols of infected red blood cells; (ii) in their reduced forms, these benzoyl metabolites can convert methemoglobin, the major nutrient of the parasite, to indigestible hemoglobin. Studies on a fluorinated suicide-substrate indicate as well that the glutathione reductase-catalyzed bioactivation of naphthoquinones is essential for the observed antimalarial activity. In conclusion, the antimalarial naphthoquinones are suggested to perturb the major redox equilibria of the targeted infected red blood cells, which might be removed by macrophages. This results in development arrest and death of the malaria parasite at the trophozoite stage

Highly colored boron-doped thiazolothiazoles from the reductive dimerization of boron isothiocyanates

Reduction of (CAAC)BBr2(NCS) (CAAC=cyclic alkyl(amino)carbene) in the presence of a Lewis base L yields tricoordinate (CAAC)LB(NCS) borylenes which undergo reversible E/Z‐isomerization. The same reduction in the absence of L yields deep blue, bis(CAAC)‐stabilized, boron‐doped, aromatic thiazolothiazoles resulting from the dimerization of dicoordinate (CAAC)B(NCS) borylene intermediates

Intensiv farbige Bor-dotierte Thiazolthiazole durch reduktive Dimerisierung von Borisothiocyanaten

Die Reduktion von (CAAC)BBr2(NCS) (CAAC=cyclisches Alkyl(amino)carben) in der Gegenwart einer Lewis-Base L liefert dreifach koordinierte (CAAC)LB(NCS)-Borylene, die eine reversible (E)/(Z)-Isomerisierung eingehen. Die gleiche Reduktion in Abwesenheit von L führt zu intensiv blauen, bis(CAAC)-stabilisierten, Bor-dotierten, aromatischen Thiazolthiazolen, die aus der Dimerisierung zweifach koordinierter (CAAC)B(NCS)-Borylenintermediate resultieren

Isolierung neutraler, mono- und dikationischer B2P2-Ringe durch Addition eines Diphosphans an eine Bor-Bor-Dreifachbindung

Das NHC-stabilisierte Diborin B2(SIDep)2 (SIDep=1,3-Bis(2,6-diethylphenyl)imidazolin-2-yliden) unterzieht sich bei Raumtemperatur einer P-P-Bindungsaktivierung mit Tetraethyldiphosphan, wobei mittels 1,2-Diphosphinierung über ein Diphosphoryldiboren in hohen Ausbeuten B2P2-Heterocyclen gebildet werden. In Abhängigkeit vom verwendeten Oxidationsmittel und Gegenion kann dieser Heterocyclus zu einem Radikalkation beziehungsweise Dikation oxidiert werden. Beginnend mit dem planaren, neutralen 1,3-Bis(alkyliden)-1,3-diborata-2,4-diphosphoniocyclobutan führt jeder Oxidationsschritt zu einer verminderten B-B-Bindungslänge und dem Verlust der Planarität durch die Kationisierung. Röntgenstrukturanalysen in Kombination mit DFT- und CASSCF/NEVPT2-Rechnungen offenbaren für die NHC-stabilisierten dikationischen B2P2-Ringe geschlossenschalige, schmetterlingsartige Strukturen, wovon die diradikaloiden Isomere mit planarem Ring in energetischer Nähe liegen

Metal-Free Intermolecular C–H Borylation of N-Heterocycles at B–B Multiple Bonds

Carbene-stabilized diborynes of the form LBBL (L = NHC or CAAC) induce rapid, high yielding, intermolecular ortho-C–H borylation at N-heterocycles at room temperature. A simple pyridyldiborene is formed when an NHC-stabilized diboryne is combined with pyridine, while a CAAC-stabilized diboryne leads to activation of two pyridine molecules to give a tricyclic alkylideneborane, which can be forced to undergo a further H-shift resulting in a zwitterionic, doubly benzo-fused 1,3,2,5-diazadiborinine by heating. Use of the extended N-heteroaromatic quinoline leads to a borylmethyleneborane under mild conditions via an unprecedented boron-carbon exchange process

Metallfreie intermolekulare C-H-Borylierung von N-Heterocyclen an B-B-Mehrfachbindungen

Carbenstabilisierte Diborine der Form LBBL (L=N-heterocyclisches Carben (NHC) oder cyclisches Alkyl(amino)carben (CAAC)) induzieren bei Raumtemperatur eine schnelle, ertragreiche, intermolekulare ortho-C-H-Borylierung an N-Heterocyclen. Ein einfaches Pyridyldiboren wird gebildet, wenn ein NHC-stabilisiertes Diborin mit Pyridin kombiniert wird, während ein CAAC-stabilisiertes Diborin zur Aktivierung von zwei Pyridinmolekülen führt, um ein tricyclisches Alkylidenboran zu bilden, das durch Erhitzen zu einem zwitterionischen, zweifach benzokondensierten 1,3,2,5-Diazadiborinin mittels einer weiteren H-Verschiebung umgelagert werden kann. Die Verwendung des verlängerten N-heteroaromatischen Chinolins führt unter milden Bedingungen über einen bisher unbekannten Bor-Kohlenstoff-Austauschprozess zu einem Borylmethylenboran