bluuebunny/crossref_metadata_2025_split huggingface dataset:
Die Bestimmung des elektrochemischen Polarisationszustandes einer Germaniumelektrode mit Hilfe der Elektroreflexion
Authors: Gobrecht H. , Thull R. , Hein F. , Schaldach M. 
Published: November 2023

AbstractHalbleiterbandstrukturuntersuchungen mit Hilfe der Elektroreflexion werden in zunehmendem Maße am Halbleiterelektrolytkontakt durchgeführt. An der Phasengrenze Germanium‐Elektrolyt konnte für den direkten Band‐Band‐Übergang der Zusammenhang zwischen elektrischer Feldstärke in der Elektrodenoberfläche und Elektroreflexionssignal gefunden werden. Umgekehrt kann damit aus dem Elektroreflexionssignal der Polarisationszustand der Germaniumelektrode ermittelt werden. Besondere Bedeutung erlangt dieses Verfahren für Elektrodenpotentialbereiche, in denen Kapazität‐ und Leitfähigkeitsmessungen durch elektrochemische Reaktionen beeinflußt werden. Damit ist es möglich, mit Hilfe der Elektroreflexion auch im thermodynamischen Nichtgleichgewicht die Bandverbiegung und damit die Feldstärke in der Germaniumoberfläche anzugeben. In diesem Zusammenhang werden Meßergebnisse mitgeteilt und diskutiert.
Experiments with Optical Image Reconstruction of High Resolution Electron Micrographs
Authors: Thon F. , Siegel B. M. 
Published: November 2023

AbstractA light optical image reconstruction apparatus, especially designed for optical filtering of high resolution phase contrast electron micrographs, is described. According to theory, in the case of pure weak phase objects such a subsequent light optical filtering of the micrographs using coherent light is equivalent to filtering in the back focal plane of the electron microscope objective lens. The effectiveness and the reliability of the apparatus was tested by reconstruction experiments using several types of filters including zone correction plates.
Die Strahlenschädigung der Objekte als Grenze für die hochauflösende Elektronenmikroskopie
Authors: Scherzer O. 
Published: November 2023

AbstractEine untere Grenze für die Gefährdung organischer Moleküle bei dem Versuch, einzelne ihrer Atome abzubilden, ist dadurch gegeben, daß die Atome bei der elastischen Ablenkung der abbildenden Elektronen einen Rückstoß erfahren, der zum Zerreißen der chemischen Bindungen führen kann. Bei dünnen Objekten hängt diese untere Grenze, außer von der Auflösungsgrenze des Instruments, noch stark ab von den Ordnungszahlen der abzubildenden Atome und des Atoms, für dessen Gefährdung man sich interessiert. Die Strahlengefährdung der Objekte hängt nur wenig da von ab, ob man Elektronen oder Protonen als abbildende Strahlung verwendet und auf welche Energie man diese Teilchen beschleunigt. Sie ist ungefähr gleich groß bei Abbildung im Dunkelfeld und im vollen oder reduzierten Hellfeld. Im Abtast‐Mikroskop werden die Objekte stärker gefährdet.Um die erforderliche Auflösung zu erhalten, müssen entweder die Objektive sphärisch korrigiert oder die Elektronen durch Protonen ersetzt oder auf mehrere Millionen Volt beschleunigt werden. Die sphärische Korrektur kann entweder durch unrunde Zusatzlinsen oder durch Zonenblenden oder durch nachträgliche rechnerische oder analog‐optische Bild‐Rekonstruktion vorgenommen werden. Sollen Kohlenstoff‐Atome in Objekten abgebildet werden, die empfindlich gegen Bestrahlung und dicker als etwa hundert Atomschichten sind, dann versprechen nur zwei Verfahren Erfolg: die Abbildung durch Phasenkontrast im Hellfeld sphärisch und chromatisch korrigierter Linsen und die Bild‐Rekonstruktion. Durch Kombination beider Verfahren kann die Auswahl der für die Rekonstruktion geeigneten Aufnahmen erleichtert und die Zahl der notwendigen Einzel‐Aufnahmen erheblich vermindert werden. Wie hoch die Objektgefährdung über der angegebenen unteren Grenze liegt, hängt von der Struktur der abzubildenden Moleküle ab.
Abschätzung der Abbildungsparameter für die Auflösung mehrerer nicht‐periodischer Atomschichten in einem Bild
Authors: Niehrs H. , Ruska E. 
Published: November 2023

AbstractUm in einer elektronenmikroskopischen Aufnahme die Atomorte eines Präparates mit mehreren Atomschichten abzubilden, muß man eine subatomare Auflösung bei großer Schärfentiefe, also bei besonders kleiner Abbildungsapertur erreichen. Die für diese Aufgabe maßgeblichen Abbildungsparameter können übersichtlich als Funktion der Betriebsgrößen Öffnungsfehler 3. Ordnung und Beschleunigungsspannung dargestellt werden. Mit der Zahl der in einer Aufnahme aufzulösenden Atomschichten eines Präparats muß die Auflösung besser, die optimale Abbildungsapertur niedriger, die Beschleunigungsspannung höher, und darf der Öffnungsfehler 3. Ordnung größer bleiben. Wegen der geforderten sehr guten Auflösung müßten solche Elektronenmikroskope starrer als bisher gebaut und ruhiger als bisher aufgestellt werden. Dazu werden Vorschläge gemacht.
Beam and Specimen: Radiation Damage and Image Resolution
Authors: Cosslett V. E. 
Published: November 2023

AbstractEnergy loss of the electron beam in the specimen affects the electron microscopical resolution, owing to chromatic aberration, and causes radiation damage by ionisation, heating and direct ejection of atoms. Measurements recently made of the energy loss in carbonaceous specimens confirm that the effect on image resolution will be negligible in very high resolution microscopy. Additional assumptions are required in order to obtain the rate of ionisation and bond breakage. On the best evidence available, it is estimated that the order of 2 chemical events will be caused during the minimum exposure needed to image an atom. The rate of ejection of atoms from carbonaceous material can be calculated rather more accurately. About 1 atom in 2500–3000 would be ejected in such an exposure, which would probably not seriously degrade a macromolecule.
Die Rolle der Blind‐Komponente bei Präzisions‐Leitfähigkeits‐Messungen
Authors: Kortüm G. , Zahn E. V. 
Published: November 2023

AbstractAls „Präzisions‐Leitfähigkeits‐Messungen”︁ sollen Messungen bezeichnet werden, deren mittlerer Fehler 0,1% ist.Leitfähigkeitsmessungen, bei denen die Blind‐Komponente nur kompensiert, aber nicht gemessen wird, können niemals Präzisions‐Leitfähigkeitsmessungen sein. Dies gilt sowohl für die Messungen hoher wie niedriger Leitwerte. Im ersten Fall muß bei der rechnerischen Eliminierung des durch den Polarisationswiderstand verursachten Meßfehlers eine Parallel‐Schaltung in eine Serien‐Schaltung umgerechnet werden. Diese Rechnung ist nur dann fehlerfrei, wenn der Zahlenwert der Blind‐Komponente mit in die Rechnung hineingenommen wird. Im zweiten Fall verfälscht der Blind‐Widerstand der parallel zur Meßstrecke liegenden Elektroden‐Kapazität die Messungen. Die Größe der Fehler kennt man nur, wenn man den Wert der Blind‐Komponente kennt.Von einer Meßbrücke für Präzisions‐Leitfähigkeits‐Messungen muß daher gefordert werden, daß sie neben der Ohmschen Komponente auch die Blind‐Komponente mißt. Da die Blind‐Komponente von der Meßfrequenz v abhängt, ist ferner zu fordern, daß eine solche Meßbrücke eine möglichst große Variation von v zuläßt, ohne daß sich damit ihre Genauigkeit und Empfindlichkeit ändern. Es wird in dieser Arbeit gezeigt, daß man bei praktischen Leitfähigkeitsmessungen den mittleren Fehler dann und nur dann auf 0,1% drücken kann, wenn man zusätzlich auch die Blind‐Komponente mißt. Ein Unterschreiten dieser Fehlergrenze ist dagegen aus meßtechnischen Gründen nur in Ausnahmefällen möglich.
Pulse Radiolysis and Polarography: Polarograms and Structure of Short‐Lived Free Radicals
Authors: Bansal K. M. , Henglein A. , Sellers R. M. 
Published: November 2023

AbstractThe irreversible oxidation and reduction waves of some 20 radicals have been investigated. They are discussed with respect to the structure of the radicals and the mechanisms of the electrode processes involved. The effects that influence the position and shape of polarographic waves include double bond formation during the electron transfer, protonation of the radicals, differences in the atomic configuration, and solvent interactions between the radicals and their electrochemical products. The observed polarographic waves are also discussed with respect to possible distributions of occupied and unoccupied electronic levels of the systems R → R+ and R → R− (R = radical).
Deviations from Internal Equilibrium in Scales Growing on Metals in Corroding Gases
Authors: Wagner Carl 
Published: November 2023

AbstractConsequences of deviations from internal equilibrium in oxide or sulfide layers growing on metals in corrosive gases are examined. Under most conditions, only small deviations occur. Thus thermodynamic concepts such as electrochemical potentials of cations, anions and electrons can be used safely.
Die Torsionsscherung nematischer Schichten in elektrischen und magnetischen Feldern
Authors: Fischer F. , Wahl J. , Waltermann T. 
Published: November 2023

AbstractDie Deformation eines homöotropen nematischen flüssigen Kristalls (MBBA) durch Torsionsscherung in elektrischen und (oder) magnetischen Feldern wird anhand photographierter Interferenzfiguren vorgestellt. Dabei werden auch zeitlich veränderliche Deformationen untersucht, die eine definierte Erzeugung von Instabilitäten sowie von elektrischen und magnetischen Wandstrukturen erlauben. Ferner werden Möglichkeiten zur Bestimmung von Materialkonstanten aus den Interferenzfiguren aufgezeigt.
Zur Dynamik von magnetisch erzeugten Deformationen in nematischen flüssigen Kristallen
Authors: Heppke G. , Schneider F. 
Published: November 2023

AbstractEs wird die Zeitabhängigkeit der Orientierung des Direktors in einer randorientierten Probe eines nematischen flüssigen Kristalls unter dem Einfluß eines Magnetfeldes theoretisch untersucht. Als experimentelles Anwendungsbeispiel wird die Wanderung von Inversionswänden betrachtet.
Speichereffekte in cholesterinischen Flüssigkeiten mit positiver DK‐Anisotropie
Authors: Walter K. H. , Krüger H. H. 
Published: November 2023

AbstractFür matrixadressierte, im Zeitmultiplexverfahren betriebene Flüssigkristall‐Anzeigen ist das Vorhandensein einer optischen Speicherung unabdingbar. Die in cholesterinischen Substanzen ausnutzbaren und bekannten Speichereffekte werden kurz beschrieben und einem neuen Effekt (Bistabilitätseffekt), der auf reiner Feldwirkung beruht und relativ kurze Einschreibzeiten aufweist, gegenübergestellt. Dieser neue Bistabilitätseffekt beruht auf den Hystereseeigenschaften des Texturübergangs cholesterinisch‐nematisch bei homöotroper Wandorientierung: In einem bestimmten Feldstärkebereich liegt in Abhängigkeit von der Vorgeschichte entweder die fokal‐konische oder die nematische Textur vor. Elektrooptische Kenndaten des Bistabilitätseffekts werden für ein spezielles Substanzgemisch gegeben.
On the Kinetics of Texture Changes in Electric Field Induced Cholesteric‐to‐Nematic Transitions
Authors: Rega H.‐U. , Sackmann E. 
Published: November 2023

AbstractThe kinetics of dc electric field induced texture changes in cholesteric phases were studied. The rapid changes in the transmission of polarized light, in the optical rotation and in the fluorescence intensity of a (dimethylaminonitro‐stilbene) fluorescence probe were measured. In a parallel static experiment the field induced texture changes as observed with a polarizing microscope were related to the above physical parameters. In addition the pitch was measured as a function of the field strength. The structural changes may be divided into three independent processes: grid deformation (at threshold field Fc1), rotation of the helix axis without change in the pitch (between F < F < 0.75 FCN) and unwinding of helical structure (at the critical field FCN). Hysteresis effects were observed for layer thicknesses comparable to the pitch. The relaxation from the field induced nematic to the planar state occurs in two separated steps characterized by different relaxation times: the retwisting of the helical structure and the rotation of the helix axis.The rapid transition to the nematic state occurs also in separated steps characterized by different rise times. Judged from the static experiment the first step involves the grid deformation and the second the rotation of the helix axis by 90°. The unwinding of the helix could not be observed by our means.For optical rotations larger than 90° the transmission transient exhibits oscillatory character. Very rapid rise times of the order od 70 μsec have been found in nematic systems doped with cholesteryl chloride.
Lateral Mobility of Pyrene in Model Membranes of Phospholipids with Different Chain Length
Authors: Galla H.‐J. , Sackmann E. 
Published: November 2023

AbstractThe coefficients of lateral diffusion, Dp, of pyrene in lipid bilayers of several 1,2‐diacyl‐phosphatidyl cholines (distearyllecithin (DSL), di‐palmitoyllecithin (DPL), dimyristoyllecithin (DML) and dilauryllecithin (DLL) above the corresponding lipid phase transition were determined. Dp was obtained from the second order rate constant, ka, of the pyrene excimer formation. It is found that the lateral mobility of an apolar molecule (such as pyrene) in the hydrophobic region of lipid lamella does not depend on the hydrocarbon chain length (Dp ≈︁ 2 · 10−7 cm2/sec at 60°C). The pyren mobility is characterized by an activation energy of ΔEp+ ≈︁ 10 kcal/mol. The experimental data are interpreted in terms of a simple model that is based on the assumption that the hopping frequency of a diffusing particle is determined by the rate of formation of free volume in the hydrocarbon moiety of the membrane. The latter is created by thermal activation of rotational isomers (essentially gtg‐kinks) in the hydrocarbon chains. The hopping frequency of the pyrene molecule is related to the jump frequency of the kinks along the hydrocarbon chains.
Proteomic and metabolomic characterizations of moyamoya disease patient sera
Authors: Guo Qingbao , Wang Qian‐Nan , Li Jingjie , Liu Simeng , Wang Xiaopeng , Yu Dan , Zou Zheng‐Xing , Gao Gan , Zhang Qian , Hao Fang‐Bin , Feng Jie , Yang Ri‐Miao , Wang Minjie , Fu Heguan , Bao Xiangyang , Duan Lian 
Published: November 2023

AbstractBackgroundThe pathogenesis of moyamoya disease (MMD) is unclear. Inflammation and immune imbalance have been identified as potential factors contributing to the occurrence and progression of MMD. However, the specific proteins and metabolites responsible for triggering this process are yet to be established. The purpose of this study is to identify differentially expressed proteins and metabolites in patients with MMD and perform Kyoto Encyclopedia of Genes and Genomes pathway integration analysis to pinpoint crucial proteins and metabolites involved in the disease.MethodsWe performed untargeted metabolomic and data‐independent acquisition proteomic analyses on the serum samples of individuals with MMD and healthy controls (HC).ResultsIn patients with MMD versus HC, 24 proteins and 60 metabolites, including 21 anionic metabolites and 39 cationic metabolites, which were significantly different, were identified. In patients with MMD, several proteins involved in inflammation and immune metabolism, such as tubulin beta‐6 and complement C4, were found to have significantly altered levels. Similarly, many metabolites involved in inflammation and immune metabolisms, such as dimethyl 4‐hydroxyisophthalate, beta‐nicotinamide mononucleotide, 2‐(3‐(4‐pyridyl)‐1H‐1,2,4‐triazol‐5‐yl)pyridine, and PC (17:1/18:2), were significantly altered. Intriguingly, these proteins and metabolites are involved in the progression of atherosclerosis through immune and inflammatory pathways, although some have never been reported in MMD. Moreover, integrated proteomics and metabolomics studies were conducted to determine shared pathways involving cholesterol metabolism, vitamin digestion, fat digestion, and absorption pathways of proteins and metabolites, which warrant further investigation.ConclusionsSignificant increases in pro‐inflammatory and immunosuppressive abilities have been observed in patients with MMD, accompanied by significant reductions in anti‐inflammatory and immune regulation. Various metabolites and proteins implicated in these processes have been identified for the first time. These findings hold immense significance for comprehending the pathogenesis of MMD and for the development of future drug therapies.
A phase 2 and pharmacological study of sapanisertib in patients with relapsed and/or refractory acute lymphoblastic leukemia
Authors: Al‐Kali Aref , Aldoss Ibrahim , Atherton Pamela J. , Strand Carrie A. , Shah Bijal , Webster Jonathan , Bhatnagar Bhavana , Flatten Karen S. , Peterson Kevin L. , Schneider Paula A. , Buhrow Sarah A. , Kong Jianping , Reid Joel M. , Adjei Alex A. , Kaufmann Scott H. 
Published: November 2023

AbstractBackgroundDespite recent approval of several new agents, relapsed acute lymphoblastic leukemia (ALL) remains challenging to treat. Sapanisertib (MLN0128/TAK‐228) is an oral TORC1/2 inhibitor that exhibited preclinical activity against ALL.MethodsWe conducted a single‐arm multi‐center Phase II study of sapanisertib monotherapy (3 mg orally daily of the milled formulation for 21 days every 28 days) in patients with ALL through the Experimental Therapeutics Clinical Trials Network (NCI‐9775).ResultsSixteen patients, 15 of whom were previously treated (median 3 prior lines of therapy), were enrolled. Major grade 3–4 non‐hematologic toxicities included mucositis (3 patients) and hyperglycemia (2 patients) as well as hepatic failure, seizures, confusion, pneumonitis, and anorexia (1 patient each). Grade >2 hematological toxicity included leukopenia (3), lymphopenia (2), thrombocytopenia, and neutropenia (1). The best response was stable disease in 2 patients (12.5%), while only 3 patients (19%) were able to proceed to Cycle 2. Pharmacokinetic analysis demonstrated drug exposures similar to those observed in solid tumor patients. Immunoblotting in serially collected samples indicated limited impact of treatment on phosphorylation of mTOR pathway substrates such as 4EBP1, S6, and AKT.ConclusionIn summary, single‐agent sapanisertib had a good safety profile but limited target inhibition or efficacy in ALL as a single agent. This trial was registered at ClinicalTrials.gov as NCT02484430.
Computational Exploration of Fluorocyclopentenyl‐purines and‐pyrimidines Derivatives as Potential Inhibitors of Epidermal Growth Factor Receptor (EGFR) for the Treatment of Breast Cancer
Authors: Abida Ejaz Syeda , Sajjad Bilal Muhammad , Aziz Mubashir , Wani Tanveer A. , Zargar Seema , Fayyaz Ammara , Hassan Sidra , Ahmed Aftab , Al Kahtani Hammad M. , Siddique Farhan 
Published: November 2023

AbstractThe Epidermal Growth Factor Receptor (EGFR) is an important therapeutic target for the treatment of a variety of epithelial malignancies, including breast cancer, in which EGFR is aberrantly expressed.The fluorocyclopentenyl‐purine‐pyrimidines derivatives, which have previously been described as powerful compounds against breast cancer, were selected to investigate their potential against EGFR using computational tools in an effort to obtain potent inhibitors with fewer adverse effects. The molecule's chemical reactivity and stability were assessed by determining the HOMO‐LUMO energy gap using density functional theory (DFT) calculations. Among all the selected compounds, PU4 displayed a HOMO‐LUMO gap of 0.191 eV. Additionally, molecular docking analysis was performed to assess the binding affinities of PU4 within the active pocket of EGFR‐TK. The compound PU4 showed potent interactions with EGFR exhibiting −32.3 kJ/mol binding energy which was found best as compared to gefitinib i. e., −27.4 kJ/mol which was further validated by molecular dynamics simulations and ADMET analysis. The results of these analyses indicate that the top hits obtained from the virtual screening possess the ability to act as effective EGFR inhibitor. Therefore, it is recommended to further investigate the inhibitory potential of these identified compounds using in vitro and in vivo approaches.
Enzymatic S‐Methylation of Thiols Catalyzed by Different O‐Methyltransferases
Authors: Abdelraheem Eman , Jockmann Emely , Li Jianyu , Günther Stefan , Andexer Jennifer N. , Hagedoorn Peter‐Leon , Hanefeld Ulf 
Published: November 2023

AbstractS‐Adenosyl‐l‐methionine (SAM)‐dependent methyltransferases (MTs) are highly chemoselective enzymes grouped in C‐, N‐, O‐, S‐ and halide MTs, depending on the (hetero) atom that acts as the methyl group acceptor. So far, OMTs present the largest group, including many well investigated candidates. The catechol OMT from mammals such as from Rattus norvegicus (RnCOMT) is involved in the metabolism of neurotransmitters like dopamine. It is known to methylate the hydroxyl of the catechol ring in the 3 position. There are also reports showing that the regioselectivity of different COMTs can vary leading to different products with methyl groups in the 3 and or 4 positions. Nevertheless, there was only O‐methylation reported for COMTs. Another related MT, the caffeate OMT involved in the lignin biosynthesis of plants has also been reported as a chemoselective enzyme. In nature, S‐methylation is a rare phenomenon with different methyl donors being involved in the methyl transfer onto sulfur atoms. Several SAM‐dependent MTs are identified as S‐methyltransferases (SMTs), these are involved in salvaging pathways and xenobiotic metabolism of cells. Here, we report a new function of three OMTs; RnCOMT, a COMT from Myxococcus xanthus (MxSafC), and a CaOMT from Prunus persica (PpCaOMT) with acceptance towards different aromatic thiol substrates with up to full conversion.
Glycerol Oligomerization over Titania‐Based Catalyst Compositions
Authors: Vlasenko Nina V. , Yanushevska Olena I. , Didenko Olga Z. , Strizhak Peter E. 
Published: November 2023

AbstractThe possibility of using TiO2‐based compositions: individual and sulfated titania, and their composites with carbon nanotubes as catalysts for glycerol oligomerization has been displayed. The effect of modification of TiO2 with sulfur and carbon nanotubes on acid‐base and catalytic characteristics in the glycerol conversion was investigated. The activation of glycerol on the catalysts has been studied using attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy. Only the samples based on sulfated titania are active over glycerol transformation, showing up to 58.7 % conversion. This is explained by the presence of strong base sites. Glycerides up to pentaglycerides, both linear and nonlinear structure are formed by glycerol oligomerization over TiO2−S. The addition of nanotubes to the catalyst reduces both the glycerol conversion (up to 10.5 %) and the yield of glycerides. However, the spectrum of the resulting products is significantly narrowed, increasing the selectivity for short‐chain glycerides: the portion of diglycerides reaches 72 %, and triglycerides 21 %. Herewith, glycerides of a linear structure only formed.
Cooperation between p‐Block Elements and Redox‐Active Ligands: Stoichiometric and Catalytic Transformations
Authors: Karnbrock Simon B. H. , Alcarazo Manuel 
Published: November 2023

AbstractThe relevance acquired by redox‐active ligands in modern catalysis stems from their facile delivery and acceptance of electrons, either to the metal they coordinate to, or directly to an incoming substrate that also binds the central metal. Doing that, they generate coordinated radicals and provide access to more than one spin state during the catalytic cycle. As a consequence, the new reaction barriers are reduced when compared to similar processes that are restricted to a single spin surface. The principles that govern this genuine approach to catalyst design are well‐established, and their implementation has allowed the development of synthetically useful catalytic transformations; however, the extension of the concept to species in which p‐block elements take the role of central atoms remains largely underdeveloped. Through discussion of the key achievements and recent progress, this Concept Article highlights this original approach to designing (organo)catalysts, discloses the progress achieved, and also reveals the many shortcomings that still exist in the field.