bluuebunny/crossref_metadata_2025_split huggingface dataset:
N‐Heterocyclic Carbene‐Catalyzed Atroposelective Synthesis of 5‐Indo‐1‐yl Pyran‐2‐ones with an N−C axis from Enals
Authors: Zhang Linxue , Wu Qianqian , Ren Min , Zhang Hailong , Zhang Xiaoxiang , Liu Jinhua , Fu Zhenqian 
Published: August 2023

AbstractA variety of 5‐indo‐1‐yl pyran‐2‐ones with an N−C axis were prepared via a carbene‐catalyzed oxidative [3+3] annulation of indole‐1‐pyruvate esters and enals. Asymmetric construction of pyran‐2‐one ring from enals ensures the realization of this strategy. The resulting compounds were converted into axially chiral N‐arylindoles with an N−C axis via a cycloaddtion aromatization.
Fluorogenic sensing of amorphous aggregates, amyloid fibers, and chaperone activity via a near‐infrared aggregation‐induced emission‐active probe
Authors: He Wei , Yang Yuanyuan , Qian Yuhui , Chen Zhuoyi , Zheng Yongxin , Zhao Wenping , Yan Chenxu , Guo Zhiqian , Quan Shu 
Published: August 2023

AbstractThe presence of protein aggregates in numerous human diseases underscores the significance of detecting these aggregates to comprehend disease mechanisms and develop novel therapeutic approaches for combating these disorders. Despite the development of various biosensors and fluorescent probes that selectively target amyloid fibers or amorphous aggregates, there is still a lack of tools capable of simultaneously detecting both types of aggregates. Herein, we demonstrate the quantitative discernment of amorphous aggregates by QM‐FN‐SO3, an aggregation‐induced emission (AIE) probe initially designed for detecting amyloid fibers. This probe easily penetrates the membranes of the widely‐used prokaryotic model organism Escherichia coli, enabling the visualization of both amorphous aggregates and amyloid fibers through near‐infrared fluorescence. Notably, the probe exhibits sensitivity in distinguishing the varying aggregation propensities of proteins, regardless of whether they form amorphous aggregates or amyloid fibers in vivo. These properties contribute to the successful application of the QM‐FN‐SO3 probe in the subsequent investigation of the antiaggregation activities of two outer membrane protein (OMP) chaperones, both in vitro and in their physiological environment. Overall, our work introduces a near‐infrared fluorescent chemical probe that can quantitatively detect amyloid fibers and amorphous aggregates with high sensitivity in vitro and in vivo. Furthermore, it demonstrates the applicability of the probe in chaperone biology and its potential as a high‐throughput screening tool for protein aggregation inhibitors and folding factors.
Impact of medical treatment for chronic rhinosinusitis on eustachian tube dysfunction
Authors: Adams Sarah M. , Derbarsegian Armo , Sedaghat Ahmad R. , Phillips Katie M. 
Published: August 2023

Key Points
CRS patients treated with medical management have improvement in ETD symptoms as reflected by lower ETDQ‐7 scores
However, appropriate CRS medical management may be limited in ability to significantly improve, or resolve, ETD
Development and evaluation of mixing mechanism of new transformable multiple impeller (AM impeller)
Authors: Furukawa Haruki , Takahashi Riki , Matsuoka Anna , Kato Yoshihito , Asayama Shinsuke , Morikawa Norihiro , Koh Seung‐Tae 
Published: August 2023

AbstractThe axial flow in the vessel was the most critical flow under the laminar region, where the Reynolds number was less than 10. The most popular impeller which generates the axial flow is a helical ribbon impeller, but the production cost is high. By combining some pitched blade impellers, authors developed a new impeller, the production cost is lower than that of the helical ribbon. The mixing performance was investigated in laminar region. The new impeller had the same mixing performance as a helical ribbon. The partial helical ribbon type has a down flow that originates from two locations and intersects twice near the mixing shaft, and the four‐stage pitched paddle type has two cylindrical down flows. AM impeller is not affected by the shaft, and it is considered to exhibit high mixing performance. The phase angle of the blades caused these characteristics of down flows of the AM impeller.
Narrow‐Pore Engineering of Vinylene‐Linked Covalent Organic Frameworks with Weak Interaction‐Triggered Multiple Responses
Authors: Zhu Lin , Zhang Qian , Meng Fancheng , Li Mengqi , Liang Qifeng , Zhang Fan 
Published: August 2023

AbstractVinylene‐linked covalent organic frameworks (COFs) are emerging as promising crystalline materials, but their narrow pore engineering is severely impeded by the weak reversibility of the carbon‐carbon double bond formation reaction, which has led to less exploration of their ultramicroporous structures and properties. Herein, we developed a single aromatic ring‐based tetratopic monomer, tetramethylpyrazine, which undergoes a smooth Knoevenegal condensation at its four arylmethly carbon atoms with linear aromatic dialdehyde monomers upon the self‐catalyzed activation of pyridine nitrogen‐containing monomers in the presence of an organic anhydride. This has resulted in the formation of two vinylene‐linked COFs, which both crystallized in orthorhombic lattices, and layered in AA stacking fashions along the vertical directions. They exhibit high surface areas and well‐tailored ultramicropore sizes up to 0.5 nm. The unique cross‐linking mode at two pairs of para‐positions of each pyrazine unit through carbon‐carbon double bonds afford them with π‐extended conjugation over the in‐plane backbones and substantial semiconducting characters. The resultant COFs can be well‐dispersed in water to form stable sub‐microparticles with negative charges (zeta potentials: ca. −30 mV), and exhibiting tunable aggregation behaviors through protonation/deprotonation. As a consequence, they exhibit pore‐size‐dependent colorimetric responses to various anions with different pKa values in high selectivity.
Biosynthesis of Cosmosporasides Reveals the Assembly Line for Fungal Hybrid Terpenoid Saccharides
Authors: Yuan Guan‐Yin , Zhang Jin‐Mei , Xu Qing‐Dong , Zhang Hua‐Ran , Hu Changhua , Zou Yi 
Published: August 2023

AbstractFungal hybrid terpenoid saccharides constitute a new and growing family of natural products with significant biomedical and agricultural activities. One representative family is the cosmosporasides, which feature oxidized terpenoid units and saccharide moieties; however, the assembly line of these building blocks has been elusive. Herein, a cos cluster from Fusarium orthoceras was discovered for the synthesis of cosmosporaside C (1) by genome mining. A UbiA family intramembrane prenyltransferase (UbiA‐type PT), a multifunctional cytochrome P450, an α,β‐hydrolase, an acetyltransferase, a dimethylallyl transferase (DMAT‐type PT) and a glycosyltransferase function cooperatively in the assembly of the scaffold of 1 using primary central metabolites. The absolute configuration at C4, C6 and C7 of 1 was also established. Our work clarifies the unexpected functions of UbiA‐type and DMAT‐type PTs and provides an example for understanding the synthetic logic of hybrid terpenoid saccharides in fungi.
Strong and Ultra‐tough Ionic Hydrogel Based on Hyperbranched Macro‐Cross‐linker: Influence of Topological Structure on Properties
Authors: Jiang Yu , Zhan Dezhi , Zhang Meng , Zhu Ying , Zhong Huiqing , Wu Yangfei , Tan Qinwen , Dong Xinhua , Zhang Daohong , Hadjichristidis Nikos 
Published: August 2023

AbstractThe application of hydrogels often suffers from their inherent limitation of poor mechanical properties. Here, a carboxyl‐functionalized and acryloyl‐terminated hyperbranched polycaprolactone (PCL) was synthesized and used as a macro‐cross‐linker to fabricate a super strong and ultra‐tough ionic hydrogel. The terminal acryloyl groups of hyperbranched PCL are chemically incorporated into the network to form covalent cross‐links, which contribute to robust networks. Meanwhile, the hydrophobic domains formed by the spontaneous aggregation of PCL chains and coordination bonds between Fe3+ and COO− groups serve as dynamic non‐covalent cross‐links, which enhance the energy dissipation ability. Especially, the influence of the hyperbranched topological structure of PCL on hydrogel properties has been well investigated, exhibiting superior strengthening and toughening effects compared to the linear one. Moreover, the hyperbranched PCL cross‐linker also endowed the ionic hydrogel with higher sensitivity than the linear one when used as a strain sensor. As a result, this well‐designed ionic hydrogel possesses high mechanical strength, superior toughness, and well ionic conductivity, exhibiting potential applications in the field of flexible strain sensors.
Unravelling the Molecular Structure and Confining Environment of an Organometallic Catalyst Heterogenized within Amorphous Porous Polymers**
Authors: Jabbour Ribal , Ashling Christopher W. , Robinson Thomas C. , Khan Arafat Hossain , Wisser Dorothea , Berruyer Pierrick , Ghosh Ashta C. , Ranscht Alisa , Keen David A. , Brunner Eike , Canivet Jérôme , Bennett Thomas D. , Mellot‐Draznieks Caroline , Lesage Anne , Wisser Florian M. 
Published: August 2023

AbstractThe catalytic activity of multifunctional, microporous materials is directly linked to the spatial arrangement of their structural building blocks. Despite great achievements in the design and incorporation of isolated catalytically active metal complexes within such materials, a detailed understanding of their atomic‐level structure and the local environment of the active species remains a fundamental challenge, especially when these latter are hosted in non‐crystalline organic polymers. Here, we show that by combining computational chemistry with pair distribution function analysis, 129Xe NMR, and Dynamic Nuclear Polarization enhanced NMR spectroscopy, a very accurate description of the molecular structure and confining surroundings of a catalytically active Rh‐based organometallic complex incorporated inside the cavity of amorphous bipyridine‐based porous polymers is obtained. Small, but significant, differences in the structural properties of the polymers are highlighted depending on their backbone motifs.
Modified corn stalk carboxymethyl cellulose, acrylic acid and SBA‐15 based composite hydrogel used for agricultural water retention
Authors: Zhang Hong , Zhang Xin , Qiao Shanpeng , Wang Bo , Zeng Xu , Ren Bo , Yang Xiaodong 
Published: August 2023

AbstractSBA‐15 is successfully incorporated into a composite superabsorbent hydrogel polymer (SAHP) by in situ graft polymerization of acrylic acid (AA) on a carboxymethyl cellulose (CMC) backbone using SBA‐15 as a filler. The structure and properties of the SAHPs are studied in detail by means of a variety of characterization methods, including Fourier transform infrared spectroscopy, X‐ray diffraction, and field emission scanning electron microscopy. And the effects of the originating mate‐rials (such as SBA‐15, initiator, cross‐linker, ratio of CMC to AA, and neutralization of AA) and pH on the water absorption properties are discussed. The obtained results show that the introduction of SBA‐15 have significant effect on the intrinsic structure of the superabsorbent. Importantly, the composite SAHP exhibit higher thermal stability and significant swelling as well as water retention capacity. The prepared SAHP show good sensitivity to various surfactant solutions, which not only have water retention applications in agriculture but also show potential applications in the field of biomaterials.
Stoichiometric Control of Guest Recognition of Self‐Assembled Palladium(II)‐Based Supramolecular Architectures
Authors: Algar Jess L. , Phillips James E. , Evans Jack D. , Preston Dan 
Published: August 2023

AbstractWe report flexible [Pd(L)2]2+ complexes where there is self‐recognition, driven by π‐π interactions between electron‐rich aromatic arms and the cationic regions they are tethered to. This self‐recognition hampers the association of these molecules with aromatic molecular targets in solution. In one case, this complex can be reversibly converted to an ‘open’ [Pd2(L)2]4+ macrocycle through introduction of more metal ion. This is accomplished by the ligand having two bidentate binding sites: a 2‐pyridyl‐1,2,3‐triazole site, and a bis‐1,2,3‐triazole site. Due to favourable hydrogen bonding, the 2‐pyridyl‐1,2,3‐triazole units reliably coordinate in the [Pd(L)2]2+ complex to control speciation: a second equivalent of Pd(II) is required to enforce coordination to bis‐triazole sites and form the macrocycle. The macrocycle interacts with a molecular substrate with higher affinity. In this fashion we are able to use stoichiometry to reversibly switch between two different species and regulate guest binding.
Verlauf und Produkte der Reduktion des Silberpolysilicats Ag2SiO3 mil Wasserstoffgas
Authors: Wodtcke Friedrich , Liebau Friedrich 
Published: August 2023

AbstractDie Kinetik der Reduktion des Ag2SiO3 wurde bei 0°C, 20°C, 40°C, 60°C und 80°C in konstantem Wasserstoffstrom untersucht und mit derjenigen der Reduktion des Ag2Si2O5 verglichen. Die Reaktionsordnung bezogen auf den Anteil an nicht reduziertem Silber ist 0 bei 0°C, 1 bei 20°C und steigt bei höheren Reduktionstemperaturen kontinuierlich bis 2,5 bei 80°C an. Es wird gefolgert, daß die Reduktion bei 0°C von der Oberfläche her erfolgt, während sie von 20°C ab gleichzeitig im gesamten Kristall abläuft, wobei die im kontinuierlichen Anstieg der Reaktionsordnung zum Ausdruck kommende Verzögerung der Reaktion auf die mit steigender Temperatur zunehmende Kondensation der bei der Reduktion gebildeten Polykieselsäure (H2SiO3)x zurückgeführt wird. Die Silberkristallite scheiden sich in bezug auf die kristallographischen Achsen der ursprünglichen Ag2SiO3‐Kristalle orientiert ab. Die hohe katalytische Aktivität derartiger Trägerkatalysatoren ist wahrscheinlich auf die bevorzugte Ausbildung der (111)‐Flächen des Silbers zurückzuführen.
O17‐NMR Study of Aqueous Electrolyte and Non‐electrolyte Solutions
Authors: Fister F. , Hertz H. G. 
Published: August 2023

AbstractIt is shown that the relaxation rate of the O17‐resonance in aqueous solution increase with increasing concentration for structure forming salts and decreases for structure breaking salts. This is precisely the behaviour which is to be expected from our knowledge of other properties of these systems. For solutes with inert alkyl groups the effect of the hydration of the second kind demands an increase of the relaxation rate of O17 which has been found to be true in this paper.Experimental results for the chemical shift of the O17 resonance for various solutions are reported and are discussed in their general connection with the chemical shifts of ionic nuclear resonances and with other pertinent observations.
Parawasserstoffumwandlung an Metallen, Oxiden und Sulfiden
Authors: Schönnagel Hans‐Jürgen 
Published: August 2023

AbstractDie Geschwindigkeit der Parawasserstoffumwandlung an den Metallen Fe, Cu, Ag und an den Oxiden Fe3O4, MnO, Cr2O3 und ZnO als Katalysator wurde als Funktion des H2O/H2‐Verhältnisses in der Gasphase gemessen, ferner an Cu2S als Funktion des H2S/H2‐Verhältnisses. An Eisen findet eine Abnahme und an Kupfer eine Zunahme der Reaktionsgeschwindigkeit mit steigendem H2O/H2‐Verhältnis statt, während an Silber die Reaktionsgeschwindigkeit unabhängig vom H2O/H2‐Verhältnis ist. An allen untersuchten Oxiden mit Ausnahme des ZnO steigt die Reaktionsgeschwindigkeit mit steigendem H2O/H2‐Verhältnis an. Die Reaktionsgeschwindigkeit an Cu2S steigt proportional (pH2S/pH2)1/2 und damit auch proportional der Konzentration an Defektelektronen in Cu2S. Eindeutig bestimmte Geschwindigkeiten der Parawasserstoff‐umwandlung an Oxiden sind im allgemeinen nur bei Vorgabe definierter H2O/H2‐Verhältnisse zu erwarten. Entsprechendes gilt für Sulfide und analoge Verbindungen.
Steady State Film Growth on Passive Iron in Neutral Solutions
Authors: Moshtev R. V. 
Published: August 2023

AbstractThe steady state growth kinetics of the oxide film on passive iron in neutral solutions was studied by galvanostatic and potentiostatic techniques. There is a good correlation of results obtained at constant c. d. and at constant potential. The experimental expressions relating to potential, layer thickness and oxidation rate make it clear that the steady state kinetic follows the classical Frenkel equation. The constants appearing in this equation were determined and compared with existing data. The temperature dependences of the passive film conductivity and of the field coefficient are also in accord with the mechanism of field assisted ionic transport over a potential barrier, as expressed by the classical rate equation.
Über den Einfluß von Schwermetallspuren auf die Kinetik des Redoxsystems Peroxidisulfat/Thiosulfat
Authors: Patat F. , Prölss H. 
Published: August 2023

AbstractSorgfältige Reinigung der verwendeten Ausgangssubstanzen, speziell des Lösungsmittels Wasser, führte zu einem Zeitgesetz zweiter Ordnung mit einer klaren ersten Ordnung, bezogen auf die Thiosulfatkonzentration. Der Ersatz des bidestillierten Wassers durch einfach destilliertes ergab Thiosulfatordnungen zwischen 0 und 1, die mit einer Überlagerung der unkatalysierten durch die Cu‐katalysierte Reaktion gedeutet werden. Die Anwendung geringster Mengen starker Komplexbildner bzw. von Fällungsreagenzien für Schwermetall‐ionen hatte eine charakteristische Verminderung der Reaktionsgeschwindigkeit bis zu einem reproduzierbaren, unteren Grenzwert zur Folge. Die unter diesen Bedingungen vorliegende unkatalysierte Reaktion, deren Aktivierungsenergie sich zu 17 kcal/mol ergab, wird durch ein einfaches Radikalschema interpretiert.Die Anwesenheit von Spuren der Schwermetalle Kupfer und Eisen verändert die Kinetik der Redoxreaktion völlig: Die für die Cu‐ und Fe‐katalysierten Reaktionen ermittelten Zeitgesetze weisen eine charakteristische nullte Ordnung bezüglich Thiosulfat auf. Die Aktivierungsenergie sinkt auf 13 bzw. 14 kcal/mol. Für die katalysierte Redoxreaktion wird ebenfalls ein Radikalschema vorgeschlagen, das den kinetischen Befunden gerecht wird. Das Auftreten von Kettenmechanismen konnte ausgeschlossen werden.
Kernresonanzuntersuchungen der Wasserstoffbrückenbindung. Die chemische Verschiebung von Aminprotonen
Authors: Suhr Harold 
Published: August 2023

AbstractDie chemische Verschiebung der NH‐Bande bei einer Reihe von primären und sekundären Aminen wurde bei unendlicher Verdünnung in Tetrachlorkohlenstoff und Dimethylsulfoxid bestimmt. Die Differenz der beiden Werte ist ein gutes Maß für die Wasserstoffbrückenakzeptorfähigkeit der Amine und ist eine lineare Funktion der Azidität.
Über die Elektronenspektren linearer Diaza‐ und Tetraaza‐Acene
Authors: Kummer Franz , Zimmermann Herbert 
Published: August 2023

AbstractDie Elektronenspektren der linearen Diaza‐ und Tetraaza‐Acene Pyrazin I, Chinoxalin II, Phenazin III, Benzo[b]phenazin IV, Dibenzo[b,i]phenazin V, Naphtho[2,3‐b]phenazin VI, Benzo [g]chinoxalino[2,3‐b]‐chinoxalin VII, Chinoxalino [2,3‐b]chinoxalin VIII und Benzo[g]chinoxalin IX wurden untersucht und mit denjenigen der homologen Acene und ihrer Monoazaderivate verglichen. Die Elektronenbanden von I‐IX konnten durch Spektrenvergleich zugeordnet werden. Die Spektren zeigen die charakteristischen Aromatenbanden 1La, 1Lb, 1Bb, (1Ba, 1Cb), die mit steigender Zahl anellierter Ringe ebenso wie bei den Acenen nach langen Wellen vorrücken. Beim Übergang von den Acenen zu den analogen Diaza‐ und Tetraaza‐Acenen wird das Intensitätsverhältnis 1Lb zu 1Lb stark zugunsten von 1Lb verschobenBei den Spektren der Diaza‐ bzw. Tetraaza‐Acene IV, VI, VII und IX beobachtet man neben den üblichen Aromatenbanden einen kurzwelligen, sehr intensiven, von den Nachbarbanden deutlich abgesetzten Übergang 1X, der in den Spektren der analogen Acene nicht aufgefunden werden konnte und dessen Klassifizierung im Rahmen des Perimetermodells offenbar unmöglich ist. Der Übergang wurde nur bei den untersuchten Heterocyclen der Symmetrie C2v gefunden, fehlt jedoch bei den Verbindungen der Symmetrie D2h.
Das Ladungsübergangsspektrum von Thiocyanat‐ und Selenocyanatkomplexen der Übergangsmetalle
Authors: Schmidtke Hans‐Herbert 
Published: August 2023

AbstractDas Spektrum einer Reihe N‐ und S‐(Se‐)gebundener Thiocyanat‐ und Selenocyanatkomplexe von Metallionen der drei Übergangsperioden wurde im sichtbaren und nahen UV‐Bereich aufgenommen. Insgesamt 47 intensive Banden von 38 verschiedenen tetra‐ und hexakoordinierten Metallkomplexen wurden als Ladungsübergangsbanden identifiziert. Die optischen Elektronegativitäten der Liganden ergeben sich zu x(‐NCS) = 2,6; x(‐SCN) = 2,9; x(‐SeCN) = 2,8. Daneben wurden weitere Elektronegativitätswerte für einige Metalle bestimmt. Das Auftreten unterschiedlicher Werte je nach Bindungsverhalten wird theoretisch erklärt. Außerdem wird die Frage diskutiert, ob bei quadratischer Symmetrie der Ligandenfeldparameter mit wachsender Zentralionenladung kleiner wird.
Application de la diffusion à l'ètude des interactions entre la Sérum Albumine Humaine et les cations métalliques
Authors: Salvinien De J. , Brun B. , Kamenka N. 
Published: August 2023

AbstractOn a essayé de mettre en évidence les interactions entre la Sérum Albumine Humaine et les ions zinc et calcium par mesure des coefficients de self‐diffusion des espèces en présence dans le milieu réactionnel.On a employé la méthode du tube capillaire. Les mesures sont faites à 25°C et 37°C en milieux tampons de différents pH. On a pu relier la mesure des coefficients de self‐diffusion an calcul de v, le nombre moyen de cations métalliques liés par molécule de protéine.
Self‐Diffusion of Spherical Ions and of Water in Aqueous solutions
Authors: Weiss Alarich , Nothnagel K. H. 
Published: August 2023

AbstractBy NMR‐Spin‐echo technique the self‐diffusion coefficients in aqueous solutions of a number of ions and of water have been measured. Measurements have been performed as a function of the concentration of the dissolved salt and of the temperature. Water (H2O) and heavy water (D2O) have been used as solvents. Only in the case of H2O, however, the self‐diffusion of the solvent has been measured. The following liquid systems have been studied in detail: LiClH2O (D,DH2O); Li2SiF6H2O (D,D,DH2O; [(CH3)4X]2YF6D2O with X  N, P, As, Sb, and Y  Si, Ge (D(CH3)4X+,DYF6−). At various concentrations the self‐diffusion coefficients of the ions and of the water as a function of the temperature may be described by an Arrhenius law. At constant concentration in some cases two different activation energies (frequency factors resp.) occur, one for an upper, the other for a lower temperature range. The result of the measurements are discussed and partially compared with theoretical calculations.
Dielectric Behaviour of solutions of Alkali Chlorides and Nitrates in the Microwave Region
Authors: Barthel J. , Behret H. , Schmithals F. 
Published: August 2023

AbstractAt 25°C the complex dielectric constants (DC) of solutions of alkali chlorides and nitrates in polar solvents are measured in the microwave region (1 GHz to 33 GHz). The interpretation of frequency dependence of the DC by relaxation processes shows increasing as well as decreasing relaxation times with increasing concentration of salt–according to the solvent.
Molecular Motion and Light Scattering in Liquids
Authors: Volterra V. , Bucaro J. A. , Litovitz T. A. 
Published: August 2023

AbstractThe use of light scattering techniques for the investigation of molecular motions in liquids is considered. In addition to orientational motion information about certain aspects of translational motion can be obtained. This information includes the details of isolated binary collisions, the correlation of successive collisions and structural relaxation time of the liquid lattice.