bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrative analysis of DNA replication origins and ORC binding sites in human cells reveals a lack of overlap between them
Authors: Tian Mengxue , Wang Zhenjia , Su Zhangli , Shibata Etsuko , Shibata Yoshiyuki , Dutta Anindya , Zang Chongzhi
Published: August 2023

DNA replication initiates from ∼50,000 origins on human chromosomes in each cell-cycle and the origins are hypothesized to be specified by binding of factors like the Origin Recognition Complex (ORC) or CTCF or other features like G-quadruplexes. We have performed an integrative analysis of 113 genome-wide human origin profiles (from five different techniques) and 5 ORC-binding site datasets to critically evaluate whether the most reproducible origins are specified by these features. Out of ∼7.5 million 300 bp chromosomal fragments reported to harbor origins by all the datasets, only 0.27% were reproducibly detected by four techniques (20,250 shared origins), suggesting extensive variability in origin usage and identification in different circumstances. 21% of the shared origins overlap with transcriptional promoters, posing a conundrum. Although the shared origins overlap more than union origins with constitutive CTCF binding sites, G-quadruplex sites and activating histone marks, these overlaps are comparable or less than that of known Transcription Start Sites, so that these features could be enriched in origins because of the overlap of origins with epigenetically open, promoter-like sequences. Only 6.4% of the 20,250 shared origins were within 1 kb from any of the ∼13,000 reproducible ORC binding sites in human cancer cells, in contrast to the nearly 100% overlap between the two in the yeast,
S. cerevisiae
. Thus, in human cancer cell-lines, replication origins appear to be specified by highly variable stochastic events dependent on the high epigenetic accessibility around promoters, without extensive overlap between the most reproducible origins and ORC-binding sites.
An open-source, high-resolution, automated fluorescence microscope
Authors: Zehrer Ando Christian , Martin-Villalba Ana , Diederich Benedict , Ewers Helge
Published: August 2023

Fluorescence microscopy is a fundamental tool in the life sciences, but the availability of sophisticated equipment required to yield high-quality, quantitative data is a major bottleneck in data production in many laboratories worldwide. This problem has long been recognized and the abundancy of low-cost electronics and the simplification of fabrication through 3D-printing have led to the emergence of open-source scientific hardware as a research field. Cost effective fluorescence microscopes can be assembled from cheaply mass-produced components, but lag behind commercial solutions in image quality. On the other hand, blueprints of sophisticated microscopes such as light-sheet or super-resolution systems, custom-assembled from high quality parts, are available, but require a high level of expertise from the user. Here, we combine the UC2 microscopy toolbox with high-quality components and integrated electronics and software to assemble an automated high-resolution fluorescence microscope. Using this microscope, we demonstrate high resolution fluorescence imaging for fixed and live samples. When operated inside an incubator, long-term live-cell imaging over several days was possible. Our microscope reaches single molecule sensitivity, and we performed single particle tracking and SMLM super-resolution microscopy experiments in cells. Our setup costs a fraction of its commercially available counterparts but still provides a maximum of capabilities and image quality. We thus provide a proof of concept that high quality scientific data can be generated by lay users with a low-budget system and open-source software. Our system can be used for routine imaging in laboratories that do not have the means to acquire commercial systems and through its affordability can serve as teaching material to students.
Multi-level processing of emotions in life motion signals revealed through pupil responses
Authors: Yuan Tian , Wang Li , Jiang Yi
Published: August 2023

Perceiving emotions from the movements of other biological entities is critical for human survival and interpersonal interactions. Here, we report that emotional information conveyed by point-light biological motion (BM) triggered automatic physiological responses as reflected in pupil size. Specifically, happy BM evoked larger pupil size than neutral and sad BM, while sad BM induced a smaller pupil response than neutral BM. Moreover, this happy over sad pupil dilation effect is negatively correlated with individual autistic traits. Notably, emotional BM with only local motion features retained could also exert modulations on pupils. Compared with intact BM, both happy and sad local BM evoked stronger pupil responses than neutral local BM starting from an earlier time point, with no difference between the happy and sad conditions. These results revealed a fine-grained pupil-related emotional modulation induced by intact BM and a coarse but rapid modulation by local BM, demonstrating multi-level processing of emotions in life motion signals. Taken together, our findings shed new light on BM emotion processing, and highlight the potential of utilizing the emotion-modulated pupil response to facilitate the diagnosis of social cognitive disorders.
Structural characterization of ligand binding and pH-specific enzymatic activity of mouse Acidic Mammalian Chitinase
Authors: Díaz Roberto Efraín , Ecker Andrew K , Correy Galen J , Asthana Pooja , Young Iris D , Faust Bryan , Thompson Michael C , Seiple Ian B , Van Dyken Steven , Locksley Richard M , Fraser James S
Published: August 2023

Chitin is an abundant biopolymer and pathogen-associated molecular pattern that stimulates a host innate immune response. Mammals express chitin-binding and chitin-degrading proteins to remove chitin from the body. One of these proteins, Acidic Mammalian Chitinase (AMCase), is an enzyme known for its ability to function under acidic conditions in the stomach but is also active in tissues with more neutral pHs, such as the lung. Here, we used a combination of biochemical, structural, and computational modeling approaches to examine how the mouse homolog (mAMCase) can act in both acidic and neutral environments. We measured kinetic properties of mAMCase activity across a broad pH range, quantifying its unusual dual activity optima at pH 2 and 7. We also solved high-resolution crystal structures of mAMCase in complex with oligomeric GlcNAcn, the building block of chitin, where we identified extensive conformational ligand heterogeneity. Leveraging these data, we conducted molecular dynamics simulations that suggest how a key catalytic residue could be protonated via distinct mechanisms in each of the two environmental pH ranges. These results integrate structural, biochemical, and computational approaches to deliver a more complete understanding of the catalytic mechanism governing mAMCase activity at different pH. Engineering proteins with tunable pH optima may provide new opportunities to develop improved enzyme variants, including AMCase, for therapeutic purposes in chitin degradation.
Task-specific invariant representation in auditory cortex
Authors: Heller Charles R , Hamersky Gregory R , David Stephen V
Published: August 2023

Categorical sensory representations are critical for many behaviors, including speech perception. In the auditory system, categorical information is thought to arise hierarchically, becoming increasingly prominent in higher-order cortical regions. The neural mechanisms that support this robust and flexible computation remain poorly understood. Here, we studied sound representations in the ferret primary and non-primary auditory cortex while animals engaged in a challenging sound discrimination task. Population-level decoding of simultaneously recorded single neurons revealed that task engagement caused categorical sound representations to emerge in non-primary auditory cortex. In primary auditory cortex, task engagement caused a general enhancement of sound decoding that was not specific to task-relevant categories. These findings are consistent with mixed selectivity models of neural disentanglement, in which early sensory regions build an overcomplete representation of the world and allow neurons in downstream brain regions to flexibly and selectively read out behaviorally relevant, categorical information.
An engineered biosensor enables dynamic aspartate measurements in living cells
Authors: Davidsen Kristian , Marvin Jonathan S , Aggarwal Abhi , Brown Timothy A , Sullivan Lucas B
Published: August 2023

Intracellular levels of the amino acid aspartate are responsive to changes in metabolism in mammalian cells and can correspondingly alter cell function, highlighting the need for robust tools to measure aspartate abundance. However, comprehensive understanding of aspartate metabolism has been limited by the throughput, cost, and static nature of the mass spectrometry (MS)-based measurements that are typically employed to measure aspartate levels. To address these issues, we have developed a green fluorescent protein (GFP)-based sensor of aspartate (jAspSnFR3), where the fluorescence intensity corresponds to aspartate concentration. As a purified protein, the sensor has a 20-fold increase in fluorescence upon aspartate saturation, with dose-dependent fluorescence changes covering a physiologically relevant aspartate concentration range and no significant off target binding. Expressed in mammalian cell lines, sensor intensity correlated with aspartate levels measured by MS and could resolve temporal changes in intracellular aspartate from genetic, pharmacological, and nutritional manipulations. These data demonstrate the utility of jAspSnFR3 and highlight the opportunities it provides for temporally resolved and high-throughput applications of variables that affect aspartate levels.
Structural basis for kinase inhibition in the tripartite E. coli HipBST toxin–antitoxin system
Authors: Bærentsen René L , Nielsen Stine V , Skjerning Ragnhild B , Lyngsø Jeppe , Bisiak Francesco , Pedersen Jan Skov , Gerdes Kenn , Sørensen Michael A , Brodersen Ditlev E
Published: August 2023

Many bacteria encode multiple toxin–antitoxin (TA) systems targeting separate, but closely related, cellular functions. The toxin of the Escherichia coli hipBA system, HipA, is a kinase that inhibits translation via phosphorylation of glutamyl-tRNA synthetase. Enteropathogenic E. coli O127:H6 encodes the hipBA-like, tripartite TA system; hipBST, in which the HipT toxin specifically targets the tryptophanyl-tRNA synthetase, TrpS. Notably, in the tripartite system, the function as antitoxin has been taken over by the third protein, HipS, but the molecular details of how activity of HipT is inhibited remain poorly understood. Here, we show that HipBST is structurally different from E. coli HipBA and that the unique HipS protein, which is homologous to the N-terminal subdomain of HipA, inhibits the kinase through insertion of a conserved Trp residue into the active site. We also show how auto-phosphorylation at two conserved sites in the kinase toxin serve different roles and affect the ability of HipS to neutralize HipT. Finally, solution structural studies show how phosphorylation affects overall TA complex flexibility.
Sustentabilidade em transações de Fusões e Aquisições: uma revisão sistemática
Authors: Ballerini Lizete de Paula , Ballerini Reginaldo Luiz , Fontes Andrea Regina Martins
Published: August 2023

A relevância de questões ambientais, sociais e de governança (ESG) na tomada de decisão das empresas, principalmente em transações de fusão e aquisição (M&A), se deve a uma série de fatores. Se destacam o interesse dos Stakeholders em práticas ESG, a regulamentação governamental, a conscientização do público, e uma crescente percepção de que as empresas com práticas ESG bem-sucedidas têm um melhor resultado a longo prazo. Este estudo tem o objetivo de sistematizar o conhecimento científico existente nas pesquisas sobre ESG e M&A, através de uma análise bibliométrica e revisão sistemática utilizando a declaração Prisma 2020. Os resultados identificaram uma série de estudos que sugerem que o investimento em ESG tem maior eficiência a longo prazo, considerando o aumento da riqueza para acionistas e do valor corporativo. Além de obter melhores resultados financeiros, melhor reputação corporativa, atrair investimentos, maior satisfação dos funcionários, e longevidade dos negócios. Os resultados desses estudos sugerem que as empresas cada vez mais consideram importantes os aspectos ESG em suas decisões. Isso se deve a uma série de fatores, incluindo os benefícios financeiros, de reputação e de risco associados a boas práticas ESG. No entanto, é importante notar que os estudos sobre ESG e M&A ainda estão em seus estágios iniciais. Mais pesquisas são necessárias para confirmar os resultados encontrados.
Estrategias para el desarrollo turístico: caso Gachantivá Boyacá-Colombia
Authors: Torres Ligia Inés Melo , Melo Claudia Lorena Ortiz , Melo Laura Tatiana Ortiz
Published: August 2023

El turismo local es una prometedora alternativa para la generación de ingresos, mejora del bienestar y calidad de vida de las comunidades rurales, donde su éxito está asociado principalmente a una asertiva mezcla de estrategias, desde la planificación, reconocimiento, valoración y gestión de todos los recursos y capacidades que posee una localidad. Este artículo muestra resultados de una experiencia realizada en el municipio de Gachantivá, departamento de Boyacá, Colombia. Mediante la investigación participación-acción y el conocimiento de actores locales, se trabajaron acciones como el levantamiento de inventario de atractivos, tipos de turismo posibles de desarrollar y construcción de un calendario turístico integral, vinculando labores agrícolas, gastronómicas, deportivas, festividades, naturaleza, clima y afluencia de turistas. Propuesta fácilmente replicable que permite identificar atractivos turísticos en distintas categorías de un territorio, logrando mayor inclusión, ofertar servicios de acuerdo con la época del año, combinar rutas turísticas; apropiar espacios para recuperación de la biodiversidad, realizar mantenimiento e innovaciones para asegurar la sostenibilidad y calidad en los servicios.
Teoria crítica a luz de Freitag: um estudo bibliométrico no Brasil
Authors: Nobre Anna Cláudia dos Santos , de Oliveira Idelmárcia Dantas , Serafini Paula Gonçalves , De Almeida Mariana Rodrigues
Published: August 2023

Esta pesquisa é fruto de lacuna em pesquisas brasileiras, conforme apresentado por Freitag (1993). Segundo a autora, o Brasil permanecia – à época – ausente do debate sobre a Teoria Crítica que vinha sendo travado de forma intensa no cenário europeu e anglo-saxônico. Assim, este artigo objetiva descrever estudos sobre Teoria Crítica publicados em periódicos brasileiros em cinco anos (2012 a 2016), por meio de uma pesquisa bibliométrica descritiva, que utilizou a plataforma Capes como fonte primária de consulta. Os resultados indicam uma produção de pesquisa ainda tímida no Brasil, com enfoque predominantemente qualitativo (100%), na área da Filosofia (56%) e por meio de ensaios teóricos (100%). Não foram identificados artigos com contribuições empíricas, demonstrando uma lacuna para futuros estudos no Brasil.
Norm-Attainable Polynomials: Characterizations and Properties in Orthogonal Polynomial Families
Authors: N. E. Mogoi , S. B Apima
Published: August 2023

Norm-attainable polynomials play a crucial role in various mathematical contexts. This research paper investigates the characterizations and properties of norm-attainable polynomials in different orthogonal polynomial families. We explore their behavior, convexity, and positive definiteness. Additionally, we establish their norm-attainability in specific intervals for various weight functions. The findings contribute to a deeper understanding of norm-attainable polynomials and their applications in approximation theory and mathematical modeling.
Genotyping by Sequencing Reveals Genetic Relatedness and Duplicates amongst Local Cassava (Manihot esculenta Crantz) Landraces and Improved Genotypes in Kenya
Authors: Orek Charles , Kyallo Martina , Oluwaseyi Shorinola , Yao Nasser
Published: August 2023

Future demand for cassava is expected to increase in order to mitigate climatic changes, sustain food security and provide raw materials for industry. To meet these demands, adoption of modern omics methods ensures reliability, precision and timely delivery of more productive and resilient varieties. A total of 112 mix of duplicate clones, diverse local cassava landraces (LARs) and improved genotypes (IMGs) were genotyped using single nucleotide polymorphisms (SNPs) generated through genotyping by sequencing (GBS) approach. About 17% (5808) of the 33672 SNPs were used for hierarchical clustering and ADMIXTURE analysis for ancestries. Approximately 48 and 52% of the germplasms respectively formed 17 independent clusters (identical clones or duplicates) and admixtures (unique or non-duplicated clones). Of the duplicates, 10 clusters were formed from LARs, four from IMGs and three from a mix of both LARs and IMGs, revealing their genetic relatedness. Approximately 71 and 29% of clusters comprised cassava accessions from the same and different geographical regions, respectively, with the geographical restriction of clusters attributed to the limited movement of planting materials across the country, possibly due to a weak seed distribution system or disease-driven quarantine measures. The historical sharing or exchange of stakes or stem cuttings by farmers was linked to the duplication of LARs, whereas IMGs duplication may be associated with convergent evolution, selection, or sharing of common parentage. The high number of admixtures or unique clones implied minimal loss of genetic diversity. These findings can aid designing efficient and effective cassava improvement programs through development of a core set of diagnostic markers.
Use of Expedited Regulatory Programs and Clinical Development Times for FDA-Approved Novel Therapeutics
Authors: Wong Alissa K. , Mooghali Maryam , Ramachandran Reshma , Ross Joseph S. , Wallach Joshua D.
Published: August 2023

This cross-sectional study evaluates the duration between application to US Food and Drug Administration (FDA) and approval for new drugs and biologics in the US from 2015 to 2022.
An Alchemist of Super‐Cooled Liquid: The Art and Craft of Danny Lane
Authors: Spiller Neil
Published: August 2023

Sculpting with glass is often the choice of artist and designer Danny Lane. He can combine it with steel, timber, acid etching and numerous other techniques and materials, yet at its root Lane's life's work is glass. He teases it to its limits for artistic effect – extruding, moulding, dripping, colouring, striating, cracking and nibbling at its edges. The other partner in his arsenal is light, the way it flickers, beams, glitters and projects. In an interview with AD Editor Neil Spiller, he reveals his thoughts on his creative history, his beloved material and his influences. Danny Lane, Etruscan Chair, 2016 This design for a glass and steel chair was originally conceived in 1986, and has been through various modifications since then; 1990s glass became 25mm thick and the metal was refined, with Jimmy Choo high‐heeled shoe tips.
Photophysics of Conjugated Oligoelectrolytes Relevant to Two‐Photon Fluorescence‐Lifetime Imaging Microscopy
Authors: Zhu Ji‐Yu , Mikhailovsky Alexander , Wei Samuel Chan Jun , Moreland Alex , Limwongyut Jakkarin , Guarrotxena Nekane , Bazan Guillermo C.
Published: August 2023

Conjugated oligoelectrolytes (COEs) comprise a class of cell‐membrane intercalating molecules that serve as effective optical reporters. However, little is known about the photophysical properties of COEs in biological environments such as buffers, cell membranes, and intracellular organelles, which is critical to optimize performance. Herein, how COE self‐assembly depends on the dielectric environment (polarity and ion content) is explored based on the representative molecule 6‐ring phenylenevinylene (PV) conjugated oligoelectrolyte (COE‐S6), and its optical properties within mammalian cells are subsequently studied. Two‐photon fluorescence lifetime imaging microscopy (FLIM), confocal laser scanning microscopy, and optical properties in solutions are brought together to obtain information about the location, accumulation, and characteristics of the local surroundings. FLIM imaging lifetime phasor plots, decays, and fluorescence spectra on stained mammalian cells provide evidence of successful COE‐S6 internalization via endocytosis. The fluorescence lifetime of COE‐S6 is identical when in A549 mammalian cells and in giant unilamellar vesicle model membranes, thereby providing a correlation between living system and artificial constructs.
Star‐Shaped Organic Semiconductor with Extraordinary Thermomechanical Property and Solution Processability for Stable Perovskite Solar Cells
Authors: Wei Yuefang , Zhang Yuyan , Ren Yutong , Zhang Bing , Yuan Yi , Zhang Jing , Wang Peng
Published: August 2023

Achieving the desired thermomechanical properties for highly solution‐processable organic semiconductors is challenging but crucial for heat tolerance of emerging optoelectronic devices. To this end, the successful synthesis of triphenylene–ethylenedioxythiophene‐dimethoxytriphenylamine (TP–ETPA), a star‐shaped organic semiconductor, is reported through a direct arylation reaction that involves ETPA, an electron donor, being grafted densely onto TP, which possesses six electron‐equivalent functionalization sites. Remarkably, TP–ETPA exhibits significantly improved hole mobility compared to 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenyl‐amine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) at a given hole density, owing to its lower energetic disorder, larger average centroid distance, and smaller reorganization energy. TP–ETPA, with a molecular weight of 2888 Da and lacking flexible chains, demonstrates extraordinary solubility in nonpolar solvents, enabling the formation of dense, pinhole‐free films through solution codeposition with an air‐doping promoter. By utilizing the p‐doped TP–ETPA composite as the hole transport layer, perovskite solar cells with an average power conversion efficiency of 23.4% are successfully fabricated. Notably, these devices display significantly enhanced operational stability and thermal stability at 85 °C. Molecular dynamics simulations reveal that the TP–ETPA‐based hole transport layer possesses a high cohesive energy density, resulting in a large elastic modulus and slow diffusion of external species.
In Situ Self‐Elimination of Defects via Controlled Perovskite Crystallization Dynamics for High‐Performance Solar Cells
Authors: Wang Shiqiang , Yang Tinghuan , Yang Yingguo , Du Yachao , Huang Wenliang , Cheng Liwei , Li Haojin , Wang Peijun , Wang Yajie , Zhang Yi , Ma Chuang , Liu Pengchi , Zhao Guangtao , Ding Zicheng , Liu Shengzhong (Frank) , Zhao Kui
Published: August 2023

Understanding and controlling crystallization is crucial for high‐quality perovskite films and efficient solar cells. Herein, the issue of defects in formamidinium lead iodide (FAPbI3) formation is addressed, focusing on the role of intermediates. A comprehensive picture of structural and carrier evolution during crystallization is demonstrated using in situ grazing‐incidence wide‐angle X‐ray scattering, ultraviolet–visible spectroscopy and photoluminescence spectroscopy. Three crystallization stages are identified: precursors to the δ‐FAPbI3 intermediate, then to α‐FAPbI3, where defects spontaneously emerge. A hydrogen‐sulfate‐based ionic liquid additive is found to enable the phase‐conversion pathway of precursors → solvated intermediates → α‐FAPbI3, during which the spontaneous generation of δ‐FAPbI3 can be effectively circumvented. This additive extends the initial growth kinetics and facilitates solvent–FA+ ion exchange, which results in the self‐elimination of defects during crystallization. Therefore, the improved crystallization dynamics lead to larger grain sizes and fewer defects within thin films. Ultimately, the improved perovskite crystallization dynamics enable high‐performance solar cells, achieving impressive efficiencies of 25.14% at 300 K and 26.12% at 240 K. This breakthrough might open up a new era of application for the emerging perovskite photovoltaic technology to low‐temperature environments such as near‐space and polar regions.
Diamond Immersion Photodetector for 193 nm Lithography
Authors: Cheng Lu , Wang Zhao , Zheng Wei
Published: August 2023

At present, most photodetectors work in atmospheric or vacuum environments, which leaves a large gap for detection under liquid conditions. However, this kind of research is of great significance, especially for the monitoring of 193 nm vacuum UV (VUV) light in the immersion lithography system underwater. Here, the p‐type diamond single crystal (PDSC) is applied as the photoelectrode for the construction of a VUV immersion photodetector with a PDSC‐ultra‐pure water‐Pt structure and a high response to 193 nm light. Under 193 nm excitation (@8 µW) and at 0 V, the PDSC immersion photodetector demonstrates a favorable characteristic of having a high responsivity of 5 mA·W−1. Due to its exceptional performance, this device has been proven to function as a highly‐sensitive and self‐powered VUV detector, with significant potential for utilization in the monitoring of 193 nm light in immersion lithography systems.
Commercial massage tool‐induced spinal epidural hematoma
Authors: Tominaga Yoshiteru , Hirayama Ichiro , Nonaka Minaho , Yano Tetsuhiro , Ishii Mitsuru
Published: August 2023

Background

Spinal epidural hematoma (SEH), which may develop into an emergency condition, is a rare disease. Here, we present the case of a patient with SEH caused by cervical massage using a commercial massage tool.

Case Presentation

A 75‐year‐old man was brought to our hospital with a chief complaint of posterior neck pain during sleep. He had used a commercial massage tool before going to bed. Upon arrival, hypotension and respiratory failure were observed. His muscle strength in both the upper and lower extremities rated 0 on the manual muscle test, and sensory loss below the papillae was observed. His symptoms resolved spontaneously after 2 h. Magnetic resonance imaging suggested a spinal cord epidural hematoma at the C2/C3 to C3/C4 level. On day 6, the patient was discharged without any impairment.

Conclusion

Fatal complications could occur by cervical massage using a commercial massage tool.
Engineering Enzymes for Environmental Sustainability
Authors: Radley Emily , Davidson John , Foster Jake , Obexer Richard , Bell Elizabeth L. , Green Anthony P.
Published: August 2023

The development and implementation of sustainable catalytic technologies is key to delivering our net‐zero targets. Here we review how engineered enzymes, with a focus on those developed using directed evolution, can be deployed to improve the sustainability of numerous processes and help to conserve our environment. Efficient and robust biocatalysts have been engineered to capture carbon dioxide (CO2) and have been embedded into new efficient metabolic CO2 fixation pathways. Enzymes have been refined for bioremediation, enhancing their ability to degrade toxic and harmful pollutants. Biocatalytic recycling is gaining momentum, with engineered cutinases and PETases developed for the depolymerization of the abundant plastic, polyethylene terephthalate (PET). Finally, biocatalytic approaches for accessing petroleum‐based feedstocks and chemicals are expanding, using optimized enzymes to convert plant biomass into biofuels or other high value products. Through these examples, we hope to illustrate how enzyme engineering and biocatalysis can contribute to the development of cleaner and more efficient chemical industry.
Gold‐Catalyzed 1,2‐Dicarbofunctionalization of Alkynes with Organohalides**
Authors: Sancheti Shashank P. , Singh Yukta , Mane Manoj V. , Patil Nitin T.
Published: August 2023

Herein, we report the first gold‐catalyzed 1,2‐dicarbofunctionalization of alkynes using organohalides as non‐prefunctionalized coupling partners. The mechanism of the reaction involves an oxidative addition/π‐activation mechanism in contrast to the migratory insertion/cis‐trans isomerization pathway that is predominantly observed with other transition metals yielding products with anti‐selectivity. Mechanistic insights include several control experiments, NMR studies, HR‐MSMS analyses, and DFT calculations that strongly support the proposed mechanism.
A Photo‐ and Thermo‐Driven Azoarene‐Based Circularly Polarized Luminescence Molecular Switch in a Liquid Crystal Host
Authors: Kang Wenxin , Tang Yuqi , Meng Xianyu , Lin Siyang , Zhang Xinfang , Guo Jinbao , Li Quan
Published: August 2023

The development of chiral optical active materials with switchable circularly polarized luminescence (CPL) signals remains a challenge. Here an azoarene‐based circularly polarized luminescence molecular switch, (S, R, S)‐switch 1 and (R, R, R)‐switch 2, are designed and prepared with an (R)‐binaphthyl azo group as a chiral photosensitive moiety and two (S)‐ or (R)‐binaphthyl fluorescent molecules with opposite or the same handedness as chiral fluorescent moieties. Both switches exhibit reversible trans/cis isomerization when irradiated by 365 nm UV light and 520 nm green light in solvent and liquid crystal (LC) media. In contrast with the control (R, R, R)‐switch 2, when switch 1 is doped into nematic LCs, polarization inversion and switching‐off of the CPL signals are achieved in the resultant helical superstructure upon irradiation with 365 nm UV and 520 nm green light, respectively. Meanwhile, the fluorescence intensity of the system is basically unchanged during this switching process. In particular, these variations of the CPL signals could be recovered after heating, realizing the true sense of CPL reversible switching. Taking advantage of the unique CPL switching, the proof‐of‐concept for “a dual‐optical information encryption system” based on the above CPL active material is demonstrated.
Zur Morphologie fester Reaktionsschichten an Metallen
Authors: Kohlschütter V. , Krähenbühl E.
Published: August 2023

1. Die Entwicklung von Reaktionsschichten, die bei der Einwirkung von Halogenen auf Kupfer und Silber entstehen, wird mikroskopisch und gravimetrisch verfolgt.

2. Die Beobachtungen führen zur Unterscheidung von drei Stadien, die als Perioden einer „pseudomorphen”︁, einer „idiomorphen”︁ Schichtbildung und einer Sammelkristallisation gedeutet werden.

3. Die Merkmale der drei Formarten und ihrer Entstehungsweise werden festgestellt und der Verlauf der Reaktion damit in Zusammenhang gebracht.

4. Der Auffassung von Tammann, daß von Anfang an eine planparallele anisotrope Lamelle mit normaler Gitterordnung entsteht, wird die Anschauung gegenübergestellt, daß sich zuerst eine hochdisperse Schicht bildet, die die aus diesem Zustand folgenden Umwandlungen nach sich zieht.
The Electrical Double Layer in Methanol
Authors: Grahame David C.
Published: August 2023

The capacity of the electrical double layer between mercury and methanolic solutions of KF, NH4F, NH4Cl, and NH4NO3 has been measured. The results at 25° are qualitatively similar to those observed in aqueous solutions at elevated temperatures, and differ from those observed in water at 25°Chiefly in the absence of the familiar “hump”. A theory of the double layer proposed earlier according to which the capacity of the inner region is a function of the surface charge density q in the absence of specific adsorption has been tested and found to be very satisfactory in methanol solutions. A qualitative explanation is proposed for the shape of the capacity curves observed in methanol at 25° and in water at elevated temperatures. No adsorption of chloride ion from methanolic solutions of NH4Cl on cathodic polarization is indicated.
Oszillographische Studien zur irreversiblen Polarisation der kathodischen Nickelabscheidung. II
Authors: Reiser H. J. , Fischer H.
Published: August 2023

An einer kathodisch polarisierten Nickelelektrode wurde das Abklingen des Galvanipotentials nach Öffnen des Elektrolysestromkreises verfolgt (Stromdichten 10−4 bis 10−1 A/cm2; Elektrolyt mit NiCl2‐Lösung bei pH = 0–5,3). Im untersuchten Zeitraum von 6 · 10−3 sec lassen sich deutlich Widerstands‐ und Aktivierungsüberspannung voneinander trennen.

Bei den höheren Stromdichten ergab sich im Zeitraum von 2–6 · 10−3 sec ein Zusammenhang zwischen den durchlaufenen Potentialwerten und dem Logarithmus der Abklingzeit. Die Mitabscheidung von Wasserstoff beeinflußte Neigung und Potentiallage der Abklingkurven. Mit zunehmendem pH‐Wert tritt offenbar sekundäre Inhibition durch anfallendes kolloidales Nickelhydroxyd auf, deren Einwirkung auf beide untersuchte Überspannungsarten merklich ist.
Über die kinetischen Reduktionsgrenzströme des Formaldehyds in der tropfenden Quecksilberelektrode
Authors: Brdicaka Rudolf
Published: August 2023

Die polarographischen Grenzströme des Formaldehyds hängen von der Reaktionsgeschwindigkeit ab, mit welcher seine polarographisch reduzierbare nicht hydratisierte aldehydische Form aus der hydratisierten nicht reduzierbaren Form gebildet wird. Das Hydratationsgleichgewicht ist zugunsten der hydratisierten Form stark verschoben; die Geschwindigkeiten, mit denen sich das Gleichgewicht einstellt, gehorchen den Gesetzen der allgemeinen acidobasischen Katalyse. Es wurden frühere Messungen der polarographischen Grenzströme des Formaldehyds in Boratpuffern und in Natriumhydroxydlösungen experimentell überprüft.

Aus den neu erhaltenen Daten wurden nach der genauen Methode von Koutecký die Werte des Produkts der Hydratationskonstante des Formaldehyds und der Geschwindigkeitskonstante der Basen (OH−, H2BO3− und H2O) berechnet, welche die Dehydratation des Formaldehyds katalysieren und gemeinsam mit der Diffusion die Größe seiner Reduktionsgrenzströme bestimmen. Die Werte wurden hierauf zur Berechnung der Grenzströme des Formaldehyds in ungepufferten KCl‐Lösungen verwendet, wo die Einstellung des Hydratationsgleichgewichts außer durch das Wasser noch von den bei der Elektroreduktion des Formaldehyds entstehenden Hydroxyl‐Ionen katalysiert wird. Die nicht‐lineare Abhängigkeit der Grenzströme von der Konzentration des Formaldehyds, sowie auch die absoluten Werte, welche aus den theoretisch abgeleiteten Beziehungen berechnet wurden, stimmen zufriedenstellend mit den gemessenen Werten überein.
Die Reaktionsketten bei dem photochemischen Umsatz von Oxalylchlorid und von Phosgen mit Kohlenwasserstoffen
Authors: Runge F.
Published: August 2023

Oxalychlorid und Phosgen spalten unter Einwirkung von kurzwelligem Licht primär Chloratome ab, die mit einem aliphatischen Kohlenwasserstoff zu HCl und einem Radikal reagieren. Dieses Radikal kann mit Oxalylchlorid, aber nicht mit Phosgen reagieren, so daß man nur im ersten Fall schließlich zu einer Carbonsäure kommt. Der Beweis für den Ablauf der Kettenreaktion wird durch Zugabe von Chlor und Ausblendung der Wellenlängen erbracht, die von Oxalylchlorid bzw. Phosgen absorbiert werden.
Zur Kenntnis der Schmelzdiagramme gesättigter Fettsäuren
Authors: Kofler Adelheid
Published: August 2023

Die Schmelzdiagramme geradzahliger Fettsäuren enthalten 3 Mischkristallphasen, wobei sich die mittlere in je einem Eutektikum und einem Peritektikum von den beiden anderen Mischphasen absetzt. Die Mittelphase wird nicht als Verbindung, sondern als stabilisierte Zwischenphase aufgefaßt. Von den Systemen einer geradzahligen mit der benachbarten ungeradzahligen wird das System Margarin‐: Stearinsäure behandelt. Die stabilen Formen der beiden Fettsäuren bilden wahrscheinlich eine lückenlose Mischkristallreihe, die jedoch im mittleren Konzentrationsbereich ebenfalls von einer Zwischenphase überdeckt wird. Bei einer Differenz von 3 C‐Atomen können auch 2 Zwischenphasen auftreten.
Untersuchungen zum Strömungsdiffusions‐Effekt. IV Zur laminaren Strömungsstruktur wäßriger Lösungen starker Elektrolyte
Authors: Tollert Hans
Published: August 2023

Kürzlich wurden vom Verfasser eine empirisch und eine theoretisch hergeleitete Beziehung für die radiale Konzentrationsverschiebung in in ruhenden Flüssigkeiten laminar sedimentierenden Schüttungen von Kugeln von Zentimetergröße mitgeteilt, die zu übereinstimmenden Ergebnissen führten. Es sollte nun festgestellt werden, ob beide Gleichungen auch für laminar strömende Elektrolytlösungen Gültigkeit besitzen. Hierzu dienten Messungen an vier verschiedenen wäßrigen Elektrolytlösungen, nämlich Kaliumchlorid, Natriumchlorid und Kupfersulfat bei etwa 0,2 und 0,02 n sowie Salzsäure bei 0,2 n Konzentration. Die gemessene Konzentrationsverschiebung wurde mit der auf Grund der Theorie des Strömungsdiffusionseffekts berechneten verglichen, wobei eine befriedigende Übereinstimmung beobachtet wurde. Der Anstieg der Konzentrationsverschiebung mit zunehmender Verdünnung wurde molekularkinetisch gedeutet. Es wurde festgestellt, daß der Prandtlsche Mischungsweg dem Strömungsdiffusionsweg entspricht, der die radiale Entfernung des Teilchens von der Rohrwand darstellt.
Zum Mechanismus der Leclanché‐Zellen
Authors: Euler Joachim
Published: August 2023

In Leclanché‐Zellen findet man mehrere stromliefernde Mechanismen, die nacheinander — nebeneinander zur Stromlieferung beitragen. Mittels einer Betrachtung der Innenwiderstände wird es möglich, die Vorgänge elektrisch zu trennen. Gleichzeitig kann die Polarisation abgespalten werden. Die stromliefernden Vorgänge lassen sich im vorliegenden Falle auf α‐ und β‐MnO2 sowie γ‐MnOOH zurückführen. Parallel dazu findet man entsprechende Röntgenreflexe. Die hier neu entwickelte Betrachtungsweise wird gestützt durch Wechselstrommessungen und durch Betrachtungen des Temperaturkoeffizienten sowie durch Beobachtungen an anderen Systemen.
Über die Durchlässigkeit der sich bei der Elektrolyse wäßriger konzentrierter Chromsäurelösungen mit und ohne Schwefelsäure auf der Kathode bildenden Schichten für Wasserstoff und Chromsäure in Abhängigkeit von der Bezugsspannung
Authors: Breiter M. , Feigl H. , Knorr C. A.
Published: August 2023

Der Gesamtprozeß der elektrolytischen Reduktion konzentrierter wäßriger Chromsäurelösungen mit und ohne Schwefelsäurezusatz konnte an einer Palladiumelektrode in zwei gesondert beobachtbare, nacheinander ablaufende Teilvorgänge zerlegt durchgeführt werden1).

Zunächst wurde I. die Palladiumelektrode in reiner fremdanionenfreier Chromsäure kathodisch mit Wasserstoff beladen bzw. übersättigt. Dabei fand die Entladung der Wasserstoffionen und der Eintritt der dabei gebildeten Wasserstoffatome in das Innere des Metalls statt, die Reaktion des Wasserstoffs an der Elektrode mit dem Wasserstoffakzeptor Chromsäure war jedoch praktisch vollständig unterbunden.

Nach Übertragung der wasserstoffhaltigen Palladiumelektrode in eine mit etwas Schwefelsäure versetzte konzentrierte Chromsäurelösung erfolgte dann ohne äußeren Stromfluß (also ohne Vorgang I) II. die Umsetzung des Wasserstoffs in Palladium mit der Chromsäure.

Solange Vorgang II unterbunden war, fand außerdem III. in geringem Umfange an der übersättigten Elektrode eine Kombination der Wasserstoffatome zu molekularem Wasserstoff statt.
Über die Eigen‐ und Fremdassoziation von o‐Phthalsäureestern
Authors: Luther H. , Stein W.
Published: August 2023

Die Ultrarotspektren von Mischreihen verschiedener Phthalsäureester mit n‐Hexan, Chloroform und Polyvinylchlorid wurden gemessen. Nach Beschreibung der experimentellen Grundlagen wird besonders auf die Bandenverschiebung der C=O‐Schwingungen in den Phthalaten eingegangen. Es wird gezeigt, daß sich qualitativ Rückschlüsse auf das Lösungsvermögen in Abhängigkeit von den strukturbeeinflußten zwischenmolekularen Wechselwirkungen ziehen lassen und daß für die Mischreihe in Hexan quantitativ Aussagen über die Mischungswärmen gemacht werden können.
Sorption, oxidation and passivity
Authors: Hackerman Norman
Published: August 2023

The strikingly large initial effects observed in passivation phenomena are attributed to a temporary change associated with sorption of a suitable specie onto the clean metal in an amount corresponding to about a monolayer. It is agreed that permanent passivity stems from a thin, insoluble film of a compound of the metal but it is suggested that it forms by migration of the metal ion into the array displayed by the sorbed species. It is postulated that the more nearly a complete sorbed monolayer forms before metal ion migration starts the more likely is the formation of a defect‐free, fissure‐free compound film. The thickness of such films should be self‐limiting kinetically and should provide long‐lived passivity because they offer minimum opportunity for meeting of the reactants. In the condition offering optimum protection they are probably amorphous with a minimal number of grain boundaries. Further thickening, by temperature increase, by large applied potential, or by increased reactivity of the environment, should lead to crystallization and increased porosity by the introduction of more grain boundary paths, actual fissures, and increased lattice permeability. This results in loss of passivity unless the coherent sorption‐initiated film can be regenerated under the external scale. The effect of solution species either on activation or on passivation are associated with permeation of the “non‐porous” film or with adsorption competition which either aids or interferes with regeneration of the sorption‐initiated film.
Der Einfluß geringer Sauerstoffmengen auf das Verhalten von Metallelektroden
Authors: Burstein R. Ch.
Published: August 2023

Es werden Ergebnisse von Untersuchungen mitgeteilt, die sich mit den ersten Stufen der Metalloxydation befassen und die mit Hilfe von Messungen der Voltaspannung und elektrochemischen Messungen durchgeführt wurden. Nimmt man an Eisenelektroden, die verschiedene Mengen Sauerstoff adsorbiert haben, in alkalischen Lösungen Stromspannungskurven auf und mißt die Elektrodenkapazität, so ergibt sich, daβ die Aufnahme kleiner Sauerstoffmengen nicht passivierend wirkt, sondern das Metall in einen aktiveren Zustand überführen kann. Aus den Untersuchungen des Sauerstoffeinflusses auf die Elektrodenaustrittsarbeit folgt, daß sich das Kontaktpotential in Abhängigkeit von den Bedingungen der Wechselwirkung des Metalls mit dem Sauerstoff ändert. Unter den Bedingungen, unter denen eine Verminderung der Austrittsarbeit des Elektrons beobachtet wird, tritt eine Aktivierung der Elektrode ein und vice versa.
Die Passivität und Korrosionsbeständigkeit der nichtrostenden Stähle
Authors: Tomaschow N. D.
Published: August 2023

Es wird über Untersuchungen berichtet, die neue Möglichkeiten zur Erhöhung der Korrosionsbeständigkeit der passivierbaren Metalle und Legierungen ergeben. Diese bestehen darin, daß das elektrochemische Potential des zu schützenden Metalls in positiver Richtung verschoben wird, und zwar entweder durch anodische Polarisation oder Zulegierung minimaler kathodischer Bestandteile oder durch Abscheidung einer sehr dünnen, nicht vollig bedeckenden Schicht eines Edelmetalls auf der Metalloberfläche.

Es wurden die Erscheinungen bei anodischer und kathodischer Polarisation der nichtrostenden Stähle in sauren Lösungen untersucht (Transpassivität, anodischer Schutz, negativer Differenzeffekt, negativer und positiver Effekt des Kathodenschutzes).
Elektrolytische Passivierung einiger Aluminiumlegierungen
Authors: Charlon Paul , Darmois Eugene
Published: August 2023

Für die Herstellung elektrolytischer Ventile besitzen Aluminiumlegierungen Vorteile gegenüber dem reinen Metall. Sie erlauben insbesondere die Verwendung von neutralen Elektrolytlösungen und von Wechselstrom. Der zeitliche Verlauf der Impedanz bei der anodischen Passivierung mit konstanter Stromdichte ergibt einen linearen Zusammenhang zwischen Zeit und reziproker Stromdichte.
Kurzvorträge zum Hauptthema Dielektrische Untersuchungen zum Relaxationsverhalten verdünnter Lösungen im Mikrowellenbereich 2. Mitteilung
Authors: Zeil Werner , Haase Joachim , Stiefvater Otto
Published: August 2023

Von Lösungen des α‐Chlornaphthalins und 9‐Bromphenanthrens in Schwefelkohlenstoff wurden Real‐und Imaginärteil der Dielektrizitätskonstanten in Abhängigkeit von der Temperatur und Konzentration im Gebiet der anomalen Dispersion bestimmt. Alle Systeme zeigen mit zunehmender Temperatur ein immer stärker werdendes Abweichen vom Debye‐ Verhalten.

Die Messungen wurden mit Hilfe von Koaxial‐ bzw. Hohlraumresonatoren durchgeführt, deren Resonanzkurven mittels Meßsendern und Frequenzmeßgeräten aufgenommen wurden.
Experimentelle Untersuchungen zum Debye‐Effekt in Ionenlösungen
Authors: Millner R.
Published: August 2023

Die durch Ultraschallwellen in elektrolytischen Lösungen ausgelösten Wechselspannungen (Debye‐Effekt) erlauben die Massenbestimmung elektrolytischer Ionen. Es wird über Untersuchungen berichtet, die an ein‐und mehrwertigen Elektrolyt‐Lösungen durchgeführt wurden. Die erzielten Ergebnisse stehen in guter Übereinstimmung mit der Theorie. Ferner wird auf den Einfluß eines dem eigentlichen Debye‐Effekt überlagerten Störeffektes hingewiesen. Es gelang weiter, den Effekt in nichtwäßrigen Ionenlösungen nachzuweisen. Aus der Größe der gemessenen Wechselspannungen lassen sich weiter Aussagen über die Wechselwirkung zwischen Ion und Lösungsmittel gewinnen.
Photosensibilisierte Sauerstoffübertragung nach einem Redoxmechanismus
Authors: Kramer Horst E. A. , Maute Alfred
Published: August 2023

Die durch Thionin photosensibilisierte Sauerstoffübertragung auf Allylthioharnstoff als. Akzeptor läuft nicht nach dem Kautsky‐Mechanismus (d.h. über Singulettsauerstoff) ab, sondern ist ein Redoxprozeß. Die Rückbildung von Thionin nach einem Photolyseblitz wurde in Abhängigkeit von der Sauerstoffkonzentration bei zwei verschiedenen Anregungsintensitäten und pH‐Werten in wäßriger Lösung untersucht. Bei hohen Sauerstoffkonzentrationen wurde eine quadratische Abhängigkeit der Thioninrückbildung von der Anregungsintensität beobachtet, was eine Reaktion zwischen zwei Photoprodukten anzeigt.

Bei hohen Konzentrationen (0,2 m) an Allylthioharnstoff hängt weder die gebildete Menge von Semithionin noch der zeitliche Verlauf des Verschwindens von Semithionin vom Sauerstoffgehalt der Lösung ab. Die Abhängigkeit der Reaktionsgeschwindigkeit von Semithionin von der Ionenstärke wurde untersucht. Aus diesen Experimenten ergibt sich, daß der Reaktionspartner von Semithionin sowohl in sauerstofffreier als auch in sauerstoffgesättigter Lösung die Ladung + 1 trägt.
Reaktive Streuung in Molekularstrahlen: Cl+Br2
Authors: Beck D. , Engelke F. , Loesch H. J.
Published: August 2023

Die Reaktion Cl + Br., wurde in gekreuzten Molekularstrahlen untersucht. Aus der Winkelverteilung des Reaktionsproduktes ClBr ergibt sich: (a) ClBr wird vorzugsweise in die vordere Hemisphäre des Schwerpunktsystems gestreut; (b) ein großer Anteil der zur Verfügung stehenden Energie geht in innere Anregung des ClBr über; (c) die Lebensdauer des übergangszustandes (ClBr2) liegt unter einer Rotationsperiode.
Elektronenspektren 2,2'‐verknüpfter Diphenyle. Polarisationsgradspektren und Modellrechnungen Teil II: Diphenyl, o‐methylsubstituierte Diphenyle, Fluoren, 9,10‐Dihydrophenanthren
Authors: Hohlneicher Georg , Dörr Friedrich , Mika Norbert , Schneider Siegfried
Published: August 2023

In einer früheren Arbeit („Teil I”︁) wurden die Elektronenspektren von solchen 2,2′‐verknüpften Diphenylen behandelt, bei denen die Konjugation entlang des Molekülperimeters besonders wesentlich erscheint (Phenanthren und 9,10‐Diazaphenanthren). In der vorliegenden Arbeit werden Verbindungen untersucht, die im Gegensatz dazu nicht vom Standpunkt des Perimetermodells aus behandelt werden können. Der Vergleich der Elektronenspektren von Diphenyl und von o‐methylsubstituierten Diphenylen mit den Ergebnissen von Modellrechnungen ermöglicht auch im Spektralbereich 45‐55 kK eine Zuordnung der Elektronenbanden des Diphenyls. Für den Bereich längerwellig 45 kK werden die Ergebnisse früherer Arbeiten bestätigt. Der auffallende Unterschied zwischen dem Elektronenspektrum des Diphenyls und den Spektren des Fluorens und des 9,10‐Dihydrophenanthrens wird aus den verschiedenen Symmetrieverhältnissen erklärt. Die Annahme einer Hyperkonjugation der Alkylbrücken erweist sich als unnötig.