bluuebunny/crossref_metadata_2025 huggingface dataset:
Mass‐Spectrometric Imaging of Electrode Surfaces—a View on Electrochemical Side Reactions
Authors: Fangmeyer Jens , Behrens Arne , Gleede Barbara , Waldvogel Siegfried R. , Karst Uwe
Published: July 2020

Electrochemical side reactions, often referred to as “electrode fouling”, are known to be a major challenge in electro‐organic synthesis and the functionality of modern batteries. Often, polymerization of one or more components is observed. When reaching their limit of solubility, those polymers tend to adsorb on the surface of the electrode, resulting in a passivation of the respective electrode area, which may impact electrochemical performance. Here, matrix‐assisted laser‐desorption/ionization mass spectrometry (MALDI‐MS) is presented as valuable imaging technique to visualize polymer deposition on electrode surfaces. Oligomer size distribution and its dependency on the contact time were imaged on a boron‐doped diamond (BDD) anode of an electrochemical flow‐through cell. The approach allows to detect weak spots, where electrode fouling may take place and provides insight into the identity of side‐product pathways.
Atroposelective Ring Opening of Cyclic Diaryliodonium Salts with Bulky Anilines Controlled by a Chiral Cobalt(III) Anion
Authors: Zhang Xue , Zhao Kun , Li Na , Yu Jie , Gong Liu‐Zhu , Gu Zhenhua
Published: July 2020

The present work demonstrates a CuCl and anionic chiral cobalt(III)‐catalyzed enantioselective ring‐opening reaction. The small‐size, ligand‐free copper species enabled the cross‐coupling of iodonium salts with a series of bulky aromatic amines in high ee values. The chiral cobalt(III) anion causes appreciable chemical shift changes of cyclic diaryliodoniums in 1H NMR spectra.
Single‐Atom Electrocatalysts from Multivariate Metal–Organic Frameworks for Highly Selective Reduction of CO2 at Low Pressures
Authors: Jiao Long , Yang Weijie , Wan Gang , Zhang Rui , Zheng Xusheng , Zhou Hua , Yu Shu‐Hong , Jiang Hai‐Long
Published: July 2020

Single‐atom catalysts (SACs) are of great interest because of their ultrahigh activity and selectivity. However, it is difficult to construct model SACs according to a general synthetic method, and therefore, discerning differences in activity of diverse single‐atom catalysts is not straightforward. Herein, a general strategy for synthesis of single‐atom metals implanted in N‐doped carbon (M1‐N‐C; M=Fe, Co, Ni and Cu) has been developed starting from multivariate metal–organic frameworks (MOFs). The M1‐N‐C catalysts, featuring identical chemical environments and supports, provided an ideal platform for differentiating the activity of single‐atom metal species. When employed in electrocatalytic CO2 reduction, Ni1‐N‐C exhibited a very high CO Faradaic efficiency (FE) up to 96.8 % that far surpassed Fe1‐, Co1‐ and Cu1‐N‐C. Remarkably, the best‐performer, Ni1‐N‐C, even demonstrated excellent CO FE at low CO2 pressures, thereby representing a promising opportunity for the direct use of dilute CO2 feedstock.
Microsatellite development and detection of admixture among three sympatric Haploblepharus species (Carcharhiniformes: Scyliorhinidae)
Authors: van Staden Michaela , Gledhill Katie Samantha , Gennari Enrico , McCord Meaghen Erica , Parkinson Matthew , Watson Ralph Gareth Andrew , Rhode Clint , Bester‐van der Merwe Aletta Elizabeth
Published: July 2020

Haploblepharus is an understudied genus comprising four recognized scyliorhinid species that are endemic to southern Africa. Species identification within this group has historically been problematic due to a high degree of morphological conservatism among congeners, further complicated by the possibility of interspecific hybridization.

This study describes the development of two microsatellite panels comprising 10 polymorphic markers for the puffadder shyshark, Haploblepharus edwardsii. The markers were characterized in 35 H. edwardsii specimens and tested for cross‐species utility in Haploblepharus fuscus, Haploblepharus pictus, and the more distantly related scyliorhinid Halaelurus natalensis.

Genetic diversity statistics were estimated for each species, and the presence of population differentiation was tested for in H. edwardsii and H. pictus. Furthermore, interspecific genetic differentiation was examined to infer the potential use of these markers for species identification as well as for detecting signatures of admixture among Haploblepharus species.

All microsatellite markers were polymorphic in each species, with polymorphism information contents ranging from 0.43 to 0.62. Population differentiation was only evident for H. pictus, where genetic discontinuity was detected among geographically distant sampling sites.

Statistically significant differentiation (fixation index between populations FST = 0.091 to 0.382) was found between all species; however, the level of differentiation between H. fuscus and H. pictus was low in comparison and seemingly at a population level rather than at a species level. Species assignment using Bayesian clustering analysis resulted in approximately 57% of 88 genotyped specimens being unambiguously assigned to a distinct genetic cluster that confirmed accurate taxonomic assignment.

Overall, the low levels of differentiation together with the presence of distinct and admixed genetic clusters suggests a recent divergence and possible contemporary hybridization within the genus Haploblepharus. As such, conservation strategies should be focused on the generic level until such a time that Haploblepharus species can be readily identified.
Topological data analysis in digital marketing
Authors: Lakshminarayan Choudur , Yin Mingzhang
Published: July 2020

The ubiquitous internet is a multipurpose platform for finding information, an avenue for social interaction, and a primary customer touch‐point as a marketplace to conduct e‐commerce. The digital footprints of browsers are a rich source of data to drive sales. We use clickstreams (clicks) to track the evolution of session‐level customer browsing for modeling. We apply Markov chains (MC) to calculate probabilities of page‐level transitions from which relevant topological features (persistence diagrams) are extracted to determine optimal points (URL pages) for marketing intervention. We use topological summaries (silhouettes, landscapes) to distinguish the buyers and nonbuyers to determine the likelihood of conversion of active user sessions. Separately, we model browsing patterns via Markov chain theory to predict users' propensity to buy within a session. Extensive analysis of data applied to a large commercial website demonstrates that the proposed approaches are useful predictors of user behavior and intent. Utilizing computational topology in digital marketing holds tremendous promise. We demonstrate the utility of topological data analysis combined with MC and present its merits and disadvantages.
Doing more and doing better are two different entities: Different patterns of family control and environmental performance
Authors: Yu Byungjun , Zeng Saixing , Chen Hongquan , Meng Xiaohua , Tam Chiming
Published: July 2020

Family firms bear two types of agency costs, including type I and type II agency problems, in corporate environmental practices: (1) Outside executives at family firms hesitate to engage in environmental strategies, which can lead to drops in profits; (2) Controlling families employ opportunistically environmental management to achieve their interests. We argue that a primary cause for the agency problems lies on ineffective internal corporate governance at family firms, which can cause loss of managerial (or power) balance between outside executives and family executives. Our findings show that family firms with ownership and strategic control (FSC), which family executives and outside executives monitor and constrain each other, can achieve the highest environmental performance. Moreover, external controls, including product market competition and provincial environmental regulations, substitute effective internal control of FSC. The environmental performance premium of FSC is more prevalent when the production market competition is lower. Family firms with ownership, operational, and strategic control (FOSC) can achieve higher environmental performance within a province with more stringent environmental regulations.
miR‐495 and miR‐5688 are down‐regulated in non‐small cell lung cancer under hypoxia to maintain interleukin‐11 expression
Authors: Zhao Meng , Chang Jiao , Liu Ran , Liu Yahui , Qi Jin , Wang Yanhui , Zhang Xinwei , Qiao Lu , Jin Yu , An Haohua , Ren Li
Published: July 2020

Background

Hypoxia is a hallmark of cancer and is associated with poor prognosis. However, the molecular mechanism by which hypoxia promotes tumor progression remains unclear. MicroRNAs dysregulation has been shown to play a critical role in the tumor and tumor microenvironment. Here, we investigated the roles of miR‐495 and miR‐5688 in human non‐small cell lung cancer (NSCLC) and their underlying mechanism.

Methods

The expression levels of miR‐495 and miR‐5688 in human NSCLC tissue specimens were measured by quantitative real‐time polymerase chain reaction (qRT‐PCR). Deferoxamine (DFO) was used to determine whether the regulation of miR‐495 and miR‐5688 under hypoxia was dependent on hypoxia‐inducible factor 1‐alpha (HIF‐1α). Furthermore, the functions of miR‐495 and miR‐5688 in tumor progression were evaluated using colony formation, 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium (MTS), wound healing, transwell assays, and xenograft model. Two algorithms, PicTAR and Targetscan, were used to predict the target gene of these two miRNAs, and dual‐luciferase reporter assay was conducted to confirm the target. The unpaired two‐tailed t test, Pearson correlation analysis, and Fisher's exact probability test were performed for statistical analyses.

Results

Two miRNAs, miR‐495 and miR‐5688, were found to participate in NSCLC progression under hypoxia. They were down‐regulated in NSCLC tissues compared with normal tissues. We determined that hypoxia led to the down‐regulation of miR‐495 and miR‐5688 in NSCLC cells, which was independent of HIF‐1α and cellular metabolic energy. In addition, miR‐495 and miR‐5688 suppressed cell proliferation, migration, and invasion in vitro. The NSCLC xenograft model showed that miR‐495 and miR‐5688 inhibited tumor formation in vivo. Interestingly, we found that miR‐495 and miR‐5688 had the same target, interleukin‐11 (IL‐11). Recombinant human IL‐11 counteracted the effects of miR‐495 and miR‐5688 on NSCLC cells, suggesting that miR‐495 and miR‐5688 executed their tumor suppressive role by repressing IL‐11 expression.

Conclusion

We found that hypoxia down‐regulated the expression levels of miR‐495 and miR‐5688 in NSCLC to enhance IL‐11 expression and tumor progression, indicating that the miR‐495/miR‐5688/IL‐11 axis may serve as a therapeutic target and potential biomarker for NSCLC.
Extending the Library of Light‐Dependent Protochlorophyllide Oxidoreductases and their Solvent Tolerance, Stability in Light and Cofactor Flexibility
Authors: Schmermund Luca , Bierbaumer Sarah , Schein Viktor K. , Winkler Christoph K. , Kara Selin , Kroutil Wolfgang
Published: July 2020

Biocatalysis is increasingly used in combination with light to develop new and more sustainable synthetic methods. Thereby, mostly a chemical photocatalyst harvesting the light energy is combined with an established enzymatic reaction, thus the biocatalyst itself does not require the light for its specific reaction. Here we expand the library of an enzyme which requires light for its natural reaction, namely the light‐dependent protochlorophyllide oxidoreductase (LPOR). This enzyme catalyzes the NADPH‐dependent reduction of a C=C in a N‐heterocycle. Out of five LPORs identified by sequence search, four were found to be well expressible in E. coli and active. Investigating the light intensity, which is an important parameter describing energy input and subsequently may enable fast reaction, it turned out that the four LPORs can stand the maximum light intensity reachable with the equipment used (1450 μmol photons m−2 s−1). However, the natural substrate and product were degraded at these conditions, allowing only 15 % of the maximum input (211 μmol photons m−2 s−1). Furthermore, the LPORs accepted seven different water miscible solvents with a solvent content of up to 20 % v/v and were active at a pH from 6 to 10. While all LPORs known to date are exclusively NADPH dependent, two LPORs identified here were active also with NADH. The cofactor selectivity could be pinned to three amino acid residues, which interestingly do not directly bind to the cofactor.
Immobilization of Ethynyl‐π‐Extended Electron Acceptors with Amino‐Terminated SAMs by Catalyst‐Free Click Reaction
Authors: Nakano Kyohei , Sanematsu Haruki , Kaji Yumiko , Takai Atsuro , Tajima Keisuke
Published: July 2020

Surface modification of SiO2 using a catalyst‐free quantitative reaction between an amine and an ethynyl‐π‐extended naphthalenediimide was investigated. A post‐reaction method, in which the catalyst‐free reaction was performed at the surface after the formation of amino‐terminated self‐assembled monolayers (SAMs), resulted in dense, uniform modification of the SiO2 surface with the naphthalenediimide molecules. Both X‐ray reflectivity and angle‐resolved X‐ray photoemission spectroscopy showed consistent results for the layer thickness and density. In contrast, a pre‐reaction method, in which an amino‐silane and the ethynyl‐π‐extended naphthalenediimide reacted first and then formed a SAM, afforded a sparse SAM on the SiO2 surface, probably due to the steric hindrance of the naphthalenediimide moieties. The in situ decoration of the SiO2 surface by a catalyst‐free quantitative reaction offers a facile route for modifying surface properties with various π‐conjugated molecules suitable for many applications.
Unveiling the Occurrence of Co(III) in NiCo Layered Electroactive Hydroxides: The Role of Distorted Environments
Authors: Hunt Diego , Oestreicher Víctor , Mizrahi Martín , Requejo Félix G. , Jobbágy Matías
Published: July 2020

Co‐ and Ni‐based layered hydroxides constitute a unique class of two‐dimensional inorganic materials with exceptional chemical diversity, physicochemical properties and outstanding performance as supercapacitors and overall water splitting catalysts. Recently, the occurrence of Co(III) in these phases has been proposed as a key factor that enhance their electrochemical performance. However, the origin of this centers and control over its contents remains as an open question. We employed the Epoxide Route to synthesize a whole set of α‐NiCo layered hydroxides. The PXRD and XAS characterization alert about the occurrence of Co(III) as a consequence of the increment in the Ni content. DFT+U simulation suggest that the shortening of the Co−O distance promotes a structural distortion in the Co environments, resulting in a double degeneration in the octahedral Co 3d orbitals. Hence, a strong modification of the electronic properties leaves the system prone to oxidation, by the appearance of Co localized electronic states on the Fermi level. This work combines a microscopic interpretation supported by a multiscale crystallochemical analysis, regarding the so‐called synergistic redox behavior of Co and Ni, offering fundamental tools for the controllable design of highly efficient electroactive materials. To the best of our knowledge, this is the first computational–experimental investigation of the electronic and structural details of α‐NiCo hydroxides, laying the foundation for the fine tuning of electronic properties in layered hydroxides.
Red/NIR Thermally Activated Delayed Fluorescence from Aza‐BODIPYs
Authors: Avellanal‐Zaballa Edurne , Prieto‐Castañeda Alejandro , García‐Garrido Fernando , Agarrabeitia Antonia R. , Rebollar Esther , Bañuelos Jorge , García‐Moreno Inmaculada , Ortiz María J.
Published: July 2020

The search for long‐lived red and NIR fluorescent dyes is challenging and hitherto scarcely reported. Herein, the viability of aza‐BODIPY skeleton as a promising system for achieving thermal activated delayed fluorescent (TADF) probes emitting in this target region is demonstrated for the first time. The synthetic versatility of this scaffold allows the design of energy and charge transfer cassettes modulating the stereoelectronic properties of the energy donors, the spacer moieties and the linkage positions. Delayed emission from these architectures is recorded in the red spectral region (695–735 nm) with lifetimes longer than 100 μs in aerated solutions at room temperature. The computational‐aided photophysical study under mild and hard irradiation regimes disclose the interplay between molecular structure and photonic performance to develop long‐lived fluorescence red emitters through thermally activated reverse intersystem crossing. The efficient and long‐lasting NIR emission of the newly synthesized aza‐BODIPY systems provides a basis to develop advanced optical materials with exciting and appealing photonic response.
Tuning the Oxidation States of Dopants: A Strategy for the Modulation of Material Photoluminescence Properties
Authors: Glais Estelle , Massuyeau Florian , Gautier Romain
Published: July 2020

Doped single‐phase materials have been widely investigated owing to their easy to implement synthesis and the variety of their properties. This Minireview covers strategies for the co‐stabilization and the ratio control of several oxidation states of dopants inserted in the same host. The tuning of the oxidation states of dopants opens up many possibilities for the optimization of specific properties and can be envisioned for various applications such as telecommunication, medicine, displays, lasers or lighting. Technics used for the quantification of each valence state of dopant are also emphasized, and the importance of high throughput methods for the discovery of efficient materials with dopants in multiple valence states is discussed.
Metal‐only Lewis Pairs of Rhodium with s, p and d‐Block Metals
Authors: Bajo Sonia , Alférez Macarena G. , Alcaide María M. , López‐Serrano Joaquín , Campos Jesús
Published: July 2020

Metal‐only Lewis pairs (MOLPs) in which the two metal fragments are solely connected by a dative M→M bond represent privileged architectures to acquire fundamental understanding of bimetallic bonding. This has important implications in many catalytic processes or supramolecular systems that rely on synergistic effects between two metals. However, a systematic experimental/computational approach on a well‐defined class of compounds is lacking. Here we report a family of MOLPs constructed around the RhI precursor [(η5‐C5Me5)Rh(PMe3)2] (1) with a series of s, p and d‐block metals, mostly from the main group elements, and investigate their bonding by computational means. Among the new MOLPs, we have structurally characterized those formed by dative bonding between 1 and MgMeBr, AlMe3, GeCl2, SnCl2, ZnMe2 and Zn(C6F5)2, as well as spectroscopically identified the ones resulting from coordination to MBArF (M=Na, Li; BArF−=[B(C6H2‐3,5‐(CF3)2)4]−) and CuCl. Some of these compounds represent unique examples of bimetallic structures, such as the first unambiguous cases of Rh→Mg dative bonding or base‐free rhodium bound germylene and stannylene species. Multinuclear NMR spectroscopy, including 103Rh NMR, is used to probe the formation of Rh→M bonds. A comprehensive theoretical analysis of those provides clear trends. As anticipated, greater bond covalency is found for the more electronegative acids, whereas ionic character dominates for the least electronegative nuclei, though some degree of electron sharing is identified in all cases.
An Imidazolium‐Based Lipid Analogue as a Gene Transfer Agent
Authors: Paulisch Tiffany O. , Bornemann Steffen , Herzog Marius , Kudruk Sergej , Roling Lena , Linard Matos Anna Livia , Galla Hans‐Joachim , Gerke Volker , Winter Roland , Glorius Frank
Published: July 2020

A dicationic imidazolium salt is described and investigated towards its application for gene transfer. The polar head group and the long alkyl chains in the backbone contribute to a lipid‐like behavior, while an alkyl ammonium group provides the ability for crucial electrostatic interaction for the transfection process. Detailed biophysical studies regarding its impact on biological membrane models and the propensity of vesicle fusion are presented. Fluorescence spectroscopy, atomic force microscopy and confocal fluorescence microscopy show that the imidazolium salt leads to negligible changes in lipid packing, while displaying distinct vesicle fusion properties. Cell culture experiments reveal that mixed liposomes containing the novel imidazolium salt can serve as plasmid DNA delivery vehicles. In contrast, a structurally similar imidazolium salt without a second positive charge showed no ability to support DNA transfection into cultured cells. Thus, we introduce a novel and variable structural motif for cationic lipids, expanding the field of lipofection agents.
A sequential split‐and‐conquer approach for the analysis of big dependent data in computer experiments
Authors: Li Chengrui , Hung Ying , Xie Minge
Published: July 2020

Massive correlated data with many inputs are often generated from computer experiments to study complex systems. The Gaussian process (GP) model is a widely used tool for the analysis of computer experiments. Although GPs provide a simple and effective approximation to computer experiments, two critical issues remain unresolved. One is the computational issue in GP estimation and prediction where intensive manipulations of a large correlation matrix are required. For a large sample size and with a large number of variables, this task is often unstable or infeasible. The other issue is how to improve the naive plug‐in predictive distribution which is known to underestimate the uncertainty. In this article, we introduce a unified framework that can tackle both issues simultaneously. It consists of a sequential split‐and‐conquer procedure, an information combining technique using confidence distributions (CD), and a frequentist predictive distribution based on the combined CD. It is shown that the proposed method maintains the same asymptotic efficiency as the conventional likelihood inference under mild conditions, but dramatically reduces the computation in both estimation and prediction. The predictive distribution contains comprehensive information for inference and provides a better quantification of predictive uncertainty as compared with the plug‐in approach. Simulations are conducted to compare the estimation and prediction accuracy with some existing methods, and the computational advantage of the proposed method is also illustrated. The proposed method is demonstrated by a real data example based on tens of thousands of computer experiments generated from a computational fluid dynamic simulator.
Happy Photometry–Tips and Tricks against the Pitfalls when using a School Photometer
Authors: Ehli Christian
Published: July 2020

Mit Hilfe von Fotometrie lässt sich auch in der Schule eine Vielzahl an naturwissenschaftlichen Projekten durchführen. Hierbei ist es empfehlenswert, eine Reihe experimenteller Parameter zu beachten. Der folgende Artikel ist eine Hilfestellung, um mögliche Störeffekte zu identifizieren und ggf. zu entfernen.
Evolution of the speech‐ready brain: The voice/jaw connection in the human motor cortex
Authors: Brown Steven , Yuan Ye , Belyk Michel
Published: July 2020

A prominent model of the origins of speech, known as the “frame/content” theory, posits that oscillatory lowering and raising of the jaw provided an evolutionary scaffold for the development of syllable structure in speech. Because such oscillations are nonvocal in most nonhuman primates, the evolution of speech required the addition of vocalization onto this scaffold in order to turn such jaw oscillations into vocalized syllables. In the present functional MRI study, we demonstrate overlapping somatotopic representations between the larynx and the jaw muscles in the human primary motor cortex. This proximity between the larynx and jaw in the brain might support the coupling between vocalization and jaw oscillations to generate syllable structure. This model suggests that humans inherited voluntary control of jaw oscillations from ancestral species, but added voluntary control of vocalization onto this via the evolution of a new brain area that came to be situated near the jaw region in the human motor cortex.
Functionalized Nanogap for DNA Read‐Out: Nucleotide Rotation and Current‐Voltage Curves
Authors: Maier Frank C. , Fyta Maria
Published: July 2020

Functionalized nanogaps embedded in nanopores show a strong potential for enhancing the detection of biomolecules, their length, type, and sequence. This detection is strongly dependent on the features of the target biomolecules, as well as the characteristics of the sensing device. In this work, through quantum‐mechanical calculations, we elaborate on representative such aspects for the specific case of DNA detection and read‐out. These aspects include the influence of single DNA nucleotide rotation within the nanogap and the current‐voltage (I‐V) characteristics of the nanogap. The results unveil a distinct variation in the electronic current across the functionalized device for the four natural DNA nucleotides with the applied voltage. These also underline the asymmetric response of the rotating nucleotides on this applied voltage and the respective variation in the rectification ratio of the device. The electronic tunneling current across the nanogap can be further enhanced through the proper choice of an applied bias voltage. We were able to correlate the enhancement of this current to the nucleotide rotation dynamics and a shift of the electronic transmission peaks towards the Fermi level. This nucleotide specific shift further reveals the sensitivity of the device in reading‐out the identity of the DNA nucleotides for all different configurations in the nanogap. We underline the important information that can be obtained from both the I‐V curves and the rectification characteristics of the nanogap device in view of accurately reading‐out the DNA information. We show that tuning the applied bias can enhance this detection and discuss the implications in view of novel functionalized nanopore sequencers.
Molecular Modification of Single Cobalt Sites Boosts the Catalytic Activity of CO2 Electroreduction into CO
Authors: Zhong Yongzhi , Kong Xiangdong , Geng Zhigang , Zeng Jie , Luo Xuan , Zhang Lin
Published: July 2020

Electroreduction of CO2 into carbonaceous fuels or industrial chemicals using renewable energy sources is an ideal way to promote global carbon recycling. Thus, it is of great importance to develop highly selective, efficient, and stable catalysts. Herein, we prepared cobalt single atoms (Co SAs) coordinated with phthalocyanine (Co SAs‐Pc). The anchoring of phthalocyanine with Co sites enabled electron transfer from Co sites to CO2 effectively via the π‐conjugated system, resulting in high catalytic performance of CO2 electroreduction into CO. During the process of CO2 electroreduction, the Faradaic efficiency (FE) of Co SAs‐Pc for CO was as high as 94.8 %. Meanwhile, the partial current density of Co SAs‐Pc for CO was −11.3 mA cm−2 at −0.8 V versus the reversible hydrogen electrode (vs RHE), 18.83 and 2.86 times greater than those of Co SAs (−0.60 mA cm−2) and commercial Co phthalocyanine (−3.95 mA cm−2), respectively. In an H‐cell system operating at −0.8 V vs RHE over 10 h, the current density and FE for CO of Co SAs‐Pc dropped by 3.2 % and 2.5 %. A mechanistic study revealed that the promoted catalytic performance of Co SAs‐Pc could be attributed to the accelerated reaction kinetics and facilitated CO2 activation.
High‐Throughput Approaches for the Discovery of Supramolecular Organic Cages
Authors: Greenaway Rebecca L. , Jelfs Kim E.
Published: July 2020

The assembly of complex molecules, such as organic cages, can be achieved through supramolecular and dynamic covalent strategies. Their use in a range of applications has been demonstrated, including gas uptake, molecular separations, and in catalysis. However, the targeted design and synthesis of new species for particular applications is challenging, particularly as the systems become more complex. High‐throughput computation‐only and experiment‐only approaches have been developed to streamline the discovery process, although are still not widely implemented. Additionally, combined hybrid workflows can dramatically accelerate the discovery process and lead to the serendipitous discovery and rationalisation of new supramolecular assemblies that would not have been designed based on intuition alone. This Minireview focuses on the advances in high‐throughput approaches that have been developed and applied in the discovery of supramolecular organic cages.
Recent Advances in Heterogeneous Photo‐Driven Oxidation of Organic Molecules by Reactive Oxygen Species
Authors: Luo Lan , Zhang Tingting , Wang Miao , Yun Rongping , Xiang Xu
Published: July 2020

The photo‐driven oxidation of organic molecules into corresponding high‐value‐added products has become a promising method in chemical synthesis. This strategy can drive thermodynamically non‐spontaneous reactions and achieve challenging thermocatalytic processes under ambient conditions. Reactive oxygen species (ROS) are not only significant intermediates for producing target products via photoinduced oxidation reactions but also contribute to the creation of sustainable chemical processes. Here, the latest advances in heterogeneous photo‐driven oxidation reactions involving ROS are summarized. The major types of ROS and their generation are introduced, and the behaviors of various ROS involved in photo‐driven processes are reviewed in terms of the formation of different bonds. Emphasis is placed on unraveling the reaction mechanisms of ROS and establishing strategies for their regulation, and the remaining challenges and perspectives are summarized and analyzed. This Review is expected to provide an in‐depth understanding of the mechanisms of ROS involved in photo‐driven oxidation processes as an important foundation for the design of efficient catalysts. Clarifying the role of ROS in oxidation reactions has important scientific significance for improving the atomic and energy efficiency of reactions in practical applications.
N‐Butylpyrrolidinone for Solid‐Phase Peptide Synthesis is Environmentally Friendlier and Synthetically Better than DMF
Authors: Kumar Ashish , Alhassan Mahama , Lopez John , Albericio Fernando , de la Torre Beatriz G.
Published: July 2020

Solid‐phase peptide synthesis (SPPS) is the method of choice for the preparation of peptides in both laboratory scale and large production. Although the methodology has been improved during the last decades allowing the achievement of long peptides and challenging sequences in good yields and purities, the process was not revised from an environmental point of view. One of the main problems in this regard is the large amount of solvents used, and therefore the tons of generated waste. Moreover, the solvent of choice for the SPPS is N,N‐dimethylformamide (DMF), which is considered as reprotoxic; thus, there is an urgent necessity to replace it with safer solvents. The DMF substitution by a green solvent is not a trivial task, because it should solubilize all the reagents and byproducts involved in the process, and, in addition to facilitating the coupling of the different amino acids, it should not favor the formation of side‐reactions compared with DMF. Herein, it was demonstrated that the use of the green solvent N‐butylpyrrolidinone (NBP) as a replacement of DMF was beneficial in two well‐documented side reactions in peptide synthesis, racemization and aspartimide formation. The use of NBP rendered a lower or equal level of racemization in the amino acids more prone to this side reaction than DMF, whilst the aspartimide formation was clearly lower when NBP was used as solvent. Our findings demonstrate that the use of a green solvent does not hamper the synthetic process and could even improve it, making it environmentally friendlier and synthetically better.
Enhancing quality of experience using peer‐to‐peer overlay on device‐to‐device communications
Authors: Tetarave Sumit , Tripathy Somanath , Ghosh Ratan
Published: July 2020

With the recent development of LTE‐A/5G technologies, data sharing among mobile devices offer an attractive opportunity to reduce Internet access. However, it requires smart strategies to share the data with low trade‐offs in time, cost, and energy. Several existing schemes offer a super‐peer‐based two‐tier model using a distributed hash table (DHT) organization for smart devices having device‐to‐device (D2D)/Bluetooth/WiFi capabilities. The primary focus of these schemes has been to reduce Internet usage by increased D2D content sharing. However, the real challenge is not in creating a two‐tier model, but evolving an efficient overlay that offers enhanced opportunities for D2D content sharing over the existing model. In this paper, we formulated a P‐median‐based selection of tier‐1 devices in a distribution network and solved it using the Lagrangian relaxation method. The tier‐2 devices become clients seeking content sharing services from tier‐1 devices. A strong motivation in this work is to raise a user's perception of the grade of service known as quality of experience (QoE). We analyzed the challenge for QoE assessment in resource‐constrained smartphones under the proposed model of enhanced D2D communication. Our focus is to establish a framework to evaluate QoE for applications and services over LTE‐A/5G networks with an improved D2D communication level. The simulation and the experimental results validate the claim that substantial improvements in QoE are possible with the proposed mathematical model for selecting and placing tier‐1 mobile devices and maintaining a DHT for D2D communication.
EXFI: Exon and splice graph prediction without a reference genome
Authors: Langa Jorge , Estonba Andone , Conklin Darrell
Published: July 2020

For population genetic studies in nonmodel organisms, it is important to use every single source of genomic information. This paper presents EXFI, a Python pipeline that predicts the splice graph and exon sequences using an assembled transcriptome and raw whole‐genome sequencing reads. The main algorithm uses Bloom filters to remove reads that are not part of the transcriptome, to predict the intron–exon boundaries, to then proceed to call exons from the assembly, and to generate the underlying splice graph. The results are returned in GFA1 format, which encodes both the predicted exon sequences and how they are connected to form transcripts. EXFI is written in Python, tested on Linux platforms, and the source code is available under the MIT License at https://github.com/jlanga/exfi.
Structure‐Functional Analysis of Hydrogen Production Catalyzed by Molecular Cobalt Complexes with Pentadentate Ligands in Aqueous Solutions
Authors: Wang Ping , Liang Guangchao , Webster Charles Edwin , Zhao Xuan
Published: July 2020

Hydrogen production from sunlight and water represents one promising solution to resolve the environmental problems caused by the consumption of fossil fuels and to meet the increasing global energy demands. Catalysts based on transition metal complexes have been extensively studied for electro‐ and photocatalytic production of hydrogen. Among the reported catalysts, molecular cobalt complexes have received special attention for hydrogen production over the past years. In this review, the recent progresses for electro‐ and photocatalytic production of hydrogen in aqueous solutions catalyzed by Co complexes with pentadentate ligands, with an emphasis of those developed in our lab, are discussed. Mechanistic investigations as well as future directions for hydrogen production by Co complexes are also discussed.
Diaminoimidazopyrimidines: Access via the Groebke–Blackburn–Bienaymé Reaction and Structural Data Mining
Authors: Konstantinidou Markella , Boiarska Zlata , Butera Roberto , Neochoritis Constantinos G. , Kurpiewska Katarzyna , Kalinowska‐Tłuscik Justyna , Dömling Alexander
Published: July 2020

Imidazopyrimidines with diverse substitution patterns are a prime class of heterocycles, present in many commercially available or late‐stage clinical trials drugs. Here, we describe a fast access to diaminoimidazopyrimidines by means of a powerful multicomponent reaction; the Groebke–Blackburn–Bienaymé reaction. We provide the design of such libraries of compounds, identifying all the structural motifs, and subsequently their synthesis. Scope and limitations are discussed, in addition to data mining in the Cambridge Structural Database and pharmacophore search with Crossminer. The presented approach highlights the vast amount of data available in the databases and provides potential future scaffold hopping alternatives for compounds with similar binding patterns. Further studies are ongoing to introduce more “drug‐like” properties into this scaffold and to investigate cellular mechanism‐based anti‐cancer behaviours.
Biosynthetically Relevant Reactivity of Polyneuridine Aldehyde
Authors: Turpin Victor , Poupon Erwan , Jullian Jean‐Christophe , Evanno Laurent
Published: July 2020

Polyneuridine aldehyde is a key intermediate in the biosynthetic routes of monoterpene indole alkaloids family of natural products. The molecule is the first biosynthetic member of the sarpagan‐type alkaloids and is an entry to the ajmalan‐type and alstophyllan‐type alkaloids. Complementary to the recent description of polyneuridine aldehyde, its reactivity was studied. Retro‐biomimetic formation of corynan‐type alkaloids (e.g., geissoschizine) and the biomimetic formation of quebrachidine, the first biosynthetic parent of the ajamalan‐type alkaloids, were performed. In addition, an unusual intramolecular carbonyl‐ene‐reaction involving the indole nucleus delivered an original polycyclic scaffold.
Potassium Concentration Alters Calibration Sensitivities of Dopamine but not Serotonin
Authors: Herrmann Mareike , Abdalla Aya , Patel Bhavik Anil
Published: July 2020

The use of carbon fibre microelectrodes and amperometric techniques for measurement of biological molecules has been widely studied. The use of calibrations to translate biological data is common practice between labs. Tris buffer is commonly used for conducting calibrations, where potassium ion concentrations are varied in buffers. However, little is known about how changes in this ion alter the calibration sensitivity of neurotransmitters. This work showcases that dopamine calibrations are highly dependent on the concentration of potassium ions, whilst serotonin is less affected. Our findings have implications on interpretation and comparison of measurements between different studies.
Electro‐oxidation of Ethanol and Methanol on Pd/C, Pd/CNFs and Pd−Ru/CNFs Nanocatalysts in Alkaline Direct Alcohol Fuel Cell
Authors: Sikeyi Ludwe L. , Matthews Thabo , Adekunle Abolanle S. , Maxakato Nobanathi W.
Published: July 2020

Pd/C, Pd/CNFs and Pd−Ru/CNFs nanocomposite materials were utilized as anode nanocatalysts in low‐temperature alkaline direct alcohol fuel cells. The palladium based nanocatalysts performance and stability were firmly relying upon the attributes of the carbon nanofibers (CNFs). CNFs were successfully synthesized employing a chemical vapour deposition method. The nanocatalysts were synthesized by dispersing Pd and Pd−Ru nanoparticles onto the CNFs surface using alcohol reduction method. The physical properties of the synthesized nanocatalysts were explored utilizing several techniques such as transmission electron microscope (TEM), scanning electron microscope‐Energy dispersive x‐ray (SEM‐EDX), X‐ray diffraction spectroscopy (XRD), X‐ray photoelectron spectroscopy (XPS) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP‐OES) and confirmed successful synthesis of Pd/C, Pd/CNFs and Pd−Ru/CNFs nanocomposite. TEM showed that Pd and Ru nanoparticles were uniformly dispersed on the CNFs support surface. ICP‐OES determined the palladium and ruthenium concentration in Pd/C, Pd/CNFs and Pd−Ru/CNFs nanocatalysts to be Pd (7.67 %), Pd (7.74 %), Pd (7.82 %) and Ru (3.22 %) respectively. The three prepared nanocatalysts were evaluated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) in the evaluation of ethanol and methanol oxidation reactions. CV, CA and EIS experiments of Pd−Ru/CNFs nanocatalyst displayed superior activity towards alcohol oxidation reaction in alkaline conditions than Pd/CNFs and commercial Pd/C nanocatalysts.
Structure and conductivity of AOT solutions in n‐hexadecane‐chloroform mixtures
Authors: Shaparenko Nikita O. , Kompan'kov Nikolay B. , Demidova Marina G. , Bulavchenko Alexander I.
Published: July 2020

The structure and conductivity of AOT (sodium bis(2‐ethylhexyl) sulfosuccinate) solutions (2.5 × 10−4–2.5 × 10−1 M) in n‐hexadecane‐chloroform mixture at the chloroform concentration from 50 to 100 vol% were studied. The diffusion ordered spectroscopy NMR study revealed that in the indicated range, the observed hydrodynamic diameter of micelles depends only on the AOT concentration and does not depend on the chloroform content. Molar fractions of free AOT molecules and those aggregated into micelles were calculated using the Lindman's law: at concentrations above 2.5 × 10−1 М, the solutions contain mostly the micelles, whereas at concentrations below 2.5 × 10−4 M, the solutions contain AOT molecules. The transition region contains both the AOT molecules and the micelles. Conductivity measurements were used to determine free charge carriers in the bulk of solutions and their contributions to conductivity.
A simple and effective method for Escherichiacoli inactivation in aqueous medium using natural based superparamagnetic coagulant
Authors: dos Santos Tássia Rhuna T. , Mateus Gustavo A. P. , de Andrade Murilo B. , Guerra Ana Carolina S. , Vieira Angélica M. S. , Bergamasco Rosângela
Published: July 2020

Escherichia coli is often used as a faecal indicator bacterium to evaluate water quality and is used as a measure to predict the presence of pathogens and their inactivation/removal is important to ensure safe drinking water. In this study γ–Fe2O3 nanoparticles were synthesized by a modified sol–gel method, followed by a subsequent functionalization process with Moringa oleifera (MO) integral seed extract and without ethanol‐extracted oil (MO‐et) for the creation of a new coagulants with antibacterial activity (γ–Fe2O3–MO and γ–Fe2O3–MO(et)). These coagulants were characterized according to their composition, morphology, structure, and surface charge. Coagulation/flocculation tests were performed with subsequent sedimentation under the influence of an external magnetic field for E. coli inactivation/removal. The results indicate that there was total inactivation of E. coli for raw water and removal of 88 and 93% for synthetic water using the coagulants γ–Fe2O3–MO and γ–Fe2O3–MO (et) respectively, demonstrating that the coagulant properties of MO and the superparamagnetic behavior of nanoparticles of γ‐Fe2O3 increased the activity of the new material, favoring the inactivation/removal of E. coli in the water treatment.
Simulation and optimization of hybrid green energy systems for desalination purposes
Authors: Vakili‐Nezhaad Gholamreza , Mishra Shivani B. , Mousa Hasan , Ziaiefar Hamidreza
Published: July 2020

Energy is the main concern in the design and implementation of desalination plants; this concern is even more significant in remote areas with limited or no access to the main power grid. This paper presents an off‐grid hybrid renewable energy assessment for a reverse osmosis desalination plant. The plant with a 10 m3 desalination capacity is located in al‐Batinah region in the north of Oman. For better assessment, the meteoritic data of the site such as temperature, wind velocity, solar radiation, and clearness index are extracted. The simulation has been done using Homer software, and all possible combinations of photovoltaic panel/wind turbine/generator/battery are calculated and compared with one another. At last, two different approaches, a complete renewable hybrid energy with and without generator backup, are compared and the results are provided. The results of the experiment show that the most economic off‐grid hybrid energy system is a combination of a 12.5 kW PV panel with 335 W energy production for each panel, a battery bank consisting of 12 batteries with 205 Ah capacity, and a generator as a backup. The cost of energy for one kWhr is $0.28; on the other hand, a hybrid renewable energy system with the combination of PV/wind turbine/battery costs $0.37 per kWhr.
Impact of the addition of carboplatin to anthracycline‐taxane‐based neoadjuvant chemotherapy on survival in BRCA1/2‐mutated triple‐negative breast cancer
Authors: Zhang Juan , Yao Lu , Liu Yiqiang , Ouyang Tao , Li Jinfeng , Wang Tianfeng , Fan Zhaoqing , Fan Tie , Lin Benyao , Xie Yuntao
Published: July 2020

Whether adding carboplatin to standard neoadjuvant chemotherapy improves survival in BRCA1/2‐mutated triple‐negative breast cancer (TNBC) is unknown. In this retrospective study, we aimed to explore the efficacy of anthracycline‐taxane (A‐T)‐based or anthracycline‐taxane/carboplatin (A‐TP)‐based neoadjuvant chemotherapy in BRCA1/2‐mutated TNBC. A total of 1585 operable primary breast cancer patients were treated with either neoadjuvant A‐T (n = 886) or A‐TP regimen (n = 699). BRCA1 and BRCA2 germline mutations were determined in all subjects. Pathological complete response (pCR), recurrence‐free survival (RFS), distant recurrence‐free survival (DRFS) and overall survival (OS) were estimated. Of the entire cohort, 102 patients (6.4%) carried a pathogenic BRCA1/2 germline mutation. After a median follow‐up of 81 months, no significant differences in survival between the A‐T and A‐TP arms were found in the entire cohort. However, among 288 TNBC patients, BRCA1/2 mutation carriers had significantly better survival when treated with the A‐TP regimen than with the A‐T regimen (5‐year RFS: 82.6% vs 47.9%; P = .024; 5‐year DRFS: 88.5% vs 46.9%; P = .010; 5‐year OS: 88.2% vs 49.9%; P = .036). Multivariate analyses revealed that the A‐TP regimen was a significantly favourable factor for RFS and DRFS and showed a trend towards better OS when compared with the A‐T regimen in BRCA1/2‐mutated TNBC (RFS: adjusted hazard ratio [HR], 0.24; 95% confidence interval [CI], 0.06‐0.91, P = .035; DRFS: HR, 0.17; 95% CI, 0.03‐0.80; P = .025; OS: HR, 0.29; 95% CI, 0.06‐1.49; P = .14). Our study suggested that BRCA1/2‐mutated TNBC patients gain a survival benefit when carboplatin is added to standard A‐T‐based neoadjuvant chemotherapy.
Nowcasting the Greek (semi‐) deposit run: Hidden uncertainty about the future currency in a Google search
Authors: Anastasiou Dimitrios , Drakos Konstantinos
Published: July 2020

We investigate whether Greek depositors' uncertainty about the future currency contains information for the observed acute depletion of deposits in the Greek banking system. We conduct a Nowcasting exercise using the Google search intensity for the term «Drachma» and document that higher search intensity leads to higher Total deposits outflows, which are primarily driven by outflows in Time deposits. We also find that the Google search intensity for the term «Drachma» exerts an asymmetric impact across One‐Day deposits and time deposits. In addition, the asymmetry is also present between firms' deposits and households' deposits. These findings support that ‘a flight‐to‐safety’ behaviour caused by uncertainty about the future currency accounts for the erosion of deposits in Greece.