bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Xanthate Route to Indolines, Indoles, and their Aza Congeners
Authors: Zard Samir Z. 
Published: April 2020

AbstractConvergent routes to a variety of indolines, indoles, oxindoles, and their aza analogues involving radical additions of xanthates are described. Three approaches are summarized. The first is the least general and relies on the generation of aryl or heteroaryl radicals starting from diazonium salts. The second involves radical addition to N‐allylanilines followed by ring‐closure onto the aromatic core. A large variety of indolines and azaindolines can thus be obtained and, in many cases, converted into the corresponding indoles and azaindoles by various methods. The synthesis of novel fluoroazaindolines and fluoroazaindoles by a rare homolytic ipso‐substitution of fluorine atoms is particularly noteworthy. The last approach hinges on the direct modification of indoles by radical addition to the pyrrole subunit of the indole nucleus. Application of this methodology to the total synthesis of melatonin and the alkaloids mersicarpine, caulerpine, and the pentacyclic skeleton of tronocarpine is briefly discussed. Most of the compounds described herein would be difficult to obtain by more traditional routes.
Discoveries and Challenges en Route to Swinhoeisterol A
Authors: Duecker Fenja L. , Heinze Robert C. , Steinhauer Simon , Heretsch Philipp 
Published: April 2020

AbstractIn this work, a full account of the authors’ synthetic studies is reported that culminated in the first synthesis of 13(14→8),14(8→7)diabeo‐steroid swinhoeisterol A as well as the related dankasterones A and B, 13(14→8)abeo‐steroids, and periconiastone A, a 13(14→8)abeo‐4,14‐cyclo‐steroid. Experiments are described in detail that provided further insight into the mechanism of the switchable radical framework reconstruction approach. By discussing failed strategies and tactics towards swinhoeisterol A, the successful route that also allowed an access to structurally closely related analogues, such as Δ22‐24‐epi‐swinhoeisterol A, is eventually presented.
A Resin‐Supported Formate Catalyst for the Transformative Reduction of Carbon Dioxide with Hydrosilanes
Authors: Pramudita Ria Ayu , Manaka Yuichi , Motokura Ken 
Published: April 2020

AbstractA heterogeneous formate anion catalyst for the transformative reduction of carbon dioxide (CO2) based on a polystyrene and divinylbenzene copolymer modified with alkylammonium formate was prepared from a widely available anion exchange resin. The catalyst preparation was easy and the characterization was carried out by using elemental analysis, Fourier transform infrared (FTIR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), and solid‐state 13C cross‐polarization/magic‐angle spinning nuclear magnetic resonance (13C CP/MAS NMR) spectroscopy. The catalyst displayed good catalytic activity for the direct reduction of CO2 with hydrosilanes, tunably yielding silylformate or methoxysilane products depending on the hydrosilanes used. The catalyst was also active for the reductive insertion of CO2 into both primary and secondary amines. The catalytic activity of the resin‐supported formate can be predicted from the FTIR spectra of the catalyst, probably because of the difference in the ionic interaction strength between the supported alkylammonium cations and formate anions. The ion pair density is thought to influence the catalytic activity, as shown by the elemental and solid‐state 13C NMR analyses.
Organoboron Derivatives of Stereoregular Phenylcyclosilsesquioxanes
Authors: Anisimov Anton A. , Drozdov Fedor V. , Vysochinskaya Yulia S. , Minyaylo Ekaterina O. , Peregudov Alexander S. , Dolgushin Fedor M. , Shchegolikhina Olga I. , Muzafarov Aziz M. 
Published: April 2020

AbstractThis study presents the synthesis of organoboron derivatives of stereoregular 4‐, 6‐, and 12‐unit phenylcyclosilsesquioxanes. All compounds obtained were isolated in good yields (70–80 %) and were fully characterized by 1H, 13C, 29Si, 11B NMR, IR spectroscopy, HRMS ESI, and elemental microanalysis. The structure of the key modifier, obtained for the first time, 4‐(tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)phenyl) dimethylvinylsilane, was also confirmed by single‐crystal XRD.
Noncovalent Functionalization of Few‐Layered Antimonene with Fullerene Clusters and Photoinduced Charge Separation in the Composite
Authors: Umeyama Tomokazu , Ohara Tomoya , Tsutsui Yusuke , Nakano Shota , Seki Shu , Imahori Hiroshi 
Published: April 2020

AbstractFew‐layered antimonene (FLSb) nanosheets were noncovalently functionalized with fullerene C60 clusters by quick addition of a poor solvent (i.e., acetonitrile) into a mixed dispersion of FLSb and C60 in a good solvent (i.e., toluene). In a flash‐photolysis time‐resolved microwave conductivity (FP‐TRMC) measurement, the FLSb‐C60 composite, (FLSb+C60)m, showed a rapid rise in transient conductivity, whereas no conductivity signal was observed in the single components, FLSb and C60. This demonstrated the occurrence of photoinduced charge separation between FLSb and C60 in (FLSb+C60)m. Furthermore, a photoelectrochemical device with an electrophoretically deposited (FLSb+C60)m film exhibited an enhanced efficiency of photocurrent generation, compared to those of the single‐components, FLSb and C60, due to the photoinduced charge separation between FLSb and C60. This work provides a promising approach for fabrication of antimonene–organic molecule composites and paves the way for their application in optoelectronics.
Modular Medical Imaging Agents Based on Azide–Alkyne Huisgen Cycloadditions: Synthesis and Pre‐Clinical Evaluation of 18F‐Labeled PSMA‐Tracers for Prostate Cancer Imaging
Authors: Böhmer Verena I. , Szymanski Wiktor , van den Berg Keimpe‐Oeds , Mulder Chantal , Kobauri Piermichele , Helbert Hugo , van der Born Dion , Reeβing Friederike , Huizing Anja , Klopstra Marten , Samplonius Douwe F. , Antunes Ines F. , Sijbesma Jürgen W. A. , Luurtsema Gert , Helfrich Wijnand , Visser Ton J. , Feringa Ben L. , Elsinga Philip H. 
Published: April 2020

AbstractSince the seminal contribution of Rolf Huisgen to develop the [3+2] cycloaddition of 1,3‐dipolar compounds, its azide–alkyne variant has established itself as the key step in numerous organic syntheses and bioorthogonal processes in materials science and chemical biology. In the present study, the copper(I)‐catalyzed azide–alkyne cycloaddition was applied for the development of a modular molecular platform for medical imaging of the prostate‐specific membrane antigen (PSMA), using positron emission tomography. This process is shown from molecular design, through synthesis automation and in vitro studies, all the way to pre‐clinical in vivo evaluation of fluorine‐18‐ labeled PSMA‐targeting ‘F‐PSMA‐MIC’ radiotracers (t1/2=109.7 min). Pre‐clinical data indicate that the modular PSMA‐scaffold has similar binding affinity and imaging properties to the clinically used [68Ga]PSMA‐11. Furthermore, we demonstrated that targeting the arene‐binding in PSMA, facilitated through the [3+2]cycloaddition, can improve binding affinity, which was rationalized by molecular modeling. The here presented PSMA‐binding scaffold potentially facilitates easy coupling to other medical imaging moieties, enabling future developments of new modular imaging agents.
Evidence of Alpha Radiolysis in the Formation of a Californium Nitrate Complex
Authors: Galley Shane S. , Gaggioli Carlo Alberto , Zeller Matthias , Celis‐Barros Cristian , Albrecht‐Schmitt Thomas E. , Gagliardi Laura , Bart Suzanne C. 
Published: April 2020

AbstractWell‐characterized complexes of transplutonium elements are scarce because of the experimental challenges of working with these elements and the rarity of the isotopes. This leads to a lack of structural and spectroscopic data needed to understand the nature of chemical bonds in these compounds. In this work, the synthesis of Cf(DOPOq)2(NO3)(py) (DOPOq=2,4,6,8‐tetra‐tert‐butyl‐1‐oxo‐1H‐phenoxazin‐9‐olate; py=pyridine) is reported, in which the nitrate anion is hypothesized to form through the α‐radiolysis‐induced reaction of pyridine and/or the ligand. Computational analysis of the electronic structure of the complex reveals that the CfIII–ligand interactions are largely ionic.
Iminodiacetic Acid as a Novel Metal‐Binding Pharmacophore for New Delhi Metallo‐β‐lactamase Inhibitor Development
Authors: Chen Allie Y. , Thomas Caitlyn A. , Thomas Pei W. , Yang Kundi , Cheng Zishuo , Fast Walter , Crowder Michael W. , Cohen Seth M. 
Published: April 2020

AbstractThe fungal natural product aspergillomarasmine A (AMA) has been identified as a noncompetitive inhibitor of New Delhi metallo‐β‐lactamase‐1 (NDM‐1) that inhibits by removing ZnII from the active‐site. The nonselective metal‐chelating properties and difficult synthesis and derivatization of AMA have hindered the development of this scaffold into a potent and selective inhibitor of NDM‐1. Iminodiacetic acid (IDA) has been identified as the metal‐binding pharmacophore (MBP) core of AMA that can be leveraged for inhibitor development. Herein, we report the use of IDA for fragment‐based drug discovery (FBDD) of NDM‐1 inhibitors. IDA (IC50=120 μM) was developed into inhibitor 23 f (IC50=8.6 μM, Ki=2.6 μM), which formed a ternary complex with NDM‐1, as evidenced by protein thermal‐shift and native‐state electrospray ionization mass spectrometry (ESI‐MS) experiments. Combining mechanistic analysis with inhibitor derivatization, the use of IDA as an alternative AMA scaffold for NDM‐1 inhibitor development is detailed.
Metastable Dianions and Dications
Authors: Quiñonero David , Alkorta Ibon , Elguero Jose 
Published: April 2020

AbstractA theoretical study of metastable dianions and dications has been carried out at the CCSD(T)//MP2 level. MX32−and LX42−(M=Li and Na, L=Be and Mg, X=F and Cl) have been considered as dianions, M3X2+(M=Li and Na, X=F and Cl), YH32+and ZH42+(Y=F and Cl and Z=O, S) as dications. Minima structures are found in all cases, but they are less stable than the corresponding dissociated pair of mono‐ions. The dissociation profile of the molecules in two mono‐ions has been explored showing in all cases a maximum that prevent their spontaneous dissociation. The strength and nature of the chemical bond in the dianions and dications have been analyzed with the QTAIM, NBO and LMOEDA method and compared to the corresponding monoanions and monocations.
A New Conducting Copolymer Bearing Electro‐Active Nitroxide Groups as Organic Electrode Materials for Batteries
Authors: Assumma L. , Kervella Y. , Mouesca J.‐M. , Mendez M. , Maurel V. , Dubois L. , Gutel T. , Sadki S. 
Published: April 2020

AbstractTo reduce the amount of conducting additives generally required for polynitroxide‐based electrodes, a stable radical (TEMPO) is combined with a conductive copolymer backbone consisting of 2,7‐bisthiophene carbazole (2,7‐BTC), which is characterized by a high intrinsic electronic conductivity. This work deals with the synthesis of this new polymer functionalized by a redox nitroxide. Fine structural characterization using electron paramagnetic resonance (EPR) techniques established that: 1) the nitroxide radicals are properly attached to the radical chain (continuous wave EPR) and 2) the polymer chain has very rigid conformations leading to a set of well‐defined distances between first neighboring pairs of nitroxides (pulsed EPR). The redox group combined with the electroactive polymer showed not only a very high electrochemical reversibility but also a perfect match of redox potentials between the de‐/doping reaction of the bisthiophene carbazole backbone and the redox activity of the nitroxide radical. This new organic electrode shows a stable capacity (about 60 mAh g−1) and enables a strong reduction in the amount of carbon additive due to the conducting‐polymer skeleton.
TRPM6 and TRPM7: Novel players in cell intercalation during vertebrate embryonic development
Authors: Runnels Loren W. , Komiya Yuko 
Published: April 2020

AbstractA common theme in organogenesis is how the final structure of organs emerge from epithelial tube structures, with the formation of the neural tube being one of the best examples. Two types of cell movements co‐occur during neural tube closure involving the migration of cells toward the midline of the embryo (mediolateral intercalation or convergent extension) as well as the deep movement of cells from inside the embryo to the outside of the lateral side of the neural plate (radial intercalation). Failure of either type of cell movement will prevent neural tube closure, which can produce a range of neural tube defects (NTDs), a common congenital disease in humans. Numerous studies have identified signaling pathways that regulate mediolateral intercalation during neural tube closure. Less understood are the pathways that govern radial intercalation. Using the Xenopus laevis system, our group reported the identification of transient receptor potential (TRP) channels, TRPM6 and TRPM7, and the Mg2+ ion they conduct, as novel and key factors regulating both mediolateral and radial intercalation during neural tube closure. Here we broadly discuss tubulogenesis and cell intercalation from the perspective of neural tube closure and the respective roles of TRPM7 and TRPM6 in this critical embryonic process.
Self‐organizing cicada choruses respond to the local sound and light environment
Authors: Sheppard Lawrence W. , Mechtley Brandon , Walter Jonathan A. , Reuman Daniel C. 
Published: April 2020

Abstract

Periodical cicadas exhibit an extraordinary capacity for self‐organizing spatially synchronous breeding behavior. The regular emergence of periodical cicada broods across the United States is a phenomenon of longstanding public and scientific interest, as the cicadas of each brood emerge in huge numbers and briefly dominate their ecosystem. During the emergence, the 17‐year periodical cicada species Magicicada cassini is found to form synchronized choruses, and we investigated their chorusing behavior from the standpoint of spatial synchrony.

Cicada choruses were observed to form in trees, calling regularly every five seconds. In order to determine the limits of this self‐organizing behavior, we set out to quantify the spatial synchronization between cicada call choruses in different trees, and how and why this varies in space and time.

We performed 20 simultaneous recordings in Clinton State Park, Kansas, in June 2015 (Brood IV), with a team of citizen‐science volunteers using consumer equipment (smartphones). We use a wavelet approach to show in detail how spatially synchronous, self‐organized chorusing varies across the forest.

We show how conditions that increase the strength of audio interactions between cicadas also increase the spatial synchrony of their chorusing. Higher forest canopy light levels increase cicada activity, corresponding to faster and higher‐amplitude chorus cycling and to greater synchrony of cycles across space. We implemented a relaxation‐oscillator‐ensemble model of interacting cicadas, finding that a tendency to call more often, driven by light levels, results in all these effects.

Results demonstrate how the capacity to self‐organize in ecology depends sensitively on environmental conditions. Spatially correlated modulation of cycling rate by an external driver can also promote self‐organization of phase synchrony.
Proton Exchange Membrane Fuel Cell Prognostics Using Genetic Algorithm and Extreme Learning Machine
Authors: Chen K. , Laghrouche S. , Djerdir A. 
Published: April 2020

AbstractThe prognostics can predict the degradation of proton exchange membrane fuel cell (PEMFC) to formulate a reasonable maintenance plan for improving its lifetime and performance. In this paper, the voltage degradation for PEMFC at different conditions is predicted, by using a novel prognostics method based on genetic algorithm (GA) and extreme learning machine (ELM). The novel prognostics method considers the effects of the PEMFC load current, relative humidity, hydrogen pressure, and temperature on the degradation for PEMFC. Firstly, the voltage degradation prediction model for PEMFC is built by the ELM. Then, the GA is adopted to determine the optimal parameter of the proposed degradation prediction model. Finally, the voltage degradation prediction of the proposed prognostics method is validated, using data derived from the PEMFC in actual postal fuel cell electric vehicle (PFCEV) at real conditions and PEMFC at dynamic load current. The experimental results show that the proposed prognostics method can obtain good voltage degradation prediction for PEMFC in PFCEV at real conditions. The proposed method achieves better voltage degradation prediction for PEMFC at dynamic load current than other traditional data‐based prognostics methods.
Eccrine porocarcinoma of the head and neck: Meta‐analysis of 120 cases
Authors: Le Nguyen‐Son , Janik Stefan , Liu David T. , Grasl Stefan , Faisal Muhammad , Pammer Johannes , Schickinger‐Fischer Bettina , Hamzavi Jafar‐Sasan , Seemann Rudolf , Erovic Boban M. 
Published: April 2020

AbstractBackgroundThe aim of the study is to analyze potential prognostic factors and to evaluate therapy strategies regarding clinical outcome in patients with eccrine porocarcinoma (EPC) of the head and neck.MethodsOne hundred and sixteen EPC cases from ninety studies and four authors' EPC cases were included in the meta‐analysis.ResultsAt an average follow up of 20.48 months, the 3‐year overall survival and regional recurrence rate were 70.3% and 19.0%, respectively. Patients without surgical treatment had a significantly worse 3‐year overall survival. Mohs microscopic surgery led to significantly less occurrence of regional recurrences compared to wide excision. An ulcerating lesion, high mitotic activity, and lymphovascular invasion were significant prognostic factors.ConclusionSurgical resection is the cornerstone in the therapy of EPC and represents the therapeutic modality that offers the best chance of disease‐free survival. Due to the high probability of recurrence, close follow‐ups are strongly recommended.
Effect of combination of curcumin and GLUT‐1 AS‐ODN on radiosensitivity of laryngeal carcinoma through regulating autophagy
Authors: Dai Li‐Bo , Yu Qi , Zhou Shui‐Hong , Bao Yang‐Yang , Zhong Jiang‐Tao , Shen Li‐Fang , Lu Zhong‐Jie , Fan Jun , Huang Ya‐Ping 
Published: April 2020

AbstractBackgroundThis study is to explore the role of curcumin and GLUT‐1 antisense oligodeoxynucleotides (AS‐ODN) on autophagy modulation‐initiated radiosensitivity.MethodsBALB/c mice were employed to establish xenograft model using Tu212 cell. The expression of autophagy‐ and apoptosis‐related proteins was determined by WB. Autophagosome was observed under transmission electron microscope. Apoptosis of tumor tissue were detected by TUNEL staining.ResultsCombinations of curcumin and GLUT‐1 AS‐ODN with 10 Gy inhibited the tumor growth by inducing apoptosis of laryngeal cancer cells followed with the enhancement of autophagy. 3‐MA also had a promotion effect on irradiation‐mediated growth inhibition possibly by depressing PI3K and on curcumin/GLUT‐1 AS‐ODN‐mediated growth inhibition potentially by regulating autophagic events. Of note, a de‐escalation of radiotherapy dose (5 Gy) along with curcumin, GLUT‐1 AS‐ODN or 3‐MA produced a stronger effect than high dosage of radiotherapy (10 Gy) alone.ConclusionsCurcumin and GLUT‐1 AS‐ODN improve the radiosensitivity of laryngeal carcinoma through regulating autophagy and inducing apoptosis.
Investigation of soil water hydrological process in the permafrost active layer using stable isotopes
Authors: Li Zongjie , Ma Jinzhu , Song Lingling , Gui Juan , Xue Jian , Zhang Baijuan , Gao Wende , Li Zongxing 
Published: April 2020

AbstractHere, we studied the isotope characteristics and source contributions of soil water in the permafrost active layer by collecting soil samples in July 2018 in Yangtze River basin. Soil moisture and temperature showed decreasing trends from 0–80 cm, and an increasing trend from 80–100 cm. The value of δ18O and δD first increased and then decreased in the soil profile of 0–100 cm; however, d‐excess increased from 0–100 cm. δ18O values became gradually positive from the southwest to northeast of the study area, while d‐excess gradually increased from southeast to northwest. The evaporation water line (EL) was δD = 7.56 δ18O + 1.50 (R2 = 0.90, p < 0.01, n = 96). Due to intense solar radiation and evaporation on the Tibetan Plateau, the elevation did not impact the surface soil. The altitude effect of the soil depths of 0–20 cm was not obvious, but the other soil layers had a significant altitude effect. Soil moisture and temperature were closely related to the stable isotopic composition of soil water. The contribution of precipitation to soil water on the sunny slope was 86%, while the contribution of the shady slope was 84%. However, the contribution of ground ice to soil water on sunny slope was 14% and the shady slope was 16%. The contribution of ground ice to soil water increased with increasing altitude on the sunny slope, but the contribution of ground ice to soil water had no obvious trend on the shady slope.
Development of automatic glioma brain tumor detection system using deep convolutional neural networks
Authors: Kalaiselvi Thiruvenkadam , Padmapriya Thiyagarajan , Sriramakrishnan Padmanaban , Priyadharshini Venugopal 
Published: April 2020

AbstractWe have developed six convolutional neural network (CNN) models for finding optimal brain tumor detection system on high‐grade glioma and low‐grade glioma lesions from voluminous magnetic resonance imaging human brain scans. Glioma is the most common form of brain tumor. The models are constructed based on the different combinations and settings of hyperparameters with conventional CNN architecture. The six models are two layers with five epochs, five layers with dropout, five layers with stopping criteria (FLSC), FLSC and dropout (FLSCD), FLSC and batch normalization (FLSCBN), and FLSCBN and dropout. The models were trained and tested with BraTS2013 and whole brain atlas data sets. Among them, FLSCBN model yielded the best classification results for brain tumor detection. Experimental results revealed that our deep learning approach was better than the conventional state‐of‐art methods.
Reduced amino acid Schiff base containing ruthenium(III) complexes: Synthesis, characterization, DNA interaction, and in vitro cytotoxicity
Authors: Zhang Zhaokuo , Yang Ziwei , Wu Yujing , Yuan Zhen , Du Jianlong , Li Lijun 
Published: April 2020

AbstractA number of reduced amino Schiff base ligands and corresponding ruthenium(III) complexes were designed and prepared based on the fact that amino acids not only possess multiple coordinate atoms but also improve the solubility of drugs in the body. The interaction of the complexes with calf thymus DNA was analyzed with spectroscopic methods of ultraviolet‐visible absorption spectra, DNA competitive binding with ethidium bromide, circular dichroism spectra, and DNA melting experiments, and DNA viscosity measurements, indicating that the complexes bind to DNA primarily in the grooving mode. With respect to the ligands, the cytotoxicity in vitro of the complexes against Hela, A549, and MCF‐7 cells was much enhanced, with most of the IC50 values less than 50 μM or even comparable with those of cisplatin.