bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exploring rare chemical phenomena using fractional nuclear charges: Thecis‐effect in N2F2
Authors: Teixeira Filipe , Melo André , Cordeiro M. Natália D. S. 
Published: May 2018

AbstractThe so calledcis‐effect, in which thecisform of an ethylenic compound is more stable than itstrans‐isomer, is a good example of a rare phenomenon described only for a few isomeric pairs. In this work, a novel approach to the study of this rare effect is attempted by changing the nuclear charges of the fluoride and nitrogen incis‐andtrans‐N2F2. This allowed the survey of a large number of isomeric pairs composed sharing the same molecular topology, while varying the electronegativity of selected atoms. The results show an increasing stabilization of thecis‐isomers when increasing the electronegativity of the fluoride atoms, in line with the accepted zeitgeist linking this effect to the electronegativity of the peripheral groups. However, a similar behavior was also found when varying the nuclear charge of the nitrogen atoms. This prompted a more in‐depth look at the electronic structure of these compounds, gathering descriptors from Bader's Quantum Theory of Atoms in Molecules. A descriptive linear model was derived from these descriptors using a two‐stage stepwise linear regression. Further inspection of the model linked the destabilization of thetrans‐isomers with a deviation from the idealized trigonal planar geometry predicted by the Valence Shell Electron Pair Repulsion model. This tendency was explained by an increase in the ionic character of the NF bonds. Furthermore, the current model suggests that the Coulombic repulsion between the two peripheral atoms in thecis‐isomers prevents such large deviations from the idealized geometry, thus, contributing to their relative stabilization. The qualitative rules governing thecis‐effect in N2F2were further tested on other compounds with a similar bond topology.
Insights into the luminescent properties of anionic cyclometalated iridium(III) complexes with ligands derived from natural products
Authors: Cortés‐Arriagada Diego , Dreyse Paulina , Salas Felipe , González Iván 
Published: May 2018

AbstractIn the search of remarkable anionic electroluminescent semiconductors to be applied in energy conversion devices such as Light Emitting Electrochemical Cells, we report the electronic, photophysical, and charge injection/transfer properties of a series of cyclometalated iridium(III) complexes through a DFT/TD‐DFT procedure. The proposed semiconductors involve bidentated ligands based on natural products (salicylic acid and boldine), and phenylpyridine and phenylpyrazole as the cyclometalating units. The proposed compounds emit in the range of 446 to 571 nm, where the boldine based compounds have red‐shifted emissions compared to their analogs with salicylic acid. Blue phosphors were obtained by the use of phenylpyrazole units; however, the ligand field is weak in these cases compared to the ligand field exerted by the phenylpyridine ligands. The latter allows the accessibility to the radiationless states for emitters below 495 nm as a result of the increased stability of the metal centered excited states; consequently, the luminescent quantum yield could be decreased. Conversely, the semiconductors with phenylpyridine units show a restricted accessibility to radiationless processes, which could result in emitters with a high luminescent quantum yield and low non‐radiative constants. Finally, the proposed anionic semiconductors show a better balance between hole/electron transfer rate compared to related cationic Ir(III) complexes; while, the easier hole‐electron injection is favored for semiconductors with salicylic acid and phenylpyridine units.
An Easy and Efficient Method for the Synthesis of Quinoxalines Using Recyclable and Heterogeneous Nanomagnetic‐Supported Acid Catalyst under Solvent‐Free Condition
Authors: Harsha Kachigere B. , Rangappa Shobith , Preetham Habbanakuppe D. , Swaroop Toreshettahally R. , Gilandoust Maryam , Rakesh Kodgahally S. , Rangappa Kanchugarakoppal S. 
Published: May 2018

AbstractSynthesis of quinoxalines from o‐phenylenediamines (o‐PDs) with electronically diversified 1,2‐diketones and α‐bromoketones via simple cyclocondensation reaction using an heterogeneous nano‐ϒ‐Fe2O3‐SO3H catalyst has been reported under solvent free condition. Low cost, easy workup, high yield, operational simplicity, less reaction time, environmentally benign nature and catalyst is magnetically retrievable and can be reused up to five catalytic cycles without significant loss in the product yields are the noteworthy features of this protocol.
Novel Phenothiazine‐5‐oxide Based Push‐Pull Molecules: Synthesis and Fine‐Tuning of Electronic, Optical and Thermal Properties
Authors: Chaudhary Shweta , Mukherjee Madhubani , Paul Tanmoy K. , Bishnoi Swati , Taraphder Srabani , Milton Marilyn D. 
Published: May 2018

AbstractA series of eight acceptor‐donor‐acceptor (A‐D‐A) type small push‐pull compounds based on non‐planar phenothiazine‐5‐oxide as central donor building block end‐capped with different accepting groups were synthesized and characterized. These A‐D‐A systems were evaluated for their electronic, optical and thermal properties by density functional theory (DFT), UV‐Vis, fluorescence, thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) methods. Single crystal X‐ray diffraction (XRD) and DFT studies revealed near‐planar geometry for N‐aryl substituted over N‐alkyl substituted phenothiazine moiety in these A‐D‐A molecules leading to better orbital overlap and stabilization through intramolecular charge transfer (ICT) transition. The HOMO‐LUMO energy gap was observed in the range of 3.70‐4.28 eV. Photoluminescence (PL) studies showed triple as well as dual fluorescence with red‐shifted spectra. Also, TGA and DTA studies indicated moderate to good thermal stability with decomposition temperature (Td) in the range of 159–302 °C.
Quantum Chemical Studies of Methane Oxidation to Methanol on a Biomimetic Tricopper Complex: Mechanistic Insights
Authors: Yeh Chen‐Hao , Yu Steve S.‐F. , Chan Sunney I. , Jiang Jyh‐Chiang 
Published: May 2018

AbstractParticulate methane monooxygenase (pMMO) is known to be the most efficient oxidizer for the conversion of methane (CH4) into methanol (CH3OH) at room temperature. Recently, the tricopper cluster complex [Cu3(7‐N‐Etppz)]1+ has been shown to mediate facile CH4 oxidation upon activation by dioxygen (O2) just like the pMMO enzyme. In this work, we investigate by unrestricted density functional theory (DFT) calculations the oxidation of CH4 on the biomimetic tricopper complex. We find that CH4 can interact with the activated tricopper complex to form a C−H⋅⋅⋅O hydrogen bond between one of the C−H bonds of CH4 and the O2 molecule activating the tricopper cluster complex. We consider both the direct “oxene insertion” mechanism as well as the “hydrogen‐atom abstraction geminal radical rebound” mechanism for the process. Our calculations indicate low kinetic barriers for both reaction pathways, accounting for why the tricopper cluster of the biomimetic complex [Cu3(7‐N‐Etppz)]1+ is a good functional model of the active site in pMMO.
Metal‐Free Selective C2‐H Amidation of 8‐Amidoquinolines by Using Isocyanide as the Source of Amide
Authors: Hao Wenyan , Wang Yuyun , Miao Jiankang , Liu Yunyun 
Published: May 2018

AbstractAn unanticipated and highly efficient selective amidation in the C2 position of 8‐amidoquinolines has been developed via C‐H bond elaboration. The method is transition‐metal‐free, operationally simple with broad functional group tolerance. In this work, isocyanide has been successfully utilized as the source of amide. Furthermore, various kinds of 8‐amidoquinolines in combination with different substituted isocyanides under oxidative condition resulted in direct access to N‐quinoline‐2‐carboxamides in good yields.
Mo0.42C0.58 Nanoparticles Embedded in Nitrogen‐Doped Carbon as Electrocatalyst towards Oxygen Reduction Reaction
Authors: Wang Hongru , Yu Yue , Wei Jiatong , Yu Xiaodan , Chen Gang , Ma Jicheng , Xing Shuangxi 
Published: May 2018

AbstractHighly dispersible Mo0.42C0.58 nanoparticles in nitrogen‐doped carbon is achieved via pyrolyzing one‐dimensional NH4Ni2Mo2O8(OH)H2O@polypyrrole nanocomposites. The formation of the Mo0.42C0.58 is realized via the reaction between the NH4Ni2Mo2O8(OH)H2O nanorod as core and the carbonized polypyrrole at a high temperature. The Mo0.42C0.58@N‐doped carbon presents satisfied catalytic activity towards oxygen reduction reaction with the half‐wave potential of 0.828 V vs. RHE (reversible hydrogen electrode), comparable to that of the commercial Pt/C catalyst. Furthermore, the sample illustrates superior stability and methanol tolerance to Pt/C. The excellent catalytic activity of the Mo0.42C0.58@N‐doped carbon can be attributed to the existence of Mo0.42C0.58 nanoparticles, the N doping in carbonized polypyrrole, and the well‐maintained one‐dimensional nanostructure.
Synthesis and in vitro Antifungal Evaluation of Novel N‐Substituted 4‐Aryl‐2‐methylimidazoles
Authors: Elejalde Nerith‐Rocio , Macías Mario , Castillo Juan‐Carlos , Sortino Maximiliano , Svetaz Laura , Zacchino Susana , Portilla Jaime 
Published: May 2018

AbstractAn efficient and regioselective synthesis of novel 4‐aryl‐2‐methyl‐N‐phenacylimidazoles 5 by a microwave‐assisted pseudo‐tricomponent reaction between acetamidine hydrochloride (3) and α‐bromoacetophenones 2 has been developed. The reduction of the carbonyl group of the ketones 5 offered the corresponding N‐(2‐hydroxyethyl)imidazoles 6 in good yields. Novel N‐substituted imidazoles 5 and 6 were tested for antifungal activity against two clinically important fungi Candida albicans and Cryptococcus neoformans. The results showed that all compounds displayed very low activity against C. albicans. In contrast, compounds 5 and 6 were active against C. neoformans. Among them, ketones 5 showed better activity than alcohols 6, with IC50 values as low as 15.6 μg/mL for some of them. The difluorinated compound 5 e showed the best activity against C. neoformans, followed by the dichlorinated derivative 5 b. The difluorinated compound 5 e showed the best activity against C. neoformans, followed by the dichlorinated derivative 5 b.
First Example of White Organic Electroluminescence Utilizing Perylene Ester Imides
Authors: Gupta Ravindra K. , Das Dipjyoti , Iyer Parameswar K. , Achalkumar Ammathnadu S. 
Published: May 2018

AbstractUtilizing a series of bay‐annulated perylene ester imides (PEIs) doped in polyvinylcarbzole (PVK) as emissive layer, host‐guest organic light emitting diodes were fabricated and the electroluminescence behaviors of these devices have been explored. The devices exhibited emission from both PVK as well as PEI mainly due to the partial Förster resonance energy transfer from PVK to the emissive dopant. In order to achieve better device performance, two different electron transport layers, BPhen and TPBi were used. A remarkable improvement in the emission brightness and lower turn on voltage was observed, when TPBi was used as an electron‐transporting layer instead of BPhen. Incorporation of TPBi resulted in a lower electron injection barrier of TPBi‐PVK interface, which facilitates more electron injection into the emissive layer thus resulting in an increased recombination at a comparatively lower voltage. Also, the intensity of blue emission from PVK was enhanced in the case of TPBi based devices, resulting in an overall white electroluminescence, which is of high technological importance.
Biotransformation and Biological Interaction of Graphene and Graphene Oxide during Simulated Oral Ingestion
Authors: Guarnieri Daniela , Sánchez‐Moreno Paola , Del Rio Castillo Antonio Esaú , Bonaccorso Francesco , Gatto Francesca , Bardi Giuseppe , Martín Cristina , Vázquez Ester , Catelani Tiziano , Sabella Stefania , Pompa Pier Paolo 
Published: May 2018

AbstractThe biotransformation and biological impact of few layer graphene (FLG) and graphene oxide (GO) are studied, following ingestion as exposure route. An in vitro digestion assay based on a standardized operating procedure (SOP) is exploited. The assay simulates the human ingestion of nanomaterials during their dynamic passage through the different environments of the gastrointestinal tract (salivary, gastric, intestinal). Physical–chemical changes of FLG and GO during digestion are assessed by Raman spectroscopy. Moreover, the effect of chronic exposure to digested nanomaterials on integrity and functionality of an in vitro model of intestinal barrier is also determined according to a second SOP. These results show a modulation of the aggregation state of FLG and GO nanoflakes after experiencing the complex environments of the different digestive compartments. In particular, chemical doping effects are observed due to FLG and GO interaction with digestive juice components. No structural changes/degradation of the nanomaterials are detected, suggesting that they are biopersistent when administered by oral route. Chronic exposure to digested graphene does not affect intestinal barrier integrity and is not associated with inflammation and cytotoxicity, though possible long‐term adverse effects cannot be ruled out.
Using Virtual Reality to Explore Science and Literacy Concepts
Authors: Hutchison Amy 
Published: May 2018

AbstractEvolving digital technologies provide opportunities to engage students in activities that go beyond print‐based reading and writing and help them develop skills for reading, writing, and communicating with digital technology. Virtual reality apps are a rapidly emerging form of digital technology that provides immersive experiences in real or imagined environments. Virtual reality creates sensory experiences that involve sight, touch, hearing, and motion to allow users to feel as though they are physically present in that environment. These types of immersive experiences can be used to engage learners in multimodal literacy practices as well as scientific practices such as forming hypotheses and interpreting data to inform courses of action. The author provides a classroom example of using virtual reality in an integrated science and literacy lesson to engage students in discovering, answering, and writing about questions they developed as they explored a virtual environment.
Persistence and modality
Authors: Mackie Penelope 
Published: May 2018

AbstractIt seems plausible to say that what changes an entity can or cannot survive depends on its persistence conditions, and that these depend, in turn, on its sortal kind. It might seem to follow that an entity cannot belong to two sortal kinds with potentially conflicting persistence conditions. Notoriously, though, this conclusion is denied by ‘contingent identity’ theorists, who hold, for example, that a permanently coincident statue and piece of clay are identical, although the persistence conditions associated with the kinds statue and piece of clay are potentially conflicting. A clash with Leibniz’s Law is avoided by treating modal predicates as what Harold Noonan has called ‘Abelardian predicates’, as in the version of ‘inconstant’ counterpart theory developed by David Lewis. In addition to other difficulties, however, there is a question whether this ‘Abelardian’ theory does justice to the intuitions expressed in such statements as that the piece of clay could, while the statue could not, have survived a radical reshaping of its matter. I present an argument, which I call ‘the vacuous satisfaction argument’, for the conclusion that the theory does indeed fail to capture the significance of such de re modal statements.
Long‐term persistence of agricultural pest insects by risk‐spreading dispersal
Authors: Gavina Maica Krizna Areja , Aoki Kotaro , Ichinose Genki , Rabajante Jomar Fajardo , Ito Hiromu , Morita Satoru , Jansen Vincent A. A. , Yoshimura Jin 
Published: May 2018

AbstractInsects are the most diverse organisms on earth consisting of more than 900 thousand species. However, only few of them are considered agricultural pests. Life history traits such as high fecundity, fast population growth, and high dispersal ability have been used to characterize agricultural pest insects. However, many other non‐pest insects also share these traits, which indicates that there has not been a decisive condition characterizing agricultural pest insects. Agricultural habitats are risky and ephemeral to pests because of pest control and harvesting. The usual arithmetic mean fitness cannot be used to measure the persistence of these pests, because the maximal mean fitness is achieved only when they exhibit no dispersal, but that leads to immediate extinction. Using a geometric mean fitness model, we propose a quantitative measure of long‐term reproductive success for agricultural pest insects. By using this approach, we can evaluate the trade‐off between long‐distance dispersal and high reproduction correctly and estimate the condition for the long‐term persistence of pest insects in agricultural habitats. We discuss some general perspectives of pest control from the proposed characterization.
Effects of running a marathon on irisin concentration in men aged over 50
Authors: Jóźków Paweł , Koźlenia Dawid , Zawadzka Katarzyna , Konefał Marek , Chmura Paweł , Młynarska Katarzyna , Kosowski Michał , Mędraś Marek , Chmura Jan , Ponikowski Piotr , Daroszewski Jacek 
Published: May 2018

Abstract
Our aim was to verify whether running a marathon is associated with changes in irisin concentration in healthy, endurance-trained men. In an observational study, we assessed baseline biochemical and fitness parameters of 28 middle-aged runners (mean ± SD age, BMI, VO2max: 58 ± 8 years; 24.5 ± 3 kg/m2; 51.1 ± 1.7 ml/kg/min). We evaluated irisin before, immediately after, and 7 days after the marathon. Irisin concentration decreased from a baseline value of 639 ± 427 to 461 ± 255 ng/ml immediately after the marathon (p < 0.05). After 7 days, it was still significantly lower than before the race, at 432 ± 146 ng/ml (p < 0.05). We found no correlations between irisin concentration and the training history of the studied subjects. We conclude that a long-distance run may have a negative impact on irisin release in men. This effect was not correlated with the training history of runners.
Measuring Geographic Migration Patterns Using Matrículas Consulares
Authors: Caballero Maria Esther , Cadena Brian C. , Kovak Brian K. 
Published: May 2018

Abstract
In this article, we show how to use administrative data from the Matrícula Consular de Alta Seguridad (MCAS) identification card program to measure the joint distribution of sending and receiving locations for migrants from Mexico to the United States. Whereas other data sources cover only a small fraction of source or destination locations or include only very coarse geographic information, the MCAS data provide complete geographic coverage of both countries, detailed information on migrants’ sources and destinations, and a very large sample size. We first confirm the quality and representativeness of the MCAS data by comparing them with well-known household surveys in Mexico and the United States, finding strong agreement on the migrant location distributions available across data sets. We then document substantial differences in the mix of destinations for migrants from different places within the same source state, demonstrating the importance of detailed substate geographical information. We conclude with an example of how these detailed data can be used to study the effects of destination-specific conditions on migration patterns. We find that an Arizona law reducing employment opportunities for unauthorized migrants decreased emigration from and increased return migration to Mexican source regions with strong initial ties to Arizona.
Cosmic‐ray Neutron Rover Surveys of Field Soil Moisture and the Influence of Roads
Authors: Schrön M. , Rosolem R. , Köhli M. , Piussi L. , Schröter I. , Iwema J. , Kögler S. , Oswald S. E. , Wollschläger U. , Samaniego L. , Dietrich P. , Zacharias S. 
Published: May 2018

AbstractMeasurements of root‐zone soil moisture across spatial scales of tens to thousands of meters have been a challenge for many decades. The mobile application of Cosmic Ray Neutron Sensing (CRNS) is a promising approach to measure field soil moisture noninvasively by surveying large regions with a ground‐based vehicle. Recently, concerns have been raised about a potentially biasing influence of local structures and roads. We employed neutron transport simulations and dedicated experiments to quantify the influence of different road types on the CRNS measurement. We found that roads introduce a substantial bias in the CRNS estimation of field soil moisture compared to off‐road scenarios. However, this effect becomes insignificant at distances beyond a few meters from the road. Neutron measurements on the road could overestimate the field value by up to 40 % depending on road material, width, and the surrounding field water content. The bias could be largely removed with an analytical correction function that accounts for these parameters. Additionally, an empirical approach is proposed that can be used without prior knowledge of field soil moisture. Tests at different study sites demonstrated good agreement between road‐effect corrected measurements and field soil moisture observations. However, if knowledge about the road characteristics is missing, measurements on the road could substantially reduce the accuracy of this method. Our results constitute a practical advancement of the mobile CRNS methodology, which is important for providing unbiased estimates of field‐scale soil moisture to support applications in hydrology, remote sensing, and agriculture.
A New Machine‐Learning Approach for Classifying Hysteresis in Suspended‐Sediment Discharge Relationships Using High‐Frequency Monitoring Data
Authors: Hamshaw Scott D. , Dewoolkar Mandar M. , Schroth Andrew W. , Wemple Beverley C. , Rizzo Donna M. 
Published: May 2018

AbstractStudying the hysteretic relationships embedded in high‐frequency suspended‐sediment concentration and river discharge data over 600+ storm events provides insight into the drivers and sources of riverine sediment during storm events. However, the literature to date remains limited to a simple visual classification system (linear, clockwise, counter‐clockwise, and figure‐eight patterns) or the collapse of hysteresis patterns to an index. This study leverages 3 years of suspended‐sediment and discharge data to show proof‐of‐concept for automating the classification and assessment of event sediment dynamics using machine learning. Across all catchment sites, 600+ storm events were captured and classified into 14 hysteresis patterns. Event classification was automated using a restricted Boltzmann machine (RBM), a type of artificial neural network, trained on 2‐D images of the suspended‐sediment discharge (hysteresis) plots. Expansion of the hysteresis patterns to 14 classes allowed for new insight into drivers of the sediment‐discharge event dynamics including spatial scale, antecedent conditions, hydrology, and rainfall. The probabilistic RBM correctly classified hysteresis patterns (to the exact class or next most similar class) 70% of the time. With increased availability of high‐frequency sensor data, this approach can be used to inform watershed management efforts to identify sediment sources and reduce fine sediment export.