bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi‐stimuli‐responsive self‐immolative polymer assemblies
Authors: Yardley Rebecca E. , Gillies Elizabeth R.
Published: August 2018

Self‐immolative polymers (SIPs) undergo depolymerization in response to the cleavage of stimuli‐responsive end‐caps from their termini. Some classes of SIPs, including polycarbamates, have depolymerization rates that depend on environmental factors such as solvent and pH. In previous work, hydrophobic SIPs have been incorporated into amphiphilic block copolymers and used to prepare nanoassemblies. However, stimuli‐responsive hydrophilic blocks have not previously been incorporated. In this work, we synthesized amphiphilic copolymers composed of a hydrophobic polycarbamate SIP block and a hydrophilic poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) block connected by a UV light‐responsive linker end‐cap. It was hypothesized that after assembly of the block copolymers into nanoparticles, chain collapse of the PDMAEMA above its lower critical solution temperature (LCST) might change the environment of the SIP block, thereby altering its depolymerization rate. Self‐assembly of the block copolymers was performed, and the depolymerization of the resulting assemblies was studied by fluorescence spectroscopy, dynamic light scattering, and NMR spectroscopy. At 20 °C, the system exhibited a selective response to the UV light. At 65 °C, above the LCST of PDMAEMA, the systems underwent more rapid depolymerization, suggesting that the increase in rate arising from the higher temperature dominated over environmental effects arising from chain collapse. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1868–1877
Synthesis and crosslinking reaction of polyacetylenes substituted with benzoxazine rings: Thermally highly stable benzoxazine resins
Authors: Goto Masahide , Miyagi Yu , Minami Masaki , Sanda Fumio
Published: August 2018

Novel polyacetylenes, poly(1) and poly(2) substituted with benzoxazine rings were synthesized by the polymerization of the corresponding acetylene monomers 1 and 2 using Rh catalysts, [(nbd)RhCl]2, and (nbd)Rh+B–Ph4 (nbd = 2,5‐norbornadiene). The polymers were heated at 250 °C under N2 to obtain the corresponding polybenzoxazine resins, poly(1)′ and poly(2)′ possessing polyacetylene main chains via the ring‐opening polymerization of the benzoxazine moieties. The polyacetylene backbones were maintained after crosslinking reaction at 250 °C, which were confirmed by Raman spectroscopy. The benzoxazine resins were thermally highly stable as evidenced by differential scanning calorimetry and thermogravimetric analysis. The surface of poly(1)′ film became hydrophilic compared to that of poly(1), while the surfaces of poly(2) and poly(2)′ films showed almost the same hydrophilicity judging from the water contact angle measurement. Poly(1)′ and poly(2)′ exhibited refractive indices smaller than those of poly(1) and poly(2). © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1884–1893
A novel fractional viscoelastic constitutive model for shape memory polymers
Authors: Pan Zhouzhou , Liu Zishun
Published: August 2018

Shape memory polymers (SMPs) are a class of smart materials which can recover from a deformed shape to their original shape by a certain external stimulus. To predict the deformation behaviors of SMPs, different constitutive models have been developed in the last few years. However, most of the constitutive models need many parameters to be determined by specific experiments and complex calibration processes. This drawback has limited their application in promoting the development of SMPs. Thus, it is imperative to develop a new constitutive model which is not only accurate, but also relatively simple. In our work, a novel fractional viscoelastic constitutive model coupling with time‐temperature superposition principle is first proposed for SMPs. Then, frequency sweep and temperature sweep experiments are conducted to determine the parameters of the model. Finally, the shape memory free recovery experiments are carried out to validate the predictive capability of the developed model. By comparing the predicted results with experimental data, we find that though our model has only eleven parameters in total, it could capture the thermomechanical behaviors of SMPs in very good agreement with experimental results. We hope the proposed new model provide researchers with guidelines in designing and optimizing of SMP applications. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1125–1134
An experimental and computational study of donor–linker–acceptor block copolymers for organic photovoltaics
Authors: Hu Zhiqi , Jakowski Jacek , Zheng Chenyu , Collison Christopher J. , Strzalka Joseph , Sumpter Bobby G. , Verduzco Rafael
Published: August 2018

Block copolymers with donor and acceptor conjugated polymer blocks provide an approach to dictating the donor–accepter interfacial structure and understanding its relationship to charge separation and photovoltaic performance. We report the preparation of a series of donor‐linker‐acceptor block copolymers with poly(3‐hexylthiophene) (P3HT) donor blocks, poly((9,9‐dioctylfluorene)‐2,7‐diyl‐alt‐[4,7‐bis(thiophen‐5‐yl)‐2,1,3‐benzothiadiazole]‐2′,2″‐diyl) (PFTBT) acceptor blocks, and varying lengths of oligo‐ethylene glycol (OEG) chains as the linkers. Morphological analysis shows that the linkers increase polymer crystallinity while a combination of optical and photovoltaic measurements shows that the insertion of a flexible spacer reduces fluorescence quenching and photovoltaic efficiencies of solution processed photovoltaic devices. Density functional theory (DFT) simulations indicate that the linking groups reduce both charge separation and recombination rates, and block copolymers with flexible linkers will likely rotate to assume a nonplanar orientation, resulting in a significant loss of overlap at the donor–linker–acceptor interface. This work provides a systematic study of the role of linker length on the photovoltaic performance of donor–linker–acceptor block copolymers and indicates that linkers should be designed to control both the electronic properties and relative orientations of conjugated polymers at the interface. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1135–1143
Feature size reduction in two‐photon polymerization by optimizing resin composition
Authors: Cônsoli Pedro M. , Otuka Adriano J. G. , Balogh Debora T. , Mendonça Cleber R.
Published: August 2018

In the last decades, an increasing refinement over submicroscopic scales has played a decisive role in boosting scientific and technological progress. When dealing with miniaturized devices, organic materials have drawn considerable attention, not only for requiring lower energies during processing but also for allowing functionalization with ease, exhibiting biocompatibility and presenting high optical quality. In this scenario, the modification of acrylate polymers by femtosecond lasers has become an important mechanism. Among the main techniques based upon this principle, two‐photon polymerization (2PP) stands out due to its capability of producing fine features. Still, 2PP has often been combined with sophisticated methods devised to further improve spatial resolution and miniaturized devices. However, such measures invariably raise the cost of the experiments by demanding either the addition of other chemical compounds or a second laser system. In this study, we discuss how the relative proportion of acrylate monomers and different concentrations of a photoinitiator influence the final dimension of structures fabricated using polymeric samples, which are widely used in 2PP experiments. Furthermore, we demonstrate that it is possible to produce finer features only by varying the proportion of these constituents, achieving linewidths on the order of 360 nm and heights on order of 300 nm. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1158–1163
Spectroscopic analysis of chlamydial major outer membrane protein in support of structure elucidation
Authors: Hepler Robert W. , Nahas Debbie D. , Lucas Bob , Kaufhold Robin , Flynn Jessica A , Galli Jennifer D. , Swoyer Ryan , Wagner James M. , Espeseth Amy S. , Joyce Joseph G. , Cook James C. , Durr Eberhard
Published: August 2018

Chlamydial major outer membrane protein (MOMP) is the major protein constituent of the bacterial pathogen Chlamydia trachomatis. Chlamydia trachomatis Serovars D–K are the leading cause of genital tract infections which can lead to infertility or ectopic pregnancies. A vaccine against Chlamydia is highly desirable but currently not available. MOMP accounts for ~ 60% of the chlamydial protein mass and is considered to be one of the lead vaccine candidates against C. trachomatis. We report on the spectroscopic analysis of C. trachomatis native MOMP Serovars D, E, F, and J as well as C. muridarum MOMP by size exclusion chromatography multi angle light scattering (SEC MALS), circular dichroism (CD) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR). MOMP was purified from the native bacterium grown in either adherent HeLa cells or in different suspension cell lines. Our results confirm that MOMP forms homo‐trimers in detergent micelles. The secondary structure composition of C. trachomatis MOMP was conserved across serovars, but different from composition of C. muridarum MOMP with a 13% (CD) to 18% (ATR‐FTIR) reduction in β‐sheet conformation for C. trachomatis MOMP. When Serovar E MOMP was isolated from suspension cell lines the α‐helix content increased by 7% (CD) to 13% (ATIR‐FTIR). Maintenance of a native‐like tertiary and quaternary structure in subunit vaccines is important for the generation of protective antibodies. This biophysical characterization of MOMP presented here serves, in the absence of functional assays, as a method for monitoring the structural integrity of MOMP.
A review on the information content of the pair density as a tool for the description of the electronic properties in molecular systems
Authors: Torres Fernando J. , Rincón Luis , Zambrano Cesar , Mora José R. , Méndez Miguel
Published: August 2018

Recent advances on the use of the information content of the pair density to understand bonding and reactivity of molecular systems are presented. Two quantities are described: (1) the information content of the like‐spin exchange‐correlation hole, χ
XC, and (2) the information content of the Coulomb hole, χ
C, of the like‐spin and the unlike‐spin cases. χ
XC is capable of describing the electron structure of molecules on the basis of chemical grounds with astonishing accuracy and provides a clear differentiation of the localization degree of electrons, belonging to different molecular basins. Furthermore, χ
XC is used as a tool to get insights in the electronic reorganization occurring along a reaction coordinate. In contrast to χ
XC, χ
C is observed to concentrate in regions between atomic shells, from which information of nonclassical weak interactions can be obtained. Some relevant problems, in which the application of χ
XC in conjunction with χ
C would be of great value, are presented.
Flagellar hyperactivation of bull and boar spermatozoa
Authors: Harayama Hiroshi
Published: August 2018

Background

In mammals, flagellar hyperactivation is indispensable to sperm fertilization with oocytes in vivo, although there are species differences in regulatory mechanisms for this event. In this study, I reviewed researches regarding hyperactivation of bull and boar spermatozoa, in comparison with those of spermatozoa from other species.

Methods

Recent publications regarding sperm hyperactivation were collected and summarized.

Results (Main findings)

In bull and boar spermatozoa, there are two types of hyperactivation “full‐type hyperactivation and nonfull‐type hyperactivation” which are equivalent to anti‐hock hyperactivation and pro‐hock hyperactivation of mouse spermatozoa, respectively, on the basis of the flagellar parts exhibiting asymmetrical beating. Full‐type hyperactivation is initiated in response to a rapid increase of cytoplasmic Ca2+ in the connecting/middle and principal pieces by the mobilization of this divalent ion from extracellular space and internal store through cation channels. Regulatory molecules for the increase of cytoplasmic Ca2+ in the connecting/middle pieces are probably different from those in the principal pieces.

Conclusion

I have proposed a hypothesis on the regulation of full‐type hyperactivation by the distinct signaling cascades leading to the increase in cytoplasmic Ca2+ between the connecting/middle and principal pieces of bull and boar spermatozoa.
Sentinel‐2 accurately maps green‐attack stage of European spruce bark beetle (Ips typographus, L.) compared with Landsat‐8
Authors: Abdullah Haidi , Skidmore Andrew K. , Darvishzadeh Roshanak , Heurich Marco
Published: August 2018

Natural disturbances induced by insect outbreaks have increased in forest ecosystems over the past decades. To minimize economic loss and prevent a mass outbreak, early detection of bark beetle green attack – a period when trees have yet to show visual signs of infestation stress – is therefore crucial to effective and timely forest management. In this study, we evaluated the ability of spectral vegetation indices extracted from Landsat‐8 and Sentinel‐2 imagery to map bark beetle green attack using principal component analysis (PCA) and partial least square discriminate analysis (PLS‐DA). A recent infestation map produced through visual interpretation of high‐resolution aerial photographs validated the final infestation output maps. Leaf spectral measurements alongside total chlorophyll and nitrogen concentration, leaf water content and leaf dry matter content were measured to assess the impact of bark beetle green attack on foliar properties. We observed that the majority of spectral vegetation indices (SVIs) calculated from Sentinel‐2, particularly red‐edge dependent indices (NDRE2 and 3) and water‐related indices (SR‐SWIR,NDWI,DSWIandLWCI), were able to discriminate healthy from infested plots. In contrast, only the water‐related indices (NDWI,DSWIandRDI) from Landsat‐8 were able to discriminate between healthy and infested plots efficiently. The total number of pixels identified as harboring a green attack that matched with ground truth data (aerial photography) was higher for Sentinel‐2 (67%) than for Landsat‐8 (36%)SVIs, indicating the elevated sensitivity of Sentinel‐2 imagery to changes induced by bark beetle green attack. We also determined that foliar chlorophyll and leaf water content were significantly higher (P < 0.05) in healthy trees than in green‐attacked trees. Our study highlights the potential of Sentinel‐2 data for the early detection of bark beetle infestations and the production of reliable infestation maps at the green‐attack stage.
Solvent‐ and Heat‐Dependent Binding Behaviors of HMeQ[6] with Alkyldiammonium Ions
Authors: Meng Ling‐Jian , Tian Xiao , Huang Sai , Lin Rui‐Lian , Liu Xin‐Hua , Zhu Qian‐Jiang , Tao Zhu , Liu Jing‐Xin
Published: August 2018

Binding interactions between hexamethyl substituted cucurbit[6]uril (HMeQ[6]) and a series of alkyldiammonium ions both in water and organic solvent media (DMSO) were investigated by various techniques. In water, the alkyl chains of the alkyldiammonium ions were encapsulated into the hydrophobic cavity of the HMeQ[6] host to form inclusion complex. In DMSO, binding interactions of HMeQ[6] host with alkyldiammonium guests generate not only normal inclusion complexes, but also special head‐inclusion complexes, in which only the NH3+ groups of the guests were engulfed into the HMeQ[6] cavity while the alkyl chains of the guests reside outside of the HMeQ[6] portals. Interestingly, some of the head‐inclusion complexes can be switched to supramolecular polymers by heating.
An Efficient Photocatalytic and Antibacterial Performance of Ni/Ce–Codoped CdS Nanostructure under Visible Light Irradiation
Authors: Ranjith Rajendran , Krishnakumar Varadharajan , Boobas Singaram , Venkatesan Jayaraman , Jayaprakash Jeyaram
Published: August 2018

In the present work, the Ni/Ce‐codoped CdS Nanoparticles (NPs) were synthesized through a hydrothermal method. The phase structure, chemical state, chemical composition, morphology and optical properties of prepared samples were characterized using X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), Energy Dispersive X‐Ray Analysis (EDX), Fourier transform infrared spectroscopy (FT‐IR), High‐resolution transmission electron microscopy (HRTEM), UV‐Vis diffuse reflectance spectroscopy (DRS), Photoluminescence (PL) spectroscopy studies and their photocatalytic activities of Rhodamine B (RhB) degradation were studied under visible light irradiation. The Ni and Ce doped CdS NPs showed higher photocatalytic activity compared to that of pure CdS, and the activity was further enhanced by codoping of Ni and Ce into CdS. The enhancement of photocatalytic activity is due to the synergistic effect of Ni and Ce ions and with a narrowed bandgap, which may facilitate inhabitation of the photogenerated charge carrier recombination. Meanwhile, the possible photocatalytic mechanism of Ni and Ce codoped CdS was proposed on the basis of trapping experiments. Additionally, the antibacterial activity of Ni/Ce codoped CdS NPs was evaluated against E. coli and S. aureus.
Theophylline Supported on Modified Silica‐Coated Magnetite Nanoparticles as a Novel, Efficient, Reusable Catalyst in Green One‐Pot Synthesis of Spirooxindoles and Phenazines
Authors: Esmaeilpour Mohsen , Sardarian Ali Reza , Firouzabadi Habib
Published: August 2018

In the present work, theophylline immobilized on superparamagnetic Fe3O4@SiO2 nanoparticles were prepared via a multistep method and was fully characterized by means of fourier transform infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE‐SEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), energy dispersive X‐ray analysis (EDX), vibration sample magnetometry (VSM), N2 adsorption‐desorption isotherm analysis, temperature‐programmed desorption of carbon dioxide (CO2‐TPD) and elemental analysis. The catalytic performance of this novel nanomagnetic catalyst has been studied in the synthesis of spirooxindole derivatives via a one‐pot three‐component reaction of isatin derivatives, malononitrile or ethyl 2‐cyanoacetate, and 5‐amino‐1,3‐dimethyluracil in excellent yields under reflux conditions in water. Also, the highly efficient, green and economical synthesis of poly‐substituted benzo[a]pyrano‐[2, 3‐c]phenazine derivatives from four component reaction of 2‐hydroxynaphthalene‐1,4‐dione, diamines, aldehydes, and malononitrile in the presence of this basic magnetic catalyst has been developed. In addition, the used catalyst could be separated conveniently from the reaction system for up to 6 runs without significant loss of its catalytic efficiency.
Structure and Properties of Sulfonated Poly(ether ether ketone) Hybrid Membrane with Polyaniline‐Chains‐Modified Graphene Oxide and Its Application for Vanadium Redox Flow Battery
Authors: Zhang Yuxia , Wang Haixia , Yu Wenkai , Shi Haifeng
Published: August 2018

A series of acid‐base hybrid membranes (SPEEK/PANi‐GO), composed of sulfonated poly(ether ether ketone) (SPEEK) and polyaniline‐functionalized graphene oxide (PANi‐GO), have been prepared and applied for vanadium redox flow battery (VRB). The chemical composition and structure for PANi‐GO nanosheets and SPEEK/PANi‐GO hybrid membranes are in detail characterized. Physicochemical properties such as ion exchange capacity, proton conductivity and vanadium ion permeability are highly based on the loadings of PANi‐GO nanofillers. The formed acid‐base pairs, originated from ‐SO3H of SPEEK and ‐NH group of PANi‐GO, decrease the swelling ratio and vanadium ion permeability. Ion selectivity shows a strong dependence upon the PANi‐GO content, and it presents a maximum value at 2% loading. VRB performance by SPEEK/PANi‐GO‐2 hybrid membrane exhibits a higher coulombic efficiency (CE: 98.5%) and energy efficiency (EE: 81.7%) at 30 mA cm−2, as compared with Nafion 117 (CE: 88.9% and EE: 72.5%) and SPEEK membrane (CE: 89.8% and EE: 69%). The self‐discharge time with SPEEK/PANi‐GO‐2 (58 h) is longer than that of Nafion 117 membrane (26 h), and a good chemical and oxidation stability is well demonstrated after 300 times charge‐discharge cycles for SPEEK/PANi‐GO‐2 hybrid membrane. These SPEEK/PANi‐GO hybrid membranes demonstrate a promising application for VRB system.
Design, Synthesis and Biological Evaluation of Triazole‐Containing 2‐Phenylindole and Salicylic Acid as Quorum Sensing Inhibitors Against Pseudomonas aeruginosa
Authors: Srinivasarao Singireddi , Nizalapur Shashidhar , Yu Tsz Tin , Wenholz Daniel Stanley , Trivedi Prakruti , Ghosh Balaram , Rangan Krishnan , Kumar Naresh , Gowri Chandra Sekhar Kondapalli Venkata
Published: August 2018

We designed and synthesized 2‐phenylindole‐amide‐triazole and salicyclic acid‐triazole analogues and characterized using NMR, MS and elemental analysis. Furthermore, single crystal was developed for N‐(2‐Phenyl‐1H‐indol‐3‐yl)‐2‐(4‐propyl‐1H‐1,2,3‐triazol‐1‐yl)acetamide (7 a), 2‐(4‐(4‐(tert‐Butyl)phenyl)‐1H‐1,2,3‐triazol‐1‐yl)‐N‐(2‐phenyl‐1H‐indol‐3‐yl)acetamide (7 h) and 3‐(1‐(4‐Ethylphenyl)‐1H‐1,2,3‐triazol‐4‐yl)‐N‐(2‐phenyl‐1H‐indol‐3‐yl)propanamide (10 j). Final compounds were screened for in vitro quorum sensing inhibitory (QSI) activity against Pseudomonas aeruginosa. The QSI activity was determined in the LasR expressing P. aeruginosa MH602 reporter strain by measuring green fluorescent protein (GFP) production. 10 j, 4‐(1‐Heptyl‐1H‐1,2,3‐triazol‐4‐yl)‐N‐(2‐phenyl‐1H‐indol‐3‐yl)butanamide (11 b) and 4‐(1‐(4‐Bromophenyl)‐1H‐1,2,3‐triazol‐4‐yl)‐N‐(2‐phenyl‐1H‐indol‐3‐yl)butanamide (11 e) exhibited promising QSI activity with 60.82, 58.89 and 54.34% at 250 μM, respectively. 1,2,3‐Triazole based salicylic acid derivatives exhibited moderate to good activity and 2‐Hydroxy‐4‐(1‐phenyl‐1H‐1,2,3‐triazol‐4‐yl)benzoic acid (17 e) is the most promising QS inhibitor with 40.28% inhibition at 250 μM. These compounds were docked into the binding site of the LasR receptor protein to understand possible binding ligand‐protein interactions. The most active compounds were subjected to cytotoxicity assay and were found to be less cytotoxic against HEK 293 cell line at 100 μM.
Preparation of α‐Iodocarbonyl Compounds: An Overall Development
Authors: Vekariya Rajesh H. , Balar Chetan R. , Sharma Vinay S. , Prajapati Neelam P. , Vekariya Mayur K. , Sharma Anuj S.
Published: August 2018

The α‐iodination of carbonyl compounds is one of the most important procedures in synthetic organic chemistry. These compounds are important precursors for carbon‐carbon, carbon‐oxygen, and carbon‐nitrogen bond formation as well as they are useful for the synthesis of various biologically important heterocyclic compounds. Despite the availability of numerous methods for the synthesis of this important class of compounds, the desired products usually suffering from some impurities such as di‐iodinated or ring iodinated products are formed in the reaction mixture. Therefore, as the essential productivity issues as well as environmental anxieties that need to be addressed to overcome this issue. In this regards, iodine (I2) and N‐iodosuccinimide (NIS) are important reagents for the production of such an important class of intermediates. In recent years considerable advances have been made for the synthesis of α‐iodo carbonyl compounds with high selectivity and purity. In this present review, we have summarized various protocols for the synthesis of α‐iodo carbonyl compounds.
Synthesis, Photophysical, Electrochemical Properties, DFT Studies and DSSC Performance of BODIPY Cored Triazole Bridged 3,6‐Ditertiary Butyl Carbazole Decorated Dendrimers
Authors: Babu Janakiraman , Ganesan Shanmugam , Karuppusamy Masiyappan , Rajakumar Perumal
Published: August 2018

A series of BODIPY cored dendrimers up to second generation decorated with 3,6‐ditertiary butyl carbazole at the surface and triazole as the bridging unit has been achieved by convergent approach. The synthesised dendrimers show excellent photophysical and electrochemical properties. All the dendrimers exhibit bi‐exponential lifetime decay, with the higher generation dendrimers (G2) exhibiting longer lifetime decay than the lower generation dendrimers. Density functional theory calculations on the synthesized dendrimers show the HOMO – LUMO energy gap as 2.42 eV with predicted absorption maximum around 425 nm. Cyclic voltammetric studies reveal that all the dendrimers exhibit irreversible oxidation‐reduction signal. Higher generation dendrimer (G2) shows a better power conversion efficiency of 2.7% than the other synthesised dendrimers when used as sensitizer in DSSC.
A Single Pd Atom Stabilized on Boron‐Vacancy of h‐BN Nanosheet: A Promising Catalyst for CO Oxidation
Authors: Esrafili Mehdi D. , Asadollahi Soheila
Published: August 2018

The possible reaction mechanisms for CO catalytic oxidation by O2 molecule on the Pd‐doped hexagonal boron nitride nanosheet (Pd‐BNNS) were studied using first‐principles calculations. The large adsorption energy of the Pd atom over the boron‐vacancy defect of BN nanosheet suggests that Pd‐BNNS could be stable under high temperatures. According to our results, the adsorption of CO over Pd‐BNNS is energetically preferable than that of O2. Three different reaction pathways of the CO oxidation are investigated comparably: the Eley‐Rideal (ER), the Langmuir‐Hinshelwood (LH) and the termolecular Eley‐Rideal (TER). Our results indicate that the CO oxidation reaction would like to take place via the TER mechanism due to its small activation energies. The calculated energy barrier for the rate‐determining step of the latter pathway is only 0.19 eV. Based on electronic structure analysis, such high catalytic activity of Pd‐BNNS can be related to the strong hybridization of the Pd‐4d and CO‐5σ/CO‐2π* states, which effectively activates the adsorbed CO molecules involved in the TER mechanism.
Straightforward Synthesis of Novel Difluorinated 2‐Hydroxyl‐Substituted Dihydroquinolones Through Selectfluor‐triggered Annulation of 2‐Aminoarylenaminones
Authors: Zhao Qing‐Lan , Xiang Hao‐Yue , Yang Chun‐Hao , Xiao Jun‐An , Xia Peng‐Ju , Chen Xiao‐Qing , Yang Hua
Published: August 2018

A series of novel difluorinated 2‐hydroxyl‐substituted dihydroquinolones have been firstly synthesized via selectfluor‐triggered tandem cyclizations of 2‐aminoarylenaminones. This new approach could occur under mild reaction conditions, and features easy operation and scalability.
Infinite distances in field space and massless towers of states
Authors: Grimm Thomas W. , Palti Eran , Valenzuela Irene
Published: August 2018

Abstract

It has been conjectured that in theories consistent with quantum gravity infinite distances in field space coincide with an infinite tower of states becoming massless exponentially fast in the proper field distance. The complex-structure moduli space of Calabi-Yau manifolds is a good testing ground for this conjecture since it is known to encode quantum gravity physics. We study infinite distances in this setting and present new evidence for the above conjecture. Points in moduli space which are at infinite proper distance along any path are characterised by an infinite order monodromy matrix. We utilise the nilpotent orbit theorem to show that for a large class of such points the monodromy matrix generates an infinite orbit within the spectrum of BPS states. We identify an infinite tower of states with this orbit. Further, the theorem gives the local metric on the moduli space which can be used to show that the mass of the states decreases exponentially fast upon approaching the point. We also propose a reason for why infinite distances are related to infinite towers of states. Specifically, we present evidence that the infinite distance itself is an emergent quantum phenomenon induced by integrating out at one-loop the states that become massless. Concretely, we show that the behaviour of the field space metric upon approaching infinite distance can be recovered from integrating out the BPS states. Similarly, at infinite distance the gauge couplings of closed-string Abelian gauge symmetries vanish in a way which can be matched onto integrating out the infinite tower of charged BPS states. This presents evidence towards the idea that also the gauge theory weak-coupling limit can be thought of as emergent.
The hierarchion, a relaxion addressing the Standard Model’s hierarchies
Authors: Davidi Oz , Gupta Rick S. , Perez Gilad , Redigolo Diego , Shalit Aviv
Published: August 2018

Abstract

We present a mechanism that addresses the electroweak, the strong CP, and the flavor hierarchies of the Standard Model (including neutrino masses) in a unified way. The naturalness of the electroweak scale is solved together with the strong CP problem by the Nelson-Barr relaxion: the relaxion field is identified with the pseudo-Nambu-Goldstone boson of an abelian symmetry with no QCD anomaly. The Nelson-Barr sector generates the “rolling” potential and the relaxion vacuum expectation value at the stopping point is mapped to the Cabibbo-Kobayashi-Maskawa phase. The same abelian symmetry accounts for the Standard Model’s mass hierarchies and flavor textures through the Froggatt-Nielsen mechanism. We show how the “backreaction” potential of the relaxion can be induced by a sterile neutrino sector, without any extra state with electroweak quantum numbers. The same construction successfully explains neutrino masses and mixings. The only light field in our model is the relaxion, which we call the hierarchion because it is central to our construction that accounts for all the Standard Model hierarchies. Given its interplay with flavor symmetries, the hierarchion can be probed in flavor-violating decays of the Standard Model fermions, motivating a further experimental effort in looking for new physics in rare decays of leptons and mesons.
Discrete quotients of 3-dimensional $$ \mathcal{N}=4 $$ Coulomb branches via the cycle index
Authors: Hanany Amihay , Sperling Marcus
Published: August 2018

Abstract

The study of Coulomb branches of 3-dimensional

$$ \mathcal{N}=4 $$

N
=
4

gauge theories via the associated Hilbert series, the so-called monopole formula, has been proven useful not only for 3-dimensional theories, but also for Higgs branches of 5 and 6-dimensional gauge theories with 8 supercharges. Recently, a conjecture connected different phases of 6-dimensional Higgs branches via gauging of a discrete global S

n

symmetry. On the corresponding 3-dimensional Coulomb branch, this amounts to a geometric S

n
-quotient. In this note, we prove the conjecture on Coulomb branches with unitary nodes and, moreover, extend it to Coulomb branches with other classical groups. The results promote discrete S

n
-quotients to a versatile tool in the study of Coulomb branches.
Supersymmetric SYK model with global symmetry
Authors: Narayan Prithvi , Yoon Junggi
Published: August 2018

Abstract

In this paper, we introduce an

$$ \mathcal{N}=1 $$

N
=
1

supersymmetric SYK model with SO(q) global symmetry. We study the large N expansion of the bi-local collective action of our model. At strong coupling limit, this model exhibits a super-reparametrization symmetry, and the SO(q) global symmetry is enhanced to a

$$ \widehat{\mathrm{SO}}(q) $$

SO
^

q

local symmetry. The corresponding symmetry algebra is the semi-direct product of the super-Virasoro and the super-Kac-Moody algebras. These emergent symmetries are spontaneously and explicitly broken, which leads to a low energy effective action: super-Schwarzian action plus an action of a super-particle on the SO(q) group manifold. We analyze the zero mode contributions to the chaotic behavior of four point functions in various SO(q) channels. In singlet channel, we show that the out-of-time-ordered correlators related to bosonic bi-locals exhibit the saturation of the chaos bound as in the non-SUSY SYK model. On the other hand, we find that the ones with fermionic bi-locals in the singlet channel have

$$ \frac{\pi }{\beta } $$

π
β

Lyapunov exponent. In the anti-symmetric channel, we demonstrate that the out-of-time-ordered correlator related to a SO(q) generator grows linearly in time. We also compute the non-zero mode contributions which give consistent corrections to the leading Lyapunov exponents from the zero modes.
Sex Disparities in Access to Surgical Care at a Single Institution in Malawi
Authors: Reid Trista D. , Wren Sherry M. , Grudziak Joanna , Maine Rebecca , Kajombo Chifundo , Charles Anthony G.
Published: August 2018

Introduction

There is a paucity of data regarding sex‐based disparities in surgical care delivery, particularly in low‐ and middle‐income countries. This study sought to determine whether sex disparities are present among patients presenting with surgical conditions in Malawi. Hypothesis compared to men, fewer women present to Kamuzu Central Hospital (KCH) with peritonitis and have longer delays in presentation for definitive care.

Methods

This study performs a retrospective analysis of prospectively collected data of all general surgery patients with peritonitis presenting to KCH in Lilongwe, Malawi, from September 2013 to April 2016. Multivariable linear and logistic regressions were used to assess the effect of sex on mortality, length of stay, operative intervention, complications, and time to presentation.

Results

Of 462 patients presenting with general surgery conditions and peritonitis, 68.8% were men and 31.2% were women. After adjustments, women had significantly higher odds of non‐operative management when compared to men (OR 2.17, 95%CI 1.30–3.62, P = 0.003), delays in presentation (adjusted mean difference 136 h, 95%CI 100–641, P = 0.05), delays to operation (adjusted mean difference 1.91 days, 95%CI 1.12–3.27, P = 0.02), and longer lengths of stay (adjusted mean difference 1.67 days, 95%CI 1.00–2.80, P = 0.05). There were no differences in complications or in‐hospital or Emergency Department mortality.

Conclusion

Sex disparities exist within the general surgery population at KCH in Lilongwe, Malawi. Fewer women present with surgical problems, and women experience delays in presentation, longer lengths of stay, and undergo fewer operations. Future studies to determine mortality in the community and driving factors of sex disparities will provide more insight.
Clinical Outcomes and Healthcare Costs Associated with Laparoscopic Appendectomy in a Middle‐Income Country with Universal Health Coverage
Authors: Buitrago Giancarlo , Junca Edgar , Eslava‐Schmalbach Javier , Caycedo Ruben , Pinillos Pilar , Leal Luis Carlos
Published: August 2018

Background

Although many studies have compared outcomes of laparoscopic appendectomy (LA) and open appendectomy (OA), some clinical and economic outcomes continue to be controversial, particularly in low–medium‐income countries. We aimed at determining clinical and economic outcomes associated with LA versus OA in adult patients in Colombia.

Methods

Retrospective, cohort study based on administrative healthcare records included all patients who underwent LA or OA in Colombia’s contributory regime between July 1, 2013, and September 30, 2015. Outcomes were 30‐day mortality rates, ICU admissions rates, length of stay (LOS), and hospital costs provided until discharge. Propensity score matching techniques were used to balance the baseline characteristics of patients (age, sex, comorbidities based on the Charlson index, insurer, and geographic location) and to estimate the average treatment effect (ATE) of LA as compared to OA over outcomes.

Results

A total of 65,625 subjects were included, 92.9% underwent OA and 7.1% LA. For the entire population, 30‐day mortality was 0.74 per 100 appendectomies (95% CI 0.67–0.81), the mean and median LOS were 3.83 days and 1 day, respectively, and the ICU admissions rate during the first 30 days was 7.92% (95% CI 7.71–8.12). The ATE shows an absolute difference in the mortality rate after 30 days of −0.35 per 100 appendectomies (p = 0.023), in favor of LA. No effects on ICU admissions or LOS were identified. LA was found to increase costs by 514.13 USD on average, with total costs of 772.78 USD for OA and 1286.91 USD for LA (p < 0.001).

Conclusions

In Colombia’s contributory regime, LA is associated with lower 30‐day mortality rate and higher hospital costs as compared to OA. No differences are found in ICU admissions or LOS.
Temporal trends of contaminants in Arctic human populations
Authors: Abass Khaled , Emelyanova Anastasia , Rautio Arja
Published: August 2018

The first Arctic Monitoring and Assessment Programme (AMAP) report was published in 1998 and followed by three assessment reports of human health (AMAP 2003, 2009 and 2015). The focus area of the AMAP reports was to monitor levels of environmental contaminants in the Arctic and to assess the health effects connected with detected levels in Arctic countries. This review gives an overview of temporal trends of contaminants and their health effects in humans of the Arctic based on data published by AMAP, as well as Russian scientific literature. Several time series of 31 contaminants in humans of the Arctic from different cohorts are reported. The lengths of time series and periods covered differ from each other. International restrictions have decreased the levels of most persistent organic pollutants in humans and food webs. Percentage changes for contaminants in human biological matrices (blood samples from children, mothers and males and breast milk samples) for the period of sampling showed declining trends in most of the monitored Arctic locations, with the exception of oxychlordane, hexachlorobenzene (HCB), 2,2′,4,4′,5,5′-hexabromodiphenyl ether (PBDE153) and perfluorinated compounds (PFCs).
Internal Diversity among “Spiritual but Not Religious” Adolescents in the United States: A Person-Centered Examination Using Latent Class Analysis
Authors: Tong Yunping , Yang Fenggang
Published: August 2018

Americans who self-identify as spiritual but not religious (SBNR) have increased in recent years. Existing studies of American religion often assume the SBNR as a homogeneous group. Recently some scholars suggest they are not all the same. Instead, SBNR people may differ in the pattern of religious practice, attitude, and affection. This study examines the heterogeneity of the SBNR using a person-centered approach of latent class analysis. We first identified four distinct types of SBNR adolescents in the Wave 2 data of the National Survey of Youth and Religion. Then, we explored how subgroups changed their religious identity over time by tracking them in Wave 3 data.
Assessing IT availability risks in smart factory networks
Authors: Häckel Björn , Hänsch Florian , Hertel Michael , Übelhör Jochen
Published: August 2018

Emerging smart manufacturing technologies combine physical production networks with digital IT systems, resulting in complex smart factory networks, which are especially vulnerable to IT security risks, such as IT component non-availabilities. Companies must employ extensive IT security measures to secure their production facilities. However, complex network structures and inherent dependencies of smart factory networks complicate corresponding investment decisions and increase the need for appropriate decision support. We develop a risk assessment model that supports companies in the investment decision-making process regarding IT security measures by identifying and evaluating the most critical areas of the information network while considering the underlying production network. For this purpose, IT availability risks are quantified by means of graph theory, matrix notation, and value-at-risk. Our model provides a structured approach and considers network structures and interdependencies. The insights gained by our model present a profound economic basis for investment decisions on IT security measures. By applying our model in an exemplary real-world setting, we analyze various IT security measures and their risk reduction effect.
Space Food and Nutrition in a Long Term Manned Mission
Authors: Oluwafemi Funmilola Adebisi , De La Torre Andrea , Afolayan Esther Morayo , Olalekan-Ajayi Bolanle Magret , Dhital Bal , Mora-Almanza Jose G. , Potrivitu George , Creech Jessica , Rivolta Aureliano
Published: August 2018

Fulfillment of space exploration mission is key, but much more important are the lives of the explorers. Keeping the astronauts alive, jolly and healthy for long term manned mission has recently being a major and important research area. A major contribution seems to be the food they eat. For short term space manned missions, astronauts food could be taken along with them from Earth, but for manned missions to the Moon, Mars and Venus which are the current research destinations for long term space missions, they must find a means for their nutrition such as growing plants and finding any other alternatives for their survival. As most of these proposed missions have being designed to be one-way missions whereby the astronauts will not come back to the Earth. Good food and nutrition for astronauts help to keep their psychology and physiology in good shape. In this paper, solutions will be made on the various alternatives for feeding astronauts in the long term missions to various celestial bodies: Moon, Mars and Venus, where the atmosphere, gravity, soil, radiation and other conditions vary from one to the other and may not support germination, growth and development of plants. Therefore, review will be done on the following: having fore knowledge of how plants will grow on these celestial bodies by simulating their soils; using mathematical/theoretical models to get the growth rate of plants in relation to the gravity available on these celestial bodies using available data from terrestrial growth (1 g growth) and microgravity/microgravity simulations facilities; getting to know how the plants will be grown such as using greenhouse method as a result of the atmosphere and radiation in these celestial bodies; and other various alternatives for growing plants and having the astronauts well-nourished such as using aeroponics and hydroponics methods. A brief discussion will also be done on food choice for astronauts considering psychosocial and cultural factors.
Application of Contiguous Rain Area (CRA) Methods to Tropical Cyclone Rainfall Forecast Verification
Authors: Chen Yingjun , Ebert Elizabeth E. , Davidson Noel E. , Walsh Kevin J. E.
Published: August 2018

This study demonstrates the useful information that can be derived from contiguous rain area (CRA) evaluation, such as systematic errors in tropical cyclone (TC) rainfall location and components of rainfall error due to incorrect predictions of location, rain volume, and rain pattern. CRA verification uses pattern matching techniques to determine the location error, as well as errors in area, mean and maximum intensity, and spatial pattern. In this study, CRA verification was applied to evaluate Australian Community Climate and Earth System Simulator (ACCESS)‐TC, the TC version of ACCESS, daily rainfall forecasts over 15 TCs in the north west Pacific ocean during 2012–2013, by comparing with Tropical Rainfall Measuring Mission (TRMM) 3B42 satellite estimates. The results showed that pattern error was the major contributor to the total TC rainfall forecast error, followed by volume and displacement. ACCESS‐TC forecasts tended to predict more rainfall closer to the TC center compared to Tropical Rainfall Measuring Mission (TRMM) 3B42 estimates. This bias occurred for different CRA rainfall thresholds, verification grid resolutions and forecast lead times. Furthermore, rain event verification showed that for short lead time (24 hr) forecasts, overestimation of rain volume was a major problem for ACCESS‐TC forecasts, while displacement error was more significant in longer lead time (72 hr) forecasts. Finally, we compared empirical probability distribution functions and radial probability distributions of rainfall in the forecasts and observations to further characterise the rain volume error. This confirmed that ACCESS‐TC tended to produce more extreme rain in the locations closer to the TC center (eyewall).
Illegal Seafood Supply Chains Can Now Be Tracked by Satellite
Authors: Kornei Katherine
Published: August 2018

Researchers pinpoint more than 10,000 likely transfers of catches between fishing vessels and cargo ships at sea. Knowing where these transfers occur can help officials crack down on illegal activity.
White House Pick for Top Science Spot Stresses Science Integrity
Authors: Showstack Randy
Published: August 2018

At his Senate confirmation hearing, Kelvin Droegemeier, Trump’s choice to head the White House Office of Science and Technology Policy, discussed plans to tackle the nation’s scientific challenges.
Spatial Features of L‐Band Equinoctial Scintillations From Equator to Low Midlatitude at Around 95°E During 2015–2016
Authors: Dutta Barsha , Kalita Bitap Raj , Bhuyan P. K. , Sharma S. , Tiwari R. C. , Wang K. , Hozumi K. , Tsugawa T. , Yokoyama T. , Le Huy M. , Pham T. T. H.
Published: August 2018

The nature and extent of the irregularities causing L‐band nighttime scintillations at a group of five stations Dibrugarh (27.5°N, 95°E, 43° dip), Kohima (25.6°N, 94.1°E, 39° dip), Aizawl (23.7°N, 92.8°E, 36° dip), Port Blair (11.6°N, 92.7°E, 9° dip), and Cocos Islands (12.2°S, 96.8°E, 43° dip) from the northern low midlatitudes to southern midlatitudes along 95°E meridian is investigated. Global Navigation Satellite System/Global Positioning System/ionosonde measurements during the equinoctial months of 2015–2016 have been utilized. The northernmost station Dibrugarh and the southernmost station Cocos Islands are magnetically conjugate. Scintillations occur more frequently around the equatorial ionization anomaly crest where the background charge density (total electron content crest‐to‐trough ratio) plays an important role. It is also observed that L‐band scintillations around this sector decrease considerably from equinoctial months of 2015 to equinoctial months of 2016. The anomalous El Niño‐Southern Oscillation and quasi‐biennial oscillation recorded during the 2015–2016 winter might have contributed partly to the suppression of irregularities (and hence scintillations) in the succeeding equinox. Strong pre‐midnight scintillations when triggered by equatorial spread F occur simultaneously at all stations. The zonal/vertical drift velocities of irregularities estimated from the time delay of occurrence of scintillations decrease from postsunset to midnight hours. On the other hand, simultaneous sporadic E and post‐midnight scintillations occur over Dibrugarh and Cocos Islands in the absence of scintillations at the equator. Azimuthal position of post‐midnight scintillations at these two locations suggests that they are the manifestation of a frontal structure of sporadic E.
Grad‐Shafranov Reconstruction of Earth's Magnetopause With Temperature Anisotropy
Authors: Chen G.‐W. , Hau L.‐N.
Published: August 2018

The Grad‐Shafranov (GS) reconstruction may recover the steady two‐dimensional magnetohydrodynamic equilibrium structure from single spacecraft data. In this study we report first results on magnetopause structure from a newly developed GS solver that includes the effects of temperature anisotropy and field‐aligned flow. Double‐polytropic laws are used as energy closure to describe various thermodynamic states for anisotropic plasmas including double‐adiabatic and isothermal conditions as special cases. The new GS solver is benchmarked and applied to a Time History of Events and Macroscale Interactions during Substorms magnetopause crossing event with field‐aligned flow and p⊥ > p∥, where p⊥ and p∥ are the pressure components perpendicular and parallel to the local magnetic field, respectively. The recovered magnetic field maps for various thermodynamic conditions show qualitatively similar features with magnetic islands imbedded within the magnetopause current. The mirror‐type anisotropy with p⊥ > p∥ may lead to relatively inflated magnetic islands as compared to the isotropic case, consistent with earlier theoretical prediction.