bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi‐stimuli‐responsive self‐immolative polymer assemblies
Authors: Yardley Rebecca E. , Gillies Elizabeth R. 
Published: August 2018

ABSTRACTSelf‐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

ABSTRACTNovel 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

ABSTRACTShape 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

ABSTRACTBlock 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

ABSTRACTIn 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

AbstractChlamydial 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

AbstractRecent 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

AbstractBackgroundIn 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.MethodsRecent 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.ConclusionI 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

AbstractNatural 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

AbstractBinding 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

AbstractIn 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

AbstractIn 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

AbstractA 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

AbstractWe 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

AbstractThe 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.