bluuebunny/crossref_metadata_2025 huggingface dataset:
Root Growth Responses of Maize (Zea mays L.) and Soybean (Glycine max L.) to Soil Compaction and Fertilization in a Ferric Acrisol
Authors: Bawa Seidu Iddrissu , Quansah Charles , Tuffour Henry Oppong , Abubakari Awudu , Melenya Caleb
Published: May 2019

Mechanical impedance to root growth is one of the most important factors determining root elongation and proliferation within a soil profile. Two pot experiments were conducted at the Department of Horticulture, KNUST, Kumasi, Ghana, to determine the impact of subsurface compaction and different fertilizer amendments on the root growth of maize (Zea mays L.) and soybean (Glycine max L.). The experiments were arranged in a factorial Completely Randomized Design (CRD) with three replications. Maize and soybean varieties, “Obaatanpa” and “Anidaso” were sown in 72 plastic buckets (36 for each crop) of 12 L volume filled with a Ferric Acrisol. The treatments were different levels of compaction, using bulk density as proxy – 1.3, 1.5 and 1.7 Mg   m-3, and fertilizer amendments of 100% poultry manure (15 g/pot), 100% NPK fertilizer (2.89 g/pot) and 50% each of poultry manure (7.5 g/pot) and NPK fertilizer (1.45 g/pot). The highest root growth occurred in the uncompacted soil and along the periphery of the soil core. The applied soil amendments significantly increased the root penetration ratio (RPR) of both crops in relation to the control. The shoot biomass of both crops decreased with increasing soil bulk density. All the applied soil amendments significantly increased the shoot biomass of maize and soybean over the control. The magnitude of response of the crops to the soil amendments was greater in soybean than in maize.
Retracted: LncRNA MALAT1 increases the stemness of gastric cancer cells via enhancing SOX2 mRNA stability
Authors: Xiao Yiwen , Pan Jingjing , Geng Qian , Wang Ge
Published: May 2019

Gastric cancer is one of the most common malignancies globally; cancer stem cells (CSCs) are regarded as being at the root of tumor progression, and there is thus a need to identify potential drugs to target CSCs. The long non‐coding RNA MALAT1 promotes epithelial–mesenchymal transition and angiogenesis in colorectal cancer, but it is unknown whether it affects the stemness of gastric cancer cells. Here, we found that knockdown (KD) of MALAT1 attenuated the stemness of non‐adherent gastric cancer cell spheroids, as evidenced by a decrease in primary and secondary spheroid formation capacity and expression of stemness markers. In contrast, overexpression (OE) of MALAT1 enhanced the stemness of adherent gastric cancer cells. Notably, KD of MALAT1 enhanced radiosensitivity and chemosensitivity of gastric cancer cell spheroids. We report that MALAT1 directly binds to sox2 mRNA (which encodes a critical master pluripotency factor), enhances the mRNA stability and increases its expression; KD of sox2 partially reversed the effect of MALAT1 OE on the stemness of gastric cancer cells. Importantly, expression of MALAT1 and sox2 exhibited a positive correlation in clinical samples. Therefore, our results indicate the existence of a novel MALAT1–sox2 axis which promotes the stemness of gastric cancer cells and may be a potential target for gastric cancer.
Nanomaterials in Superlubricity
Authors: Zhai Wenzheng , Zhou Kun
Published: May 2019

The vanishing friction, known as superlubricity, is potentially a significant performance indicator in the development of nanostructured materials and has become increasingly important for realizing energy saving and extending the life of mechanical components. Herein, a systematic review of recent progress in nanomaterials for achieving the superlubric state is provided, beginning with a brief introduction of nanostructured materials in superlubricity and its wide potential applications. Subsequently, a detailed discussion of experimental and simulation works on the different spatial structures of nanomaterials associated with size effects ranging from 0D to 3D nanostructures is given, with an emphasis on solid and liquid superlubricity. Finally, this work concludes with perspectives on the challenges and future directions for developing nanomaterials in the field of superlubricity.
A Review on Dielectric Breakdown in Thin Dielectrics: Silicon Dioxide, High‐k, and Layered Dielectrics
Authors: Palumbo Felix , Wen Chao , Lombardo Salvatore , Pazos Sebastian , Aguirre Fernando , Eizenberg Moshe , Hui Fei , Lanza Mario
Published: May 2019

Thin dielectric films are essential components of most micro‐ and nanoelectronic devices, and they have played a key role in the huge development that the semiconductor industry has experienced during the last 50 years. Guaranteeing the reliability of thin dielectric films has become more challenging, in light of strong demand from the market for improved performance in electronic devices. The degradation and breakdown of thin dielectrics under normal device operation has an enormous technological importance and thus it is widely investigated in traditional dielectrics (e.g., SiO2, HfO2, and Al2O3), and it should be further investigated in novel dielectric materials that might be used in future devices (e.g., layered dielectrics). Understanding not only the physical phenomena behind dielectric breakdown but also its statistics is crucial to ensure the reliability of modern and future electronic devices, and it can also be cleverly used for other applications, such as the fabrication of new‐concept resistive switching devices (e.g., nonvolatile memories and electronic synapses). Here, the fundamentals of the dielectric breakdown phenomenon in traditional and future thin dielectrics are revised. The physical phenomena that trigger the onset, structural damage, breakdown statistics, device reliability, technological implications, and perspectives are described.
Ultrathin and Ultrasmooth Gold Films on Monolayer MoS2
Authors: Yakubovsky Dmitry I. , Stebunov Yury V. , Kirtaev Roman V. , Ermolaev Georgy A. , Mironov Mikhail S. , Novikov Sergey M. , Arsenin Aleksey V. , Volkov Valentyn S.
Published: May 2019

Sub‐10 nm continuous metal films are promising candidates for flexible and transparent nanophotonics and optoelectronic applications. In this article, it is demonstrated that monolayer MoS2 is a perspective adhesion layer for the deposition of continuous conductive gold films with a thickness of only 3–4 nm. Optical properties of continuous ultrathin gold films deposited on 2D MoS2 grown by chemical vapor deposition are investigated by spectroscopic ellipsometry over a wide wavelength range (300–3300 nm). Results show that optical losses in ultrathin films increase with decreasing thickness due to the fine‐grained structure and the presence of a small number of voids, however, they exhibit metallic properties down to a thickness of 3–4 nm. The atomic‐scale MoS2 interfaces can be transferred to any substrate and thus open up new opportunities for the creation of metasurfaces and a new type of van der Waals heterostructures with atomically thin metal layers.
The Role of Photochemical Reactions in the Development of Advanced Soft Materials for Biomedical Applications
Authors: Fernandez‐Villamarin Marcos , Brooks Laura , Mendes Paula M.
Published: May 2019

In the biomedical field, many innovative materials to improve diagnosis and treatment of diseases are currently being developed. The ability to respond to different stimuli is one of the more interesting properties of such materials. Light, as one of the nature's elementary stimuli, offers an attractive and flexible stimulus for controlling the properties and functions of biomedical‐related materials. As such, photoresponsive systems have been increasingly pursued and finding applications in various biomedical settings, ranging from tissue engineering for the fabrication of bespoke tissue scaffolds to drug delivery, aims at manipulating treatment distribution inside the human body. Efforts have also been devoted to the development of highly efficient methods to control biological activity and bring us closer to mimicking impressive biological actuators. In this progress report, an overview of recent developments in the field is provided and current challenges discussed. Key strategies tailored to address specific issues are examined, offering useful perspectives for future designs.
Preserving the Emission Lifetime and Efficiency of a Monolayer Semiconductor upon Transfer
Authors: Eizagirre Barker Simone , Wang Shaojun , Godiksen Rasmus H. , Castellanos Gabriel W. , Berghuis Matthijs , Raziman T. V. , Curto Alberto G. , Gómez Rivas Jaime
Published: May 2019

Monolayer transition metal dichalcogenides (TMDs) are promising semiconductors for nanoscale photonics and optoelectronics due to their strong interactions with light. However, processes that integrate TMDs into nanophotonic and optoelectronic devices can introduce defects in the monolayers, resulting in lower emission efficiency. Quality control is therefore needed to process monolayer semiconductors effectively. Through micro‐photoluminescence and fluorescence lifetime imaging measurements, this work investigates the effects of encapsulation on the optical properties of TMD monolayers, focusing on the impact of different processing techniques and different dielectric environments. Spin coating a polymer layer on top of a TMD monolayer is shown to significantly reduce its emission lifetime and efficiency. In contrast, the soft transfer of a monolayer deposited on a polymer superstrate can preserve its intrinsic emission properties almost perfectly in various dielectric environments. This approach can be widely applied to integrate TMDs into devices and heterostructures while protecting sample quality, and demonstrates that intrinsic quantum efficiency and photoluminescence lifetimes of TMDs can be preserved upon transfer to different dielectric substrates.
Electroluminescent Warm White Light‐Emitting Diodes Based on Passivation Enabled Bright Red Bandgap Emission Carbon Quantum Dots
Authors: Jia Haoran , Wang Zhibin , Yuan Ting , Yuan Fanglong , Li Xiaohong , Li Yunchao , Tan Zhan'ao , Fan Louzhen , Yang Shihe
Published: May 2019

The development of efficient red bandgap emission carbon quantum dots (CQDs) for realizing high‐performance electroluminescent warm white light‐emitting diodes (warm‐WLEDs) represents a grand challenge. Here, the synthesis of three red‐emissive electron‐donating group passivated CQDs (R‐EGP‐CQDs): R‐EGP‐CQDs‐NMe2, ‐NEt2, and ‐NPr2 is reported. The R‐EGP‐CQDs, well soluble in common organic solvents, display bright red bandgap emission at 637, 642, and 645 nm, respectively, reaching the highest photoluminescence quantum yield (QY) up to 86.0% in ethanol. Theoretical investigations reveal that the red bandgap emission originates from the rigid π‐conjugated skeleton structure, and the ‐NMe2, ‐NEt2, and ‐NPr2 passivation plays a key role in inducing charge transfer excited state in the π‐conjugated structure to afford the high QY. Solution‐processed electroluminescent warm‐WLEDs based on the R‐EGP‐CQDs‐NMe2, ‐NEt2, and ‐NPr2 display voltage‐stable warm white spectra with a maximum luminance of 5248–5909 cd m−2 and a current efficiency of 3.65–3.85 cd A−1. The warm‐WLEDs also show good long‐term operational stability (L/L0 > 80% after 50 h operation, L0: 1000 cd m−2). The electron‐donating group passivation strategy opens a new avenue to realizing efficient red bandgap emission CQDs and developing high‐performance electroluminescent warm‐WLEDs.
Stable Metallic Enrichment in Conductive Filaments in TaOx‐Based Resistive Switches Arising from Competing Diffusive Fluxes
Authors: Ma Yuanzhi , Goodwill Jonathan M. , Li Dasheng , Cullen David A. , Poplawsky Jonathan D. , More Karren L. , Bain James A. , Skowronski Marek
Published: May 2019

Oxide‐based resistive‐switching devices hold promise for solid‐state memory technology. Information encoding is accomplished by electrically switching the device between two nonvolatile states with low and high resistance states (LRS/HRS). It is generally accepted that the change between these states is due to the motion of oxygen vacancies forming a continuous (LRS) or gapped (HRS) filament between the electrodes. Direct assessments of filaments are rare due to their small size and the difficulty of locating the filament. Electron microscopy experiments reveal the filament structure and chemistry in TaO2.0 ± 0.2‐based 150 × 150 nm2 devices with cross‐sectional geometry after forming with power dissipation lower than 1 mW. The filaments appear to be roughly hourglass‐shaped with a diameter of less than 10 nm and are composed of Ta‐rich and O‐poor mostly amorphous material with local compositions as Ta‐rich as TaO0.4. The as‐formed HRS has a gap up to 10 nm wide located next to the anode and composed of nearly stoichiometric TaO2.5. The tantalum and oxygen distribution is consistent with filaments formed by the motion of both Ta and O driven by temperature gradients (Soret effect) and an electric field. This interpretation points towards a new compact model of resistive‐switching devices.
Cold‐Sintered C0G Multilayer Ceramic Capacitors
Authors: Wang Dawei , Zhou Di , Song Kaixin , Feteira Antonio , Randall Clive A. , Reaney Ian M.
Published: May 2019

Multilayer ceramic capacitors (MLCCs) based on (Bi0.95Li0.05)(V0.9Mo0.1)O4‐Na2Mo2O7 (BLVMO‐NMO), with εr = 39, temperature coefficient of capacitance, TCC ≈ ±0.01%, and tan δ = 0.01 at 1 MHz, are successfully fabricated by a cold‐sintering process at 150 °C. Scanning electron microscopy of the MLCCs combined with EDS mapping, X‐ray diffraction, and Raman spectroscopy reveals well‐laminated and undistorted dielectric layers composed of BLVMO and NMO discrete phases separated by Ag internal electrodes. Prototypes show comparable properties to C0G MLCCs (TCC = ±30 ppm °C−1 from −55 to +125 °C) currently commercially fabricated at 1100 °C using CaZrO3‐based dielectrics with glass sintering aids and Ni internal electrodes.
Type‐Switchable Inverter and Amplifier Based on High‐Performance Ambipolar Black‐Phosphorus Transistors
Authors: Zhang Le , Shao Li Yang , Gu Guoqiang , Wang Taihong , Sun Xiao Wei , Chen Xiaolong
Published: May 2019

Black phosphorus (BP), an emerging 2D layered material, is promising for nanoelectronic applications due to its high carrier mobility and saturation velocity. A high performance ambipolar BP field‐effect transistor (FET), fully assembled from 2D materials, is demonstrated. It exhibits two‐terminal mobility of 540 cm2 V−1 s−1 for holes and 250 cm2 V−1 s−1 for electrons at room temperature. The ambipolar charge transport of the BP FET allows it to operate as a p‐ and n‐type switchable inverter with operating frequency up to 160 kHz through simply changing the polarity of the supply voltage. At the same time, the voltage gain of the inverter is higher than 1, suggesting that it is suitable for logic‐circuit applications. Moreover, it is shown that the ambipolar BP FET can function as an output‐polarity controllable amplifier through tuning of the input and supply voltages. This demonstration paves the way for future BP applications in logic circuits.
Colonization, Baker's law, and the evolution of gynodioecy in Hawaii: implications from a study of Lycium carolinianum
Authors: Miller Jill S. , Blank Caitlin M. , Levin Rachel A.
Published: May 2019

Premise

As Baker’s law suggests, the successful colonization of oceanic islands is often associated with uniparental reproduction (self‐fertility), but the high incidence of dimorphism (dioecy, gynodioecy) on islands complicates this idea. Lycium carolinianum is widespread, occurring on the North American mainland and the Hawaiian Islands. We examined Baker's ideas for mainland and island populations of L. carolinianum and examined inbreeding depression as a possible contributor to the evolution of gynodioecy on Maui.

Methods

Controlled crosses were conducted in two mainland populations and two populations in Hawaii. Treatments included self and cross pollination, unmanipulated controls, and autogamy/agamospermy. Alleles from the self‐incompatibility S‐RNase gene were isolated and compared between mainland and island populations. Given self‐compatibility in Hawaii, we germinated seeds from self‐ and cross‐ treatments and estimated inbreeding depression using seven traits and a measure of cumulative fitness.

Results

Mainland populations of Lycium carolinianum are predominately self‐incompatible with some polymorphism for self‐fertility, whereas Hawaiian populations are self‐compatible. Concordantly, S‐RNase allelic diversity is reduced in Hawaii compared to the mainland. Hawaiian populations also exhibit significant inbreeding depression.

Conclusions

Self‐compatibility in Hawaii and individual variation in self‐fertility in mainland populations suggests that a colonization filter promoting uniparental reproduction may be acting in this system. Comparison of S‐RNase variation suggests a collapse of allelic diversity and heterozygosity at the S‐RNase locus in Hawaii, which likely contributed to mate limitation upon arrival to the Pacific. Inbreeding depression coupled with autonomous self‐fertilization may have led to the evolution of gynodioecy on Maui.
Early Childhood Teachers’ Lives in Context: Implications for Professional Development in Under‐Resourced Areas
Authors: Schwartz Kate , Cappella Elise , Aber J. Lawrence , Scott Marc A. , Wolf Sharon , Behrman Jere R.
Published: May 2019

This study explores the personal, professional, and contextual conditions faced by early childhood education (ECE) teachers in under‐resourced settings and how these relate to teacher responsiveness to professional development (PD): namely, teacher attrition (a sign of PD failure when occurring shortly after PD), take‐up of offered PD, adherence to PD training/materials, and quality of implementation. We use data from six disadvantaged districts in the Greater Accra Region of Ghana and PD focused on implementation of a national, play‐based curriculum. Descriptive statistics indicate that ECE teachers (n = 302) face a multitude of barriers to high quality teaching across the bioecological model. Multilevel mixed effects models find that teachers with low job satisfaction are more likely to leave the school within the academic year. Teachers with moderate to severe depression are less likely to attend PD trainings. Senior teachers and those with poverty risks are less likely to adhere to PD material. Teachers with many time demand barriers are more likely to adhere to material. They also implement the content at higher observed quality as do teachers with bachelor's degrees and early childhood development (ECD) training. Take‐up of PD also predicts quality of implementation. Practice and research implications are discussed.
Schimke immunoosseous dysplasia and management considerations for vascular risks
Authors: Beleford Daniah T. , Diab Mohammad , Qubty William F. , Malloy Mary J. , Long Roger K. , Shieh Joseph T.
Published: May 2019

Schimke immunoosseous dysplasia (SIOD) is a multisystemic condition characterized by early arteriosclerosis and progressive renal insufficiency, among other features. Many SIOD patients have severe, migraine‐like headaches, transient neurologic attacks, or cerebral ischemic events. Cerebral events could be exacerbated or precipitated by hypertension, and it is unclear how these are related to arteriosclerotic changes as dyslipidemia is also a feature of SIOD. The correlation between hypercholesterolemia and cardiovascular risk in SIOD is unclear. Also, the etiology and management of headaches is not well characterized. Here we report our clinical observations in the management of SIOD in a patient who was diagnosed in school age despite early signs and symptoms. We describe biallelic variants, including a previously unreported c.1931G>A (p.Arg644Gln) variant in SMARCAL1. We specifically investigated whether migraine‐like headaches and progressive nephropathy may be related to blood pressure dysregulation. We found a correlation between tighter blood pressure regulation using ambulatory blood pressure monitoring and a subjective decrease in headache symptoms. We discuss blood pressure medication management in SIOD. We also characterize dyslipidemia relative to atherosclerosis risks and provide new management strategies to consider for optimizing care.
The people or the place? An analysis of the protective factors of hate crime in multiethnic neighbourhoods in Australia
Authors: Benier Kathryn
Published: May 2019

Hate crime creates significant problems for individual victims and the social fabric of a community more broadly. Victimisation is most likely to occur around the victim's own neighbourhood, yet few studies examine how the neighbourhood context influences hate crime. This study uses data from the Australian Community Capacity Study involving 4,400 participants in 148 neighbourhoods in Brisbane. It examines whether it is characteristics of place (such as attitudes toward diversity, place attachment and social cohesion) that reduce hate crime, or whether it is interactions with fellow residents (such as frequency of neighbourly exchanges, number of friends, and number of acquaintances in the neighbourhood) that shelter residents from hate crime. Results demonstrate that characteristics of a place provide important protective factors against hate crime in the neighbourhood, rather than the number of social‐interactions between residents.
Effect of the hyaluronic acid‐poloxamer hydrogel on skin‐wound healing: in vitro and in vivo studies
Authors: Li Xiaojuan , Li Aimin , Feng Fan , Jiang Qiyu , Sun Huiwei , Chai Yantao , Yang Ruichuang , Wang Zhijie , Hou Jun , Li Ruisheng
Published: May 2019

Background

Recent research into skin injury and wound healing has focused mainly on post‐trauma hemostasis, infection prevention, dermal regeneration and angiogenesis. However, less attention has been paid to air permeability and moisture loss prevention which also play important roles in injury healing.

Methods

In the present work, we prepared a hyaluronic acid‐poloxamer (HA‐POL) hydrogel and tested the therapeutic effect of the hydrogel on skin‐wound healing.

Results

The HA‐POL hydrogel transformed from sol to gel at 30°C, close to body temperature, and had stable moisturizing properties. HA‐POL hydrogel promoted skin‐wound healing and increased protein accumulation in the wound area. HA‐POL hydrogel allowed greater air permeability than Band‐aid, a typical wound covering. Results from transwell assays showed that the HA‐POL hydrogel effectively isolated skin‐wounds from bacterial invasion.

Conclusion

This work demonstrates the advantages of using HA‐POL gel materials in the treatment of cutaneous wounds.
Synthesis of Selenium‐Triphosphates (dNTPαSe) for More Specific DNA Polymerization
Authors: Hu Bei , Wang Yitao , Sun Shichao , Yan Weizhu , Zhang Chong , Luo Danyan , Deng Huiling , Hu Lillian R. , Huang Zhen
Published: May 2019

2′‐Deoxynucleoside 5′‐(alpha‐P‐seleno)‐triphosphates (dNTPαSe) have been conveniently synthesized using a protection‐free, one‐pot strategy. One of two diastereomers of each dNTPαSe can be efficiently recognized by DNA polymerases, while the other is neither a substrate nor an inhibitor. Furthermore, this Se‐atom modification can significantly inhibit non‐specific DNA polymerization caused by mis‐priming. Se–DNAs amplified with dNTPαSe via polymerase chain reaction have sequences identical to the corresponding native DNA. In conclusion, a simple strategy for more specific DNA polymerization has been established by replacing native dNTPs with dNTPαSe.
Near‐Infrared‐Emitting Nitrogen‐Doped Nanographenes
Authors: Yamato Kairi , Sekiya Ryo , Suzuki Kaho , Haino Takeharu
Published: May 2019

The quantum‐size effect, which enables nanographenes to emit photoluminescence (PL) in the UV to visible region, has inspired intense research. However, the control of the PL properties of nanographenes through manipulation of their π‐system by post‐modifications is not well developed. By utilizing a ring‐closure reaction between an aromatic 1,2‐dicarboxylic acid and a 1,8‐naphthalenediamine derivative, which produces a perimidine framework, nitrogen‐doped nanographenes were realized. Two nanographenes produced by a one‐pot reaction of edge‐oxidized nanographene (GQD‐2) with 1,8‐naphthalenediamine derivatives (GQD‐1 a and GQD‐1 b) displayed an absorption band extending to >1000 nm; furthermore, the PL wavelength of GQD‐1 a was significantly red‐shifted into the near‐infrared (NIR) region in which it can be used for bioimaging. Time‐dependent DFT calculations of model nanographenes showed that the functional groups narrow the HOMO–LUMO gap, realizing the NIR‐emitting nanographenes.
Diterpenbiosynthese in Actinomyceten: Studien an Cattleyensynthase und Phomopsensynthase
Authors: Rinkel Jan , Steiner Simon T. , Dickschat Jeroen S.
Published: May 2019

Drei Diterpensynthasen aus Actinomyceten wurden studiert. Das erste Enzym aus Streptomyces cattleya produzierte die neue Verbindung Cattleyen. Zwei weitere Enzyme aus Nocardia testacea und Nocardia rhamnosiphila wurden als Phomopsensynthasen identifiziert. Der Cyclisierungsmechanismus der Cattleyensynthase und der EI‐MS‐Fragmentierungsmechanismus ihres Produktes wurden extensiv durch Inkubationsexperimente mit isotopenmarkierten Vorläufern studiert. Oxidative Transformationen erweiterten den chemischen Strukturraum dieser einzigartigen Diterpene.
Cryogenic Exfoliation of Non‐layered Magnesium into Two‐Dimensional Crystals
Authors: Zhang Chen , Xu Yingfeng , Lu Ping , Wei Chenyang , Zhu Chenxi , Yao Heliang , Xu Fangfang , Shi Jianlin
Published: May 2019

Physical exfoliation of layered precursors is one of the most prevailing techniques to prepare two‐dimensional (2D) crystals, which, however, is considered to be intrinsically inapplicable to non‐layered bulks. Now, plane cleavage differentiation is identified in metallic magnesium at cryogenic temperature (CT), and a cryogenic exfoliation strategy of non‐layered magnesium into 2D crystals is developed. The cleavage anisotropy of the Mg lattice in response to the external mechanical stress originates from the CT‐induced specific inactivation of basal slip, which results in the basal cleavage perpendicular to c axis. The exfoliated novel 2D Mg crystals exhibit remarkable localized surface plasmon resonances, holding great promise for the applications in harvesting and converting solar energy. Beyond creating a new member for the burgeoning 2D family, this study may provide a useful tool for the physical exfoliations of various non‐layered materials.
Intermolecular C−H Amidation of (Hetero)arenes to Produce Amides through Rhodium‐Catalyzed Carbonylation of Nitrene Intermediates
Authors: Yuan Si‐Wen , Han Hui , Li Yan‐Lin , Wu Xueli , Bao Xiaoguang , Gu Zheng‐Yang , Xia Ji‐Bao
Published: May 2019

Amide bond formation is one of the most important reactions in organic chemistry because of the widespread presence of amides in pharmaceuticals and biologically active compounds. Existing methods for amides synthesis are reaching their inherent limits. Described herein is a novel rhodium‐catalyzed three‐component reaction to synthesize amides from organic azides, carbon monoxide, and (hetero)arenes via nitrene‐intermediates and direct C−H functionalization. Notably, the reaction proceeds in an intermolecular fashion with N2 as the only by‐product, and either directing groups nor additives are required. The computational and mechanistic studies show that the amides are formed via a key Rh‐nitrene intermediate.
Uranocenium: Synthesis, Structure, and Chemical Bonding
Authors: Guo Fu‐Sheng , Chen Yan‐Cong , Tong Ming‐Liang , Mansikkamäki Akseli , Layfield Richard A.
Published: May 2019

Abstraction of iodide from [(η5‐C5iPr5)2UI] (1) produced the cationic uranium(III) metallocene [(η5‐C5iPr5)2U]+ (2) as a salt of [B(C6F5)4]−. The structure of 2 consists of unsymmetrically bonded cyclopentadienyl ligands and a bending angle of 167.82° at uranium. Analysis of the bonding in 2 showed that the uranium 5f orbitals are strongly split and mixed with the ligand orbitals, thus leading to non‐negligible covalent contributions to the bonding. Investigation of the dynamic magnetic properties of 2 revealed that the 5f covalency leads to partially quenched anisotropy and fast magnetic relaxation in zero applied magnetic field. Application of a magnetic field leads to dominant relaxation by a Raman process.
Kinetic Treatments for Catalyst Activation and Deactivation Processes based on Variable Time Normalization Analysis
Authors: Martínez‐Carrión Alicia , Howlett Michael G. , Alamillo‐Ferrer Carla , Clayton Adam D. , Bourne Richard A. , Codina Anna , Vidal‐Ferran Anton , Adams Ralph W. , Burés Jordi
Published: May 2019

Progress reaction profiles are affected by both catalyst activation and deactivation processes occurring alongside the main reaction. These processes complicate the kinetic analysis of reactions, often directing researchers toward incorrect conclusions. We report the application of two kinetic treatments, based on variable time normalization analysis, to reactions involving catalyst activation and deactivation processes. The first kinetic treatment allows the removal of induction periods or the effect of rate perturbations associated with catalyst deactivation from kinetic profiles when the quantity of active catalyst can be measured. The second treatment allows the estimation of the activation or deactivation profile of the catalyst when the order of the reactants for the main reaction is known. Both treatments facilitate kinetic analysis of reactions suffering catalyst activation or deactivation processes.
Diterpene Biosynthesis in Actinomycetes: Studies on Cattleyene Synthase and Phomopsene Synthase
Authors: Rinkel Jan , Steiner Simon T. , Dickschat Jeroen S.
Published: May 2019

Three diterpene synthases from actinomycetes have been studied. The first enzyme from Streptomyces cattleya produced the novel compound cattleyene. The other two enzymes from Nocardia testacea and Nocardia rhamnosiphila were identified as phomopsene synthases. The cyclisation mechanism of cattleyene synthase and the EIMS fragmentation mechanism of its product were extensively studied by incubation experiments with isotopically labelled precursors. Oxidative transformations expanded the chemical space of these unique diterpenes.
Viscoelastic Conjugated Polymer Fluids
Authors: Shinohara Akira , Pan Chengjun , Guo Zhenfeng , Zhou Liyang , Liu Zhonghua , Du Lei , Yan Zhichao , Stadler Florian J. , Wang Lei , Nakanishi Takashi
Published: May 2019

The introduction of optoelectronic functions into viscoelastic polymers can yield highly sophisticated soft materials for biomedical devices and autonomous robotics. However, viscoelasticity and excellent optoelectronic properties are difficult to achieve because the presence of a large number of π‐conjugated moieties drastically stiffens a polymer. Here, we report a variation of additive‐free viscoelastic conjugated polymers (VE‐CPs) at room temperature by using an intact π‐conjugated backbone and bulky, yet flexible, alkyl side chains as “internal plasticizers.” Some of these polymers exhibit gel‐ and elastomer‐like rheological behaviors without cross‐linking or entanglement. Furthermore, binary blends of these VE‐CPs exhibit a never‐seen‐before dynamic miscibility with self‐restorable and mechanically induced fluorescence color changes.
Aqueous Platinum(II)‐Cage‐Based Light‐Harvesting System for Photocatalytic Cross‐Coupling Hydrogen Evolution Reaction
Authors: Zhang Zeyuan , Zhao Zhengqing , Hou Yali , Wang Heng , Li Xiaopeng , He Gang , Zhang Mingming
Published: May 2019

Photosynthesis is a process wherein the chromophores in plants and bacteria absorb light and convert it into chemical energy. To mimic this process, an emissive poly(ethylene glycol)‐decorated tetragonal prismatic platinum(II) cage was prepared and used as the donor molecule to construct a light‐harvesting system in water. Eosin Y was chosen as the acceptor because of its good spectral overlap with that of the metallacage, which is essential for the preparation of light‐harvesting systems. Such a combination showed enhanced catalytic activity in catalyzing the cross‐coupling hydrogen evolution reaction, as compared with eosin Y alone. This study offers a pathway for using the output energy from the light‐harvesting system to mimic the whole photosynthetic process.
Poly(arylenevinylene)s through Ring‐Opening Metathesis Polymerization of an Unsymmetrical Donor‐Acceptor Cyclophane
Authors: Elacqua Elizabeth , Gregor Maria
Published: May 2019

Reported are well‐defined donor‐acceptor alternating copolymers prepared using ring‐opening metathesis polymerization (ROMP). Unsymmetrical cyclophanedienes comprising electron‐donating (4‐methoxy‐1‐(2‐ethylhexyl)oxy)benzene (MEH) and electron‐accepting benzothiadiazole (BT) rings were synthesized from the corresponding [3.3]dithiaparacyclophanes. ROMP of the strained unsymmetrical and “electronically‐ambiguous” cyclophanedienes proceeded in a controlled manner in the presence of either Hoveyda–Grubbs II or Grubbs II initiator in wake of both steric and electronic encumbrance. The resulting polymers, comprising alternating BT and MEH‐PPV units, are achieved in molecular weights exceeding 20k with Đ values ranging from 1.1–1.4. The living nature of the polymerization is verified through the formation of rod‐coil and rod‐rod block copolymers. Our strategy to develop previously unrealized polymers from functional building blocks featuring a locked‐in D‐A unit is significant in a field striving to achieve well‐defined and sequence‐specific materials.
Boosting the electrochemical performance of Li4Ti5O12 through nitrogen‐doped carbon coating
Authors: Lu Guixia , Liu Jiurong , Huang Weibo , Wang Xinzhen , Wang Fenglong
Published: May 2019

The poor electronic conductivity restricts the wide applications of Li4Ti5O12 as anode materials in Li‐ion batteries. We report a facile approach to fabricate nitrogen‐doped carbon‐coated Li4Ti5O12 through carbonizing pyrrole and pyridine at different temperatures. Comparative experiments demonstrated that the carbon content plays a key role in governing the cycling performance and rate capability of Li4Ti5O12. The composites with higher carbon content exhibited superior cycling performance, and the composite prepared at 600 °C using pyridine as the carbon source gave the best cycling and rate performance.
An Efficient Strategy for the Production of Epoxidized Oils: Natural Deep Eutectic Solvent‐Based Enzymatic Epoxidation
Authors: Zhang Tianyu , Ma Yunjian , Tan Chin Ping , Hollmann Frank , Wang Jianrong , Yang Bo , Wang Yonghua
Published: May 2019

Poor H2O2‐resistance by enzymes is a key bottleneck in the epoxidation process of oil by enzymatic methods. In this study, the stability of three lipases, from Aspergillus oryzae lipase (AOL), Aspergillus fumigatus lipase B (AflB), and marine Janibacter (MAJ1), in the presence of H2O2 was evaluated in different types of natural deep eutectic solvents (NADES). This stability was strengthened significantly in the NADES compared to the buffer. Specifically, AOL retained 84.7% of its initial activity in the presence of choline chloride/sorbitol (1:1 M ratio) and 3 mol L−1 H2O2 after 24 h incubation at 40°C. In addition, the two‐phase epoxidation process was optimized with AOL in ChCl/sorbitol to reach up to 96.8% conversion under the optimized conditions (molar ratio of octanoic acid/H2O2/C=C‐bonds = 0.3:1.5:1, enzyme loading of 15 U g−1 of soybean oil, ChCl/sorbitol content of 70.0% of the weight of hydrophilic phase, and reaction temperature of 50°C). Moreover, the lipase dispersed in NADES retained approximately 66% of its initial activity after being used for seven batch cycles. Overall, NADES‐based enzymatic epoxidation is a feasible and promising strategy for the synthesis of epoxidized oils.
Cellulose‐based formaldehyde adsorbents with large capacities: Efficient use of polyethylenimine for graphene oxide stabilization in alkaline–urea system
Authors: Yin Yihui , Wang Zhenxing , Wang Sijie , Pu Junwen
Published: May 2019

A cellulose‐based polyethylenimine modified graphene oxide (PEI‐GO) composite aerogel is fabricated through the alkaline–urea aqueous system. Inspired from the performance of nanocarriers in gene delivery, this article proposes a pathway to disperse GO in the green environment with strong electrolyte concentrations via the decorated branched PEI. The entire aqueous system shows good miscibility and stability. Meanwhile, the dynamic light scattering results indicate that PEI‐GO and cellulose chains become entangled to form a new supramolecular complex in the alkaline–urea solution, and a “hand” model is devised accordingly. The efficient dispersion of PEI‐GO (1–0.1%) over the entire cellulose support structure (3%) enables the resultant aerogel to exhibit a gaseous formaldehyde adsorption capacity, that is, 8.51 times greater than the pure cellulose aerogel under ambient temperatures. This dual function opens up enormous opportunities to process cellulose‐based GO materials in this green and inexpensive solvent with strong electrolyte concentrations. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47860.
Conductive sizing for improving electrical conductivity of carbon fiber/polyaryl ether ketone/AgNWs composites
Authors: Audoit Jérémie , Cortes Luis Quiroga , Racagel Sébastien , Lonjon Antoine , Dantras Eric , Lacabanne Colette
Published: May 2019

The aim of this work is to enhance the electrical conductivity of PAEK/continuous carbon fiber (CF) composites while maintaining their mechanical properties. A conductive sizing was elaborated by mixing polyetherimide (PEI) with silver nanoplates (AgNpts) in suspension in dichloromethane. An aqueous PEI formulation was used as insulating sizing reference. The presence of AgNpts into the sizing enhances electrical conductivity up to 0.2 S.m−1 for a silver content ∼ 0.2 vol % without any modification of mechanical properties. The influence of conductive sizing on PAEK–AgNWs/CF was observed. For low AgNWs content lower (<1 vol %); the conductive sizing increases the electrical conductivity of the composite by one decade. This result shows that both types of Ag particles participate to the conductive path. For higher AgNWs content, electrical conductivity (200 S.m−1) is independent from the AgNpts content: the conductive path is only constituted by AgNWs. Mechanical properties of such composites show that the value of the conservative modulus is almost the same, while the dissipative modulus slightly increases. The global mechanical properties of the composite are preserved despite the addition of the CF, AgNWs, and AgNpts. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47872.
Thermal and nondestructive analysis of high density polyethylene filled with milled salago fiber
Authors: Pouriman Mohammadhosein , Dahresobh Ali , Moradipour Mahsa , Caparanga Alvin R.
Published: May 2019

Fillers are utilized for different purposes. In plastic industry, fillers are mainly used to extend the bulk of the compound; however, they can also improve physical properties, materials processing, and reduce cycle time of plastics. In this article, high‐density polyethylene was filled with untreated and 5% alkaline‐treated salago fiber, and thereafter the thermal and nondestructive properties of the composites were investigated. It was found that the chemical treatment of fiber increased the thermal stability and the mean coefficient value of linear thermal expansion of the treated composites as compared to the untreated ones. Moreover, the increase of fiber content in composites increased the crystallinity level while decreased the thermal capacity and melting temperature of the composites. The zinc, calcium, and phosphorus contents were found to be within the industry‐acceptable range for elemental contents in polyolefins. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47873.
A novel underwater acoustically transparent material: Fluorosilicone polyester polyurethane
Authors: Li Zhihua , Shen Yuting , Gu Xiaohong , Li Junjie , Gao Yuan
Published: May 2019

A novel fluorosilicone polyester polyurethane (FSPU) was successfully synthesized with polycaprolactone diol, toluene diisocyanate, hydroxyl fluorosilicone oil (FSO), and a chain extender, 2,4‐diamino‐3,5‐dimethyl thiotoluene (E‐300). It was characterized by Fourier transform infrared spectroscopy, dynamic mechanical analysis, and scanning electron microscopy. The water resistance, mechanics, and acoustic properties of the material were tested with an optical contact angle measuring device, an electronic universal testing machine, and sound field measurement, respectively. The results show that the water resistance of FSPU gradually improved with increasing FSO. Compared to that of polyurethane (PU), the water contact angle of FSPU at 50 wt % FSO increased to 111.7°, and the water absorption reached a minimum of 0.8%. The glass‐transition temperature of FSPU reached –44.1°C; this was lower than that of PU. Moreover, the insertion losses of this material at 600 and 1000 kHz were only 129.2 and 267.3 dB/m, respectively; these values were 20.5 and 13.6% lower, respectively, than that of PU. The results indicate that FSPU had an excellent water resistance and acoustic performance and a low glass‐transition temperature and is an ideal material for underwater acoustically transparent materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 47894.
Nano‐indentation for probing mechanical properties of nanocomposites based on ethylene butyl acrylate copolymer and carbon black
Authors: Bentoumi Mohamed , Mdarhri Ahmed , Montagne Alex , Nourdine Ali , El Aboudi Ilham , Iost Alain
Published: May 2019

Mechanical properties of heterogeneous systems based on carbon black (CB) filled semi‐crystalline ethylene butyl acrylate (EBA) copolymer nanocomposites are characterized using nano‐indentation technique. The size effect and CB content dependence on the deformation behavior at room temperature were investigated. The phenomenology for hardness response (H) indicates a typical enhancement of the H when the indentation depth (h) decreases as for the usual elastomeric materials. All H–h curves, fitted according to the Meyer's empirical power law and Franck elasticity model, highlight the so‐called length‐scale‐dependent deformation. Similar trend is observed for the elastic modulus. Furthermore, it is evidenced that the increases of CB content increases the mechanical properties of composites, that is, hardness and elastic modulus. This behavior can be mainly related, on the one hand, to the change of the meso‐structure, formed by the interconnected network of polymer and the aggregates of CB particles and to the nature of the polymer matrix, on the other hand. The mechanical properties characterized from micro and submicron indentations were compared to that characterized at macroscopic scale to highlight the possible correlations between the two scales. This investigation can interest many applications of polymer composites for rubber technology such as tires industry, soft robotic, and adhesives. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47897.
Interface compatibility and mechanisms of improved mechanical performance of starch/poly(lactic acid) blend reinforced by bamboo shoot shell fibers
Authors: Guan Mingjie , Zhang Zhiwei , Yong Cheng , Du Keke
Published: May 2019

Bamboo shoot shell fibers (BSSFs)/starch/poly(lactic acid) (PLA) ternary composites were prepared by blending BSSFs to starch/PLA matrices for the purpose of expanding BSSFs applications to enhance starch/PLA composites and creating a new low‐cost biodegradable composite. The effects of BSSFs content (0–40 wt %) on the physical–mechanical properties were tested and interface compatibility and its mechanism to mechanical performance of BSSFs/starch/PLA composites were characterized by SEM‐EDS, TG. The results showed that the mechanical strength, surface wettability, and water absorption of the composites continued improving when the BSSFs content increased from 0% to 20 wt %. However, mechanical modulus increased with increase in BSSFs content. The results of fracture microstructure and thermal property exhibited a good interfacial compatibility at low content of BSSFs and an interface debonding at high content of BSSFs. These investigations indicated that the BSSFs reinforcement to the composite is not consistent with interface compatibility of the ternary composites. The composites should be considered as a kind of green and low‐cost biodegradable materials to replace traditional single‐phase or multiphase materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 47899.
Improved tribological properties of polyimide composites by micro–nano reinforcement
Authors: Song Jingfu , Yu Yuanhao , Zhao Gai , Qiu Jinhao , Ding Qingjun
Published: May 2019

The hydroxylate carbon nanotubes (CNTs) were grafted by chemical method on the surface of the oxidized carbon fibers (CF) to improve the mechanical and tribological properties of polyimide (PI). The microstructure and fracture surface of the polyimide composites indicated that CF–CNTs hybrid as a multiscale reinforcement can distribute into the PI matrix homogeneously. Tribo‐tests further showed that CF–CNTs hybrid had a better effect on hardness increment, impact strength enhancement, friction reduction, and wear resistance. Compared to the neat PI, the friction coefficient and wear rate of CF–CNTs/PI composite deceased by 23.2 and 55.9%, respectively. In particular, the loading capacity and high speed resistance of CF–CNTs/PI composite were greatly improved. The corresponding wear mechanisms were also discussed by observing the worn surface of the PI composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47900.
Epizootic effect and aftermath in a pilot whale population
Authors: Verborgh Philippe , Gauffier Pauline , Brévart Clémentine , Giménez Joan , Esteban Ruth , Carbou Morgane , Debons Elodie , de Stephanis Renaud
Published: May 2019

Over the last three decades, emerging infectious diseases have resulted in large mortalities in wild populations.

Different strains of Morbillivirus have infected cetaceans all over the world and caused at least seven epizootics since the 1980s, but few data exist on their effect at the population level.

The demographic effect of a morbillivirus epizootic was studied on a well‐monitored resident population of long‐finned pilot whales in the Strait of Gibraltar.

Results show decreases in population size and apparent survival rate, especially in males, as well as negative population growth rates during the epizootic and the following years.

Although different anthropogenic and natural factors may have acted in conjunction, the epizootic was most likely the cause of this observed decline.

This epizootic, and potential future ones, may put the population's future at even greater risk, and their habitat is threatened by increasing anthropogenic stress.
Examining users' partial query modification patterns in voice search
Authors: Sa Ning , Yuan Xiaojun (Jenny)
Published: May 2019

This article investigates how to improve the effectiveness of voice search systems. Earlier research found that participants employed voice search much less frequently than keyboard search. The main reasons that participants disliked voice search are system mistakes and the inability to modify queries. In keyboard search, query reformulation is facilitated by partial query modification, which is not supported by most of the current voice search systems. Consequently, users need to speak the complete query in voice search even with only minor changes. This article focuses on examining partial query modification during voice search through a Wizard of Oz user experiment. It examines if users would prefer partial query modification and how they perform it in voice search. Thirty‐two participants participated in the experiment. Results indicated that when given the opportunity, the users performed more partial query modifications than complete queries. Common partial query modification strategies and patterns emerged from the experiment. The results can be used to improve the voice search system design and benefit the research community in general. System implications and future work were discussed.