bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial emission distribution and carrier recombination dynamics in regularly arrayed InGaN/GaN quantum structure nanocolumns
Authors: Oto Takao , Mizuno Yutaro , Miyagawa Rin , Kano Tatsuya , Yoshida Jun , Ema Kazuhiro , Kishino Katsumi
Published: September 2016

Emission mechanisms in regularly arrayed InGaN/GaN quantum structures on GaN nanocolumns were investigated, focusing on the spatial emission distribution at the nanocolumn tops and the carrier recombination dynamics. The double-peak emission originated from the dot- and well-like InGaN areas with different In compositions was observed. From the results regarding the spatial emission distribution, we proposed a simple analytical approach to evaluating the carrier recombination dynamics using the rate equations based on the two energy states. The considerable six lifetimes can be uniquely determined from the experimental results. Carrier transfer from the high- to the low-energy state is dominant at high temperatures, producing the increased total emission efficiency of the inner low-energy area. In addition, the internal quantum efficiency should not be simply discussed using only the integrated intensity ratio between low and room temperatures because of the carrier transfer from high- to low-energy states.
Optimized modification of gold nanoparticles with a self-assembled monolayer for suppression of nonspecific binding in DNA assays
Authors: Esashika Keiko , Saiki Toshiharu
Published: September 2016

Homogeneous DNA assays using gold nanoparticles (AuNPs) require the reduction of nonspecific binding between AuNPs to improve sensitivity in detecting the target molecule. In this study, we employed alkanethiol self-assembled monolayers (SAMs) for modifying the AuNP surface to attain both good dispersability and high hybridization efficiency. The alkanethiol SAMs enhance the repulsive interaction between AuNPs, reducing nonspecific binding and promoting the extension of surface-immobilized ssDNA into the solvent, thus enhancing the hybridization process. Introduction of oligoethylene glycol into the alkanethiol prevented nonspecific binding caused by the entanglement of alkane chains. Finally, the conditions were optimized by controlling the surface charge density through the introduction of a COOH group at the alkanethiol terminus, resulting in the complete blocking of nonspecific binding and the maintenance of high hybridization efficiency.
Insights from a refined decomposition of cloud feedbacks
Authors: Zelinka Mark D. , Zhou Chen , Klein Stephen A.
Published: September 2016

Decomposing cloud feedback into components due to changes in several gross cloud properties provides valuable insights into its physical causes. Here we present a refined decomposition that separately considers changes in free tropospheric and low cloud properties, better connecting feedbacks to individual governing processes and avoiding ambiguities present in a commonly used decomposition. It reveals that three net cloud feedback components are robustly nonzero: positive feedbacks from increasing free tropospheric cloud altitude and decreasing low cloud cover and a negative feedback from increasing low cloud optical depth. Low cloud amount feedback is the dominant contributor to spread in net cloud feedback but its anticorrelation with other components damps overall spread. The ensemble mean free tropospheric cloud altitude feedback is roughly 60% as large as the standard cloud altitude feedback because it avoids aliasing in low cloud reductions. Implications for the “null hypothesis” climate sensitivity from well‐understood and robustly simulated feedbacks are discussed.
Global modeling of tropospheric iodine aerosol
Authors: Sherwen Tomás M. , Evans Mat J. , Spracklen Dominick V. , Carpenter Lucy J. , Chance Rosie , Baker Alex R. , Schmidt Johan A. , Breider Thomas J.
Published: September 2016

Natural aerosols play a central role in the Earth system. The conversion of dimethyl sulfide to sulfuric acid is the dominant source of oceanic secondary aerosol. Ocean emitted iodine can also produce aerosol. Using a GEOS‐Chem model, we present a simulation of iodine aerosol. The simulation compares well with the limited observational data set. Iodine aerosol concentrations are highest in the tropical marine boundary layer (MBL) averaging 5.2 ng (I) m−3 with monthly maximum concentrations of 90 ng (I) m−3. These masses are small compared to sulfate (0.75% of MBL burden, up to 11% regionally) but are more significant compared to dimethyl sulfide sourced sulfate (3% of the MBL burden, up to 101% regionally). In the preindustrial, iodine aerosol makes up 0.88% of the MBL burden sulfate mass and regionally up to 21%. Iodine aerosol may be an important regional mechanism for ocean‐atmosphere interaction.
Assessing the relative effects of emissions, climate means, and variability on large water supply systems
Authors: Whateley Sarah , Brown Casey
Published: September 2016

Some of the greatest societal risks of climate change rise from the potential impacts to water supply. Yet prescribing adaptation policies in the near term is made difficult by the uncertainty in climate projections at relevant spatial scales and the conflating effects of uncertainties in emissions, model error, and internal variability. In this work, a new framework is implemented to explore the vulnerability of reservoir systems in the northeastern U.S. to climate change and attribute vulnerabilities to changes in mean climate, natural variability, or emission scenarios. Analysis of variance is used to explore the contributions of uncertainties to system performance. Diagnosing the relative risks to water supply will help water resource engineers better adapt to uncertain future conditions. The results indicate that uncertainty in water supply system performance can be attributed mostly to uncertainty in internal variability over policy‐relevant planning horizons, and thus, adaptation efforts should focus on managing variability.
Elucidating the role of vegetation in the initiation of rainfall‐induced shallow landslides: Insights from an extreme rainfall event in the Colorado Front Range
Authors: McGuire Luke A. , Rengers Francis K. , Kean Jason W. , Coe Jeffrey A. , Mirus Benjamin B. , Baum Rex L. , Godt Jonathan W.
Published: September 2016

More than 1100 debris flows were mobilized from shallow landslides during a rainstorm from 9 to 13 September 2013 in the Colorado Front Range, with the vast majority initiating on sparsely vegetated, south facing terrain. To investigate the physical processes responsible for the observed aspect control, we made measurements of soil properties on a densely forested north facing hillslope and a grassland‐dominated south facing hillslope in the Colorado Front Range and performed numerical modeling of transient changes in soil pore water pressure throughout the rainstorm. Using the numerical model, we quantitatively assessed interactions among vegetation, rainfall interception, subsurface hydrology, and slope stability. Results suggest that apparent cohesion supplied by roots was responsible for the observed connection between debris flow initiation and slope aspect. Results suggest that future climate‐driven modifications to forest structure could substantially influence landslide hazards throughout the Front Range and similar water‐limited environments where vegetation communities may be more susceptible to small variations in climate.
How fast is the middle‐lower crust flowing in eastern Tibet? A constraint from geodetic observations
Authors: Yi Shuang , Freymueller Jeffrey T. , Sun Wenke
Published: September 2016

Various geophysical observations, including seismological and magnetotelluric imaging, have implied that the deep crust beneath eastern Tibet may be partially melted and flowing faster than the brittle upper crust. However, it is still unclear how much faster the deep crust is flowing. Geodetic observations, which are more sensitive to dynamic changes, provide constraints on the flow rate of the middle and lower crust (MLC). Three‐dimensional GPS velocities show that deformation within the brittle upper crust contributes little (0.02 ± 0.02 mm/yr) to the overall surface uplift (2.7 ± 0.3 mm/yr). Therefore, two plausible models for the surface uplift are discussed, which are consistent with the geodetic constraints. In the deep crustal flow model, crustal thickening requires the horizontal flow rate of the MLC to be 330%–710% of the rate of motion of the upper crust, and the deepening of the Moho is only up to 35% of that required to maintain isostatic balance; isostasy may not be maintained over the geodetic timescale. In the hybrid model of deep crustal flow and convective lithospheric detachment, the Moho is uprising, and only weak or moderate (130%–250%) deep crustal flow is required, which results in moderate present‐day crustal thickening beneath eastern Tibet. This result improves our understanding of the plateau construction and dynamics and also offers advice for numerical simulations.
Numerical upscaling in 2‐D heterogeneous poroelastic rocks: Anisotropic attenuation and dispersion of seismic waves
Authors: Rubino J. Germán , Caspari Eva , Müller Tobias M. , Milani Marco , Barbosa Nicolás D. , Holliger Klaus
Published: September 2016

The presence of stiffness contrasts at scales larger than the typical pore sizes but smaller than the predominant seismic wavelengths can produce seismic attenuation and velocity dispersion in fluid‐saturated porous rocks. This energy dissipation mechanism is caused by wave‐induced fluid pressure diffusion among the different components of the probed geological formations. In many cases, heterogeneities have elongated shapes and preferential orientations, which implies that the overall response of the medium is anisotropic. In this work, we propose a numerical upscaling procedure that permits to quantify seismic attenuation and phase velocity considering fluid pressure diffusion effects as well as generic anisotropy at the sample's scale. The methodology is based on a set of three relaxation tests performed on a 2‐D synthetic rock sample representative of the medium of interest. It provides a complex‐valued frequency‐dependent equivalent stiffness matrix through a least squares procedure. We also derive an approach for computing various poroelastic fields associated with the considered sample in response to the propagation of a seismic wave with arbitrary incidence angle. Using this approach, we provide an energy‐based estimation of seismic attenuation. A comprehensive numerical analysis indicates that the methodology is suitable for handling complex media and different levels of overall anisotropy. Comparisons with the energy‐based estimations demonstrate that the dynamic‐equivalent viscoelastic medium assumption made by the numerical upscaling procedure is reasonable even in the presence of high levels of overall anisotropy. This work also highlights the usefulness of poroelastic fields for the physical interpretation of seismic wave phenomena in strongly heterogeneous and complex media.
Resonant Ultrasound Spectroscopy studies of Berea sandstone at high temperature
Authors: Davis Eric S. , Sturtevant Blake T. , Sinha Dipen N. , Pantea Cristian
Published: September 2016

Resonant Ultrasound Spectroscopy was used to determine the elastic moduli of Berea sandstone from room temperature to 478 K. Sandstone is a common component of oil reservoirs, and the temperature range was chosen to be representative of typical downhole conditions, down to about 8 km. In agreement with previous works, Berea sandstone was found to be relatively soft with a bulk modulus of approximately 6 GPa as compared to 37.5 GPa for α‐quartz at room temperature and pressure. It was found that Berea sandstone undergoes a ~17% softening in bulk modulus between room temperature and 385 K, followed by an abnormal behavior of similar stiffening between 385 K and 478 K.
In situ and space‐based observations of the Kelud volcanic plume: The persistence of ash in the lower stratosphere
Authors: Vernier Jean‐Paul , Fairlie T. Duncan , Deshler Terry , Natarajan Murali , Knepp Travis , Foster Katie , Wienhold Frank G. , Bedka Kristopher M. , Thomason Larry , Trepte Charles
Published: September 2016

Volcanic eruptions are important causes of natural variability in the climate system at all time scales. Assessments of the climate impact of volcanic eruptions by climate models almost universally assume that sulfate aerosol is the only radiatively active volcanic material. We report satellite observations from the Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite after the eruption of Mount Kelud (Indonesia) on 13 February 2014 of volcanic materials in the lower stratosphere. Using these observations along with in situ measurements with the Compact Optical Backscatter AerosoL Detector (COBALD) backscatter sondes and optical particle counters (OPCs) made during a balloon field campaign in northern Australia, we find that fine ash particles with a radius below 0.3 µm likely represented between 20 and 28% of the total volcanic cloud aerosol optical depth 3 months after the eruption. A separation of 1.5–2 km between the ash and sulfate plumes is observed in the CALIOP extinction profiles as well as in the aerosol number concentration measurements of the OPC after 3 months. The settling velocity of fine ash with a radius of 0.3 µm in the tropical lower stratosphere is reduced by 50% due to the upward motion of the Brewer‐Dobson circulation resulting a doubling of its lifetime. Three months after the eruption, we find a mean tropical clear‐sky radiative forcing at the top of the atmosphere from the Kelud plume near −0.08 W/m2after including the presence of ash; a value ~20% higher than if sulfate alone is considered. Thus, surface cooling following volcanic eruptions could be affected by the persistence of ash and should be considered in climate simulations.
On the variability of ozone in the equatorial eastern Pacific boundary layer
Authors: Gómez Martín J. C. , Vömel H. , Hay T. D. , Mahajan A. S. , Ordóñez C. , Parrondo Sempere M. C. , Gil‐Ojeda M. , Saiz‐Lopez A.
Published: September 2016

Observations of surface ozone (O3) mixing ratios carried out during two ground‐based field campaigns in the Galápagos Islands are reported. The first campaign, Primera Investigación sobre la Química, Evolución y Reparto de Ozono, was carried out from September 2000 to July 2002. The second study, Climate and HAlogen Reactivity tropicaL EXperiment, was conducted from September 2010 to March 2012. These measurements complement the Southern Hemisphere ADditional OZonesonde observations made with weekly to monthly frequency at Galápagos. In this work, the daily, intraseasonal, seasonal and interannual variability of O3 in the marine boundary layer are described and compared to those observed in other tropical locations. The O3 diurnal cycle shows two regimes: (i) photochemical destruction followed by nighttime recovery in the cold season (July to November) and (ii) daytime advection and photochemical loss followed by nighttime depositional loss associated to windless conditions in the warm season (February to April). Wavelet spectral analysis of the intraseasonal variability of O3 reveals components with periods characteristic of tropical instability waves. The O3 seasonal variation in Galápagos is typical of the Southern Hemisphere, with a maximum in August and a minimum in February–March. Comparison with other measurements in remote tropical ocean locations shows that the change of the surface O3 seasonal cycle across the equator is explained by the position of the Intertropical Convergence Zone and the O3 levels upwind.
Geomorphological and geochemistry changes in permafrost after the 2002 tundra wildfire in Kougarok, Seward Peninsula, Alaska
Authors: Iwahana Go , Harada Koichiro , Uchida Masao , Tsuyuzaki Shiro , Saito Kazuyuki , Narita Kenji , Kushida Keiji , Hinzman Larry D.
Published: September 2016

Geomorphological and thermohydrological changes to tundra, caused by a wildfire in 2002 on the central Seward Peninsula of Alaska, were investigated as a case study for understanding the response from ice‐rich permafrost terrain to surface disturbance. Frozen and unfrozen soil samples were collected at burned and unburned areas, and then water isotope geochemistry and cryostratigraphy of the active layer and near‐surface permafrost were analyzed to investigate past hydrological and freeze/thaw conditions and how this information could be recorded within the permafrost. The development of thermokarst subsidence due to ice wedge melting after the fire was clear from analyses of historical submeter‐resolution remote sensing imagery, long‐term monitoring of thermohydrological conditions within the active layer, in situ surveys of microrelief, and geochemical signals recorded in the near‐surface permafrost. The resulting polygonal relief coincided with depression lines along an underground ice wedge network, and cumulative subsidence to 2013 was estimated as at least 10.1 to 12.1 cm (0.9–1.1 cm/year 11 year average). Profiles of water geochemistry in the ground indicated mixing or replenishment of older permafrost water with newer meteoric water, as a consequence of the increase in active layer thickness due to wildfire or past thaw event. Our geocryological analysis of cores suggests that permafrost could be used to reconstruct the permafrost degradation history for the study site. Distinct hydrogen and oxygen isotopic compositions above the Global Meteoric Water Line were found for water from these sites where permafrost degradation with geomorphological change and prolonged surface inundation were suggested.
Characterization of initial current pulses in negative rocket‐triggered lightning with sensitive magnetic sensor
Authors: Lu Gaopeng , Zhang Hongbo , Jiang Rubin , Fan Yanfeng , Qie Xiushu , Liu Mingyuan , Sun Zhuling , Wang Zhichao , Tian Ye , Liu Kun
Published: September 2016

We report the new measurement of initial current pulses in rocket‐triggered lightning with a broadband magnetic sensor at 78 m distance. The high sensitivity of our sensor makes it possible to detect weak ripple deflections (as low as 0.4 A) that are not readily resolved in the typical measurements of channel‐base current in rocket‐triggered lightning experiments. The discernible magnetic pulses within 1 ms after the inception of a sustained upward positive leader from the triggering wire can be classified into impulsive pulses and ripple pulses according to the discernibility of separation between individual pulses. The time scale (usually >20 µs) of ripple pulses is substantially longer than the leading impulsive pulses (with time scales typically <10 µs), and the amplitude is significantly reduced, whereas there is no considerable difference in the interpulse pulse. Along with our previous finding on the burst of magnetic pulses during the initial continuous current in rocket‐triggered lightning, the new measurements suggest that the stepwise propagation might be a persistent feature for the upward positive leader in rocket‐triggered lightning, and the stepping of positive leader early in triggered lightning could be characterized with the observation of ripple pulses. The precedence of impulsive magnetic pulse measured at 78 m range relative to the arrival of corresponding current pulse at the channel base indicates that the ionization wave launched by individual stepping of positive leader propagates downward along the triggering wire at a mean velocity of 1.23 × 108 m/s to 2.25 × 108 m/s.
Electric Field and Gradient Microstructure for Cooperative Driving of Directional Motion of Underwater Oil Droplets
Authors: Tian Dongliang , He Linlin , Zhang Na , Zheng Xi , Dou Yuhai , Zhang Xiaofang , Guo Zhenyan , Jiang Lei
Published: September 2016

Driving a liquid droplet with control of directional motion on a solid surface, by introducing a surface wettability gradient or external stimuli, has attracted considerable research attention. There still remain challenges, however, due to the slow response rate and slow speed of continuous liquid droplet motion on the structured surface. Here, an approach to continuously drive the underwater oil droplet with control of directional motion by the cooperative effects of an electric field and the gradient of a porous polystyrene microstructure is demonstrated. The gradient microstructure induces the liquid droplet to take on an asymmetrical shape, causing unbalanced pressure on both ends to orient the droplet for motion in a particular direction. Meanwhile, the electric field decreases the contact area and the corresponding viscous drag between the droplet and the gradient‐structured surface. Then, the unbalanced pressure pushes the underwater oil droplet to move directionally and continuously at a certain voltage. This work provides a new strategy to control underwater oil droplets and realize unidirectional motion. It is also promising for the design of new smart interface materials for applications such as electrofluidic displays, biological cell and particle manipulation, and other types of microfluidic devices.
Criticality: Concept to Enhance the Piezoelectric and Electrocaloric Properties of Ferroelectrics
Authors: Weyland Florian , Acosta Matias , Koruza Jurij , Breckner Patrick , Rödel Jürgen , Novak Nikola
Published: September 2016

Compositional engineering with a focus on structural phase transitions has been considered as the most important approach for enhancement of the functional properties of ferroelectric materials due to the critical fluctuation of physical properties. Of special interest are electric‐field‐induced phase transitions, which can terminate in a liquid–vapor‐type critical point with a strong enhancement of functional properties. Whereas the critical point in liquid–vapor space considers changes in temperature and pressure, the critical point in this study is placed in electric field–temperature diagrams. In single crystals, temperature and electric field of a critical point are sharply defined and therefore not appealing for practical applications. However, in ceramics, it is demonstrated that the orientational dependence of the critical point leads to a broadened temperature and electric field range. The presence of a diffuse critical point in ceramics provides a conceptually novel approach for the enhancement of functional properties, such as piezoelectric and electrocaloric (EC) responses, as validated here on the example of the 0.75Bi1/2Na1/2TiO3‐0.25SrTiO3 lead‐free relaxor ferroelectric ceramics. The realization of a broad criticality range will further facilitate the development of the piezoelectric and EC materials and provide an alternative concept to manipulate the functional properties by application of an electric field.
Supra‐Amphiphiles for Functional Assemblies
Authors: Kang Yuetong , Tang Xiaoyan , Cai Zhengguo , Zhang Xi
Published: September 2016

Supra‐amphiphiles refer to amphiphiles which are fabricated on the basis of various noncovalent interactions and dynamic covalent bonds, including host‐guest interaction, charge‐transfer interaction, electrostatic interaction, imine bonds, etc. In this feature article, recent progresses of supra‐amphiphiles from molecular architecture to functional assemblies will be summarized. A few topics will be specially addressed, including where supra‐amphipihles functions as surfactants, and also in the areas of chemical analysis, nanocarriers, photodynamic therapy, surface modification and catalysis.
Microwave Combustion for Modification of Transition Metal Oxides
Authors: Wan Jun , Yao Xu , Gao Xiang , Xiao Xu , Li Tianqi , Wu Jiabin , Sun Wanmei , Hu Zhimi , Yu Huimin , Huang Liang , Liu Meilin , Zhou Jun
Published: September 2016

The introduction of oxygen vacancy for transition metal oxide is an effective method to tune their conductivity. Here, microwave combustion method is used to quickly synthesize reduced metal oxides and graphene hybrid composite in several minutes. Among these as‐synthesized composites, the reduced orthorhombic Nb2O5 and graphene oxide (rNb2O5/rGO) composite demonstrates great electrochemical performance with a reversible specific capacity of 726.2 C g−1 at 2 mV s−1 in organic electrolyte as well as a good capacity retention of 87% after 3000 cycles at 10 A g−1. It is believed that this strategy can be a common route to quickly produce oxygen vacancy in oxides and satisfy much more application requirements even for the possibility of industrialization.
NIR‐Activated Supersensitive Drug Release Using Nanoparticles with a Flow Core
Authors: Wang Junxia , Liu Yang , Ma Yinchu , Sun Chunyang , Tao Wei , Wang Yucai , Yang Xianzhu , Wang Jun
Published: September 2016

Near infrared (NIR) light‐activated supersensitive drug release via photothermal conversion is of particular interest due to its advantages in spatial and temporal control. However, such supersensitive drug release is rarely reported for polymeric nanoparticles. In this study, polymeric nanoparticles observed with flowable core can achieve NIR‐activated supersensitive drug release under the assistance of photothermal agent. It is demonstrated that only 5 s NIR irradiation (808 nm, 0.3 W cm−2) leads to 17.8% of doxorubicin (DOX) release, while its release is almost completely stopped when the NIR laser is switched off. In contrast, the control, poly(d,l‐lactide) nanoparticles with rigid cores, do not exhibit such supersensitive effect. It is demonstrated that intraparticle temperature is notably increased during photothermal conversion by detecting fluorescein lifetime using a time‐correlated single photon counting (TCSPC) technique, which is the main driving force for such supersensitive drug release from hydrophobic flow core. In contrast, rigid chain of nanoparticular core hinders drug diffusion. Furthermore, such NIR light‐activated supersensitive drug release is demonstrated, which significantly enhances its anticancer efficacy, resulting in overcoming of the resistance of cancer cells against DOX treatment in vitro and in vivo. This simple and highly universal strategy provides a new approach to fabricate NIR light‐activated supersensitive drug delivery systems.
A Low Temperature Route toward Hierarchically Structured Titania Films for Thin Hybrid Solar Cells
Authors: Song Lin , Abdelsamie Amr , Schaffer Christoph J. , Körstgens Volker , Wang Weijia , Wang Tianyi , Indari Efi Dwi , Fröschl Thomas , Hüsing Nicola , Haeberle Tobias , Lugli Paolo , Bernstorff Sigrid , Müller‐Buschbaum Peter
Published: September 2016

The requirement of high‐temperature calcination for titanium dioxide in (solid‐state) dye‐sensitized solar cells (DSSCs) implies challenges with respect to reduced energy consumption and the potential for flexible photovoltaic devices. Moreover, the use of dye molecules increases production costs and leads to problems related with dye bleaching. Therefore, fabrication of dye‐free hybrid solar cells at low temperature is a promising alternative for current DSSC technology. In this work the authors fabricate hierarchically structured titania thin films by combining a polystyrene‐block‐polyethylene oxide template assisted sol–gel synthesis with nano‐imprint lithography at low temperatures. The achieved films are filled with poly(3‐hexylthiophene) to form the active layer of hybrid solar cells. The surface morphology is probed via scanning electron microscopy and atomic force microscopy, and the bulk film morphology is examined with grazing incidence X‐ray scattering. Good light absorption by the active layer is proven by UV–vis spectroscopy. An enhancement in light absorption is observed and ascribed to light scattering in mesoporous titania films with imprinted superstructures. Accordingly a better photovoltaic performance is found for nano‐imprinted solar cells at various angles of light incidence.
From The Mine to Cancer Therapy: Natural and Biodegradable Theranostic Silicon Nanocarriers from Diatoms for Sustained Delivery of Chemotherapeutics
Authors: Maher Shaheer , Kumeria Tushar , Wang Ye , Kaur Gagandeep , Fathalla Dina , Fetih Gihan , Santos Abel , Habib Fawzia , Evdokiou Andreas , Losic Dusan
Published: September 2016

Drug delivery using synthetic nanoparticles including porous silicon has been extensively used to overcome the limitations of chemotherapy. However, their synthesis has many challenges such as lack of scalability, high cost, and the use of toxic materials with concerning environmental impact. Nanoscale materials obtained from natural resources are an attractive option to address some of these disadvantages. In this paper, a new mesoporous biodegradable silicon nanoparticle (SiNP) drug carrier obtained from natural diatom silica mineral available from the mining industry is presented. Diatom silica structures are mechanically fragmented and converted into SiNPs by simple and scalable magnesiothermic reduction process. Results show that SiNPs have many desirable properties including high surface area, high drug loading capacity, strong luminescence, biodegradability, and no cytotoxicity. The in‐vitro release results from SiNPs loaded with anticancer drugs (doxorubicin) demonstrate a pH‐dependent and sustained drug release with enhanced cytotoxicity against cancer cells. The cells study using doxorubicin loaded SiNPs shows a significantly enhanced cytotoxicity against cancer cells compared with free drug, suggesting their considerable potential as theranostic nanocarriers for chemotherapy. Their low‐cost manufacturing using abundant natural materials and outstanding chemotherapeutic performance has made them as a promising alternative to synthetic nanoparticles for drug delivery applications.
Oxygen Vacancy Dependence of Magnetic Behavior in the LaAlO3/SrTiO3 Heterostructures
Authors: Hu Hai‐Long , Ao Lei , Pham Anh , Wang Danyang , Wang Yu , Chen Zhigang , Kong Charlie , Tan Thiam Teck , Zu Xiaotao , Li Sean
Published: September 2016

The discovery of magnetism at the LaAlO3/SrTiO3 heterostructures has attracted a lot of interests in regards to the origin of magnetic properties appearing in this nonmagnetic system. In this paper, the existence of a robust ferromagnetic state in the LaAlO3/SrTiO3 heterostructures is demonstrated. The oxygen vacancy dependence of magnetic phenomena demonstrates the correlation between the magnetic properties and the oxygen vacancies. The strong ferromagnetism can be also manipulated by controlling the partial pressure of oxygen during the film deposition process. The well‐controlled magnetism may open an avenue for the applications of magnetic storage and spintronics with the LaAlO3/SrTiO3 heterostructures.
Atomic Layer Deposition for Lithium‐Based Batteries
Authors: Ma Lu , Nuwayhid Ramsay B. , Wu Tianpin , Lei Yu , Amine Khalil , Lu Jun
Published: September 2016

With the increasing demand for energy at a low cost and minimal environmental impact, the development of next‐generation high‐performance batteries has drawn considerable attention. Owing to the capability of forming conformal coatings of thin films and nanoparticles, atomic layer deposition (ALD) has shown great potential in deposition and surface modification of electrode materials with various nanostructures, deposition of solid‐state electrolyte, and fabrication of electrochemical catalysts. This paper reviews the recent development and applications of ALD in Li‐based batteries, especially beyond Li‐ion systems, and provides suggestions for further development of ALD techniques for these batteries.
Triazolobenzothiadiazole‐Based Copolymers for Polymer Light‐Emitting Diodes: Pure Near‐Infrared Emission via Optimized Energy and Charge Transfer
Authors: Murto Petri , Minotto Alessandro , Zampetti Andrea , Xu Xiaofeng , Andersson Mats R. , Cacialli Franco , Wang Ergang
Published: September 2016

A series of new near‐infrared (NIR) emitting copolymers, based on a low band gap 6‐(2‐butyloctyl)‐4,8‐di(thiophen‐2‐yl)‐[1,2,3]triazolo[4′,5′:4,5]benzo[1,2‐c]‐[1,2,5]thiadiazole (TBTTT) fluorophore copolymerized into a high band gap poly[3,3′‐ditetradecyl‐2,2′‐bithiophene‐5,5′‐diyl‐alt‐5‐(2‐ethylhexyl)‐4H‐thieno[3,4‐c]pyrrole‐4,6(5H)‐dione‐1,3‐diyl] (P2TTPD) host backbone, for polymer light‐emitting diode (PLED) applications is reported. PLEDs fabricated from the host polymer (P2TTPD‐0) show external quantum efficiencies (EQEs) up to 0.49% at 690 nm, with turn‐on voltage (Von) at only 2.4 V. By incorporating the TBTTT segments into the host polymer backbone, pure NIR emission peaking at ca. 900 nm is obtained with Von remaining below 5 V. This work demonstrates that such a low Von can be attributed to efficient intrachain energy and/or charge transfer to the TBTTT sites. When the NIR emitting copolymer (P2TTPD‐10) is blended with P2TTPD‐0, the TBTTT are confined to well‐separated polymer chains. As a result, the EQE from the blend is lower and the Von higher than that obtained from the pure copolymer (P2TTPD‐1.0) with equal content of TBTTT. An analogous copolymer (P4T‐1.0), consisting of poly[3,3′‐ditetradecyl‐2,2′:5′,2′′:5′′,2′′′‐quaterthiophene‐5,5′′′‐diyl] (P4T) as the host and 1% TBTTT as the NIR emitter, further demonstrates that pure NIR emission can be obtained only through optimized molecular orbital energy levels, as in P2TTPD‐1.0, which minimizes chances for either charge trapping or exciton splitting.
Electrically Pumped Whispering Gallery Mode Lasing from Au/ZnO Microwire Schottky Junction
Authors: Bashar Sunayna B. , Wu Chunxia , Suja Mohammad , Tian Hao , Shi Wenhao , Liu Jianlin
Published: September 2016

Au/ZnO microwire Schottky diodes are fabricated. The devices exhibit typical Schottky diode I–V behavior with a turn‐on voltage of about 0.72 V. The hexagonal ZnO microwires act as whispering gallery mode (WGM) lasing microcavities. Under forward bias, a three‐microwire device exhibits WGM ultraviolet lasing spectra with a quality factor of about 1287. Output power of the laser has been measured at various injection currents, indicating threshold behavior with a threshold current of about 59 mA. Due to limited hole injection in the operation of Schottky diode, the lasing is a result of an excitonic recombination within the WGM cavity.
Application of the Solvent Dimethyl Sulfoxide/Tetrabutyl‐Ammonium Acetate as Reaction Medium for Mix‐Acylation of Pulp
Authors: Yu Yongqi , Jiang Zeming , Miao Jiaojiao , Liu Yang , Zhang Liping
Published: September 2016

An important cellulose mixed ester, cellulose acetate butyrate (CAB), was successfully prepared in tetrabutylammonium acetate (TBAA)/dimethyl sulfoxide (DMSO) system. The structure of the cellulose derivative was characterized with a Fourier Transform IR spectrometer and analyzed using 13C cross‐polarization magic angle spinning nuclear magnetic resonance. The degree of substitution (DS) of the samples prepared was calculated according to 1H‐NMR analysis. And the solubility of CAB was investigated in a wide range of traditional organic solvents such as 2‐methyl‐ethyl ketone, dichloromethane and ethyl acetate. The thermal properties of the product were analyzed by TGA analysis. The surface morphology of the esters was characterized with a field emission‐scanning electron microscopy (FE‐SEM). The relationship among surface morphology, solubility, and DS of the cellulose mixed ester was discussed. Moreover, TBAA and DMSO were recovered by vacuum distillation, which was characterized by Fourier transform infrared spectroscopy.
Superconducting YBa2Cu3O7–δ Nanocomposites Using Preformed ZrO2 Nanocrystals: Growth Mechanisms and Vortex Pinning Properties
Authors: De Keukeleere Katrien , Cayado Pablo , Meledin Alexander , Vallès Ferran , De Roo Jonathan , Rijckaert Hannes , Pollefeyt Glenn , Bruneel Els , Palau Anna , Coll Mariona , Ricart Susagna , Van Tendeloo Gustaaf , Puig Teresa , Obradors Xavier , Van Driessche Isabel
Published: September 2016

Although high temperature superconductors are promising for power applications, the production of low‐cost coated conductors with high current densities—at high magnetic fields—remains challenging. A superior superconducting YBa2Cu3O7–δ nanocomposite is fabricated via chemical solution deposition (CSD) using preformed nanocrystals (NCs). Preformed, colloidally stable ZrO2 NCs are added to the trifluoroacetic acid based precursor solution and the NCs' stability is confirmed up to 50 mol% for at least 2.5 months. These NCs tend to disrupt the epitaxial growth of YBa2Cu3O7–δ, unless a thin seed layer is applied. A 10 mol% ZrO2 NC addition proved to be optimal, yielding a critical current density JC of 5 MA cm−2 at 77 K in self‐field. Importantly, this new approach results in a smaller magnetic field decay of JC(H//c) for the nanocomposite compared to a pristine film. Furthermore, microstructural analysis of the YBa2Cu3O7–δ nanocomposite films reveals that different strain generation mechanisms may occur compared to the spontaneous segregation approach. Yet, the generated nanostrain in the YBa2Cu3O7–δ nanocomposite results in an improvement of the superconducting properties similar to the spontaneous segregation approach. This new approach, using preformed NCs in CSD coatings, can be of great potential for high magnetic field applications.
MXene‐on‐Paper Coplanar Microsupercapacitors
Authors: Kurra Narendra , Ahmed Bilal , Gogotsi Yury , Alshareef Husam N.
Published: September 2016

A simple and scalable direct laser machining process to fabricate MXene‐on‐paper coplanar microsupercapacitors is reported. Commercially available printing paper is employed as a platform in order to coat either hydrofluoric acid‐etched or clay‐like 2D Ti3C2 MXene sheets, followed by laser machining to fabricate thick‐film MXene coplanar electrodes over a large area. The size, morphology, and conductivity of the 2D MXene sheets are found to strongly affect the electrochemical performance due to the efficiency of the ion‐electron kinetics within the layered MXene sheets. The areal performance metrics of Ti3C2 MXene‐on‐paper microsupercapacitors show very competitive power‐energy densities, comparable to the reported state‐of‐the‐art paper‐based microsupercapacitors. Various device architectures are fabricated using the MXene‐on‐paper electrodes and successfully demonstrated as a micropower source for light emitting diodes. The MXene‐on‐paper electrodes show promise for flexible on‐paper energy storage devices.
Enantioselective Hydrogenation of Ketones Catalyzed by Chiral Cobalt Complexes Containing PNNP Ligand
Authors: Zhang Dong , Zhu En‐Ze , Lin Zhi‐Wei , Wei Zan‐Bin , Li Yan‐Yun , Gao Jing‐Xing
Published: September 2016

Novel chiral cobalt complexes containing a PNNP‐type ligand were synthesized using a straightforward method. The structures of the cobalt complexes have been fully characterized by X‐ray crystallography, high resolution mass spectrometry (HRMS), and electron paramagnetic resonance (EPR). Using H2 as the hydrogen source, the cobalt‐catalyzed asymmetric hydrogenation of various ketones was investigated, and the corresponding chiral alcohols were afforded with up to 99 % yield and 95 % ee. To the best of our knowledge, this is the first example of a cobalt‐catalyzed enantioselective hydrogenation of ketones with molecular hydrogen.
Escherichia coli–derived and Staphylococcus aureus–derived extracellular vesicles induce MUC5AC expression via extracellular signal related kinase 1/2 and p38 mitogen‐activated protein kinase in human airway epithelial cells
Authors: Bae Chang Hoon , Choi Yoon Seok , Song Si‐Youn , Kim Yoon‐Keun , Kim Yong‐Dae
Published: September 2016

Background

Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) release extracellular vesicles (EVs). E. coli–derived and S. aureus–derived EVs are associated with neutrophilic respiratory inflammation. In neutrophilic respiratory inflammation of human, expression of mucin is increased in airway epithelial cells and is associated with increased morbidity and mortality of the affected patients. However, no study on the effects of EVs on expression of mucin genes has been reported in airway epithelial cells. Therefore, this study was conducted in order to examine the effects and the brief signaling pathways of E. coli–derived and S. aureus–derived EVs on MUC5AC expression in human airway epithelial cells.

Methods

In mucin‐producing human NCI‐H292 airway epithelial cells and primary cultures of normal nasal epithelial cells, the effects and signaling pathways of E. coli–derived and S. aureus–derived EVs on MUC5AC expression were examined using reverse transcription–polymerase chain reaction (RT‐PCR), real‐time PCR, enzyme immunoassay, and immunoblot analysis with several specific inhibitors and small interfering RNA (siRNA).

Results

E. coli–derived and S. aureus–derived EVs induced MUC5AC expression. E. coli–derived and S. aureus–derived EVs significantly activated phosphorylation of extracellular signal related kinase 1/2 (ERK1/2) mitogen‐activated protein kinase (MAPK) and p38 MAPK. ERK1/2 MAPK inhibitor, p38 MAPK inhibitor, ERK1/2 MAPK siRNA, and p38 MAPK siRNA significantly blocked E. coli–derived and S. aureus–derived EVs induced MUC5AC messenger RNA (mRNA) expression.

Conclusion

The results of this study suggest that E. coli–derived and S. aureus–derived EVs induced MUC5AC expression via ERK1/2 and p38 MAPK signaling pathways in human airway epithelial cells.
In Situ Observation of Hydrogen‐Induced Surface Faceting for Palladium–Copper Nanocrystals at Atmospheric Pressure
Authors: Jiang Ying , Li Hengbo , Wu Zhemin , Ye Wenying , Zhang Hui , Wang Yong , Sun Chenghua , Zhang Ze
Published: September 2016

Nanocrystal (NC) morphology, which decides the number of active sites and catalytic efficiency, is strongly determined by the gases involved in synthesis, treatment, and reaction. Myriad investigations have been performed to understand the morphological response to the involved gases. However, most prior work is limited to low pressures, which is far beyond realistic conditions. A dynamic morphological evolution of palladium–copper (PdCu) NC within a nanoreactor is reported, with atmospheric pressure hydrogen at the atomic scale. In situ transmission electron microscopy (TEM) videos reveal that spherical PdCu particles transform into truncated cubes at high hydrogen pressure. First principles calculations demonstrate that the surface energies decline with hydrogen pressure, with a new order of γH‐001<γH‐110<γH‐111 at 1 bar. A comprehensive Wulff construction based on the corrected surface energies is perfectly consistent with the experiments. The work provides a microscopic insight into NC behaviors at realistic gas pressure and is promising for the shaping of nanocatalysts by gas‐assisted treatments.
Combining Nitrogen‐Doped Graphene Sheets and MoS2: A Unique Film–Foam–Film Structure for Enhanced Lithium Storage
Authors: Shan Ting‐Tian , Xin Sen , You Ya , Cong Huai‐Ping , Yu Shu‐Hong , Manthiram Arumugam
Published: September 2016

With a notable advantage in terms of capacity, molybdenum disulfide has been considered a promising anode material for building high‐energy‐density lithium‐ion batteries. However, its intrinsically low electronic conductivity and unstable electrochemistry lead to poor cycling stability and inferior rate performance. We herein describe the scalable assembly of free‐standing MoS2–graphene composite films consisting of nitrogen‐doped graphene and ultrathin honeycomb‐like MoS2 nanosheets. The composite has a unique film–foam–film hierarchical top‐down architecture from the macroscopic to the microscopic and the nanoscopic scale, which helps rendering the composite material highly compact and leads to rapid ionic/electronic access to the active material, while also accommodating the volume variation of the sulfide upon intercalation/deintercalation of Li. The unique structural merits of the composite lead to enhanced lithium storage.
Frustrated Lewis Pair Catalyzed Dehydrogenative Oxidation of Indolines and Other Heterocycles
Authors: Maier Alexander F. G. , Tussing Sebastian , Schneider Tobias , Flörke Ulrich , Qu Zheng‐Wang , Grimme Stefan , Paradies Jan
Published: September 2016

An acceptorless dehydrogenation of heterocycles catalyzed by frustrated Lewis pairs (FLPs) was developed. Oxidation with concomitant liberation of molecular hydrogen proceeded in high to excellent yields for N‐protected indolines as well as four other substrate classes. The mechanism of this unprecedented FLP‐catalyzed reaction was investigated by mechanistic studies, characterization of reaction intermediates by NMR spectroscopy and X‐ray crystal analysis, and by quantum‐mechanical calculations. Hydrogen liberation from the ammonium hydridoborate intermediate is the rate‐determining step of the oxidation. The addition of a weaker Lewis acid as a hydride shuttle increased the reaction rate by a factor of 2.28 through a second catalytic cycle.
Morphologically dependent alternating‐current and direct‐current breakdown strength in silica–polypropylene nanocomposites
Authors: Krentz Timothy , Khani Mohammad M. , Bell Michael , Benicewicz Brian C. , Nelson J. Keith , Zhao Su , Hillborg Henrik , Schadler Linda S.
Published: September 2016

In this article, we report the synthesis of a new bimodal surface ligand morphology on silica nanoparticles. Combining grafting‐to and grafting‐from approaches, in this study, we demonstrated the efficacy of anthracene surface modification for improving the dielectric breakdown strength (DBS) under alternating‐current and direct‐current conditions and that of a matrix‐compatible polymer brush for controlling the nanofiller (NF) dispersion. Ligand‐modified spherical colloidal SiO2 nanoparticles (∼14 nm in diameter) were mixed into polypropylene, and the resulting dispersion was improved over the unmodified particles, as shown with transmission electron microscopy. The results suggest that the electronic structure of the anthracene‐modified particle surface was critical to the improvement in DBS. In addition, the DBS of the composite was shown to depend on the dispersion state of the filler and the mode of stress; this indicated that the individually dispersed nanoparticles were not necessarily the optimal morphology for all stress conditions. Additionally, the precise nature of the matrix‐compatible brush was less important than the NF dispersion it produced. The bimodal grafted architectural design has provided a promising solution for the control of the dispersion and surface properties, especially for high‐molecular‐weight polymer matrices. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44347.
Gold nanoparticle patterned on PANI nanowire modified transducer for the simultaneous determination of neurotransmitters in presence of ascorbic acid and uric acid
Authors: Sadanandhan Neethu K. , Devaki Sudha J.
Published: September 2016

In the present work, we have electrochemically deposited polyaniline nanowires (PANIS) on glassy carbon electrode (GCE) from its monomer liquid crystalline template of anilinium‐3‐pentadecyl phenyl sulphonic acid (An+ PDPSA−). Further, electrode was modified by the electrochemical patterning of gold nanoparticles on the PANIS/GCE (PANIS/Au/GCE) by electrodeposition through chronoamperometry. Modified electrode characterized by electrochemical impedance, morphology, XRD, electroactive surface area, and later demonstrated its efficacy for the individual and simultaneous sensing of dopamine, ascorbic acid, serotonin, and uric acid. Finally, its performance in the real sample (blood serum) was evaluated. The superior electrocatalytic performance with higher sensitivity suggested that the modified electrode can be used as an excellent transducer for the sensing of neurotransmitters. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44351.