bluuebunny/crossref_metadata_2025 huggingface dataset:
Mixed-crystal effect on the scintillation properties of organic–inorganic layered perovskite-type compounds
Authors: Kawano Naoki , Koshimizu Masanori , Sun Yan , Yahaba Natsuna , Fujimoto Yutaka , Yanagida Takayuki , Asai Keisuke
Published: January 2014

We investigated mixed-crystal effects on the luminescence and scintillation properties of organic–inorganic layered perovskite-type compounds. The luminescence and scintillation decay accelerated as the iodine content increased. The radiative and non-radiative decay rates under both ultraviolet and X-ray radiation were calculated; quantum efficiency was used under ultraviolet radiation. The radiative decay rate was almost constant with increasing iodine content under both types of radiation; however, the non-radiative decay rate increased with increasing iodine content. These results indicate that the mixed-crystal effects on the luminescence and scintillation properties are governed by non-radiative processes. Besides, the scintillation decay time was longer than the luminescence decay time although the rise times for both profiles were similar, suggesting that the energy transfer from the organic to the inorganic layer had no effect on the scintillation properties. Moreover, these time profiles became similar with increasing iodine content in the inorganic layer. These results suggest that the difference between the two types of decay can be associated with the scintillation process in the inorganic layer.
Focused ion beam as a tool for graphene technology: Structural study of processing sequence by electron microscopy
Authors: Rius Gemma , Tavabi Amir H. , Mestres Narcis , Eryu Osamu , Tanji Takayoshi , Yoshimura Masamichi
Published: January 2014

Electron microscopy (EM) techniques are used to investigate the microstructure of ultrathin carbon layers obtained by focused ion beam induced deposition (FIBID). The investigation determines the crystalline structure, chemical bonding and elemental contents of FIBID-C materials. The effect of a thermal treatment to the ultrathin C films is analyzed. As-deposited FIBID-C is a metastable material transforming at mid-high temperatures. Evidence of its graphitization by metal catalysis is presented. Understanding of the heat transformation and crystallization is established based on the observations. Specifically, carbonization, H desorption decomposition, and graphitization, driven by high temperature metal-induced crystallization, are the identified processes. Demonstration of the graphitization of ultrathin FIBID-C enables a strategy towards graphene integrative planar technologies.
Effects of gas flow rate on structural features of ZnO nanowire arrays fabricated on silicon substrate
Authors: Ishiyama Takeshi , Fujii Tsutomu , Ishii Yuya , Fukuda Mitsuo
Published: January 2014

Arrays of single-crystal zinc oxide (ZnO) nanowires have been synthesized on silicon substrates by vapor–liquid–solid growth techniques. The effect of growth conditions including the substrate temperature and Ar gas flow rate on the growth properties of ZnO nanowire arrays were studied. Structural and optical characteristics were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) spectroscopy. The XRD measurements showed that the single-crystal nanowires exhibited growth in the (002) direction. SEM images of the ZnO nanowire arrays grown at various Ar gas flow rates indicated that the alignment and structural features of the ZnO nanowires were affected by the gas flow rate. The PL of the ZnO nanowire arrays exhibited strong UV emission at 380 nm and weak green emission at approximately 510 nm. A blue shift and broadening of the UV emission were observed with increasing Ar gas flow rate.
Synthesis and characterization of intercalated few-layer graphenes
Authors: Sato Shogo , Ichikawa Hiroaki , Iwata Nobuyuki , Yamamoto Hiroshi
Published: January 2014

Toward achieving room-temperature superconductivity, FeCl3-intercalated few-layer graphenes (FeCl3-FLGs) and Ca-intercalated few-layer graphenes (Ca-FLGs) were synthesized. FeCl3-FLGs were synthesized by the two-zone method and Ca-FLGs were synthesized using Ca–Li alloy. The Raman spectra of the FeCl3-FLGs showed a lower-intensity peak at 1607 cm−1 than that of the corresponding bare G. The peak at 1607 cm−1 suggested that the sample was stage 4–5 FeCl3-FLGs. The room-temperature electrical resistivity of FeCl3-FLGs was 2.65 × 10−5 Ω·m, which linearly decreased with decreasing temperature with a marked change occurring at approximately 200 K. From a XRD pattern of Ca-FLGs, we concluded that Ca is intercalated in FLGs. The room-temperature resistivity of Ca-FLGs was 3.45 × 10−5 Ω·m, which increased with decreasing temperature.
Determining factor of median diameter in intermetallic compound nanoparticles prepared by pulsed wire discharge
Authors: Nagasawa Shinobu , Koishi Tetsuya , Tokoi Yoshinori , Suzuki Tsuneo , Nakayama Tadachika , Suematsu Hisayuki , Niihara Koichi
Published: January 2014

The preparation of NiAl intermetallic compound nanoparticles was carried out by pulsed wire discharge (PWD) using twisted pure Ni and Al wires in N2 ambient gas with varying number of turns of the wire (N
t), energy ratio (K), and ambient gas pressure (P). From the voltage and current waveforms during the wire heating, the energy deposition ratio up to the voltage peak (K
p) was calculated. It increased with an increase in N
t to 0.4 turns/mm and with increases in K and P. Under all the conditions, with an increase in K
p, the Ni composition ratio of the prepared particles (C
Ni) became closer to that of the wire (= 51.2 mol %). Furthermore, the collection rate (R
c) increased and the median particle diameter (d
50) decreased. In particular, the change in d
50 due to the change in N
t was not predicted by the relationship of d
50 and D
th in our previous report. Single-phase NiAl intermetallic compound nanoparticles were successfully prepared under the condition in which N
t is 0.4 turns/mm, K is 3.4, and P is 100 kPa, where relatively high value of K
p was obtained. From these results, K
p was determined to be an important factor that determines the composition, collection rate, and median diameter of intermetallic compound nanoparticles synthesized by PWD using different kinds of twisted wires under various experimental conditions. This may be because of the selective wire heating in high-resistance parts that are associated with the introduction of lattice defects and/or necks by overwinding.
Carbon nanotube growth from films of Langmuir–Blodgett deposited Fe nanoparticles with filler molecules
Authors: Kuriyama Naoki , Takezawa Akihiro , Kanasugi Osamu , Nara Ryuta , Kushida Masahito
Published: January 2014

Independently controlling the number density and diameter of Fe nanoparticles (FeNPs) used as a catalyst for vertically aligned carbon nanotube (VA-CNT) growth is difficult by conventional methods. In this study, mixed solutions of FeNPs and palmitic acid (C16) used as filler molecules were prepared to prevent the thermal aggregation of FeNPs and control the number density of VA-CNTs. FeNPs mixed with C16 monolayer films were prepared on the water surface and deposited on SiO2/Si substrates by the Langmuir–Blodgett (LB) technique. VA-CNTs were synthesized by a thermal chemical vapor deposition method using acetylene gas. Furthermore, we studied the optimum hydrogen reduction temperature and time of FeNPs used as a catalyst to encourage VA-CNT growth. By controlling the ratio of FeNP catalyst to C16 as a filler molecule in the LB film and optimizing hydrogen reduction condition, we were able to control the number density and diameter of FeNPs independently.
Quantized exciton–exciton recombination in undoped and hole-doped single-walled carbon nanotubes
Authors: Nishihara Taishi , Yamada Yasuhiro , Okano Makoto , Kanemitsu Yoshihiko
Published: January 2014

We studied the quantized exciton Auger recombination in undoped and hole-doped single-walled carbon nanotubes (SWCNTs) by means of transient absorption spectroscopy and theoretical calculations. In undoped SWCNTs, a fast decay component appears under strong photoexcitation owing to two-exciton Auger recombination. The exciton decay dynamics is well explained by the quantized exciton Auger recombination model that takes into consideration the dark-exciton state. In hole-doped SWCNTs, the fast decay component is drastically reduced even under strong photoexcitation. We calculated the temporal evolution of the exciton population in hole-doped samples by considering exciton–hole interactions and the hole-number distribution in SWCNTs, and found it to be in good agreement with the experimental results.
Development of accurate two-dimensional dose-imaging detectors using atomic-scale color centers in Ag-activated phosphate glass and LiF thin films
Authors: Kurobori Toshio , Matoba Akinari
Published: January 2014

Novel disk-type X-ray two-dimensional (2D) imaging detectors have been developed by utilising atomic-scale defects as minimum luminescent units such as radiation-induced Ag-related species in Ag-activated phosphate glass and F-aggregated centres in lithium fluoride (LiF) thin films. Such luminescent detectors are based on the radiophotoluminescence (RPL) and photoluminescence (PL) phenomena, respectively. Accurate accumulated 2D dose distributions with a high spatial resolution of micron order over large areas and a wide dynamic range covering 8 orders of magnitude were rapidly reconstructed and were successfully demonstrated for the first time by combining the Ag-doped glass with LiF thin films. These detectors should be suitable for X- and gamma-ray imaging in radiation diagnostics and clinical radiotherapy.
Small device-to-device variation of 6,13-bis(triisopropylsilylethynyl)pentacene field-effect transistor arrays fabricated by a flow-coating method
Authors: Sakamoto Kenji , Bulgarevich Kirill , Miki Kazushi
Published: January 2014

Bottom-contact/bottom-gate-type organic field-effect transistor (OFET) arrays have been fabricated using a flow-coating method, and the device-to-device variation has been examined. The flow-coated active layer of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-PEN) was composed of arrays of needle-shaped crystals whose long axes were aligned along the flow-coating direction. By measuring the electrical characteristics of one hundred twenty OFETs with the channel current direction parallel or perpendicular to the flow-coating direction, we evaluated the device-to-device variation in the device properties. The field-effect hole mobilites (average ± standard deviation) for the parallel and perpendicular OFET sets were 0.51 ± 0.03 and 0.12 ± 0.03 cm2·V−1·s−1, respectively. The small standard deviations clearly show the high spatial uniformity of the TIPS-PEN active layer. The much smaller relative standard deviation, a measure of device-to-device variation, for the parallel OFET set (6%) can be attributed to a high degree of alignment of needle-shaped TIPS-PEN crystals along the flow-coating direction.
All solution-processed amorphous oxide thin-film transistors using UV/O3 treatment
Authors: Umeda Kenichi , Miyasako Takaaki , Sugiyama Ayumu , Tanaka Atsushi , Suzuki Masayuki , Tokumitsu Eisuke , Shimoda Tatsuya
Published: January 2014

In the fabrication of amorphous oxide thin-film transistors (TFTs) by all-solution process, an ultraviolet–ozone (UV/O3) treatment and solution materials were adopted. By applying the UV/O3 treatment for solution-processed In2−

x
Ga
x
ZnO4 channel layers, enhancement of TFT characteristics was achieved. In particular, the most appropriate metal composition for the In2−

x
Ga
x
ZnO4 system with UV/O3 treatment was found to be x = 1.0. In addition to the channel layers, solution-processed LaNiO3, Bi–Nb–O/La–Ta–O stacked layer, and ITO films were formed as the gate electrode, gate insulator, and source and drain electrodes, respectively, for TFT fabrication. Using UV/O3 treatment and solution materials, all-solution-processed amorphous oxide TFTs were successfully fabricated, and superior TFT properties, including an on–off current ratio of 107, a threshold voltage of 1.6 V, a subthreshold swing of 200 mV/decade, and a field-effect mobility of 0.49 cm2 V−1 s−1, were achieved.
Flexible PTB7:PC71BM bulk heterojunction solar cells with a LiF buffer layer
Authors: Yanagidate Tatsuki , Fujii Shunjiro , Ohzeki Masaya , Yanagi Yuichiro , Arai Yuki , Okukawa Takanori , Yoshida Akira , Kataura Hiromichi , Nishioka Yasushiro
Published: January 2014

Bulk heterojunction solar cells were fabricated using poly[4,8-bis[(2-ethylhexyl)oxy]benzo [1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl] (PTB7) and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) after a layer of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) was deposited on a flexible indium tin oxide (ITO)-coated polyethylene terephthalate substrate. The fabricated structures were Al/LiF/PTB7:PC71BM/PEDOT:PSS/ITO with or without a lithium fluoride (LiF) buffer layer, and the effect of the LiF buffer layer on the performance of the solar cells was investigated. The LiF layer significantly increased the open-circuit voltages and fill factors of the solar cells, presumably because of the work function shift of the aluminum cathode. As a result, the conversion efficiency increased from 2.31 to 4.02% owing to the presence of the LiF layer. From the results of a stability test, it was concluded that the inserted LiF layer acted as a shielding and scavenging protector, which prevented the intrusion of some chemical species into the active layer, thereby improving the lifetime of the unpakcaged devices.
Effect of the solvent used to prepare the photoactive layer on the performance of inverted bulk heterojunction polymer solar cells
Authors: Kuwabara Takayuki , Kuzuba Mitsuhiro , Emoto Natsumi , Yamaguchi Takahiro , Taima Tetsuya , Takahashi Kohshin
Published: January 2014

The initial performance and subsequent degradation of inverted polymer solar cells [indium–tin oxide/titanium oxide (TiO
x
)/[6,6]-phenyl C61 butyric acid methyl ester (PCBM): regioregular poly(3-hexylthiophene) (P3HT)/poly(3,4-ethylenedioxylenethiophene):poly(4-styrene sulfonic acid)/Au, TiO
x
cell] are studied by photocurrent–voltage measurements as well as ac impedance spectroscopy (IS) and carrier mobility measurements. The TiO
x
cells containing a P3HT:PCBM layer prepared from a solution of chlorobenzene (CB) showed a maximum power conversion efficiency (PCE) of 2.23%. In contrast, the TiO
x
cells containing a P3HT:PCBM layer prepared from a solution of 1,2,3,4-tetrahydronaphthalene (tetralin) containing 2 vol % 1,8-octanedithiol (ODT) exhibited a maximum PCE of 2.92%. However, after exposure to light irradiation for 100 h, the maximum PCE of the tetralin:ODT cell decreased to 68% of its initial value. On the other hand, over 96% of the maximum PCE was maintained in the CB cell after 100 h of irradiation. The IS measurement results suggest that the degradation of the Tetralin:ODT cell was caused by a morphological change of the P3HT:PCBM layer that made efficient photoinduced charge separation difficult.
Bulk-heterojunction organic solar cells sandwiched by solution processed molybdenum oxide and titania nanosheet layers
Authors: Itoh Eiji , Goto Yoshinori , Fukuda Katsutoshi
Published: January 2014

The contributions of ultrathin titania nanosheet (TN) crystallites were studied in both an inverted bulk-heterojunction (BHJ) cell in an indium–tin oxide (ITO)/titania nanosheet (TN)/poly(3-hexylthiophene) (P3HT):phenyl-C61-butyric acid methylester (PCBM) active layer/MoO
x
/Ag multilayered photovoltaic device and a conventional BHJ cell in ITO/MoO
x
/P3HT:PCBM active layer/TN/Al multilayered photovoltaic device. The insertion of only one or two layers of poly(diallyldimethylammonium chloride) (PDDA) and TN multilayered film prepared by the layer-by-layer deposition technique effectively decreased the leakage current and increased the open circuit voltage (V
OC), fill factor (FF), and power conversion efficiency (η). The conventional cell sandwiched between a solution-processed, partially crystallized molybdenum oxide hole-extracting buffer layer and a TN electron extracting buffer layer showed comparable cell performance to a device sandwiched between vacuum-deposited molybdenum oxide and TN layers, whereas the inverted cell with solution-processed molybdenum oxide showed a poorer performance probably owing to the increment in the leakage current across the film. The abnormal S-shaped curves observed in the inverted BHJ cell above V
OC disappeared with the use of a polyfluorene-based cationic semiconducting polymer as a substitute for an insulating PDDA film, resulting in the improved cell performance.
The UV and visible spectra of chlorine peroxide: Constraining the atmospheric photolysis rate
Authors: Young I. A. K. , Jones R. L. , Pope F. D.
Published: January 2014

The photolysis of chlorine peroxide (ClOOCl) is a key chemical step in the depletion of polar stratospheric ozone. As such, precise measurements of the absorption cross sections for ClOOCl are required. In this paper we provide two critical pieces of laboratory data with which to constrain the rate of ozone depletion. First, we provide an optically pure ClOOCl spectrum in the photolytically important UV wavelength region (200–350 nm). Second, we provide the first ever measurement of the ClOOCl spectrum in the visible region (509–536 nm) conclusively demonstrating the photolysis of ClOOCl to be negligible in this spectral region. The visible measurement is important because it can be used to anchor other previously recorded UV spectra and hence reduce the uncertainty in the ClOOCl photolysis rate. The calculated photolysis rate from this study indicates that the current models of stratospheric ozone depletion are correct.
Electrodynamics of the Martian dynamo region near magnetic cusps and loops
Authors: Riousset Jeremy A. , Paty Carol S. , Lillis Robert J. , Fillingim Matthew O. , England Scott L. , Withers Paul G. , Hale John P. M.
Published: January 2014

Strong and inhomogeneous remanent magnetization on Mars results in a complex pattern of crustal magnetic fields. The geometry and topology of these fields lead to atmospheric electrodynamic structures that are unique among the bodies of the solar system. In the atmospheric dynamo region (∼100−250 km altitude), ions depart from the gyropath due to collisions with neutral particles, while electron motion remains governed by electromagnetic drift. This differential motion of the charge carriers generates electric currents, which induce a perturbation field. The electromagnetic changes ultimately alter the behavior of the local ionosphere beyond the dynamo region. Here we use multifluid modeling to investigate the dynamics around an isolated magnetic cusp and around magnetic loops or arcades representative of the magnetic topology near, for example, Terra Sirenum. Our results show consistent, circular patterns in the electric current around regions with high local field strength, with possible consequences on atmospheric escape of charged particles.
Substorm onset process: Ignition of auroral acceleration and related substorm phases
Authors: Morioka Akira , Miyoshi Yoshizumi , Kasaba Yasumasa , Sato N. , Kadokura Akira , Misawa Hiroaki , Miyashita Yukinaga , Mann Ian
Published: January 2014

The substorm onset process was studied on the basis of the vertical evolution of auroral acceleration regions derived from auroral kilometric radiation (AKR) spectra and Pi pulsations on the ground. The field‐aligned auroral acceleration at substorm onset demonstrated two distinct phases. Low‐altitude acceleration (h~3000–5000 km), which accompanied auroral initial brightening, prebreakup Pi2, and direct current of ultralow frequency (DC‐ULF) pulsation were first activated and played an important role (precondition) in the subsequent substorm expansion phase onset. Prebreakup Pi2 is suggestive of the ballooning mode wave generation, and negative decrease in DC‐ULF suggests increasing field‐aligned current (FAC). We called this stage the substorm initial phase. A few minutes after this initial phase onset, high‐altitude acceleration, which accompanied auroral breakup and poleward expansion with breakup Pi1 and Pi2 pulsations, suddenly broke out in an altitude range from 8000 to 16,000 km. Thus, substorm expansion onset originated in the magnetosphere‐ionosphere (M‐I) coupling region, i.e., substorm ignition in the M‐I coupling region. Statistical investigations revealed that about 65% of earthward flow bursts observed in the plasma sheet were accompanied by enhanced low‐altitude AKR, suggesting that flow braking of bursts causes FAC and resulting low‐altitude field‐aligned acceleration in the M‐I coupling region. On the basis of these observations, we propose a substorm onset scenario in which FAC that originated from the braking of plasma flow bursts first enhances low‐altitude acceleration (substorm initial phase onset) and then the increasing FAC induces current‐driven instability in the M‐I coupling region, which leads to high‐altitude acceleration and resulting substorm expansion phase onset.
Origins of topography in the western U.S.: Mapping crustal and upper mantle density variations using a uniform seismic velocity model
Authors: Levandowski Will , Jones Craig H. , Shen Weisen , Ritzwoller Michael H. , Schulte‐Pelkum Vera
Published: January 2014

To investigate the physical basis for support of topography in the western U.S., we construct a subcontinent scale, 3‐D density model using ~1000 estimated crustal thicknesses and S velocity profiles to 150 km depth at each of 947 seismic stations. Crustal temperature and composition are considered, but we assume that mantle velocity variations are thermal in origin. From these densities, we calculate crustal and mantle topographic contributions. Typical 2σ uncertainty of topography is ~500 m, and elevations in 84% of the region are reproduced within error. Remaining deviations from observed elevations are attributed to melt, variations in crustal quartz content, and dynamic topography; compositional variations in the mantle, while plausible, are not necessary to reproduce topography. Support for western U.S. topography is heterogeneous, with each province having a unique combination of mechanisms. Topography due to mantle buoyancy is nearly constant (within ~250 m) across the Cordillera; relief there (>2 km) results from variations in crustal chemistry and thickness. Cold mantle provides ~1.5 km of ballast to the thick crust of the Great Plains and Wyoming craton. Crustal temperature variations and dynamic pressures have smaller magnitude and/or more localized impacts. Positive gravitational potential energy (GPE) anomalies (~2 × 1012N/m) calculated from our model promote extension in the northern Basin and Range and near the Sierra Nevada. Negative GPE anomalies (−3 × 1012N/m) along the western North American margin and Yakima fold and thrust belt add compressive stresses. Stresses derived from lithospheric density variations may strongly modulate tectonic stresses in the western U.S. continental interior.
Highly Aligned Nanofibrous Scaffold Derived from Decellularized Human Fibroblasts
Authors: Xing Qi , Vogt Caleb , Leong Kam W. , Zhao Feng
Published: January 2014

Native tissues are endowed with a highly organized nanofibrous extracellular matrix (ECM) that directs cellular distribution and function. The objective of this study is to create a purely natural, uniform, and highly aligned nano­fibrous ECM scaffold for potential tissue engineering applications. Synthetic nanogratings (130 nm in depth) are used to direct the growth of human dermal fibroblasts for up to 8 weeks, resulting in a uniform 70 μm‐thick fibroblast cell sheet with highly aligned cells and ECM nanofibers. A natural ECM scaffold with uniformly aligned nanofibers of 78 ± 9 nm in diameter is generated after removing the cellular components from the fibroblast sheet. The elastic modulus of the scaffold is well maintained after the decellularization process because of the preservation of elastin fibers. Reseeding human mesenchymal stem cells (hMSCs) shows the excellent capacity of the scaffold in directing and supporting cell alignment and proliferation along the underlying fibers. The scaffold's biocompatibility is further examined by an in vitro inflammation assay with seeded macrophages. The aligned ECM scaffold induces a significantly lower immune response compared to its unaligned counterpart, as detected by the pro‐inflammatory cytokines secreted from macrophages. The aligned nanofibrous ECM scaffold holds great potential in engineering organized tissues.
Defect‐Tolerant Nanocomposites through Bio‐Inspired Stiffness Modulation
Authors: Beese Allison M. , An Zhi , Sarkar Sourangsu , Nathamgari S. Shiva P. , Espinosa Horacio D. , Nguyen SonBinh T.
Published: January 2014

A biologically inspired, multilayer laminate structural design is deployed into nanocomposite films of graphene oxide‐poly(methyl methacrylate) (GO‐PMMA). The resulting multilayer GO‐PMMA films show greatly enhanced mechanical properties compared to pure‐graphene‐oxide films, with up to 100% increases in stiffness and strength when optimized. Notably, a new morphology is observed at fracture surfaces: whereas pure‐graphene‐oxide films show clean fracture surfaces consistent with crack initiation and propagation perpendicular to the applied tensile load, the GO‐PMMA multilayer laminates show terracing consistent with crack stopping and deflection mechanisms. As a consequence, these macroscopic GO‐PMMA films become defect‐tolerant and can maintain their tensile strengths as their sample volumes increase. Linear elastic fracture analysis supports these observations by showing that the stiffness modulation introduced by including PMMA layers within a graphene oxide film can act to shield or deflect cracks, thereby delaying failure and allowing the material to access more of its inherent strength. Together, these data clearly demonstrate that desirable defect‐tolerant traits of structural biomaterials can indeed be incorporated into graphene‐ oxide‐based nanocomposites.
Exciton–Polaron‐Induced Aggregation of Wide‐Bandgap Materials and its Implication on the Electroluminescence Stability of Phosphorescent Organic Light‐Emitting Devices
Authors: Wang Qi , Sun Bin , Aziz Hany
Published: January 2014

The degradation mechanisms of phosphorescent organic light‐emitting devices (PhOLEDs) are studied. The results show that PhOLED degradation is closely linked to interactions between excitons and positive polarons in the host material of the emitter layer (EML), which lead to its aggregation near the EML/electron transport layer (ETL) interface. This exciton–polaron‐induced aggregation (EPIA) is associated with the emergence of new emission bands at longer wavelengths in the electroluminescence spectra of these materials, which can be detected after prolonged device operation. Such EPIA processes are found to occur in a variety of wide‐bandgap materials commonly used as hosts in PhOLEDs and are correlated with device degradation. Quite notably, the extent of EPIA appears to correlate with the material's bandgap rather than with the glass‐transition temperature. The findings uncover a new degradation mechanism, caused by polaron‐exciton interactions, that appears to be behind the lower stability of OLEDs utilizing wide‐bandgap materials in general. The same degradation mechanism can be expected to be present in other organic optoelectronic devices.
Structure and Optical Properties of Multilayers Carbon Nanotubes/PEEK Nanocomposites
Authors: Ahmad Ishaq , Rakha Sobia A. , Yan Long , Zhou Xingtai , Ma Guohong , Munir Arshad
Published: January 2014

Using sheet‐by‐sheet method, multiwalled carbon nanotubes (MWCNTs)/polyetheretherketone (PEEK) multilayered composites are manufactured. The shielding efficiencies and dielectric constants of the MWCNTs/PEEK composites are investigated in the frequency range of 0.1–1.6 THz using terahertz time domain spectroscopy (THz‐TDS). The MWCNTs/PEEK composite with a carbon‐nanotubes fraction of 1.2% turns to be metallic. Moreover, compared with multilayered graphite/PEEK and single layered MWCNTs/PEEK composites, the multilayered MWCNTs/PEEK composites present excellent terahertz absorptive with a frequency response consistent with Drude's free‐electron model.
Congenital nasal pyriform aperture stenosis and ocular albinism co‐occurring in a sibship with a maternally‐inherited 97 kb Xp22.2 microdeletion
Authors: Somsen David , Davis‐Keppen Laura , Crotwell Patricia , Flanagan Jason , Munson Patrick , Stein Quinn
Published: January 2014

Congenital Nasal Pyriform Aperture Stenosis (CNPAS) is a rare congenital malformation caused by overgrowth of the maxillary bone. We report on two patients, brothers born 3 and 1½ years apart, both presented at birth with radiographically diagnosed CNPAS. Both siblings also were born with ocular albinism, which is known to have X‐linked inheritance. Subsequent genetic testing demonstrated a 97 kb deletion in the p arm of the X chromosome in both siblings and their mother. This deletion encompasses a gene known to cause ocular albinism (GPR143), as well as partial deletion of two other genes, TBL1X and SHROOM2. This is the first reported case of CNPAS in siblings, both males, sharing a maternally inherited Xp22.2 deletion. © 2014 Wiley Periodicals, Inc.
Frequency of FMR1 gene mutation and CGG repeat polymorphism in intellectually disabled children in Pakistan
Authors: Fatima Tasneem , Zaidi Syed Aley Hasan , Sarfraz Noorjehan , Perween Siddiqa , Khurshid Faraz , Imtiaz Fauzia
Published: January 2014

Fragile X syndrome is considered the most common heritable form of X‐linked intellectual disability (ID). The syndrome is caused by silencing of the fragile X mental retardation 1 gene (Xq27.3) due to hypermethylation. This mutation results in absence or deficit of its protein product, the fragile X mental retardation protein (FMRP) that affects synaptic plasticity in neurons, hence leads to brain dysfunction. The syndrome is widely distributed throughout the world. This study reported for the first time the frequency of the fragile X mental retardation 1 gene mutations in intellectually disabled children in Pakistan. We recruited 333 intellectually disabled children and 250 normal children with age ranging from 5 to 18 years for this study. Genomic DNA was extracted from peripheral blood and full mutations were identified by methylation sensitive PCR using primers corresponding to modified methylated and unmethylated DNA. Southern blot was used for confirmation of the results. The frequency of fragile X syndrome with full mutation was found as 4.8%. It was 6.5% in males as opposed to 0.9% in females; 29 CGG repeats were found as the most common allele; 31.5% in the intellectually disabled and 34% in control subjects. In Pakistan intellectual disability is considered as a social stigma for the individuals and their families. Due to lack of knowledge and cultural background people make such patients and families isolated. This study will increase public awareness about the intellectual disability and importance of prenatal screening and genetic counseling for vulnerable families. © 2014 Wiley Periodicals, Inc.
Parental smoking and allergic rhinitis in children
Authors: Salehi Maryam , Bakhshaee Mehdi , Ashtiani Sara Jafari , Najafi Mona , Sehatbakhsh Samineh , Hossainzadeh Mana
Published: January 2014

Background

Parental smoking is one of the controversial risk factors associated with allergic rhinitis. The aim of this study was to investigate the relationship between parental smoking and allergic rhinitis; considering confounding factors.

Methods

A cross‐sectional study was conducted on 671 children aged 2 to 7 years. Random cluster sampling was used to select the participants. The signs and symptoms of allergic rhinitis in children were assessed through standard questionnaires and physical examinations.

Results

In the multivariate analysis, parental smoking (odds ratio [OR] 1.07; 95% confidence interval [CI], 0.48–2.41) was not a significant risk factor for allergic rhinitis; positive family history of allergy was the only significant factor among other factors (OR 23.64; 95% CI, 11.63–48.04). Sex (OR 1.16; 95% CI, 0.60–2.24), family size (OR 1.06; 95% CI, 0.22–5.05), family income (OR 0.60; 95% CI, 0.24–1.47), and parents’ education (OR 1.79; 95% CI, 0.61–5.20) were not statistically significant.

Conclusion

The findings suggest that there is no significant relationship between parental smoking and allergic rhinitis.
A Regio‐ and Stereoselective ω‐Transaminase/Monoamine Oxidase Cascade for the Synthesis of Chiral 2,5‐Disubstituted Pyrrolidines
Authors: O'Reilly Elaine , Iglesias Cesar , Ghislieri Diego , Hopwood Jennifer , Galman James L. , Lloyd Richard C. , Turner Nicholas J.
Published: January 2014

Biocatalytic approaches to the synthesis of optically pure chiral amines, starting from simple achiral building blocks, are highly desirable because such motifs are present in a wide variety of important natural products and pharmaceutical compounds. Herein, a novel one‐pot ω‐transaminase (TA)/monoamine oxidase (MAO‐N) cascade process for the synthesis of chiral 2,5‐disubstituted pyrrolidines is reported. The reactions proceeded with excellent enantio‐ and diastereoselectivity (>94 % ee; >98 % de) and can be performed on a preparative scale. This methodology exploits the complementary regio‐ and stereoselectivity displayed by both enzymes, which ensures that the stereogenic center established by the transaminase is not affected by the monoamine oxidase, and highlights the potential of this multienzyme cascade for the efficient synthesis of chiral building blocks.
Broadly Applicable Z‐ and Diastereoselective Ring‐Opening/Cross‐Metathesis Catalyzed by a Dithiolate Ru Complex
Authors: Koh Ming Joo , Khan R. Kashif M. , Torker Sebastian , Hoveyda Amir H.
Published: January 2014

A broadly applicable Ru‐catalyzed protocol for Z‐selective ring‐opening/cross‐metathesis (ROCM) is disclosed. In addition to reactions relating to terminal alkenes of different sizes, the first examples of Z‐selective ROCM processes involving heteroaryl olefins, 1,3‐dienes, and O‐ and S‐substituted alkenes as well as allylic and homoallylic alcohols are reported. Z‐Selective transformations with an α‐substituted allylic alcohol are shown to afford congested Z alkenes with high diastereoselectivity. Transformations are performed in the presence of 2.0–5.0 mol % of a recently disclosed Ru‐based dithiolate complex that can be easily prepared in a single step from commercially available starting materials. Typically, transformations proceed at ambient temperature and are complete within eight hours; products are obtained in up to 97 % yield, >98:2 Z/E, and >98:2 diastereomeric ratio. The present investigations reveal a mechanistically significant attribute of the Ru‐based dithiolates that arises from electrostatic interactions with anionic S‐based ligands.
A Multicomponent Ni‐, Zr‐, and Cu‐Catalyzed Strategy for Enantioselective Synthesis of Alkenyl‐Substituted Quaternary Carbons
Authors: McGrath Kevin P. , Hoveyda Amir H.
Published: January 2014

The availability of enantiomerically enriched carbonyl‐containing compounds is essential to the synthesis of biologically active molecules. Since catalytic enantioselective conjugate addition (ECA) reactions directly generate the latter valuable class of molecules, the design and development of such protocols represents a compelling objective in modern chemistry. Herein, we disclose the first solution to the problem of ECA of alkenyl groups to acyclic trisubstituted enones, an advance achieved by adopting an easily modifiable and fully catalytic approach. The requisite alkenylaluminum reagents are synthesized with exceptional site‐ and/or stereoselectivity by a Ni‐catalyzed hydroalumination process, and the necessary enones are prepared through a site‐ and stereoselective zirconocene‐catalyzed carboalumination/acylation reaction. The all‐catalytic procedure is complete within four hours, furnishing the desired products in up to 77 % overall yield and 99:1 enantiomeric ratio.
Crystal Structure of Metallo DNA Duplex Containing Consecutive Watson–Crick‐like T–HgII–T Base Pairs
Authors: Kondo Jiro , Yamada Tom , Hirose Chika , Okamoto Itaru , Tanaka Yoshiyuki , Ono Akira
Published: January 2014

The metallo DNA duplex containing mercury‐mediated T–T base pairs is an attractive biomacromolecular nanomaterial which can be applied to nanodevices such as ion sensors. Reported herein is the first crystal structure of a B‐form DNA duplex containing two consecutive T–HgII–T base pairs. The HgII ion occupies the center between two T residues. The N3‐HgII bond distance is 2.0 Å. The relatively short HgII‐HgII distance (3.3 Å) observed in consecutive T–HgII–T base pairs suggests that the metallophilic attraction could exist between them and may stabilize the B‐form double helix. To support this, the DNA duplex is largely distorted and adopts an unusual nonhelical conformation in the absence of HgII. The structure of the metallo DNA duplex itself and the HgII‐induced structural switching from the nonhelical form to the B‐form provide the basis for structure‐based design of metal‐conjugated nucleic acid nanomaterials.
Blending of TiO2 nanoparticles with cellulose acetate polymer: to study the effect on morphology and gas permeation of blended membranes
Authors: Farrukh Sarah , Javed Sofia , Hussain Arshad , Mujahid Muhammad
Published: January 2014

Cellulose acetate–titania (CA–TiO2) nanoparticles blended membranes were fabricated using diffusion‐induced phase separation process to observe the effect of inorganic nanofillers on the surface topography and gas permeation properties of CA membrane. Self‐synthesized TiO2 nanoparticles using sol gel reflux condensation were employed as nanofillers, which is the anatase phase of TiO2 with crystallite size of 5–10 nm. The synthesized membranes were characterized using scanning electron microscopy and atomic force microscopy techniques to study the nanoscale distribution of TiO2 nanoparticles, surface roughness, and pores generation in blended membranes, with increasing nanoparticles' concentration in polymer matrix. The permeability of CO2 was found to be increased for CA–TiO2 blended membranes. The CO2/CH4 selectivity up to 23.3 was documented. © 2014 Curtin University of Technology and John Wiley & Sons, Ltd.
Preparation and characterization of bis‐[1,3,5]triazinyl diazenes and their utilization as flame retardants in polypropylene films
Authors: Tirri Teija , Aubert Melanie , Pawelec Weronika , Wilén Carl‐Eric , Pfaendner Rudolf , Hoppe Holger , Roth Michael , Sinkkonen Jari
Published: January 2014

A series of bis‐[1,3,5]triazinyl diazenes and two metal complexes thereof were synthesized and tested as new flame retardants in polypropylene films. It was observed that electron withdrawing triazinyl ring substituent (i.e., Cl and phenyl moieties) improved the thermal stability of diazene compounds, whereas electron donating groups (i.e., methoxy, dimethylamino, and ethylthio moieties) had a destabilizing effect. TGA, DTA/DSC, NMR, and ATR‐FTIR were used for the characterization. Quantum mechanical modeling (Gaussian 09) was also utilized to facilitate the interpretation of the NMR data. Bis‐(4,6‐dichloro‐[1,3,5]triazin‐2‐yl)‐diazene 1 and bis‐(4,6‐dimethoxy‐[1,3,5]triazin‐2‐yl)‐diazene 2 were found to be effective flame retardants in polypropylene films and DIN4102‐1 B2 classification was reached already at a loading of 0.5 wt %. Interestingly, the copper complex of 2 showed even higher fire retardant activity than its precursor 2, whereas the corresponding zinc complex exhibited lower flame retardant efficacy than its precursor. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40413.
Production and isolation of chitosan from Aspergillus terreus and application in tin(II) adsorption
Authors: Cheng Li‐Chun , Wu Tzung‐Shian , Wang Jian‐Wen , Wu Szu‐Han , Chung Mei‐Hui , Kuo Yi‐Ming , Tsai Cheng‐Hsien
Published: January 2014

Fed‐batch fermentation was used for biomass and fungal chitosan production by Aspergillus terreus (BCRC 32068) grown in a potato dextrose agar medium. The polysaccharides were extracted by an alkali–acid treatment, and structural investigations by X‐ray diffraction, Fourier transform infrared analysis, and viscosity and thermal analysis were done. A high level of chitosan was extracted from A. terreus; this implied that it was feasible to produce chitosan from industrial waste mycelia. Fungal chitosan derived from A. terreus showed the highest adsorption capacity for Sn(II). The order of Sn(II) adsorption capacity for these chitosanaceous materials was Fungal chitosan > Chitin > Biomass. Fungal chitosan derived from A. terreus was well correlated with Langmuir's isotherm model. The maximum capacity for Sn(II) sorption deduced from the use of the Langmuir isotherm equation was 303 mg/g; this was significantly higher than that of A. terreus. Fungal chitosan is an easy and cost‐effective material for the abatement of pollution. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40436.
Gas permeation properties of poly(2,5‐benzimidazole) derivative membranes
Authors: Jiang Can , Jie Xingming , Kang Guodong , Liu Dandan , Cao Yiming , Yuan Quan
Published: January 2014

In this article, three novel polymers based on poly(2,5‐benzimidazole) (ABPBI) were synthesized by introducing propyl, isobutyl or n‐butyl groups to its side chain through an alkyl substitution reaction. FTIR and 13C NMR were applied to confirm the formation of corresponding chemical groups. Their physical properties including crystallinity, thermal stability, mechanical strength, and micro‐morphology were also characterized. Their solubility in common solvents were also tested to see if the modification will bring any improvement. Gas permeation properties of three derivative membranes prepared by a casting and solvent‐evaporation method were tested with pure gases including H2, N2, O2, CH4, and CO2. It has been revealed that gas with a smaller molecular size owned a larger permeability. This means gas permeation in all prepared membranes should be diffusivity selective. Among all three modified ABPBI membranes, isobutyl substitution modified ABPBI (IBABPBI) showed the best selectivity of H2 over other gases such as N2 (∼185) and CO2 (∼6.3) with a comparable permeability (∼9.33 barrer) when tested at 35°C and 3.0 atm. Testing temperature increase facilitated gas permeation for all three membranes obviously; while in term of gas selectivity temperature increase showed diverse alteration because it brought variable impact on gas solubility of different gases. Even so, IBABPBI membrane still owned acceptable selectivity of H2 over N2 (∼118) and CO2 (∼6.3) with an almost doubled permeability (∼17.5 barrer) when tested at 75°C and 3.0 atm. Additional tests showed that running at high pressure did not bring any obvious deterioration to gas separation performance of IBABPBI membrane. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40440.
PDP1 REGULATES ENERGY METABOLISM THROUGH THE IIS‐TOR PATHWAY IN THE RED FLOUR BEETLE, Tribolium castaneum
Authors: Li Zhiqian , Jiang Jianhao , Chen Yazhou , You Lang , Huang Yongping , Tan Anjiang , Li Zhiqian , Jiang Jianhao , Niu Baolong , Meng Zhiqi
Published: January 2014

The PAR‐domain protein 1 (PDP1) is essential for locomotor activity of insects. However, its functions in insect growth and development have not been studied extensively, which prompted our hypothesis that PDP1 acts in energy metabolism. Here we report identification of TcPDP1 in the red flour beetle, Tribolium castaneum, and its functional analysis by RNAi. Treating larvae with dsTcPDP1 induced pupae developmental arrestment, accompanied by accelerated fat body degradation. dsTcPDP1 treatments in adults resulted in reduced female fecundity. Disruption of TcPDP1 expression affected the transcription of genes involved in insulin signaling transduction and mechanistic target of rapamycin (mTOR) pathway. These results support our hypothesis that TcPDP1 acts in energy metabolism in T. castaneum.
Brazilian bibliometric coauthorship networks
Authors: Mena‐Chalco Jesús Pascual , Digiampietri Luciano Antonio , Lopes Fabrício Martins , Cesar Roberto Marcondes
Published: January 2014

The Brazilian Lattes Platform is an important academic/résumé data set that registers all academic activities of researchers associated with different major knowledge areas. The academic information collected in this data set is used to evaluate, analyze, and document the scientific production of research groups. Information about the interactions between Brazilian researchers in the form of coauthorships, however, has not been analyzed. In this article, we identified and characterized Brazilian academic coauthorship networks of researchers registered in the Lattes Platform using topological properties of graphs. For this purpose, we explored (a) strategies to develop a large Lattes curricula vitae data set, (b) an algorithm for identifying automatic coauthorships based on bibliographic information, and (c) topological metrics to investigate interactions among researchers. This study characterized coauthorship networks to gain an in‐depth understanding of the network structures and dynamics (social behavior) among researchers in all available major Brazilian knowledge areas. In this study, we evaluated information from a total of 1,131,912 researchers associated with the eight major Brazilian knowledge areas: agricultural sciences; biological sciences; exact and earth sciences; humanities; applied social sciences; health sciences; engineering; and linguistics, letters, and arts.
Metagenomic insights into the human gut resistome and the forces that shape it
Authors: Forslund Kristoffer , Sunagawa Shinichi , Coelho Luis P. , Bork Peer
Published: January 2014

We show how metagenomic analysis of the human gut antibiotic resistome, compared across large populations and against environmental or agricultural resistomes, suggests a strong anthropogenic cause behind increasing antibiotic resistance in bacteria. This area has been the subject of intense and polarized debate driven by economic and political concerns; therefore such recently available insights address an important need. We derive and compare antibiotic resistomes of human gut microbes from 832 individuals from ten different countries. We observe and describe significant differences between samples from these countries in the gut resistance potential, in line with expectations from antibiotic usage and exposure in medical and food production contexts. Our results imply roles for both of these sources in increased resistance among pathogens in recent history. In contrast, other available metadata such as age, body mass index, sex, or health status have little effect on the antibiotic resistance potential of human gut microbes.

Also watch the Video Abstract.