bluuebunny/crossref_metadata_2025 huggingface dataset:
Elastic anisotropy modeling of Kimmeridge shale
Authors: Vasin Roman N. , Wenk Hans‐Rudolf , Kanitpanyacharoen Waruntorn , Matthies Siegfried , Wirth Richard
Published: June 2013

Anisotropy of elastic properties in clay‐rich sedimentary rocks has been of long‐standing interest. These rocks are cap rocks of oil and gas reservoirs, as well as seals for carbon sequestration. Elasticity of shales has been approached by direct velocity measurements and by models based on microstructures. Here we are revisiting the classical Kimmeridge shale studied by Hornby (1998) by first quantifying microstructural features such as phase volume fractions, grain shapes and grain orientations, and pore distributions with advanced analytical methods and then using this information in different models to explain bulk elastic properties. It is shown that by application of a self‐consistent algorithm based on Eshelby's (1957) model of inclusions in a homogeneous medium, it is possible to explain most experimental elastic constants, though some discrepancies remain which may be due to the interpretation of experimental data. Using a differential effective medium approach, an almost perfect agreement with experimental stiffness coefficients can be obtained, though the physical basis of this method may be questionable. The influence of single crystal elastic properties, grain shapes, preferred orientation, and volume and shapes of pores on elastic properties of shale is explored.
Importance of thermochemical pressurization in the dynamic weakening of the Longmenshan Fault during the 2008 Wenchuan earthquake: Inferences from experiments and modeling
Authors: Chen Jianye , Yang Xiaosong , Duan Qingbao , Shimamoto Toshi , Spiers Christopher J.
Published: June 2013

We determined the internal structure and mineral composition of the Yingxiu‐Beichuan fault zone at the Zhaojiagou exposure and measured frictional and transport properties of the fault rocks collected to gain a better understanding of dynamic weakening mechanisms during seismic fault motion. This fault is a major fault in the Longmenshan fault system that caused the 2008 Wenchuan earthquake. The exposure studied is located midway along the surface rupture, close to where the largest coseismic displacement occurred. High‐velocity friction experiments reveal exponential slip weakening from a peak friction toward a steady state value. Slip weakening is more pronounced for water‐dampened gouge than dry gouge, suggesting thermal pressurization. The fault gouge has a very low permeability (< 10−21 m2 at 165 MPa effective pressure) and is surrounded by fault breccia with a permeability of 10−19 to 10−17 m2, grading into less permeable, fractured country rocks. The fault zone thus exhibits a “conduit/barrier” structure, allowing fluid flow only in the breccia zone. We numerically modeled coseismic slip weakening including thermal pressurization and mineral dehydration/decarbonation, basing our calculation on measured frictional and transport properties and on the slip history inferred for the Wenchuan earthquake. The results indicate that (1) thermochemical pressurization played an important role in causing dynamic slip weakening, (2) the slip‐weakening distance is similar to the seismologically determined values, and (3) pore pressures might have exceeded the normal stress, thus maintaining temperatures below 600°C. Interestingly, enough heat was generated to fully remove and thermally pressurize the interlayer water from smectite, contributing an excess pore pressure of ~ 6 MPa. In addition, we found that the incorporation of state‐dependent fluid properties predicts much more efficient fluid pressurization than using constant properties. The dramatic weakening predicted probably offers a compelling explanation for the large coseismic displacement and slip acceleration observed near Beichuan city.
Laterally propagating slow slip events in a rate and state friction model with a velocity‐weakening to velocity‐strengthening transition
Authors: Hawthorne J. C. , Rubin A. M.
Published: June 2013

We investigate the behavior of simulated slow slip events using a rate and state friction model that is steady state velocity weakening at low slip speeds but velocity strengthening at high slip speeds. Our simulations are on a one‐dimensional (line) fault, but we modify the elastic interactions to mimic the elongate geometry frequently observed in slow slip events. Simulations exhibit a number of small events as well as periodic large events. The large events propagate approximately steadily “along strike,” and stress and slip rate decay gradually behind the propagating front. Their recurrence intervals can be determined by considering what is essentially an energy balance requirement for long‐distance propagation. It is possible to choose the model parameters such that the simulated events have the stress drops, slip velocities, and propagation rates observed in Cascadia.
Cloud radiative forcing of the diurnal cycle climate of the Canadian Prairies
Authors: Betts Alan K. , Desjardins Raymond , Worth Devon
Published: June 2013

This analysis uses 40 years of hourly observations of temperature (T), relative humidity (RH), and opaque cloud cover from 14 climate stations across the Canadian Prairies to analyze the diurnal cycle climate, represented by the mean T and RH and their diurnal ranges. From April to October, when incoming shortwave radiation dominates over longwave cooling, maximum temperature and the diurnal ranges of T and RH increase with decreasing opaque cloud cover, while minimum temperature is almost independent of cloud. During the winter period, both maximum and minimum temperatures fall with decreasing cloud, as longwave cooling dominates over the net shortwave flux, which is reduced by the high solar zenith angle and surface reflection by snow. We relate the daily mean opaque cloud cover to the longwave and shortwave cloud forcing and the effective cloud albedo, using multiyear measurements of downward shortwave and longwave fluxes, and longwave fluxes under clear skies from historical weather reanalysis. We provide quadratic fits to compute effective cloud albedo and net longwave fluxes from opaque cloud cover. During the warm season, the daytime rise of temperature is related to the net radiation, and the nighttime fall is related to the net longwave cooling. The diurnal range of T, RH, and all the net radiative fluxes have a quasi‐linear dependence on the effective cloud albedo. This gives a seasonal climate perspective on the coupled land‐surface system of T, RH, and cloud cover over the Canadian Prairies, and the winter transitions in snowy climates.
Comprehensive assessment of tibial plateau morphology in total knee arthroplasty: Influence of shape and size on anthropometric variability
Authors: Dai Yifei , Bischoff Jeffrey E.
Published: June 2013

Better understanding of proximal tibia morphology can lead to improvements in total knee arthroplasty (TKA) through development of tibial tray families that adequately reflect the diversity of global anatomy using an appropriate number of components. We quantified variations in proximal tibial morphology at the TKA level and characterized differences attributable to gender and ethnicity. Virtual TKA was performed on digital models of 347 tibiae, spanning both genders and multiple ethnicities. The geometry of the resection profile was quantified using both a comprehensive set of morphological measurements (reflecting size and shape) and principal component analysis (PCA). The dominant statistical modes of variation were associated primarily with size (plateau dimensions, radii, and area), with lesser contributions associated with asymmetry and aspect ratios. Medial and lateral AP dimensions were strongly correlated with plateau ML width, with minimal differences in correlations due to gender or ethnicity. In conclusion, clinically relevant differences in proximal tibia morphology at the level of TKA resections across genders and multiple ethnicities can be attributed largely to variations in overall proximal tibial size, not gender‐ or ethnic‐specific shape variations. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1643–1652, 2013
Optimized extraction and characterization of antimicrobial phenolic compounds from mangosteen (Garcinia mangostana L.) cultivation and processing waste
Authors: Palakawong Choothaweep , Sophanodora Pairat , Toivonen Peter , Delaquis Pascal
Published: June 2013

BACKGROUND

Applications for antimicrobials derived from the mangosteen (Garcinia mangostana L.) plant are presently restricted by high production costs. Extraction from cultivation or processing waste streams using a solvent‐free approach could lessen to permit commercial applications in food processing and preservation.

RESULTS

Phenolics were extracted from mangosteen bark, leaf and fruit pericarp in methanol and in water using response surface methodology to optimize recovery. Initial examination of antimicrobial effects revealed a lack of antimicrobial activity against fungi and weak activity against the Gram‐negative bacteria Escherichia coli and Salmonella typhimurium. In contrast, extracts prepared from bark or fruit pericarp exhibited strong pH‐dependent bacteriostatic and bactericidal effects against Listeria monocytogenes and Staphylococcus aureus. Activity was slightly weaker in aqueous extracts due to lower concentrations of tartaric acid esters and flavonols than in methanolic extracts. Measurement of propidium iodide uptake and ATP leakage indicated that the extracts induced damage to the membrane of Gram‐positive bacteria.

CONCLUSION

Extracts of mangosteen bark and fruit pericarp contain mixtures of phenolic compounds with activity against Gram‐positive bacteria, notably Listeria monocytogenes. Extraction of phenolics from mangosteen waste could yield fractions for potential applications in the formulation of low‐cost processing aids or sanitizers for the food industry. © 2013 Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri‐Food Canada, Journal of the Science of Food and Agriculture © 2013 Society of Chemical Industry
GC–MS study of compounds isolated from Coffea arabica flowers by different extraction techniques
Authors: Stashenko Elena E. , Martínez Jairo René , Cárdenas‐Vargas Silvia , Saavedra‐Barrera Rogerio , Durán Diego Camilo
Published: June 2013

Headspace (HS), extractive, and distillative methods were employed to isolate volatile and semivolatile compounds from fresh Coffea arabica flowers. Static HS solid‐phase microextraction (HS‐SPME), microwave‐assisted HS‐SPME (MW‐HS‐SPME) with simultaneous hydrodistillation, and extraction with hexane or supercritical CO2‐isolated mixtures in which around 150 different chemical substances were identified or tentatively identified by GC–MS analysis. n‐Pentadecane (20–37% relative peak area, RPA) was the most abundant compound in the HS fractions from fresh flowers, followed by 8‐heptadecene (8–20% RPA) and geraniol (6–14% RPA). Hydrocarbons (mostly C13–C30 paraffins) were the predominant compound class in all the sorptive extractions (HS‐SPME, MW‐HS‐SPME, distillate), followed by terpenoids or oxygenated compounds (which varied with the isolation technique). Caffeine, a distinctive component of coffee fruits and beans, was also found in relatively high amounts in the supercritical CO2 extract of C. arabica flowers.
Comparison of nonaqueous hydrophilic interaction chromatography with aqueous normal‐phase chromatography on hydrosilated silica‐based stationary phases
Authors: Soukup Jan , Jandera Pavel
Published: June 2013

We investigated the retention behavior of phenolic acids in nonaqueous normal‐phase (NP) LC with buffered methanol/acetonitrile mobile phases on hydrosilated silica‐based stationary phases. The silica hydride, Diamond hydride, Bidentate C18, and Cholesterol columns showed a higher retention of phenolic acids in the nonaqueous mobile phases than in aqueous NP mobile phases. There are some selectivity differences between the aqueous and nonaqueous mobile phases, but generally the resolution and selectivity are better in the aqueous systems. The retention of the phenolic acids tested decreased with increasing concentration of methanol in the mobile phase, up to 20% v/v methanol. At increased temperatures, the retention factors and peak widths decrease in both NP modes, showing linear ln k versus 1/T plots, due to a single retention mechanism over the temperature range from 25°C up to the column stability limit, however, the best separations are achieved at low temperatures. The enthalpic and entropic contributions to the retention were determined, and the differences between the aqueous and nonaqueous modes are possibly due to the adsorbed water layer.
Movement disorders in GLUT1 deficiency syndrome respond to the modified Atkins diet
Authors: Leen Wilhelmina G. , Mewasingh Leena , Verbeek Marcel M. , Kamsteeg Erik‐Jan , van de Warrenburg Bart P. , Willemsen Michel A.
Published: June 2013

Background

Movement disorders are a prominent feature of glucose transporter‐1 (GLUT1) deficiency syndrome (GLUT1DS). First‐choice treatment is a ketogenic diet, but compliance is poor. We have investigated the effect of the modified Atkins diet as an alternative treatment for movement disorders in GLUT1DS.

Methods

Four patients with GLUT1DS ages 15 to 30 years who had movement disorders as the most prominent feature were prospectively evaluated after initiation of the modified Atkins diet. Movement disorders included dystonia, ataxia, myoclonus, and spasticity, either continuous or paroxysmal, triggered by action or exercise. Duration of treatment ranged from 3 months to 16 months.

Results

All patients reached mild to moderate ketosis and experienced remarkable improvement in the frequency and severity of paroxysmal movement disorders. Cognitive function also improved subjectively.

Conclusions

The modified Atkins diet is an effective and feasible alternative to the ketogenic diet for the treatment of GLUT1DS‐related paroxysmal movement disorders in adolescence and adulthood. © 2013 International Parkinson and Movement Disorder Society
Optimizing contrast agent concentration and spoiled gradient echo pulse sequence parameters for catheter visualization in MR‐guided interventional procedures: An analytic solution
Authors: Sussman Marshall S. , Lindner Uri , Haider Masoom , Kucharczyk Walter , Hlasny Eugen , Trachtenberg John
Published: June 2013

Purpose

A critical requirement of MR‐guided interventions is the visualization of an instrument (e.g., catheter, needle) during the procedure. One approach is to fill the instrument with a contrast agent. Previously, the optimization of contrast agent visualization was performed only empirically. In the present study, an analytic optimization of contrast agent SNR efficiency was performed for a spoiled gradient echo pulse sequence.

Methods

Optimal flip angle, repetition time, echo time, and contrast agent concentration were derived analytically. The solution is valid for any contrast agent, provided the relationship between T1, T2, and doping concentration is known.

Results

Phantom experiments validated the analytic optimization for Gd‐ and MnCl2‐based contrast agents. Results showed excellent agreement between experimentally predicted and theoretically observed magnetization behavior. In vivo experiments demonstrated optimized contrast agent visualization in brain, heart, and prostate applications. The results demonstrated the large SNR that can be achieved with analytic optimization. As a practical guideline, an 11% dilution of 500 mMol/L Gd‐DTPA solution, repetition time ≈ 4 ms, echo time ≈ 1 ms, and θ ≈ 65° was found to provide a large SNR.

Conclusion

This study derived and validated a method for analytically optimizing contrast agent SNR efficiency. This information may be useful for visualizing instruments during MR‐guided interventions. Magn Reson Med 70:333–340, 2013. © 2013 Wiley Periodicals, Inc.
Stability and Oxidation Products of Hydrolysable Tannins in Basic Conditions Detected by HPLC/DAD–ESI/QTOF/MS
Authors: Tuominen Anu , Sundman Terhi
Published: June 2013

Introduction

Hydrolysable tannins occur in plants that are used for food or medicine by humans or herbivores. Basic conditions can alter the structures of tannins, that is, the oxidation of phenolic groups can lead to the formation of toxic quinones. Previously, these labile quinones and other oxidation products have been studied with colorimetric or electron paramagnetic resonance methods, which give limited information about products.

Objective

To study the stability and oxidation products of hydrolysable tannins in basic conditions using HPLC with a diode‐array detector (DAD) combined with electrospray ionisation (ESI) and quadrupole time‐of‐flight (QTOF) MS.

Methods

Three galloyl glucoses, four galloyl derivatives with different polyols and three ellagitannins were purified from plants. The incubation reactions of tannins were monitored by HPLC/DAD at five pH values and in reduced oxygen conditions. Reaction products were identified based on UV spectra and mass spectral fragmentation obtained with the high‐resolution HPLC/DAD–ESI/QTOF/MS. The use of a base‐resistant HPLC column enabled injections without the sample pre‐treatment and thus detection of short‐lived products.

Results

Hydrolysable tannins were unstable in basic conditions and half‐lives were mostly less than 10 min at pH 10. Degradation rates were faster at pH 11 but slower at milder pH. The HPLC analyses revealed that various products were formed and identified to be the result of hydrolysis, deprotonation and oxidation. Interestingly, the main hydrolysis product was ellagic acid; it was also formed from galloyl glucoses that do not contain oxidatively coupled galloyl groups in their initial structures.

Conclusion

HPLD/DAD–ESI/QTOF/MS was an efficient method for the identification of polyphenol oxidation products and showed how different pH conditions determine the fate of hydrolysable tannins. Copyright © 2013 John Wiley & Sons, Ltd.
Morphology and properties of highly filled iPP/TiO2 nanocomposites
Authors: Zohrevand Ahmad , Ajji Abdellah , Mighri Frej
Published: June 2013

Nanocomposites based on isotactic polypropylene (iPP) and titanium dioxide (TiO2) nanoparticle containing 1–15 vol% (4.6–45.5 wt%) of the nanoparticle were prepared by the melt blending process. The effect of an anhydride‐modified polypropylene as a compatibilizer on dispersion of TiO2 nanoparticles was assessed using SEM. TGA and DSC analysis were performed to study the thermal properties of the nanocomposites. Crystalline structures of iPP in the presence of TiO2 were analyzed by XRD. Mechanical properties of the nanoparticles were measured and a micromechanical analysis was applied to quantify interface interaction between the polymer and particle. SEM results revealed improvement of TiO2 particle dispersion by adding the compatibilizer. It was shown that the thermal stability and crystalline structure of the nanocomposite are significantly affected by the state of particle dispersion. TiO2 nanoparticles were shown to be strong β‐nucleating agents for iPP, especially at concentrations less than 5 vol%. Presence of the β‐structure crystals reduced the elastic modulus and yield strength of the nanocomposites. Micromechanical analysis showed enhanced interaction between organic and inorganic phases of the compatibilized nanocomposites. POLYM. ENG. SCI., 54:874–886, 2014. © 2013 Society of Plastics Engineers
Cure characterization of Cycom 977‐2A carbon/epoxy composites for quickstep processing
Authors: Khan Laraib A. , Kausar Ayesha , Hussain Syed Tajammul , Iqbal Zafar , Day Richard J. , Syed Ahmed Shuja , Khan Zaffar M.
Published: June 2013

In this effort, Quickstep, a relatively a new technique, have been employed for manufacturing of composite materials. The cure schedule provided by a prepreg manufacturer is usually designed for autoclave or other traditional processing techniques and thermosetting resin systems are formulated for ramp rate curing 2–3 K min−1. While in case of Quickstep processing, ramp rates of 15 K min−1 can be achieved, thus changing the chemorheology of resin. The cure process of 977‐2A carbon/epoxy composites was evaluated for Quickstep processing using differential scanning calorimetry (DSC), dynamic mechanical and thermal analysis, and Fourier transformed infrared and results were compared with cure cycle employed for autoclave curing. Optimum hold time for Quickstep processing at upper curing temperature (180°C) was determined using DSC. The hold time of 120 min at 180°C was found to be suitable for Quickstep cure cycle, producing a panel of similar degree of cure to that achieved through autoclave processing schedule. Final degree of cure was dependent on time spent at upper cure temperature and slightly on initial steps of the cure cycle which was used to control the resin flow, fiber wetting, and void removal. Quickstep processed samples exhibited higher Tg and crosslink density and similar molecular network structure to the autoclave cured samples. POLYM. ENG. SCI., 54:887–898, 2014. © 2013 Society of Plastics Engineers
Novel injection molding foaming approaches using gas‐laden pellets with N2, CO2, and N2 + CO2 as the blowing agents
Authors: Sun Xiaofei , Turng Lih‐Sheng
Published: June 2013

A novel method of producing injection molded parts with a foamed structure has been developed. It has been named supercritical fluid‐laden pellet injection molding foaming technology (SIFT). Compared with conventional microcellular foaming technologies, it lowers equipment costs without sacrificing the production rate, making it a good candidate for mass producing foamed injection molded parts. Both N2 and CO2 can be suitably used in this process as the physical blowing agent. However, due to their distinct physical properties, it is necessary to understand the influence of their differences over the process and the outcomes. Comparisons were made in this study between using CO2 and N2 as the blowing agents in terms of the part morphologies, as well as the shelf life and gas desorption process of the gas‐laden pellets. After gaining a good understanding of the SIFT process and the gas‐laden pellets, a novel foam injection molding approach combining the SIFT process with microcellular injection molding was proposed in this study. Both N2 and CO2 can be introduced into the same foaming process as the coblowing agents in a two‐step manner. Using an optimal content ratio for the blowing agents, as well as the proper sequence of introducing the gases, foamed parts with a much better morphology can be produced by taking advantage of the benefits of both blowing agents. In this study, the theoretical background is discussed and experimental results show that this combined approach leads to significant improvements in foam cell morphology for low density polyethylene, polypropylene, and high impact polystyrene using two different mold geometries. POLYM. ENG. SCI., 54:899–913, 2014. © 2013 Society of Plastics Engineers
Photoinduced reverse atom transfer radical polymerization of methyl methacrylate using camphorquinone/benzhydrol system
Authors: Taskin Omer Suat , Yilmaz Gorkem , Tasdelen Mehmet Atilla , Yagci Yusuf
Published: June 2013

A versatile initiating system composed of camphorquinone/benzhydrol and CuIIBr2/N,N,N′,N″,N″‐pentamethyldiethylenetriamine for photoinduced reverse atom transfer radical polymerization has been developed. The control experiments, where each component is eliminated in the reaction, serve as a direct verification of the mechanism. There is poor or no control over the polymerization of methyl methacrylate in the absence of either camphorquinone or benzhydrol. The experimental molecular weights are considerably higher than theoretical values and the obtained polymers show slightly broad molecular weight distributions ranging from 1.13 to 1.51 in the process. Although at relatively lower polymerization rates, the addition of an alkyl halide to the system leads to a better control of the polymerization as reflected by the improved molecular weight distribution and chain‐end functionality. © 2013 Society of Chemical Industry
Blue fluorescent conductive poly(9,10‐di(1‐naphthalenyl)‐2‐vinylanthracene) homopolymer and its highly soluble copolymers with styrene or 9‐vinylcarbazole
Authors: Wang Jianli , Leung Louis M , SO Shu‐Kong , Chan Cyrus YH
Published: June 2013

A new blue fluorescent monomer, 9,10‐di(1‐naphthalenyl)‐2‐vinylanthracene, was designed and synthesized in good yield. Its homopolymer poly(9,10‐di(1‐naphthalenyl)‐2‐vinylanthracene) (P(ADN)) and soluble conductive vinyl copolymers poly[(9,10‐di(1‐naphthalenyl)‐2‐vinylanthracene)‐co‐styrene] (P(ADN‐co‐S)) and poly[(9,10‐di(1‐naphthalenyl)‐2‐vinylanthracene)‐co‐(9‐vinylcarbazole)] (P(ADN‐co‐VK)) were synthesized using free radical solution polymerization. All the polymers showed high glass transition mid‐point temperatures (203 to 237 °C) and good thermal stabilities. The photoluminescence emission of the copolymers was similar to that of P(ADN) (with two maxima at 423 and 442 nm). The lifetimes of P(ADN‐co‐S) (6.82 to 7.91 ns) were all slightly less than that of P(ADN) (8.40 ns). The lifetime of P(ADN‐co‐VK) increased from 7.8 to 8.8 ns with an increase in VK content. The fluorescence quantum yields of P(ADN‐co‐S) showed an overall increasing tendency from 0.42 to 0.58. The quantum efficiencies of P(ADN‐co‐VK) decreased from 0.36 to 0.19 with an increase of VK fraction. With increasing S/VK content, the highest occupied molecular orbital of P(ADN‐co‐S)/P(ADN‐co‐VK) ranged from −5.58 to −5.73 eV, which was similar to that of P(ADN) (−5.71 eV). The band gaps of P(ADN‐co‐S) and P(ADN‐co‐VK) were about 2.97 eV, which were equal to that of P(ADN), and smaller than that of 2‐methyl‐9,10‐di(1‐naphthalenyl)anthracene (MADN) (3.04 eV) and poly(9‐vinylcarbazole) (3.54 eV). Preliminary electroluminescence results were obtained for a homojunction device with the configuration ITO/MoO3 (20 nm)/P(ADN)/LiF (1 nm)/Al (100 nm), which achieved only 30–50 cd m−2, due to P(ADN) having a low mobility of 4.7 × 10−8 cm2 V−1 s−1 compared to that of its model compound MADN of 6.5 × 10−4 cm2 V−1 s−1. © 2013 Society of Chemical Industry
Photoinduced Ordering Transition in Microdroplets of Liquid Crystals with Azo‐Dendrimer
Authors: Lee Guksik , Araoka Fumito , Ishikawa Ken , Momoi Yuichi , Haba Osamu , Yonetake Koichiro , Takezoe Hideo
Published: June 2013

Ordering transitions are observed in azo‐dendrimer‐dissolved nematic liquid crystal (NLC) droplets dispersed in a glycerol matrix. The dendrimer molecules are spontaneously attached at the interface between NLC and glycerol, so that the nematic directors orient perpendicular to the interface, in the radial configuration. Photoisomerization makes the directors be tangential to the interface, in a photoinduced ordering transition from radial to bipolar structure. Similar experiments are conducted both in cholesteric (Ch) and smectic‐A (SmA) LC droplets. Complicated photoinduced ordering transitions are also observed in Ch and SmA droplets, and the associated molecular orientation changes are discussed. Photoisomerizable azo‐dendrimer molecules provide a possible way to control orientation, even in microdroplet systems in which the interface cannot be treated by conventional surface agents.
Synthesis of a Au‐on‐Pd Heteronanostructure Stabilized by Citrate and its Catalytic Application
Authors: Wang Zhifei , Zheng Shuang , Wan Neng , Zhang Liming , Wang Qilong , He Nongyue , Huang Yaji
Published: June 2013

The preparation of Au‐on‐Pd heteronanostructure (HNS) using citrate‐stabilized polycrystalline Pd nanoparticles (NPs) as the seeds is described. The resulting Au‐on‐Pd HNS is characterized and it is found that the formation of Au‐on‐Pd HNS depends greatly on a ratio between Pd seeds and AuCl4− ions added and the optimal molar ratio is 10:1. If fewer AuCl4− ions are added (Pd/Au ratio is 100:1), the growth of Au NPs only occurs on part of the Pd seeds’ surface. The addition of more AuCl4− ions (Pd/Au ratio is 5:1) hinders the growth of Au NPs on the Pd seeds’ surface. To demonstrate the catalytic performance, the electrochemistry oxidation of ethanol and the reduction of p‐nitrophenol by NaBH4 are chosen to examine the catalytic activity of Au‐on‐Pd HNS. Pd seeds, Au NPs, and poly(vinyl pyrrolidone) (PVP)‐stabilized PdAu nanoalloy are used as the references for comparison. In the first reaction, the catalytic reactivity of Au‐on‐Pd HNS is better than that of corresponding pure Pd or Au NPs, while the opposite occurs for the latter reaction. The catalytic activity of Au‐on‐Pd HNS is much higher than that of PVP‐stabilized PdAu nanoalloy.
Enhanced dielectric permittivity of fluorine polyimide matrix with embedded graphene
Authors: Liu Jingni , Song Jingda , Qi Shengli , Tian Guofeng , Wu Dezhen
Published: June 2013

A polymer nanohybrid material with enhanced dielectric permittivity was prepared using the fluorine‐containing polyimide (PI) 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride/4,4′‐oxydianiline (6FDA/ODA) as matrix and graphene as conductive filler in our present work. Studies on the dielectric properties of the 6FDA/ODA–graphene nanohybrid films show that the dielectric permittivity (ε) can be significantly enhanced by the layer‐by‐layer structure of graphene and the presence of fluorine also has an important influence on the improvement of ε. The percolation theory and microcapacitor model are used to explain the change of dielectric properties and a percolation threshold fc = 0.0152 (2.45 wt%) was obtained by a linear‐fit calculation.

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(© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hole mobility and remote scattering in strained InGaSb quantum well MOSFET channels with Al2O3 oxide
Authors: Kumar Madisetti Shailesh , Chidambaram Thenappan , Nagaiah Padmaja , Tokranov Vadim , Yakimov Michael , Oktyabrsky Serge
Published: June 2013

Hall mobility and major scattering mechanisms in surface and buried MBE grown strained InGaSb quantum well (QW) MOSFET channels with in‐situ grown Al2O3 gate oxide are analyzed as a function of sheet hole density, top‐barrier thickness and temperature. Mobility dependence on Al0.8Ga0.2Sb top‐barrier thickness shows that the relative contribution of interface‐related scattering is as low as ∼30% in the surface QW channel. An InAs top capping layer reduces the interface scattering even further; the sample with 3 nm total top‐barrier thickness demonstrates mobility of 980 cm2/Vs giving sheet resistance of 4.3 kΩ/sq, very close to the minimum QW resistance in the bulk. The mobility–temperature dependences indicate that the interface‐related scattering is dominated by remote Coulomb scattering at hole densities <1 × 1012 cm–2. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Broadband slot array antenna with full‐space steerable pattern in a composite right/left‐handed waveguide
Authors: Navarro‐Tapia María , Esteban Jaime , Camacho‐Peñalosa Carlos
Published: June 2013

The aim of this paper is twofold. On the one hand, to provide a better understanding of a composite right/left‐handed (CRLH) waveguide, going into those aspects of interest for an antenna designer. A longitudinal slot as a radiating element has been considered to be studied and compared with its classic counterpart. On the other hand, to present the new design approach that is needed when using the CRLH waveguide technology to built array antennas. To that end, a slot array antenna has been designed, built, and measured. The simulations and measurements are in excellent agreement, confirming not only the backward‐to‐forward beam steering and broadband far‐field performance, but also the validity of the design procedure used.
A feedback technique for unsatisfiable UML/OCL class diagrams
Authors: Shaikh Asadullah , Wiil Uffe Kock
Published: June 2013

In Model‐Driven Development (MDD), detection of model defects is necessary for correct model transformations. Formal verification tools and techniques can to some extent verify models. However, scalability is a serious issue in relation to verification of complex UML/OCL class diagrams. We have proposed a model slicing technique that slices the original model into submodels to address the scalability issue. A submodel can be detected as unsatisfiable if there are no valid values for one or more attributes of an object in the diagram or if the submodel provides inconsistent conditions on the number of objects of a given type. In this paper, we propose a novel feedback technique through model slicing that detects unsatisfiable submodels and their integrity constraints among the complex hierarchy of an entire UML/OCL class diagram. The software developers can therefore focus their revision efforts on the incorrect submodels while ignoring the rest of the model. Copyright © 2013 John Wiley & Sons, Ltd.
Impact of introduction of mid‐trimester scan on pregnancy outcome of open spina bifida in The Netherlands
Authors: Fleurke‐Rozema J. H. , Vogel T. A. , Voskamp B. J. , Pajkrt E. , van den Berg P. P. , Beekhuis J. R. , Bilardo C. M. , Brouwer O. F. , de Walle H. E. K. , Snijders R. J. M.
Published: June 2013

Objective

To examine the impact of introduction of the mid‐trimester scan on pregnancy outcome in cases of open spina bifida in two regions of The Netherlands.

Methods

This was a retrospective cohort study of 190 cases of open spina bifida diagnosed pre‐ or postnatally, with an estimated date of delivery between 2003 and 2011.

Results

With implementation of the mid‐trimester scan the percentage of cases of open spina bifida detected before the 24th week of pregnancy increased from 43% to 88%. The rise in prenatal detection rate was associated with a significant increase in the number of terminated pregnancies and a decrease in the rate of perinatal loss; the percentage of children born alive did not change significantly. In the subgroup that underwent a scan between 18 and 24 weeks of pregnancy, cranial signs were present in 94.4% of cases.

Conclusion

Introduction of the mid‐trimester scan has led to an increase in early identification of pregnancies complicated by open spina bifida. Pregnancies previously destined to end in perinatal loss are now terminated whilst pregnancies with a relatively good prognosis are frequently continued; the number of children with open spina bifida who are born alive has not changed significantly. Our study confirms that prenatal diagnosis is usually triggered by visualization of a lemon‐shaped skull or a banana‐shaped cerebellum. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.
Outcome of first‐trimester fetal abdominal cysts: cohort study and review of the literature
Authors: Khalil A. , Cooke P. C. , Mantovani E. , Bhide A. , Papageorghiou A. T. , Thilaganathan B.
Published: June 2013

ABSTRACT

Objectives

The aims of this study were to ascertain the outcome of fetuses with an abdominal cyst detected at 11–14 weeks' gestation in our unit and to undertake a review of cases reported in the literature.

Methods

This was a retrospective study that included all fetuses found to have an abdominal cyst on ultrasound examination at 11–14 weeks, identified over a 14‐year period. Pregnancy management and outcome were ascertained from maternal and neonatal records. We also performed a review of the literature using a systematic search strategy, to identify the outcome of similar cases and propose a management algorithm.

Results

Fourteen cases were identified during the study period, of which four had associated abnormalities. Of the 10 isolated cases, the cyst had resolved at follow‐up scan in eight (80.0%), one fetus died in utero at 15 weeks' gestation and the other case underwent surgery for a choledochal cyst 9 weeks after birth. An additional 19 cases were reported in the literature. In eight fetuses there were associated structural abnormalities, of which four had a diagnosis of anorectal malformation after birth. In two of these four, the cyst resolved in the second trimester. Of those cases with an isolated cyst (n = 11), the cyst resolved in seven (63.6%). The remainder were variably diagnosed as hepatic cyst, ileal duplication or choledochal cyst.

Conclusion

Fetal abdominal cysts at 11–14 weeks' gestation are rare. They constitute an isolated finding in the majority of cases and are usually associated with a good perinatal outcome. In view of the reported association with anorectal and other gastrointestinal malformations, perinatal assessment is recommended, even if the cyst resolves during pregnancy. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.
A general geomorphological recession flow model for river basins
Authors: Biswal Basudev , Nagesh Kumar D.
Published: June 2013

Recession flows in a basin are controlled by the temporal evolution of its active drainage network (ADN). The geomorphological recession flow model (GRFM) assumes that both the rate of flow generation per unit ADN length (q) and the speed at which ADN heads move downstream (c) remain constant during a recession event. Thereby, it connects the power law exponent of –dQ/dt versus Q (discharge at the outlet at time t) curve, α, with the structure of the drainage network, a fixed entity. In this study, we first reformulate the GRFM for Horton‐Strahler networks and show that the geomorphic α (αg) is equal to
, where D is the fractal dimension of the drainage network. We then propose a more general recession flow model by expressing both q and c as functions of Horton‐Strahler stream order. We show that it is possible to have α =α g for a recession event even when q and c do not remain constant. The modified GRFM suggests that α is controlled by the spatial distribution of subsurface storage within the basin. By analyzing streamflow data from 39 U.S. Geological Survey basins, we show that α is having a power law relationship with recession curve peak, which indicates that the spatial distribution of subsurface storage varies across recession events.
Geochemical and geophysical responses during the infiltration of fresh water into the contaminated saprolite of the Oak Ridge Integrated Field Research Challenge site, Tennessee
Authors: Revil A. , Wu Y. , Karaoulis M. , Hubbard S. S. , Watson D. B. , Eppehimer J. D.
Published: June 2013

At the Oak Ridge Integrated Field Research Challenge (IFRC) site, Tennessee, the saprolitic aquifer was contaminated by leaks from the former S‐3 disposal ponds between 1951 and 1983. The chemistry of the contaminant plume is also episodically impacted by fresh meteoritic water infiltrating vertically from a shallow variably saturated perched zone and the ditch surrounding the former S‐3 ponds. We performed a column experiment using saprolite from the contaminated aquifer to understand the geochemical and complex electrical conductivity signatures associated with such events. The changes in the pH and pore water ionic strength are responsible for measurable changes in both the in‐phase and quadrature conductivities. The pore water conductivity can be related to the nitrate concentration (the main ionic species in the plume) while the release of uranium is controlled by the pH. We developed a simple model to determine the pore water conductivity and pH from the recorded complex conductivity. This model is applied to time‐lapse resistivity data at the IFRC site. Time‐lapse inversion of resistivity data, performed with an active time constrain approach, shows the occurrence of an infiltration event during the winter of 2008–2009 with a dilution of the pore water chemistry and an increase of the pH. A simple numerical simulation of the infiltration of fresh water into the unconfined contaminated aquifer is consistent with this scenario.
Gross primary productivity of phytoplankton and planktonic respiration in inland floodplain wetlands of southeast Australia: habitat‐dependent patterns and regulating processes
Authors: Kobayashi Tsuyoshi , Ralph Timothy J. , Ryder Darren S. , Hunter Simon J.
Published: June 2013

Gross primary productivity (GPP) of phytoplankton and planktonic respiration (PR) (i.e., planktonic metabolism) are critical pathways for carbon transformation in many aquatic ecosystems. In inland floodplain wetlands with variable inundation regimes, quantitative measurements of GPP and PR are rare and their relationships with wetland environmental conditions are largely unknown. We measured PR and the GPP of phytoplankton using light and dark biological oxygen demand bottles in open waters of channel and non‐channel floodplain habitats of inland floodplain wetlands of southeast Australia that had been inundated by environmental water. Overall, GPP varied from 3.7 to 405.5 mg C m−3 h−1 (mean ± standard error: 89.4 ± 9.2 mg C m−3 h−1, n = 81), PR from 1.5 to 251.6 mg C m−3 h−1 (43.2 ± 5.6 mg C m−3 h−1, n = 81), and GPP/PR from 0.2 to 15.6 (3.0 ± 0.3, n = 81). In terms of wetland environmental conditions, total nitrogen (TN) ranged from 682.0 to 14,700.0 mg m−3 (mean ± standard error: 2,643.0 ± 241.6 mg m−3, n = 81), total phosphorus (TP) from 48.0 to 1,405.0 mg m−3 (316.8 ± 31.4 mg m−3, n = 81), and dissolved organic carbon (DOC) from 1.9 to 46.3 g m−3 (22.0 ± 1.6 g m−3, n = 81). Using ordinary least‐squares multiple regression analyses, the rates of GPP and PR, and their ratio (GPP/PR) were modeled as a function of TN, TP, and DOC that had been measured concomitantly. The “best” models predicted GPP and GPP/PR ratio in channel habitats as a function of DOC; and GPP, PR, and GPP/PR in non‐channel floodplain habitats as a function of TN and/or TP. The models explained between 46 and 74 % of the variance in channel habitats and between 17 and 87 % of the variance in non‐channel floodplain habitats. Net autotrophy (mean GPP/PR 3.0) of planktonic metabolism in our work supports the prevailing view that wetlands are a net sink for carbon dioxide. We propose a nutrient‐DOC framework, combined with hydrological and geomorphological delineations, to better predict and understand the planktonic metabolism in inland floodplain wetlands.
Differential Regulation of ABCA1 and Macrophage Cholesterol Efflux by Elaidic and Oleic Acids
Authors: Shao Fei , Ford David A.
Published: June 2013

Trans fatty acid consumption is associated with an increased risk of coronary heart disease. This increased risk has been attributed to decreased levels of HDL cholesterol and increased levels of LDL cholesterol. However, the mechanism by which trans fatty acid modulates cholesterol transit remains poorly defined. ATP‐binding cassette transporter A1 (ABCA1)‐mediated macrophage cholesterol efflux is the rate‐limiting step initiating apolipoprotein A‐I lipidation. In this study, elaidic acid, the most abundant trans fatty acid in partially hydrogenated vegetable oil, was shown to stabilize macrophage ABCA1 protein levels in comparison to that of its cis fatty acid isomer, oleic acid. The mechanism responsible for the disparate effects of oleic and elaidic acid on ABCA1 levels was through accelerated ABCA1 protein degradation in cells treated with oleic acid. In contrast, no apparent differences were observed in ABCA1 mRNA levels, and only minor changes were observed in Liver X receptor/Retinoic X receptor promoter activity in cells treated with elaidic and oleic acid. Efflux of both tracers and cholesterol mass revealed that elaidic acid slightly increased ABCA1‐mediated cholesterol efflux, while oleic acid led to decreased ABCA1‐mediated efflux. In conclusion, these studies show that cis and trans structural differences in 18 carbon n‐9 monoenoic fatty acids variably impact cholesterol efflux through disparate effects on ABCA1 protein degradation.
Surface modification of cobalt oxide nanoparticles using phosphonomethyl iminodiacetic acid followed by folic acid: a biocompatible vehicle for targeted anticancer drug delivery
Authors: Chattopadhyay Sourav , Dash Sandeep Kumar , Ghosh Totan , Das Debasis , Pramanik Panchanan , Roy Somenath
Published: June 2013

The aim of our study was to prepare multifunctional, biocompatible nanoparticles for site-specific drug delivery. Hydrophilic nanoparticles with surface-adorned amine, carboxyl, or aldehyde groups, to be later used for bio-conjugation, were designed using phosphonomethyl iminodiacetic acid (PMIDA) as the coupling agent. These PMIDA-coated cobalt oxide nanoparticles (PMIDA-CoO) were further functionalized with folic acid (FA), using simple technique. The particles show excellent aqueous dispersion stability in physiological pH without any deterioration in hydrodynamic size. The cytotoxicity and internalization efficiency of these nanocarriers have been evaluated on folate receptor over expressed KB and folate receptor lower expressed KG1a cells. Anticancer drugs such as doxorubicin and methotrexate were successfully attached to the folic acid-decoded PMIDA-CoO nanoparticles by simple reactions. Anticancer drug-loaded nanoparticles (FA-PMIDA-CoO) exhibit elevated cytotoxicity and induce apoptosis in cancer cells, which were confirmed by flow cytometry. Fluorescence microscopy study shows the higher amount of internalization of the noncomplex by KB cells, which clearly demonstrated that cells overexpressing the human folate receptor internalized a higher level of these nanoparticles–folate conjugates than folate receptor-negative control cells.
A systematic review and thematic synthesis of qualitative studies on maternal emergency transport in low‐ and middle‐income countries
Authors: Wilson Amie , Hillman Sarah , Rosato Mikey , Skelton John , Costello Anthony , Hussein Julia , MacArthur Christine , Coomarasamy Arri
Published: June 2013

Background

Most maternal deaths are preventable with emergency obstetric care; therefore, ensuring access is essential. There is little focused information on emergency transport of pregnant women.

Objectives

The literature on emergency transport of pregnant women in low‐ and middle‐income countries (LMICs) was systematically reviewed and synthesized to explore current practices, barriers, and facilitators for transport utilization.

Search strategy

MEDLINE, EMBASE, BNI, Cochrane Library, CINAHL, African Index Medicus, ASSIA, QUALIDATA, RHL, and Science Citation Index (inception to April 2012) were searched without language restriction.

Selection criteria: Studies using qualitative methodology and reporting on emergency transportation in LMICs were included.

Data collection and analysis

Thematic framework and synthesis through examination and translation of common elements were used to analyze and synthesize the data.

Main results

Twenty‐nine articles were included. Eight major themes were identified: time for transport; transport options; geography; local support; autonomy; culture; finance; and ergonomics. Key issues were transport availability; transport speed; terrain; meteorology; support; dependence for decision making; cultural issues; cost; and lack of safe, comfortable positioning during transport.

Conclusion

Themes should be appreciated within local contexts to illuminate barriers and facilitators. Potential solutions include motorcycle ambulance programs, collaboration with taxi services, community education, subsidies, and vehicle maintenance.