bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study of the Tang Dynasty Tax Textiles (Yongdiao Bu) from Turfan
Authors: WANG BINGHUA , WANG HELEN
Published: July 2013

The Tang dynasty tax system is often referred to as zuyongdiao 租庸調, with each of these three terms having a specific meaning. Zu was the annual collection of 2 piculs, roughly 120 litres of grain (su 粟) per head. Yong was the annual corvée (labour) duty of 21 days per head, which could be substituted and paid for in silk or cloth, or the cloth-paid-in-place-of-annual-corvée tax. Diao was the tax in kind, payable in textiles (substitutions of other goods were sometimes permitted). In silk-producing areas the diao tax per head was 2 decafeet of silk, payable in ling-twill, juan-silk or silk thread (si 絲) and 3 ounces of silk floss (simian 絲綿). In areas that did not produce silk, the diao tax was 2 decafeet, 5 feet of hemp cloth and 3 pounds of hemp yarn.
How the Residents of Turfan used Textiles as Money, 273–796ce
Authors: HANSEN VALERIE , RONG XINJIANG
Published: July 2013

Textiles, grain, coins; people living in the Silk Road oasis of Turfan, 160 km south-east of Urumqi in today's Xinjiang, used all three items as money between 273 and 769. The city of Gaochang (some 40 km east of today's Turfan) was one of the most important cities on the northern route around the Taklamakan Desert, and many of its inhabitants were buried in the adjacent Astana and Karakhoja graveyards. The region's dry climate has preserved an extensive group of paper documents dating to before, and after, the Tang conquest of the city in 640. The residents of Turfan buried their dead with shoes, belts, hats and clothing made from recycled paper with writing on it. These records offer an unparalleled glimpse of how people living along the Silk Road used textiles as currency.
Were Textiles used as Money in Khotan in the Seventh and Eighth Centuries?
Authors: DUAN QING , WANG HELEN
Published: July 2013

The kingdom of Khotan lay 2,628 kilometres to the north-west of the Tang capital at Chang'an. Strategically located in the south-west of the Taklamakan Desert, Khotan was a meeting point of different ethnic groups, languages, cultures and traditions, and was renowned as a centre of Buddhism. With its unique combination of influences, Khotanese society was quite different from that of Turfan to the north of the Taklamakan. In addition to the indigenous practices and traditions that developed in Khotan, this kingdom was always under the influence of major external political powers: Khotan was a vassal kingdom of the Hephtalites or Turkic peoples during the sixth century, came under increasing Chinese influence in the seventh and eighth centuries, was under Tibetan occupation from the 790s to 840s, and thereafter under the Chinese again. The secular documentary evidence from Khotan, written in Khotanese and Chinese, from the seventh and eighth centuries reflects everyday life there, and reveals the impact of Chinese administrative changes on traditional practices.
Glossary of Textile Terminology (Based on the Documents from Dunhuang and Turfan)
Authors: ZHAO FENG , WANG LE
Published: July 2013

This glossary presents 80 items of textile terminology that are found in the Chinese documents from Dunhuang and Turfan, or in historical texts. Some of these terms can be identified with actual textiles found at sites in north-western China. Readers should be aware that there are variations in textile terminology in this international field of research: for example, we have used “plain weave” where other textile specialists might prefer “tabby”; and “damask” where others might prefer “twill”.
Global well-posedness for 3D Navier–Stokes equations with ill-prepared
initial data
Authors: Paicu Marius , Zhang Zhifei
Published: July 2013

We study the global well-posedness of 3D Navier–Stokes equations for a class of large
initial data. This type of data slowly varies in the vertical direction (expressed as
a function of $\varepsilon {x}_{3} $), and it is ill-prepared in the sense that its norm in ${C}^{- 1} $ will blow up at the rate ${\varepsilon }^{- \alpha } $ for $\frac{1}{2} \lt \alpha \lt 1$ as $\varepsilon $ tends to zero.
Is Energy Resolution Still an Important Specification in EDS?
Authors: Thompson Keith
Published: July 2013

Energy Dispersive Spectroscopy (EDS) X-ray detectors have undergone a wave of technology enhancements since the first silicon drift-based EDS detector (SDD) was commercially introduced roughly 15 years ago. The first such EDS systems featured an active area of 5 mm2, an energy resolution between 160 eV–200 eV, and a maximum collection rate approaching only 100,000 input counts/second.
Simultaneous EELS/EDS Composition Mapping at Atomic Resolution Using Fast STEM Spectrum-Imaging
Authors: Longo Paolo , Thomas Paul , Aitouchen Aziz , Schaffer Bernhard , Twesten Ray D.
Published: July 2013

With advancements in aberration-corrected electron optics, the resolution in scanning transmission electron microscopy (STEM) has been significantly improved. More importantly, the reduction of the probe size and the increase of the probe current density enable the acquisition of elemental maps at the atomic scale in a fast manner using both EELS and EDS. With the latest generations of EELS spectrometers, atomic resolution compositional and chemical maps allow interfaces, oxidation state, and even single atoms to be examined with increasing detail. These improvements have also enabled elemental and chemical maps to be acquired rapidly using both low- and high-energy edges from elements across the periodic table, including heavy atoms such Au or Pt. On the EDS side, the introduction of large-area silicon drift detectors (SDD) has allowed these high-beam-current sources to be fully utilized. Improved detector area and support for higher count rates, compared to the previous generation of EDS detectors, allows the acquisition of EDS intensity maps from most types of material in the STEM, even for moderately thin samples. For the case of light elements, the reduced detector dead layer of SDD-based systems partially overcomes the very low florescence yield typical of low-energy X-ray lines. Also as reported in, atomic-level X-ray maps using fast detectors and bright sources can now be collected under some conditions. Because EDS and EELS provide complementary information about the sample, and are both generated with the electron beam, it would be wasteful to not acquire both datasets with every sample run.
Imaging Cosmic Ray Particles with a Light Microscope Scientific Digital Camera
Authors: McNamara George
Published: July 2013

Cosmic ray particles were discovered by Victor Hess on August 7, 1912, leading to his co-winning the Nobel Prize in Physics in 1936. Initially thought to be rays (photons), in the 1920s they were recognized as being charged particles. I describe in this article how I acquire and process images of cosmic ray particles (CRPs) on a microscope with a digital camera in the imaging core facility I manage.
Economic analysis of private and public benefits of corn, switchgrass and mixed grass systems in Eastern South Dakota
Authors: Bourlion Nelly , Janssen Larry , Miller Michael
Published: July 2013

The objective of this research is to develop an economic analysis of different crop mix biofuels programs for meeting ethanol and sustainability demands. Primary data are from South Dakota State University field experiments on farms located in east-central South Dakota. The data include 4 years of field data, three crop systems (mixed grass, switchgrass and corn), two residue treatments (no removal, removal of biomass), and three landscape positions (back slope, crest and foot slope). A representative farm model and five scenarios are developed to conduct a full budget analysis over a 12-year period. Public benefits are evaluated, using the benefit transfer method to value ecosystem services, by allocating a dollar value to three environmental variables; carbon sequestration, reduction of sedimentation and pheasant production. Stochastic simulation results are compared for each of the five scenarios, one with only annualized net private returns, and one including the value of environmental benefits. Results indicate that: (1) the conventional continuous corn scenario has the highest net returns over the 12-year budget, (2) carbon sequestration represents 80% of the environmental benefits, and (3) the added economic value of ecosystem services does not provide enough incentives for farmers to convert from corn production to grass production.
Structural insights into substrate recognition in proton‐dependent oligopeptide transporters
Authors: Guettou Fatma , Quistgaard Esben M , Trésaugues Lionel , Moberg Per , Jegerschöld Caroline , Zhu Lin , Jong Agnes Jin Oi , Nordlund Pär , Löw Christian
Published: July 2013

Short‐chain peptides are transported across membranes through promiscuous proton‐dependent oligopeptide transporters (POTs)—a subfamily of the major facilitator superfamily (MFS). The human POTs, PEPT1 and PEPT2, are also involved in the absorption of various drugs in the gut as well as transport to target cells. Here, we present a structure of an oligomeric POT transporter from Shewanella oneidensis (PepTSo2), which was crystallized in the inward open conformation in complex with the peptidomimetic alafosfalin. All ligand‐binding residues are highly conserved and the structural insights presented here are therefore likely to also apply to human POTs.
H2O2-responsive molecularly engineered polymer nanoparticles as ischemia/reperfusion-targeted nanotherapeutic agents
Authors: Lee Dongwon , Bae Soochan , Hong Donghyun , Lim Hyungsuk , Yoon Joo Heung , Hwang On , Park Seunggyu , Ke Qingen , Khang Gilson , Kang Peter M.
Published: July 2013

The main culprit in the pathogenesis of ischemia/reperfusion (I/R) injury is the overproduction of reactive oxygen species (ROS). Hydrogen peroxide (H2O2), the most abundant form of ROS produced during I/R, causes inflammation, apoptosis and subsequent tissue damages. Here, we report H2O2-responsive antioxidant nanoparticles formulated from copolyoxalate containing vanillyl alcohol (VA) (PVAX) as a novel I/R-targeted nanotherapeutic agent. PVAX was designed to incorporate VA and H2O2-responsive peroxalate ester linkages covalently in its backbone. PVAX nanoparticles therefore degrade and release VA, which is able to reduce the generation of ROS and exert anti-inflammatory and anti-apoptotic activity. In hind-limb I/R and liver I/R models in mice, PVAX nanoparticles specifically reacted with overproduced H2O2 and exerted highly potent anti-inflammatory and anti-apoptotic activities that reduced cellular damages. Therefore, PVAX nanoparticles have tremendous potential as nanotherapeutic agents for I/R injury and H2O2-associated diseases.
Insights into the Reactivity of Gold: an Analysis of FTIR and HRTEM Studies
Authors: Boccuzzi Flora , Manzoli Maela , Chiorino Anna , Vindigni Floriana
Published: July 2013

The reactivity of different gold‐based catalysts has been examined and re‐discussed on the basis of the most recent literature data, mainly looking at the characterization data obtained by FTIR spectroscopy and HRTEM microscopy. In particular, the CO oxidation reactions at 90 K and at room temperature have been discussed. By comparing samples with different gold particle sizes and different supports it has been deduced that the sites responsible for the adsorption and the reactive activation of CO and O2 are the gold edge sites, in proximity to the support oxygen‐vacancy defects. These defects may produce electron‐rich gold atoms, which may be relevant for oxygen activation and dissociation. As for the water–gas shift reaction, an important role of support sites at the borderline with the gold sites, where water and CO in mutual interaction may be activated, has been proposed. Moreover, a role of oxygen adsorbed on gold particles near oxygen vacancies of the support in the oxidative dehydrogenation of methanol and in the furfural oxidative esterification has been discussed. All the above summarized points confirm the importance of the dual perimeter sites in the catalytic activity of gold catalysts.
Design and study of enhanced wideband transition between coplanar waveguide and broadside coupled stripline
Authors: Lu Wen‐jun , Tong Heng , Bo Ya‐ming , Zhu Hong‐bo
Published: July 2013

Enhanced wideband transition between coplanar waveguide (CPW) and broadside coupled stripline (BCS) with arbitrary characteristic impedance ratio is developed on a basis of an improved tightly coupling, via‐hole‐free structure. The E‐field of CPW gradually changes to that of BCS within a wide bandwidth with ratio up to 10.4:1. Parametric studies of the transition are carried out and four different back‐to‐back prototypes are simulated, fabricated and measured. It is shown that maximum operation bandwidth from 1.16 to 12.01 GHz for return loss higher than 10 dB and average insertion loss of 1.41 dB can be obtained.
Inkjet printed dipole antennas on textiles for wearable communications
Authors: Chauraya Alford , Whittow William G. , Vardaxoglou J(Yiannis) C. , Li Yi , Torah Russel , Yang Kai , Beeby Steve , Tudor John
Published: July 2013

This study presents an inkjet printed textile antenna realised using a novel fabrication methodology. Conventionally, it is very difficult to inkjet print onto textiles because of surface roughness. This study demonstrates how this can be overcome by developing an interface coated layer which bonds to a standard polyester cotton fabric, creating a smooth surface. A planar dipole antenna has been fabricated, simulated and measured. This study includes DC resistance, RF reflection coefficient results and antenna radiation patterns. Efficiencies of greater than 60% have been achieved with only one layer of conducting ink. The study demonstrates that the interface layer saves considerable time and cost in terms of the number of inkjet layers needed whilst also improving the printing resolution.
Synthesis of sheet‐like nanoscaled ZnO and Ag/ZnO composite nanocrystals and their electrocatalytic properties
Authors: Pan Lu , Xu Bo , Tang Jing , Wang Fengwu
Published: July 2013

Sheet‐like ZnO Ag/ZnO composites were synthesised by calcination of each precursor prepared via a hydrothermal treatment. The samples were characterised by thermogravimetric analysis and differential thermal gravimetric analysis, X‐ray diffraction, scanning electron microscopy and transmission electron microscopy technologies. The results showed that ZnO and Ag/ZnO composite nanosheets were composed of nanoparticles. The electrocatalytic performances of the samples modified on a glassy carbon electrode for p ‐nitrophenol, K2CrO4 and H2O2 reduction in a basic solution, respectively, were investigated using a cyclic voltammetry method. The results revealed that ZnO and Ag/ZnO composites with Ag content from 1 to 5% all exhibited an enhanced catalytic activity by comparing with a bare glassy carbon electrode. Among the samples, Ag/ZnO composite with 4% Ag displayed the highest catalytic activity for p ‐nitrophenol, and H2O2, but the one with 3% Ag content showed the highest catalytic activity for K2CrO4 reduction.
Synthesis and electromagnetic properties of Fe/SiO2 yolk/shell nanospheres with improved oxidation resistance
Authors: Fu Li‐Shun , Jiang Jian‐Tang , Xu Cheng‐Yan , Gong Yuan‐Xun , Zhen Liang
Published: July 2013

Nearly monodispersed Fe/SiO2 yolk/shell nanospheres with an average diameter of about 250 nm were synthesised by hydrogen‐thermal reduction of Fe3O4/SiO2 precursor nanospheres. The morphology of products and precursors was characterised in three stages of preparation. Electrical conductivity magnetic properties and electromagnetic properties in the microwave band of Fe/SiO2 yolk/shell nanospheres were investigated. The eddy current effect in Fe/SiO2 yolk/shell nanospheres was effectively suppressed because of separation of ultrafine iron particles by silica shells, indicating that the eddy current effect can be suppressed only by separating iron particles and it is not related to the interface of iron and sillica. A reflection loss of −12.5 dB and an effective absorption band with a bandwith of 3.3 GHz were simultaneously obtained for Fe/SiO2 yolk/shell nanospheres‐containing coatings with thickness of 2 mm. Compared with bare Fe particles obtained from Fe3O4 precursor nanospheres, oxidation resistance of Fe/SiO2 yolk/shell nanospheres was improved because of the existence of silica shells.
Small‐sized silicon‐on‐insulator lateral insulated gate bipolar transistor for larger forward bias safe operating area and lower turnoff energy
Authors: Fu Qiang , Zhang Bo , Luo Xiaorong , Wang Zhigang , Li Zhaoji
Published: July 2013

This Letter presents a novel small‐sized lateral insulated gate bipolar transistor on silicon‐on‐insulator substrate (SOI‐LIGBT), which features a lowly doped p ‐type pillar alongside the oxide trench in the drift region. The variation in vertical doping termination technology is also proposed for the first time. The p ‐pillar layer leads to electric field reshaping in the y ‐direction, and homogenises current flow lines under the gate and cathode. It results in a very wide forward bias safe operating area (FBSOA) for the proposed SOI‐LIGBT, which is obviously improved by over 50% compared with the deep‐oxide trench SOI‐LIGBT (DT SOI‐LIGBT). Moreover, at the same forward voltage drop of 1 V, the turnoff energy loss for the proposed SOI‐LIGBT is reduced by 28.5 and 81.2% compared with those of DT SOI‐LIGBT and the conventional SOI‐LIGBT, respectively.
Pesticide residues rapid detection in vegetables real samples based on nanomaterial‐modified acetylcholinesterase biosensor
Authors: Sun Xia , Qiao Lu , Sun Xiaoxu , Wang Xiangyou
Published: July 2013

In this reported work, an acetylcholinesterase (AChE) biosensor based on chitosan‐Prussian blue‐multiwall carbon nanotubes‐hollow gold nanospheres (Chit‐PB‐MWNTs‐HGNs) film was used for detecting pesticide residues in vegetable samples. Three different kinds of sample extraction methods were investigated, such as the oscillation extraction method, the ultrasonication and the centrifugation extraction method and the ultrasonication and filtration extraction method. By comparison, the ultrasonication and centrifugation extraction method was the most appropriate and efficient for the AChE biosensor. After treatment by ultrasonication and centrifugation extraction, the recoveries of the pesticides from vegetable samples were from 76.8 to 105.9% with relative standard deviation lower than 12.68%. Subsequently, the detection results with the AChE biosensor were compared with the standard gas chromatography method. The results indicated that the proposed sample pretreatment method was applicable to the AChE biosensor for pesticide residues detection in real vegetable samples.
Effect of Ni–Co codoping on structure and electrical properties of multiferroic BiFeO3 nanoparticles
Authors: Hossain Sk Mazaffar , Mukherjee Ayan , Basu Soumen , Pal Mrinal
Published: July 2013

Ni and Co doped nanocrystalline BiFeO3 (BFO) have been prepared using a facile sol–gel technique. The effects of codoping on the crystal structure, morphology and electrical properties are investigated. X‐ray diffraction and high‐resolution transmission electron microscopy studies confirm the phase purity and growth of BFO nanoparticles. The heat‐flow measurement using a differential thermal analyser shows an endothermic peak between 1070 and 1100 K representing ferroelectric to paraelectric phase transition. A systematic electrical conductivity study of these nanoparticles delineates that resistivity increases for doped BFO samples which is very much desirable for device applications of multiferroics.
Characterisation and properties of purely acrylic latex with submicro particle size prepared with mixed surfactants of sodium dodecyl benzene sulphonate and allyloxy nonylphenoxy propanol polyoxyethylene ether
Authors: Chen Lijun , Jiang Wei
Published: July 2013

The purely acrylic latex with submicro particle size was prepared via semi‐continuous seeded emulsion polymerisation of butyl acrylate and methyl methacrylate in water phase initiated with potassium persulphate and emulsified with mixed surfactants of sodium dodecyl benzene sulphonate and allyloxy nonylphenoxy propanol polyoxyethylene ether (ANPPE). The structure of the resultant latex is confirmed with Fourier transform infrared spectroscopy spectrum. Differential scanning calorimetry also confirms that the resultant latex is a type of random copolymer and the consistency among the chain segment is fairly good. Influences of the amount of ANPPE on the properties of the resultant latex and its film were investigated in detail. Results show that the contact angle of the film first is increased and then decreased with the increase of the amount of SN‐10. The glass transition temperature of the film is decreased with the increase of the amount of SN‐10. However, the particle size of the latex is increased with the increase of the amount of SN‐10.
Monocrystalline silicon nanowires and nanosheets as anodes of lithium‐ion battery: synthesis in mass production and low cost
Authors: Wang Qi , Chen Zhao‐Hui , Xing Li‐Li
Published: July 2013

Monocrystalline silicon nanowires and nanosheets are prepared in mass production by the novel electroless etching method. Low‐cost silicon powders are used as precursors. The initial capacities of silicon nanowires and nanosheets as lithium‐ion battery (LIB) anodes are up to 4311 and 4426 mAh/g, respectively. After ten cycles, the reversible capacity maintains 2318 and 2791 mAh/g for nanowires and nanosheets, respectively. The capacity and cyclability of nanosheets is slightly higher than that of nanowires. Such a behaviour is attributed to their finite lateral sizes and enhanced open‐edges, which can facilitate Li ion diffusion and decrease overvoltage associated with Li–Si alloying reaction. The presented results open a way for synthesising silicon nanostructures as LIB anodes in mass production and low cost.
Facile synthesis and characterisation of hexagonal magnetite nanoplates
Authors: Zhu Jianjun , Li Di , Jiang Deli , Chen Min
Published: July 2013

Hexagonal magnetite (Fe3O4) nanoplates were synthesised using a facile hydrothermal route, where ß‐cyclodextrin and urea were used as a reducing agent and a modifier, respectively. It was found that the obtained hexagonal Fe3O4 nanoplates had an average diameter of about 400 nm and thickness in the range of 40–80 nm. The effects of the concentration of urea and pH value on the formation of Fe3O4 nanoplates are discussed. A possible formation mechanism for the hexagonal Fe3O4 nanoplates is proposed. Magnetic studies revealed that the hexagonal Fe3O4 nanoplates exhibited a relatively high saturation magnetisation of 78.93 emu/g and a coercivity of less than 200 Oe at room temperature, which indicates that the as‐prepared Fe3O4 nanoplates are ferromagnetic.
Raman spectroscopic image analysis on micropatterned graphene
Authors: Choi Wooseok , Park Joonkyu , Jung Jongwan , Seo Yongho , Ahn Jinho , Park In‐Sung
Published: July 2013

A study has been conducted on patterned graphene with widths in the range of 0.1–4 μm which was grown by chemical vapour deposition and patterned by electron beam lithography. The microscopic behaviour of the Raman spectrum was investigated using image mapping from Raman spectroscopic data. Among three main peaks (D‐band, G‐band and 2D‐band), the two‐dimensional (2D) peak was clear even in 200 nm width graphene, however the D‐band signal was very weak, confirming low defect concentration. It was found that the 2D‐band line width was decreased as the width became narrower, which was explained by refining the electronic band structure because of confined sample size. The 2D‐ and G‐band intensities were decreased by reducing the width because the laser beam spot size was greater than the width of the sample and the effective area generating the signal was reduced.
Photocatalytic activity of Cu doped TiO2 nanoparticles and comparison of two main doping procedures
Authors: Behnajady Mohammad A. , Taba Hatam , Modirshahla Nasser , Shokri Mohammad
Published: July 2013

In this reported work, TiO2 nanoparticles containing anatase‐rutile and pure rutile phases were prepared by sol–gel and hydrolysis in acidic solution methods, respectively. Two general procedures, doping during synthesis (DDS) via a hydrolysis method and doping on the provided TiO2 nanoparticles (DOP) that is performed by the impregnation method have been studied by doping copper to these nanoparticles. The photocatalytic activity was evaluated by photodegradation of C.I. Acid Red 27 as a model contaminant. The prepared samples were characterised by X‐ray diffraction, atomic absorption flame emission spectroscopy and scanning electron microscopy. It is found that the photosensitised degradation activity can be enhanced by doping an appropriate amount of Cu. Photocatalytic activity results indicated that samples that have been doped by the DDS procedure show higher photocatalytic efficiency than samples doped by the DOP procedure.
Ag2O/Ag3PO4 heterostructures: highly efficient and stable visible‐light‐induced photocatalyst for degradation of methyl orange and phenol
Authors: Wang Ping‐Quan , Bai Yang , Luo Ping‐Ya , Liu Jian‐Yi
Published: July 2013

Ag2O/Ag3PO4 heterostructures photocatalysis was prepared for the first time. Photocatalytic tests displayed that the Ag2O/Ag3PO4 heterostructures possessed a much higher degradation rate of methyl orange and phenol than pure Ag3PO4 under visible light. The enhanced photocatalytic activity could be attributed to effective separation of photogenerated carriers driven by photoinduced potential difference generated at the Ag2O/Ag3PO4 heterojunction interface. Repetitive tests showed that the Ag2O/Ag3PO4 heterostructures maintained high stability over several cycles, and it had better regeneration capability under mild conditions. The good stability could be attributed to the protection of insoluble Ag2O nanoparticles on the surfaces of Ag3PO4 crystals in aqueous solution.
Fabrication and characterisation of functional gradient hydroxyapatite reinforced poly (ether ether ketone) biocomposites
Authors: Yusong Pan , Qianqian Shen , Yan Chen
Published: July 2013

Biomaterials usually require simultaneous possession of excellent performances such as bioactivity, mechanical and bio‐tribological properties to meet biomedical application requirements. In this reported work, the bioactive and mechanical properties of biocomposites were simultaneously optimised according to the functional gradient design idea. The functional gradient nano‐hydroxyapatite reinforced polyetheretherketone (nano‐HA/PEEK) biocomposites were fabricated through the layer‐by‐layer casting method and incorporation with thermal pressure moulding technology. The microstructure and morphology were investigated by X ‐ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). The result of the XRD study verified that the crystallinity of the PEEK matrix obviously improved after heat treatment. The SEM observation revealed that the size of HA particles in the biocomposites was in the nanometre scale. Furthermore, two typical morphologies such as encapsulated‐ and dimple‐like microstructures were observed by SEM. The FTIR study showed that the interaction between nano‐HA particles and the PEEK molecule existed. Both the SEM and FTIR studies results revealed that the morphology and microstructure in the functional gradient HA/PEEK biocomposites were beneficial for the improvement of the mechanical properties of the gradient biocomposites.
Effects of a remote binding partner on the electric field and electric field gradient at an atom in a weakly bound trimer
Authors: Mackenzie Rebecca B. , Timp Brooke A. , Mo Yirong , Leopold Kenneth R.
Published: July 2013

Microwave spectra are reported for the C3v symmetric complexes Kr–SO3 and Kr–SO3–CO. The S–C distance in the trimer, 2.871(9) Å, is the same as that previously determined for SO3–CO to within the estimated uncertainties. The Kr–S distances are 3.438(3) Å and 3.488(6) Å in Kr–SO3 and Kr–SO3–CO, respectively, indicating that the addition of CO to Kr–SO3 increases the Kr–S distance by 0.050(9) Å. Measurements of the 83Kr nuclear quadrupole coupling constants provide direct probes of the electric field gradient at the Kr nucleus, and a comparison between the two systems reflects the degree to which the CO influences the electronic structure of the krypton atom. Although the Kr and CO in the trimer are on opposite sides of the SO3 and thus are not in direct contact, the addition of CO to Kr–SO3 reduces the electric field gradient at the Kr nucleus by 18%. Calculations using the block localized wavefunction decomposition method are performed to understand the physical origins of this change. While the magnitudes of both the electric field and the electric field gradient at the Kr nucleus decrease upon addition of the CO to Kr–SO3, the changes are shown to arise from rather complex combinations of geometrical distortion, electrostatic, polarization, and electron transfer effects. For the electric field, the electrostatic term accounts for the largest portion of the reduction, while for the electric field gradient, polarization and structural change of the Kr–SO3 moiety make the primary contributions. Despite significant changes in the electronic environment at the Kr nucleus, calculated binding energies indicate that the interactions are largely additive, with the binding energy of the trimer very nearly equal to the sum of the Kr–SO3 and SO3–CO binding energies.
Molecular dynamics of polyisoprene/polystyrene oligomer blends: The role of self-concentration and fluctuations on blend dynamics
Authors: Harmandaris Vagelis , Doxastakis Manolis
Published: July 2013

The effect of self-concentration and intermolecular packing on the dynamics of polyisoprene (PI)/polystyrene (PS) blends is examined by extensive atomistic simulations. Direct information on local structure of the blend system allows a quantitative calculation of self- and effective composition terms at various length scales that are introduced to proposed models of blend dynamics. Through a detailed statistical analysis, the full distribution of relaxation times associated with reorienation of carbon-hydrogen bonds was extracted and compared to literature experimental data. A direct relation between relaxation times and local effective composition is found. Following an implementation of a model involving local composition as well as concentration fluctuations the relevant length scales characterizing the segmental dynamics of both components were critically examined. For PI, the distribution of times becomes narrower for the system with the lowest PS content and then broadens as more PS is added. This is in contrast to the slow component (PS), where an extreme breadth is found for relaxation times in the 25/75 system prior to narrowing as we increase PI concentration. The chain dynamics was directly quantified by diffusion coefficients as well as the terminal (maximum) relaxation time of each component in the mixed state. Strong coupling between the friction coefficients of the two components was predicted that leads to very similar chain dynamics for PI and PS, particularly for high concentrations of PI. We attribute this finding to the rather short oligomers (below the Rouse regime) studied here as well as to the rather similar size of PI and PS chains. The ratio of the terminal to the segmental relaxation time, τterm/τseg, c, presents a clear qualitative difference for the constituents: for PS the above ratio is almost independent of blend composition and very similar to the pure state. In contrast, for PI this ratio depends strongly on the composition of the blend; i.e., the terminal relaxation time of PI increases more than its segmental relaxation time, as the concentration of PS increases, resulting into a larger terminal/segmental ratio. We explain this disparity based on the different length scales characterizing dynamics. The relevant length for the segmental dynamics of PI is about 0.4–0.6 nm, smaller than chain dimensions which are expected to characterize terminal dynamics, whereas for PS associated length scales are similar (about 0.7–1.0 nm) rendering a uniform change with mixing.
Flux pinning mechanism in BaFe1.9Ni0.1As2 single crystals: Evidence for fluctuation in mean free path induced pinning
Authors: Shahbazi M. , Wang X. L. , Choi K. Y. , Dou S. X.
Published: July 2013

The flux pinning mechanism of BaFe1.9Ni0.1As2 superconducting crystals have been investigated systematically by magnetic measurements up to 13 T at various temperatures. The field dependence of the critical current density, Jc, was analysed within the collective pinning model. A remarkably good agreement between the experimental results and theoretical δl pinning curve is obtained, which indicates that pinning in BaFe1.9Ni0.1As2 crystal originates from spatial variation of the mean free path. Moreover, the normalized pinning force density, Fp, curves versus h = B/Birr (Birr is the irreversibility field) were scaled using the Dew-Hughes model. Analysis suggests that point pinning alone cannot explain the observed field variation of Fp.
Cation-cation contact pairing in water: Guanidinium
Authors: Shih Orion , England Alice H. , Dallinger Gregory C. , Smith Jacob W. , Duffey Kaitlin C. , Cohen Ronald C. , Prendergast David , Saykally Richard J.
Published: July 2013

The formation of like-charge guanidinium-guanidinium contact ion pairs in water is evidenced and characterized by X-ray absorption spectroscopy and first-principles spectral simulations based on molecular dynamics sampling. Observed concentration-induced nitrogen K-edge resonance shifts result from π* state mixing and the release of water molecules from each first solvation sphere as two solvated guanidinium ions associate into a stacked pair configuration. Possible biological implications of this counterintuitive cation-cation pairing are discussed.
Band gap and structure of single crystal BiI3: Resolving discrepancies in literature
Authors: Podraza Nikolas J. , Qiu Wei , Hinojosa Beverly B. , Xu Haixuan , Motyka Michael A. , Phillpot Simon R. , Baciak James E. , Trolier-McKinstry Susan , Nino Juan C.
Published: July 2013

Bismuth tri-iodide (BiI3) is an intermediate band gap semiconductor with potential for room temperature gamma-ray detection applications. Remarkably, very different band gap characteristics and values of BiI3 have been reported in literature, which may be attributed to its complicated layered structure with strongly bound BiI6 octahedra held together by weak van der Waals interactions. Here, to resolve this discrepancy, the band gap of BiI3 was characterized through optical and computational methods and differences among previously reported values are discussed. Unpolarized transmittance and reflectance spectra in the visible to near ultraviolet (UV-Vis) range at room temperature yielded an indirect band gap of 1.67 ± 0.09 eV, while spectroscopic ellipsometry detected a direct band gap at 1.96 ± 0.05 eV and higher energy critical point features. The discrepancy between the UV-Vis and ellipsometry results originates from the low optical absorption coefficients (α ∼ 102 cm−1) of BiI3 that renders reflection-based ellipsometry insensitive to the indirect gap for this material. Further, electronic-structure calculations of the band structure by density functional theory methods are also consistent with the presence of an indirect band gap of 1.55 eV in BiI3. Based on this, an indirect band gap with a value of 1.67 ± 0.09 eV is considered to best represent the band gap structure and value for single crystal BiI3.
On the Kolmogorov inertial subrange developing from Richtmyer-Meshkov instability
Authors: Tritschler V. K. , Hickel S. , Hu X. Y. , Adams N. A.
Published: July 2013

We present results of well-resolved direct numerical simulations (DNS) of the turbulent flow evolving from Richtmyer-Meshkov instability (RMI) in a shock-tube with square cross section. The RMI occurs at the interface between a mixture of O2 and N2 (light gas) and SF6 and acetone (heavy gas). The interface between the light and heavy gas is accelerated by a Ma = 1.5 planar shock wave. RMI is triggered by a well-defined multimodal initial disturbance at the interface. The DNS exhibit grid-resolution independent statistical quantities and support the existence of a Kolmogorov-like inertial range with a k−5/3 scaling unlike previous simulations found in the literature. The results are in excellent agreement with the experimental data of Weber et al. [“Turbulent mixing measurements in the Richtmyer-Meshkov instability,” Phys. Fluids 24, 074105 (2012)]10.1063/1.4733447.
Investigation of the spin-lattice relaxation of 13CO and 13CO2 adsorbed in the metal-organic frameworks Cu3(btc)2 and Cu3−xZnx(btc)2
Authors: Gul-E-Noor Farhana , Michel Dieter , Krautscheid Harald , Haase Jürgen , Bertmer Marko
Published: July 2013

The 13C nuclear spin-lattice relaxation time of 13CO and 13CO2 molecules adsorbed in the metal-organic frameworks (MOFs) Cu2.97Zn0.03(btc)2 and Cu3(btc)2 is investigated over a wide range of temperatures at resonance frequencies of 75.468 and 188.62 MHz. In all cases a mono-exponential relaxation is observed, and the 13C spin-lattice relaxation times (T1) reveal minima within the temperature range of the measurements and both frequencies. This allows us to carry out a more detailed analysis of the 13C spin relaxation data and to consider the influence due to the spectral functions of the thermal motion. In a model-free discussion of the temperature dependence of the ratios T1 (T)/T1,min we observe a motional mechanism that can be described by a single correlation time. In relation to the discussion of the relaxation mechanisms this can be understood in terms of dominating translational motion with mean jump distance being larger than the minimum distances between neighboring adsorption sites in the MOFs. A more detailed discussion of the jump-like motion observed here might be carried out on the basis of self-diffusion coefficients. From the present spin relaxation measurements activation energies for the local motion of the adsorbed molecules in the MOFs can be estimated to be 3.3 kJ/mol and 2.2 kJ/mol, for CO and CO2 molecules, respectively. Finally, our findings are compared with our recent results derived from the 13C line shape analysis.
Transport of finite size particles in confined narrow channels: Diffusion, coherence, and particle separation
Authors: Ai Bao-Quan , Wu Jian-Chun
Published: July 2013

Transport of the finite size spherical Brownian particles is investigated in confined narrow channels with varying cross-section width. Applying the Fick-Jacobs approximation, we obtain the expressions of the particle current, the effective diffusion coefficient, and the coherence level of Brownian transport (the Péclet number). For the case of the biased constant force, the dependencies of the nonlinear mobility, the effective diffusion coefficient, and the Péclet number on the particle size exhibit striking behaviors. The Péclet number decreases with increasing the radius of the particle which shows that the big sizes of the particles reduce the coherence level of Brownian transport. There exists an optimized value of the radius at which the effective diffusion coefficient is maximal. For the case of the asymmetric unbiased force, due to the competition between the spatial asymmetry and the temporal asymmetry, the transport directions of the particles depend very sensitively on the size of the particle. Particles larger than a given threshold radius move to the left, whereas particles smaller than that move to the right. Therefore, one can separate particles of different radii and make them move towards opposite directions.
Aerodynamic effects of wing corrugation at gliding flight at low Reynolds numbers
Authors: Meng Xue Guang , Sun Mao
Published: July 2013

Corrugation gives an insect-wing the advantages of low mass, high stiffness, and low membrane stress. Researchers are interested to know if it is also advantageous aerodynamically. Previous works reported that corrugation enhanced the aerodynamic performance of wings at gliding flight. However, Reynolds numbers considered in these studies were higher than that of gliding insects. The present study showed that in the Reynolds number range of gliding insects, corrugation had negative aerodynamic effects. We studied aerodynamic effects of corrugation at gliding motion using the method of computational fluid dynamics, in the Reynolds number range of Re = 200–2400. Different corrugation patterns were considered. The effect of corrugation on aerodynamic performance was identified by comparing the aerodynamic forces between the corrugated and flat-plate wings, and the underlying flow mechanisms of the corrugation effects were revealed by analyzing the flow fields and surface pressure distributions. The findings are as follows: (1) the effect of corrugation is to decrease the lift, and change the drag only slightly (at 15°–25° angles of attack, lift is decreased by about 16%; at smaller angles of attack, the percentage of lift reduction is even larger because the lift is small). (2) Two mechanisms are responsible for the lift reduction. One is that the pleats at the lower surface of the corrugated wing produce relatively strong vortices, resulting in local low-pressure regions on the lower surface of the wing. The other is that corrugation near the leading edge pushes the leading-edge-separation layer slightly upwards and increases the size of the separation bubble above the upper surface, reducing the “suction pressure,” or increasing the pressure, on the upper surface.
Prediction of turbulence control for arbitrary periodic spanwise wall movement
Authors: Cimarelli Andrea , Frohnapfel Bettina , Hasegawa Yosuke , De Angelis Elisabetta , Quadrio Maurizio
Published: July 2013

In order to generalize the well-known spanwise-oscillating-wall technique for drag reduction, non-sinusoidal oscillations of a solid wall are considered as a means to alter the skin-friction drag in a turbulent channel flow. A series of direct numerical simulations is conducted to evaluate the control performance of nine different temporal waveforms, in addition to the usual sinusoid, systematically changing the wave amplitude and the period for each waveform. The turbulent average spanwise motion is found to coincide with the laminar Stokes solution that is constructed, for the generic waveform, through harmonic superposition. This allows us to define and compute, for each waveform, a new penetration depth of the Stokes layer which correlates with the amount of turbulent drag reduction, and eventually to predict both turbulent drag reduction and net energy saving rate for arbitrary waveforms. Among the waveforms considered, the maximum net energy saving rate is obtained by the sinusoidal wave at its optimal amplitude and period. However, the sinusoid is not the best waveform at every point in the parameter space. Our predictive tool offers simple guidelines to design waveforms that outperform the sinusoid for given (suboptimal) amplitude and period of oscillation. This is potentially interesting in view of applications, where physical limitations often preclude the actuator to reach its optimal operating conditions.
A novel correction scheme for DFT: A combined vdW-DF/CCSD(T) approach
Authors: Hermann Jan , Bludský Ota
Published: July 2013

A system-specific but very accurate density functional theory (DFT) correction scheme is proposed for precise calculations of adsorbent–adsorbate interactions by combining the non-empirical van der Waals density functional (vdW-DF) method and the empirical DFT/CC correction scheme to reach accuracy of the coupled clusters method with single, double and perturbative triple excitations (CCSD(T)). The new approach is applied to small molecules (CH4, CO2, H2, H2O, N2) interacting with silica surfaces and purely siliceous microporous solids. The vdW-DF/CC results for a perfectly reconstructed α-quartz surface are consistent with other dispersion-corrected DFT methods. Corrected for ZPVE, the vdW-DF/CC enthalpies of adsorption in pure-silica zeolite LTA (ΔHads(0 K)) of 3.6 and 5.2 kcal/mol for methane and carbon dioxide, respectively, are in excellent agreement with experimental values of 3.6 and 5.0 kcal/mol. The very high accuracy of the new scheme and its relatively easy use and numerical stability as compared to the earlier DFT/CC scheme offer a straightforward solution for obtaining reliable predictions of adsorption energies.
Spatiotemporal drift-diffusion simulations of analog ionic memristors
Authors: Greenlee Jordan D. , Shank Joshua C. , Brooks Tellekamp M. , Alan Doolittle W.
Published: July 2013

Analog memristors that exhibit an electronic conductivity change in response to ionic motion have been simulated using the finite element method. Several physical mechanisms are considered for the redistribution of dopants within the device and all result in minimal resistance changes. The mechanisms considered that result in minimal resistance changes are initial ion concentration, hole mobility dependence on acceptor concentration, and geometry. In contrast, ion extraction results in a significant change in the simulated analog memristor resistance (many orders of magnitude). It is determined that if ions can be repeatedly cycled without damage to the crystal structure, ion extraction is the optimal analog ionic memristor operation mechanism. Given this conclusion, battery technology materials known for their robustness in spite of repeated ion extraction/replacement should be considered for reliable analog memristor applications.
Metal nanoparticle field-effect transistor
Authors: Cai Yuxue , Michels Jan , Bachmann Julien , Klinke Christian
Published: July 2013

We demonstrate that by means of a local top-gate current oscillations can be observed in extended, monolayered films assembled from monodisperse metal nanocrystals—realizing transistor function. The oscillations in this metal-based system are due to the occurrence of a Coulomb energy gap in the nanocrystals which is tunable via the nanocrystal size. The nanocrystal assembly by the Langmuir-Blodgett method yields homogeneous monolayered films over vast areas. The dielectric oxide layer protects the metal nanocrystal field-effect transistors from oxidation and leads to stable function for months. The transistor function can be reached due to the high monodispersity of the nanocrystals and the high super-crystallinity of the assembled films. Due to the fact that the film consists of only one monolayer of nanocrystals and all nanocrystals are simultaneously in the state of Coulomb blockade the energy levels can be influenced efficiently (limited screening).