bluuebunny/crossref_metadata_2025 huggingface dataset:
RECONSTRUCTION ART AND DISCIPLINARY PRACTICE: ALAN SORRELL AND THE NEGOTIATION OF THE ARCHAEOLOGICAL RECORD
Authors: Perry Sara , Johnson Matthew
Published: July 2014

Alan Sorrell is best known today as a ‘reconstruction artist’, employed between the 1930s and the 1970s by the Ministry of Works and other bodies to produce reconstructions of ancient monuments and re-creations of ancient life. The archive containing many of his papers, working drawings, correspondence and other material was temporarily loaned to the Society of Antiquaries of London for study in 2010–11, and is now publicly accessible via the Sorrell family. This paper reports on initial research into the Sorrell archive and other documentary sources, funded through a British Academy Small Grant. We discuss how the archive throws new light not just on Sorrell's career and achievements, but on the intellectual and professional development of archaeology as a whole in the mid-twentieth century.
Assessing the efficacy of direct conservation interventions: clutch protection of the leatherback marine turtle in the Dominican Republic
Authors: Revuelta Ohiana , León Yolanda M. , Broderick Annette C. , Feliz Pablo , Godley Brendan J. , Balbuena Juan A. , Mason Andrea , Poulton Kate , Savoré Stefania , Raga Juan A. , Tomás Jesús
Published: July 2014

The beaches of Jaragua National Park in the Dominican Republic are the country's last known major nesting site for the leatherback marine turtle Dermochelys coriacea. This nesting aggregation is threatened by widespread illegal egg take, and clutch relocation and artificial incubation have been carried out as protection measures since 1974. We assess the efficacy of such efforts and investigate how artificial incubation may be influencing the success and sex ratios of clutches. We compare hatching success, incubation duration and embryo mortality in in-situ clutches (n = 43) with those incubated artificially at sites in the east and west of the Park (n = 35 and n = 31, respectively). Our results show that in the west, artificial incubation significantly decreases hatching success in clutches. In the east the duration of incubation is increased, which we predict would result in an increase in the number of males from these clutches. Clutch relocation is currently the only viable conservation option for clutches on eastern beaches because of illegal egg take but action is needed to ensure that the natural sex ratio is not distorted. However, on the western beaches in situ clutch incubation seems possible through beach protection. Further community engagement and enforcement are required to improve conservation measures at eastern beaches if long-term, less sustainable intervention is to be avoided.
Successful emergency cardiac pacing and permanent pacemaker insertion in a preterm 29-week gestation hydropic baby with congenital complete heart block
Authors: Beake Matthew Jonathan , Bhole Vinay , Johnston Tracey , Rasiah Shree Vishna
Published: July 2014

A preterm 29-week gestation baby was delivered because of gross foetal hydrops secondary to congenital complete heart block. Despite a poor prognosis, she survived stabilisation and received emergency epicardial pacing followed by permanent pacemaker insertion on day 13, weighing 1.2 kg.
Implementation of a Titrated Oxygen Protocol in the Out-of-Hospital Setting
Authors: Bosson Nichole , Gausche-Hill Marianne , Koenig William
Published: July 2014

Oxygen is one of the most frequently-used therapeutic agents in medicine and the most commonly administered drug by prehospital personnel. There is increasing evidence of harm with too much supplemental oxygen in certain conditions, including stroke, chronic obstructive pulmonary disease (COPD), neonatal resuscitations, and in postresuscitation care. Recent guidelines published by the British Thoracic Society (BTS) advocate titrated oxygen therapy, but these guidelines have not been widely adapted in the out-of-hospital setting where high-flow oxygen is the standard. This report is a description of the implementation of a titrated oxygen protocol in a large urban-suburban Emergency Medical Services (EMS) system and a discussion of the practical application of this out-of-hospital protocol.

BossonN,Gausche-HillM,KoenigW.Implementation of a titrated oxygen protocol in the out-of-hospital setting.Prehosp Disaster Med.2014;28(4):1-6.
Periodic Cation Segregation in Cs0.44[Nb2.54W2.46O14] Quantified by High-Resolution Scanning Transmission Electron Microscopy
Authors: Heidelmann Markus , Barthel Juri , Cox Gerhard , Weirich Thomas E.
Published: July 2014

The atomic structure of Cs0.44[Nb2.54W2.46O14] closely resembles the structure of the most active catalyst for the synthesis of acrylic acid, the M1 phase of
${\rm Mo}_{{{\rm 10}}} {\rm V}_{{\rm 2}}^{{{\rm 4{\plus}}}} {\rm Nb}_{2} {\rm TeO}_{{{\rm 42}{\minus}x}} $
. Consistently with observations made for the latter compound, the high-angle electron scattering signal recorded by scanning transmission electron microscopy shows a significant intensity variation, which repeats periodically with the projected crystallographic unit cell. The occupation factors for the individual mixed Nb/W atomic columns are extracted from the observed intensity variations. For this purpose, experimental images and simulated images are compared on an identical intensity scale, which enables a quantification of the cation distribution. According to our analysis specific sites possess low tungsten concentrations of 25%, whereas other sites have tungsten concentrations above 70%. These findings allow us to refine the existing structure model of the target compound, which has until now described a uniform distribution of the niobium and tungsten atoms in the unit cell, showing that the similarity between Cs0.44[Nb2.54W2.46O14] and the related catalytic compounds also extends to the level of the cation segregation.
Comparative analysis of the interaction between habitat and growth form in diatoms
Authors: Nakov Teofil , Ashworth Matt , Theriot Edward C
Published: July 2014

We characterized the evolutionary history of growth form (solitary–colonial) and its interaction with species’ habitat (planktonic–benthic) across a multi-gene phylogeny encompassing a broad sample of the order-level diversity of diatoms. We treated these characters broadly, modeling the evolution of aggregation of cells into a colony irrespective of the way aggregation is achieved, and relating the growth form to a broad concept of niche location: in the plankton or benthos. The results showed that habitat shifts are rare implying conservatism in niche location at the level of large clades. On the other hand, the evolutionary history of growth form is more dynamic with evolutionary rates that vary across the tree. Analyses of a possible interaction revealed that shifts in growth form are independent of habitat and that traversing between habitats does not hinge upon species’ growth form. Our findings help to fill a gap in the understanding of diatom niche and growth form macroevolution and contribute toward a platform for the comparative study of the mechanisms underlying diatom species and functional diversity.
The association between air pollution and mortality in Thailand
Authors: Guo Yuming , Li Shanshan , Tawatsupa Benjawan , Punnasiri Kornwipa , Jaakkola Jouni J. K. , Williams Gail
Published: July 2014

Bayesian statistical inference with a case-crossover design was used to examine the effects of air pollutants {Particulate matter <10 μm in aerodynamic diameter (PM10), sulphur dioxide (SO2) and ozone (O3)} on mortality. We found that all air pollutants had significant short-term impacts on non-accidental mortality. An increase of 10 μg/m3 in PM10, 10 ppb in O3, 1 ppb in SO2 were associated with a 0.40% (95% posterior interval (PI): 0.22, 0.59%), 0.78% (95% PI: 0.20, 1.35%) and 0.34% (95% PI: 0.17, 0.50%) increase of non-accidental mortality, respectively. O3 air pollution is significantly associated with cardiovascular mortality, while PM10 is significantly related to respiratory mortality. In general, the effects of all pollutants on all mortality types were higher in summer and winter than those in the rainy season. This study highlights the effects of exposure to air pollution on mortality risks in Thailand. Our findings support the Thailand government in aiming to reduce high levels of air pollution.
Derivatization and analysis of levoglucosan and PAHs in ambient air particulate matter by moderate temperature thermal desorption coupled with GC/MS
Authors: Grandesso Emanuela , Ballesta Pascual Pérez
Published: July 2014

A thermal desorption method followed by GC/MS analysis has been developed for efficient analysis of levoglucosan and PAHs in particulate matter.
Entrapment in giant polymersomes of an inorganic oscillatory chemical reaction and resulting chemo-mechanical coupling
Authors: Pereira de Souza Tereza , Perez-Mercader Juan
Published: July 2014

We present the entrapment of a fully oscillating BZ reaction inside a polymersome and report on the subsequent polymersome chemomechanics.
Self-assembly of sodium 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoate into ultralong microbelts
Authors: Zhao Hongyan , Chen Hongbiao , Gao Yong , Li Huaming
Published: July 2014

Ultralong SDB microbelts with interesting optical and electrical properties were successfully fabricated by the poor solvent mediated self-assembly method.
Reduction mechanisms of additives on Si anodes of Li-ion batteries
Authors: Martínez de la Hoz Julibeth M. , Balbuena Perla B.
Published: July 2014

Lithiated Si anodes facilitate reduction of carbonate additives through multiple electron transfers.
Insights into the Cr(iii) catalyzed isomerization mechanism of glucose to fructose in the presence of water using ab initio molecular dynamics
Authors: Mushrif Samir H. , Varghese Jithin J. , Vlachos Dionisios G.
Published: July 2014

In water, the partially hydrolyzed Cr complex [Cr(H2O)5OH]+2is the active species for glucose isomerization and not the unhydrolyzed, hexahydrated Cr+3.
Phosphorus availability explains patterns in a productivity indicator in temperate semi-natural vegetation
Authors: Rowe E. C. , Smart S. M. , Emmett B. A.
Published: July 2014

Spatial variation in a trait-based indicator of plant productivity was mainly explained by an axis of variation from wet, organic soils to drier, mineral soils. However, extractable phosphorus explained residual variation considerably better than did mineralisable nitrogen.
Laser-induced vibration of a thin soap film
Authors: Emile Olivier , Emile Janine
Published: July 2014

We report on the vibration of a thin soap film based on the optical radiation pressure force.
Split and flow: reconfigurable capillary connection for digital microfluidic devices
Authors: Lapierre Florian , Harnois Maxime , Coffinier Yannick , Boukherroub Rabah , Thomy Vincent
Published: July 2014

How to take advantage of superhydrophobic microgrids to address the problem of coupling continuous to digital microfluidic systems? A reconfigurable capillary connection for digital microfluidic devices is presented.
Nickel translocation between metallochaperones HypA and UreE in Helicobacter pylori
Authors: Yang Xinming , Li Hongyan , Cheng Tianfan , Xia Wei , Lai Yau-Tsz , Sun Hongzhe
Published: July 2014

Directin vitroandin vivoevidence as well as molecular details of nickel translocation mediated by HypA–UreE interaction.
Synthetic endeavours towards oxasqualenoid natural products containing 2,5-disubstituted tetrahydrofurans – eurylene and teurilene
Authors: Sheikh Nadeem S.
Published: July 2014

Given the unique structural features of oxasqualenoid natural products and their cytotoxicity, representative examples from oxasqualenoids, eurylene and teurilene have been briefly reviewed. Both compounds possess cis- and trans-2,5-disubstituted tetrahydrofuran rings and represent chiral and achiral facets found in this class of natural products.
Synthesis of 3,3-disubstituted-2,3-dihydroazanaphthoquinones via simultaneous alkyne oxidation and nitrile hydration of ortho-alkynylarenenitriles
Authors: Sakthivel Karuppusamy , Srinivasan Kannupal
Published: July 2014

Simultaneous activation of alkynes and nitriles in o-alkynylarenenitriles in the presence of Pd(OAc)2/H2O/(±)-CSA afforded 3,3-disubstituted-2,3-dihydroazanaphthoquinones in moderate to excellent yields.
The Escherichia coli glucuronylsynthase promoted synthesis of steroid glucuronides: improved practicality and broader scope
Authors: Ma Paul , Kanizaj Nicholas , Chan Shu-Ann , Ollis David L. , McLeod Malcolm D.
Published: July 2014

Steroid glucuronides can be quickly and conveniently prepared on the milligram scale using theE. coliglucuronylsynthase enzyme followed by purification with solid-phase extraction.
One-pot controllable synthesis of oligo(carbonate-ether) triol using a Zn-Co-DMC catalyst: the special role of trimesic acid as an initiation-transfer agent
Authors: Liu Shunjie , Qin Yusheng , Chen Xuesi , Wang Xianhong , Wang Fosong
Published: July 2014

Oligo(carbonate-ether) triol with controllable Mn and CU was synthesized by using TMA as a novel chain initiation-transfer agent catalyzed by Zn-Co-DMC.
A new halide-free efficient reaction-controlled phase-transfer catalyst based on silicotungstate of [(C18H37)2(CH3)2N]3[SiO4H(WO5)3] for olefin epoxidation, oxidation of sulfides and alcohols with hydrogen peroxide
Authors: Ma Baochun , Zhao Wei , Zhang Fuming , Zhang Yingshuai , Wu Songyun , Ding Yong
Published: July 2014

A new environmentally benign and highly efficient reaction-controlled phase-transfer catalyst for olefin epoxidation, sulfide and alcohol oxidation was developed.
Selective adsorption of contaminants on Pb(Zr,Ti)O3 surfaces shown by X-ray photoelectron spectroscopy
Authors: Ştoflea Laura Elena , Apostol Nicoleta Georgiana , Trupină Lucian , Teodorescu Cristian Mihail
Published: July 2014

Lead zirco-titanate single crystal layers exhibit an increased affinity for adsorbing polar contaminating molecules on areas with outwards polarization.
A piezoelectric cryogenic heat switch
Authors: Jahromi Amir E. , Sullivan Dan F.
Published: July 2014

We have measured the thermal conductance of a mechanical heat switch actuated by a piezoelectric positioner, the PZHS (PieZo electric Heat Switch), at cryogenic temperatures. The thermal conductance of the PZHS was measured between 4 K and 10 K, and on/off conductance ratios of about 100–200 at lowest and highest measures temperature were achieved when the positioner applied its maximum force of 8 N, respectively. We discuss the advantages of using this system in cryogenic applications, and estimate the ultimate performance of an ideal PZHS.
Invited Review Article: The Chandra X-ray Observatory
Authors: Schwartz Daniel A.
Published: July 2014

The Chandra X-ray Observatory is an orbiting x-ray telescope facility. It is one of the National Aeronautics and Space Administration's four “Great Observatories” that collectively have carried out astronomical observations covering the infrared through gamma-ray portion of the electromagnetic spectrum. Chandra is used by astronomers world-wide to acquire imaging and spectroscopic data over a nominal 0.1–10 keV (124–1.24 Å) range. We describe the three major parts of the observatory: the telescope, the spacecraft systems, and the science instruments. This article will emphasize features of the design and development driven by some of the experimental considerations unique to x-ray astronomy. We will update the on-orbit performance and present examples of the scientific highlights.
Determining diffusion coefficients of ionic liquids by means of field cycling nuclear magnetic resonance relaxometry
Authors: Kruk D. , Meier R. , Rachocki A. , Korpała A. , Singh R. K. , Rössler E. A.
Published: July 2014

Field Cycling Nuclear Magnetic Resonance (FC NMR) relaxation studies are reported for three ionic liquids: 1-ethyl-3- methylimidazolium thiocyanate (EMIM-SCN, 220–258 K), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4, 243–318 K), and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6, 258–323 K). The dispersion of 1H spin-lattice relaxation rate R1(ω) is measured in the frequency range of 10 kHz–20 MHz, and the studies are complemented by 19F spin-lattice relaxation measurements on BMIM-PF6 in the corresponding frequency range. From the 1H relaxation results self-diffusion coefficients for the cation in EMIM-SCN, BMIM-BF4, and BMIM-PF6 are determined. This is done by performing an analysis considering all relevant intra- and intermolecular relaxation contributions to the 1H spin-lattice relaxation as well as by benefiting from the universal low-frequency dispersion law characteristic of Fickian diffusion which yields, at low frequencies, a linear dependence of R1 on square root of frequency. From the 19F relaxation both anion and cation diffusion coefficients are determined for BMIM-PF6. The diffusion coefficients obtained from FC NMR relaxometry are in good agreement with results reported from pulsed- field-gradient NMR. This shows that NMR relaxometry can be considered as an alternative route of determining diffusion coefficients of both cations and anions in ionic liquids.
Microfluidic sterilization
Authors: Zhang Rui , Huang Jie , Xie Fei , Wang Baojun , Chu Ming , Wang Yuedan , Li Haichao , Wang Wei , Zhang Haixia , Wu Wengang , Li Zhihong
Published: July 2014

Nowadays, microfluidics is attracting more and more attentions in the biological society and has provided powerful solutions for various applications. This paper reported a microfluidic strategy for aqueous sample sterilization. A well-designed small microchannel with a high hydrodynamic resistance was used to function as an in-chip pressure regulator. The pressure in the upstream microchannel was thereby elevated which made it possible to maintain a boiling-free high temperature environment for aqueous sample sterilization. A 120 °C temperature along with a pressure of 400 kPa was successfully achieved inside the chip to sterilize aqueous samples with E. coli and Staphylococcus aureus inside. This technique will find wide applications in portable cell culturing, microsurgery in wild fields, and other related micro total analysis systems.
Structural and orientation effects on electronic energy transfer between silicon quantum dots with dopants and with silver adsorbates
Authors: Vinson N. , Freitag H. , Micha D. A.
Published: July 2014

Starting from the atomic structure of silicon quantum dots (QDs), and utilizing ab initio electronic structure calculations within the Förster resonance energy transfer (FRET) treatment, a model has been developed to characterize electronic excitation energy transfer between QDs. Electronic energy transfer rates, KEET, between selected identical pairs of crystalline silicon quantum dots systems, either bare, doped with Al or P, or adsorbed with Ag and Ag3, have been calculated and analyzed to extend previous work on light absorption by QDs. The effects of their size and relative orientation on energy transfer rates for each system have also been considered. Using time-dependent density functional theory and the hybrid functional HSE06, the FRET treatment was employed to model electronic energy transfer rates within the dipole-dipole interaction approximation. Calculations with adsorbed Ag show that: (a) addition of Ag increases rates up to 100 times, (b) addition of Ag3 increases rates up to 1000 times, (c) collinear alignment of permanent dipoles increases transfer rates by an order of magnitude compared to parallel orientation, and (d) smaller QD-size increases transfer due to greater electronic orbitals overlap. Calculations with dopants show that: (a) p-type and n-type dopants enhance energy transfer up to two orders of magnitude, (b) surface-doping with P and center-doping with Al show the greatest rates, and (c) KEET is largest for collinear permanent dipoles when the dopant is on the outer surface and for parallel permanent dipoles when the dopant is inside the QD.
Thermal conductivity measurement of a Sb2Te3 phase change nanowire
Authors: Saci Abdelhak , Battaglia Jean-Luc , Kusiak Andrzej , Fallica Roberto , Longo Massimo
Published: July 2014

The c-axis thermal conductivity of a Sb2Te3 nanowire is measured using the scanning thermal microscopy technique within the 3ω mode. The contact parameters, in terms of boundary contact resistance and contact area radius, are measured in specific configurations, and the values found are assumed not to vary within the nanowire case. The method does not require handling or suspending the nanowire. The measured thermal conductivity at room temperature is found to be in a good agreement with that of the bulk, since the nanowire characteristic dimension in the diffusion direction is larger than the phonon mean free path.
Xe
2 gerade Rydberg states observed in the afterglow of a microplasma by laser spectroscopy of $a^3 {\rm \Sigma }_u^ + ( {1_u,O_u^ - })$a3Σu+(1u,Ou−) absorption in the green (545–555 nm) and near-infrared (675–800 nm)
Authors: Wagner C. J. , Galvin T. C. , Eden J. G.
Published: July 2014

Bound←bound transitions of the Xe dimer at small internuclear separation (R < 4.0 Å) have been observed in the 545–555 nm and 675–800 nm spectral regions by laser spectroscopy in the afterglow of a pulsed Xe microplasma with a volume of ∼160 nl. Transient suppression of Xe2 $A^1 {\rm \Sigma }_u^ + ( {O_u^ + }) \to X^1 {\rm \Sigma }_g^ + ( {O_g^ + })$A1Σu+(Ou+)→X1Σg+(Og+) emission in the vacuum ultraviolet (∼172 nm), induced by laser excitation of ${\rm \Omega }_g \leftarrow a^3 {\rm \Sigma }_u^ + ( {1_u,O_u^ - })$Ωg←a3Σu+(1u,Ou−) [Rydberg←Rydberg] transitions of the molecule, has confirmed the existence of structure between 720 and 770 nm (reported by Killeen and Eden [J. Chem. Phys. 84, 6048 (1986)]) but also reveals red-degraded vibrational bands extending to wavelengths beyond 800 nm. Spectral simulations based on calculations of Franck-Condon factors for assumed ${\rm \Omega }_g \leftarrow a^3 {\rm \Sigma }_u^ + $Ωg←a3Σu+ transitions involving Ω = 0±,1 gerade Rydberg states suggest that the upper level primarily responsible for the observed spectrum is an Ω = 1 state correlated, in the separated atom limit, with Xe(5p6 1S0) + Xe(5p5 6p) and built on a predominantly A2Π3/2g molecular ion core. Specifically, the spectroscopic constants for the upper state of the $1_g \leftarrow 1_u,O_u^ \pm $1g←1u,Ou± absorptive transitions are determined to be Te = 13 000 ± 150 cm−1, $\omega _e^\prime = 120 \pm 10\,{\rm cm}^{ - 1} $ωe′=120±10 cm −1, $\omega _e^\prime x_e^\prime = 1.1 \pm 0.4\,{\rm cm}^{ - 1} $ωe′xe′=1.1±0.4 cm −1, De = 3300 ± 300 cm−1, and ${\rm \Delta }R_e = R_e^\prime - R_e^{\prime \prime } = 0.3 \pm 0.1\ {\rm {\AA}}$ΔRe=Re′−Re″=0.3±0.1Å which are in general agreement with the theoretical predictions of the pseudopotential hole-particle formalism, developed by Jonin and Spiegelmann [J. Chem. Phys. 117, 3059 (2002)], for both the (5)1g and $( 3)O_g^ + $(3)Og+ states of Xe2. These spectra exhibit the most extensive vibrational development, and provide evidence for the first molecular core-switching transition, observed to date for any of the rare gas dimers at small R (<4 Ǻ). Experiments in the green (545–555 nm) also provide improved absorption spectra, relative to data reported in 1986 and 1999, associated with Xe2 Rydberg states derived from the Xe(7p) orbital.
Alternative optical concept for electron cyclotron emission imaging
Authors: Liu J. X. , Milbourne T. , Bitter M. , Delgado-Aparicio L. , Dominguez A. , Efthimion P. C. , Hill K. W. , Kramer G. J. , Kung C. , Kubota S. , Kasparek W. , Lu J. , Pablant N. A. , Park H. , Tobias B.
Published: July 2014

The implementation of advanced electron cyclotron emission imaging (ECEI) systems on tokamak experiments has revolutionized the diagnosis of magnetohydrodynamic (MHD) activities and improved our understanding of instabilities, which lead to disruptions. It is therefore desirable to have an ECEI system on the ITER tokamak. However, the large size of optical components in presently used ECEI systems have, up to now, precluded the implementation of an ECEI system on ITER. This paper describes a new optical ECEI concept that employs a single spherical mirror as the only optical component and exploits the astigmatism of such a mirror to produce an image with one-dimensional spatial resolution on the detector. Since this alternative approach would only require a thin slit as the viewing port to the plasma, it would make the implementation of an ECEI system on ITER feasible. The results obtained from proof-of-principle experiments with a 125 GHz microwave system are presented.
Magnetic and electric bulge-test instrument for the determination of coupling mechanical properties of functional free-standing films and flexible electronics
Authors: Yu Zejun , Mao Weiguo , Li Faxin , Feng Xue , Pei Yongmao , Fang Daining
Published: July 2014

For the first time a novel multi-field bulge-test instrument which enables measurements of the biaxial mechanical properties and electro-magnetic-mechanical coupling effect of free-standing films in external magnetic/electric fields was proposed. The oil pressure was designed with two ranges, 0–1 MPa for elastic small deformation and 0–7 MPa for plastic/damage large deformation. A magnetic field that was horizontal and uniform in the film plane was supplied by a hollow cylindrical magnet. The magnitude could be changed from 0 to 10 000 Oe by adjusting the position of the testing film. Meanwhile, an electric field applied on the film was provided by a voltage source (Maximum voltage: 1000 V; Maximum current: 1 A). Various signals related to deformation, mechanical loading, magnetic field, and electric field could be measured simultaneously without mutual interference, which was confirmed by the coincidence of the measured P-H curves for titanium (Ti)/nickel (Ni) specimens with/without external fields. A hardening phenomenon under magnetic/electric fields was observed for Ni and lead zirconate titanate specimens. The multi-field bulge-test instrument will provide a powerful research tool to study the deformation mechanism of functional films and flexible electronics in the coupling field.
Density functional theory approach to gold-ligand interactions: Separating true effects from artifacts
Authors: Koppen Jessica V. , Hapka Michał , Modrzejewski Marcin , Szczęśniak Małgorzata M. , Chałasiński Grzegorz
Published: July 2014

Donor-acceptor interactions are notoriously difficult and unpredictable for conventional density functional theory (DFT) methodologies. This work presents a reliable computational treatment of gold-ligand interactions of the donor-acceptor type within DFT. These interactions require a proper account of the ionization potential of the electron donor and electron affinity of the electron acceptor. This is accomplished in the Generalized Kohn Sham framework that allows one to relate these properties to the frontier orbitals in DFT via the tuning of range-separated functionals. A donor and an acceptor typically require different tuning schemes. This poses a problem when the binding energies are calculated using the supermolecular method. A two-parameter tuning for the monomer properties ensures that a common functional, optimal for both the donor and the acceptor, is found. A reliable DFT approach for these interactions also takes into account the dispersion contribution. The approach is validated using the water dimer and the (HAuPH3)2 aurophilic complex. Binding energies are computed for Au4 interacting with the following ligands: SCN−, benzenethiol, benzenethiolate anion, pyridine, and trimethylphosphine. The results agree for the right reasons with coupled-cluster reference values.
A molecular dynamics study of ambient and high pressure phases of silica: Structure and enthalpy variation with molar volume
Authors: Rajappa Chitra , Sringeri S. Bhuvaneshwari , Subramanian Yashonath , Gopalakrishnan J.
Published: July 2014

Extensive molecular dynamics studies of 13 different silica polymorphs are reported in the isothermal-isobaric ensemble with the Parrinello-Rahman variable shape simulation cell. The van Beest-Kramer-van Santen (BKS) potential is shown to predict lattice parameters for most phases within 2%–3% accuracy, as well as the relative stabilities of different polymorphs in agreement with experiment. Enthalpies of high-density polymorphs – CaCl2-type, α-PbO2-type, and pyrite-type – for which no experimental data are available as yet, are predicted here. Further, the calculated enthalpies exhibit two distinct regimes as a function of molar volume—for low and medium-density polymorphs, it is almost independent of volume, while for high-pressure phases a steep dependence is seen. A detailed analysis indicates that the increased short-range contributions to enthalpy in the high-density phases arise not only from an increased coordination number of silicon but also shorter Si–O bond lengths. Our results indicate that amorphous phases of silica exhibit better optimization of short-range interactions than crystalline phases at the same density while the magnitude of Coulombic contributions is lower in the amorphous phase.
Quantum dynamical study of the O(1D) + CH4 → CH3 + OH atmospheric reaction
Authors: Ben Bouchrit R. , Jorfi M. , Ben Abdallah D. , Jaidane N. , González M. , Bussery-Honvault B. , Honvault P.
Published: July 2014

Time independent quantum mechanical (TIQM) scattering calculations have been carried out for the O(1D) + CH4(X1A1) → CH3(X2A2″) + OH(X2Π) atmospheric reaction, using an ab initio ground potential energy surface where the CH3 group is described as a pseudo-atom. Total and state-to-state reaction probabilities for a total angular momentum J = 0 have been determined for collision energies up to 0.5 eV. The vibrational and rotational state OH product distributions show no specific behavior. The rate coefficient has been calculated by means of the J-shifting approach in the 10–500 K temperature range and slightly depends on T at ordinary temperatures (as expected for a barrierless reaction). Quantum effects do not influence the vibrational populations and rate coefficient in an important way, and a rather good agreement has been found between the TIQM results and the quasiclassical trajectory and experimental ones. This reinforces somewhat the reliability of the pseudo-triatomic approach under the reaction conditions explored.
Optimal driving of isothermal processes close to equilibrium
Authors: Bonança Marcus V. S. , Deffner Sebastian
Published: July 2014

We investigate how to minimize the work dissipated during nonequilibrium processes. To this end, we employ methods from linear response theory to describe slowly varying processes, i.e., processes operating within the linear regime around quasistatic driving. As a main result, we find that the irreversible work can be written as a functional that depends only on the correlation time and the fluctuations of the generalized force conjugated to the driving parameter. To deepen the physical insight of our approach, we discuss various self-consistent expressions for the response function, and derive the correlation time in closed form. Finally, our findings are illustrated with several analytically solvable examples.
The gas-liquid surface tension of argon: A reconciliation between experiment and simulation
Authors: Goujon Florent , Malfreyt Patrice , Tildesley Dominic J.
Published: July 2014

We present a simulation of the liquid-vapor interface of argon with explicit inclusion of the three-body interactions. The three-body contributions to the surface tension are calculated using the Kirkwood-Buff approach. Monte Carlo calculations of the long-range corrections to the three-body contribution are calculated from the radial distribution function g(2)(z1, cos θ12, r12). Whereas the effective two-body potentials overestimate the surface tension by more than 15%, the inclusion of the three-body potential provides an excellent agreement with the experimental results for temperatures up to 15 K below the critical temperature. We conclude that the three-body interactions must be explicitly included in accurately modelling the surface tension of argon.
Glass transition of ionic liquids under high pressure
Authors: Ribeiro Mauro C. C. , Pádua Agílio A. H. , Gomes Margarida F. Costa
Published: July 2014

The glass transition pressure at room temperature, pg, of six ionic liquids based on 1-alkyl-3-methylimidazolium cations and the anions [BF4]−, [PF6]−, and bis(trifluromethanesulfonyl)imide, [NTf2]−, has been obtained from the pressure dependence of the bandwidth of the ruby fluorescence line in diamond anvil cells. Molar volume, Vm(pg), has been estimated by a group contribution model (GCM) developed for the ionic liquids. A density scaling relation, TVγ, has been considered for the states Vm(pg, 295 K) and Vm(Tg, 0.1 MPa) using the simplifying condition that the viscosity at the glass transition is the same at pg at room temperature and at atmospheric pressure at Tg. Assuming a constant γ over this range of density, a reasonable agreement has been found for the γ determined herein and that of a previous density scaling analysis of ionic liquids viscosities under moderate conditions. Further support for the appropriateness of extrapolating the GCM equation of state to the GPa pressure range is provided by comparing the GCM and an equation of state previously derived in the power law density-scaling regime.
Measurements of elastic properties of langatate at liquid helium temperatures for design of ultra low loss mechanical systems
Authors: Goryachev Maxim , Abbé Philippe , Dulmet Bernard , Bourquin Roger , Galliou Serge
Published: July 2014

We present full characterisation of acoustic wave devices based on the fully synthetic crystalline material at the liquid helium temperature range required for the design of ultra low loss mechanical systems in many areas of research, including frequency control and fundamental measurements. Temperature coefficients of the effective elastic tensor of Langatate (LGT) in Lagrangian representation are determined for the temperature range of 3.8–15 K. The Lagrangian formalism is mandatory in the analysed situation since the expansion coefficients of the LGT are still unknown at these temperatures. The measurement method involves a set of high-quality resonators of various cut angles and uses measurements of frequency-temperature relations to extract the temperature coefficients of the elastic tensor. In addition, power sensitivity of LGT resonators at cryogenic temperatures is determined and dominant loss mechanism is identified.
An acoustic absorber implemented by graded index phononic crystals
Authors: Liang Yu-Jui , Chen Lien-Wen , Wang Ching-Cheng , Chang I-Ling
Published: July 2014

In this paper, we proposed the implementation of a two-dimensional omnidirectional and broadband acoustic absorber using graded index phononic crystals as the shell with an inner absorbing core. The phononic crystal was consisted of circular steel rod arranged as square lattice in air background. The plane wave expansion method was used to obtain the band diagram of the phononic crystal from which the effective refractive index could be computed. The radially distributed refractive index of the acoustic absorber was achieved by placing steel rods with spatially varying radii. The finite element method was employed in order to confirm the acoustic properties of the designed device. Numerical simulations illustrated that the acoustic waves were bent toward the central area by the outer shell and absorbed by the inner core of the implemented acoustic absorber. Furthermore, it was demonstrated that the implemented acoustic absorber could operate independent of the incident wave directions for a relative wide range of frequencies.
Synchrotron-based measurement of the impact of thermal cycling on the evolution of stresses in Cu through-silicon vias
Authors: Okoro Chukwudi , Levine Lyle E. , Xu Ruqing , Hummler Klaus , Obeng Yaw
Published: July 2014

One of the main causes of failure during the lifetime of microelectronics devices is their exposure to fluctuating temperatures. In this work, synchrotron-based X-ray micro-diffraction is used to study the evolution of stresses in copper through-silicon via (TSV) interconnects, “as-received” and after 1000 thermal cycles. For both test conditions, significant fluctuations in the measured normal and shear stresses with depth are attributed to variations in the Cu grain orientation. Nevertheless, the mean hydrostatic stresses in the “as-received” Cu TSV were very low, at (16 ± 44) MPa, most likely due to room temperature stress relaxation. In contrast, the mean hydrostatic stresses along the entire length of the Cu TSV that had undergone 1000 thermal cycles (123 ± 37) MPa were found to be eight times greater, which was attributed to increased strain-hardening. The evolution in stresses with thermal cycling is a clear indication that the impact of Cu TSVs on front-end-of-line (FEOL) device performance will change through the lifetime of the 3D stacked dies, and ought to be accounted for during FEOL keep-out-zone design rules development.
Measurement error of surface-mounted fiber Bragg grating temperature sensor
Authors: Yi Liu , Zude Zhou , Erlong Zhang , Jun Zhang , Yuegang Tan , Mingyao Liu
Published: July 2014

Fiber Bragg grating (FBG) sensors are extensively used to measure surface temperatures. However, the temperature gradient effect of a surface-mounted FBG sensor is often overlooked. A surface-type temperature standard setup was prepared in this study to investigate the measurement errors of FBG temperature sensors. Experimental results show that the measurement error of a bare fiber sensor has an obvious linear relationship with surface temperature, with the largest error achieved at 8.1 °C. Sensors packaged with heat conduction grease generate smaller measurement errors than do bare FBG sensors and commercial thermal resistors. Thus, high-quality packaged methods and proper modes of fixation can effectively improve the accuracy of FBG sensors in measuring surface temperatures.
Investigation of fade-out mechanism of resonance modes in optical transmission using stacked metallic sub-wavelength slit arrays
Authors: Tokuda Yasunori , Sakaguchi Koichiro , Takano Keisuke , Fukushima Takehiro , Hangyo Masanori
Published: July 2014

We investigated the behavior of optical transmission modes in stacked systems composed of metallic sub-wavelength slit-array plates separated by air gaps using simulations based on the finite-difference time-domain method. In double- and triple-stacked structures without a lateral displacement between the plates, the Fabry-Perot-like waveguide resonance modes are classified according to whether the resonance frequencies depend strongly on the air-gap spacing. By introducing a lateral displacement of the plates for both double- and triple-stacked structures, we found that the modes of one category, which were barely affected by changes in the air-gap spacing without the displacement, vary their resonance frequencies considerably when the optical paths are extremely narrow within the air-gap regions and, then, rapidly but continuously attenuate through mixing with the modes of the other category. We demonstrate that this marked behavior results from a manifest distortion in the spatial distribution of the electromagnetic fields for the modes of the first category, induced by the boundary condition at the slit ends changing from open-open to open-closed. Although all resonance modes in the two-tier system disappear continuously through cooperative mode mixing, some modes remain in the three-tier system that vanishes independently and discontinuously as the optical paths become blocked. These findings are indispensable for practical applications and for gaining a deeper understanding of this type of metamaterial.
Cost effective nanostructured copper substrates prepared with ultrafast laser pulses for explosives detection using surface enhanced Raman scattering
Authors: Hamad Syed , Podagatlapalli G. Krishna , Mohiddon Md. Ahamad , Soma Venugopal Rao
Published: July 2014

Ultrafast laser pulses induced surface nanostructures were fabricated on a copper (Cu) target through ablation in acetone, dichloromethane, acetonitrile, and chloroform. Surface morphological information accomplished from the field emission scanning electron microscopic data demonstrated the diversities of ablation mechanism in each case. Fabricated Cu substrates were utilized exultantly to investigate the surface plasmon (localized and propagating) mediated enhancements of different analytes using surface enhance Raman scattering (SERS) studies. Multiple utility of these substrates were efficiently demonstrated by collecting the SERS data of Rhodamine 6G molecule and two different secondary explosive molecules such as 5-amino-3-nitro-l,2,4-triazole and trinitrotoluene on different days which were weeks apart. We achieved significant enhancement factors of >105 through an easily adoptable cleaning procedure.
Experimental study on vertical scaling of InAs-on-insulator metal-oxide-semiconductor field-effect transistors
Authors: Kim SangHyeon , Yokoyama Masafumi , Nakane Ryosho , Ichikawa Osamu , Osada Takenori , Hata Masahiko , Takenaka Mitsuru , Takagi Shinichi
Published: July 2014

We have investigated effects of the vertical scaling on electrical properties in extremely thin-body InAs-on-insulator (-OI) metal-oxide-semiconductor field-effect transistors (MOSFETs). It is found that the body thickness (Tbody) scaling provides better short channel effect (SCE) control, whereas the Tbody scaling also causes the reduction of the mobility limited by channel thickness fluctuation (δTbody) scattering (μfluctuation). Also, in order to achieve better SCEs control, the thickness of InAs channel layer (Tchannel) scaling is more favorable than the thickness of MOS interface buffer layer (Tbuffer) scaling from a viewpoint of a balance between SCEs control and μfluctuation reduction. These results indicate necessity of quantum well channel structure in InAs-OI MOSFETs and these should be considered in future transistor design.
Charge tunneling and trapping in Er stabilized β-MnO2 films for memory applications
Authors: Cui Jian , Ji Ting , Nie Tianxiao , Jiang Zuimin
Published: July 2014

Recently, the memory effect was observed in Er stabilized β-MnO2 metal oxide semiconductor structure. In this work, the electric properties and mechanism of charge tunneling and trapping are studied by combining frequency-dependent capacitance-voltage curves, variable sweep range capacitance-voltage curves, and current-voltage curves. The charge traps are identified to be deep donors in β-MnO2. The deep donor level is close to the valance band, which results in the asymmetric enlargement in variable sweep range capacitance-voltage curves. Resonant tunneling and Fowler-Nordheim tunneling mechanisms are observed at low and high voltages, respectively. All these phenomena can be explained by the proposed model as a whole. The experimental evidence shows that Er-stabilized β-MnO2 is a good candidate charge storage material in nonvolatile memory devices.
Voltage polarity manipulation of the magnetoresistance sign in organic spin valve devices
Authors: Jiang S. W. , Chen B. B. , Wang P. , Zhou Y. , Shi Y. J. , Yue F. J. , Ding H. F. , Wu D.
Published: July 2014

The spin transport in organic spin valve (OSV) devices has been systematically investigated by inserting a low work function material Al between ferromagnetic electrode and organic layer. The resistance and current-voltage curve symmetry are dramatically altered as increasing Al thickness, indicating that an electron-unipolar OSV is obtained. Moreover, the magnetoresistance sign depends on the voltage polarity for certain Al thickness. We attribute this phenomenon to the Fermi and the lowest unoccupied molecular orbits energies of the two electrodes responding to the spin injection and detection, respectively. These findings provide a simple approach to control both the carrier type and the spin direction simultaneously.
Growth and characterization of horizontal GaN wires on silicon
Authors: Zou Xinbo , Lu Xing , Lucas Ryan , Kuech Thomas F. , Choi Jonathan W. , Gopalan Padma , May Lau Kei
Published: July 2014

We report the growth of in-plane GaN wires on silicon by metalorganic chemical vapor deposition. Triangular-shaped GaN microwires with semi-polar sidewalls are observed to grow on top of a GaN/Si template patterned with nano-porous SiO2. With a length-to-thickness ratio ∼200, the GaN wires are well aligned along the three equivalent 〈112¯0〉 directions. Micro-Raman measurements indicate negligible stress and a low defect density inside the wires. Stacking faults were found to be the only defect type in the GaN wire by cross-sectional transmission electron microscopy. The GaN wires exhibited high conductivity, and the resistivity was 20–30 mΩ cm, regardless of the wire thickness. With proper heterostructure and doping design, these highly aligned GaN wires are promising for photonic and electronic applications monolithically integrated on silicon.
High precision two-dimensional strain mapping in semiconductor devices using nanobeam electron diffraction in the transmission electron microscope
Authors: Baumann Frieder H.
Published: July 2014

A classical method used to characterize the strain in modern semiconductor devices is nanobeam diffraction (NBD) in the transmission electron microscope. One challenge for this method lies in the fact that the smaller the beam becomes, the more difficult it becomes to analyze the resulting diffraction spot pattern. We show that a carefully designed fitting algorithm enables us to reduce the sampling area for the diffraction patterns on the camera chip dramatically (∼1/16) compared to traditional settings without significant loss of precision. The resulting lower magnification of the spot pattern permits the presence of an annular dark field detector, which in turn makes the recording of images for drift correction during NBD acquisition possible. Thus, the reduced sampling size allows acquisition of drift corrected NBD 2D strain maps of up to 3000 pixels while maintaining a precision of better than 0.07%. As an example, we show NBD strain maps of a modern field effect transistor (FET) device. A special filtering feature used in the analysis makes it is possible to measure strain in silicon devices even in the presence of other crystalline materials covering the probed area, which is important for the characterization of the next generation of devices (Fin-FETs).
Actively bias-controlled metamaterial to mimic and modulate electromagnetically induced transparency
Authors: Meng Dejia , Wang Shuyang , Sun Xiaoliang , Gong Rongzhou , Chen Changhong
Published: July 2014

We present an active microwave metamaterial composed of orthogonally arranged cut wires and positive-intrinsic-negative diodes, having capability of high-speed response. When a forward voltage is applied to turn the diodes on, analogue spectral response of a classical electromagnetically induced transparency is observed at 6.13 GHz for destructive interference between dipolar and quadrupolar resonances in the cut wires. Besides, experiments demonstrate that around the frequency, response amplitude is modulated continuously by sweeping the bias, and intensity modulation depth is up to 85%. Surface current distributions verify that the diode conductivity decides coupling efficiency of the resonant fields and consequent the amplitude. Simulated and measured spectra are in good agreement.