bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of injectable organic–inorganic hybrid for bone tissue repair
Authors: Dessì Mariagemiliana , Raucci Maria Grazia , Zeppetelli Stefania , Ambrosio Luigi
Published: May 2012

Injectable bone substitutes are rapidly gained success in tissue engineering applications for their less invasive surgical aspect. Here, the design and the characterization of a novel degradable paste of PCL reinforced with nanocrystals of hydroxyapatite have been presented aiming to mimic natural tissue. Nanohydroxyapatite has been successfully synthesized via sol–gel technique. Dynamic and steady state viscoelastic properties of the solutions and paste were investigated to control the kinetic of phase transition. Correspondingly, the morphology and composition were characterized via TEM, EDAX, and thermal analysis. Injection test underlines the completely ability of the paste of being injected without altering its features. Preliminary biological study showed that the composite paste is not cytotoxic. The synergistic rheological and biological properties, combined with the positive effect of chemical synthesis method indicate that the composite paste is very suitable as local bone substitute in low‐load areas. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2012.
Left anterior descending artery occlusion secondary to blunt chest trauma diagnosed by comprehensive echocardiography and coronary angiography
Authors: Sun Lin , Li Zhi‐an , Zhao Ying , Han Jiancheng , Henein Michael Y.
Published: May 2012

Blunt chest trauma can cause serious complications, but coronary artery occlusion is rare. In a 19‐year‐old man, 40 days after a motorcycle accident, comprehensive echocardiography detected left anterior descending artery occlusion and left ventricular dysfunction, which was confirmed by coronary angiography and ventriculography. Echocardiography was also able to confirm restored left anterior descending artery flow and improved left ventricular function after coronary artery bypass grafting. © 2012 Wiley Periodicals, Inc. J Clin Ultrasound, 2012;
Polymethacrylate‐based monolithic capillary column with weak cation exchange functionalities for capillary electrochromatography
Authors: Aydoğan Cemil , Tuncel Ali , Denizli Adil
Published: May 2012

Polymethacrylate‐based monolith with weak cation exchange functionalities was prepared in capillary column (i.d. 100 μm, o.d. 375 μm) by in situ polymerization of butyl methacrylate, ethylene dimethacrylate and N‐methacryloyl‐L‐glutamic acid in presence of porogens. The porogen mixture included N,N‐dimethyl formamide and phosphate buffer. The preparation procedure of stationary phase contained the synthesis of monomer, silanization of capillary inner wall and in situ polymerization. The use of amino acid based monomer for the monolith synthesis is one of the originalities of this novel approach. N‐methacryloyl‐L‐glutamic acid has two carboxyl functionalities. The separation of the solutes were performed at different acetonitrile/phosphate buffer and acetonitrile/sodium hydroxide contents. The applied voltage for the alkyl benzenes was changed between +5 and +30 kV. CEC separations of alkyl benzenes, acidic, basic, phenolic and some polycylic aromatic compounds were succesfully performed under capillary‐electrochromatography mode with cathodic electroosmotic flow.
Bioassay‐guided isolation of antioxidants from Astragalus altaicus by combination of chromatographic techniques
Authors: Yang Chunyan , Yang Yi , Aisa Haji Akber , Xin Xuelei , Ma Hairong , Yili Abulimiti , Zhao Yongxin
Published: May 2012

An efficient method for bioassay‐guided preparative isolation of antioxidants from the n‐butanol extract of Astragalus altaicus Bunge was ingeniously developed by combination of silica gel column chromatography and high‐speed counter‐current chromatography. Under the bioassay‐guidance of antioxidant activities, the antioxidants were gradually separated from the crude sample of Astragalus altaicus Bunge by silica gel column chromatography and high‐speed counter‐current chromatography. Silica gel column chromatography separation was performed with chloroform, chloroform–methanol (100:1∼5:1, v/v) and chloroform–methanol–water (5:1:0.1∼2:1:0.1, v/v/v). High‐speed counter‐current chromatography separation was performed with a two‐phase solvent system composed of ethyl acetate–n‐butanol–water (2:1:6, v/v/v), which was successfully selected by thin layer chromatography analysis, at a flow rate of 1.5 mL/min. As a result, isorhamnetin‐3‐gentiobioside (20.8 mg), rutin (82.0 mg), and narcissin (12.8 mg) were obtained for the first time from 200 mg of the crude sample, ABS‐5 of Astragalus altaicus Bunge. The purities were all at over 95% by high‐performance liquid chromatography analysis, and their structures were unambiguously identified by mass spectroscopy, 1H, and 13C nuclear magnetic resonance spectroscopy. Antioxidant activities of the three compounds were also assayed by in vitro ABTS [2,2′‐azino‐bis‐(3‐ethylbenzothiazoline‐6‐sulphonic acid) diamonium salt] radical cation scavenging activity. Among them, rutin possessed the highest antioxidant capacity with SC50 value of 22.15 μg/mL.
Scoring protein interaction decoys using exposed residues (SPIDER): A novel multibody interaction scoring function based on frequent geometric patterns of interfacial residues
Authors: Khashan Raed , Zheng Weifan , Tropsha Alexander
Published: May 2012

Accurate prediction of the structure of protein–protein complexes in computational docking experiments remains a formidable challenge. It has been recognized that identifying native or native‐like poses among multiple decoys is the major bottleneck of the current scoring functions used in docking. We have developed a novel multibody pose‐scoring function that has no theoretical limit on the number of residues contributing to the individual interaction terms. We use a coarse‐grain representation of a protein–protein complex where each residue is represented by its side chain centroid. We apply a computational geometry approach called Almost‐Delaunay tessellation that transforms protein–protein complexes into a residue contact network, or an undirectional graph where vertex‐residues are nodes connected by edges. This treatment forms a family of interfacial graphs representing a dataset of protein–protein complexes. We then employ frequent subgraph mining approach to identify common interfacial residue patterns that appear in at least a subset of native protein–protein interfaces. The geometrical parameters and frequency of occurrence of each “native” pattern in the training set are used to develop the new SPIDER scoring function. SPIDER was validated using standard “ZDOCK” benchmark dataset that was not used in the development of SPIDER. We demonstrate that SPIDER scoring function ranks native and native‐like poses above geometrical decoys and that it exceeds in performance a popular ZRANK scoring function. SPIDER was ranked among the top scoring functions in a recent round of CAPRI (Critical Assessment of PRedicted Interactions) blind test of protein–protein docking methods. Proteins 2012; © 2012 Wiley Periodicals, Inc.
Ionization and double‐excitations within the framework of the G‐particle‐hole hypervirial equation method
Authors: Valdemoro Carmela , Alcoba Diego R. , Tel Luis M.
Published: May 2012

Recently, through the use of one‐electron excitation operators, the set of low‐lying excited states of several electronic systems was obtained within the framework of the Hermitian Operator method combined with the G‐particle‐hole Hypervirial equation method [Valdemoro et al., J. Math. Chem. 2012, 50, 492]. The main aim of this article is to extend our study by including higher‐order excitations as well as extended ionization and electron affinity operators. Several examples show the convenience of this extension to improve the accuracy of the results in some relevant cases. Through the use of geminal excitations, the algebra of the formal derivations is considerably simplified. © 2012 Wiley Periodicals, Inc.
TRANSFERABILITY OF HYDRAULIC PREFERENCE MODELS FOR AQUATIC MACROINVERTEBRATES
Authors: Lamouroux N. , Mérigoux S. , Dolédec S. , Snelder T. H.
Published: May 2012

Quantifying the transferability across stream reaches and sampling occasions of models relating the density of aquatic taxa to microhabitat hydraulics are important for increasing our understanding of the mechanisms explaining microhabitat selection. We revisited data collected at multiple occasions in two regions, that is, in nine reaches of seven German streams and in four reaches of a large French river, to provide detailed information by taxon on the transferability of hydraulic preferences of aquatic macroinvertebrates. In each region and for each taxon, we tested the statistical significance of a regional preference model relating density to microhabitat hydraulics simultaneously in all surveys (i.e. reach–occasion combinations). The transferability of hydraulic preferences was assessed using cross‐validation procedures within each region. The regional models showed significant associations with microhabitat hydraulics for 56% of the 151 taxa collected in Germany and for 67% of 66 taxa in France. Cross validations indicated that regional models significantly explained density variations within independent surveys for 60% of the cases in Germany and 54% in France. We conclude that both regional and survey‐specific models are useful in specific studies, depending on the taxa considered and the spatial extent and objectives of the application. Graphs of all raw data and models are supplied as supporting information. Copyright © 2012 John Wiley & Sons, Ltd.
Is the Exponent 3/2 Justified in Analysis of Loading Curve of Pyramidal Nanoindentations?
Authors: Troyon M. , Abbès F. , Garcia Guzman J. A.
Published: May 2012

Kaupp and Naimi‐Jamal (2010) claimed that the analysis of published loading curves reveals the exponent 3/2 to the depth for nanoindentations with sharp pyramidal or conical tips. To demonstrate this, they plotted the load vs. the penetration depth to the power 3/2. We show, through examples, the authors’ assertion is not credible because the methodology used is misleading and it cannot be asserted that the exponent 3/2 has a universal validity that applies to all kinds of materials. SCANNING 34: 410‐417, 2012. © 2012 Wiley Periodicals, Inc.
Thermodynamic Parameters of Anionic Surfactant‐Quaternary Phosphonium Bromides Systems at the Cloud Point
Authors: Khan Ziya Ahmad , Albishri Hassan M. , Ghazali Arniza , Ahmad Tanweer
Published: May 2012

The thermodynamics of clouding in an anionic surfactant, sodium dodecyl sulfate (SDS) and quaternary phosphonium bromides systems in the presence of glycerol are reported. The standard Gibbs energy change of solubilization (ΔsG°) for all of the additives was found to be negative. The standard enthalpy change (ΔsH°) and the standard entropy change (TΔsS°) values were found to be negative as well as positive depending upon the type and nature of the additive. The results were explained on the basis of their nature, effect on the water structure, and solubilization of these additives either in the micellar or aqueous phase.
‘Permanent’ Care: Is the Story in the Data?
Authors: Humphreys Cathy
Published: May 2012

Planning for ‘permanency’ or a ‘family for life’ has been an aspiration for many children in the out-of-home care system who are unable to return to live with their parents. It is a concept derived from research, which indicates that children who ‘drift in care’ have generally poorer outcomes than those who find at least a more stable, if not ‘permanent’, home. This article examines the Australian Institute of Health and Welfare [AIHW] data that reports publicly on child protection and children in out-of-home care to find evidence about how Australian children in out-of-home care are faring against this dimension of the care experience. Little can be said on the basis of this data. The article is written as a ‘think piece’ to raise questions about why, if such a dimension of the care experience is considered important for a significant group of children, the data is so opaque.
Posterior semicircular canal occlusion for intractable benign positional vertigo: outcome in 55 ears in 53 patients operated upon over 20 years
Authors: Ahmed R M , Pohl D V , MacDougall H G , Makeham T , Halmagyi G M
Published: May 2012

Objective:

To report the outcome of posterior semicircular canal occlusion surgery for intractable benign positional vertigo, regarding vertigo cure rate and hearing and balance outcomes.

Methods:

Retrospective review of 53 patients presenting with benign positional vertigo, unresponsive to repositioning manoeuvres, who eventually underwent posterior canal occlusion, over a 20 year period.

Results:

From 1991 to 2011, 5364 benign positional vertigo patients were treated in our balance disorders clinic; 53 of those who failed to respond to repositioning underwent posterior canal occlusion. All 53 were cured of their benign positional vertigo. Nine suffered some symptomatic permanent hearing loss (>20 dB at low and >25 dB at high frequencies). Ten patients suffered caloric vestibular function deterioration, with mild but permanent subjective imbalance in five; a further 10 patients with no post-operative caloric test changes also had some permanent imbalance. Benign positional vertigo later developed in the operated ear lateral canal in two patients and in the opposite ear posterior canal in eight patients. Two patients needed bilateral sequential posterior canal occlusion.

Conclusion:

Posterior canal occlusion is a highly effective treatment for intractable benign positional vertigo, with what is probably an acceptable risk to hearing and balance: five of six patients will have no hearing problem and nine of 10 no balance problem after surgery.
Eternity, knowledge, and freedom
Authors: DIEKEMPER JOSEPH
Published: May 2012

This article addresses the problem of divine foreknowledge and human freedom by developing a modified version of Boethius' solution to the problem – one that is meant to cohere with a dynamic theory of time and a conception of God as temporal. I begin the article by discussing the traditional Boethian solution, and a defence of it due to Kretzmann and Stump. After canvassing a few of the objections to this view, I then go on to offer my own modified Boethian solution, according to which temporal reality is fundamentally dynamic, but truth is not. My claim is that there are eternally existing, tenseless propositions, with determinate truth values, but that these are made true by events that come into existence, and are not themselves eternal.
On grounding God's knowledge of the probable
Authors: JENSEN JENNIFER
Published: May 2012

A common objection to the Molinist account of divine providence states that counterfactuals of creaturely freedom (CCFs) lack grounds. Some Molinists appeal to brute counterfactual facts about the subject of the CCF in order to ground CCFs. Others argue that CCFs are grounded by the subject's actions in nearby worlds. In this article, I argue that Open Theism's account of divine providence employs would-probably conditionals that are most plausibly grounded by either brute facts about the subject of these conditionals or non-actual entities. As a result, Open Theism's revision of the traditional notion of divine providence is unmotivated. The Molinist can ground CCFs just as easily as the Openist can ground would-probably conditionals but the Molinist has the advantage of maintaining a robust account of divine providence.
Representation, Replication, Reproduction: The Legacy of Charles V in Sculpted Rulers' Portraits of the Sixteenth and Early Seventeenth Century
Authors: Kaufmann Thomas DaCosta
Published: May 2012

All rulers' portraits are, in several senses, forms of representation. In the first and most obvious instance, all portraits epitomize one of the basic functions of visual art as imitation (mimesis). Portraits represent a person by providing his or her likeness. The Renaissance sculptor Vincenzo Danti (1530–1576), a contemporary of the artists discussed here, pointed to this basic mimetic function when he defined one of the fundamental forms of artistic imitation as ritrarre, using a verb related to the Italian word for portrait, ritratto. Because they are works in three dimensions, sculpted portraits may approach this end even more directly, as seen in the sculpted heritage of Charles V that is the subject of this paper. In any case, hyperrealist works of the 1970s and wax sculpture of the past, including a small wax sculpture of Emperor Rudolf II with a favorite hound (London, Victoria and Albert Museum) (see Figure 1), demonstrate that sculpture may make the effort to portray individuals as close to life as possible.
Performing the Rest Cure: Mrs Patrick Campbell's Ophelia, 1897
Authors: Gregory Fiona
Published: May 2012

In 1897 audiences welcomed Johnston Forbes-Robertson's new interpretation of Hamlet to the London stage, and his sane, intelligent Prince was received as an exciting departure from tradition. Mrs Patrick Campbell's own experiments with the role of Ophelia in this production were not so warmly greeted, critics describing her playing as ‘curiously weak’ and ‘unconvincing and unimpressive’. Campbell had rejected the conventional model of the character as emblematic of the prettiness and pathos exemplified by Ellen Terry, and instead offered a vacant, depressive, ‘beaten’ Ophelia. In this article, Fiona Gregory examines the influences behind this choice, including the actress's own experience of mental illness and the notorious ‘rest cure’. The reception of the performance is read in terms of contemporary attitudes to Ophelia and mental illness, as well as of responses to Campbell and her celebrity identity in the visual arts. Ultimately, Campbell's performance of Ophelia can be read as a ‘witness account’ of neurasthenia and the ‘rest cure’, to stand alongside texts such as Charlotte Perkins Gilman's story ‘The Yellow Wallpaper’. Fiona Gregory lectures in the Centre for Theatre and Performance at Monash University, and has published work on the career of actress Judith Anderson, Australian cultural history, and Victorian and Edwardian writers. She is currently undertaking a wide-ranging study of actresses and mental illness from the nineteenth century to the present day, drawing on historical examples and literary and cultural representations to consider the intersections of ‘hysteria’ and the ‘histrionic’.
Letter to a Dead Playwright: Daily Grind, Vicki Reynolds, and Archive Fever
Authors: D'Cruz Glenn
Published: May 2012

’Nothing is less reliable, nothing is less clear today than the word “archive”,’ observed Jacques Derrida in his book Archive Fever: a Freudian Impression (1996). This paper reflects on the unsettling process of establishing (or commencing) an archive for the Melbourne Workers Theatre, to form part of the AusStage digital archive which records information on live performance in Australia. Glenn D'Cruz's paper juxtaposes two disparate but connected registers of writing: an open letter to a deceased Australian playwright, Vicki Reynolds, and a critical reflection on the politics of the archive with reference to Derrida's account of archive fever, which he characterizes as an ‘irrepressible desire to return to the origin, a homesickness, a nostalgia for the return to the most archaic place of absolute commencement’. Using Derrida's commentary on questions of memory, authority, inscription, hauntology, and heritage to identify some of the philosophical and ethical aporias he encountered while working on the project, D’Cruz pays particular attention to what Derrida calls the spectral structure of the archive, and stages a conversation with the ghosts that haunt the digitized Melbourne Workers Theatre documents. He also unpacks the logic of Derrida's so-called messianic account of the archive, which ‘opens out of the future’, thereby affirming the future-to-come, and unsettling the normative notion of the archive as a repository for what has passed. Glenn D’Cruz teaches at Deakin University, Australia. He is the author of Midnight's Orphans: Anglo-Indians in Post/Colonial Literature (Peter Lang, 2006) and editor of Class Act: Melbourne Workers Theatre 1987–2007 (Vulgar Press, 2007).
Imaging meso‐scale ionospheric structures
Authors: Burston Robert
Published: May 2012

The accuracy and capacity to resolve meso‐scale structures of a four dimensional ionospheric imaging algorithm in the circumstance of data from dense networks of permanent GNSS ground receiver stations were investigated. Simulation studies were conducted in order to be able to assess the performance of the algorithm over the entire imaged region. The Multi‐instrument Data Assimilation Software (MIDAS) algorithm was used for this purpose. Simulated input data in Receiver Independent Exchange Format (RINEX) were produced by calculating slant Total Electron Content (sTEC) values for satellite to receiver raypaths through an artificially generated ionosphere. Modeling these signals including Differential Code Biases (DCBs) and noise had negligible impact on the output from the imaging algorithm when compared with modeled signals that included neither. Comparing the output from MIDAS using a range of grid definitions show that finer grids have improved capacity to resolve meso‐scale structures in the input model but over all are less accurate than coarser grids. The greatest errors occur in low‐data regions of the grid and where structures in the input have the greatest gradients in vertical Total Electron Content (vTEC). A good compromise between the conflicting needs of resolution and accuracy is given by a grid defined with 2° × 2° latitude by longitude local horizontal grid divisions.
Frequency-selective plasmonic wave propagation through the overmoded waveguide with photonic-band-gap slab arrays
Authors: Shin Young-Min
Published: May 2012

Confined propagation of guided waves through the periodically corrugated channel sandwiched between two staggered dielectric photonic-band-gap slab arrays is investigated with the band-response analysis. Numerical simulations show that longitudinally polarized evanescent waves within the band gap propagate with insertion loss of ∼−0.2 to 1 dB (−0.05 to 0.4 dB/mm at G-band) in the hybrid band filter. This structure significantly suppresses low energy modes and higher-order-modes beyond the band-gap, including background noises, down to ∼−45 dB. This would enable the single-mode propagation in the heavily over-moded waveguide (TEM-type), minimizing abnormal excitation probability of trapped modes. This band filter could be integrated with active and passive RF components for electron beam and optoelectronic devices.
Dopant effects on the photoluminescence of interstitial-related centers in ion implanted silicon
Authors: Johnson B. C. , Villis B. J. , Burgess J. E. , Stavrias N. , McCallum J. C. , Charnvanichborikarn S. , Wong-Leung J. , Jagadish C. , Williams J. S.
Published: May 2012

The dopant dependence of photoluminescence (PL) from interstitial-related centers formed by ion implantation and a subsequent anneal in the range 175–525 °C is presented. The evolution of these centers is strongly effected by interstitial-dopant clustering even in the low temperature regime. There is a significant decrease in the W line (1018.2 meV) PL intensity with increasing B concentration. However, an enhancement is also observed in a narrow fabrication window in samples implanted with either P or Ga. The anneal temperature at which the W line intensity is optimized is sensitive to the dopant concentration and type. Furthermore, dopants which are implanted but not activated prior to low temperature thermal processing are found to have a more detrimental effect on the resulting PL. Splitting of the X line (1039.8 meV) arising from implantation damage induced strain is also observed.
Efficient quantum-classical method for computing thermal rate constant of recombination: Application to ozone formation
Authors: Ivanov Mikhail V. , Babikov Dmitri
Published: May 2012

Efficient method is proposed for computing thermal rate constant of recombination reaction that proceeds according to the energy transfer mechanism, when an energized molecule is formed from reactants first, and is stabilized later by collision with quencher. The mixed quantum-classical theory for the collisional energy transfer and the ro-vibrational energy flow [M. Ivanov and D. Babikov, J. Chem. Phys. 134, 144107 (2011)]10.1063/1.3576103 is employed to treat the dynamics of molecule + quencher collision. Efficiency is achieved by sampling simultaneously (i) the thermal collision energy, (ii) the impact parameter, and (iii) the incident direction of quencher, as well as (iv) the rotational state of energized molecule. This approach is applied to calculate third-order rate constant of the recombination reaction that forms the 16O18O16O isotopomer of ozone. Comparison of the predicted rate vs. experimental result is presented.
Nanocrystalline-to-amorphous transition in nanolaminates grown by low temperature atomic layer deposition and related mechanical properties
Authors: Raghavan R. , Bechelany M. , Parlinska M. , Frey D. , Mook W. M. , Beyer A. , Michler J. , Utke I.
Published: May 2012

We report on a comprehensive structural and nanoindentation study of nanolaminates of Al2O3 and ZnO synthesized by atomic layer deposition (ALD). By reducing the bilayer thickness from 50 nm to below 1 nm, the nanocrystal size could be controlled in the nanolaminate structure. The softer and more compliant response of the multilayers as compared to the single layers of Al2O3 and ZnO is attributed to the structural change from nanocrystalline to amorphous at smaller bilayer thicknesses. It is also shown that ALD is a unique technique for studying the inverse Hall-Petch softening mechanism (E. Voce and D. Tabor, J. Inst. Metals 79(12), 465 (1951)) related to grain size effects in nanomaterials.
Highly efficient thermal glue for carbon nanotubes based on azide polymers
Authors: Ni Yuxiang , Le Khanh Hung , Chalopin Yann , Bai Jinbo , Lebarny Pierre , Divay Laurent , Volz Sebastian
Published: May 2012

Equilibrium molecular dynamics (EMD) simulations and experimental data show that the thermal contact resistance (TCR) between carbon nanotube (CNT) and azide-functionalized polymer with C-N bond is significantly decreased compared to that with Van der Waals force interaction. EMD simulations indicate that C-N covalent bond between CNT and polymer is the most efficient way to reduce TCR, and we measured the lowest thermal interface resistance of Si/CNT/Polymer/Cu thermal interface material as 1.40 mm2 KW−1 with CNTs of 10 μm length. These results provide useful information for future designs of thermal glue for carbon-based materials with better thermal conduction.
High fraction of substitutional phosphorus in a (100) diamond epilayer with low surface roughness
Authors: Pinault-Thaury M.-A. , Berini B. , Stenger I. , Chikoidze E. , Lusson A. , Jomard F. , Chevallier J. , Barjon J.
Published: May 2012

For high power electronics, diamond is a promising semiconductor with phosphorus being the current substitutional donor. However, up to now, in (100) oriented grown diamond, only a small fraction of phosphorus atoms is incorporated in substitutional sites (<30%) and the epilayer surface exhibits macrosteps. In this work, we present a (100) phosphorus-doped diamond epilayer where ∼100% of the phosphorus atoms are incorporated in substitutional sites. The film exhibits a low surface roughness (RMS = 0.5 nm). Our epilayer is conductive (ρ = 5.0 × 106 Ω · cm at 300 K) and neutral phosphorus are detected in infrared absorption.
A study on density functional theory of the effect of pressure on the formation and migration enthalpies of intrinsic point defects in growing single crystal Si
Authors: Sueoka Koji , Kamiyama Eiji , Kariyazaki Hiroaki
Published: May 2012

In 1982, Voronkov presented a model describing point defect behavior during the growth of single crystal Si from a melt and derived an expression to predict if the crystal was vacancy- or self-interstitial-rich. Recently, Vanhellemont claimed that one should take into account the impact of compressive stress introduced by the thermal gradient at the melt/solid interface by considering the hydrostatic pressure dependence of the formation enthalpy of the intrinsic point defects. To evaluate the impact of thermal stress more correctly, the pressure dependence of both the formation enthalpy (Hf) and the migration enthalpy (Hm) of the intrinsic point defects should be taken into account. Furthermore, growing single crystal Si is not under hydrostatic pressure but almost free of external pressure (generally in Ar gas under reduced pressure). In the present paper, the dependence of Hf and Hm on the pressure P, or in other words, the pressure dependence of the formation energy (Ef) and the relaxation volume (vf), is quantified by density functional theory calculations. Although a large number of ab initio calculations of the properties of intrinsic point defects have been published during the last years, calculations for Si crystals under pressure are rather scarce. For vacancies V, the reported pressure dependences of HfV are inconsistent. In the present study, by using 216-atom supercells with a sufficient cut-off energy and mesh of k-points, the neutral I and V are found to have nearly constant formation energies EfI and EfV for pressures up to 1 GPa. For the relaxation volume, vfI is almost constant while vfV decreases linearly with increasing pressure P. In case of the hydrostatic pressure Ph, the calculated formation enthalpy HfI and migration enthalpy HmI at the [110] dumbbell site are given by HfI = 3.425 − 0.057 × Ph (eV) and HmI = 0.981 − 0.039 × Ph (eV), respectively, with Ph given in GPa. The calculated HfV and HmV dependencies on Ph given by HfV = 3.543 − 0.021 × Ph2 − 0.019 × Ph (eV) and HmV = 0.249 + 0.018 × Ph2 − 0.037 × Ph (eV), respectively. These results indicate that, when assuming that the pre-factors in the Arrhenius equation are not influenced, hydrostatic pressure up to 1 GPa leads to a slight increase of the thermal equilibrium concentration and diffusion of vacancies but this increase is much smaller than that of self-interstitials. The thermal stress in growing Si crystal is compressive, and thus the point defects are under internal pressure. Taking into account the differences in the enthalpies of point defects between hydrostatic pressure and internal pressure, Si crystal shifts to being V-rich with an increase in thermal stress during crystal growth.
Sequential three-step three-photon near-infrared quantum splitting in β-NaYF4:Tm3+
Authors: Yu D. C. , Ye S. , Peng M. Y. , Zhang Q. Y. , Wondraczek L.
Published: May 2012

We report on sequential three-step three-photon near-infrared (NIR) quantum splitting in Tm3+-doped β-NaYF4, where an incident blue photon around 470 nm is split into three NIR photons (1165, 1466, and 1800 nm). The underlying mechanism is analyzed by means of static and dynamic photoemission spectroscopy. Here, an experimental total quantum yield of ∼32% is obtained. When quenching due to residual hydroxyl groups and other defect species can be overcome, numerical analyses indicate a theoretical maximum quantum yield of 158%, suggesting application in efficient spectral converters.
Low-temperature dielectric response of NaTaO3 ceramics and films
Authors: Tkach A. , Almeida A. , Moreira J. Agostinho , Perez de la Cruz J. , Romaguera-Barcelay Y. , Vilarinho P. M.
Published: May 2012

In this work, NaTaO3 ceramics are prepared by conventional mixed oxide method and NaTaO3 films are deposited by RF magnetron sputtering on Si/SiO2/TiO2/Pt substrates. The dielectric response of the obtained NaTaO3 ceramics and films is analyzed as a function of frequency and temperature. Between 1 kHz and 1 MHz, the dielectric permittivity of NaTaO3 ceramics is frequency independent and increases on cooling up to ∼324, which is the highest value ever reported for NaTaO3 ceramics. In contrast, NaTaO3 films exhibit a dielectric relaxation between ∼20 and 30 K, following the Arrhenius law with activation energy ∼51 meV and pre-exponential term ∼10−15 s and attributed to polaron hopping.
Nm-scale measurements of fast surface potential transients in an AlGaN/GaN high electron mobility transistor
Authors: Cardwell D. W. , Arehart A. R. , Poblenz C. , Pei Y. , Speck J. S. , Mishra U. K. , Ringel S. A. , Pelz J. P.
Published: May 2012

Fast, bias-induced, surface potential transients (SPTs) and conductance transients (CTs) were simultaneously measured on an AlGaN/GaN high electron mobility transistor. SPTs measured near the drain-side gate edge and CTs have nearly the same shape and are well-fit with two exponentials having room-temperature time constants of 4.2 ms and 36 ms, likely indicating emission from two trap species. Kelvin probe force microscopy was used to measure SPTs. Electrostatic simulations of SPT amplitudes, which account for the measured probe/sample geometry, are consistent with a uniform trapped surface charge density of 7 × 1012 electrons/cm2 extending 200 nm from the drain-side gate edge.
The relaxation of intrinsic compressive stress in complementary metal-oxide-semiconductor transistors by additional N ion implantation treatment with atomic force microscope-Raman stress extraction
Authors: Liao M.-H. , Chen C.-H. , Chang L.-C. , Yang C. , Kao S.-C.
Published: May 2012

Based on the stress extraction and measurement by atomic force microscope-Raman technique with the nanometer level space resolution, the high compressive stress about 550 MPa on the Si active region (OD) is observed for the current complementary metal-oxide-semiconductor (CMOS) transistor. During the thermal budget for the standard manufacture process of the current CMOS transistor, the difference of thermal expansion coefficients between Si and Shallow Trench Isolation (STI) oxide results in this high compressive stress in Si OD and further degrades the electron carrier mobility seriously. In order to relax this intrinsic processed compressive stress in Si OD and try to recover this performance loss, the novel process is proposed in this work in addition to the usage of one-side pad SiN layer. With this novel process of additional N-ion implantation (IMP) treatment in STI oxide, it can be found that the less compressive stress about 438 MPa in Si OD can be achieved by the smaller difference of thermal expansion coefficients between Si and N-doped SiO2 STI oxide. The formation of Si-N bonding in N-doped SiO2 STI region can be monitored by Fourier transform infrared spectroscopy spectra and thermal expansion coefficients for Si, SiO2, and SiN are 2.6 ppm/K, 0.4 ppm/K, and 2.87 ppm/K, respectively. The effective relaxation of intrinsic processed compressive stress in Si OD about 112 MPa (from 550 MPa to 438 MPa) by this proposed additional N IMP treatment contributes ∼14% electron carrier mobility enhancement/recovery. The experimental electrical data agree well with the theoretical piezoelectricity calculation for the strained-Si theory.
Elastic, dielectric, and piezoelectric anomalies and Raman spectroscopy of 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3
Authors: Damjanovic Dragan , Biancoli Alberto , Batooli Leili , Vahabzadeh Amirhossein , Trodahl Joe
Published: May 2012

The solid solution 0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT) is a promising lead-free piezoelectric material with exceptionally high piezoelectric coefficients. The strong response is related to structural instabilities close to ambient temperature. We report here on temperature-induced anomalies in the dielectric, piezoelectric, and elastic coefficients and Raman spectroscopy of ceramic BCZT. The data indicate ferroelectric-ferroelectric structural phase transitions in this material in addition to those previously reported. An anomaly is also observed above the Curie temperature TC and is associated with the loss of polar structure that persists thirty degrees above TC.
Entropy-enthalpy compensation may be a useful interpretation tool for complex systems like protein-DNA complexes: An appeal to experimentalists
Authors: Starikov E. B. , Nordén B.
Published: May 2012

In various chemical systems, enthalpy-entropy compensation (EEC) is a well-known rule of behavior, although the physical roots of it are still not completely understood. It has been frequently questioned whether EEC is a truly physical phenomenon or a coincidence due to trivial mathematical connections between statistical-mechanical parameters—or even simpler: A phantom effect resulting from the misinterpretation of experimental data. Here, we review EEC from another standpoint using the notion of correlation, which is essential for the method of factor analysis but is not conventional in physics and chemistry. We conclude that the EEC may be rationalized in terms of hidden (not directly measurable with the help of the current experimental set-up) but physically real factors, implying a Carnot-cycle model in which a micro-phase transition (MPT) plays a crucial role. Examples of such MPTs underlying physically valid EEC should be typically cooperative processes in supramolecular aggregates, like changes of structured water at hydrophobic surfaces, conformational transitions upon ligand-biopolymer binding, and so on. The MPT notion could help rationalize the occurrence of EEC in connection with hydration and folding of proteins, enzymatic reactions, functioning of molecular motors, DNA de- and rehybridization, as well as similar phenomena.
Terahertz coherent control of surface plasmon polariton propagation in subwavelength metallic hole arrays
Authors: Li Gaofang , Jin Zuanming , Xue Xin , Lin Xian , Ma Guohong , Hu Shuhong , Dai Ning
Published: May 2012

We demonstrate the terahertz coherent control of extraordinary transmission through subwavelength metallic hole arrays with double terahertz pulses. The interference of excitations of surface plasmon polaritons (SPPs) by two THz pulses sequence is employed to control the propagation of SPPs in the periodical structure. As a result, the THz wave transmission is controllable by adjusting the arriving time of the control THz pulse. Our results reveal that THz extraordinary transmission in subwavelength structure arises from the excitation of SPPs of the structures, which provides a universal ultrafast means to control the SPPs motion in various THz subwavelength structures.
Electron impact excitation of the ã 3B1u electronic state in C2H4: An experimentally benchmarked system?
Authors: Do T. P. T. , Nixon K. L. , Fuss M. , García G. , Blanco F. , Brunger M. J.
Published: May 2012

We report on differential and integral cross section measurements for the electron impact excitation of the lowest-lying triplet electronic state (ã 3B1u) in ethylene (C2H4). The energy range of the present experiments was 9 eV–50 eV, with the angular range of the differential cross section measurements being 15°–90°. As the ground electronic state of C2H4 is a 1Ag state, this singlet → triplet excitation process is expected to be dominated by exchange scattering. The present angular distributions are found to support that assertion. Comparison, where possible, with previous experimental results from the University of Fribourg group shows very good agreement, to within the uncertainties on the measured cross sections. Agreement with the available theories, however, is generally marginal with the theories typically overestimating the magnitude of the differential cross sections. Notwithstanding that, the shapes of the theoretical angular distributions were in fact found to be in good accord with the corresponding experimental results.
Dynamical process of KrF pulsed excimer laser crystallization of ultrathin amorphous silicon films to form Si nano-dots
Authors: Chen Guran , Xu Jun , Xu Wei , Sun Hongcheng , Mu Weiwei , Sun Shenghua , Ma Zhongyuan , Huang Xinfan , Chen Kunji
Published: May 2012

Molecular dynamics (MD) simulations based on the Tersoff potential have been developed to study the laser-induced crystallization of amorphous silicon (a-Si) film with ultrathin thickness to form size-controllable Si nano-dots. The influences of laser fluence and a-Si film thickness on the crystallization process were discussed. Classic nucleation theory was used to explain the results of the MD simulations. The constrain effect of a-Si films thickness on the formation of Si nano-dots was evaluated accordingly.
Improved emission efficiency of a-plane GaN light emitting diodes with silica nano-spheres integrated into a-plane GaN buffer layer
Authors: Park S. H. , Park J. , You D.-J. , Joo K. , Moon D. , Jang J. , Kim D.-U. , Chang H. , Moon S. , Song Y.-K. , Lee G.-D. , Jeon H. , Xu J. , Nanishi Y. , Yoon E.
Published: May 2012

A simple and inexpensive technique to improve the emission efficiency of nonpolar a-plane light emitting diodes (LEDs) is proposed. The 3-dimensional growth nature of a-plane GaN was utilized to form the regrowth template of a-plane GaN. Subsequently, the controlled integration of silica nano-spheres (CIS) into the regrowth template is performed to improve the crystal quality of a-plane GaN by epitaxial lateral overgrowth method. In addition, the CIS improves light extraction by the scattering process. The light output power from the CIS a-plane GaN LEDs showed 130%–150% increase compared to that of LED without silica nano-spheres.
Beyond power laws: A new approach for analyzing single molecule photoluminescence intermittency
Authors: Riley E. A. , Hess C. M. , Whitham P. J. , Reid P. J.
Published: May 2012

The photoluminescence intermittency (PI) exhibited by single emitters has been studied for over a decade. To date, the vast majority of PI analyses involve parsing the data into emissive and non-emissive events, constructing histograms of event durations, and fitting these histograms to either exponential or power law probability distributions functions (PDFs). Here, a new method for analyzing PI data is presented where the data are used directly to construct a cumulative distribution function (CDF), and maximum-likelihood estimation techniques are used to determine the best fit of a model PDF to the CDF. Statistical tests are then employed to quantitatively evaluate the hypothesis that the CDF (data) is represented by the model PDF. The analysis method is outlined and applied to PI exhibited by single CdSe/CdS core-shell nanocrystals and the organic chromophore violamine R isolated in single crystals of potassium-acid phthalate. Contrary to previous studies, the analysis presented here demonstrates that the PI exhibited by these systems is not described by a power law. The analysis developed here is also used to quantify heterogeneity within PI data obtained from a collection of CdSe/CdS nanocrytals, and for the determination of statistically significant changes in PI accompanying perturbation of the emitter. In summary, the analysis methodology presented here provides a more statistically robust approach for analyzing PI data.
Design and analysis of multi-color confocal microscopy with a wavelength scanning detector
Authors: Do Dukho , Chun Wanhee , Gweon Dae-Gab
Published: May 2012

Spectral (or multi-color) microscopy has the ability to detect the fluorescent light of biological specimens with a broad range of wavelengths. Currently, the acousto-optic tunable filter (AOTF) is widely used in spectral microscopy as a substitute for a multiple-dichroic mirror to divide excitation and emission signals while maintaining sufficient light efficiency. In addition, systems which utilize an AOTF have a very fast switching speed and high resolution for wavelength selection. In this paper, confocal-spectral microscopy is proposed with a particular spectrometer design with a wavelength-scanning galvano-mirror. This enables the detection of broadband (480–700 nm) fluorescence signals by a single point detector (photomultiplier tube) instead of a CCD pixel array. For this purpose, a number of optical elements were applicably designed. A prism is used to amplify the dispersion angle, and the design of the relay optics matches the signals to the diameter of the wavelength-scanning galvano-mirror. Also, a birefringent material known as calcite is used to offset the displacement error at the image plane depending on the polarization states. The proposed multi-color confocal microscopy with the unique detection body has many advantages in comparison with commercial devices. In terms of the detection method, it can be easily applied to other imaging modalities.
Relaxation and jump dynamics of water at the mica interface
Authors: Malani Ateeque , Ayappa K. G.
Published: May 2012

The orientational relaxation dynamics of water confined between mica surfaces is investigated using molecular dynamics simulations. The study illustrates the wide heterogeneity that exists in the dynamics of water adjacent to a strongly hydrophilic surface such as mica. Analysis of the survival probabilities in different layers is carried out by normalizing the corresponding relaxation times with bulk water layers of similar thickness. A 10-fold increase in the survival times is observed for water directly in contact with the mica surface and a non-monotonic variation in the survival times is observed moving away from the mica surface to the bulk-like interior. The orientational relaxation time is highest for water in the contact layer, decreasing monotonically away from the surface. In all cases the ratio of the relaxation times of the 1st and 2nd rank Legendre polynomials of the HH bond vector is found to lie between 1.5 and 1.9 indicating that the reorientational relaxation in the different water layers is governed by jump dynamics. The orientational dynamics of water in the contact layer is particularly novel and is found to undergo distinct two-dimensional hydrogen bond jump reorientational dynamics with an average waiting time of 4.97 ps. The waiting time distribution is found to possess a long tail extending beyond 15 ps. Unlike previously observed jump dynamics in bulk water and other surfaces, jump events in the mica contact layer occur between hydrogen bonds formed by the water molecule and acceptor oxygens on the mica surface. Despite slowing down of the water orientational relaxation near the surface, life-times of water in the hydration shell of the K+ ion are comparable to that observed in bulk salt solutions.
Real-time analysis and selection of methylated DNA by fluorescence-activated single molecule sorting in a nanofluidic channel
Authors: Cipriany Benjamin R. , Murphy Patrick J. , Hagarman James A. , Cerf Aline , Latulippe David , Levy Stephen L. , Benítez Jaime J. , Tan Christine P. , Topolancik Juraj , Soloway Paul D. , Craighead Harold G.
Published: May 2012

Epigenetic modifications, such as DNA and histone methylation, are responsible for regulatory pathways that affect disease. Current epigenetic analyses use bisulfite conversion to identify DNA methylation and chromatin immunoprecipitation to collect molecules bearing a specific histone modification. In this work, we present a proof-of-principle demonstration for a new method using a nanofluidic device that combines real-time detection and automated sorting of individual molecules based on their epigenetic state. This device evaluates the fluorescence from labeled epigenetic modifications to actuate sorting. This technology has demonstrated up to 98% accuracy in molecule sorting and has achieved postsorting sample recovery on femtogram quantities of genetic material. We have applied it to sort methylated DNA molecules using simultaneous, multicolor fluorescence to identify methyl binding domain protein-1 (MBD1) bound to full-duplex DNA. The functionality enabled by this nanofluidic platform now provides a workflow for color-multiplexed detection, sorting, and recovery of single molecules toward subsequent DNA sequencing.