bluuebunny/crossref_metadata_2025 huggingface dataset:
The calculation of adiabatic-connection curves from full configuration-interaction densities: Two-electron systems
Authors: Teale A. M. , Coriani S. , Helgaker T.
Published: March 2009

The Lieb formulation of density-functional theory is briefly reviewed and its straightforward generalization to arbitrary electron-electron interaction strengths discussed, leading to the introduction of density-fixed and potential-fixed adiabatic connections. An iterative scheme for the calculation of the Lieb functionals under the appropriate constraints is outlined following the direct optimization approach of Wu and Yang [J. Chem. Phys. 118, 2498 (2003)]. First- and second-order optimization schemes for the calculation of accurate adiabatic-connection integrands are investigated and compared; the latter is preferred both in terms of computational efficiency and accuracy. The scheme is applicable to systems of any number of electrons. However, to determine the accuracy that may be achieved, the present work focuses on two-electron systems for which a number of simplifications may be exploited. The procedure is applied to the helium isoelectronic series and the H2 molecule. The resulting adiabatic-connection curves yield the full configuration-interaction exchange-correlation energies extrapolated to the basis-set limit. The relationship between the Kohn–Sham and natural orbitals as functions of the electron-electron interaction strength is explored in detail for H2. The accuracy with which the exchange-correlation contributions to the modified local potential can be determined is discussed. The new accurate adiabatic-connection curves are then compared with some recently investigated approximate forms calculated using accurate full configuration-interaction input data. This study demonstrates that the adiabatic-connection integrand may be determined accurately and efficiently, providing important insights into the link between the Kohn–Sham and traditional quantum-chemical treatments of the exchange-correlation problem in electronic-structure theory.
Density functional study of the adsorption and van der Waals binding of aromatic and conjugated compounds on the basal plane of MoS2
Authors: Moses Poul Georg , Mortensen Jens J. , Lundqvist Bengt I. , Nørskov Jens K.
Published: March 2009

Accurate calculations of adsorption energies of cyclic molecules are of key importance in investigations of, e.g., hydrodesulfurization (HDS) catalysis. The present density functional theory (DFT) study of a set of important reactants, products, and inhibitors in HDS catalysis demonstrates that van der Waals interactions are essential for binding energies on MoS2 surfaces and that DFT with a recently developed exchange-correlation functional (vdW-DF) accurately calculates the van der Waals energy. Values are calculated for the adsorption energies of butadiene, thiophene, benzothiophene, pyridine, quinoline, benzene, and naphthalene on the basal plane of MoS2, showing good agreement with available experimental data, and the equilibrium geometry is found as flat at a separation of about 3.5 Å for all studied molecules. This adsorption is found to be due to mainly van der Waals interactions. Furthermore, the manifold of adsorption-energy values allows trend analyses to be made, and they are found to have a linear correlation with the number of main atoms.
Fast off-lattice Monte Carlo simulations with “soft” repulsive potentials
Authors: Wang Qiang , Yin Yuhua
Published: March 2009

The basic idea of fast off-lattice Monte Carlo (FOMC) simulations is to use “soft” repulsive potentials that allow particle overlapping in continuum Monte Carlo (MC) simulations. For multichain systems, this gives much faster chain relaxation and better sampling of the configurational space than conventional molecular simulations using “hard” excluded-volume interactions that prevent particle overlapping. Such coarse-grained models are particularly suitable for the study of equilibrium properties of soft materials. Since soft potentials are commonly used in polymer field theories, it is another advantage of FOMC simulations that using the same Hamiltonian in both FOMC simulations and the theories enables quantitative comparisons between them without any parameter fitting to unambiguously reveal the consequences of approximations in the theories. Moreover, FOMC simulations can be performed with various chain models and in any statistical ensemble, and all the advanced off-lattice MC techniques proposed to date can be implemented to further improve the sampling efficiency. We have performed canonical-ensemble FOMC simulations with an isotropic soft pair potential for three systems: we first used (small-molecule) soft spheres to demonstrate the improved sampling of FOMC simulations over conventional molecular simulations; we then used single-chain simulations to show that the effects of excluded-volume interactions can be well captured by the soft repulsive potential; finally, for compressible homopolymer melts, we compared FOMC results with those under the random-phase approximation to demonstrate that FOMC simulations can be used to unambiguously and quantitatively reveal the fluctuation/correlation effects in the system. In addition, we examined in detail in our single-chain simulations the spatial discretization scheme used in all previous FOMC simulations.
Enhanced conformational sampling of nucleic acids by a new Hamiltonian replica exchange molecular dynamics approach
Authors: Curuksu Jeremy , Zacharias Martin
Published: March 2009

Although molecular dynamics (MD) simulations have been applied frequently to study flexible molecules, the sampling of conformational states separated by barriers is limited due to currently possible simulation time scales. Replica-exchange (Rex)MD simulations that allow for exchanges between simulations performed at different temperatures (T-RexMD) can achieve improved conformational sampling. However, in the case of T-RexMD the computational demand grows rapidly with system size. A Hamiltonian RexMD method that specifically enhances coupled dihedral angle transitions has been developed. The method employs added biasing potentials as replica parameters that destabilize available dihedral substates and was applied to study coupled dihedral transitions in nucleic acid molecules. The biasing potentials can be either fixed at the beginning of the simulation or optimized during an equilibration phase. The method was extensively tested and compared to conventional MD simulations and T-RexMD simulations on an adenine dinucleotide system and on a DNA abasic site. The biasing potential RexMD method showed improved sampling of conformational substates compared to conventional MD simulations similar to T-RexMD simulations but at a fraction of the computational demand. It is well suited to study systematically the fine structure and dynamics of large nucleic acids under realistic conditions including explicit solvent and ions and can be easily extended to other types of molecules.
Switching of 800 nm femtosecond laser pulses using a compact PMN-PT modulator
Authors: Adany Peter , Price E. Shane , Johnson Carey K. , Zhang Run , Hui Rongqing
Published: March 2009

A voltage-controlled birefringent cell based on ceramic PMN-PT material is used to enable fast intensity modulation of femtosecond laser pulses in the 800 nm wavelength window. The birefringent cell based on a PMN-PT compound has comparatively high electro-optic response, allowing for a short interaction length of 3 mm and thus very small size, low attenuation of 0.16 dB, and negligible broadening for 100 fs optical pulses. As an application example, agile wavelength tuning of optical pulses is demonstrated using the soliton self-frequency shift in a photonic crystal fiber. By dynamically controlling the optical power into the fiber, this system switches the wavelength of 100 fs pulses from 900 nm to beyond 1120 nm with less than 5 μs time. In addition, a feedback system stabilizes the wavelength drift against external conditions resulting in high wavelength stability.
A model of threading dislocation density in strain-relaxed Ge and GaAs epitaxial films on Si (100)
Authors: Wang G. , Loo R. , Simoen E. , Souriau L. , Caymax M. , Heyns M. M. , Blanpain B.
Published: March 2009

Strain relaxation in large lattice-mismatched epitaxial films, such as Ge and III-V materials on Si, introduces high threading dislocation densities (TDDs). A thermodynamic model of TDD dependence on film thickness is developed. According to this model, the quasiequilibrium TDD of a given strain-relaxed film scales down with the inverse square of its thickness. The quasiequilibrium TDDs in both Ge and GaAs films follow this model consistently. Our model predicts the lowest possible TDD of a large lattice-mismatched film on Si (100), which is determined by the dislocation glide activation energy and the film thickness.
Three-dimensional organic field-effect transistors with high output current and high on-off ratio
Authors: Uno Mayumi , Doi I. , Takimiya K. , Takeya J.
Published: March 2009

High-performance three-dimensional organic field-effect transistors are developed with multiple vertical channels of organic semiconductors. Advanced processes of vacuum depositing high-mobility and air-stable dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene thin films on a series of horizontally elongated vertical walls have maximized the output current to 0.60 A/cm2 area with the application of −10 V for both drain-source and gate voltages. The on-off ratio is as high as 106. Carrier mobility of the organic semiconductor is typically 0.30 cm2/V s and deviation among ten devices is within 10%. The performance meets requirement for such application as driving organic light-emitting diodes in active-matrix displays.
Highly sensitive anisotropic magnetoresistance magnetometer for Eddy-current nondestructive evaluation
Authors: He D. F. , Tachiki M. , Itozaki H.
Published: March 2009

Using a commercially available anisotropic magnetoresistance (AMR) sensor of HMC1001, we developed a sensitive magnetometer. It could operate in amplifier mode or feedback mode. The magnetic field sensitivity of the AMR sensor was about 3.2 mV/V G. When the AMR sensor was biased by a voltage of 24 V, the magnetic field resolutions of the AMR magnetometer were about 12 pT/√Hz at 1 kHz and 20 pT/√Hz at 100 Hz. We used the AMR magnetometer for Eddy-current nondestructive evaluation in unshielded environment.
High performance InxCeyCo4Sb12 thermoelectric materials with in situ forming nanostructured InSb phase
Authors: Li Han , Tang Xinfeng , Zhang Qingjie , Uher Ctirad
Published: March 2009

n -Type skutterudites InxCeyCo4Sb12 with in situ forming nanostructured InSb phase have been prepared by a melt-quench-anneal-spark plasma sintering method. Doping of In results in a nanostructured InSb phase with the grain size of 10–80 nm that is evenly distributed on the boundaries of the skutterudite matrix. The nanostructured InSb phase has a strong influence on phonon scattering and leads to a notable suppression of the lattice thermal conductivity of InxCeyCo4Sb12. The combined effect of In and Ce doping results in high performance skutterudite materials. The highest thermoelectric figure of merit ZT=1.43 is achieved at 800 K in the In0.2Ce0.15Co4Sb12 compound.
Interface properties of InAs quantum dots produced by antimony surfactant-mediated growth: Etching of segregated antimony and its impact on the photoluminescence and lasing characteristics
Authors: Guimard Denis , Ishida Mitsuru , Li Lin , Nishioka Masao , Tanaka Yu , Sudo Hisao , Yamamoto Tsuyoshi , Kondo Hayato , Sugawara Mitsuru , Arakawa Yasuhiko
Published: March 2009

We present a method that improves the emission efficiency of InAs quantum dots (QDs) fabricated by antimony surfactant-mediated metal organic chemical vapor deposition. This process consists of removing the excess segregated antimony from the surface of InAs/Sb:GaAs QDs by applying a high arsenic pressure before capping. In such a way, one benefits from the advantages of InAs/Sb:GaAs QDs (high density, low coalescence) without the formation of antimony-induced nonradiative defects. Finally, we show that this better QD interface quality results in a strong decrease of the threshold current densities of InAs/Sb:GaAs QD lasers in the 1.3 μm band.
Parametric amplification and wavelength conversion in the 1040–1090 nm band by use of a photonic crystal fiber
Authors: Sylvestre T. , Kudlinski A. , Mussot A. , Gleyze J. F. , Jolly A. , Maillotte H.
Published: March 2009

Highly efficient parametric amplification and wavelength conversion have been demonstrated in the 1040–1090 nm band. A nonlinear photonic crystal fiber was used to provide the anomalous dispersion required for phase matching at 1 μm. A 40 dB maximum gain and +35 dB idler conversion efficiency have been achieved in the subnanosecond pulsed regime and by using a spectrally filtered supercontinuum source as a small signal.
Direct observation of the charge carrier concentration in organic field-effect transistors by electron spin resonance
Authors: Tanaka Hisaaki , Watanabe Shun-ichiro , Ito Hiroshi , Marumoto Kazuhiro , Kuroda Shin-ichi
Published: March 2009

Charge carrier concentration in operating field-effect transistor (FET) of regioregular poly(3-hexylthiophene) has been directly determined by electron spin resonance (ESR). ESR signals of field-induced polarons are observed around g=2.003 under the application of negative gate-source voltage (Vgs). Upon applying drain-source voltage (Vds), ESR intensity decreases linearly in the low Vds region, reaching to about 50% of the initial intensity at the pinch-off point (Vds≅Vgs). For larger absolute values of Vds, it becomes nearly Vds independent. These behaviors are well explained by the change in the carrier concentration obtained by the FET theory using gradual channel approximation.
Enhanced two-photon absorption of CdS nanocrystal rods
Authors: Li Xiangping , van Embden Joel , Chon James W. M. , Gu Min
Published: March 2009

In this letter we report that CdS nanocrystals are reshaped into an elongated rod form for increasing two-photon absorption. CdS quantum rods with uniform rod dimensions have been synthesized and their two-photon absorption cross section in solution has been characterized using the z-scan method and the two-photon induced fluorescence study. The absorption cross section was found to be 20.9×10−46 cm4/s photon−1 under two-photon excitation at wavelength 800 nm, which is an order of magnitude larger than that of CdS quantum dots of similar diameters. The higher two-photon absorption coefficient establishes the potential of this class of quantum rods for various photonic applications.
Electrical-optical signal mixing and multiplication (2→22 GHz) with a tunnel junction transistor laser
Authors: Then H. W. , Wu C. H. , Walter G. , Feng M. , Holonyak N.
Published: March 2009

A tunnel junction is incorporated at the collector of a transistor laser to provide an effective method for voltage-controlled modulation via internal (intracavity) Franz–Keldysh photon-assisted tunneling. Electrical-optical signal mixing above threshold is made possible by the nonlinear coupling of the optical field to the base emitter-to-collector carrier transport and the base-to-collector electron tunneling. Microwave signal mixing with a common-emitter tunnel junction transistor laser is demonstrated with a pair of input sinusoidal signals: one (f1=2.0 GHz) at the base using current modulation and the other (f2=2.1 GHz) at the collector using voltage modulation, producing an optical output with harmonics of up to (4f1+7f2)=22.7 GHz, despite being limited by amplifier bandwidth.
Regulation of DNMT1 stability through SET7-mediated lysine methylation in mammalian cells
Authors: Estève Pierre-Olivier , Chin Hang Gyeong , Benner Jack , Feehery George R. , Samaranayake Mala , Horwitz Gregory A. , Jacobsen Steven E. , Pradhan Sriharsa
Published: March 2009

Inheritance of epigenetic information encoded by cytosine DNA methylation patterns is crucial for mammalian cell survival, in large part through the activity of the maintenance DNA methyltransferase (DNMT1). Here, we show that SET7, a known histone methyltransferase, is involved in the regulation of protein stability of DNMT1. SET7 colocalizes and directly interacts with DNMT1 and specifically monomethylates Lys-142 of DNMT1. Methylated DNMT1 peaks during the S and G2phases of the cell cycle and is prone to proteasome-mediated degradation. Overexpression of SET7 leads to decreased DNMT1 levels, and siRNA-mediated knockdown of SET7 stabilizes DNMT1. These results demonstrate that signaling through SET7 represents a means of DNMT1 enzyme turnover.
Enhancement of 1,25-dihydroxyvitamin D3-mediated suppression of experimental autoimmune encephalomyelitis by calcitonin
Authors: Becklund Bryan R. , Hansen Donald W. , DeLuca Hector F.
Published: March 2009

The active form of vitamin D, 1α,25-dihydroxyvitamin D3[1,25(OH)2D3], suppresses disease development in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS). However, complete disease prevention only occurs with doses that dramatically elevate serum calcium levels, thus limiting the usefulness of 1,25(OH)2D3as a potential MS therapeutic agent. Because calcitonin (CT) is believed to be released by hypercalcemia and has been shown to be anti-inflammatory, we examined whether suppression of EAE by 1,25(OH)2D3could be mediated either in part or entirely by CT. Continuous administration of pharmacological doses of CT did not prevent EAE. However, a combination of CT and a subtherapeutic dose of 1,25(OH)2D3additively suppressed EAE without causing hypercalcemia. Moreover, CT decreased the dose of 1,25(OH)2D3required for disease suppression. Our results suggest that CT may be a significant factor but cannot account entirely for 1,25(OH)2D3-mediated suppression of EAE.
Thermodynamic equilibrium between blue and green copper sites and the role of the protein in controlling function
Authors: Ghosh Somdatta , Xie Xiangjin , Dey Abhishek , Sun Yan , Scholes Charles P. , Solomon Edward I.
Published: March 2009

A combination of spectroscopies and density functional theory calculations indicate that there are large temperature-dependent absorption spectral changes present in green nitrite reductases (NiRs) due to a thermodynamic equilibrium between a green and a blue type 1 (T1) copper site. The axial methionine (Met) ligand is unconstrained in the oxidized NiRs, which results in an enthalpically favored (Δ
H
≈4.6 kcal/mol) Met-bound green copper site at low temperatures, and an entropically favored (
T
Δ
S
≈4.5 kcal/mol, at room temperature) Met-elongated blue copper site at elevated temperatures. In contrast to the NiRs, the classic blue copper sites in plastocyanin and azurin show no temperature-dependent behavior, indicating that a single species is present at all temperatures. For these blue copper proteins, the polypeptide matrix opposes the gain in entropy that would be associated with the loss of the weak axial Met ligand at physiological temperatures by constraining its coordination to copper. The potential energy surfaces of Met binding indicate that it stabilizes the oxidized state more than the reduced state. This provides a mechanism to tune down the reduction potential of blue copper sites by >200 mV.
The influences of harmony motives and implicit beliefs on conflict styles of the collectivist
Authors: Lim Lena L.
Published: March 2009

The collectivist preference for nonconfrontational conflict styles is usually attributed to the influences of the Confucian value of harmony, which promotes tolerance of interpersonal transgression. Harmony has two distinct motives in collectivistic Asian societies (Leung, 1997): harmony enhancement is affective in nature and represents a genuine concern for relationship harmony, while disintegration avoidance is instrumental in nature and sees harmony maintenance as a means to other ends. Hence, as predicted, harmony enhancement is positively related to the use of integrating and compromising, while disintegration avoidance is positively related to the use of avoiding and obliging and is negatively related to the use of integrating during a conflict with a peer in a collectivistic society, Singapore. Besides examining this from a motivational perspective, the study also examines the role of implicit beliefs of personality on one's choice of conflict styles. The two implicit theories of personality refer to the two different assumptions the lay person has about the mutability of personal attributes; an entity theorist believes that personal attributes are fixed and nonmalleable qualities, while an incremental theorist sees personal attributes as qualities that can be developed and changed. Results reveal that incrementalist implicit beliefs also significantly predicted the use of integrating. Harmony enhancement represents a genuine concern for relationship harmony and involves feelings of closeness, unity, and trust. The finding that integrating is predicted by a harmony enhancement motivation suggests the importance of fostering collectivist values of interdependence and feelings of unity and trust so as to encourage the use of integrating to discuss the opposing views openly and constructively. The present study also underscores the benefit of learning an incremental theory to be open to the positive changes in others and work toward improving the relationship and the situation during a conflict.
Transport mechanisms in the outer region of RFX-mod
Authors: Vianello N. , Martines E. , Agostini M. , Alfier A. , Canton A. , Cavazzana R. , De Masi G. , Fassina A. , Lorenzini R. , Scarin P. , Serianni G. , Spagnolo S. , Spizzo G. , Spolaore M. , Zuin M.
Published: March 2009

Transport properties of the edge region of RFPs are characterized by complicated mechanisms further entangled by the complex magnetic topology. Recently on RFX-mod (Sonato 2003 Fusion Eng. Des.
66–68 161) the use of an efficient feedback system for MHD control allowed the achievement of an unprecedented plasma current for an RFP, of up to 1.6 MA, with an improvement in the confinement properties. This is accompanied by an amelioration of the magnetic boundary and the observation of different MHD regimes, moving from low current multiple helical regime, to high current quasi-single helical ones. At a low plasma current (I
p ≈ 300–400 kA) in multiple helicity discharge the plasma parameter profiles at the edge are strongly influenced by the presence of m = 0 islands which flatten the temperature profile and modify substantially both the electric drift flow and the
E
×
B
shear. The particle diffusion coefficient and the thermal conductivity χe in this regime are 10–20 m2 s−1 and 100–200 m2 s−1, respectively. Both temperature and pressure characteristic scale lengths are found to scale favourably with the decrease in the secondary modes achieved through the increase in the plasma current. The same trend is observed for the thermal conductivity, and the recently discovered single helical axis states (Lorenzini et al 2008 Phys. Rev. Lett.
101 025005) exhibit an edge χe reduced by a factor of up to 40%. Finally the perpendicular flow at the edge is found to scale with the density normalized to the Greenwald density with a saturation at values around n/n
G ≈ 0.35.
Comparison of in situ time-series of temperature with gridded sea surface temperature datasets in the North Atlantic
Authors: Hughes Sarah L. , Holliday N. Penny , Colbourne Eugene , Ozhigin Vladimir , Valdimarsson Hedinn , Østerhus Svein , Wiltshire Karen
Published: March 2009

Hughes, S. L., Holliday, N. P., Colbourne, E., Ozhigin, V., Valdimarsson, H., Østerhus, S., and Wiltshire, K. 2009. Comparison of in situ time-series of temperature with gridded sea surface temperature datasets in the North Atlantic. – ICES Journal of Marine Science, 66: 1467–1479. Analysis of the effects of climate variability and climate change on the marine ecosystem is difficult in regions where long-term observations of ocean temperature are sparse or unavailable. Gridded sea surface temperature (SST) products, based on a combination of satellite and in situ observations, can be used to examine variability and long-term trends because they provide better spatial coverage than the limited sets of long in situ time-series. SST data from three gridded products (Reynolds/NCEP OISST.v2., Reynolds ERSST.v3, and the Hadley Centre HadISST1) are compared with long time-series of in situ measurements from ICES standard sections in the North Atlantic and Nordic Seas. The variability and trends derived from the two data sources are examined, and the usefulness of the products as a proxy for subsurface conditions is discussed.
Potential impacts of climate change on the winter distribution of Afro-Palaearctic migrant passerines
Authors: Barbet-Massin Morgane , Walther Bruno A , Thuiller Wilfried , Rahbek Carsten , Jiguet Frédéric
Published: March 2009

We modelled the present and future sub-Saharan winter distributions of 64 trans-Saharan migrant passerines to predict the potential impacts of climate change. These predictions used the recent ensemble modelling developments and the latest IPCC climatic simulations to account for possible methodological uncertainties. Results suggest that 37 species would face a range reduction by 2100 (16 of these by more than 50%); however, the median range size variation is −13 per cent (from −97 to +980%) under a full dispersal hypothesis. Range centroids were predicted to shift by 500±373 km. Predicted changes in range size and location were spatially structured, with species that winter in southern and eastern Africa facing larger range contractions and shifts. Predicted changes in regional species richness for these long-distance migrants are increases just south of the Sahara and on the Arabian Peninsula and major decreases in southern and eastern Africa.
How range shifts induced by climate change affect neutral evolution
Authors: McInerny G.J , Turner J.R.G , Wong H.Y , Travis J.M.J , Benton T.G
Published: March 2009

We investigate neutral evolution during range shifts in a strategic model of a metapopulation occupying a climate gradient. Using heritable, neutral markers, we track the spatio-temporal fate of lineages. Owing to iterated founder effects (‘mutation surfing’), survival of lineages derived from the leading range limit is enhanced. At trailing limits, where habitat suitability decreases, survival is reduced (mutations ‘wipe out’). These processes alter (i) the spatial spread of mutations, (ii) origins of persisting mutations and (iii) the generation of diversity. We show that large changes in neutral evolution can be a direct consequence of range shifting.
Identification and dynamics of a cryptic suture zone in tropical rainforest
Authors: Moritz C , Hoskin C.J , MacKenzie J.B , Phillips B.L , Tonione M , Silva N , VanDerWal J , Williams S.E , Graham C.H
Published: March 2009

Suture zones, shared regions of secondary contact between long-isolated lineages, are natural laboratories for studying divergence and speciation. For tropical rainforest, the existence of suture zones and their significance for speciation has been controversial. Using comparative phylogeographic evidence, we locate a morphologically cryptic suture zone in the Australian Wet Tropics rainforest. Fourteen out of 18 contacts involve morphologically cryptic phylogeographic lineages, with mtDNA sequence divergences ranging from 2 to 15 per cent. Contact zones are significantly clustered in a suture zone located between two major Quaternary refugia. Within this area, there is a trend for secondary contacts to occur in regions with low environmental suitability relative to both adjacent refugia and, by inference, the parental lineages. The extent and form of reproductive isolation among interacting lineages varies across species, ranging from random admixture to speciation, in one case via reinforcement. Comparative phylogeographic studies, combined with environmental analysis at a fine-scale and across varying climates, can generate new insights into suture zone formation and to diversification processes in species-rich tropical rainforests. As arenas for evolutionary experimentation, suture zones merit special attention for conservation.
Complexity of the human cerebral circulation
Authors: Panerai Ronney B
Published: March 2009

The cerebral circulation shows both structural and functional complexity. For time scales of a few minutes or more, cerebral blood flow (CBF) and other cerebrovascular parameters can be shown to follow a random fractal point process. Some studies, but not all, have also concluded that CBF is non-stationary. System identification techniques have been able to explain a substantial fraction of the CBF variability by applying linear and nonlinear multivariate models with classical determinants of flow (arterial blood pressure, arterial CO
2
and cerebrovascular resistance, CVR) as inputs. These findings raise the hypothesis that fractal behaviour is not inherent to CBF but might be simply transmitted from its determinants. If this is the case, future investigations could focus on the complexity of the residuals or the unexplained variance of CBF. In the low-frequency range (below 0.15 Hz), changes in CVR due to pressure and metabolic autoregulation represent an important contribution to CBF variability. A small body of work suggests that parameters describing cerebral autoregulation can also display complexity, presenting significant variability that might also be non-stationary. Fractal analysis, entropy and other nonlinear techniques have a role to play to shed light on the complexity of cerebral autoregulation.
Multiscale, multiorgan and multivariate complexity analyses of cardiovascular regulation
Authors: Cerutti Sergio , Hoyer Dirk , Voss Andreas
Published: March 2009

Cardiovascular system complexity is confirmed by both its generally variegated structure of physiological modelling and the richness of information detectable from processing of the signals involved in it, with strong linear and nonlinear interactions with other biological systems. In particular, this behaviour may be accordingly described by means of what we call MMM paradigm (i.e. multiscale, multiorgan and multivariate). Such an approach to the cardiovascular system emphasizes where the genesis of its complexity is potentially allocated and how it is possible to detect information from it. No doubt that processing signals from multi-leads of the same system (multivariate), from the interaction of different physiological systems (multiorgan) and integrating all this information across multiple scales (from genes, to proteins, molecules, cells, up to the whole organ) could really provide us with a more complete look at the overall phenomenon of cardiovascular system complexity, with respect to the one which is obtainable from its single constituent parts. In this paper, some examples of approaches are discussed for investigating the cardiovascular system in different time and spatial scales, in studying a different organ involvement (such as sleep, depression and multiple organ dysfunction) and in using a multivariate approach via various linear and nonlinear methods for cardiovascular risk stratification and pathology assessment.
Coherence analysis between respiration and heart rate variability using continuous wavelet transform
Authors: Keissar Kobi , Davrath Linda R , Akselrod Solange
Published: March 2009

The continuous wavelet transform (CWT) is specifically efficient in the analysis of transient and non-stationary signals. As such, it has become a powerful candidate for time–frequency analysis of cardiovascular variability. CWT has already been established as a valid tool for the analysis of single cardiovascular signals, providing additional insights into the autonomous nervous system (ANS) activity and its control mechanism. Intercorrelation between cardiovascular signals elucidates the function of ANS central control and the peripheral reflex mechanisms. Wavelet transform coherence (WTC) can provide insight into the transient linear order of the regulatory mechanisms, via the computation of time–frequency maps of the time-variant coherence. This paper presents a framework for applying WTC for quantitative analysis of coherence in cardiovascular variability research. Computer simulations were performed to estimate the accuracy of the WTC estimates and a method for determining the coherence threshold for specific frequency band was developed and evaluated. Finally, we demonstrated, in two representative situations, the dynamic behaviour of respiration sinus arrhythmia through the analysis of the WTC between heart rate and respiration signals. This emphasizes that CWT and its application to WTC is a useful tool for dynamic analysis of cardiovascular variability.
Measurement and regulation of cardiac ventricular repolarization: from the QT interval to repolarization morphology
Authors: Couderc Jean-Philippe
Published: March 2009

Ventricular repolarization (VR) is a crucial step in cardiac electrical activity because it corresponds to a recovery period setting the stage for the next heart contraction. Small perturbations of the VR process can predispose an individual to lethal arrhythmias. In this review, I aim to provide an overview of the methods developed to analyse static and dynamic aspects of the VR process when recorded from a surface electrocardiogram (ECG). The first section describes the list of physiological and clinical factors that can affect the VR. Technical aspects important to consider when digitally processing ECGs are provided as well. Special attention is given to the analysis of the effect of heart rate on the VR and its regulation by the autonomic nervous system. The final section provides the rationale for extending the analysis of the VR from its duration to its morphology. Several modelling techniques and measurement methods will be presented and their role within the arena of cardiac safety will be discussed.
Recent advances in biomimetic sensing technologies
Authors: Johnson E.A.C , Bonser R.H.C , Jeronimidis G
Published: March 2009

The importance of biological materials has long been recognized from the molecular level to higher levels of organization. Whereas, in traditional engineering, hardness and stiffness are considered desirable properties in a material, biology makes considerable and advantageous use of softer, more pliable resources. The development, structure and mechanics of these materials are well documented and will not be covered here. The purpose of this paper is, however, to demonstrate the importance of such materials and, in particular, the functional structures they form. Using only a few simple building blocks, nature is able to develop a plethora of diverse materials, each with a very different set of mechanical properties and from which a seemingly impossibly large number of assorted structures are formed. There is little doubt that this is made possible by the fact that the majority of biological ‘materials’ or ‘structures’ are based on fibres and that these fibres provide opportunities for functional hierarchies. We show how these structures have inspired a new generation of innovative technologies in the science and engineering community. Particular attention is given to the use of insects as models for biomimetically inspired innovations.
Diffraction features due to ordered distribution of twin boundaries in orthorhombic Ni–Mn–Ga crystals
Authors: Ustinov A. , Olikhovska L. , Glavatska N. , Glavatskyy I.
Published: March 2009

The diffraction intensity distributions for orthorhombic crystals containing the ordered twin boundaries of the system (110), 〈1{\overline 1}0〉 were calculated in the kinematic approach using the Monte Carlo computer simulation technique. A simple model of short-range order in the arrangement of the twin boundaries was assumed to generate the nano-twinned structure. Analysis of the intensity distributions showed that such a twin boundary distribution results in the formation of extra peaks along the reciprocal lattice rods that are perpendicular to the close-packed planes. These extra peak intensities and positions are dependent on the most probable distances between the twin boundaries and on the degree of short-range order.
Anomalous grazing incidence small-angle X-ray scattering of carbon-encapsulated Au and Cu clusters
Authors: Simon Jean-Paul , Babonneau David , Drouet Michel , Lyon Olivier
Published: March 2009

Nanocomposite films consisting of Au and/or Cu nanoclusters embedded in amorphous carbon matrices were characterized by anomalous grazing incidence small-angle X-ray scattering (AGISAXS) using synchrotron radiation. Whenever relative intensities can be measured with precision, it is shown that AGISAXS, being element specific, is a powerful method for separating the scattering contributions of two types of metallic nanoclusters. Two methodologies to analyse AGISAXS data are compared; the differential method appears the most efficient since it permits separation of the scattering from one type of nanocluster from the other contributions including other types of nanocluster, surface roughness or defects.
Leuconostoc citreum HJ‐P4 (KACC 91035) regulates immunoglobulin E in an ovalbumin‐induced allergy model and induces interleukin‐12 through nuclear factor‐kappa B and p38/c‐Jun N‐terminal kinases signaling in macrophages
Authors: Kang Hee , Oh Yoo‐Joung , Ahn Kyoo‐Seok , Eom Hyun‐Ju , Han NamSoo , Kim Yoon‐Bum , Sohn Nak‐Won
Published: March 2009

Leuconostoc citreum (L. citreum) HJ‐P4 (KACC 91035) is one of the major predominant species in kimchi fermentation in Korea. The purpose of the present study was to test the immunomodulatory capacity of L. citreum to modulate the IgE‐mediated allergic response and to examine the involvement of NF‐κB and MAPK in IL‐12 production in macrophages. Balb/c mice were sensitized with OVA/alum and oral administration of L. citreum to the mice began before or after the OVA sensitization. Protein and mRNA expression of Th1 cytokines in splenocytes by L. citreum in vitro was measured. The role of NF‐κB and MAPK such as p38, ERK1/2 and JNK in L. citreum‐induced IL‐12 was investigated in peritoneal macrophages and RAW264.7 cell lines. L. citreum inhibited the serum levels of total IgE, IgG1 and IgG2a altogether and increased OVA‐specific IFN‐γ production in splenocytes from pre‐ and post‐sensitized animals. However, the downregulation of IL‐4 and IL‐5 production was observed only in the pre‐sensitization group. The ability of L. citreum to stimulate IFN‐γ was dependent on its induction of IL‐12. NF‐κB, p38 and JNK were mainly involved in L. citreum‐induced IL‐12 production. In conclusion, the current study demonstrated that L. citreum is able to regulate serum IgE generation at the induction and effector phases of allergic response through overall control over antibody production and that its involvement of IL‐12 production was mediated through NF‐κB and p38/JNK. Taken together, the use of L. citreum can be useful in preventing the development and progression of IgE production.
Association between antibody response against cytomegalovirus strain‐specific glycoprotein H epitopes and HLA‐DR
Authors: Ishibashi Kei , Tokumoto Tadahiko , Shirakawa Hiroki , Hashimoto Koichi , Kushida Nobuhiro , Yanagida Tomohiko , Shishido Keiichi , Aikawa Ken , Yamaguchi Osamu , Toma Hiroshi , Tanabe Kazunari , Suzutani Tatsuo
Published: March 2009

The gH of CMV is a major target for strain‐specific neutralizing antibodies. To verify whether there is a correlation between HLA‐DR type and strain‐specific antibodies, antibodies against CMV gH in potential donors and recipients for renal transplantation were investigated. Among 471 subjects, 404 (86%) showed reactivity to CMV gH, but no antibodies against gH were detected in 67 (14%) subjects. The positive rates were over 80% in most HLA subpopulations. Fewer subjects with HLA‐DR10 and DR11 had antibodies to CMV gH than did those without HLA‐DR10 and DR11. HLA‐DR10 and DR11 may be associated with fewer/non‐responders for strain‐specific neutralizing antibodies.
Alcohol‐related cirrhosis—early abstinence is a key factor in prognosis, even in the most severe cases
Authors: Verrill Clare , Markham Hannah , Templeton Alexa , Carr Norman J. , Sheron Nick
Published: March 2009

Aims  To determine the effect of pathological severity of cirrhosis on survival in patients with alcohol‐related cirrhosis.

Design  Liver biopsies from 100 patients were scored for Laennec score of severity of cirrhosis, and medical notes were reviewed to determine various clinical factors, including drinking status. Up‐to‐date mortality data were obtained using the National Health Service Strategic Tracing Service.

Setting  Southampton General Hospital between 1 January 1995 and 31 December 2000.

Participants  A total of 100 consecutive patients with biopsy proven alcohol‐induced liver cirrhosis.

Measurements  Laennec score of severity of cirrhosis and mortality.

Findings  Most surprisingly, the severity of cirrhosis on biopsy had little impact on survival; indeed, early death was more likely in patients with the least severe cirrhosis. Abstinence from alcohol at 1 month after diagnosis of cirrhosis was the more important factor determining survival with a 7‐year survival of 72% for the abstinent patients versus 44% for the patients continuing to drink.

Conclusions  It is never too late to stop drinking, even with the most severe degrees of cirrhosis on biopsy. Early drinking status is the most important factor determining long‐term survival in alcohol‐related cirrhosis.
Are adolescents who moderate their cannabis use at lower risk of later regular and dependent cannabis use?
Authors: Swift Wendy , Coffey Carolyn , Carlin John B. , Degenhardt Louisa , Calabria Bianca , Patton George C.
Published: March 2009

Aims  To examine whether moderation of cannabis use among adolescent cannabis users is associated with reductions in cannabis use frequency and risk of dependence in young adulthood.

Design  Ten‐year representative cohort study with six surveys in adolescence (mean age 14.9–17.4 years) and two in young adulthood (mean age 20.7 and 24.1 years).

Participants  Inception cohort of 1943 Victorian secondary school students (96% response rate), with 1520 (78% of adolescent participants) interviewed in the final wave.

Measurements  Participants were classified into six groups according to the maximum level of adolescent use and the extent of subsequent moderation in such use: non‐users, occasional to abstinence, occasional persisting, weekly to abstinence, weekly to occasional and weekly persisting. Outcome measures were weekly+ cannabis use and DSM‐IV cannabis dependence at 20 and 24 years.

Findings  Thirty‐one per cent reported cannabis use during adolescence. Most adolescent users had moderated their use: from occasional to abstinence (71% of occasional users), weekly to abstinence or weekly to occasional (28% and 48% of weekly+ users, respectively). By age 24, both occasional use groups were at similar, elevated risk of regular and dependent cannabis use compared to non‐users. Weekly+ adolescent users were at greatest risk of these outcomes, although the weekly to abstinence group exhibited lower risk than those in the weekly persisting and weekly to occasional groups, who were at similar risk.

Conclusions  While many young people have dynamic cannabis use patterns, a pattern of moderating adolescent cannabis use was associated with less risk of later problematic use than among those persisting, but risks were still elevated substantially compared with never‐users.
Post induction arrhythmia in a renal patient: an unexpected risk factor
Authors: Srivastava A. , Ahmed Khan M. , Watkiss J.
Published: March 2009

A 44 year‐old woman was anaesthetised for a transplant nephrectomy. About 10 min after induction of anaesthesia she had several runs of ventricular tachycardia followed by ventricular fibrillation requiring 30 s of cardiopulmonary resuscitation, after which she reverted to sinus rhythm. Review of her chest X‐ray, suggested that the haemodialysis catheter (Permcath™) position may have precipitated this event. However, subsequent investigation found that she had toxic serum levels of sotalol, with a prolonged corrected QT interval on the electrocardiogram. She was started on sotalol while her renal graft was functioning well but it was not reviewed when the graft started to fail and she had to commence haemodialysis. This led to the accumulation of sotalol and explains her serum sotalol value of 7.1 mg.l−1 on the day of the event. Concentrations greater than 2.5 mg.l−1 are generally considered toxic.
Mortality related to anaesthesia in France: analysis of deaths related to airway complications*
Authors: Auroy Y. , Benhamou D. , Péquignot F. , Bovet M. , Jougla E. , Lienhart A.
Published: March 2009

Death certificates from the French national mortality database for the calendar year 1999 were reviewed to analyse cases in which airway complications had contributed to peri‐operative death. Respiratory deaths (and comas) found in a previous national 1978–82 French survey (1 : 7960; 95% CI 1 : 12 700 to 1 : 5400) were compared with the death rate found in the present one: 1 : 48 200 (95% CI 1 : 140 000 to 1 : 27 500). In 1999, deaths associated with failure of the breathing circuit and equipment were no longer encountered and no death was found to be related to undetected hypoxia in the recovery unit. Deaths related to difficult intubation also occurred at a lower rate than in the previous report (1 : 46 000; 95% CI 1 : 386 000 to 1 : 13 000) in 1978–82 vs 1 : 176 000 (95% CI 1 : 714 000 to 1 : 46 000) in 1999, a fourfold reduction. In most cases, there were both inadequate practice and systems failure (inappropriate communication between staff, inadequate supervision, poor organisation). This large French survey shows that deaths associated with respiratory complications during anaesthesia have been strikingly reduced during this 15‐year period.
Point of care measurement of plasma creatinine in critically ill patients with acute kidney injury
Authors: Udy A. , O’Donoghue S. , D’Intini V. , Healy H. , Lipman J.
Published: March 2009

We report the utility of an enzymatic point of care system for estimation of plasma creatinine concentration in critically ill patients with acute kidney injury. Multiple measurements were obtained from a heterogenous population admitted to a multi‐disciplinary intensive care unit. The acute kidney injury network guidelines were used to identify and stratify patients based on the creatinine concentration. Central laboratory values were used as comparators to assess the precision and bias of the system. Overall, point of care measurements correlated well with central pathology results (R2 = 0.991, p < 0.001), although there tended to be a small negative bias in patients with acute kidney injury (3 μmol.l−1). The accuracy of point of care measurement is within clinically acceptable limits and given the much shorter turn around time can be used to identify and monitor patients with acute kidney injury in the critical care environment.