bluuebunny/crossref_metadata_2025 huggingface dataset:
DYNAMIC CONTROLLABILITY WITH OVERLAPPING TARGETS: OR WHY TARGET INDEPENDENCE MAY NOT BE GOOD FOR YOU
Authors: ACOCELLA NICOLA , DI BARTOLOMEO GIOVANNI , HALLETT ANDREW HUGHES
Published: March 2007

We generalize some recent results developed in static policy games with multiple players, to a dynamic context. We find that the classical theory of economic policy, static or dynamic, can be usefully applied to a strategic context of difference games: if one player satisfies theGolden Rule, then either all other players' policies are ineffective with respect to the dynamic target variables shared with that player. Or no Nash Feedback Equilibrium can exist, unless they all share target values for those variables. We extend those results to the case in which there are also nondynamic targets, to show that policy effectiveness (a Nash equilibrium) can continue to exist if some players satisfy theGolden Rulebut target values differ between players in their nondynamic targets. We demonstrate the practical importance of these results by showing how policy effectiveness (a policy equilibrium) can appear or disappear with small variations in the expectations process or policy rule in a widely used model of monetary policy with the possibility of target independence.
A NOTE ON THE CONSEQUENCES OF AN ENDOGENOUS DISCOUNTING DEPENDING ON THE ENVIRONMENTAL QUALITY
Authors: LE KAMA ALAIN AYONG , SCHUBERT KATHELINE
Published: March 2007

Our intention is to study, in the framework of a very simple optimal growth model, the consequences on the optimal paths followed by consumption and the environmental quality of an endogenous discounting. Consumption directly comes from the use of environmental services and so is a direct cause of environmental degradation. The environment is valued both as a source of consumption and as an amenity. For a sustainability concern, we introduce an endogenous discount rate growing with the environmental quality, and compare the optimal growth paths with the ones obtained in the usual case of exogenous and constant discounting. We show that the convergence of the environmental quality toward a steady state occurs only for a very special configuration of the parameters in the exogenous discounting case, whereas it occurs generically in the endogenous discounting one. This happens for a utility discount rate becoming sufficiently high when the environmental quality is high and sufficiently low when the environmental quality is poor. In this case, then, endogenous discounting with a positive marginal discount rate allows us to avoid the depletion of the environment.
Conventional analyses of data from dietary validation studies may misestimate reporting accuracy: illustration from a study of the effect of interview modality on children's reporting accuracy
Authors: Smith Albert F , Domel Baxter Suzanne , Hardin James W , Nichols Michele D
Published: March 2007

Objective

To compare two approaches to analysing energy- and nutrient-converted data from dietary validation (and relative validation) studies – conventional analyses, in which the accuracy of reported items is not ascertained, and reporting-error-sensitive analyses, in which reported items are classified as matches (items actually eaten) or intrusions (items not actually eaten), and reported amounts are classified as corresponding or overreported.

Design

Subjects were observed eating school breakfast and lunch, and interviewed that evening about that day's intake. For conventional analyses, reference and reported information were converted to energy and macronutrients; thent-tests, correlation coefficients and report rates (reported/reference) were calculated. For reporting error-sensitive analyses, reported items were classified as matches or intrusions, reported amounts were classified as corresponding or overreported, and correspondence rates (corresponding amount/reference amount) and inflation ratios (overreported amount/reference amount) were calculated.

Subjects

Sixty-nine fourth-grade children (35 girls) from 10 elementary schools in Georgia (USA).

Results

For energy and each macronutrient, conventional analyses found that reported amounts were significantly less than reference amounts (everyP < 0.021; pairedt-tests); correlations between reported and reference amounts exceeded 0.52 (everyP < 0.001); and median report rates ranged from 76% to 95%. Analyses sensitive to reporting errors found median correspondence rates between 67% and 79%, and that median inflation ratios, which ranged from 7% to 17%, differed significantly from 0 (everyP < 0.0001; sign tests).

Conclusions

Conventional analyses of energy and nutrient data from dietary reporting validation (and relative validation) studies may overestimate accuracy and mask the complexity of dietary reporting error.
Determination of the Number of Cells in Preimplantation Embryos by Using Noninvasive Optical Quadrature Microscopy in Conjunction with Differential Interference Contrast Microscopy
Authors: Newmark Judith A. , II William C. Warger , Chang ChihChing , Herrera Gustavo E. , Brooks Dana H. , DiMarzio Charles A. , Warner Carol M.
Published: March 2007

The number of cells in a preimplantation embryo is directly correlated to the health and viability of the embryo. There are currently no methods to count the number of cells in late-stage preimplantation embryos noninvasively. We assessed the ability of optical quadrature microscopy (OQM) to count the number of cells in mouse preimplantation embryos noninvasively. First, to test for possible light toxicity, we exposed two-cell mouse embryos to OQM and differential interference contrast (DIC) microscopy and assessed their ability to develop to the blastocyst stage. We found no inhibition of development from either mode of microscopy for up to 2 h of light exposure. We also imaged eight-cell to morula stage mouse preimplantation embryos by OQM nd developed two methods for counting the number of cells. The contour signature method (CSM) used OQM images alone and the phase subtraction method (PSM) used both OQM and DIC images. We compared both methods to standard cell counting techniques and found that the PSM was superior to all other noninvasive cell counting methods. Our work on mouse embryos should be applicable to human embryos. The ability to correctly count the number of cells in human preimplantation embryos could lead to the transfer of fewer embryos in in vitro fertilization (IVF) clinics and consequently a lower rate of high-risk multiple-infant births.
EELS Spectroscopy of Iron Fluorides and FeFx/C Nanocomposite Electrodes Used in Li-Ion Batteries
Authors: Cosandey Frederic , Al-Sharab Jafar F. , Badway Fadwa , Amatucci Glenn G. , Stadelmann Pierre
Published: March 2007

A new type of positive electrode for Li-ion batteries has been developed recently based on FeF3/C and FeF2/C nanocomposites. The microstructural and redox evolution during discharge and recharge processes was followed by electron energy loss spectroscopy (EELS) to determine the valence state of Fe by measuring the Fe L3line energy shift and from Fe L3/L2line intensity ratios. In addition, transition metal fluorides were found to be electron beam sensitive, and the effect of beam exposure on EELS spectra was also investigated. The EELS results indicate that for both FeF3/C and FeF2/C nanocomposite systems, a complete reduction of iron to FeOis observed upon discharge to 1.5 V with the formation of a finer FeO/LiF subnanocomposite (∼7 nm). Upon complete recharging to 4.5 V, EELS data reveal a reoxidation process to a Fe2+state with the formation of a carbon metal fluoride nanocomposite related to the FeF2structure.
Fractal and Image Analysis of Morphological Changes in the Actin Cytoskeleton of Neonatal Cardiac Fibroblasts in Response to Mechanical Stretch
Authors: Fuseler John W. , Millette Clarke F. , Davis Jeffery M. , Carver Wayne
Published: March 2007

Cardiac fibroblasts are the most numerous cells in the heart and are critical in the formation and normal functioning of the organ. Cardiac fibroblasts are firmly attached to and surrounded by extracellular matrix (ECM). Mechanical forces transmitted through interaction with the ECM can result in changes of overall cellular shape, cytoskeletal organization, proliferation, and gene expression of cardiac fibroblasts. These responses may be different in the normally functioning heart, when compared with various pathological conditions, including inflammation or hypertrophy. It is apparent that cellular phenotype and physiology, in turn, are affected by multiple signal transduction pathways modulated directly by the state of polymerization of the actin cytoskeleton. Morphological changes in actin organization resulting from response to adverse conditions in fibroblasts and other cell types are basically descriptive. Some studies have approached quantifying changes in actin cytoskeletal morphology, but these have involved complex and difficult procedures. In this study, we apply image analysis and non-Euclidian geometrical fractal analysis to quantify and describe changes induced in the actin cytoskeleton of cardiac fibroblasts responding to mechanical stress. Characterization of these rapid responses of fibroblasts to mechanical stress may provide insight into the regulation of fibroblasts behavior and gene expression during heart development and disease.
Belowground carbon turnover in a temperate ombrotrophic bog
Authors: Blodau Christian , Roulet Nigel T. , Heitmann Tobias , Stewart Heather , Beer Julia , Lafleur Peter , Moore Tim R.
Published: March 2007

To examine belowground carbon (C) turnover in peatlands, we measured fluxes of carbon dioxide (CO2) and methane (CH4) by chamber measurements, estimated respiration by in situ incubations of peat, and in situ production of dissolved carbon (CO2; CH4; and dissolved organic carbon, DOC) by pore water modeling at an ombrotrophic temperate bog. Ecosystem respiration (ER) averaged 205 mmol m−2 d−1 in summer and was related to temperature, but not water table position, and in situ rates of heterotrophic respiration in the unsaturated zone were also temperature‐dependent, with Q10 = 5.0 − 6.4. In the saturated zone, concentrations of 0.1 − 2.5 mmol L−1 (CO2), 0 to 0.6 mmol L−1 (CH4), and <10 − 120 mg L−1 (DOC) were recorded. Turnover was dominated by DOC unrelated to respiration, which ranged from <0.5 to 7 mmol m−2 d−1 and amounted on average to < 1% of ER. Peat decomposition constants kd were 0.060 yr−1 to 0.034 yr−1 in the unsaturated and <0.002 yr−1 in the saturated zone. Monthly averages of CH4 fluxes ranged from 0 to 1.6 mmol m−2 d−1 and were higher than modeled diffusive fluxes when threshold concentrations for CH4 ebullition were recorded closer to the peatland surface. Our results suggest that the saturated zone is of little relevance to ER in this dry temperate bog and that mobilization of DOC is a potentially more relevant process. Temperature is a more important control on ER than water table position because most of the ER is generated close to the peatland surface. Concurrent, moderate increases in temperature and soil moisture are thus likely to increase losses of CO2 from ER and of CH4 from this type of peatland.
Structural trend line pattern and strain partitioning around the Gibraltar Arc accretionary wedge: Insights as to the mode of orogenic arc building
Authors: Balanyá J. C. , Crespo‐Blanc A. , Díaz Azpiroz M. , Expósito I. , Luján M.
Published: March 2007

Mediterranean tectonics results in tight orogenic arcs enclosing back‐arc basins of oceanic or thinned continental lithosphere. The Gibraltar Arc cannot be explained solely by the Europe‐Africa plate convergence; therefore complementary mechanisms have been proposed. Most of them imply a westward motion of the arc and a general transpressive regime on both branches (Betic and Rif chains). A structural revision made along the western Gibraltar Arc allows us to generate a detailed kynematic map and to introduce new constraints on the possible arc formation mechanisms. Our results suggest that the strain partitioned into two main types of structures: structures accommodating suborthogonal shortening (folds and thrusts) and structures accommodating arc‐parallel stretching (normal faults, conjugate strike‐slip faults, and distributed minor structures). On the basis of the fan pattern depicted by the slip direction of contractional structures and the homogeneous distribution of arc‐parallel stretching, an arc formation mode close to the piedmont glacier type is suggested.
Formula representation of auroral ionospheric O+ outflows based on systematic simulations with effects of soft electron precipitation and transverse ion heating
Authors: Zeng W. , Horwitz J. L.
Published: March 2007

Systematic Dynamic Fluid Kinetic (DyFK) model simulations are conducted to obtain a simulation‐based formula representation of the O+ outflow flux level versus the energy flux of soft electron precipitation, and wave spectral density of transverse wave heating in the high‐latitude auroral region. Based on results of 140 DyFK simulations of auroral outflows, we depict the O+ outflows at the ends of these two hour simulation runs in spectrogram form versus these parameters. We also approximate the results by the formula representation: = 8.8(3.0 × 105 + 2fe1.4 × 107)(tanh (8Dwave) + 0.2Dwave0.6), where is the O+ number flux in cm−2/s at 3 RE mapped to 1000 km altitude, fe is the electron precipitation energy flux in ergs cm−2/s, and Dwave is the wave electric field spectral density at O+ gyrofrequency at 1 RE in (mV)2 m−2 Hz−1. This formula representation provides a convenient way to set the boundary conditions of the ionosphere in global magnetosphere simulation since the ionosphere is the important plasma source of the magnetosphere.
Significance of the riparian vegetation dynamics on meandering river morphodynamics
Authors: Perucca E. , Camporeale C. , Ridolfi L.
Published: March 2007

A river and its surrounding riparian vegetation are two dynamical systems that interact through several hydrological, geomorphological, and ecological processes. This work focuses on the role played by vegetation on meandering river morphodynamics: River planform evolution forces the riparian vegetation dynamics, which, in turn, affect the mechanical characteristics of the river banks and influence the meandering dynamics of the river itself. It follows that despite the fact that a traditional engineering approach considers vegetation as a static element the study of river morphodynamics should be coupled with the riparian vegetation evolution. To this end, a fluid dynamic model of meandering rivers is here coupled with a process‐based model for the riparian biomass dynamics. The feedback of vegetation on river morphology is provided by a relation that links the biomass density to the bank erodibility. The numerical results highlight (1) the remarkable effects of the vegetation dynamics on meander evolution and (2) the role of the temporal scales of vegetation growth and decay in relation to typical morphodynamic scales. In particular, the differences with respect to the constant erodibility case can be of the order of tens or hundreds of meters (10–20% of the meander wavelength), and peculiar meander shapes that do not show the usual marked upstream skewness emerge.
The imaging property of photoacoustic Fourier imaging and tomography using an acoustic lens imaging system
Authors: Wan Wei , Liang Ruisheng , Tang Zhilie , Chen Zhanxu , Zhang Hanchao , He Yongheng
Published: March 2007

The theory of photoacoustic tomography imaging using an acoustic lens imaging system has been investigated, and the photoacoustic (PA) Fourier imaging property of an acoustic lens is presented. The theoretical results show that an acoustic lens is able to realize two-dimensional PA Fourier imaging and the focal depth of the acoustic lens is 20mm. The PA signals with the advantage of time resolution can be resolved in time domain by time-resolved technique. Therefore, this long focal depth characteristic of the acoustic lens can be combined with time-resolved technique to realize PA tomography imaging. It is demonstrated by experiments that this method is able to provide PA tomography images of biological tissue. The images are clear and contrast sharply with their backgrounds. The depth resolution is 1.54mm.
Experimentally validated quantitative linear model for the device physics of elastomeric microfluidic valves
Authors: Kartalov Emil P. , Scherer Axel , Quake Stephen R. , Taylor Clive R. , Anderson W. French
Published: March 2007

A systematic experimental study and theoretical modeling of the device physics of polydimethylsiloxane “pushdown” microfluidic valves are presented. The phase space is charted by 1587 dimension combinations and encompasses 45–295μm lateral dimensions, 16–39μm membrane thickness, and 1–28psi closing pressure. Three linear models are developed and tested against the empirical data, and then combined into a fourth-power-polynomial superposition. The experimentally validated final model offers a useful quantitative prediction for a valve’s properties as a function of its dimensions. Typical valves (80–150μm width) are shown to behave like thin springs.
Ab initio and analytical intermolecular potential for ClO–H2O
Authors: Du Shiyu , Francisco Joseph S. , Schenter Gregory K. , Garrett Bruce C.
Published: March 2007

In recent years, the ClO free radical has been found to play an important role in the ozone removal processes in the atmosphere. In this work, the authors present a potential energy surface scan of the ClO∙H2O system with high-level ab initio methods. Because of the existence of low-lying excited states of the ClO∙H2O complex and their potential impact on the chemical behavior of the ClO radical in the atmosphere, the authors perform the potential energy surface scan at the CCSD(T)/aug-cc-pVTZ level of theory of both the first excited and ground states. Analytical potentials for both ground and excited states, with the ClO and H2O units held fixed at their optimized geometries and with anisotropic atomic polarizabilities modeling the physics of the unpaired electron in the ClO radical, were built based on a Thole-type model. The two minima of the ClO∙H2O complex are recovered by the analytical potential.
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potential and sticky-sphere fluids
Authors: Rickayzen G. , Heyes D. M.
Published: March 2007

The authors investigate the behavior of a model fluid for which the interaction energy between molecules at a separation r is of the form 4ε[(σ∕r)2n−(σ∕r)n], where ε and σ are constants and n is a large integer. The particular properties they study are the pressure p, the mean square force ⟨F2⟩, the elastic shear modulus at infinite frequency G∞, the bulk modulus at infinite frequency K∞, and the potential energy per molecule u. They show that if n is sufficiently large it is possible to derive the properties of the system in terms of two parameters, the values of the cavity function and of its derivative at the position r=σ. As an example they examine in detail the cases with n=144 and n=72 for three different temperatures and they test the theory by comparison with a computer simulation of the system. They use the simulated pressure and the average mean square force to determine the two parameters and use these values to evaluate other properties; it is found that the theory produces results which agree with computer simulation to within approximately 3%. It is also shown that the model, when the parameter n is large, is equivalent to Baxter’s sticky-sphere model with the strength of the adhesion determined by the value of n and the temperature. They use Baxter’s solution of the Percus-Yevick equations for the sticky-sphere model to determine the cavity function and from that the values of the same properties. In this second approach there are no free parameters to determine from simulation; all properties are completely determined by the theory. The results obtained agree with computer simulation only to within approximately 6%. This suggests that for this model one needs a better approximation to the cavity function than that provided by the Percus-Yevick solution. Nevertheless, the model looks promising for the study of (typically small) colloidal liquids where the range of attraction is short but finite when compared to its diameter, in contrast to Baxter’s sticky-sphere limit where the attractive interaction range is taken to be infinitely narrow. The continuous function approach developed here enables important physical properties such as the infinite shear modulus to be computed, which are finite in experimental systems but are undefined in the sticky-sphere model.
Dynamical spin response of itinerant electrons close to a quantum critical point
Authors: Schlottmann P.
Published: March 2007

The dynamical spin susceptibility χ″(ω,Q), which is of relevance to inelastic neutron scattering, is calculated for an itinerant antiferromagnet (AF) close to a quantum critical point (QCP). The model consists of nested Fermi surfaces of an electron pocket and a hole pocket separated by a wave vector Q, which give rise to itinerant AF for a repulsive interaction between the carriers. The order can gradually be suppressed by mismatching the nesting and a QCP is obtained as TN→0. For the tuned QCP a quasielastic peak in χ″(ω,Q) with a linewidth proportional to T is obtained.
Perpendicular exchange bias mechanism in FePt∕FeMn multilayers
Authors: Phuoc Nguyen N. , Suzuki Takao
Published: March 2007

A systematic study of parallel and perpendicular exchange biases in FePt∕FeMn multilayers fabricated onto MgO(001) substrates by ion beam sputter deposition system was conducted. The blocking temperature of parallel exchange bias was found to be higher than that of the perpendicular one. The discrepancy was interpreted as due to the spin canting out of plane at the interface. A systematic simulation based on the Landau-Lifshitz-Gilbert equation was carried out, which was in reasonable agreement with the assumption of spin canting out of plane, suggesting the state of nonuniform distribution of spin direction at the interface.
Influence of the domain structure of nano-oxide layers on the transport properties of specular spin valves
Authors: Ventura J. , Sousa J. B. , Veloso A. , Freitas P. P.
Published: March 2007

Specular spin valves show enhanced giant magnetoresistive ratio when compared to other simpler, spin valve structures as a result of specular reflection in nano-oxide layers (NOLs) formed by the partial oxidation of the CoFe pinned and free layers. The oxides forming the NOL were recently shown to order antiferromagnetically below T∼175K. Here we study the training effect in MnIr∕CoFe∕NOL∕CoFe∕Cu∕CoFe∕NOL specular spin valves at low temperatures (15K). We observed that the training effect is related to the nano-oxide layer antiferromagnet ordering and to the evolution of the corresponding domain structure with the number of cycles performed. This allowed us to study the influence of the NOL domain structure on the magnetotransport of specular spin valves.
Quasirelativistic theory. II. Theory at matrix level
Authors: Liu Wenjian , Kutzelnigg Werner
Published: March 2007

The Dirac operator in a matrix representation in a kinetically balanced basis is transformed to the matrix representation of a quasirelativistic Hamiltonian that has the same electronic eigenstates as the original Dirac matrix (but no positronic eigenstates). This transformation involves a matrix X, for which an exact identity is derived and which can be constructed either in a noniterative way or by various iteration schemes, not requiring an expansion parameter. Both linearly convergent and quadratically convergent iteration schemes are discussed and compared numerically. The authors present three rather different schemes, for each of which even in unfavorable cases convergence is reached within three or four iterations, for all electronic eigenstates of the Dirac operator. The authors present the theory both in terms of a non-Hermitian and a Hermitian quasirelativistic Hamiltonian. Quasirelativistic approaches at the matrix level known from the literature are critically analyzed in the frame of the general theory.
Analysis of the gradient-diffusion hypothesis in large-eddy simulations based on transport equations
Authors: da Silva Carlos B. , Pereira José C. F.
Published: March 2007

The gradient-diffusion hypothesis is frequently used in numerical simulations of turbulent flows involving transport equations. In the context of large-eddy simulations (LES) of turbulent flows, one modeling trend involves the use of transport equations for the subgrid-scale (SGS) kinetic energy and SGS scalar variance. In virtually all models using these equations, the diffusion terms are lumped together, and their joint effect is modeled using a “gradient-diffusion” model. In this work, direct numerical simulations of homogeneous isotropic turbulence are used to analyze the local dynamics of these terms and to assess the performance of the “gradient-diffusion” hypothesis used in their modeling. For this purpose a priori tests are used to assess the influence of the Reynolds and Schmidt numbers and the size of the implicit grid filter in this modeling assumption. The analysis uses correlations, variances, skewnesses, flatnesses, probability density functions, and joint probability density functions. The correlations and joint probability density functions show that provided the filter width is within or close to the dissipative range the diffusion terms pertaining to the SGS kinetic energy and SGS scalar variance transport equations are well represented by a gradient-diffusion model. However, this situation changes dramatically for both equations when considering inertial range filter sizes and high Reynolds numbers. The reason for this lies in part in a loss of local balance between the SGS turbulent diffusion and diffusion caused by grid/subgrid-scale (GS/SGS) interactions, which arises at inertial range filter sizes. Moreover, due to the deficient modeling of the diffusion by SGS pressure-velocity interactions, the diffusion terms in the SGS kinetic energy equation are particularly difficult to reconcile with the gradient-diffusion assumption. In order to improve this situation, a new model, inspired by Clark’s SGS model, is developed for this term. The new model shows very good agreement with the exact SGS pressure-velocity term in a priori tests and better results than the classical model in a posteriori (LES) tests.
Fabrication and characterization of TiSi2∕Si heteronanocrystal metal-oxide-semiconductor memories
Authors: Zhu Yan , Li Bei , Liu Jianlin
Published: March 2007

Ti Si 2 ∕ Si heteronanocrystals on ultrathin oxide was fabricated with self-aligned silicidation method. Compared with Si nanocrystal memory device, TiSi2∕Si heteronanocrystal metal-oxide-semiconductor memory device shows higher writing saturation level, faster writing/erasing speed, longer retention, and larger memory window. Therefore, heteronanocrystals are very promising to replace Si nanocrystals for future nonvolatile memory applications.
Deformation effect on electronic and optical properties of nanographite ribbons
Authors: Chang C. P. , Wu B. R. , Chen R. B. , Lin M. F.
Published: March 2007

The electronic structures of deformed nanographite ribbons are calculated from the Huckel tight-binding model. They strongly depend on the uniaxial strain and the ribbon geometry (edge structure and width). The uniaxial strain significantly affects the subband spacings and the energy dispersions. A monotonous relation between the uniaxial strain and the state energies is absent. For armchair ribbons, the uniaxial strain drastically changes the energy gap and thus leads to the semiconductor-metal transition. The dependence of energy gap on strain is determined by the ribbon width. The large strain could also induce the subband crossing. On the other hand, zigzag ribbons remain metallic during the variation of the strain. Armchair and zigzag ribbons, respectively, behave as zigzag and armchair nanotubes. The calculated absorption spectrum exhibits rich peak structures, mainly owing to the divergent density of states of the one-dimensional subbands. The uniaxial-strain effects on optical excitations are strong for armchair ribbons, but weak for zigzag ribbons.
Photoconductivity in molecularly doped poly(methylmethacrylate) sandwich cells
Authors: Kishore V. C. , Dhanya R. , Kartha C. Sudha , Sreekumar K. , Joseph Rani
Published: March 2007

Poly(methyl)methacrylate was made photoconducting by molecular doping and the photoconductivity was investigated using modulated photocurrent technique. Low-temperature current-voltage measurements showed that the transport mechanism was thermally activated hopping. An experimental investigation of the photoconductivity action spectrum along with theoretical calculation enabled an estimation of the diffusion coefficient of the material. The presence of states with a distribution of lifetimes could be understood from the frequency response of the photocurrent. The photocurrent was due to the field-assisted dissociation of these states.
Electrophoretic transport through channels of periodically varying cross section
Authors: Yariv Ehud , Dorfman Kevin D.
Published: March 2007

We analyze the electrophoretic transport of a point-sized Brownian particle in a narrow channel of periodically varying cross section. The mean long-time transport coefficients (effective velocity and dispersivity) are calculated using generalized Taylor-Aris dispersion (macrotransport) theory for spatially periodic media. Analytical results for slowly varying geometries are obtained using a long-wavelength perturbation scheme for both O(1) and large Péclet numbers.
Simplified description of microwave plasma discharge for chemical vapor deposition of diamond
Authors: Yamada Hideaki , Chayahara Akiyoshi , Mokuno Yoshiaki
Published: March 2007

A fluid model to prescribe microwave plasma is proposed. The conservation equations for electron are reduced to only one differential equation. Therefore, the computational cost is also reduced as small as possible. One may extend functions of existing program for vacuum field analysis to microwave plasma simulator by coupling this differential equation with Maxwell equations. While the model is quite simple, this model can prescribe distributions of electron temperature as well as the number density, whereas effects of inelastic collisions with ions and neutrals are taken into account. Test calculation is carried out in three dimensional system and well reproduces experimental observation and prediction obtained by other model.
Plasmonic excitation of organic double heterostructure solar cells
Authors: Mapel J. K. , Singh M. , Baldo M. A. , Celebi K.
Published: March 2007

The authors demonstrate that thin film organic photovoltaic cells are efficient detectors of surface plasmon polaritons (SPPs). For λ=532nm radiation in a Kretschmann configuration, the external quantum efficiency in fullerene–copper phthalocyanine photovoltaic cells is doubled at resonance to 12%. In thin heterojunction organic photovoltaics, SPP detection relies on a substantial increase in absorption when the incoming radiation is coupled to guided SPPs rather than unguided photons. SPP scattering and nonradiative losses are negligible; however, optical modeling shows that cathode metal penetration into the neighboring organic semiconductor is a major source of loss for SPP or photonic excitation.
High-pressure and high-temperature annealing as an activation method for ion-implanted dopants in diamond
Authors: Ueda K. , Kasu M. , Makimoto T.
Published: March 2007

The authors show that high-pressure and high-temperature (HPHT) annealing is very effective for the activation of ion-implanted dopants in diamond. The HPHT annealing condition is located in the thermodynamically stable region for diamond in the phase diagram and is, therefore, much more efficient for the recovery of implantation-induced damage and for the activation of ion-implanted dopants than thermal annealing in vacuum. The B-implanted film after HPHT annealing showed a high mobility of 632cm2∕Vs with a sheet hole concentration of 4.8×1010cm−2 at 300K and the doping efficiency of ∼7%. The mobility is the highest so far for ion-implanted diamond. In the entire annealing temperature range, the HPHT annealing is more efficient than the thermal annealing in vacuum.
Pressure-tuned colossal improvement of thermoelectric efficiency of PbTe
Authors: Ovsyannikov Sergey V. , Shchennikov Vladimir V.
Published: March 2007

The variations in thermoelectric (TE) efficiencies æ of lead chalcogenide compounds (p-PbTe, n-PbTe, p-Pb0.55Te0.45, p-Pb1−xSnxTe1−y, p-PbSe, and p-PbS) at room temperature for the pressure P range of P∼0–10GPa are reported. A colossal (∼100 times) pressure-tuned improvement of æ is found for PbTe-based crystals under application of P∼2–3GPa. The employed high-pressure cell with synthetic diamond anvils is a model of a simple and effective TE device.
Dissecting Changing Rural Development Policy Networks: The Case of Greece
Authors: Papadopoulos Apostolos G , Liarikos Constantinos
Published: March 2007

Rural development has, in recent years, become a major area of EU policy, to the extent that the term has even begun to be overused in signifying a new shift in EU rural policy. The result has been a great deal of misunderstanding and numerous divergent interpretations of both the concept and the practice. Although rural development existed as a policy domain before the arrival of the accentuated ‘Second Pillar’ of the reformed Common Agricultural Policy, the fact is that an increasingly Europeanized approach to rural development funding, programming, and administration has developed in the post-1999 period. In this paper we argue that the study of rural development policy will gain a great deal from using a policy network approach to interpret the dynamics of evolving rural development policy within member states. Our main aim is to analyze and interpret the newly emerging Rural Development Policy Network in Greece, which aspires to separate itself from a strong and resistant Agricultural Policy Network. The example of Greece suits the purpose of the paper not only because of Greece's continuing reliance on agriculture and the centrality of the latter in sustaining rural livelihoods, but most importantly due to the institutional arrangements developed around it, which are characterized by a prevalence of agricultural interests at the expense of wider rural concerns. The concern of this paper is with the mechanisms of transition, and to a lesser extent with its outcome. One major finding is that the policy network approach to the study of rural development policy in Greece brings to light a certain transformation in policy structures, mechanisms, and administration. This transformation is not so evident at the level of policy style and/or policy outcome. Due to it having been labeled a ‘laggard’ member state, Greece has been affected by the Europeanization of rural development policy and has to some extent transformed its policy-making procedures accordingly. At the same time, the process of Europeanization has acted to empower civil society mechanisms and actors.
Plugging the Accountability Gap? Evaluating the Effectiveness of Regional Scrutiny
Authors: Ashworth Rachel , Snape Stephanie , Aulakh Sundeep
Published: March 2007

The UK government contends that regional assemblies can assist in reducing the democratic deficit in the English regions. This paper presents a preliminary assessment of the new scrutiny role performed by the assemblies. Our conceptual framework identifies five variables which might influence the effectiveness of regional scrutiny. Regional scrutiny is found to be quite distinct from that conducted by parliament, local government, and other devolved institutions. Analysis of qualitative data suggests that regional scrutiny has been limited by a lack of clearly defined powers, inadequate technical support, and an often ‘cosy’ relationship between assemblies and their Regional Development Agencies. We conclude that regional assemblies urgently require appropriate legitimacy, powers, and resources in order to prevent the accountability gap from widening.
Social dominance and breeding activity in Spanish ibex (Capra pyrenaica) maintained in captivity
Authors: Santiago-Moreno J. , Gómez-Brunet A. , Toledano-Díaz A. , Pulido-Pastor A. , López-Sebastián A.
Published: March 2007

The relationship between ovulatory activity and social dominance was determined in 10 Spanish ibex females by recording their plasma progesterone and plasma cortisol levels. In a second experiment, the influence of dominance status on the establishment of pregnancy after introduction to males during late anoestrous (late October) was evaluated in another nine females. Dominance hierarchies were established in both groups by noting agonistic interactions between the individual females. Six high-ranking females of the 10 ibexes without male contact showed ovulatory activity with 1–3 progesterone cycles. The first progesterone cycle appeared in December (18 December ± 4 days). Dominance status correlated with age (R = 0.86, P < 0.01), bodyweight (R = 0.96, P < 0.001) and the number of progesterone cycles (R = 0.82, P < 0.01). Cortisol differences were associated with differences in reproductive function rather than social status per se. Introduction to males during late anoestrous brought forward the initiation of ovulatory activity (14 November ± 5 days) and resulted in three pregnancies in females with higher dominance ranks. The results suggest that social interactions are important in the control of ovulatory activity in the Spanish ibex.
On-line Monitoring of End-tidal Propofol Concentration in Anesthetized Patients
Authors: Takita Akira , Masui Kenichi , Kazama Tomiei
Published: March 2007

Background

Propofol (2,6-diisopropylphenol) has some volatility, so it can be detected in expired breath of individuals receiving intravenous propofol. This study measured volatile propofol exhaled by patients and investigated the relation between exhaled and plasma propofol concentrations.

Methods

Nineteen patients with American Society of Anesthesiologists physical status I or II who were undergoing elective surgery participated in this two-part study. In study 1 (n = 11), anesthesia was induced with 2 mg/kg propofol, 0.1 mg/kg vecuronium, and 2 microg/kg fentanyl. After intubation, propofol was administered continuously for 60 min at each of three rates: 3, 6, and 9 mg x kg(-1) x h(-1). Blood samples were obtained just before each change in the infusion rate, and the plasma concentrations of propofol were measured. The exhaled propofol concentration was measured continuously by means of proton transfer mass spectrometry. End-tidal propofol concentrations during blood sampling were averaged and compared with plasma propofol concentrations. In study 2 (n = 8), after induction of anesthesia, patients received a bolus injection of 2 mg/kg propofol, and the exhaled propofol concentration was measured.

Results

Volatile propofol was detected in expired gas from all study patients. From study 1, the authors obtained 24 paired data points, i.e., concentrations of end-tidal and plasma propofol. With Bland-Altman analysis, bias +/- precision was 5.2 +/- 10.4 with 95% limits of agreement of -15.1 and 25.6. In study 2, the exhaled propofol concentration curve showed an obvious peak in all patients.

Conclusions

Agreement between plasma and exhaled propofol concentrations suggests that proton transfer mass spectrometry can be used for real-time propofol monitoring.
Current Practices in Sedation and Analgesia for Mechanically Ventilated Critically Ill Patients
Authors: Payen Jean-Francois , Chanques Gérald , Mantz Jean , Hercule Christiane , Auriant Igor , Leguillou Jean-Luc , Binhas Michèle , Genty Céline , Rolland Carole , Bosson Jean-Luc
Published: March 2007

Background

The authors conducted a patient-based survey of practices to fully describe the assessment and the management of pain and sedation of a large cohort of mechanically ventilated patients during their first week of intensive care unit (ICU) stay.

Methods

A total of 1,381 adult patients were included in a prospective, observational study in 44 ICUs in France. Pain and sedation assessment, analgesic and sedative use, and analgesic management during procedural pain were collected on days 2, 4, and 6 of the ICU stay.

Results

The observed rates of assessment on day 2 for sedation (43%) and analgesia (42%) were significantly smaller than that of use of sedatives (72%) and opioids (90%), also noted on days 4 and 6. The use of protocols/guidelines for sedation/analgesia in the ICU reduced the proportion of patients who were treated, although not evaluated. A large proportion of assessed patients were in a deep state of sedation (40-50%). Minor changes in the dosages of the main prescribed agents for sedation (midazolam, propofol) and analgesia (sufentanil, fentanyl, morphine, remifentanil) were found across 6 days of the patient's ICU stay. Procedural pain was specifically managed for less than 25% of patients; during those procedures, the proportion of patients with pain significantly increased from the baseline pain evaluation.

Conclusions

Excessively deep states of sedation and a lack of analgesia during painful procedures must be prevented. To facilitate systematic pain and sedation assessment and to adjust daily drug dosages accordingly, it seems crucial to promote educational programs and elaboration of protocols/guidelines in the ICU.
Regional Gas Exchange and Cellular Metabolic Activity in Ventilator-induced Lung Injury
Authors: Musch Guido , Venegas Jose G. , Bellani Giacomo , Winkler Tilo , Schroeder Tobias , Petersen Bodil , Harris R Scott , Vidal Melo Marcos F.
Published: March 2007

Background

Alveolar overdistension and repetitive derecruitment-recruitment contribute to ventilator-induced lung injury (VILI). The authors investigated (1) whether inflammatory cell activation due to VILI was assessable by positron emission tomography and (2) whether cell activation due to dynamic overdistension alone was detectable when other manifestations of VILI were not yet evident.

Methods

The authors assessed cellular metabolic activity with [(18)F]fluorodeoxyglucose and regional gas exchange with [(13)N]nitrogen. In 12 sheep, the left ("test") lung was overdistended with end-inspiratory pressure of 50 cm H(2)O for 90 min, while end-expiratory derecruitment of this lung was either promoted with end-expiratory pressure of -10 cm H(2)O in 6 of these sheep (negative end-expiratory pressure [NEEP] group) or prevented with +10 cm H(2)O in the other 6 (positive end-expiratory pressure [PEEP] group) to isolate the effect of overdistension. The right ("control") lung was protected from VILI.

Results

Aeration decreased and shunt fraction increased in the test lung of the NEEP group. [(18)F]fluorodeoxyglucose uptake of this lung was higher than that of the control lung and of the test lung of the PEEP group, and correlated with neutrophil count. When normalized by tissue fraction to account for increased aeration of the test lung in the PEEP group, [(18)F]fluorodeoxyglucose uptake was elevated also in this group, despite the fact that gas exchange had not yet deteriorated after 90 min of overdistension alone.

Conclusion

The authors could detect regional neutrophil activation in VILI even when end-expiratory derecruitment was prevented and impairment of gas exchange was not evident. Concomitant end-expiratory derecruitment converted this activation into profound inflammation with decreased aeration and regional shunting.
Isoflurane Depresses the Response of Inspiratory Hypoglossal Motoneurons to Serotonin In Vivo
Authors: Brandes Ivo F. , Zuperku Edward J. , Stucke Astrid G. , Hopp Francis A. , Jakovcevic Danica , Stuth Eckehard A. E.
Published: March 2007

Background

Endogenous serotonin (5-HT) provides important excitatory drive to inspiratory hypoglossal motoneurons (IHMNs). In vitro studies show that activation of postsynaptic 5-HT receptors decreases a leak K+ channel conductance and depolarizes hypoglossal motoneurons (HMNs). In contrast, volatile anesthetics increase this leak K+ channel conductance, which causes neuronal membrane hyperpolarization and depresses HMN excitability. Clinical studies show upper airway obstruction, indicating HMN depression, even at subanesthetic concentrations. The authors hypothesized that if anesthetic activation of leak K+ channels caused neuronal depression in vivo, this effect could be antagonized with serotonin. In this case, the neuronal response to picoejected serotonin would be greater during isoflurane than with no isoflurane.

Methods

Studies were performed in decerebrate, vagotomized, paralyzed, and mechanically ventilated dogs during hypercapnic hyperoxia. The authors studied the effect of approximately 0.3 minimum alveolar concentration (MAC) isoflurane on the spontaneous discharge frequency patterns of single IHMNs and on the neuronal response to picoejection of 5-HT.

Results

Normalized data (mean +/- SD, n = 19) confirmed that 0.3 +/- 0.1 MAC isoflurane markedly reduced the spontaneous peak discharge frequency by 48 +/- 19% (P < 0.001) and depressed the slope of the spontaneous discharge patterns. The increase in neuronal frequency in response to 5-HT was reduced by 34 +/- 22% by isoflurane (P < 0.001).

Conclusion

Subanesthetic concentrations of isoflurane strongly depressed canine IHMNs in vivo. The neuronal response to 5-HT was also depressed by isoflurane, suggesting that anesthetic activation of leak K+ channels, which is expected to result in a larger 5-HT response, was not a dominant mechanism in this depression.
Subhypnotic Doses of Isoflurane Impair Auditory Discrimination in Rats
Authors: Burlingame Rita H. , Shrestha Sneha , Rummel Michael R. , Banks Matthew I.
Published: March 2007

Background

Isoflurane at subhypnotic doses is known to affect cellular and network activity in the auditory pathway, but the behavioral effects of these concentrations of isoflurane on auditory processing have not been tested previously. The authors tested the hypothesis that subhypnotic doses of isoflurane would impair auditory discrimination in rats.

Methods

Rats were tested on their ability to discriminate up versus down frequency-modulated sweeps using three different pairs of sweeps ("Long," "Med," "Short"), whose frequency range and duration were varied systematically to make the discrimination more difficult. Rats were tested daily in the absence and presence of isoflurane at 0.2% or 0.4%. The effects of isoflurane (0%, 0.2%, and 0.4%) on performance (= % correct) and efficiency (= time/trial) were assessed using regression analysis.

Results

The effect of isoflurane was stimulus-dependent: performance for the Long stimulus pair was unaffected by isoflurane, performance on the Med stimulus pair was impaired only by 0.4% isoflurane, and performance on the Short stimulus pair was impaired by both 0.2% and 0.4% isoflurane. In contrast, isoflurane decreased efficiency equally for all stimulus pairs at 0.4% and had no effect at 0.2%.

Conclusions

The stimulus dependence of the effect of isoflurane on performance suggests that it is unlikely this effect was secondary to effects on memory, motivation, or motor function. These data indicate that doses of isoflurane known to produce modest effects on neural responses alter cortical sensory processing.