bluuebunny/crossref_metadata_2025_split huggingface dataset:
Time-lapse imaging of subglacial drainage conditions using three-dimensional inversion of borehole electrical resistivity data
Authors: Kulessa Bernd , Hubbard Bryn , Brown Giles H. 
Published: November 2007

AbstractWe recorded electrical resistivity data at the base of four boreholes drilled through Haut Glacier d’Arolla, Switzerland. The data were acquired repetitively every hour over two diurnal hydrological cycles in the late melt season, separated by 10 days. Constrained three-dimensional (3-D) data inversion allowed reconstruction of hourly variations in bulk resistivity in the subglacial sediment layer. Inverted resistivity models reflect the establishment of channelized subglacial drainage in the study area between the two hydrological cycles, in agreement with previous work. Daily variations in bulk and water resistivity are in phase, and bulk resistivity amplitudes decrease away from the subglacial channel. Using selected electrical–hydraulic relationships, we estimate metre-scale changes in the hydraulic conductivity and porosity of the subglacial sediment layer, accounting for increasing clay content and decreasing median grain radius with distance from the channel. Hydraulic conductivity and porosity were respectively calculated to decrease from (6.4 ± 2.1) × 10–2ms–1 and 0.34 ± 0.01 at the channel to (3.3 ± 2.2) × 10–2ms–1 and 0.26 ± 0.01 at a distance of 5m from it. The hydraulic conductivity estimates are in agreement with previously inferred values, and the porosity estimates fall within the expected range for unlithified subglacial sediments. We conclude that collection and inversion of repeat 3-D subglacial resistivity data is feasible and has the capacity to generate multidimensional images of subglacial hydraulic processes and properties.
Characteristics of subglacial drainage systems deduced from load-cell measurements
Authors: Lappegard Gaute , Kohler Jack , Jackson Miriam , Hagen Jon Ove 
Published: November 2007

AbstractRock tunnels beneath Engabreen, northern Norway, permit access to the ice-bedrock interface beneath a 210 m thick glacier. Eight load cells have been installed in the bedrock of the glacier sole along a 22 m transect. With some interruptions, the load cells have been logged at 15 min intervals since December 1992; here we analyse the records until 2003. Load-cell signals measure stresses acting normal to the bedrock, and usually log the pressure of the thin water film between the basal ice and the bed. Occasionally there are distinct pressure events, characterized by short-lived (hours) local minima, often followed by a maximum before decaying to background load-cell pressure. The amplitudes of these pressure events are of the order of 0.01–1 MPa and depend on the placement of the sensor and the state of the subglacial drainage system. We identify winter and summer pressure regimes. The winter regime is characterized by few pressure events of large pressure amplitude influencing all load cells. A lag of 0–6 days is observed between surface forcing (rain) and pressure events during winter. The summer regime typically has periods of daily pressure events of low amplitude. No delay is seen between surface forcing and pressure events during the summer regime. In summer, the onset of a pressure event is correlated with a local maximum of the derivative of the subglacial discharge record, whereas no such relation is found during the winter regime. The transition from winter to summer (May/June) is easily detectable and is strongly correlated with a rapid increase in subglacial discharge and the transition to a dominating R-channel system. The autumn transition is less clearly defined, but has usually occurred by the beginning of November. Stress bridging, an increase in bed pressure at the edge of low-pressure channels, is recorded during the summer regime. Water pressures at the bed are connected or unconnected to the drainage system. Pressure increases in the connected system, beyond local normal stress values, lead to an uplift of the connected system and a pressure drop in the unconnected system. The occurrence of pressure events is determined by the capacity of the drainage system. Uplift is controlled by local normal stress values and not mean ice-overburden pressure.
Na2SO4 and MgSO4 salts during the Holocene period derived by high-resolution depth analysis of a Dome Fuji ice core
Authors: Iizuka Yoshinori , Hondoh Takeo , Fujii Yoshiyuki 
Published: November 2007

AbstractWe analyzed the profiles of ionic chemical species in three 500 mm sections of an ice core from Dome Fuji, Antarctica, dated 3.0, 8.9 and 13.3 kyr BP (before present), and compared the profiles to those in the surface snow. The 3.0 and 8.9 kyr sections are from the Holocene and the 13.3 kyr section slightly predates the Holocene. The analyses were done on 2 mm thick slices within each section. At each depth, the primary ionic species were Na+, H+, Cl– and SO42 A The SO42, Na+ and Mg2+ levels varied with depth in each section over distances ranging from several millimeters to several centimeters. Also, the correlation coefficients between Na+ and SO4 and between Mg2+ and SO42 for each depth were 0.90 or greater, in contrast to the value of 0.59 or less in the surface snow (defined here as 0–3.4 m from the surface). These results suggest that almost all Na+ and Mg2+ in the Holocene ice exists as Na2SO4 and MgSO4 salts, and the formation of these salts occurs not only in the atmosphere during transport, but also in the firn layer.
Effects of spatial discretization in ice-sheet modelling using the shallow-ice approximation
Authors: Van Den Berg J. , Van De Wal R.S.W. , Oerlemans J. 
Published: November 2007

AbstractThis paper assesses a two-dimensional, vertically integrated ice model for its numerical properties in the calculation of ice-sheet evolution on a sloping bed using the shallow-ice approximation. We discuss the influence of initial conditions and individual model parameters on the model’s numerical behaviour, with emphasis on varying spatial discretizations. The modelling results suffer badly from numerical problems. They show a strong dependence on gridcell size and we conclude that the widely used gridcell spacing of 20 km is too coarse. The numerical errors are small in each single time-step, but increase non-linearly over time and with volume change, as a result of feedback of the mass balance with height. We propose a new method for the calculation of the surface gradient near the margin, which improves the results significantly. Furthermore, we show that we may use dimension analysis as a tool to explain in which situations numerical problems are to be expected.
Density Functional Theory Study of the Cinchona Thiourea‐ Catalyzed Henry Reaction: Mechanism and Enantioselectivity
Authors: Hammar Peter , Marcelli Tommaso , Hiemstra Henk , Himo Fahmi 
Published: November 2007

AbstractWe report a density functional theory investigation of the enantioselective Cinchona thiourea‐catalyzed Henry reaction of aromatic aldehydes with nitromethane. We show that two pathways (differing in the binding modes of the reactants to the catalyst) are possible for the formation of the CC bond, and that they have comparable reaction barriers. The enantioselectivity is investigated, and our results are in agreement with the experimentally observed solvent dependence of the reaction.
Ruthenium/Halide Catalytic System for CC Bond Forming Reaction between Alkynes and Unsaturated Carbonyl Compounds
Authors: Nishimura Takahiro , Washitake Yosuke , Uemura Sakae 
Published: November 2007

AbstractA ruthenium complex [triruthenium dodecacarbonyl, Ru3(CO)12] in the presence of bis(triphenylphosphine)iminium chloride ([PPN]Cl) catalyzes the conjugate addition of terminal alkynes to alkyl acrylates to give high yields of γ,δ‐alkynyl esters. On the other hand, the linear codimerization reaction of terminal alkynes with alkyl acrylates proceeds in the presence of a catalytic amount of Ru3(CO)12 and lithium iodide to give the corresponding conjugate dienes. These two different types of catalytic carbon‐carbon bond forming reactions are controlled only by the nature of halide ions, either a chloride or an iodide, with other conditions being kept almost the same.
Decolorization of colored poly(ethylene terephthalate) bottle flakes using hydrogen peroxide
Authors: Gupta Mohit , Bandi Suneel A. , Mehta Sanjay , Schiraldi David A. 
Published: November 2007

AbstractA novel process for the oxidative decolorization of green and blue colored poly(ethylene terephthalate) (PET) bottle flakes, using an aqueous solution of hydrogen peroxide (H2O2) has been developed. A strong dependence of H2O2 concentration and temperature on decolorization rate has been found. The decolorized flakes were characterized for color and intrinsic viscosity (IV) values; decolorized flakes exhibit color values similar to those of colorless recycled PET. The IV of peroxide bleached PET flakes indicated a decrease in PET molecular weight, which correlated with the severity of decolorization conditions. Despite decreases in PET IV values, the bleached flake still exhibited useful PET molecular weights. The consumption of H2O2 during the bleaching process was quantified titrating residual peroxide with a standardized potassium permanganate solution. H2O2 consumption rates of 0.3–0.9 g per gram of green PET flake were measured, depending on the specific bleaching conditions used. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008
A distributed virtual reality‐based system for neonatal decision‐making training
Authors: Holobar A. , Divjak M. , Prelog I. , Korošec D. , Zazula D. 
Published: November 2007

AbstractIn many fields of education, there is a significant gap between theoretical study and practical apprenticeship, which training in virtual environments (VEs) can close. Recently, a standalone prototype for virtual reality (VR)‐based training in neonatal decision‐making, called Virtual Delivery Room (VIDERO) was developed. This prototype enables a simple and time‐efficient simulation of the arbitrary postnatal critical situations. The purpose behind this paper is twofold: to outline the role of trainee's immersion into VIDERO environment and to addresses the need for assessment and upgrading of training scenarios. In particular, the distributed services enabling fine‐tuning of both virtual patient's behavioral model and trainee's interventions through the practice and user interactions in shared VE are described. © 2007 wiley Periodicals, Inc. Comput Appl Eng Educ 15: 329–339, 2007; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20120
Multiple‐modulation‐multiple‐echo magnetic resonance
Authors: Sigmund Eric E. , Cho Hyungjoon , Song Yi‐Qiao 
Published: November 2007

AbstractWe describe several applications of a versatile pulse sequence family employing multiple spin echoes within one acquisition to accelerate multidimensional experiments. The core sequence, called multiple modulation multiple echo, measures the maximal set of spin echoes generated from a set of RF pulses with unequal time spacings. These echoes can be modulated individually to exhibit different encoding. As a result, one scan of the sequence determines a series of data points as a function of the specific encoding mechanism. The variety of realizations of this sequence includes single shot measurements of diffusion or flow in 1D, 2D, and single‐scan 2D slice‐selective imaging. The essential spin dynamics of such sequences is introduced and their applications are reviewed. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 358–377, 2007.
Heterogeneous expression of SNAP‐25 in rat and human brain
Authors: Garbelli Rita , Inverardi Francesca , Medici Valentina , Amadeo Alida , Verderio Claudia , Matteoli Michela , Frassoni Carolina 
Published: November 2007

AbstractSynaptosomal associated protein of 25 kDa (SNAP‐25) is a SNARE component of the exocytotic apparatus involved in the release of neurotransmitter. We used multiple‐labeling immunofluorescence, confocal microscopy, and ultrastructural immunocytochemistry to examine the expression of SNAP‐25 in excitatory and inhibitory terminals from different rat and human brain areas. Glutamatergic and GABAergic terminals were identified by staining for the vesicular glutamate transporter (vGLUT1), glutamic acid decarboxylase (GAD67), or the vesicular GABA transporter (vGAT). In all examined areas GABAergic terminals did not display detectable levels of SNAP‐25, whereas glutamatergic terminals expressed the protein to a variable extent. Codistribution analysis revealed a high colocalization between pixels detecting SNAP‐25 labeling and pixels detecting vGLUT1 immunoreactivity. On the contrary, a low degree of pixel colocalization, comparable to that between two unrelated antigens, was detected between SNAP‐25 and vGAT, thus suggesting a random overlap of immunofluorescence signals. Our immunofluorescence evidence was supported by ultrastructural data, which clearly confirmed that SNAP‐25 was undetectable in GABAergic terminals identified by both their typical morphology and specific staining for GABA. Interestingly, our ultrastructural results confirmed that a subset of glutamatergic synapses do not contain detectable levels of SNAP‐25. The present study extends our previous findings obtained in rodent hippocampus and provides evidence that SNAP‐25 expression is highly variable between different axon terminals both in rat and human brain. The heterogeneous distribution of SNAP‐25 may have important implications not only in relation to the function of the protein as a SNARE but also in the control of network excitability. J. Comp. Neurol. 506:373–386, 2008. © 2007 Wiley‐Liss, Inc.
Modularity, reuse, and hierarchy: Measuring complexity by measuring structure and organization
Authors: Hornby Gregory S. 
Published: November 2007

AbstractTo develop better complexity measures, a reasonable approach is to base them on those principles of design that designers use. Modularity, reuse, and hierarchy (MR&H) have been identified by engineers as useful principles for designing complex systems, and these characteristics can be seen in Nature. Here, we develop metrics for each of MR&H, and then use them to develop several metrics of structure and organization. Further, we propose to evaluate complexity measures both empirically and on a set of abstract object‐construction examples. After applying these tests to a handful of previously defined complexity measures, as well as ones we define here, we find that only two of our measures pass both sets of tests. © 2007 Wiley Periodicals, Inc. Complexity, 2007
A Polymer‐Bound Oxidovanadium(IV) Complex Prepared from an L‐Cysteine‐Derived Ligand for the Oxidative Amination of Styrene
Authors: Maurya Mannar R. , Kumar U. , Correia Isabel , Adão Pedro , Costa Pessoa João 
Published: November 2007

AbstractThe ligand H2sal‐cys (I) derived from salicylaldehyde and L‐cysteine has been covalently bonded to chloromethylated polystyrene cross‐linked with 5 % divinylbenzene. Upon treatment with [VO(acac)2] in dimethylformamide (DMF) the polystyrene‐bound ligand PS‐H2sal‐cys (II) gave the oxidovanadium(IV) complex, PS‐[VO(sal‐cys)·DMF] (1). The corresponding neat complex, [VO(sal‐eta)]2 (2), has also been prepared similarly in methanol. These complexes have been characterised by IR, electronic, EPR spectroscopic studies, magnetic susceptibility measurements and thermal as well as scanning electron micrographs studies. Complex [VO(sal‐eta)]2 exhibits a medium intensity band at 980 cm–1 in the IR spectrum due to ν(V=O) stretch. Broad features of the EPR spectrum for the neat complex along with magnetic susceptibility studies suggest the presence of antiferromagnetic exchange interaction between two vanadium centers in close proximity. Both complexes catalyze the oxidative amination of styrene, in mild basic conditions, with secondary amines (diethylamine, imidazole, and benzimidazole) and gave a mixture of two aminated products in good yields. Amongst the two aminated products, the anti‐Markovnikov product is favored over the Markovnikov one due to the steric hindrance posed by the secondary amines. The polymer‐anchored heterogeneous catalyst is free from leaching during catalytic action and recyclable.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Numerical simulations of droplet formation in a cross‐junction microchannel by the lattice Boltzmann method
Authors: Wu Long , Tsutahara Michihisa , Kim LaeSung , Ha ManYeong 
Published: November 2007

AbstractAn immiscible liquid–liquid multiphase flow in a cross‐junction microchannel was numerically studied using the lattice Boltzmann method. An improved, immiscible lattice BGK model was proposed by introducing surface tension force based on the continuum surface force (CSF) method. Recoloring step was replaced by the anti‐diffusion scheme in the mixed region to reduce the side‐effect and control the thickness of the interface. The present method was tested by the simulation of a static bubble. Laplace's law and spurious velocities were examined. The results show that our model is more advantageous for simulations of immiscible fluids than the existing immiscible lattice BGK models. Computational results of multiphase flow in a cross‐junction microchannel were obtained and analyzed based on dimensionless numbers. It is found that the flow pattern is decided mostly by the capillary number at a small inlet flux. However, at the same capillary number, a large inlet flux will lead to much smaller droplet generation. For this case, the flow is determined by both the capillary number and the Weber number. Copyright © 2007 John Wiley & Sons, Ltd.
High‐order 𝒞1 finite‐element interpolating schemes—Part II: Nonlinear semi‐Lagrangian shallow‐water models
Authors: Djoumna G. , Le Roux D. Y. , Pierre R. 
Published: November 2007

AbstractThe finite‐element, semi‐implicit, and semi‐Lagrangian methods are used on unstructured meshes to solve the nonlinear shallow‐water system. Several 𝒞1 approximation schemes are developed for an accurate treatment of the advection terms. The employed finite‐element discretization schemes are the P–P1 and P2–P1 pairs. Triangular finite elements are attractive because of their flexibility for representing irregular boundaries and for local mesh refinement. By tracking the characteristics backward from both the interpolation and quadrature nodes and using 𝒞1 interpolating schemes, an accurate treatment of the nonlinear terms and, hence, of Rossby waves is obtained. Results of test problems to simulate slowly propagating Rossby modes illustrate the promise of the proposed approach in ocean modelling. Copyright © 2007 John Wiley & Sons, Ltd.
Tactile‐associated fMRI recruitment of the cervical cord in healthy subjects
Authors: Agosta Federica , Valsasina Paola , Caputo Domenico , Rocca Maria A. , Filippi Massimo 
Published: November 2007

AbstractUsing spinal cord functional magnetic resonance imaging (fMRI), 12 right‐handed healthy subjects were scanned during a tactile stimulation of the palm of the right hand. The task‐related mean signal change was computed for all activated voxels within the cervical cord, and separately, in the four cord quadrants (right and left anterior, right and left posterior) from C5 to C8. The frequency of fMRI activity at each cord level was obtained by assigning a score of 25% at each active quadrant and by averaging the percentage of active quadrants at each level of all subjects. The difference in the occurrence of fMRI activity (a) in right versus left, and anterior versus posterior cord, and (b) among the different cord levels, was evaluated using a random effect logistic regression model, with the frequency of fMRI activity as the dependent variable and the subject as the grouping factor. The task‐related mean signal change of all activated voxels of the cord was 3.2% (SD = 0.8%). During the tactile stimulation, subjects showed a higher occurrence of fMRI cord activity in the right than in the left cervical cord (odds ratio = 2.25, 95% confidence interval = 1.31–3.87, P = 0.003). A significant heterogeneity in frequency of fMRI activity between cord levels was also observed (P < 0.001), with the highest frequencies of fMRI activity detected at C6 and C7. Spinal cord fMRI enables to obtain reliable physiological information on the activity of human spinal circuits associated to tactile stimulation. This holds significant promise for a better planning and conduct of studies of people with diseased spinal cords. Hum Brain Mapp 2009. © 2007 Wiley‐Liss, Inc.
Dealing with celebrity and accountability in the top job
Authors: Ranft Annette L. , Ferris Gerald R. , Perryman Alexa A. 
Published: November 2007

AbstractToday, human resource executives assume prominent leadership roles in their firms and play important roles in the strategy process. Along with the expansion and evolution of the HR function, the responsibilities of coordination, control, and accountability for organizations and their leaders, particularly the CEO, remain. Forming strong relationships with CEOs thus is viewed as one way to encourage HR's prominence in the firm's overall success, particularly its financial health. In recent years, CEOs' presence in the mass media has surged as well, with some CEOs achieving celebrity status. Celebrity status has the potential to increase CEO discretion, decrease CEO accountability, and expand firm resources. As such, achieving celebrity status can affect the relationship between CEOs and HR executives in regard to accountability. In this article, we discuss accountability as a key job demand and address some of the complexities and dynamics of CEO accountability. © 2007 Wiley Periodicals, Inc.
In vitro cytotoxicity of single‐walled carbon nanotube/biodegradable polymer nanocomposites
Authors: Shi Xinfeng , Sitharaman Balaji , Pham Quynh P. , Spicer Patrick P. , Hudson Jared L. , Wilson Lon J. , Tour James M. , Raphael Robert M. , Mikos Antonios G. 
Published: November 2007

AbstractInjectable nanocomposites made of biodegradable poly(propylene fumarate) and the crosslinking agent propylene fumarate–diacrylate as well as each of three forms of single‐walled carbon nanotubes (SWNTs) were evaluated for their in vitro cytotoxicity. Unreacted components, crosslinked networks, and degradation products of the nanocomposites were investigated for their effects on cell viability using a fibroblast cell line in vitro. The results did not reveal any in vitro cytotoxicity for purified SWNTs, SWNTs functionalized with 4‐tert‐butylphenylene, and ultra‐short SWNTs at 1– 100 μg/mL concentrations. Moreover, nearly 100% cell viability was observed on all crosslinked nanocomposites and cell attachment on their surfaces was comparable with that on tissue culture polystyrene. The degradation products of the nanocomposites displayed a dose‐dependent adverse effect on cells, which was partially due to increased osmolarity by the conditions of accelerated degradation and could be overcome at diluted concentrations. These results demonstrate that all three tested nanocomposites have favorable cytocompatibility for potential use as scaffolds for bone tissue engineering applications. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 2008