bluuebunny/crossref_metadata_2025 huggingface dataset:
Conditional second-order short-crested water waves applied to extreme wave episodes
Authors: JENSEN JØRGEN JUNCHER
Published: December 2005

A derivation of the mean second-order short-crested wave pattern and associated wave kinematics, conditional on a given magnitude of the wave crest, is presented. The analysis is based on the second-order Sharma and Dean finite-water wave theory. A comparison with a measured extreme wave profile, the Draupner New Year Wave, shows a good agreement in the mean, indicating that this second-order wave can be a good identifier of the shape and occurrence of extreme wave events. A discussion on its use as an initial condition for a fully nonlinear three-dimensional surface wave analysis is given.
Mixing and dissipation in particle-driven gravity currents
Authors: NECKER F. , HÄRTEL C. , KLEISER L. , MEIBURG E.
Published: December 2005

Results are presented from a high-resolution computational study of particle-driven gravity currents in a plane channel. The investigation was conducted in order to obtain better insight into the energy budget and the mixing behaviour of such flows. Two- and three-dimensional simulations are discussed, and the effects of different factors influencing the flow are examined in detail. Among these are the aspect ratio of the initial suspension reservoir, the settling speed of the particles, and the initial level of turbulence in the suspension. While most of the study is concerned with the lock-exchange configuration, where the initial height of the suspension layer is equal to the height of the channel, part of the analysis is also done for a deeply submerged case. Here, the suspension layer is only one-tenth of the full channel height. Concerning the energy budget, a careful analysis is undertaken of dissipative losses in the flow. Dissipative losses arising from the macroscopic fluid motion are distinguished from those due to the microscopic flow around each sedimenting particle. It is found that over a large range of settling velocities and suspension reservoir aspect ratios, sedimentation accounts for roughly half of all dissipative losses. The analysis of the mixing behaviour of the flow concentrates on the mixing between interstitial and ambient fluid, which are taken to be of identical density. The former is assumed to carry a passive contaminant, whose dispersion with time is analysed qualitatively and quantitatively by means of Lagrangian markers. The simulations show the mixing between interstitial and ambient fluid to be more intense for larger values of the particle settling velocity. Finally, the question is addressed of whether or not initial turbulence in the suspension may exert a significant effect on the flow evolution. To this end, results from three simulations with widely different levels of initial kinetic energy are compared. While the initial turbulence level strongly affects the mixing within the current, it has only a small influence on the front velocity and the overall sedimentation rate.
Spreading of a drop of neutrally buoyant suspension
Authors: NICOLAS MAXIME
Published: December 2005

The spreading of suspension drops on a flat surface is studied using mixtures of liquid and density-matched particles. As expected from an energy balance model, the spreading factor is reduced with increasing particle volume fraction. This decrease is quantitatively understood through an effective viscosity coefficient. However, for large drop Reynolds number, the particles are not uniformly distributed into a spread drop but form an annulus. For higher impact velocities, a particle-induced break-up of the drop is observed.
Displacement of a three-dimensional immiscible droplet in a duct
Authors: KANG QINJUN , ZHANG DONGXIAO , CHEN SHIYI
Published: December 2005

The displacement of a three-dimensional immiscible droplet subject to gravitational forces in a duct is studied with the lattice Boltzmann method. The effects of the contact angle and capillary number (the ratio of viscous to surface forces) on droplet dynamics are investigated. It is found that there exists a critical capillary number for a droplet with a given contact angle. When the actual capillary number is smaller than the critical value, the droplet moves along the wall and reaches a steady state. When the capillary number is greater than the critical value, one or more small droplets pinch off from the wall or from the rest of the droplet, depending on the contact angle and the specific value of the capillary number. As the downstream part of the droplet is pinching off, a bottleneck forms and its area continues decreasing until reaching zero. The general trend found in a previous two-dimensional study that the critical capillary number decreases as the contact angle increases is confirmed. It is shown that at a fixed capillary number above the critical value, increasing the contact angle results in a larger first-detached portion. At a fixed contact angle, increasing the capillary number results in an increase of the size of the first detached droplet for $\theta\,{=}\,78^\circ$ and $\theta\,{=}\,90^\circ$, but a decrease for $\theta\,{=}\,118^\circ$. It is also found that the droplet is stretched longer as the capillary number becomes larger. For a detaching droplet, the maximal velocity value occurs near the bottleneck between the up-and downstream parts of the droplet and the shear stress there reaches a local maximum. The three-dimensional effects are most clearly seen for $\theta\,{=}\, 90^\circ$, where the wetted length and wetted area vary in the opposite direction and the shape of the interface between the wall and the droplet is distorted severely from the original round shape.
On the orientation of stiff fibres suspended in turbulent flow in a planar contraction
Authors: PARSHEH MEHRAN , BROWN MATTHEW L. , AIDUN CYRUS K.
Published: December 2005

The influence of turbulence on the orientation state of a dilute density matched suspension of stiff fibres at high Reynolds number in a planar contraction is investigated. High-speed imaging and laser-Doppler velocimetry techniques are used to quantify fibre orientation distribution and turbulent characteristics. A nearly homogeneous isotropic grid-generated turbulent flow is introduced at the contraction inlet. Flow Reynolds number and inlet turbulent characteristics are varied in order to determine their effects on orientation distribution. The orientation anisotropy is shown to be accurately modelled by a Fokker-Planck type equation. Results show that rotational diffusion is highly influenced by inlet turbulent characteristics and decays exponentially with convergence ratio. Furthermore, the effect of turbulent energy production in the contraction is shown to be negligible. Also, the results show that the flow Reynolds number has negligible effect on the development of orientation anisotropy, and the influence of turbulence on fibre rotation is negligible for rotational Péclet number $\gt$10.
A numerical study on the evolution and structure of a stress-driven free-surface turbulent shear flow
Authors: TSAI WU-TING , CHEN SHI-MING , MOENG CHIN-HOH
Published: December 2005

Turbulent shear flow beneath a flat free surface driven by a surface stress is simulated numerically to gain a better understanding of the hydrodynamic processes governing the scalar transfer across the air-water interface. The simulation is posed to mimic the subsequent development of a wind-driven shear layer as in a previous experiment except that the initiation of the surface waves is inhibited, thus focusing on the boundary effect of the stress-imposed surface on the underlying turbulent flow and vice versa. Despite the idealizations inherent in conducting the simulation, the computed flow exhibits the major surface features, qualitatively similar to those that appear in the laboratory and field experiments. Two distinct surface signatures, namely elongated high-speed streaks and localized low-speed spots, are observed in the simulated flow. Including temperature as a passive tracer and describing an upward heat flux at the surface, we obtain high-speed streaks that are colder and low-speed spots that are warmer than the surrounding regions. The high-speed streaks, arranged with somewhat equal cross-spacing of centimetres scale, are formed by an array of streamwise jets within the viscous sublayer immediately next to the surface. Beneath the streaks, counter-rotating streamwise vortex pairs are observed among other prevailing elongated vortices. However, they are significantly shorter in length and more irregular than their corresponding high-speed streaks at the surface. Accompanying the more organized high-speed streaks, localized regions of low streamwise velocity emerge randomly on the surface. These low-speed spots are attributed to strong upwelling flows which disrupt the viscous sublayer and also bring up the submerged fluids of low streamwise velocity. The occasional interruptions of the streamwise high-speed jets by the upwelling flows account for bifurcation or dislocation of the surface streaks. Statistics of the turbulence are presented and their implications for the formation of the flow structures are discussed.
Crossflow instability in rotor-stator flows with axial inward throughflow
Authors: PONCET S. , CHAUVE M.-P.
Published: December 2005

From visualizations and velocity measurements, we study the formation of new spiral patterns at the periphery of a rotor-stator cavity when an axial inward throughflow is superimposed. We determine the transition diagram for a given intermediate aspect ratio in the plane (${\hbox {\it Re}},V_z$), where ${\hbox {\it Re}}$ is the rotational Reynolds number and $V_z$ the axial velocity in the radial gap between the rotating disk and the shroud. Both techniques are used to characterize the frequency, the azimuthal wavenumber, the inclination angle of the spirals and to localize them axially and radially. We also show that this new instability is a crossflow instability due to the strong competition between rotation and throughflow.
Priority setting in health – a political economy perspective
Authors: GODDARD MARIA , HAUCK KATHARINA , PREKER ALEX , SMITH PETER C.
Published: December 2005

Most countries face high demands on their health care systems and have limited resources with which to meet them. Priority setting seeks to address these problems by proposing rules to decide which groups of patients or disease areas should secure favoured access to limited health care resources. The economic approach towards priority setting, particularly in the form of cost-effectiveness analysis, is commonly advocated. However, despite many decades of refinement of the technical and methodological issues arising from the use of economic evaluation in priority setting, decision makers continue to diverge frequently from the principles of economic evaluation. Our approach in this paper is to highlight the potential contribution of models of political economy to understanding what constitutes rational behaviour when agents operate within political and institutional constraints. We argue that there may be potentially greater benefits to be gained from exploration and analysis of priority setting using models based on concepts such as median voter and competing interest groups, than from further efforts to refine the techniques of economic evaluation.
Catalytic Activity of β‐Amylase from Barley in Different Pressure/Temperature Domains
Authors: Heinz Volker , Buckow Roman , Knorr Dietrich
Published: December 2005

The depolymerization of starch by β‐amylase during exposure to hydrostatic pressure up to 700 MPa and within a temperature range from 20 to 70 °C has been investigated. Inactivation of the enzyme as well as alterations in conversion speed in response to combined pressure‐temperature treatments were assessed by analyzing the kinetic rate constants. At 200 MPa a significant stabilization of the enzyme against heat inactivation was observed. However, high pressure also impedes the catalytic reaction and a progressive reduction of the conversion rate constants with increasing pressure was found at all temperatures investigated. For the overall reaction of maltose liberation from soluble starch in ACES buffer at pH 5.6 an optimum was identified at 106 MPa and at 63 °C, which is approximately 7 °C above the local maximum at ambient pressure (0.1 MPa). Gelatinization of nonsoluble starch granules in response to pressure‐temperature (p‐T) treatment has been inspected by phase‐contrast microscopy and yielded circular curves of identical effect in the p‐T plane.
Directional Surface Plasmon‐Coupled Emission from a 3 nm Green Fluorescent Protein Monolayer
Authors: Kostov Yordan , Smith Derek S. , Tolosa Leah , Rao Govind , Gryczynski Ignacy , Gryczynski Zygmunt , Malicka Joanna , Lakowicz Joseph R.
Published: December 2005

High‐sensitivity detection schemes are of great interest for a number of applications. Unfortunately, such schemes are usually high‐cost. We demonstrate a low‐cost approach to a high‐sensitivity detection scheme based on surface plasmon‐coupled emission (SPCE). The SPCE of a monomolecular layer of green fluorescent protein (GFP) is reported here. The protein was electrostatically attached to a thin, SiO2‐protected silver film deposited on a quartz substrate. The visible, directional emission of GFP was observed at a sharp, well‐defined angle of 47.5° from the normal to the coupling prism, and the spectrum corresponded to that of GFP. The SPCE resulting from the reverse Kretschmann configuration showed a 12‐fold enhancement over the free space fluorescence. The directional emission was 97% p‐polarized. The directionality and high polarization can be coupled with the intrinsic spectral resolution of SPCE to be used in the design miniaturized spectrofluorometers. The observation of SPCE in the visible region of the spectrum from a monolayer of protein opens up new possibilities in protein‐based sensing.
Bioprocess Engineering Issues That Would Be Faced in Producing a DNA Vaccine at up to 100 m3 Fermentation Scale for an Influenza Pandemic
Authors: Hoare Mike , Levy M. Susana , Bracewell Daniel G. , Doig Steven D. , Kong Simyee , Titchener‐Hooker Nigel , Ward John M. , Dunnill Peter
Published: December 2005

The risk of a pandemic with a virulent form of influenza is acknowledged by the World Health Organization (WHO) and other agencies. Current vaccine production facilities would be unable to meet the global requirement for vaccine. As a possible supplement a DNA vaccine may be appropriate, and bioprocess engineering factors bearing on the use of existing biopharmaceutical and antibiotics plants to produce it are described. This approach addresses the uncertainty of timing of a pandemic that precludes purpose‐built facilities. The strengths and weaknesses of alternative downstream processing routes are analyzed, and several gaps in public domain information are addressed. The conclusion is that such processing would be challenging but feasible.
Production of Oligoglucuronans by Enzymatic Depolymerization of Nascent Glucuronan
Authors: Delattre Cédric , Michaud Philippe , Keller Cyril , Courtois Bernard , Courtois Josiane
Published: December 2005

An original bioreactor process for production of oligoglucuronans was developed using the Sinorhizobium meliloti M5N1CS strain that produces glucuronan. This anionic homopolysaccharide was composed of β‐d‐(1,4)‐glucopyranosyluronic residues variably O‐acetylated at C‐3 and/or C‐2 positions according to culture conditions. It was depolymerized during its biosynthesis by addition of a fungal glucuronan lyase activity in broths. After purification by tangential ultrafiltration and low‐pressure liquid chromatography, 1H NMR and ESI‐Q/TOF‐MS characterized the poly‐ and oligoglucuronic acid fractions. This enzymatic bioreactor strategy authorized the production in gram quantity of an unsaturated and no acetylated oligoglucuronan with a degree of polymerization of 3.
Engineering Select Physical Properties of Cross‐Linked Red Blood Cells and a Simple a Priori Estimation of Their Efficacy as an Oxygen Delivery Vehicle within the Context of a Hepatic Hollow Fiber Bioreactor
Authors: Gordon Jason E. , Dare Matthew R. , Palmer Andre F.
Published: December 2005

Bovine red blood cells (bRBCs) can potentially provide a simplistic and economic means of improving oxygenation within hollow fiber (HF) bioreactor cell cultures. Bovine RBCs are also interesting since many of their physical properties can be altered as a result of glutaraldehyde (G) cross‐linking. Cross‐linking bRBCs produces an oxygen carrier that is expected to be beneficial under specific circumstances (i.e., delivery of oxygen to cells that are sensitive to free hemoglobin (Hb) and cells that require low inlet oxygen tensions). We have examined the osmotic stability and electrophoretic mobility of cross‐linked bRBCs and observed that cross‐linking improves osmotic stability while minimally impacting electrophoretic mobility. The oxygen binding/dissociation properties (P50 and n) of cross‐linked bRBCs were also measured, and under the reported reaction conditions, cross‐linking increased the oxygen affinity and reduced the cooperativity of bRBCs. A basic Krogh tissue cylinder model was then utilized to provide a quick a priori estimate of oxygen delivery and release to hepatocytes housed within a HF bioreactor in order to demonstrate potential oxygenation benefits arising with both normal and cross‐linked bRBC media supplementation. This model showed that bRBCs generally improved oxygen delivery and release to HF cell cultures and that cross‐linked bRBCs are particularly beneficial in specifically targeting oxygen delivery to cells maintained at low inlet oxygen tensions. Additionally, the model showed that bRBC supplementation can significantly improve oxygen delivery without requiring extreme bRBC concentrations.
Hydrogen Production from Glucose by Anaerobes
Authors: Ogino Hiroyasu , Miura Takashi , Ishimi Kosaku , Seki Minoru , Yoshida Hiroyuki
Published: December 2005

Various anaerobes were cultivated in media containing glucose. When 100 mL of thioglycollate medium containing 2.0% (w/v) glucose was used, Clostridium butyricum ATCC 859, NBRC 3315, and NBRC 13949 evolved 227–243 mL of biogas containing about 180 mL of hydrogen in 1 day. Although some strains had some resistance against oxygen, C. butyricum ATCC 859 and 860 did not have it. C.butyricum NBRC 3315 and Enterobacter aerogenes NBRC 13534 produced hydrogen in the presence of glucose or pyruvic acid, and E. aerogenes NBRC 13534 produced hydrogen by not only glucose and pyruvic acid but also dextrin, sucrose, maltose, galactose, fructose, mannose, and mannitol. When a medium containing 0.5% (w/v) yeast extract and 2.0% (w/v) glucose was used, E. aerogenes NBRC 13534 evolved more biogas and hydrogen than C. butyricum NBRC 3315 in the absence of reducing agent.
Rhamnolipid Surfactants: An Update on the General Aspects of These Remarkable Biomolecules
Authors: Nitschke Marcia , Costa Siddhartha G. V. A. O. , Contiero Jonas
Published: December 2005

Pseudomonas strains are able to biosynthesize rhamnose‐containing surfactants also known as rhamnolipids. These surface‐active compounds are reviewed with respect to chemical structure, properties, biosynthesis, and physiological role, focusing on their production and the use of low‐cost substrates such as wastes from food industries as alternative carbon sources. The use of inexpensive raw materials such as agroindustrial wastes is an attractive strategy to reduce the production costs associated with biosurfactant production and, at same time, contribute to the reduction of environmental impact generated by the discard of residues, and the treatment costs. Carbohydrate‐rich substrates generated low rhamnolipid levels, whereas oils and lipid‐rich wastes have shown excellent potential as alternative carbon sources.
Proteolytically Degradable Hydrogels with a Fluorogenic Substrate for Studies of Cellular Proteolytic Activity and Migration
Authors: Lee Soo‐Hong , Miller Jordan S. , Moon James J. , West Jennifer L.
Published: December 2005

We have developed proteolytically degradable hydrogels with covalently immobilized fluorogenic protease substrates to visualize extracellular proteolytic activity and cell migration in three dimensions. Dye quenched‐bovine serum albumin (DQ‐BSA), a quenched, proteolytically activated fluorogenic substrate, was conjugated to poly(ethylene glycol) (PEG)‐monoacrylate, and the product (DQ‐BSA‐PEG) was then covalently incorporated into proteolytically degradable and cell adhesive PEG hydrogels via photopolymerization. The DQ‐BSA‐PEG substrate in solution and incorporated into hydrogels exhibited significantly enhanced fluorescence after exposure to enzymes. Fibroblasts seeded within this hydrogel spread in three dimensions and extended lamellipodia. Cell migration and proteolytic activity were visualized using confocal microscopy. Proteolytic activity was concentrated near cell surfaces and remained present in the tracks where cell migration had occurred.
Flux Balance Analysis of Photoautotrophic Metabolism
Authors: Shastri Avantika A. , Morgan John A.
Published: December 2005

Photosynthesis is the principal process responsible for fixation of inorganic carbon dioxide into organic molecules with sunlight as the energy source. Potentially, many chemicals could be inexpensively produced by photosynthetic organisms. Mathematical modeling of photoautotrophic metabolism is therefore important to evaluate maximum theoretical product yields and to deeply understand the interactions between biochemical energy, carbon fixation, and assimilation pathways. Flux balance analysis based on linear programming is applied to photoautotrophic metabolism. The stoichiometric network of a model photosynthetic prokaryote,Synechocystissp. PCC 6803, has been reconstructed from genomic data and biochemical literature and coupled with a model of the photophosphorylation processes. Flux map topologies for the hetero‐, auto‐, and mixotrophic modes of metabolism under conditions of optimal growth were determined and compared. The roles of important metabolic reactions such as the glyoxylate shunt and the transhydrogenase reaction were analyzed. We also theoretically evaluated the effect of gene deletions or additions on biomass yield and metabolic flux distributions.
Deactivation of Formate Dehydrogenase (FDH) in Solution and at Gas‐Liquid Interfaces
Authors: Bommarius Andreas S. , Karau Andreas
Published: December 2005

Enzymes, increasingly important in the synthesis of fine chemicals and pharmaceutical intermediates, are often insufficiently stable under reacting conditions. We have investigated the stability, in homogeneous aqueous solution and at gas‐liquid interfaces, of formate dehydrogenase (FDH), important for cofactor regeneration, from Candida boidinii and overexpressed in E. coli. When exposed to mechanical stress, residual activity, [E]t/[E]0, and residual protein were found to scale proportionally with gas‐liquid surface area in the bubble column, verifying a surface‐driven process, and with time and total throughput in a gear pump, but did not seem to be influenced much by shear in a Couette viscometer. All FDH variants are deactivated by chaotropes but not kosmotropes: the first‐order deactivation constant kd correlates well with the Jones‐Dole coefficient B but not well with the surface tension increment Δσ of various concentrated ammonium salt solutions. This finding might provide guidance for focusing the search for quantitative theories of Hofmeister effects.
Noninvasive Diagnosis of a Single Cell with a Probe Beam
Authors: Wu Xing‐Zheng , Terada Satoshi
Published: December 2005

It is important to distinguish a living/dead cell in cell culture, especially in the regenerate medicine field including cell therapy, since those cells are usually in short supply and consequently the ex vivo culture process should be operated strictly. Conventional methods for distinguishing a living from a dead cell usually require labeling with a dye, which spoils the culture of the cell. Here we show a simple noninvasive method for diagnosing a dead or alive cell with a probe beam. If a cell is alive, the active transport of materials across the cell membrane causes a change of concentration gradients, and this change further induces a change of deflection of a probe beam passing through a vicinity of the cell membrane. If a cell is dead, no or little change in deflection of the probe beam is induced because no or little active materials movement across the cell membrane exists. The deflection of the probe beam is monitored, and judgment on whether a cell is dead or alive from the deflection signal agreed with the conventional decision.
Enhanced Production of Hydroperoxides by Immobilized Lipoxygenase in the Presence of Cyclodextrins
Authors: Pérez‐Gilabert Manuela , García‐Carmona Francisco
Published: December 2005

The advantages of the presence of cyclodextrins in a reaction catalyzed by immobilized lipoxygenase at neutral pH are reported for the first time. The steady‐state rate in the presence of β‐cyclodextrins was seven times higher than in control experiments using the same concentration of linoleic acid; furthermore the percentage of substrate conversion (and product accumulation) obtained in the presence of β‐cyclodextrins was higher than in the control assays. The optimum concentration of free linoleic acid coincided with the critical micellar concentration for linoleic acid at neutral pH. The operational stability of the immobilized enzyme increased in the presence of β‐cyclodextins, while an increase in the percentage of 13‐HPOD was also observed.
An Immobilized Biotin Ligase: Surface Display of Escherichia coli BirA on Saccharomycescerevisiae
Authors: Parthasarathy Ranganath , Bajaj Jitin , Boder Eric T.
Published: December 2005

The Escherichia coli biotin ligase enzyme BirA has been extensively used in recent years to generate site‐specifically biotinylated proteins via a biotin acceptor peptide tag. In the present study, BirA was displayed for the first time on the yeast Saccharomyces cerevisiae using the Aga1p‐Aga2p platform and assayed using a peptide‐tagged protein as the substrate. The enzyme is fully functional and resembles the soluble form in many of its properties, but the yeast‐displayed enzyme demonstrates stability and reusability on the time scale of weeks. Thus, the yeast‐displayed BirA system represents a facile and highly economical alternative for producing site‐specifically biotinylated proteins.
Children’s Block Balancing Revisited: No Evidence for Representational Redescription
Authors: Krist Horst , Horz Holger , Schönfeld Tina
Published: December 2005

According to the theory of representational redescription (RR theory, Karmiloff-Smith, 1992 ), children’s reasoning is grounded on implicit knowledge. This initial knowledge is first consolidated and then subjected to reiterative cycles of representational redescription, leading to knowledge of increasing accessibility. As one important piece of evidence supporting RR theory a U-shaped developmental trend regarding children’s ability to balance asymmetrical blocks has been reported. To assess whether this trend is a robust phenomenon, we investigated how 4-, 5-, 6-, and 8-year-olds (N = 65) attempted to balance symmetrical and asymmetrical blocks on a narrow support. Independent from block type, we found quasi-linear improvements with age in all performance measures. These results question the robustness of the U-shaped developmental trend regarding children’s block balancing and fail to provide any evidence for representational redescription.
Fostering Diagrammatic Reasoning in Science Education
Authors: Hardy Ilonca , Schneider Michael , Jonen Angela , Stern Elsbeth , Möller Kornelia
Published: December 2005

In a study with 56 third-graders, we tested whether reasoning with line graphs can be enhanced by representational activities within a curriculum on floating and sinking of objects in water. We hypothesized that representing mass and volume on the opposite arms of a balance beam allows the simultaneous consideration of both dimensions for a representation of density, and therefore will be particularly helpful for drawing inferences from the slopes of line graphs. In an experimental classrooms study, half of the students used the balance beam, while the other half worked with self-constructed representations. Five months after the instructional unit, students who had been familiarized with the quantitative interpretation of proportional information on the balance beam outperformed students who had worked with self-constructed representation in their interpretation of line graphs referring to density, but only marginally when referring to speed.
An examination of the process and magnitude of ionospheric plasma supply to the magnetosphere
Authors: Huddleston M. M. , Chappell C. R. , Delcourt D. C. , Moore T. E. , Giles B. L. , Chandler M. O.
Published: December 2005

The contribution of ionospheric plasma to the Earth's magnetosphere has been recognized for more than 3 decades. The magnitude of this contribution has become more evident over that same time period with the observed magnitude of the low‐energy ionospheric supply increasing as the measurement techniques improved. Estimates based on Dynamics Explorer measurements in the mid‐1980s suggested that the ionospheric plasma supply is sufficient to populate the plasmasphere, plasma trough, plasma sheet, and magnetotail lobes. Recent measurements from the Thermal Ion Dynamics Experiment on the Polar spacecraft have been used in conjunction with an ion trajectory model to reexamine the process and magnitude of the ionospheric supply of magnetospheric plasma. These measurements reveal the energy, pitch angle, and flux characteristics of the upward flowing polar wind over broad regions of the high‐latitude ionosphere. Onboard measurement of spacecraft potential is found to be a fundamental element in interpreting the measured ion outflow. Newly derived polar wind fluxes are determined to be near 6.0 × 107 ions cm−2 s−1 at 5000 km altitude during local winter and magnetically quiet conditions. Using the measured ionospheric source characteristics in combination with the trajectory code reveals the nature of the ionospheric/magnetosphere filling process and shows that the ionospheric source is sufficient to supply the observed densities and energies of the plasma sheet and magnetotail lobes. Many of the ionospheric particles are further transformed to ring current energies and locations after circulation through the plasma sheet. This measurement/calculation approach is able to show which regions of the high‐latitude ionosphere are important for plasma sheet/ring current filling. The ionospheric sources used in the calculations include the dominant polar wind, the cleft ion fountain, and the auroral zone.
Hyperpycnal river flows from an active mountain belt
Authors: Dadson Simon , Hovius Niels , Pegg Stuart , Dade W. Brian , Horng M. J. , Chen H.
Published: December 2005

Rivers draining the tectonically active island of Taiwan commonly discharge suspended sediment to the ocean at hyperpycnal concentrations (>40 kg m−3), typically during typhoon‐driven floods. During the period 1970–1999, between 99 and 115 Mt yr−1 of sediment was discharged at hyperpycnal sediment concentrations from Taiwan to the sea. This amount represents 30–42% of the total sediment discharge from Taiwan to the ocean. The spatial distribution of hyperpycnal discharge broadly mirrors the pattern of total sediment discharge, and rivers draining catchments having recent earthquakes and weak rocks, such as the Choshui and Erhjen, discharge up to 50–70% of their sediment at hyperpycnal concentrations. Following the Chi‐Chi earthquake, the frequency of hyperpycnal flows increased, because of an earthquake‐driven increase in sediment supply. Landslides triggered by the Chi‐Chi earthquake have resulted in an increase in the concentration of suspended sediment in rivers for a given water discharge. In turn, the threshold flood discharge required to generate hyperpycnal flow has decreased, and so hyperpycnal flows are occurring more frequently. Our findings suggest that if hyperpycnal plumes evolve into bottom‐hugging gravity currents descending to and ultimately debouching in the deep sea, earthquakes may be recorded as bundles of turbidites.
Deglacial paleoceanographic history of the Bay of Plenty, New Zealand
Authors: Samson Catherine R. , Sikes Elisabeth L. , Howard William R.
Published: December 2005

We present sea surface temperature (SST) records with centennial‐scale resolution from the Bay of Plenty, north of New Zealand. Foraminiferal assemblage‐based paleo‐SST estimates provide a deglacial record of SST since 16.5 14C ka. Average Holocene SSTs are 15.6°C for winter and 20.3°C for summer, whereas average glacial values were 14.2°C for winter and 19.5°C for summer. Compared to modern time, cooling of SSTs at the Last Glacial Maximum (LGM) was ∼0.9°C in winter and ∼1.5°C in summer. The shift from glacial to Holocene temperatures began at 14.25 14C ka, warming by ∼2°C until 12.85 14C ka when temperatures dipped back to glacial values at 11.65 14C ka. The timing of this return to glacial‐like SST correlates well with the Antarctic Cold Reversal (ACR) rather than the Younger Dryas and documents that the influence of the ACR extended into the subtropics of the Southern Hemisphere, at least in this region of the southwest Pacific. By 10.55 14C ka an SST maximum in summer SSTs of up to 3°C warmer than modern occurred (∼24°C), after which SST dropped, remaining at present‐day temperatures since 9.3 14C ka. This early Holocene climatic optimum has been widely noted in the Southern Ocean, and this record indicates that this phenomenon also extended into the subtropics to the north of New Zealand.
Northwest Africa upwelling and the Atlantic climate variability
Authors: Polo Irene , de Fonseca Belén Rodríguez , Sheinbaum Julio
Published: December 2005

Summer Subtropical North Atlantic (SNA) Sea Surface Temperature (SST) anomalies have recently been connected to winter atmospheric variability in the Atlantic European sector. Wind‐induced surface heat flux changes are believed to be the major cause of SNA SST anomalies. However, the impact of coastal upwelling off northwest Africa, on SNA SST variability has been overlooked. Since the area is known to have a richer dynamical behavior than other regions of the central SNA, subsurface thermal anomalies are included in our analysis. Results show that this upwelling region affects significantly the patterns of co‐variability between climatically relevant variables, suggesting that more intricate processes may be involved in generating surface anomalies that, in turn, may influence the European sector climate variability.
High‐speed camera observations of negative ground flashes on a millisecond‐scale
Authors: Ballarotti M. G. , Saba M. M. F. , Pinto O.
Published: December 2005

A study of cloud‐to‐ground lightning characteristics based on high‐speed camera observations of 455 flashes related to 40 thunderstorms is presented. The Brazilian Lightning Location Network (RINDAT) was used to calculate the polarity and the distance of the flashes to the camera. In some cases, a fast electric field flat antenna was also used to calculate the time difference between strokes on a microsecond‐scale. Some general features of the data set are briefly presented. This paper is focused on two specific characteristics observed in video records with a frame a rate of 1,000 frames/s: (i) six strokes presenting two ground terminations that were simultaneously connected for some milliseconds, (ii) and a high number of continuing current occurrences with durations less than 10 ms.
On the annual cycle of coastal and open ocean satellite chlorophyll off Chile (18°–40°S)
Authors: Yuras Gabriel , Ulloa Osvaldo , Hormazábal Samuel
Published: December 2005

High resolution SeaWiFS (Sea‐viewing Wide Field‐of‐view Sensor) chlorophyll and satellite wind data (1997–2004) are used to analyze the coastal and oceanic behavior of sea surface chlorophyll (CHL) concentration in the eastern boundary current system off Chile (18°–40°S). Two contrasting regimes are evident; a coastal regime, where CHL maximum occurs during summer, coinciding with the maximum upwelling‐favorable wind stress and an offshore regime, where the CHL maximum is in winter and is not related to the maximum wind (stress, curl). Moreover, our analysis reveals that the annual coastal CHL cycle is strong along the entire latitudinal extension, contrary to previous observations that showed a weak seasonal cycle off northern Chile. Averaging ocean‐color data across spatial domains where different forcings and processes operate will lead to unreliable retrieval of pigment biomass. Proper characterization of biological processes in upwelling and coastal regions requires deriving statistics over the relevant spatial scales.
A 10‐year integrated atmospheric water vapor record using precision filter radiometers at two high‐alpine sites
Authors: Nyeki S. , Vuilleumier L. , Morland J. , Bokoye A. , Viatte P. , Mätzler C. , Kämpfer N.
Published: December 2005

Measurements of integrated water vapor (IWV) density using precision filter radiometers (PFRs) at two high‐alpine, mid‐latitude stations in the Swiss Alps are reported. Both sites, Davos (1590 m asl) and Jungfraujoch (JFJ; 3580 m asl), exhibited a maximum IWV in summer and minimum in winter. Annual mean IWV was 6.7 (±3.9; 1 std) kg m−2 from 1995 to 2005 and 2.2 (±1.5) kg m−2 from 1999 to 2005, respectively. Co‐located GPS measurements exhibited a small positive IWV bias (GPS – PFR) at Davos (0.4 kg m−2) and a large negative bias at JFJ (−1.5 kg m−2). Microwave radiometer IWV at JFJ agreed well with PFR IWV suggesting that GPS IWV suffers from unmodeled effects. Linear IWV trend analysis indicated no significant trend at either Davos or JFJ for clear‐sky periods. The GPS‐IWV time series is at present too short to determine the trend for all‐weather conditions.
Subseasonal organization of ocean chlorophyll: Prospects for prediction based on the Madden‐Julian Oscillation
Authors: Waliser Duane E. , Murtugudde Ragu , Strutton Peter , Li Jui‐Lin
Published: December 2005

Analysis of satellite ocean color and rainfall data shows that the Madden‐Julian Oscillation (MJO) produces systematic and significant variations in ocean surface Chlorophyll (Chl) in a number of regions across the tropical Indian and Pacific Oceans, including the northern Indian Ocean, a broad expanse of the northwestern tropical Pacific Ocean, and a number of near‐coastal areas in the far eastern Pacific Ocean. Potential mechanisms for this modulation are examined with the result that wind‐induced vertical entrainment at the base of the ocean mixed layer appears to play an important role. Given evidence that the MJO is predictable with 2–3 week lead‐times, surface Chl may also be predictable at similar lead times with implications for the fishing industry and public health sectors concerned with cholera epidemics.
Geomorphic control of radionuclide diffusion in desert soils
Authors: Pelletier Jon D. , Harrington Charles D. , Whitney John W. , Cline Michael , DeLong Stephen B. , Keating Gordon , Ebert K. Teryn
Published: December 2005

Diffusion is a standard model for the vertical migration of radionuclides in soil profiles. Here we show that diffusivity values inferred from fallout 137Cs profiles in soils on the Fortymile Wash alluvial fan, Nye County, Nevada, have a strong inverse correlation with the age of the geomorphic surface. This result suggests that radionuclide‐bound particles are predominantly transported by infiltration rather than by bulk‐mixing processes such as wetting/drying, freeze/thaw, and bioturbation. Our results provide a preliminary basis for using soil‐geomorphic mapping, point‐based calibration data, and the diffusion model to predict radionuclide transport in desert soils within a pedotransfer‐function approach.
Three‐dimensional MHD simulation study of the structure at the leading part of a reconnection jet
Authors: TanDokoro Ryoji , Fujimoto Masaki
Published: December 2005

We have performed three‐dimensional MHD simulations of magnetic reconnection to investigate the structure of a reconnection jet. Our simulation results show that the leading edge of a reconnection jet deforms to put on a significantly complicated structure. In a randomly perturbed environment, smaller scale structure develops rapidly and finally the front of the reconnection jet becomes turbulent. In contrast when the initial perturbation is composed of a single sinusoidal mode, coherent magnetic bubbles are generated. The magnetic bubbles elongate significantly when the wavelength is small giving onset to a secondary instability that may subsequently lead to turbulence. We interpret the deformation of the jet front to be due to excitation of the Rayleigh‐Taylor/ballooning‐like instability and emphasize the significance of the three‐dimensionality in considering the dynamics of a reconnection jet.
Observations of F layer electron density profiles modulated by planetary wave type oscillations in the equatorial ionospheric anomaly region
Authors: Fagundes P. R. , Pillat V. G. , Bolzan M. J. A. , Sahai Y. , Becker‐Guedes F. , Abalde J. R. , Aranha S. L. , Bittencourt J. A.
Published: December 2005

A digital ionosonde of the type known as the Canadian Advanced Digital Ionosonde (CADI) is operational at São José dos Campos (23.2°S, 45.9°W), Brazil. This ionospheric sounding station is located under the southern crest of the ionospheric equatorial anomaly. The F layer electron density profile presents considerable day‐to‐day variability, even during undisturbed conditions, and this variability is still one of the less understood aspects of the physics of the ionosphere. The propagation of waves into the ionosphere may play an important role in this day‐to‐day ionospheric variability. In this paper we present a new technique that uses multifrequency virtual height variations, from ionospheric sounding observations at this low‐latitude station, to investigate how the F layer is modulated by planetary wave type oscillations. We have also considered the possible influence of oscillations due to solar origin (solar rotation variation). In the present study, observations during the months of June to September 2003 (season of low‐range type equatorial spread F occurrence at this location) have been used. The present study indicates the presence of 2‐day (the observed 3‐day periods are possibly associated with the quasi 2‐day oscillations), 5‐day, 10‐day, and 16‐day periods related to planetary wave type oscillations due to tropospheric sources during all the day. Also, it appears that during the day and dusk times, the longer periods 24–30 days are related to solar rotation (27 days), whereas the shorter periods 9–17 days have possibly some influence from half solar rotation (13.5 days). During the nighttime, possibly the short period oscillations 3–9 days may have some influence from the geomagnetic disturbances.
Low‐frequency waves and instabilities in stratified, gyrotropic plasmas with arbitrary distribution functions
Authors: Ferrière K. M. , André N.
Published: December 2005

We study the nature and stability of low‐frequency waves in collisionless, gyrotropic (P⊥ ≠ P∥), multi‐component plasmas, characterized by arbitrary distribution functions. The ambient medium is assumed to be stratified perpendicular to the magnetic field, with a scale height much larger than the wavelength of our waves, and the whole system is allowed to rotate. We show that the waves are generally non‐adiabatic, and we identify the four physical causes of their non‐adiabatic behavior. We also derive a global necessary condition for stability, which, quite remarkably, consists of the simple superposition of a criterion against instabilities triggered by thermal pressure anisotropies and a criterion against instabilities triggered by stratification. In the case of a nonrotating bi‐Maxwellian plasma, our stability condition turns out to be not only necessary, but also sufficient.
Flow discharge and sediment transport models for estimating a minimum timescale of hydrological activity and channel and delta formation on Mars
Authors: Kleinhans M. G.
Published: December 2005

This paper summarizes state‐of‐the‐art models for water flow and sediment transport and suggests implications for the sediment grain size distribution, transport process, and delta formation. The flow velocity in Martian outflow channels is commonly calculated from the Manning equation, which is dimensionally incorrect and masks the large uncertainty of the reconstructed flow velocity. More modern friction predictors based on surface grain size distribution are tested on 190 rivers on Earth including moderately catastrophic events. The uncertainty for the flow velocity is a factor of 3–4. The sediment transport is commonly assumed to amount to 40% of the water flux (hyperconcentration), but this is only true for special conditions. A debris‐flow origin of the channels is unlikely. Application of modern sediment transport models to typical Martian conditions indicates orders of magnitude smaller sediment fluxes dominated by bed load transport, resulting in much larger timescales for sediment emplacement in crater lake deltas and in the potential northern ocean. This is in part caused by the unexpected grain size distribution of the sediment derived from observations of landers and of delta morphologies. The implied duration of hydrological activity and channel and delta formation is of the order of 103–106 years, which is still very short on the geological timescale of Mars.
Quantifying absolute water content of minerals using near‐infrared reflectance spectroscopy
Authors: Milliken Ralph E. , Mustard John F.
Published: December 2005

Fundamental and overtone vibrational absorptions of H2O and OH− observed in reflectance spectra in the 1.3–5.0 μm wavelength region may be used to estimate the absolute or relative amount of water in particulate materials. Laboratory reflectance spectra of five hydrated materials (sodium and magnesium montmorillonite, sulfate, zeolite, and palagonite) with initial water contents ranging from 6 to 20 wt % were measured under decreased relative humidity and heated conditions to control their absolute water content. Relationships between absolute water content and water‐related absorptions were quantified using common band parameters (e.g., band depth and mean optical path length). Parameters calculated using fundamental O‐H stretching absorptions within the 3 μm region show trends with water content that are consistent among the samples, whereas those calculated using combination O‐H stretch and H‐O‐H bend absorptions in the 1.9 μm region do not. There appears to be no correlation between water absorptions near 1.9 μm and absolute water content that is independent of composition or between these absorptions and their counterparts near ∼2.9–3.1 μm. Combination overtone absorptions near 1.9 μm therefore are not expected to be reliable estimators of water content for mixtures of minerals. A parameter we call normalized optical path length (NOPL) exhibits a strong exponential correlation to absolute water content for the 3 μm region. On the basis of our current laboratory data, the NOPL parameter can be used to estimate H2O content within ±1 wt % or better over a wide range of water contents for the five materials examined. In addition to estimating the water content of laboratory samples, these methods can also be used to map the hydration state of planetary surfaces using high‐resolution visible‐near‐infrared spacecraft data.