bluuebunny/crossref_metadata_2025 huggingface dataset:
Interannual variability in the freshwater content of the Indonesian‐Australian Basin
Authors: Phillips Helen E. , Wijffels Susan E. , Feng Ming
Published: February 2005

An average freshening of 0.2 psu, extending from 100°E to Australia, 25°S to Indonesia and down to 180 m depth, persisted for more than 3 years from 1999 to 2002. We map the anomaly using CTD profiles from Argo floats and suggest that the dominant forcing for the anomaly is surface freshwater flux over the Indonesian seas that is advected into the region. Using historical CTD data and surface freshwater flux reanalysis products we show that the Indonesian Australian Basin experiences strong interannual variability in upper ocean freshwater content and that the recent fresh event, a result of a long‐lasting La Niña, is unprecedented during the last 25 years.
Post‐perovskite phase transition and mineral chemistry in the pyrolitic lowermost mantle
Authors: Murakami Motohiko , Hirose Kei , Sata Nagayoshi , Ohishi Yasuo
Published: February 2005

Phase relations of a natural mantle composition were determined up to 126 GPa and 2450 K by in‐situ x‐ray diffraction measurements in a laser‐heated diamond‐anvil cell (LHDAC). MgSiO3‐rich perovskite (MgPv) transforms to a post‐perovskite phase (MgPP) at about 113 GPa and 2500 K (400‐km above the core‐mantle boundary) and the lowermost mantle consists of MgPP, (Mg, Fe)O magnesiowüstite (Mw), and CaSiO3‐rich perovskite (CaPv). Chemical analyses on recovered samples using transmission electron microscope (TEM) show that the distribution of iron significantly changes at the post‐perovskite phase transition. A strong enrichment of iron in Mw leads to the unique geophysical and geochemical properties of the lowermost mantle.
Statistical properties of low‐frequency waves and ion beams in the plasma sheet boundary layer: Geotail observations
Authors: Takada T. , Seki K. , Hirahara M. , Fujimoto M. , Saito Y. , Hayakawa H. , Mukai T.
Published: February 2005

Statistical properties of low‐frequency (0.01–0.1 Hz) electromagnetic waves and their relations to ion distribution functions in “transition regions” from lobe to the plasma sheet, which include the plasma sheet boundary layer (PSBL) and boundary plasma sheet, are investigated based on 5‐year data of the Geotail spacecraft observations in XGSM = [−31, −15] and ∣YGSM∣ < 5 RE. It is shown that the amplitude of the magnetic field fluctuations increases with increasing plasma β (the ratio of the plasma thermal pressure to the magnetic pressure), while the electric field amplitude decreases in high‐β regions. These tendencies are consistent with a decrease of the local Alfvén velocity (VA) in the transition region with increasing β. The statistical results also indicate that the low‐frequency wave power has clear correlation with the energy flux of ion flows parallel to the magnetic field. If 10% of the beam energy is converted to the wave power, the ion beams could be the source of free energy of the large‐amplitude electromagnetic waves. The estimated Poynting flux of the waves is distributed in the range from 1.0 × 10−6 to 5.6 × 10−2 mW/m2. The maximum Poynting flux is the same order of the pointing flux of Alfvén waves observed by the Polar spacecraft at altitudes of 4–7 RE, when mapped along converging magnetic field lines to the ionosphere at an altitude of 100 km. The good agreement of the Poynting fluxes is consistent with the idea that the low‐frequency electromagnetic waves in the tail PSBL are the source of kinetic Alfvén waves in the high‐latitude auroral regions. The results of partial moment calculations with data bins selected by careful eye inspection for each 12‐s ion data during large‐amplitude wave events show that in most of the events, the relative drift speed between cold‐core and hot‐beam ion components is below 2 VA, the density ratio of the cold‐core to the hot‐beam is typically a few tens of percent, and the beam component has a strong temperature anisotropy of T∥/T⟂ ∼ 0.44. The linear dispersion analysis using the observed distribution functions suggests the importance of the ion cyclotron anisotropy instability modified by the existence of cold‐core ions for the generation of low‐frequency large‐amplitude electromagnetic waves in the PSBL.
A statistical analysis of low‐frequency magnetic pulsations at cusp and cap latitudes in Antarctica
Authors: Francia P. , Lanzerotti L. J. , Villante U. , Lepidi S. , Di Memmo D.
Published: February 2005

We report a statistical analysis of low‐frequency magnetic variations (magnetic pulsations, 0.8–7 mHz) at South Pole (74°S corrected geomagnetic latitude) and Terra Nova Bay (80°S) during 1996. The results show that at South Pole (at cusp latitudes) the pulsation power exhibits two maxima during the day, one in the local premidnight and the other in the morning. The first maximum disappears when the analysis is restricted to northward interplanetary magnetic field conditions (Bz > 1 nT), suggesting that it might be associated to substorm phenomena. During closed magnetospheric conditions, when the cusp is expected to be located poleward with respect to the station, the spectral and polarization characteristics of pulsations between 1 and 3 mHz suggest that resonant oscillations of the outermost closed field lines commonly occur at South Pole in the local morning. At Terra Nova Bay, in the polar cap, the pulsation power is much lower and its diurnal variation is characterized by a single maximum, which occurs around local noon, when the station approaches the cusp. The corresponding polarization pattern indicates that Terra Nova Bay is always located poleward with respect to resonant field lines.
Cross sections for electron capture and loss by keV oxygen atoms in collisions with CO and CO2
Authors: Lindsay B. G. , Yu W. S. , Stebbings R. F.
Published: February 2005

Interpretation of the energetic neutral atom data from the ASPERA‐3 instrument aboard the ESA Mars Express spacecraft requires knowledge of the relevant charge‐changing atomic collision cross sections. Important among these are collisions involving energetic O atoms, and absolute cross sections are reported here for electron capture and loss by 1–5 keV oxygen atoms incident on CO and CO2 for scattering angles between 0.02° and 1.73° in the laboratory frame. All of the differential cross sections are forward peaked, but those for electron loss decrease particularly slowly with scattering angle at low energies indicating that many of the colliding particles suffer significant deviation.
A new theory of bubble formation in magma
Authors: Yamada Kou , Tanaka Hidekazu , Nakazawa Kiyoshi , Emori Hiroyuki
Published: February 2005

We have newly developed an accurate theoretical model of bubble formation in supersaturated magma with a relatively low viscosity under the formulation by Toramaru (1995). Such a model is essential in deriving considerable information from the data of bubble nucleation in the recent decompression experiments. We obtain analytical solutions for the time evolution of the nucleation rate and the number density of nucleated bubbles in cases with constant decompression rates and constant supersaturation pressures. Both the bubble number density and the duration time of nucleation obtained in this study are larger than those obtained by Toramaru by a factor of 10. We find that the uncertainty of several orders in the classical nucleation rate has little effect on the final number density of bubbles in cases of continuous decompression. In the formulation by Toramaru, a spatially uniform volatile concentration surrounding the growing bubbles is assumed. We also construct a nonuniform concentration model and subsequently show that an uniform concentration model is valid for the evaluation of the bubble number density. Finally, we apply our model to the recent decompression experiments and indirectly estimate the surface tensions of the rhyolitic melt with only H2O and with H2O and CO2. Our indirect estimates indicate that the surface tensions for 7 wt % H2O dissolved in melt are 0.08 ± 0.01 N m−1 for samples with no CO2 and 0.07 ± 0.01 N m−1 for samples with a considerable amount of CO2, respectively. These estimations are consistent with the available experimental values of the surface tension.
Total, Partial, and Differential Ionization Cross Sections in Proton–Hydrogen Atom Collisions in the Energy Region of 0.1–10 keV/u
Authors: Pichl Lukáš , Zou Shiyang , Kimura Mineo , Murakami Izumi , Kato Takako
Published: February 2005

Single-differential, partial, and total ionization cross sections for the proton–hydrogen atom collision system in the energy region of 0.1–10 keV/u are determined by using the molecular-orbital close-coupling method within a semiclassical formalism. The present cross sections are in an excellent agreement with the recent experiments of Shah et al. [J. Phys. B. 31, L757 (1998)], but decrease more rapidly than the cross sections measured by Pieksma et al. [Phys. Rev. Lett. 73, 46 (1994)] with decreasing energy. The numerical data for all calculated cross sections are included in this paper. A critical evaluation of the existing data for the ionization process in the keV energy range is performed both for the experiment and theory. The recommended data are obtained from a converged close-coupling expansion, which in total includes 362 bound and continuum channels with their wave functions augmented by the electron translation factor in order to insure the correct scattering boundary condition.
Solitonlike excitations in a one-dimensional electrical transmission line
Authors: Pelap François B. , Faye Mansour M.
Published: February 2005

Dynamics of modulated waves is studied in a one-dimensional discrete nonlinear electrical transmission line. Contribution of a linear dispersive capacitance is appreciated and it is shown via a reductive perturbation method that evolution of such waves in this system is governed by a higher order nonlinear Schrödinger equation. Passing through the Stokes wave analysis, a generalized criterion for the Benjamin–Feir instability in the network is presented and exact solutions of the obtained wave equation are determined by the means of the Pathria and Morris approach.
P
T
symmetric models with nonlinear pseudosupersymmetry
Authors: Sinha A. , Roy P.
Published: February 2005

By applying the higher order Darboux algorithm to an exactly solvable non-Hermitian PT symmetric potential, we obtain a hierarchy of new exactly solvable non-Hermitian PT symmetric potentials with real spectra. It is shown that the symmetry underlying the potentials so generated and the original one is nonlinear pseudosupersymmetry. We also show that this formalism can be used to generate a larger class of new solvable potentials when applied to non-Hermitian systems.
The complete T→V,R energy conversion in three-body collisions within the hard sphere model
Authors: Azriel Vladimir M. , Rusin Lev Yu. , Sevryuk Mikhail B.
Published: February 2005

It is shown that in hard sphere (impulsive) collisions of atoms with diatomic molecules, complete conversion of the collision energy into the internal energy of the diatomic partner is possible for any number of impacts between the elastic balls representing the particles. The corresponding collision geometries and relations between the masses of the particles are described in detail.
Scalar-threshold dependence and internal dynamics in turbulent jets
Authors: Aguirre Roberto C. , Catrakis Haris J.
Published: February 2005

The scalar-threshold dependence of internal interfaces in turbulent jets is examined above the mixing transition with an experimental database generated from high-resolution three-dimensional space-time measurements using laser-induced fluorescence and digital-imaging techniques. Quadratic dependence on scalar threshold is found for the volume of fluid enclosed by internal interfaces over a wide range of thresholds. Linear dependence on scalar threshold is found for the interfacial surface area over the same range of thresholds. The observed behavior can be accounted for by physical modeling based on the dynamics of internal large-scale well-mixed regions.
Chaotic mixing in thermocapillary-driven microdroplets
Authors: Grigoriev Roman O.
Published: February 2005

Liquid microdroplets represent a convenient system for studies of mixing by chaotic advection in discrete microscopic volumes. The mixing properties of the flows in microdroplets are governed by their symmetries, which give rise to invariant surfaces serving as barriers to transport. Thorough mixing via chaotic advection requires destruction of all such invariant surfaces. To illustrate this idea, we demonstrate that quick and thorough mixing inside a spherical microdroplet suspended in a layer of substrate fluid can be obtained by moving the droplet along a two-dimensional path using temperature-induced surface tension gradients. The use of flow invariants also provides a convenient way to analyze the mixing properties of flows in many other experimental implementations.
The effect of added polymers on the formation of drops ejected from a nozzle
Authors: Shore Heather J. , Harrison Graham M.
Published: February 2005

The presence of small amounts of polymer in Newtonian solvents can have a significant impact on the flow behavior of these fluids in extension-dominated flows. This study investigates the effect of elasticity on the on-demand drop formation through the use of low viscosity elastic liquids. A high-speed camera is employed to observe drops ejected from a nozzle. The drops are created using a piezoelectric sleeve that contracts around a nozzle forcing fluid out. We observe that the satellite drops commonly produced with Newtonian fluids of identical shear viscosity in the same geometry can be suppressed when polymers with sufficient molecular weight are added. For our nozzle, the minimum required molecular weight is 300k PEO at a concentration of 25 ppm. However, the resultant increased elasticity in the solution requires a greater pulse strength to eject the drop. In addition, the fluids containing polymers have a longer thread, a longer time to separation, and a lower velocity than the Newtonian fluids with similar shear viscosity.
Spraying modes in coaxial jet electrospray with outer driving liquid
Authors: Chen Xiaopeng , Jia Laibing , Yin Xiezhen , Cheng Jiusheng , Lu Jian
Published: February 2005

Coaxial jet electrospray is a technique to generate microencapsules, which uses electric forces to create a coaxial microjet from two immiscible liquids. Compound droplets with narrow size distribution are produced after the jet breaks up. In this paper, the spraying modes are investigated experimentally with proper flow rates of the inner and outer liquids. Ethanol/glycerol/tween mixture (outer liquid) and cooking oil (inner liquid) are fed into the gap between outer and inner capillaries and the inner capillary, respectively. The spraying modes presented in our experiments are “dripping mode,” “dripping mode in spindle,” “cone-jet mode,” “pulse mode in cone,” and “multijets mode” sequentially, as the applied voltage increases. The region of stable cone-jet mode extends with decrease of the outer liquid flow rate and increase of the inner one. It is found that the spray phenomena are mainly determined by properties of the outer liquid, which is viscous and electric conductive enough. A rudimentary physical model is developed, in which both the viscosity and liquid interface tension are taken into account.
Liquid–vapor and liquid–liquid phase equilibria of the Brodholt–Sampoli–Vallauri polarizable water model
Authors: Jedlovszky Pál , Vallauri Renzo
Published: February 2005

Liquid–vapor and liquid–liquid phase equilibria of the polarizable Brodholt–Sampoli–Vallauri water model have been investigated by Gibbs ensemble Monte Carlo computer simulations. The coexisting liquid and vapor densities and energy of vaporization of the model is found to be in a reasonable agreement with experimental data in the entire temperature range of liquid–vapor coexistence. The critical temperature and density of the model are found to be 615K and 0.278g∕cm3, respectively, close to the experimental values of 647.1K and 0.322g∕cm3. In the supercooled state two distinct liquid–liquid coexistence regions are observed. The existence of liquid–liquid phase separation of a polarizable water model is demonstrated for the first time.
Why is the band model not contradictory to molecular theory in organic electroluminescence?
Authors: Xu Zheng , Qu Chong , Teng Feng , Zhang Fujun , Meng Lijian , Xu Xurong
Published: February 2005

In organic electroluminescence there is a sharp contradiction between the applicability of band model and molecular theory. This contradiction arose from the very beginning of extended study. In this report we studied the blue spectral shift in the newly discovered solid state cathodoluminescence when the applied voltage is increased. There are three different kinds of spectra in three intervals of applied voltage. The reason of this spectral shift is found to be the field ionization of exciton. The switching on of recombination starts only after the beginning of this field ionization. The exciton emission obeys molecular theory and the recombination obeys band model. Thus the demarcation is the appearance of field ionization of excitons. Since the ionization changes with electric field continuously, there is a region of coexistence of these two processes.
Crystallite size effect on the hole mobility of uniaxially aligned copper phthalocyanine thin-film field-effect transistors
Authors: Ofuji Masato , Ishikawa Ken , Takezoe Hideo , Inaba Katsuhiko , Omote Kazuhiko
Published: February 2005

We fabricated copper phthalocyanine (CuPc) thin-film field-effect transistors (FETs) with three different orientations of CuPc with respect to channels. The substrate rubbing treatment induced uniaxial orientation in CuPc layers, yielding higher hole mobility (∼0.02cm2∕Vs) than that of untreated FETs. Although the rubbing treatment bore high-aspect-ratio (>10) CuPc domains oriented to rubbing direction, the mobility anisotropy of the film was only 1.4. This discrepancy was explained by analyzing grazing-incidence x-ray diffraction profiles, i.e.: (1) In-plane mean size of crystals was smaller than their appearance in atomic force microscopy, and (2) the crystallites were much shorter in the apparent long-hand direction (11nm) than the direction perpendicular to it (44nm).
The effect of C60 doping on the device performance of organic light-emitting diodes
Authors: Lee Jun Yeob , Kwon Jang Hyuk
Published: February 2005

The effect of C60 doping in the hole transport layer on the device performance of phosphorescent light-emitting diodes was investigated by changing the C60 content from 0% to 3%. Doping of C60 in 1,3,5-tris(N,N-bis-(4,5-methoxyphenyl)-aminophenyl)benzol resulted in efficient hole injection and low driving voltage at high luminance. In addition, the lifetime of the phosphorescent device was improved significantly by introducing a C60 molecule in the hole transport layer. The C60-doped device showed an extended lifetime of 1400 h compared with 700 h of the undoped device.
Optical properties of single-crystalline α-Si3N4 nanobelts
Authors: Zhang Ligong , Jin Hua , Yang Weiyou , Xie Zhipeng , Miao Hezhuo , An Linan
Published: February 2005

The optical properties of single-crystalline α-Si3N4 nanobelts synthesized via catalyst-assisted pyrolysis of polymeric precursor were characterized by absorption, photoluminescence (PL) and photoluminescence excitation (PLE). The optical absorption spectrum showed that the nanobelts exhibited indirect absorption behavior with optical band gap of ∼5.0eV. Three broad peaks centered at 1.8, 2.3, and 3.0eV were observed from the room-temperature PL spectrum of the nanobelts. The PLE spectra suggested the existence of multifold energy levels within the gap. A qualitative model was proposed to explain the observed absorption, PL and PLE spectra.
Observed trapping of minority-carrier electrons in p-type GaAsN during deep-level transient spectroscopy measurement
Authors: Johnston S. W. , Kurtz S. R. , Friedman D. J. , Ptak A. J. , Ahrenkiel R. K. , Crandall R. S.
Published: February 2005

Deep-level transient spectroscopy measurements on a reverse-biased p-type GaAsN Schottky diode grown by metalorganic chemical vapor deposition show a minority-carrier trap signal corresponding to an electron trap having an activation energy of about 0.2eV. The proportion of trapped electrons agrees with that of modeled defect states near the Schottky-barrier metal interface whose occupation is affected by changing reverse-bias conditions. Estimates of thermionic emission provide adequate filling of the traps with electrons from the metal. The inclusion of a GaAs layer between the metal and GaAsN layer reduces the electron-trapping signal.
Visual Orientation in a Mirror World Tilted 90°
Authors: Howard Ian P , Hu Gang , Saxe Rebecca , Zacher James E
Published: February 2005

Previously, we showed that many supine observers in a furnished room tilted 90° perceive themselves and the room as upright. We called this the “levitation illusion” because the arms feel weightless when held out from the body. We now report that a familiar scene viewed by supine observers through a mirror at 45° appears vertical when, optically, it is horizontal and above the head. However, the body feels pitched upright only partially. This visual-righting effect, like the levitation illusion, is due to the polarity axis of the scene being accepted as vertical even in the presence of conflicting information from the gravity sense organs. In experiment 1 we tested the potency of objects containing either intrinsic polarity (due to familiar tops and bottoms) or extrinsic polarity (due to support relationships) to generate a visual-righting illusion. To almost all observers, a blank surface seen in the mirror appeared like a ceiling. A scene containing an object with intrinsic polarity, such as a chair or person, seen in the mirror appeared vertical to almost all observers. A scene containing a pair of objects with only extrinsic polarity, such as a ball on a shelf (but not a ball under a shelf), also appeared vertical to most observers. In experiment 2 we found that a polarised scene was more likely to produce a visual-righting illusion when it was arranged as a view through a window rather than as a picture inside a room.
Auditory — Visual Interactions in the Perception of a Ball's Path
Authors: Ecker Adam J , Heller Laurie M
Published: February 2005

We carried out two experiments to measure the combined perceptual effect of visual and auditory information on the perception of a moving object's trajectory. All visual stimuli consisted of a perspective rendering of a ball moving in a three-dimensional box. Each video was paired with one of three sound conditions: silence, the sound of a ball rolling, or the sound of a ball hitting the ground. We found that the sound condition influenced whether observers were more likely to perceive the ball as rolling back in depth on the floor of the box or jumping in the frontal plane. In a second experiment we found further evidence that the reported shift in path perception reflects perceptual experience rather than a deliberate decision process. Instead of directly judging the ball's path, observers judged the ball's speed. Speed is an indirect measure of the perceived path because, as a result of the geometry of the box and the viewing angle, a rolling ball would travel a greater distance than a jumping ball in the same time interval. Observers did judge a ball paired with a rolling sound as faster than a ball paired with a jumping sound. This auditory – visual interaction provides an example of a unitary percept arising from multisensory input.
Local-scale mapping of benthic habitats to assess representation in a marine protected area
Authors: Stevens Tim , Connolly Rod M.
Published: February 2005

Macrobenthic habitat types were classified and mapped using a compact video array at 78 sites spaced 5 km apart in Moreton Bay, Australia. The area mapped was about 2400 km2 and extended from estuarine shallow subtidal waters to offshore areas to the 50-m isobath. Nine habitat types were recognised, with only one on hard substrate, and their representation within an existing marine protected area was assessed. Only two habitat types were represented in highly protected (no-take) zones, with less than 3% of the total area of each habitat type included. The habitat mapping characterised several habitat types not previously described in the area and located deep-water algal and soft coral reefs not previously reported. Seagrass beds were encountered in several locations where their occurrence was either unknown or had not previously been quantified. The study represents the most spatially comprehensive survey of epibenthos undertaken in Moreton Bay, with over 40 000 m2 sampled. Derived habitat maps provide a robust basis for inclusion of representative examples of all habitat types in marine protected area planning in, and adjacent to, Moreton Bay. The utility of video data to conduct a low-cost habitat survey over a comparatively large area was also demonstrated. The method used has potentially wide application for the survey and design of marine protected areas.
A circuit for navigation in
Caenorhabditis elegans
Authors: Gray Jesse M. , Hill Joseph J. , Bargmann Cornelia I.
Published: February 2005

Caenorhabditis elegans
explores its environment by interrupting its forward movement with occasional turns and reversals. Turns and reversals occur at stable frequencies but irregular intervals, producing probabilistic exploratory behaviors. Here we dissect the roles of individual sensory neurons, interneurons, and motor neurons in exploratory behaviors under different conditions. After animals are removed from bacterial food, they initiate a local search behavior consisting of reversals and deep omega-shaped turns triggered by AWC olfactory neurons, ASK gustatory neurons, and AIB interneurons. Over the following 30 min, the animals disperse as reversals and omega turns are suppressed by ASI gustatory neurons and AIY interneurons. Interneurons and motor neurons downstream of AIB and AIY encode specific aspects of reversal and turn frequency, amplitude, and directionality. SMD motor neurons help encode the steep amplitude of omega turns, RIV motor neurons specify the ventral bias of turns that follow a reversal, and SMB motor neurons set the amplitude of sinusoidal movement. Many of these sensory neurons, interneurons, and motor neurons are also implicated in chemotaxis and thermotaxis. Thus, this circuit may represent a common substrate for multiple navigation behaviors.
Positive selection of primate
TRIM5
α identifies a critical species-specific retroviral restriction domain
Authors: Sawyer Sara L. , Wu Lily I. , Emerman Michael , Malik Harmit S.
Published: February 2005

Primate genomes encode a variety of innate immune strategies to defend themselves against retroviruses. One of these, TRIM5α, can restrict diverse retroviruses in a species-specific manner. Thus, whereas rhesus TRIM5α can strongly restrict HIV-1, human TRIM5α only has weak HIV-1 restriction. The biology of TRIM5α restriction suggests that it is locked in an antagonistic conflict with the proteins encoding the viral capsid. Such antagonistic interactions frequently result in rapid amino acid replacements at the protein–protein interface, as each genetic entity vies for evolutionary dominance. By analyzing its evolutionary history, we find strong evidence for ancient positive selection in the primate
TRIM5
α gene. This selection is strikingly variable with some of the strongest selection occurring in the human lineage. This history suggests that
TRIM5
α evolution has been driven by antagonistic interactions with a wide variety of viruses and endogenous retroviruses that predate the origin of primate lentiviruses. A 13-aa “patch” in the SPRY protein domain bears a dense concentration of positively selected residues, potentially implicating it as an antiviral interface. By using functional studies of chimeric
TRIM5
α genes, we show that this patch is generally essential for retroviral restriction and is responsible for most of the species-specific antiretroviral restriction activity. Our study highlights the power of evolutionary analyses, in which positive selection identifies not only the age of genetic conflict but also the interaction interface where this conflict plays out.
Host selection by the generalist aphid Myzus persicae (Hemiptera: Aphididae) and its subspecies specialized on tobacco, after being reared on the same host
Authors: Troncoso A.J. , Vargas R.R. , Tapia D.H. , Olivares-Donoso R. , Niemeyer H.M.
Published: February 2005

Decision-making during host selection by phytophagous insects has proved to be related to host range, with specialists taking faster decisions than generalists; however, this pattern fails to materialize in some host selection studies performed with aphids. Differences found in testing designs point to rearing effects on aphid host selection. To test whether specialization patterns derive from the nature of the aphid or as a consequence of rearing environment, host selection behaviours were compared between the generalist Myzus persicae (Sulzer) s.s. and its subspecies specialized on tobacco when reared on a common host and offered the choice of an alternative host and a non-host plant. Pre-alighting (host finding and attraction towards host volatiles) and post-alighting (leaf surface exploration and probing) behaviours did not differ between the generalist and the tobacco-specialist, except in the allocation of time to probing behaviour; furthermore, all specialists chose the host on which they performed best. Thus, although the specialist was not faster than the generalist, it showed a higher level of commitment to its preferred host plant.
Is gastric ulceration different in normal and malnourished rats?
Authors: Paula A. C. B. , Gracioso J. S. , Toma W. , Bezerra R. , Saad M. A. J. , Lucca I. M. S. De , Carneiro E. M. , Brito A. R. M. Souza
Published: February 2005

Protein malnutrition can adversely affect all tissues. The aim of the present study was to test the hypothesis that protein deprivation influences gastric ulcer formation, as well as metabolism and organ growth, in rats. In the present study, there was a significant reduction in the body and organ weight of rats fed a low-protein diet (P<0·001). Malnourished rats were less susceptible to ulceration of the gastric mucosa in ethanol and indomethacin models of acute gastric ulcers when compared with rats fed a normoproteic diet (17 % protein). Mucus production and prostaglandin E2 formation increased in malnourished rats, possibly explaining the lower number of acute ulcers in these animals. Pylorus ligature altered gastric juice composition (increased pH and gastric volume, and decreased total acid concentration) in the animal group fed a low-protein diet compared with the group fed a diet containing 17 % protein (P<0·05). The gastric mucosa was more damaged in malnourished rats than in normal rats evaluated for 14 d after acetic acid injection (P<0·001). Malnourished rats exhibited resistance to acute gastric lesions, owing to an increase in prostaglandin GE2 release and mucus secretion, which protected their gastric mucosa. This phenomenon was not seen in subchronic gastric ulceration.
Ectopic Expression of an Activated RAC inArabidopsisDisrupts Membrane Cycling
Authors: Bloch Daria , Lavy Meirav , Efrat Yael , Efroni Idan , Bracha-Drori Keren , Abu-Abied Mohamad , Sadot Einat , Yalovsky Shaul
Published: February 2005

Rho GTPases regulate the actin cytoskeleton, exocytosis, endocytosis, and other signaling cascades. Rhos are subdivided into four subfamilies designated Rho, Racs, Cdc42, and a plant-specific group designated RACs/Rops. This research demonstrates that ectopic expression of a constitutive active Arabidopsis RAC, AtRAC10, disrupts actin cytoskeleton organization and membrane cycling. We created transgenic plants expressing either wild-type or constitutive active AtRAC10 fused to the green fluorescent protein. The activated AtRAC10 induced deformation of root hairs and leaf epidermal cells and was primarily localized in Triton X-100–insoluble fractions of the plasma membrane. Actin cytoskeleton reorganization was revealed by creating double transgenic plants expressing activated AtRAC10 and the actin marker YFP-Talin. Plants were further analyzed by membrane staining with N-[3-triethylammoniumpropyl]-4-[p-diethylaminophenylhexatrienyl] pyridinium dibromide (FM4-64) under different treatments, including the protein trafficking inhibitor brefeldin A or the actin-depolymeryzing agents latrunculin-B (Lat-B) and cytochalasin-D (CD). After drug treatments, activated AtRAC10 did not accumulate in brefeldin A compartments, but rather reduced their number and colocalized with FM4-64–labeled membranes in large intracellular vesicles. Furthermore, endocytosis was compromised in root hairs of activated AtRAC10 transgenic plants. FM4-64 was endocytosed in nontransgenic root hairs treated with the actin-stabilizing drug jasplakinolide. These findings suggest complex regulation of membrane cycling by plant RACs.
Cholesterol and Fatty Acids Regulate Dynamic Caveolin Trafficking through the Golgi Complex and between the Cell Surface and Lipid Bodies
Authors: Pol Albert , Martin Sally , Fernández Manuel A. , Ingelmo-Torres Mercedes , Ferguson Charles , Enrich Carlos , Parton Robert G.
Published: February 2005

Caveolins are a crucial component of plasma membrane (PM) caveolae but have also been localized to intracellular compartments, including the Golgi complex and lipid bodies. Mutant caveolins associated with human disease show aberrant trafficking to the PM and Golgi accumulation. We now show that the Golgi pool of mainly newly synthesized protein is detergent-soluble and predominantly in a monomeric state, in contrast to the surface pool. Caveolin at the PM is not recognized by specific caveolin antibodies unless PM cholesterol is depleted. Exit from the Golgi complex of wild-type caveolin-1 or -3, but not vesicular stomatitis virus-G protein, is modulated by changing cellular cholesterol levels. In contrast, a muscular dystrophy-associated mutant of caveolin-3, Cav3P104L, showed increased accumulation in the Golgi complex upon cholesterol treatment. In addition, we demonstrate that in response to fatty acid treatment caveolin can follow a previously undescribed pathway from the PM to lipid bodies and can move from lipid bodies to the PM in response to removal of fatty acids. The results suggest that cholesterol is a rate-limiting component for caveolin trafficking. Changes in caveolin flux through the exocytic pathway can therefore be an indicator of cellular cholesterol and fatty acid levels.
The Yeast Phosphotyrosyl Phosphatase Activator Is Part of the Tap42–Phosphatase Complexes
Authors: Zheng Yin , Jiang Yu
Published: February 2005

Phosphotyrosyl phosphatase activator PTPA is a type 2A phosphatase regulatory protein that possesses an ability to stimulate the phosphotyrosyl phosphatase activity of PP2A in vitro. In yeast Saccharomyces cerevisiae, PTPA is encoded by two related genes, RRD1 and RRD2, whose products are 38 and 37% identical, respectively, to the mammalian PTPA. Inactivation of either gene renders yeast cells rapamycin resistant. In this study, we investigate the mechanism underling rapamycin resistance associated with inactivation of PTPA in yeast. We show that the yeast PTPA is an integral part of the Tap42–phosphatase complexes that act downstream of the Tor proteins, the target of rapamycin. We demonstrate a specific interaction of Rrd1 with the Tap42–Sit4 complex and that of Rrd2 with the Tap42–PP2Ac complex. A small portion of PTPA also is found to be associated with the AC dimeric core of PP2A, but the amount is significantly less than that associated with the Tap42-containing complexes. In addition, our results show that the association of PTPA with Tap42–phosphatase complexes is rapamycin sensitive, and importantly, that rapamycin treatment results in release of the PTPA-phosphatase dimer as a functional phosphatase unit.
Ubiquitylation of a Melanosomal Protein by HECT-E3 Ligases Serves as Sorting Signal for Lysosomal Degradation
Authors: Lévy Frédéric , Muehlethaler Katja , Salvi Suzanne , Peitrequin Anne-Lise , Lindholm Cecilia K. , Cerottini Jean-Charles , Rimoldi Donata
Published: February 2005

The production of pigment by melanocytic cells of the skin involves a series of enzymatic reactions that take place in specialized organelles called melanosomes. Melan-A/MART-1 is a melanocytic transmembrane protein with no enzymatic activity that accumulates in vesicles at the trans side of the Golgi and in melanosomes. We show here that, in melanoma cells, Melan-A associates with two homologous to E6-AP C-terminus (HECT)-E3 ubiquitin ligases, NEDD4 and Itch, and is ubiquitylated. Both NEDD4 and Itch participate in the degradation of Melan-A. A mutant Melan-A lacking ubiquitin-acceptor residues displays increased half-life and, in pigmented cells, accumulates in melanosomes. These results suggest that ubiquitylation regulates the lysosomal sorting and degradation of Melan-A/MART-1 from melanosomes in melanocytic cells.
Hypoxia-inducible Factor Regulates αvβ3 Integrin Cell Surface Expression
Authors: Cowden Dahl Karen D. , Robertson Sarah E. , Weaver Valerie M. , Simon M. Celeste
Published: February 2005

Hypoxia-inducible factor (HIF)-deficient placentas exhibit a number of defects, including changes in cell fate adoption, lack of fetal angiogenesis, hypocellularity, and poor invasion into maternal tissue. HIF is a heterodimeric transcription factor consisting of α and β aryl hydrocarbon receptor nuclear translocator or ARNT) subunits. We used undifferentiated trophoblast stem (TS) cells to characterize HIF-dependent adhesion, migration, and invasion. Arnt-/-and Hifα-/-TS cells exhibit reduced adhesion and migration toward vitronectin compared with wild-type cells. Furthermore, this defect is associated with decreased cell surface expression of integrin αvβ3 and significantly decreased expression of this integrin in focal adhesions. Because of the importance of adhesion and migration in tumor progression (in addition to placental development), we examined the affect of culturing B16F0 melanoma cells in 1.5% oxygen (O2). Culturing B16F0 melanoma cells at 1.5% O2resulted in increased αvβ3 integrin surface expression and increased adhesion to and migration toward vitronectin. Together, these data suggest that HIF and O2tension influence placental invasion and tumor migration by increasing cell surface expression of αvβ3 integrin.
Origin and Chemical Variation of Brazilian Propolis
Authors: Salatino Antonio , Teixeira Érica Weinstein , Negri Giuseppina , Message Dejair
Published: February 2005

Propolis is a hive product containing chiefly beeswax and plant‐derived substances such as resin and volatile compounds. Propolis has been used as an antiseptic and wound healer since ancient times and interest for the product has increased recently. Probably few plant species contribute as major resin sources. Green propolis derives mainly from vegetative apices of Baccharis dracunculifolia (alecrim plants). However, wide variation detected in the chemical composition suggests contributions from alternative resin plant sources. Predominant components of the resin of green propolis are cinnamic acids, chiefly compounds bearing prenyl groups. Terpenoid compounds, such as sesqui, di and pentacyclic triterpenoids, have been detected in many, but not all, samples investigated. Propolis research has uncovered potentialities of substances previously isolated from plants and has detected constituents of plant origin that would hardly be known otherwise.
Understanding the relationship between the primary structure of proteins and its propensity to be soluble on overexpression in Escherichia coli
Authors: Idicula‐Thomas Susan , Balaji Petety V.
Published: February 2005

Solubility of proteins on overexpression in Escherichia coli is a manifestation of the net effect of several sequence‐dependent and sequence‐independent factors. This study aims to delineate the relationship between the primary structure and solubility on overexpression. The amino acid sequences of proteins reported to be soluble or to form inclusion bodies on overexpression in E. coli under normal growth conditions were analyzed. The results show a positive correlation between thermostability and solubility of proteins, and an inverse correlation between the in vivo half‐life of proteins and solubility. The amino acid (Asn, Thr, Tyr) composition and the tripeptide frequency of the protein were also found to influence its solubility on overexpression. The amino acids that were seen to be present in a comparatively higher frequency in inclusion body‐forming proteins have a higher sheet propensity, whereas those that are seen more in soluble proteins have a higher helix propensity; this is indicative of a possible correlation between sheet propensity and inclusion body formation. Thus, the present analysis shows that thermostability, in vivo half‐life, Asn, Thr, and Tyr content, and tripeptide composition of a protein are correlated to the propensity of a protein to be soluble on overexpression in E. coli. The precise mechanism by which these properties affect the solubility status of the overexpressed protein remains to be understood.
TESTING LONG‐HORIZON PREDICTIVE ABILITY WITH HIGH PERSISTENCE, AND THE MEESE–ROGOFF PUZZLE*
Authors: Rossi Barbara
Published: February 2005

A well‐known puzzle in international finance is that a random walk predicts exchange rates better than economic models. I offer a potential explanation. When exchange rates and fundamentals are highly persistent, long‐horizon forecasts of economic models are biased by the estimation error. When this bias is big, a random walk will forecast better, even if the economic model is true. I propose a test for equal predictability in the presence of high persistence. It shows that the poor forecasting ability of economic models does not imply that the models are not good descriptions of the data.
Long‐term effects of computer training of phonological awareness in kindergarten
Authors: Segers Eliane , Verhoeven Ludo
Published: February 2005

The present study examined the long‐term effects of a computer intervention for the development of phonological awareness in Dutch kindergartners. Native Dutch and immigrant children worked with the software 15 min/week during one school year. Following a pretest – interim test – post‐test – retention test design, the effects on rhyming, phonemic segmentation, auditory blending, and grapheme knowledge were assessed. The intervention showed significant immediate effects on rhyming and grapheme knowledge. The time spent on the computer games also correlated with the learning gains for the experimental group. In the first grade, retention effects were demonstrated after 4 months of formal reading education.
Genetic relationships among members of the Ichthyobodo necator complex: implications for the management of aquaculture stocks
Authors: Callahan H A , Litaker R W , Noga E J
Published: February 2005

Ichthyobodo necator (costia) is a common and important flagellate parasite that infests the skin and gills of many freshwater and marine fish. Costia infestations are often fatal and cause significant aquaculture losses worldwide. Recently it has been demonstrated that Ichthyobodo is a multispecies complex with differing host preferences. Knowing if those species have broad or narrow host specificity has important implications for the management of costia. To address the question of host specificity, genomic DNA was isolated from Ichthyobodo trophonts collected from rainbow trout, Oncorhynchus mykiss, koi, Cyprinus carpio, mirror carp, C. carpio, goldfish, Carassius auratus, channel catfish, Ictalurus punctatus, swordtail, Xiphophorus helleri, and Japanese flounder, Paralichthys olivaceus. The small subunit ribosomal RNA (SSU rRNA) gene from each isolate was analysed with previously published Ichthyobodo sequences using Bayesian phylogenetic methods. The internal transcribed spacers (ITS) from six isolates were also PCR‐amplified, cloned and sequenced. Both the SSU rRNA phylogenetic analysis and the ITS rRNA sequence data support grouping the 22 Ichthyobodo isolates examined into a complex of nine different species. Many of these species were frequently isolated from multiple hosts, indicating that exchange of infested fish from one region to another has a high potential for spreading the disease. In one instance, the same species was obtained from marine and freshwater fish, further suggesting that certain Ichthyobodo species may not be limited by salinity.
A test of models of fluvial architecture and palaeosol development: Camp Rice Formation (Upper Pliocene‐Lower Pleistocene), southern Rio Grande rift, New Mexico, USA
Authors: MACK GREG H. , MADOFF RISA D.
Published: February 2005

Numerical, experimental and theoretical models of fluvial architecture and palaeosol development are tested with outcrops of Upper Pliocene‐Lower Pleistocene sediment in the southern Rio Grande rift, New Mexico. The sediment was deposited and subsequently exhumed in the Jornada del Muerto basin, a westward‐tilted half graben whose footwall corresponds to the Rincon Hills and San Diego Mountain fault blocks. The axial river, the ancestral Rio Grande, shared time between the Jornada del Muerto basin and the adjacent Corralitos basin. The ancestral Rio Grande entered the Jornada del Muerto basin via a gap between the footwall blocks, periodically flowing southward towards San Diego Mountain, or making a broad northward sweep into the northern fluvial salient towards the Rincon Hills fault block and unfaulted northern edge of the basin. Ten logged sections up to 35 m thick are correlated using the top of the formation (La Mesa surface), a 1·59 Ma pumice conglomerate, and a ground‐water carbonate/opal bed. Additionally, one of the sections is dated by reversal magnetostratigraphy. Consistent with the model of Bridge & Leeder (1979) and Bridge & Mackey (1993a), differential tilting of the Jornada del Muerto half graben resulted in sections directly adjacent to the faults that consist almost exclusively of multistorey channel sands/sandstones, whereas more distal sections contain a greater proportion of crevasse‐splay fine sand and overbank mudstone and calcic palaeosols. Along the axis of the northern fluvial salient, a northward decrease in channel/floodplain ratio, a decrease in channel recurrence interval from 171 kyr to 685 kyr, and an increase in the maturity of calcic palaeosols are consistent with southward tilt of the unfaulted northern edge of the basin. An upsection decrease in sediment accumulation rate in the northern fluvial salient from 0·036 mm/ yr to 0·017 mm/ yr corresponds to an increase in the ratio of channel/floodplain facies and in the number of multistorey channel sands/sandstones, and is consistent with the model of Bridge & Leeder (1979) in which avulsion frequency is independent of sediment accumulation rate. Stage II and III calcic palaeosols indicate 103−105 year of landscape stability and soil formation between periods of floodplain deposition in response not only to basin tilting but also because the ancestral Rio Grande had multiple paths within the Jornada del Muerto basin and shared time between the Corralitos and Jornada del Muerto basins.