bluuebunny/crossref_metadata_2025 huggingface dataset:
Derivatization by 6‐aminoquinolyl‐N‐hydroxysuccinimidyl carbamate for enhancing the ionization yield of small peptides and glycopeptides in matrix‐assisted laser desorption/ionization and electrospray ionization mass spectrometry
Authors: Ullmer Roman , Plematl Alexander , Rizzi Andreas
Published: April 2006

The characterization of glycosylation in proteins by mass spectrometry (MS) is often impeded by strong suppression of ionization of glycopeptides in the presence of non‐glycosylated peptides. Glycopeptides with a large carbohydrate part and a short peptide backbone are particularly affected by this problem. To meet the goal of generating mass spectra exhibiting glycopeptide coverages as complete as possible, derivatization of glycopeptides offers a practical way to increase their ionization yield. This paper investigated derivatization with 6‐aminoquinolyl‐N‐hydroxysuccinimidyl carbamate (AQC) which is a rapid labeling technique commonly used for fluorescence detection in high‐performance liquid chromatography (HPLC) and capillary electrophoresis (CE). As test samples we used peptides and glycopeptides obtained by enzymatic digestion of three different glycoproteins, i.e., human antithrombin, chicken ovalbumin, and bovine α1‐acid‐glycoprotein. It was found that AQC derivatization resulted in strongly increased signal intensities when analyzing small peptides and glycopeptides by matrix‐assisted laser desorption/ionization (MALDI)‐MS. For these compounds the limit of detection could be reduced to low fmol amounts. Without derivatization only glycopeptides containing large peptide backbones were detected by MALDI‐MS. This effect was even significant when glycopeptides were pre‐separated and enriched by means of lectin affinity chromatography before MALDI‐MS analysis and when using electrospray ionization (ESI). This labeling method, applied in combination with MS detection for the first time, was found to be well suited for the enhancement of detection sensitivity for small glycopeptides in MALDI‐MS analysis and thus for reducing the need for pre‐separation steps. Copyright © 2006 John Wiley & Sons, Ltd.
Identification of the gene encoding hydroxyacid‐oxoacid transhydrogenase, an enzyme that metabolizes 4‐hydroxybutyrate
Authors: Kardon Tamas , Noël Gaëtane , Vertommen Didier , Van Schaftingen Emile
Published: April 2006

To identify the sequence of hydroxyacid‐oxoacid transhydrogenase (HOT), responsible for the oxidation of 4‐hydroxybutyrate in mammalian tissues, we have purified this enzyme from rat liver and obtained partial sequences of proteins coeluting with the enzymatic activity in the last purification step. One of the identified proteins was ‘iron‐dependent alcohol dehydrogenase’, an enzyme encoded by a gene present on human chromosome 8q 13.1 and distantly related to bacterial 4‐hydroxybutyrate dehydrogenases. The identification of this protein as HOT was confirmed by showing that overexpression of the mouse homologue in HEK cells resulted in the appearance of an enzyme catalyzing the α‐ketoglutarate‐dependent oxidation of 4‐hydroxybutyrate to succinate semialdehyde.
Expression of human PQBP‐1 in Drosophila impairs long‐term memory and induces abnormal courtship
Authors: Yoshimura Natsue , Horiuchi Daisuke , Shibata Masao , Saitoe Minoru , Qi Mei-ling , Okazawa Hitoshi
Published: April 2006

Frame shift mutations of the polyglutamine binding protein‐1 (PQBP1) gene lead to total or partial truncation of the C‐terminal domain (CTD) and cause mental retardation in human patients. Interestingly, normal Drosophila homologue of PQBP‐1 lacks CTD. As a model to analyze the molecular network of PQBP‐1 affecting intelligence, we generated transgenic flies expressing human PQBP‐1 with CTD. Pavlovian olfactory conditioning revealed that the transgenic flies showed disturbance of long‐term memory. In addition, they showed abnormal courtship that male flies follow male flies. Abnormal functions of PQBP‐1 or its binding partner might be linked to these symptoms.
Mannose hyperbranched dendritic polymers interact with clustered organization of DC‐SIGN and inhibit gp120 binding
Authors: Tabarani Georges , Reina José J. , Ebel Christine , Vivès Corinne , Lortat-Jacob Hugues , Rojo Javier , Fieschi Franck
Published: April 2006

DC‐SIGN (dendritic cell‐specific ICAM‐3 grabbing non‐integrin) is a C‐type lectin receptor of dendritic cells and is involved in the initial steps of numerous infectious diseases. Surface plasmon resonance has been used to study the affinity of a glycodendritic polymer with 32 mannoses, to DC‐SIGN. This glycodendrimer binds to DC‐SIGN surfaces in the submicromolar range. This binding depends on a clustered organization of DC‐SIGN mimicking its natural organization as microdomain in the dendritic cells plasma membrane. Moreover, this compound inhibits DC‐SIGN binding to the HIV glycoprotein gp120 with an IC50 in the micromolar range and therefore can be considered as a potential antiviral drug.
Potassium channels as tumour markers
Authors: Stühmer Walter , Alves Frauke , Hartung Franziska , Zientkowska Marta , Pardo Luis A.
Published: April 2006

An increasing number of ion channels are being found to be causally involved in diseases, giving rise to the new field of “channelopathies”. Cancer is no exception, and several ion channels have been linked to tumour progression. Among them is the potassium channel EAG (Ether‐a‐go‐go). Over 75% of tumours have been tested positive using a monoclonal antibody specific for EAG, while inhibition of this channel decreased the proliferation of EAG expressing cells. The inhibition of EAG is accomplished using RNA interference, functional anti‐EAG1 antibodies, or (unspecific) EAG channel blockers. Fluorescently labelled recombinant Fab fragments recognizing EAG allow the distribution of EAG to be visualized in an in vivo mouse tumour model.
Managing beyond the factory walls: Effects of four types of strategic integration on manufacturing plant performance
Authors: Swink Morgan , Narasimhan Ram , Wang Cynthia
Published: April 2006

In this paper we focus on the integration of strategic objectives and process knowledge that a manufacturing factory collects from its external interfaces. Using data from a variety of manufacturing industries, this study examines four different types of strategic integration at the manufacturing plant level. We use a path analytic approach to simultaneously assess the contributions of the various types of integration to manufacturing‐based competitive capabilities and business level performance. In addition, we examine the intervening roles that manufacturing‐based competitive capabilities play in mediating the relationships between strategic integration and business performance. We find that each type of integration activity has unique benefits and detriments. These findings extend prior studies of manufacturing and supply chain integration by broadening the theory relating to strategic integration. The results also provide implications for manufacturing managers who seek to design integration policies and associated resource deployments.
Doming in compressional orogenic settings: New geochronological constraints from the NW Himalaya
Authors: Robyr Martin , Hacker Bradley R. , Mattinson James M.
Published: April 2006

In the central and southeastern parts of the Himalayas, the High Himalayan Crystalline (HHC) high‐grade rocks are mainly exhumed in the frontal part of the range, as a consequence of a tectonic exhumation controlled by combined thrusting along the Main Central Thrust (MCT) and extension along the South Tibetan Detachment System (STDS). In the NW Himalaya, however, the hanging wall of the MCT in the frontal part of the range consists mainly of low‐ to medium‐grade metasediments (Chamba zone), whereas most of the amphibolite facies to migmatitic gneisses of the HHC of Zanskar are exposed in a more internal part of the orogen as a large‐scale dome structure referred to as the Gianbul dome. This Gianbul dome is cored by migmatitic paragneisses formed at peak conditions of 800°C and 8 kbar. This migmatitic core is symmetrically surrounded by rocks of the sillimanite, kyanite ± staurolite, garnet, biotite, and chlorite mineral zones. The structural data from the Miyar‐Gianbul Valley section reveal that the Gianbul dome is bounded by two major converging thrust zones, the Miyar Thrust Zone and the Zanskar Thrust Zone, which were reactivated as ductile zones of extension referred to as the Khanjar Shear Zone (KSZ) and the Zanskar Shear Zone (ZSZ), respectively. Geochronological dating of monazites from various migmatites and leucogranite in the core of the Gianbul dome indicates ages between 26.6 and 19.8 Ma. These results likely reflect a high‐temperature stage of the exhumation history of the HHC of Zanskar and consequently constrain the onset of extension along both the ZSZ and the KSZ to start shortly before 26.6 Ma. Several recent models interpret that ductile extrusion of the high‐grade, low‐viscosity migmatites of HHC reflects combined extension along the ZSZ and thrusting along the MCT. Hence our new data constrain the onset of the thrusting along the MCT to start shortly before 26.6 Ma.
Heterogeneous freezing of ammonium sulfate and sodium chloride solutions by long chain alcohols
Authors: Cantrell Will , Robinson Carly
Published: April 2006

High molecular weight organic compounds emitted during biomass burning can be transported to high altitudes where they may affect ice processes through heterogeneous nucleation. We show that freezing of solutions of ammonium sulfate and sodium chloride catalyzed by long chain alcohols is roughly consistent with the hypothesis that the water activity at the mean freezing temperature is a constant offset from the water activity at the melting point of the solution, though films of the longer chain alcohols may undergo structural changes at higher salt concentrations which cause a deviation from the constant offset. The heterogeneous nucleation rate coefficient, averaged over all solutions, alcohols, and droplet sizes is 6.0 × 104 ± 4.0 × 104 cm−2 s−1, with no dependence on any of those parameters.
Climate sensitivity to ocean dimethylsulphide emissions
Authors: Gunson J. R. , Spall S. A. , Anderson T. R. , Jones A. , Totterdell I. J. , Woodage M. J.
Published: April 2006

The production of dimethylsulphide (DMS) by ocean phytoplankton is hypothesized to form part of a feedback process on global climate. Changes in the DMS flux to the atmosphere cause changes to aerosols for cloud formation, leading to changes in the amount of radiation reaching the ocean, and hence on the planktonic production of DMS. This hypothesis has been investigated using a coupled ocean‐atmosphere general circulation model (COAGCM) that includes an ocean ecosystem model and an atmospheric sulphur cycle. Ocean DMS concentrations are parameterised as a function of chlorophyll, nutrient and light. The results of several sensitivity experiments are presented showing significant global climate change responses to perturbations in ocean DMS production. A small negative feedback from climate change onto ocean DMS production is found and the implications are discussed.
Fault‐perpendicular aftershock clusters following the 2003 Mw = 5.0 Big Bear, California, earthquake
Authors: Chi Wu‐Cheng , Hauksson Egill
Published: April 2006

To explore aftershock‐triggering mechanisms for the 2003 Big Bear, California earthquake sequence, we determined differential travel‐times and applied the double‐difference technique to relocate these events, which formed three clusters. The main cluster coincides with the 3 km long northwest striking sub‐vertical mainshock fault. The other two sub‐vertical clusters, located at opposite ends of the mainshock rupture, are almost perpendicular to the mainshock fault, contradicting the 60° separation angle of conjugate faults as predicted from frictional laws. Allowing for a 30° uncertainty in the cataloged strike, dip and rake values about 75% of the aftershocks are strike‐slip as determined from first motion and complete waveform moment tensor inversions. We use a mainshock conceptual slip model to derive Coulomb Failure Stress regions, and assess correlations between stress increases and aftershock locations. We conclude that the perpendicular aftershock clusters were triggered by the mainshock static stress perturbation.
A structural study of an interior layered deposit in southwestern Candor Chasma, Valles Marineris, Mars, using high resolution stereo camera data from Mars Express
Authors: Fueten F. , Stesky R. , MacKinnon P. , Hauber E. , Gwinner K. , Scholten F. , Zegers T. , Neukum G.
Published: April 2006

An interior layered deposit (ILD) within Western Candor Chasma of Valles Marineris, Mars, is examined using data from the High Resolution Stereo Camera of the Mars Express mission. Most ILD layers dip in the same direction as the topographic slope. Exposed, rotated fault blocks of basement lithology appear to penetrate the cover of this ILD deposit in at least two locations. These features suggest a simple drape morphology over basement topography consisting of rotated fault blocks. This interpretation constrains possible hypotheses of ILD formation and suggests a limit on total volume of ILD material. Draping implies low‐energy deposition, either subaerially or in deep water, and that the total volume of ILD is considerably less than indicated by the size of the mound. A dark competent unit unconformably caps part of the ILD indicating a multistage depositional history.
Self‐gravity wakes in Saturn's A ring measured by stellar occultations from Cassini
Authors: Colwell J. E. , Esposito L. W. , Sremčević M.
Published: April 2006

An azimuthal brightness asymmetry in Saturn's A ring is caused by ephemeral agglomerations that continually form under the mutual gravity of the ring particles only to be torn apart by Keplerian shear. We calculate the shape and spacing of the self‐gravity wakes from Cassini stellar occultations. The wakes are highly flatttened structures, with height/width ratio of 0.15 to 0.37, increasing outward across the A ring. The spacing between wakes increases with their height from a low value in the inner A ring of less than the wake width to >3 times the wake width in the outer third of the ring. The opacity of gaps between wakes also increases in the outer part of the ring where the wakes appear to be less coherent than in the inner and middle A ring. We calculate the vertical opacity of the A ring is 15–35% higher than previously reported.
Climate model fidelity and projections of climate change
Authors: Shukla J. , DelSole T. , Fennessy M. , Kinter J. , Paolino D.
Published: April 2006

Relative entropy, which is a measure of the difference between two probability distributions, has been calculated for the simulations of the climate of the 20th century from 13 climate models and the observed surface air temperature during the past 100 years. This quantity is used as a measure of model fidelity: a small value of relative entropy indicates that a given model's distribution is close to the observed. It is found that there is an inverse relationship between relative entropy and the sensitivity of the model to doubling of the concentration of CO2. The models that have lower values of relative entropy, hence have higher fidelity in simulating the present climate, produce higher values of global warming for a doubling of CO2. This suggests that the projected global warming due to increasing CO2 is likely to be closer to the highest projected estimates among the current generation of climate models.
Morphology of the ultraviolet Io footprint emission and its control by Io's location
Authors: Gérard Jean‐Claude , Saglam Adem , Grodent Denis , Clarke John T.
Published: April 2006

A total of 74 images of the ultraviolet footprint of the Io flux tube (IFT) on Jupiter's upper atmosphere made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope have been analyzed to characterize their location, morphology, and brightness distribution. The observations cover a wide range of central meridian Jovian longitudes and Io orbital positions and include north and south footprint emissions. Comparing the location of the IFT with that expected from the VIP4 model of the Jovian magnetic field, we find that the lead angle is generally not significantly different from zero in the System III longitude sector 125°–195°. Instead, the lead angles reach about 8° in the 50° sector, coinciding with a region of possible magnetic anomaly. We observe that the brightness of the main footprint shows intrinsic intensity changes that appear to be controlled by the system III longitude of Io and its position above or below the center of the torus. The size of the primary spot magnetically maps into a region varying from 1 to over 10 Io diameters in Io's orbital plane. Multiple footprints are observed with varying brightness relative to the mean spot. The number of spots is found to increase as Io gets closer to the torus outer edge facing the spots. The separation between the first and second spots is typically 1°–3° of longitude and increases when Io is displaced from the torus center in the direction of the IFT signature. These features confirm that Alfvén waves play an important role and generate energization of precipitated electrons. However, the observed variation of the FUV spot structure with Io's position appears inconsistent with models where reflections of Alfvén wings occur between the torus boundary and Jupiter's ionosphere. Instead, the multiple spots apparently correspond to electron precipitation generated by Alfvén waves reflected inside the plasma torus.
Crustal heat production in the Superior Province, Canadian Shield, and in North America inferred from heat flow data
Authors: Perry H. K. C. , Jaupart C. , Mareschal J.‐C. , Bienfait G.
Published: April 2006

Measurements of heat flow and U, Th, K concentrations are used to determine the amount of heat generated in various belts of the Superior Province, the largest Archean craton on Earth. These data allow estimates of the average crustal heat production and indicate compositional differences between upper and lower crustal assemblages. The bulk average heat production of the Superior Province crust is 0.64 μW m−3and is almost the same in different belts of slightly different ages, illustrating the remarkable uniformity of crust‐building mechanisms. In the wider context of the North American continent, the bulk crustal heat production decreases from 1.0 μW m−3in the oldest Slave Province to a minimum of 0.55 μW m−3in the Paleo‐Proterozoic Trans‐Hudson Orogen. It increases in younger provinces, culminating with a high value of 1.05 μW m−3in the Phanerozoic Appalachian Province. In all provinces, U and Th enrichment is systematically associated with sedimentary accumulations. A crustal differentiation index is obtained by calculating the ratio between the average values of heat production at the surface and in the bulk crust. The differentiation index is correlated with the bulk average heat production, which suggests that crustal differentiation processes are largely driven by internal radiogenic heat.
Microphysical modeling of southern polar dehydration during the 1998 winter and comparison with POAM III observations
Authors: Benson C. M. , Drdla K. , Nedoluha G. E. , Shettle E. P. , Hoppel K. W. , Bevilacqua R. M.
Published: April 2006

Stratospheric dehydration and high aerosol extinctions are examined for the 1998 Antarctic winter using the Integrated Microphysics and Aerosol Chemistry on Trajectories (IMPACT) model and data obtained by the Polar Ozone and Aerosol Measurement (POAM) III instrument. The model is applied to individual air parcels which are advected along 3‐D trajectories using the United Kingdom Meteorological Office (UKMO) global wind and temperature fields. Model results are compared to water vapor and aerosol extinction measurements obtained with the POAM instrument. Results suggest that the water vapor mixing ratio at the end of the season is predicted with reasonable accuracy. However, dehydration occurs more rapidly in the simulation than is indicated by the POAM data. In addition to dehydration results, the frequency of high aerosol extinction measurements is examined for all model runs and compared to POAM data. The aerosol extinction comparisons are consistent with the assumption that heterogeneous nitric acid trihydrate (NAT) freezing occurs in approximately 1% of all particles. Various model parameters influencing ice cloud microphysics are altered to examine their effects on both the water vapor mixing ratio and high aerosol extinction events. While a reduction in the ice accommodation coefficient and an increase in the ice nucleation barrier both improve the agreement in the water vapor mixing ratio, the agreement in aerosol extinction is worsened. Extinction comparisons suggest that the model results are consistent with either high or low NAT‐ice lattice compatibility factors, although intermediate values agree poorly with POAM data. The extent of dehydration is highly dependent on temperature; therefore, an uncertainty as small as ±1 K in the UKMO temperature fields may significantly change the model results.
Partial least squares modeling to quantify lunar soil composition with hyperspectral reflectance measurements
Authors: Li Lin
Published: April 2006

Partial least squares (PLS) and principal component regression (PCR) are applied to lunar highland and mare soil data characterized by the Lunar Soil Characterization Consortium (LSCC) for prediction of abundance of lunar soil chemistry and minerals. The goal of this study is to develop a tool for predicting the abundance of chemical and mineral constituents of lunar soils from reflectance data. To determine the best model, the optimal number of PLS components is selected through the cross‐validation. The results obtained from PLS and PCR using mean centered and normalized data are compared. The comparison indicates that using mean centered and normalized data has an insignificant effect on estimates of the soil chemical and mineral abundance. Both PLS and PCR perform well in predicting chemical abundance based on prediction errors. For most of minerals considered, one of PLS models always gives the best estimate of mineral abundances. PLS is preferred over PCR in estimation of lunar soil chemical mineral abundances because the first model uses fewer components than the second model. It is concluded that PLS has potential to be applied to lunar hyperspectral imagery (M3 mission) for compositional predictions.
Venusian channel formation as a subsurface process
Authors: Lang Nicholas P. , Hansen Vicki L.
Published: April 2006

We constructed detailed geologic maps of channels within three widely separated regions using Magellan synthetic aperture radar (SAR) imagery and altimetry radar data in order to understand the operative processes involved in Venusian channel formation. Channels in each region cut topographic highs including ridges and shield edifices with no deflection of the channel course by surface topography. We argue that these relationships are difficult to reconcile with the widely held view that Venusian channels represent surface processes, whether constructional or erosional. We conclude that the channels evolved through subsurface fluid flow, which involved local stoping and transport of overlying material; that is, these channels were carved from below, rather than from above. We postulate that at least some Venusian channels form because of subsurface fluid flow along a shallow crustal interface that forms the boundary between overlying low backscatter surface materials and underlying basal materials. Fluid movement along the interface may facilitate piecemeal stoping and erosion of the local surface materials from below, eventually resulting in the formation of channel traces exposed at the surface. The low backscatter material which hosts the channels in this study also hosts abundant coalescing shields and associated deposits, which may represent shield terrain.
A hybrid linear‐neural model for river flow forecasting
Authors: Chetan M. , Sudheer K. P.
Published: April 2006

This paper presents a novel hybrid linear‐neural (LN) model formulation to effectively model rainfall‐runoff processes. The central idea of the proposed model framework is that the hidden layer of an artificial neural network (ANN) model be designed with a combination of linear and nonlinear neurons. A training algorithm for the proposed model is designed based on minimum description length criteria. The advantage of the algorithm is that the final architecture of the LN model is arrived at during the training process, thus avoiding selection from a class of models. The proposed model has been developed and evaluated for its performance for forecasting the river flow of Kolar basin, in India. The values of three performance evaluation criteria, namely, the coefficient of efficiency, the root‐mean‐square error, and the coefficient of correlation, were found to be very good and consistent for flows forecasted 1 hour in advance by the LN model. The value of the relative error in peak flow prediction was within reasonable limits for the model. The forecasts by the LN model at higher lead times (up to 6 hours) are found to be good. A relative evaluation of LN model performance with that of an ANN model and of a multiple linear regression model indicates that the LN model effectively combines the strength of the other two, implying that the LN model seems to be well suited to exploit the information to model the nonlinear dynamics of the rainfall‐runoff process.
A regional coupled surface water/groundwater model of the Okavango Delta, Botswana
Authors: Bauer Peter , Gumbricht Thomas , Kinzelbach Wolfgang
Published: April 2006

In the endorheic Okavango River system in southern Africa a balance between human and environmental water demands has to be achieved. The runoff generated in the humid tropical highlands of Angola flows through arid Namibia and Botswana before forming a large inland delta and eventually being consumed by evapotranspiration. With an approximate size of about 30,000 km2, the Okavango Delta is the world's largest site protected under the convention on wetlands of international importance, signed in 1971 in Ramsar, Iran. The extended wetlands of the Okavango Delta, which sustain a rich ecology, spectacular wildlife, and a first‐class tourism infrastructure, depend on the combined effect of the highly seasonal runoff in the Okavango River and variable local climate. The annual fluctuations in the inflow are transformed into vast areas of seasonally inundated floodplains. Water abstraction and reservoir building in the upstream countries are expected to reduce and/or redistribute the available flows for the Okavango Delta ecosystem. To study the impacts of upstream and local interventions, a large‐scale (1 km2 grid), coupled surface water/groundwater model has been developed. It is composed of a surface water flow component based on the diffusive wave approximation of the Saint‐Venant equations, a groundwater component, and a relatively simple vadose zone component for calculating the net water exchange between land and atmosphere. The numerical scheme is based on the groundwater simulation software MODFLOW‐96. Since the primary model output is the spatiotemporal distribution of flooded areas and since hydrologic data on the large and inaccessible floodplains and tributaries are sparse and unreliable, the model was not calibrated with point hydrographs but with a time series of flooding patterns derived from satellite imagery (NOAA advanced very high resolution radiometer). Scenarios were designed to study major upstream and local interventions and their expected impacts in the Delta. The scenarios' results can help decision makers strike a balance between environmental and human water demands in the basin.
Fluorescence excitation and emission spectroscopy of the ÃA″1←X̃A′1 system of CHBr
Authors: Deselnicu Mihaela , Tao Chong , Mukarakate Calvin , Reid Scott A.
Published: April 2006

We report fluorescence excitation and emission spectra of CHBr in the 450–750nm region. A total of 30 cold bands involving the pure bending levels 20n with n=2–8 and combination bands 20n301(n=1–8), 20n302(n=1–6), 20n303(n=1–2), 10120n(n=5–7), 10120n301(n=4–6), and 10120n302(n=5) in the ÃA″1←X̃A′1 system were observed, in addition to a number of hot bands. The majority of these are reported and/or rotationally analyzed here for the first time. Spectra were measured under jet-cooled conditions using a pulsed discharge source, and rotational analysis yielded band origins and rotational constants for both bromine isotopomers (CHBr79,CHBr81). The derived ÃA″1 vibrational intervals are combined with results of [Yu et al. J. Chem. Phys. 115, 5433 (2001)] to derive barriers to linearity for the 2n, 2n31, and 2n32 progressions. The ÃA″1 state C–H stretching frequency is determined here for the first time, and the observed ν3 dependence of the Br79–Br81 isotope splitting in the ÃA″1 state is in good agreement with theoretical expectations. Our dispersed fluorescence spectra probe the vibrational structure of the X̃A′1 state up to ∼9000cm−1 above the vibrationless level; the total number of levels observed is more than twice that previously reported. As first reported by [Chen et al. J. Mol. Spectrosc. 209, 254 (2001)], these spectra reveal numerous perturbations due to spin-orbit interaction with the low-lying ãA″3 state. The results of a Dunham expansion fit of the ground state vibrational term energies, and comparisons with previous experimental and theoretical studies, are reported. Our results lead to several revised assignments, including the X̃A′1 C–H stretching fundamental. Globally, the vibrational frequencies of X̃A′1, ãA″3, and ÃA″1 are in excellent agreement with theoretical predictions.
Reproducible attachment of micrometer sized particles to atomic force microscopy cantilevers
Authors: Mak L. H. , Knoll M. , Weiner D. , Gorschlüter A. , Schirmeisen A. , Fuchs H.
Published: April 2006

We present a method, which allows attaching micrometer sized spheres to an atomic force microscope cantilever in a reproducible manner. Spheres of different size with a minimum amount of glue are attached to a predefined position on the cantilever. This is performed by using an optical microscope and a laser-pulled micropipette, which guarantees nondestructive handling of the delicate cantilever beams. The method employs a simple setup consisting of a stereomicroscope and a micromanipulator. Images of the modified cantilevers were taken with a scanning electron microscope to clarify the position of the glued spheres on the cantilever. Electron dispersive x-ray analysis reveals that the surface of the microsphere is not covered with the glue, except at the contact area to the cantilever.
Energy resolved two-dimensional soft x-ray radiography with a micropattern gas detector
Authors: Pacella Danilo , Bellazzini Ronaldo , Finkenthal Michael
Published: April 2006

This article discusses the use of energy resolved two-dimensional soft x-ray imaging (ERXI), in the range of 2–8keV, to study and investigate composition and depth of different materials. This technique represents a new approach in which imaging is merged with multienergy analysis, performed with spectral scans in 25 energy subintervals. The detector used is a micropattern gas detector with gas electron multiplier as amplifying structure, pixel readout board with 144pixels (12×12), and electronics for photon counting for each pixel. As the detector works in a proportional regime, images in adjustable energy windows (independently for each pixel) can be acquired. Energy resolution enhances the contrast and the imaging capability providing more information of the transparencies of the materials under investigations. Contact radiographies have been made with samples of four different materials: CaCl, organic fat matter, aluminum, and thin plastic tape. The resulting data transparency curves for these materials have been derived. These curves demonstrate the value of ERXI at high performances (high efficiency, high dynamics, and high contrast), potentially relevant for many future applications.
Ion implantation based selective synthesis of silica nanowires on silicon wafers
Authors: Sood Dinesh Kumar , Sekhar Praveen Kumar , Bhansali Shekhar
Published: April 2006

A new method for selective growth of silica nanowires on silicon wafers is demonstrated by using ion implantation through a mask. Pd ions are implanted into Si (100) to form nanoclusters of Pd. The nanoclusters get activated and act as catalyst silicide seeds for nanowire growth, when heated in an open tube quartz furnace, using Ar as carrier gas. Silica nanowires grow selectively only on the implanted region. The vapor-liquid-solid model of nanowire formation is shown to be valid. This method facilitates controlled localized and directed bottom-up growth of silica nanowires and may enable applications such as in on-chip optoelectronics, biosensors, microantennae, and metallic nanotubes.
Effect of high-temperature annealing on the residual strain and bending of freestanding GaN films grown by hydride vapor phase epitaxy
Authors: Paskova T. , Hommel D. , Paskov P. P. , Darakchieva V. , Monemar B. , Bockowski M. , Suski T. , Grzegory I. , Tuomisto F. , Saarinen K. , Ashkenov N. , Schubert M.
Published: April 2006

The effect of high-temperature high-pressure annealing on the residual strain, bending, and point defect redistribution of freestanding hydride vapor phase epitaxial GaN films was studied. The bending was found to be determined by the difference in the in-plane lattice parameters in the two faces of the films. The results showed a tendency of equalizing the lattice parameters in the two faces with increasing annealing temperature, leading to uniform strain distribution across the film thickness. A nonmonotonic behavior of structural parameters with increasing annealing temperature was revealed and related to the change in the point defect content under the high-temperature treatment.
High sensitivity surface plasmon resonance sensor based on phase interrogation at optimal incident wavelengths
Authors: Chiang Hai-Pang , Lin Jing-Lun , Chen Zhi-Wei
Published: April 2006

It is demonstrated that ultrahigh sensitivity of glucose refractive index measurement can be achieved via surface plasmon resonance excitation in which the phase difference between p- and s-polarized reflected waves is monitored as a function of the incident angle. Sensitivity with values down to the order of 10−8 is obtained by performing the measurements at optimal incident wavelengths. This represents an order of magnitude improvement compared to the previously reported values in the literature.
Thermomigration in SnPb composite flip chip solder joints
Authors: Huang Annie T. , Gusak A. M. , Tu K. N. , Lai Yi-Shao
Published: April 2006

We have used composite flip chip solder joints to study thermomigration. The composite solder joint has 97Pb3Sn on the Si side and eutectic 37Pb63Sn on the substrate side. Redistribution of Sn and Pb occurs in thermomigration, and we found that Sn has moved to the Si side (the hot end) and Pb to the substrate side (the cold end). We estimate the driving force that a temperature gradient of 1000°C∕cm or a temperature difference of 10°C across a solder joint of 100μm in diameter is sufficient to induce the thermomigration.
Effects of nitrogen source and ectomycorrhizal association on growth and δ15N of two subtropical Eucalyptus species from contrasting ecosystems
Authors: Schmidt Susanne , Handley Linda L. , Sangtiean Tanuwong
Published: April 2006

Ectomycorrhizal (EM) associations facilitate plant nitrogen (N) acquisition, but the contribution of EM associations to tree N nutrition is difficult to ascertain in ecosystems. We studied the abilities of subtropical EM fungi and nutritionally contrasting Eucalyptus species, Eucalyptus grandis W.Hill ex Maiden and Eucalyptus racemosa Cav, to use N sources in axenic and soil cultures, and determined the effect of EM fungi on plant N use and plant 15N natural abundance (δ15N). As measured by seedling growth, both species showed little dependence on EM when growing in the N-rich minerotrophic soil from E. grandis rainforest habitat or in axenic culture with inorganic N sources. Both species were heavily dependent on EM associations when growing in the N-poor, organotrophic soil from the E. racemosa wallum habitat or in axenic culture with organic N sources. In axenic culture, EM associations enabled both species to use organic N when supplied with amide-, peptide- or protein-N. Grown axenically with glutamine- or protein-N, δ15N of almost all seedlings was lower than source N. The δ15N of all studied organisms was higher than the N source when grown on glutathione. This unexpected 15N enrichment was perhaps due to preferential uptake of an N moiety more 15N-enriched than the bulk molecular average. Grown with ammonium-N, the δ15N of non-EM seedlings was mostly higher than that of source N. In contrast, the δ15N of EM seedlings was mostly lower than that of source N, except at the lowest ammonium concentration. Discrimination against 15N was strongest when external ammonium concentration was high. We suggest that ammonium assimilation via EM fungi may be the cause of the often observed distinct foliar δ15N of EM and non-EM species, rather than use of different N sources by species with different root specialisations. In support of this notion, δ15N of soil and leaves in the rainforest were similar for E. grandis and co-occurring non-mycorrhizal Proteaceae. In contrast, in wallum forest, E. racemosa leaves and roots were strongly 15N-depleted relative to wallum soil and Proteaceae leaves. We conclude that foliar δ15N may be used in conjunction with other ecosystem information as a rapid indicator of plant dependency on EM associations for N acquisition.
EcoMeristem, a model of morphogenesis and competition among sinks in rice. 1. Concept, validation and sensitivity analysis
Authors: Luquet Delphine , Dingkuhn Michael , Kim HaeKoo , Tambour Ludovic , Clement-Vidal Anne
Published: April 2006

Because of rapid advances in functional genomics there is an increasing demand for models simulating complex traits, such as the physiological and environmental controls of plant morphology. This paper describes, validates and explores the behaviour of the structural–functional model EcoMeristem, developed for cereals in the context of the Generation Challenge Program (GCP; CGIAR). EcoMeristem constructs the plant on the basis of an organogenetic body plan, driven by intrinsic (genetic) behavioural norms of meristems. These norms consist of phenological–topological rules for organ initiation and pre-dimensioning (sink creation) and rules enabling feedbacks of the plant’s resource status on the organogenetic processes. Plant resource status is expressed by a state variable called Internal Competition Index (Ic) calculated daily as the ratio of assimilate source (supply) over the sum of active sinks (demand). Ic constitutes an internal signal analogous to sugar signalling. Ic affects potential phytomer size, tiller initiation, leaf senescence, and carbohydrate storage and mobilisation. The model was calibrated and tested on IR64 rice grown in controlled environments, and validated with field observations for the same cultivar (Philippines). Observed distributions and dynamics of soluble sugars and starch in plant organs supported the model concepts of internal competition and the role of reserves as a buffer for Ic fluctuations. Model sensitivity analyses suggested that plant growth and development depend not only on assimilate supply, but also on organogenesis-based demand. If true, this conclusion has important consequences for crop improvement strategies.
EcoMeristem, a model of morphogenesis and competition among sinks in rice. 2. Simulating genotype responses to phosphorus deficiency
Authors: Dingkuhn Michael , Luquet Delphine , Kim HaeKoo , Tambour Ludovic , Clement-Vidal Anne
Published: April 2006

Phenotypic plasticity enables plants to adjust their morphology and phenology to variable environments. Although potentially important for crop breeding and management, the physiology and genetics of plasticity traits are poorly understood, and few models exist for their study. In the previous paper of this series, the structural–functional model EcoMeristem was described and field validated for vegetative-stage rice. This study applies the model to an experimental study on phosphorus deficiency effects on two morphologically contrasting rice cultivars, IR64 and Azucena, grown in controlled environments under hydroponics culture. Phosphorus deficiency caused severe biomass growth reductions in the shoot but not in the root, thus increasing the root / shoot weight ratio. It also inhibited tiller formation and leaf elongation, prolonged the phyllochron, and increased carbohydrate reserve pools in the plant. Analysis aided by the model identified inhibition of leaf extension and tillering as primary effects of the stress. Physiological feedback probably led to longer phyllochron, greater reserve accumulation and root growth stimulation. The main effect of P deficiency appeared to be a reduction in demand for assimilates in the shoot while photosynthetic radiation use efficiency remained nearly constant, resulting in spill-over of excess assimilates into reserve compartments and root growth. The results are discussed in the light of future applications of EcoMeristem for phenotyping and genetic analyses of phenotypic plasticity.
Somatic cell nuclear transfer in buffalos: effect of the fusion and activation protocols and embryo culture system on preimplantation embryo development
Authors: Simon Liz , Veerapandian C. , Balasubramanian S. , Subramanian A.
Published: April 2006

The present study was conducted primarily to evaluate several factors that affect the nuclear transfer programme in water buffalos, in which relatively few studies have been performed. Embryos reconstructed with quiescent fetal fibroblasts and metaphase II cytoplasts were matured for 24 h, and activation was found to be comparatively better than in those matured for 30 h. A significantly higher proportion of embryos fused (52.0 ± 1.9) and cleaved (51.2 ± 1.7) when the couplets were fused 4–6 h before activation than when fused and activated simultaneously (46.5 ± 1.6 and 44.5 ± 2.0, respectively). Development of nuclear transfer embryos to the blastocyst stage (4.8 ± 2.2) was supported by a commercially available sequential medium, and cleavage (76.5 ± 2.8) was significantly higher in this medium compared with cleavage in TCM-199 with oviduct epithelial cell coculture (45.6 ± 1.5) and synthetic oviduct fluid (21.8 ± 6.6). Of the 16 cloned embryos transferred, none resulted in pregnancy. The present study demonstrates that optimal numbers of cloned buffalo blastocysts can be obtained from oocytes matured for 24 h, fused 3–4 h before activation and cultured in a commercially available sequential media (G1/G2), thus providing further information to enable successful nuclear transfer in buffalos.
Collegial decision making based on social amplification leads to optimal group formation
Authors: Amé Jean-Marc , Halloy José , Rivault Colette , Detrain Claire , Deneubourg Jean Louis
Published: April 2006

Group-living animals are often faced with choosing between one or more alternative resource sites. A central question in such collective decision making includes determining which individuals induce the decision and when. This experimental and theoretical study of shelter selection by cockroach groups demonstrates that choices can emerge through nonlinear interaction dynamics between equal individuals without perfect knowledge or leadership. We identify a simple mechanism whereby a decision is taken on the move with limited information and signaling and without comparison of available opportunities. This mechanism leads to optimal mean benefit for group individuals. Our model points to a generic self-organized collective decision-making process independent of animal species.
Exotic taxa less related to native species are more invasive
Authors: Strauss Sharon Y. , Webb Campbell O. , Salamin Nicolas
Published: April 2006

Some species introduced into new geographical areas from their native ranges wreak ecological and economic havoc in their new environment. Although many studies have searched for either species or habitat characteristics that predict invasiveness of exotic species, the match between characteristics of the invader and those of members of the existing native community may be essential to understanding invasiveness. Here, we find that one metric, the phylogenetic relatedness of an invader to the native community, provides a predictive tool for invasiveness. Using a phylogenetic supertree of all grass species in California, we show that highly invasive grass species are, on average, significantly less related to native grasses than are introduced but noninvasive grasses. The match between the invader and the existing native community may explain why exotic pest species are not uniformly noxious in all novel habitats. Relatedness of invaders to the native biota may be one useful criterion for prioritizing management efforts of exotic species.
Chronic activation in presymptomatic amyotrophic lateral sclerosis (ALS) mice of a feedback loop involving Fas, Daxx, and FasL
Authors: Raoul C. , Buhler E. , Sadeghi C. , Jacquier A. , Aebischer P. , Pettmann B. , Henderson C. E. , Haase G.
Published: April 2006

The reasons for the cellular specificity and slow progression of motoneuron diseases such as ALS are still poorly understood. We previously described a motoneuron-specific cell death pathway downstream of the Fas death receptor, in which synthesis of nitric oxide (NO) is an obligate step. Motoneurons from ALS model mice expressing mutant SOD1 showed increased susceptibility to exogenous NO as compared with controls. Here, we report a signaling mechanism whereby NO leads to death of mutant, but not control, motoneurons. Unexpectedly, exogenous NO triggers expression of Fas ligand (FasL) in cultured motoneurons. In mutant SOD1
G93A
and SOD1
G85R
, but not in control motoneurons, this up-regulation results in activation of Fas, leading through Daxx to phosphorylation of p38 and further NO synthesis. This Fas/NO feedback amplification loop is required for motoneuron death
in vitro
.
In vivo
, mutant SOD1
G93A
and SOD1
G85R
mice show increased numbers of positive motoneurons and Daxx nuclear bodies weeks before disease onset. Moreover, FasL up-regulation is reduced in the presence of transgenic dominant-negative Daxx. We propose that chronic low-level activation of the Fas/NO feedback loop may underlie the motoneuron loss that characterizes familial ALS and may help to explain its slowly progressive nature.