bluuebunny/crossref_metadata_2025 huggingface dataset:
Contour tracking of an unknown planar object by regulating force for mobile robot navigation
Authors: Jung Seul , Jeon Poongwoo , Hsia T. C.
Published: September 2006

In this paper, a novel contour-tracking control method of an unknown planar object by lateral force regulation for wheeled mobile robot navigation is presented. The robot is required to follow the contour of an unknown object toward the goal position. Based on mobile robot dynamic equations, a force-control algorithm is proposed to maintain constant contact with a planar object. Measured contact force from an object is used not only to regulate a contact force in a lateral direction, but also to control the orientation angle of the robot to avoid collision with an object. Simulation and experiment of contour-tracking tasks of a wheeled mobile robot are conducted. Experimental results show that the contact force is well-regulated, and the robot arrives at the goal position successfully.
Molecular evidence for infection by HTLV-2 among individuals with negative serological screening tests for HTLV antibodies
Authors: ISHAK R. , VALLINOTO A. C. R. , AZEVEDO V. N. , VICENTE A. C. P. , HALL W. W. , ISHAK M. O. G.
Published: September 2006

Previous serological studies on the Arara do Laranjal Indian group revealed extensive HTLV-2 infections. A collection of 97 new samples from the Arara were found repeatedly negative using three different commercial enzyme immunoassays. Eight samples that exhibited optical density readings close to the cut-off value were re-evaluated using Western blot (GeneLab 2.4, Singapore) assay. One sample was found to be non-reactive, five exhibited indeterminate patterns, one was classified as HTLV, and one was confirmed as HTLV-2. Peripheral blood mononuclear cell DNA of the eight samples were subjected to nested PCR and restriction fragment length polymorphism (RFLP) analysis of thepXandenvregions, and nucleotide sequencing of the 5′-LTRregion. All produced amplification products ofpX, butenvcould be amplified in only one sample with the commonly used primers. RFLP analysis of thepXregion usingTaqI confirmed HTLV-2 infection. Nucleotide sequencing of the 5′-LTRregion was performed in three samples (HTLV-2, HTLV and indeterminate based on Western blot pattern). Phylogenetic analysis of a 449-nt fragment using the Neighbour-Joining method clearly demonstrated that the three samples clustered within the HTLV-2c molecular subtype. The present study confirms the wide dissemination of the HTLV-2c subtype among linguistically and culturally distinct Amazonian Indian groups, and emphasizes the unique occurrence of infection by this subtype in Brazil. Moreover, it emphasizes the limitation of employing the present serological screening assays in blood banks, epidemiological studies, and the importance of molecular assays in the confirmatory procedures for the primary detection of HTLV-2 infections.
The Implementation of a ‘Signs of Sepsis’ Learning Resource for a Post-Anaesthetic Care Unit
Authors: Inch Jessica
Published: September 2006

The following article centres on the justification, planning and implementation of a ‘Sepsis Learning Package’ for nursing students and qualified practitioners. This takes the form of a CDROM and web site, and is concerned with the recently spotlighted area of severe sepsis recognition and the related physiology. This was initially utilised in an orthopaedic post-anaesthetic recovery unit (PACU) that doubles as a high-dependency area. This unit is prone to readmissions from the ward environment with ‘sepsis’ being among the many diagnoses. This therefore highlights the need for all staff, both ward and PACU, to recognise the signs and symptoms before the condition progresses. The unit greatly values the sharing of knowledge, in the form of group teaching sessions and scenarios. However, there was great potential for a separate vessel for learning that made use of the computers in the work environment and in turn provided some interesting advantages.
Physical‐biological interactions in North Pacific oxygen variability
Authors: Deutsch Curtis , Emerson Steven , Thompson LuAnne
Published: September 2006

We investigate the temporal variability of oxygen in the upper water column of the North Pacific using a hindcast ocean model. The model embeds simple biogeochemical cycles of nutrients and O2 within an isopycnal circulation model that is forced at the surface by historical atmospheric conditions. The resulting O2 variability is spatially and temporally complex, but includes large‐scale O2 decreases between the 1980s and 1990s in the subpolar region, and simultaneous O2 increases in the subtropics. These simulated changes are similar in pattern to those observed along repeat transects (Emerson et al., 2004), suggesting that the model captures key mechanisms of late twentieth century O2 variability in the North Pacific. Additional simulations were performed to distinguish O2 changes due to variability in biology, ventilation, and circulation. Regional trends in export production drive significant oxygen changes that are focused in the upper thermocline, where remineralization rates are largest. However, shallow biological O2 changes are often balanced by opposing physically driven O2 changes. In contrast, physical processes of ventilation and circulation are found to be the dominant cause of model O2 variability in the lower ventilated thermocline, where observed O2 anomalies are the largest. These results suggest that O2 variability in the lower ventilated thermocline may be a useful tracer of physical climate change in the North Pacific, while changes in the biological pump may be difficult to detect on the basis of O2 trends alone. Continued analysis of historical patterns of subsurface O2 variability will provide important further tests of these conclusions.
Stratospheric Aerosol and Gas Experiment (SAGE) II and III aerosol extinction measurements in the Arctic middle and upper troposphere
Authors: Treffeisen R. E. , Thomason L. W. , Ström J. , Herber A. B. , Burton S. P. , Yamanouchi T.
Published: September 2006

In recent years, substantial effort has been expended toward understanding the impact of tropospheric aerosols on Arctic climate and chemistry. A significant part of this effort has been the collection and documentation of extensive aerosol physical and optical property data sets. However, the data sets present significant interpretive challenges because of the diverse nature of these measurements. Among the longest continuous records is that by the spaceborne Stratospheric Aerosol and Gas Experiment (SAGE) II. Although SAGE tropospheric measurements are restricted to the middle and upper troposphere, they may be able to provide significant insight into the nature and variability of tropospheric aerosol, particularly when combined with ground and airborne observations. This paper demonstrates the capacity of aerosol products from SAGE II and its follow‐on experiment SAGE III to describe the temporal and vertical variations of Arctic aerosol characteristics. We find that the measurements from both instruments are consistent enough to be combined. Using this combined data set, we detect a clear annual cycle in the aerosol extinction for the middle and upper Arctic troposphere.
Formaldehyde distribution over North America: Implications for satellite retrievals of formaldehyde columns and isoprene emission
Authors: Millet Dylan B. , Jacob Daniel J. , Turquety Solène , Hudman Rynda C. , Wu Shiliang , Fried Alan , Walega James , Heikes Brian G. , Blake Donald R. , Singh Hanwant B. , Anderson Bruce E. , Clarke Antony D.
Published: September 2006

Formaldehyde (HCHO) columns measured from space provide constraints on emissions of volatile organic compounds (VOCs). Quantitative interpretation requires characterization of errors in HCHO column retrievals and relating these columns to VOC emissions. Retrieval error is mainly in the air mass factor (AMF) which relates fitted backscattered radiances to vertical columns and requires external information on HCHO, aerosols, and clouds. Here we use aircraft data collected over North America and the Atlantic to determine the local relationships between HCHO columns and VOC emissions, calculate AMFs for HCHO retrievals, assess the errors in deriving AMFs with a chemical transport model (GEOS‐Chem), and draw conclusions regarding space‐based mapping of VOC emissions. We show that isoprene drives observed HCHO column variability over North America; HCHO column data from space can thus be used effectively as a proxy for isoprene emission. From observed HCHO and isoprene profiles we find an HCHO molar yield from isoprene oxidation of 1.6 ± 0.5, consistent with current chemical mechanisms. Clouds are the primary error source in the AMF calculation; errors in the HCHO vertical profile and aerosols have comparatively little effect. The mean bias and 1σ uncertainty in the GEOS‐Chem AMF calculation increase from <1% and 15% for clear skies to 17% and 24% for half‐cloudy scenes. With fitting errors, this gives an overall 1σ error in HCHO satellite measurements of 25–31%. Retrieval errors, combined with uncertainties in the HCHO yield from isoprene oxidation, result in a 40% (1σ) error in inferring isoprene emissions from HCHO satellite measurements.
Mapping erosion‐sensitive areas after wildfires using fieldwork, remote sensing, and geographic information systems techniques on a regional scale
Authors: Pérez‐Cabello F. , de la Riva Fernández J. , Montorio Llovería R. , García‐Martín A.
Published: September 2006

Alterations in the hydrological cycle following wildfire due to the loss of ground cover vegetation and changes in soil properties have been documented in many studies. Nevertheless, the rapid process of vegetation recovery reduces such negative effects. Vegetation cover before fire, fire severity, and geophysical properties are important factors that control spatial discontinuities involved in the vegetation‐covering process. The objective of this study was to estimate the probability of high erosion in order to map erosion‐sensitive areas after fire. The analysis was carried out in different plant communities burnt by summer wildfires in the pre‐Pyrenean area (Spain). Three‐year Landsat Thematic Mapper (TM) images have been used for mapping wildfire areas and severity levels. Conversion to spectral reflectance has been applied for radiometric correction by normalizing topographic and atmospheric effects. Likewise, other physical variables have also been incorporated into the geographic information system (GIS): vegetation types, parent material, illumination, slope, aspect, and precipitation. The dependent variable has been characterized by means of fieldwork and a photointerpretation process based on high‐resolution digital aerial orthophotographs taken 11–12 years after the fire. Different logistic regression models have been used for mapping the probability of erosion. Results indicate that prefire normalized difference vegetation index values and aspect are the most important variables for estimating erosion‐sensitive areas after fire (Nagelkerke r2 = 0.66; Kappa values = 0.65). Finally, the use of nonparametric models with environmental digital information based on GIS can facilitate the management of burnt areas.
Trends in water market activity and price in the western United States
Authors: Brown Thomas C.
Published: September 2006

Over 2000 water market transactions that occurred in the western United States from 1990 to 2003 were examined to learn who sold to whom and for what purpose, how much water was involved, and how much it sold for. The transactions show that much more water changes hands via leases than via sales of water rights. Public agencies and irrigators are the most common lessors, with lessees being fairly evenly distributed across types of buyers. However, with water rights sales, irrigators are by far the most common sellers and municipalities the most common buyers. Across the West in general, the number of leases has been rising in recent years, as have their prices. The prices of water right sales have also been rising, but the number of sales has not. The price of water is highly variable both within and between western states, reflecting the localized nature of the factors that affect water prices.
Dust devil tracks and wind streaks in the North Polar Region of Mars: A study of the 2007 Phoenix Mars Lander Sites
Authors: Drake Nathan B. , Tamppari Leslie K. , Baker R. David , Cantor Bruce A. , Hale Amy S.
Published: September 2006

The 65–72 latitude band of the North Polar Region of Mars, where the 2007 Phoenix Mars Lander will land, was studied using satellite images from the Mars Global Surveyor (MGS) Mars Orbiter Camera Narrow‐Angle (MOC‐NA) camera. Dust devil tracks (DDT) and wind streaks (WS) were observed and recorded as surface evidence for winds. No active dust devils (DDs) were observed. 162 MOC‐NA images, 10.3% of total images, contained DDT/WS. Phoenix landing Region C (295–315W) had the highest concentration of images containing DDT/WS per number of available images (20.9%); Region D (130–150W) had the lowest (3.5%). DDT and WS direction were recorded for Phoenix landing regions A (110–130W), B (240–260W), and C to infer local wind direction. Region A showed dominant northwest‐southeast DDT/WS, Region B showed dominant north‐south, east‐west and northeast‐southwest DDT/WS, and region C showed dominant west/northwest – east/southeast DDT/WS. Results indicate the 2007 Phoenix Lander has the highest probability of landing near DDT/WS in landing Region C. Based on DDT/WS linearity, we infer Phoenix would likely encounter directionally consistent background wind in any of the three regions.
Evaluation of new GRACE time‐variable gravity data over the ocean
Authors: Chambers Don P.
Published: September 2006

Monthly GRACE gravity field models from the three science processing centers (CSR, GFZ, and JPL) are analyzed for the period from February 2003 to April 2005 over the ocean. The data are used to estimate maps of the mass component of sea level at smoothing radii of 500 km and 750 km. In addition to using new gravity field models, a filter has been applied to estimate and remove systematic errors in the coefficients that cause erroneous patterns in the maps of equivalent water level. The filter is described and its effects are discussed. The GRACE maps have been evaluated using a residual analysis with maps of altimeter sea level from Jason‐1 corrected for steric variations using the World Ocean Atlas 2001 monthly climatology. The mean uncertainty of GRACE maps determined from an average of data from all 3 processing centers is estimated to be less than 1.8 cm RMS at 750 km smoothing and 2.4 cm at 500 km smoothing, which is better than was found previously using the first generation GRACE gravity fields.
Role of large‐scale soil structure in organic carbon turnover: Evidence from California grassland soils
Authors: Ewing Stephanie A. , Sanderman Jonathan , Baisden W. Troy , Wang Yang , Amundson Ronald
Published: September 2006

We characterized the effect of large‐scale (>20 mm) soil physical structure on the age and recalcitrance of soil organic carbon (SOC) in upper (A) and lower (B) horizons of grassland soils from California's Central Valley. The radiocarbon content of SOC from surfaces and interiors of large‐scale soil structural units (“peds”) was measured in order to characterize the spatial distribution of soil C pools with distinct residence times. The radiocarbon content of CO2 released following sieving was used to identify the C that is readily respired upon physical disturbance of soil structure. We found the longest SOC residence times in the interiors of peds from subsurface B horizons, where limited bioturbation leads to stable large‐scale structure. The radiocarbon value of this interior SOC (Δ14C = −555‰) indicates that this pool has been protected from decomposition for thousands of years. Similarly ancient C (Δ14C = −596‰) was released upon physical disruption of subsurface B horizons from a similar soil, indicating that this SOC was old, but chemically labile. With cultivation, the C released upon physical disruption of B horizons was even older (Δ14C = −812‰) than in the uncultivated soil. In uncultivated A horizons, which are subject to continuous bioturbation, large‐scale structure resulted in contrasting SOC pools only in the surface horizon, where “bomb” C effects are strong. A horizon incubations also suggested effects of smaller‐scale structure. Loss of the labile SOC that is physically protected by large‐scale structure contributes to the rapid reduction in natural soil C inventories following cultivation.
Phase Change Enthalpies and Entropies of Liquid Crystals
Authors: Acree William E. , Chickos James S.
Published: September 2006

The thermochemical behavior of more than 3000 organic compounds known to form liquid crystals is reported along with references to the original literature. A group additivity approach used to estimate total phase change entropies of organic molecules applied to 627 of these liquid crystals is found to significantly overestimate their total phase change entropies. Comparison of experimental and estimated values also show significant scatter relative to database compounds. The origins of these discrepancies are discussed in terms of a model used to explain liquid crystal formation.
Recommended Liquid–Liquid Equilibrium Data. Part 4. 1-Alkanol–Water Systems
Authors: Góral Marian , Wiśniewska-Gocłowska Barbara , Mączyński Andrzej
Published: September 2006

The recommended liquid–liquid equilibrium (LLE) data for 19 binary 1-alkanol–water systems have been obtained after critical evaluation of all data (527 data sets) reported in the open literature up to the end of 2004. An equation for prediction of the 1-alkanol solubility was developed. The predicted 1-alkanol solubility was used for calculation of water solubility in the second liquid phase. The LLE calculations were done with the equation of state appended with a chemical term proposed by Góral. The recommended data were presented in the form of individual pages containing tables and all the references.
Comment on “Quasirelativistic theory equivalent to fully relativistic theory” [J. Chem. Phys. 123, 241102 (2005)]
Authors: Filatov Michael
Published: September 2006

The connection between the exact quasirelativistic approach developed in the title reference [W. Kutzelnigg and W. Liu, J. Chem. Phys. 123, 241102 (2005)] and the method of elimination of the small component in matrix form developed previously by Dyall is explicitly worked out. An equation that links Hermitian and non-Hermitian formulations of the exact quasirelativistic theory is derived. Besides establishing a kinship between the existing formulations, the proposed equation can be employed for the derivation of new formulations of the exact quasirelativistic theory.
Relaxed core projector-augmented-wave method
Authors: Marsman M. , Kresse G.
Published: September 2006

We extend the full-potential projector-augmented-wave method beyond the frozen core approximation, i.e., include the self-consistent optimization of the core charge density, in such a manner that the valence wave functions remain orthogonal to the core. The method consists of an on-the-fly repseudization of the all-electron problem, solving for the self-consistent core charge density within a spherical approximation. The key ideas in our procedure are to keep the projector functions fixed throughout the electronic minimization and to derive the new pseudopartial waves from these original projector functions, at each step of the electronic minimization procedure. Results of relaxed core calculations for atomic interconfigurational energies, structural energy differences between bulk phases of Fe, atomization energies of a subset of Pople’s G2-1 set, and the Rh 3d surface core level shifts for the (3×3)-Rh(111) surface at 1∕3 CO coverage are presented.
Electron energy distribution functions in low-pressure inductively coupled bounded plasmas
Authors: Meige Albert , Boswell Rod W.
Published: September 2006

The electron energy distribution function (EEDF) in a low-pressure inductively coupled plasma confined between two infinite plates separated by 10cm is investigated using a one-dimensional particle-in-cell simulation including Monte Carlo collisions. At low pressure, where the electron mean free path is of the order of or greater than the system length, the EEDF is close to Maxwellian, except for its tail, depleted at high energy. We give clear evidence that this depletion is mostly due to the high-energy electrons escaping to the walls. As a result of the EEDF nonlocality, the break energy, for which the depletion of the Maxwellian starts, is found to track the plasma potential. At a higher pressure, the electron mean free paths of the various elastic and inelastic collisions become shorter than the system length, resulting in a loss of nonlocality and the break energy of the distribution function moves to energies lower than the plasma potential.
Relativistic Hamiltonian guiding center drift formalism in anisotropic pressure magnetic coordinates
Authors: Cooper W. A. , Graves J. P. , Jucker M. , Isaev M. Yu.
Published: September 2006

A Hamiltonian formulation of the relativistic guiding center drifts is extended to anisotropic pressure plasmas. The magnetic coordinates devised by Boozer are adapted to the anisotropic pressure model and retain canonical properties for two-dimensional and three-dimensional toroidal plasma equilibria including finite electrostatic perturbations provided that any electromagnetic perturbation only alters the parallel component of the vector potential. A mapping technique from arbitrary flux coordinates is outlined. A direct evaluation of the relativistic drift velocity recovers the equations of motion derived from the Hamiltonian formalism except for ignorable higher order terms in the evolution of the canonical angular variables and the effective parallel gyroradius.
Improving the stability of organic light-emitting devices by using a thin Mg anode buffer layer
Authors: Aziz Hany , Luo Yichun , Xu Gu , Popovic Zoran D.
Published: September 2006

Introducing a thin Mg layer at the hole injection contact of organic light-emitting devices remarkably improves their operational stability. Devices in which a ∼2.5nm thick Mg layer is inserted between the indium tin oxide anode and a tetrafluoro-tetracyanoquinodimethane-doped hole transport material layer exhibit a significantly longer lifetime compared to similar devices without the Mg layer. After 600h of operation at a current density of 62.5mA∕cm2 with a 50% duty cycle, the luminance of devices containing the Mg layer decreases by only ∼10% of the initial value. The stability enhancement resulting from using the Mg layer is attributed to improved balance in charge injection at the anode and cathode contacts.
Bias-crafted magnetic tunnel junctions with bistable spin-dependent states
Authors: Bowen M. , Maurice J.-L. , Barthélémy A. , Prod’homme P. , Jacquet E. , Contour J.-P. , Imhoff D. , Colliex C.
Published: September 2006

The authors have observed stable, reversible two-resistance states with substantial tunneling magnetoresistances of opposite signs in La0.7Sr0.3MnO3∕SrTiO3∕Co1−xCrx junctions. Electron energy loss spectroscopy studies reveal the segregation and oxidation of electrochemically reactive chromium at that interface, resulting in oxygen vacancies in the oxide barrier. Bias-induced switching between the two junction states is argued to reflect the incidence of these barrier defects at and near the electrically unstable SrTiO3∕Co1−xCrx interface. This affirms bias crafting as an additional lever in spintronic research across semiconducting spacers.
Evidence of room temperature sp-d exchange in InMnAs epitaxial films
Authors: Chiu P. T. , Wessels B. W.
Published: September 2006

Reflection magnetic circular dichroism (MCD) spectrum was measured from 1.6to3.0eV to determine the nature of sp-d exchange in epitaxial InMnAs thin films. At room temperature and an applied field of 0.5T, the MCD spectrum is composed of two types of transitions: a negative peak centered between 2.60 and 2.68eV and a broad, negative response from 1.6to3.0eV. For both transitions, ferromagnetic hysteresis and saturation are observed. The negative peak is attributed to the L-point critical transitions of InMnAs at 2.53 and 2.79eV, respectively. The MCD enhancement at the L point is consistent with room temperature sp-d exchange splitting in metal organic vapor phase epitaxy grown InMnAs. The sp-d exchange is attributed to magnetic Mn dimers and trimers in the InMnAs. In contrast, the broad, featureless spectral response is consistent with spin dependent transitions between the Mn impurity band and conduction band.
Carbon nanotube based microfocus field emission x-ray source for microcomputed tomography
Authors: Liu Zejian , Yang Guang , Lee Yueh Z. , Bordelon David , Lu Jianping , Zhou Otto
Published: September 2006

Microcomputed tomography is now widely used for in vivo small animal imaging for cancer studies. Achieving high imaging quality of live objects requires the x-ray source to have both high spatial and temporal resolutions. Preliminary studies have shown that carbon nanotube (CNT) based field emission x-ray source has significant intrinsic advantages over the conventional thermionic x-ray tube including better temporal resolution and programmability. Here we report the design and characterization of a CNT based field emission x-ray source that also affords a high spatial resolution. The device uses modified asymmetric Einzel lenses for electron focusing and an elliptical shaped CNT cathode patterned by photolithography. Stable and small isotropic x-ray focal spot sizes were obtained.
Metal Schottky diodes on Zn-polar and O-polar bulk ZnO
Authors: Allen M. W. , Alkaisi M. M. , Durbin S. M.
Published: September 2006

Planar Pd, Pt, Au, and Ag Schottky diodes with low ideality factors were fabricated on the Zn-polar (0001) and O-polar (0001¯) faces of bulk, single crystal ZnO wafers. The diodes were characterized by current-voltage and capacitance-voltage measurements. A polarity effect was observed for Pt and Pd diodes with higher quality barriers achieved on the O-polar face. No significant polarity effect was observed for Au or Ag diodes. The highest barriers were achieved with Ag as the Schottky metal with barrier heights varying between 0.77 and 1.02eV. This is possibly due to varying degrees of oxidation of the Ag contacts.
Radial textured carbon nanoflake spherules
Authors: Shang N. G. , Staedler T. , Jiang X.
Published: September 2006

A unique type of carbon structure, radial textured carbon nanoflake spherules, has been synthesized by a microwave plasma assisted chemical vapor deposition method. The spherules with a diameter of 1.2–35μm consist of a number of radially distributed carbon nanoflakes growing from a common core. The constituent nanoflakes are interlaced and perpendicular to the surface of spherules, forming a large amount of open edge planes. Thus, the carbon nanoflake spherules are isotropic graphite with a larger surface area and higher surface activity, which can be demonstrated by Raman scattering spectroscopy with two characteristic peaks of 860 and 1140cm−1.
Voltage drop in an (AlxGa1−x)0.5In0.5P light-emitting diode probed by Kelvin probe force microscopy
Authors: Katzer Kl.-D. , Mertin W. , Bacher G. , Jaeger A. , Streubel K.
Published: September 2006

The authors report on quantitative investigations of the voltage drop across the heterostructure layer sequence of an operating AlGaInP light-emitting diode via Kelvin probe force microscopy for different external biases between −2.0 and +1.86V. In the low voltage regime, most of the voltage drops in the active layer. For bias voltages above +1.5V, however, they found an additional voltage drop on the p side of the device, which reduces the power efficiency of the light-emitting diode.
High permittivity quaternary metal (HfTaTiOx) oxide layer as an alternative high-κ gate dielectric
Authors: Li Hong-Jyh , Price J. , Gardner Mark , Lu Nan , Kwong Dim-Lee
Published: September 2006

The authors investigated the optical and electrical properties of the high permittivity (κ) metal oxides, HfTiO and HfTaTiO, using HfO2 as a reference and compared their material properties against their electrical performance. HfTiO has a higher κ value but its band offset is relatively smaller and, therefore, it has greater gate leakage current than HfO2. HfTaTiO has an even higher κ value which compensates for the impact of its small band offset. In addition, HfO2 was found to have more defect states than the other two films, which caused a larger hysteresis in the capacitance-voltage scan and degraded channel mobility.
Analysis and control of the active area scaling effect on white organic light emitting diodes towards lighting applications
Authors: Piliego C. , Mazzeo M. , Salerno M. , Cingolani R. , Gigli G. , Moro A.
Published: September 2006

The authors investigate the scaling of the performances on white organic light emitting diode in devices having active regions ranging from 0.25to9cm2. They observe a drop in the luminance and in the current density with increasing active area of the devices. A model where both these effects are ascribed to the spread of the current leakage on the indium tin oxide surface is proposed. To limit the consequences of these effects on the device performances, they insert a pattern of metal stripes onto the anode contact. This results in a device with a maximum luminance of 1800cd∕m2 on a surface of 9cm2.
Magnetoelectric emission in a magnetic ferroelectric Er-doped (Ba,Sr)TiO3
Authors: Shimada Y. , Matsubara M. , Kaneko Y. , He J. P. , Tokura Y.
Published: September 2006

As the system where both space-inversion and time-reversal symmetries are broken simultaneously, the authors have investigated an Er3+-doped ferroelectric (Ba,Sr)TiO3 single crystal under magnetic field, in which the luminescent magnetic Er3+ ion occupies a noncentrosymmetric site. The k-directional dichroism, termed the optical magnetoelectric (OME) effect, was verified in the I13∕24→I15∕24 emission (λ∼1.55μm) by the reversal of magnetic field and spontaneous polarization. The observed nonreciprocity ΔI∕I∼0.5% at 3000Oe implies the possibility of the application of the OME effect to the function of an optical isolator.
Perturbation theory of Φ-value analysis of two-state protein folding: Relation between pfold and Φ values
Authors: Berezhkovskii Alexander , Szabo Attila
Published: September 2006

In protein folding, the transition state ensemble is defined as the set of conformations with pfold=1∕2, where the pfold of a conformation is the probability that starting from this conformation the protein folds before it unfolds. Experimentally, this ensemble is probed by the Φ-value analysis, where Φ is the ratio of the changes in the logarithms of the folding rate and the equilibrium constant when the system is perturbed by a mutation. We show that for a two-state protein the Φ value can be expressed in terms of the perturbation and only the first two eigenfunctions of the evolution operator (e.g., a rate matrix) of the wild-type protein. The first eigenfunction is the equilibrium probability distribution while the second is proportional to pfold, thus establishing a formal relation between pfold and Φ values. In addition to providing insight into the theoretical foundation of the Φ-value analysis, our results may prove practically useful in performing such analyses within the framework of models containing a large number of states.
Direct screening of solution phase combinatorial libraries encoded with externally sensitized photolabile tags
Authors: Kottani Rudresha , Valiulin Roman A. , Kutateladze Andrei G.
Published: September 2006

Solution phase combinatorial chemistry holds an enormous promise for modern drug discovery. Much needed are direct methods to assay such libraries for binding of biological targets. An approach to encoding and screening of solution phase libraries has been developed based on the conditional photorelease of externally sensitized photolabile tags. The encoding tags are released into solution only when a sought-for binding event occurs between the ligand and the receptor, outfitted with an electron-transfer sensitizer. The released tags are analyzed in solution revealing the identity of the lead ligand or narrowing the range of potential leads.
Killer whales are capable of vocal learning
Authors: Foote Andrew D , Griffin Rachael M , Howitt David , Larsson Lisa , Miller Patrick J.O , Rus Hoelzel A
Published: September 2006

The production learning of vocalizations by manipulation of the sound production organs to alter the physical structure of sound has been demonstrated in only a few mammals. In this natural experiment, we document the vocal behaviour of two juvenile killer whales,
Orcinus orca
, separated from their natal pods, which are the only cases of dispersal seen during the three decades of observation of their populations. We find mimicry of California sea lion (
Zalophus californianus
) barks, demonstrating the vocal production learning ability for one of the calves. We also find differences in call usage (compared to the natal pod) that may reflect the absence of a repertoire model from tutors or some unknown effect related to isolation or context.
Evaluating candidate agents of selective pressure for cystic fibrosis
Authors: Poolman Eric M , Galvani Alison P
Published: September 2006

Cystic fibrosis is the most common lethal single-gene mutation in people of European descent, with a carrier frequency upwards of 2%. Based upon molecular research, resistances in the heterozygote to cholera and typhoid fever have been proposed to explain the persistence of the mutation. Using a population genetic model parameterized with historical demographic and epidemiological data, we show that neither cholera nor typhoid fever provided enough historical selective pressure to produce the modern incidence of cystic fibrosis. However, we demonstrate that the European tuberculosis pandemic beginning in the seventeenth century would have provided sufficient historical, geographically appropriate selective pressure under conservative assumptions. Tuberculosis has been underappreciated as a possible selective agent in producing cystic fibrosis but has clinical, molecular and now historical, geographical and epidemiological support. Implications for the future trajectory of cystic fibrosis are discussed. Our result supports the importance of novel investigations into the role of arylsulphatase B deficiency in cystic fibrosis and tuberculosis.
Spatial and temporal distribution of bluetongue and its Culicoides vectors in Bulgaria
Authors: PURSE B. V. , NEDELCHEV N. , GEORGIEV G. , VELEVA E. , BOORMAN J. , DENISON E. , VERONESI E. , CARPENTER S. , BAYLIS M. , MELLOR P. S.
Published: September 2006

Abstract Surveillance of Culicoides (Diptera: Ceratopogonidae) biting midges was carried out between 2001 and 2003, at 119 sites within a 50 × 50‐km grid distributed across Bulgaria, using light trap collections around the time of peak adult midge abundance. Sentinel and ad hoc serum surveillance of hosts susceptible to bluetongue infection was carried out at around 300 sites between 1999 and 2003. Following the initial incursion of bluetongue virus 9 (BTV‐9) into Bourgas province in 1999, affecting 85 villages along the southern border, a further 76 villages were affected along the western border in 2001, with outbreaks extending as far north as 43.6°N. The BTV‐9 strain in circulation was found to have a low pathogenicity for Bulgarian sheep populations, with less than 2% of susceptible individuals becoming sick and seroconversions detected up to 30 km from recorded outbreaks in the south. The major Old World vector Culicoides imicola Kieffer was not detected among over 70 000 Culicoides identified in summer collections, suggesting that BTV‐9 transmission in Bulgaria was primarily carried out by indigenous European vectors. The most likely candidates, the Palaearctic species complexes – the Culicoides obsoletus Meigen and C. pulicaris L. complexes – were widespread and abundant across the whole country. The C. obsoletus complex represented 75% of all individuals trapped in summer and occurred in high catch sizes (up to 15 000 individuals per night) but was not found across all outbreak sites, indicating that both Palearctic complexes probably played a role in transmission. Within the C. pulicaris complex, only C. pulicaris s.s., C. punctatus Meigen and C. newsteadi Austen were sufficiently abundant and prevalent to have been widely involved in transmission, whilst within the C. obsoletus complex most trapped males were C. obsoletus s.s. Adult vectors were found to be largely absent from sites in west Bulgaria for a period of at least 3 months over winter, which, taken along with the spatiotemporal pattern of outbreaks in the region between years, indicates the virus may be overwintering here by an alternative mechanism – either by covert persistence in the vertebrate host or possibly by persistence in larval stages of the vector.
Dieldrin resistance in the malaria vector Anopheles gambiae in Ghana
Authors: BROOKE B. D. , HUNT R. H. , MATAMBO T. S. , KOEKEMOER L. L. , VAN WYK P. , COETZEE M.
Published: September 2006

Abstract Anopheles gambiae Giles s.s. (Diptera: Culicidae) is one of the principal vectors of malaria in the Ashanti region of central Ghana. High levels of resistance to dieldrin were recorded in a wild‐caught sample from Obuasi (south of Kumasi) as well as a laboratory colony established using material from the wild population. Cytogenetic analysis of wild‐caught and laboratory samples revealed chromosomal polymorphism for inversions 2La and 2Rb. Although inversion 2La has previously been shown to be associated with dieldrin resistance in certain other laboratory strains originating from West Africa, there was no obvious association between inversion karyotype assortment and the resistance phenotype in the Obuasi population. In addition, polymerase chain reaction analysis indicated the presence of the alanine296 to glycine mutation in the GABA (γ amino‐butyric acid) receptor (which has been mapped to a chromosomal position within inversion 2La). This mutation has previously been shown to be associated with dieldrin resistance in the same An. gambiae laboratory strains of West African origin. Our data show only a weak association between the dieldrin resistance phenotype and the presence of this mutation, suggesting that another dieldrin resistance mechanism is operational in the Obuasi population. Biochemical and synergist exposure assays suggest a metabolic component, probably mediated by monooxygenase P450 enzymes. We conclude that dieldrin resistance in the An. gambiae population of the Obuasi region occurs at a high level – most likely in the absence of selection – and that control of the resistance phenotype is polyfactorial and must include components other than mutations in the GABA receptor locus.
Arabidopsis SPO11‐2 functions with SPO11‐1 in meiotic recombination
Authors: Stacey Nicola J. , Kuromori Takashi , Azumi Yoshitaka , Roberts Gethin , Breuer Christian , Wada Takuji , Maxwell Anthony , Roberts Keith , Sugimoto‐Shirasu Keiko
Published: September 2006

The Spo11 protein is a eukaryotic homologue of the archaeal DNA topoisomerase VIA subunit (topo VIA). In archaea it is involved, together with its B subunit (topo VIB), in DNA replication. However, most eukaryotes, including yeasts, insects and vertebrates, instead have a single gene for Spo11/topo VIA and no homologues for topo VIB. In these organisms, Spo11 mediates DNA double‐strand breaks that initiate meiotic recombination. Many plant species, in contrast to other eukaryotes, have three homologues for Spo11/topo VIA and one for topo VIB. The homologues in Arabidopsis, AtSPO11‐1, AtSPO11‐2 and AtSPO11‐3, all share 20–30% sequence similarity with other Spo11/topo VIA proteins, but their functional relationship during meiosis or other processes is not well understood. Previous genetic evidence suggests that AtSPO11‐1 is a true orthologue of Spo11 in other eukaryotes and is required for meiotic recombination, whereas AtSPO11‐3 is involved in DNA endo‐reduplication as a part of the topo VI complex. In this study, we show that plants homozygous for atspo11‐2 exhibit a severe sterility phenotype. Both male and female meiosis are severely disrupted in the atspo11‐2 mutant, and this is associated with severe defects in synapsis during the first meiotic division and reduced meiotic recombination. Further genetic analysis revealed that AtSPO11‐1 and AtSPO11‐2 genetically interact, i.e. plants heterozygous for both atspo11‐1 and atspo11‐2 are also sterile, suggesting that AtSPO11‐1 and AtSPO11‐2 have largely overlapping functions. Thus, the three Arabidopsis Spo11 homologues appear to function in two discrete processes, i.e. AtSPO11‐1 and AtSPO11‐2 in meiotic recombination and AtSPO11‐3 in DNA replication.
Plastidial phosphorylase is required for normal starch synthesis in Chlamydomonas reinhardtii
Authors: Dauvillée David , Chochois Vincent , Steup Martin , Haebel Sophie , Eckermann Nora , Ritte Gerhard , Ral Jean‐Philippe , Colleoni Christophe , Hicks Glenn , Wattebled Fabrice , Deschamps Philippe , D'Hulst Christophe , Liénard Luc , Cournac Laurent , Putaux Jean‐Luc , Dupeyre Danielle , Ball Steven G.
Published: September 2006

Among the three distinct starch phosphorylase activities detected in Chlamydomonas reinhardtii, two distinct plastidial enzymes (PhoA and PhoB) are documented while a single extraplastidial form (PhoC) displays a higher affinity for glycogen as in vascular plants. The two plastidial phosphorylases are shown to function as homodimers containing two 91‐kDa (PhoA) subunits and two 110‐kDa (PhoB) subunits. Both lack the typical 80‐amino‐acid insertion found in the higher plant plastidial forms. PhoB is exquisitely sensitive to inhibition by ADP‐glucose and has a low affinity for malto‐oligosaccharides. PhoA is more similar to the higher plant plastidial phosphorylases: it is moderately sensitive to ADP‐glucose inhibition and has a high affinity for unbranched malto‐oligosaccharides. Molecular analysis establishes that STA4 encodes PhoB. Chlamydomonas reinhardtii strains carrying mutations at the STA4 locus display a significant decrease in amounts of starch during storage that correlates with the accumulation of abnormally shaped granules containing a modified amylopectin structure and a high amylose content. The wild‐type phenotype could be rescued by reintroduction of the cloned wild‐type genomic DNA, thereby demonstrating the involvement of phosphorylase in storage starch synthesis.
Role of Gbx2 and Otx2 in the formation of cochlear ganglion and endolymphatic duct
Authors: Miyazaki Hiromitsu , Kobayashi Toshimitsu , Nakamura Harukazu , Funahashi Jun‐ichi
Published: September 2006

The boundary of gene expression of transcription factors often plays a role in making a signaling center in development. In the otic vesicle, Gbx2 is expressed in the dorso‐medial region including the endolymphatic duct, and Otx2 in the ventral region. Fgf10 is expressed between their expression boundaries, and the cochleovestibular ganglion develops close to the medial side of the Fgf10 expressing domain. Similar expression patterns are observed in the central nervous system, where Otx2 and Gbx2 expression abut at the mid–hindbrain boundary, and the repressive interaction between Otx2 and Gbx2 defines the mid–hindbrain boundary. These analogous expression patterns raise a question about the role of the interaction between Gbx2 and Otx2 in the otic vesicle. To address this, we misexpressed Gbx2 and Otx2 to the otic epithelium. Ectopic Gbx2 expression could repress Otx2 expression and vice versa. In addition, Fgf10 expression was repressed and cochlear ganglion formation was interfered with. Moreover, endolymphatic duct was severely hypomorphic in the Otx2 misexpressing embryos. These results suggest that the interaction between Gbx2 and Otx2 in developing inner ear defines Fgf10 expression domain to induce the cochlear ganglion. It is also suggested that Gbx2 expression is important for the formation of the endolymphatic duct.
Hindgut specification and cell‐adhesion functions of Sphox11/13b in the endoderm of the sea urchin embryo
Authors: Arenas‐Mena César , Cameron R. Andrew , Davidson Eric H.
Published: September 2006

Sphox11/13b is one of the two hox genes of Strongylocentrotus purpuratus expressed in the embryo. Its dynamic pattern of expression begins during gastrulation, when the transcripts are transiently located in a ring of cells at the edge of the blastopore. After gastrulation, expression is restricted to the anus–hindgut region at the boundary between the ectoderm and the endoderm. The phenotype that results when translation of Sphox11/13b mRNA is knocked down by treatment with morpholino antisense oligonucleotides (MASO) suggests that this gene may be indirectly involved in cell adhesion functions as well as in the proper differentiation of the midgut–hindgut and midgut–foregut sphincters. The MASO experiments also reveal that Sphox11/13b negatively regulates several downstream endomesoderm genes. For some of these genes, Sphox11/13b function is required to restrict expression to the midgut by preventing ectopic expression in the hindgut. The evolutionary conservation of these functions indicates the general roles of posterior Hox genes in regulating cell‐adhesion, as well as in spatial control of gene regulatory network subcircuits in the regionalizing gut.
Defects in electronics and their significance for structural integrity
Authors: PLUMBRIDGE W. J.
Published: September 2006

With Electronics likely to become a major area of interest to structural integrity practitioners, the paper aims to introduce the field from a structural integrity perspective. The Industry is presently facing two major challenges: continued miniaturisation and the implementation of lead‐free technology associated with interconnections. Following a consideration of the background of both aspects, a brief outline of typical components and production processes is presented. Attention is then focussed upon possible defects that may arise during manufacture, and under the, often, complex conditions of service. Comparisons are drawn with more traditional applications of structural integrity, and the fresh challenges associated with the utilisation of a new generation of solder alloys, and with micro and near‐nano dimensions, are introduced.
The development of area discrimination and its implications for number representation in infancy
Authors: Brannon Elizabeth M. , Lutz Donna , Cordes Sara
Published: September 2006

This paper investigates the ability of infants to attend to continuous stimulus variables and how this capacity relates to the representation of number. We examined the change in area needed by 6‐month‐old infants to detect a difference in the size of a single element (Elmo face). Infants successfully discriminated a 1:4, 1:3 and 1:2 change in the area of the Elmo face but failed to discriminate a 2:3 change. In addition, the novelty preference was linearly related to the ratio difference between the novel and familiar area. Results suggest that Weber's Law holds for area discriminations in infancy and also reveal that at 6 months of age infants are equally sensitive to number, time and area.