bluuebunny/crossref_metadata_2025 huggingface dataset:
Crosslinguistic evidence for the diminutive advantage: gender agreement in Russian and Serbian children
Authors: šEVA NADA , KEMPE VERA , BROOKS PATRICIA J. , MIRONOVA NATALIJA , PERSHUKOVA ANGELINA , FEDOROVA OLGA
Published: January 2007

Our previous research showed that Russian children commit fewer gender-agreement errors with diminutive nouns than with their simplex counterparts. Experiment 1 replicates this finding with Russian children (N=24, mean 3;7, range 2;10–4;6). Gender agreement was recorded from adjective usage as children described animal pictures given just their names, varying in derivational status (diminutive/simplex), novelty, and gender. Experiment 2 extends the gender-agreement elicitation methodology developed for Russian to Serbian, a language with similar morphosyntactic structure but considerably fewer diminutives in child-directed speech. Serbian children (N=22, mean age 3;8, range 3;0–4;1), exhibited an advantage for diminutive nouns of almost the same magnitude as the Russian children. The fact that the diminutive advantage was found in a language with a low frequency of diminutives in the input suggests that morphophonological homogeneity of word clusters and membership in dense neighbourhoods are important factors that contribute to the reduction of inflectional errors during language development.
Betavulgaris L. Suspension Cultures Permeabilized with Triton X‐100 Retain Cell Viability and Betacyanines Production Ability: A Digital Image Analysis Study
Authors: Trejo‐Tapia Gabriela , Cuevas‐Celis Jonathan , Salcedo‐Morales Guadalupe , Luis Trejo‐Espino José , Arenas‐Ocampo Martha L. , Jiménez‐Aparicio Antonio
Published: January 2007

The influence of Triton X‐100 on Beta vulgaris L. permeabilized cell culture viability, regrowth, and ability to produce betacyanines was evaluated in this study. A non‐destructive method based on the analysis of images in the RGB (red, green, blue) system was developed to estimate betacyanines content. A treatment for 15 min with 0.7 mM Triton X‐100 induced the release of 30% of betacyanines without loss of cell viability (≥70%). After this permeabilization treatment, B. vulgaris cultures regrew normally, reaching a maximum biomass concentration of 48% higher than non‐permeabilized cultures after 14 days of culture. Also, maximum betacyanines concentration was only 25% lower than that of non‐permeabilized cultures.
Alignment‐Based Approach for Durable Data Storage into Living Organisms
Authors: Yachie Nozomu , Sekiyama Kazuhide , Sugahara Junichi , Ohashi Yoshiaki , Tomita Masaru
Published: January 2007

The practical realization of DNA data storage is a major scientific goal. Here we introduce a simple, flexible, and robust data storage and retrieval method based on sequence alignment of the genomic DNA of living organisms. Duplicated data encoded by different oligonucleotide sequences was inserted redundantly into multiple loci of the Bacillus subtilis genome. Multiple alignment of the bit data sequences decoded by B. subtilis genome sequences enabled the retrieval of stable and compact data without the need for template DNA, parity checks, or error‐correcting algorithms. Combined with the computational simulation of data retrieval from mutated message DNA, a practical use of this alignment‐based method is discussed.
Validation and development of a new hailstone formation theory: Numerical simulations of a strong hailstorm occurring over the Qinghai‐Tibetan Plateau
Authors: Kang Fengqin , Zhang Qiang , Lu Shihua
Published: January 2007

Hailstorms occur frequently over the northeastern border of the Qinghai‐Tibetan Plateau and its surroundings because of the combined geographical and meteorological features of this region. Formation and growth of the hailstones in a typical hailstorm are simulated using a three‐dimensional (3‐D) cloud model with hail‐bin microphysics developed by the Institute of Atmospheric Physics of the Chinese Academy of Sciences (IAP/CAS). The information of the large‐scale circulations for the cloud model was provided by the MM5V3 model. The results show that (1) the water content of each hailstone bin is significantly large in the “cave channels”; (2) at the initial stage of hail formation, there is another high water content region consisting of small ice particles (D < 1 mm), graupel and hail embryos (1 mm < D < 5 mm), as well as small hailstones (5 mm < D < 10 mm), around the altitude of −30 ∼ −50°C above the high water content center associated with the “cave channels”; between them there is a gap of lower water content, which means that the main mechanisms of hail formation are different in those two regions; (3) as the hail and rain fall, the maximum center at higher level drops until it merges with a lower equivalent; the larger the hail particles are, the earlier the maximum centers merge with each other; (4) during the hailstorm dissipation period the downdraft occurs in the region of “cave channels” and the “cave channels” fade; however, it is still the center of high hail water content, even though all updraft airflow turns to downdraft airflow; (5) “cave channels” are not the only regions of hailstones formation, but are nonetheless effective in the growth of hailstones, so which should be the main region of suppressing hail growth from small to large.
Seasonal cycle of N2O: Analysis of data
Authors: Jiang Xun , Ku Wai Lim , Shia Run‐Lie , Li Qinbin , Elkins James W. , Prinn Ronald G. , Yung Yuk L.
Published: January 2007

We carried out a systematic study of the seasonal cycle and its latitudinal variation in the nitrous oxide (N2O) data collected by National Oceanic and Atmospheric Administration–Global Monitoring Division (NOAA‐GMD) and the Advanced Global Atmospheric Gases Experiment (AGAGE). In order to confirm the weak seasonal signal in the observations, we applied the multitaper method for the spectrum analysis and studied the stations with significant seasonal cycle. In addition, the measurement errors must be small compared with the seasonal cycle. The N2O seasonal cycles from seven stations satisfied these criteria and were analyzed in detail. The stations are Alert (82°N, 62°W), Barrow (71°N, 157°W), Mace Head (53°N, 10°W), Cape Kumukahi (19°N, 155°W), Cape Matatula (14°S, 171°W), Cape Grim (41°S, 145°E) and South Pole (90°S, 102°W). The amplitude (peak to peak) of the seasonal cycle of N2O varies from 0.29 ppb (parts‐per‐billion by mole fraction in dry air) at the South Pole to 1.15 ppb at Alert. The month at which the seasonal cycle is at a minimum varies monotonically from April (South Pole) to September (Alert). The seasonal cycle in the Northern Hemisphere shows the influence of the stratosphere; the seasonal cycle of N2O in the Southern Hemisphere suggests greater influence from surface sources. Preliminary estimates are obtained for the magnitude of the seasonally varying sources needed to account for the observations.
Observation of glacial isostatic adjustment in “stable” North America with GPS
Authors: Sella Giovanni F. , Stein Seth , Dixon Timothy H. , Craymer Michael , James Thomas S. , Mazzotti Stephane , Dokka Roy K.
Published: January 2007

Motions of three hundred and sixty Global Positioning System (GPS) sites in Canada and the United States yield a detailed image of the vertical and horizontal velocity fields within the nominally stable interior of the North American plate. By far the strongest signal is the effect of glacial isostatic adjustment (GIA) due to ice mass unloading during deglaciation. Vertical velocities show present‐day uplift (∼10 mm/yr) near Hudson Bay, the site of thickest ice at the last glacial maximum. The uplift rates generally decrease with distance from Hudson Bay and change to subsidence (1–2 mm/yr) south of the Great Lakes. The “hinge line” separating uplift from subsidence is consistent with data from water level gauges along the Great Lakes, showing uplift along the northern shores and subsidence along the southern ones. Horizontal motions show outward motion from Hudson Bay with complex local variations especially in the far field. Although the vertical motions are generally consistent with the predictions of GIA models, the horizontal data illustrate the need and opportunity to improve the models via more accurate descriptions of the ice load and laterally variable mantle viscosity.
Energetic electrons injected into Saturn's neutral gas cloud
Authors: Paranicas C. , Mitchell D. G. , Roelof E. C. , Mauk B. H. , Krimigis S. M. , Brandt P. C. , Kusterer M. , Turner F. S. , Vandegriff J. , Krupp N.
Published: January 2007

We demonstrate that the population of 20–410 keV electrons observed in Saturn's inner magnetosphere result principally from recent injections. Electrons at these energies appear to survive only up to a few days in the neutral gas cloud emitted by gas jets in Enceladus's southern hemisphere. Ions of similar energies have much shorter lifetimes in the gas cloud because of charge‐exchange with the ambient neutrals. We have been able to associate fluxes at different energies and times with a single past injection based on the morphology of electron spectrograms from measurements made by Cassini's Magnetospheric Imaging Instrument (MIMI). Once injected, electrons disperse in longitude but the age of the initial injection and its approximate longitude can be reconstructed. Furthermore, the shape of time‐dispersed features argues against rigid corotation of the magnetospheric plasma, or a fraction thereof, and instead favors L‐dependent flow shear.
An analysis of the momentum forcing in the high‐latitude lower thermosphere
Authors: Kwak Y.‐S. , Richmond A. D.
Published: January 2007

We analyze the dynamics of the high‐latitude thermsopheric wind system below 170 km for negative IMF Bz by using a fully nonlinear model with a realistic distribution of the forcing. A transition of the forcing patterns and their relative contribution to the high‐latitude lower thermospheric wind system occurs around 123 km under various conditions, weak or strong IMF, summer or winter. Winds around and above 123 km are sustained by the gradient‐wind balance among divergent/convergent pressure gradient, Coriolis, and horizontal momentum advection (mainly centrifugal) accelerations. Below 123 km winds are maintained by the approximate balance of divergent/convergent pressure gradient, Coriolis, and Hall ion drag accelerations through modified geostrophy. The dominant contribution to the wind tendency (time rate of change) is the rotational component of the ion drag acceleration. The wind tendency above 123 km tends to resemble rotational Pedersen ion drag acceleration well, which reflects a rotated pattern of the E × B velocity. Near and below 123 km the wind tendency is also affected by the rotational component of the Hall ion drag acceleration whose pattern no longer closely resembles the pattern of the E × B velocity, and the wind pattern can differ significantly from that well above 123 km. Simulations for different strengths of the IMF and different seasons indicate that largely divergent/convergent Coriolis and horizontal momentum advection accelerations tend approximately to balance with the horizontal pressure gradient (as well as with divergent/convergent ion drag at lower altitudes) under various conditions. As the forcing increases the radius of curvature of the strong winds also tends to increase, so that the centrifugal acceleration does not increase quadratically with the maximum wind speed, and the tendency for a rough balance between the Coriolis and horizontal momentum advection accelerations in the duskside vortex above 123 km is maintained.
Analysis of reflectance spectra of UV‐absorbing aerosol scenes measured by SCIAMACHY
Authors: de Graaf M. , Stammes P. , Aben E. A. A.
Published: January 2007

Reflectance spectra from 280–1750 nm of typical desert dust aerosol (DDA) and biomass burning aerosol (BBA) scenes over oceans are presented, measured by the space‐borne spectrometer Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). DDA and BBA are both UV‐absorbing aerosols, but their effect on the top‐of‐atmosphere (TOA) reflectance is different due to differences in the way mineral aerosols and smoke reflect and absorb radiation. Mineral aerosols are typically large, inert particles, found in warm, dry continental air. Smoke particles, on the other hand, are usually small particles, although often clustered, chemically very active and highly variable in composition. Moreover, BBA are hygroscopic and over oceans BBA were invariably found in cloudy scenes. TOA reflectance spectra of typical DDA and BBA scenes were analyzed, using radiative transfer simulations, and compared. The DDA spectrum was successfully simulated using a layer with a bimodal size distribution of mineral aerosols in a clear sky. The spectrum of the BBA scene, however, was determined by the interaction between cloud droplets and smoke particles, as is shown by simulations with a model of separate aerosol and cloud layers and models with internally and externally mixed aerosol/cloud layers. The occurrence of clouds in smoke scenes when sufficient water vapor is present usually prevents the detection of optical properties of these aerosol plumes using space‐borne sensors. However, the Absorbing Aerosol Index (AAI), a UV color index, is not sensitive to scattering aerosols and clouds and can be used to detect these otherwise obscured aerosol plumes over clouds. The amount of absorption of radiation can be expressed using the absorption optical thickness. The absorption optical thickness in the DDA case was 0.42 (340 nm) and 0.14 (550 nm) for an aerosol layer of optical thickness 1.74 (550 nm). In the BBA case the absorption optical thickness was 0.18 (340 nm) and 0.10 (550 nm) for an aerosol/cloud layer of optical thickness 20.0 (550 nm). However, this reduced the cloud albedo by about 0.2 (340 nm) and 0.15 (550 nm). This method can be an important tool to estimate the global impact of absorption of shortwave radiation by smoke and industrial aerosols inside clouds.
Mars Odyssey Gamma Ray Spectrometer elemental abundances and apparent relative surface age: Implications for Martian crustal evolution
Authors: Hahn Brian C. , McLennan Scott M. , Taylor G. Jeffrey , Boynton William V. , Dohm James M. , Finch Mike J. , Hamara David K. , Janes Daniel M. , Karunatillake Suniti , Keller John M. , Kerry Kristopher E. , Metzger Albert E. , Williams Remo M. S.
Published: January 2007

Quantifying secular variations in the chemical composition of the Martian crust provides unique insights into the processes that have guided the evolution of the Martian crust‐mantle system. Using global abundances for a suite of elements determined by the Gamma Ray Spectrometer (GRS) on board the Mars Odyssey spacecraft and global mapping of apparent surface age adapted from existing geologic maps in the USGS Martian Geologic Investigation series, we report the average abundance of K, Th, Fe, Cl, H, and Si for the major Martian geologic epochs (Noachian, Hesperian, and Amazonian). Average GRS‐determined K and Th abundances generally decrease by 9% and 7%, respectively, between the Hesperian and the Amazonian, possibly implying evolving magma chemistry throughout major resurfacing events (although the effects of surficial alteration processes cannot be entirely discounted). GRS‐determined Fe and Cl averages increase by 12% and 19%, respectively, with younger apparent relative surface age, suggesting the possible mobilization and transport of these elements through aqueous processes (although an igneous origin for the variation in Fe also cannot be excluded). While H abundance does vary with surface age, the relationship is likely not governed by geologic processes. No statistically reliable apparent surface age relation was found for Si.
Antimicrobial activity of omwaprin, a new member of the waprin family of snake venom proteins
Authors: Nair Dileep G. , Fry Bryan G. , Alewood Paul , Kumar Prakash P. , Kini R. Manjunatha
Published: January 2007

We have isolated and characterized omwaprin, a 50-amino-acid cationic protein from the venom of inland taipan (Oxyuranus microlepidotus). It is a new member of the waprin family of snake venom proteins. A synthetic gene was designed and constructed for expressing the recombinant protein in Escherichia coli. Recombinant omwaprin was used for carrying out functional analyses. The protein is non-toxic to Swiss albino mice at doses of up to 10 mg/kg when administered intraperitoneally. However, it shows selective and dose-dependant antibacterial activity against Gram-positive bacteria. The minimum inhibitory doses were in the range 2–10 μg for selected species of bacteria in radial diffusion assays. The antibacterial activity is salt-tolerant up to 350 mM NaCl. However, omwaprin lost its antibacterial activity upon reduction and alkylation of its cysteine residues, or upon deletion of six N-terminal amino acid residues, four of which are positively charged. These observations indicate that the three-dimensional structure constrained by four disulfide bonds and the N-terminal residues are essential for its activity. The mechanism of action is via membrane disruption, as shown by scanning electron microscopy. Importantly, omwaprin lacks haemolytic activity on human erythrocytes. This demonstrates the specificity of omwaprin for bacterial membranes. Unlike other reported WAP (whey acidic protein) domain-containing antibacterial proteins, including elafin, EPPIN (epididymal proteinase inhibitor), SWAM1 and SWAM2 [single WAP (whey acidic protein) motif proteins 1 and 2] and SLPI (secretory leucocyte proteinase inhibitor), omwaprin shows species-specific activity on the Gram-positive bacteria tested.
SARP, a new alternatively spliced protein phosphatase 1 and DNA interacting protein
Authors: Browne Gareth J. , Fardilha Margarida , Oxenham Senga K. , Wu Wenjuan , Helps Nicholas R. , da Cruz E Silva Odete A. B. , Cohen Patricia T. W. , Cruz E Silva Edgar F. da
Published: January 2007

PP1 (protein phosphatase 1) is a ubiquitously expressed serine/threonine-specific protein phosphatase whose activity towards different substrates appears to be mediated via binding to specific proteins that play critical regulatory and targeting roles. In the present paper we report the cloning and characterization of a new protein, termed SARP (several ankyrin repeat protein), which is shown to interact with all isoforms of PP1 by a variety of techniques. A region encompassing a consensus PP1-binding motif in SARP (K354VHF357) modulates endogenous SARP–PP1 activity in mammalian cells. This SARP–PP1 interaction motif lies partially within the first ankyrin repeat in contrast with other proteins [53BP2 (p53 binding protein 2), MYPT1/M110/MBS (myosin binding protein of PP1) and TIMAP (transforming growth factor β inhibited, membrane-associated protein)], where a PP1-binding motif precedes the ankyrin repeats. Alternative mRNA splicing produces several isoforms of SARP from a single human gene at locus 11q14. SARP1 and/or SARP2 (92–95 kDa) are ubiquitously expressed in all tissues with high levels in testis and sperm, where they are shown to interact with both PP1γ1 and PP1γ2. SARP3 (65 kDa) is most abundant in brain where SARP isoforms interact with both PP1α and PP1γ1. SARP is highly abundant in the nucleus of mammalian cells, consistent with the putative nuclear localization signal at the N-terminus. The presence of a leucine zipper near the C-terminus of SARP1 and SARP2, and the binding of mammalian DNA to SARP2, suggests that SARP1 and SARP2 may be transcription factors or DNA-associated proteins that modulate gene expression.
Seven Dictyostelium discoideum phosphodiesterases degrade three pools of cAMP and cGMP
Authors: Bader Sonya , Kortholt Arjan , Van Haastert Peter J. M.
Published: January 2007

The Dictyostelium discoideum genome uncovers seven cyclic nucleotide PDEs (phosphodiesterases), of which six have been characterized previously and the seventh is characterized in the present paper. Three enzymes belong to the ubiquitous class I PDEs, common in all eukaryotes, whereas four enzymes belong to the rare class II PDEs that are present in bacteria and lower eukaryotes. Since all D. discoideum PDEs are now characterized we have calculated the contribution of each enzyme in the degradation of the three important pools of cyclic nucleotides: (i) extracellular cAMP that induces chemotaxis during aggregation and differentiation in slugs; (ii) intracellular cAMP that mediates development; and (iii) intracellular cGMP that mediates chemotaxis. It appears that each cyclic nucleotide pool is degraded by a combination of enzymes that have different affinities, allowing a broad range of substrate concentrations to be degraded with first-order kinetics. Extracellular cAMP is degraded predominantly by the class II high-affinity enzyme DdPDE1 and its close homologue DdPDE7, and in the multicellular stage also by the low-affinity transmembrane class I enzyme DdPDE4. Intracellular cAMP is degraded by the DdPDE2, a class I enzyme regulated by histidine kinase/phospho-relay, and by the cAMP-/cGMP-stimulated class II DdPDE6. Finally, basal intracellular cGMP is degraded predominantly by the high-affinity class I DdPDE3, while the elevated cGMP levels that arise after receptor stimulation are degraded predominantly by a cGMP-stimulated cGMP-specific class II DdPDE5. The analysis shows that the combination of enzymes is tuned to keep the concentration and lifetime of the substrate within a functional range.
Charter Airlines: Have They a Future?
Authors: Buck Simon , Lei Zheng
Published: January 2007

The purpose of this paper is to examine the modern charter airlines and highlight some recent significant changes. A discussion of vertical integration between tour operators and charter carriers sets the foundation for the study focus. Key features of charter airlines are examined in comparison with full-service and no-frills scheduled airlines. In response to the competitive challenge posed by the latter, charter airlines have adopted a variety of strategies further to enhance seat-only sales. The implications arising are also discussed.
Impact of the 9/11 Terrorist Attacks on the Return and Risk of Airline Stocks
Authors: Kim Hyunjoon , Gu Zheng
Published: January 2007

This study examined the impact of the 9/11 terrorist attacks on the return and risk of airline stocks traded on US stock markets. It compared the returns, total risk and systematic risk for these stocks during the 60 weeks before and 60 weeks after the 9/11 events. A one-way paired t-test was conducted to determine whether the stock returns and relevant risks were significantly different in the pre- and post-9/11 periods. The results show that while the average weekly return of the airline stocks did not change significantly after the 9/11 events, their systematic and total risks increased significantly regardless of firm size. The findings suggest that although airlines cannot do much about high financial leverage at present, they may still lower their operating leverage by cutting payroll expenses and hedging against fuel price fluctuation. A lower operating leverage should help airlines improve their stock performance in terms of both return and risk.
Reoperationalising the Loyalty Framework
Authors: Petrick James F.
Published: January 2007

The purpose of this study was to operationalise loyalty as a segmentation tool utilising both psychological and behavioural measures (as suggested by Backman, 1988), while recognising the vast differences between the types of loyalty possible by acknowledging the differences between first time visitors and actual ‘loyal’ visitors (as suggested by Opperman, 2000). Secondary purposes of the study included the identification of differences between the segments derived. The proposed framework identified an easy to utilise, and effective segmentation tool. It was also revealed that the proposed framework can be very useful for segmenting cruise passengers into distinct homogeneous groups. Specific managerial implications are discussed.
Stochastic Multivariable Approach to Modelling Tourism Area Life Cycles
Authors: Karplus Yuval , Krakover Shaul
Published: January 2007

Butler's (1980) tourist area cycle of evolution is re-examined by its application to the Dead Sea resort area in Israel. The objective of the study is to examine the validity of the model's tourism life cycles curve while using a stochastic regression expression that should not necessarily yield to the logistic curve suggested by Butler. The regression model is a compound of endogenous and exogenous variables incorporated in an interactive manner with the temporal development process. Monthly bed-night data for the years 1974–2000 are used as a measure of demand. Besides time, accumulated investment in terms of hotel rooms is applied as an endogenous variable and a security indicator is applied as an exogenous variable. The suggested interactive regression was found to perform better (R =0.92) than the temporal expression (R =0.70). Despite the selection of a stochastic flexible model, the Dead Sea development pattern was found to conform to Butler's tourist area cycle of evolution model.
The Role of the Chef in Flight Catering
Authors: Jones Peter
Published: January 2007

A recent study from the University of Surrey has looked at the role and competencies of chefs in our industry. The report, ‘Flight catering chefs in the UK, USA and Japan: Production workers, process managers, or development gurus?’, suggests three very different roles and related competencies. It also found that thinking about these roles was different in each of the three countries researched.
Developing a Scenario Planning Process Using a Blank Piece of Paper
Authors: Yeoman Ian , McMahon-Beattie Una
Published: January 2007

VisitScotland is the national tourism organisation for Scotland, primarily responsible for marketing Scotland as a destination. The agency is also the Scottish Executive's (Government) principal adviser on policy matters relating to tourism and has the ambition to be the best national tourism organisation in the world. In order to reach this goal, it is committed to futures thinking, in particular using scenario planning in order to frame this thinking. This paper describes how VisitScotland designed a scenario planning process based upon three clusters: A scenario planning group, environmental scanning; and a forecasting model/economic analysis.
How to Present Results from Logistic Regression Analysis in Hospitality and Tourism Research
Authors: Thrane Christer
Published: January 2007

Many papers in hospitality and tourism research use logistic regression as the multivariate estimation strategy. When the results from these models are presented, only the logistic regression coefficients are usually reported. This is unfortunate since these coefficients have no intuitive metric. Hence, it is very difficult both for other researchers and for laymen to evaluate if the effects of the independent variables in question have important effects on the dependent variable or not. By using logistic regression coefficients from two real datasets as input in simple calculations, this paper shows how the question of the independent variables' net and relative importance can be more satisfactorily assessed.
Casino Markets: A Study of Tourist and Local Patrons
Authors: Hinch Tom , Walker Gordon J.
Published: January 2007

This paper compares the socio-demographic characteristics and motivations of tourists from Alberta who visit casinos while travelling, with Albertans who patronise local casinos; and tourists from Alberta for whom a casino visit was a major trip activity versus those for whom it was a minor activity. Data were collected from 900 residents of Alberta's two major metropolitan areas who had visited a casino in the previous 12 months. Findings demonstrate that tourist patrons are more likely to be female, to have a university education and to have management or professional occupations. They are also more likely to be motivated by social or communal goals and less likely to be motivated by risk seeking than local patrons. Those tourists for whom casino gaming is a major trip activity are more strongly motivated by risk-taking and the wish to escape their regular lives than are tourists for whom gaming is a minor trip activity. Differences also exist in terms of several key travel profile dimensions.
A Location-Based Mobile Tourist Guide
Authors: Curran Kevin , Smith Keith
Published: January 2007

Global positioning systems have enabled the accurate measurement of very large distance and in conjunction with ubiquitous Wi-Fi hotspots have enabled the widespread adoption of location-based tourism application which utilise online mapping services to provide users with accurate directions. This paper documents an ‘E-Local Advisor’ application which provides street maps, directions and location of local services. The application works by receiving signals from the GPS service which interact with online mapping services that are accessed through outdoor Wi-Fi hotspots. Tourists can locate places of interest, find out where they are and query the system for exact directions from one location to another.
Chaotic electron trajectories in a realizable helical wiggler with axial magnetic field
Authors: Esmaeilzadeh Mahdi , Fallah Mohammad S. , Willett Joseph E.
Published: January 2007

Chaotic behavior of relativistic electron motion in a free-electron laser with realizable helical wiggler and axial magnetic field is investigated by using Pioncaré maps and Liapunov exponents. It is shown that in the presence of low to medium axial magnetic field, the motion of the electron may be chaotic. The effect of high axial magnetic field on electron dynamics causes the motion to become regular and nonchaotic. The chaotic behavior of electron motion in the absence of self-fields and axial magnetic field is due to the spatial inhomogeneities of the realizable helical wiggler magnetic field.
Transport modeling in ionomeric polymer transducers and its relationship to electromechanical coupling
Authors: Wallmersperger Thomas , Leo Donald J. , Kothera Curt S.
Published: January 2007

Ionomeric polymer transducers consist of an ion-conducting membrane sandwiched between two metal electrodes. Application of a low voltage (<5V) to the polymer produces relatively large bending deformation (>2% strain) due to the transport of ionic species within the polymer matrix. A computational model of transport and electromechanical transduction is developed for ionomeric polymer transducers. The transport model is based upon a coupled chemoelectrical multifield formulation and computes the spatiotemporal volumetric charge density profile to an applied potential at the boundaries. The current induced in the polymer is computed using the isothermal transient ionic current associated with surface charge accumulation at the electrodes induced by nonzero volumetric charge density within the polymer. The stress induced in the polymer is assumed to be a summation of linear and quadratic functions of the volumetric charge density. Euler-Bernoulli beam mechanics are used to compute the bending deflection of the transducer to an applied potential. The diffusion coefficient and permittivity of the polymer is identified from the measured current density to a step change in the applied potential. A comparison between the measured data and the predicted response demonstrates that this model accurately predicts the current discharge due to the applied potential at voltages over the range of 50–500mV. Furthermore, the measured strain response is accurately predicted by determining the two parameters of the mechanics model that relates volumetric charge density to induced stress. The coupled model with parameters identified from the step response analysis is used to predict the harmonic response of the current and the bending strain. Comparisons between measured data and simulations illustrate that the coupled transport-mechanics model accurately predicts the magnitude and trends associated with the current response and strain output. Excellent agreement is obtained at excitation periods above approximately 1s while good agreement is obtained at longer excitation periods. The transport model highlights the importance of the asymmetry that develops at large applied potentials and long excitation periods in the volumetric charge density due to the fixed anionic species in the polymer.
A rheo-optical apparatus for real time kinetic studies on shear-induced alignment of self-assembled soft matter with small sample volumes
Authors: Laiho Ari , Ikkala Olli
Published: January 2007

In soft materials, self-assembled nanoscale structures can allow new functionalities but a general problem is to align such local structures aiming at monodomain overall order. In order to achieve shear alignment in a controlled manner, a novel type of rheo-optical apparatus has here been developed that allows small sample volumes and in situ monitoring of the alignment process during the shear. Both the amplitude and orientation angles of low level linear birefringence and dichroism are measured while the sample is subjected to large amplitude oscillatory shear flow. The apparatus is based on a commercial rheometer where we have constructed a flow cell that consists of two quartz teeth. The lower tooth can be set in oscillatory motion whereas the upper one is connected to the force transducers of the rheometer. A custom made cylindrical oven allows the operation of the flow cell at elevated temperatures up to 200 °C. Only a small sample volume is needed (from 9 to 25 mm3), which makes the apparatus suitable especially for studying new materials which are usually obtainable only in small quantities. Using this apparatus the flow alignment kinetics of a lamellar polystyrene-b-polyisoprene diblock copolymer is studied during shear under two different conditions which lead to parallel and perpendicular alignment of the lamellae. The open device geometry allows even combined optical/x-ray in situ characterization of the alignment process by combining small-angle x-ray scattering using concepts shown by Polushkin et al. [Macromolecules 36, 1421 (2003)].
Stress induced leakage current mechanism in thin Hf-silicate layers
Authors: Paskaleva A. , Lemberger M. , Bauer A. J.
Published: January 2007

Stress induced leakage current (SILC) in thin Hf-silicate layers and the mechanisms of its creation are examined. A very strong polarity and thickness dependence as well as partial recovery of SILC are observed. It is suggested that the trapping in preexisting sites influences SILC by two ways: (1) it could be the first stage of defect generation mechanism leading to the permanent component of SILC and (2) it is fully responsible for the partial recovery of SILC. Therefore, the origin of SILC in Hf silicate is distinctly different from that of SiO2. The physical origin of the preexisting sites is also discussed.
Order relaxation of a poled azo dye in a high Tg, fully aromatic polyimide
Authors: Quatela Alessia , De Matteis Fabio , Casalboni Mauro , Stella Federica , Colombo Marco , Zaopo Antonio
Published: January 2007

A guest-host polymer system with potential use in electro-optic devices is discussed. The polymer host is a high Tg, fully aromatic polyimide and the guest chromophore is disperse red 19. Relaxation mechanisms of polar order after electric field alignment procedure have been investigated by measuring the isothermal decay of the macroscopic nonlinear optical coefficient d333 at different temperatures below glass transition temperature (Tg), upon the removal of the poling electric field. All the decay curves can be fitted by a double exponential function. Below Tg, the slower relaxation time shows an Arrhenius temperature dependence. An extrapolation to room temperature allows to predict the time stability which results to be longer than 30years. In addition, absorption spectra measurements of the films were performed before and immediately after poling procedure to estimate independently the polar order of the dipoles through the decrease of the absorption coefficients.
Inverse scattering method for square matrix nonlinear Schrödinger equation under nonvanishing boundary conditions
Authors: Ieda Jun’ichi , Uchiyama Masaru , Wadati Miki
Published: January 2007

Matrix generalization of the inverse scattering method is developed to solve the multicomponent nonlinear Schrödinger equation with nonvanishing boundary conditions. It is shown that the initial value problem can be solved exactly. The multi-soliton solution is obtained from the Gel’fand-Levitan-Marchenko [Amer. Math. Soc. Transl. 1, 253 (1955)] equation.
Incursive discretization, system bifurcation, and energy conservation
Authors: Antippa Adel F. , Dubois Daniel M.
Published: January 2007

Incursive discretization of the classical harmonic oscillator leads to system bifurcation. The resulting hyperincursive representation has two alternative distinct algorithms of ordered, serial, noncommuting instructions, and admits solutions having a discretized classical total energy that is perfectly conserved and phase space trajectories that are fully stable at all time scales. Hyperincursive representations can be generated for any Hamiltonian system.
Space charge layers in organic field-effect transistors with Gaussian or exponential semiconductor density of states
Authors: Paasch G. , Scheinert S.
Published: January 2007

Space charge layers (SCLs) in metal-insulator-semiconductor (MIS) structures are critical for the operation of field-effect transistors (FETs). For many organic semiconductors, transport takes place as hopping in Gaussian or exponentially distributed states. However, existing theoretical descriptions of a SCL and advanced device simulation programs suppose a density of states other than a Gaussian or an exponential, employing often the nondegenerate limit for the concentrations. We present results of a simulation study for the MIS structure as the basic module of the FET and for a thin semiconducting layer on a metal substrate. The second system was extensively investigated by photoelectron spectroscopy to characterize the metal-organics interface occurring at the source/drain contact of FETs and as anode and cathode in organic light emitting diodes. For broader distributions, the densities deviate strongly from the nondegenerate limit which leads indeed in a MIS structure to a strong deviation of the dependence of the surface electric field (and, hence, the areal charge) on the surface potential. However, as one can control only the gate voltage directly, the dependency on this quantity determines device operation. For the variations of the layer thickness and gate insulator thickness, and doping in the wide range of interest, this dependency deviates only slightly from the nondegenerate approximation, essentially in the depletion region by a flatband voltage shift. In the accumulation region, which is determinative for FET operation, the remaining deviation can be removed almost perfectly by considering this flatband voltage shift. For the thin organic layer on a metal substrate, numerical simulations confirm the applicability of an analytical approximation for band bending and floating potential [G. Paasch et al., J. Appl. Phys. 93, 6084 (2003)] for the nondegenerate case and for the exponential distribution. Indeed, for small barriers at the interface, a band bending of up to the order of 100 meV can occur within the first 2 nm near the interface. In the interpretation of photoemission data such contribution will appear as part of the measured interface dipole.
Pulse propagation and nonlinear harmonic generation in free electron laser oscillators
Authors: Dattoli G. , Ottaviani P. L. , Pagnutti S.
Published: January 2007

In this paper we present an analysis of the intracavity harmonic generation in free electron laser amplifier operating with short pulses. Various features are investigated. We discuss, in particular, the dependence of the harmonic power and of the width of the associated pulses on the cavity mismatch. It is shown that very short and robust pulses can be generated by suitably setting the cavity desynchronism.
Alloying of GaNxAs1−x with InNxAs1−x: A simple formula for the band gap parametrization of Ga1−yInyNxAs1−x alloys
Authors: Kudrawiec R.
Published: January 2007

It has been shown that the band gap energy of dilute nitride ternary alloys (Ga1−yInyNxAs1−x in this case) can be predicted by knowing the band gap energy for dilute nitride binary alloys (GaNxAs1−x and InNxAs1−x alloys in this case) and a bowing parameter. The band gap energy for GaNxAs1−x and InNxAs1−x can be calculated after the band anticrossing (BAC) model [W. Shan et al., Phys. Rev. Lett. 82, 1221 (1999)] or other formula, whereas the bowing parameter can be assumed to be the same as for the GaInAs alloy. This approach does not require the BAC parameters related to Ga1−yInyNxAs1−x and can be applied for other dilute nitride ternary alloys. The obtained band gap predictions are in good agreement with available experimental data for as-grown GaInNAs materials. It means that the proposed energy gap parametrization corresponds to the random environment of N atoms by Ga and In atoms since alloying of GaNxAs1−x with InNxAs1−x also corresponds to alloying of Ga-rich environment of N atoms (which is expected for the as-grown GaInNAs material with low indium content) with In-rich environment of N atoms (which is expected for the as-grown GaInNAs material with high indium content).
The structure of sputter-deposited Co2MnSi thin films deposited on GaAs(001)
Authors: Kohn A. , Lazarov V. K. , Singh L. J. , Barber Z. H. , Petford-Long A. K.
Published: January 2007

The structure of Co2MnSi thin films on GaAs(001) has been characterized by transmission electron microscopy in order to evaluate the feasibility of achieving spin injection into GaAs from such electrodes. The films were dc-magnetron sputtered and varied in thickness between 15 and 260 nm with substrate temperatures during growth of 250, 300, and 374 °C. All films exhibited a polycrystalline structure with mainly an L21 type crystallographic symmetry, and a high degree of preferred orientation with the GaAs. A reaction with the GaAs substrate, rich in Mn and As, occurs for deposition even of the 15 nm thick film, creating zones that exhibit an epitaxial relation with the substrate. Between this reaction zone and the film, a continuous interlayer forms, which is rich in Ga, and several nanometers thick. Films thicker than 35 nm were found to be stoichiometric in chemical composition, while thinner films were deficient in Mn and richer in Si. Decreasing the substrate temperature resulted in reduction of the extent of the reaction with the substrate, but also reduced the crystallographic ordering of the Co2MnSi layer. Finally, both kinematic and dynamic simulations of selected-area electron diffraction patterns demonstrate that this technique may not be a sensitive methodology to detect Co-Mn antisite defects and off-stoichiometry compositions. These defects may be responsible for the approximately 55% spin polarization measured in these films, rather than the full spin polarization expected from this theoretically predicted half-metal.
Analysis of electron interactions in dielectric gases
Authors: Olivet Aurelio , Duque Daniel , Vega Lourdes F.
Published: January 2007

We present and discuss results concerning electron interactions processes of dielectric gases and their relationship with the macroscopic behavior of these gases, in particular, with their dielectric strength. Such analysis is based on calculating energies of reactions for molecular ionization, dissociative ionization, parent negative ion formation, and dissociative electron attachment processes. We hypothesize that the estimation of the required energy for a reduced number of processes that take place in electrically stressed gases could be related to the gas’ capability to manage the electron flow during an electrical discharge. All calculations were done with semiempirical quantum chemistry methods, including an initial optimization of molecular geometry and heat of formation of the dielectric gases and all of species that appear during electron interaction reactions. The performance of semiempirical methods Austin model 1 and Parametric model 3 (PM3) was compared for several compounds, PM3 being superior in most cases. Calculations performed for a sample of nine dielectric gases show that electron attachment and detachment processes occur in different energy bands that do not overlap for any value of the dielectric strength. We have also analyzed the relationship between dielectric strength and two physical properties: electron affinity and ionization energy. Calculations performed for 43 dielectric gases show no clear correlation between them, although certain guidelines for the qualitative estimation of dielectric strength can still be assessed.
Nonresonant kinetic instabilities of a relativistic plasma in a uniform magnetic field: Longitudinal and transverse mode coupling effects
Authors: Tautz R. C. , Schlickeiser R. , Lerche I.
Published: January 2007

The stability properties of relativistic plasmas embedded in a uniform magnetic field are investigated for longitudinal and transverse modes and with coupling effects between these modes. The direction of wave propagation in the plasma is not necessarily either parallel or transverse to the ambient magnetic field. The basic dispersion relation equations are given for arbitrary propagation directions. Detailed examination is focused on perpendicular wave propagation in this paper. The concept of neutral points in wave number space, introduced by Harris [Phys. Rev. Lett. 2, 34 (1959)], is generalized to allow for the inclusion of ion effects and the effects of fluctuating magnetic fields. Starting from the relativistic conductivity tensor, an expansion procedure for low wave frequencies is used to determine the stability properties in the neighborhood of neutral points and in the frequency regime below the ion cyclotron frequency. The bulk plasma properties determine stability or instability but the mode structure is derivable only from a particle kinetic picture, as with Weibel [Phys. Rev. Lett. 2, 83 (1959)] instabilities, and not from a magnetohydrodynamic description. For monoenergetic plasma distribution functions of electrons and ions, as well as for electrons and positrons, numerical examples are given to illustrate the neutral points and the unstable wave number regimes.
Geometric integration of the electromagnetic two-body problem
Authors: De Luca Jayme
Published: January 2007

The equations of motion of the two-body problem of Dirac’s electrodynamics of point charges consist of a delay equation for the proton and a delay equation for the electron. These equations involve the third derivative of the charges’s position and have runaway solutions, which make forward numerical integration troublesome. Dirac’s equations of motion are algebraic-delay equations, involving a degenerate linear form of the past accelerations. A Fredholm alternative yields a system of second-order delay equations of motion plus a constraint on the initial segment of trajectory. Here we use the Fredholm constraint as a geometric tool to derive covariant second-order equations of motion in position for backward time integration. We also extend the backward integration scheme to include a generalized version of Dirac’s theory that includes two delays.