bluuebunny/crossref_metadata_2025 huggingface dataset:
The L2 acquisition of a phonological variable: the case of /l/ deletion in French
Authors: HOWARD MARTIN , LEMÉE ISABELLE , REGAN VERA
Published: April 2006

This article is situated within the recent strand of SLA research which applies variationist sociolinguistic methods to the study of the acquisition of sociolinguistic variation by the L2 speaker. Whilst that research has tended to focus on the study of morphological and morphosyntactic variables, this article aims to investigate a number of acquisitional trends identified in previous research in relation to phonological variation, namely the variable deletion of /l/ by Irish advanced L2 speakers of French in both an instructed and study abroad environment. Based on quantitative results using GoldVarb 2001, the study further illuminates the difficulty that the acquisition of sociolinguistic variation poses to the instructed L2 speaker, who is found to make minimal use of informal sociolinguistic variants. In contrast, contact with native speakers in the native speech community is seen to allow the L2 speaker to make considerable sociolinguistic gains, not only in relation to the acquisition of the informal variant in itself, but also in relation to the underlying native speaker grammatical system as indicated by the constraint ordering at work behind use of the variable.
Investment choices? County borough health expenditure in inter-war England and Wales
Authors: LEVENE ALYSA , POWELL MARTIN , STEWART JOHN
Published: April 2006

This article examines the level of expenditure on health care provision in English and Welsh county boroughs during the inter-war period. It focuses in particular on key individual services such as maternity and child welfare to show that while there was a general trend to increased municipal health care expenditure, when this is disaggregated significant variations emerge between services, between boroughs and over time. It is argued that such analysis is of itself revealing, previously neglected and necessary for further qualitative analysis of the as yet little understood inter-war municipal medicine sector.
Urban narratives: Italian and Greek-Cypriot representations of community in post-war Leicester
Authors: BURRELL KATHY
Published: April 2006

The concept of community is frequently used to describe urban ethnic minority groups. What this term actually means to the community members themselves, however, is often left unexplored. Using interviews undertaken with Italian and Greek-Cypriot residents of Leicester, this article analyses how the notion of community is recognized, understood and projected from within. Key findings include the observation that the discussion of community is framed in very particular ways, both historically and spatially; that the concept of community is used as a metaphor for the expression of wider issues of urban ownership and belonging; and that ultimately the real essence of community lies less in the significance of physical structures and more in a series of fluid social interactions, underpinned by a shared code of cultural norms and values.
Magical Thinking in Obsessive-Compulsive Disorder, Panic Disorder and the General Community
Authors: Einstein Danielle A. , Menzies Ross G.
Published: April 2006

Magical Ideation was examined in 71 individuals across four groups matched, where possible, for gender and age. These groups were: (1) Obsessive Compulsive Disorder (OCD) patients with cleaning compulsions (n = 11); (2) OCD patients with checking compulsions (n = 20); (3) panic disorder patients with minimal obsessive compulsive symptoms (n = 19); (4) a “normal” control group with minimal obsessive compulsive symptoms (n = 21). The Magical Ideation Scale (MI, Eckblad and Chapman, 1983), the Obsessive Compulsive Inventory- Short Version (OCI-SV; Foa et al., 2002) and the Maudsley Obsessional-Compulsive Inventory (MOCI, Hodgson and Rachman, 1977) were administered to all participants. A one-way Anova was conducted with four planned contrasts. As expected, the OCD groups obtained magical ideation scores higher than the normal subjects. This suggests that OCD patients engage in more magical thinking tendencies than non-anxious controls. Similarly, OCD participants obtained a mean magical ideation score significantly higher than the panic disorder group, suggesting that obsessional compulsive patients are more likely to exhibit magical thinking than individuals with panic disorder. Of note, panic disorder and control group means on MI did not differ significantly. Finally, individuals with obsessive cleaning compulsions displayed higher levels of magical thinking compared to individuals with obsessive checking compulsions, despite no difference in severity of their obsessive compulsive symptoms. This observation was counter to previous findings (Einstein and Menzies, 2004a; Einstein and Menzies, 2004b).
What Is Special About Social Network Analysis?
Authors: van Duijn Marijtje A. J. , Vermunt Jeroen K.
Published: April 2006

In a short introduction on social network analysis, the main characteristics of social network data as well as the main goals of social network analysis are described. An overview of statistical models for social network data is given, pointing at differences and similarities between the various model classes and introducing the most recent developments in social network modeling.
Random Effects Models for Personal Networks
Authors: Vermunt Jeroen K. , Kalmijn Matthijs
Published: April 2006

We propose analyzing personal or ego-centered network data by means of two-level generalized linear models. The approach is illustrated with an example in which we assess whether personal networks are homogenous with respect to marital status after controlling for age homogeneity. In this example, the outcome variable is a bivariate categorical response variable (alter’s marital status and age category). We apply both factor-analytic parametric and latent-class-based nonparametric random effects models and compare the results obtained with the two approaches. The proposed models can be estimated with the Latent GOLD program for latent class analysis.
Applying SIENA
Authors: Steglich Christian , Snijders Tom A. B. , West Patrick
Published: April 2006

We give a nontechnical introduction into recently developed methods for analyzing the coevolution of social networks and behavior(s) of the network actors. This coevolution is crucial for a variety of research topics that currently receive a lot of attention, such as the role of peer groups in adolescent development. A family of dynamic actor-driven models for the coevolution process is sketched, and it is shown how to use the SIENA software for estimating these models. We illustrate the method by analyzing the coevolution of friendship networks, taste in music, and alcohol consumption of teenagers.
Collection of Ego-Centered Network Data with Computer-Assisted Interviews
Authors: Gerich Joachim , Lehner Roland
Published: April 2006

Although ego-centered network data provide information that is limited in various ways as compared with full network data, an ego-centered design can be used without the need for a priori and researcher-defined network borders. Moreover, ego-centered network data can be obtained with traditional survey methods. However, due to the dynamic structure of the questionnaires involved, a great effort is required on the part of either respondents (with self-administration) or interviewers (with face-to-face interviews). As an alternative, we will show the advantages of using CASI (computer-assisted self-administered interview) methods for the collection of ego-centered network data as applied in a study on the role of social networks in substance use among college students.
Long‐term record of atmospheric CO2 and stable isotopic ratios at Waliguan Observatory: Seasonally averaged 1991–2002 source/sink signals, and a comparison of 1998–2002 record to the 11 selected sites in the Northern Hemisphere
Authors: Zhou Lingxi , White James W. C. , Conway Thomas J. , Mukai Hitoshi , MacClune Kenneth , Zhang Xiaochun , Wen Yupu , Li Jinlong
Published: April 2006

This paper investigates seasonally averaged atmospheric CO2 source or sink signals observed at Waliguan Baseline Observatory (WLG, 36°17′N, 100°54′E, 3816 m asl) in western China from 1991 to 2002. Both linear and geometric mean regressions as well as statistical significance test were performed between detrended CO2 and stable isotope monthly data by means of Keeling Model and Miller‐Tans Model. The estimated slope Δδ13C/ΔCO2 due to the seasonality in CO2 and δ13C is (−0.050 ± 0.004)‰ ppm−1, the mean source/sink isotopic signatures δs (i.e., δ13Cs and δ18Os) are (−26.159 ± 1.924)‰ and (−7.662 ± 2.113)‰, respectively, and the mean atmospheric δ13C discrimination δdis (i.e., δs minus δbg) where the δbg is the isotopic value of the background atmosphere was (−18.174 ± 1.959)‰ by the Keeling Model, in agreement with results from other continental background sites in the Northern Hemisphere. We suggest that exchange with terrestrial biosphere dominates the observed CO2, δ13C and δ18O seasonal cycles at WLG. In addition, atmospheric CO2 and δ13C data from 11 selected NH sites in the NOAA ESRL air sampling network from 1998 to 2002 were analyzed and compared to the WLG data for the same period to better address common and specific features observed in this region. The annual cycle amplitude differences, secular and seasonal Δδ13C/ΔCO2 discrepancies among sites will be useful to better understand carbon uptake and release especially on the Eurasian continent. The estimated δs during certain times at each specific site could possibly provide useful information on CO2 fluxes.
Inverse estimates of anthropogenic CO2 uptake, transport, and storage by the ocean
Authors: Mikaloff Fletcher S. E. , Gruber N. , Jacobson A. R. , Doney S. C. , Dutkiewicz S. , Gerber M. , Follows M. , Joos F. , Lindsay K. , Menemenlis D. , Mouchet A. , Müller S. A. , Sarmiento J. L.
Published: April 2006

Regional air‐sea fluxes of anthropogenic CO2 are estimated using a Green's function inversion method that combines data‐based estimates of anthropogenic CO2 in the ocean with information about ocean transport and mixing from a suite of Ocean General Circulation Models (OGCMs). In order to quantify the uncertainty associated with the estimated fluxes owing to modeled transport and errors in the data, we employ 10 OGCMs and three scenarios representing biases in the data‐based anthropogenic CO2 estimates. On the basis of the prescribed anthropogenic CO2 storage, we find a global uptake of 2.2 ± 0.25 Pg C yr−1, scaled to 1995. This error estimate represents the standard deviation of the models weighted by a CFC‐based model skill score, which reduces the error range and emphasizes those models that have been shown to reproduce observed tracer concentrations most accurately. The greatest anthropogenic CO2 uptake occurs in the Southern Ocean and in the tropics. The flux estimates imply vigorous northward transport in the Southern Hemisphere, northward cross‐equatorial transport, and equatorward transport at high northern latitudes. Compared with forward simulations, we find substantially more uptake in the Southern Ocean, less uptake in the Pacific Ocean, and less global uptake. The large‐scale spatial pattern of the estimated flux is generally insensitive to possible biases in the data and the models employed. However, the global uptake scales approximately linearly with changes in the global anthropogenic CO2 inventory. Considerable uncertainties remain in some regions, particularly the Southern Ocean.
Twenty‐first‐century climate change commitment from a multi‐model ensemble
Authors: Teng Haiyan , Buja Lawrence E. , Meehl Gerald A.
Published: April 2006

Climate change commitment in the 21st ‐century due to human activity in the 20th century is quantified using output from 16 global coupled general circulation models. With the atmospheric composition held constant at year 2000 values, the global annual mean surface temperature anomaly stabilizes with an additional warming over and above what already occurred in the 20th century of +0.5° ± 0.2°C by the end of the 21st century. The magnitude is about 0.1°C warmer in the models with the 20th century volcanic aerosol than those models without. The multi‐model ensemble (from 6 models) globally averaged sea level rises +10 ± 3cm by 2100 and does not show signs of leveling off. The committed winter warming pattern is characterized by polar amplification due in part to ice albedo feedback, with a further committed warming of above 1.0°C and 0.6°C in the Arctic and Antarctic regions, respectively. The tropical surface temperature pattern shows an El Nino‐like response, with consequent changes in precipitation over the tropics. Thus, even after GHGs are stabilized, the multi‐model results show that the climate continues to change with similar patterns to those when GHGs are continuously increasing, but these changes are due to the thermal inertia of the climate system reacting to the radiative forcing from the atmospheric composition changes applied during the 20th century.
First light from the Far‐Infrared Spectroscopy of the Troposphere (FIRST) instrument
Authors: Mlynczak Martin G. , Johnson David G. , Latvakoski Harri , Jucks Kenneth , Watson Mike , Kratz David P. , Bingham Gail , Traub Wesley A. , Wellard Stanley J. , Hyde Charles R. , Liu Xu
Published: April 2006

We present first light spectra that were measured by the newly‐developed Far‐Infrared Spectroscopy of the Troposphere (FIRST) instrument during a high‐altitude balloon flight from Ft. Sumner, NM on 7 June 2005. FIRST is a Fourier Transform Spectrometer designed to measure accurately the far‐infrared (15 to 100 μm; 650 to 100 wavenumbers, cm−1) emission spectrum of the Earth and its atmosphere. The flight data successfully demonstrated the FIRST instrument's ability to observe the entire energetically significant infrared emission spectrum (50 to 2000 cm−1) at high spectral and spatial resolution on a single focal plane in an instrument with one broad spectral bandpass beamsplitter. Comparisons with radiative transfer calculations demonstrate that FIRST accurately observes the very fine spectral structure in the far‐infrared. Comparisons also show excellent agreement between the atmospheric window radiance measured by FIRST and by instruments on the NASA Aqua satellite that overflew the FIRST flight. FIRST opens a new window on the spectrum that can be used for studying atmospheric radiation and climate, cirrus clouds, and water vapor in the upper troposphere.
Influence of the Northern Hemisphere annular mode on ENSO by modulating westerly wind bursts
Authors: Nakamura Tetsu , Tachibana Yoshihiro , Honda Meiji , Yamane Shozo
Published: April 2006

The influence of the Northern Hemisphere annular mode (NAM) on the El Niño/Southern Oscillation (ENSO) was examined using 41‐year reanalysis data and an atmospheric general circulation model (AGCM). Significant lag correlations between the NAM index for spring and the Niño‐3 index for the following winter were revealed. An anomalous lower tropospheric westerly associated with modulation of the westerly wind burst (WWB) over the western tropical Pacific in spring often coincided with the positive phase of the NAM and extended eastward during summer and autumn. Then, warm sea surface temperature (SST) anomalies reflecting El Niño appeared over the eastern tropical Pacific in early winter. In an AGCM experiment in which SSTs were fixed as a climatological‐mean monthly distribution, the interannual modulation of WWB was significantly associated with NAM variability in spring, supporting the possible influence of the NAM in spring on an ENSO outbreak the following winter.
Strong shaking in Los Angeles expected from southern San Andreas earthquake
Authors: Olsen K. B. , Day S. M. , Minster J. B. , Cui Y. , Chourasia A. , Faerman M. , Moore R. , Maechling P. , Jordan T.
Published: April 2006

The southernmost San Andreas fault has a high probability of rupturing in a large (greater than magnitude 7.5) earthquake sometime during the next few decades. New simulations show that the chain of sedimentary basins between San Bernardino and downtown Los Angeles form an effective waveguide that channels Love waves along the southern edge of the San Bernardino and San Gabriel Mountains. Earthquake scenarios with northward rupture, in which the guided wave is efficiently excited, produce unusually high long‐period ground motions over much of the greater Los Angeles region, including intense, localized amplitude modulations arising from variations in waveguide cross‐section.
Local earthquake (LE) tomography with joint inversion for P‐ and S‐wave velocities using structural constraints
Authors: Tryggvason Ari , Linde Niklas
Published: April 2006

In local earthquake (LE) tomography for P‐ and S‐wave velocities (or Vp/Vs ratios), constraints punishing deviations from a given Vp/Vs ratio are often used. In a synthetic model test we demonstrate that though such constraints inhibit unreasonable Vp/Vs ratio variations, they bias the resulting Vp/Vs ratios. As an alternative approach, structural constraints based on the cross‐product of the model gradients can be used to constrain the joint P‐ and S‐wave inversion. We show that the resulting models are as low in artifacts as if a Vp/Vs damping was used, but the resulting Vp/Vs ratios are less biased, which is important for a quantitative interpretation of physical properties and processes in the Earth.
Correlation between the phase of the moon and the occurrences of microearthquakes in the Tamba region through point‐process modeling
Authors: Iwata Takaki , Katao Hiroshi
Published: April 2006

We study the correlation between the phase of the moon and the occurrence of microearthquakes in the Tamba region, close to the fault of the 1995 Kobe earthquake. The existence of the correlation during the two‐year period following the Kobe earthquake was suggested in a previous study. First, in this study, we investigate the statistical significance of such correlation. Using point‐process modeling and AIC (Akaike Information Criterion), we confirm that the existence of the correlation is statistically significant. Second, we investigate the temporal variation of the correlation during the four‐year period following the Kobe earthquake. The result of the second analysis indicates that the correlation is strongest just after the Kobe earthquake and that it then becomes weaker year by year.
Comparisons of electron energy deposition derived from observations of lower thermospheric nitric oxide and from X‐ray bremsstrahlung measurements
Authors: Sætre C. , Barth C. A. , Stadsnes J. , Østgaard N. , Bailey S. M. , Baker D. N. , Gjerloev J. W.
Published: April 2006

Previous studies have shown the connection between electron precipitation and the excess amounts of nitric oxide at auroral latitudes. In this study the electron energy deposition derived from thermospheric nitric oxide (NO) measurements is compared with the electron energy deposition derived from X‐ray bremsstrahlung measurements. The electron energy deposition is derived from nitric oxide densities by use of a photochemical model for nitric oxide and is referred to as the modeled energy deposition. The comparisons are made for the beginning of five geomagnetic storms in 1998: 21 March, 2 May, 14 June, 26 June, and 16 July. By using these quite different methods to derive the total electron energy deposition (4–100 keV), the results show that we have a generally good understanding of the physics and chemistry of the energy transfer from electron precipitation in the lower thermosphere. The comparisons also show some discrepancies. The modeled energy deposition is typically larger than the energy deposition derived from X‐ray bremsstrahlung in the beginning of the storm period, whereas later on in the storm the energy deposition derived from X‐ray measurements is largest. The cases where the modeled energy deposition is largest is probably due to production of NO occurring before the bremsstrahlung measurements. The systematic underestimate of the calculated energy deposition could be due to uncertainties in the reaction rates or in the characteristic electron energy used in the photochemical model. The effects from horizontal neutral wind on the NO gas from the production on the nightside to the observations on the dayside can also be a source of discrepancy.
Effect of water on the dislocation creep microstructure and flow stress of quartz and implications for the recrystallized grain size piezometer
Authors: Stipp Michael , Tullis Jan , Behrens Harald
Published: April 2006

Deformation experiments on Black Hills quartzite with three different initial water contents (as‐is, water‐added, and vacuum‐dried) were carried out in the dislocation creep regime in order to evaluate the effect of water on the recrystallized grain size/flow stress piezometer. Samples were deformed in axial compression at temperatures of 750°–1100°C, strain rates between 2 × 10−7 s−1 and 2 × 10−4 s−1 and strains up to 46% using a molten salt assembly in a Griggs apparatus. An increase of the initial water content at otherwise constant deformation conditions caused a decrease in flow stress, an effect known as hydrolytic weakening. The total water content of the starting material was analyzed by Karl Fischer titration (KFT) and Fourier transform infrared (IR) spectroscopy, and quenched samples were analyzed microstructurally and by IR. Changes in the dynamic recrystallization microstructure correlate with changes in flow stress, but there is no independent effect of temperature, strain rate or water content. IR absorption spectra of the deformed spectra indicate that different water contents were maintained in the three sample sets throughout the experiments. However, the amounts of water measured within the vacuum‐dried (∼260 ± 40 ppm H2O), the as‐is (∼340 ± 50 ppm H2O), and the water‐added (∼430 ± 110 ppm H2O) samples are significantly smaller than the initial content of the quartzite (∼640 ± 50 ppm H2O). Water from the inclusions in the starting material adds to the free fluid phase along the grain boundaries, which probably controls the water fugacity and the flow strength, but this water is largely lost during IR sample preparation. Vacuum‐dried as well as water‐added samples have the same recrystallized grain size/flow stress relationship as the piezometer determined for as‐is samples. No independent effect of water on the piezometric relationship has been detected.
An evaluation of factors influencing pore pressure in accretionary complexes: Implications for taper angle and wedge mechanics
Authors: Saffer Demian M. , Bekins Barbara A.
Published: April 2006

At many subduction zones, accretionary complexes form as sediment is off‐scraped from the subducting plate. Mechanical models that treat accretionary complexes as critically tapered wedges of sediment demonstrate that pore pressure controls their taper angle by modifying basal and internal shear strength. Here, we combine a numerical model of groundwater flow with critical taper theory to quantify the effects of sediment and décollement permeability, sediment thickness, sediment partitioning between accretion and underthrusting, and plate convergence rate on steady state pore pressure. Our results show that pore pressure in accretionary wedges can be viewed as a dynamically maintained response to factors which drive pore pressure (source terms) and those that limit flow (permeability and drainage path length). We find that sediment permeability and incoming sediment thickness are the most important factors, whereas fault permeability and the partitioning of sediment have a small effect. For our base case model scenario, as sediment permeability is increased, pore pressure decreases from near‐lithostatic to hydrostatic values and allows stable taper angles to increase from ∼2.5° to 8°–12.5°. With increased sediment thickness in our models (from 100 to 8000 m), increased pore pressure drives a decrease in stable taper angle from 8.4°–12.5° to <2.5–5°. In general, low‐permeability and thick incoming sediment sustain high pore pressures consistent with shallowly tapered geometry, whereas high‐permeability and thin incoming sediment should result in steep geometry. Our model results compare favorably with available data from active accretionary complexes. Active margins characterized by a significant proportion of fine‐grained sediment within the incoming section, such as northern Antilles and eastern Nankai, exhibit thin taper angles, whereas those characterized by a higher proportion of sandy turbidites, such as Cascadia, Chile, and Mexico, have steep taper angles. Observations from active margins also indicate a strong trend of decreasing taper angle (from >15° to <4°) with increased sediment thickness (from <1 to 7 km). One key implication is that hydrologic properties may strongly influence the strength of the crust in a wide range of geologic settings.
Seasonal dynamics and ecosystem impact of mesozooplankton at station ALOHA based on optical plankton counter measurements
Authors: Huntley M. E. , Lopez M. D. G. , Zhou M. , Landry M. R.
Published: April 2006

Abundances of mesozooplankton‐sized particles were measured at 45‐m depth at station ALOHA (22.75°N, 158°W) during 18 cruises from February 1995 through December 1996 with an optical plankton counter (OPC). Mesozooplankton were also sampled with oblique net tows to 155 m depth. Vertical OPC profiles showed uniform total abundance in the upper mixed layer, usually >45 m. OPC and net data agreed with respect to total abundance, size composition, abundance of individual size classes, and seasonal cycle of abundance. We found no evidence for significant contributions to OPC particle counts by diatom aggregates, Trichodesmium spp., or detritus. Variations in OPC estimates of abundance are well explained by diel behavior and seasonal cycles of species that dominate mesozooplankton abundance, of which 80% are copepods. The summer maximum in mesozooplankton abundance is due primarily to the increase of the six smallest OPC size classes (<1.15 mm equivalent spherical diameter), dominated by 14 nonmigrating copepod species that account for more than 95% of average copepod abundance. Seasonal cycles of zooplankton egestion estimated from OPC measurements were highly correlated, and comparable in magnitude, with observed sinking flux measurements of both C and N. Sinking flux at the base of the euphotic zone was 0.67 and 0.77 mol C m−2 yr−1 and 81 and 87 mmol N m−2 yr−1, for 1995 and 1995, respectively. The potential contribution of mesozooplankton egestion in the mixed layer, based on OPC measurements, accounts for 95% and 90% of C and 86% and 81% of N, respectively.
Structure and dynamics of the summertime atmospheric boundary layer over the Antarctic Plateau: 1. Measurements and model validation
Authors: van As Dirk , van den Broeke Michiel R. , Helsen Michiel M.
Published: April 2006

Profile mast, tethersonde and radiosonde measurements are used to describe the structure and dynamics of the summertime atmospheric boundary layer over the slightly sloping snow surface at Kohnen base (75°00′S, 0°04′E, 2892 m above sea level), located on the interior plateau of East Antarctica. During a 4‐day clear‐sky period at the end of summer, we found a shallow but dynamic boundary layer. Net radiation contributed between −40 and +35 W m−2 to the surface energy balance and was negative on average; the sensible and latent heat fluxes contributed less than 10 W m−2 and 1 W m−2, respectively; the subsurface heat flux mostly counteracted the radiative flux. Owing to nighttime radiative cooling at the surface an increasingly deep stable layer formed with a temperature deficit of over 12 K. Within this layer we observed a katabatically driven low‐level jet which increased in altitude from 20 to 70 m during the night and persisted up to noon. By that time a shallow mixed layer was deepening and warming underneath the stable layer. The mixed layer obtained a maximum depth of 70 m halfway through the afternoon. During the experiment the ABL was near saturation. The observations were used to validate a one‐dimensional atmospheric boundary layer model.
Cloud clearing of Atmospheric Infrared Sounder hyperspectral infrared radiances using stochastic methods
Authors: Cho Choongyeun , Staelin David H.
Published: April 2006

A novel stochastic algorithm is presented for estimating Atmospheric Infrared Sounder (AIRS) radiances in the 3.7–15.4 micron spectral band that would be observed from space in the absence of clouds. This algorithm examines 3 × 3 sets of 15‐km AIRS fields of view, selects the clearest fields, and then estimates a single cloud‐cleared infrared spectrum for the 3 × 3 set using a series of simple linear and nonlinear operations on both the infrared and companion Advanced Microwave Sounding Unit (AMSU) microwave channels. These instruments were launched on the NASA Aqua satellite in May 2002. The algorithm was both trained and tested within 70° of the equator using global numerical weather analyses generated by the European Center for Medium‐range Weather Forecasts (ECMWF); these analyses were converted to radiances using the SARTA v1.05 equation of radiative transfer. The RMS differences between the AIRS 4‐ and 15‐micron CO2‐band observations and the corresponding ECMWF/SARTA radiances over nighttime ocean are ∼0.2–0.3 K for ∼60 selected channels with weighting functions peaking at tropospheric altitudes down to the surface for the best 28% of all soundings selected using only AIRS data. For a larger ensemble of 314 channels the corresponding range was 0.27–0.40 K. Latitudes 30–70° yielded RMS differences of 0.26–0.78 K over land at night for the same 314 channels. Mean differences were largely eliminated by training the estimates using independent global observations made on the same 3 test days, which were spaced over 2 months.
A hybrid source apportionment model integrating measured data and air quality model results
Authors: Schichtel Bret A. , Malm William C. , Gebhart Kristi A. , Barna Michael G. , Knipping Eladio M.
Published: April 2006

The Big Bend Regional Aerosol and Visibility (BRAVO) study was an intensive air quality study designed to understand the causes of haze in Big Bend National Park. Daily speciated fine aerosols were measured from July through October 1999 at 37 sites located mostly in Texas. In support of BRAVO, two chemical transport models (CTMs) were used to apportion particulate sulfate at Big Bend and other sites in Texas to sources in the eastern and western United States, Texas, Mexico, and the Carbón I and II coal‐fired power plants, located 225 km southeast of Big Bend in Mexico. Analysis of the CTM source attribution results and comparison to results from receptor models revealed systematic biases. To reduce the multiplicative biases, a hybrid source apportionment model, based on inverse modeling, was developed that adjusted the initial CTM source contributions so the modeled sulfate concentrations optimally fit the measured data, resulting in refined daily source contributions. The method was tested using synthetic data and successfully reduced source attribution biases. The refined sulfate source attribution results reduced the initial eastern U.S. contribution to Big Bend, averaged over the BRAVO study period, from ∼40% to ∼30%, while Mexico's contribution increased from 24–32% to ∼40%. The contribution from the Carbón facility increased from ∼14% to over 20%. Contributions from Texas and the western United States changed little, with final contributions of ∼16% and 5–9%, respectively. The increase in Mexico's contribution is consistent with more recent SO2 emissions estimates that indicate that the BRAVO Mexican SO2 emissions were underestimated. Source attribution results for other monitoring sites in west Texas were similar to results at Big Bend. In eastern Texas, the eastern United States accounted for up to 70% of the measured sulfate, with Texas contributing ∼20–30%.
Cloud optical thickness and effective particle radius derived from transmitted solar radiation measurements: Comparison with cloud radar observations
Authors: Kikuchi Nobuhiro , Nakajima Teruyuki , Kumagai Hiroshi , Kuroiwa Hiroshi , Kamei Akihide , Nakamura Ryosuke , Nakajima Takashi Y.
Published: April 2006

A method is presented for determining the optical thickness and effective particle radius of stratiform clouds containing liquid water drops in the absence of drizzle from transmitted solar radiation measurements. The procedure compares measurements of the cloud transmittance from the ground at water‐absorbing and nonabsorbing wavelengths with lookup tables of the transmittance precomputed for plane‐parallel, vertically homogeneous clouds. The optical thickness derived from the cloud transmittance may be used to retrieve vertical profiles of cloud microphysics in combination with the radar reflectivity factor. To do this, we also present an algorithm for solving the radar equation with a constraint of the optical thickness at the visible wavelength. Observations of clouds were made in August and September 2003 at Koganei, Tokyo, Japan, using a PREDE i‐skyradiometer and a 95‐GHz cloud radar Super Polarimetric Ice Crystal Detection and Explication Radar (SPIDER). The optical thickness and effective radius of water clouds were derived from the i‐skyradiometer. Then, the vertical profile of the effective radius was retrieved from SPIDER, using the optical thickness determined from the i‐skyradiometer. We found that the effective radii derived by using these two instruments were in good agreement.
Gas‐phase products and secondary aerosol yields from the ozonolysis of ten different terpenes
Authors: Lee Anita , Goldstein Allen H. , Keywood Melita D. , Gao Song , Varutbangkul Varuntida , Bahreini Roya , Ng Nga L. , Flagan Richard C. , Seinfeld John H.
Published: April 2006

The ozonolyses of six monoterpenes (α‐pinene, β‐pinene, 3‐carene, terpinolene, α‐terpinene, and myrcene), two sesquiterpenes (α‐humulene and β‐caryophyllene), and two oxygenated terpenes (methyl chavicol and linalool) were conducted individually in Teflon chambers to examine the gas‐phase oxidation product and secondary organic aerosol (SOA) yields from these reactions. Particle size distribution and number concentration were monitored and allowed for the calculation of the SOA yield from each experiment, which ranged from 1 to 54%. A proton transfer reaction mass spectrometer (PTR‐MS) was used to monitor the evolution of gas‐phase products, identified by their mass to charge ratio (m/z). Several gas‐phase oxidation products, formaldehyde, acetaldehyde, formic acid, acetone, acetic acid, and nopinone, were identified and calibrated. Aerosol yields, and the yields of these identified and calibrated oxidation products, as well as many higher m/z oxidation products observed with the PTR‐MS, varied significantly between the different parent terpene compounds. The sum of measured oxidation products in the gas and particle phase ranged from 33 to 77% of the carbon in the reacted terpenes, suggesting there are still unmeasured products from these reactions. The observations of the higher molecular weight oxidation product ions provide evidence of previously unreported compounds and their temporal evolution in the smog chamber from multistep oxidation processes. Many of the observed ions, including m/z 111 and 113, have also been observed in ambient air above a Ponderosa pine forest canopy, and our results confirm they are consistent with products from terpene + O3 reactions. Many of these products are stable on the timescale of our experiments and can therefore be monitored in field campaigns as evidence for ozone oxidative chemistry.
DMS sea‐air transfer velocity: Direct measurements by eddy covariance and parameterization based on the NOAA/COARE gas transfer model
Authors: Blomquist B. W. , Fairall C. W. , Huebert B. J. , Kieber D. J. , Westby G. R.
Published: April 2006

Estimates of the DMS sea‐air transfer velocity (kDMS) derived from direct flux measurements are poorly modeled by parameterizations based solely on wind speed and Schmidt number. DMS and CO2 flux measurements show to be a stronger function of wind speed than kDMS. The NOAA/COARE gas flux parameterization, incorporating the bubble‐mediated gas transfer theory of Woolf (1997), appears to do a better job reproducing the observations for both gases, illustrating the importance of trace gas solubility in sea‐air exchange. The development of gas transfer parameterizations based on physical principles is still in its infancy, but recent advances in direct flux measurement methods provide an opportunity to evaluate the success of various modeling approaches for this critical geophysical process.
Dual-plane stereo particle image velocimetry measurements of velocity gradient tensor fields in turbulent shear flow. I. Accuracy assessments
Authors: Mullin John A. , Dahm Werner J. A.
Published: April 2006

Results are presented from quantitative assessments of the accuracy of velocity gradients measured by a dual-plane stereo particle image velocimetry (DSPIV) technique that allows direct, highly resolved, nonintrusive measurements of all nine simultaneous components of the velocity gradient tensor fields ∂ui∕∂xj at the quasi-universal intermediate and small scales of turbulent shear flows. The present results systematically determine the sources of errors in DSPIV measurements and the resulting accuracy of velocity gradients obtained from such measurements. Intrinsic errors resulting from asymmetric stereo imaging are found by synthetic particle imaging to be no larger than 0.8%. True particle imaging in finite-thickness light sheets is found from single-plane imaging tests to produce net errors in measured velocity differences of 6% for in-plane components and 10% for out-of-plane components. Further errors from limits on the accuracy of independent dual light sheet generation and positioning are found from coincident-plane imaging tests to produce overall errors of 9% and 16% in the in-plane and out-of-plane velocity differences. Practical DSPIV velocity gradient component measurements are found from separated-plane imaging tests in a turbulent shear flow to show excellent similarity in on-diagonal (i=j) and off-diagonal (i≠j) components of ∂ui∕∂xj, as well as mean-square gradient values showing agreement within 1%–4% of ideal isotropic limit values. The resulting measured divergence values are consistent with overall rms errors obtained from the coincident-plane imaging tests. Collectively, these results establish the accuracy with which all nine simultaneous components of the velocity gradient tensor fields ∂ui∕∂xj can be obtained from DSPIV measurements at the quasi-universal intermediate and small scales of turbulent shear flows.
Liquid-liquid phase separation and static light scattering of concentrated ternary mixtures of bovine α and γB crystallins
Authors: Thurston George M.
Published: April 2006

We have used light scattering, turbidimetry, and thermodynamic analysis to study the phase diagram of concentrated aqueous mixtures of the bovine lens proteins, γB crystallin, and α crystallin. We find that dilute α crystallin raises the phase separation temperature of concentrated γB crystallin, while more concentrated α crystallin suppresses phase separation. Very concentrated α∕γB mixtures can reversibly cloud above 37°C, even though γB alone phase separates only below temperatures near 0°C, and α does not phase separate. At the scattering vector magnitude used, high-concentration α∕γB mixtures scatter less light than the weighted average of their component α and γB solutions, while low-concentration α∕γB mixtures scatter more than such a weighted average. We use a mean-field thermodynamic analysis of such ternary mixtures to show that the observed light scattering and phase boundaries of α and γB crystallin mixtures give evidence for prominent local fluctuations of relative protein composition. In the single phase, these fluctuations scatter comparatively little light, but are associated with enhanced thermodynamic instability. By applying this analysis to the experimental tie lines we estimate the magnitude of the saddlelike component of the free energy near the aqueous-γB critical point.
Field-dependent thermal and electrical transports in Cu∕CoFe multilayer
Authors: Yang Y. , Zhu J.-G. , White R. M. , Asheghi M.
Published: April 2006

This paper reports field-dependent thermal and electrical conductivity measurements of a 144 nm thick Cu∕CoFe giant magnetoresistive multilayer made of extremely thin periodic layers (12 and 21 Å for CoFe and Cu layers, respectively), using steady-state Joule heating and electrical resistance thermometry in suspended bridges between 300 and 380 K. Large decreases in the electrical and thermal resistivities from antiparallel to parallel alignment of the magnetization in the film, referred to as the giant magnetoresistance (GMR) and giant magnetothermal resistance (GMTR), are observed. GMR ratios of 17% and 12% and large GMTR ratios of 25% and 58% are measured at 300 and 380 K, respectively. It is concluded that different electron scattering rates for charge and heat transports in the ferromagnetic CoFe layer are responsible for the difference between the GMR and GMTR ratios. While the previous works only reported the relative change in thermal conductance due to applied magnetic field, the present manuscript reports the absolute value of the field-dependent thermal conductivity of Cu∕CoFe multilayer.
The dynamic susceptibility in glass forming molecular liquids: The search for universal relaxation patterns II
Authors: Blochowicz T. , Gainaru C. , Medick P. , Tschirwitz C. , Rössler E. A.
Published: April 2006

The susceptibility spectra of ten molecular glass formers are completely interpolated by an extension of the generalized gamma distribution of correlation times. The data cover at least 15 decades in frequency and the interpolation includes both α peak and excess wing. It is shown that the line shape parameters and the time constant of the α relaxation are related to each other. Master curves are identified by a scaling procedure that involves only three parameters, namely, the glass transition temperature Tg, the fragility m, and the excess wing exponent at Tg. This holds independent of whether a further secondary relaxation peak is present or not. Above a crossover temperature Tx this unique evolution of the line shape parameters breaks down, and a crossover to a simple peak susceptibility without excess wing is observed. Here, the frequency-temperature superposition principle holds in good approximation up to temperatures well above the melting point. It turns out that the crossover coincides with the temperature at which the low-temperature Vogel-Fulcher law starts to fail upon heating. Thus, the so-called Stickel temperature gets a more physical meaning as it marks a qualitative change in the evolution of the susceptibility spectra of glass formers. Moreover, the interrelation of the line shape parameters can explain why the “Nagel scaling” works in some approximation. Our study demonstrates that the excess wing in molecular glass formers is a secondary relaxation, which is linked to the α process in a unique way.
Dielectric constant engineering with polymethylmethacrylate-graphite metastate composites in the terahertz region
Authors: Seo M. A. , Lee J. W. , Kim D. S.
Published: April 2006

A method for manufacturing terahertz absorber is presented. Varying fractions of graphite powder are mixed with the host poly methylmethacrylate powder and compress molded. The shielding efficiency, together with real and imaginary parts of the dielectric constant, is unambiguously determined by terahertz time domain spectroscopy in the continuous frequency range of 0.1–1.6THz. While the composites are absorptive in most of the frequency range with relatively small reflection, it turns metallic at a high enough graphite fraction of 35.7%: there exists a zero crossing of the real part of dielectric function εr(ω) to negative values below 0.22THz. Our method provides an easy-to-control way of manufacturing terahertz absorbers with a wide range of shielding efficiency and low reflectance.
A numerical study of relaxation in a two dimensional dipolar lattice
Authors: Jiménez Rolando Placeres , Zayas Fidel Guerrero , M’Peko Jean Claude , Eiras Jose Antonio
Published: April 2006

A dynamic model is proposed for ferroelectrics. The mathematical model is a system of nonlinear differential equations that results from considered dipole-dipole and dipole external field interaction for each dipole. All the simulations are carried out integrating numerically the system of ordinary differential equations for a plane dipole arrangement. On simulation of relaxation of polarization in time domain a potential law is found, in good agreement with experimental evidence. The influence of several parameters in system response is discussed. Finally, hysteresis loop was obtained and shows noise behavior.
Vibrational excitons in α-helical polypeptides: Multiexciton self-trapping and related infrared transient absorption
Authors: Tsivlin Dmitry V. , Meyer Hans-Dieter , May Volkhard
Published: April 2006

Based on the multiexciton expansion of a model Hamiltonian, an accurate quantum-dynamical description of vibrational states formed by amide modes in α-helical polypeptides is presented. Using the multiconfiguration time-dependent Hartree method, linear and pump-probe infrared absorption spectra are calculated by numerical time propagation of the exciton-chain vibrational wave function. The formation of self-trapped exciton states is discussed within the approximation of adiabatic excitons and within the full quantum description.
Spatial distribution of soft x-ray line emissions from aluminum plasma excited by a pair of femtosecond-laser pulses
Authors: Okano Yasuaki , Oguri Katsuya , Nishikawa Tadashi , Nakano Hidetoshi
Published: April 2006

We measured the time-integrated, spatially resolved spectra of soft x rays emitted from laser-induced aluminum plasma to characterize its spatial features. The plasma was excited by an intense femtosecond-laser pulse with a controlled artificial prepulse at intensities of 9.9×1015 and 6.4×1014W∕cm2, respectively. The dependence of the spectra on the time intervals between the main pulse and the prepulse was obtained for delay times of 0–3ns. The strongest emissions in soft x-ray range occurred in a narrow region less than 50μm from the target surface. In contrast to the continuum spectrum, the prepulse technique causes the Al3+2p6−2p53s emission to extend more than 600μm from the target surface. We showed that the line emission can be separated spatially from the other continuum component of the emission spectra and that the extension length increased with increases in the pulse-separation time.
Frequency mixing characteristics of room temperature resonant tunneling diodes at 100 and 200GHz
Authors: Hori Toshihiro , Ozono Tetsuro , Orihashi Naoyuki , Asada Masahiro
Published: April 2006

Frequency mixing characteristics are examined for room temperature resonant tunneling diodes at 100GHz in the fundamental mode and at 200GHz in the second harmonic mode. At the peak voltage of the dc I-V curves, the output signal level was the highest for fundamental mixing and the lowest as a dip for second harmonic mixing. Experimentally obtained data are compared with the values calculated by a circuit analysis with finite sinusoidal voltage swings. The results indicate that the experimental results are in good agreement with the numerical predictions without capacitance for detection, fundamental mixing, and second harmonic mixing. Particularly, mixing characteristics with large input power, which cannot be treated by small signal analysis, are well explained by the model used here.