bluuebunny/crossref_metadata_2025 huggingface dataset:
Panel Conditioning in Longitudinal Studies: Evidence From Labor Force Items in the Current Population Survey
Authors: Halpern-Manners Andrew , Warren John Robert
Published: August 2012

Does participating in a longitudinal survey affect respondents’ answers to subsequent questions about their labor force characteristics? In this article, we investigate the magnitude of panel conditioning or time-in-survey biases for key labor force questions in the monthly Current Population Survey (CPS). Using linked CPS records for household heads first interviewed between January 2007 and June 2010, our analyses are based on strategic within-person comparisons across survey months and between-person comparisons across CPS rotation groups. We find considerable evidence for panel conditioning effects in the CPS. Panel conditioning downwardly biases the CPS-based unemployment rate, mainly by leading people to remove themselves from its denominator. Across surveys, CPS respondents (claim to) leave the labor force in greater numbers than otherwise equivalent respondents who are participating in the CPS for the first time. The results cannot be attributed to panel attrition or mode effects. We discuss implications for CPS-based research and policy as well as for survey methodology more broadly.
Interface Biology of Implants
Authors: Rychly Joachim
Published: August 2012

To successfully apply implant materials for regenerative processes in the body, understanding the mechanisms at the interface between cells or tissues and the artificial material is of critical importance. This topic is becoming increasing relevant for clinical applications. For the fourth time, around 200 scientists met in Rostock, Germany for the international symposium “Interface Biology of Implants”. The aim of the symposium is to promote interdisciplinary dialogue between scientists from different disciplines. The symposium also emphasizes the need of this applied scientific field for permanent input from basic sciences.
Familial hypertrophic cardiomyopathy related E180G mutation increases flexibility of human cardiac α‐tropomyosin
Authors: Loong Campion K.P. , Zhou Huan-Xiang , Bryant Chase P.
Published: August 2012

α‐Tropomyosin (αTm) is central to Ca2+‐regulation of cardiac muscle contraction. The familial hypertrophic cardiomyopathy mutation αTm E180G enhances Ca2+‐sensitivity in functional assays. To investigate the molecular basis, we imaged single molecules of human cardiac αTm E180G by direct probe atomic force microscopy. Analyses of tangent angles along molecular contours yielded persistence length corresponding to ∼35% increase in flexibility compared to wild‐type. Increased flexibility of the mutant was confirmed by fitting end‐to‐end length distributions to the worm‐like chain model. This marked increase in flexibility can significantly impact systolic and possibly diastolic phases of cardiac contraction, ultimately leading to hypertrophy.
Retracted: miR‐518b is down‐regulated, and involved in cell proliferation and invasion by targeting Rap1b in esophageal squamous cell carcinoma
Authors: Zhang Mingxin , Zhou Suna , Zhang Lingmin , Zhang Jia , Cai Hui , Zhu Jinxiang , Huang Chen , Wang Jiansheng
Published: August 2012

MicroRNAs (miRNAs) represent a class of small non‐coding RNAs that regulate gene expression at the post‐transcriptional levels. Recent studies show that miRNAs may function as oncogenes or tumor suppressor genes. In this study, we demonstrated that miR‐518b was down‐regulated in esophageal squamous cell carcinoma (ESCC) tissues and correlated with metastasis and survival. miR‐518b suppressed the proliferation by inducing apoptosis and repressed the invasion in ESCC cells, but had no effect on the cell cycle. Furthermore, Rap1b was revealed to be directly regulated by miR‐518b. These findings indicate that miR‐518b may function as a tumor suppressor by targeting Rap1b in the development of ESCC and has important clinical and prognostic value.
Micro-bubble morphologies following drop impacts onto a pool surface
Authors: Thoroddsen S. T. , Thoraval M.-J. , Takehara K. , Etoh T. G.
Published: August 2012

When a drop impacts at low velocity onto a pool surface, a hemispheric air layer cushions and can delay direct contact. Herein we use ultra-high-speed video to study the rupture of this layer, to explain the resulting variety of observed distribution of bubbles. The size and distribution of micro-bubbles is determined by the number and location of the primary punctures. Isolated holes lead to the formation of bubble necklaces when the edges of two growing holes meet, whereas bubble nets are produced by regular shedding of micro-bubbles from a sawtooth edge instability. For the most viscous liquids the air film contracts more rapidly than the capillary–viscous velocity through repeated spontaneous ruptures of the edge. From the speed of hole opening and the total volume of micro-bubbles we conclude that the air sheet ruptures when its thickness approaches ${\ensuremath{\sim} }100~\mathrm{nm} $.
Does the Parent–Child Relationship Contribute to Children's and Parents’ Anxiety?
Authors: Matthewson Mandy , Smith Rosanne Burton , Montgomery Iain
Published: August 2012

This study explored which parent–child relationship factors are most important in predicting children's and parents’ anxiety. The participants were 52 fathers, 52 mothers, 30 sons and 30 daughters. Parents completed a measure of anxiety and a measure of the parent–child relationship. Children completed two measures of anxiety. Mothers’ communication was found to be the only significant predictor of sons’ anxiety. Daughters’ anxiety was significantly predicted by fathers’ communication and mothers’ satisfaction with parenting. These findings signal the important role the opposite-sex parent has in children's anxiety. Moreover, feeling supported as a parent and having the ability to communicate effectively with their children are important predictors of parents’ wellbeing.
Sex Differences in Mate Preferences in Australia: Exploring Evolutionary and Social-Economic Theories
Authors: March Evita , Bramwell Ann
Published: August 2012

Extensive research on sex differences in mate preferences has found that men desire the physical attractiveness of a potential partner more than do women, and women desire the status and resources potential partner more than do men. The aim of the current study was to explore these sex differences in mate preferences specifically in the Australian culture, a culture that has not yet received attention in mate preferences literature. The current study predicted Australian men and women would exhibit traditional sex differences in mate preferences. The current study also aimed to explore the effect of variation in Australian women's socio-economic status (SES) and their corresponding ratings of characteristics in a potential partner. One hundred and forty-four Australian participants completed a mate selection questionnaire and results supported traditional sex differences in mate preferences. Results also found that women's SES had no effect on desirability of status and resources, but positively related to desirability of physical attractiveness in a potential partner. Results are discussed in terms of evolutionary and social-economic theories.
Modeling and robust backstepping control of an underactuated quadruped robot in bounding motion
Authors: Kazemi Hamed , Majd Vahid Johari , Moghaddam Majid M.
Published: August 2012

In this paper, a model-based exponential stabilization of a quadruped robot is studied in bounding motion. The dynamics of the five-link planar underactuated mechanical model of the quadruped robot with four actuated joints system is derived. It is shown that the dynamical equation of the proposed simplified model belongs to a class of second-order nonholonomic mechanical systems which cannot be stabilized by any smooth time-invariant state feedback. Utilizing a coordinate transformation based on the so-called normalized momentum, a robust backstepping control method is presented for the quadruped robot. Both theoretical analysis and numerical simulations show that the robust backstepping controller can stabilize the underactuated quadruped robot so that it could balance on its rear legs and track a desired trajectory. Despite the model parameter uncertainties, the robustness of the controller is maintained. The simulation results show the effectiveness of the proposed method.
Sketching across design domains: Roles and formalities
Authors: Eckert Claudia , Blackwell Alan , Stacey Martin , Earl Christopher , Church Luke
Published: August 2012

To complement studies on design sketching within particular phases of design processes in specific design domains, this paper analyzes descriptions of design processes given by designers from a wide variety of fields. This research forms part of a wider project on comparisons across design domains and draws attention to the many types and properties of sketches in different contexts. Further, it focuses on the multiple roles that sketching can take in idea generation, as well as in reasoning and communicating design ideas. In particular this paper examines how the different types and roles of sketches can be more or less formal and how this can lead to misunderstandings.
The influence of sketch quality on perception of product-idea creativity
Authors: Kudrowitz Barry , Te Paula , Wallace David
Published: August 2012

This paper explores the relationship between the quality of a sketch and how others perceive the creativity of the idea portrayed by the sketch. In this study, sketch quality is characterized through its line work, perspective, and proportions. Four different toaster ideas were each sketched by four people with different backgrounds and levels of sketching proficiency. Then, 360 reviewers ranked the toasters for idea creativity, referring to a set of four sketches: one sketch for each toaster concept. The level of sketch quality for each toaster concept was varied among one of four quality levels. Higher quality idea sketches were found to correlate with higher creativity rank (p> 0.005), and lower quality sketches correlated with a lower creativity rank (p> 0.0005). A toaster idea portrayed with the highest quality level of sketch was 2.3 times more likely to be ranked as the most creative idea within the given set of idea sketches. The results underscore the importance of how an idea is presented, and support the need for sketching instruction in engineering and design curriculum.
Sketch-based shape exploration using multiscale free-form surface editing
Authors: Orbay Günay , Yümer Mehmet Ersın , Kara Levent Burak
Published: August 2012

The hierarchical construction of solid models with current computer-aided design systems provide little support in creating and editing free-form surfaces commonly encountered in industrial design. In this work, we propose a new design exploration method that enables sketch-based editing of free-form surface geometries where specific modifications can be applied at different levels of detail. This multilevel detail approach allows the designer to work from existing models and make alterations at coarse and fine representations of the geometry, thereby providing increased conceptual flexibility during modeling. At the heart of our approach lies a multiscale representation of the geometry obtained through a spectral analysis on the discrete free-form surface. This representation is accompanied by a sketch-based surface editing algorithm that enables edits to be made at different levels. The seamless transfer of modifications across different levels of detail facilitates a fluid exploration of the geometry by eliminating the need for a manual specification of the shape hierarchy. We demonstrate our method with several design examples.
Validation of a quantitative FFQ for a study of diet and risk of colorectal adenoma among Japanese Brazilians
Authors: Pakseresht Mohammadreza , Miyajima Nelson Tomio , Shelton Andrew , Iwasaki Motoki , Tsugane Shoichiro , Le Marchand Loic , Sharma Sangita
Published: August 2012

Objective

To assess the validity of a 161-item quantitative FFQ (QFFQ) that was developed to evaluate dietary risk factors for a colorectal adenoma case–control study.

Design

A cross-sectional validation study of the QFFQ against 4 d food diary using Pearson correlation coefficients, cross-classification, weighted κ statistics and Bland–Altman plotting.

Setting

Two hospitals in São Paulo, Brazil.

Subjects

Ninety-seven healthy Japanese-Brazilian adults (40–75 years) were recruited. One participant was excluded from the analysis due to unusual energy intake report.

Results

Mean daily nutrient intakes from the QFFQ were higher than from the food diary. The mean Pearson correlation coefficient for nutrient intakes between the QFFQ and the average of the 4 d food diary was 0·43, and increased to 0·45 after correcting correlations for attenuation due to residual day-to-day variation in the food diary measurements. Adjustment for total energy and further adjustment for age and gender decreased the correlation; however, 77 % of observations remained in the same or adjacent quartiles with a mean weighted κ of 0·22. Bland–Altman plots on loge-transformed data showed no linear trend between the differences and means for energy, fat, protein, total folate and vitamin C. Compared with the food diary, the QFFQ showed consistently reasonable performance for dietary fibre, total folate, retinol, riboflavin and vitamin C.

Conclusions

This investigation supports the relative validity of the QFFQ as a method for assessing long-term dietary intake. The instrument will be a useful tool in the analysis of diet–adenoma associations in the case–control study.
Observations on cohesive bed reworking by waves: Atchafalaya Shelf, Louisiana
Authors: Sahin Cihan , Safak Ilgar , Sheremet Alexandru , Mehta Ashish J.
Published: August 2012

Wave, current, acoustic backscatter and suspended sediment concentration measurements (both single‐point and vertical profiles estimated by conversion of acoustic backscatter data) are used to investigate wave‐current‐cohesive sediment interaction on the muddy Atchafalaya inner shelf. During an energetic storm, we propose that bed state follows a cycle of dilation due to fluidization, erosion, deposition with fluid mud formation and consolidation. A one‐dimensional‐vertical cohesive sediment transport model is calibrated using current and concentration profiles to estimate the physical parameters that could not be measured directly, e.g., bottom stresses. Estimated bed position and computed bottom stresses suggest that the critical erosion threshold is in the range of 0.3 Pa to 0.5 Pa. The study site is impacted by a sediment‐laden fresh water plume coming from the Atchafalaya River mouth. Bed density evolution during the storm is estimated from vertical sediment exchange between the water column and the bed excluding the duration of passage of a sediment‐carrying water front. The values are in the range of 1,030 kg/m3 to 1,200 kg/m3and indicate that the bed density increases during the erosion phase and decreases during deposition. At the end of the storm, it shows a steady increasing trend during hindered settling and exceeds the space‐filling value during consolidation. Both the critical erosion shear stress and bed density values are consistent with the results of laboratory tests on samples from the experimental site.
Linking statistical bias description to multiobjective model calibration
Authors: Reichert P. , Schuwirth N.
Published: August 2012

In the absence of model deficiencies, simulation results at the correct parameter values lead to an unbiased description of observed data with remaining deviations due to observation errors only. However, this ideal cannot be reached in the practice of environmental modeling, because the required simplified representation of the complex reality by the model and errors in model input lead to errors that are reflected in biased model output. This leads to two related problems: First, ignoring bias of output in the statistical model description leads to bias in parameter estimates, model predictions and, in particular, in the quantification of their uncertainty. Second, as there is no objective choice of how much bias to accept in which output variable, it is not possible to design an “objective” model calibration procedure. The first of these problems has been addressed by introducing a statistical (Bayesian) description of bias, the second by suggesting the use of multiobjective calibration techniques that cannot easily be used for uncertainty analysis. We merge the ideas of these two approaches by using the prior of the statistical bias description to quantify the importance of multiple calibration objectives. This leads to probabilistic inference and prediction while still taking multiple calibration objectives into account. The ideas and technical details of the suggested approach are outlined and a didactical example as well as an application to environmental data are provided to demonstrate its practical feasibility and computational efficiency.
Application of Bayesian geostatistics for evaluation of mass discharge uncertainty at contaminated sites
Authors: Troldborg Mads , Nowak Wolfgang , Lange Ida V. , Santos Marta C. , Binning Philip J. , Bjerg Poul L.
Published: August 2012

Mass discharge estimates are increasingly being used when assessing risks of groundwater contamination and designing remedial systems at contaminated sites. Such estimates are, however, rather uncertain as they integrate uncertain spatial distributions of both concentration and groundwater flow. Here a geostatistical simulation method for quantifying the uncertainty of the mass discharge across a multilevel control plane is presented. The method accounts for (1) heterogeneity of both the flow field and the concentration distribution through Bayesian geostatistics, (2) measurement uncertainty, and (3) uncertain source zone and transport parameters. The method generates conditional realizations of the spatial flow and concentration distribution. An analytical macrodispersive transport solution is employed to simulate the mean concentration distribution, and a geostatistical model of the Box‐Cox transformed concentration data is used to simulate observed deviations from this mean solution. By combining the flow and concentration realizations, a mass discharge probability distribution is obtained. The method has the advantage of avoiding the heavy computational burden of three‐dimensional numerical flow and transport simulation coupled with geostatistical inversion. It may therefore be of practical relevance to practitioners compared to existing methods that are either too simple or computationally demanding. The method is demonstrated on a field site contaminated with chlorinated ethenes. For this site, we show that including a physically meaningful concentration trend and the cosimulation of hydraulic conductivity and hydraulic gradient across the transect helps constrain the mass discharge uncertainty. The number of sampling points required for accurate mass discharge estimation and the relative influence of different data types on mass discharge uncertainty is discussed.
Carbon cycle dynamics following the end‐Triassic mass extinction: Constraints from paired δ13Ccarb and δ13Corg records
Authors: Bachan Aviv , van de Schootbrugge Bas , Fiebig Jens , McRoberts Christopher A. , Ciarapica Gloria , Payne Jonathan L.
Published: August 2012

Constraining the carbon isotopic changes associated with the end‐Triassic mass extinction is key to understanding the causes of the extinction and dynamics of recovery from it. Yet the pattern and timing of δ13C variation surrounding the extinction remain poorly constrained. Here we present close to 1000 new δ13C measurements from six newly sampled sections in Italy. We observe a sharp negative excursion in δ13Ccarb coincident with the disappearance of the Triassic fauna, and two positive excursions above it. The negative δ13Ccarb excursion in these sections does not occur in δ13Corg suggesting a possible diagenetic origin. In contrast, the interval of elevated δ13C occurs in both carbonate and organic carbon, suggesting that it is likely to be a primary feature. The positive excursions in the Lombardy Basin (southern Alps) and Mt. Cefalo (southern Apennines) appear to be time correlative on the basis of their position above the disappearance of characteristically Triassic biota. However, it is less certain that they are time correlative with positive excursions in other sections worldwide, as few options exist that honor both bio‐ and chemostratigraphy. Nonetheless, similarity to other events that are interpreted as global, as well as carbon cycle considerations, suggest that the isotopic enrichment is best interpreted to reflect a shift in the isotope composition of the global surface carbon reservoir. Our data indicate that perturbation of the global carbon cycle was not confined to the immediate vicinity of the extinction interval, but rather persisted for substantial length of geologic time afterwards.
Changes in European summer temperature variability revisited
Authors: Fischer E. M. , Rajczak J. , Schär C.
Published: August 2012

Summer temperature variability has been projected to increase in Central Europe in response to anthropogenic greenhouse gas forcing. Based on an unprecedented set of global and regional climate models from the ENSEMBLES project, we assess the robustness of these projections on interannual to daily time scales. In comparison to previous analyses using PRUDENCE simulations, we find a more diverse climate change signal for interannual summer temperature variability and a clear dependence upon present‐day model performance. Models that realistically represent present‐day variability, tend to consistently project increasing interannual variability at the end of the 21st century. We demonstrate that the partitioning of latent and sensible heat fluxes controlled by soil moisture is crucial to understand the projected changes across the multi‐model experiment. The projected increase in daily summer temperature variability is more robust and consistently simulated by all models. Likewise, all models consistently project reduced daily temperature variability in winter. Thus, it is a robust signal across the entire ensemble that in summer and south‐central Europe hot extremes warm stronger than the mean, and in winter and northern Europe cold extremes warm stronger than mean temperatures.
Dissolved organic matter export from a forested watershed during Hurricane Irene
Authors: Yoon Byungman , Raymond Peter A.
Published: August 2012

We incorporate high‐resolution time‐series data to calculate the total amount of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) transported during Hurricane Irene in Esopus Creek in New York (August 2011). During this 200‐yr event the Esopus Creek experienced a 330‐fold discharge increase and a 4‐fold increase in concentration, resulting in the export of roughly 43% and 31% of its average annual DOC and DON fluxes, respectively, in just 5 days. The source of this large dissolved organic matter (DOM) flux also shifted during its course and showed an increased contribution of aromatic organic matter. We conclude that more frequent large events due to climate change will increase the export of terrigenous dissolved organic matter, and potentially impact the water quality and biogeochemistry of lakes and coastal systems. In addition, we show that the use of conventional models for extreme events lead to erroneous flux calculations, unless supported by high resolution data collected during the events.
How large are projected 21st century storm track changes?
Authors: Harvey B. J. , Shaffrey L. C. , Woollings T. J. , Zappa G. , Hodges K. I.
Published: August 2012

Projected changes in the extra‐tropical wintertime storm tracks are investigated using the multi‐model ensembles from both the third and fifth phases of the World Climate Research Programme's Coupled Model Intercomparison Project (CMIP3 and CMIP5). The aim is to characterize the magnitude of the storm track responses relative to their present‐day year‐to‐year variability. For the experiments considered, the ‘middle‐of‐the‐road’ scenarios in each CMIP, there are regions of the Northern Hemisphere where the responses of up to 40% of the models exceed half of the inter‐annual variability, and for the Southern Hemisphere there are regions where up to 60% of the model responses exceed half of the inter‐annual variability.
Impact of diatom‐diazotroph associations on carbon export in the Amazon River plume
Authors: Yeung Laurence Y. , Berelson William M. , Young Edward D. , Prokopenko Maria G. , Rollins Nick , Coles Victoria J. , Montoya Joseph P. , Carpenter Edward J. , Steinberg Deborah K. , Foster Rachel A. , Capone Douglas G. , Yager Patricia L.
Published: August 2012

Offshore tropical river plumes are associated with areas of high N2 fixation (diazotrophy) and biological carbon drawdown. Episodic blooms of the diatom Hemiaulus hauckii and its diazotrophic cyanobacterial symbiont Richelia intracellularisare believed to dominate that carbon drawdown, but the mechanism is not well understood. We report primary productivity associated with blooms of these diatom‐diazotroph assemblages (DDAs) in the offshore plume of the Amazon River using simultaneous measurements of O2/Ar ratios and the triple‐isotope composition of dissolved O2. In these blooms, we observe peaks in net community productivity, but relatively small changes in gross primary productivity, suggesting that DDA blooms increase the ecosystem carbon export ratio more than twofold. These events of enhanced export efficiency lead to biological uptake of dissolved inorganic carbon and silicate, whose longer mixed‐layer residence times otherwise obscure the differential impact of DDAs. The shorter‐term rate estimates presented here are consistent with the results derived from longer‐term geochemical tracers, confirming that DDAs drive a significant biological CO2 pump in tropical oceans.
Evolution of CIR storm on 22 July 2009
Authors: Perez J. D. , Grimes E. W. , Goldstein J. , McComas D. J. , Valek P. , Billor N.
Published: August 2012

Global images of ion intensities are deconvolved from TWINS ENA images during the main and recovery phase of a CIR storm on 22 July 2009. The global spatial ion images taken at different times, along with solar wind data, geomagnetic activity indices, geosynchronous orbit observations, and in situ measurements from the THEMIS mission provide a picture of the evolution of the ring current during both the main phase and early recovery phase of the storm. Major features of the evolution are consistent with expectations based upon time dependent geomagnetic indices, e.g., SYM/H and ASY/H, and geosynchronous orbit detection of dipolarizations from GOES 11 and 12. Direct comparisons are made with in situ THEMIS ESA and SST spectral measurements. The peak energy of the ion spectrum in the ring current is seen to decrease in the recovery phase. The time evolution of the ion energy spectra over the range from 2.5 to 97.5 keV at the spatial peaks of the ring current in the inner magnetosphere obtained from ENA images is presented for the first time.
Effect of cloud cover and atmospheric circulation patterns on the observed surface solar radiation in Europe
Authors: Chiacchio Marc , Vitolo Renato
Published: August 2012

This study aims at quantifying the most important factors affecting variations in downward surface shortwave radiation (DSW) in Europe including cloud cover and atmospheric circulation patterns. The role of observed cloud cover on DSW was analyzed through generalized linear models using DSW measurements obtained from the Global Energy Balance Archive during 1971–1996. Stations of DSW in Europe were selected to assess how they were affected by clouds. Overall cloud cover had a statistically significant negative relationship and a non‐significant positive relationship on DSW for relatively nearby and distant cloud cover stations, respectively. The exception was west‐central Europe where a significant negative effect over the whole continent was found suggesting an association with larger cloud structures. This showed that point DSW measurements can be spatially representative for larger scale variability. In line with other studies we found a strong seasonal effect of cloud cover on DSW mainly in northern Europe in spring and summer and in southern Europe in winter and autumn. The North Atlantic Oscillation was most important in winter with a significant negative effect in northern to central Europe and a positive non‐significant effect in the south. The Mediterranean Oscillation exhibited mainly a positive effect in winter with significance in southern Europe and non‐significance in central Europe. The North Sea Caspian Pattern primarily showed a positive effect with significance in east‐central and northern Europe in spring and summer. The interrelationship found between these climatic variables could improve the understanding of a linkage to temperature and precipitation patterns in Europe.
Analytical estimation of droplet concentration at cloud base
Authors: Pinsky M. , Khain A. , Mazin I. , Korolev A.
Published: August 2012

In the present study a new method of calculating droplet concentration near cloud base is proposed. The ratio of maximum supersaturation Smax to the liquid water mixing ratio when Smax is reached near cloud base is found to be universal, and it does not depend on the vertical velocity w and droplet number concentration N. It is found that Smax depends on vertical velocity as Smax ∝ w3/4 and on droplet concentration as Smax ∝ N−1/2. The droplet concentration calculated using the simple approach agrees well with exact solutions obtained numerically using high precision parcel models. Comparison with the results of other parameterizations is presented. It is demonstrated that the approach proposed in the study can be applied to an arbitrary form of activation spectra or any CCN size distribution given either analytically or by tables. Moreover, it can be applied for the cases when the CCN size spectrum changes with time. Temperature dependencies of Smax and related quantities are analyzed.
GOES‐10 microphysical retrievals in marine warm clouds: Multi‐instrument validation and daytime cycle over the southeast Pacific
Authors: Painemal David , Minnis Patrick , Ayers J. Kirk , O'Neill Larry
Published: August 2012

The daytime evolution of warm cloud microphysical properties over the southeast Pacific during October–November 2008 is investigated with optical/infrared retrievals from the Tenth Geostationary Operational Environmental Satellite (GOES‐10) imager. GOES‐10 retrievals, produced at NASA Langley Research Center, are validated against in situ aircraft observations and with independent satellite observations. Comparisons with in situ observations reveal high linear correlations (r) for cloud effective radius (re) and optical thickness (τ) (r = 0.89 and 0.69 respectively); nevertheless, a GOES‐10 positive mean re bias of 2.3 μm is apparent, and consistent with other previously reported satellite biases. Smaller biases are found for liquid water path (LWP) and an adiabatic‐based cloud droplet number concentration (Nd), both variables derived by combining re and τ.In addition, GOES‐10 observations are well correlated with their Moderate Resolution Imaging Spectroradiometer (MODIS) counterparts, but with smaller biases and root‐mean‐square errors for the Aqua satellite passes, arguably associated with a better calibrated MODIS‐Aqua instrument relative to MODIS‐Terra. Furthermore, the excellent agreement between GOES‐10 LWP and microwave‐based satellite retrievals, especially at high solar zenith angles (>60°), provide further evidence of the utility of using GOES‐10 retrievals to represent the daytime cloud cycle. In terms of the daytime cycle, GOES‐10 observations show an afternoon minimum in LWP and an increase thereafter, consistent with satellite microwave climatologies. Theτ cycle explains most of the LWP variance with both variables in phase, minima near noon along the coast, and a 13:30–14:00 local solar time (LST) minimum offshore. In contrast, re is not exactly in phase with LWP and τ, having a minimum approximately at 12:30 LST throughout the domain. A unique feature is a striking re maximum along the coast at 16:15 LST, concomitant with a faster τ recovery. An explanation for a coastal reafternoon maximum is lacking although this is consistent with an enhancement of the updraft velocity reported in previous modeling studies. Finally, the GOES‐derived Nd (Nd ∝ τ1/2 re−5/2) shows a complex daytime cycle with maxima at 7:15 and 13:15 LST. While the first maximum is driven by large τ, the second one is mainly explained by a minimum in re.
Soil heterogeneity in Mojave Desert shrublands: Biotic and abiotic processes
Authors: Caldwell Todd G. , Young Michael H. , McDonald Eric V. , Zhu Jianting
Published: August 2012

Geological and ecological processes play critical roles in the evolution of desert piedmonts. Feedback between fast cyclic biotic and slow cumulative pedogenic processes on arid alluvial fan systems results in a heterogeneous landscape of interspace and canopy microsites. Defining the spatial extent between these processes will allow a better connection to ecosystem service and climate change. We use a soil chronosequence in the Mojave Desert and high spatial resolution infiltrometer measurements along transects radiating from canopies of perennial shrubs to assess the extent of biotic and abiotic processes and the heterogeneity of soil properties in arid shrublands. Results showed higher saturated conductivity under vegetation regardless of surface age, but it was more conspicuous on older, developed soils. At proximal locations to the shrub, bulk density, soil structure grade, silt, and clay content significantly increased radially from the canopy, while sand and organic material decreased. Soil properties at distal locations 2–5 times the canopy radius had no significant spatial correlation. The extent of the biotic influence of the shrub was 1.34 ± 0.32 times the canopy radius. Hydraulic properties were weakly correlated in space, but 75% of the variance could be attributed to sand content, soil structure grade, mean‐particle diameter, and soil organic material, none of which are exclusively biotic or abiotic. The fast cyclic biotic processes occurring under vegetation are clearly overprinted on slow cumulative abiotic processes, resulting in the deterministic variability observed at the plant scale.
Impact of radar‐rainfall error structure on estimated flood magnitude across scales: An investigation based on a parsimonious distributed hydrological model
Authors: Cunha Luciana K. , Mandapaka Pradeep V. , Krajewski Witold F. , Mantilla Ricardo , Bradley Allen A.
Published: August 2012

The goal of this study is to diagnose the manner in which radar‐rainfall input affects peak flow simulation uncertainties across scales. We used the distributed physically based hydrological model CUENCAS with parameters that are estimated from available data and without fitting the model output to discharge observations. We evaluated the model's performance using (1) observed streamflow at the outlet of nested basins ranging in scale from 20 to 16,000 km2 and (2) streamflow simulated by a well‐established and extensively calibrated hydrological model used by the US National Weather Service (SAC‐SMA). To mimic radar‐rainfall uncertainty, we applied a recently proposed statistical model of radar‐rainfall error to produce rainfall ensembles based on different expected error scenarios. We used the generated ensembles as input for the hydrological model and summarized the effects on flow sensitivities using a relative measure of the ensemble peak flow dispersion for every link in the river network. Results show that peak flow simulation uncertainty is strongly dependent on the catchment scale. Uncertainty decreases with increasing catchment drainage area due to the aggregation effect of the river network that filters out small‐scale uncertainties. The rate at which uncertainty changes depends on the error structure of the input rainfall fields. We found that random errors that are uncorrelated in space produce high peak flow variability for small scale basins, but uncertainties decrease rapidly as scale increases. In contrast, spatially correlated errors produce less scatter in peak flows for small scales, but uncertainty decreases slowly with increasing catchment size. This study demonstrates the large impact of scale on uncertainty in hydrological simulations and demonstrates the need for a more robust characterization of the uncertainty structure in radar‐rainfall. Our results are diagnostic and illustrate the benefits of using the calibration‐free, multiscale framework to investigate uncertainty propagation with hydrological models.
Tactical NAV: Innovation in the US Army
Authors: Adams Dennis A , Ives Blake , Junglas Iris
Published: August 2012

Increasingly, employees are innovating with their own consumer technologies (such as smartphones and tablets), rather than looking to their companies’ IT departments to lead technical innovation. This can give rise to tension between employees and IT departments, and this tension is particularly pronounced in the US military, where long systems development times run headlong into young, technology-savvy soldiers arriving in camp with smartphones, sophisticated applications, and high expectations. In this case study, this phenomenon plays out in the person of a US Army Captain who, using resources obtained via the Internet and while on a tour of duty in Afghanistan, develops and sells an inexpensive iPhone application – Tactical NAV – that provides soldiers with a sophisticated navigation tool.
Shear and dielectric responses of propylene carbonate, tripropylene glycol, and a mixture of two secondary amides
Authors: Gainaru Catalin , Hecksher Tina , Olsen Niels Boye , Böhmer Roland , Dyre Jeppe C.
Published: August 2012

Propylene carbonate and a mixture of two secondary amides, N-methylformamide and N-ethylacetamide, are investigated by means of broadband dielectric and mechanical shear spectroscopy. The similarities between the rheological and the dielectric responses of these liquids and of the previously investigated tripropylene glycol are discussed within a simple approach that employs an electrical circuit for describing the frequency-dependent behavior of viscous materials. The circuit is equivalent to the Gemant-DiMarzio-Bishop model, but allows for a negative capacitive element. The circuit can be used to calculate the dielectric from the mechanical response and vice versa. Using a single parameter for a given system, good agreement between model calculations and experimental data is achieved for the entire relaxation spectra, including secondary relaxations and the Debye-like dielectric peak in the secondary amides. In addition, the predictions of the shoving model are confirmed for the investigated liquids.
Correlation between charge transport and electroluminescence properties of Si-rich oxide/nitride/oxide-based light emitting capacitors
Authors: Berencén Y. , Ramírez J. M. , Jambois O. , Domínguez C. , Rodríguez J. A. , Garrido B.
Published: August 2012

The electrical and electroluminescence (EL) properties at room and high temperatures of oxide/nitride/oxide (ONO)-based light emitting capacitors are studied. The ONO multidielectric layer is enriched with silicon by means of ion implantation. The exceeding silicon distribution follows a Gaussian profile with a maximum of 19%, centered close to the lower oxide/nitride interface. The electrical measurements performed at room and high temperatures allowed to unambiguously identify variable range hopping (VRH) as the dominant electrical conduction mechanism at low voltages, whereas at moderate and high voltages, a hybrid conduction formed by means of variable range hopping and space charge-limited current enhanced by Poole-Frenkel effect predominates. The EL spectra at different temperatures are also recorded, and the correlation between charge transport mechanisms and EL properties is discussed.
Self-interaction correction in a real-time Kohn-Sham scheme: Access to difficult excitations in time-dependent density functional theory
Authors: Hofmann D. , Kümmel S.
Published: August 2012

We present a real-time Kohn-Sham propagation scheme for the self-interaction correction (SIC). The multiplicative Kohn-Sham potential is constructed in real-time and real-space based on the generalized optimized effective potential equation. We demonstrate that this approach yields promising results for a wide range of test systems, including hydrogen terminated silicon clusters, conjugated molecular chains, and molecular charge-transfer systems. We analyze the nature of excitations by calculating transition densities from the time evolution and by evaluating the time-dependent exchange-correlation potential. A properly constructed Kohn-Sham SIC potential shows a time-dependent field-counteracting behavior. These favorable characteristics of the exchange-correlation potential may be lost in approximations such as the SIC-Slater potential.
Transport of airborne particles in straight and curved microchannels
Authors: Schaap Allison , Chu Winnie C. , Stoeber Boris
Published: August 2012

The measurement of airborne particles is important for environmental and exposure monitoring. Microfluidic technologies present potential advantages for aerosol monitoring but have been applied very little to the handling of airborne particles. In this paper, we examine the flow focusing and cross-streamline diffusion of aerosols in straight microchannels, and the size-based lateral displacement of aerosols caused by centrifugal forces in a curved channel. We present calculations, simulations, and experimental results verifying the models: measurements of the focusing and diffusion of 0.2 μm and 0.75 μm particles in straight channels and of the size-dependent lateral displacement of particles between 0.2 μm and 2 μm in curved channels are demonstrated and shown to match well with the simulations. We observe lateral dispersion of the particles: particles closer to the top and bottom wall of the channel experience less lateral displacement than particles near the center due to the flow velocity distribution across the channel cross section. These results confirm that the microchannel techniques presented are a viable method for the size-based manipulation of airborne particles.
Numerical study on the effects of non-dimensional parameters on drop-on-demand droplet formation dynamics and printability range in the up-scaled model
Authors: Kim Eunjeong , Baek Jehyun
Published: August 2012

The droplet formation dynamics from a drop-on-demand printhead is numerically investigated with regard to the printability range. The numerical simulation is carried out using a volume-of-fluid model, and the qualitative effects of non-dimensional parameters on the droplet formation dynamics are evaluated. To determine the printability range, within which the droplet is ejected in a stable manner without satellite droplets, extensive numerical simulations are carried out by varying the viscosity and surface tension. Generally, the printability range is determined by a Z number, which is the inverse of the Ohnesorge number (Oh). However, it is found that the Z number alone is insufficient for describing the droplet formation dynamics. Other important non-dimensional parameters such as the Reynolds number (Re), Weber number (We), and capillary number (Ca) should also be taken into consideration. For studying the printability, the droplet formation dynamics are divided into five different regimes, and a regime map based on the Z, We, and Ca is proposed.
Development of frequency modulation reflectometer for KSTAR tokamak: Data analysis based on Gaussian derivative wavelet
Authors: Seo Seong-Heon , Lee K. D.
Published: August 2012

A frequency modulation reflectometer has been developed to measure the density profile of the KSTAR tokamak. It has two channels operating in X-mode in the frequency range of Q band (33–50 GHz) and V band (50–75 GHz). The full band is swept in 20 μs. The mixer output is directly digitized at the sampling rate of 100 MSamples/s. A new phase detection algorithm is developed to analyze both amplitude and frequency modulated signal. The algorithm is benchmarked for a synthesized amplitude modulation-frequency modulation signal. This new algorithm is applied to the data analysis of KSTAR reflectometer.
Surface instabilities of minority chains in dense polymer brushes: A comparison of density functional theory and quasi-off-lattice self-consistent field theory
Authors: Egorov S. A. , Romeis D. , Sommer J.-U.
Published: August 2012

This work studies surface instabilities in switchable homopolymer brushes where the minority chain differs in length from the brush chains. Both off-lattice numerical self-consistent field theory and classical density functional theory are employed. It is found that the two methods agree well with each other as long as the same equation of state for the polymer chains is used.
Forces on a boiling bubble in a developing boundary layer, in microgravity with g-jitter and in terrestrial conditions
Authors: van der Geld C. W. M. , Colin C. , Segers Q. I. E. , Pereira da Rosa V. H. , Yoshikawa H. N.
Published: August 2012

Terrestrial and microgravity flow boiling experiments were carried out with the same test rig, comprising a locally heated artificial cavity in the center of a channel near the frontal edge of an intrusive glass bubble generator. Bubble shapes were in microgravity generally not far from those of truncated spheres, which permitted the computation of inertial lift and drag from potential flow theory for truncated spheres approximating the actual shape. For these bubbles, inertial lift is counteracted by drag and both forces are of the same order of magnitude as g-jitter. A generalization of the Laplace equation is found which applies to a deforming bubble attached to a plane wall and yields the pressure difference between the hydrostatic pressures in the bubble and at the wall, Δp. A fully independent way to determine the overpressure Δp is given by a second Euler-Lagrange equation. Relative differences have been found to be about 5% for both terrestrial and microgravity bubbles. A way is found to determine the sum of the two counteracting major force contributions on a bubble in the direction normal to the wall from a single directly measurable quantity. Good agreement with expectation values for terrestrial bubbles was obtained with the difference in radii of curvature averaged over the liquid-vapor interface, ⟨(1/R2 − 1/R1)⟩, multiplied with the surface tension coefficient, σ. The new analysis methods of force components presented also permit the accounting for a surface tension gradient along the liquid-vapor interface. No such gradients were found for the present measurements.
Flow states in two-dimensional Rayleigh-Bénard convection as a function of aspect-ratio and Rayleigh number
Authors: van der Poel Erwin P. , Stevens Richard J. A. M. , Sugiyama Kazuyasu , Lohse Detlef
Published: August 2012

In this numerical study on two-dimensional Rayleigh-Bénard convection we consider 107 ⩽ Ra ⩽ 1012 in aspect-ratio 0.23 ⩽ Γ ⩽ 13 samples. We focus on several cases. First, we consider small aspect-ratio cells, where at high Ra number we find a sharp transition from a low Ra number branch towards a high Ra number branch, due to changes in the flow structure. Subsequently, we show that the influence of the aspect-ratio on the heat transport decreases with increasing aspect-ratio, although even at very large aspect-ratio of Γ ≈ 10 variations up to 2.5% in the heat transport as a function of Γ are observed. Finally, we observe long-lived transients up to at least Ra = 109, as in certain aspect-ratio cells we observe different flow states that are stable for thousands of turnover times.