bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of voltage pulse width on the discharge characteristics in an atmospheric dielectric-barrier-discharge plasma jet
Authors: Uchida Giichiro , Takenaka Kosuke , Setsuhara Yuichi 
Published: October 2015

Abstract
We present here the analysis of the discharge characteristics of a He dielectric-barrier-discharge (DBD) plasma jet operated in the voltage duty ratio of 20 to 80% under the condition of driving voltage frequency 5 kHz. Discharge strength is sensitive to the voltage pulse width, and the pulse width of 70 µs, which corresponds to the duty ratio of 35%, leads to high O optical emission intensity. We also performed time-resolved optical emission measurements in a transient pulse discharge driven by various voltage duty ratios. Two distinct pulse discharges are observed in the rising and falling periods of the positive rectangular voltage, and the first and second discharges have a peak intensity of optical emission at different duty ratio. The observations indicate that an adequate voltage pulse width could ignite a strong discharge both in the rising and falling period of applied voltage, which could produce a large amount of reactive excited O atoms.
Getting the most out of RNA-seq data analysis
Authors: Khang Tsung Fei , Lau Ching Yee 
Published: October 2015

Background.A common research goal in transcriptome projects is to find genes that are differentially expressed in different phenotype classes. Biologists might wish to validate such gene candidates experimentally, or use them for downstream systems biology analysis. Producing a coherent differential gene expression analysis from RNA-seq count data requires an understanding of how numerous sources of variation such as the replicate size, the hypothesized biological effect size, and the specific method for making differential expression calls interact. We believe an explicit demonstration of such interactions in real RNA-seq data sets is of practical interest to biologists.Results.Using two large public RNA-seq data sets—one representing strong, and another mild, biological effect size—we simulated different replicate size scenarios, and tested the performance of several commonly-used methods for calling differentially expressed genes in each of them. We found that, when biological effect size was mild, RNA-seq experiments should focus on experimental validation of differentially expressed gene candidates. Importantly, at least triplicates must be used, and the differentially expressed genes should be called using methods with high positive predictive value (PPV), such as NOISeq or GFOLD. In contrast, when biological effect size was strong, differentially expressed genes mined from unreplicated experiments using NOISeq, ASC and GFOLD had between 30 to 50% mean PPV, an increase of more than 30-fold compared to the cases of mild biological effect size. Among methods with good PPV performance, having triplicates or more substantially improved mean PPV to over 90% for GFOLD, 60% for DESeq2, 50% for NOISeq, and 30% for edgeR. At a replicate size of six, we found DESeq2 and edgeR to be reasonable methods for calling differentially expressed genes at systems level analysis, as their PPV and sensitivity trade-off were superior to the other methods’.Conclusion.When biological effect size is weak, systems level investigation is not possible using RNAseq data, and no meaningful result can be obtained in unreplicated experiments. Nonetheless, NOISeq or GFOLD may yield limited numbers of gene candidates with good validation potential, when triplicates or more are available. When biological effect size is strong, NOISeq and GFOLD are effective tools for detecting differentially expressed genes in unreplicated RNA-seq experiments for qPCR validation. When triplicates or more are available, GFOLD is a sharp tool for identifying high confidence differentially expressed genes for targeted qPCR validation; for downstream systems level analysis, combined results from DESeq2 and edgeR are useful.
Tracing terrestrial DOC in the Baltic Sea—A 3‐D model study
Authors: Fransner Filippa , Nycander Jonas , Mörth Carl‐Magnus , Humborg Christoph , Markus Meier H. E. , Hordoir Robinson , Gustafsson Erik , Deutsch Barbara 
Published: October 2015

AbstractThe fate of terrestrial organic matter brought to the coastal seas by rivers and its role in the global carbon cycle are still not very well known. Here the degradation rate of terrestrial dissolved organic carbon (DOCter) is studied in the Baltic Sea, a subarctic semienclosed sea, by releasing it as a tracer in a 3‐D circulation model and applying linear decay constants. A good agreement with available observational data is obtained by parameterizing the degradation in two rather different ways: one by applying a decay time on the order of 10 years to the whole pool of DOCter and one by dividing the DOCter into one refractory pool and one pool subject to a decay time on the order of 1 year. The choice of parameterization has a significant effect on where in the Baltic Sea the removal takes place, which can be of importance when modeling the full carbon cycle and the CO2 exchange with the atmosphere. In both cases the biogeochemical decay operates on time scales less than the water residence time. Therefore, only a minor fraction of the DOCter reaches the North Sea, whereas approximately 80% is removed by internal sinks within the Baltic Sea. This further implies that DOCter mineralization is an important link in land‐sea‐atmosphere cycling of carbon in coastal and shelf seas that are heavily influenced by riverine DOC.
The observed impacts of South Asian summer monsoon on the local atmosphere and the near‐surface turbulent heat exchange over the Southeast Tibet
Authors: Zhou Libo , Zou Han , Ma Shupo , Li Fei , Zhu Jinhuan , Li Peng , Zhang Yu 
Published: October 2015

AbstractThe Southeast Tibet is an important region of the Tibetan Plateau bearing the interaction between the Tibetan and the neighbor atmospheric systems. The South Asian summer monsoon (SASM) as a basic climate system in Asia could impact the local atmosphere and the near‐surface heat exchange process in the Southeast Tibet. An observational campaign, Observation on the Surface‐to‐air Exchange Processes in Southeast Tibet (OSEP2013), was carried out in this region during SASM in 2013. The atmospheric parameters and turbulent heat fluxes were observed and averaged over three different land surfaces of the inhomogeneous landscape during the observation campaign. Results show clear SASM impacts on the local atmosphere and near‐surface heat exchange in the Southeast Tibet. The South Asian summer monsoon was onset on 1 June 2013 and experienced a south phase and north phase during OSEP2013. The convection and humidity were increased in the Southeast Tibet by SASM, especially during the north phase. The observation domain received low radiation energy due to the convective clouds brought by SASM, and the soil and air temperatures were lowered as consequence. In addition, the air humidity was increased over this region by the wet air transportation of SASM circulation. The sensible and latent heat transfers were decreased by the low land‐air temperature difference and high air humidity during SASM. The latent heat transfer dominated the total heat transfer in the Southeast Tibet due to the low sensible heat transfer in the SASM situation, and the domination was increased as the sensible heat transfer was further decreased during the SASM north phase.
Ionosonde observations of ionospheric disturbances due to the 15 February 2013 Chelyabinsk meteor explosion
Authors: Pradipta Rezy , Valladares Cesar E. , Doherty Patricia H. 
Published: October 2015

AbstractWe report the results of our investigations on the potential ionospheric effects caused by the 15 February 2013 Chelyabinsk meteor explosion. We used the data from a number of digisonde stations located in Europe and Russia to detect the traveling ionospheric disturbances (TIDs) likely to have been caused by the meteor explosion. We found that certain characteristic signatures of the TIDs can be identified in individual ionogram records, mostly in the form of Y‐forking/splitting of the ionogram traces. Based on the arrival times of the disturbances, we have inferred the overall propagation speed of the TIDs from Chelyabinsk to be 171 ± 14 m/s.
Resolving daily wave 4 nonmigrating tidal winds at equatorial and midlatitudes with WINDII: DE3 and SE2
Authors: Cho Young‐Min , Shepherd Gordon 
Published: October 2015

AbstractThe Wind Imaging Interferometer observed nonmigrating tidal winds from 90 to 260 km during daytime and at 99 and 250 km during the night and found that the amplitudes and phases of the daytime and nighttime extracted wave 4 for a given day were different, indicating the presence of more than one component. The objective of this study is to resolve those components. Local time versus longitude propagation plots over individual seasons revealed the diurnal eastward propagating wave number 3 (DE3), the semidiurnal eastward propagating wave number 2 (SE2) and the stationary planetary wave number 4 (SPW4). Using a fitting procedure for individual days it was then found possible to determine the amplitudes and phases of DE3 and SE2 and the amplitude of SPW4 for each day, using a constant phase for the SPW4 obtained from the propagation plot. These DE3 and SE2 values were compared with data‐constrained model results yielding good agreement at 99 km but with mixed agreement at 250 km. Time series analysis of 164 days duration showed considerable variability in the amplitudes of the zonal wind for DE3 with the SPW4 tending to follow; DE3 power spectral peaks occurred near 12, 16, and 32 days. The SE2 showed less variability, also displaying spectral peaks but shifted from the DE3 peaks. Monthly averages of the DE3 and SE2 show that the DE3 is predominant at the equatorial mesosphere/lower thermosphere region. On the other hand, the SE2 is uniformly present at lower and midlatitudes and all altitudes.
Determining the magnetic attempt time τ0, its temperature dependence, and the grain size distribution from magnetic viscosity measurements
Authors: Berndt Thomas , Muxworthy Adrian R. , Paterson Greig A. 
Published: October 2015

AbstractA new method to determine the atomic attempt time τ0 of magnetic relaxation of fine particles, which is central to rock and soil magnetism and paleomagnetic recording theory, is presented, including the determination of its temperature dependence, and simultaneously the grain size distribution of a sample. It is based on measuring a series of zero‐field magnetic viscous decay curves for saturation isothermal remanent magnetization at various different temperatures that are later joined together on a single grain size scale from which the grain size distribution and attempt time are determined. The attempt time was determined for three samples containing noninteracting, single‐domain titanomagnetites of different grain sizes for temperatures between 27 K and 374 K. No clear temperature‐dependent trend was found; however, values varied significantly from one sample to the other: from 10−11 to 10−8s; in particular, the sample containing multiple magnetic phases had an effective attempt time significantly lower than the more homogeneous samples, thereby questioning the applicability of the simple Néel‐Arhennius equation for magnetic relaxation for composite materials.
Role of regional thermal contrast over West Asia in interannual variation in atmospheric moisture transportation over the Indian Ocean and neighboring areas at summer monsoon onset
Authors: Watanabe Takeshi 
Published: October 2015

AbstractThe low‐level temperature contrast over West Asia influences the interannual variation in water vapor transportation over the northern and equatorial Indian Ocean and neighboring monsoon area. A composite analysis that takes into account the thermal contrast over West Asia during the monsoon seasonal transition is performed based on the reanalysis and merged observational precipitation data sets. The positive (negative) low‐level thermal contrast anomaly over the Iranian Plateau (IP) strengthens (weakens) the thermal contrast over the Arabian Sea. The low‐level westerly anomaly develops earlier in the positive IP thermal contrast years than in the negative years. As a result, water vapor transport varies. This variation in water vapor transport in turn has an influence on the abrupt increase in precipitation over South Asia and the Arabian Sea and the decrease over equatorial East Africa. The variation in low‐level temperature over the IP precedes the variation of precipitation over these regions by a few pentads. A numerical experiment using the Lagrangian particle dispersion model agrees with the results of the composite analysis. Particles are emitted from the western tropical Indian Ocean region from the preonset to onset period. Results of numerical experiments concerning positive IP thermal contrast years show that particles can be transported into South Asia and the Arabian Sea before the climatological Asian summer monsoon onset pentad. However, small amounts of particles arrive in South Asia and the Arabian Sea at the onset period in negative IP years. The transport into equatorial East Africa becomes weak earlier in positive IP years.
Global observations and modeling of nonmigrating diurnal tides generated by tide‐planetary wave interactions
Authors: Lieberman R. S. , Riggin D. M. , Ortland D. A. , Oberheide J. , Siskind D. E. 
Published: October 2015

AbstractAdvective processes that couple planetary waves with tides have long been proposed as sources of nonmigrating diurnal tides. This paper reports observations of short‐term variability in global observations of nonmigrating tides predicted to arise from the interaction of the migrating diurnal tide (DW1) with a quasi‐stationary planetary wave number one (PW1). PW1 and tidal definitions are extracted from satellite temperatures and high‐altitude meteorological analyses. During winter months, the evolution of westward traveling diurnal tides with zonal wave number 2 (DW2) generally tracks that of strong‐amplitude stratospheric PW1. DW1 and PW1 spectra are used to compute nonlinear tidal forcing terms arising from advection. We then examine the response of a primitive equation model to the observation‐based nonlinear forcing. The model experiments indicate that meridional advection of PW1 zonal momentum by DW1 is a significant source of lower thermospheric DW2. Modeled DW2 amplitudes are very consistent with observed DW2 amplitudes when stratospheric PW1 penetrates to equatorial latitudes. The model experiments also indicate that the interaction can imprint short‐term variability associated with wintertime PW1 upon DW2 in the summer hemisphere and the lower thermosphere.
Large methane emissions from a subarctic lake during spring thaw: Mechanisms and landscape significance
Authors: Jammet Mathilde , Crill Patrick , Dengel Sigrid , Friborg Thomas 
Published: October 2015

AbstractThe ice‐cover season and subsequent spring thaw are thought to be of particular importance for the biogeochemical cycle of northern lakes and wetlands. Yet the magnitude of their methane emissions during an entire cold season is uncertain due to scarce measurements. While wetlands are known to be the highest natural emitters of methane, emissions from northern lakes are an uncertain component of terrestrial carbon budgets. To evaluate the importance of methane emissions from a subarctic lake during winter and spring, surface methane fluxes were recorded with the eddy covariance method in a subarctic fen‐type wetland and in an adjacent shallow lake, from freezeup to complete ice out. The fen was a steady emitter of methane throughout winter. While no detectable flux was observed from the ice‐covered lake surface during winter, it was the largest methane source of the landscape in spring, with a cumulative release 1.7‐fold higher than at the fen, accounting for 53% of annual lake emissions. The high temporal resolution of the measurements allowed making a direct link between breakdown of the temperature stratification after ice breakup and the highest release of methane from the lake surface. A sediment upwelling at the end of the thaw season likely contributed to these emissions. We suggest that, unlike wetlands, shallow seasonally ice‐covered lakes can have their highest methane emission potential in the cold season, likely dominating the spring methane release of subarctic landscapes with high lake coverage.
Local‐ and landscape‐scale impacts of clear‐cuts and climate change on surface water dissolved organic carbon in boreal forests
Authors: Oni Stephen K. , Tiwari Tejshree , Ledesma José L. J. , Ågren Anneli M. , Teutschbein Claudia , Schelker Jakob , Laudon Hjalmar , Futter Martyn N. 
Published: October 2015

AbstractForest harvesting and climate change may significantly increase concentrations and fluxes of dissolved organic carbon (DOC) in boreal surface waters. However, the likely magnitude of any effect will vary depending on the landscape‐element type and spatial scale. We used a chain of hydrological, empirical, and process‐based biogeochemical models coupled to an ensemble of downscaled Regional Climate Model experiments to develop scenario storylines for local‐ and landscape‐scale effects of forest harvesting and climate change on surface water DOC concentrations and fluxes. Local‐scale runoff, soil temperature, and DOC dynamics were simulated for a range of forest and wetland landscape‐element types and at the larger landscape scale. The results indicated that climate change will likely lead to greater winter flows and earlier, smaller spring peaks. Both forest harvesting and climate change scenarios resulted in large increases in summer and autumn runoff and higher DOC fluxes. Forest harvesting effects were clearly apparent at local scales. While at the landscape scale, approximately 1 mg L−1 (or 10%) of the DOC in surface waters can be attributed to clear‐cuts, both climate change and intensified forestry can each increase DOC concentrations by another 1 mg L−1 in the future, which is less than that seen in many waterbodies recovering from acidification. These effects of forestry and climate change on surface water DOC concentrations are additive at a landscape scale but not at the local scale, where a range of landscape‐element specific responses were observed.
Large‐eddy simulation of the transient and near‐equilibrium behavior of precipitating shallow convection
Authors: Seifert Axel , Heus Thijs , Pincus Robert , Stevens Bjorn 
Published: October 2015

AbstractLarge‐eddy simulation is used to study the sensitivity of trade wind cumulus clouds to perturbations in cloud droplet number concentrations. We find that the trade wind cumulus system approaches a radiative‐convective equilibrium state, modified by net warming and drying from imposed large‐scale advective forcing. The system requires several days to reach equilibrium when cooling rates are specified but much less time, and with less sensitivity to cloud droplet number density, when radiation depends realistically on the vertical distribution of water vapor. The transient behavior and the properties of the near‐equilibrium cloud field depend on the microphysical state and therefore on the cloud droplet number density, here taken as a proxy for the ambient aerosol. The primary response of the cloud field to changes in the cloud droplet number density is deepening of the cloud layer. This deepening leads to a decrease in relative humidity and a faster evaporation of small clouds and cloud remnants constituting a negative lifetime effect. In the near‐equilibrium regime, the decrease in cloud cover compensates much of the Twomey effect, i.e., the brightening of the clouds, and the overall aerosol effect on the albedo of the organized precipitating cumulus cloud field is small.
The structure of gravel‐bed flow with intermediate submergence: A laboratory study
Authors: Mohajeri S. H. , Grizzi S. , Righetti M. , Romano G. P. , Nikora V. 
Published: October 2015

AbstractThe paper reports an experimental study of the flow structure over an immobile gravel bed in open channel at intermediate submergence, with particular focus on the near‐bed region. The experiments consisted of velocity measurements using three‐component (stereoscopic) Particle Image Velocimetry (PIV) in near‐bed horizontal plane and two‐component PIV in three vertical planes that covered three distinctly different hydraulic scenarios where the ratio of flow depth to roughness height (i.e., relative submergence) changes from 7.5 to 10.8. Detailed velocity measurements were supplemented with fine‐scale bed elevation data obtained with a laser scanner. The data revealed longitudinal low‐momentum and high‐momentum “strips” in the time‐averaged velocity field, likely induced by secondary currents. This depth‐scale pattern was superimposed with particle‐scale patches of flow heterogeneity induced by gravel particle protrusions. A similar picture emerged when considering second‐order velocity moments. The interaction between the flow field and gravel‐bed protrusions is assessed using cross correlations of velocity components and bed elevations in a horizontal plane just above gravel particle crests. The cross correlations suggest that upward and downward fluid motions are mainly associated with upstream‐facing and lee sides of particles, respectively. Results also show that the relative submergence affects the turbulence intensity profiles for vertical velocity over the whole flow depth, while only a weak effect, limited to the near‐bed region, is noticed for streamwise velocity component. The approximation of mean velocity profiles with a logarithmic formula reveals that log‐profile parameters depend on relative submergence, highlighting inapplicability of a conventional “universal” logarithmic law for gravel‐bed flows with intermediate submergence.
Decarboxylative and Denitrative Trifluoromethylation for the Synthesis of CvinylCF3 Compounds with Togni (II) Reagent
Authors: Ma Jing‐jing , Yi Wen‐bin , Lu Guo‐ping , Cai Chun 
Published: October 2015

AbstractA highly efficient dimethylformamide (DMF)‐promoted decarboxylative trifluoromethylation of α,β‐unsaturated carboxylic acids with Togni (II) reagent under metal‐free conditions has been developed. The reactions showed good yields, high stereoselectivities and excellent functional group tolerance. Mechanistic studies confirmed that free‐radical processes were involved in this system since the CF3 radical had been clearly trapped by scavengers. This method has been extended to the denitrative trifluoromethylation of β‐nitrostyrenes in the presence of an iron(III) catalyst.magnified image
Palladium‐Catalyzed Olefination and Arylation of Polyfluoroarenes Using Molecular Oxygen as the Sole Oxidant
Authors: Huang Qiufeng , Zhang Xinyu , Qiu Lin , Wu Jiajun , Xiao Hanbing , Zhang Xiaofeng , Lin Shen 
Published: October 2015

AbstractThe palladium‐catalyzed cross‐dehydrogenative‐coupling of polyfluoroarenes with alkenes or simple arenes has been developed. The approach is characterized by using atmospheric pressure of molecular oxygen as the sole oxidant, and provides a straightforward and environmentally benign route to functionalized polyfluoroarenes.magnified image