bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inversion model of soil salinity in alfalfa covered farmland based on sensitive variable selection and machine learning algorithms
Authors: Ma Hong , Zhao Wenju , Duan Weicheng , Ma Fangfang , Li Congcong , Li Zongli 
Published: September 2024

Purpose
Timely and accurate monitoring of soil salinity content (SSC) is essential for precise irrigation management of large-scale farmland. Uncrewed aerial vehicle (UAV) low-altitude remote sensing with high spatial and temporal resolution provides a scientific and effective technical means for SSC monitoring. Many existing soil salinity inversion models have only been tested by a single variable selection method or machine learning algorithm, and the influence of variable selection method combined with machine learning algorithm on the accuracy of soil salinity inversion remain further studied.

Methods
Firstly, based on UAV multispectral remote sensing data, by extracting the spectral reflectance of each sampling point to construct 30 spectral indexes, and using the pearson correlation coefficient (PCC), gray relational analysis (GRA), variable projection importance (VIP), and support vector machine-recursive feature elimination (SVM-RFE) to screen spectral index and realize the selection of sensitive variables. Subsequently, screened and unscreened variables as model input independent variables, constructed 20 soil salinity inversion models based on the support vector machine regression (SVM), back propagation neural network (BPNN), extreme learning machine (ELM), and random forest (RF) machine learning algorithms, the aim is to explore the feasibility of different variable selection methods combined with machine learning algorithms in SSC inversion of crop-covered farmland. To evaluate the performance of the soil salinity inversion model, the determination coefficient (R2), root mean square error (RMSE) and performance deviation ratio (RPD) were used to evaluate the model performance, and determined the best variable selection method and soil salinity inversion model by taking alfalfa covered farmland in arid oasis irrigation areas of China as the research object.

Results
The variable selection combined with machine learning algorithm can significantly improve the accuracy of remote sensing inversion of soil salinity. The performance of the models has been improved markedly using the four variable selection methods, and the applicability varied among the four methods, the GRA variable selection method is suitable for SVM, BPNN, and ELM modeling, while the PCC method is suitable for RF modeling. The GRA-SVM is the best soil salinity inversion model in alfalfa cover farmland, with Rv2 of 0.8888, RMSEv of 0.1780, and RPD of 1.8115 based on the model verification dataset, and the spatial distribution map of soil salinity can truly reflect the degree of soil salinization in the study area.

Conclusion
Based on our findings, the variable selection combined with machine learning algorithm is an effective method to improve the accuracy of soil salinity remote sensing inversion, which provides a new approach for timely and accurate acquisition of crops covered farmland soil salinity information.
Incidência dos casos de obesidade na faixa-etária pediátrica: um estudo epidemiológico
Authors: Reimão Gabriella Abib Martins , Beber Uiara Jones , Ribeiro Mateus Oliveira , Porcino Fernanda Rodrigues , Francischini Vitor Gabriel Silva , Almeida Carolina de Godoy 
Published: September 2024

A obesidade é apresentada como uma doença crônica não transmissível, de origem multifatorial e com repercussão sistêmica. Os casos de obesidade infantil aumentaram com a pandemia mundial causada pela Covid-19. O diagnóstico clínico para obesidade infantil ocorre por meio da anamnese, dados nutrológicos (anamnese alimentar), exame físico (peso, altura, IMC, circunferência abdominal) e exames complementares. Esse trabalho tem o objetivo de realizar uma análise quantitativa e temporal sobre as características epidemiológicas da obesidade em crianças com idade de 1 a 14 anos no período de Janeiro de 2013 a Dezembro de 2023. Metodologia: Trata-se de um estudo epidemiológico embasados a partir dos dados do departamento de informação de saúde do SUS (Sistema Único de Saúde). As variáveis utilizadas foram: internações hospitalares, óbitos, faixa etária, cor/raça, sexo, gastos hospitalares e macrorregião de saúde. Resultado: 1.021 internações ocorreram por obesidade. Ainda que a região Sul tenha sido a mais notificada quanto a quantidade de internações, a região Sudeste foi a região com maior númuro de óbitos por obesidade no país. A maior faixa-etária acometida foi entre 15 e 19 anos (Adolescentes jovens). O sexo feminino foi o gênero mais afetado por essa patologia. Em relação à etnia, mais pacientes brancos são internados. Conclusão: a realização destes estudos é essencial para o desenvolvimento de políticas públicas voltadas ao diagnóstico, tratamento e notificação adequada dos casos de obesidade infantil no país. Por tratar-se de um estudo baseado em dados secundários, algumas limitações se fazem presentes, portanto, mais estudos epidemiológicos devem ser conduzidos.
What proportion of riverine nutrients reaches the open ocean?
Authors: Sharples Jonathan , Middelburg Jack J. , Fennel Katja , Jickells Timothy D. 
Published: December 2016

AbstractGlobally, rivers deliver significant quantities of nitrogen (N) and phosphorus (P) to the coastal ocean each year. Currently, there are no viable estimates of how much of this N and P escapes biogeochemical processing on the shelf to be exported to the open ocean; most models of N and P cycling assume that either all or none of the riverine nutrients reach the open ocean. We address this problem by using a simple mechanistic model of how a low‐salinity plume behaves outside an estuary mouth. The model results in a global map of riverine water residence times on the shelf, typically a few weeks at low latitudes and up to a year at higher latitudes, which agrees well with observations. We combine the map of plume residence times on the shelf with empirical relationships that link residence time to the proportions of dissolved inorganic N (DIN) and P (DIP) exported and use a database of riverine nutrient loads to estimate the global distribution of riverine DIN and DIP supplied to the open ocean. We estimate that 75% of DIN and 80% of DIP reaches the open ocean. Ignoring processing within estuaries yields annual totals of 17 Tg DIN and 1.2 Tg DIP reaching the open ocean. For DIN this supply is about 50% of that supplied via atmospheric deposition, with significant east‐west contrasts across the main ocean basins. The main sources of uncertainty are exchange rates across the shelf break and the empirical relationships between nutrient processing and plume residence time.
Automatic classification of endogenous landslide seismicity using the Random Forest supervised classifier
Authors: Provost F. , Hibert C. , Malet J.‐P. 
Published: December 2016

AbstractThe deformation of slow‐moving landslides developed in clays induces endogenous seismicity of mostly low‐magnitude events (ML<1). Long seismic records and complete catalogs are needed to identify the type of seismic sources and understand their mechanisms. Manual classification of long records is time‐consuming and may be highly subjective. We propose an automatic classification method based on the computation of 71 seismic attributes and the use of a supervised classifier. No attribute was selected a priori in order to create a generic multi‐class classification method applicable to many landslide contexts. The method can be applied directly on the results of a simple detector. We developed the approach on the seismic network of eight sensors of the Super‐Sauze clay‐rich landslide (South French Alps) for the detection of four types of seismic sources. The automatic algorithm retrieves 93% of sensitivity in comparison to a manually interpreted catalog considered as reference.
Kinetic Alfvén wave explanation of the Hall fields in magnetic reconnection
Authors: Dai Lei , Wang Chi , Zhang Yongcun , Lavraud Benoit , Burch James , Pollock Craig , Torbert Roy B. 
Published: December 2016

AbstractMagnetic reconnection is initiated in a small diffusion region but can drive global‐scale dynamics in Earth's magnetosphere, solar flares, and astrophysical systems. Understanding the processes at work in the diffusion region remains a main challenge in space plasma physics. Recent in situ observations from Magnetospheric Multiscale and Time History of Events and Macroscale Interactions during Substorms reveal that the electric field normal to the reconnection current layer, often called the Hall electric field (En), is mainly balanced by the ion pressure gradient. Here we present theoretical explanations indicating that this observation fact is a manifestation of kinetic Alfvén waves (KAWs) physics. The ion pressure gradient represents the finite gyroradius effect of KAW, leading to ion intrusion across the magnetic field lines. Electrons stream along the magnetic field lines to track ions, resulting in field‐aligned currents and the associated pattern of the out‐of‐plane Hall magnetic field (Bm). The ratio ΔEn/ΔBm is on the order of the Alfvén speed, as predicted by the KAW theory. The KAW physics further provides new perspectives on how ion intrusion may trigger electric fields suitable for reconnection to occur.
Decade‐long deep‐ocean warming detected in the subtropical South Pacific
Authors: Volkov Denis L. , Lee Sang‐Ki , Landerer Felix W. , Lumpkin Rick 
Published: December 2016

AbstractThe persistent energy imbalance at the top of the atmosphere, inferred from satellite measurements, indicates that the Earth's climate system continues to accumulate excess heat. As only sparse and irregular measurements of ocean heat below 2000 m depth exist, one of the most challenging questions in global climate change studies is whether the excess heat has already penetrated into the deep ocean. Here we perform a comprehensive analysis of satellite and in situ measurements to report that a significant deep‐ocean warming occurred in the subtropical South Pacific Ocean over the past decade (2005–2014). The local accumulation of heat accounted for up to a quarter of the global ocean heat increase, with directly and indirectly inferred deep ocean (below 2000 m) contribution of 2.4 ± 1.4 and 6.1–10.1 ± 4.4%, respectively. We further demonstrate that this heat accumulation is consistent with a decade‐long intensification of the subtropical convergence, possibly linked to the persistent La Niña‐like state.
Role of nonlinear ocean dynamic response to wind on the asymmetrical transition of El Niño and La Niña
Authors: An Soon‐Il , Kim Ji‐Won 
Published: December 2016

AbstractTo understand why El Niño is frequently followed by La Niña while the opposite occurs rarely, we analyze the inherent asymmetry in a delayed negative feedback loop in the framework of delayed oscillator theory using observational data. The asymmetrical response of the ocean wave to wind is much larger than that of the wind intensity to sea surface temperature (SST) and that of the subsurface temperature to thermocline. Strong oceanic response during El Niño compared to La Niña is presumably due to the relatively shallow mean thermocline over the western Pacific, which efficiently traps the atmospheric momentum in the shallow upper ocean, and the asymmetrical wind pattern response to SST. A modified delayed oscillator model experiment verifies that the asymmetrical ocean wave response to wind is more important in the asymmetrical transition of El Niño and La Niña than asymmetrical wind intensity response to SST and asymmetrical subsurface temperature response to thermocline.
Cross‐scale observations of the 2015 St. Patrick's day storm: THEMIS, Van Allen Probes, and TWINS
Authors: Goldstein J. , Angelopoulos V. , De Pascuale S. , Funsten H. O. , Kurth W. S. , LLera K. , McComas D. J. , Perez J. D. , Reeves G. D. , Spence H. E. , Thaller S. A. , Valek P. W. , Wygant J. R. 
Published: December 2016

AbstractWe present cross‐scale magnetospheric observations of the 17 March 2015 (St. Patrick's Day) storm, by Time History of Events and Macroscale Interactions during Substorms (THEMIS), Van Allen Probes (Radiation Belt Storm Probes), and Two Wide‐angle Imaging Neutral‐atom Spectrometers (TWINS), plus upstream ACE/Wind solar wind data. THEMIS crossed the bow shock or magnetopause 22 times and observed the magnetospheric compression that initiated the storm. Empirical models reproduce these boundary locations within 0.7 RE. Van Allen Probes crossed the plasmapause 13 times; test particle simulations reproduce these encounters within 0.5 RE. Before the storm, Van Allen Probes measured quiet double‐nose proton spectra in the region of corotating cold plasma. About 15 min after a 0605 UT dayside southward turning, Van Allen Probes captured the onset of inner magnetospheric convection, as a density decrease at the moving corotation‐convection boundary (CCB) and a steep increase in ring current (RC) proton flux. During the first several hours of the storm, Van Allen Probes measured highly dynamic ion signatures (numerous injections and multiple spectral peaks). Sustained convection after ∼1200 UT initiated a major buildup of the midnight‐sector ring current (measured by RBSP A), with much weaker duskside fluxes (measured by RBSP B, THEMIS a and THEMIS d). A close conjunction of THEMIS d, RBSP A, and TWINS 1 at 1631 UT shows good three‐way agreement in the shapes of two‐peak spectra from the center of the partial RC. A midstorm injection, observed by Van Allen Probes and TWINS at 1740 UT, brought in fresh ions with lower average energies (leading to globally less energetic spectra in precipitating ions) but increased the total pressure. The cross‐scale measurements of 17 March 2015 contain significant spatial, spectral, and temporal structure.
Validity of 2‐D electromagnetic approaches to estimate log‐amplitude and phase variances due to 3‐D ionospheric irregularities
Authors: Galiègue Hélène , Féral Laurent , Fabbro Vincent 
Published: December 2016

AbstractTo limit the computation time and the computer resource, 2‐D numerical approaches such as 2‐D parabolic wave equation (2‐D PWE) associated with 1‐D multiple phase screens (1‐D MPS) are classically used to estimate ionospheric scintillation effects on radio wave propagation. However, in the ionosphere, the turbulent fluctuations of the electron density responsible for the scintillation effects are clearly a three‐dimensional process. This paper quantitatively assesses the errors potentially induced by the 3‐D to 2‐D dimensional reduction to predict ionospheric effects in terms of log‐amplitude and phase variances. To that purpose, the ionospheric electron density fluctuations are described by an anisotropic turbulent spectrum with three axes of anisotropy. On the one hand, considering four typical configurations (two equatorial and two polar radio links), scintillation effects are evaluated numerically, using 3‐D and 2‐D PWE‐MPS numerical techniques. Some consequences of the dimensional reduction are then qualitatively discussed. On the other hand, an analytical framework that solves the 3‐D and 2‐D propagation equations in the line‐of‐sight coordinate system is proposed. Under weak scattering assumption, it allows assessing analytically the consequences of the dimensional reduction whatever the geometry of the transionospheric radio link and, finally, allows 2‐D numerical schemes to be used advisedly for the prediction of ionospheric scintillation effects.
Spatial and seasonal variations of secondary organic aerosol from terpenoids over China
Authors: Ding Xiang , Zhang Yu‐Qing , He Quan‐Fu , Yu Qing‐Qing , Shen Ru‐Qin , Zhang Yanli , Zhang Zhou , Lyu Su‐Jun , Hu Qi‐Hou , Wang Yue‐Si , Li Long‐Feng , Song Wei , Wang Xin‐Ming 
Published: December 2016

AbstractA majority of global secondary organic aerosol (SOA) comes from terpenoids. In this study, we carried out a 1 year nationwide observation of pinenes (α‐ and β‐pinene) and SOA tracers from monoterpenes (SOAM) and β‐caryophyllene (SOAC) over China for the first time. SOAM and SOAC tracers ranged from 9.80 to 49.0 ng m−3 and 1.72 to 7.72 ng m−3, respectively, with high levels in southern China. Pinenes ranged from 34 to 102 parts per trillion by volume, with α‐pinene dominant over β‐pinene. SOAM tracers were correlated between paired sites, suggesting a regional impact of SOAM, while pinenes were uncorrelated between sites due to their rapid oxidation. High levels of SOAM tracers were observed in spring and summer. However, at the Hailun site in Northeast China, SOAM tracers increased during winter. The positive correlation between SOAM tracers and the biomass burning (BB) tracer levoglucosan during winter at Hailun indicated that the unexpected increase of SOAM was associated with BB. The SOAC tracer, β‐caryophyllenic acid, increased during winter and was positively correlated with levoglucosan, suggesting substantial contributions from BB to SOAC production in wintertime. Together with SOA tracers from isoprene, these tracers were applied to estimate biogenic secondary organic carbon (BSOC) from isoprene, monoterpenes, and β‐caryophyllene. The annual average BSOC was 0.91 ± 0.41 μgC m−3,with the majority from monoterpenes and the highest level in Southwest China. BSOC was elevated from April to September and was lowest in January and February. BSOC composition dramatically changed from a monoterpene majority in fall‐spring to an isoprene majority in summer.
Controls on the early Holocene collapse of the Bothnian Sea Ice Stream
Authors: Clason Caroline C. , Greenwood Sarah L. , Selmes Nick , Lea James M. , Jamieson Stewart S. R. , Nick Faezeh M. , Holmlund Per 
Published: December 2016

AbstractNew high‐resolution multibeam data in the Gulf of Bothnia reveal for the first time the subglacial environment of a Bothnian Sea Ice Stream. The geomorphological record suggests that increased meltwater production may have been important in driving rapid retreat of Bothnian Sea Ice during deglaciation. Here we apply a well‐established, one‐dimensional flow line model to simulate ice flow through the Gulf of Bothnia and investigate controls on retreat of the ice stream during the post‐Younger Dryas deglaciation of the Fennoscandian Ice Sheet. The relative influence of atmospheric and marine forcings are investigated, with the modeled ice stream exhibiting much greater sensitivity to surface melting, implemented through surface mass balance and hydrofracture‐induced calving, than to submarine melting or relative sea level change. Such sensitivity is supported by the presence of extensive meltwater features in the geomorphological record. The modeled ice stream does not demonstrate significant sensitivity to changes in prescribed ice stream width or overall bed slope, but local variations in basal topography and ice stream width result in nonlinear retreat of the grounding line, notably demonstrating points of short‐lived retreat slowdown on reverse bed slopes. Retreat of the ice stream was most likely governed by increased ice surface meltwater production, with the modeled retreat rate less sensitive to marine forcings despite the marine setting.
Denitrification in upland of China: Magnitude and influencing factors
Authors: Wang Jinyang , Yan Xiaoyuan 
Published: December 2016

AbstractA better understanding of influencing factors and accurate estimate of soil denitrification is a global concern. Here we present a synthesis of 300 observations of denitrification in Chinese upland soils from 39 field and laboratory studies using the acetylene inhibition technique. The results of a linear mixed model analysis showed that the rates of soil denitrification were significantly affected by crop type, soil organic carbon, soil pH, the measurement period, and the rate of N application. The emission factor (EF) and N2O/(N2O + N2) ratio for soil denitrification were on average 2.11 ± 0.17% and 0.508 ± 0.020, respectively. Our meta‐analysis indicated that N fertilization increased soil denitrification by 311% (95% CI: 279–346%) and 112% (95% CI: 66–171%) in the field and laboratory studies, respectively. Substantial interactive effects between soil properties and N fertilization on soil denitrification were found. Although the highest values of both the rate of denitrification and the EF were found in vegetable fields, the size of the stimulating effect of N fertilization on soil denitrification was lower in vegetable fields than in maize and wheat fields. These results suggest that the crop‐specific effect is important and that vegetable fields are potential hot spots of denitrification in Chinese uplands. Based on either the EF or the N2O/(N2O + N2) ratio obtained, the estimated amount of total denitrification from the upland soils was an order of magnitude lower than that from budget calculations, suggesting that the acetylene inhibition technique may significantly underestimate denitrification in Chinese upland soils.
Root traits explain observed tundra vegetation nitrogen uptake patterns: Implications for trait‐based land models
Authors: Zhu Qing , Iversen Colleen M. , Riley William J. , Slette Ingrid J. , Vander Stel Holly M. 
Published: December 2016

AbstractOngoing climate warming will likely perturb vertical distributions of nitrogen availability in tundra soils through enhancing nitrogen mineralization and releasing previously inaccessible nitrogen from frozen permafrost soil. However, arctic tundra responses to such changes are uncertain, because of a lack of vertically explicit nitrogen tracer experiments and untested hypotheses of root nitrogen uptake under the stress of microbial competition implemented in land models. We conducted a vertically explicit 15N tracer experiment for three dominant tundra species to quantify plant N uptake profiles. Then we applied a nutrient competition model (N‐COM), which is being integrated into the ACME Land Model, to explain the observations. Observations using an 15N tracer showed that plant N uptake profiles were not consistently related to root biomass density profiles, which challenges the prevailing hypothesis that root density always exerts first‐order control on N uptake. By considering essential root traits (e.g., biomass distribution and nutrient uptake kinetics) with an appropriate plant‐microbe nutrient competition framework, our model reasonably reproduced the observed patterns of plant N uptake. In addition, we show that previously applied nutrient competition hypotheses in Earth System Land Models fail to explain the diverse plant N uptake profiles we observed. Our results cast doubt on current climate‐scale model predictions of arctic plant responses to elevated nitrogen supply under a changing climate and highlight the importance of considering essential root traits in large‐scale land models. Finally, we provided suggestions and a short synthesis of data availability for future trait‐based land model development.