bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of self‐efficacy beliefs in learning English as a foreign language among young Indonesians
Authors: Anam Syafi’ul , Stracke Elke
Published: January 2019

This article examines the role of self‐efficacy beliefs in learning English as a foreign language in an Indonesian primary school setting. Self‐efficacy is a significant motivational factor affecting the cognitive and behavioral engagement of learners (Linnenbrink & Pintrich, 2003). The study adopted a mixed‐methods research design that involved the administration of a questionnaire (N = 516), an English proficiency test (N = 516), and a semistructured interview (N = 12). The participants of the study were sixth graders from 12 primary schools in the Indonesian province of East Java. The quantitative findings indicate a relationship between self‐efficacy and language ability, which the interview findings support by pointing to the different cognitive and motivational engagement of the students who held different self‐efficacy levels. These findings provide empirical evidence for the motivational role of self‐efficacy beliefs in language learning. The article ends with practical implications for using EFL instructional processes in the Indonesian primary school context.
A primer on turbulence in hydrology and hydraulics: The power of dimensional analysis
Authors: Katul Gabriel , Li Dan , Manes Costantino
Published: January 2019

The apparent random swirling motion of water is labeled “turbulence,” which is a pervasive state of the flow in many hydrological and hydraulic transport phenomena. Water flow in a turbulent state can be described by the momentum conservation equations known as the Navier–Stokes (NS) equations. Solving these equations numerically or in some approximated form remains a daunting task in applications involving natural systems thereby prompting interest in alternative approaches. The apparent randomness of swirling motion encodes order that may be profitably used to describe water movement in natural systems. The goal of this primer is to illustrate the use of a technique that links aspects of this ordered state to conveyance and transport laws. This technique is “dimensional analysis”, which can unpack much of the complications associated with turbulence into surprisingly simplified expressions. The use of this technique to describing water movement in streams as well as water vapor movement in the atmosphere is featured. Particular attention is paid to bulk expressions that have received support from a large body of experiments such as flow‐resistance formulae, the Prandtl‐von Karman log‐law describing the mean velocity shape, Monin‐Obukhov similarity theory that corrects the mean velocity shape for thermal stratification, and evaporation from rough surfaces. These applications illustrate how dimensional analysis offers a pragmatic approach to problem solving in sciences and engineering.

This article is categorized under:

Science of Water > Methods

Science of Water > Hydrological Processes
AK‐DA: An efficient method for the fatigue assessment of wind turbine structures
Authors: Huchet Quentin , Mattrand Cécile , Beaurepaire Pierre , Relun Nicolas , Gayton Nicolas
Published: January 2019

Lifetime damage estimation is a complex and demanding task that needs to be performed during the design of offshore wind turbine structures. A general damage analysis framework is proposed by the certification bodies. Therein the total lifetime of the structure is considered as a series of elementary situations combining structural and environmental states. For a given structural state, the loading environment is described using statistical parameters such as the wind mean speed at hub height or the peak spectral period of the sea. An estimation of the structural response is to be computed for each of the environmental combinations of parameters, therefore leading to tens of thousands simulations. The cost of a single simulation makes this process often unfeasible for engineers who are usually forced to reduce the number of simulations considering industrial feedback with risks of potential lack of representativity of results. This paper aims at presenting a novel method for the reduction of the simulation costs relative to the long‐term damage estimation (relative to a design load case) and based on the so‐called adaptive Kriging approach. From on a reduced set of observations (multiphysics simulator runs), a Kriging metamodel is here used to approximate the damage model response for all the nonsimulated sets of environmental parameters. The latter are subsequently used to assess the long‐term damage as presented in the standards. The statistical measure of the metamodel error of prediction is used into an iterative structure in order to progressively enrich the design of experiments with informative sets of environmental parameters. This allows us minimizing the global uncertainty of the approximation. The proposed algorithm, hereafter called the AK‐DA for “Adaptive Kriging Damage Assessment,” is illustrated with two industrial cases of fatigue analyses for the NREL 5MW reference monopile structure and its direct application
Hyperparameters and tuning strategies for random forest
Authors: Probst Philipp , Wright Marvin N. , Boulesteix Anne‐Laure
Published: January 2019

The random forest (RF) algorithm has several hyperparameters that have to be set by the user, for example, the number of observations drawn randomly for each tree and whether they are drawn with or without replacement, the number of variables drawn randomly for each split, the splitting rule, the minimum number of samples that a node must contain, and the number of trees. In this paper, we first provide a literature review on the parameters' influence on the prediction performance and on variable importance measures. It is well known that in most cases RF works reasonably well with the default values of the hyperparameters specified in software packages. Nevertheless, tuning the hyperparameters can improve the performance of RF. In the second part of this paper, after a presenting brief overview of tuning strategies, we demonstrate the application of one of the most established tuning strategies, model‐based optimization (MBO). To make it easier to use, we provide thetuneRangerR package that tunes RF with MBO automatically. In a benchmark study on several datasets, we compare the prediction performance and runtime oftuneRangerwith other tuning implementations in R and RF with default hyperparameters.

This article is categorized under:

Algorithmic Development > Biological Data Mining

Algorithmic Development > Statistics

Algorithmic Development > Hierarchies and Trees

Technologies > Machine Learning
An advanced review on text mining in medicine
Authors: Luque Carmen , Luna José M. , Luque Maria , Ventura Sebastian
Published: January 2019

Health care professionals produce abundant textual information in their daily clinical practice and this information is stored in many diverse sources and, generally, in textual form. The extraction of insights from all the gathered information, mainly unstructured and lacking normalization, is one of the major challenges in computational medicine. In this respect, text mining (TM) assembles different techniques to derive valuable insights from unstructured textual data so it has led to be especially relevant in medicine. The aim of this paper is therefore to provide an extensive review of existing techniques and resources to perform TM tasks in medicine. In this review, more than 90 relevant research studies have been analyzed, describing the most important practical applications, terminological resources, tools, and open challenges of TM in medicine.

This article is categorized under:

Application Areas > Health Care

Algorithmic Development > Biological Data Mining

Algorithmic Development > Hierarchies and Trees

Algorithmic Development > Ensemble Methods
Transcatheter aortic valve replacement in atypical valve anatomy using the Lotus valve
Authors: Xu Q. , Liu X. , Jiang J. , He Y. , Zhu Q. , Gao F. , Du F. , He W. , Cheng J. , Kong M. , Pu Z. , Zhou Q. , Gooley R. , Wang J.
Published: January 2019

Background

In the West, the safety and efficacy of the Lotus valve have been demonstrated; however, data in the Chinese population are still lacking. Few studies have compared the clinical outcomes of transcatheter aortic valve replacement (TAVR) with the Lotus valve in patients with bicuspid or tricuspid aortic valve stenosis. Our aim was to assess TAVR outcomes with the Lotus aortic valve in a Chinese patient cohort.

Methods

In total, 23 symptomatic, high-surgical risk patients with severe aortic valve stenosis were enrolled. Among them, nine patients (39%) had bicuspid aortic valves, and three patients had a large annulus dimension. The Lotus valve was successfully implanted in all patients. To facilitate accurate positioning, partial re-sheathing was attempted in ten patients (43.5%), while one patient had a full retrieval. One-year clinical follow-up was completed in all patients.

Results

There were no deaths, strokes, or major adverse cardiac and cerebrovascular events in 22 of the 23 patients at 30 days; the all-cause mortality rate at 1 year was 4.4% (1 of 23 patients). The mean aortic valve gradient decreased from 51.5 ± 8.8 mm Hg at baseline to 13.4 ± 4.9 mm Hg (p < 0.001) and the valve area increased from 0.6 ± 0.2 cm2 to 1.5 ± 0.4 cm2 (p < 0.001) at 30 days. Paravalvular leakage was absent or mild (22%), and no patient had severe paravalvular leakage. Six patients (26.1%) required a postprocedural pacemaker. There was no difference regarding the procedural and the 1‑year outcomes between patients with bicuspid and tricuspid aortic valve stenosis.

Conclusion

Our single-center experience demonstrated that the Lotus valve is feasible and effective for Chinese patients with aortic valve stenosis, including atypical cases with bicuspid aortic valves or large aortic annulus size.
Addressing the envisioned world problem: a case study in human spaceflight operations
Authors: Miller Matthew J. , Feigh Karen M.
Published: January 2019

The construction of future technological systems in work domains that do not yet exist, known as the envisioned world problem, is an increasingly important topic for designers, particularly given the rapid rate of technological advancement in the modern era. This paper first discusses the theoretical underpinnings of using cognitive work analysis (CWA) for developing a decision support system (DSS) situated within the envisioned world problem and recasts the problem as pathway-dependent processes. Using this pathway-dependent framework, each stage of the envisioning process is described to reveal how human factors experts can link existing work domains to envisioned instances. Finally, a case study example of the envisioning process that incorporates CWA modelling is demonstrated as it pertains to the advancement of the human spaceflight domain. As a result, this paper provides a unified treatment of the envisioned world problem with an end-to-end example of one approach to designing future technologies for future work domains.
Modelling smooth- and transitionally rough-wall turbulent channel flow by leveraging inner–outer interactions and principal component analysis
Authors: Wu Sicong , Christensen Kenneth T. , Pantano Carlos
Published: January 2019

Direct numerical simulations (DNS) of turbulent channel flow over rough surfaces, formed from hexagonally packed arrays of hemispheres on both walls, were performed at friction Reynolds numbers $Re_{\unicode[STIX]{x1D70F}}=200$, $400$ and $600$. The inner normalized roughness height $k^{+}=20$ was maintained for all Reynolds numbers, meaning all flows were classified as transitionally rough. The spacing between hemispheres was varied within $d/k=2$–$4$. The statistical properties of the rough-wall flows were contrasted against a complementary smooth-wall DNS at $Re_{\unicode[STIX]{x1D70F}}=400$ and literature data at $Re_{\unicode[STIX]{x1D70F}}=2003$ revealing strong modifications of the near-wall turbulence, although the outer-layer structure was found to be qualitatively consistent with smooth-wall flow. Amplitude modulation (AM) analysis was used to explore the degree of interaction between the flow in the roughness sublayer and that of the outer layer utilizing all velocity components. This analysis revealed stronger modulation effects, compared to smooth-wall flow, on the near-wall small-scale fluctuations by the larger-scale structures residing in the outer layer irrespective of roughness arrangement and Reynolds number. A predictive inner–outer model based on these interactions, and exploiting principal component analysis (PCA), was developed to predict the statistics of higher-order moments of all velocity fluctuations, thus addressing modelling of anisotropic effects introduced by roughness. The results show excellent agreement between the predicted near-wall statistics up to fourth-order moments compared to the original statistics from the DNS, which highlights the utility of the PCA-enhanced AM model in generating physics-based predictions in both smooth- and rough-wall turbulence.
Experiments on a jet in a crossflow in the low-velocity-ratio regime
Authors: Klotz L. , Gumowski K. , Wesfreid J. E.
Published: January 2019

The hairpin instability of a jet in a crossflow (JICF) for a low jet-to-crossflow velocity ratio is investigated experimentally for a velocity ratio range of $R\in (0.14,0.75)$ and crossflow Reynolds numbers $Re_{D}\in (260,640)$. From spectral analysis we characterize the Strouhal number and amplitude of the hairpin instability as a function of $R$ and $Re_{D}$. We demonstrate that the dynamics of the hairpins is well described by the Landau model, and, hence, that the instability occurs through Hopf bifurcation, similarly to other hydrodynamical oscillators such as wake behind different bluff bodies. Using the Landau model, we determine the precise threshold values of hairpin shedding. We also study the spatial dependence of this hydrodynamical instability, which shows a global behaviour.
Electrokinetic energy conversion of two-layer fluids through nanofluidic channels
Authors: Ding Zhaodong , Jian Yongjun , Tan Wenchang
Published: January 2019

Based on the Onsager reciprocal relation in the linear response regime, we first clarify the equivalence of thermodynamic and electric circuit analyses for electrokinetic energy conversion. Then we present a streaming-potential-based nanofluidic energy conversion system which comprises two immiscible fluids that form a flat interface in a slit-like channel. The validity of the Onsager reciprocal relation to such a two-fluid system is verified. The performance of such an energy converter is illustrated by considering two concrete oil–water systems with different properties. In both cases, we predict that the binary system with a thin oil layer increases both the maximum output power and the energy conversion efficiency, and this enhancement depends strongly on the mobile charges present at the oil–water interface, the salt concentration and the interface location. Concretely, for negatively charged interfaces, we find that the optimal efficiency increases with the interfacial charge for relatively thin oil layers; while for relatively thick oil layers, the interfacial charge has the opposite effect (i.e. reduction effect) on the energy conversion efficiency in the ranges of the parameters. We further investigate these systems from the viewpoint of energy transfer by deriving the related energy equation. We find that viscous dissipation consumes most of the power (more than 90 %), in both single-phase and two-fluid flows. However, the ratio of the viscous dissipation to the power input decreases with increase of the interfacial charge density for the case of a relatively thin oil layer in two-fluid flows. Meanwhile, although the presence of interfacial charges can lead to an increase in electrical dissipation, the amount of the increased power consumption is less than that of the reduced viscous dissipation in the case of a thin oil layer. Therefore, for two-fluid energy converters, the total power consumption can be reduced and the efficiency is improved.
Groundstates for Choquard type equations with Hardy–Littlewood–Sobolev lower critical exponent
Authors: Cassani Daniele , Van Schaftingen Jean , Zhang Jianjun
Published: January 2019

For the Choquard equation, which is a nonlocal nonlinear Schrödinger type equation,$$-\Delta u+V_{\mu, \nu} u=(I_\alpha\ast \vert u \vert ^{({N+\alpha})/{N}}){ \vert u \vert }^{{\alpha}/{N}-1}u,\quad {\rm in} \ {\open R}^N, $$where$N\ges 3$,Vμ,ν:ℝN → ℝ is an external potential defined for μ, ν > 0 andx ∈ ℝNbyVμ,ν(x) = 1 − μ/(ν2 + |x|2) and$I_\alpha : {\open R}^N \to 0$is the Riesz potential for α ∈ (0,N), we exhibit two thresholds μν, μν > 0 such that the equation admits a positive ground state solution if and only if μν < μ < μνand no ground state solution exists for μ < μν. Moreover, if μ > max{μν,N2(N − 2)/4(N + 1)}, then equation still admits a sign changing ground state solution provided$N \ges 4$or in dimensionN= 3 if in addition 3/2 < α < 3 and$\ker (-\Delta + V_{\mu ,\nu }) = \{ 0\} $, namely in the non-resonant case.
Induction for locally compact quantum groups revisited
Authors: Kalantar Mehrdad , Kasprzak Paweł , Skalski Adam , Sołtan Piotr M.
Published: January 2019

In this paper, we revisit the theory of induced representations in the setting of locally compact quantum groups. In the case of induction from open quantum subgroups, we show that constructions of Kustermans and Vaes are equivalent to the classical, and much simpler, construction of Rieffel. We also prove in general setting the continuity of induction in the sense of Vaes with respect to weak containment.
Dating Gordion: the Timing and Tempo of Late Bronze and Early Iron Age Political Transformation
Authors: Kealhofer Lisa , Grave Peter , Voigt Mary M
Published: January 2019

Gordion has long served as an archaeological type site for Iron Age central Anatolia and provided pioneering radiocarbon (14C) determinations as reported in the first issue ofRadiocarbon(1959). Absolute dating of key events at Gordion continue to reshape our understanding of regional development and interaction in the Iron Age, with a major conflagration in the late 9th BCE century at this site the most recent focus of attention (DeVries et al. 2003). Here we present the latest series of14C determinations for Gordion from Late Bronze Age and Early Iron Age contexts. Fifteen absolute dates provide a critical new framework for establishing the timing and tempo of cultural transformation from the collapse of the Hittite Empire through to the subsequent formation of the Phrygian polity that dominated central Anatolia from the 9th to the 7th c. BCE. This chronometric revision transforms our perspective on the LBA/EIA transition at this site: from disengagement from Hittite hegemony in the 12th c. BCE, to the precocious emergence of the Phrygian capital in the early 9th c. BCE.
Eight New Late Pleistocene/Early Holocene AMS Dates from the Southeastern Baltic
Authors: Philippsen Bente , Ivanovaitė Livija , Makhotka Kirill , Sauer Florian , Riede Felix , Olsen Jesper
Published: January 2019

Only a limited number of radiometric dates for the Final Palaeolithic and the first half of the Mesolithic are available from the southeastern Baltic. This paper presents eight new Late Pleistocene/Early Holocene radiocarbon accelerator mass spectrometry (14C AMS) ages of osseous artifacts housed at the Kaliningrad Regional Museum of History and Art. These artifacts include one piece of worked reindeer (Rangifer tarandus) antler, three axes of the so-called Lyngby type, one bone point, one uniserial harpoon, one so-called bâton percé antler shaft, and one slotted bone. All the samples were successfully dated and yielded five Late Pleistocene and three Early Holocene ages, including the hitherto earliest age for human occupation in the Eastern Baltic. The dates include not only a surprisingly early date for a bone point (for this region), but also some dates that contradict expected ages based on traditional typological assessment. Our study significantly adds to the still small number of existing absolutely dated artifacts from the region and proposes new ways of viewing the Final Palaeolithic and Early Mesolithic chronology in the southeastern Baltic.
Comparing proxy rated quality of life of people living with dementia in care homes
Authors: Robertson S. , Cooper C. , Hoe J. , Lord K. , Rapaport P. , Marston L. , Cousins S. , Lyketsos C. G. , Livingston G.
Published: January 2019

Background

Improving quality of life (QOL) for people with dementia is a priority. In care homes, we often rely on proxy ratings from staff and family but we do not know if, or how, they differ in care homes.

Methods

We compared 1056 pairs of staff and family DEMQOL-Proxy ratings from 86 care homes across England. We explored factors associated with ratings quantitatively using multilevel modelling and, qualitatively, through thematic analysis of 12 staff and 12 relative interviews.

Results

Staff and family ratings were weakly correlated (ρs = 0.35). Median staff scores were higher than family's (104 v. 101; p < 0.001). Family were more likely than staff to rate resident QOL as ‘Poor’ (χ2 = 55.91, p < 0.001). Staff and family rated QOL higher when residents had fewer neuropsychiatric symptoms and severe dementia. Staff rated QOL higher in homes with lower staff:resident ratios and when staff were native English speakers. Family rated QOL higher when the resident had spent longer living in the care home and was a native English. Spouses rated residents’ QOL higher than other relatives. Qualitative results suggest differences arise because staff felt good care provided high QOL but families compared the present to the past. Family judgements centre on loss and are complicated by decisions about care home placement and their understandings of dementia.

Conclusion

Proxy reports differ systematically between staff and family. Reports are influenced by the rater:staff and family may conceptualise QOL differently.
Kinematics-Based Simulation and Animation of Articulated Rovers Traversing Uneven Terrains
Authors: Tarokh Mahmoud , Ho Huy Dang
Published: January 2019

The paper develops a simulation and animation environment for high-mobility rovers based on kinematic modeling. Various kinematic chains starting from the rover body to the wheels are analyzed and aggregated to obtain the model of the rover body motion in terms of the wheel motions. This model is then used to determine the actuations of the joints, wheels speed, and steering motors to achieve a desired motion of the rover over uneven terrain while avoiding loss of balance and tip-over. The simulation environment consists of a number of modules, including terrain and trajectory generation, and kinematic models for rover actuation and navigation. The animation of the rover motion over various terrains is developed, which allows observing the rover from various viewpoints and interacting with the system through a graphical user interface. The performance of the overall system is demonstrated by modeling a high-mobility space exploration rover, and the responses of the rover on uneven terrains are provided, which show the usefulness of the proposed modeling, simulation, and animation scheme.
Proceduralism, Political Embeddedness and Death Penalty Lawyers in China
Authors: Lu Hong , Trejbalova Tereza , Liang Bin
Published: January 2019

Research suggests that cause lawyers are a diverse group. Death penalty lawyers with attachment to political institutions and a strong commitment to procedurals tend to have a unique path to professional identification, participation in the legal process and acquiring the ability to affect case outcomes. Borrowing from Hilbink's typologies and Liu and Halliday's analytical framework, this study examines in detail the practices of proceduralist and progressive elite lawyers. It uses a high-profile capital case, the Nian Bin case, as a case study to analyse the motivation and strategies of the lead defence lawyer in the context of progressive proceduralist cause lawyers. Relevant theoretical and policy implications as well as suggestions for future studies are discussed.
Observations of the first electromagnetic counterpart to a gravitational wave source by the TOROS collaboration
Authors: Macri Lucas M. , Díaz Mario C. , Lambas Diego Garcia ,   the TOROS collaboration
Published: January 2019

We present the results of prompt optical follow-up of the electromagnetic counterpart of GW170817 by the Transient Optical Robotic Observatory of the South Collaboration (TOROS). We detected highly significant dimming in the light curves of the counterpart over the course of only 80 minutes of observations obtained ~35 hr after the trigger with the T80-South telescope. A second epoch of observations, obtained ~59 hr after the event with the EABA 1.5m telescope, confirms the fast fading nature of the transient. The observed colors of the counterpart suggest that this event was a “blue kilonova” relatively free of lanthanides.
CHAPTER II: TWENTY NINTH GENERAL ASSEMBLY BUSINESS SESSIONS
Authors: Kaifu Norio
Published: January 2019

The President of the IAU, Prof. Norio Kaifu, welcomed the delegates and members to this first business session of the General Assembly. The President invited the General Secretary, Dr. Thierry Montmerle, to start the business session.
CHAPTER II: TWENTY NINTH GENERAL ASSEMBLY BUSINESS SESSIONS
Authors: Kaifu Norio
Published: January 2019

The President of the IAU, Prof. Norio Kaifu, welcomed the delegates and members to the second business session of the General Assembly. The President invited the General Secretary, Dr. Thierry Montmerle, to start the business session.
Correcting micronutrient deficiencies before sleeve gastrectomy may be useful in preventing early postoperative micronutrient deficiencies
Authors: Schiavo Luigi , Pilone Vincenzo , Rossetti Gianluca , Romano Mafalda , Pieretti Gorizio , Schneck Anne-Sophie , Iannelli Antonio
Published: January 2019

Abstract. Micronutrient deficiencies (MD) shortly after sleeve gastrectomy (SG) are frequent and patients with obesity often show MD preoperatively. Our aim was to assess whether the correction of MD before SG could play a role in preventing early postoperative MD. Eighty patients (58 females, 22 males) who underwent SG were evaluated retrospectively. Patients were divided according to whether they had received preoperative MD correction (Group A, n = 42; 30 females, 12 males) or not (Group B, n = 38; 28 females, 10 males). Micronutrient status was assessed preoperatively, at 3 and 12-months after SG in both groups. After SG, Group A and Group B patients received the same multivitamin supplement and followed the same diet. Nutrient intake of all patients was evaluated by food frequency questionnaires. Before SG, patients of Group A had no MD, whereas patients of Group B were mostly deficient in vitamin B12 (10.5%, 3 women, 1 man), folate (15.8%, 5 women, 1 man), 25-vitamin D (39.5%, 10 women, 5 men), iron (26.3%, 8 women, 2 men), and zinc (7.9%, 2 women, 1 men). At 3- and 12-month follow-up, no patient in group A had developed new MD, whereas all patients of Group B continued to be deficient in one or more micronutrient, despite systematic postoperative supplementation. No statistical differences (p<0.05) in estimated nutrient intake were observed in either group. Based on our findings, we are able to support the hypothesis that pre-SG correction of MD may be useful in preventing early post-SG MD.
Toward High‐Resolution Period‐Dependent Seismic Monitoring of Tropical Cyclones
Authors: Retailleau Lise , Gualtieri Lucia
Published: January 2019

Pioneering work in the midtwentieth century laid the foundation for our understanding of secondary microseism generation by tropical cyclones. Yet, tracking their sources and linking them to the mechanisms that generate these signals remain challenging. Here, we successfully retrieve the seismic sources associated with Typhoon Ioke (2006) with an unprecedented 3‐hr resolution and in the entire secondary microseism period band (T= 2–9 s). Our results indicate that the seismic sources follow the tropical cyclone at a constant distance from its center, corresponding to 34‐kt winds. We also assess the link between the generation of the long‐period secondary microseism signals and the increase of the typhoon propagation speed. This accurate location of seismic sources may provide a new data set for imaging the Earth's interior and allow for new insights on the interaction between the atmosphere, the ocean, and the solid Earth.
Midlatitudinal Special Airglow Structures Generated by the Interaction Between Propagating Medium‐Scale Traveling Ionospheric Disturbance and Nighttime Plasma Density Enhancement at Magnetically Quiet Time
Authors: Sun Longchang , Xu Jiyao , Xiong Chao , Zhu Yajun , Yuan Wei , Hu Lianhuan , Liu Weijun , Chen Gang
Published: January 2019

This paper reports a special midlatitudinal medium‐scale traveling ionospheric disturbance (MSTID) event, accompanied by a poleward surge of airglow depletion/enhancement and a bifurcation of depletion during the magnetically quiet period. These special structures were generated during a decreasing height of ionosphere with nighttime plasma density enhancement and increment of airglow emission intensity possibly caused by a passing‐by midnight brightness wave. We suggest that the interaction of the passing‐by MSTID and nighttime plasma density enhancement resulted in the poleward surge and bifurcation of airglow depletion. The nighttime plasma density enhancement could feed the high plasma density to interact with the airglow depletions of MSTID, causing the poleward surge and bifurcation of airglow depletion by the secondary gradient drift instability. The poleward surged airglow enhancement within two adjacent depletions of MSTID is also firstly reported in this study.
How the Inhomogeneity of Wet Sea Salt Aerosols Affects Direct Radiative Forcing
Authors: Wang Zheng , Bi Lei , Yi Bingqi , Zhang Xiaoyu
Published: January 2019

Sea salt aerosols were assumed to be homogeneous spheres in most climate models. However, observations show that sea salt particles are inhomogeneous during the deliquesce and crystallization processes. Using a two‐layer sphere model, we found that backscattering of solar radiation associated with sea salts is underestimated in homogeneous sea salt models. The Community Earth System Model is used to assess the inhomogeneity effect on direct radiative forcing. For global climate model simulation, the inhomogeneity effect on radiative transfer is found to be small as high RHs over widespread oceans suppress the impact of inhomogeneity. On the other hand, in coastal regions, the inhomogeneity effect can cause up to 10% radiative forcing difference of sea salt aerosols. The inhomogeneity effect of sea salt aerosols has to be considered over coastal regions, especially in the Mediterranean, Australia, and the eastern coast of South America.
Scattering Radiation Pattern Atlas: What Anisotropic Elastic Properties Can Body Waves Resolve?
Authors: Kazei Vladimir , Alkhalifah Tariq
Published: January 2019

Full‐waveform inversion (FWI) optimizes the subsurface properties of geophysical Earth models in such a way that the modeled data, based on these subsurface properties, match the observed data. The anisotropic properties, whether monoclinic, orthorhombic, triclinic, or vertical transversally isotropic (VTI), of the subsurface, be it a fractured reservoir or the core‐mantle boundary, are necessary to describe the observed wave phenomena. There are no principal limitations on the complexity of the anisotropy that can be inverted using FWI. However, the question remains—what kind of anisotropic descriptions of the elastic properties of the Earth can or cannot be inverted reliably from seismic waveforms? We reveal the resolution that can be achieved through reconstructions of each elastic parameter by building vertical resolution patterns from the scattering radiation patterns of body waves. A visual analysis of these patterns indicates “trade‐offs,” that is, perturbations of parameters that have the same reflection‐based scattering patterns as other perturbations. Each trade‐off leads to an apparent ambiguity in the inversion, which must be addressed by additional assumptions, constraints, or regularizations. For orthorhombic media, we find the exact trade‐offs that exist between parameters. Our parameterization isolates the VTI parameters, and therefore, we also obtain trade‐offs for every scattering mode for VTI media. We discover that only monoclinic parameters are recoverable from the first‐order scattering of monotypic waves. We summarize the trade‐offs in tables for easy reference. This paper is intended to be useful for researchers setting up anisotropic FWI problems, and interpreting or controlling the quality of such inversions.
Model‐Derived Uncertainties in Deep Ocean Temperature Trends Between 1990 and 2010
Authors: Garry F. K. , McDonagh E. L. , Blaker A. T. , Roberts C. D. , Desbruyères D. G. , Frajka‐Williams E. , King B. A.
Published: January 2019

We construct a novel framework to investigate the uncertainties and biases associated with estimates of deep ocean temperature change from hydrographic sections and demonstrate this framework in an eddy‐permitting ocean model. Biases in estimates from observations arise due to sparse spatial coverage (few sections in a basin), low frequency of occupations (typically 5–10 years apart), mismatches between the time period of interest and span of occupations, and from seasonal biases relating to the practicalities of sampling during certain times of year. Between the years 1990 and 2010, the modeled global abyssal ocean biases are small, although regionally some biases (expressed as a heat flux into the 4,000‐ to 6,000‐m layer) can be up to 0.05 W/m2. In this model, biases in the heat flux into the deep 2,000‐ to 4,000‐m layer, due to either temporal or spatial sampling uncertainties, are typically much larger and can be over 0.1 W/m2 across an ocean. Overall, 82% of the warming trend deeper than 2,000 m is captured by hydrographic section‐style sampling in the model. At 2,000 m, only half the model global warming trend is obtained from observational‐style sampling, with large biases in the Atlantic, Southern, and Indian Oceans. Biases due to different sources of uncertainty can have opposing signs and differ in relative importance both regionally and with depth, revealing the importance of reducing temporal and spatial uncertainties in future deep ocean observing design.
Pacific Ocean Forcing and Atmospheric Variability Are the Dominant Causes of Spatially Widespread Droughts in the Contiguous United States
Authors: Baek Seung H. , Smerdon Jason E. , Seager Richard , Williams A. Park , Cook Benjamin I.
Published: January 2019

The contributions of oceanic and atmospheric variability to spatially widespread summer droughts in the contiguous United States (hereafter, pan‐CONUS droughts) are investigated using 16‐member ensembles of the Community Climate Model version 3 (CCM3) forced with observed sea surface temperatures (SSTs) from 1856–2012. The employed SST forcing fields are either (i) global or restricted to the (ii) tropical Pacific or (iii) tropical Atlantic to isolate the impacts of these two ocean regions on pan‐CONUS droughts. Model results show that SST forcing of pan‐CONUS droughts originates almost entirely from the tropical Pacific because of atmospheric highs from the northern Pacific to eastern North America established by La Niña conditions, with little contribution from the tropical Atlantic. Notably, in all three model configurations, internal atmospheric variability influences pan‐CONUS drought occurrence by as much or more than the ocean forcing and can alone cause pan‐CONUS droughts by establishing a dominant high centered over the U.S. montane west. Similar results are found for the Community Atmosphere Model version 5 (CAM5). Model results are compared to the observational record, which supports model‐inferred contributions to pan‐CONUS droughts from La Niñas and internal atmospheric variability. While there may be an additional association with warm Atlantic SSTs in the observational record, this association is ambiguous due to the limited number of observed pan‐CONUS droughts. The ambiguity thus opens the possibility that the observational results are limited by sampling over the twentieth century and not at odds with the suggested dominance of Pacific Ocean forcing in the model ensembles.
The Effects of PM2.5 Concentrations and Relative Humidity on Atmospheric Visibility in Beijing
Authors: Wang Xiaoyan , Zhang Renhe , Yu Wei
Published: January 2019

Atmospheric visibility is often used as a proxy for ambient air quality. However, in addition to the concentrations of particulate matter, visibility is also affected by meteorological conditions. The relative contributions of PM2.5 concentrations and meteorological conditions to visibility are not yet clear. In this study, the individual contributions of PM2.5 concentrations and the relative humidity (RH) to the visibility are measured based on observations at 12 stations in Beijing. We find that visibility decreases quickly as PM2.5 concentrations increase at clean condition and decreases slowly when PM2.5 concentrations exceed 100 μg/m3. The visibility decreases linearly as PM2.5 concentrations increase when PM2.5 concentrations lower than 50 μg/m3; however, there tends to be an exponential relationship as PM2.5 concentrations increase. The PM2.5 concentrations can explain 50% of the variance in visibility in clean and high‐humidity environments, whereas this fraction decreases to 10–15% when the PM2.5 concentrations exceed 200 μg/m3. In contrast, RH has little effect on visibility under dry conditions. When the RH exceeds 40%, atmospheric visibility tends to display an inversely proportional and exponential relationship with RH under polluted and clean conditions, respectively. Under high‐humidity and highly polluted conditions, up to 40% of the variance in visibility is associated with RH. The PM2.5 concentrations dominate the variations in visibility under dry or low PM2.5 concentrations, and the contributions of RH become increasingly important as PM2.5 concentrations and humidity increase. The difference of aerosol types and weather conditions increase the uncertainties of correlation coefficients between visibility and PM2.5/RH. This study emphasizes the atmospheric conditions when employing visibility as a proxy for air pollution.
Patterns and Controls of Light Use Efficiency in Four Contrasting Forest Ecosystems in Yunnan, Southwest China
Authors: Fei Xue‐Hai , Song Qing‐Hai , Zhang Yi‐Ping , Yu Gui‐Rui , Zhang Lei‐Ming , Sha Li‐Qing , Liu Yun‐Tong , Xu Kun , Chen Hui , Wu Chuan‐Sheng , Chen Ai‐Guo , Zhang Shu‐Bin , Liu Wei‐Wei , Huang Hua , Deng Yun , Qin Hai‐Lang , Li Pei‐Guang , Grace John
Published: January 2019

Ecosystem light use efficiency (LUE) is a critical parameter in estimating CO2 uptake by vegetation from climatological and satellite data. However, the spatiotemporal dynamics and biophysical regulations of ecosystem‐level LUE are not well understood, resulting in large uncertainties in the estimation of gross primary productivity (GPP) using LUE‐based models. In this study, we used eddy covariance to explore spatiotemporal variations and controls of LUE in four contrasting forest ecosystems (savanna, tropical rainforest, subtropical evergreen forest, and subalpine coniferous forest). Based on 27 site years of data, we found that (1) the multiyear mean LUE was 0.063, 0.251, 0.247, and 0.140 g C· mol photon−1 in the four contrasting ecosystems, respectively; (2) the LUE in the wet season (May–October) was higher than that in the dry season in all studied ecosystems; (3) the leaf area index controlled GPP and LUE significantly and explained 74%, 29%, 54%, and 36% of the variation in GPP and 51%, 19%, 41%, and 54% of the variation in LUE in the four contrasting ecosystems, respectively; (4) path analysis revealed the critical roles of GPP and vapor pressure deficit in controlling LUE in these four forest ecosystems; and (5) under warming scenarios, LUE may decrease in savanna but increase in the other three ecosystems, while decreasing precipitation (P) may reduce LUE in the ecosystems studied. This study improves our understanding of the influence of biophysical factors on LUE and demonstrates how LUE changes with variations in temperature, soil moisture, and leaf area index, thereby improving estimations of large‐scale carbon exchange/cycling.
Groundwater‐Derived DIC and Carbonate Buffering Enhance Fluvial CO2 Evasion in Two Australian Tropical Rivers
Authors: Duvert Clément , Bossa Mylène , Tyler Kyle J. , Wynn Jonathan G. , Munksgaard Niels C. , Bird Michael I. , Setterfield Samantha A. , Hutley Lindsay B.
Published: January 2019

Despite recent evidence suggesting that groundwater inputs of dissolved inorganic carbon (DIC) to rivers can contribute substantially to the fluvial evasion of carbon dioxide (CO2), groundwater is seldom integrated into fluvial carbon budgets. Also, unclear is the way equilibria between CO2 and ionic forms of carbonate will affect CO2 evasion from rivers. We conducted longitudinal river surveys of radon and carbon along two rivers of tropical Australia and developed a mass balance framework to assess the influence of groundwater‐derived inorganic carbon and carbonate buffering on CO2 evasion rates. The mean CO2 evasion flux totaled 8.5 and 2.3 g·C·m−2·day−1 for the two rivers, with considerable spatial variations that we attributed primarily to changes in groundwater inflow rates (minima and maxima per river reach 1.2–45.1 and 0.2–13.4 g·C·m−2·day−1). In the larger river system, inflowing groundwater delivered on average 6.7 g·C·m−2·day−1 as dissolved CO2—almost 10 times as much as the CO2 produced via river metabolism—and 21.6 g·C·m−2·day−1 as ionic forms. In both rivers, these groundwater‐derived inputs were a mixture of biogenic and geogenic carbon sources. Spatialized estimates of the carbonate buffering flux revealed that in reaches where CO2 evasion was particularly high, the carbonate system was able to maintain high CO2 concentrations by adjustment of carbonate equilibria. This process was likely triggered by high groundwater inflow rates. Our findings suggest that both groundwater inputs and carbonate equilibria need to be accounted for in fluvial carbon budgets, particularly in high‐alkalinity rivers.
Analogue Modeling of Plate Rotation Effects in Transform Margins and Rift‐Transform Intersections
Authors: Farangitakis G.‐P. , Sokoutis D. , McCaffrey K. J. W. , Willingshofer E. , Kalnins L. M. , Phethean J. J. J. , van Hunen J. , van Steen V.
Published: January 2019

Transform margins are first‐order tectonic features that accommodate oceanic spreading. Uncertainties remain about their evolution, genetic relationship to oceanic spreading, and general structural character. When the relative motion of the plates changes during the margin evolution, further structural complexity is added. This work investigates the evolution of transform margins and associated rift‐transform intersections, using an analogue modeling approach that simulates changing plate motions. We investigate the effects of different crustal rheologies by using either (a) a two‐layer brittle‐ductile configuration to simulate upper and lower continental crust, or (b) a single layer brittle configuration to simulate oceanic crust. The modeled rifting is initially orthogonal, followed by an imposed plate vector change of 7° that results in oblique rifting and plate overlap (transpression) or underlap (transtension) along each transform margin. This oblique deformation reactivates and overprints earlier orthogonal structures and is representative of natural examples. We find that (a) a transtensional shift in the plate direction produces a large strike‐slip principal displacement zone, accompanied by en‐echelon oblique‐normal faults that accommodate the horizontal displacement until the new plate motion vector is stabilized, while (b) a transpressional shift produces compressional structures such as thrust fronts in a triangular zone in the area of overlap. These observations are in good agreement with natural examples from the Gulf of California (transtensional) and Tanzania Coastal Basin (transpressional) shear margins and illustrate that when these deformation patterns are present, a component of plate vector change should be considered in the evolution of transform margins.
Trends and Interannual Variability in Terrestrial Water Storage Over the Eastern United States, 2003–2016
Authors: Cao Qian , Clark Elizabeth A. , Mao Yixin , Lettenmaier Dennis P.
Published: January 2019

We examine the relative contributions of root zone soil moisture (SM) and groundwater (GW) storage to trends and interannual variability in total water storage (TWS) from essentially the entire Gravity Recovery and Climate Experiment (GRACE) record (2003–2016). Our study region is the Eastern United States where GW generally is shallow, and we use observations and simulations from a suite of land surface models (LSMs) where observations are not available. We first consider Illinois, which has a long‐term network of SM sensors and observation wells. We assessed the uncertainties in GRACE TWS in comparison with the observation‐based TWS using observed SM, well‐derived GW, and model‐reconstructed snow water equivalent. We evaluated LSM SM compared with observations over Illinois; generally good agreement encouraged us to use the LSM‐ensemble average SM, well‐derived GW, and Snow Data Assimilation System snow water equivalent over the entire Eastern United States to examine the relative contribution of storage components to GRACE TWS over this larger domain. Taken together, the three components explained 2%–85% of interannual variability in GRACE TWS across the 2‐digit Hydrologic Unit Code regions. Root zone SM was the dominant contributor to the interannual variability (but not trends) of GRACE TWS over much of the Eastern United States. We also compared three independent approaches to estimating GW: well data, baseflow observations, and GRACE. Despite much smaller magnitudes of variation, baseflow‐derived GW correlated more highly with well‐derived GW over the eastern‐most and Upper Mississippi regions, while GRACE‐derived GW matched better with well‐derived GW over the remaining regions.