bluuebunny/crossref_metadata_2025 huggingface dataset:
Demagnetizing the drill string magnetic interference in Far North and in Pakistan
Authors: Lalji Shaine Mohammadali , Haneef Javed , Khan Muhammad Arqam , Ali Syed Imran
Published: November 2019

Drilling in Barents Sea proves to be a challenging task, as this region is situated in auroral zones having high geomagnetic latitude, where magnetic interferences develop from magnetic field and magnetic materials inside subsurface are quite common. For this region, monitoring of magnetic field is utterly significant as any fluctuations can distort the tool sensor performance with ultimately enlarging the uncertainty in azimuth. To guide a well to its desire location, measurement while drilling (MWD) tool needs to be operated with utmost precision; however, its accuracy compromises as a result of magnetic interferences from drill string and nearby magnetic material. The performance of this tool depends upon its sensors. Any distortion in sensor performance can lead to problems such as multiple sidetracking and increase in overall project cost. Furthermore, the same BHA was also placed in a region of Pakistan and the impact drill string interference was observed. It was discovered that the interferences that had tremendous impact on magnetometer Z-component in Barents Sea had a drastic reduction in the region of Pakistan as it is situated in low latitude, where uncertainty in azimuth is low. In this work, an exemplary bottom-hole assembly (BHA) was analyzed and the impact of individual drill string components interferences was observed on the MWD sensors. It was perceived that the bit was responsible for creating the major distortion in MWD sensor. Apart from that, it was also investigated that the location of the well also plays a vital role in this distortion. This intervention in the sensors is created by a vast difference between the used actual length and the recommended length of nonmagnetic drill collar in the BHA. Numerically, it was investigated that if the physical distance between the sensors and bit is increased, then this interference is reduced. It was also apparent that the Z-component of the magnetometer was utterly distorted because of this interference, while the X- and Y-components were proved to be independent of these interferences. It was further examined that the effects of latitude and longitude play a significant role in the course of changing the impact of these errors on magnetization.
Online Aristotelian Character Friendship as an Augmented Form of Penpalship
Authors: Kristjánsson Kristján
Published: November 2019

This paper adds ammunition to recent arguments for the possibility of online character friendships in the Aristotelian sense. It does so by exploring sustained and deep email correspondence orepalshipas a potential venue for the creation, development and maintenance of character friendships, and by drawing an analogy with a historically famous example ofpenpalship: that forged between Voltaire and Catherine the Great. It is argued that epalships allow for various technological extensions in the cyberworld of today that were not available to Voltaire and Catherine; and that augmented with those extensions, there is even more reason for seeing epalships as potentially making the grade as true character friendships than traditional penpalships. However, despite being potentially categorisable as character friendships, mature epalships are vulnerable to the same problems and pitfalls as other examples of character friendships, and perhaps even more so: pitfalls that were mostly overlooked by Aristotle himself.
Molecular and cytogenetic description of somatic hybrids between Gentiana cruciata L. and G. tibetica King
Authors: Tomiczak Karolina
Published: November 2019

Somatic hybridization provides an opportunity to create cells with new genetic constitution. Here, the interspecific somatic hybrid plants regenerated in vitro following fusion of cell suspension–derived protoplasts of tetraploid Cross Gentian (Gentiana cruciata L., 2n = 52) with protoplasts released from mesophyll tissue of another tetraploid species, Tibetan Gentian (G. tibetica King, 2n = 52), were studied. According to the results of genome analyses with AFLP, ISSR, and CAPS markers, all somatic hybrids were genetically closer to “suspension” fusion partner G. cruciata than to “mesophyll” partner G. tibetica, but they got G. tibetica chloroplasts. Chromosome counting revealed little variation in the number of chromosomes in hybrid’s cells (2n = 88 or 2n = 90), although all plants possessed similar nuclear DNA content which remained stable even after 2 years of in vitro culture. Fluorescence in situ hybridization (FISH) showed that hybrids possessed 4 to 7 chromosomes bearing 5S rDNA sites and 6 or 7 chromosomes with 35S rDNA sites. A part of FISH signals was smaller than those observed in the parental species, which could indicate the loss of rDNA sequences. Genomic in situ hybridization (GISH) showed the predominance of the number of G. cruciata chromosomes over chromosomes of G. tibetica. However, a significant level of cross-hybridization was observed for about one-third of hybrid chromosomes, indicating a high degree of homeology between the genomes of G. cruciata and G. tibetica.
Two New Phenolic Constituents from the Stems of Euphorbia griffithii
Authors: Kaunda Joseph Sakah , Zhang Ying-Jun
Published: November 2019

Phytochemical studies on MeOH extract of stems ofEuphorbia griffithiiled to the isolation of one new hydrolyzable tannin dimer, corilagiffithiin (1) and one new galloyl-glucoside (2), alongside six known ones (3–8). Their structures and absolute configurations were determined by in depth spectroscopic analyses and comparison of their 1D NMR and MS data with literature reported values. Configurations of sugar moieties were determined by acidic hydrolysis and subsequent GC analysis of their corresponding trimethylsilylatedl-cysteine adduct. At a concentration of 50 μM, compounds1–3showed no anti-inflammatory activities.

Graphic Abstract
Functionalised microwave sensors for real-time monitoring of copper and zinc concentration in mining-impacted water
Authors: Frau I. , Wylie S. R. , Byrne P. , Cullen J. D. , Korostynska O. , Mason A.
Published: November 2019

Microwave spectroscopy has been identified as a novel and inexpensive method for the monitoring of water pollutants. Integrating microwave sensors with developed coatings is a novel strategy to make the sensing system more specific for a target contaminant. This study describes the determination of copper and zinc concentration in water in both laboratory-prepared and acquired mine water samples from two abandoned mining areas in Wales, UK. Uncoated sensors immersed in samples spiked with 1.25 mg/L concentrations of copper and zinc, using the standard addition method, were able to quantify the concentration at 0.44 GHz with a strong linear correlation (R2 = 0.99) for the reflection coefficient magnitude (|S11|). Functionalised microwave sensors with l-cysteine, chitosan and bismuth zinc cobalt oxide-based coatings have shown improvement in the sensing performance. Specifically, the linear correlation at 0.91–1.00 GHz between |S11| and a polluted water sample spiked with Cu showed a higher (R2 = 0.98), sensitivity (1.65 ΔdB/mg/L) and quality factor (135) compared with uncoated sensors (R2 = 0.88, sensitivity of 0.82 ΔdB/mg/L and Q-factor 30.7). A Lorentzian peak fitting function was applied for performing advanced multiple peak analysis and identifying the changes in the resonant frequency peaks which are related to the change in metal ion content. This novel sensor platform offers the possibility of in situ monitoring of toxic metal concentrations in mining-impacted water, and multiple peak features, such as area, full width half maximum, centre and height of the peaks, have the possibility to offer higher specificity for similar toxic metals, as between copper and zinc ions.
Effects of Corbicula fluminea on the nutrient concentration and phytoplankton biomass of tropical reservoirs
Authors: Chappell Jessica , Whitmire Stefanie , Sotomayor-Ramírez David , Martínez-Rodríguez Gustavo
Published: November 2019

Invasive bivalves are known to negatively impact aquatic ecosystems across the globe. Previous research has demonstrated invasive bivalves can shift nutrients from the water column to the sediment, harm native bivalves, and reduce phytoplankton biomass. However, bivalve effects vary with species and the region where the invasion occurs. Therefore, we used mesocosm experiments to examine the impact of invasive Corbicula fluminea on nutrient concentration and phytoplankton biomass in the water column of mesotrophic and eutrophic Puerto Rican reservoirs. We used four treatments to determine the effect of C. fluminea on the water column. We found C. fluminea did not have a significant effect on the ammonium, nitrate, or phosphorus concentration in either the mesotrophic or eutrophic mesocosm experiments. Additionally, C. fluminea presence did not significantly alter phytoplankton biomass, though Synedra dominated the phytoplankton community when C. fluminea were absent. While C. fluminea may not have caused an effect in the water column as it was potentially phytoplankton limited, the mesocosm experiment conditions reflect the natural environment, indicating phytoplankton limitation could be an issue in the reservoirs. Our findings suggest C. fluminea does not have a large effect on nutrient concentration or phytoplankton biomass in eutrophic and mesotrophic Puerto Rican reservoirs. This study represents the first effort to examine the effects of C. fluminea presence on the water column of a tropical reservoir.
Plastic bags as simple photobioreactors for cyanobacterial hydrogen production outdoors in Moscow region
Authors: Shastik Evgeny , Romanova Anastasiya , Laurinavichene Tatyana , Petushkova Ekaterina , Sakurai Hidehiro , Tsygankov Anatoly
Published: November 2019

The application of transparent plastic bags with a gas barrier layer as inexpensive photobioreactors for H2 production by the cyanobacterium Anabaena sp. PCC 7120 ∆Hup mutant cells was explored outdoors in Moscow region for the first time. Two experiments were performed in July and August, the average daily temperature being 21.7 and 20.6 °C, the average daily light intensity being 290 and 340 µmol photon m−2 s−1 in experiment #1 and #2, respectively. The maximal H2 production rate was 20.6 mL day−1 L−1 of culture, with accumulation of 33.2 mL L−1 during 5 days and a final H2 content of 1.1% (v/v). Molecular nitrogen added to the Ar gas at 3.3% significantly affected neither the rate nor the duration of H2 production. Low morning temperatures as well as high daytime light intensities (especially at low cell concentrations) seemed to reduce the H2 production rate. The activities obtained were lower as compared to the previously reported data. It could be attributable to suboptimal weather conditions and simple device arrangement. However, results prove that H2 production by cyanobacteria is still feasible outdoors in plastic bags, the cheapest photobioreactors.
Enhanced adsorptive removal of Indigo carmine dye performance by functionalized carbon nanotubes based adsorbents from aqueous solution: equilibrium, kinetic, and DFT study
Authors: Dastgerdi Zeinab Hoseini , Meshkat Seyyed Salar , Esrafili Mehdi D.
Published: November 2019

The present work considers an adsorptive removal of Indigo carmine (IC) dye onto nanotube carbon (CNTs). The pure CNTs were prepared via chemical vapor deposition (CVD) method utilizing methane gas as a carbon source at 1000 °C in a quartz tube. The morphology and surface chemical structure of the adsorbents were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption/desorption technique, and thermal gravity analysis (TGA). The parameters of the IC dye adsorption, such as initial concentration, contact time, pH, and mass-loaded adsorbent, were evaluated. The kinetic study confirmed that a pseudo-second-order model was best fitted to the adsorption data. The removal efficiency of adsorption onto pure and COOH-functionalized CNTs was 84% and 98.7% at 15 min, respectively. The equilibrium results were fitted well to the Langmuir isotherm model. The adsorption capacity of the CNT and COOH–CNT was 88.5 and 136 mg/g, respectively. The reusability of the adsorbents was studied, and after eight cycles, the efficiency decreased to 70%. Moreover, the density functional theory calculations confirmed that the functionalization of CNTs with COOH groups improves the adsorption properties of IC due to the formation of hydrogen-bonding interactions.
Laser-Etched Stretchable Graphene–Polymer Composite Array for Sensitive Strain and Viscosity Sensors
Authors: Jiang Yuting , Wang Yang , Wu Heting , Wang Yuanhao , Zhang Renyun , Olin Håkan , Yang Ya
Published: November 2019

The ability to control surface wettability and liquid spreading on textured surfaces is of interest for extensive applications. Soft materials have prominent advantages for producing the smart coatings with multiple functions for strain sensing. Here, we report a simple method to prepare flexible hydrophobic smart coatings using graphene–polymer films. Arrays of individual patterns in the films were created by laser engraving and controlled the contact angle of small drops by pinning the contact lines in a horizontal tensile range of 0–200%. By means of experiments and model, we demonstrate that the ductility of drops is relied on the height-to-spacing ratio of the individual pattern and the intrinsic contact angle. Moreover, the change of drop size was utilized to measure the applied strain and liquid viscosity, enabling a strain sensitivity as high as 1068 μm2/%. The proposed laser-etched stretchable graphene–polymer composite has potential applications in DNA microarrays, biological assays, soft robots, and so on.
Enamine/Transition Metal Combined Catalysis: Catalytic Transformations Involving Organometallic Electrophilic Intermediates
Authors: Afewerki Samson , Córdova Armando
Published: November 2019

The concept of merging enamine activation catalysis with transition metal catalysis is an important strategy, which allows for selective chemical transformations not accessible without this combination. The amine catalyst activates the carbonyl compounds through the formation of a reactive nucleophilic enamine intermediate and, in parallel, the transition metal activates a wide range of functionalities such as allylic substrates through the formation of reactive electrophilic π-allyl-metal complex. Since the first report of this strategy in 2006, considerable effort has been devoted to the successful advancement of this technology. In this chapter, these findings are highlighted and discussed.
Responses of US multinational firms to a temporary repatriation tax holiday: A literature review and synthesis
Authors: Dong Qi Flora , Cao Yiting , Zhao Xin , Deshmukh Ashutosh
Published: November 2019

The effect of tax policy on the repatriation of foreign earnings is a topic of ongoing discussion among policymakers, academics, and the popular press. It has become more salient due to the 2017 Tax Cuts and Jobs Act (TCJA), which permanently removed repatriation tax. This paper synthesizes the academic literature examining US multinational firms’ responses to the repatriation tax holiday initiated by the 2004 American Jobs Creation Act (AJCA), which temporarily reduced the tax on the repatriation of foreign earnings. By synthesizing firm responses to the temporary tax reduction, we identify similarities and differences in: (1) theories about why and when repatriation tax affects firms’ repatriation decisions; (2) empirical evidence of whether repatriation tax affects firms’ repatriation decisions; and (3) empirical evidence of whether repatriation tax affects firms’ investment decisions. The analyses provide insights into the effect of the permanent removal of repatriation tax under the TCJA and explore avenues for future research. This synthesis of the AJCA literature informs tax research and practice as well as policymaking.
Meta‐analytic approaches for examining complexity and heterogeneity in studies of adolescent development
Authors: Parr Nicholas J. , Schweer‐Collins Maria L. , Darlington Todd M. , Tanner‐Smith Emily E.
Published: November 2019

Introduction

In the field of adolescent development, meta‐analysis offers valuable tools for synthesizing and assessing cumulative research evidence on the effectiveness of programs, practices, and policies intended to promote healthy adolescent development. When examining the impact of a program implemented across multiple primary studies, variation is often observed in the methodological attributes of those primary studies, such as their implementation methods, program components, participant characteristics, outcome measurement, and the systems in which programs are deployed. Differences in methodological attributes of primary studies represented in a meta‐analysis, referred to as complexity, can yield variation in true effects across primary studies, which is described as heterogeneity.

Methods

We discuss heterogeneity as a parameter of interest in meta‐analysis, introducing and demonstrating both graphical and statistical methods for evaluating the magnitude and impact of heterogeneity. We discuss approaches for presenting characteristics of heterogeneity in meta‐analytic findings, and methods for identifying and statistically controlling for aspects of methodological complexity that may contribute to variation in effects across primary studies.

Results

Topics and methods related to assessing and explaining heterogeneity were contextualized in the field of adolescent development using a sample of primary studies from a large meta‐analysis examining the effectiveness of brief alcohol interventions for youth. We highlighted approaches currently underutilized in the field and provided R code for key methods to broaden their use.

Conclusions

By discussing various heterogeneity statistics, visualizations, and explanatory methods, this article provides the applied developmental researcher a foundational understanding of complexity and heterogeneity in meta‐analysis.
Impact of Visual Impairment on the Wellbeing and Functional Disability of Patients with Glaucoma in India
Authors: Dubey Suneeta , Bedi Harleen , Bedi Manveen , Matah Preeti , Sahu Jigyasa , Mukherjee Saptarshi , Chauhan Lokesh
Published: November 2019

Purpose:

To investigate the impact of glaucoma-associated vision loss on quality of life and social functioning in Indians.

Methods:

A cross-sectional study with prospective enrollment was conducted. Participants were divided as: mild, moderate, and severe. Severity of glaucoma was stratified by the degree of binocular visual field loss in accordance with the Nelson Glaucoma Severity Scale (NGSS). The Glaucoma Quality of Life-15 (GQL-15) and a self-developed social function scale (SFS) were utilized to assess patients' wellbeing.

Results:

A total of 260 patients (mean ± SD age = 58.1 ± 12.01 years; 106 females) participated in the study. Univariate analyses revealed a significant relationship between final quality of life score and number of anti-glaucoma medications (P = 0.01), previous surgeries (P = 0.00), patients age (P = 0.00), patients education level (P = 0.02), and severity of glaucoma (P = 0.00). Previous surgeries (P = 0.04) and severity of glaucoma (P = 0.00) were significant predictors of GQL-15 summary score. With increasing glaucoma severity, patients noted greater difficulty with peripheral vision, glare and dark adaptation, and outdoor tasks (P < 0.0001). Severe glaucoma also impacted patients' functional performance—a significant decline was observed in sense of personal (P < 0.0001) and social wellbeing (P < 0.0001).

Conclusions:

Patients with advanced glaucoma report significant decline in functioning, their ability to interact in community, take care of self, and do leisure activities. Glaucoma imposes greater social burden on the elderly by impacting their sense of personal safety. Targeted visual and social rehabilitative programs are necessary to improve their wellbeing and independent functioning.
A Practical Introduction to Regression Discontinuity Designs
Authors: Cattaneo Matias D. , Idrobo Nicolás , Titiunik Rocío
Published: November 2019

In this Element and its accompanying second Element, A Practical Introduction to Regression Discontinuity Designs: Extensions, Matias Cattaneo, Nicolás  Idrobo, and Rocıìo Titiunik provide an accessible and practical guide for the analysis and interpretation of regression discontinuity (RD) designs that encourages the use of a common set of practices and facilitates the accumulation of RD-based empirical evidence. In this Element, the authors discuss the foundations of the canonical Sharp RD design, which has the following features: (i) the score is continuously distributed and has only one dimension, (ii) there is only one cutoff, and (iii) compliance with the treatment assignment is perfect. In the second Element, the authors discuss practical and conceptual extensions to this basic RD setup.
Nonmonotonic Effects of Salinity on Wettability Alteration and Two‐Phase Flow Dynamics in PDMS Micromodels
Authors: Karadimitriou Nikolaos K. , Mahani Hassan , Steeb Holger , Niasar Vahid
Published: November 2019

The interaction between fluid‐fluid and solid‐fluid interfacial forces and surface roughness controls the wettability. The ionic strength is the most important factor that controls electrostatic forces. Thus, a modification of the ionic strength can potentially lead to a change of the wettability, as shown in recent experimental works related to low‐salinity waterflooding, which is an enhanced oil recovery technology. Despite the significant research published on this topic, for the first time, we present how a change of the ionic strength alters the wettability in a pore network micromodel made of silanized polydimethylsiloxane (PDMS). We visualized the invasion of brine in an elongated hydrophobic PDMS micromodel, initially saturated with Fluorinert. Under different injection rates and ionic strengths and using image processing, we quantified the contact angle distribution in the flow network, the recovery curve with time, the brine breakthrough time, and the temporal change of resident saturation. The results imply that there is an optimal range of salinity at which saturation change accelerates and the breakthrough saturation maximizes, which highlights the concept of optimal salinity in wettability alteration. Also, we observed a shift of the contact angle distribution toward a more water‐wet state. Given the nonmonotonic trend of the breakthrough saturation with brine salinity, as well as recovery time versus the ionic strength, we conclude that the induced surface roughness is not the primary drive behind the accelerated saturation change. Therefore, the recovery time difference can be primarily attributed to the local alterations of the wetting properties of the porous medium due to the change of the ionic strength.
Fishway Entrance Gate Experiments With Adult American Shad
Authors: Mulligan K. B. , Haro A. , Towler B. , Sojkowski B. , Noreika J.
Published: November 2019

The goal of this multiyear study was to examine how changes to an upstream fishway entrance impacted the passage rate of adult American shad (Alosa sapidissima). We evaluated a total of nine treatment conditions that consisted of three fishway entrance gate types and three submergence depths (i.e., the water surface elevation of the tailwater relative to the height of the gate crest). Approximately 2,000 wild, actively migrating shad participated in one of the 64 total trials (6–8 trials per treatment) that were conducted for this experiment. The three fishway entrance gate types were the vertical gate (the most common entrance gate type used in fishways), the overshot gate (less common in fishways), and the reversed overshot gate (novel to fishways). The submergence depths ranged from 30.5 to 91.4 cm above the gate crest. Increases to the submergence depth were shown to be the most influential predictor variable of passage time, followed by gate type and river temperature. The reversed overshot and overshot gates outperformed the vertical gate with the best performance occurring for the newly introduced reversed overshot gate type. The results of this study provide guidance on methods to improve fishway attraction and entry rates to numerous state and federal resource agencies and the hydropower industry.
Sparks May Reveal the Nature of Ash Plumes
Authors: Derouin Sarah
Published: November 2019

In lab experiments and models, researchers uncover how ash can affect the standing shock waves of erupting volcanoes. Their findings may lead to new predictions of volcanic ash hazards.
Making Sense of Local Climate Projections
Authors: Rosendahl Derek , McPherson Renee , Wootten Adrienne , Mullens Esther , Blackband Jessica , Bryan Alex
Published: November 2019

Hands-on training, collaboration with scientists, and practice using real-world challenges give planners and decision-makers confidence to work with climate model information.
Plankton Biodiversity Mapped Globally
Authors: Cartier Kimberly
Published: November 2019

A team of scientists sailed around the world to catalog the diversity of plankton species in the ocean. Their findings have important economic implications as climate warms.
Geometry of the Deep Calabrian Subduction (Central Mediterranean Sea) From Wide‐Angle Seismic Data and 3‐D Gravity Modeling
Authors: Dellong David , Klingelhoefer Frauke , Dannowski Anke , Kopp Heidrun , Murphy Shane , Graindorge David , Margheriti Lucia , Moretti Milena , Barreca Giovanni , Scarfì Luciano , Polonia Alina , Gutscher Marc‐Andre
Published: November 2019

The Calabrian subduction zone is one of the narrowest arcs on Earth and a key area to understand the geodynamic evolution of the Mediterranean and other marginal seas. Here in the Ionian Sea, the African plate subducts beneath Eurasia. Imaging the boundary between the downgoing slab and the upper plate along the Calabrian subduction zone is important for assessing the potential of the subduction zone to generate megathrust earthquakes and was the main objective of this study. Here we present and analyze the results from a 380‐km‐long, wide‐angle seismic profile spanning the complete subduction zone, from the deep Ionian Basin and the accretionary wedge to NE Sicily, with additional constraints offered by 3‐D gravity modeling and the analysis of earthquake hypocenters. The velocity model for the wide‐angle seismic profile images thin oceanic crust throughout the basin. The Calabrian backstop extends underneath the accretionary wedge to about 100 km SE of the coast. The seismic model was extended in depth using earthquake hypocenters. The combined results indicate that the slab dip increases abruptly from 2–3° to 60–70° over a distance of ≤50 km underneath the Calabrian backstop. This abrupt steepening is likely related to the rollback geodynamic evolution of the narrow Calabrian slab, which shows great similarity to the shallow and deep geometry of the Gibraltar slab.
Direct Observation of Subrelativistic Electron Precipitation Potentially Driven by EMIC Waves
Authors: Capannolo L. , Li W. , Ma Q. , Chen L. , Shen X.‐C. , Spence H. E. , Sample J. , Johnson A. , Shumko M. , Klumpar D. M. , Redmon R. J.
Published: November 2019

Electromagnetic ion cyclotron (EMIC) waves are known to typically cause electron losses into Earth's upper atmosphere at >~1 MeV, while the minimum energy of electrons subject to efficient EMIC‐driven precipitation loss is unresolved. This letter reports electron precipitation from subrelativistic energies of ~250 keV up to ~1 MeV observed by the Focused Investigations of Relativistic Electron Burst Intensity, Range and Dynamics (FIREBIRD‐II) CubeSats, while two Polar Operational Environmental Satellites (POES) observed proton precipitation nearby. Van Allen Probe A detected EMIC waves (~0.7–2.0 nT) over the similar L shell extent of electron precipitation observed by FIREBIRD‐II, albeit with a ~1.6 magnetic local time (MLT) difference. Although plasmaspheric hiss and magnetosonic waves were also observed, quasi‐linear calculations indicate that EMIC waves were the most efficient in driving the electron precipitation. Quasi‐linear theory predicts efficient precipitation at >0.8–1 MeV (due to H‐band EMIC waves), suggesting that other mechanisms are required to explain the observed subrelativistic electron precipitation.
Nanogoethite as a Potential Indicator of Remagnetization in Red Beds
Authors: Huang Wentao , Jackson Michael J. , Dekkers Mark J. , Solheid Peat , Zhang Bo , Guo Zhaojie , Ding Lin
Published: November 2019

Red beds are well‐known for recording stable natural remanent magnetization (NRM). However, discriminating primary NRM from secondary remanence in red beds is difficult. The Paleogene Nangqian red beds in eastern Tibetan Plateau variably record an overprint related to nearby magmatism and thus provide a great opportunity to characterize remagnetization in red beds. Through comprehensive rock magnetic, Mössbauer spectroscopic, and petrographic analyses, we find that remagnetization was controlled by temperature. Remagnetized red beds contain abundant authigenic hematite and goethite, with some larger grains unblocking at the Néel temperatures and the remainder (nanoparticles) unblocking at lower temperatures. In contrast, red beds retaining primary NRM are characterized by dominance of detrital hematite and magnetite, presence of fine‐grained authigenic hematite, and absence of authigenic goethite and magnetite. High temperature behaviors of NRM/susceptibility are indicative of remagnetization, but the presence of goethite appears to be a more sensitive criterion for diagnosing remagnetization in red beds.
Assessment of ICESat‐2 Ice Sheet Surface Heights, Based on Comparisons Over the Interior of the Antarctic Ice Sheet
Authors: Brunt K. M. , Neumann T. A. , Smith B. E.
Published: November 2019

We collected kinematic Global Navigation Satellite Systems (GNSS) surface height data, on a 750‐km ground‐based traverse of the flat interior of the Antarctic ice sheet, for comparison with Ice, Cloud, and Land Elevation Satellite‐2 (ICESat‐2) surface heights. Vertical errors in the GNSS data are estimated to be 5.6 cm, comparable to results from a previous traverse and with year‐to‐year comparisons. Comparisons of the GNSS heights and 6 months of ICESat‐2 ATL03 photon‐based heights and ATL06 segment‐based heights indicate that the accuracy and precision of ICESat‐2 data are comparable to that of results from the ICESat mission: ATL03 is currently accurate to better than 5 cm with better than 13 cm of surface measurement precision, while ATL06 is currently accurate to better than 3 cm with better than 9 cm of surface measurement precision.
Significant Spatial Variability in Radar‐Derived West Antarctic Accumulation Linked to Surface Winds and Topography
Authors: Dattler Marissa E. , Lenaerts Jan T. M. , Medley Brooke
Published: November 2019

Across the Antarctic Ice Sheet, accumulation heavily influences firn compaction and surface height changes. Therefore, accumulation varies over short distances (<25 km), complicating the derivation of ice sheet mass changes from altimetry and reducing how accurately field measurements can be spatially extrapolated. However, current atmospheric reanalyses have grid spacings (>25 km) that are too coarse to resolve this variability. To address this limitation, we construct a fine‐scale accumulation product from airborne snow radar observations by superimposing along‐track fluctuations in accumulation onto an atmospheric reanalysis product. Our resulting airborne product reflects large‐scale (>25 km) orographic precipitation patterns while providing robust and unprecedented insight into Antarctic accumulation variability on subgrid scales. On these smaller scales, we find significant, regionally dependent accumulation variability (σrelative>40%). This variability in accumulation is correlated with variability in topographic surface slope in the wind direction (p<0.01), confirming that subgrid‐scale accumulation variability is driven by snow redistribution by wind.
HL‐TWiM Empirical Model of High‐Latitude Upper Thermospheric Winds
Authors: Dhadly Manbharat S. , Emmert John T. , Drob Douglas P. , Conde Mark G. , Aruliah Anasuya , Doornbos Eelco , Shepherd Gordon G. , Wu Qian , Makela Jonathan J. , Niciejewski Rick J. , Lee Changsup , Jee Geonhwa , Ridley Aaron J.
Published: November 2019

We present an empirical model of thermospheric winds (High‐latitude Thermospheric Wind Model [HL‐TWiM]) that specifies F region high‐latitude horizontal neutral winds as a function of day of year, latitude, longitude, local time, and geomagnetic activity. HL‐TWiM represents the large‐scale neutral wind circulation, in geomagnetic coordinates, for the given input conditions. The model synthesizes the most extensive collection to date of historical high‐latitude wind measurements; it is based on statistical analyses of several decades of F region thermospheric wind measurements from 21 ground‐based stations (Fabry‐Perot Interferometers and Scanning Doppler Imaging Fabry‐Perot Interferometers) located at various northern and southern high latitudes and two space‐based instruments (UARS WINDII and GOCE). The geomagnetic latitude and local time dependences in HL‐TWiM are represented using vector spherical harmonics, day of year and longitude variations are represented using simple harmonic functions, and the geomagnetic activity dependence is represented using quadratic B splines. In this paper, we describe the HL‐TWiM formulation and fitting procedures, and we verify the model against the neutral wind databases used in its formulation. HL‐TWiM provides a necessary benchmark for validating new wind observations and tuning our physical understanding of complex wind behaviors. Results show stronger Universal Time variation in winds at southern than northern high latitudes. Model‐data intra‐annual comparisons in this study show semiannual oscillation‐like behavior of GOCE winds, rarely observed before in wind data.