bluuebunny/crossref_metadata_2025 huggingface dataset:
Alternating N2 gas injection as a potential technique for enhanced gas recovery and CO2 storage in consolidated rocks: an experimental study
Authors: Mohammed Nuhu , Abbas Abubakar Jibrin , Enyi Godpower C. , Suleiman Salihu M. , Edem Donatus E. , Abba Muhammad Kabir
Published: June 2020

The promotion of enhanced gas recovery (EGR) and CO2 storage is still shrouded in contention and is not well accepted, due to the excessive in situ CO2 mixing with the nascent natural gas. This adulterates the recovered CH4 and thus results in a high sweetening process cost thereby making the technique impractical. This has not only limited the field application of EGR in actual projects to a few trails but renders it uneconomical. This study aims to present, experimentally, alternating N2 injection as a potential technique for EGR and CO2 storage in sandstone rock cores. A laboratory core flooding experiment was carried out to simulate a detailed process of unsteady-state methane (CH4) displacement using Bandera grey core plug. This was carried out at 40 °C, 1500 psig, and 0.4 ml/min injection rate by alternative injection of N2 and CO2 in succession designed to suit the application based on optimum operating conditions. The results show that both CO2 storage capacity and CH4 recovery improved significantly when gas alternating gas (GAG) injection was considered. The best results were observed at lower N2 cushion volumes (1 and 2 PV). Therefore, the GAG injection method with N2 as cushion gas can potentially increase both CO2 storage and CH4 recovery of the gas reservoir. This technique if employed will assert the current position and provide vital information for further researches aimed at promoting environmental sustainability and economic viability of the EGR and CO2 sequestration processes.
Evaluation of the size of time windows for the travelling salesman problem in delivery operations
Authors: Budak Gerçek , Chen Xin
Published: June 2020

A great challenge in operational research is to apply time-efficient algorithms to find the optimal solutions to the travelling salesman problem (TSP) and its many variations. The TSP with time windows (TSPTW) arises due to intense pressure for business to improve customer service. As online shopping becomes more popular, customer satisfaction increases if customers can decide when their orders are delivered to them. Customers may choose a time window, which is defined by an earliest delivery time and a latest delivery time, during which the package is delivered. Delivering packages to multiple customers is a typical TSPTW. One main challenge for a delivery business is to determine the size of the time window (i.e., the difference between the latest and earliest delivery times), which affects delivery cost and customer satisfaction. Although many previous studies investigated the TSPTW, none of those focused on the size of time windows. This study is the first that experiments with different time window sizes and determines their impact on tour duration, customer satisfaction, and solution time of the optimal delivery routes. The experiment results show that increasing the size of the time window decreases tour duration and customer satisfaction and increases solution time. Decreasing the size of the time window increases tour duration and customer satisfaction and decreases solution time. A small solution time is necessary for the scheduling of deliveries to many customers. A large solution time prevents a delivery business from delivering packages using optimal routes, which increases delivery cost and decreases customer satisfaction. The results of this study indicate that a general guideline for business is to allow customers to choose a time window size that is within the cost limit but is sufficiently small to maximize customer satisfaction and optimize delivery routes.
Enduring Attitudes and Contextual Interest: When and Why Attitude Surveys Still Matter in the Online Consumer Decision Journey
Authors: Pauwels Koen , Van Ewijk Bernadette
Published: June 2020

Consumers leave traces of key interest to managers on their journey to purchase. Next to traditional survey-based attitudes, readily available online metrics now show aggregate consumer actions. But how do survey response metrics and online action metrics relate to each other? To what extent do they explain and predict brand sales across consumer categories? This article shows that surveys and online behavior provide complementary information for brand managers. Times series data for 32 brands in 14 categories reveal low correlations but substantial dual causality between survey metrics and online actions. Combining both types of metrics greatly increases the model's power to explain and predict brand sales in low-involvement categories. By contrast, high-involvement categories do not gain much from adding survey-based attitudes to a model including online behavior metrics. The authors synthesize these generalizations in a new framework relating enduring attitudes to the contextual interest expressed by online actions. This new framework helps managers assess both types of metrics to drive brand performance depending on whether their goal is short-term sales or long-term brand health.
Perianastomotic cyst following rectosigmoidectomy due to adenocarcinoma of the proximal rectum: a case report
Authors: Sena Fernando Simões de , Nogueira Raquel Ferreira , Barroso Lorena de Oliveira , Santos Marco Antônio Miranda dos , Leite Sinara Mônica de Oliveira
Published: June 2020

The implantation cyst occurs from the imprisonment and subsequent proliferation of the colonic mucosa below the submucosa during mechanical stapling. The understanding and definition of the evaluation protocol of these lesions is important, since they can generate the need for a new complex surgical procedure and cause anxiety in patients and surgeons. This case reports the occurrence of a subepithelial lesion in follow-up imaging of a patient who underwent videolaparoscopic rectosigmoidectomy for adenocarcinoma of the proximal rectum, submitted to an endoscopic attempt to drain/detangle the lesion and subsequent histopathological analysis showing colic mucosa without changes. In line with Katsumata, it is suggested to asymptomatic patients without alteration of the CEA or suspicious imaging signs a follow up with periodic imaging methods. For symptomatic patients with normal CEA, or whose lesions are growing at follow-up exams, it is suggested to continue with the investigation, with biopsy and/or effluent sample for histopathological study in addition to an attempt at symptomatic resolution. Finally, in the presence of an alteration in CEA, despite symptoms, it is suggested that the lesion be managed as a suspected local tumor recurrence.
Ex Vivo Radiation Leads to Opposing Neurite Growth in Whole Ganglia vs Dissociated Cultured Pelvic Neurons
Authors: Randolph Joshua T. , Pak Elena S. , Koontz Bridget F. , Hannan Johanna L.
Published: June 2020

Background

Prostatic radiation therapy (RT) often causes erectile dysfunction (ED) and the mechanisms governing RT-induced ED are unclear with a lack of therapeutic strategies.

Aim

To determine the effects of ex vivo RT on major pelvic ganglion (MPG) neuron survival, and neurite growth in whole vs dissociated culture.

Methods

MPGs were removed and irradiated (0 or 8 Gy) from male Sprague Dawley rats. For dissociated culture, MPG neurons were digested in collagenase/dispase and cultured on coverslips. Immunofluorescent staining for beta-tubulin III (TUBB3; neuron marker), neuronal nitric oxide synthase (nNOS; nitrergic marker), tyrosine hydroxylase (TH; sympathetic marker), and terminal deoxynucleotidyl transferase dUTP nick end labeling assessed neurite length, branching, autonomic neuron density, and apoptosis. For whole organ culture, MPGs were grown in Matrigel. Gene expression of apoptotic markers (caspase 1, 3), TUBB3, nNOS, TH, and Schwann cells (Sox10, Krox20, glial fibrillary acid protein) was measured in whole organ cultured MPGs by quantitative polymerase chain reaction.

Outcomes

After 72 hours, neurite length, branching, autonomic neuron density, and apoptosis were assessed, and gene expression was measured.

Results

RT increased apoptosis in dissociated neurons measured by terminal deoxynucleotidyl transferase dUTP nick end labeling (P < .001) and whole MPG culture via upregulation of caspase 3 gene expression (P < .05). Nitrergic neurons were markedly decreased in irradiated dissociated culture (P < .05), while nNOS gene expression was upregulated in irradiated whole organ culture (P < .05). The proportion of dissociated sympathetic neurons and whole organ TH gene expression remained unchanged after RT. Interestingly, RT dissociated neurites were 22% shorter than controls, while RT whole organ neurites were 15% longer than controls (P < .01). MPG Schwann cells markers (Sox10, Krox20) were elevated after RT in whole organ culture.

Clinical Translation

Prostatic RT leads to increased neuronal cell death and less erectogenic nitrergic neurons contributing to ED.

Strengths & Limitations

The advantages of dissociated neuron culture include distinct neurites which are easily measured for apoptosis, length/branching, and specific neuron types. In contrast, whole MPG culture is advantageous as it contains all the supporting cells present in vivo.

Conclusion

The 2 different culture methods demonstrated opposing neurite growth after RT indicating the importance of supporting cell network to promote pelvic neuron neuritogenesis and survival following RT.
Evaluating the Impact of Penile Girth Discrepancy on Patient Bother in Men with Peyronie's Disease: An Observational Study
Authors: Salter Carolyn A. , Nascimento Bruno , Terrier Jean-Etienne , Taniguchi Hisanori , Bernie Helen , Miranda Eduardo , Jenkins Lawrence , Schofield Elizabeth , Mulhall John P.
Published: June 2020

Background

Men with Peyronie's disease (PD) may experience penile narrowing. Little data on penile girth changes and their psychosocial impact exist.

Aim

To assess girth discrepancy in men with PD and its association with patient bother.

Methods

This was a retrospective observational study. All patients with PD at our institution who were seen in the sexual medicine clinic and who completed 3 validated instruments the PD questionnaire (PDQ), Self-Esteem and Relationship (SEAR) questionnaire, and a depression questionnaire, the Center for Epidemiologic Studies Depression Scale (CES-D), and a curvature assessment were included. Patient and PD characteristics are described. Associations of instability and bother to girth differences are assessed. 2 outcomes for girth differences are classified as (i) girth difference of ≥ 1 cm vs less and (ii) girth differences of ≥10% vs less. Unadjusted and adjusted effects of PD and patient characteristics are assessed on the outcome of high bother using logistic regression models.

Outcomes

The main outcomes of this study were penile girth changes, instability, and questionnaire scores. High bother was defined as a PDQ bother score of ≥9.

Results

A total of131 men had midshaft curvature and were the focus of the study. Their mean age was 59 ± 9 (range 31–78) years. PD duration was 16 ± 25 (range 1–180) months, with a mean degree of primary curvature of 37 ± 20o. Mean girth difference between base and point of maximum curvature was 0.78 ± 0.53 cm equating to a mean girth difference at point of maximum curvature of 6 ± 4%. Instability was present in 53% of men. There were 54 men with a girth difference of ≥ 1 cm and 23 men with a ≥10% change in girth. There was no difference in CES-D, SEAR, or PDQ domain scores or high bother in men with significant girth changes. Univariable analysis of predictors of high bother included the degree of curvature (odds ratio [OR]: 1.06; P < .001), instability (OR 6.62; P < .001), CES-D sum (OR 1.09; P = .002), and SEAR score (OR 0.96; P = .001). On multivariate analysis, only the degree of primary curvature was predictive of high bother (OR 1.06; P < .001).

Clinical Implications

Penile girth changes have little impact on overall psychosocial well-being. The degree of penile curvature is the primary predictor of patient bother.

Strengths and Limitations

Strengths include a large patient population and use of validated questionnaires. Limitations include single-center, retrospective study and subjective instability grading.

Conclusions

Penile girth discrepancy in men with PD has limited psychosocial impact. Clinically significant bother was associated with the degree of primary curvature.
Radiologic anatomy of the round window relevant to cochlear implantation and inner ear drug delivery
Authors: Nguy Peter L. , Saidha Sheela , Jay Ann , Jeffrey Kim H. , Hoa Michael
Published: June 2020

Objective

To determine anatomic relationships and variation of the round window membrane to bony surgical landmarks on computed tomography.

Study design

Retrospective imaging review.

Methods

100 temporal bone images were evaluated. Direct measurements were obtained for membrane position. Vector distances and angulation from umbo and bony annulus were calculated from image viewer software coordinates.

Results

The angle of round window membrane at junction with cochlear basal turn was (42.1 ± 8.6)°. The membrane's position relative to plane of the facial nerve through facial recess was (14.7 ± 5.2)° posterior from a reference line drawn through facial recess to carotid canal. Regarding transtympanic drug delivery, the round window membrane was directed 4.1 mm superiorly from the inferior annulus and 5.4 mm anteriorly from the posterior annulus. The round window membrane on average was angled superiorly from the inferior annulus (77.1 ± 27.9)° and slightly anteriorly from the posterior annulus (19.1 ± 11.1°). The mean distance of round window membrane from umbo was 4 mm and posteriorly rotated 30° clockwise from a perpendicular drawn from umbo to inferior annulus towards posterior annulus. Together, these measurements approximate the round window membrane in the tympanic membrane's posteroinferior quadrant.

Conclusions

These radiologic measurements demonstrate normal variations seen in round window anatomy relative to facial recess approach and bony tympanic annulus, providing a baseline to assess round window insertion for cochlear implantation and outlines anatomic factors affecting transtympanic drug delivery.
Surface and Atmospheric Driven Variability of the Single‐Layer Urban Canopy Model Under Clear‐Sky Conditions Over London
Authors: Tsiringakis A. , Holtslag A. A. M. , Grimmond Sue , Steeneveld G. J.
Published: June 2020

Urban canopy models (UCMs) are parametrization schemes that are used to improve weather forecasts in urban areas. The performance of UCMs depends on understanding potential uncertainty sources that can generally originate from the (a) urban surface parameters, (b) atmospheric forcing, and (c) physical description. Here, we investigate the relative importance of surface and atmospheric driven model sensitivities of the single‐layer urban canopy model when fully interactive with a 1‐D configuration of the Weather Research and Forecasting model (WRF). The impact of different physical descriptions in UCMs and other key parameterization schemes of WRF is considered. As a case study, we use a 54‐hr period with clear‐sky conditions over London. Our analysis is focused on the surface radiation and energy flux partitioning and the intensity of turbulent mixing. The impact of changes in atmospheric forcing and surface parameter values on model performance appears to be comparable in magnitude. The advection of potential temperature, aerosol optical depth, exchange coefficient and roughness length for heat, surface albedo, and the anthropogenic heat flux are the most influential. Some atmospheric forcing variations have similar impact on the key physical processes as changes in surface parameters. Hence, error compensation may occur if one optimizes model performance using a single variable or combinations that have potential for carryover effects (e.g., temperature). Process diagrams help differences to be understood in the physical description of different UCMs, boundary layer, and radiation schemes and between the model and the observations.
A Geothermal Heat Flux Map of Antarctica Empirically Constrained by Seismic Structure
Authors: Shen Weisen , Wiens Douglas A. , Lloyd Andrew J. , Nyblade Andrew A.
Published: June 2020

The geothermal heat flux (GHF) is an important boundary condition for modeling the movement of the Antarctic ice sheet but is difficult to measure systematically at a continental scale. Earlier GHF maps suffer from low resolution and possibly biased assumptions in tectonism and crustal heat generation, resulting in significant uncertainty. We present a new GHF map for Antarctica constructed by empirically relating the upper mantle structure to known GHF in the continental United States. The new map, compared with previously seismologically determined one, has improved resolution and lower uncertainties. New features in this map include high GHF in the southern Transantarctic Mountains where warmer uppermost mantle is introduced by lithospheric removal and in the Thwaites Glacier region. Additionally, a modest GHF in the central West Antarctic Rift system near the Siple Coast and an absence of large‐scale regions with GHF greater than 90 mW/m2 are found.
Rapid Cooling and Increased Storminess Triggered by Freshwater in the North Atlantic
Authors: Oltmanns M. , Karstensen J. , Moore G. W. K. , Josey S. A.
Published: June 2020

Recent winters have been unique due to the rapid and extreme cooling of the subpolar North Atlantic. Here, we present a novel view on its causes and consequences. Combining in‐situ observations with remote sensing and atmospheric reanalysis data, we show that increased freshening of the subpolar region gives rise to a faster surface cooling in fall and winter. Large freshwater events, in particular, result in pronounced cold anomalies with sharp temperature gradients that promote an enhanced storminess. The storms reinforce the cooling by driving stronger heat losses and modulating the surface flow. Consistent with this mechanism, past freshwater events have been followed by cold anomalies in winter of approximately −2°C and increases in the North Atlantic Oscillation index of up to ∼0.6 within 3 years. We expect that future freshwater discharges into the North Atlantic will amplify the cold anomaly and trigger an enhanced wintertime storminess with far‐reaching climatic implications.
Effects of Lateral Entrainment Mixing With Entrained Aerosols on Cloud Microphysics
Authors: Chen Jingyi , Liu Yangang , Zhang Minghua
Published: June 2020

The effects of entrained environment air and aerosols on cloud properties remain a critical yet understudied topic. This study first introduces a new entraining cloud parcel model considering entrained aerosols. With entrained aerosols represented by a newly introduced parameter, the impacts of entrainment rate and entrained aerosols on cloud microphysical properties are investigated. The results show that the relationships between entrainment rate and cloud microphysical properties are highly nonlinear when the entrained aerosols vary. With the lateral entrainment mixing, a new phenomenon is revealed that the height of maximum parcel supersaturation cannot be reached when the entrainment rate is beyond a certain critical value. This new critical entrainment rate is different from the critical entrainment rate defined by Barahona and Nenes (2007, https://doi.org/10.1029/2007JD008473), beyond which clouds cannot form. This finding has important implications for developing parameterization of droplet activation, which is based primarily on the assumption of the existence of maximum supersaturation.
Critical Fluid Injection Volumes for Uncontrolled Fracture Ascent
Authors: Davis Timothy , Rivalta Eleonora , Dahm Torsten
Published: June 2020

Hydrofracturing is a routine industrial technique whose safety depends on fractures remaining confined within the target rock volume. Both observations and theoretical models show that, if the fluid volume is larger than a critical value, pockets of fluid can propagate large distances in the Earth's crust in a self‐sustained, uncontrolled manner. Existing models for such critical volumes are unsatisfactory; most are two‐dimensional and depend on poorly constrained parameters (typically the fracture length). Here we derive both analytically and numerically in three‐dimensional scale‐independent critical volumes as a function of only rock and fluid properties. We apply our model to gas, water, and magma injections in laboratory, industrial, and natural settings, showing that our critical volumes are consistent with observations and can be used as conservative estimates. We discuss competing mechanisms promoting fracture arrest, whose quantitative study could help to assess more comprehensively the safety of hydrofracturing operations.
Parallel Electrostatic Waves Associated With Turbulent Plasma Mixing in the Kelvin‐Helmholtz Instability
Authors: Wilder F. D. , Schwartz S. J. , Ergun R. E. , Eriksson S. , Ahmadi N. , Chasapis A. , Newman D. L. , Burch J. L. , Torbert R. B. , Strangeway R. J. , Giles B. L.
Published: June 2020

The Kelvin‐Helmholtz Instability (KHI) is thought to be an important driver of mass and momentum transfer from the solar wind to the Earth's magnetosphere. We present observations from NASA's Magnetospheric Multiscale mission of ion acoustic‐like waves associated with turbulence during the KHI interval on 8 September 2015. These parallel electrostatic waves are nonlinear, can have amplitudes in excess of 100 mV/m, and may be associated with a field‐aligned potential drop. We perform a survey of all vortices in the 8 September 2015 event, investigating the occurrence of electrostatic waves below the ion plasma frequency. We find that they tend to occur in the turbulent region in the middle of the KHI vortices, independent of the presence of compressed or intermittent currents. This suggests that the waves occur in the presence of plasma mixing in the vortex region and that they may play a part in the overall turbulent dissipation process.
Quantifying Fluid‐Wettable Effective Pore Space in the Utica and Bakken Oil Shale Formations
Authors: Zhang Yuxiang , Hu Qinhong , Barber Troy J. , Bleuel Markus , Anovitz Lawrence M. , Littrell Kenneth
Published: June 2020

Combined (ultra‐) small angle neutron scattering measurements [(U)SANS] and a contrast matching technique were employed to quantify the porosity and pore size distribution from 1 nm to 10 μm and to differentiate accessible (open) pores and inaccessible (closed) pores with respect to organophilic and hydrophilic fluids for two Utica and two Bakken shale samples. The results indicate that around 40–70% of the pores in the Utica oil shales (mixed carbonate mudstone) are accessible to oil, and 34–37% of the pore surfaces are water‐wet. In contrast, the Bakken oil shales (mixed siliceous mudstone and carbonate/siliceous mudstone), which have high total organic carbon contents, have a higher proportion of isolated pore space that is not preferentially wet by oil or water, with less than 36% of the pores accessible to both fluids. In addition, for both formations, pores less than 3 nm in diameter are not oil accessible (organic matter related) but water accessible (clay tactoids related).
Disproving the Bodélé Depression as the Primary Source of Dust Fertilizing the Amazon Rainforest
Authors: Yu Yan , Kalashnikova Olga V. , Garay Michael J. , Lee Huikyo , Notaro Michael , Campbell James R. , Marquis Jared , Ginoux Paul , Okin Gregory S.
Published: June 2020

Motivated by the ongoing debates about the relative contribution of specific North African dust sources to the transatlantic dust transport to the Amazon Basin, the current study integrates a suite of satellite observations into a novel trajectory analysis framework to investigate dust transport from the leading two North African dust sources, namely, the Bodélé depression and El Djouf. In particular, this approach provides observation‐constrained quantification of the dust's dry and wet deposition along its transport pathways and is validated against multiple satellite observations. The current large ensemble trajectory simulations identify favorable transport pathways from the El Djouf across the Atlantic Ocean with respect to seasonal rain belts. The limited potential for long‐range transport of dust from the Bodélé depression is attributed to the currently identified extensive near‐source dust removal primarily by dry and wet deposition during boreal winter and summer, respectively.
Mechanisms Underlying Recent Arctic Atlantification
Authors: Asbjørnsen Helene , Årthun Marius , Skagseth Øystein , Eldevik Tor
Published: June 2020

Recent warming and reduced sea ice concentrations in the Atlantic sector of the Arctic Ocean are the main signatures of ongoing Arctic “Atlantification.” The mechanisms driving the warming trends are nevertheless still debated, particularly regarding the relative importance of oceanic and atmospheric heat fluxes. Here, heat budgets along main Atlantic water pathways through the Barents Sea and Fram Strait are constructed to investigate the mechanisms of Atlantification during 1993–2014. The largest warming trends occur south of the winter ice edge, with ocean advection as the main driver. Warming in the marginal ice zone is mainly due to low surface heat loss from the 1990s to the mid‐2000s. In the ice‐covered northwestern Barents Sea, ocean advection and air‐sea heat fluxes act in concert to drive a gradual warming of the upper ocean. Despite a weakened stratification, no evidence is found of vertical oceanic temperature fluxes driving this upper‐ocean warming.
Prominent Daytime TEC Enhancements Under the Quiescent Condition of January 2017
Authors: Huang Fuqing , Lei Jiuhou , Zhang Ruilong , Li Na , Gu Shengyang , Yu You , Liu Libo , Owolabi Charles , Ning Baiqi , Li Guozhu , Zhong Jiahao , Dang Tong , Ren Dexin , Yi Wen , Luan Xiaoli , Xue Xianghui , Yu Tao , Li Faquan , Dou Xiankang , Yoshikawa Akimasa
Published: June 2020

It is well known that the ionospheric electron densities in the F‐region usually undergo day‐to‐day variability with the magnitude of ~20–35%, associated with the solar as well as geomagnetic activities and the meteorological forcing from the lower atmosphere. In this study, we reported remarkable enhancements in the total electron content (TEC) from the Beidou geostationary (GEO) satellites during the quiescent geophysical condition of January 2017 prior to the arrival of the sudden stratosphere warming (SSW). The daytime TEC around the equatorial ionization anomaly region increased by 75–160% and lasted for several days. The equatorial electrojet and Sq current in the ionospheric E‐region at low and middle latitudes showed the corresponding increase during the TEC enhancement interval. The possible contributions from the variations of solar EUV flux and geomagnetic activity are ruled out. Our further analysis showed that the diurnal tides in the temperature from Sounding of the Atmosphere using Broadband Emission Radiometry and the solar and lunar semidiurnal tides of neutral winds from two radars over China became strong during this period of interest. These results suggest that the lower atmospheric tidal forcing could contribute to the great and long‐duration TEC enhancement in the ionosphere even though the SSW had not happened yet.
Universal Scaling of Thin Current Sheets
Authors: Zelenyi L. M. , Malova H. V. , Grigorenko E. E. , Popov V. Yu , Dubinin E. M.
Published: June 2020

Thin current sheets (TCSs) with thicknesses about ion Larmor radii are widespread in space. It is important to describe their equilibrium structure allowing them to store and then explosively release the accumulated free energy. When ions are moving along quasi‐adiabatic trajectories while magnetized electrons follow guiding center drift orbits, TCSs can be described within the framework of a hybrid approach. The thickness of the embedded electron sheet remains uncertain because of the scale‐free character of electron motion. In this work, we propose a novel analytical model of the multilayer TCS that provides a universal expression describing the inner (embedded) electron sheet in dependence of TCS characteristics. An unusual property of the embedded electron layer revealed in this analysis is the nonlinear profile of the magnetic field in the inner layer: B(z) ~ z1/3, which conforms excellently with MAVEN observations of 43 TCSs in the Martian magnetotail.
The Contribution of Sprite Streamers to the Chemical Composition of the Mesosphere‐Lower Thermosphere
Authors: Pérez‐Invernón F. J. , Malagón‐Romero A. , Gordillo‐Vázquez F. J. , Luque A.
Published: June 2020

Sprites are mesospheric filamentary discharges that liberate and accelerate large quantities of electrons. They produce local enhancements of some chemical species and fast (millisecond) optical emissions. In this work, we couple a self‐consistent 2‐D model of sprites with an extensive chemical scheme to calculate the injection of chemical species by one sprite streamer in the mesosphere 0.85 ms after its onset. The N, NO, and N2O injections per streamer are about 1021 atoms, 6 × 1019 molecules, and 1018 molecules, respectively. According to our results, longer simulations are necessary to determine the role of sprites in the concentration of N2O in the mesosphere. We also calculate the contribution of sprite glows to space‐based photometers of the Atmosphere‐Space Interactions Monitor and the Tool for the Analysis of RAdiations from lightNIngs and Sprites.
Aeolian Creep Transport: Theory and Experiment
Authors: Wang Peng , Zhang Jie , Dun Hongchao , Herrmann Hans J. , Huang Ning
Published: June 2020

Aeolian sand transport drives geophysical phenomena, such as bedform evolution and desertification. Creep plays a crucial, yet poorly understood, role in this process. We present a model for aeolian creep, making quantitative predictions for creep fluxes, which we verify experimentally. We discover that the creep transport rate scales like the Shields number to the power 5/2, clearly different from the laws known for saltation. We derive this 5/2 power scaling law from our theory and confirm it with meticulous wind tunnel experiments. We calculate the creep flux and layer thickness in steady state exactly and for the first time study the relaxation of the flux toward saturation, obtaining an analytic expression for the relaxation time.
Temperature Proxies as a Solution to Biased Sampling of Lake Methane Emissions
Authors: Jansen Joachim , Thornton Brett F. , Wik Martin , MacIntyre Sally , Crill Patrick M.
Published: June 2020

Lake emissions of the climate forcing trace gas methane (CH4) are spatiotemporally variable, but biases in flux measurements arising from undersampling are poorly quantified. We use a multiyear data set (2009–2017) of ice‐free CH4 emissions from three subarctic lakes obtained with bubble traps (n = 14,677), floating chambers (n = 1,306), and surface concentrations plus a gas transfer model (n = 535) to quantify these biases and evaluate corrections. Sampling primarily in warmer summer months, as is common, overestimates the ice‐free season flux by a factor 1.4–1.8. Temperature proxies based on Arrhenius functions that closely fit measured fluxes (R2 ≥ 0.93) enable gap filling the colder months of the ice‐free season and reduce sampling bias. Ebullition (activation energy 1.36 eV) expressed greater temperature sensitivity than diffusion (1.00 eV). Resolving seasonal and interannual variability in fluxes with proxies requires ∼135 sampling days for ebullition, and 22 and 14 days for diffusion via models and chambers, respectively.
Elevation Changes of the Fennoscandian Ice Sheet Interior During the Last Deglaciation
Authors: Lane T. P. , Paasche Ø. , Kvisvik B. , Adamson K. R. , Rodés Á. , Patton H. , Gomez N. , Gheorghiu D. , Bakke J. , Hubbard A.
Published: June 2020

The dynamics and paleo‐glaciology of ice sheet interiors during the last deglaciation are poorly constrained, hindering ice sheet model reconstructions. We provide direct evidence of Fennoscandian Ice Sheet (FIS) interior behavior during deglaciation through surface exposure dating. Our results demonstrate early thinning of the FIS, prior to the Younger Dryas (YD, 12.8–11.7 ka). Interior thinning in central Norway was concurrent with retreat along the coastline, exposing ice‐free mountainous tracts, potentially as early as 20–15 ka. The FIS then formed moraines in these ice‐free tracts during the YD. This is contrary to current hypotheses advocating a landscape fully covered by cold, inactive ice during this period. Present empirical and model reconstructions fail to capture rapid interior downwastage, increasing uncertainties in ice sheet volume estimates and sea level contributions.
Experimental Determination of the Conditions Associated With “Zebra Stripe” Pattern Generation in the Earth's Inner Radiation Belt and Slot Region
Authors: Lejosne Solène , Mozer Forrest S.
Published: June 2020

The “zebra stripes” are peaks and valleys commonly present in the spectrograms of energetic particles trapped in the Earth's inner belt and slot region. Several theories have been proposed over the years to explain their generation, structure, and evolution. Yet, the plausibility of various theories has not been tested due to a historical lack of ground truth, including in situ electric field measurements. In this work, we leverage the new visibility offered by the database of Van Allen Probes electric drift measurements to reveal the conditions associated with the generation of zebra stripe patterns. Energetic electron fluxes by the Radiation Belt Storm Probes Ion Composition Experiment between 1 January 2013 and 31 December 2015 are systematically analyzed to determine 370 start times associated with the generation of zebra stripes. Statistical analyses of these events reveal that the zebra stripes are usually created during substorm onset, a time at which prompt penetration electric fields are present in the plasmasphere. All the pieces of experimental evidence collected are consistent with a scenario in which the prompt penetration electric field associated with substorm onset leads to a sudden perturbation of the trapped particle drift motion. Subsequent drift echoes constitute the zebra stripes. This study exemplifies how the analysis of trapped particle dynamics in the inner belt and slot region provides complementary information on the dynamics of plasmaspheric electric fields. It is the first time that the signature of prompt penetration electric fields is detected in near‐equatorial electric field measurements below L = 3.
Observational Validation of Cutoff Models as Boundaries of Solar Proton Event Impact Area
Authors: Heino Erkka , Partamies Noora
Published: June 2020

High energy protons accelerated during solar proton events (SPEs) can access the Earth's middle atmosphere at high and middle latitudes causing large‐scale ionization and chemical changes. In this study, we have compared the performance of two cutoff latitude models that predict the limit of the SPE impact area in the atmosphere during 73 SPEs from 1997 to 2010. We use observations from 13 riometer stations and the D Region Absorption Prediction (DRAP) model to test the performance of the two cutoff latitude models by Dmitriev et al. (2010, https://doi.org/10.1029/2010JA015380) and Nesse Tyssøy and Stadsnes (2015, https://doi.org/10.1002/2014JA020508). We find similar performance from the two cutoff latitude models with respect to observations, but the Dmitriev et al. (2010, https://doi.org/10.1029/2010JA015380) model performs slightly better when observations are contrasted with the DRAP model results. The better performing model is also continuous with magnetic local time and particle energy, making it more suited for future use in climate model proton forcing. SPE forcing is currently included in climate models with a single static cutoff latitude limit at 60° geomagnetic latitude. In reality, the area that the solar protons can access is not static but varies with particle rigidity and geomagnetic conditions. We estimate that the SPE impact area is overestimated 90% of the time by this single static cutoff limit and the average overestimation of the impact area is about 15–25% for protons with energies <32 MeV.
Particle‐in‐Cell Simulations of Characteristics of Rising‐Tone Chorus Waves in the Inner Magnetosphere
Authors: Ke Yangguang , Lu Quanming , Gao Xinliang , Wang Xueyi , Chen Lunjin , Wang Shaojie , Wang Shui
Published: June 2020

Whistler mode chorus waves in the Earth's inner magnetosphere are usually composed of discrete elements, and each element can be characterized by the following properties: the amplitude, the duration, the frequency span, and the frequency chirping rate. Using a one‐dimensional (1‐D) particle‐in‐cell (PIC) simulation code, we study the dependence of these properties of a rising‐tone chorus on the number density nheq/nc0 and temperature anisotropy AT of energetic electrons at the magnetic equator. The whistler waves are first excited around the magnetic equator by anisotropic energetic electrons and then develop into a rising‐tone chorus when they leave away from the equator. During the propagation toward the pole, the rising‐tone chorus with nearly constant frequency span first enhances and then decays. Its frequency chirping rate declines in the early stage and then gradually increases. Meanwhile, the chorus duration is quite the opposite due to propagation effect. Over a suitable range of nheq/nc0 to generate rising‐tone chorus, the frequency chirping rate of the excited rising‐tone chorus first increases and then saturates, while its saturated amplitude, duration, and frequency span have a rising tendency with the increasing nheq/nc0. As for AT, the frequency chirping rate of the generated rising‐tone chorus is increasing with the increase of AT that is consistent with prediction of nonlinear theory, while the duration is just the opposite. Our simulation study can give a further understanding of the generation and propagation of rising‐tone chorus waves.
ECTACI: European Climatology and Trend Atlas of Climate Indices (1979–2017)
Authors: Peña‐Angulo D. , Reig‐Gracia F. , Domínguez‐Castro F. , Revuelto J. , Aguilar E. , van der Schrier G. , Vicente‐Serrano S. M.
Published: June 2020

A fundamental key to understanding climate change and its implications is the availability of databases with wide spatial coverage, over a long period of time, with constant updates and high spatial resolution. This study describes a newly gridded data set and its map viewer “European Climatology and Trend Atlas of Climate Indices” (ECTACI), which contains four statistical parameters (climatology, coefficient of variation, slope, and significant trend) from 125 standard climate indices for the whole Europe at 0.25° grid intervals from 1979 to 2017 at various temporal scales (monthly, seasonal, and annual). In addition, this study shows, for the first time, the general trends of a wide variety of updated standard climate indices at seasonal and annual scales for the whole of Europe, which could be a useful tool for climate analysis and its impact on different sectors and socioeconomic activities. The data set and ECTACI map viewer are available for free (http://ECTACI.csic.es/).
What Ecohydrologic Separation Is and Where We Can Go With It
Authors: Sprenger Matthias , Allen Scott T.
Published: June 2020

The “ecohydrologic separation” hypothesis challenged assumptions of translatory flow through the rooting zone. However, studies aiming to test ecohydrologic separation have largely done so with insufficient discussion of infiltration and rooting zone recharge processes and instead have mostly focused on either isotopic differences between stream water and plant water or the presence of fractionated isotope ratios in plant water. Based on extensively observed heterogeneities in soils and watersheds, we posit that differences in isotopic compositions of water in plants, streams, and other subsurface pools are expected in most scenarios. Interpretation of those plant‐and‐stream water isotopic differences is important, but diagnosing the role of any specific process is typically confounded by the diversity of potential mechanisms contributing to those isotopic differences. Thus, we should progress from simply describing their occurrences and refocus the discussion of ecohydrologic separation on how heterogeneous infiltration and root uptake processes lead to such differences. Consequently, we outline areas where plant and soil‐water stable isotope data may be useful for advancing our understanding and representation of soil‐water transport and plant‐water recharge.
Neonatal sevoflurane exposure induces impulsive behavioral deficit through disrupting excitatory neurons in the medial prefrontal cortex in mice
Authors: Xie Linghua , Liu Yue , Hu Yuhan , Wang Bei , Zhu Zhirui , Jiang Yilei , Suo Yaojun , Hu Miaofeng , Gao Jing , Ullah Rahim , Hu Zhiyong
Published: June 2020

Sevoflurane, in particular multiple exposures, has been reported to cause the abnormal neurological development including attention-deficit/hyperactivity disorder (ADHD). This study is to investigate ADHD-like impulsivity in adult mice after repeated sevoflurane exposures at the neonatal stage. Six-day-old pups were exposed to 60% oxygen in the presence or absence of 3% sevoflurane for 2 h and the treatment was administrated once daily for three consecutive days. To assess the impulsivity, the cliff avoidance reaction (CAR) was carried out at the 8th week. Our results showed that repeated sevoflurane treatment increased the number of jumps and shortened the jumping latency in the CAR test. The cortices were harvested for immunostaining to detect c-Fos and calmodulin-dependent protein kinase IIα (CaMKIIα) expression in the medial prefrontal cortex (mPFC). We found that mPFC neurons, especially excitatory neurons, were highly activated and related to impulsive behavior. The activation viruses (AAV-CaMKIIα-hM3Dq) were injected to evaluate the effects of specific activation of mPFC excitatory neurons on impulsive behavior in the presence of clozapine-N-oxide (CNO). Likewise, the inhibitory viruses (AAV-CaMKIIα-hM4Di) were injected in the sevoflurane group to explore whether the mPFC excitatory neuronal inhibition reduced the impulsivity. Our results revealed that chemogenetic activation of mPFC excitatory neurons induced impulsive behavior whereas inhibition of mPFC excitatory neurons partially rescued the deficit. These results indicate that repeated sevoflurane exposures at the critical time induce impulsive behavior accompanied with overactivation of mPFC excitatory neurons in adult stages. This work may further extend to understand the ADHD-like impulsive behavior of the anesthetic neurotoxicity.
Curcumin-enhanced antitumor effects of sorafenib via regulating the metabolism and tumor microenvironment
Authors: Man Shuli , Yao Jingwen , Lv Panpan , Liu Yu , Yang Li , Ma Long
Published: June 2020

In this study, curcumin enhanced antitumor effects of sorafenib via regulating the metabolism and tumor microenvironment.
M4LiBe4P7O24 and M4Li(Li3P)P7O24 (M = Cs, Rb): deep-ultraviolet nonlinear-optical phosphates with a tetrahedra-substituted paracelsian-like framework
Authors: Chen Yi-Gang , Yang Chunyu , Wang Fang , Guo Yao , Jiang Xingxing , Zhang Xian-Ming
Published: June 2020

Paracelsian-like beryllophosphates M4LiBe4P7O24 and tetrahedra-substituted phases M4Li(Li3P)P7O24 (M = Cs, Rb) undergo structural transformation originating from the nature of tetrahedral cations.
The effect of introducing an ether group into an imidazolium-based ionic liquid in binary mixtures with DMSO
Authors: Zhou Yu , Xu Xianzhen , Wang Zonghua , Gong Shida , Chen Hong , Yu Zhiwu , Kiefer Johannes
Published: June 2020

Combined DFT and FTIR investigations reveal interesting hydrogen bonding interactions between dimethyl sulfoxide and an ether-functionalized imidazolium-based ionic liquid.
A C3-symmetrical tripodal acylhydrazone organogelator for the selective recognition of cyanide ions in the gel and solution phases: practical applications in food samples
Authors: Sharma Shilpa , Kumari Manisha , Singh Narinder
Published: June 2020

A low-molecular-weight organogelator is developed which can selectively sense cyanide ions in solution and in the supramolecular gel phase.
Time‐limited pseudo‐optimal ‐model order reduction
Authors: Zulfiqar Umair , Sreeram Victor , Du Xin
Published: June 2020

A model order reduction algorithm is presented that generates a reduced‐order model of the original high‐order model, which ensures high fidelity within the desired time interval. The reduced model satisfies a subset of the first‐order optimality conditions for the time‐limited ‐model reduction problem. The algorithm uses a computationally efficient Krylov subspace‐based framework to generate the reduced model, and it is applicable to large‐scale systems. The reduced‐order model is parameterised to enforce a subset of the first‐order optimality conditions in an iteration‐free way. The authors also propose an adaptive framework of the algorithm, which ensures a monotonic decay in the error irrespective of the choice of interpolation points and tangential directions. The efficacy of the algorithm is validated on benchmark model reduction problems.
Backstepping‐based sliding mode fault‐tolerant control for linear interconnected parabolic distributed parameter systems
Authors: Xu Yongyuan , Yang Hao , Jiang Bin , Cocquempot Vincent
Published: June 2020

This study considers the fault‐tolerant control (FTC) issue for a class of linear interconnected parabolic distributed parameter systems by utilising the backstepping‐based sliding mode control technique. The original interconnected system, which suffers from process/actuator faults and matched disturbances, is converted into a stable target system by using an invertible backstepping transformation. Two types of kernel functions, the distinct diffusivity and the same diffusivity, are obtained. A sliding mode FTC scheme is developed to eliminate the destabilising effects caused by process/actuator faults and matched disturbances. An industrial application example is presented to validate the applicability and the relevance of the developed methodology.
Time‐varying formation of second‐order discrete‐time multi‐agent systems under non‐uniform communication delays and switching topology with application to UAV formation flying
Authors: Wang Jianhua , Han Liang , Li Xiaoduo , Dong Xiwang , Li Qingdong , Ren Zhang
Published: June 2020

In this study, the time‐varying formation control problem for the second‐order discrete‐time multi‐agent systems is investigated, where both the non‐uniform communication time‐delays and switching topology are taken into account. A linear discrete‐time formation protocol is developed based on the neighbouring relative position and velocity information. Using the state transformation method and properties of the stochastic matrix, the formation feasibility condition is given and sufficient conditions for the discrete‐time multi‐agent systems to accomplish the time‐varying formation are established. An unmanned aerial vehicles (UAVs) formation experiment platform is constructed. Using four quadrotor UAVs, UAV formation flying experiments are performed to verify the effectiveness and reliability of the discrete‐time formation protocol. The experimental results show that the theoretical results can be used to deal with the time‐varying formation control problem for multiple UAVs system with communication delays and switching topology.