bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Flux‐Based Threshold for Anaerobic Activity in the Ocean
Authors: Zakem Emily J. , Lauderdale Jonathan M. , Schlitzer Reiner , Follows Michael J. 
Published: January 2021

AbstractAnaerobic microbial activity in the ocean causes losses of bioavailable nitrogen and emission of nitrous oxide to the atmosphere, but its predictability at global scales remains limited. Resource ratio theory suggests that anaerobic activity becomes sustainable when the ratio of oxygen to organic matter supply is below the ratio required by aerobic metabolisms. Here, we demonstrate the relevance of this framework at the global scale using three‐dimensional ocean datasets, providing a new interpretation of existing observations. Evaluations of the location and extent of anoxic zones and a diagnostic rate of pelagic nitrogen loss are consistent with previous estimates. However, we demonstrate that a threshold based on substrate‐supply fluxes is qualitatively different from a threshold based solely on the ambient oxygen concentration. This implies that use of the flux‐based threshold in global biogeochemical models can result in different predictions of anaerobic activity and nitrogen loss.
A 21st Century Warming Threshold for Sustained Greenland Ice Sheet Mass Loss
Authors: Noël B. , van Kampenhout L. , Lenaerts J. T. M. , van de Berg W. J. , van den Broeke M. R. 
Published: January 2021

AbstractUnder anticipated future warming, the Greenland ice sheet (GrIS) will pass a threshold when meltwater runoff exceeds the accumulation of snow, resulting in a negative surface mass balance (SMB < 0) and sustained mass loss. Here, we dynamically and statistically downscale the outputs of an Earth system model to 1 km resolution to infer that a Greenland near‐surface atmospheric warming of 4.5 ± 0.3°C—relative to preindustrial—is required for GrIS SMB to become persistently negative. Climate models from CMIP5 and CMIP6 translate this regional temperature change to a global warming threshold of 2.7 ± 0.2°C. Under a high‐end warming scenario, this threshold may be reached around 2055, while for a strong mitigation scenario it will likely not be passed. Depending on the emissions scenario taken, our method estimates 6–13 cm sea level rise from GrIS SMB by the year 2100.
Deep Waters in British Columbia Mainland Fjords Show Rapid Warming and Deoxygenation From 1951 to 2020
Authors: Jackson Jennifer M. , Bianucci Laura , Hannah Charles G. , Carmack Eddy C. , Barrette Jessy 
Published: January 2021

AbstractMany complex fjord systems cross British Columbia's coastline. A 70 year (1951–2020) time series analysis of temperature, salinity, and oxygen in four such fjords between ∼54 and 50oN (Douglas Channel, Rivers Inlet, Knight Inlet and Bute Inlet) shows that changes were greatest in deep waters between the sill and the bottom. In Rivers, Knight and Bute Inlet, the deep water temperature increased by 1.2–1.3°C over 70 years, up to two times the global average for open ocean waters at corresponding depths, while salinity increased by 0.1–0.2, and oxygen decreased by 0.4–0.7 mLL−1. The most northern inlet, Douglas Channel, showed a temperature increase of 0.8°C from 1951 to 2016, while trends in oxygen and salinity were not statistically significant. An analysis of Apparent Oxygen Utilization suggests that the deep waters in Douglas Channel are more readily exchanged with the outer coast than the three other fjords.
Reduced Lower Mississippi River Discharge During the Medieval Era
Authors: Wiman Charlotte , Hamilton Brynnydd , Dee Sylvia G. , Muñoz Samuel E. 
Published: January 2021

AbstractChanges in climate are expected to influence discharge of the lower Mississippi River, but projections disagree on whether discharge will increase or decrease over the coming century. Using a reconstructed median peak annual flow for the past 1,500 years based on geomorphic scaling laws, we show that discharge on the lower Mississippi River decreased during the Medieval era (c. 1000–1200 CE)—a period of regionally warm and dry conditions that serves as a partial analog for projected warming. These changes in discharge inferred from channel morphology track discharge simulated in the Community Earth System Model Last Millennium Ensemble. Simulations show that decreased Medieval era discharge is driven primarily by regionally enhanced evapotranspiration. Our findings are consistent with 21st century projections of decreased discharge on the lower Mississippi River under moderate greenhouse forcing scenarios, and demonstrate consistency between reconstructed and simulated discharge over the last millennium.
Greenland Ice Sheet Mass Balance (1992–2020) From Calibrated Radar Altimetry
Authors: Simonsen Sebastian B. , Barletta Valentina R. , Colgan William T. , Sørensen Louise Sandberg 
Published: January 2021

AbstractWe present the first 1992–2020 record of Greenland Ice Sheet (GrIS) mass balance derived from multisatellite Ku‐band altimetry. We employ an empirical approach as an alternative detailed to radar‐propagation modeling, and instead convert elevation changes observed by radar altimetry into mass changes using spatiotemporal calibration fields. This calibration field is derived from a machine learning approach that optimizes the prediction of a previously published mass balance field as a function of ice sheet variables. Our mass balance record shows a GrIS contribution of 12.1 ± 2.3 mm sea‐level equivalent since 1992, with more than 80% of this contribution occurring after 2003. Our record also suggests that the 2017 hydrological year is the first year in the 21st century which, within uncertainties, the GrIS was in balance. Overall, the 28‐year radar‐derived mass balance record we present highlights the potential of the method to provide operational mass balance estimates derived from multisatellite Ku‐band altimetry.
Field Observation Evidence for Kink Points in the Vertical Kinetic Energy Flux Profiles of Wind‐Blown Sand Over Gobi and Its Significance
Authors: Tan Lihai , Qu Jianjun , Wang Tao , Zhang Kai , An Zhishan 
Published: January 2021

AbstractWind‐blown sand over Gobi can cause severe sand abrasion. The vertical flux profiles, especially that of the kinetic energy (KE), determine the erosion intensity. However, the vertical distribution of the KE flux of wind‐blown sand over Gobi remains poorly understood. Here, we report comprehensive field‐based measurements of the vertical flux profiles of wind‐blown sand over three typical Gobi surfaces during four transport events. The results show that unlike the exponential decrease in the particle count flux with height, the KE flux profile curve was non‐monotonic and could be well fitted by a Pearson VII function. The height where the maximum KE flux density occurred (kink points) ranged from 0.09 to 0.15 m above the ground. In addition, the non‐monotonic KE flux profiles primarily emerged during periods of strong transport and were mainly caused by large saltating sand particles due to their high KE as they rebounded from the grain‐bed collision.
GLONASS Observation of Artificial Field‐Aligned Plasma Irregularities Near Magnetic Zenith During EISCAT HF Experiment
Authors: Sato H. , Rietveld M. T. , Jakowski N. 
Published: January 2021

AbstractWe report on simultaneous observation of artificial plasma density irregularities near the magnetic zenith (MZ) by incoherent scatter radar and GNSS satellite in the high latitude. During an EISCAT (European Incoherent Scatter Scientific Association) HF heating experiment, a GLONASS satellite signal intersected the disturbed ionospheric volume along the local magnetic field lines. The satellite signal amplitude and phase were simultaneously perturbed when the electron temperature increased in the F region through O‐mode HF waves. The field‐aligned irregularities (FAIs) and associated density perturbations are most significantly found in the MZ direction. The growth of FAI reached the saturation level in 30 s while large‐scale electron density perturbation on the order of 0.1 TECU developed in a few minutes. The observed density perturbations agree well with recent numerical studies of FAI generation due to the thermal self‐focusing process.
Constraining Southern Ocean CO2 Flux Uncertainty Using Uncrewed Surface Vehicle Observations
Authors: Sutton A. J. , Williams N. L. , Tilbrook B. 
Published: January 2021

AbstractRemote, harsh conditions of the Southern Ocean challenge our ability to observe the region’s influence on the climate system. Southern Ocean air‐sea CO2 flux estimates have significant uncertainty due to the reliance on limited ship‐dependent observations in combination with satellite‐based and interpolated data products. We utilize a new approach, making direct measurements of air‐sea CO2, wind speed, and surface ocean properties on an Uncrewed Surface Vehicle (USV). In 2019, the USV completed the first autonomous circumnavigation of Antarctica providing hourly CO2 flux estimates. Using this unique data set to constrain potential error in different measurements and propagate those through the CO2 flux calculation, we find that different wind speed products and sampling frequencies have the largest impact on CO2 flux estimates with biases that range from −4% to +20%. These biases and poorly constrained interannual variability could account for discrepancies between different approaches to estimating Southern Ocean CO2 uptake.
A Novel Method for Deriving the Vary‐Chap Scale Height Profile in the Topside Ionosphere
Authors: Wang Sicheng , Huang Sixun , Fang Hanxian 
Published: January 2021

AbstractThe modeling of topside ionospheric electron density using height‐varying scale height methods have received increasing attention. The modified Chapman function with a variable scale height, known as Vary‐Chap function, can well represent the topside electron density profiles, and is considered as a promising direction to improve the International Reference Ionosphere model. In order to facilitate modeling, a new formula with four unknown coefficients is proposed to fit the Vary‐Chap scale height, and these unknowns can be determined by the least squares technique. The approximated electron density profile is reconstructed by using the fitted scale height, and its average percentage error relative to the measured electron density profile is quantitatively analyzed by using the Alouette/ISIS topside sounder data sets and COSMIC radio occultation databases, and the accuracies of five other approaches (i.e., Nava et al., 2008, https://doi.org/10.1016/j.jastp.2008.01.015; Nusmei et al., 2012, https://doi.org/10.1029/2012RS004989; Porl et al., 2019, https://doi.org/10.1007/s10712-019-09521-3; Reinisch et al., 2007, https://doi.org/10.1016/j.asr.2006.05.032; Wu et al., 2020, https://doi.org/10.1029/2019JA027637) to approximate the topside electron density profiles are also compared. From the perspective of average percentage error, our formula performs well to reconstruct the topside electron density profiles, especially at the altitudes between hmF2 and hmF2 + 1,200 km.
Compositional Mapping of the Nili Patera Feldspathic Unit: Extent and Implications for Formation
Authors: Eggers Gabriel L. , Wray James J. , Dufek Josef 
Published: January 2021

AbstractDecades of study of the igneous martian crust concluded that it was primarily basaltic, but a range of new investigations find evidence of evolved compositions. Foremost of these is a highly feldspathic unit within the Nili Patera caldera of Syrtis Major, the only detection with preserved volcanic context but which nonetheless remains ambiguous in exact composition and formation. We conduct compositional mapping of this feldspathic unit via near‐infrared spectroscopy from the Compact Reconnaissance Imaging Spectrometer for Mars instrument and find that the unit occupies at minimum 104 km2 at high confidence and an additional 41 km2 at moderately high confidence, meaning the unit is locally significant. We compare our mapping with that inferred from geomorphology and find that while texture and albedo are useful proxies, they are not perfectly reliable as substitutes for thorough compositional investigation. Study of the boundary between the feldspathic unit and surrounding mafic rock indicates the former formed early and may extend locally in the subsurface. We consider what compositional mixtures could explain the conflicting interpretations derived from visible/near‐infrared and thermal infrared spectroscopy, concluding it is likely due to thermophysical differences between the light‐toned feldspathic unit and the infilling dark mafic sand. We discuss proposed plutonic and volcanic formation scenarios for the feldspathic unit, considering Earth analogs and implications for the parent magmatic system, and offer observations in rock texture and composition that would clarify.
A Simple Correction Term to Model Infiltration in Water‐Repellent Soils
Authors: Abou Najm M. R. , Stewart Ryan D. , Di Prima Simone , Lassabatere Laurent 
Published: January 2021

AbstractSoil water repellency can substantially alter hydrologic processes, particularly the ability of soils to infiltrate water. Water repellency often changes through time, making it difficult to simulate infiltration behaviors of water‐repellent soils using standard models. Here, we propose a simple rate‐based correction term that starts with a value of zero at the beginning of the infiltration process (t = 0) and asymptotically approaches 1 as time increases, thus simulating decreasing soil water repellency through time. The correction term can be used with any infiltration model. For this study, we selected a simple two‐term infiltration equation and then, using two data sets of infiltration measurements conducted in soils with varying water repellency, compared model error with versus without the added term. The correction substantially reduced model error, particularly in more repellent soils. At the same time, the rate constant parameter introduced in the new model may be useful to better understand dynamics of soil water repellency and to provide more consistent interpretations of hydraulic properties in water‐repellent soils.
Protective role of estrogen against excessive erythrocytosis in Monge’s disease
Authors: Azad Priti , Villafuerte Francisco C. , Bermudez Daniela , Patel Gargi , Haddad Gabriel G. 
Published: January 2021

AbstractMonge’s disease (chronic mountain sickness (CMS)) is a maladaptive condition caused by chronic (years) exposure to high-altitude hypoxia. One of the defining features of CMS is excessive erythrocytosis with extremely high hematocrit levels. In the Andean population, CMS prevalence is vastly different between males and females, being rare in females. Furthermore, there is a sharp increase in CMS incidence in females after menopause. In this study, we assessed the role of sex hormones (testosterone, progesterone, and estrogen) in CMS and non-CMS cells using a well-characterized in vitro erythroid platform. While we found that there was a mild (nonsignificant) increase in RBC production with testosterone, we observed that estrogen, in physiologic concentrations, reduced sharply CD235a+ cells (glycophorin A; a marker of RBC), from 56% in the untreated CMS cells to 10% in the treated CMS cells, in a stage-specific and dose-responsive manner. At the molecular level, we determined that estrogen has a direct effect on GATA1, remarkably decreasing the messenger RNA (mRNA) and protein levels of GATA1 (p < 0.01) and its target genes (Alas2, BclxL, and Epor, p < 0.001). These changes result in a significant increase in apoptosis of erythroid cells. We also demonstrate that estrogen regulates erythropoiesis in CMS patients through estrogen beta signaling and that its inhibition can diminish the effects of estrogen by significantly increasing HIF1, VEGF, and GATA1 mRNA levels. Taken altogether, our results indicate that estrogen has a major impact on the regulation of erythropoiesis, particularly under chronic hypoxic conditions, and has the potential to treat blood diseases, such as high altitude severe erythrocytosis.
Measurement of urinary pesticide biomarkers among Latina farmworkers in southwestern Idaho
Authors: Curl Cynthia L. , Meierotto Lisa , Castellano Rebecca L. Som , Spivak Meredith R. , Kannan Kurunthachalam 
Published: January 2021

Abstract
Background
Women who work in agriculture may have greater risk of pesticide exposure than men who share this occupation. Despite an increase in the fraction of the agricultural workforce comprised by women, few studies have characterized pesticide exposure in the USA with a focus on among these workers.

Objective
This pilot study aimed to describe pesticide exposure in a cohort of Latina farmworkers in farming communities in southwestern Idaho.

Methods
We collected urine samples from 29 Latina farmworkers, which were analyzed for 11 pesticide biomarkers. We evaluated the effect of pesticide spray season on urinary biomarker levels, and explored the effect of self-reported status as a pesticide handler on measured exposures.

Results
No significant differences were found between biomarker levels in samples collected during the nonspray and spray seasons. We observed 11 extreme outlying values in samples collected during the pesticide spray season. The most extreme outlying values (MDA: 51.7 ng/mL; 3-PBA: 11.8 ng/mL; trans-DCCA: 23.4 ng/mL; and 2,4-D: 31.1 ng/mL) were all provided during the spray season by women who reported loading, mixing or applying pesticides.

Conclusions
These results provide suggestive evidence that Latina farmworkers who handle pesticides during the spray season may be at an increased risk of exposure to organophosphate and pyrethroid insecticides, as well as the herbicide 2,4-D. We recommend that future research into pesticide exposures among farmworkers should include particular focus on this group.
AHA1 upregulates IDH1 and metabolic activity to promote growth and metastasis and predicts prognosis in osteosarcoma
Authors: Zheng Diwei , Liu Weihai , Xie Wenlin , Huang Guanyu , Jiang Qiwei , Yang Yang , Huang Jiarong , Xing Zihao , Yuan Mengling , Wei Mengning , Li Yao , Yin Junqiang , Shen Jingnan , Shi Zhi 
Published: January 2021

AbstractOsteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents. Although activator of HSP90 ATPase activity 1 (AHA1) is reported to be a potential oncogene, its role in osteosarcoma progression remains largely unclear. Since metabolism reprogramming is involved in tumorigenesis and cancer metastasis, the relationship between AHA1 and cancer metabolism is unknown. In this study, we found that AHA1 is significantly overexpressed in osteosarcoma and related to the prognosis of osteosarcoma patients. AHA1 promotes the growth and metastasis of osteosarcoma both in vitro and in vivo. Mechanistically, AHA1 upregulates the metabolic activity to meet cellular bioenergetic needs in osteosarcoma. Notably, we identified that isocitrate dehydrogenase 1 (IDH1) is a novel client protein of Hsp90-AHA1. Furthermore, the IDH1 protein level was positively correlated with AHA1 in osteosarcoma. And IDH1 overexpression could partially reverse the effect of AHA1 knockdown on cell growth and migration of osteosarcoma. Moreover, high IDH1 level was also associated with poor prognosis of osteosarcoma patients. This study demonstrates that AHA1 positively regulates IDH1 and metabolic activity to promote osteosarcoma growth and metastasis, which provides novel prognostic biomarkers and promising therapeutic targets for osteosarcoma patients.
p53 is required for nuclear but not mitochondrial DNA damage-induced degeneration
Authors: Geden Matthew J. , Romero Selena E. , Deshmukh Mohanish 
Published: January 2021

AbstractWhile the consequences of nuclear DNA damage have been well studied, the exact consequences of acute and selective mitochondrial DNA (mtDNA) damage are less understood. DNA damaging chemotherapeutic drugs are known to activate p53-dependent apoptosis in response to sustained nuclear DNA damage. While it is recognized that whole-cell exposure to these drugs also damages mtDNA, the specific contribution of mtDNA damage to cellular degeneration is less clear. To examine this, we induced selective mtDNA damage in neuronal axons using microfluidic chambers that allow for the spatial and fluidic isolation of neuronal cell bodies (containing nucleus and mitochondria) from the axons (containing mitochondria). Exposure of the DNA damaging drug cisplatin selectively to only the axons induced mtDNA damage in axonal mitochondria, without nuclear damage. We found that this resulted in the selective degeneration of only the targeted axons that were exposed to DNA damage, where ROS was induced but mitochondria were not permeabilized. mtDNA damage-induced axon degeneration was not mediated by any of the three known axon degeneration pathways: apoptosis, axon pruning, and Wallerian degeneration, as Bax-deficiency, or Casp3-deficiency, or Sarm1-deficiency failed to protect the degenerating axons. Strikingly, p53, which is essential for degeneration after nuclear DNA damage, was also not required for degeneration induced with mtDNA damage. This was most evident when the p53-deficient neurons were globally exposed to cisplatin. While the cell bodies of p53-deficient neurons were protected from degeneration in this context, the axons farthest from the cell bodies still underwent degeneration. These results highlight how whole cell exposure to DNA damage activates two pathways of degeneration; a faster, p53-dependent apoptotic degeneration that is triggered in the cell bodies with nuclear DNA damage, and a slower, p53-independent degeneration that is induced with mtDNA damage.
Aberrant development of pancreatic beta cells derived from human iPSCs with FOXA2 deficiency
Authors: Elsayed Ahmed K. , Younis Ihab , Ali Gowher , Hussain Khalid , Abdelalim Essam M. 
Published: January 2021

AbstractFOXA2 has been identified as an essential factor for pancreas development and emerging evidence supports an association between FOXA2 and diabetes. Although the role of FOXA2 during pancreatic development is well-studied in animal models, its role during human islet cell development remains unclear. Here, we generated induced pluripotent stem cells (iPSCs) from a patient withFOXA2haploinsufficiency (FOXA2+/−iPSCs) followed by beta-cell differentiation to understand the role of FOXA2 during pancreatic beta-cell development. Our results showed thatFOXA2haploinsufficiency resulted in aberrant expression of genes essential for the differentiation and proper functioning of beta cells. At pancreatic progenitor (PP2) and endocrine progenitor (EPs) stages, transcriptome analysis showed downregulation in genes associated with pancreatic development and diabetes and upregulation in genes associated with nervous system development and WNT signaling pathway. Knockout of FOXA2 in control iPSCs (FOXA2−/−iPSCs) led to severe phenotypes in EPs and beta-cell stages. The expression of NGN3 and its downstream targets at EPs as well as INSUILIN and GLUCAGON at the beta-cell stage, were almost absent in the cells derived from FOXA2−/−iPSCs. These findings indicate that FOXA2 is crucial for human pancreatic endocrine development and its defect may lead to diabetes based on FOXA2 dosage.