bluuebunny/crossref_metadata_2025_split huggingface dataset:
Traumatic Resin Ducts in Alaska Mountain Hemlock Trees Provide a New Proxy for Winter Storminess
Authors: Gaglioti Benjamin V. , Mann Daniel H. , Williams A. Park , Wiles Gregory C. , Stoffel Markus , Oelkers Rose , Jones Benjamin M. , Andreu‐Hayles Laia 
Published: May 2019

AbstractWinter is a critical season for land‐surface feedbacks and ecosystem processes; however, most high‐latitude paleo‐environmental reconstructions are blind to cold season conditions. Here we introduce a winter‐sensitive, paleo‐proxy record that is based on the relative frequency of tangential rows of traumatic resin ducts (TRDs) in the annual growth rings of mountain hemlocks (Tsuga mertensiana) growing near treeline in Southeast Alaska. Hemlocks produce a row of TRDs in the earlywood portion of their annual rings in response to cambial damage incurred during winter. Multidecadal bouts of TRD production were followed by growth‐leader replacement, reaction wood formation, and divergence in radial growth between storm‐damaged trees and less exposed mountain hemlock forests. These patterns are consistent with TRDs being a response to tree damage caused by ice and snowstorms, a conclusion supported by the krummholz tree architecture at these sites. This relationship is further corroborated by significant correlations between our TRD record and the strength of the wintertime Aleutian Low (AL) pressure system that is linked to tree‐damaging agents like wind, precipitation, and ice storm strength in Southeast Alaska. The combined TRD/krummholz architecture record indicates that abrupt shifts between strong and weak AL phases occurred every several decades since CE 1700 and that the 1800s had relatively long AL phases with heavy snowpacks. In addition to describing the magnitude and tempo of wintertime climate change in Northwestern North America, these results suggest that North Pacific Decadal Variability underlies the long‐term dynamics of treeline ecosystems along the northeast Pacific coast.
Exploring the Head Versus Tail‐End Dichotomy on Yield and Farm Incomes in Smallholder Irrigation Schemes in Tanzania
Authors: Manero Ana , Wheeler Sarah Ann , Zuo Alec , Mdemu Makarius 
Published: May 2019

AbstractVariations in water supply and their impact on farm production in smallholder irrigation schemes are often associated with the location of irrigators at either the head or tail‐end, with tail‐enders usually considered to be at a severe disadvantage. However, it is rare that the impact of multidimensional proxies of water (capturing adequacy, timing, and location) on farm production and income have been evaluated in conjunction with other relevant variables. Using GIS analysis, this study combines irrigation household surveys, irrigation area characteristics, and cadastral data from two smallholder irrigation schemes in southern Tanzania. The results indicate that location at both the head‐end and tail‐end had a negative significant impact on farm yields, but not farm incomes. Also, being further downstream the secondary canals (but not necessarily away from the system's intake) had a significant negative effect on both yields and incomes. Surprisingly, increased tomato production drove a decline in incomes, thus raising the importance of crop selection and productivity barriers linked to markets and knowledge. In absence of actual quantitative measures of water supply, this study concludes that using a multidimensional water proxy can uncover important effects that would otherwise remain overlooked by the widespread head versus tail‐end dichotomy, commonly used in the study of water distribution within smallholder irrigation systems.
An Objective Procedure for Delineating the Circumpolar Vortex
Authors: Bushra Nazla , Rohli Robert V. 
Published: May 2019

AbstractThe broad‐scale, steering atmospheric circulation in the Northern Hemisphere, represented by the tropospheric circumpolar vortex (CPV), is an important driver of environmental processes. The area and circularity of the CPV are analyzed hereby delineating the leading edge of the CPV at the steepest 500‐hPa geopotential height gradient globally. The daily CPV area and circularity were aggregated to monthly averages for contrast with measurements identified in previous research for the overlapping period of record (1979–2001). Accuracy of representation of the CPV is assessed through correlations to air‐sea teleconnections known to be associated with broad‐scale, extratropical steering circulation. Correlation to monthly teleconnection indices suggests that the new method allows for improvements in the calculation of area and circularity of the 500‐hPa manifestation of the CPV. These improvements justify extension of the calculation of the standardized CPV area and circularity for the 1979–2017 period of record. Results largely mirror those for the shorter time series, with the Arctic Oscillation, North Atlantic Oscillation, and Pacific‐North American teleconnection showing stronger links to CPV area and circularity than El Niño–Southern Oscillation and Pacific Decadal Oscillation. Collectively, these results suggest that the use of a singular indicator isohypse and/or monthly averaged data to represent the CPV may oversimplify analyses, especially for identifying past and future longwave ridges and troughs. This finding is important because the amplitudes and positions of the undulations in the broad‐scale flow exert the most important impacts on variability at both low‐ and high‐frequency time periods.
Anomalous Sound Velocities of Antigorite at High Pressure and Implications for Detecting Serpentinization at Mantle Wedges
Authors: Wang Duojun , Liu Tao , Chen Ting , Qi Xintong , Li Baosheng 
Published: May 2019

AbstractElastic properties of antigorite are important for interpretation of seismic mapping of serpentinization in the mantle wedge above subducting slabs. The compressional (VP) and shear (VS) wave velocities in pure antigorite aggregates were measured simultaneously up to 8.4 GPa by ultrasonic interferometry. We found that VP increases monotonically with pressure while VS increases with pressure up to about 3 GPa but undergoes a negative pressure dependence above 4 GPa. Compared to other mantle minerals, antigorite exhibits significantly lower P and S wave velocities as well as a higher VP/VS ratio at upper mantle pressures. We modeled velocity reductions manifesting through the formation of antigorite in mantle peridotite and provide compelling evidence that seismic anomalies with low‐velocity and high VP/VS ratios is caused by varying degrees of serpentinization in subduction zones.
Squeeze Dispersion and the Effective Diapycnal Diffusivity of Oceanic Tracers
Authors: Wagner Gregory L , Flierl Glenn , Ferrari Raffaele , Voet Gunnar , Carter Glenn S , Alford Matthew H , Girton James B 
Published: May 2019

AbstractWe describe a process called “squeeze dispersion” in which the squeezing of oceanic tracer gradients by waves, eddies, and bathymetric flow modulates diapycnal diffusion by centimeter to meter‐scale turbulence. Due to squeeze dispersion, the effective diapycnal diffusivity of oceanic tracers is different and typically greater than the average “local” diffusivity, especially when local diffusivity correlates with squeezing. We develop a theory to quantify the effects of squeeze dispersion on diapycnal oceanic transport, finding formulas that connect density‐averaged tracer flux, locally measured diffusivity, large‐scale oceanic strain, the thickness‐weighted average buoyancy gradient, and the effective diffusivity of oceanic tracers. We use this effective diffusivity to interpret observations of abyssal flow through the Samoan Passage reported by Alford et al. (2013, https://doi.org/10.1002/grl.50684) and find that squeezing modulates diapycnal tracer dispersion by factors between 0.5 and 3.
Methane Sources in the Waters of Lake Michigan and Lake Superior as Revealed by Natural Radiocarbon Measurements
Authors: Joung DongJoo , Leonte Mihai , Kessler John D. 
Published: May 2019

AbstractThe methane dynamics in the waters of Lakes Michigan and Superior, components of the North American Great Lake system, were investigated using measurements of methane concentration and natural radiocarbon (14C‐CH4) dissolved in these lake waters. All 14C‐CH4 measurements were above modern levels regardless of location and depth with a range of 117‐145% modern carbon (pMC). Methane concentrations in the deep basin of both lakes were low, ranging from 3.3 to 4.3 nM, with minimal vertical variation. However, the concentrations of CH4 increased toward coastal areas in both lakes, possibly due to higher groundwater inputs and aerobic methanogenesis associated with primary productivity. Except for one site, 14C‐CH4 dissolved in the waters of Lake Michigan was greater than in Lake Superior by ~12 pMC, a difference that was likely due to inputs of excess 14CH4 from nuclear power plants along the coast of Lake Michigan.
Triggered Plasmaspheric Hiss: Rising Tone Structures
Authors: Zhu Hui , Liu Xu , Chen Lunjin 
Published: May 2019

AbstractIn this study, a rare hiss event observed by Van Allen Probe is reported and the possible generation is investigated based on wave and plasma measurements. The results suggest that the normal hiss (from 0.05fce to 0.5fce) with dominantly equatorward Poynting fluxes is locally generated by plasma sheet electrons via cyclotron instability. The low‐frequency band (from 30 Hz to 0.05fce) with a mixture of equatorward and poleward Poynting fluxes is probably due to multiple reflections inside the plasmasphere. Such difference in the two bands is confirmed by the calculation of minimum energy of resonant electrons and local growth rate. Moreover, the analysis on the fine structures of normal hiss waves shows that besides the expected incoherent structure (below 1 kHz), several rising tone elements are measured above 1 kHz. The rising tone structures are probably triggered by the incoherent hiss part below 1 kHz, which is rarely reported before.
A 250‐Year European Drought Inventory Derived From Ensemble Hydrologic Modeling
Authors: Moravec Vojtěch , Markonis Yannis , Rakovec Oldrich , Kumar Rohini , Hanel Martin 
Published: May 2019

AbstractWe present a 250‐year (1766–2015) inventory of European meteorological, hydrological, and agricultural droughts derived from ensemble simulations of the mesoscale Hydrological Model (mHM). The inventory of droughts takes into account an ensemble of 100 simulations from the hydrological model, allowing for assessment of how different meteorological forcing and model parameterizations affect a drought ranking. For the most extreme droughts, the variability in the ranking of drought events is low, while for the years with moderate precipitation deficits, the variability increases. Despite the underlying uncertainties, our drought inventory shows increased recurrence of soil moisture droughts in the Mediterranean and declining spatial extent of hydrological drought in Central Europe over the last three decades.
A New Technique for Estimating the Lifetime of Bursts of Electron Precipitation From Sounding Rocket Measurements
Authors: Hecht J. H. , Clemmons J. H. , Lessard M. R. , Kenward D. L. , Sadler F. B. , Fritz B. A. , Evans J. S. , Lynch K. A. 
Published: May 2019

AbstractAt 0735 UT on 13 December 2015, the Rocket Experiment for Neutral Upwelling‐2 experiment launched north toward the auroral cusp region from Andoya, Norway. The instrumented rocket included an electron spectrometer, photometers that measured the auroral redline and greenline, and an instrument that measured ionospheric thermal electron temperature. On the down leg, just south of Svalbard, the rocket entered a region of poleward moving auroral forms that were characterized by narrow structures due to a combination of spatial and temporal variations. A noticeable feature was that the redline to greenline brightness ratio was much smaller than expected. A model is developed that shows that these emissions can be used to estimate the lifetimes of bursty electron precipitation. This model is shown to be consistent with some poleward moving auroral form lifetimes being on the order of 100 ms. The correlation between the precipitation and temperature bursts suggest that some transport occurred.
Evaluating Indices of Blocking Anticyclones in Terms of Their Linear Relations With Surface Hot Extremes
Authors: Chan Pak‐Wah , Hassanzadeh Pedram , Kuang Zhiming 
Published: May 2019

AbstractChanges in frequencies of blocking anticyclones are sometimes used to explain changes in surface hot extremes. However, there is no consensus on the definition of blocking anticyclones, and several indices have been developed to measure them. Here we linearly regress interannual variations of hemispheric continental summer surface hot extreme area on the corresponding variations of blocking anticyclones in the ERA‐Interim reanalysis data and use cross‐validation test error to measure the blocking‐extreme link. Relative mean square validation error is at least 0.91 (relative to no knowledge of blocking) for existing indices defined on 500‐hPa geopotential height, when summed over land and ocean. This can be reduced to 0.55, largely by excluding blocks over ocean and optimizing parameters/thresholds and partly by using anomaly‐based or anomaly‐reversal hybrid indices. This framework helps to quantify the association of hot extremes and blocks with an uncertainty estimate and can be used for other extremes as well.
Properties of Magnetic Reconnection and FTEs on the Dayside Magnetopause With and Without Positive IMF Bx Component During Southward IMF
Authors: Hoilijoki S. , Ganse U. , Sibeck D. G. , Cassak P. A. , Turc L. , Battarbee M. , Fear R. C. , Blanco‐Cano X. , Dimmock A. P. , Kilpua E. K. J. , Jarvinen R. , Juusola L. , Pfau‐Kempf Y. , Palmroth M. 
Published: May 2019

AbstractThis paper describes properties and behavior of magnetic reconnection and flux transfer events (FTEs) on the dayside magnetopause using the global hybrid‐Vlasov code Vlasiator. We investigate two simulation runs with and without a sunward (positive) Bx component of the interplanetary magnetic field (IMF) when the IMF is southward. The runs are two‐dimensional in real space in the noon‐midnight meridional (polar) plane and three‐dimensional in velocity space. Solar wind input parameters are identical in the two simulations with the exception that the IMF is purely southward in one but tilted 45° toward the Sun in the other. In the purely southward case (i.e., without Bx) the magnitude of the magnetosheath magnetic field component tangential to the magnetopause is larger than in the run with a sunward tilt. This is because the shock normal is perpendicular to the IMF at the equatorial plane, whereas in the other run the shock configuration is oblique and a smaller fraction of the total IMF strength is compressed at the shock crossing. Hence, the measured average and maximum reconnection rate are larger in the purely southward run. The run with tilted IMF also exhibits a north‐south asymmetry in the tangential magnetic field caused by the different angle between the IMF and the bow shock normal north and south of the equator. Greater north‐south asymmetries are seen in the FTE occurrence rate, size, and velocity as well; FTEs moving toward the Southern Hemisphere are larger in size and observed less frequently than FTEs in the Northern Hemisphere.
Thank You to Our 2018 Peer Reviewers
Authors: Pincus Robert , Blyth Eleanor , Griffies Stephen M. 
Published: May 2019

AbstractAs the editors of a scientific journal, we are privileged to have box seats to the peer review process. We watch as reviewers shine a new light on authors' work, identifying weakness in conception or expression, suggesting refinements, urging authors to clarify a point or better support an argument. The process is occasionally uncomfortable but it is almost always respectful and constructive and papers are uniformly better for this input. At the Journal of Advances in Modeling Earth Systems (JAMES) we are fortunate to have a pool of reviewers who volunteer their time, insight, knowledge, and intelligence to improve the work of their colleagues and peers. It is no small task: In 2018, we received 715 reviews by 494 individuals. On behalf of the entire editorial board and our authors we thank you all for your selfless contributions to strengthening our community.
Transport With Bimolecular Reactions in a Fracture‐Matrix System: Analytical Solutions With Applications to In Situ Chemical Oxidation
Authors: Arshadi Masoud , Rajaram Harihar 
Published: May 2019

AbstractWe present analytical solutions for transport with bimolecular reactions in a single fracture embedded within an infinite rock matrix. The fracture and matrix are initially assumed to contain one aqueous species (B) at a uniform concentration. A second aqueous species (A) is injected into the fracture and reacts with B and an additional immobile species (N) in the rock matrix. Under these conditions, moving reaction fronts form and propagate along the fracture and into the rock matrix. We employ a composite similarity variable involving two space variables to derive analytical solutions for all species concentrations and the geometry of reaction fronts in the fracture and matrix. The behavior of the reaction‐diffusion equations in the rock matrix is posed as a Stefan problem. For uniform advection in the fracture, our analytical solutions establish that the reaction fronts propagate as the square root of time in both the matrix and the fracture. Our analytical solutions agree very well with numerical simulations. We extend our analytical solutions to nonuniform flows in the fracture by invoking a travel‐time transformation. We present applications of our analytical solutions to in situ chemical oxidation of dense nonaqueous phase liquids in fractured rock, wherein an oxidant (A, e.g., permanganate) is injected through fractures and consumed by bimolecular reactions with dissolved dense nonaqueous phase liquids (B, e.g., trichloroethylene) and natural organic matter (N) in the fracture and rock matrix. Our analytical solutions are also relevant to a broad class of reactive transport problems in fracture‐matrix systems where moving reaction fronts occur.
WISH: wavefront imaging sensor with high resolution
Authors: Wu Yicheng , Sharma Manoj Kumar , Veeraraghavan Ashok 
Published: May 2019

AbstractWavefront sensing is the simultaneous measurement of the amplitude and phase of an incoming optical field. Traditional wavefront sensors such as Shack-Hartmann wavefront sensor (SHWFS) suffer from a fundamental tradeoff between spatial resolution and phase estimation and consequently can only achieve a resolution of a few thousand pixels. To break this tradeoff, we present a novel computational-imaging-based technique, namely, the Wavefront Imaging Sensor with High resolution (WISH). We replace the microlens array in SHWFS with a spatial light modulator (SLM) and use a computational phase-retrieval algorithm to recover the incident wavefront. This wavefront sensor can measure highly varying optical fields at more than 10-megapixel resolution with the fine phase estimation. To the best of our knowledge, this resolution is an order of magnitude higher than the current noninterferometric wavefront sensors. To demonstrate the capability of WISH, we present three applications, which cover a wide range of spatial scales. First, we produce the diffraction-limited reconstruction for long-distance imaging by combining WISH with a large-aperture, low-quality Fresnel lens. Second, we show the recovery of high-resolution images of objects that are obscured by scattering. Third, we show that WISH can be used as a microscope without an objective lens. Our study suggests that the designing principle of WISH, which combines optical modulators and computational algorithms to sense high-resolution optical fields, enables improved capabilities in many existing applications while revealing entirely new, hitherto unexplored application areas.
Loss of TET2 and TET3 in regulatory T cells unleashes effector function
Authors: Yue Xiaojing , Lio Chan-Wang J. , Samaniego-Castruita Daniela , Li Xiang , Rao Anjana 
Published: May 2019

AbstractTET enzymes oxidize 5-methylcytosine to 5-hydroxymethylcytosine and other oxidized methylcytosines in DNA. Here we examine the role of TET proteins in regulatory T (Treg) cells. Tet2/3fl/flFoxp3Cre mice lacking Tet2 and Tet3 in Treg cells develop inflammatory disease, and Treg cells from these mice show altered expression of Treg signature genes and upregulation of genes involved in cell cycle, DNA damage and cancer. In littermate mice with severe inflammation, both CD4+Foxp3+ and CD4+Foxp3− cells show strong skewing towards Tfh/Th17 phenotypes. Wild-type Treg cells in mixed bone marrow chimeras and in Tet2/3fl/flFoxp3WT/Cre heterozygous female mice are unable to rescue the aberrant properties of Tet2/3fl/flFoxp3Cre Treg cells. Treg cells from Tet2/3fl/flFoxp3Cre mice tend to lose Foxp3 expression, and transfer of total CD4+ T cells isolated from Tet2/3fl/flFoxp3Cre mice could elicit inflammatory disease in fully immunocompetent mice. Together, these data indicate that Tet2 and Tet3 are guardians of Treg cell stability and immune homeostasis.
Capicua regulates neural stem cell proliferation and lineage specification through control of Ets factors
Authors: Ahmad Shiekh Tanveer , Rogers Alexandra D. , Chen Myra J. , Dixit Rajiv , Adnani Lata , Frankiw Luke S. , Lawn Samuel O. , Blough Michael D. , Alshehri Mana , Wu Wei , Marra Marco A. , Robbins Stephen M. , Cairncross J. Gregory , Schuurmans Carol , Chan Jennifer A. 
Published: May 2019

AbstractCapicua (Cic) is a transcriptional repressor mutated in the brain cancer oligodendroglioma. Despite its cancer link, little is known of Cic’s function in the brain. We show that nuclear Cic expression is strongest in astrocytes and neurons but weaker in stem cells and oligodendroglial lineage cells. Using a new conditional Cic knockout mouse, we demonstrate that forebrain-specific Cic deletion increases proliferation and self-renewal of neural stem cells. Furthermore, Cic loss biases neural stem cells toward glial lineage selection, expanding the pool of oligodendrocyte precursor cells (OPCs). These proliferation and lineage effects are dependent on de-repression of Ets transcription factors. In patient-derived oligodendroglioma cells, CIC re-expression or ETV5 blockade decreases lineage bias, proliferation, self-renewal, and tumorigenicity. Our results identify Cic as an important regulator of cell fate in neurodevelopment and oligodendroglioma, and suggest that its loss contributes to oligodendroglioma by promoting proliferation and an OPC-like identity via Ets overactivity.