bluuebunny/crossref_metadata_2025 huggingface dataset:
A Pedogenic Model for the Magnetic Enhancement of Late Miocene Fluvial‐Lacustrine Sediments From the Xining Basin, NE Tibetan Plateau
Authors: Zan Jinbo , Kang Jian , Yan Maodu , Fang Xiaomin , Li Xiaojing , Guan Chong , Zhang Weilin , Fang Yahui
Published: August 2018

Continuous sequences of Cenozoic fluvial‐lacustrine sediments are well preserved in the northeastern edge of the Tibetan Plateau (TP), and they provide a good opportunity to improve our understanding of the tectonic uplift and paleoenvironmental evolution of the NE TP. To date, however, the factors controlling the variations in the magnetic properties of these fluvial‐lacustrine sediments remain complex and ambiguous. Here we systematically assess the contribution of pedogenesis to the magnetic enhancement of late Miocene fluvial‐lacustrine sediments in the Xining Basin, using a combination of rock magnetic, diffuse reflectance spectroscopy, and geochemical methods. Our results demonstrate that the magnetic concentration parameters show a long‐term increasing trend since the late Miocene, with two dramatic increases at ~11 and 9 Ma. Based on the examination of several factors that may affect the magnetic properties of fluvial‐lacustrine sediments in the NE TP, we argue that an accelerated drying process in waterlogged environments, induced by late Miocene global cooling or/and tectonic uplift, may have caused the changes from anaerobic to aerobic conditions and resulted in the observed stepwise increases in pedogenic intensity. The two dramatic increases in magnetic parameters are closely related to intensified aridification and tectonic activity in the NE TP at ~11 and 9 Ma, respectively. These observations suggest that the pedogenic magnetic enhancement model, caused by the disappearance of a waterlogged and reducing pedogenic environment since the late Miocene, should be reconsidered as a possible factor explaining the magnetic properties of fluvial‐lacustrine sediments in the NE TP.
Delayed and Quasi‐Synchronous Response of Tropical Atlantic Surface Salinity to Rainfall
Authors: Grodsky Semyon A. , Carton James A.
Published: August 2018

Zonally elongated patterns of tropical Atlantic rainfall variability associated with the Atlantic meridional (dipole) and the El Niño‐Southern Oscillation (ENSO) modes extend over the ocean and adjacent land and lead to a complex sea surface salinity (SSS) response. SSS response to local ocean rainfall is quasi‐instantaneous, while SSS response to land rainfall is delayed through river hydrology. Amazon rainfall associated with the Atlantic meridional mode concentrates over coastal north‐east Brazil and results in a fast Amazon response. In contrast, ENSO rainfall occupies vast inland areas and results in 3‐ to 7‐month delayed Amazon discharge response. Although ocean profile analyses represent well interannual SSS forced by open ocean rainfall, they miss interannual SSS in the plume. Including thermosalinograph transect data improves the representation of plume SSS, but its dynamic is better captured by ocean reanalyses. In Simple Ocean Data Assimilation, the plume SSS anomaly persists several months following the peak of land rainfall and is mixed out by seasonally accelerating winds in boreal winter. Its discharge‐correlated magnitude is only a modest few tenths of PSU. Perhaps, such weak projection of continental discharge variations on simulated SSS is not surprising due to other factors contributing in this dynamically active western boundary area. Significant transient variability in local currents not associated with rainfall/discharge variability is a factor explaining why ocean analyses based on occasional profile observations fail in resolving the rain‐induced SSS in the Amazon plume.
Role of SST Patterns on Surface Wind Modulation of a Heavy Midlatitude Precipitation Event
Authors: Meroni Agostino N. , Parodi Antonio , Pasquero Claudia
Published: August 2018

The mechanisms controlling the influence of the sea surface temperature (SST) structure on the surface winds are studied by means of numerical simulations run with a nonhydrostatic fully compressible state‐of‐the‐art numerical model in a realistic midlatitudes setup, leading to the 9 October 2014 Genoa heavy rainfall event. Starting from a simulation with high‐resolution submesoscale eddy‐permitting SST field, the surface temperature boundary conditions are changed to enhance, reduce, or smooth the SST gradient. It is found that the marine atmospheric boundary layer responds to the submesoscale SST forcing structures over time scales of the order of hours. In particular, through the downward momentum mixing mechanism, the presence of SST horizontal gradients impacts the spatial structure of the surface wind convergence, which can displace the convective heavy rain bands that develop over the sea.
Evaluating Different Machine Learning Methods for Upscaling Evapotranspiration from Flux Towers to the Regional Scale
Authors: Xu Tongren , Guo Zhixia , Liu Shaomin , He Xinlei , Meng Yangfanyu , Xu Ziwei , Xia Youlong , Xiao Jingfeng , Zhang Yuan , Ma Yanfei , Song Lisheng
Published: August 2018

Evapotranspiration (ET) is a vital variable for land‐atmosphere interactions that links surface energy balance, water, and carbon cycles. The in situ techniques can measure ET accurately but the observations have limited spatial and temporal coverage. Modeling approaches have been used to estimate ET at broad spatial and temporal scales, while accurately simulating ET at regional scales remains a major challenge. In this study, we upscale ET from eddy covariance flux tower sites to the regional scale with machine learning algorithms. Five machine learning algorithms are employed for ET upscaling including artificial neural network, Cubist, deep belief network, random forest, and support vector machine. The machine learning methods are trained and tested at 36 flux towers sites (65 site years) across the Heihe River Basin and are then applied to estimate ET for each grid cell (1 km × 1 km) within the watershed and for each day over the period 2012–2016. The artificial neural network, Cubist, random forest, and support vector machine algorithms have almost identical performance in estimating ET and have slightly lower root‐mean‐square error than deep belief network at the site scale. The random forest algorithm has slightly lower relative uncertainty at the regional scale than other methods based on three‐cornered hat method. Additionally, the machine learning methods perform better over densely vegetated conditions than barren land or sparsely vegetated conditions. The regional ET generated from the machine learning approaches captured the spatial and temporal patterns of ET at the regional scale.
Continuous Assimilation of Lightning Data Using Time‐Lagged Ensembles for a Convection‐Allowing Numerical Weather Prediction Model
Authors: Wang Haoliang , Liu Yubao , Zhao Tianliang , Liu Yuewei , Xu Mei , Shen Si , Jiang Yin , Yang Honglong , Feng Shuanglei
Published: August 2018

In this study, a lightning data assimilation method based on the time‐lagged ensembles for predicting severe convection is presented. With the lightning data assimilation scheme, the background error covariances are computed using time‐lagged ensembles, which consist of deterministic forecasts from eight forecast cycles initialized every 3 hr. Pseudo‐observations of graupel mixing ratio (qg) are retrieved from total lightning rates by utilizing empirical vertical profiles obtained from the simulation results of the previous forecast cycles, and the corresponding observation errors are estimated according to the uncertainties in the lightning observations and the empirical vertical profiles of qg. The increments of the model state variables are computed with the Kalman gain matrices and are continuously ingested into the Weather Research and Forecasting model via nudging terms acting on the prognostic equations over each time step during model integration. The effect of the lightning data assimilation scheme on convection analysis and forecast was assessed through a case study of a severe convective event, which took place in the Guangdong of China. Assimilating lightning data recovered many of the observed convective cells, suppressed the spurious convection, and corrected the displacement errors of the convective systems. Quantitative verifications indicate that forecast skills were improved mainly in the convective regions with the impact of assimilating lightning data on stratiform regions being overall less effective.
Disentangling Impacts of Dynamic and Thermodynamic Components on Late Summer Rainfall Anomalies in East Asia
Authors: Oh Hyoeun , Ha Kyung‐Ja , Timmermann Axel
Published: August 2018

This study has examined relative contributions of dynamic and thermodynamic components to East Asian summer monsoon (EASM), compared to the others over Asia. We have decomposed of moisture budget into the dynamic and thermodynamic components composing of interannual variability of the EASM. As represented by the moisture budget, the Asian monsoon is mostly caused by changes in winds (dynamic component); interestingly, changes in moisture (thermodynamic component) play an important role in monsoon rainfall anomalies only for East Asia (27.09%). In terms of the dynamic component over East Asia, strong continental heating, resulting in enhanced land‐sea contrast, is identified as crucial to a local development of winds toward East Asia, and it ultimately strengthens a meridional wind, which is accompanied by the western North Pacific subtropical high. In addition, the negative winter North Atlantic Oscillation could induce the enhanced moisture advection term of the dynamic component over East Asia through barotropic Rossby wave propagation. The thermodynamic component has a localized effect on net precipitation at midlatitudes, with an enhanced wave train pattern with a zonal wavenumber‐5, which reinforces the Okhotsk high. These distinct large‐scale circulation patterns together create favorable conditions for heavy rainfall over East Asia when the two components are positively in‐phase. Here we have also described that the extreme heavy rainfall is noticeable when the Eurasian blocking occurs. This study is expected to improve the detailed predictability of the EASM by understanding the two components to prevent disaster risks in terms of extreme rainfall.
The Life Cycles of Ice Crystals Detrained From the Tops of Deep Convection
Authors: Jensen Eric J. , van den Heever Susan C. , Grant Leah D.
Published: August 2018

Extensive anvil cirrus clouds generated by deep convection have important impacts on the Earth's radiation budget and climate. We use growth‐sedimentation trajectory calculations to investigate the life cycles of anvil ice crystals as they are advected downwind from their convective source. Temperature, water vapor, and wind fields from a cloud‐resolving model simulation of an isolated cumulonimbus cloud are used to drive the calculations. Ice crystals are initialized in the main upper‐level detrainment zone with a size distribution based on in situ measurements made in a convective core at about 12 km. Advection, deposition growth, and sedimentation of thousands of sample ice crystals are tracked over about 2.5 hr; neither aggregation of ice crystals nor radiative effects are included. Results support the importance of deposition growth and gravitational size sorting in the evolution of the anvil cirrus. Most ice crystals initialized with maximum dimensions larger than about 200 μm fall out of the anvil and sublimate in subsaturated air below within about 2 hr. Few small ice crystals are present in the lower part of the mature anvil. Vapor deposition growth accounts for about 50% of the ice mass remaining after about 2 hr. Ice crystals larger than about 50 μm in the mature anvil have grown substantially by deposition of vapor. This result is consistent with the predominance of bullet rosette habits observed in mature anvils. Variations in ice crystal fall speeds and growth rates associated with ice crystal habit assumptions have little impact on the ice crystal life cycles.
Variations of Thunderstorm Charge Structures in West Texas on 4 June 2012
Authors: Chmielewski Vanna C. , Bruning Eric C. , Ancell Brian C.
Published: August 2018

This study documents an environment for which small changes therein significantly impacted electrification and for which current theories of electrification lacked the ability to discriminate storm polarity. Thirty single‐cell and multicell storms from 1900 to 2200 UTC on 4 June 2012 over a 150‐ by 100‐km West Texas region were examined. Some of these storms had anomalous charge structures (primarily positive charge in the midlevels at −10 °C to −30 °C or 6.3 to 8.8 km above MSL locally) and some normal (primarily negative at midlevels), even though they existed concurrently and did not statistically differ in overall flash sizes, flash rates, radar volume, or echo top height. Overall, the normal storms ingested lower equivalent potential temperature surface air and were estimated to experience lower convective available potential energy than the anomalous storms, as observed in other studies. They were, however, estimated to have smaller warm cloud depth and surface dew point temperatures, contrary to expectations. Significant overlap between the storm environments suggested that lower instability may have contributed to some storms becoming normally electrified, but it was not a sufficient condition. Additionally, there had been previous convection in the region dominated by normal‐polarity storms. A Weather Research and Forecasting ensemble suggested that the previous convection moistened the midlevels of the atmosphere near cloud base. We propose that future studies investigate dry‐air entrainment as an additional, intertwined environmental factor that could decrease droplet sizes and effective warm rain processes, promoting positive graupel charging in the midlevels and anomalous charge structures.
Spectral Trends of the Surface Regolith in Lunar Craters
Authors: Sim Chae Kyung , Kim Sungsoo S.
Published: August 2018

Using topography‐corrected reflectance maps of the Moon, we present a new methodology for quantifying the spectral distribution of craters in the 750 nm reflectance and 950 nm/750 nm reflectance ratio space (R‐C space) and investigate how the spectral trend changes as the crater matures and degrades. Considering more than 3,495 craters across the Moon, we calculate three parameters to describe spectral trends of the pixels in each crater: 95th‐percentile length, clockwise rotation angle from the horizontal line, and statistical skewness along the principal axis of the distribution, as well as median values of the reflectance and the reflectance ratio. We find that the shape of the spectral trend of a crater in R‐C space becomes shorter, steeper, and more skewed toward the upper left as it optically matures and topographically degrades. Skewness shows a similar relationship to topographical degradation in both mare and highland craters. The skewness is useful in age estimation because it can be calculated easily from reflectance data and is applicable to craters of large size or in low‐iron‐content regions where a topographic model is currently not available. Using these three parameters, one can define the representative trends of a group of craters. We show representative trends of craters with various iron contents at different latitudes. The trends are parallel to one another, with offset controlled by latitude and radial rotation controlled by local iron content; these observations integrate the results of previous studies that reported the two behaviors individually.
A Climate Index Optimized for Longshore Sediment Transport Reveals Interannual and Multidecadal Littoral Cell Rotations
Authors: Anderson Dylan , Ruggiero Peter , Antolínez José A. A. , Méndez Fernando J. , Allan Jonathan
Published: August 2018

A recent 35‐year endpoint shoreline change analysis revealed significant counterclockwise rotations occurring in north‐central Oregon, USA, littoral cells that extend 10s of kilometers in length. While the potential for severe El Niños to contribute to littoral cell rotations at seasonal to interannual scale was previously recognized, the dynamics resulting in persistent (multidecadal) rotation were unknown, largely due to a lack of historical wave conditions extending back multiple decades and the difficulty of separating the timescales of shoreline variability in a high energy region. This study addresses this question by (1) developing a statistical downscaling framework to characterize wave conditions relevant for longshore sediment transport during data‐poor decades and (2) applying a one‐line shoreline change model to quantitatively assess the potential for such large embayed beaches to rotate. A climate INdex was optimized to capture variability in longshore wave power as a proxy for potential LOngshore Sediment Transport (LOST_IN), and a procedure was developed to simulate many realizations of potential wave conditions from the index. Waves were transformed dynamically with Simulating Waves Nearshore to the nearshore as inputs to a one‐line model that revealed shoreline rotations of embayed beaches at multiple time and spatial scales not previously discernible from infrequent observations. Model results indicate that littoral cells respond to both interannual and multidecadal oscillations, producing comparable shoreline excursions to extreme El Niño winters. The technique quantitatively relates morphodynamic forcing to specific climate patterns and has the potential to better identify and quantify coastal variability on timescales relevant to a changing climate.
Climate Variability Controls on CO2 Consumption Fluxes and Carbon Dynamics for Monsoonal Rivers: Evidence From Xijiang River, Southwest China
Authors: Zhong Jun , Li Si‐Liang , Liu Jing , Ding Hu , Sun Xiaole , Xu Sheng , Wang Tiejun , Ellam Rob M. , Liu Cong‐Qiang
Published: August 2018

The feedbacks of climate variability on CO2 consumption fluxes and carbon dynamics are thought to play an important role in moderating the global carbon cycle. High‐frequency sampling campaigns and analyses were conducted in this study to investigate temporal variations of river water chemistry and the impacts of climate variability on CO2 consumption fluxes and carbon dynamics for the Xijiang River, Southwest China. Physical processes modify biogeochemical processes, so major ions display different responses to changing discharge. The annual CO2 consumption rate is (6.8 ± 0.2) × 106 ton/year by carbonate weathering and (2.4 ± 0.3) × 106 ton/year by silicate weathering. The annual CO2 consumption flux is much higher than most world rivers, and strong CO2 consumption capacities are observed in catchments in Southwest China. Lower negative δ13CDIC values are found in the high‐flow season which corresponds with high temperatures compared to those in the low‐flow season. High discharge will accelerate material transport, and high temperatures will increase primary production in the catchment, both of which can be responsible for the shift of δ13CDIC values in the high‐flow season. Increased mineral weathering and biological carbon influx in the catchment are the main factors controlling carbon dynamics. Overall, these findings highlight the sensitivity of CO2 consumption fluxes and carbon dynamics in response to climate variability in the riverine systems.
Identifying Critical Climate Periods for Vegetation Growth in the Northern Hemisphere
Authors: Chen Chen , He Bin , Guo Lanlan , Zhang Yafeng , Xie Xiaoming , Chen Ziyue
Published: August 2018

Vegetation‐climate relationships have been extensively investigated in previous studies, yet the critical seasons and corresponding climate factors influencing annual vegetation growth in a changing climate remain unclear. Relying on Global Inventory Modeling and Mapping Studies NDVI3g data and climate data from 1982 to 2013, this study explored the responses of vegetation growth to climate changes in the Northern Hemisphere (NH), with an emphasis on vegetation changes and legacy effects during different seasons. We further identified the most critical season in terms of vegetation growth. We found an apparent seasonal shift in the influence of climate change on vegetation growth in the NH. In addition, we observed legacy effects of climate change on vegetation growth throughout the seasons. Winter temperatures exerted a positive impact on vegetation growth during the following spring in Europe and central North America. Spring precipitation was an important factor for summer vegetation growth in dry areas. Using partial least squares regression, the relative importance of seasonal climatic factors on annual vegetation growth conditions were determined. This study finds that the vegetation in more than 40% of the NH is controlled by temperature, especially spring temperatures (12.8%). Precipitation and solar radiation were the dominant climate factors influencing vegetation growth in 29.9% and 29.1% of vegetated regions, respectively. Furthermore, compared with the period from 1983 to 1997, the influence of seasonal solar radiation on vegetation growth increased in the NH during the period from 1998 to 2013. This phenomenon was accompanied by reductions in the influence of spring and summer temperatures.
Carbon Dioxide and Methane Dynamics in a Small Boreal Lake During Winter and Spring Melt Events
Authors: Denfeld B. A. , Klaus M. , Laudon H. , Sponseller R. A. , Karlsson J.
Published: August 2018

In seasonally ice‐covered lakes, carbon dioxide (CO2) and methane (CH4) emission at ice‐off can account for a significant fraction of the annual budget. Yet knowledge of the mechanisms controlling below lake‐ice carbon (C) dynamics and subsequent CO2 and CH4 emissions at ice‐off is limited. To understand the control of below ice C dynamics, and C emissions in spring, we measured spatial variation in CO2, CH4, and dissolved inorganic and organic carbon from ice‐on to ice‐off, in a small boreal lake during a winter with sporadic melting events. Winter melt events were associated with decreased surface water DOC in the forest‐dominated basin and increased surface water CH4 in the mire‐dominated basin. At the whole‐lake scale, CH4 accumulated below ice throughout the winter, whereas CO2 accumulation was greatest in early winter. Mass‐balance estimates suggest that, in addition to the CO2 and CH4 accumulated during winter, external inputs of CO2 and CH4 and internal processing during ice‐melt could represent significant sources of C gas emissions during ice‐off. Moreover, internal processing of CO2 and CH4 worked in opposition, with production of CO2 and oxidation of CH4 dominating at ice‐off. These findings have important implications for how small boreal lakes will respond to warmer winters in the future; increased winter melt events will likely increase external inputs below ice and thus alter the extent and timing of CO2 and CH4 emissions to the atmosphere at ice‐off.
Historical Reanalysis: What, How, and Why?
Authors: Slivinski Laura C.
Published: August 2018

Historical reanalyses combine observations of past weather with simulations from modern numerical weather prediction models to provide a consistent, global history of the weather. Recently, a new reanalysis was released that allows observations of the ocean to impact the atmosphere and vice versa. “CERA‐20C: A Coupled Reanalysis of the Twentieth Century” by P. Laloyaux et al. (2018, https://doi.org/10.1029/2018MS001273) describes the first coupled centennial reanalysis, thereby providing more balanced estimates of the ocean‐atmosphere system and allowing for a broader range of studies of the entire Earth system. Results suggest that similar methods could also be leveraged to improve modern weather forecasts.
An X Band Radio Channel Model for Propagation Through the Solar Corona
Authors: Stocker A. J. , Siddle D. R. , Warrington E. M. , Mariotti G. , Silvestri D. , Zeqaj A. , Tortora P. , Argyriou A. , De Vicente J. , Abello R. , Mercolino M.
Published: August 2018

Spacecraft communication systems operating at X band are strongly affected when the propagation path passes close to the Sun (which can be characterized by the Sun‐Earth‐Probe, SEP, angle). In this paper, a channel model that can generate a time series of signal amplitude and phase, and hence the signal in‐phase and quadrature values, is presented. For X band, the channel model reproduces the observations well for SEP > 0.8°. While the model has not been experimentally validated at SEP angles below 0.8°, the behavior is consistent with measurements reported in the literature and is therefore likely to be suitable for use, with caution, in that region too.
Mantle Flow and Deforming Continents: From India‐Asia Convergence to Pacific Subduction
Authors: Jolivet Laurent , Faccenna Claudio , Becker Thorsten , Tesauro Magdala , Sternai Pietro , Bouilhol Pierre
Published: August 2018

The formation of mountain belts or rift zones is commonly attributed to interactions between plates along their boundaries, but the widely distributed deformation of Asia from Himalaya to the Japan Sea and other back‐arc basins is difficult to reconcile with this notion. Through comparison of the tectonic and kinematic records of the last 50 Ma with seismic tomography and anisotropy models, we show that the closure of the former Tethys Ocean and the extensional deformation of East Asia can be best explained if the asthenospheric mantle transporting India northward, forming the Himalaya and the Tibetan Plateau, reaches East Asia where it overrides the westward flowing Pacific mantle and contributes to subduction dynamics, distributing extensional deformation over a 3,000‐km wide region. This deep asthenospheric flow partly controls the compressional stresses transmitted through the continent‐continent collision, driving crustal thickening below the Himalayas and Tibet and the propagation of strike‐slip faults across Asian lithosphere further north and east, as well as with the lithospheric and crustal flow powered by slab retreat east of the collision zone below East and SE Asia. The main shortening direction in the deforming continent between the collision zone and the Pacific subduction zones may in this case be a proxy for the direction of flow in the asthenosphere underneath, which may become a useful tool for studying mantle flow in the distant past. Our model of the India‐Asia collision emphasizes the role of asthenospheric flow underneath continents and may offer alternative ways of understanding tectonic processes.
Evidence for an Early Silurian Synorogenic Basin Within the Metamorphic Hinterland of the North Atlantic Caledonides: Insights From the U‐Pb Zircon Geochronology of the Funzie Conglomerate, Shetland, Scotland
Authors: Biejat S. , Strachan R. A. , Storey C. D. , Lancaster P. J.
Published: August 2018

The spectacular kilometer‐thick Funzie Conglomerate is a deformed and metamorphosed high‐energy sedimentary deposit that occurs in Shetland (Scottish Caledonides). Its age and tectonic significance in relation to Early Ordovician (485–475 Ma) and Late Ordovician (450–445 Ma) accretionary orogenic events and the culminating Silurian (430–425 Ma) continental collision and closure of the Iapetus Ocean have hitherto been unknown. U‐Pb zircon dating indicates that the clast population of the conglomerate was derived from easterly sources comprising Neoproterozoic metasedimentary rocks and the northern extension of the Ordovician‐Silurian Midland Valley Arc that formed during Iapetus closure. A lower age limit of 440 Ma is indicated by the ages of the youngest matrix detrital zircon grains and the youngest granitic clast. Deformation and metamorphism of the conglomerate is attributed to sinistrally oblique extension at ca. 430 Ma that excised at least 10 km of crustal section. Sedimentation of the conglomerate is therefore constrained to a 10‐myr time span (440–430 Ma). The tectonic setting is interpreted as a synorogenic basin that received detritus from, and was buried by, advancing thrust nappes during the Early Silurian collision of Laurentia and Baltica. Tectonic burial was followed rapidly by ductile deformation during oblique extensional unroofing of the metamorphic pile and accounts for preservation of the Funzie Conglomerate as a rare example of a synorogenic basin within the metamorphic hinterland of the North Atlantic Caledonides.
Generalizing Agarwal's Method for the Interpretation of Recovery Tests Under Non‐Ideal Conditions
Authors: Trabucchi Michela , Carrera Jesús , Fernàndez‐Garcia Daniel
Published: August 2018

Pumping tests are performed during aquifer characterization to gain conceptual understanding about the system through diagnostic plots and to estimate hydraulic properties. Recovery tests consist of measuring head response in observation and/or pumping wells after pumping termination. They are especially useful when the pumping rate cannot be accurately controlled. They have been traditionally interpreted using Theis' recovery method, which yields robust estimates of effective transmissivity but does not provide information about the conceptual model. Agarwal proposed a method that has become standard in the oil industry, to obtain both early and late time reservoir responses to pumping from recovery data. However, the validity of the method has only been tested to a limited extent. In this work, we analyze Agarwal's method in terms of both drawdowns and log derivatives for non‐ideal conditions: leaky aquifer, presence of boundaries, and one‐dimensional flow. Our results show that Agarwal's method provides excellent recovery plots (i.e., the drawdown curve that would be obtained during pumping) and parameter estimates for nearly all aquifer conditions, provided that a constant pumping rate is used and the log derivative at the end of pumping is constant, which is too limiting for groundwater hydrology practice, where observation wells are usually monitored. We generalize Agarwal's method by (1) deriving an improved equivalent time for time‐dependent pumping rate and (2) proposing to recover drawdown curves by extrapolating the pumping phase drawdowns. These yield excellent diagnostic plots, thus facilitating the conceptual model analysis for a broad range of conditions.
Second harmonic generation hotspot on a centrosymmetric smooth silver surface
Authors: Galanty Matan , Shavit Omer , Weissman Adam , Aharon Hannah , Gachet David , Segal Elad , Salomon Adi
Published: August 2018

Second harmonic generation (SHG) is forbidden for materials with inversion symmetry, such as bulk metals. Symmetry can be broken by morphological or dielectric discontinuities, yet SHG from a smooth continuous metallic surface is negligible. Using non-linear microscopy, we experimentally demonstrate enhanced SHG within an area of smooth silver film surrounded by nanocavities. Nanocavity-assisted SHG is locally enhanced by more than one order of magnitude compared to a neighboring silver surface area. Linear optical measurements and cathodoluminescence (CL) imaging substantiate these observations. We suggest that plasmonic modes launched from the edges of the nanocavities propagate onto the smooth silver film and annihilate, locally generating SHG. In addition, we show that these hotspots can be dynamically controlled in intensity and location by altering the polarization of the incoming field. Our results show that switchable nonlinear hotspots can be generated on smooth metallic films, with important applications in photocatalysis, single-molecule spectroscopy and non-linear surface imaging.
Microbial connectivity and sorting in a High Arctic watershed
Authors: Comte Jérôme , Culley Alexander I , Lovejoy Connie , Vincent Warwick F
Published: August 2018

Aquatic ecosystems in the High Arctic are facing unprecedented changes as a result of global warming effects on the cryosphere. Snow pack is a central feature of northern landscapes, but the snow microbiome and its microbial connectivity to adjacent and downstream habitats have been little explored. To evaluate these aspects, we sampled along a hydrologic continuum at Ward Hunt Lake (latitude 83°N) in the Canadian High Arctic, from snow banks, water tracks in the permafrost catchment, the upper and lower strata of the lake, and the lake outlet and its coastal marine mixing zone. The microbial communities were analyzed by high-throughput sequencing of 16 and 18S rRNA to determine the composition of potentially active Bacteria, Archaea and microbial Eukarya. Each habitat had distinct microbial assemblages, with highest species richness in the subsurface water tracks that connected the melting snow to the lake. However, up to 30% of phylotypes were shared along the hydrologic continuum, showing that many taxa originating from the snow can remain in the active fraction of downstream microbiomes. The results imply that changes in snowfall associated with climate warming will affect microbial community structure throughout all spatially connected habitats within snow-fed polar ecosystems.
Emergence of winner-takes-all connectivity paths in random nanowire networks
Authors: Manning Hugh G. , Niosi Fabio , da Rocha Claudia Gomes , Bellew Allen T. , O’Callaghan Colin , Biswas Subhajit , Flowers Patrick F. , Wiley Benjamin J. , Holmes Justin D. , Ferreira Mauro S. , Boland John J.
Published: August 2018

Nanowire networks are promising memristive architectures for neuromorphic applications due to their connectivity and neurosynaptic-like behaviours. Here, we demonstrate a self-similar scaling of the conductance of networks and the junctions that comprise them. We show this behavior is an emergent property of any junction-dominated network. A particular class of junctions naturally leads to the emergence of conductance plateaus and a “winner-takes-all” conducting path that spans the entire network, and which we show corresponds to the lowest-energy connectivity path. The memory stored in the conductance state is distributed across the network but encoded in specific connectivity pathways, similar to that found in biological systems. These results are expected to have important implications for development of neuromorphic devices based on reservoir computing.
Iridophores as a source of robustness in zebrafish stripes and variability in Danio patterns
Authors: Volkening Alexandria , Sandstede Björn
Published: August 2018

Zebrafish (Danio rerio) feature black and yellow stripes, while related Danios display different patterns. All these patterns form due to the interactions of pigment cells, which self-organize on the fish skin. Until recently, research focused on two cell types (melanophores and xanthophores), but newer work has uncovered the leading role of a third type, iridophores: by carefully orchestrated transitions in form, iridophores instruct the other cells, but little is known about what drives their form changes. Here we address this question from a mathematical perspective: we develop a model (based on known interactions between the original two cell types) that allows us to assess potential iridophore behavior. We identify a set of mechanisms governing iridophore form that is consistent across a range of empirical data. Our model also suggests that the complex cues iridophores receive may act as a key source of redundancy, enabling both robust patterning and variability within Danio.
Neonatal brain injury causes cerebellar learning deficits and Purkinje cell dysfunction
Authors: Sathyanesan Aaron , Kundu Srikanya , Abbah Joseph , Gallo Vittorio
Published: August 2018

Premature infants are more likely to develop locomotor disorders than term infants. In a chronic sub-lethal hypoxia (Hx) mouse model of neonatal brain injury, we recently demonstrated the presence of cellular and physiological changes in the cerebellar white matter. We also observed Hx-induced delay in Purkinje cell (PC) arborization. However, the behavioral consequences of these cellular alterations remain unexplored. Using the Erasmus Ladder to study cerebellar behavior, we report the presence of locomotor malperformance and long-term cerebellar learning deficits in Hx mice. Optogenetics experiments in Hx mice reveal a profound reduction in spontaneous and photoevoked PC firing frequency. Finally, treatment with a gamma-aminobutyric acid (GABA) reuptake inhibitor partially rescues locomotor performance and improves PC firing. Our results demonstrate a long-term miscoordination phenotype characterized by locomotor malperformance and cerebellar learning deficits in a mouse model of neonatal brain injury. Our findings also implicate the developing GABA network as a potential therapeutic target for prematurity-related locomotor deficits.
Universal holonomic quantum gates over geometric spin qubits with polarised microwaves
Authors: Nagata Kodai , Kuramitani Kouyou , Sekiguchi Yuhei , Kosaka Hideo
Published: August 2018

A microwave shares a nonintuitive phase called the geometric phase with an interacting electron spin after an elastic scattering. The geometric phase, generally discarded as a global phase, allows universal holonomic gating of an ideal logical qubit, which we call a geometric spin qubit, defined in the degenerate subspace of the triplet spin qutrit. We here experimentally demonstrate nonadiabatic and non-abelian holonomic quantum gates over the geometric spin qubit on an electron or nitrogen nucleus. We manipulate purely the geometric phase with a polarised microwave in a nitrogen-vacancy centre in diamond under a zero-magnetic field at room temperature. We also demonstrate a two-qubit holonomic gate to show universality by manipulating the electron−nucleus entanglement. The universal holonomic gates enable fast and fault-tolerant manipulation for realising quantum repeaters interfacing between universal quantum computers and secure communication networks.
Uphill production of dihydrogen by enzymatic oxidation of glucose without an external energy source
Authors: Suraniti Emmanuel , Merzeau Pascal , Roche Jérôme , Gounel Sébastien , Mark Andrew G. , Fischer Peer , Mano Nicolas , Kuhn Alexander
Published: August 2018

Chemical systems do not allow the coupling of energy from several simple reactions to drive a subsequent reaction, which takes place in the same medium and leads to a product with a higher energy than the one released during the first reaction. Gibbs energy considerations thus are not favorable to drive e.g., water splitting by the direct oxidation of glucose as a model reaction. Here, we show that it is nevertheless possible to carry out such an energetically uphill reaction, if the electrons released in the oxidation reaction are temporarily stored in an electromagnetic system, which is then used to raise the electrons’ potential energy so that they can power the electrolysis of water in a second step. We thereby demonstrate the general concept that lower energy delivering chemical reactions can be used to enable the formation of higher energy consuming reaction products in a closed system.
Combining spectroscopic and isotopic techniques gives a dynamic view of phosphorus cycling in soil
Authors: Helfenstein Julian , Tamburini Federica , von Sperber Christian , Massey Michael S. , Pistocchi Chiara , Chadwick Oliver A. , Vitousek Peter M. , Kretzschmar Ruben , Frossard Emmanuel
Published: August 2018

Current understanding of phosphorus (P) cycling in soils can be enhanced by integrating previously discrete findings concerning P speciation, exchange kinetics, and the underlying biological and geochemical processes. Here, we combine sequential extraction with P K-edge X-ray absorption spectroscopy and isotopic methods (33P and 18O in phosphate) to characterize P cycling on a climatic gradient in Hawaii. We link P pools to P species and estimate the turnover times for commonly considered P pools. Dissolved P turned over in seconds, resin-extractable P in minutes, NaOH-extractable inorganic P in weeks to months, and HCl-extractable P in years to millennia. Furthermore, we show that in arid-zone soils, some primary mineral P remains even after 150 ky of soil development, whereas in humid-zone soils of the same age, all P in all pools has been biologically cycled. The integrative information we provide makes possible a more dynamic, process-oriented conceptual model of P cycling in soils.
Ductile deformation mechanism in semiconductor α-Ag2S
Authors: Li Guodong , An Qi , Morozov Sergey I. , Duan Bo , Goddard William A. , Zhang Qingjie , Zhai Pengcheng , Snyder G. Jeffrey
Published: August 2018

Inorganic semiconductor α-Ag2S exhibits a metal-like ductile behavior at room temperature, but the origin of this high ductility has not been fully explored yet. Based on density function theory simulations on the intrinsic mechanical properties of α-Ag2S, its underlying ductile mechanism is attributed to the following three factors: (i) the low ideal shear strength and multiple slip pathways under pressure, (ii) easy movement of Ag–S octagon framework without breaking Ag−S bonds, and (iii) a metallic Ag−Ag bond forms which suppresses the Ag–S frameworks from slipping and holds them together. The easy slip pathways (or easy rearrangement of atoms without breaking bonds) in α-Ag2S provide insight into the understanding of the plastic deformation mechanism of ductile semiconductor materials, which is beneficial for devising and developing flexible semiconductor materials and electronic devices.
Evidence for Ussurian tube-nosed bats (Murina ussuriensis) hibernating in snow
Authors: Hirakawa Hirofumi , Nagasaka Yu
Published: August 2018

Surviving winter is a challenge for endothermic animals living at high latitudes. In bats, some species migrate to milder climates in winter, but others presumably stay and hibernate in thermally buffered roosts. However, we know little about where, or in what roosts bats hibernate. Ussurian tube-nosed bats (Murina ussuriensis) have occasionally been observed under or near the surface of snow. We collected the details of those accounts and used our own observations to conclude that these bats hibernate in snow. To our knowledge, this is the first evidence of hibernation in snow for bats, and second for mammals, following polar bears (Ursus maritimus) denning in snow.
PMLPR: A novel method for predicting subcellular localization based on recommender systems
Authors: Mirzaei Mehrabad Elnaz , Hassanzadeh Reza , Eslahchi Changiz
Published: August 2018

The importance of protein subcellular localization problem is due to the importance of protein’s functions in different cell parts. Moreover, prediction of subcellular locations helps to identify the potential molecular targets for drugs and has an important role in genome annotation. Most of the existing prediction methods assign only one location for each protein. But, since some proteins move between different subcellular locations, they can have multiple locations. In recent years, some multiple location predictors have been introduced. However, their performances are not accurate enough and there is much room for improvement. In this paper, we introduced a method, PMLPR, to predict locations for a protein. PMLPR predicts a list of locations for each protein based on recommender systems and it can properly overcome the multiple location prediction problem. For evaluating the performance of PMLPR, we considered six datasets RAT, FLY, HUMAN, Du et al., DBMLoc and Höglund. The performance of this algorithm is compared with six state-of-the-art algorithms, YLoc, WOLF-PSORT, prediction channel, MDLoc, Du et al. and MultiLoc2-HighRes. The results indicate that our proposed method is significantly superior on RAT and Fly proteins, and decent on HUMAN proteins. Moreover, on the datasets introduced by Du et al., DBMLoc and Höglund, PMLPR has comparable results. For the case study, we applied the algorithms on 8 proteins which are important in cancer research. The results of comparison with other methods indicate the efficiency of PMLPR.
Mitochondrial ribosomal proteins involved in tellurite resistance in yeast Saccharomyces cerevisiae
Authors: Pontieri Paola , Hartings Hans , Di Salvo Marco , Massardo Domenica R. , De Stefano Mario , Pizzolante Graziano , Romano Roberta , Troisi Jacopo , Del Giudice Angelica , Alifano Pietro , Del Giudice Luigi
Published: August 2018

A considerable body of evidence links together mitochondrial dysfunctions, toxic action of metalloid oxyanions, and system and neurodegenerative disorders. In this study we have used the model yeast Saccharomyces cerevisiae to investigate the genetic determinants associated with tellurite resistance/sensitivity. Nitrosoguanidine-induced K2TeO3-resistant mutants were isolated, and one of these mutants, named Sc57-Te5R, was characterized. Both random spore analysis and tetrad analysis and growth of heterozygous (TeS/Te5R) diploid from Sc57-Te5R mutant revealed that nuclear and recessive mutation(s) was responsible for the resistance. To get insight into the mechanisms responsible for K2TeO3-resistance, RNA microarray analyses were performed with K2TeO3-treated and untreated Sc57-Te5R cells. A total of 372 differentially expressed loci were identified corresponding to 6.37% of the S. cerevisiae transcriptome. Of these, 288 transcripts were up-regulated upon K2TeO3 treatment. About half of up-regulated transcripts were associated with the following molecular functions: oxidoreductase activity, structural constituent of cell wall, transporter activity. Comparative whole-genome sequencing allowed us to identify nucleotide variants distinguishing Sc57-Te5R from parental strain Sc57. We detected 15 CDS-inactivating mutations, and found that 3 of them affected genes coding mitochondrial ribosomal proteins (MRPL44 and NAM9) and mitochondrial ribosomal biogenesis (GEP3) pointing out to alteration of mitochondrial ribosome as main determinant of tellurite resistance.
Endogenous HIF2A reporter systems for high-throughput functional screening
Authors: Zaini M. Nazhif , Patel Saroor A. , Syafruddin Saiful E. , Rodrigues Paulo , Vanharanta Sakari
Published: August 2018

Tissue-specific transcriptional programs control most biological phenotypes, including disease states such as cancer. However, the molecular details underlying transcriptional specificity is largely unknown, hindering the development of therapeutic approaches. Here, we describe novel experimental reporter systems that allow interrogation of the endogenous expression of HIF2A, a critical driver of renal oncogenesis. Using a focused CRISPR-Cas9 library targeting chromatin regulators, we provide evidence that these reporter systems are compatible with high-throughput screening. Our data also suggests redundancy in the control of cancer type-specific transcriptional traits. Reporter systems such as those described here could facilitate large-scale mechanistic dissection of transcriptional programmes underlying cancer phenotypes, thus paving the way for novel therapeutic approaches.