bluuebunny/crossref_metadata_2025 huggingface dataset:
Nearshore Flow Patterns in a Complex, Tidally Driven System in Summer: Part I. Model Validation and Circulation
Authors: Conlon LeAnn M. , Xue Huijie , Morello Scott L. , Yund Philip O.
Published: March 2018

Circulation models are often validated with respect to temporal rather than spatial variability, yet spatial variability is often very important for many questions subsequently addressed with the models. We validated a high‐resolution nearshore circulation model using both temporal and spatial data sets and used the model to investigate small‐scale nearshore flow patterns along the complex eastern Maine coast. The Finite Volume Coastal Ocean Model (FVCOM) was run from April to September 2014. In the temporal comparison, the model captured variation in sea level (model skill of 0.98) and the seasonal warming trend (model skill of 0.94). Temperature fluctuations were largely due to horizontal temperature divergence, implying the sensitivity to the forcing at the open boundary. To evaluate spatial variation in performance, we calculated model skill for current profile transects, which ranged from 0.99 to 0.60 in the east/west direction and 0.99 to 0.62 in the north/south direction. The combination of temporal and spatial validation improved confidence in the model's ability to recreate realistic flow patterns. Residual currents across the entrance to the bays showed flows that move out of the bays via the upper western side and into the bays in the lower water column before surfacing on the eastern side. As the coastal current passed by headlands and islands, eddies formed in the wake of several of them. Residual flows varied among months and location along the shelf. This model is a valuable first step in understanding how particulates move through such a complex and variable nearshore region.
Transformation of Deep Water Masses Along Lagrangian Upwelling Pathways in the Southern Ocean
Authors: Tamsitt V. , Abernathey R. P. , Mazloff M. R. , Wang J. , Talley L. D.
Published: March 2018

Upwelling of northern deep waters in the Southern Ocean is fundamentally important for the closure of the global meridional overturning circulation and delivers carbon and nutrient‐rich deep waters to the sea surface. We quantify water mass transformation along upwelling pathways originating in the Atlantic, Indian, and Pacific and ending at the surface of the Southern Ocean using Lagrangian trajectories in an eddy‐permitting ocean state estimate. Recent related work shows that upwelling in the interior below about 400 m depth is localized at hot spots associated with major topographic features in the path of the Antarctic Circumpolar Current, while upwelling through the surface layer is more broadly distributed. In the ocean interior upwelling is largely isopycnal; Atlantic and to a lesser extent Indian Deep Waters cool and freshen while Pacific deep waters are more stable, leading to a homogenization of water mass properties. As upwelling water approaches the mixed layer, there is net strong transformation toward lighter densities due to mixing of freshwater, but there is a divergence in the density distribution as Upper Circumpolar Deep Water tends become lighter and dense Lower Circumpolar Deep Water tends to become denser. The spatial distribution of transformation shows more rapid transformation at eddy hot spots associated with major topography where density gradients are enhanced; however, the majority of cumulative density change along trajectories is achieved by background mixing. We compare the Lagrangian analysis to diagnosed Eulerian water mass transformation to attribute the mechanisms leading to the observed transformation.
Influence of Barrier Wind Forcing on Heat Delivery Toward the Greenland Ice Sheet
Authors: Fraser Neil J. , Inall Mark E.
Published: March 2018

A high‐resolution numerical hydrodynamic model of Kangerdlugssuaq Fjord and the adjacent southeast Greenland shelf region was constructed in order to investigate the dynamics of fjord‐shelf exchange. Recent studies have suggested that rapid exchange flows, driven by along‐shelf barrier wind events, are the dominant agent of exchange between fjord and shelf. These events are prone to occur during the winter, when freshwater forcing is minimal and observations of the fjord interior are scarce. Subglacial freshwater discharge was held at zero, so that any buoyancy‐driven overturning circulation was driven by melting alone. The model described a geostrophically balanced background flow transporting water masses between the fjord mouth and the glacier terminus, indicating that rotational effects are of order‐one importance. Barrier wind events were found to trigger coastally trapped internal wave activity within fjord, temporarily enhancing exchange and vertical mixing, and causing warm water to oscillate in the along‐fjord direction. These internal waves were also found to enhance the background flow via Stokes' drift. Heat delivery through the fjord mouth was smaller than that recorded in summer observations, however the system is more effective at delivering this heat to the head of the fjord. There exists the potential for wintertime melting at the ice‐ocean interface to be significant to the same order as summertime melting.
Observation‐Driven Estimation of the Spatial Variability of 20th Century Sea Level Rise
Authors: Hamlington B. D. , Burgos A. , Thompson P. R. , Landerer F. W. , Piecuch C. G. , Adhikari S. , Caron L. , Reager J. T. , Ivins E. R.
Published: March 2018

Over the past two decades, sea level measurements made by satellites have given clear indications of both global and regional sea level rise. Numerous studies have sought to leverage the modern satellite record and available historic sea level data provided by tide gauges to estimate past sea level rise, leading to several estimates for the 20th century trend in global mean sea level in the range between 1 and 2 mm/yr. On regional scales, few attempts have been made to estimate trends over the same time period. This is due largely to the inhomogeneity and quality of the tide gauge network through the 20th century, which render commonly used reconstruction techniques inadequate. Here, a new approach is adopted, integrating data from a select set of tide gauges with prior estimates of spatial structure based on historical sea level forcing information from the major contributing processes over the past century. The resulting map of 20th century regional sea level rise is optimized to agree with the tide gauge‐measured trends, and provides an indication of the likely contributions of different sources to regional patterns. Of equal importance, this study demonstrates the sensitivities of this regional trend map to current knowledge and uncertainty of the contributing processes.
Investigation of Lightning Flash Locations in Isolated Convection Using LMA Observations
Authors: Fuchs Brody R. , Rutledge Steven A.
Published: March 2018

Using Lightning Mapping Arrays (LMAs), lightning flash locations in three dimensions have been investigated using multiple methods. Approximately 500,000 flashes were analyzed to reveal the variability of lightning initiation and propagation within convective storms. These flashes were produced by over 4,000 isolated convective storms during one warm season across diverse weather regimes in northern Alabama, Washington, D.C., central Oklahoma, and northeastern Colorado. Lightning locations are analyzed within the context of radar reflectivities and examined for vertical variability. Results show that storms in Colorado preferentially produced flashes at lower altitudes and in regions of higher reflectivity compared to the other regions. The regional differences in flash altitudes are largely attributed to the prevalence of anomalous polarity storms (middle‐ or low‐level dominant positive charge) in Colorado, as anomalous storms produced a majority of flashes at lower altitudes compared to storms with normal polarity charge structures (middle‐level negative charge). Conversely, anomalous storms are exceedingly rare in the other regions of study. The differences in flash altitudes are coincident with discrepancies between annual average densities estimated by satellite observations and LMA. Specifically, large differences in annual average flash density estimates exist in northeastern Colorado, which are not present in the other regions, suggesting that the lower altitude flashes in Colorado may be more difficult to detect by satellites.
Intralake Heterogeneity of Thermal Responses to Climate Change: A Study of Large Northern Hemisphere Lakes
Authors: Woolway R. Iestyn , Merchant Christopher J.
Published: March 2018

Lake surface water temperature (LSWT) measurements from various sources illustrate that lakes are warming in response to climate change. Most previous studies of geographical distributions of lake warming have tended to utilize data with limited spatial resolution of LSWTs, including single‐point time series. Spatially resolved LSWT time series are now available from satellite observations, and some studies have investigated previously the intralake warming patterns in specific lakes (e.g., North American Great Lakes). However, across‐lake comparisons of intralake warming differences have not yet been investigated at a large, across‐continental scale, thus limiting our understanding of how intralake warming patterns differ more broadly. In this study, we analyze up to 20 years of satellite data from 19 lakes situated across the Northern Hemisphere, to investigate how LSWT changes vary across different lake surfaces. We find considerable intralake variability in warming trends across many lakes. The deepest areas of large lakes are characterized by a later onset of thermal stratification, a shorter stratified warming season and exhibit longer correlation timescales of LSWT anomalies. We show that deep areas of large lakes across the Northern Hemisphere as a result tend to display higher rates of warming of summer LSWT, arising from a greater temporal persistence in deep areas of the temperature anomalies associated with an earlier onset of thermal stratification. Utilization of single‐point LSWT trends to represent changes in large lakes therefore suppresses important aspects of lake responses to climate change, whereas spatially resolved LSWT measurements can be exploited to provide more comprehensive understanding.
Stable Isotopes of Precipitation During Tropical Sumatra Squalls in Singapore
Authors: He Shaoneng , Goodkin Nathalie F. , Kurita Naoyuki , Wang Xianfeng , Rubin Charles Martin
Published: March 2018

Sumatra Squalls, organized bands of thunderstorms, are the dominant mesoscale convective systems during the intermonsoon and southwest monsoon seasons in Singapore. To understand how they affect precipitation isotopes, we monitored the δ value of precipitation daily and continuously (every second and integrated over 30 s) during all squalls in 2015. We found that precipitation δ18O values mainly exhibit a “V”‐shape pattern and less commonly a “W”‐shape pattern. Variation in δ18O values during a single event is about 1 to 6‰ with the lowest values mostly observed in the stratiform zone, which agrees with previous observations and modeling simulations. Reevaporation can significantly affect δ values, especially in the last stage of the stratiform zone. Daily precipitation is characterized by periodic negative shifts in δ value, largely associated with the squalls rather than moisture source change. The shifts can be more than 10‰, larger than intraevent variation. Initial δ18O values of events are highly variable, and those with the lowest values also have the lowest initial values. Therefore, past convective activities in the upwind area can significantly affect the δ18O, and convection at the sampling site has limited contribution to isotopic variability. A significant correlation between precipitation δ18O value and regional outgoing longwave radiation and rainfall in the Asian monsoon region and western Pacific suggests that regional organized convection probably drives stable isotopic compositions of precipitation. A drop in the frequency of the squalls in 2015 is related to weak organized convection in the region caused by El Niño.
Effects of Cryospheric Change on Alpine Hydrology: Combining a Model With Observations in the Upper Reaches of the Hei River, China
Authors: Chen R. , Wang G. , Yang Y. , Liu J. , Han C. , Song Y. , Liu Z. , Kang E.
Published: March 2018

Cryospheric changes have great effects on alpine hydrology, but these effects are still unclear owing to rare observations and suitable models in the western cold regions of China. Based on long‐term field observations in the western cold regions of China, a cryospheric basin hydrological model was proposed to evaluate the cryospheric effects on streamflow in the upper Hei River basin (UHR), and the relationship between the cryosphere and streamflow was further discussed with measured data. The Norwegian Earth System Model outputs were chosen to project future streamflow under scenarios Representative Concentration Pathways (RCP)2.6, RCP4.5, and RCP8.5. The cryospheric basin hydrological model results were well validated by the measured precipitation, streamflow, evapotranspiration, soil temperature, glacier and snow cover area, and the water balance of land cover in the UHR. The moraine‐talus region contributed most of the runoff (60%), even though it made up only about 20% of the area. On average, glacier and snow cover, respectively, contributed 3.5% and 25.4% of the fresh water to the streamflow in the UHR between 1960 and 2013. Because of the increased air temperature (2.9°C/54a) and precipitation (69.2 mm/54a) over the past 54 years, glacial and snowmelt runoff increased by 9.8% and 12.1%, respectively. The increase in air temperature brought forward the snowmelt flood peak and increased the winter flow due to permafrost degradation. Glaciers may disappear in the near future because of their small size, but snowmelt would increase due to increases in snowfall in the higher mountainous areas, and the basin runoff would increase slightly in the future.
Investigating the Origin of Continual Radio Frequency Impulses During Explosive Volcanic Eruptions
Authors: Behnke S. A. , Edens H. E. , Thomas R. J. , Smith C. M. , McNutt S. R. , Van Eaton A. R. , Cimarelli C. , Cigala V.
Published: March 2018

Volcanic lightning studies have revealed that there is a relatively long‐lasting source of very high frequency radiation associated with the onset of explosive volcanic eruptions that is distinct from radiation produced by lightning. This very high frequency signal is referred to as “continual radio frequency (CRF)” due to its long‐lasting nature. The discharge mechanism producing this signal was previously hypothesized to be caused by numerous, small (10–100 m) leader‐forming discharges near the vent of the volcano. To test this hypothesis, a multiparametric data set of electrical and volcanic activity occurring during explosive eruptions of Sakurajima Volcano in Japan was collected from May to June 2015. Our observations show that a single CRF impulse has a duration on the order of 160 ns (giving an upper limit on discharge length of 10 m) and is distinct from near‐vent lightning discharges that were on the order of 30 m in length. CRF impulses did not produce discernible electric field changes and occurred in the absence of a net static electric field. Lightning mapping data and infrared video observations of the eruption column showed that CRF impulses originated from the gas thrust region of the column. These observations indicate that CRF impulses are not produced by small, leader‐forming discharges but rather are more similar to a streamer discharge, likely on the order of a few meters in length.
The Optical Properties of Limonene Secondary Organic Aerosols: The Role of NO3, OH, and O3 in the Oxidation Processes
Authors: Peng Chao , Wang Weigang , Li Kun , Li Junling , Zhou Li , Wang Lingshu , Ge Maofa
Published: March 2018

Limonene, a typical proxy of monoterpenes emitted from biogenic sources, plays an important role in secondary organic aerosol (SOA) formation. However, the optical properties of SOA generated from limonene under various oxidation pathways remain poorly understood. In this study, we investigate the refractive index (RI) of limonene SOA produced from four oxidation conditions with cavity ring‐down spectrometer (CRDS) and photoacoustic extinctiometer operated at 532 and 375 nm. Our results show that there is a significant difference in RI values of SOA produced from NO3 oxidation compared to other oxidation pathways. The mean values of RI of SOA produced from NO3 oxidation, NOx oxidation, OH oxidation with NOx‐free, and O3 oxidation experiments are 1.578, 1.469, 1.495, and 1.494 at 532 nm; and 1.591, 1.527, 1.513, and 1.537 at 375 nm, respectively, while no detectable absorption is found in all oxidation conditions. We attribute the high RI values of SOA by NO3 oxidation to two factors: a large proportion of organic nitrates and high‐molecular‐weight dimers/oligomers in the SOA. Our study results indicate that the nighttime chemistry may significantly influence the optical properties of limonene oxidation products. The RI values of limonene SOA generated under various oxidation conditions at different wavelengths retrieved in our laboratory experiments could help improve the model predictions for evaluating the effect of biogenic SOA on the global radiative forcing as well as climate change.
Global Scale Analysis of Martian Landslide Mobility and Paleoenvironmental Clues
Authors: Crosta Giovanni Battista , De Blasio Fabio Vittorio , Frattini Paolo
Published: March 2018

The mobility of landslides on Mars is studied based on a database of 3,118 events. To establish the volume of the landslides for the whole data set based on the deposit area, a new volume‐area relationship based on a representative data set of 222 landslides is used. By plotting the H/L ratio between fall height H and runout L versus volume, the landslide mobility is analyzed and compared with existing empirical relationships for Martian and terrestrial landslides. By analyzing the mobility in terms of normalized residuals, that is, the relative deviation of the H/L ratio from the data set best‐fit line, mobility is found to depend on both the landslide location on Mars and the landslide typology. This allows us to identify four different types of high‐mobility (hypermobile) landslides. Three classes of high‐mobility landslides are associated respectively to meteoroid impact, the Olympus Mons aureoles, and landslides with Toreva‐block failure style, and their mobility can be explained by the peculiar flow mechanics. The fourth class includes landslides associated with isolated craters, those in the regions wetted by the putative Oceanus Borealis, and the ones at high latitudes. We suggest that the common factor behind all the hypermobile landslides of this fourth kind is the presence of ice. This is confirmed by our data showing that landslides increase in mobility with latitude. The latitudinal trend mirrors the distribution of ice as detected by radar, neutron probes, and the presence of glacial and layered ejecta morphologies. Because the overall landslide distribution supports the presence of ice‐lubricated conditions, two ice lubrication models are presented showing how ice melting within or underneath the landslides could enhance mobility. By proper analysis in terms of apparent friction residuals, we find that the mobility of landslides in Valles Marineris with the largest landslide concentration is lower than average. We explain this circumstance partly from the smaller role of ice in equatorial Valles Marineris and partly because the collapses from high slope relief imply high‐speed impact with the floor valley confinement, loss of momentum, and decrease in mobility. Environmental consequences imply that the present subsurface ice distribution may have been persistent throughout the Amazonian period.
An Evaluation of Nitrate, fDOM, and Turbidity Sensors in New Hampshire Streams
Authors: Snyder Lisle , Potter Jody D. , McDowell William H.
Published: March 2018

A state‐of‐the‐art network of water quality sensors was established in 2012 to gather year‐round high temporal frequency hydrochemical data in streams and rivers throughout the state of New Hampshire. This spatially extensive network includes eight headwater stream and two main stem river monitoring sites, spanning a variety of stream orders and land uses. Here we evaluate the performance of nitrate, fluorescent dissolved organic matter (fDOM), and turbidity sensors included in the sensor network. Nitrate sensors were first evaluated in the laboratory for interference by different forms of dissolved organic carbon (DOC), and then for accuracy in the field across a range of hydrochemical conditions. Turbidity sensors were assessed for their effectiveness as a proxy for concentrations of total suspended solids (TSS) and total particulate C and N, and fDOM as a proxy for concentrations of dissolved organic matter. Overall sensor platform performance was also examined by estimating percentage of data loss due to sensor failures or related malfunctions. Although laboratory sensor trials show that DOC can affect optical nitrate measurements, our validations with grab samples showed that the optical nitrate sensors provide a reliable measurement of NO3 concentrations across a wide range of conditions. Results showed that fDOM is a good proxy for DOC concentration (r2 = 0.82) but is a less effective proxy for dissolved organic nitrogen (r2 = 0.41). Turbidity measurements from sensors correlated well with TSS (r2 = 0.78), PC (r2 = 0.53), and PN (r2 = 0.51).
Sociohydrological Impacts of Water Conservation Under Anthropogenic Drought in Austin, TX (USA)
Authors: Breyer Betsy , Zipper Samuel C. , Qiu Jiangxiao
Published: March 2018

Municipal water providers increasingly respond to drought by implementing outdoor water use restrictions to reduce urban water withdrawals and maintain water availability. However, restricting urban outdoor water use to support watershed‐scale drought resilience may generate unanticipated cross‐scale interactions, for example, by altering drought response and recovery in urban vegetation or urban streamflow. Despite this, urban water conservation is rarely conceptualized or modeled as endogenous to the water cycle. Here we investigate cross‐scale interactions among urban water conservation and water availability, water use, and sociohydrological response in Austin, TX (USA) during a recent anthropogenic (human‐influenced) drought. Multiscalar statistical analyses demonstrated that outdoor water conservation for reservoir management at the municipal scale produced responses that can cascade both “upward” from the city to the watershed (e.g., decoupling streamflow patterns upstream and downstream of Austin at the watershed scale) and “downward” to exert heterogeneous effects within the city (e.g., redistributing water along a socioeconomic gradient at submunicipal scales, with effects on terrestrial and aquatic ecosystems). We suggest that adapting to anthropogenic drought through irrigation curtailment requires sustained engagement between hydrology and social sciences to integrate socioeconomic status and political feedbacks within and among irrigator groups into the water cycle. Findings from this cross‐disciplinary study highlight the importance of a multiscalar and spatially explicit perspectives in urban sociohydrology research to uncover how water conservation as adaptation to anthropogenic drought links hydrological processes with issues of socioeconomic inequality and spatiotemporal scale in the Anthropocene.
Predictability and Quantification of Complex Groundwater Table Dynamics Driven by Irregular Surface Water Fluctuations
Authors: Xin Pei , Wang Shen S. J. , Shen Chengji , Zhang Zeyu , Lu Chunhui , Li Ling
Published: March 2018

Shallow groundwater interacts strongly with surface water across a quarter of global land area, affecting significantly the terrestrial eco‐hydrology and biogeochemistry. We examined groundwater behavior subjected to unimodal impulse and irregular surface water fluctuations, combining physical experiments, numerical simulations, and functional data analysis. Both the experiments and numerical simulations demonstrated a damped and delayed response of groundwater table to surface water fluctuations. To quantify this hysteretic shallow groundwater behavior, we developed a regression model with the Gamma distribution functions adopted to account for the dependence of groundwater behavior on antecedent surface water conditions. The regression model fits and predicts well the groundwater table oscillations resulting from propagation of irregular surface water fluctuations in both laboratory and large‐scale aquifers. The coefficients of the Gamma distribution function vary spatially, reflecting the hysteresis effect associated with increased amplitude damping and delay as the fluctuation propagates. The regression model, in a relatively simple functional form, has demonstrated its capacity of reproducing high‐order nonlinear effects that underpin the surface water and groundwater interactions. The finding has important implications for understanding and predicting shallow groundwater behavior and associated biogeochemical processes, and will contribute broadly to studies of groundwater‐dependent ecology and biogeochemistry.
New Observations Disagree With Previous Interpretations of Surface Rupture Along the Himalayan Frontal Thrust During the Great 1934 Bihar‐Nepal Earthquake
Authors: Wesnousky Steven G. , Kumahara Yasuhiro , Nakata Takashi , Chamlagain Deepak , Neupane Prajwal
Published: March 2018

Reinvestigation reveals observations that do not support prior claims that the great Mw 8.4 Bihar‐Nepal earthquake produced surface rupture along the Himalayan Frontal Thrust of Nepal. While it may be viewed as reasonable to suggest that the Main Himalayan Frontal Thrust was the source of the 1934 Bihar‐Nepal earthquake on geophysical grounds, decisive and substantiating geological evidence that it produced surface rupture along the trace of the Himalayan Frontal Thrust remains lacking.
Analysis of Intense Z‐Mode Emission Observed During the Cassini Proximal Orbits
Authors: Menietti J. D. , Averkamp T. F. , Ye S.‐Y. , Sulaiman A. H. , Morooka M. W. , Persoon A. M. , Hospodarsky G. B. , Kurth W. S. , Gurnett D. A. , Wahlund J.‐E.
Published: March 2018

The role of Z‐mode emission in the diffusive scattering and resonant acceleration of electrons is believed to be important at Saturn. A survey of the “5 kHz” component of this emission at Saturn earlier reported strong intensity in the lower density regions where the ratio of plasma frequency to cyclotron frequency, fp/fc < 1. At Saturn this occurs along the inner edge of the Enceladus torus near the equator and at higher latitudes. Using the Cassini Radio and Plasma Wave Science instrument observations during the Cassini proximal orbits, we have now identified these emissions extending down to and within the ionosphere. Wave polarization measurements and unique frequency cutoffs are used to positively identify the wave mode. Analogous to the role of whistler mode chorus at Earth, Saturn Z‐mode emissions may interact with electrons contributing to the filling or depleting of Saturn's inner radiation belts.
Defining Flood Zone Transitions in Low‐Gradient Coastal Regions
Authors: Bilskie M. V. , Hagen S. C.
Published: March 2018

Worldwide, coastal, and deltaic communities are susceptible to flooding from the individual and combined effects of rainfall excess and astronomic tide and storm surge inundation. Such flood events are a present (and future) cause of concern as observed from recent storms such as the 2016 Louisiana flood and Hurricanes Harvey, Irma, and Maria. To assess flood risk across coastal landscapes, it is advantageous to first delineate flood transition zones, which we define as areas susceptible to hydrologic and coastal flooding and their collective interaction. We utilize numerical simulations combining rainfall excess and storm surge for the 2016 Louisiana flood to describe a flood transition zone for southeastern Louisiana. We show that the interaction of rainfall excess with coastal surge is nonlinear and less than the superposition of their individual components. Our analysis provides a foundation to define flooding zones across coastal landscapes throughout the world to support flood risk assessments.
Autocorrelation Study of Solar Wind Plasma and IMF Properties as Measured by the MAVEN Spacecraft
Authors: Marquette Melissa L. , Lillis Robert J. , Halekas J. S. , Luhmann J. G. , Gruesbeck J. R. , Espley J. R.
Published: March 2018

It has long been a goal of the heliophysics community to understand solar wind variability at heliocentric distances other than 1 AU, especially at ∼1.5 AU due to not only the steepening of solar wind stream interactions outside 1 AU but also the number of missions available there to measure it. In this study, we use 35 months of solar wind and interplanetary magnetic field (IMF) data taken at Mars by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft to conduct an autocorrelation analysis of the solar wind speed, density, and dynamic pressure, which is derived from the speed and density, as well as the IMF strength and orientation. We found that the solar wind speed is coherent, that is, has an autocorrelation coefficient above 1/e, over roughly 56 hr, while the density and pressure are coherent over smaller intervals of roughly 25 and 20 hr, respectively, and that the IMF strength is coherent over time intervals of approximately 20 hr, while the cone and clock angles are considerably less steady but still somewhat coherent up to time lags of roughly 16 hr. We also found that when the speed, density, pressure, or IMF strength is higher than average, the solar wind or IMF becomes uncorrelated more quickly, while when they are below average, it tends to be steadier. This analysis allows us to make estimates of the values of solar wind plasma and IMF parameters when they are not directly measured and provide an approximation of the error associated with that estimate.
Scattering Matrix for Typical Urban Anthropogenic Origin Cement Dust and Discrimination of Representative Atmospheric Particulates
Authors: Liu Jia , Zhang Yongming , Zhang Qixing , Wang Jinjun
Published: March 2018

The complete scattering matrix for cement dust was measured as a function of scattering angle from 5° to 160° at a wavelength of 532 nm, as a representative of mineral dust of anthropogenic origin in urban areas. Other related characteristics of cement dust, such as particle size distribution, chemical composition, refractive index, and micromorphology, were also analyzed. For this objective, a newly improved apparatus was built and calibrated using water droplets. Measurements of water droplets were in good agreement with Lorenz‐Mie calculations. To facilitate the direct applicability of measurements for cement dust in radiative transfer calculation, the synthetic scattering matrix was computed and defined over the full scattering angle range from 0° to 180°. The scattering matrices for cement dust and typical natural mineral dusts were found to be similar in trends and angular behaviors. Angular distributions of all matrix elements were confined to rather limited domains. To promote the application of light‐scattering matrix in atmospheric observation and remote sensing, discrimination methods for various atmospheric particulates (cement dust, soot, smolder smoke, and water droplets) based on the angular distributions of their scattering matrix elements are discussed. The ratio −F12/F11 proved to be the most effective discrimination method when a single matrix element is employed; aerosol identification can be achieved based on −F12/F11 values at 90° and 160°. Meanwhile, the combinations of −F12/F11 with F22/F11 (or (F11 − F22)/(F11 + F22)) or −F12/F11 with F44/F11 at 160° can be used when multiple matrix elements at the same scattering angle are selected.
protaTETHER – a method for the incorporation of variable linkers in protein fusions reveals impacts of linker flexibility in a PKAc‐GFP fusion protein
Authors: Norris Jessica L. , Hughes Robert M.
Published: March 2018

Protein fusions are of fundamental importance in the study of cellular biology and the elucidation of cell signaling pathways, and the importance of linkers for the proper function of protein fusions is well documented in the literature. However, there are few convenient methods available to experimentalists for the systematic implementation of linkers in protein fusions. In this work, we describe a universal approach to the creation and insertion of focused linker libraries into protein fusions. This process, deemed protaTETHER, utilizes reiterative oligomer design, PCR‐mediated linker library generation, and restriction enzyme‐free cloning methods in a straightforward, three‐step cloning process. We utilize a fusion between the catalytic subunit of cAMP‐dependent protein kinase A (PKAc) and green fluorescent protein (GFP) for the development of the protaTETHER method, implementing small linker libraries that vary by length, sequence, and predicted secondary structural elements. We analyze the impact of linker length and sequence on the expression, activity, and subcellular localization of the PKAc‐GFP fusions, and use these results to select a PKAc‐GFP fusion construct with robust expression and enzymatic activity. Based upon the results of both biochemical experiments and molecular modeling, we determine that linker flexibility is more important than linker length for optimal kinase activity and expression.
Low‐cost Kinect Version 2 imaging system for breath hold monitoring and gating: Proof of concept study for breast cancer VMAT radiotherapy
Authors: Edmunds David M. , Gothard Lone , Khabra Komel , Kirby Anna , Madhale Poonam , McNair Helen , Roberts David , Tang KK , Symonds‐Tayler Richard , Tahavori Fatemeh , Wells Kevin , Donovan Ellen
Published: March 2018

Voluntary inspiration breath hold (VIBH) for left breast cancer patients has been shown to be a safe and effective method of reducing radiation dose to the heart. Currently, VIBH protocol compliance is monitored visually. In this work, we establish whether it is possible to gate the delivery of radiation from an Elekta linac using the Microsoft Kinect version 2 (Kinect v2) depth sensor to measure a patient breathing signal. This would allow contactless monitoring during VMAT treatment, as an alternative to equipment–assisted methods such as active breathing control (ABC). Breathing traces were acquired from six left breast radiotherapy patients during VIBH. We developed a gating interface to an Elekta linac, using the depth signal from a Kinect v2 to control radiation delivery to a programmable motion platform following patient breathing patterns. Radiation dose to a moving phantom with gating was verified using point dose measurements and a Delta4 verification phantom. 60 breathing traces were obtained with an acquisition success rate of 100%. Point dose measurements for gated deliveries to a moving phantom agreed to within 0.5% of ungated delivery to a static phantom using both a conventional and VMAT treatment plan. Dose measurements with the verification phantom showed that there was a median dose difference of better than 0.5% and a mean (3% 3 mm) gamma index of 92.6% for gated deliveries when using static phantom data as a reference. It is possible to use a Kinect v2 device to monitor voluntary breath hold protocol compliance in a cohort of left breast radiotherapy patients. Furthermore, it is possible to use the signal from a Kinect v2 to gate an Elekta linac to deliver radiation only during the peak inhale VIBH phase.
Toward Immunocompetent 3D Skin Models
Authors: Pupovac Aleta , Senturk Berna , Griffoni Chiara , Maniura‐Weber Katharina , Rottmar Markus , McArthur Sally L.
Published: March 2018

3D human skin models provide a platform for toxicity testing, biomaterials evaluation, and investigation of fundamental biological processes. However, the majority of current in vitro models lack an inflammatory system, vasculature, and other characteristics of native skin, indicating scope for more physiologically complex models. Looking at the immune system, there are a variety of cells that could be integrated to create novel skin models, but to do this effectively it is also necessary to understand the interface between skin biology and tissue engineering as well as the different roles the immune system plays in specific health and disease states. Here, a progress report on skin immunity and current immunocompetent skin models with a focus on construction methods is presented; scaffold and cell choice as well as the requirements of physiologically relevant models are elaborated. The wide range of technological and fundamental challenges that need to be addressed to successfully generate immunocompetent skin models and the steps currently being made globally by researchers as they develop new models are explored. Induced pluripotent stem cells, microfluidic platforms to control the model environment, and new real‐time monitoring techniques capable of probing biochemical processes within the models are discussed.
Current Concepts in Meniscus Tissue Engineering and Repair
Authors: Bilgen Bahar , Jayasuriya Chathuraka T. , Owens Brett D.
Published: March 2018

The meniscus is the most commonly injured structure in the human knee. Meniscus deficiency has been shown to lead to advanced osteoarthritis (OA) due to abnormal mechanical forces, and replacement strategies for this structure have lagged behind other tissue engineering endeavors. The challenges include the complex 3D structure with individualized size parameters, the significant compressive, tensile and shear loads encountered, and the poor blood supply. In this progress report, a review of the current clinical treatments for different types of meniscal injury is provided. The state‐of‐the‐art research in cellular therapies and novel cell sources for these therapies is discussed. The clinically available cell‐free biomaterial implants and the current progress on cell‐free biomaterial implants are reviewed. Cell‐based tissue engineering strategies for the repair and replacement of meniscus are presented, and the current challenges are identified. Tissue‐engineered meniscal biocomposite implants may provide an alternative solution for the treatment of meniscal injury to prevent OA in the long run, because of the limitations of the existing therapies.
Recent Advances in Magnetic‐Nanomaterial‐Based Mechanotransduction for Cell Fate Regulation
Authors: Wu Congyu , Shen Yajing , Chen Mengwei , Wang Kun , Li Yongyong , Cheng Yu
Published: March 2018

Remote control of cells and the regulation of cell events at the molecular level are of great interest in the biomedical field. In addition to chemical compounds and genes, mechanical forces play a pivotal role in regulating cell fate, which have prompted the rapid growth of mechanobiology. From a perspective of nanotechnology, magnetic nanomaterials (MNs) are an appealing option for mechanotransduction due to their capabilities in spatiotemporal manipulation of mechanical forces via the magnetic field. As a newly developed paradigm, magneto‐mechanotransduction is harnessed to physically regulate cell fate for biomedical applications. Here, the critical factors that determine the magnetomechanical forces induced by MNs in mechanotransduction are briefly reviewed. Recent innovative approaches and their underlying mechanisms for controlling cell fate are highlighted, which offer possibilities for the remote mechanical manipulation of cells and biomolecules in a precise manner. Promising applications including regenerative medicine and cancer treatment based on magnetomechanical stimulation through MNs are also addressed. Perspectives and challenges in MN‐based mechanotransduction are commented.
Tackling Energy Loss for High‐Efficiency Organic Solar Cells with Integrated Multiple Strategies
Authors: Zuo Lijian , Shi Xueliang , Jo Sae Byeok , Liu Yun , Lin Fracis , Jen Alex K.‐Y.
Published: March 2018

Limited by the various inherent energy losses from multiple channels, organic solar cells show inferior device performance compared to traditional inorganic photovoltaic techniques, such as silicon and CuInGaSe. To alleviate these fundamental limitations, an integrated multiple strategy is implemented including molecular design, interfacial engineering, optical manipulation, and tandem device construction into one cell. Considering the close correlation among these loss channels, a sophisticated quantification of energy‐loss reduction is tracked along with each strategy in a perspective to reach rational overall optimum. A novel nonfullerene acceptor, 6TBA, is synthesized to resolve the thermalization and VOC loss, and another small bandgap nonfullerene acceptor, 4TIC, is used in the back sub‐cell to alleviate transmission loss. Tandem architecture design significantly reduces the light absorption loss, and compensates carrier dynamics and thermalization loss. Interfacial engineering further reduces energy loss from carrier dynamics in the tandem architecture. As a result of this concerted effort, a very high power conversion efficiency (13.20%) is obtained. A detailed quantitative analysis on the energy losses confirms that the improved device performance stems from these multiple strategies. The results provide a rational way to explore the ultimate device performance through molecular design and device engineering.
EGaIn–Metal Interfacing for Liquid Metal Circuitry and Microelectronics Integration
Authors: Ozutemiz Kadri Bugra , Wissman James , Ozdoganlar Osman Burak , Majidi Carmel
Published: March 2018

Eutectic gallium–indium (EGaIn) has attracted significant attention in recent years for its use in soft and stretchable electronics. However, advances in scalable fabrication approaches and effective electromechanical interfaces between liquid metal (LM) traces and microelectronics are still needed to create functional soft and stretchable electronics. In this study, EGaIn–metal interfacing for the effective integration of surface‐mount microelectronics with LM interconnects is investigated. The electrical interconnects are produced by creating copper patterns on a soft‐elastomer substrate, and subsequently exposing the substrate to EGaIn, which selectively wets the Cu traces. To create strong electromechanical connection between EGaIn and microelectronics, the terminals of the LM‐coated traces are “soldered” to the metal pins of the packaged microelectronic circuits using a novel HCl‐vapor treatment. In combination, the fabrication and microelectronics‐interfacing approaches enable creating stretchable circuits composed of LM wiring and packaged microelectronics. It is found that the HCl‐vapor treatment significantly improves electrical conductivity at the LM–pin interface while enhancing the strain limit of the soft circuits and the reproducibility of the interface. The applicability of this approach in creating soft‐matter circuits is demonstrated through two illustrative examples—a circuit with a digital 9‐axis inertial measurement unit and a temperature sensor; and a circuit with a 3‐axis analog accelerometer.
3D Hybrids of Interconnected Porous Carbon Nanosheets/Vertically Aligned Polyaniline Nanowires for High‐Performance Supercapacitors
Authors: Zhang Wang , Jin Xuanzhen , Chai Hua , Diao Guowang , Piao Yuanzhe
Published: March 2018

3D hybrids of interconnected porous carbon (PC) nanosheets/vertically aligned polyaniline (Pani) nanowires are prepared by a cost‐effective facile approach and used as high‐performance supercapacitor electrodes. The 3D PC/Pani hybrids are obtained by a simple in situ growth of Pani on 3D PC with a high specific surface area and good electrochemical performance fabricated via a one‐step thermal pyrolysis of potassium citrate. The 3D PC/Pani hybrids show an excellent specific capacitance of 512 F g−1 at 1 A g−1 in the three‐electrode configuration, which is attributed to the synergistic effect of PC and Pani in the composite. In addition, the as‐assembled asymmetric supercapacitor of PC/Pani composites exhibits good capacitive properties and a long‐term cycling stability of 91% after 3000 cycles at 5 A g−1. Owing to its cost‐effective preparation and high electrochemical performance, the PC/Pani hybrid composite has significant potential for use as practical electrode materials of supercapacitors.
Color‐by‐Blue QD‐Emissive LCD Enabled by Replacing RGB Color Filters with Narrow‐Band GR InP/ZnSeS/ZnS QD Films
Authors: Kang Hyelim , Kim Sohee , Oh Ji Hye , Yoon Hee Chang , Jo Jung‐Ho , Yang Heesun , Do Young Rag
Published: March 2018

Color‐by‐blue quantum dot (QD)‐emissive liquid‐crystal displays (LCDs) with eco‐friendly, green, red (GR) InP/ZnSeS/ZnS QD films are introduced to overcome the disadvantages of conventional color‐by‐white color filter (CF)‐assisted LCDs, such as a narrow viewing angle, low external device efficiency of these types of LCDs, and a restricted color gamut. In this study, the color‐by‐blue InP‐based QD‐emissive LCD consists of a blue (B) light‐emitting diode (LED) and GR InP‐based QD films sandwiched between a light recycling filter and a long‐wavelength pass dichroic filter. The GR InP‐based QDs are synthesized with a high photoluminescence quantum yield (>77%) and narrow bandwidth (<40 nm), which are suitable for display applications. The overall enhancement of InP‐based QD‐emissive LCDs, in this case by the enhanced efficiency of a blue LED backlight transmitted through the LC shutter compared to a white LED backlight and the improved efficiency of the enlarged color gamut, is 2.42 times that of a conventional red, green, and blue (RGB) CF‐LCD with a GR phosphor‐converted (pc)‐LED (a B LED + R K2SiF6:Mn + G β‐SiAlON:Eu phosphor) backlight. Therefore, this considerable enhancement of the external efficiency of a QD‐emissive LCD makes it more feasible as a replacement for conventional RGB CF‐assisted LCDs.
High‐Performance Electrochromic Optical Shutter Based on Fluoran Dye for Visibility Enhancement of Augmented Reality Display
Authors: Kim Gyeong Woo , Kim Yong Cheol , Ko Ik Jang , Park Jin Hwan , Bae Hyeong Woo , Lampande Raju , Kwon Jang Hyuk
Published: March 2018

In this paper, a high‐performance electrochromic optical shutter (ECOS) based on fluoran dye and an augmented reality (AR) display system comprising of ECOS are proposed. The electrochromic reactions of the fluoran dye that transmit or absorb visible light depending on its redox state are activated by the protons generated from hydroquinone derivatives, thereby significantly improved visible light absorption and decreased driving voltage. The visible light‐absorbing function of ECOS is a sole solution for overcoming the main issue of low visibility of displayed images under strong ambient light conditions in optical see‐through head‐mounted displays (OST‐HMDs) implementing augmented reality. The proposed AR display effectively solves the problem by significantly increasing the ambient contrast ratio and color gamut of the displayed image on OST‐HMD even in the strong ambient light condition due to the excellent visible light‐absorbing function of ECOS.
Isocoumarins: General Aspects and Recent Advances in their Synthesis
Authors: Saikia Pallabi , Gogoi Sanjib
Published: March 2018

Being an important constituent of naturally occurring lactones with diverse biological activities and as a pivotal intermediate in heterocycle synthesis, the isocoumarin motif has claimed vast interest in synthetic and medicinal research. The methodologies for the synthesis of isocoumarins involve particularly metal‐catalyzed reactions as well as various intramolecular and intermolecular cyclization reactions. The transition metal complexes of palladium, copper, rhodium, ruthenium, iridium, nickel, zinc and silver are frequently used for the construction of this scaffold. Electrophilic cyclization, oxyboration, and iodocyclization reactions are also known to afford isocoumarins. This review article attempts to highlight the recent advances in their synthesis along with general aspects such as natural occurrence, biological activities, etc. of this particular heterocyclic scaffold.

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