bluuebunny/crossref_metadata_2025 huggingface dataset:
Temporal Changes in Stress Drop, Frictional Strength, and Earthquake Size Distribution in the 2011 Yamagata‐Fukushima, NE Japan, Earthquake Swarm, Caused by Fluid Migration
Authors: Yoshida Keisuke , Saito Tatsuhiko , Urata Yumi , Asano Youichi , Hasegawa Akira
Published: December 2017

In this study, we investigated temporal variations in stress drop and b‐value in the earthquake swarm that occurred at the Yamagata‐Fukushima border, NE Japan, after the 2011 Tohoku‐Oki earthquake. In this swarm, frictional strengths were estimated to have changed with time due to fluid diffusion. We first estimated the source spectra for 1,800 earthquakes with 2.0 ≤ MJMA < 3.0, by correcting the site‐amplification and attenuation effects determined using both S waves and coda waves. We then determined corner frequency assuming the omega‐square model and estimated stress drop for 1,693 earthquakes. We found that the estimated stress drops tended to have values of 1–4 MPa and that stress drops significantly changed with time. In particular, the estimated stress drops were very small at the beginning, and increased with time for ~50 days. Similar temporal changes were obtained for b‐value; the b‐value was very high (b ~ 2) at the beginning, and decreased with time, becoming approximately constant (b ~ 1) after ~50 days. Patterns of temporal changes in stress drop and b‐value were similar to the patterns for frictional strength and earthquake occurrence rate, suggesting that the change in frictional strength due to migrating fluid not only triggered the swarm activity but also affected earthquake and seismicity characteristics. The estimated high Q−1 value, as well as the hypocenter migration, supports the presence of fluid, and its role in the generation and physical characteristics of the swarm.
Is There a Link Between Mineralogy, Petrophysics, and the Hydraulic and Seismic Behaviors of the Soultz‐sous‐Forêts Granite During Stimulation? A Review and Reinterpretation of Petro‐Hydromechanical Data Toward a Better Understanding of Induced Seismicity and Fluid Flow
Authors: Meller Carola , Ledésert Béatrice
Published: December 2017

In the framework of the European Soultz‐sous‐Forêts enhanced geothermal system (EGS) in Alsace, France, 20 years of scientific and preindustrial tests had to be performed before the site began production of electricity in 2008. Stimulation tests were designed to enhance the permeability because most of the numerous natural fractures that crosscut the granite body were sealed by secondary minerals that crystallized as an effect of the circulation of local hot brines. The deep‐seated granitic reservoir is located between 4,500 and 5,000 m depths. Hydraulic stimulations were conducted in the four deep wells (GPK1, GPK2, GPK3, and GPK4) inducing different microseismic event patterns, which cannot be explained by tectonic structures alone. In the present work, we provide a review of the hydraulic tests and reinterpret them in the light of mineralogical data obtained along the boreholes. A clear relationship appears between mineralogy (mainly clay and calcite content) and the petrophysical, mechanical, and hydraulic behaviors of the rock mass. High calcite contents are correlated with an abundance of clay minerals, low Young's modulus, low magnetic susceptibility, and variation in spectral gamma ray. Microearthquakes are generated in the fresh granite zones, while clay and calcite‐rich zones, linked with hydrothermal alteration, might behave aseismically during hydraulic stimulations. These findings highlight the importance of a detailed knowledge of the petrography of a reservoir to conduct an effective stimulation while keeping the seismic hazard at a minimum.
A Systematic Comparison of Particle Filter and EnKF in Assimilating Time‐Averaged Observations
Authors: Liu Huaran , Liu Zhengyu , Lu Feiyu
Published: December 2017

The particle filter (PF) and the ensemble Kalman filter (EnKF) are two promising and popularly adopted types of ensemble‐based data assimilation methods for paleoclimate reconstruction. However, no systematic comparison between them has been attempted. We compare these two uncertainty based methods in pseudoproxy experiments where synthetic seasonal mean sea surface temperature observations are assimilated. Their skills are evaluated with regards to local, hemispherically averaged and globally averaged analysis error, and their ability to capture large‐scale modes of variability. It is found that the EAKF (Ensemble Adjustment Kalman filter, a variant of EnKF) performs better than the PF with only one third of the ensemble size, despite PF's theoretical superiority in allowing for non‐Gaussian statistics and nonlinear dynamics. The success of the EAKF is attributed to the facts that (1) Gaussian assumption is somewhat appropriate for this application; (2) The EAKF is less sensitive to sampling errors than the PF due to the different methodological natures. Sixteen members are enough to estimate accurate covariance for the EAKF, but 48 (even 96) members still underrepresent the state space of high‐dimensional system for the PF. Our study highlights the importance of a large localization radius in the application of the EnKF to paleoclimate reconstruction due to the sparse proxy network and suggests that additional techniques, such as localization or clustered particle filter, are needed to improve the PF for paleoclimate reconstruction, in addition to the simple importance resampling currently adopted by most research.
Investigating Local and Remote Terrestrial Influence on Air Masses at Contrasting Antarctic Sites Using Radon‐222 and Back Trajectories
Authors: Chambers S. D. , Choi T. , Park S.‐J. , Williams A. G. , Hong S.‐B. , Tositti L. , Griffiths A. D. , Crawford J. , Pereira E.
Published: December 2017

We report on the first summer of high‐sensitivity radon measurements from a two‐filter detector at Jang Bogo Station (Terra Nova Bay) and contrast them with simultaneous observations at King Sejong Station (King George Island). King Sejong radon concentrations were characteristic of a marine baseline station (0.02–0.3 Bq m−3), whereas Jang Bogo values were highly variable (0.06–5.2 Bq m−3), mainly due to emissions from exposed coastal ground (estimated mean flux 0.09–0.11 atoms cm−2 s−1) and shallow atmospheric mixing depths. For wind speeds of ≤3.5 m s−1 the influence of local radon emissions became increasingly more prominent at both sites. A cluster analysis of back trajectories from King Sejong (62°S) revealed a fairly even distribution between air masses that had passed recently over South America, the Southern Ocean, and Antarctica, whereas at Jang Bogo (75°S) 80% of events had recently passed over the Ross Ice Shelf and West Antarctica, 12% were synoptically forced over Cape Adare, and 8% were associated with subsidence over the Antarctic interior and katabatic flow to the station. When cross‐checked against radon concentrations, only half of the back trajectories ending at Jang Bogo that had indicated distant contact with nonpolar southern hemisphere continents within the past 10 days showed actual signs of terrestrial influence. A simple‐to‐implement technique based on high‐pass filtered absolute humidity is developed to distinguish between predominantly katabatic, oceanic, and near‐coastal air masses for characterization of trace gas and aerosol measurements at coastal East Antarctic sites.
Multi‐Timescale Analysis of the Spatial Representativeness of In Situ Soil Moisture Data within Satellite Footprints
Authors: Molero B. , Leroux D. J. , Richaume P. , Kerr Y. H. , Merlin O. , Cosh M. H. , Bindlish R.
Published: December 2017

We conduct a novel comprehensive investigation that seeks to prove the connection between spatial scales and timescales in surface soil moisture (SM) within the satellite footprint (~50 km). Modeled and measured point series at Yanco and Little Washita in situ networks are first decomposed into anomalies at timescales ranging from 0.5 to 128 days, using wavelet transforms. Then, their degree of spatial representativeness is evaluated on a per‐timescale basis by comparison to large spatial scale data sets (the in situ spatial average, SMOS, AMSR2, and ECMWF). Four methods are used for this: temporal stability analysis (TStab), triple collocation (TC), percentage of correlated areas (CArea), and a new proposed approach that uses wavelet‐based correlations (WCor). We found that the mean of the spatial representativeness values tends to increase with the timescale but so does their dispersion. Locations exhibit poor spatial representativeness at scales below 4 days, while either very good or poor representativeness at seasonal scales. Regarding the methods, TStab cannot be applied to the anomaly series due to their multiple zero‐crossings, and TC is suitable for week and month scales but not for other scales where data set cross‐correlations are found low. In contrast, WCor and CArea give consistent results at all timescales. WCor is less sensitive to the spatial sampling density, so it is a robust method that can be applied to sparse networks (one station per footprint). These results are promising to improve the validation and downscaling of satellite SM series and the optimization of SM networks.
Latitudinal and Seasonal Variations of Vertical Wave Number Spectra of Three‐Dimensional Winds Revealed by Radiosonde Observations
Authors: Zhang Shao Dong , Huang Chun Ming , Huang Kai Ming , Gong Yun , Chen Gang , Gan Quan , Zhang Ye Hui
Published: December 2017

Aiming at investigating the vertical wave number spectral features of three‐dimensional winds in the lower atmosphere as well as their latitudinal and seasonal variations, we analyzed 11 year (1998–2008) radiosonde data from 92 United States stations in the Northern Hemisphere. The spatiotemporal variation of the horizontal wind spectral amplitude agrees well with that of the inertial gravity wave energy, revealing that the observed horizontal wind spectra are mainly attributed to the inertial gravity waves. The horizontal wind spectral slope is systematically and climatologically less negative than the canonical value of −3. For the first time we found that the vertical wind spectrum is much shallower than the horizontal wind spectrum over a wide latitude region, with slopes varying in −1.1 to −0.2 (−0.6 to 0.1) in the troposphere (lower stratosphere). Besides the slopes, the height, latitudinal, and seasonal variations of the vertical wind spectral showed evident difference from those of the horizontal wind spectrum. These differences are due to the horizontal and vertical wind spectra that might be constituted mainly by low and high frequency waves, respectively. Both the horizontal wind and vertical wind spectra exhibit evident universal features, which are more prominent in the lower stratosphere than in the troposphere, where it is thought to be the main source region of gravity waves, implying that the dynamical processes in the wave propagation might be the main cause of the universal spectrum. The background wind was found to have significant impact on the horizontal wind spectrum but has only weak impact on the vertical wind spectrum.
Porosity and Salt Content Determine if Subduction Can Occur in Europa's Ice Shell
Authors: Johnson Brandon C. , Sheppard Rachel Y. , Pascuzzo Alyssa C. , Fisher Elizabeth A. , Wiggins Sean E.
Published: December 2017

Motivated by recent evidence for subduction in Europa's ice shell, we explore the geophysical feasibility of this process. Here we construct a simple model to track the evolution of porosity and temperature within a slab that is forced to subduct. We also vary the initial salt content in Europa's ice shell and determine the buoyancy of our simulated subducting slab. We find that porosity and salt content play a dominant role in determining whether the slab is nonbuoyant and subduction in Europa's ice shell is actually possible. Generally, we find that initially low porosities and high salt contents within the conductive lid are more conducive to subduction. If salt contents are laterally homogenous, and Europa has a reasonable surface porosity of ϕ0 = 0.1, the conductive portion of Europa's shell must have salt contents exceeding ~22% for subduction to occur. However, if salt contents are laterally heterogeneous, with salt contents varying by a few percent, subduction may occur for a surface porosity of ϕ0 = 0.1 and overall salt contents of ~5%. Thus, we argue that under plausible conditions, subduction in Europa's ice shell is possible. Moreover, assuming that subduction is actively occurring or has occurred in Europa's recent past provides important constraints on the structure and composition of the ice shell.
A Two‐Step K‐Ar Experiment on Mars: Dating the Diagenetic Formation of Jarosite from Amazonian Groundwaters
Authors: Martin P. E. , Farley K. A. , Baker M. B. , Malespin C. A. , Schwenzer S. P. , Cohen B. A. , Mahaffy P. R. , McAdam A. C. , Ming D. W. , Vasconcelos P. M. , Navarro‐González R.
Published: December 2017

Following K‐Ar dating of a mudstone and a sandstone, a third sample has been dated by the Curiosity rover exploring Gale Crater. The Mojave 2 mudstone, which contains relatively abundant jarosite, yielded a young K‐Ar bulk age of 2.57 ± 0.39 Ga (1σ precision). A two‐step heating experiment was implemented in an effort to resolve the K‐Ar ages of primary and secondary mineralogical components within the sample. This technique involves measurement of 40Ar released in low‐temperature (500°C) and high‐temperature (930°C) steps, and a model of the potassium distribution within the mineralogical components of the sample. Using this method, the high‐temperature step yields a K‐Ar model age of 4.07 ± 0.63 Ga associated with detrital plagioclase, compatible with the age obtained on the Cumberland mudstone by Curiosity. The low‐temperature step, associated with jarosite mixed with K‐bearing evaporites and/or phyllosilicates, gave a youthful K‐Ar model age of 2.12 ± 0.36 Ga. The interpretation of this result is complicated by the potential for argon loss after mineral formation. Comparison with the results on Cumberland and previously published constraints on argon retentivity of the individual phases likely to be present suggests that the formation age of the secondary materials, correcting for plausible extents of argon loss, is still less than 3 Ga, suggesting post‐3 Ga aqueous processes occurred in the sediments in Gale Crater. Such a result is inconsistent with K‐bearing mineral formation in Gale Lake and instead suggests postdepositional fluid flow at a time after surface fluvial activity on Mars is thought to have largely ceased.
Linkages Among Climate, Fire, and Thermoerosion in Alaskan Tundra Over the Past Three Millennia
Authors: Chipman M. L. , Hu F. S.
Published: December 2017

Amplified Arctic warming may facilitate novel tundra disturbance regimes, as suggested by recent increases in the rate and extent of thermoerosion and fires in some tundra areas. Thermoerosion and wildfire can exacerbate warming by releasing large permafrost carbon stocks, and interactions between disturbance regimes can lead to complex ecosystem feedbacks. We conducted geochemical and charcoal analyses of lake sediments from an Alaskan lake to identify thermoerosion and fire events over the past 3,000 years. Thermoerosion was inferred from lake sediments in the context of modern soil data from retrogressive thaw slumps (RTS). Magnetic susceptibility (MS), Ca:K, and Ca:Sr increased with depth in modern RTS soils and were higher on recently exposed than older slump surfaces. Peaks in bulk density, % CaCO3, Ca:K, Ca:Sr, and MS values in the sediments suggest at least 18 thermoerosion events in the Loon Lake watershed over the past 3,000 years. Charcoal analysis identifies 22 fires over the same period at this site. Temporal variability in these records suggests climate‐driven responses of both thermoerosion and fire disturbance regimes, with fewer RTS episodes and fire events during the Little Ice Age than the Medieval Climate Anomaly. Moreover, RTS activity lagged behind catchment fires by 20–30 years (>90% confidence interval), implying that fires facilitated thermoerosion on decadal time scales, possibly because of prolonged active‐layer deepening following fire and postfire proliferation of insulative shrub cover. These results highlight the potential for complex interactions between climate, vegetation, and tundra disturbance in response to ongoing warming.
Effects of Drought Manipulation on Soil Nitrogen Cycling: A Meta‐Analysis
Authors: Homyak Peter M. , Allison Steven D. , Huxman Travis E. , Goulden Michael L. , Treseder Kathleen K.
Published: December 2017

Many regions on Earth are expected to become drier with climate change, which may impact nitrogen (N) cycling rates and availability. We used a meta‐analytical approach on the results of field experiments that reduced precipitation and measured N supply (i.e., indices of N mineralization), soil microbial biomass, inorganic N pools (ammonium (NH4+) and nitrate (NO3−)), and nitrous oxide (N2O) emissions. We hypothesized that N supply and N2O emissions would be relatively insensitive to precipitation reduction and that reducing precipitation would increase extractable NH4+ and NO3− concentrations because microbial processes continue, whereas plant N uptake diminishes with drought. In support of this hypothesis, extractable NH4+ increased by 25% overall with precipitation reduction; NH4+ also increased significantly with increasing magnitude of precipitation reduction. In contrast, N supply and extractable NO3− did not change and N2O emissions decreased with reduced precipitation. Across studies microbial biomass appeared unchanged, yet from the diversity of studies, it was clear that proportionally smaller precipitation reductions increased microbial biomass, whereas larger proportional reductions in rainfall reduced microbial biomass; there was a positive intercept (P = 0.005) and a significant negative slope (P = 0.0002) for the regression of microbial biomass versus % precipitation reduction (LnR = −0.009 × (% precipitation reduction) + 0.4021). Our analyses imply that relative to other N variables, N supply is less sensitive to reduced precipitation, whereas processes producing N2O decline. Drought intensity and duration, through sustained N supply, may control how much N becomes vulnerable to loss via hydrologic and gaseous pathways upon rewetting dry soils.
COMP report: CPQR technical quality control guideline for medical linear accelerators and multileaf collimators
Authors: Kirkby Charles , Ghasroddashti Esmaeel , Angers Crystal Plume , Zeng Grace , Barnett Erin
Published: December 2017

The Canadian Organization of Medical Physicists (COMP), in close partnership with the Canadian Partnership for Quality Radiotherapy (CPQR) has developed a series of Technical Quality Control (TQC) guidelines for radiation treatment equipment. These guidelines outline the performance objectives that equipment should meet in order to ensure an acceptable level of radiation treatment quality. The TQC guidelines have been rigorously reviewed and field tested in a variety of Canadian radiation treatment facilities. The development process enables rapid review and update to keep the guidelines current with changes in technology (the most updated version of this guideline can be found on the CPQR website). This particular TQC details recommended quality control testing for medical linear accelerators and multileaf collimators.
Xeroderma pigmentosum is a definite cause of Huntington's disease‐like syndrome
Authors: Garcia‐Moreno Hector , Fassihi Hiva , Sarkany Robert P.E. , Phukan Julie , Warner Thomas , Lehmann Alan R. , Giunti Paola
Published: December 2017

Xeroderma pigmentosum is characterized by cutaneous, ophthalmological, and neurological features. Although it is typical of childhood, late presentations can mimic different neurodegenerative conditions. We report two families presenting as Huntington's disease‐like syndromes. The first case (group G) presented with neuropsychiatric features, cognitive decline and chorea. Typical lentigines were only noticed after the neurological disease started. The second case (group B) presented adult‐onset chorea and neuropsychiatric symptoms after an aggressive ocular melanoma. Xeroderma pigmentosum can manifest as a Huntington's Disease‐like syndrome. Classic dermatological and oncological features have to be investigated in choreic patients with negative genetic tests for Huntington's disease‐like phenotypes.
Neurospheres on Patterned PEDOT:PSS Microelectrode Arrays Enhance Electrophysiology Recordings
Authors: Pas Jolien , Pitsalidis Charalampos , Koutsouras Dimitrios A. , Quilichini Pascale P. , Santoro Francesca , Cui Bianxiao , Gallais Laurent , O'Connor Rodney P. , Malliaras George G. , Owens Róisín M.
Published: December 2017

Microelectrode arrays (MEAs) are a versatile diagnostic tool to study neural networks. Culture of primary neurons on these platforms allows for extracellular recordings of action potentials. Despite many advances made in the technology to improve such recordings, the recording yield on MEAs remains sparse. Here, enhanced recording yield is shown induced by varying cell densities on poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate)‐coated MEAs. It is demonstrated that high cell densities (900 cells mm−2) of primary cortical cells increase the number of recording electrodes by 53.1% ± 11.3%, compared with low cell densities (500 cells mm−2) with 6.3% ± 1.4%. To further improve performance, 3D clusters known as neurospheres are cultured on the MEAs, significantly increasing single unit activity recordings. Extensive spike sorting is performed to analyze the unit activity recording multiple neurons with a single microelectrode. Finally, patterning of polyethylene glycol diacrylate through laser ablation is demonstrated, as a means to more precisely confine neurospheres on top of the electrodes. The possibility of recording single neurons with multiple neighboring electrodes is shown. Overall, a total recording yield of 21.4% is achieved, with more than 90% obtained from electrodes with neurospheres, maximizing the functionality of these planar MEAs as effective tools to study pharmacology‐based effects on neural networks.
Mechanoregulation of Myofibroblast Fate and Cardiac Fibrosis
Authors: Kim Peter , Chu Nick , Davis Jennifer , Kim Deok‐Ho
Published: December 2017

During myocardial infarction, myocytes die and are replaced by a specialized fibrotic extracellular matrix, otherwise known as scarring. Fibrotic scarring presents a tremendous hemodynamic burden on the heart, as it creates a stiff substrate, which resists diastolic filling. Fibrotic mechanisms result in permanent scarring which often leads to hypertrophy, arrhythmias, and a rapid progression to failure. Despite the deep understanding of fibrosis in other tissues, acquired through previous investigations, the mechanisms of cardiac fibrosis remain unclear. Recent studies suggest that biochemical cues as well as mechanical cues regulate cells in myocardium. However, the steps in myofibroblast transdifferentiation, as well as the molecular mechanisms of such transdifferentiation in vivo, are poorly understood. This review is focused on defining myofibroblast physiology, scar mechanics, and examining current findings of myofibroblast regulation by mechanical stress, stiffness, and topography for understanding fibrotic disease dynamics.
The Neuroinflammatory Response to Nanopatterning Parallel Grooves into the Surface Structure of Intracortical Microelectrodes
Authors: Ereifej Evon S. , Smith Cara S. , Meade Seth M. , Chen Keying , Feng He , Capadona Jeffrey R.
Published: December 2017

The smooth surface structure of intracortical microelectrodes implanted within the nanometer‐scale architecture of brain tissue may contribute to the foreign body response. Here, the neuroinflammatory response to nanopatterning surface grooves etched directly on nonfunctional Michigan‐style microelectrodes is explored. Rats implanted with nanopatterned silicon microelectrodes are compared to smooth control implants to observe the effects the grooves have on neuroinflammation. Histology and real‐time PCR at 2 and 4 weeks postimplantation quantify glial cell reactivity and activation, inflammation, oxidative stress, and neuronal survival. Histological observations of glial cells and blood–brain barrier permeability do not show appreciable differences between the nanopatterned and control implants. However, silicon microelectrodes with nanopatterned grooves have more high mobility group box 1 (HMGB1) gene expression at 2 weeks and less nitric oxide synthase (NOS2) gene expression at 4 weeks compared to control surfaces. Control samples have increased NOS2, HMGB1, and tumor necrosis factor gene expression from 2 to 4 weeks, while nanopatterned implants have significant decrease in CD14 gene expression from 2 to 4 weeks. Collectively the results indicate that etching nanopatterned grooves do not reduce histological markers of neuroinflammation compared to control implants, but gene expression results encourage further investigation.
Ultrafast Nanoscale Polymer Coating on Porous 3D Structures Using Microwave Irradiation
Authors: Choi Woongchul , Choi Kyungwho , Yu Choongho
Published: December 2017

Thin polymer coatings are very popular, but the coatings on uneven surfaces or porous 3D structures are difficult to obtain with traditional methods. The pores are easily clogged due to nonuniform polymer curing processes caused by inevitable macroscale temperature gradients from their hotter outer to colder inner sides. Here an ultrafast and simple fabrication method is developed to obtain nanoscale coating layers on the inner and outer surfaces of a porous 3D sponge‐like carbon nanotube (CNT). Microwave irradiation rapidly and selectively heats the CNT immersed in a mixture solution of an uncured polymer and a diluent solvent, solidifying the polymer only adjacent to the CNT with five repeated 3 s microwave irradiation. The coating layers can be controlled by adjusting the concentration of the uncured polymer in the solution and controlling the CNT temperature via microwave power and irradiation time. The nanoscale coating strongly ties the junction between CNTs without filling the pores with the polymer, resulting in excellent resilience to compressive stress with large strains (≈180 kPa at 60%), which is maintained throughout repeated 8000 cycles of 0–60% strain. The unfilled pores allow for maintaining the low thermal conductivity, ≈26 mW m−1 K−1, and the electrical resistance is varied with strain. This facile selective polymer curing methodology can be utilized in processing various materials with uneven surfaces or pores.
Hofmeister Effect‐Assisted One Step Fabrication of Ductile and Strong Gelatin Hydrogels
Authors: He Qingyan , Huang Yan , Wang Shaoyun
Published: December 2017

Hydrogels with high strength and ductility are normally prepared from synthetic polymers, and most protein‐based hydrogels are soft and brittle. Here, a strong, ductile gelatin hydrogel is prepared by simply soaking a virgin gelatin gel in an ammonium sulfate solution. The polymer chains in the covalent, crosslink‐free network can freely move to homogeneously distribute stress, and more importantly, the highly kosmotropic ammonium sulfate ions greatly enhance the hydrophobic interactions and chain bundling within the gelatin gels. As a result, the treated hydrogels have an extraordinary ultimate strength (compressive and tensile strains of over 99% and 500%, respectively, and stresses of 12 and 3 MPa) superior to that of common protein gels. The physical crosslinks introduced by the Hofmeister effect can rapidly absorb energy and sustain large deformations via decrosslinking and dissociation, which result in energy dissipation and antifatigue properties. The effects of the gelatin and (NH4)2SO4 concentrations on the hydrogel mechanics are evaluated, and the possible strengthening mechanism is discussed. The effect of various ions in the Hofmeister series on the gelatin hydrogel is also investigated. Kosmotropic ions enhance the mechanical properties, whereas chaotropic ions soften and dissolve the gel.
Biomimetic Chitin–Silk Hybrids: An Optically Transparent Structural Platform for Wearable Devices and Advanced Electronics
Authors: Hong Moo‐Seok , Choi Gwang‐Mun , Kim Joohee , Jang Jiuk , Choi Byeongwook , Kim Joong‐Kwon , Jeong Seunghwan , Leem Seongmin , Kwon Hee‐Young , Hwang Hyun‐Bin , Im Hyeon‐Gyun , Park Jang‐Ung , Bae Byeong‐Soo , Jin Jungho
Published: December 2017

The cuticles of insects and marine crustaceans are fascinating models for man‐made advanced functional composites. The excellent mechanical properties of these biological structures rest on the exquisite self‐assembly of natural ingredients, such as biominerals, polysaccharides, and proteins. Among them, the two commonly found building blocks in the model biocomposites are chitin nanofibers and silk‐like proteins with β‐sheet structure. Despite being wholly organic, the chitinous protein complex plays a key role for the biocomposites by contributing to the overall mechanical robustness and structural integrity. Moreover, the chitinous protein complex alone without biominerals is optically transparent (e.g., dragonfly wings), thereby making it a brilliant model material system for engineering applications where optical transparency is essentially required. Here, inspired by the chitinous protein complex of arthropods cuticles, an optically transparent biomimetic composite that hybridizes chitin nanofibers and silk fibroin (β‐sheet) is introduced, and its potential as a biocompatible structural platform for emerging wearable devices (e.g., smart contact lenses) and advanced displays (e.g., transparent plastic cover window) is demonstrated.
Advances in Nanoporous Anodic Alumina‐Based Biosensors to Detect Biomarkers of Clinical Significance: A Review
Authors: Rajeev Gayathri , Prieto Simon Beatriz , Marsal Lluis F. , Voelcker Nicolas H.
Published: December 2017

There is a strong and growing demand for compact, portable, rapid, and low‐cost devices to detect biomarkers of interest in clinical and point‐of‐care diagnostics. Such devices aid in early diagnosis of diseases without the need to rely on expensive and time‐consuming large instruments in dedicated laboratories. Over the last decade, numerous biosensors have been developed for detection of a wide range of clinical biomarkers including proteins, nucleic acids, growth factors, and bacterial enzymes. Various transduction techniques have been reported based on biosensor technology that deliver substantial advances in analytical performance, including sensitivity, reproducibility, selectivity, and speed for monitoring a wide range of human health conditions. Nanoporous anodic alumina (NAA) has been used extensively for biosensing applications due to its inherent optical and electrochemical properties, ease of fabrication, large surface area, tunable properties, and high stability in aqueous environment. This review focuses on NAA‐based biosensing systems for detection of clinically significant biomarkers using various detection techniques with the main focus being on electrochemical and optical transduction methods. The review covers an overview of the importance of biosensors for biomarkers detection, general (surface and structural) properties and fabrication of NAA, and NAA‐based biomarker sensing systems.
Recent Progress in Micro/Nanoreactors toward the Creation of Artificial Organelles
Authors: Godoy‐Gallardo Maria , York‐Duran Maria J. , Hosta‐Rigau Leticia
Published: December 2017

Artificial organelles created from a bottom up approach are a new type of engineered materials, which are not designed to be living but, instead, to mimic some specific functions inside cells. By doing so, artificial organelles are expected to become a powerful tool in biomedicine. They can act as nanoreactors to convert a prodrug into a drug inside the cells or as carriers encapsulating therapeutic enzymes to replace malfunctioning organelles in pathological conditions. For the design of artificial organelles, several requirements need to be fulfilled: a compartmentalized structure that can encapsulate the synthetic machinery to perform an enzymatic function, as well as a means to allow for communication between the interior of the artificial organelle and the external environment, so that substrates and products can diffuse in and out the carrier allowing for continuous enzymatic reactions. The most recent and exciting advances in architectures that fulfill the aforementioned requirements are featured in this review. Artificial organelles are classified depending on their constituting materials, being lipid and polymer‐based systems the most prominent ones. Finally, special emphasis will be put on the intracellular response of these newly emerging systems.
Iron Oxide Nanoparticles: Innovative Tool in Cancer Diagnosis and Therapy
Authors: Martinkova Pavla , Brtnicky Martin , Kynicky Jindrich , Pohanka Miroslav
Published: December 2017

Although cancer is one of the most dangerous and the second most lethal disease in the world, current therapy including surgery, chemotherapy, radiotherapy, etc., is highly insufficient not in the view of therapy success rate or the amount of side effects. Accordingly, procedures with better outcomes are highly desirable. Iron oxide nanoparticles (IONPs) present an innovative tool—ideal for innovation and implementation into practice. This review is focused on summarizing some well‐known facts about pharmacokinetics, toxicity, and the types of IONPs, and furthermore, provides a survey of their use in cancer diagnosis and therapy.
Peptide‐Functionalized Polyurethane Coatings Prepared via Grafting‐To Strategy to Selectively Promote Endothelialization
Authors: Ding Xin , Chin Willy , Lee Chuen Neng , Hedrick James L. , Yang Yi Yan
Published: December 2017

Endothelialization, formation of endothelial cells (ECs) layer on cardiovascular implant surface, is considered an ideal approach to prevent restenosis (renarrowing of blood vessel mainly due to the accumulation of proliferated vascular smooth muscle cells, SMCs) and thrombosis. In this study, the possibility of using polyurethane (PU) as a coating platform for functionalization with peptide to enhance endothelialization on implants is explored. PUs are synthesized through metal‐free organocatalytic polymerization followed by chemical conjugation with an EC‐specific REDV peptide through thiol–ene reaction. Meanwhile, the free isocyanate groups of PU allow for covalent grafting of REDV‐functionalized PU (PU/REDV) to silanize implant materials (nitinol and PET). PU/REDV coating with peptide grafting density of ≈2 nmol cm−2 selectively accommodates primary human umbilical vein ECs (HUVECs) and retards spreading of primary human umbilical artery SMCs (HUASMCs). In addition, a layer of HUVECs is formed within 3 d on PU/REDV‐coated surfaces, while proliferation of HUASMCs is inhibited. The selectivity is further confirmed by coculture of HUVECs and HUASMCs. Moreover, the PU/REDV‐coated surfaces are less thrombogenic as evidenced by reduced number and activity of adhered platelets. Therefore, PU/REDV can be potentially used as a coating of cardiovascular implants to prevent restenosis and thrombosis by promoting endothelialization.
Biomaterials‐Based Approaches to Tumor Spheroid and Organoid Modeling
Authors: Thakuri Pradip Shahi , Liu Chun , Luker Gary D. , Tavana Hossein
Published: December 2017

Evolving understanding of structural and biological complexity of tumors has stimulated development of physiologically relevant tumor models for cancer research and drug discovery. A major motivation for developing new tumor models is to recreate the 3D environment of tumors and context‐mediated functional regulation of cancer cells. Such models overcome many limitations of standard monolayer cancer cell cultures. Under defined culture conditions, cancer cells self‐assemble into 3D constructs known as spheroids. Additionally, cancer cells may recapitulate steps in embryonic development to self‐organize into 3D cultures known as organoids. Importantly, spheroids and organoids reproduce morphology and biologic properties of tumors, providing valuable new tools for research, drug discovery, and precision medicine in cancer. This Progress Report discusses uses of both natural and synthetic biomaterials to culture cancer cells as spheroids or organoids, specifically highlighting studies that demonstrate how these models recapitulate key properties of native tumors. The report concludes with the perspectives on the utility of these models and areas of need for future developments to more closely mimic pathologic events in tumors.
Multiorgan Microphysiological Systems for Drug Development: Strategies, Advances, and Challenges
Authors: Wang Ying I. , Carmona Carlos , Hickman James J. , Shuler Michael L.
Published: December 2017

Traditional cell culture and animal models utilized for preclinical drug screening have led to high attrition rates of drug candidates in clinical trials due to their low predictive power for human response. Alternative models using human cells to build in vitro biomimetics of the human body with physiologically relevant organ–organ interactions hold great potential to act as “human surrogates” and provide more accurate prediction of drug effects in humans. This review is a comprehensive investigation into the development of tissue‐engineered human cell‐based microscale multiorgan models, or multiorgan microphysiological systems for drug testing. The evolution from traditional models to macro‐ and microscale multiorgan systems is discussed in regards to the rationale for recent global efforts in multiorgan microphysiological systems. Current advances in integrating cell culture and on‐chip analytical technologies, as well as proof‐of‐concept applications for these multiorgan microsystems are discussed. Major challenges for the field, such as reproducibility and physiological relevance, are discussed with comparisons of the strengths and weaknesses of various systems to solve these challenges. Conclusions focus on the current development stage of multiorgan microphysiological systems and new trends in the field.
Improving Defect‐Based Quantum Emitters in Silicon Carbide via Inorganic Passivation
Authors: Polking Mark J. , Dibos Alan M. , de Leon Nathalie P. , Park Hongkun
Published: December 2017

Defect‐based color centers in wide‐bandgap crystalline solids are actively being explored for quantum information science, sensing, and imaging. Unfortunately, the luminescent properties of these emitters are frequently degraded by blinking and photobleaching that arise from poorly passivated host crystal surfaces. Here, a new method for stabilizing the photoluminescence and charge state of color centers based on epitaxial growth of an inorganic passivation layer is presented. Specifically, carbon antisite‐vacancy pairs (CAV centers) in 4H‐SiC, which serve as single‐photon emitters at visible wavelengths, are used as a model system to demonstrate the power of this inorganic passivation scheme. Analysis of CAV centers with scanning confocal microscopy indicates a dramatic improvement in photostability and an enhancement in emission after growth of an epitaxial AlN passivation layer. Permanent, spatially selective control of the defect charge state can also be achieved by exploiting the mismatch in spontaneous polarization at the AlN/SiC interface. These results demonstrate that epitaxial inorganic passivation of defect‐based quantum emitters provides a new method for enhancing photostability, emission, and charge state stability of these color centers.
Octahedral Distortions at High‐Temperature Superconducting La2CuO4 Interfaces: Visualizing Jahn–Teller Effects
Authors: Suyolcu Y. Eren , Wang Yi , Sigle Wilfried , Baiutti Federico , Cristiani Georg , Logvenov Gennady , Maier Joachim , van Aken Peter A.
Published: December 2017

Tuning the octahedral network represents a promising route for achieving new properties and functionalities in perovskite‐based oxide heterostructures. One of the interface‐mediated phenomena occurring in complex oxides is the Jahn—Teller (JT) effect. With the purpose of investigating octahedral distortions at interfaces showing high‐temperature interface superconductivity, atomic layer‐by‐layer oxide molecular‐beam epitaxy grown bilayers consisting of three unit cells, overdoped metallic La1.6M0.4CuO4, and three unit cells undoped insulating La2CuO4, where M represents a divalent dopant (namely, Ba2+, Sr2+, and Ca2+), are studied. The local crystal structure, chemistry, and dopant distribution are probed by analytical spherical‐aberration‐corrected scanning transmission electron microscopy. Here, the interrelation between the cationic size mismatch between dopant (M2+) and host La3+ ions and the local structure are reported, and the impact of the dopant distribution on the structural (CuO6 octahedra elongation) local properties is discussed. A clear correlation between dopant size and local lattice deformations is highlighted. Moreover, a relation between the nature of superconductivity (bulk vs interface) and JT distortions of the anionic sublattice is suggested.
Controlling Wrinkle Propagation in the Bilayer System with Thickness‐Gradient
Authors: Lim Jongcheon , Choi Se‐Jin , Kim Pilnam
Published: December 2017

In this paper, a novel strategy to control the orientation of nanowrinkles by applying a thickness‐gradient to a bilayer‐system is presented. Surface modification by plasma treatment on ultraviolet light‐curable polysiloxane‐based resin applies biaxial compressive strain, resulting in the formation of randomly oriented nanowrinkles over a large‐area. The thickness‐gradient of the resin, given by the meniscus formed between the groove made with patterned polydimethylsiloxane (PDMS) after spin‐coating of the resin, directed wrinkle propagation. Given the propagation orientation, nanowrinkles were well aligned over a large‐area using a simple and accessible method.
A Combined Electrochemical‐Microfluidic Strategy for the Microscale‐Sized Selective Modification of Transparent Conductive Oxides
Authors: Lamberti Francesco , Salmaso Stefano , Zambon Alessandro , Brigo Laura , Malfanti Alessio , Gatti Teresa , Agnoli Stefano , Granozzi Gaetano , Brusatin Giovanna , Elvassore Nicola , Giomo Monica
Published: December 2017

Surface chemical functionalization of transparent conductive oxides (TCOs) is helpful for a wide range of technological applications, ranging from solar cells to biomedical devices, as it allows to tune the electrical, optical, and morphological properties of TCOs toward the desired goal. The electrochemical grafting technique is a surface modification methodology affording robust coatings with tuneable properties and has the potential to be exploited for modifying TCO surfaces. However, due to technical limitations, like the use of a 3‐electrode cell and the need for low pH‐solutions, this approach has not been recurrently applied. Here a novel electrochemical‐microfluidic combined methodology is used where the use of a microchannel drives the spatially controlled covalent grafting of reagents on a TCO surface. To corroborate the validity of this approach in producing more complex chemical structures localized on selected microscale‐sized areas, where a first electrochemical grafting step takes place, an electrochemical glucose biosensor is realized through a layer‐by‐layer approach that shows a remarkable limit of detection in the micromolar concentration range. The sensing mechanism is based on an efficient electron transfer from glucose to the functionalized TCO surface. Biosensor performance is conveniently tuned by acting on the number of enzymatic units loaded onto the biosensor‐tree.
A Novel Fold‐Based Design Approach toward Printable Soft Robotics Using Flexible 3D Printing Materials
Authors: Keong Benjamin Ang Wee , Hua Raye Yeow Chen
Published: December 2017

Soft robotic technologies have been known to have various advantages over their rigid counterparts due to their compliant and deformable properties. They can carry out delicate object manipulation and perform complex maneuvers in confined spaces, which traditional robotics has difficulty with. The most widely adopted fabrication method for traditional soft elastomeric fluidic actuators is mold‐casting, which is cumbersome and involves several manual steps. Therefore, a substantial variability in performance and quality of these actuators arises directly from the manufacturing process. This paper presents on a novel fold‐based design of a 3D‐printed soft pneumatic bending actuator. In contrast to other works that rely on high‐end multimaterial 3D printers, a consumer‐grade open source 3D printer to fabricate soft pneumatic actuators in a fast and cheap way using fused deposition modeling technology has been adapted. This allows for consistency in both the quality of the actuators and their mechanical performance. The key findings in (1) a 3D‐printed fold‐based actuator fabrication process, (2) actuator characterization, and (3) a design‐centric approach toward different bending profiles for different applications are presented.
Print‐Light‐Synthesis of Platinum Nanostructured Indium‐Tin‐Oxide Electrodes for Energy Research
Authors: Lesch Andreas
Published: December 2017

Print‐light‐synthesis is a new concept for the large‐scale in situ fabrication of nanoparticles and structures on large substrates. Here, Pt nanoparticles are synthesized on indium tin oxide (ITO) coated glass slides by using combined inkjet printing and photonic curing operated under ambient conditions and with low material usage. A formulated chloroplatinic acid based ink provides stable and reproducible jetting, optimized ink–substrate interaction and fast ink drying to create well‐defined thin precursor films acting as nanoreactors. The precursor loading is precisely controlled by the printing parameters. Then, a short light pulse from a Xe flash lamp fully converts the printed Pt precursor containing film into pure Pt nanoparticles. The optimum precursor coverage is ≈1 µg mm−2 Pt consuming as less as ≈50 nL mm−2 of ink. Neither reducing nor capping agents are used resulting in pure Pt nanoparticles (30 nm average size) and micrometer‐size aggregates. The nanostructures are well‐adhered to the ITO substrate and show a stable electrochemical performance for the oxygen reduction reaction. The fast and cost‐effective process optimization in terms of ink formulation, substrate pre‐treatment, inkjet printing resolution, and post‐processing for the rapid fabrication of Pt nano‐ and microparticle‐coated ITO electrodes is presented and discussed.
In Vivo Photoacoustic Imaging of Brain Injury and Rehabilitation by High‐Efficient Near‐Infrared Dye Labeled Mesenchymal Stem Cells with Enhanced Brain Barrier Permeability
Authors: Li Weitao , Chen Ronghe , Lv Jing , Wang Hongke , Liu Yu , Peng Ya , Qian Zhiyu , Fu Guo , Nie Liming
Published: December 2017

Stem cell migration and interaction with pathology are critical to understand the complexity and status of disease recovery progress. However, the dynamic visualization still remains a great challenge due to imaging technical limitation, cell labeling difficulty, or blood–brain barrier (BBB). Herein, fast photoacoustic tomography (PAT) with optical molecular probes is applied to noninvasively monitor traumatic brain injury (TBI) and its rehabilitation. The vascular distribution and TBI hemorrhage are clearly imaged, longitudinally monitored, and quantified. Bone mesenchymal stem cells (BMSCs) labeled with modified Prussian blue particles (PBPs), excellent near‐infrared dyes and photoacoustic contrasts, are intravenously injected to the mice for improved observation and efficient therapy. BMSCs are demonstrated to be capable of overcoming BBB with enhanced delivery of PBPs to the brain parenchyma. Notably, the versatile BMSCs are observed by PAT to home to the damage region and repair the ruptured vasculature. Moreover, the wound treated by BMSCs exhibits much faster recovery speed than that without treatment. These findings can potentially provide a new noninvasive and high‐resolution approach to image TBI, monitor recovery process, and especially trace BMSCs. This study will stimulate extensive researches on brain diseases and provide promising strategies of dye labeled BMSCs in regenerative medicine.