bluuebunny/crossref_metadata_2025 huggingface dataset:
Orbitally Forced Hyperstratification of the Oligocene South Atlantic Ocean
Authors: Liebrand Diederik , Raffi Isabella , Fraguas Ángela , Laxenaire Rémi , Bosmans Joyce H. C. , Hilgen Frederik J. , Wilson Paul A. , Batenburg Sietske J. , Beddow Helen M. , Bohaty Steven M. , Bown Paul R. , Crocker Anya J. , Huck Claire E. , Lourens Lucas J. , Sabia Luciana
Published: March 2018

Pelagic sediments from the subtropical South Atlantic Ocean contain geographically extensive Oligocene ooze and chalk layers that consist almost entirely of the calcareous nannofossil Braarudosphaera. Poor recovery and the lack of precise dating of these horizons in previous studies has limited the understanding of the number of acmes, their timing and durations, and therefore their likely cause. Here we present a high‐resolution, astronomically tuned stratigraphy of Braarudosphaera oozes (29.5–27.9 Ma) from Ocean Drilling Program Site 1264 in the southeastern Atlantic Ocean. We identify seven episodes with highly abundant Braarudosphaera. Four of these acme events coincide with maxima and three with minima in the ~110 and 405‐kyr paced eccentricity cycles. The longest lasting acme event corresponds to a pronounced minimum in the ~2.4‐Myr eccentricity cycle. In the modern ocean, Braarudosphaera occurrences are limited to shallow marine and neritic settings, and the calcified coccospheres of Braarudosphaera are probably produced during a resting stage in the algal life cycle. Therefore, we hypothesize that the Oligocene acmes point to extensive and episodic (hyper) stratified surface water conditions, with a shallow pycnocline that may have served as a virtual seafloor and (partially/temporarily) prevented the coccospheres from sinking in the pelagic realm. We speculate that hyperstratification was either extended across large areas of the South Atlantic basin, through the formation of relatively hyposaline surface waters, or eddy contained through strong isopycnals at the base of eddies. Astronomical forcing of atmospheric and/or oceanic circulation could have triggered these conditions through either sustained rainfall over the open ocean and adjacent land masses or increased Agulhas Leakage.
Diagenetic Attenuation of Carbon Isotope Excursion Recorded by Planktic Foraminifers During the Paleocene‐Eocene Thermal Maximum
Authors: Kozdon Reinhard , Kelly D. Clay , Valley John W.
Published: March 2018

Earth surface temperatures warmed by ~5 °C during an ancient (~56 Ma) global warming event referred to as the Paleocene‐Eocene thermal maximum (PETM). A hallmark of the PETM is a carbon isotope excursion (CIE) signaling the release of massive amounts of 13C‐depleted carbon into the ocean‐atmosphere system, but substrate‐specific differences in the CIE magnitude are a source of uncertainty for estimating the mass of carbon emitted. Here we report that secondary ion mass spectrometry (SIMS)‐based in situ measurements of δ13C in minute (7 μm) domains of planktic foraminifer shells (Ocean Drilling Program Site 865, central Pacific Ocean) yield a CIE that is ~2‰ larger than that delineated by conventional “whole‐shell” δ13C values for this same PETM record. SIMS‐based measurements on diagenetic crystallites yield δ13C values (~2.8‰) that fall between those of pre‐CIE and CIE planktic foraminifer shells, indicating that the crystallites are an amalgamated blend of pre‐CIE and CIE carbonates. This suggests that diagenesis shifts the whole‐shell δ13C compositions of pre‐CIE and CIE foraminifers found in samples straddling the base of the PETM interval toward the intermediate δ13C composition of the crystallites, thereby dampening the amplitude of the isotopic excursion. The diagenetic process envisioned would be most consequential for carbonate‐rich PETM records that have suffered chemical erosion of pre‐CIE carbonate. Given that the domains targeted for SIMS analysis may not be pristinely preserved, we consider the 4.6‰ excursion in our SIMS‐based δ13C record to be a conservative estimate of the full CIE for surface ocean dissolved inorganic carbon.
Varactor‐Tunable Frequency Selective Surface With an Appropriate Embedded Bias Network
Authors: Lin Baoqin , Guo Jianxin , Chu Peng , Li Nan , Wu Lan , Liu Xiangwen
Published: March 2018

In this work, a varactor‐tunable frequency selective surface (FSS) is proposed; it is based on a common FSS composed of annular ring slot cells, in which four varactors are loaded on each annular ring slot to dynamically tune its resonant frequency in real time. In addition, an appropriate embedded bias network is added to introduce a same direct current bias voltage for each varactor. Numerical simulations demonstrate that the resonant‐frequency of the proposed FSS can be tuned over a 77.2% wide frequency range from 2.73 to 6.16 GHz by altering the capacitance of the varactors from 1.0 to 0.1 pF; moreover, the embedded bias network has little effect on the band‐pass response, and the minimum of the reflection coefficients is less than −24 dB at all times. Finally, one effective experimental validation is carried out. The proposed tunable FSS possesses the merits of wide tuning range and high transmittance; thus, it has great potential applications in the design of tunable radomes or adaptive screening of unwanted wireless transmissions.
Lightning Sferics: Analysis of the Instantaneous Phase and Frequency Inferred From Complex Waveforms
Authors: Liu Zhongjian , Koh Kuang Liang , Mezentsev Andrew , Enno Sven‐Erik , Sugier Jacqueline , Fullekrug Martin
Published: March 2018

Analysis of very low frequency lightning waveforms, or radio sferics, can contribute to research into lower ionosphere perturbations and the corresponding atmospheric chemistry. Lightning waveforms can also be characterized on the basis of their propagation distance from receivers in order to study radio wave propagation. A bank of average waveforms, that is, the waveform bank, <1,000 km with a spatial resolution of 10 km has been produced, based on the lightning waveforms recorded in Europe on 8 August 2014. These average lightning waveforms at different distances exhibit a sequence of consecutive maxima resulting from ionospheric reflections, named sky waves. The spectral waveform bank shows a sequence of consecutive modal maxima at different frequencies depending on distance. The Hilbert transform is applied to produce complex lightning waveforms, which provide additional information to the original real waveforms alone, that is, the instantaneous phase and frequency. The time differences calculated from the instantaneous phases of complex lightning waveforms give the minimum arrival time difference error when compared to other analyzed signal processing methods. The derivative of the instantaneous phase, that is, the instantaneous frequency, represents the amplitude‐weighted average of frequency components at maximum amplitude according to theory and numerical simulation. In real experiments, the instantaneous frequency can be understood as the median value of the real frequency distribution calculated at maximum amplitude. It is found that the instantaneous frequencies at maximum amplitudes are distance dependent. This finding might enable the development of a novel method to determine lightning distances in the future.
TMz/TEz Vector Potentials Due to an Arbitrarily Oriented Dipole in 3‐D Space in the Presence of an Infinite Dielectric Cylinder
Authors: Neese J. W. , Jackson D. R. , Zheng Y. , Thomsen L. A.
Published: March 2018

This manuscript provides a new formulation for the classic electromagnetic scattering problem of a point dipole source in the presence of an infinite lossy dielectric cylinder embedded within a lossy space. The formulation is in terms of the TMz and TEz vector potential components (scalar potentials) Az and Fz for an arbitrary dipole orientation. A new Bessel function identity, apparently derived here for the first time, shows that the new solution is equivalent to the previous dyadic vector wave function solutions that solve for the electric and magnetic fields directly. Expressions for the scattered potential coefficients, for a dipole inside or outside the cylinder, can be reduced to a linear set of two equations that has a simple closed‐form solution. The new potential formulation should find application in the numerical solution of various problems in electromagnetics and geophysics involving tunnels or other structures that can be modeled as cylinders.
Coronal Magnetic Structure of Earthbound CMEs and In Situ Comparison
Authors: Palmerio E. , Kilpua E. K. J. , Möstl C. , Bothmer V. , James A. W. , Green L. M. , Isavnin A. , Davies J. A. , Harrison R. A.
Published: March 2018

Predicting the magnetic field within an Earth‐directed coronal mass ejection (CME) well before its arrival at Earth is one of the most important issues in space weather research. In this article, we compare the intrinsic flux rope type, that is, the CME orientation and handedness during eruption, with the in situ flux rope type for 20 CME events that have been uniquely linked from Sun to Earth through heliospheric imaging. Our study shows that the intrinsic flux rope type can be estimated for CMEs originating from different source regions using a combination of indirect proxies. We find that only 20% of the events studied match strictly between the intrinsic and in situ flux rope types. The percentage rises to 55% when intermediate cases (where the orientation at the Sun and/or in situ is close to 45°) are considered as a match. We also determine the change in the flux rope tilt angle between the Sun and Earth. For the majority of the cases, the rotation is several tens of degrees, while 35% of the events change by more than 90°. While occasionally the intrinsic flux rope type is a good proxy for the magnetic structure impacting Earth, our study highlights the importance of capturing the CME evolution for space weather forecasting purposes. Moreover, we emphasize that determination of the intrinsic flux rope type is a crucial input for CME forecasting models.
Rollback Orogeny Model for the Evolution of the Swiss Alps
Authors: Kissling Edi , Schlunegger Fritz
Published: March 2018

The construction of the European Alps and the Himalayas has been related to the convergence and subsequent collision of two continental plates. Nearly all models of orogeny build on this concept, and all of them relate the stacking of nappes and the buildup of topography to compressional forces at work in response to the collision between two continental plates. For the central European Alps, however, these models fail to explain the first‐order observations of a mountain belt, which particularly includes the striking isostatic imbalance between the low surface topography and the thick crust beneath the Alps. Here we review and synthesize data on the geologic architecture of the central Alps, the chronology and pattern of crustal deformation, and information about the deep crustal structure derived from seismic tomography. Furthermore, we discuss the intrinsic and explicit assumptions in the kinematic models of Alpine evolution in the context of plate tectonic considerations. We combine these views with progress in understanding that has been gained through subduction and collision, isostatic mass and force balancing and with information that has been collected on the modern seismic regime. We conclude that a rollback orogeny model for the European plate offers the most suitable concept to explain the ensemble of surface and deep lithosphere observations. In this model gravity forces drive the evolution of the orogen and the construction of surface topography is accomplished without the requirement of a hard collision between two continents.
An Extended Trajectory Mechanics Approach for Calculating the Path of a Pressure Transient: Derivation and Illustration
Authors: Vasco D. W.
Published: March 2018

Following an approach used in quantum dynamics, an exponential representation of the hydraulic head transforms the diffusion equation governing pressure propagation into an equivalent set of ordinary differential equations. Using a reservoir simulator to determine one set of dependent variables leaves a reduced set of equations for the path of a pressure transient. Unlike the current approach for computing the path of a transient, based on a high‐frequency asymptotic solution, the trajectories resulting from this new formulation are valid for arbitrary spatial variations in aquifer properties. For a medium containing interfaces and layers with sharp boundaries, the trajectory mechanics approach produces paths that are compatible with travel time fields produced by a numerical simulator, while the asymptotic solution produces paths that bend too strongly into high permeability regions. The breakdown of the conventional asymptotic solution, due to the presence of sharp boundaries, has implications for model parameter sensitivity calculations and the solution of the inverse problem. For example, near an abrupt boundary, trajectories based on the asymptotic approach deviate significantly from regions of high sensitivity observed in numerical computations. In contrast, paths based on the new trajectory mechanics approach coincide with regions of maximum sensitivity to permeability changes.
The Lower Ionospheric VLF/LF Response to the 2017 Great American Solar Eclipse Observed Across the Continent
Authors: Cohen M. B. , Gross N. C. , Higginson‐Rollins M. A. , Marshall R. A. , Gołkowski M. , Liles W. , Rodriguez D. , Rockway J.
Published: March 2018

We present observations from 11 very low frequency (VLF)/low‐frequency (LF) receivers across the continental United States during the 21 August 2017 “Great American Solar Eclipse.” All receivers detected transmissions from VLF/LF beacons below 50 kHz, while seven also recorded LF beacons above 50 kHz, yielding dozens of individual transmitter‐receiver radio links. Our observations show two separable superimposed signatures: (1) a gradual rise and fall in signal levels visible on almost all paths as the eclipse advances and then declines, as VLF attenuation is reduced by the changing ionosphere under an eclipsed Sun, and (2) direct reflective scattering off the narrow 100‐km‐wide totality spot, observed more uniquely when the transmitter or receiver, if not both, are relatively close to the totality spot.
Large‐Scale Structure of Subauroral Polarization Streams During the Main Phase of a Severe Geomagnetic Storm
Authors: He Fei , Zhang Xiao‐Xin , Wang Wenbin , Liu Libo , Ren Zhi‐Peng , Yue Xinan , Hu Lianhuan , Wan Weixing , Wang Hui
Published: March 2018

In this study, we present multisatellite observations of the large‐scale structures of subauroral polarization streams (SAPS) during the main phase of a severe geomagnetic storm that occurred on 31 March 2001. Observations by the Defense Meteorological Satellite Program F12 to F15 satellites indicate that the SAPS were first generated around the dusk sector at the beginning of the main phase. The SAPS channel then expanded toward the midnight sector and moved to lower latitudes as the main phase progressed. The peak velocity, latitudinal width, latitudinal alignment, and longitudinal span of the SAPS channel were highly dynamic during the storm main phase. The large westward velocities of the SAPS were located in the region of low electron densities, associated with low ionospheric conductivity. The large‐scale structures of the SAPS also corresponded closely to those of the region‐2 field‐aligned currents, which were mainly determined by the azimuthal pressure gradient of the ring current.
Forward Modeling of Thermally Activated Single‐Domain Magnetic Particles Applied to First‐Order Reversal Curves
Authors: Lanci Luca , Kent Dennis V.
Published: March 2018

Theoretical first‐order reversal curves (FORCs) were generated by numerically solving a thermally activated Stoner‐Wohlfarth model for assemblages of randomly oriented magnetic particles. The thermally activated Stoner‐Wohlfarth model extends previous models based on Preisach theory. The new numerical simulations show that the shapes of reversal curves and the FORC distributions are significantly modified by the effect of the thermal energy only if superparamagnetic particles are predominant. However, most assemblages containing moderate amounts of superparamagnetic particles are hardly distinguishable from stable single‐domain assemblages. The most relevant thermal effect is a reduction of coercivity that translates in a shift of the FORC distribution toward the origin. Not all of the distinctive characteristics previously predicted for superparamagnetic grain assemblages were confirmed by our calculations, and most of the observed modifications due to thermal effects can be considered minor. A direct comparison with hysteresis parameters shows that these simpler experiments can be equally effective in characterizing viscous and superparamagnetic particles.
Coherent Seismic Arrivals in the P Wave Coda of the 2012 Mw 7.2 Sumatra Earthquake: Water Reverberations or an Early Aftershock?
Authors: Fan Wenyuan , Shearer Peter M.
Published: March 2018

Teleseismic records of the 2012 Mw 7.2 Sumatra earthquake contain prominent phases in the P wave train, arriving about 50 to 100 s after the direct P arrival. Azimuthal variations in these arrivals, together with back‐projection analysis, led Fan and Shearer (, https://doi.org/10.1002/2016GL067785) to conclude that they originated from early aftershock(s), located ∼150 km northeast of the mainshock and landward of the trench. However, recently, Yue et al. (, https://doi.org/10.1002/2017GL073254) argued that the anomalous arrivals are more likely water reverberations from the mainshock, based mostly on empirical Green's function analysis of a M6 earthquake near the mainshock and a water phase synthetic test. Here we present detailed back‐projection and waveform analyses of three M6 earthquakes within 100 km of the Mw 7.2 earthquake, including the empirical Green's function event analyzed in Yue et al. (, https://doi.org/10.1002/2017GL073254). In addition, we examine the waveforms of three M5.5 reverse‐faulting earthquakes close to the inferred early aftershock location in Fan and Shearer (, https://doi.org/10.1002/2016GL067785). These results suggest that the reverberatory character of the anomalous arrivals in the mainshock coda is consistent with water reverberations, but the origin of this energy is more likely an early aftershock rather than delayed and displaced water reverberations from the mainshock.
The Penetration of Solar Radiation Into Carbon Dioxide Ice
Authors: Chinnery H. E. , Hagermann A. , Kaufmann E. , Lewis S. R.
Published: March 2018

Icy surfaces behave differently to rocky or regolith‐covered surfaces in response to irradiation. A key factor is the ability of visible light to penetrate partially into the subsurface. This results in the solid‐state greenhouse effect, as ices can be transparent or translucent to visible and shorter wavelengths, while opaque in the infrared. This can lead to significant differences in shallow subsurface temperature profiles when compared to rocky surfaces. Of particular significance for modeling the solid‐state greenhouse effect is the e‐folding scale, otherwise known as the absorption scale length, or penetration depth, of the ice. While there have been measurements for water ice and snow, pure and with mixtures, to date, there have been no such measurements published for carbon dioxide ice. After an extensive series of measurements we are able to constrain the e‐folding scale of CO2 ice for the cumulative wavelength range 300 to 1,100 nm, which is a vital parameter in heat transfer models for the Martian surface, enabling us to better understand surface‐atmosphere interactions at Mars' polar caps.
Predictors of childhood trajectories of overt and indirect aggression: An interdisciplinary approach
Authors: Aimé Carla , Paquette Daniel , Déry Michèle , Verlaan Pierrette
Published: March 2018

The aim of this study was to advance our understanding of the development of aggression in boys and girls by testing a model combining insights from both evolutionary theory and developmental psychology. A sample of 744 children (348 girls) between six and 13 years old was recruited in schools with high deprivation indices. Half of the sample (N = 372; 40.1% girls) had received special educational services for behavioral and/or socio‐emotional problems. Two trajectories for overt aggression and two trajectories for indirect aggression were identified and binomial logistic regressions were used to identify environmental predictors and sex‐specific patterns of these trajectories. Results indicated that peer rejection predicted overt aggression and indirect aggression and that extraversion and male sex predicted overt aggression. The results also showed that interaction between parental practices and some child temperament traits predicted overt aggression (coercion and lack of supervision associated with extraversion or low effortful control) or indirect aggression (coercion and neglect associated with negative affect or low effortful control), and the absence of a father figure predicted high indirect aggression in girls.
Verification of Acuros XB dose algorithm using 3D printed low‐density phantoms for clinical photon beams
Authors: Zavan Rodolfo , McGeachy Philip , Madamesila Joseph , Villarreal‐Barajas Jose‐Eduardo , Khan Rao
Published: March 2018

The transport‐based dose calculation algorithm Acuros XB (AXB) has been shown to accurately account for heterogeneities primarily through comparisons with Monte Carlo simulations. This study aims to provide additional experimental verification of AXB for clinically relevant flattened and unflattened beam energies in low density phantoms of the same material. Polystyrene slabs were created using a bench‐top 3D printer. Six slabs were printed at varying densities from 0.23 to 0.68 g/cm3, corresponding to different density humanoid tissues. The slabs were used to form different single and multilayer geometries. Dose was calculated with Eclipse™ AXB 11.0.31 for 6MV, 15MV flattened and 6FFF (flattening filter free) energies for field sizes of 2 × 2 and 5 × 5 cm2. EBT3 film was inserted into the phantoms, which were irradiated. Absolute dose profiles and 2D Gamma analyses were performed for 96 dose planes. For all single slab configurations and energies, absolute dose differences between the AXB calculation and film measurements remained <3% for both fields in the high‐dose region, however, larger disagreement was seen within the penumbra. For the multilayered phantom, percentage depth dose with AXB was within 5% of discrete film measurements. The Gamma index at 2%/2 mm averaged 98% in all combinations of fields, phantoms and photon energies. The transport‐based dose algorithm AXB is in good agreement with the experimental measurements for small field sizes using 6MV, 6FFF and 15MV beams adjacent to various low‐density heterogeneous media. This work provides preliminary experimental grounds to support the use of AXB for heterogeneous dose calculation purposes.
Seronegative antibody‐mediated neurology after immune checkpoint inhibitors
Authors: Wilson Robert , Menassa David A. , Davies Alexander J. , Michael Sophia , Hester Joanna , Kuker Wilhelm , Collins Graham P. , Cossins Judith , Beeson David , Steven Neil , Maddison Paul , Rinaldi Simon , Jacob Saiju , Irani Sarosh R.
Published: March 2018

Checkpoint inhibitor medications have revolutionized oncology practice, but frequently induce immune‐related adverse events. During autoimmune neurology practice over 20 months, we prospectively identified four patients with likely antibody‐mediated neurological diseases after checkpoint inhibitors: longitudinally extensive transverse myelitis, Guillain–Barré syndrome, and myasthenia gravis. All patients shared three characteristics: symptoms commenced 4 weeks after drug administration, responses to conventional immunotherapies were excellent, and autoantibodies traditionally associated with their syndrome were absent. However, serum immunoglobulins from the myelitis and Guillain–Barré syndrome patients showed novel patterns of tissue reactivity. Vigilance is required for antibody‐mediated neurology after checkpoint inhibitor administration. This phenomenon may inform the immunobiology of antibody‐mediated diseases.
Estimation of intrathecal IgG synthesis: simulation of the risk of underestimation
Authors: Bonnan Mickael , Gianoli‐Guillerme Mariana , Courtade Henri , Demasles Stéphanie , Krim Elsa , Marasescu Raluca , Dréau Hervé , Debeugny Stéphane , Barroso Bruno
Published: March 2018

Objective

The low level of passively diffused IgG through the blood–brain barrier is sufficient to blur the estimation of intrathecal IgG synthesis (ITS). Therefore, this estimation requires a mathematical calculation derived from empirical laws, but the range of normal values in healthy controls is wide enough to prevent a precise calculation. This study investigated the precision of various methods of ITS estimations and their application to two clinical situations: plasma exchange and immune suppression targeting ITS.

Methods

Based on a mathematical model of ITS, we constructed a population of healthy controls and applied a tunable ITS.

Results

We demonstrate the following results: underestimation of ITS is common at individual level but true ITS is well fitted by cohorts; QIgG increases after plasma exchange; IgGLoc calculation based on Qlim falsely increases when QAlb decreases; the sample size required to demonstrate a decrease in ITS increases exponentially with larger QAlb.

Interpretation

Studies evaluating changes in ITS level should be adjusted to QAlb. Low amounts of ITS could be largely underestimated.
Determining One‐Year Trajectories of Low‐Back–Related Leg Pain in Primary Care Patients: Growth Mixture Modeling of a Prospective Cohort Study
Authors: Ogollah Reuben O. , Konstantinou Kika , Stynes Siobhán , Dunn Kate M.
Published: March 2018

Objective

The clinical presentation and outcome of patients with back and leg pain in primary care are heterogeneous and may be better understood by identification of homogeneous and clinically meaningful subgroups. Subgroups of patients with different back pain trajectories have been identified, but little is known about the trajectories for patients with back‐related leg pain. This study sought to identify distinct leg pain trajectories, and baseline characteristics associated with membership of each group, in primary care patients.

Methods

Monthly data on leg pain intensity were collected over 12 months for 609 patients participating in a prospective cohort study of adult patients seeking health care for low‐back and leg pain, including sciatica, of any duration and severity, from their general practitioner. Growth mixture modeling was used to identify clusters of patients with distinct leg pain trajectories. Trajectories were characterized using baseline demographic and clinical examination data. Multinomial logistic regression was used to predict latent class membership, with a range of covariates.

Results

Four patient clusters were identified: improving mild pain (58%), persistent moderate pain (26%), persistent severe pain (13%), and improving severe pain (3%). Clusters showed statistically significant differences in a number of baseline characteristics.

Conclusion

Four trajectories of leg pain were identified. Clusters 1, 2, and 3 were generally comparable to back pain trajectories, while cluster 4, with major improvement in pain, is infrequently identified. Awareness of such distinct patient groups improves understanding of the course of leg pain and may provide a basis of classification for intervention.
A modular adaptive control design with ISS analysis for nonminimum phase hypersonic vehicle models
Authors: Mannava A. , Serrani A.
Published: March 2018

Air‐breathing hypersonic vehicles typically exhibit a nonminimum phase behavior when altitude is controlled via lift generation. This phenomenon prohibits the use of classical inversion‐based control techniques. Dynamic models of these vehicles are also subject to parametric uncertainties and unmodeled dynamics related to flexible effects of the fuselage. In this paper, we present a modular adaptive control method that achieves asymptotic setpoint tracking in both airspeed and altitude using thrust and elevator deflection as the only control inputs for a generic longitudinal model of a hypersonic cruise. The nonminimum phase problem is overcome through output redefinition, with altitude controlled by pitching moment. The internal dynamics, flight path angle, and altitude are then stabilized by saturating the interconnections and exploiting local stability properties. A new technique for the use of saturation functions in error coordinate is presented. The adaptive controller for altitude uses a pitch rate observer combined with projection. This control augmentation decouples the parameter estimation errors from internal dynamics, allowing for the use of small‐gain arguments. Simulation results from a vehicle model with flexible effects and parametric uncertainty are included to demonstrate control effectiveness.
A model reference tracking based on an active fault tolerant control for LPV systems
Authors: Rabaoui B. , Rodrigues M. , Hamdi H. , BenHadj Braiek N.
Published: March 2018

This work deals with the problem of a model reference tracking based on the design of an active fault tolerant control for linear parameter‐varying systems affected by actuator faults and unknown inputs. Linear parameter‐varying systems are described by a polytopic representation with measurable gain scheduling functions. The main contribution is to design an active fault tolerant controller whose control law is described by an adaptive proportional integral structure. This one requires 3 types of online information, which are reference outputs, measured real outputs, and the fault estimation provided by a model reference, sensors, and an adaptive polytopic observer, respectively. These types of information are used to reconfigure the designed controller, which is able to compensate the fault effects and to make the closed‐loop system able to track reference outputs in spite of the presence of actuator faults and disturbances. The controller and the observer gains are obtained by solving a set of linear matrices inequalities. Performances of the proposed method are compared to another previous method to underline the relevant results.
Molecular Fluorescence and Photoacoustic Imaging in the Second Near‐Infrared Optical Window Using Organic Contrast Agents
Authors: Jiang Yuyan , Pu Kanyi
Published: March 2018

Noninvasive near‐infrared (NIR) light ranging from 650 to 1000 nm (NIR‐I) is widely employed in fundamental research and clinical applications; however, a recently discovered second NIR (NIR‐II) window from 1000 to 1700 nm exhibits even better deep‐tissue imaging capability due to reduced photon scattering, minimized tissue autofluorescence, and increased applicable power at longer wavelengths. This review focuses on recent advances of organic contrast agents developed for in vivo fluorescence and photoacoustic imaging in the NIR‐II optical window. The superiority of the NIR‐II over the NIR‐I window for molecular imaging is first discussed in detail, followed by discussion of fluorescence and photoacoustic imaging of cancer, vasculature, and the brain using organic contrast agents in the NIR‐II window. At last, challenges and perspectives of organic contrast agents for NIR‐II in vivo imaging are suggested.
Characterization of Spatial Distribution of Electrolyte in Molten Carbonate Fuel Cell Cathodes
Authors: Wejrzanowski Tomasz , Gluch Jürgen , Ibrahim Samih Haj , Cwieka Karol , Milewski Jarosław , Zschech Ehrenfried
Published: March 2018

High‐resolution computed X‐ray tomography (XCT) is applied in this study to characterize the microstructure of Molten Carbonate Fuel Cell (MCFC) cathodes after operation, where a “virgin cathode” formed by porous nickel has been in situ oxidized and infiltrated by liquid electrolyte. This technique extends state‐of‐the art methodology to characterize pores such as porosity analysis using Mercury porosimetry. XCT enables 3D imaging of the internal structure of the electrodes including all components present at the cathode side, particularly NiO, pores, and electrolyte. The quantitative 3D microstructure analysis based on high‐resolution XCT provides topological information for each component and their mutual spatial distribution, which is significant for the enhancement of the MCFC performance. In particular, volume fraction, specific surface area, continuity of each phase, as well as the Triple Phase Boundary (TPB) density are calculated from the experimental data. The results indicate that superior properties of the multi‐modal pore sized cathode, used in this study, can be attributed to the formation of three self‐interpenetrating networks of pathways for the transport of gasses, electrons, as well as ions throughout pores, NiO, and electrolyte, respectively.
Making Ultrafast High‐Capacity Anodes for Lithium‐Ion Batteries via Antimony Doping of Nanosized Tin Oxide/Graphene Composites
Authors: Zoller Florian , Peters Kristina , Zehetmaier Peter M. , Zeller Patrick , Döblinger Markus , Bein Thomas , Sofer Zdeneˇk , Fattakhova‐Rohlfing Dina
Published: March 2018

Tin oxide‐based materials attract increasing attention as anodes in lithium‐ion batteries due to their high theoretical capacity, low cost, and high abundance. Composites of such materials with a carbonaceous matrix such as graphene are particularly promising, as they can overcome the limitations of the individual materials. The fabrication of antimony‐doped tin oxide (ATO)/graphene hybrid nanocomposites is described with high reversible capacity and superior rate performance using a microwave assisted in situ synthesis in tert‐butyl alcohol. This reaction enables the growth of ultrasmall ATO nanoparticles with sizes below 3 nm on the surface of graphene, providing a composite anode material with a high electric conductivity and high structural stability. Antimony doping results in greatly increased lithium insertion rates of this conversion‐type anode and an improved cycling stability, presumably due to the increased electrical conductivity. The uniform composites feature gravimetric capacity of 1226 mAh g−1 at the charging rate 1C and still a high capacity of 577 mAh g−1 at very high charging rates of up to 60C, as compared to 93 mAh g−1 at 60C for the undoped composite synthesized in a similar way. At the same time, the antimony‐doped anodes demonstrate excellent stability with a capacity retention of 77% after 1000 cycles.
Adaptive Crystallite Kinetics in Homogenous Bilayer Oxide Memristor for Emulating Diverse Synaptic Plasticity
Authors: Yin Jun , Zeng Fei , Wan Qin , Li Fan , Sun Yiming , Hu Yuandong , Liu Jialu , Li Guoqi , Pan Feng
Published: March 2018

A critical routine for memristors applied to neuromorphic computing is to approximate synaptic dynamic behaviors as closely as possible. A type of homogenous bilayer memristor with a structure of W/HfOy/HfOx/Pt is designed and constructed in this paper. The memristor replicates the structure and oxygen vacancy (VO) distribution of a complete synapse and its Ca2+ distribution, respectively, after the forming process. The detailed characterizations of its atomic structure and phase transformation in and near the conductive channel demonstrate that the crystallite kinetics are adaptively coupled with the VO migration prompted by directional external bias. The extrusion (injection) of the VOs and the subsequent crystallite coalescence (separation), phase transformation, and alignment (misalignment) resemble closely the Ca2+ flux and neurotransmitter dynamics in chemical synapses. Such adaptation and similarity allow the memristor to emulate diverse synaptic plasticity. This study supplies a kinetic process of conductive channel theory for bilayer memristors. In addition, our memristor has very low energy consumption (5–7.5 fJ per switching for a 0.5 µm diameter device, compatible with a synaptic event) and is therefore suitable for large‐scale integration used in neuromorphic networks.
Bioinspired Surfaces with Superamphiphobic Properties: Concepts, Synthesis, and Applications
Authors: Liu Hui , Wang Yandong , Huang Jianying , Chen Zhong , Chen Guoqiang , Lai Yuekun
Published: March 2018

Among diverse wetting phenomena in surface science, superamphiphobicity is regarded as one of the most special super‐antiwetting states. In this paper, a systematic summary is presented to cover the characterization of surface wettability, the construction techniques, and selected functional applications. With respect to fabrication techniques, the following three types of technology routes, viz., “pre‐texturing + post‐modifying,” “pre‐modifying + post‐texturing,” and in situ one‐step construction will be discussed. The merits and demerits of each technology route are discussed. It is vital to rationally design or adopt appropriate construction strategies in diverse conditions. Appropriately constructed superamphiphobic multifunctional surfaces can be applied in many fields, however, most have not been scaled‐up and utilized for practical applications due to some specific difficulties required to be resolved in the future. These challenges and further outlook for super‐antiwetting surfaces are discussed in this review.
Polarized Optoelectronics of CsPbX3 (X = Cl, Br, I) Perovskite Nanoplates with Tunable Size and Thickness
Authors: Sheng Xuexi , Chen Gaoyu , Wang Chong , Wang Weiqi , Hui Junfeng , Zhang Qi , Yu Kehan , Wei Wei , Yi Mingdong , Zhang Mian , Deng Yu , Wang Peng , Xu Xiangxing , Dai Zhihui , Bao Jianchun , Wang Xun
Published: March 2018

Low dimensional semiconductor nanomaterials have shown their tailorable properties for a variety of promising applications in decades. Here a general strategy to synthesize all‐inorganic CsPbX3 (X = Cl, Br, I or their mixture) perovskite 2D nanoplates by introducing additional metal halides MX'2 or MX'3 (M = Cu, Zn, Al or Pb, etc.; X' = Cl, Br or I) is reported. These CsPbX3 perovskite nanoplates have uniform thickness and tunable size, which can be feasibly controlled by the component and ratio of the metal halides, temperature, time, and ligands. The well‐defined morphology of the nanoplates makes them ideal building blocks for the self‐assembly in the face‐to‐face and column‐by‐column arrangement. Compared to the optically isotropic CsPbX3 nanocubes, the 2D CsPbX3 nanoplates exhibit remarkable polarized UV–vis absorption and photoluminescence not only in liquid solvent and solid resin matrix, but also in self‐assembled films. An optoelectronic photodetector sensitive for linear polarized light is fabricated to demonstrate the proof‐of‐concept.
Electric Field Assisted Microfluidic Platform for Generation of Tailorable Porous Microbeads as Cell Carriers for Tissue Engineering
Authors: Costantini Marco , Guzowski Jan , Żuk Paweł J. , Mozetic Pamela , De Panfilis Simone , Jaroszewicz Jakub , Heljak Marcin , Massimi Mara , Pierron Maxime , Trombetta Marcella , Dentini Mariella , Święszkowski Wojciech , Rainer Alberto , Garstecki Piotr , Barbetta Andrea
Published: March 2018

Injection of cell‐laden scaffolds in the form of mesoscopic particles directly to the site of treatment is one of the most promising approaches to tissue regeneration. Here, a novel and highly efficient method is presented for preparation of porous microbeads of tailorable dimensions (in the range ≈300–1500 mm) and with a uniform and fully interconnected internal porous texture. The method starts with generation of a monodisperse oil‐in‐water emulsion inside a flow‐focusing microfluidic device. This emulsion is later broken‐up, with the use of electric field, into mesoscopic double droplets, that in turn serve as a template for the porous microbeads. By tuning the amplitude and frequency of the electric pulses, the template droplets and the resulting porous bead scaffolds are precisely produced. Furthermore, a model of pulsed electrodripping is proposed that predicts the size of the template droplets as a function of the applied voltage. To prove the potential of the porous microbeads as cell carries, they are tested with human mesenchymal stem cells and hepatic cells, with their viability and degree of microbead colonization being monitored. Finally, the presented porous microbeads are benchmarked against conventional microparticles with nonhomogenous internal texture, revealing their superior performance.
High‐Speed 3D Printing of Millimeter‐Size Customized Aspheric Imaging Lenses with Sub 7 nm Surface Roughness
Authors: Chen Xiangfan , Liu Wenzhong , Dong Biqin , Lee Jongwoo , Ware Henry Oliver T. , Zhang Hao F. , Sun Cheng
Published: March 2018

Advancements in three‐dimensional (3D) printing technology have the potential to transform the manufacture of customized optical elements, which today relies heavily on time‐consuming and costly polishing and grinding processes. However the inherent speed‐accuracy trade‐off seriously constrains the practical applications of 3D‐printing technology in the optical realm. In addressing this issue, here, a new method featuring a significantly faster fabrication speed, at 24.54 mm3 h−1, without compromising the fabrication accuracy required to 3D‐print customized optical components is reported. A high‐speed 3D‐printing process with subvoxel‐scale precision (sub 5 µm) and deep subwavelength (sub 7 nm) surface roughness by employing the projection micro‐stereolithography process and the synergistic effects from grayscale photopolymerization and the meniscus equilibrium post‐curing methods is demonstrated. Fabricating a customized aspheric lens 5 mm in height and 3 mm in diameter is accomplished in four hours. The 3D‐printed singlet aspheric lens demonstrates a maximal imaging resolution of 373.2 lp mm−1 with low field distortion less than 0.13% across a 2 mm field of view. This lens is attached onto a cell phone camera and the colorful fine details of a sunset moth's wing and the spot on a weevil's elytra are captured. This work demonstrates the potential of this method to rapidly prototype optical components or systems based on 3D printing.
Nonlinear Optics with 2D Layered Materials
Authors: Autere Anton , Jussila Henri , Dai Yunyun , Wang Yadong , Lipsanen Harri , Sun Zhipei
Published: March 2018

2D layered materials (2DLMs) are a subject of intense research for a wide variety of applications (e.g., electronics, photonics, and optoelectronics) due to their unique physical properties. Most recently, increasing research efforts on 2DLMs are projected toward the nonlinear optical properties of 2DLMs, which are not only fascinating from the fundamental science point of view but also intriguing for various potential applications. Here, the current state of the art in the field of nonlinear optics based on 2DLMs and their hybrid structures (e.g., mixed‐dimensional heterostructures, plasmonic structures, and silicon/fiber integrated structures) is reviewed. Several potential perspectives and possible future research directions of these promising nanomaterials for nonlinear optics are also presented.
High‐Voltage Lithium‐Metal Batteries Enabled by Localized High‐Concentration Electrolytes
Authors: Chen Shuru , Zheng Jianming , Mei Donghai , Han Kee Sung , Engelhard Mark H. , Zhao Wengao , Xu Wu , Liu Jun , Zhang Ji‐Guang
Published: March 2018

Rechargeable lithium‐metal batteries (LMBs) are regarded as the “holy grail” of energy‐storage systems, but the electrolytes that are highly stable with both a lithium‐metal anode and high‐voltage cathodes still remain a great challenge. Here a novel “localized high‐concentration electrolyte” (HCE; 1.2 m lithium bis(fluorosulfonyl)imide in a mixture of dimethyl carbonate/bis(2,2,2‐trifluoroethyl) ether (1:2 by mol)) is reported that enables dendrite‐free cycling of lithium‐metal anodes with high Coulombic efficiency (99.5%) and excellent capacity retention (>80% after 700 cycles) of Li||LiNi1/3Mn1/3Co1/3O2 batteries. Unlike the HCEs reported before, the electrolyte reported in this work exhibits low concentration, low cost, low viscosity, improved conductivity, and good wettability that make LMBs closer to practical applications. The fundamental concept of “localized HCEs” developed in this work can also be applied to other battery systems, sensors, supercapacitors, and other electrochemical systems.
Reducing Architecture Limitations for Efficient Blue Perovskite Light‐Emitting Diodes
Authors: Gangishetty Mahesh K. , Hou Shaocong , Quan Qimin , Congreve Daniel N.
Published: March 2018

Light‐emitting diodes utilizing perovskite nanocrystals have generated strong interest in the past several years, with green and red devices showing high efficiencies. Blue devices, however, have lagged significantly behind. Here, it is shown that the device architecture plays a key role in this lag and that NiOx, a transport layer in one of the highest efficiency devices to date, causes a significant reduction in perovskite luminescence lifetime. An alternate transport layer structure which maintains robust nanocrystal emission is proposed. Devices with this architecture show external quantum efficiencies of 0.50% at 469 nm, seven times higher than state‐of‐the‐art devices at that wavelength. Finally, it is demonstrated that this architecture enables efficient devices across the entire blue‐green portion of the spectrum. The improvements demonstrated here open the door to efficient blue perovskite light‐emitting diodes.
Surface Immobilization of Transition Metal Ions on Nitrogen‐Doped Graphene Realizing High‐Efficient and Selective CO2 Reduction
Authors: Bi Wentuan , Li Xiaogang , You Rui , Chen Minglong , Yuan Ruilin , Huang Weixin , Wu Xiaojun , Chu Wangsheng , Wu Changzheng , Xie Yi
Published: March 2018

Electrochemical conversion of CO2 to value‐added chemicals using renewable electricity provides a promising way to mitigate both global warming and the energy crisis. Here, a facile ion‐adsorption strategy is reported to construct highly active graphene‐based catalysts for CO2 reduction to CO. The isolated transition metal cyclam‐like moieties formed upon ion adsorption are found to contribute to the observed improvements. Free from the conventional harsh pyrolysis and acid‐leaching procedures, this solution‐chemistry strategy is easy to scale up and of general applicability, thus paving a rational avenue for the design of high‐efficiency catalysts for CO2 reduction and beyond.
Misorientation‐Angle‐Dependent Phase Transformation in van der Waals Multilayers via Electron‐Beam Irradiation
Authors: Kim Un Jeong , Lee Hyangsook , Lee Woojin , Jeong Hye Yun , Kim Hyun , Han Gang Hee , Lee Hyo Sug , Park Yeonsang , Roh Young‐Geun , Lee Young Hee , Lee Eunha , Hwang Sung Woo
Published: March 2018

Misorientation‐angle dependence on layer thickness is an intriguing feature of van der Waals materials, which causes stark optical gain and electrical transport modulation. However, the influence of misorientation angle on phase transformation is not determined yet. Herein, this phenomenon in a MoS2 multilayer via in situ electron‐beam irradiation is reported. An AA′‐stacked MoS2 bilayer undergoes structural transformation from the 2H semiconducting phase to the 1T′ metallic phase, similar to a MoS2 monolayer, which is confirmed via in situ transmission electron microscopy. Moreover, non‐AA′ stacking, which has no local AA′ stacking order in the Moiré pattern, does not reveal such a phase transformation. While a collective sliding motion of chalcogen atoms easily occurs during the transformation in AA′ stacking, in non‐AA′ stacking it is suppressed by the weak van der Waals strength and by the chalcogen atoms interlocked at different orientations, which disfavor their kinetics by the increased entropy of mixing.