bluuebunny/crossref_metadata_2025 huggingface dataset:
Turning a pyroelectric infrared motion sensor into a high-accuracy presence detector by using a narrow semi-transparent chopper
Authors: Liu Haili , Wang Ya , Wang Kevin , Lin Hanbing
Published: December 2017

Pyroelectric infrared (PIR) sensors are the most popular presence detectors. However, their applications are limited to motion detection only, as the pyroelectric sensing element is only sensitive to radiated heat power fluctuation. This letter reports a chopped PIR (C-PIR) presence sensor, capable of detecting both the stationary and the moving occupants at high accuracy by introducing a narrow semi-transparent optical chopper to shutter the incident radiation periodically. More importantly, even though the narrow chopper can efficiently shutter the unidirectional infrared (IR) power radiated by stationary occupants, it has near-zero influence on the omnidirectional power radiated from the ambient environment. Therefore, the voltage difference generated by the C-PIR sensor between occupied and unoccupied scenarios can be directly used for identifying the presence of stationary occupants with high-accuracy. For moving occupant detection, the optical chopper can barely affect the variation of the radiated power and thus lead to the same high-accuracy detection as the on-board PIR. An approximate theoretical model is created to illustrate the physics and dynamics of IR radiation shuttered by the optical chopper. Parametric studies, experimental characterization, and empirical analysis were performed to obtain the optimal setting of the chopper in terms of its thickness and chopping frequency. Experimental results reveal that the C-PIR sensor can detect stationary occupants for up to 4.0 m and moving occupants for up to 8.0 m, while maintaining an accuracy of 100%. The field of view of the C-PIR was found at 110° horizontally and 90° vertically, consistent with that of the on-board PIR sensor.
Maximal trace distance between isoenergetic bosonic Gaussian states
Authors: Volkoff T. J.
Published: December 2017

We locate the set of pairs (ρ1, ρ2) of Gaussian states of a single mode electromagnetic field that exhibit maximal trace distance subject to the energy constraint ⟨a†a⟩ρ1=⟨a†a⟩ρ2=E. Any such pair allows to achieve the minimum possible error in the task of binary distinguishability of two single mode, isoenergetic Gaussian quantum signals. In particular, we show that the logarithm of the minimal error probability for distinguishing two maximally trace distant, isoenergetic Gaussian states scales as −E2, less than the achievable scaling of the minimal error probability for distinguishing, e.g., a pair of isoenergetic Heisenberg-Weyl coherent states with energy E or a pair of isoenergetic quadrature squeezed states with energy E. For the case of a field consisting of M > 1 modes, we locate the set of pairs of maximally trace distant isoenergetic, isocovariant Gaussian states. These results have basic applications in the theory of continuous variable quantum communications with Gaussian states of light.
Neoclassical quasilinear theory in the superbanana plateau regime and banana kinetics in tokamaks
Authors: Shaing K. C.
Published: December 2017

Neoclassical quasilinear transport theory, which is part of a more general theory that unifies neoclassical and quasilinear theories, is extended to the superbanana plateau regime for low frequency (of the order of the drift frequency) electrostatic fluctuations. The physics mechanism that is responsible for the transport losses in this regime is the superbanana plateau resonance. Besides the usual magnetic drifts, Doppler shifted mode frequency also contributes to the resonance condition. Because the characteristic frequency involved in the resonance is of the order of the drift frequency, which is lower than either the bounce or the transit frequency of the particles, the transport losses are higher than the losses calculated in the conventional quasilinear theory. The important effects of the finite banana width, i.e., banana kinetics, are included and are found to reduce the transport losses for short wavelength modes. The implications on the energetic alpha particle energy loss are discussed.
Using laser to trigger a large positive magnetoresistive effect in nonmagnetic Si-based metal-oxide-semiconductor structure
Authors: Zou Bugao , Zhou Peiqi , Zou Jiaren , Gan Zhikai , Mei Chunlian , Wang Hui
Published: December 2017

A colossal positive magnetoresistive effect triggered by a laser was observed in a nonmagnetic Si-based metal-oxide-semiconductor structure. The positive magnetoresistance was greatly promoted compared to the case with no laser illumination. In addition, it shows high sensitivity to the magnetic field intensity above a certain threshold at room temperature, making it an appealing candidate for magnetic field detection. Moreover, the magnetoresistance can be regulated by the position of laser beams, which enables us to tailor the devices to meet various needs. We attribute this effect to the anisotropy of the carrier transport characteristics in our structure. The work suggests a different approach to develop laser-controlled magnetic devices and may greatly improve the performance of existing magnetoresistance-based devices.
Ground state atoms confined in a real Rydberg and complex Rydberg-Scarf II potential
Authors: Mansoori Kermani Maryam
Published: December 2017

In this work, a system of two ground state atoms confined in a one-dimensional real Rydberg potential was modeled. The atom-atom interaction was considered as a nonlocal separable potential (NLSP) of rank one. This potential was assumed because it leads to an analytical solution of the Lippmann-Schwinger equation. The NLSPs are useful in the few body problems that the many-body potential at each point is replaced by a projective two-body nonlocal potential operator. Analytical expressions for the confined particle resolvent were calculated as a key function in this study. The contributions of the bound and virtual states in the complex energy plane were obtained via the derived transition matrix. Since the low energy quantum scattering problems scattering length is an important quantity, the behavior of this parameter was described versus the reduced energy considering various values of potential parameters. In a one-dimensional model, the total cross section in units of the area is not a meaningful property; however, the reflectance coefficient has a similar role. Therefore the reflectance probability and its behavior were investigated. Then a new confined potential via combining the complex absorbing Scarf II potential with the real Rydberg potential, called the Rydberg-Scarf II potential, was introduced to construct a non-Hermitian Hamiltonian. In order to investigate the effect of the complex potential, the scattering length and reflectance coefficient were calculated. It was concluded that in addition to the competition between the repulsive and attractive parts of both potentials, the imaginary part of the complex potential has an important effect on the properties of the system. The complex potential also reduces the reflectance probability via increasing the absorption probability. For all numerical computations, the parameters of a system including argon gas confined in graphite were considered.
A combined electronic structure and molecular dynamics approach to computing the OH vibrational feature of strongly hydrogen-bonded carboxylic acids
Authors: Van Hoozen Brian L. , Petersen Poul B.
Published: December 2017

Medium and strong hydrogen bonds give rise to vibrational features that can span several hundreds of wavenumbers and have unusual line shapes. For example, dimers consisting of carboxylic acids hydrogen-bonded to nitrogen-containing aromatic bases exhibit a vibrational feature that spans over 900 cm−1 and contains two very broad peaks. In this report, we demonstrate how this feature can be reproduced using a combined molecular dynamics (MD) and electronic structure “spectral map” approach, which has been very successful in modeling the vibrational spectrum of water in different environments. In this approach, spectral maps are created, relating the transition frequencies and probabilities to the electric field along the OH bond, which are obtained from the density functional theory calculations of snapshots taken from a classical MD simulation. This map was used to compute the spectral properties of thousands of geometries of the pyridine-acetic acid dimer sampled by a MD simulation, which were used to compute the overall spectral feature. It was found that this approach reproduced the experimental spectrum better than the previous dimer stretch approaches (which were based on describing the dimer geometries harmonically) through a more accurate sampling of dimer geometries. The broadness of these vibrational features largely originates from the range of geometries present in the condensed phase, while the unusual line shape is caused by strong Fermi resonances.
Formation of soap bubbles by gas jet
Authors: Zhou Maolei , Li Min , Chen Zhiyuan , Han Jifeng , Liu Dong
Published: December 2017

Soap bubbles can be easily generated by various methods, while their formation process is complicated and still worth studying. A model about the bubble formation process was proposed in the study by Salkin et al. [Phys. Rev. Lett. 116, 077801 (2016)] recently, and it was reported that the bubbles were formed when the gas blowing velocity was above one threshold. However, after a detailed study of these experiments, we found that the bubbles could be generated in two velocity ranges which corresponded to the laminar and turbulent gas jet, respectively, and the predicted threshold was only effective for turbulent gas flow. The study revealed that the bubble formation was greatly influenced by the aerodynamics of the gas jet blowing to the film, and these results will help to further understand the formation mechanism of the soap bubble as well as the interaction between the gas jet and the thin liquid film.
Coexistence of non-volatile bi-polar resistive switching and tunneling magnetoresistance in spatially confined La0.3Pr0.4Ca0.3MnO3 films
Authors: Jeon J. , Jung J. , Chow K. H.
Published: December 2017

We report the coexistence of non-volatile bi-polar resistive switching (RS) and tunneling magnetoresistance (TMR) in spatially confined La0.3Pr0.4Ca0.3MnO3 films grown on LaAlO3 substrates. At certain temperatures, the arrangement of electronic phase domains in these narrow systems mimics those found in heterostructured metal-insulator-metal devices. The relative spin orientations between adjacent ferromagnetic metallic phase domains enable the TMR effect, while the creation/annihilation of conduction filaments between the metallic phase domains produces the RS effect.
Synthesis of complex organic molecules in simulated methane rich astrophysical ices
Authors: Esmaili Sasan , Bass Andrew D. , Cloutier Pierre , Sanche Léon , Huels Michael A.
Published: December 2017

It has been proposed that organic molecules required for life on earth may be formed by the radiation processing of molecular ices in space environments, e.g., within our solar system. Such processes can be studied in the laboratory with surface science analytical techniques and by using low-energy electron (LEE) irradiation to simulate the effects of the secondary electrons that are generated in great abundance whenever ionizing radiation interacts with matter. Here we present new measurements of 70 eV LEE irradiation of multilayer films of CH4, 18O2, and CH4/18O2 mixtures (3:1 ratio) at 22 K. The electron stimulated desorption (ESD) yields of cations and anions have been recorded as a function of electron fluence. At low fluence, the prompt desorption of more massive multi-carbon or C—O containing cationic fragments agrees with our earlier measurements. However, new anion ESD signals of C2−, C2H−, and C2H2− from CH4/18O2 mixtures increase with fluence, indicating the gradual synthesis (and subsequent electron-induced fragmentation) of new, more complex species containing several C and possibly O atoms. Comparisons between the temperature programed desorption (TPD) mass spectra of irradiated and unirradiated films show the electron-induced formation of new chemical species, the identities of which are confirmed by reference to the NIST database of electron impact mass spectra and by TPD measurements of films composed of the proposed products. New species observed in the TPD of irradiated mixture films include C3H6, C2H5OH, and C2H6. Furthermore, X-ray photoelectron spectroscopy of irradiated films confirms the formation of C—O, C=O, and O=C—O— bonds of newly formed molecules. Our experiments support the view that secondary LEEs produced by ionizing radiation drive the chemistry in irradiated ices in space, irrespective of the radiation type.
A polarized view on DNA under tension
Authors: van Mameren Joost , Vermeulen Karen , Wuite Gijs J. L. , Peterman Erwin J. G.
Published: December 2017

In the past decades, sensitive fluorescence microscopy techniques have contributed significantly to our understanding of the dynamics of DNA. The specific labeling of DNA using intercalating dyes has allowed for quantitative measurement of the thermal fluctuations the polymers undergo. On the other hand, recent advances in single-molecule manipulation techniques have unraveled the mechanical and elastic properties of this intricate polymer. Here, we have combined these two approaches to study the conformational dynamics of DNA under a wide range of tensions. Using polarized fluorescence microscopy in conjunction with optical-tweezers-based manipulation of YOYO-intercalated DNA, we controllably align the YOYO dyes using DNA tension, enabling us to disentangle the rapid dynamics of the dyes from that of the DNA itself. With unprecedented control of the DNA alignment, we resolve an inconsistency in reports about the tilted orientation of intercalated dyes. We find that intercalated dyes are on average oriented perpendicular to the long axis of the DNA, yet undergo fast dynamics on the time scale of absorption and fluorescence emission. In the overstretching transition of double-stranded DNA, we do not observe changes in orientation or orientational dynamics of the dyes. Only beyond the overstretching transition, a considerable depolarization is observed, presumably caused by an average tilting of the DNA base pairs. Our combined approach thus contributes to the elucidation of unique features of the molecular dynamics of DNA.
Large-eddy simulation of shallow turbulent wakes behind a conical island
Authors: Ouro Pablo , Wilson Catherine A. M. E. , Evans Paul , Angeloudis Athanasios
Published: December 2017

Large-Eddy Simulations (LESs) and experiments were employed to study the influence of water depth on the hydrodynamics in the wake of a conical island for emergent, shallow, and deeply submerged conditions. The Reynolds numbers based on the island’s base diameter for these conditions range from 6500 to 8125. LES results from the two shallower conditions were validated against experimental measurements from an open channel flume and captured the characteristic flow structures around the cone, including the attached recirculation region, vortex shedding, and separated shear layers. The wake was impacted by the transition from emergent to shallow submerged flow conditions with more subtle changes in time-averaged velocity and instantaneous flow structures when the submergence increases further. Despite differences in the breakdown of the separated shear layers, vortex shedding, and the upward flow region on the leeward face (once the cone’s apex is submerged), similar flow structures to cylinder flow were observed. These include an arch vortex tilted in the downstream direction and von Karman vortices in the far-wake. Spectra of velocity time series and the drag coefficient indicated that the vortex shedding was constrained by the overtopping flow layer, and thus the shedding frequency decreased as the cone’s apex became submerged. Finally, the generalised flow structures in the wake of a submerged conical body are outlined.
Local environments of atomic clusters and the effect on dynamics in CuZr metallic glass-forming liquids
Authors: Li F. X. , Li M. Z.
Published: December 2017

The effect of local environments of various atomic clusters on the dynamics in CuZr metallic glass-forming liquids was investigated via classical molecular dynamics simulations. It is found that atomic clusters exhibit different local connectivity, leading to different local environments, even for the same type of clusters. Moreover, local environments of atomic clusters are found to have a different impact on dynamics in supercooled liquids. For pentagon-rich clusters such as ⟨0,0,12,0⟩ and ⟨0,1,10,2⟩, the dynamics becomes slower with increasing connectivity in both α and β relaxation time scales. In contrast, as local connectivity increases, atomic mobility of connected ⟨0,3,6,4⟩ clusters is enhanced. The evolution of atomic symmetries in clusters with local connectivity is found to be the underlying structural basis for the correlation between local environments and dynamics of atomic clusters. These findings indicate that local environments of atomic clusters are more critical in the relaxation dynamics and the dynamical heterogeneity in metallic glass-forming liquids.
Multi-excitonic emission from Stranski-Krastanov GaN/AlN quantum dots inside a nanoscale tip
Authors: Mancini L. , Moyon F. , Houard J. , Blum I. , Lefebvre W. , Vurpillot F. , Das A. , Monroy E. , Rigutti L.
Published: December 2017

Single-dot time-resolved micro-photoluminescence spectroscopy and correlated electron tomography (ET) have been performed on self-assembled GaN/AlN quantum dots isolated within a field-emission nanoscale tip by focused ion beam (FIB). Despite the effect of the FIB, the system conserves the capability of emitting light through multi-excitonic complexes. The optical spectroscopy data have then been correlated with the electronic structure and lifetime parameters that could be extracted using the structural parameters obtained by ET via a 6 band k.p model. A biexciton-exciton cascade could be identified and thoroughly analysed. The biexciton-exciton states exhibit a non-negligible polarization component along the [0001] polar crystal axis, indicating a significant valence band mixing, while the relationship between exciton energy and biexciton binding energy is consistent with a hybrid character of the biexciton.
Graphene-enhanced gallium nitride ultraviolet photodetectors under 2 MeV proton irradiation
Authors: Miller Ruth A. , So Hongyun , Chiamori Heather C. , Dowling Karen M. , Wang Yongqiang , Senesky Debbie G.
Published: December 2017

The electrical characteristics of gallium nitride (GaN) ultraviolet (UV) photodetectors with graphene and semitransparent Ni/Au electrodes subjected to 2 MeV proton irradiation are reported and compared. Graphene is shown to have a very high transmittance (87%) in the UV regime (365 nm) compared to semitransparent Ni/Au (3 nm/10 nm) films (32%). Correspondingly, microfabricated graphene/GaN photodetectors showed a much higher pre-irradiation responsivity of 3388 A/W, while that of semitransparent Ni/Au/GaN photodetectors was 351 A/W. For both types of electrodes, intermittent current-voltage measurements performed during 2 MeV proton irradiation showed minimal variation up to a fluence of approximately 3.8 × 1013 cm−2. Additionally, Raman spectroscopy of 200 keV proton beam, 3.8 × 1013 cm−2 irradiated graphene showed minimal disorder with only a 6% increase in ID/IG compared to pre-irradiated graphene. These results support the use of graphene-enhanced GaN UV photodetectors in radiation-rich environments such as deep space.
Control of light polarization by voltage in excitonic metasurface devices
Authors: Lobanov S. V. , Gippius N. A. , Tikhodeev S. G. , Butov L. V.
Published: December 2017

We propose active metasurface devices where the state of emitted light is controlled by voltage. Based on the simulations of expected emission spectra, we present the concept of a light emitting device with the voltage controlled wavelength and degree of linear polarization of emission. The device combines the ability of metasurfaces to control light with a wavelength-tunable light source based on indirect excitons in coupled quantum well heterostructures.
Control of interlayer physics in 2H transition metal dichalcogenides
Authors: Wang Kuang-Chung , Stanev Teodor K. , Valencia Daniel , Charles James , Henning Alex , Sangwan Vinod K. , Lahiri Aritra , Mejia Daniel , Sarangapani Prasad , Povolotskyi Michael , Afzalian Aryan , Maassen Jesse , Klimeck Gerhard , Hersam Mark C. , Lauhon Lincoln J. , Stern Nathaniel P. , Kubis Tillmann
Published: December 2017

It is assessed in detail both experimentally and theoretically how the interlayer coupling of transition metal dichalcogenides controls the electronic properties of the respective devices. Gated transition metal dichalcogenide structures show electrons and holes to either localize in individual monolayers, or delocalize beyond multiple layers—depending on the balance between spin-orbit interaction and interlayer hopping. This balance depends on the layer thickness, momentum space symmetry points, and applied gate fields. The design range of this balance, the effective Fermi levels, and all relevant effective masses is analyzed in great detail. A good quantitative agreement of predictions and measurements of the quantum confined Stark effect in gated MoS2 systems unveils intralayer excitons as the major source for the observed photoluminescence.
Fabrication of Mg-X-O (X = Fe, Co, Ni, Cr, Mn, Ti, V, and Zn) barriers for magnetic tunnel junctions
Authors: Yakushiji K. , Kitagawa E. , Ochiai T. , Kubota H. , Shimomura N. , Ito J. , Yoda H. , Yuasa S.
Published: December 2017

We fabricated magnetic tunnel junctions with a 3d-transition material(X)-doped MgO (Mg-X-O) barrier, and evaluated the effect of the doping on magnetoresistance (MR) and microstructure. Among the variations of X (X = Fe, Co, Ni, Cr, Mn, Ti, V, and Zn), X = Fe and Mn showed a high MR ratio of more than 100%, even at a low resistance-area product of 3 Ωμm2. The microstructure analysis revealed that (001) textured orientation formed for X = Fe and Mn despite substantial doping (about 10 at%). The elemental mappings indicated that Fe atoms in the Mg-Fe-O barrier were segregated at the interfaces, while Mn atoms were evenly involved in the Mg-Mn-O barrier. This suggests that MgO has high adaptability for Fe and Mn dopants in terms of high MR ratio.
Assessment of off-stoichiometric Zr33-xFe52+xSi15 C14 Laves phase compounds as permanent magnet materials
Authors: Gabay A. M. , Hadjipanayis G. C.
Published: December 2017

Recently, Fe-based rare-earth-free compounds with non-cubic crystal structures were proposed as a base for permanent magnets which would not rely on critical elements. In this work, two series of alloys, Zr27Fe73-wSiw (0 ≤ w ≤ 15) and Zr33-xFe52+xSi15 (0 ≤ x ≤ 11), were prepared and characterized after annealing at 1538 K in order to determine the fundamental magnetic properties of the C36 and C14 hexagonal Laves phase compounds. A mixture of the cubic C15 and Zr6Fe23 structures was observed instead of the expected C36 structure. The hexagonal C14 was found in all Zr33-xFe52+xSi15 alloys with its lattice parameters linearly decreasing as the Fe(Si) atoms occupy the Zr sites in the Laves phase crystal structure. The solubility limit of Fe in the C14 structure at 1538 K corresponds to x = 9.5. The Curie temperature of the C14 compounds increases with deviation from the Laves phase stoichiometry from 290 K to 530 K. The room-temperature spontaneous magnetization also increases reaching, after correcting for the non-magnetic impurities, a value of 6.7 kG. The magnetocrystalline anisotropy of the off-stoichiometric C14 Laves phase was found to be uniaxial with the easy magnetization direction parallel to the hexagonal axis. Unfortunately, the anisotropy field, which does not exceed 10 kOe, is not sufficiently high to make the compounds interesting as permanent magnet materials.
3D unsteady computations of evaporative instabilities in a sessile drop of ethanol on a heated substrate
Authors: Semenov Sergey , Carle Florian , Medale Marc , Brutin David
Published: December 2017

Droplets are ubiquitous and have been studied for a century; however, their internal flow pattern and related instabilities that occur in the course of evaporation are not fully understood yet. In this paper, we report our investigation results on an ethanol drop evaporating onto a heated substrate under weightlessness conditions and with a pinned contact line. They have been obtained from both experiments and 3D unsteady computations in order to determine what kind of instabilities develop. Our one-sided model demonstrates quantitative agreement with experiments and confirms that experimentally observed instabilities are driven by thermo-capillary stress and not by the gas convection. Post-processed infrared images drawn from computations led us to conclude that the experimentally observed thermo-convective instabilities, which look very similar to hydrothermal waves in the infrared spectrum, are actually nothing else than unsteady Benard-Marangoni instabilities.
Influences of top electrode reduction potential and operation ambient on the switching characteristics of tantalum oxide resistive switching memories
Authors: Ding Tse-Ming , Chen Yi-Ju , Jeng Jiann-Shing , Chen Jen-Sue
Published: December 2017

Modulation of the oxygen distribution is liable for the electrical performance of oxide-based devices. When the top electrode (TE) is deposited on the active layer, an oxygen exchange layer (OEL) may be formed at the interface. Oxygen ions can be absorbed and offered in OEL to assist resistive switching (RS). In this study, the impact of different TEs (Al, Zr, Ta and Au) on the active layer TaOx is investigated. TEs are chosen based on the reduction potential (E0Al=-2.13V, E0Zr=-1.55V, E0Ta=-0.75V, E0Au=1.52V), which determines whether OEL is formed. Based on TEM micrographs, as the difference of TE reduction potential to E0Ta becomes more negative, a thicker OEL exists. We find that Zr TE device has the most stable I-V characteristic and data retention, while Al TE device suffers from the reset failure, and Au TE device fails to switch. Moreover, we fabricate two different thicknesses (20 nm and 120 nm) of Zr TE and alter the operation ambient to vacuum (10-5 Torr) to study the influence on RS. The magnitude of reset voltage becomes larger when the devices are measured in vacuum ambient. According to these findings, the RS mechanism with different TE materials, thicknesses and at the different operation ambient is established.
Effect of magnetic field annealing on soft magnetic properties of Co71Fe2Si14-xB9+xMn4 amorphous alloys with low permeability
Authors: Fan Xingdu , Li Meng , Zhang Tao , Yuan Chenchen , Shen Baolong
Published: December 2017

The effect of transverse magnetic field annealing (TFA) on soft magnetic properties of Co71Fe2Si14-xB9+xMn4 amorphous alloys was investigated with the aim of reducing effective permeability (μe). It was revealed that the increasing B content improved thermal stability, increased saturation magnetic flux density (Bs) of as-quenched alloys, while the samples exhibited a slightly larger coercivity (Hc) when the atom percentages of Si and B were similar. Permeability decreased dramatically after TFA. The decrease of permeability mainly depended on annealing temperature and magnetic field intensity. Besides, flat hysteresis loops were obtained after TFA, Lorentz micrograph observation revealed the TFA sample exhibited denser magnetic domain walls, which confirmed it was more difficult to be saturated. The Co71Fe2Si9B14Mn4 alloy was successful prepared with low μe of 3020, low Hc of 1.7 A/m and high resistance to DC bias 6 times that of as-quenched alloy at the DC field of 300 A/m.
Engineering of Eu dopant segregation in colquiriite-type fluoride single crystal scintillators
Authors: Yokota Yuui , Yamaji Akihiro , Kurosawa Shunsuke , Ohashi Yuji , Kamada Kei , Yoshikawa Akira
Published: December 2017

Colquiriite-type Eu-doped LiCaAlF6 and LiSrAlF6 (Eu:LiCAF and Eu:LiSAF) scintillator single crystals were grown using Al metal as a starting material to improve the Eu dopant segregation. All Eu:LiCAF and Eu:LiSAF single crystals using Al metal (Eu,AlM:LiCAF and Eu,AlM:LiSAF) indicated high transparency and effective segregation coefficients (keff) of Eu2%,AlM1%:LiCAF and Eu2%,AlM1%:LiSAF single crystals were significantly improved to the value of 0.40 and 0.99, respectively. EuF3 starting material reacted with Al metal before colquiriite-type phase was generated. As a result, Eu3+ ion in EuF3 was changed to Eu2+ ion which could be incorporated into Ca2+ and Sr2+ sites easily.
Dynamic behavior of ultra large graphene-based membranes using electrothermal transduction
Authors: Al-mashaal A. K. , Wood G. S. , Torin A. , Mastropaolo E. , Newton M. J. , Cheung R.
Published: December 2017

This letter reports an experimental study of an electrothermal actuator made from an ultra-large graphene-based bilayer thin film with a diameter to thickness aspect ratio of ∼10 000. Suspended thin films consisting of multilayer graphene and 350–500 nm-thick Poly(methyl methacrylate) have been transferred over circular cavities with a diameter of 3.5 mm. The use of bilayer materials with different mechanical and thermal properties results in thin film structures that can be induced to vibrate mechanically under the electrothermal transduction mechanism. The dynamic response of the bilayer has been investigated electrothermally by driving the structures with a combination of alternating current and direct current actuation voltages (Vac and Vdc) and characterizing their resonant frequencies. It has been found that the bilayer thin film structure behaves as a membrane. In addition, the actuation configurations affect not only the amplitude of vibration but also the tuning of the resonant frequency of the vibrating membranes. The existence of Joule heating-induced tension lowers the mechanical stiffness of the membrane and hence shifts the resonant frequency downwards by −108187 ppm. A resonant frequency of 3.26 kHz with a vibration amplitude of 4.34 nm has been achieved for 350 nm-thick membranes under actuation voltages of 1 V of Vac and 8 V of Vdc.
Stabilizing ultra-thin black phosphorus with in-situ-grown 1 nm-Al2O3 barrier
Authors: Galceran R. , Gaufres E. , Loiseau A. , Piquemal-Banci M. , Godel F. , Vecchiola A. , Bezencenet O. , Martin M.-B. , Servet B. , Petroff F. , Dlubak B. , Seneor P.
Published: December 2017

Exfoliated black phosphorus is a 2D semiconductor with promising properties for electronics, spintronics, and optoelectronics. Nevertheless, its rapid degradation in air renders its integration and use in devices particularly challenging—even more so for smaller thicknesses for which the degradation rate is tremendously enhanced. In order to effectively protect the thinnest flakes, we present here an approach based on an in-situ dielectric capping to avoid all contact with air. Optical microscopy, Raman spectroscopy, and atomic force microscopy studies confirm that 1 nm of Al2O3 efficiently passivates exfoliated black phosphorus (below 5 layers) on Si/SiO2 substrates. Such an ultrathin and transparent passivation layer can act as a tunnel barrier allowing for black phosphorus devices processing without passivation layer removal.
New families of vortex patch equilibria for the two-dimensional Euler equations
Authors: Xue B. B. , Johnson E. R. , McDonald N. R.
Published: December 2017

Various modified forms of contour dynamics are used to compute multipolar vortex equilibria, i.e., configurations of constant vorticity patches which are invariant in a steady rotating frame. There are two distinct solution families for “N + 1” point vortex-vortex patch equilibria in which a finite-area central patch is surrounded by N identical point vortices: one with the central patch having opposite-signed vorticity and the other having same-signed vorticity to the satellite vortices. Each solution family exhibits limiting states beyond which no equilibria can be found. At the limiting state, the central patch of a same-signed equilibrium acquires N corners on its boundary. The limiting states of the opposite-signed equilibria have cusp-like behaviour on the boundary of the central patch. Linear stability analysis reveals that the central patch is most linearly unstable as it approaches the limiting states. For equilibria comprising a central patch surrounded by N identical finite-area satellite patches, again two distinct families of solutions exist: one with the central patch and satellite patches having the same-signed vorticity and the other in which they are opposite-signed. In each family, there are two limiting behaviours in which either the central patch or the satellite patches develop corners or cusps. Streamline plots and time-dependent simulations indicate that opposite-signed multipolar equilibria are robust structures and same-signed equilibria are generally less stable. Streamlines also reveal stable and unstable (saddle point) stagnation points, indicating the existence of new equilibria in which additional patches of vorticity are “grown” at the stagnation points. Examples of such equilibria are computed, and a general numerical routine is briefly described for finding even more complex finite-area equilibria. Finally, new nested polygonal vortex equilibria consisting of two sets of polygonally arranged vortex patches (named “N + N” equilibria here) are computed for two distinct cases: one with the corners of the polygons aligned with each other and the other when they are staggered. Various limiting states are computed for these equilibria. Time-dependent simulations reveal that the aligned equilibria are susceptible to instability, while the staggered equilibria survive a relatively long time. In some parameter regimes, following instability, these structures evolve into known structures such as “N + 1” multipolar vortex equilibria and N-polygon co-rotating equilibria.
Nonlinear benefit-cost optimization-based selection of insulation material and window type: A case study in Turkey
Authors: Üçtuğ Fehmi Görkem , Ağralı Semra
Published: December 2017

In this study, we maximize the energy savings of a hypothetical household by choosing an optimal insulation material with its optimal thickness and also the optimal window type. We develop a nonlinear mixed integer optimization model that maximizes the net present value of the benefits obtained by insulation over the lifespan of the house. Savings are calculated based on the gains from the electricity usage for air conditioning during cooling-required days and the fuel usage for heaters in heating-required days. The heat transfer calculations consider conductive, convective, and radiative components simultaneously. The optimization model takes the climate conditions of the region where the house is located, the consumer's desired indoor temperature, and the properties of the insulation options; then, it returns a combination of selected insulation materials with its optimum thickness and window type as output. We applied the optimization model developed to hypothetical houses in four different climatic regions of Turkey for different lifespans. For all reasonable lifespans, the model choses stonewool as the ideal insulation material. For high interest rates, single windows or double-glazed windows are preferable, but as the interest rate decreases and the net present value of the energy-savings increases, the model prefers triple-glazed windows as the ideal material. Erzurum, a city in climatic region 4, characterized by very cold winters and cool summers, was found to require the highest optimum insulation thickness, and the economic return resulting from the above-mentioned energy-saving actions was also found to be the highest in the case of Erzurum. In all the regions, the energy-saving investments were found to be feasible via applying the feasibility assessment techniques of net present value and payback period. The model developed in this study is applicable to any household as long as the required input data are available.
Synchronization control in multiplex networks of nonlinear multi-agent systems
Authors: He Wangli , Xu Zhiwei , Du Wenli , Chen Guanrong , Kubota Naoyuki , Qian Feng
Published: December 2017

This paper is concerned with synchronization control of a multiplex network, in which two different kinds of relationships among agents coexist. Hybrid coupling, including continuous linear coupling and impulsive coupling, is proposed to model the coexisting distinguishable interactions. First, by adding impulsive controllers on a small portion of agents, local synchronization is analyzed by linearizing the error system at the desired trajectory. Then, global synchronization is studied based on the Lyapunov stability theory, where a time-varying coupling strength is involved. To further deal with the time-varying coupling strength, an adaptive updating law is introduced and a corresponding sufficient condition is obtained to ensure synchronization of the multiplex network towards the desired trajectory. Networks of Chua's circuits and other chaotic systems with double layers of interactions are simulated to verify the proposed method.
Ecological history of the koala and implications for management
Authors: Jurskis Vic
Published: December 2017

Assessments of the conservation status of koalas and trends in their population have been based on mostly unstated false assumptions about their pre-European status and on notions that either they were naturally regulated by their predators, chiefly Aborigines and dingoes, or that they somehow ‘self-regulated’ their fecundity. Closer examination of their ecological history suggests that frequent mild burning by Aborigines maintained eucalypt forests having fewer, mostly healthy trees, fewer young trees, canopies comprising mostly hard and dry leaves with low nutrient content, and, consequently, very few koalas. European explorers did not see them because they were solitary animals occupying large home ranges. After burning was disrupted, koalas responded to increased food resources in dense new growth of eucalypts and in stressed trees continually turning over new foliage. An export skin industry flourished. When their food resources were depleted by clearing or ringbarking of new growth and/or death of declining stands during droughts, koalas crashed back to low levels. Koalas continue to irrupt and decline through much of their range according to changing land management. Wildlife managers should re-assess their status and their management from a clear historical and ecological perspective.
Dispersal limitation promotes the diversification of the mammalian gut microbiota
Authors: Moeller Andrew H. , Suzuki Taichi A. , Lin Dana , Lacey Eileen A. , Wasser Samuel K. , Nachman Michael W.
Published: December 2017

Significance

Mammals harbor communities of gut bacteria that regulate host health, requiring an understanding of the processes that govern the evolution of gut microbiotas. We investigated the diversification of mammalian gut microbiotas by surveying the gut microbiotas of 136 pairs of wild mammalian species living throughout the Americas. These comparisons indicated that physical distance produces barriers to bacterial dispersal that appear to accelerate compositional divergence between the gut microbiotas of mammalian species over evolutionary time. In contrast, contact between host species, such as that between predators and prey, leads to widespread bacterial transmission and the homogenization of microbiotas within mammalian communities. Our findings suggest that spatial limits on bacterial dispersal generate and maintain mammalian gut bacterial diversity across the western hemisphere.
Critical dynamics in population vaccinating behavior
Authors: Pananos A. Demetri , Bury Thomas M. , Wang Clara , Schonfeld Justin , Mohanty Sharada P. , Nyhan Brendan , Salathé Marcel , Bauch Chris T.
Published: December 2017

Significance

Complex adaptive systems exhibit characteristic dynamics near tipping points such as critical slowing down (declining resilience to perturbations). We studied Twitter and Google search data about measles from California and the United States before and after the 2014–2015 Disneyland, California measles outbreak. We find critical slowing down starting a few years before the outbreak. However, population response to the outbreak causes resilience to increase afterward. A mathematical model of measles transmission and population vaccine sentiment predicts the same patterns. Crucially, critical slowing down begins long before a system actually reaches a tipping point. Thus, it may be possible to develop analytical tools to detect populations at heightened risk of a future episode of widespread vaccine refusal.
Effect of oil palm sustainability certification on deforestation and fire in Indonesia
Authors: Carlson Kimberly M. , Heilmayr Robert , Gibbs Holly K. , Noojipady Praveen , Burns David N. , Morton Douglas C. , Walker Nathalie F. , Paoli Gary D. , Kremen Claire
Published: December 2017

Significance

Demand for agricultural commodities is the leading driver of tropical deforestation. Many corporations have pledged to eliminate forest loss from their supply chains by purchasing only certified “sustainable” products. To evaluate whether certification fulfills such pledges, we applied statistical analyses to satellite-based estimates of tree cover loss to infer the causal impact of a third-party certification system on deforestation and fire within Indonesian oil palm plantations. We found that certification significantly reduced deforestation, but not fire or peatland clearance, among participating plantations. Moreover, certification was mostly adopted in older plantations that contained little remaining forest. Broader adoption by oil palm growers is likely needed for certification to have a large impact on total forest area lost to oil palm expansion.
Machine learning shows association between genetic variability in
PPARG
and cerebral connectivity in preterm infants
Authors: Krishnan Michelle L. , Wang Zi , Aljabar Paul , Ball Gareth , Mirza Ghazala , Saxena Alka , Counsell Serena J. , Hajnal Joseph V. , Montana Giovanni , Edwards A. David
Published: December 2017

Significance

Preterm birth affects 11% of births globally; 35% of infants develop long-term neurocognitive problems, and prematurity leads to the loss of 75 million disability adjusted life years per annum worldwide. Imaging studies have shown that these infants have extensive alterations in brain development, but little is known about the molecular or cellular mechanisms involved. This imaging genetics study found a strong association between abnormal cerebral connectivity and variability in the
PPARG
gene, implicating PPARG signaling in abnormal white-matter development in preterm infants and suggesting a tractable new target for therapeutic research.
Noncanonical thyroid hormone signaling mediates cardiometabolic effects in vivo
Authors: Hönes G. Sebastian , Rakov Helena , Logan John , Liao Xiao-Hui , Werbenko Eugenie , Pollard Andrea S. , Præstholm Stine M. , Siersbæk Majken S. , Rijntjes Eddy , Gassen Janina , Latteyer Sören , Engels Kathrin , Strucksberg Karl-Heinz , Kleinbongard Petra , Zwanziger Denise , Rozman Jan , Gailus-Durner Valerie , Fuchs Helmut , Hrabe de Angelis Martin , Klein-Hitpass Ludger , Köhrle Josef , Armstrong David L. , Grøntved Lars , Bassett J. H. Duncan , Williams Graham R. , Refetoff Samuel , Führer Dagmar , Moeller Lars C.
Published: December 2017

Significance

This study changes our understanding of how thyroid hormone acts. Thyroid hormone receptors are considered typical nuclear receptors that bind to DNA and, after binding, alter the expression of their target genes and regulate physiological responses. Nevertheless, we show that thyroid hormone still mediates important physiological effects in mice expressing mutant receptors that cannot bind DNA. These are predominantly linked to energy metabolism and include glucose and triglyceride concentrations, body temperature, locomotor activity, and heart rate. This study provides in vivo evidence that thyroid hormone receptors mediate physiologically relevant effects that are independent of DNA binding and direct activation of gene expression.
Appetite suppressive role of medial septal glutamatergic neurons
Authors: Sweeney Patrick , Li Changhong , Yang Yunlei
Published: December 2017

Significance

Feeding behavior is composed of emotional, hedonic, and homeostatic aspects. It is therefore important to dissect neuron populations that control feeding and emotions and determine their interactions. In this study, we report a neuronal population involved in suppressing food intake in the septum, a brain region relaying information encoded in higher-level brain regions to downstream targets in the hypothalamus. We find that the septal glutamatergic neurons exert anorexic effects without overtly influencing locomotion or anxiety behavior, representing a promising cellular entry point for future studies investigating higher-level control of feeding.
Zooplankton can actively adjust their motility to turbulent flow
Authors: Michalec François-Gaël , Fouxon Itzhak , Souissi Sami , Holzner Markus
Published: December 2017

Significance

Zooplankton possess narrow swimming capabilities, yet are capable of active locomotion amid turbulence. By decoupling the relative velocity of swimming zooplankton from that of the underlying flow, we provide evidence for an active adaptation that allows these small organisms to modulate their swimming effort in response to background flow. This behavioral response results in reduced diffusion at substantial turbulence intensity. Adjusting motility provides fitness advantage because it enables zooplankton to retain the benefits of self-locomotion despite the constraints enforced by turbulence transport. Vigorous swimming and reduced diffusion oppose turbulence advection, can directly affect the dispersal of zooplankton populations, and may help these organisms to actively control their distribution in dynamic environments.
Brain urea increase is an early Huntington’s disease pathogenic event observed in a prodromal transgenic sheep model and HD cases
Authors: Handley Renee R. , Reid Suzanne J. , Brauning Rudiger , Maclean Paul , Mears Emily R. , Fourie Imche , Patassini Stefano , Cooper Garth J. S. , Rudiger Skye R. , McLaughlan Clive J. , Verma Paul J. , Gusella James F. , MacDonald Marcy E. , Waldvogel Henry J. , Bawden C. Simon , Faull Richard L. M. , Snell Russell G.
Published: December 2017

Significance

We present evidence for the presymptomatic dysregulation of urea metabolism in Huntington’s disease (HD). We identified increased levels of a urea transporter transcript and other osmotic regulators in the striatum of our prodromal sheep model of HD and a concomitant increase in striatal and cerebellar urea. Elevated urea was also detected in brain tissue from postmortem HD cases, including cases with low-level cell loss, implying that increased brain urea in HD is not just a product of end-stage cachexia. Disruption of urea metabolism is known to cause neurologic impairment and could initiate neurodegeneration and the symptoms of HD. Our findings suggest that lowering brain levels of urea and/or ammonia would be a worthwhile therapeutic target in HD.