bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of atmosphere-ocean interactions in supermodeling the tropical Pacific climate
Authors: Shen Mao-Lin , Keenlyside Noel , Bhatt Bhuwan C. , Duane Gregory S.
Published: December 2017

The supermodel strategy interactively combines several models to outperform the individual models comprising it. A key advantage of the approach is that nonlinear improvements can be achieved, in contrast to the linear weighted combination of individual unconnected models. This property is found in a climate supermodel constructed by coupling two versions of an atmospheric model differing only in their convection scheme to a single ocean model. The ocean model receives a weighted combination of the momentum and heat fluxes. Optimal weights can produce a supermodel with a basic state similar to observations: a single Intertropical Convergence zone (ITCZ), with a western Pacific warm pool and an equatorial cold tongue. This is in stark contrast to the erroneous double ITCZ pattern simulated by both of the two stand-alone coupled models. By varying weights, we develop a conceptual scheme to explain how combining the momentum fluxes of the two different atmospheric models affects equatorial upwelling and surface wind feedback so as to give a realistic basic state in the tropical Pacific. In particular, we propose a mechanism based on the competing influences of equatorial zonal wind and off-equatorial wind stress curl in driving equatorial upwelling in the coupled models. Our results show how nonlinear ocean-atmosphere interaction is essential in combining these two effects to build different sea surface temperature structures, some of which are realistic. They also provide some insight into observed and modelled tropical Pacific climate.
Simulating climate with a synchronization-based supermodel
Authors: Selten Frank M. , Schevenhoven Francine J. , Duane Gregory S.
Published: December 2017

The SPEEDO global climate model (an atmosphere model coupled to a land and an ocean/sea-ice model with about 250.000 degrees of freedom) is used to investigate the merits of a new multi-model ensemble approach to the climate prediction problem in a perfect model setting. Two imperfect models are generated by perturbing parameters. Connection terms are introduced that synchronize the two models on a common solution, referred to as the supermodel solution. A synchronization-based learning algorithm is applied to the supermodel through the introduction of an update rule for the connection coefficients. Connection coefficients cease updating when synchronization errors between the supermodel and solutions of the “true” equations vanish. These final connection coefficients define the supermodel. Different supermodel solutions, but with equivalent performance, are found depending on the initial values of the connection coefficients during learning. The supermodels have a climatology and a climate response to a CO2 increase in the atmosphere that is closer to the truth as compared to the imperfect models and the standard multi-model ensemble average, showing the potential of the supermodel approach to improve climate predictions.
Heat source location and natural convection in a C-shaped enclosure saturated by a nanofluid
Authors: Mohebbi Rasul , Izadi Mohsen , Chamkha Ali J.
Published: December 2017

In this work, the effect of the presence of a heat source and its location on natural convection in a C-shaped enclosure saturated by a nanofluid is investigated numerically using the lattice Boltzmann method. Fifteen cases consisting of different heat source locations attached to an isolated wall of the enclosure have been considered to achieve the best configuration at different Rayleigh numbers (103-106) and various solid volume fractions of the nanofluid (0-0.05). Results are shown in terms of the streamlines, isothermal lines, velocity profiles, and the local and average Nusselt numbers. The numerical solution is benchmarked against published results from previous studies for validation, and a good agreement is demonstrated. According to the results, at Ra = 103, the maximum Nusselt number is achieved when the heat source is located within the upper horizontal cavity. Moreover, at higher Rayleigh numbers (Ra = 106) and locations of the heat source within the vertical cavity yield the best Nusselt numbers. Compared to the base fluid and at low Rayleigh numbers, the increase in the Nusselt number of the nanofluid is not found to be dependent on the location of the heat source. However, for high Rayleigh numbers, the maximum increase is obtained when the heat source is located in the upper part of the vertical.
The onset of dissipation in high-temperature superconductors: Self-field experiments
Authors: Talantsev E. F. , Strickland N. M. , Wimbush S. C. , Crump W. P.
Published: December 2017

The transport critical current, Ic, is usually defined in terms of a threshold electric field criterion, Ec, with the convention Ec = 1 μV/cm chosen somewhat arbitrarily to provide “reasonably small” electric power dissipation in practical devices. Thus Ic is not fundamentally determined. However, recently it has been shown that the self-field critical current of thin-film superconductors is indeed a fundamental property governed only by the London penetration depth of the material. Here we reconsider the definition of the critical current and resolve this apparent contradiction. We measure the field distribution across the width of both first-generation and second-generation high-temperature superconducting tapes as the transport current is increased from zero to Ic. We identify a threshold current, Ic,surfB, at which the local surface magnetic flux density, Bsurf, abruptly crosses over from a non-linear to a linear dependence on the transport current, as measured at any point on the superconductor surface. This results from the current distribution across the tape width transitioning from non-uniform to uniform. This coincides with the onset of dissipation and immediately precedes the appearance of a measureable electric field. In the present examples Ic,surfB is 12–15% lower than an Ic determined by the Ec criterion. We propose the transition of Bsurf(I) from non-linear to linear as a more fundamental criterion for determining transport critical currents.
Mass, momentum, and energy flux conservation between linear and nonlinear steady-state wave groups
Authors: Liu Zeng , Xu Dali , Liao Shijun
Published: December 2017

This paper provides a mass, momentum, and energy flux conservation analysis between the linear and nonlinear steady-state wave groups. Convergent high-order solutions for nonlinear wave groups with multiple steady-state near resonances in deep water have been obtained by means of the homotopy analysis method. The small divisors associated with nearly resonant components are transformed to singularities that are originally caused by exact resonances by a piecewise auxiliary linear operator. Both two primary components and other nearly resonant ones are considered in the initial guess to search for finite amplitude wave groups. It is found that as nonlinearity of wave groups increases, more wave components appear in the spectrum due to the nearly resonant interactions. The nonlinear wave fields change from the initial bi-chromatic waves that contain only two nontrivial primary components into the steady-state resonant waves that contain both two primary components and other nearly resonant ones. The conservation of mean rates of mass, momentum, and energy fluxes is established between the nonlinear wave groups and linear waves that are combined by two primary components with the same frequencies as in nonlinear wave groups. Comparison of the linear and nonlinear wave fields shows that the nearly resonant components influence the wave field distribution significantly: the nonlinear free surfaces have more peaked crests, steeper troughs, and more flatten wave nodes, and the related velocities at the crests and troughs increase more rapidly with the nonlinearity. All of these findings are helpful to enrich and deepen our understanding about nonlinear wave groups.
Quantum kinetic expansion in the spin-boson model: Matrix formulation and system-bath factorized initial state
Authors: Gong Zhihao , Tang Zhoufei , Wang Haobin , Wu Jianlan
Published: December 2017

Within the framework of the hierarchy equation of motion (HEOM), the quantum kinetic expansion (QKE) method of the spin-boson model is reformulated in the matrix representation. The equivalence between the two formulations (HEOM matrices and quantum operators) is numerically verified from the calculation of the time-integrated QKE rates. The matrix formulation of the QKE is extended to the system-bath factorized initial state. Following a one-to-one mapping between HEOM matrices and quantum operators, a quantum kinetic equation is rederived. The rate kernel is modified by an extra term following a systematic expansion over the site-site coupling. This modified QKE is numerically tested for its reliability by calculating the time-integrated rate and non-Markovian population kinetics. For an intermediate-to-strong dissipation strength and a large site-site coupling, the population transfer is found to be significantly different when the initial condition is changed from the local equilibrium to system-bath factorized state.
Influence of neutrino beam on the Jeans instability in a magnetized quantum plasma
Authors: Prajapati R. P.
Published: December 2017

The influence of propagation dynamics of intense neutrino beams on the hydrodynamic Jeans instability in a magnetized quantum plasma is investigated. The dynamics of a self-gravitating, magnetized electron-ion quantum plasma weakly interacting with neutrinos are considered in a neutrino magnetohydrodynamic model. The modified dispersion relations of Jeans instability and fast neutrino-driven short wavelength instability are established using a linear perturbation method. In oblique propagation, the Jeans instability condition is modified due to the presence of neutrino beam effects, whereas no effect was observed in parallel and perpendicular propagations. The neutrino beam density stabilizes, while the free energy of the neutrino beam destabilizes the growth rate of Jeans instability. The estimated Jeans time scale is comparable to the time scale of supernova explosion. The time scale of neutrino beam instability is much shorter than the Jeans time scale which results in faster neutrino mixing in the gravitational collapse of the system. The consequences of neutrino beam interactions with a magnetized, self-gravitating quantum plasma have been addressed in astrophysical environments.
Effects of gas temperature in the plasma layer on RONS generation in array-type dielectric barrier discharge at atmospheric pressure
Authors: Yoon Sung-Young , Yi Changho , Eom Sangheum , Park Seungil , Kim Seong Bong , Ryu Seungmin , Yoo Suk Jae
Published: December 2017

In this work, we studied the control of plasma-produced species under a fixed gas composition (i.e., ambient air) in a 10 kHz-driven array-type dielectric barrier atmospheric-pressure plasma discharge. Instead of the gas composition, only the gas velocity was controlled. Thus, the plasma-maintenance cost was considerably lower than methods such as external N2 or O2 injection. The plasma-produced species were monitored using Fourier transformed infrared spectroscopy. The discharge properties were measured using a voltage probe, current probe, infrared camera, and optical emission spectroscopy. The results showed that the major plasma products largely depend on the gas temperature in the plasma discharge layer. The gas temperature in the plasma discharge layer was significantly different to the temperature of the ceramic adjacent to the plasma discharge layer, even in the small discharge power density of ∼15 W/cm2 or ∼100 W/cm3. Because the vibrational excitation of N2 was suppressed by the higher gas flow, the major plasma-produced species shifted from NOx in low flow to O3 in high flow.
Soft nanoimprint lithography on SiO2 sol-gel to elaborate sensitive substrates for SERS detection
Authors: Hamouda Frédéric , Bryche Jean-François , Aassime Abdelhanin , Maillart Emmanuel , Gâté Valentin , Zanettini Silvia , Ruscica Jérémy , Turover Daniel , Bartenlian Bernard
Published: December 2017

This paper presents a new alternative fabrication of biochemical sensor based on surface enhanced Raman scattering (SERS) by soft nanoimprint lithography (S-NIL) on SiO2 sol-gel. Stabilization of the sol-gel film is obtained by annealing which simplifies the manufacturing of these biosensors and is compatible with mass production at low cost. This detector relies on a specific pattern of gold nanodisks on a thin gold film to obtain a better sensitivity of molecules’ detection. Characterizations of SERS devices were performed on a confocal Raman microspectrophotometer after a chemical functionalization. We report a lateral collapse effect on poly(diméthylsiloxane) (PDMS) stamp for specific nanostructure dimensions. This unintentional effect is used to evaluate S-NIL resolution in SiO2 sol-gel.
Micromodel observations of evaporative drying and salt deposition in porous media
Authors: Rufai Ayorinde , Crawshaw John
Published: December 2017

Most evaporation experiments using artificial porous media have focused on single capillaries or sand packs. We have carried out, for the first time, evaporation studies on a 2.5D micromodel based on a thin section of a sucrosic dolomite rock. This allowed direct visual observation of pore-scale processes in a network of pores. NaCl solutions from 0 wt. % (de-ionized water) to 36 wt. % (saturated brine) were evaporated by passing dry air through a channel in front of the micromodel matrix. For de-ionized water, we observed the three classical periods of evaporation: the constant rate period (CRP) in which liquid remains connected to the matrix surface, the falling rate period, and the receding front period, in which the capillary connection is broken and water transport becomes dominated by vapour diffusion. However, when brine was dried in the micromodel, we observed that the length of the CRP decreased with increasing brine concentration and became almost non-existent for the saturated brine. In the experiments with brine, the mass lost by evaporation became linear with the square root of time after the short CRP. However, this is unlikely to be due to capillary disconnection from the surface of the matrix, as salt crystals continued to be deposited in the channel above the matrix. We propose that this is due to salt deposition at the matrix surface progressively impeding hydraulic connectivity to the evaporating surface.
Probing ultrafast dynamics of solid-density plasma generated by high-contrast intense laser pulses
Authors: Jana Kamalesh , Blackman David R. , Shaikh Moniruzzaman , Lad Amit D. , Sarkar Deep , Dey Indranuj , Robinson Alex P. L. , Pasley John , Ravindra Kumar G.
Published: December 2017

We present ultrafast dynamics of solid-density plasma created by high-contrast (picosecond contrast ∼10−9), high-intensity (∼4 × 1018 W/cm2) laser pulses using time-resolved pump-probe Doppler spectrometry. Experiments show a rapid rise in blue-shift at early time delay (2–4.3 ps) followed by a rapid fall (4.3–8.3 ps) and then a slow rise in blue-shift at later time delays (>8.3 ps). Simulations show that the early-time observations, specifically the absence of any red-shifting of the reflected probe, can only be reproduced if the front surface is unperturbed by the laser pre-pulse at the moment that the high intensity pulse arrives. A flexible diagnostic which is capable of diagnosing the presence of low-levels of pre-plasma formation would be useful for potential applications in laser-produced proton and ion production, such as cancer therapy and security imaging.
Role of CoFeB thickness in electric field controlled sub-100 nm sized magnetic tunnel junctions
Authors: Lourembam James , Huang Jiancheng , Lim Sze Ter , Gerard Ernult Franck
Published: December 2017

We report a comprehensive study on the role of the free layer thickness (tF) in electric-field controlled nanoscale perpendicular magnetic tunnel junctions (MTJs), comprising of free layer structure Ta/Co40Fe40B20/MgO, by using dc magnetoresistance and ultra-short magnetization switching measurements. Focusing on MTJs that exhibits positive effective device anisotropy (Keff), we observe that both the voltage-controlled magnetic anisotropy (ξ) and voltage modulation of coercivity show strong dependence on tF. We found that ξ varies dramatically and unexpectedly from ∼−3 fJ/V-m to ∼−41 fJ/V-m with increasing tF. We discuss the possibilities of electric-field tuning of the effective surface anisotropy term, KS as well as an additional interfacial magnetoelastic anisotropy term, K3 that scales with 1/tF2. Voltage pulse induced 180° magnetization reversal is also demonstrated in our MTJs. Unipolar switching and oscillatory function of switching probability vs. pulse duration can be observed at higher tF, and agrees well with the two key device parameters — Keff and ξ.
Minor-Cu doped soft magnetic Fe-based FeCoBCSiCu amorphous alloys with high saturation magnetization
Authors: Li Yanhui , Wang Zhenmin , Zhang Wei
Published: December 2017

The effects of Cu alloying on the amorphous-forming ability (AFA) and magnetic properties of the P-free Fe81Co5B11C2Si1 amorphous alloy were investigated. Addition of ≤ 1.0 at.% Cu enhances the AFA of the base alloy without significant deterioration of the soft magnetic properties. The Fe80.5Co5B11C2Si1Cu0.5 alloy with the largest critical thickness for amorphous formation of ∼35 μm possesses a high saturation magnetization (Bs) of ∼1.78 T, low coercivity of ∼14.6 A/m, and good bending ductility upon annealing in a wide temperature range of 513–553 K with maintaining the amorphous state. The fabrication of the new high-Fe-content Fe-Co-B-C-Si-Cu amorphous alloys by minor doping of Cu gives a guideline to developing high Bs amorphous alloys with excellent AFA.
Tunable electronic and optical properties of gas molecules adsorbed monolayer graphitic ZnO: Implications for gas sensor and environment monitoring
Authors: Zhang Wei , Du Qikui , Zhang Lifa
Published: December 2017

Due to the large surface area and the peculiar electronic characters, great attention has been paid to 2D materials for the gas sensing applications. Here, using the hybrid density functional calculations, we systematically study the adsorptions of gas molecules on the monolayer graphitic ZnO (g-ZnO), including CO, H2, H2O, H2S, NH3, NO, NO2, O2, and SO2. For most of the molecules, g-ZnO shows superior sensing performance to the well-known MoS2, black phosphorus, blue phosphorus, antimonene, and germanene. H2S, NO, NO2, and SO2 act as charge acceptors, and CO, H2, H2O, and NH3 serve as charge donors. These molecules also induce distinct modifications to the electronic structures, work functions, and optical adsorptions. NO, NO2, and O2 form flat bands in the bandgaps of the spin-up or spin-down states, whereas other molecules mainly tune the bandgaps and the orbital couplings. In particular, g-ZnO is most likely to adsorb the atmospheric pollutant SO2, which has the strongest interaction through hybridizing its widely broadened 2p orbitals with the 3d orbitals of g-ZnO. Moreover, the improved visible light absorption is demonstrated in the NO2 adsorbed g-ZnO. Our results not only confirm that the electronic and optical properties of g-ZnO can be effectively tuned by the selective adsorption of gas molecules but also provide insightful guidance for the potential application of g-ZnO in the field of gas sensors.
Zero Prandtl-number rotating magnetoconvection
Authors: Ghosh Manojit , Pal Pinaki
Published: December 2017

We investigate instabilities and chaos near the onset of Rayleigh-Bénard convection of electrically conducting fluids with free-slip, perfectly electrically and thermally conducting boundary conditions in the presence of uniform rotation about the vertical axis and horizontal external magnetic field by considering zero Prandtl-number limit (Pr → 0). Direct numerical simulations (DNSs) and low-dimensional modeling of the system are done for the investigation. Values of the Chandrasekhar number (Q) and the Taylor number (Ta) are varied in the range 0 < Q, Ta ≤ 50. Depending on the values of the parameters in the chosen range and the choice of initial conditions, the onset of convection is found be either periodic or chaotic. Interestingly, it is found that chaos at the onset can occur through four different routes, namely, homoclinic, intermittent, period doubling, and quasiperiodic routes. Homoclinic and intermittent routes to chaos at the onset occur in the presence of weak magnetic field (Q < 2), while the period doubling route is observed for relatively stronger magnetic field (Q ≥ 2) for one set of initial conditions. On the other hand, the quasiperiodic route to chaos at the onset is observed for another set of initial conditions. However, the rotation rate (value of Ta) also plays an important role in determining the nature of convection at the onset. Analysis of the system simultaneously with DNSs and low-dimensional modeling helps us to clearly identify different flow regimes concentrated near the onset of convection and understand their origins. The periodic or chaotic convection at the onset is found to be connected with rich bifurcation structures involving subcritical pitchfork, imperfect pitchfork, supercritical Hopf, imperfect homoclinic gluing, and Neimark-Sacker bifurcations.
Convergence of highly parallel stray field calculation using the fast multipole method on irregular meshes
Authors: Palmesi P. , Abert C. , Bruckner F. , Suess D.
Published: December 2017

Fast stray field calculation is commonly considered of great importance for micromagnetic simulations, since it is the most time consuming part of the simulation. The Fast Multipole Method (FMM) has displayed linear O(N) parallelization behavior on many cores. This article investigates the error of a recent FMM approach approximating sources using linear—instead of constant—finite elements in the singular integral for calculating the stray field and the corresponding potential. After measuring performance in an earlier manuscript, this manuscript investigates the convergence of the relative L2 error for several FMM simulation parameters. Various scenarios either calculating the stray field directly or via potential are discussed.
Collision of dust ion acoustic multisolitons in a non-extensive plasma using Hirota bilinear method
Authors: El-Labany S. K. , El-Taibany W. F. , Behery E. E. , Fouda S. M.
Published: December 2017

The collision of two, four, and six dust ion acoustic solitons (DIASs) in an unmagnetized non-extensive plasma is studied. The dispersion characteristics are analyzed. Using the extended Poincaré-Lighthill-Kue method, two different Korteweg–de Vries (KdV) equations are derived for the colliding DIASs. The Hirota's direct bilinear method is applied to get the multisoliton solutions for the derived KdV equations. It is found that the non-extensive parameter for electrons plays a significant role in the collision process, in such a way that the amplitude of the solitons increases as the non-extensive parameter increases.
Parametric decay instability of an obliquely propagating ordinary wave in the electron cyclotron frequency range
Authors: Gusakov E. Z. , Popov A. Yu.
Published: December 2017

The possibility of the low-power-threshold parametric decay of an obliquely propagating ordinary wave to an upper hybrid wave and a low-hybrid wave is analysed under conditions of nonmonotonic plasma density profile in a magnetic trap. The instability threshold and growth rate are derived explicitly. The analytical results are illustrated under the conditions typical of the ordinary mode fundamental electron cyclotron resonance heating harmonic experiments at the FTU tokamak.
Complex magnetic properties and large magnetocaloric effects in RCoGe (R=Tb, Dy) compounds
Authors: Zhang Yan , Dong Qiaoyan , Zheng Xinqi , Liu Yanli , Zuo Shulan , Xiong JieFu , Zhang Bo , Zhao Xin , Li Rui , Liu Dan , Hu Feng-xia , Sun Jirong , Zhao Tongyun , Shen Baogen
Published: December 2017

Complicated magnetic phase transitions and Large magnetocaloric effects (MCEs) in RCoGe (R=Tb, Dy) compounds have been reported in this paper. Results show that the TbCoGe compounds have a magnetic phase transition from antiferromagnetic to paramagnetic (AFM-PM) at TN∼16 K, which is close to the value reported by neutron diffraction. The DyCoGe compound undergoes complicated phase changes from 2 K up to 300 K. The peak at 10 K displays a phase transition from antiferromagnetic to ferromagnetic (AFM-FM). In particular, a significant ferromagnetic to paramagnetic (FM-PM) phase transition was found at the temperature as high as 175 K and the cusp becomes more abrupt with the magnetic field increasing from 0.01 T to 0.1 T. The maximum value of magnetic entropy change of TbCoGe and DyCoGe compounds achieve 14.5 J/kg K and 11.5 J/kg K respectively for a field change of 0-5 T. Additionally, the correspondingly considerable refrigerant capacity value of 260 J/kg and 242 J/kg are also obtained respectively, suggesting that both TbCoGe and DyCoGe compounds could be considered as good candidates for low temperature magnetic refrigerant.
Kinetic-scale flux rope reconnection in periodic and line-tied geometries
Authors: Sauppe J. P. , Daughton W.
Published: December 2017

The collisionless reconnection of two parallel flux ropes driven by both the coalescence and kink instabilities is examined using fully kinetic simulations in periodic and line-tied geometries. The three-dimensional reconnection rate is computed from the maximum of the quasi-potential, Ξ≡−∫E·dℓ, where the integral of the electric field is taken along the magnetic field lines across the system. In periodic simulations in which the kink mode is nearly suppressed, reconnection is driven by the coalescence instability, and the peak rate is within 3%–8% of comparable 2D simulations. When a strong kink growth is observed, the peak reconnection rate drops by 10%–25%, and there is a larger drop for lower guide field. With line-tied boundary conditions, the kink instability plays a key role in allowing the flux ropes to interact and partially reconnect. In this limit, the field lines with maximum quasi-potential are associated with a quasi-separatrix layer, and the electric field along these special field lines is supported predominantly by the divergence of the electron pressure tensor. Both of these features, along with the observed reconnection rate, are consistent with recent laboratory experiments on kinetic-scale flux ropes. In kinetic simulations, the non-gyrotropic pressure tensor terms contribute significantly more to the reconnecting electric field than do the gyrotropic terms, while contributions from the electron inertia are significant for field lines adjacent to the quasi-separatrix layer.
Near-infrared refractive index of synthetic single crystal and polycrystalline diamonds at high temperatures
Authors: Yurov V. Yu. , Bushuev E. V. , Popovich A. F. , Bolshakov A. P. , Ashkinazi E. E. , Ralchenko V. G.
Published: December 2017

We measured the refractive index n(T) and thermo-optical coefficient β(T) = (1/n)(dn/dT) of high quality synthetic diamonds from room temperature to high temperatures, up to 1520 K, in near-infrared spectral range at wavelength 1.56 μm, using a low-coherence interferometry. A type IIa single crystal diamond produced by high pressure–high temperature technique and a transparent polycrystalline diamond grown by chemical vapor deposition were tested and revealed a very close n(T) behavior, with n = 2.384 ± 0.001 at T = 300 K, monotonically increasing to 2.428 at 1520 K. The n(T) data corrected to thermal expansion of diamond are well fitted with 3rd order polynomials, and alternatively, with the Bose-Einstein model with an effective oscillator frequency of 970 cm−1. Almost linear n(T) dependence is observed above 800 K. The thermo-optical coefficient is found to increase monotonically from (0.6 ± 0.1) × 10−5 K−1 (300 K) to (2.0 ± 0.1) × 10−5 K−1 (1300 K) with a tendency to saturation at >1200 K. These β(T) values are an order of magnitude lower than those known for Si, GaAs, and InP. The obtained results significantly extend the temperature range, where the refractive index of diamond was previously measured.
Towards on-chip photon-pair bell tests: Spatial pump filtering in a LiNbO3 adiabatic coupler
Authors: Solntsev Alexander S. , Liu Tong , Boes Andreas , Nguyen Thach G. , Wu Che Wen , Setzpfandt Frank , Mitchell Arnan , Neshev Dragomir N. , Sukhorukov Andrey A.
Published: December 2017

Nonlinear optical waveguides enable the integration of entangled photon sources and quantum logic gates on a quantum photonic chip. One of the major challenges in such systems is separating the generated entangled photons from the pump laser light. In this work, we experimentally characterize double-N-shaped nonlinear optical adiabatic couplers designed for the generation of spatially entangled photon pairs through spontaneous parametric down-conversion, while simultaneously providing spatial pump filtering and keeping photon-pair states pure. We observe that the pump photons at a wavelength of 671 nm mostly remain in the central waveguide, achieving a filtering ratio of over 20 dB at the outer waveguides. We also perform classical characterization at the photon-pair wavelength of 1342 nm and observe that light fully couples from an input central waveguide to the outer waveguides, showing on chip separation of the pump and the photon-pair wavelength.
The ion cyclotron turbulence generated by a low frequency kinetic Alfvén wave and turbulent heating of ions
Authors: Mikhailenko V. S. , Mikhailenko V. V. , Lee Hae June
Published: December 2017

The ion cyclotron instability driven by a strong kinetic Alfvén wave is investigated as a possible source of anisotropic heating of ions in the sun's corona. We present a novel model of a plasma with coupled inhomogeneous current and shearing flow, which results from the particle's motion in the electric field of the kinetic Alfvén wave of finite wavelength. The investigation is performed employing the non-modal kinetic theory grounded on the shearing mode approach. The solution of the governing linear integral equation for the perturbed potential displays that the flow velocity shear, which for the corona conditions may be above the growth rate of the ion cyclotron instability in the plasma with steady current, changes the exponential growth of the ion cyclotron potential on the power function of time, that impedes the growth of the unstable ion cyclotron wave and reduces the turbulent heating rate of ions across the magnetic field.
Improved free-energy landscape reconstruction of bacteriorhodopsin highlights local variations in unfolding energy
Authors: Heenan Patrick R. , Yu Hao , Siewny Matthew G. W. , Perkins Thomas T.
Published: December 2017

Precisely quantifying the energetics that drive the folding of membrane proteins into a lipid bilayer remains challenging. More than 15 years ago, atomic force microscopy (AFM) emerged as a powerful tool to mechanically extract individual membrane proteins from a lipid bilayer. Concurrently, fluctuation theorems, such as the Jarzynski equality, were applied to deduce equilibrium free energies (ΔG0) from non-equilibrium single-molecule force spectroscopy records. The combination of these two advances in single-molecule studies deduced the free-energy of the model membrane protein bacteriorhodopsin in its native lipid bilayer. To elucidate this free-energy landscape at a higher resolution, we applied two recent developments. First, as an input to the reconstruction, we used force-extension curves acquired with a 100-fold higher time resolution and 10-fold higher force precision than traditional AFM studies of membrane proteins. Next, by using an inverse Weierstrass transform and the Jarzynski equality, we removed the free energy associated with the force probe and determined the molecular free-energy landscape of the molecule under study, bacteriorhodopsin. The resulting landscape yielded an average unfolding free energy per amino acid (aa) of 1.0 ± 0.1 kcal/mol, in agreement with past single-molecule studies. Moreover, on a smaller spatial scale, this high-resolution landscape also agreed with an equilibrium measurement of a particular three-aa transition in bacteriorhodopsin that yielded 2.7 kcal/mol/aa, an unexpectedly high value. Hence, while average unfolding ΔG0 per aa is a useful metric, the derived high-resolution landscape details significant local variation from the mean. More generally, we demonstrated that, as anticipated, the inverse Weierstrass transform is an efficient means to reconstruct free-energy landscapes from AFM data.
Current-driven thermo-magnetic switching in magnetic tunnel junctions
Authors: Kravets A. F. , Polishchuk D. M. , Pashchenko V. A. , Tovstolytkin A. I. , Korenivski V.
Published: December 2017

We investigate switching of magnetic tunnel junctions (MTJs) driven by the thermal effect of the transport current through the junctions. The switching occurs in a specially designed composite free layer, which acts as one of the MTJ electrodes, and is due to a current-driven ferro-to-paramagnetic Curie transition with the associated exchange decoupling within the free layer leading to magnetic reversal. We simulate the current and heat propagation through the device and show how heat focusing can be used to improve the power efficiency. The Curie-switch MTJ demonstrated in this work has the advantage of being highly tunable in terms of its operating temperature range, conveniently to or just above room temperature, which can be of technological significance and competitive with the known switching methods using spin-transfer torques.
An ab initio CASSCF study of zero field splitting fluctuations in the octet ground state of aqueous [Gd(iii)(HPDO3A)(H2O)]
Authors: Khan Shehryar , Pollet Rodolphe , Vuilleumier Rodolphe , Kowalewski Jozef , Odelius Michael
Published: December 2017

In this work, we present ab initio calculations of the zero-field splitting (ZFS) of a gadolinium complex [Gd(iii)(HPDO3A)(H2O)] sampled from an ab initio molecular dynamics (AIMD) simulation. We perform both post-Hartree-Fock (complete active space self-consistent field—CASSCF) and density functional theory (DFT) calculations of the ZFS and compare and contrast the methods with experimental data. Two different density functional approximations (TPSS and LC-BLYP) were investigated. The magnitude of the ZFS from the CASSCF calculations is in good agreement with experiment, whereas the DFT results in varying degrees overestimate the magnitude of the ZFS for both functionals and exhibit a strong functional dependence. It was found in the sampling over the AIMD trajectory that the fluctuations in the transient ZFS tensor derived from DFT are not correlated with those of CASSCF nor does the magnitude of the ZFS from CASSCF and DFT correlate. From the fluctuations in the ZFS tensor, we extract a correlation time of the transient ZFS which is on the sub-picosecond time scale, showing a faster decay than experimental estimates.
Monolayer nanoparticle-covered liquid marbles derived from a sol-gel coating
Authors: Li Xiaoguang , Wang Yiqi , Huang Junchao , Yang Yao , Wang Renxian , Geng Xingguo , Zang Duyang
Published: December 2017

A sol-gel coating consisting of hydrophobic SiO2 nanoparticles (NPs) was used to produce monolayer NP-covered (mNPc) liquid marbles. The simplest approach was rolling a droplet on this coating, and an identifiable signet allowed determination of the coverage ratio of the resulting liquid marble. Alternatively, the particles were squeezed onto a droplet surface with two such coatings, generating surface buckling from interfacial NP jamming, and then a liquid marble was produced via a jamming-relief process in which water was added into the buckled droplet. This process revealed an ∼7% reduction in particle distance after interfacial jamming. The mNPc liquid marbles obtained by the two methods were transparent with smooth profiles, as naked droplets, and could be advantageously used in fundamental and applied researches for their unique functions.
Pseudospins and topological edge states in elastic shear waves
Authors: Li Jing , Wang Jian , Wu Shiqiao , Mei Jun
Published: December 2017

We present a new framework to realize topological edge states in elastic shear waves in a two-dimensional (2D) phononic crystal (PC). The PC has a simple structure and is composed of a triangular array of core-shell cylinders embedded in an epoxy background. By tuning the geometrical parameters of the cylinders, band inversion between E1 and E2 eigenstates can be achieved at the Brillouin zone (BZ) center, which signifies a topological phase transition from a trivial PC to a nontrivial PC. An effective Hamiltonian is developed to characterize the topology of the PC around the Γ point, and spin Chern numbers are identified as the appropriate topological invariant. Helical edge states are formed at the interface between topologically distinct PCs, and these edge modes exhibit interesting one-way propagation behaviors with little backscattering. With full-wave simulations, we unambiguously demonstrate the robustness of the edge states against different types of defects, which is due to the nontrivial topology of the system. These unidirectional and robust transport phenomena of elastic shear wave thus offer people a new degree of freedom to control and manipulating elastic waves and are expected to find potential applications in diverse fields.
Modulating PL and electronic structures of MoS2/graphene heterostructures via interlayer twisting angle
Authors: Du Luojun , Yu Hua , Liao Mengzhou , Wang Shuopei , Xie Li , Lu Xiaobo , Zhu Jianqi , Li Na , Shen Cheng , Chen Peng , Yang Rong , Shi Dongxia , Zhang Guangyu
Published: December 2017

Stacking two-dimensional materials into van der Waals heterostructures with distinct interlayer twisting angles opens up new strategies for electronic structure and physical property engineering. Here, we investigate how the interlayer twisting angles affect the photoluminescence (PL) and Raman spectra of the MoS2/graphene heterostructures. Based on a series of heterostructure samples with different interlayer twisting angles, we found that the PL and Raman spectra of the monolayer MoS2 in these heterostructures are strongly twisting angle dependent. When the interlayer twisting angle evolves from 0° to 30°, both the PL intensity and emission energy increase, while the splitting of the E2g Raman mode decreases gradually. The observed phenomena are attributed to the twisting angle dependent interlayer interaction and misorientation-induced lattice strain between MoS2 and graphene.
Simultaneous measurements of transport and poroelastic properties of rocks
Authors: Hasanov Azar K. , Prasad Manika , Batzle Michael L.
Published: December 2017

A novel laboratory apparatus has been developed for simultaneous measurements of transport and poroelastic rock properties. These transport and poroelastic properties at reservoir pressure and temperature conditions are required inputs for various geoscience applications, such as reservoir simulation, basin modeling, or modeling of pore pressure generation. Traditionally, the transport and poroelastic properties are measured separately using, for example, the oscillating pore pressure method to measure hydraulic transport properties, static strain measurements for elastic properties, and pore volumometry for storage capacity. In addition to time, the separate set of measurements require either aliquot cores or subjecting the same core to multiple pressure tests. We modified the oscillating pore pressure method to build an experimental setup, capable of measuring permeability, storage capacity, and pseudo-bulk modulus of rocks simultaneously. We present here the test method, calibration measurements (capillary tube), and sample measurements (sandstone) of permeability and storage capacity at reservoir conditions. We establish that hydraulically measured storage capacities were overestimated by an order of magnitude when compared to elastically derived ones. Our concurrent measurement of elastic properties during the hydraulic experiment provides an independent constraint on storage capacity.
Interplay of structure, elasticity, and dynamics in actin-based nematic materials
Authors: Zhang Rui , Kumar Nitin , Ross Jennifer L. , Gardel Margaret L. , de Pablo Juan J.
Published: December 2017

Significance

Thermotropic liquid crystals (LCs) are central to a wide range of commercial and emerging technologies. Lyotropic, aqueous-based LCs are common in nature, but applications have been scarce. The current understanding of their behavior is limited, and manipulating their mechanical and dynamic characteristics has been challenging. Here we show that the elasticity and temporal evolution of biopolymer-based nematic systems can be inferred from simple optical microscopy measurements, and that their mechanical properties can be manipulated by adjusting certain molecular characteristics, such as the product of length and concentration. It is also shown that the dynamic evolution of the resulting materials can be understood and predicted on the basis of a free energy functional originally developed for the study of thermotropic systems.
KLU
suppresses megasporocyte cell fate through SWR1-mediated activation of
WRKY28
expression in
Arabidopsis
Authors: Zhao Lihua , Cai Hanyang , Su Zhenxia , Wang Lulu , Huang Xinyu , Zhang Man , Chen Piaojuan , Dai Xiaozhuan , Zhao Heming , Palanivelu Ravishankar , Chen Xuemei , Qin Yuan
Published: December 2017

Significance

In flowering plants, the female germ line begins as a single cell known as the megaspore mother cell (MMC) in each ovule. The mechanisms that restrict MMC fate to a single cell remain largely unknown. We show that the
Arabidopsis
cytochrome P450 gene
KLU
acts through the chromatin remodeling complex SWR1 to promote
WRKY28
expression in ovule primordia. We show that
WRKY28
is expressed in a few somatic cells surrounding the MMC and is required to inhibit these cells from acquiring the MMC-like cell fate. Consistent with non–cell-autonomous
KLU
activity,
KLU
-expressing cells and
WRKY28
-expressing cells are neither identical nor adjacently positioned. Our study demonstrates that cell–cell interactions involving only somatic cells in ovule primordia ensure the specification of a single MMC.
PARP1-dependent eviction of the linker histone H1 mediates immediate early gene expression during neuronal activation
Authors: Azad Gajendra Kumar , Ito Kenji , Sailaja Badi Sri , Biran Alva , Nissim-Rafinia Malka , Yamada Yasuhiro , Brown David T. , Takizawa Takumi , Meshorer Eran
Published: December 2017

Neuronal stimulation leads to immediate early gene (IEG) expression through calcium-dependent mechanisms. In recent years, considerable attention has been devoted to the transcriptional responses after neuronal stimulation, but relatively little is known about the changes in chromatin dynamics that follow neuronal activation. Here, we use fluorescence recovery after photobleaching, biochemical fractionations, and chromatin immunoprecipitation to show that KCl-induced depolarization in primary cultured cortical neurons causes a rapid release of the linker histone H1 from chromatin, concomitant with IEG expression. H1 release is repressed by PARP inhibition, PARP1 deletion, a non-PARylatable H1, as well as phosphorylation inhibitions and a nonphosphorylatable H1, leading to hindered IEG expression. Further, H1 is replaced by PARP1 on IEG promoters after neuronal stimulation, and PARP inhibition blocks this reciprocal binding response. Our results demonstrate the relationship between neuronal excitation and chromatin plasticity by identifying the roles of polyadenosine diphosphate ribosylation and phosphorylation of H1 in regulating H1 chromatin eviction and IEG expression in stimulated neurons.
Cytotoxic granule endocytosis depends on the Flower protein
Authors: Chang Hsin-Fang , Mannebach Stefanie , Beck Andreas , Ravichandran Keerthana , Krause Elmar , Frohnweiler Katja , Fecher-Trost Claudia , Schirra Claudia , Pattu Varsha , Flockerzi Veit , Rettig Jens
Published: December 2017

Cytotoxic T lymphocytes (CTLs) kill target cells by the regulated release of cytotoxic substances from granules at the immunological synapse. To kill multiple target cells, CTLs use endocytosis of membrane components of cytotoxic granules. We studied the potential calcium dependence of endocytosis in mouse CTLs on Flower, which mediates the calcium dependence of synaptic vesicle endocytosis in Drosophila melanogaster. Flower is predominantly localized on intracellular vesicles that move to the synapse on target cell contact. Endocytosis is entirely blocked at an early stage in Flower-deficient CTLs and is rescued to wild-type level by reintroducing Flower or by raising extracellular calcium. A Flower mutant lacking binding sites for the endocytic adaptor AP-2 proteins fails to rescue endocytosis, indicating that Flower interacts with proteins of the endocytic machinery to mediate granule endocytosis. Thus, our data identify Flower as a key protein mediating granule endocytosis.
Elizabethkingia anophelis: Clinical Experience of an Academic Health System in Southeastern Wisconsin
Authors: Figueroa Castro Carlos E , Johnson Carrie , Williams Mary , VanDerSlik April , Graham Mary Beth , Letzer David , Ledeboer Nathan , Buchan Blake W , Block Timothy , Borlaug Gwen , Munoz-Price L Silvia
Published: December 2017

In late 2015 and early 2016, 11 patients were identified with cultures positive for Elizabethkingia anophelis in our health system. All patients had positive blood cultures upon admission. Chart review showed that all had major comorbidities and recent health care exposure. The attributable mortality rate was 18.2%.
Objective Validation of Perfusion-Based Human Cadaveric Simulation Training Model for Management of Internal Carotid Artery Injury in Endoscopic Endonasal Sinus and Skull Base Surgery
Authors: Shen Jasper , Hur Kevin , Zhang Zhipeng , Minneti Michael , Pham Martin , Wrobel Bozena , Zada Gabriel
Published: December 2017

BACKGROUND

The emergence of minimally invasive endoscopic endonasal skull base surgery has necessitated reproducible and realistic simulators of rare vascular injuries.

OBJECTIVE

To assess the face and content validity of an innovative perfusion-based cadaveric model developed to simulate internal carotid artery (ICA) injury during endoscopic surgery.

METHODS

Otolaryngology and neurosurgery trainees attempted 3 consecutive trials of endoscopic control of a parasellar ICA injury, with standardized technical feedback. Time to hemostasis (TTH) and blood loss were trended. All participants completed validated questionnaires using a 5-point Likert scale to assess the domains of confidence gain, face validity, content validity, and curriculum applicability.

RESULTS

Among all participants (n = 35), TTH and mean blood loss significantly decreased between first vs second attempt (P = .005), and first vs third attempt (P = .03). Following the first attempt, trainees experienced an average 63% reduction in blood loss and 59% reduction in TTH. In the quartile of most improved participants, average blood loss reduction was 1115 mL (84% reduction) and TTH of 259 s (84% reduction). There were no significant differences between trainees of varying postgraduate year or specialty. Average pre and postprocedural confidence scores were 1.38 and 3.16, respectively (P < .0001). All trainees reported model realism, which achieved mean face validity 4.82 ± 0.41 and content validity 4.88 ± 0.33.

CONCLUSION

The perfusion-based human cadaveric ICA injury model achieves high ratings of face and content validity across all levels of surgical trainees, and enables safe, realistic simulation for standardized skull base simulation and future curriculum development. Objective improvements in performance metrics may translate to improved patient outcomes.