bluuebunny/crossref_metadata_2025 huggingface dataset:
Granularity impact on hotspot formation and local chemistry in shocked nanostructured RDX
Authors: Bidault X. , Pineau N.
Published: December 2018

The nanostructuration of energetic materials results in interesting properties. In particular, the detonation of carbon-rich explosives leads to the formation of nanodiamonds, the size of which is linked to the initial size of the explosive nanograins. This correlation could come from the role played by the granularity in the shock properties, especially the local temperature, which could be enhanced when the shock front crosses the various interfaces and nanoporosities of the material. More generally, the granularity-dependent reactivity also concerns some aspects of the sensitivity of energetic materials and subsequent inhibition or safety issues. In order to investigate this hypothesis, we perform classical and reactive molecular dynamics shock-simulations on cyclotrimethylene trinitramine (RDX), a common high-explosive. We design various nanogranular structures using the body-centered-cubic stacking of nanoparticles shaped as Kelvin cells (truncated octahedra) with slightly-bumped faces. The nanograin size and the bump radius allow to independently control the porosity value and its nanostructure. We show that the global shock properties, especially the temperature, are sensitive to the porosity value but not to the nanograin size. The porosity nanostructure has a local impact, enhancing the temperature heterogeneities between the inter- and intra-grain regions by a few hundred degrees and slowing down the thermal homogenization. For a given porosity, the larger the nanograins, the larger and the hotter the hotspots. In such hotspots, the local chemistry is significantly modified, resulting in a larger reactivity with a quicker formation of some final products. We suggest that the quicker consumption of heteroatoms (namely, H, O, and N) along with higher local temperatures is likely to impact the formation process of solid carbonaceous phases.
Preferential host-guest coordination of nonactin with ammonium and hydroxylammonium
Authors: Martínez–Haya Bruno , Avilés–Moreno Juan Ramón , Gámez Francisco , Berden Giel , Oomens Jos
Published: December 2018

The biological activity of the macrocycle nonactin is intimately related to its ionophore properties and ability to act as a selective cation carrier. The competitive binding of small protonated amines constitutes a particularly key issue in the biochemistry of nonactin, which finds application in sensing and extraction technologies. In this study, isolated complexes of nonactin with ammonium and hydroxylammonium are investigated with infrared action spectroscopy and quantum chemical computations. The focus of the investigation is on the coordination achieved by the protonated guest with the oxygen atoms of either the oxolane groups or the carboxyl groups in the ester linkages of the macrocyle host and their relative contributions to the stability of the complexes. The experimental and computational data converge to a preferred coordination arrangement associated with a tight binding of the N—Hδ+ bonds with the oxolane groups. In the NH4+ complex, this results in a compact complex of S4 symmetry. In contrast, symmetry is disrupted in the NH3OH+ complex, as it incorporates a bifurcated coordination of the —OH bond with a carbonyl group and an oxolane group of the host, involving also a more stretched arrangement of the nonactin backbone. These gas-phase conformations are in agreement with the structures postulated for these complexes in condensed phases, from previous Raman and crystallographic experiments.
Skew Pieri algebras of the general linear group
Authors: Kim Sangjib , Lee Soo Teck , Wang Yi
Published: December 2018

Let V be an irreducible polynomial representation of the general linear group GLn=GLn(C) and let α1, …, αq be nonnegative integers less than or equal to n. We call a description of the irreducible decomposition of the tensor product V⊗Λα1(Cn)⊗⋯⊗Λαq(Cn) an iterated skew Pieri rule for GLn. In this paper, we define a family of complex algebras whose structure encodes an iterated skew Pieri rule for GLn, and we call these algebras iterated skew Pieri algebras. Our main goal is to construct a basis for each of these algebras thereby giving explicit highest weight vectors in the above tensor product.
Determination of full S-parameters of a low-loss two-port device from uncalibrated measurements
Authors: Hasar U. C.
Published: December 2018

A procedure has been proposed for the determination of full scattering (S-) parameters of a low-loss two-port device using uncalibrated waveguide measurements of four configurations (thru, non-reflecting line, device, and reflection-line with the device). It is shown that to uniquely determine forward and backward reflection S-parameters of the device, S-parameters of a reflecting line (reflection-symmetric or reflection-asymmetric) in series with the device should be used. We first validated our proposed method from simulated S-parameters and then extracted full S-parameters of three different two-port devices [waveguide cells partially loaded by low-loss dielectric samples—polyethylene, polyvinyl chloride, and alumina (with 99.5% concentration) samples] using symmetric and asymmetric reflecting lines. Next, we also compared the complex permittivities of the polyethylene and polyvinyl chloride samples inside two different devices using extracted S-parameters from our formalism with the complex permittivities of the same samples measured by a calibration-dependent method. A good agreement between measured and extracted complex permittivities is observed, demonstrating the accuracy of our proposed method. Finally, we carried out ten independent measurements to determine at each frequency the average and maximum and minimum values (thus changes from the average) of extracted full S-parameters of a low-loss two-port device to evaluate the total uncertainty in measuring these parameters by our method. We note from this analysis that if the S-parameters of a low-loss two-port device will be determined using a reflecting line with symmetric reflections, then attention should be paid in implementing a reflecting line with symmetric reflections since any deviation from the symmetric property of the reflecting line could increase the overall uncertainty.
Effect of the chemical environment of the DNA guanine quadruplex on the free energy of binding of Na and K ions
Authors: Sharawy Mahmoud , Consta Styliani
Published: December 2018

Guanine quadruplex (G-quadruplex) structures play a vital role in stabilizing the DNA genome and in protecting healthy cells from transforming into cancer cells. The structural stability of G-quadruplexes is greatly enhanced by the binding of monovalent cations such as Na+ or K+ into the interior axial channel. We computationally study the free energy of binding of Na+ and K+ ions to two intramolecular G-quadruplexes that differ considerably in their degree of rigidity and the presence or absence of terminal nucleotides. The goal of our study is two-fold. On the one hand, we study the free energy of binding every ion, which complements the experimental findings that report the average free energy for replacing Na+ with K+ ions. On the other hand, we examine the role of the G-quadruplex structure in the binding free energy. In the study, we employ all-atom molecular dynamics simulations and the alchemical transformation method for the computation of the free energies. To compare the cation-dependent contribution to the structural stability of G-quadruplexes, we use a two-step approach to calculate the individual free energy difference ΔG of binding two Na+ and two K+ to two G-quadruplexes: the unimolecular DNA d[T2GT2(G3T)3] (Protein Data Bank ID 2M4P) and the human telomeric DNA d[AGGG(TTAGGG)3] (PDB ID 1KF1). In contrast to the experimental studies that estimate the average free energy of binding, we find a varying difference of approximately 2–9 kcal/mol between the free energy contribution of binding the first and second cation, Na+ or K+. Furthermore, we found that the free energy of binding K+ is not affected by the chemical nature of the two quadruplexes. By contrast, Na+ showed dependency on the G-quadruplex structure; the relatively small size allows Na+ to explore larger configurational space than K+. Numerical results presented here may offer reference values for future design of cationic drug-like ligands that replace the metal ions in G-quadruplexes.
Third harmonic scattering in liquids
Authors: Shelton David P.
Published: December 2018

Third harmonic scattering (THS) from liquids has been observed and analyzed in several recent papers. It is considered to be analogous to second harmonic scattering (hyper-Rayleigh scattering) and to provide a means for measuring the second hyperpolarizability tensor of molecules in a liquid. However, the observed signal for a pure solvent is in fact mainly due to coherent third harmonic generation followed by Rayleigh scattering and direct incoherent THS (direct THS) makes only a small contribution (<2% for parallel polarized THS). This invalidates the internal reference method and the polarization analysis that has been applied for pure liquids. Theoretical comparison for the two processes, extensive experimental measurements for CCl4 liquid, SiO2 glass, and CCl2F2 gas and survey measurements for D2O, CDCl3, CD3CN, and (CD3)2SO liquid, are presented.
A centrifuge method to determine the solid–liquid phase behavior of eutectic mixtures
Authors: van den Bruinhorst Adriaan , Kollau Laura J. B. M. , Kroon Maaike C. , Meuldijk Jan , Tuinier Remco , Esteves A. Catarina C.
Published: December 2018

The centrifuge method is a novel, equilibrium-based, analytical procedure that allows the construction of solid–liquid phase diagrams of binary eutectic mixtures. In this paper, the development, optimization, and successful verification of the centrifuge method are described. Contrary to common dynamic analysis techniques—differential scanning calorimetry and hot-stage microscopy—the studied mixtures are equilibrated at constant temperature. Therefore, the mixtures do not need to be recrystallized from the melt during analysis. This offers a great advantage for mixtures that exhibit strong supercooling behavior rather than direct crystallization. The centrifuge method was verified by reproducing the binary eutectic phase behavior of both the nearly ideal biphenyl–bibenzyl system and the strongly non-ideal deep eutectic solvent (DES) urea–choline chloride, which is prone to supercooling. Hence, the centrifuge method offers an alternative route to common dynamic analysis techniques for the quantification of the liquid range of DESs and other binary eutectic mixtures.
Axisymmetric scalable magneto-gravitational trap for diamagnetic particle levitation
Authors: Houlton J. P. , Chen M. L. , Brubaker M. D. , Bertness K. A. , Rogers C. T.
Published: December 2018

We report on the design, construction, and use of axisymmetric magnetic traps for levitating diamagnetic particles. The magnetic traps each consist of two pole pieces passively driven by a neodymium iron boron (NdFeB) permanent magnet. The magnetic field configuration between the pole pieces combined with the earth’s gravitational field forms a 3D confining potential capable of levitating a range of diamagnetic substances, e.g., graphite powder, silica microspheres, and gallium nitride (GaN) powder and nanowires. Particles trap stably at atmosphere and in high-vacuum for periods up to weeks with lifetimes largely determined by choices made to actively destabilize the trap. We describe the principles of operation, finite element design, approximate closed-form results for design rules, and examples of operation of such traps.
Switching of biaxial synthetic antiferromagnets: A micromagentic study
Authors: Ackermann Michael S. , Emori Satoru
Published: December 2018

We simulate the switching behavior of nanoscale synthetic antiferromagnets (SAFs), inspired by recent experimental progress in spin-orbit-torque switching of crystal antiferromagnets. The SAF consists of two ferromagnetic thin films with in-plane biaxial anisotropy and interlayer exchange coupling. Staggered field-like Rashba spin-orbit torques from the opposite surfaces of the SAF induce a canted net magnetization, which triggers an orthogonal torque that drives 90° switching of the Néel vector. Such dynamics driven by the field-like spin-orbit torque allows for faster switching with increased Gilbert damping, without a significant detrimental increase of the threshold switching current density. Our results point to the potential of SAFs as model systems, based on simple ferromagnetic metals, to mimic antiferromagnetic device physics.
Rheological properties of super critical CO2 with CuO: Multi-scale computational modeling
Authors: Khaledialidusti Rasoul , Mishra Abhishek Kumar , Barnoush Afrooz
Published: December 2018

A multi-scale computational methodology based on the density functional theory and molecular dynamics has been used to investigate the rheological properties of super critical CO2 with CuO nano-particle (NP). Density functional theory which treats the electron density as the central variable has been used to explore the adsorption of CO2 molecules on the two most stable CuO surfaces [i.e., (111) and (011)] at absolute zero. The results of this theory would provide valuable information to make CuO NPs with the surface where the CO2 adsorption is maximum in order to have a stronger mono-layer of adsorbed CO2 molecules on the surface of the NP which is the most crucial factor in formation of a stable nanofluid. The results show that the CO2 molecule is adsorbed more strongly on the (011) surface with an adsorption energy of −99.06 kJ/mol compared to the (111) surface. A computational methodology based on molecular dynamics has been used to evaluate the enhancement of the rheological properties of the super-critical CO2 liquid based nanofluid at different temperatures and pressures. In this scale, first, the CO2 liquid has been modeled by employing the condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field potential and the fluid properties computed are in excellent agreement with the literature and experiment values. Second, the nanofluid has been modeled in order to study the enhancement of the fluid properties with the CuO NPs. The charged optimized many-body force field potential has been employed to consider the effect of the charge transferring between the NPs and liquid molecules and breaking of existing bonds and the formation of new bonds. The COMPASS force field potential is also employed for the interactions between CO2 molecules. The combination of these potentials is quite a new approach for the study of the super-critical (SC)-CO2 based nanofluid. The results show that the viscosity of the SC-CO2 is enhanced between 1.3 and 2.5 times under the temperature and pressure conditions studied.
Dissociation of CHD3 on Cu(111), Cu(211), and single atom alloys of Cu(111)
Authors: Gerrits Nick , Migliorini Davide , Kroes Geert-Jan
Published: December 2018

In order to model accurately reactions of polyatomic molecules with metal surfaces important for heterogeneous catalysis in industry, the Specific Reaction Parameter (SRP) approach to density functional theory has been developed. This approach has been shown to describe the dissociation of CHD3 on Ni(111), Pt(111), and Pt(211) with chemical accuracy. In this work, predictions have been made for the reaction of CHD3 on Cu(111) and Cu(211) using barriers, elbow plots, and ab initio molecular dynamics. Future experiments could hopefully prove the transferability of the SRP functional to systems in which methane reacts with flat and stepped surfaces of adjacent groups of the periodic table, by comparison with our predictions. Moreover, the effect of a so-called single atom alloy on the reactivity of methane is investigated by making predictions for CHD3 on Pt–Cu(111) and Pd–Cu(111). It is found that the reactivity is only increased for Pt–Cu(111) near the alloyed atom, which is not only caused by the lowering of the barrier height but also by changes in the dynamical pathway and reduction of energy transfer from methane to the surface.
Optically isolated millimeter-wave detector for the Toroidal Plasma Experiment
Authors: Baquero-Ruiz M. , Alberti S. , Chellaï O. , Furno I. , Goodman T. , Manke F. , Micheletti P. , Plyushchev G. , Skrivervik A. K.
Published: December 2018

We have designed and built an optically isolated millimeter-wave detection system to prevent interference from a nearby, powerful, 2.45 GHz microwave source in millimeter-wave propagation experiments in the TORoroidal Plasma EXperiment (TORPEX). A series of tests demonstrates excellent system noise immunity and the ability to observe effects that cannot be resolved in a setup using a bare Schottky diode detector.
Calculation of the water-octanol partition coefficient of cholesterol for SPC, TIP3P, and TIP4P water
Authors: Espinosa Jorge R. , Wand Charlie R. , Vega Carlos , Sanz Eduardo , Frenkel Daan
Published: December 2018

We present a numerical study of the relative solubility of cholesterol in octanol and water. Our calculations allow us to compare the accuracy of the computed values of the excess chemical potential of cholesterol for several widely used water models (SPC, TIP3P, and TIP4P). We compute the excess solvation free energies by means of a cavity-based method [L. Li et al., J. Chem. Phys. 146(21), 214110 (2017)] which allows for the calculation of the excess chemical potential of a large molecule in a dense solvent phase. For the calculation of the relative solubility (“partition coefficient,” log10Po/w) of cholesterol between octanol and water, we use the OPLS/AA force field in combination with the SPC, TIP3P, and TIP4P water models. For all water models studied, our results reproduce the experimental observation that cholesterol is less soluble in water than in octanol. While the experimental value for the partition coefficient is log10Po/w= 3.7, SPC, TIP3P, and TIP4P give us a value of log10Po/w = 4.5, 4.6, and 2.9, respectively. Therefore, although the results for the studied water models in combination with the OPLS/AA force field are acceptable, further work to improve the accuracy of current force fields is needed.
Theoretical analysis of spectral precision in spectroscopic single-molecule localization microscopy
Authors: Song Ki-Hee , Dong Biqin , Sun Cheng , Zhang Hao F.
Published: December 2018

Spectroscopic single-molecule localization microscopy (sSMLM) is a novel super-resolution imaging technology, which simultaneously records the nanoscopic location and the corresponding full emission spectrum of every stochastic single-molecule emission event. This spectroscopic imaging capability of sSMLM necessitates the establishment of a theoretical foundation of the newly introduced spectral precision and to guide the system design and optimization. Based on numerical simulation and analytical solution, we introduced such a theoretical model to analyze spectral precision by considering the main system parameters, including signal and background shot noises, readout noise, and the spectral calibration procedure. Using this model, we demonstrated the delicate balance among these parameters in achieving the optimal spectral precision and discovered that the best spectral precision can only be achieved at a particular system spectral dispersion. For example, with a given signal of 3000 photons and a readout noise of 2 e-, a system spectral dispersion of 1.6 nm/pixel is required for sSMLM to achieve the highest spectral precision of 1.31 nm.
Pressure-induced structural change and nucleation in liquid aluminum
Authors: Khan Salman Ali , Wang X. D. , Cao Q. P. , Zhang D. X. , Jiang J. Z.
Published: December 2018

The relationship between the atomic structure and dynamics of liquid aluminum (Al) has been studied at 1500 K as a function of pressure via ab initio molecular dynamics simulations. The origin of the structural evolution is unveiled by various techniques. The structure factor and the mean square displacement data indicate the fortuity of a crystalline-like phase at 25 GPa, first evolving into the metastable body-centered cubic-like local order, followed by face-centered cubic, which is different from the crystallization mechanism proposed for the liquid Al by Desgranges and Delhommelle [J. Chem. Phys. 127, 144509 (2007)]. The three-dimensional structural analysis demonstrates the concentration of distorted icosahedron-like clusters, e.g., Voronoi <0, 3, 6, 3> and <0, 2, 8, 2>, which are closely correlated with crystal nucleation and growth. Crystallization in the liquid Al is distinctly correlated with the bond orientational order (Q6) fluctuations, instead of density fluctuations, where the temperature or pressure comparison on the local atomic structure in the liquid Al and degree of crystallization is also elucidated. The electronic structure study reveals that at ambient pressure, some valence electrons are already localized, showing a strong tendency of electron pairing with each other in the interstitial regions.
Measuring displacement currents during fabrication of Mg/Si Schottky diodes due to band-bending evolution
Authors: Hagemann Ulrich , Huba Kornelia , Nienhaus Hermann
Published: December 2018

The generation of a rectifying metal-semiconductor contact forms a charge depletion layer in the semiconductor surface. The resulting space charge leads to a surface band bending and the formation of a Schottky barrier. The present study introduces an unconventional method to measure and monitor the surface band bending during metal atom deposition by recording the displacement current between the metal and the semiconductor. Magnesium atoms are evaporated at 130 K onto hydrogen-passivated p-Si(001) surfaces. During deposition, the time-dependent reverse current in the diode is detected. A sharp current peak of a few nA can be attributed to the displaced charge when the first monolayers of the Mg film are formed. The currents are proportional to the number of Mg atoms impinging onto the surface. Integrating the observed displacement currents over time yields the total space charge densities at the interface between 8 and 23 nC/cm2. This is in excellent agreement with the calculated value for a Schottky barrier of 0.5 eV and assuming flatband condition for hydrogen-passivated Si(001) surfaces.
Common microscopic structural origin for water’s thermodynamic and dynamic anomalies
Authors: Shi Rui , Russo John , Tanaka Hajime
Published: December 2018

Water displays a vast array of unique properties, known as water’s anomalies, whose origin remains subject to hot debate. Our aim in this article is to provide a unified microscopic physical picture of water’s anomalies in terms of locally favored structures, encompassing both thermodynamic and dynamic anomalies, which are often attributed to different origins. We first identify locally favored structures via a microscopic structural descriptor that measures local translational order and provide direct evidence that they have a hierarchical impact on the anomalies. At each state point, the strength of thermodynamic anomalies is directly proportional to the amount of locally favored structures, while the dynamic properties of each molecule depend on the local structure surrounding both itself and its nearest neighbors. To incorporate this, we develop a novel hierarchical two-state model. We show by extensive simulations of two popular water models that both thermodynamic and kinetic anomalies can be almost perfectly explained by the temperature and pressure dependence of these local and non-local versions of the same structural descriptor, respectively. Moreover, our scenario makes three unique predictions in supercooled water, setting it apart from other scenarios: (1) Presence of an “Arrhenius-to-Arrhenius” crossover upon cooling, as the origin of the apparent “fragile-to-strong” transition; (2) maximum of dynamic heterogeneity around 20 K below the Widom line and far above the glass transition; (3) violation of the Stokes-Einstein-Debye relation at ∼2Tg, rather than 1.2Tg typical of normal glass-formers. These predictions are verified by recent measurement of water’s diffusion at very low temperatures (point 1) and discoveries from our extensive simulations (points 2-3). We suggest that the same scenario may generally apply to water-like anomalies in liquids tending to form locally favored structures, including not only other important tetrahedral liquids such as silicon, germanium, and silica, but also metallic and chalcogenide liquids.
The Rb2 31Πg state: Observation and analysis
Authors: Arndt Phillip T. , Sovkov Vladimir B. , Ma Jie , Pan Xinhua , Beecher David S. , Tsai Jeng Y. , Guan Yafei , Lyyra A. Marjatta , Ahmed Ergin H.
Published: December 2018

This paper reports observations and analysis of the Rb2 31Πg state. A total of 323 rovibrational term values spanning the range of the rotational quantum number J = 7 through 77 and the vibrational quantum number v = 2 through 23 (about 1/3 of the potential well depth) were measured using the optical–optical double resonance technique. The term values are simulated within a model of a piece-wise multi-parameter potential energy function based on the generalized splines. This function not only enables a reproduction of the experimental data with a reasonable quality but also approximates the available ab initio function in its whole range with a uniform accuracy.
Selenium-iodide: A low melting point eutectic semiconductor
Authors: Voss L. F. , Murphy J. W. , Shao Q. , Henderson R. A. , Frye C. D. , Stoyer M. A. , Nikolic R. J.
Published: December 2018

Inorganic liquid semiconductors are of interest in harsh radiological environments, flexible electronics, and for direct printing of semiconductor devices. Many elemental and compound liquid semiconductors exist, although the lowest melting point is observed for Se at 221 °C. Recently, reports of liquid Se-S systems have shown betavoltaic and alphavoltaic power generation as a liquid with a reduced melting point of 105 °C. Here, we show the ability to depress the melting point to 57 °C by using equal atomic fractions of selenium and iodine while maintaining semiconducting behavior. A heterojunction structure using ITO and n-GaN as the contacts was selected based on chemical compatibility and predicted band lineups. Electrical and optical measurements were used to deduce the electronic and transport properties of the mixture.
The two faces of capacitance: New interpretations for electrical impedance measurements of perovskite solar cells and their relation to hysteresis
Authors: Jacobs Daniel A. , Shen Heping , Pfeffer Florian , Peng Jun , White Thomas P. , Beck Fiona J. , Catchpole Kylie R.
Published: December 2018

Perovskite solar cells are notorious for exhibiting transient behavior not seen in conventional inorganic semiconductor devices. Significant inroads have been made into understanding this fact in terms of rapid ion migration, now a well-established property of the prototype photovoltaic perovskite MAPbI3 and strongly implicated in the newer mixed compositions. Here, we study the manifestations of ion migration in frequency-domain small-signal measurements, focusing on the popular technique of Electrical Impedance Spectroscopy (EIS). We provide new interpretations for a variety of previously puzzling features, including giant photoinduced low-frequency capacitance and negative capacitance in a variety of forms. We show that these apparently strange measurements can be rationalized by the splitting of AC current into two components, one associated with charge-storage and the other with the quasi-steady-state recombination current of electrons and holes. The latter contribution to the capacitance can take either a positive or a negative sign and is potentially very large when slow, voltage-sensitive processes such as ion migration are at play. Using numerical drift-diffusion semiconductor models, we show that giant photoinduced capacitance, inductive loop features, and low-frequency negative capacitance all emerge naturally as consequences of ion migration via its coupling to quasi-steady-state electron and hole currents. In doing so, we unify the understanding of EIS measurements with the comparably well-developed theory of rate dependent current-voltage (I-V) measurements in perovskite cells. Comparing the two techniques, we argue that EIS is more suitable for quantifying I-V hysteresis than conventional methods based on I-V sweeps and demonstrate this application on a variety of cell types.
Generating symmetric graphs
Authors: Klickstein Isaac , Sorrentino Francesco
Published: December 2018

Symmetry in graphs which describe the underlying topology of networked dynamical systems plays an essential role in the emergence of clusters of synchrony. Many real networked systems have a very large number of symmetries. Often one wants to test new results on large sets of random graphs that are representative of the real networks of interest. Unfortunately, existing graph generating algorithms will seldom produce graphs with any symmetry and much less ones with desired symmetry patterns. Here, we present an algorithm that is able to generate graphs with any desired symmetry pattern. The algorithm can be coupled with other graph generating algorithms to tune the final graph’s properties of interest such as the degree distribution.
Maximizing the quality factor to mode volume ratio for ultra-small photonic crystal cavities
Authors: Wang Fengwen , Christiansen Rasmus Ellebæk , Yu Yi , Mørk Jesper , Sigmund Ole
Published: December 2018

Small manufacturing-tolerant photonic crystal cavities are systematically designed using topology optimization to enhance the ratio between the quality factor and mode volume, Q/V. For relaxed manufacturing tolerance, a cavity with a bow-tie shape is obtained which confines light beyond the diffraction limit into a deep-subwavelength volume. Imposition of a small manufacturing tolerance still results in efficient designs, however, with diffraction-limited confinement. Inspired by numerical results, an elliptic ring grating cavity concept is extracted via geometric fitting. Numerical evaluations demonstrate that for small sizes, topology-optimized cavities enhance the Q/V-ratio by up to two orders of magnitude relative to standard L1 cavities and more than one order of magnitude relative to shape-optimized L1 cavities. An increase in cavity size can enhance the Q/V-ratio by an increase in the Q-factor without a significant increase in V. Comparison between optimized and reference cavities illustrates that significant reduction of V requires big topological changes in the cavity.
High performance microsupercapacitors based on a nano-micro hierarchical carbon electrode by direct laser writing
Authors: Kwon Soongeun , Kim Geehong , Lim Hyungjun , Kim Jaegu , Choi Kee-Bong , Lee JaeJong
Published: December 2018

We have demonstrated a direct laser writing (DLW) process that uses a femtosecond laser to fabricate a nano-micro hierarchical structure for a large capacitance microsupercapacitor (MSC) electrode. By applying a two-photon polymerization-based DLW technique, a photoresist (PR) nano-pillar pattern was fabricated on a pre-defined PR interdigitated electrode (PR-IDE) pattern to form a nano-micro hierarchical structure. Carbon pyrolysis converted a PR-IDE with a nano-micro hierarchical structure to a PR derived carbon (PRC)-IDE while maintaining the aspect ratio of the pillar structure. The electrochemical performance of the PRC-MSC is improved by introducing the nano-pillar pattern to the PRC-IDE, resulting in larger areal capacitance of the as-fabricated PRC-IDE compared to the PRC-IDE with a micropattern only. The PRC-IDE with a nano-micro hierarchical structure in this study could be further applied as a backbone electrode structure for a high power pseudo-capacitor.
Measuring Lyapunov exponents of large chaotic systems with global coupling by time series analysis
Authors: Shimizu Taro P. , Takeuchi Kazumasa A.
Published: December 2018

Despite the prominent importance of the Lyapunov exponents for characterizing chaos, it still remains a challenge to measure them for large experimental systems, mainly because of the lack of recurrences in time series analysis. Here, we develop a method to overcome this difficulty, valid for highly symmetric systems such as systems with global coupling, for which the dimensionality of recurrence analysis can be reduced drastically. We test our method numerically with two globally coupled systems, namely, logistic maps and limit-cycle oscillators with global coupling. The evaluated exponent values are successfully compared with the true ones obtained by the standard numerical method. We also describe a few techniques to improve the accuracy of the proposed method.
Joseph Mark Gani 1924–2016
Authors: Seneta Eugene
Published: December 2018

Joe Gani, as he was universally known, was born in Cairo, Egypt, on 15 December 1924 and died in Canberra on 12 April 2016. A visionary leader, mentor, and brilliant organizer, he created the Journal of Applied Probability, and was Chief of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Division of Mathematics and Statistics. A distinguished academic career included posts at the Universities of Sheffield, Kentucky, California at Santa Barbara, and the Australian National University. His numerous research contributions are dominated by stochastic modelling, especially epidemic theory.
Preferences for rural specialist health care in the treatment of Parkinson's disease: exploring the role of community-based nursing specialists
Authors: Coady Veronica , Warren Narelle , Bilkhu Nancy , Ayton Darshini
Published: December 2018

People living with Parkinson’s disease (PWPD) in rural areas have limited access to local condition-specific care. This paper examines the healthcare preferences of PWPD living in rural areas and how a community-driven initiative to employ a movement disorder nurse (MDN) functioned to address barriers to health services access. A qualitative design facilitated an understanding of how interactions with the health system shaped PWPD and their carer’s experiences of living in a regional community. A total of 42 semi-structured interviews were conducted 6–9 months apart; 19 interviews with PWPD and 23 dyadic interviews. The findings support the contention that specialist care can be effectively delivered through allied health professionals in some settings. In particular, having access to a specialist MDN can cushion the effects of living with Parkinson’s disease in regional and rural areas where continuity of care and access to timely support is often difficult for people to find. The quality of social support provided by the MDN may increase people’s ability to cope in the face of an unpredictable disease course. This is consistent with prior research, which identified that a specialist nurse or allied health services for people living with chronic conditions is enhances quality of life.
Opportunities to observe and measure intangible inputs to innovation: Definitions, operationalization, and examples
Authors: Keller Sallie , Korkmaz Gizem , Robbins Carol , Shipp Stephanie
Published: December 2018

Measuring the value of intangibles is not easy, because they are critical but usually invisible components of the innovation process. Today, access to nonsurvey data sources, such as administrative data and repositories captured on web pages, opens opportunities to create intangibles based on new sources of information and capture intangible innovations in new ways. Intangibles include ownership of innovative property and human resources that make a company unique but are currently unmeasured. For example, intangibles represent the value of a company’s databases and software, the tacit knowledge of their workers, and the investments in research and development (R&D) and design. Through two case studies, the challenges and processes to both create and measure intangibles are presented using a data science framework that outlines processes to discover, acquire, profile, clean, link, explore the fitness-for-use, and statistically analyze the data. The first case study shows that creating organizational innovation is possible by linking administrative data across business processes in a Fortune 500 company. The motivation for this research is to develop company processes capable of synchronizing their supply chain end to end while capturing dynamics that can alter the inventory, profits, and service balance. The second example shows the feasibility of measurement of innovation related to the characteristics of open source software through data scraped from software repositories that provide this information. The ultimate goal is to develop accurate and repeatable measures to estimate the value of nonbusiness sector open source software to the economy. This early work shows the feasibility of these approaches.
Scientific prize network predicts who pushes the boundaries of science
Authors: Ma Yifang , Uzzi Brian
Published: December 2018

Scientific prizes confer credibility to persons, ideas, and disciplines, provide financial incentives, and promote community-building celebrations. We examine the growth dynamics and interlocking relationships found in the worldwide scientific prize network. We focus on understanding how the knowledge linkages among prizes and scientists’ propensities for prizewinning relate to knowledge pathways between disciplines and stratification within disciplines. Our data cover more than 3,000 different scientific prizes in diverse disciplines and the career histories of 10,455 prizewinners worldwide for over 100 years. We find several key links between prizes and scientific advances. First, despite an explosive proliferation of prizes over time and across the globe, prizes are more concentrated within a relatively small group of scientific elites, and ties among elites are highly clustered, suggesting that a relatively constrained number of ideas and scholars push the boundaries of science. For example, 64.1% of prizewinners have won two prizes and 13.7% have won five or more prizes. Second, certain prizes strongly interlock disciplines and subdisciplines, creating key pathways by which knowledge spreads and is recognized across science. Third, genealogical and coauthorship networks predict who wins multiple prizes, which helps to explain the interconnectedness among celebrated scientists and their pathbreaking ideas.
Molecular basis for the acid-initiated uncoating of human enterovirus D68
Authors: Liu Yue , Sheng Ju , van Vliet Arno L. W. , Buda Geeta , van Kuppeveld Frank J. M. , Rossmann Michael G.
Published: December 2018

Enterovirus D68 (EV-D68) belongs to a group of enteroviruses that contain a single positive-sense RNA genome surrounded by an icosahedral capsid. Like common cold viruses, EV-D68 mainly causes respiratory infections and is acid-labile. The molecular mechanism by which the acid-sensitive EV-D68 virions uncoat and deliver their genome into a host cell is unknown. Using cryoelectron microscopy (cryo-EM), we have determined the structures of the full native virion and an uncoating intermediate [the A (altered) particle] of EV-D68 at 2.2- and 2.7-Å resolution, respectively. These structures showed that acid treatment of EV-D68 leads to particle expansion, externalization of the viral protein VP1 N termini from the capsid interior, and formation of pores around the icosahedral twofold axes through which the viral RNA can exit. Moreover, because of the low stability of EV-D68, cryo-EM analyses of a mixed population of particles at neutral pH and following acid treatment demonstrated the involvement of multiple structural intermediates during virus uncoating. Among these, a previously undescribed state, the expanded 1 (“E1”) particle, shows a majority of internal regions (e.g., the VP1 N termini) to be ordered as in the full native virion. Thus, the E1 particle acts as an intermediate in the transition from full native virions to A particles. Together, the present work delineates the pathway of EV-D68 uncoating and provides the molecular basis for the acid lability of EV-D68 and of the related common cold viruses.
Skill discrepancies between research, education, and jobs reveal the critical need to supply soft skills for the data economy
Authors: Börner Katy , Scrivner Olga , Gallant Mike , Ma Shutian , Liu Xiaozhong , Chewning Keith , Wu Lingfei , Evans James A.
Published: December 2018

Rapid research progress in science and technology (S&T) and continuously shifting workforce needs exert pressure on each other and on the educational and training systems that link them. Higher education institutions aim to equip new generations of students with skills and expertise relevant to workforce participation for decades to come, but their offerings sometimes misalign with commercial needs and new techniques forged at the frontiers of research. Here, we analyze and visualize the dynamic skill (mis-)alignment between academic push, industry pull, and educational offerings, paying special attention to the rapidly emerging areas of data science and data engineering (DS/DE). The visualizations and computational models presented here can help key decision makers understand the evolving structure of skills so that they can craft educational programs that serve workforce needs. Our study uses millions of publications, course syllabi, and job advertisements published between 2010 and 2016. We show how courses mediate between research and jobs. We also discover responsiveness in the academic, educational, and industrial system in how skill demands from industry are as likely to drive skill attention in research as the converse. Finally, we reveal the increasing importance of uniquely human skills, such as communication, negotiation, and persuasion. These skills are currently underexamined in research and undersupplied through education for the labor market. In an increasingly data-driven economy, the demand for “soft” social skills, like teamwork and communication, increase with greater demand for “hard” technical skills and tools.
People use less information than they think to make up their minds
Authors: Klein Nadav , O’Brien Ed
Published: December 2018

Significance

People readily categorize things as good or bad, a welcome adaptation that enables action and reduces information overload. The present research reveals an unforeseen consequence: People do not fully appreciate this immediacy of judgment, instead assuming that they and others will consider more information before forming conclusions than they and others actually do. This discrepancy in perceived versus actual information use reveals a general psychological bias that bears particular relevance in today’s information age. Presumably, one hopes that easy access to abundant information fosters uniformly more-informed opinions and perspectives. The present research suggests mere access is not enough: Even after paying costs to acquire and share ever-more information, people then stop short and do not incorporate it into their judgments.
Bioenergy cropland expansion may offset positive effects of climate change mitigation for global vertebrate diversity
Authors: Hof Christian , Voskamp Alke , Biber Matthias F. , Böhning-Gaese Katrin , Engelhardt Eva Katharina , Niamir Aidin , Willis Stephen G. , Hickler Thomas
Published: December 2018

Climate and land-use change interactively affect biodiversity. Large-scale expansions of bioenergy have been suggested as an important component for climate change mitigation. Here we use harmonized climate and land-use projections to investigate their potential combined impacts on global vertebrate diversity under a low- and a high-level emission scenario. We combine climate-based species distribution models for the world’s amphibians, birds, and mammals with land-use change simulations and identify areas threatened by both climate and land-use change in the future. The combined projected effects of climate and land-use change on vertebrate diversity are similar under the two scenarios, with land-use change effects being stronger under the low- and climate change effects under the high-emission scenario. Under the low-emission scenario, increases in bioenergy cropland may cause severe impacts in biodiversity that are not compensated by lower climate change impacts. Under this low-emission scenario, larger proportions of species distributions and a higher number of small-range species may become impacted by the combination of land-use and climate change than under the high-emission scenario, largely a result of bioenergy cropland expansion. Our findings highlight the need to carefully consider both climate and land-use change when projecting biodiversity impacts. We show that biodiversity is likely to suffer severely if bioenergy cropland expansion remains a major component of climate change mitigation strategies. Our study calls for an immediate and significant reduction in energy consumption for the benefit of both biodiversity and to achieve the goals of the Paris Agreement.
Speleothem record of geomagnetic South Atlantic Anomaly recurrence
Authors: Trindade Ricardo I. F. , Jaqueto Plinio , Terra-Nova Filipe , Brandt Daniele , Hartmann Gelvam A. , Feinberg Joshua M. , Strauss Becky E. , Novello Valdir F. , Cruz Francisco W. , Karmann Ivo , Cheng Hai , Edwards R. Lawrence
Published: December 2018

The diminishing strength of the Earth’s magnetic dipole over recent millennia is accompanied by the increasing prominence of the geomagnetic South Atlantic Anomaly (SAA), which spreads over the South Atlantic Ocean and South America. The longevity of this feature at millennial timescales is elusive because of the scarcity of continuous geomagnetic data for the region. Here, we report a unique geomagnetic record for the last ∼1500 y that combines the data of two well-dated stalagmites from Pau d’Alho cave, located close to the present-day minimum of the anomaly in central South America. Magnetic directions and relative paleointensity data for both stalagmites are generally consistent and agree with historical data from the last 500 y. Before 1500 CE, the data adhere to the geomagnetic model ARCH3K.1, which is derived solely from archeomagnetic data. Our observations indicate rapid directional variations (>0.1°/y) from approximately 860 to 960 CE and approximately 1450 to 1750 CE. A similar pattern of rapid directional variation observed from South Africa precedes the South American record by 224 ± 50 y. These results confirm that fast geomagnetic field variations linked to the SAA are a recurrent feature in the region. We develop synthetic models of reversed magnetic flux patches at the core–mantle boundary and calculate their expression at the Earth’s surface. The models that qualitatively resemble the observational data involve westward (and southward) migration of midlatitude patches, combined with their expansion and intensification.
Dietary versatility of Early Pleistocene hominins
Authors: Lüdecke Tina , Kullmer Ottmar , Wacker Ulrike , Sandrock Oliver , Fiebig Jens , Schrenk Friedemann , Mulch Andreas
Published: December 2018

Significance

Clumped and stable isotope data of paleosol carbonate and fossil tooth enamel inform about paleoenvironments of Early Pleistocene hominins. Data on woodland- vs. grassland-dominated ecosystems, soil temperatures, aridity, and the diet of
Homo rudolfensis
and
Paranthropus boisei ca.
2.4 Ma show that they were adapted to C
3
resources in wooded savanna environments in relatively cool and wet climates in the Malawi Rift. In contrast, time-equivalent
Paranthropus
living in open and drier settings in the northern East African Rift relied on C
4
plants, a trend that became enhanced after 2 Ma, while southern African
Paranthropus
persistently relied mainly on C
3
resources. In its early evolutionary history,
Homo
already showed a high versatility, suggesting that Pleistocene
Homo
and
Paranthropus
were already dietary generalists.