bluuebunny/crossref_metadata_2025 huggingface dataset:
Association of Platelet-to-Lymphocyte Ratio and Neutrophil-to-Lymphocyte Ratio with the Risk of Thromboembolism and Mortality in Patients with Cancer
Authors: Grilz Ella , Posch Florian , Königsbrügge Oliver , Schwarzinger Ilse , Lang Irene , Marosi Christine , Pabinger Ingrid , Ay Cihan
Published: October 2018

Patients with cancer are at risk of developing venous and arterial thromboembolism (VTE and ATE). Elevated platelet-to-lymphocyte (PLR) and neutrophil-to-lymphocyte ratios (NLR) have been suggested as potential biomarkers for cancer-associated chronic inflammation, VTE and mortality. We investigated the association between PLR and NLR with VTE, ATE and mortality in patients with cancer. Within a prospective cohort study, we followed-up patients with newly diagnosed or progressing cancer for objectively confirmed, symptomatic VTE, ATE and death. Fine and Gray competing-risk regression was used to model the risk of VTE and ATE. Overall survival was analysed with Kaplan–Meier estimators. From 2003 to 2013, 1,469 patients with solid cancer (median age: 61 years; 47.3% female) were recruited and followed for 2 years. Overall, 128 (8.7%) patients developed VTE, 41 (2.8%) ATE and 643 (43.8%) patients died. The sub-distribution hazard ratios (SHRs) for VTE per doubling of PLR and NLR were 1.0 (95% confidence interval [CI]: 0.8–1.3, p = 0.899) and 1.2 (1.0–1.4, p = 0.059), respectively. For ATE, the SHR per doubling of PLR and NLR were 1.0 (0.7–1.5, p = 0.940) and 1.2 (0.9–1.6, p = 0.191), respectively. A higher PLR (hazard ratio [HR] per doubling = 1.5, 1.4–1.7, p < 0.001) and a higher NLR (HR per doubling = 1.5, 1.4–1.7, p < 0.001) were associated with an increased risk of mortality after adjusting for age, sex and cancer stage. There was no statistically significant association between NLR and VTE occurrence in patients with cancer. Neither PLR nor NLR were associated with the risk of ATE. Both elevated PLR and NLR were independently associated with a twofold increased risk of mortality.
Resonant interactions of rotational water waves in the equatorial f-plane approximation
Authors: Basu B. , Martin C. I.
Published: October 2018

We investigate here the resonance phenomenon in periodic unidirectional water waves in flows of constant vorticity governed by the equatorial f-plane approximation. The relevance of such water waves displaying a one dimensional wave vector is also underlined in the paper—in the context of equatorial capillary-gravity water waves—and serves as the basis for the resonance analysis which is carried out by means of dispersion relations for equatorial water waves that were quite recently derived [see the work of Constantin, Differ. Integr. Equations 26(3-4), 237–252 (2013) and Martin, Nonlinear Anal.: Theory, Methods Appl. 96, 1–17 (2014)]. We show that, while gravity water waves do not exhibit three-wave resonance, the four-wave resonance occurs irrespective of the vorticity.
Local martingales associated with Schramm-Loewner evolutions with internal symmetry
Authors: Koshida Shinji
Published: October 2018

We consider Schramm-Loewner evolutions (SLEs) with internal degrees of freedom that are associated with representations of affine Lie algebras, following group theoretical formulation of SLEs. We reconstruct the SLEs considered by Bettelheim et al. [Phys. Rev. Lett. 95, 251601 (2005)] and Alekseev et al. [Lett. Math. Phys. 97, 243–261 (2011)] in correlation function formulation. We also explicitly formulate stochastic differential equations on internal degrees of freedom for Heisenberg algebras and the affine sl2. Our formulation enables us to find several local martingales associated with SLEs with internal degrees of freedom from computation on a representation of an affine Lie algebra. Indeed, we formulate local martingales associated with SLEs with internal degrees of freedom described by Heisenberg algebras and the affine sl2. We also find an affine sl2 symmetry of a space of SLE local martingales for the affine sl2.
Differentiating resting brain states using ordinal symbolic analysis
Authors: Quintero-Quiroz Carlos , Montesano Luis , Pons Antonio J. , Torrent M. C. , García-Ojalvo Jordi , Masoller Cristina
Published: October 2018

Symbolic methods of analysis are valuable tools for investigating complex time-dependent signals. In particular, the ordinal method defines sequences of symbols according to the ordering in which values appear in a time series. This method has been shown to yield useful information, even when applied to signals with large noise contamination. Here, we use ordinal analysis to investigate the transition between eyes closed (EC) and eyes open (EO) resting states. We analyze two electroencephalography datasets (with 71 and 109 healthy subjects) with different recording conditions (sampling rates and the number of electrodes in the scalp). Using as diagnostic tools the permutation entropy, the entropy computed from symbolic transition probabilities, and an asymmetry coefficient (that measures the asymmetry of the likelihood of the transitions between symbols), we show that the ordinal analysis applied to the raw data distinguishes the two brain states. In both datasets, we find that, during the EC-EO transition, the EO state is characterized by higher entropies and lower asymmetry coefficient, as compared to the EC state. Our results thus show that these diagnostic tools have the potential for detecting and characterizing changes in time-evolving brain states.
On stability and instability of standing waves for the nonlinear Schrödinger equation with an inverse-square potential
Authors: Bensouilah Abdelwahab , Dinh Van Duong , Zhu Shihui
Published: October 2018

We consider the stability of standing waves for the focusing nonlinear Schrödinger equation with an inverse-square potential. Using the profile decomposition arguments, we show that in the L2-subcritical case, i.e., 0<α<4d, the sets of ground state standing waves are orbitally stable. In the L2-critical case, i.e., α=4d, we show that ground state standing waves are strongly unstable by blow-up.
The surface eroding thermocouple for fast heat flux measurement in DIII-D
Authors: Ren J. , Donovan D. , Watkins J. , Wang H. Q. , Rudakov D. , Murphy C. , McLean A. , Lasnier C. , Unterberg E. , Thomas D. , Boivin R.
Published: October 2018

A novel type of surface eroding thermocouple (SETC) has been tested and demonstrated in the small angle slot (SAS) divertor of DIII-D for fast local heat flux measurements. The thermojunction of the SETC is formed between two thin (10 μm) ribbons, which are filed over to create microfiber junctions. These thermocouples are able to be exposed directly to the plasma at surface temperatures exceeding 2000 °C and are capable of sub-10 ms time resolution. Before installation in SAS, the SETCs were exposed in the lower DIII-D divertor during L-mode and H-mode discharges, from which results are presented. In preliminary tests, SETCs proved to be a qualified diagnostic to accurately measure both the intra-edge localized mode (ELM) and inter-ELM heat flux during H-mode shots with high frequency ELMs (hundreds of Hz) and to resolve heat flux profiles during strike point sweeps. The heat fluxes measured by using SETCs are consistent with the heat fluxes measured by using IR cameras and Langmuir probes. These new diagnostic capabilities will complement the existing IR camera measurements and will be of particularly significant value to measure surface heat flux in the SAS divertor or other regions where the IR camera lacks line of sight.
Simulation, design, and first test of a multi-energy soft x-ray (SXR) pinhole camera in the Madison Symmetric Torus (MST)
Authors: Delgado-Aparicio L. F. , Wallace J. , Yamazaki H. , VanMeter P. , Reusch L. , Nornberg M. , Almagari A. , Maddox J. , Luethi B. , Rissi M. , Donath T. , Den Hartog D. , Sarff J. , Weix P. , Goetz J. , Pablant N. , Hill K. , Stratton B. , Efthimion P. , Takase Y. , Ejiri A. , Ono M.
Published: October 2018

A multi-energy soft x-ray pinhole camera has been designed and built for the Madison Symmetric Torus reversed field pinch to aid the study of particle and thermal-transport, as well as MHD stability physics. This novel imaging diagnostic technique combines the best features from both pulse-height-analysis and multi-foil methods employing a PILATUS3 x-ray detector in which the lower energy threshold for photon detection can be adjusted independently on each pixel. Further improvements implemented on the new cooled systems allow a maximum count rate of 10 MHz per pixel and sensitivity to the strong Al and Ar emission between 1.5 and 4 keV. The local x-ray emissivity will be measured in multiple energy ranges simultaneously, from which it is possible to infer 1D and 2D simultaneous profile measurements of core electron temperature and impurity density profiles with no a priori assumptions of plasma profiles, magnetic field reconstruction constraints, high-density limitations, or need of shot-to-shot reproducibility. The expected time and space resolutions will be 2 ms and <1 cm, respectively.
Prediction of SOC of lead-acid battery in pure electric vehicle based on BSA-RELM
Authors: Wu Zhongqiang , Shang Mengyao , Shen Dandan , Qi Songqi
Published: October 2018

The state of charge (SOC) of lead-acid batteries plays an important role in battery management systems. Aiming at the problem that the SOC of lead-acid batteries in pure electric vehicles cannot be measured directly, a novel algorithm based on a robust extreme learning machine (RELM) optimized by the bird swarm algorithm (BSA) is proposed in this paper. RELM overcomes the shortcoming that an extreme learning machine (ELM) cannot deal with outliers and improves the prediction accuracy of ELM. BSA is used to optimize the numbers of hidden layer nodes and the adjustment factors of RELM. The problem that the numbers of the hidden layer nodes and the adjustment factor are difficult to determine is solved, which can further improve the convergence speed of RELM and help to find the global optimal value. The main parameters which affect the SOC of batteries such as current, voltage, temperature, and internal resistance have been collected by the advanced vehicle simulation software ADVISOR to model and test. Simulation results show that compared to other algorithms such as back propagation neural network, radical basis function neural network, and fuzzy neural network, BSA-RELM has a higher prediction accuracy.
Motional Stark effect imaging first results on the DIII-D tokamak
Authors: Thorman Alex , Michael Clive , Howard John , Victor Brian , Holcomb Chris , Allen Steve
Published: October 2018

A motional Stark effect (MSE) imaging diagnostic was benchmarked against existing conventional MSE polarimeters on the DIII-D tokamak and delivered new capabilities for measuring the magnetic pitch angle from 2 neutral beams and on the high field side of DIII-D. Line integration across flux surfaces was considerable for the radial view utilised; nevertheless, the imaging MSE measurements from both beams were self-consistent and in close agreement with conventional MSE measurements. The ferroelectric liquid crystal waveplate used in the imaging polarimeter was discovered to have spatially non-uniform retardance; hence, it is necessary for the calibration source to replicate the ray paths of the neutral beam emission through the optical system.
Initial operation results of NE213 scintillation detector for time-resolved measurements on triton burnup in KSTAR
Authors: Jo Jungmin , Cheon MunSeong , Kim Junghee , Lim Soobin , Isobe M. , Ogawa K. , Nishitani T. , Park Seugil , Murata I. , Chung Kyoung-Jae , Hwang Y. S.
Published: October 2018

In time-resolved measurement for triton burnup in Korea Superconducting Tokamak Advanced Research (KSTAR) deuterium plasmas, an NE213 liquid scintillation detector was installed and operated during the 2017 KSTAR campaign. The detector is composed of an NE213 scintillator (50 mm in diameter and 10 mm in thickness) and a photomultiplier tube (PMT). The PMT anode signal was processed under a data acquisition system which contains a field programmable gate array circuit and pulse processing software that is capable of discriminating gamma-ray and neutron pulse signals. In order to determine an appropriate threshold level for the 14 MeV neutron signal resulting from triton burnup, the NE213 scintillation detector was calibrated by using d-d and d-t neutron generators at the National Fusion Research Institute and Intense 14 MeV Neutron Source Facility, OKTAVIAN, Osaka University, Japan. The detector was installed on KSTAR with a 10 mm thick soft-iron stray magnetic field shield and a radiation shield which consists of 100 mm thick lead blocks and 200 mm thick borated polyethylene blocks. A discrimination range for d-t neutron was determined based on test results from neutron generators and KSTAR. Data points selected from the discrimination range were consistent with the classical triton confinement characteristics. In conclusion, under condition of an input counting rate of 1.9 × 105 counts per second (CPS), the detector is able to measure triton burnup signals up to 500 CPS for various plasma parameters.
Initial beam emission spectroscopy diagnostic system on HL-2A tokamak
Authors: Ke R. , Wu Y. F. , McKee G. R. , Yan Z. , Jaehnig K. , Xu M. , Kriete M. , Lu P. , Wu T. , Morton L. A. , Qin X. , Song X. M. , Cao J. Y. , Ding X. T. , Duan X. R.
Published: October 2018

A beam emission spectroscopy system is being developed and deployed on the HL-2A tokamak to measure local low wavenumber (k⊥ρi < 1) density fluctuations by measuring the Doppler-shifted emission from a 50 kV deuterium heating neutral beam. High spatial resolution (Δr ≤ 1 cm, Δz ≤ 1.5 cm) measurements are achieved with customized in-vacuum optics. High frequency, high-gain preamplifiers sample the light intensity at a Nyquist frequency of 1 MHz and achieve a high S/N ratio via high optical throughput, low-noise preamplifiers, and high quantum efficiency photodiodes. A first set of 16 detector channels [configured in an 8 (radial) × 2 (poloidal) array] has been installed and tested at HL-2A, covering the radial range r/a = 0.8–1.1. The frequency and wavenumber spectra have been measured under different plasma conditions. Initial measurements have demonstrated the capability of measuring edge plasma density fluctuation spectra and the poloidal flow velocity fields with a high S/N ratio.
Simultaneous visualization of wall motion, beam propagation, and implosion symmetry on the National Ignition Facility (invited)
Authors: Izumi N. , Meezan N. B. , Johnson S. , Woodworth B. N. , Woods T. , Jones O. S. , Landen O. L. , Kroll J. J. , Vonhof S. , Nikroo A. , Jaquez J. , Kangas K. , Bailey C. , Hardy M. , Ehrlich R. , Ralph J. , Town R. Pj. , Bradley D. K. , Hinkel D. E. , Moore A. S. , Divol L. , Young C. , Moody J. D.
Published: October 2018

Achieving a symmetric implosion in National Ignition Facility indirect drive targets requires understanding and control of dynamic changes to the laser power transport in the hohlraum. We developed a new experimental platform to simultaneously visualize wall-plasma motion and dynamic laser power transport in the hohlraum and are using it to investigate correlations of these measurements with the imploded capsule symmetry. In a series of experiments where we made one single parameter variation, we show the value of this new platform in developing an understanding of laser transport and implosion symmetry. This platform also provides a new way to evaluate dynamic performance of advanced hohlraum designs.
Zeeman spectroscopy as a method for determining the magnetic field distribution in self-magnetic-pinch diodes (invited)
Authors: Patel S. G. , Johnston M. D. , Webb T. J. , Bennett N. L. , Welch D. R. , Gilgenbach R. M. , Cuneo M. E. , Kiefer M. L. , Leckbee J. J. , Mazarakis M. G. , Muron D. J. , Renk T. J. , Simpson S. C. , Doron R. , Biswas S. , Mikitchuk D. , Maron Y.
Published: October 2018

In the self-magnetic-pinch diode, the electron beam, produced through explosive field emission, focuses on the anode surface due to its own magnetic field. This process results in dense plasma formation on the anode surface, consisting primarily of hydrocarbons. Direct measurements of the beam’s current profile are necessary in order to understand the pinch dynamics and to determine x-ray source sizes, which should be minimized in radiographic applications. In this paper, the analysis of the C IV doublet (580.1 and 581.2 nm) line shapes will be discussed. The technique yields estimates of the electron density and electron temperature profiles, and the method can be highly beneficial in providing the current density distribution in such diodes.
Complexity and irreducibility of dynamics on networks of networks
Authors: Rydin Gorjão Leonardo , Saha Arindam , Ansmann Gerrit , Feudel Ulrike , Lehnertz Klaus
Published: October 2018

We study numerically the dynamics of a network of all-to-all-coupled, identical sub-networks consisting of diffusively coupled, non-identical FitzHugh–Nagumo oscillators. For a large range of within- and between-network couplings, the network exhibits a variety of dynamical behaviors, previously described for single, uncoupled networks. We identify a region in parameter space in which the interplay of within- and between-network couplings allows for a richer dynamical behavior than can be observed for a single sub-network. Adjoining this atypical region, our network of networks exhibits transitions to multistability. We elucidate bifurcations governing the transitions between the various dynamics when crossing this region and discuss how varying the couplings affects the effective structure of our network of networks. Our findings indicate that reducing a network of networks to a single (but bigger) network might not be accurate enough to properly understand the complexity of its dynamics.
Magnetoresistance, magnetic, and dielectric properties of LuFe2O4 prepared by ebeam-assisted solid state reaction
Authors: Rai R. C. , Pawlak J. , Hinz J. , Pascolini M. , DeMarco M.
Published: October 2018

We present structural, magnetoresistance, magnetic, Mössbauer, and dielectric properties of polycrystalline LuFe2O4 prepared by an electron-beam assisted solid state reaction. The x-ray diffraction pattern shows the single phase LuFe2O4 sample, and the ferrimagnetic transition temperature is measured at 240 K, followed by the two low-temperature transitions at 210 K and 140 K, respectively. The magnetic properties including the M-H hysteresis loops exhibit a strong temperature dependence and possibly indicate that LuFe2O4 enters a spin-glass state below 100 K. The iron Mössbauer measurement at 300 K indicates two Fe sites. The resistivity follows Mott’s variable-range hopping model, ρ∝exp(T0/T)1/4, indicating the electron hopping between Fe2+ and Fe3+. The magnetoresistance effects up to 2.5% at 5 T in the ferrimagnetic state were observed, and the effects could be caused by the field-induced changes in the electron hopping processes. The frequency-dependent complex dielectric constant has been found to be strongly influenced by the contact effects, and the intrinsic ferroelectricity of LuFe2O4 could not be ascertained.
Roughening of GaN homoepitaxial surfaces due to step meandering and bunching instabilities and their suppression in hydride vapor phase epitaxy
Authors: Fujikura Hajime , Konno Taichiro
Published: October 2018

In this letter, we have shown that well-known surface instabilities in crystal growth, i.e., in-phase step meandering and step bunching, are the main causes of surface roughening of GaN homoepitaxial layers on vicinal +c-oriented GaN substrates. Both instabilities were effectively suppressed in hydride vapor phase epitaxy (HVPE) under appropriate conditions, which produced highly smooth as-grown surfaces suitable for reproducible device fabrication. Wavy surface morphologies, often observed in homoepitaxial GaN layers grown not only by HVPE but also by metal-organic chemical vapor deposition (MOCVD), were found to be covered by an array of meandered bunched steps consisting of m- and a-oriented sections. Because the bunched steps meandered in an in-phase fashion, facets consisting of m- and a-oriented bunched steps formed narrow macro-steps and wide macro-terraces, respectively, leading to the formation of ridges and grooves in-between the facets. Although the use of a substrate with large off-angles (≥0.4°) effectively suppressed the step meandering, i.e., wavy surface morphology, it induced a strong tendency for step bunching. Only growth on surfaces having relatively small off-angles (0.25°), under conditions providing large degrees of adatom desorption, i.e., at high temperatures or low V/III-ratios, suppressed both the meandering and bunching instabilities simultaneously and produced highly smooth as-grown surfaces. The use of the HVPE method seems better than the use of the MOCVD method in this strategy to increase the surface flatness of GaN homoepitaxial layers because it can maintain a sufficiently high growth rate even with a large degree of adatom desorption.
A portable low-power integrated current and temperature laser controller for high-sensitivity gas sensor applications
Authors: Li Ning , Qiu Xuanbing , Wei Yongbo , Zhang Enhua , Wang Jianshuai , Li Chuanliang , Peng Ying , Wei Jilin , Meng Huiyan , Wang Gao , Zang Zhenzhong
Published: October 2018

A low-noise, low power, high modulation-bandwidth design integrated laser current and temperature driver with excellent long-term stability is described. The current driver circuit is based on the Hall-Libbrecht design. A high sensitivity and a stable driver current were obtained using a differential amplifier and an integral amplifier. The set-point voltage for the current driver came from an ultra-compact, ultra-low temperature coefficient voltage reference chip or the digital to analog convertor output of a microcontroller or a modulation signal. An integral temperature chip, referred to as ADN8834, was used to drive the thermoelectric cooler controller of the distributed feedback (DFB) laser. The internal amplifier acquired the feedback current of the temperature sensor. The proportional-integral-derivative parameters such as proportion, integration, and derivative were set by external resistors. The short- and long-term stability and linearity of the developed laser driver were tested using a DFB laser with a central wavelength of 6991 cm−1. The laser driver was validated for high-sensitivity gas sensing of CO2 and C2H2 via a laser absorption spectroscopy experiment. The limits of detection were less than 11.5 ppm and 0.124 ppm for CO2 and C2H2, respectively. Direct absorption measurements and the 1-f and 2-f demodulation signals confirmed the capabilities of the proposed laser driver system in high-sensitivity gas sensing applications. The driver unit can readily be accommodated into many portable laser sensing devices for industrial applications.
Precisely controllable n-type doping in MoTe2 field effect transistors by hydrazine treatment
Authors: Chen Wenjie , Liang Renrong , Wang Jing , Xu Jun
Published: October 2018

An accurate and controllable n-type doping method for MoTe2 field effect transistors is developed by hydrazine treatment. It is shown that hydrazine molecules are absorbed physically without a new substance being formed, as determined by X-ray photoelectron spectroscopy measurements. The conduction type, electron concentrations, and minimum conductivity points in the transfer characteristics could be modulated precisely for a wide range by varying the concentration of hydrazine solution. Compared to pristine MoTe2 control devices, the electron concentrations are changed from 9.67 × 1011 cm−2 to 3.46 × 1012 cm−2 in the n-type regime, while the electron current on/off ratio is increased from 104 to 106 after 5 wt. % of hydrazine treatment. It is also interesting to observe that the ambipolar window increases almost linearly as the device temperature is reduced from 260 K to 5 K. The effective Schottky barrier heights for electrons in hydrazine treated MoTe2 field-effect transistors are extracted and found to be lower than 0.024 eV, indicating that the thermionic emission is not dominated. Furthermore, a lateral MoTe2 p–n junction with a rectification ratio higher than 103 and an ideality factor of around 1.66 is demonstrated through selective doping. This developed unique method of n-type doping and p-n junction creates an opportunity to fabricate high performance functional devices based on 2D layered materials.
Gradings on the real form e6,−14
Authors: Draper Cristina , Guido Valerio
Published: October 2018

Six fine gradings on the real form e6,−14 are described, precisely those ones coming from fine gradings on the complexified algebra. The universal grading groups are Z23×Z32, Z26, Z×Z24, Z27, Z×Z25, and Z2×Z23.
Perspective: Crossing the Widom line in no man’s land: Experiments, simulations, and the location of the liquid-liquid critical point in supercooled water
Authors: Hestand Nicholas J. , Skinner J. L.
Published: October 2018

The origin of liquid water’s anomalous behavior continues to be a subject of interest and debate. One possible explanation is the liquid-liquid critical point hypothesis, which proposes that supercooled water separates into two distinct liquids at low temperatures and high pressures. According to this hypothesis, liquid water’s anomalies can be traced back to the critical point associated with this phase separation. If such a critical point actually exists, it is located in a region of the phase diagram known as No Man’s Land (NML), where it is difficult to characterize the liquid using conventional experimental techniques due to rapid crystallization. Recently, however, experimentalists have managed to explore NML near the proposed location of the Widom line (i.e., the Kanno-Angell line), thereby providing valuable information concerning the liquid-liquid critical point hypothesis. In this perspective, we analyze these experimental results, in conjunction with molecular dynamics simulations based on the E3B3 water model and discuss their implications for the validity of the liquid-liquid critical point hypothesis and the possible location of water’s second critical point.
Nonlinear gyrokinetic particle simulation of dissipative trapped electron mode
Authors: Zhao C. , Xiao Y.
Published: October 2018

Electron turbulence induced by the trapped electron mode has been widely studied. The dissipative trapped electron mode (DTEM) is an important candidate for tokamak edge turbulence. Nonlinear gyrokinetic particle simulations based on edge parameters are carried out to investigate the collisional effects on the nonlinear transport of DTEM turbulence. It is found that the collisions can induce a low level radially inward electron transport for the DTEM turbulence, which is closely related to the phase difference between the radial turbulent motion and perturbed density fluctuation induced by collisional dissipation. We observe an inverse spectral cascade of the turbulence during the nonlinear DTEM saturation, which is caused by quasimode scattering induced by trapped electrons and important for determining the magnitude of turbulent transport. The nonlinear transport of DTEM is found to be inversely proportional to the collisional frequency by gyrokinetic simulation, which is consistent with the prediction of quasilinear theory.
Measurement and multilayer model of cooling of gold nanoparticles: Transient thermoreflectance experiments and multilayer analytical modeling
Authors: Green Brian G. , Budy Stephen M. , Reed Scott M. , Siemens Mark E.
Published: October 2018

We derive an analytical model of diffusive thermal transport in multilayer structures of spherical symmetry and apply it to transient thermoreflectance measurements of gold nanoparticles embedded in a polymer matrix. This multilayer approach significantly improves the quantitative measurement of material thermal properties, in comparison with single-layer methods. The model adapts the typical planar transfer matrix model to a spherical geometry, and we apply it to transient thermoreflectance (TTR) experiments on gold nanoparticles embedded in a polymer matrix, to published TTR data for aqueous platinum nanoparticles, and also to example systems of aqueous gold and platinum nanoparticles. We measure a thermal boundary conductance value of 410MW/m2K at the nanoparticle gold/polymer interface. The sensitivity of the TTR signal to system thermal properties is predicted as a function of the particle/matrix thermal boundary resistance (TBR), and we discuss the differentiation of TBR and capping layer effects on a TTR signal.
Orbital-free approximations to the kinetic-energy density in exchange-correlation MGGA functionals: Tests on solids
Authors: Tran Fabien , Kovács Péter , Kalantari Leila , Madsen Georg K. H. , Blaha Peter
Published: October 2018

A recent study of Mejia-Rodriguez and Trickey [Phys. Rev. A 96, 052512 (2017)] showed that the deorbitalization procedure (replacing the exact Kohn-Sham kinetic-energy density by an approximate orbital-free expression) applied to exchange-correlation functionals of the meta-generalized gradient approximation (MGGA) can lead to important changes in the results for molecular properties. For the present work, the deorbitalization of MGGA functionals is further investigated by considering various properties of solids. It is shown that depending on the MGGA, common orbital-free approximations to the kinetic-energy density can be sufficiently accurate for the lattice constant, bulk modulus, and cohesive energy. For the bandgap, calculated with the modified Becke-Johnson MGGA potential, the deorbitalization has a larger impact on the results.
Study on edge localized mode during plasma vertical swing in HL-2A tokamak
Authors: Wu N. , Chen S. Y. , Mou M. L. , Tang C. J. , Song X. M. , Yang Z. C. , Yu D. L. , Xu J. Q. , Jiang M. , Ji X. Q. , Wang S. , Li B. , Liu L. ,   HL-2A Team
Published: October 2018

An experiment on edge localized modes (ELMs) during the vertical swing is performed in HL-2A tokamak. ELM mitigation is observed when the plasma moves upward. The plasma column expands accompanied by a decrease in both lower triangularity and the absolute value of local magnetic shear at the outer mid-plane during the upward moving. The critical pressure gradient in pedestal is reduced for the mitigating case according to the linear simulation based on peeling-ballooning theory. The physics of the ELM crash process is also explored through nonlinear simulation. For the mitigating case, small current drive for low-n modes and a weak ion diamagnetic effect on high-n modes lead to a higher dominant mode and a wider growth rate spectrum, which result in weak turbulence transport and a small ELM size.
Sub-Doppler slit jet infrared spectroscopy of astrochemically relevant cations: The NH stretching mode in ND3H+
Authors: Chang Chih-Hsuan , Scrape Preston G. , Nesbitt David J.
Published: October 2018

High-resolution rotationally resolved spectra of the N–H stretch vibrational mode (ν1) of jet-cooled ND3H+ ions are collected and analyzed in a sub-Doppler slit-jet infrared spectrometer. The isotopomeric ammonium ions are generated by proton transfer from H3+ to ND3 in a discharge of an ND3/H2 gas mixture, whereby the slit jet expansion cools the nascent ND3H+ ions into lower rotational states. Rotational assignments are confirmed by four-line combination differences that agree to within the spectrometer precision (9 MHz). Based on precision two-line ground-state combination differences and a symmetric top Hamiltonian, the B, DJ, and DJK rotational constants for the ground vibrational state of ND3H+ are determined with high precision for the first time. Approximate rotational constants for the ν1 excited state are also determined, with a band origin at 3316.8425(19) cm−1 and in remarkable (∼0.1 cm−1) agreement with high level anharmonic theoretical predictions by Guo and co-workers [J. Phys. Chem. A, 120, 2185 (2016)]. Our results allow us to predict several low-J pure rotational transitions of ND3H+, which we hope will support future studies of this important ion in laboratory and astronomical rotational spectroscopy.
Torsional splitting and the four-fold barrier to internal rotation: The rotational spectra of vinylsulfur pentafluoride
Authors: Orellana W. , Stephens Susanna L. , Pringle Wallace C. , Groner Peter , Novick Stewart E. , Cooke S. A.
Published: October 2018

Vinylsulfur pentafluoride (VSPF), a molecule with a four-fold internal rotor, —SF4, has been studied with high resolution Fourier transform microwave spectroscopy. We believe that this is the first report of resolved four-fold internal rotation. As such, we have presented the tools needed to understand and analyze such a problem. These include debugging the ERHAM computer program necessary to fit the spectra and the free rotor to high barrier correlation diagram necessary to understand the torsional states of the four-fold rotor. The A, E, and B torsional state rotational transitions are well resolved and assigned. Spectroscopic transitions of four isotopologues of VSPF, H2C=CH—SF5, the normal isotopologue, and the singly substituted 34S and 13C isotopologues were measured and assigned. Contrary to expectation, the A torsional state could not be fit with only a semi-rigid Hamiltonian. The barrier to internal rotation, V4, is found to be 227 cm−1. Ab initio calculations at the MP2 aug-cc-pVQZ level of theory and basis set were performed and the results of this calculation are compared to our experimental results.
Anharmonic vibrational spectroscopy of polycyclic aromatic hydrocarbons (PAHs)
Authors: Mulas Giacomo , Falvo Cyril , Cassam-Chenaï Patrick , Joblin Christine
Published: October 2018

While powerful techniques exist to accurately account for anharmonicity in vibrational molecular spectroscopy, they are computationally very expensive and cannot be routinely employed for large species and/or at non-zero vibrational temperatures. Motivated by the study of Polycyclic Aromatic Hydrocarbon (PAH) emission in space, we developed a new code, which takes into account all modes and can describe all infrared transitions including bands becoming active due to resonances as well as overtone, combination, and difference bands. In this article, we describe the methodology that was implemented and discuss how the main difficulties were overcome, so as to keep the problem tractable. Benchmarking with high-level calculations was performed on a small molecule. We carried out specific convergence tests on two prototypical PAHs, pyrene (C16H10) and coronene (C24H12), aiming at optimising tunable parameters to achieve both acceptable accuracy and computational costs for this class of molecules. We then report the results obtained at 0 K for pyrene and coronene, comparing the calculated spectra with available experimental data. The theoretical band positions were found to be significantly improved compared to harmonic density functional theory calculations. The band intensities are in reasonable agreement with experiments, the main limitation being the accuracy of the underlying calculations of the quartic force field. This is a first step toward calculating moderately high-temperature spectra of PAHs and other similarly rigid molecules using Monte Carlo sampling.
Interfacial energy band and phonon scattering effect in Bi2Te3-polypyrrole hybrid thermoelectric material
Authors: Kim Cham , Baek Ju Young , Lopez David Humberto , Kim Dong Hwan , Kim Hoyoung
Published: October 2018

We hybridized n-type Bi2Te3 with an inexpensive and abundantly available conducting polymer, polypyrrole, to obtain a bulk-structured hybrid material in which the interfacial energy band and the phonon scattering effects should occur at the interface of the two components. The obtained hybrid material inevitably exhibited a lower electrical conductivity than pristine Bi2Te3, which may be attributable to carrier scattering at the interfacial energy barrier. However, the hybrid material completely compensated for this loss in electrical conductivity with a significant increase in the Seebeck coefficient, and thus it retained the power factor with no loss. In addition, the hybrid material displayed a much lower thermal conductivity than pristine Bi2Te3 owing to the phonon scattering effect. The hybrid material exhibited significant decoupling of the electrical and thermal properties, thus affording state-of-the-art figures of merit (ZT ∼ 0.98 at 25 °C, ZTmax ∼ 1.21 at 100 °C, and ZTave ∼ 1.18 at 50–150 °C) that exceed those of most of the previously reported n-type Bi2Te3 or Bi2(Te,Se)3 materials.
Toward the theory of the Yukawa potential
Authors: del Valle J. C. , Nader D. J.
Published: October 2018

Using three different approaches Perturbation Theory (PT), the Lagrange Mesh Method (LMM), and the variational method, we study the low-lying states of the Yukawa potential. First orders of PT, in powers of the screening parameter, are calculated in the framework of the non-linearization procedure. It is found that the Padé approximants to PT series together with the LMM provide highly accurate values of energy and the positions of the radial nodes of the wave function. The most accurate results, at present, of the critical screening parameters for some low-lying states and the first coefficients in the expansion of the energy at the critical parameter are presented. A locally accurate and compact trial function for the eigenfunctions of the low-lying states is discovered. This function used as a zeroth order entry in PT leads to energies as precise as those of Padé approximants and LMM. Finally, a compact analytical expression for the energy, that reproduces at least 6 decimal digits in the entire physical range of the screening parameter, is found.
Plasma polarization grating for circularly polarized high-order harmonic generation
Authors: Xie Duan , Ye Weimin , Jiao Jinlong , Zhang Shijie , Zhao Na , Zhou Hongyu , Zhuo Hongbin
Published: October 2018

Polarization grating (PG) is a kind of optical element based on the Pancharatnam-Berry phase, providing a unique capability of manipulating the polarization properties of output beams [Bomzon et al., Opt. Lett. 27, 1141–1143 (2002) and Oh and Escuti, Opt. Lett. 33, 2287–2289 (2008)]. Here, we extend this concept into the nonlinear domain of high-order harmonic generation from the laser-solid interaction. Through theoretical analysis and numerical simulations, we proposed a scheme of two non-collinear relativistic lasers of opposite handedness interacting with a solid target to generate angularly isolated, circularly polarized harmonics of both left and right handedness simultaneously. The physical mechanism was described as the confluence of PG and relativistically oscillating mirror, which can be defined as a new mechanism: “relativistically oscillating polarization grating mechanism.” This work provides a useful method for developing bright, near-monochromatic, short-wavelength radiation sources with desirable polarization for a broad range of applications.
Communication: Nucleation rates of supersaturated aqueous NaCl using a polarizable force field
Authors: Jiang Hao , Debenedetti Pablo G. , Panagiotopoulos Athanassios Z.
Published: October 2018

In this work, we use molecular dynamics simulations with a polarizable force field, namely, the modified AH/BK3 model [J. Kolafa, J. Chem. Phys. 145, 204509 (2016)], in combination with the forward flux sampling technique, to calculate the rates of homogeneous nucleation of NaCl from supersaturated aqueous solutions at 298 K and 1 bar. A non-polarizable model that reproduces the experimental equilibrium solubility {AH/TIP4P-2005 of Benavides et al. [J. Chem. Phys. 147, 104501 (2017)]} is also used for comparison. Nucleation rates calculated from the polarizable force field are found to be in good agreement with experimental measurements, while the non-polarizable model severely underestimates the nucleation rates. These results, in combination with our earlier study of a different non-polarizable force field [H. Jiang et al., J. Chem. Phys. 148, 044505 (2018)], lead to the conclusion that nucleation rates are sensitive to the details of force fields, and a good representation of nucleation rates may not be feasible using available non-polarizable force fields, even if these reproduce the equilibrium salt solubility. Inclusion of polarization could be important for an accurate prediction of nucleation rates in salt solutions.
Communication: The pole structure of the dynamical polarizability tensor in equation-of-motion coupled-cluster theory
Authors: Nanda Kaushik D. , Krylov Anna I. , Gauss Jürgen
Published: October 2018

In this letter, we investigate the pole structure of dynamical polarizabilities computed within the equation-of-motion coupled-cluster (EOM-CC) theory. We show, both theoretically and numerically, that approximate EOM-CC schemes such as, for example, the EOM-CC singles and doubles model exhibit an incorrect pole structure in which the poles that reflect the excitations from the target state (i.e., the EOM-CC state) are supplemented by artificial poles due to excitations from the CC reference state. These artificial poles can be avoided by skipping the amplitude response and reverting to a sum-over-states formulation. While numerical results are generally in favor of such a solution, its major drawback is that this scheme violates size extensivity.
A coupled pseudoforce model for quantum plasmon excitations
Authors: Akbari-Moghanjoughi M.
Published: October 2018

A coupled nonlinear pseudoforce system is derived from hydrodynamic equations for the nonlinear electron plasma oscillations in an electron-ion plasma with arbitrarily degenerate electron fluid in a background fixed ion potential. The dynamics of the fully nonlinear electron plasma excitations are studied using this generalized coupled pseudoforce model including the damping and driving pseudoforce elements. The fully nonlinear plasma oscillations are shown to be of quite different nature in the extreme classical and quantum limits. In particular, high frequency quantum oscillations due to electron tunneling effect modulates the ordinary large amplitude low frequency periodic Langmuir excitations in the quantum plasma regime. It is shown that such characteristic quantum oscillations appear due to the electron wavefunction overlap which also appear on the quantum shock wave structures. It is found that the stimulation of dense plasmas with the driving frequency matching that of characteristic quantum oscillations leads to the chaotic behavior of the electron fluid. The presented coupled pseudoforce theory can be used to investigate a large number of interesting nonlinear phenomena such as the quantum electron fluid chaos and turbulence, autoresonance phenomenon, quantum harmonic generation, nonlinear resonances, and bistability of quantum electron plasma oscillations.
Systematic revision and phylogenetic reassessment of the centipede genera Rhysida Wood, 1862 and Alluropus Silvestri, 1912 (Chilopoda: Scolopendromorpha) in Southeast Asia, with further discussion of the subfamily Otostigminae
Authors: Siriwut Warut , Edgecombe Gregory D. , Sutcharit Chirasak , Tongkerd Piyoros , Panha Somsak
Published: October 2018

Phylogenetic relationships of two morphologically similar scolopendrid genera, Rhysida Wood, 1862, and Alluropus Silvestri, 1912, were investigated based on broad-scale taxonomic sampling from SE Asia, India and Australia. Morphological revision and molecular phylogenetics using three loci validate seven Rhysida species in SE Asia and Australia: R. lithobioides (Newport, 1845), R. longipes (Newport, 1845), R. immarginata (Porat, 1876), R. nuda (Newport, 1845), R. carinulata (Haase, 1887), R. singaporiensis Verhoeff, 1937 and R. polyacantha Koch, 1985. The nominal SE Asian species R. leviventer Attems, 1953 and R. marginata Attems, 1953 are placed in junior subjective synonymy with R. lithobioides and Alluropus calcaratus (Pocock, 1891), respectively. The monotypic genus Alluropus is redescribed, molecular phylogeny recovering it nesting together with Indo-Australian Rhysida. Taxonomic revision reassigned R. calcarata Pocock, 1891 to Alluropus based on its morphological and molecular similarity to the type, A. demangei Silvestri, 1912, the differences between putative species being sexual variation. Two morphologically distinct allopatric populations of A. calcaratus, comb. nov. (= A. demangei, syn. nov.) were found in the Indochina subregion. Phylogenetic relationships in Otostigminae remain unsettled because clades within several genera lack significant support, although Rhysida consistently falls into two clades that are not each other’s closest relative.
Ecological speciation in darkness? Spatial niche partitioning in sibling subterranean spiders (Araneae : Linyphiidae : Troglohyphantes)
Authors: Mammola Stefano , Arnedo Miquel A. , Pantini Paolo , Piano Elena , Chiappetta Nicolò , Isaia Marco
Published: October 2018

Speciation in subterranean habitats is commonly explained as the result of divergent selection in geographically isolated populations; conversely, the contribution of niche partitioning in driving subterranean species diversification has been rarely quantified. The present study integrated molecular and morphological data with a hypervolume analysis based on functional traits to investigate a potential case of parapatric speciation by means of niche differentiation in two sibling spiders inhabiting contiguous subterranean habitats within a small alpine hypogean site. Troglohyphantes giachinoi, sp. nov. and T. bornensis are diagnosed by small details of the genitalia, which are likely to be involved in a reproductive barrier. Molecular analysis recovered the two species as sister, and revealed a deep genetic divergence that may trace back to the Messinian (~6 million years ago). The hypervolume analysis highlighted a marginal overlap in their ecological niches, coupled with morphological character displacement. Specifically, T. giachinoi, sp. nov. exhibits morphological traits suitable for thriving in the smaller pores of the superficial network of underground fissures (Milieu Souterrain Superficiel, MSS), whereas T. bornensis shows a greater adaptation to the deep subterranean habitat. Our results suggest that different selective regimes within the subterranean environment, i.e. deep caves v. MSS, may either drive local speciation or facilitate contiguous distributions of independently subterranean adapted species.