bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrafast dynamics of 2-thiouracil investigated by time-resolved Auger spectroscopy
Authors: Lever F , Mayer D , Picconi D , Metje J , Alisauskas S , Calegari F , Düsterer S , Ehlert C , Feifel R , Niebuhr M , Manschwetus B , Kuhlmann M , Mazza T , Robinson M S , Squibb R J , Trabattoni A , Wallner M , Saalfrank P , Wolf T J A , Gühr M 
Published: November 2020

Abstract
We present time-resolved ultraviolet-pump x-ray probe Auger spectra of 2-thiouracil. An ultraviolet induced shift towards higher kinetic energies is observed in the sulfur 2p Auger decay. The difference Auger spectra of pumped and unpumped molecules exhibit ultrafast dynamics in the shift amplitude, in which three phases can be recognized. In the first 100 fs, a shift towards higher kinetic energies is observed, followed by a 400 fs shift back to lower kinetic energies and a 1 ps shift again to higher kinetic energies. We use a simple Coulomb-model, aided by quantum chemical calculations of potential energy states, to deduce a C–S bond expansion within the first 100 fs. The bond elongation triggers internal conversion from the photoexcited S2 to the S1 state. Based on timescales, the subsequent dynamics can be interpreted in terms of S1 nuclear relaxation and S1-triplet internal conversion.
Identifications of extreme ultraviolet spectra of Br-like to Ni-like neodymium ions using an electron beam ion trap
Authors: Suzuki C , Dipti  , Yang Y , Gall A , Silwal R , Sanders S , Naing A , Tan J , Takacs E , Ralchenko Yu 
Published: November 2020

Abstract
Accurate extreme ultraviolet spectra of open N-shell neodymium (Nd) ions were recorded at the electron beam ion trap facility of the National Institute of Standards and Technology. The measurements were performed for nominal electron beam energies in the range of 0.90 keV to 2.31 keV. The measured spectra were then compared with the spectra simulated by a collisional-radiative model utilizing atomic data produced with a fully relativistic atomic structure code. Consequently, 59 lines from Br-like to Ni-like Nd ions were unambiguously identified, most of which were newly assigned in this study. The wavelengths of 9 known lines from Ni-, Cu- and Zn-like Nd ions were in excellent agreement with previous measurements.
Double-plate calibration for coil capacitance effect and application in high-frequency eddy-current testing
Authors: Xu Jin , Lei Yinzhao 
Published: November 2020

Abstract
In high-frequency eddy-current testing, the coil impedance is often seriously affected by the capacitance effect, while the existing calibration method only corrects the capacitive couplings within the coil itself and ignores the coupling between the coil and the conductor. Combined with the equivalent circuit, a correction method for both the capacitive couplings is proposed using single-plate calibration. Furthermore, considering the skin effect at high frequencies, which leads to the calculation error of coil impedance, a modified impedance is introduced in the equivalent circuit and the double-plate calibration is presented. Using the two proposed methods and the existing calibration method, the experimental values of the coil impedance were respectively corrected when the coil was on a single-coated plate (titanium coating and TiAl6V4 titanium alloy substrate), and compared with the theoretical values between 1 and 100 MHz. The results show a sequentially improved correction effect of the existing calibration method, single-plate calibration, and double-plate calibration. Combined with the Levenberg–Marquardt method, the double-plate calibration was applied to the parameter measurement of the conductive plate with tens of micrometer coating. Through analyzing the sensitivity function of each tested parameter, we employed the inductance to calculate the substrate conductivity at hundreds of kilohertz and the resistance to calculate the coating thickness and conductivity at tens of megahertz. The parameters of three single-coated plates with coating thicknesses of 23 μm, 32 μm and 52 μm were respectively tested, and the results show that the relative measurement errors of all parameters are less than 15%.
Synthesis of deep red emitting Cu–In–Zn–Se/ZnSe quantum dots for dual-modal fluorescence and photoacoustic imaging
Authors: Sheng Yang , Li Shuai , Sun Yixin , Zhang Rong , Zhao Xinyu , Tan Mei Chee 
Published: November 2020

Abstract
CuInSe2 quantum dots (QDs) are one of the most important Cd-free fluorescent probes; they usually exhibited low fluorescence intensity, suggesting that a considerable amount of absorbed photon energy was lost as heat. In this study we aimed to improve the fluorescence intensity of CuInSe2 QDs and investigate their photoacoustic (PA) signal resulting from the heat dissipation, which was previously rarely reported. Cu–In–Zn–Se/ZnSe QDs were synthesized by adopting two strategies of Zn doping and ZnSe shell growth. It was found that there was an upper limit for Zn concentration beyond which the fluorescence intensity began to decrease. In addition, a blue shift of the emission peak of Cu–In–Zn–Se/ZnSe QDs was observed at high concentrations of ZnSe precursor due to the diffusion of excessive Zn. To prepare the dual-modal fluorescence and PA imaging probe, poly(maleic anhydride-alt-1-octadecene) (PMAO) modified with polyethylene glycol (PEG) was coated on the QDs, which led to a slight reduction in fluorescence. Cellular labeling on HeLa cells was performed to demonstrate the utility of these probes for fluorescence imaging. We further studied the in vitro PA imaging capabilities of the Cu–In–Zn–Se/ZnSe/PMAO-g-PEG nanoparticles, which showed a distinct PA signal beyond 1.0 mg ml−1. The current work demonstrated that a moderate amount of Zn doping is necessary for enhancing fluorescence and there is a limit beyond which the fluorescence will be diminished. We also demonstrated the proof of concept that Cu–In–Zn–Se/ZnSe QDs are able to serve as a potential PA imaging contrast agent.
Tunable parametric amplification of a graphene nanomechanical resonator in the nonlinear regime
Authors: Su Zi-Jia , Ying Yue , Song Xiang-Xiang , Zhang Zhuo-Zhi , Zhang Qing-Hang , Cao Gang , Li Hai-Ou , Guo Guang-Can , Guo Guo-Ping 
Published: November 2020

Abstract
Parametric amplification is widely used in nanoelectro-mechanical systems to enhance the transduced mechanical signals. Although parametric amplification has been studied in different mechanical resonator systems, the nonlinear dynamics involved receives less attention. Taking advantage of the excellent electrical and mechanical properties of graphene, we demonstrate electrical tunable parametric amplification using a doubly clamped graphene nanomechanical resonator. By applying external microwave pumping with twice the resonant frequency, we investigate parametric amplification in the nonlinear regime. We experimentally show that the extracted coefficient of the nonlinear Duffing force α and the nonlinear damping coefficient η vary as a function of external pumping power, indicating the influence of higher-order nonlinearity beyond the Duffing (∼x
3) and van der Pol (∼

x

2

d
x

d
t

) types in our device. Even when the higher-order nonlinearity is involved, parametric amplification still can be achieved in the nonlinear regime. The parametric gain increases and shows a tendency of saturation with increasing external pumping power. Further, the parametric gain can be electrically tuned by the gate voltage with a maximum gain of 10.2 dB achieved at the gate voltage of 19 V. Our results will benefit studies on nonlinear dynamics, especially nonlinear damping in graphene nanomechanical resonators that has been debated in the community over past decade.
Extreme value distributions of observation recurrences
Authors: Caby Th , Faranda D , Vaienti S , Yiou P 
Published: November 2020

Abstract
We study analytically and numerically the extreme value distribution of observables defined along the temporal evolution of a dynamical system. The convergence to the Gumbel law of observable recurrences gives information on the fractal structure of the image of the invariant measure by the observable. We provide illustrations on idealized and physical systems.
On some rigorous aspects of fragmented condensation
Authors: Dimonte Daniele , Falconi Marco , Olgiati Alessandro 
Published: November 2020

Abstract
In this paper we discuss some aspects of fragmented condensation from a mathematical perspective. We first propose a simple way of characterizing finite fragmentation. Then, inspired by recent results of semiclassical analysis applied to bosonic systems with infinitely many degrees of freedom, we address the problem of persistence of fragmented condensation. We show that the latter occurs in interacting systems, in the mean-field regime, and in the limit of large gap of the one-body Hamiltonian.
Vertical GaN power rectifiers: interface effects and switching performance
Authors: Yang Shu , Han Shaowen , Sheng Kuang 
Published: November 2020

Abstract
The emergence of free-standing GaN substrates enables the development of vertical GaN-on-GaN devices with high-power ratings and high frequencies. The Schottky interface plays an important role in determining the current transport mechanisms and the forward/reverse electrical performance of the vertical GaN Schottky barrier diodes. Moreover, given its direct bandgap and ultrashort minority carrier lifetime, it is of particular interest and importance to evaluate the fast switching performance of the vertical GaN power rectifiers. In this paper, we discuss the technology, physical mechanisms and characterizations of vertical GaN power rectifiers with high-quality interfaces and fast switching performances, including: (a) accurate characterization and carrier transport mechanisms of the Schottky interface; (b) Schottky interface engineering with optimized post-metallization annealing and a tunneling-enhancement layer; (c) fast reverse recovery performance that is characterized by high-speed board-level tests. The investigations and analysis on the interface effects and switching performance of the vertical GaN power rectifiers are valuable for high-efficiency and high-frequency power electronics applications.
Ponderomotively assisted ionization injection in plasma wakefield accelerators
Authors: Zeng Ming , de la Ossa Alberto Martinez , Osterhoff Jens 
Published: November 2020

Abstract
An injection scheme is proposed to realize electron trapping in sub-relativistic plasma wakefield accelerators. A laser under oblique angle of incidence ionizes a dopant gas in plasma and ponderomotively accelerates the released electrons into the direction of wake propagation. This process enables electron trapping in the wakefield even for a wakefield potential below the trapping threshold. We study the scheme theoretically and by means of particle-in-cell (PIC) simulations to demonstrate high-quality beam formation and acceleration with sub-micrometer normalized emittances and sub-percent uncorrelated energy spreads.
Constraints on neutrino mass in the scenario of vacuum energy interacting with cold dark matter after Planck 2018
Authors: Li Hai-Li , Zhang Jing-Fei , Zhang Xin 
Published: November 2020

Abstract
In this work, we investigate the constraints on the total neutrino mass in the scenario of vacuum energy interacting with cold dark matter (abbreviated as IΛCDM) by using the latest cosmological observations. We consider four typical interaction forms, i.e.

Q
=
β
H

ρ

de

,

Q
=
β
H

ρ

c

,

Q
=
β

H

0

ρ

de

, and

Q
=
β

H

0

ρ

c

, in the IΛCDM scenario. To avoid the large-scale instability problem in interacting dark energy models, we employ the extended parameterized post-Friedmann method for interacting dark energy to calculate the perturbation evolution of dark energy in these models. The observational data used in this work include the cosmic microwave background (CMB) measurements from the Planck 2018 data release, the baryon acoustic oscillation (BAO) data, the type Ia supernovae (SN) observation (Pantheon compilation), and the 2019 local distance ladder measurement of the Hubble constant H
0 from the Hubble Space Telescope. We find that, compared with those in the ΛCDM+

∑

m

ν

model, the constrains on

∑

m

ν

are looser in the four IΛCDM+

∑

m

ν

models. When considering the three mass hierarchies of neutrinos, the constraints on

∑

m

ν

are tightest in the degenerate hierarchy case and loosest in the inverted hierarchy case. In addition, in the four IΛCDM+

∑

m

ν

models, the values of coupling parameter β are larger using the CMB+BAO+SN+H
0 data combination than that using the CMB+BAO+SN data combination, and β > 0 is favored at more than 1σ level when using CMB+BAO+SN+H
0 data combination. The issue of the H
0 tension is also discussed in this paper. We find that, compared with the ΛCDM+

∑

m

ν

model, the H
0 tension can be alleviated in the IΛCDM+

∑

m

ν

model to some extent.
Sputtering of the beryllium tungsten alloy Be2W by deuterium atoms: molecular dynamics simulations using machine learned forces
Authors: Chen L. , Kaiser A. , Probst M. , Shermukhamedov S. 
Published: November 2020

Abstract
Material erosion and fuel retention will limit the life and the performance of thermonuclear fusion reactors. In this work, sputtering, reflection and retention processes are atomistically modeled by simulating the non-cumulative sputtering by deuterium projectiles on a beryllium–tungsten alloy surface. The forces for the molecular dynamics trajectories were machine learned from density functional theory with a neural network architecture. Our data confirms and supplements previous results for simulated sputtering rates. In the non-cumulative scenario we simulate, we did not observe reaction mechanisms leading to swift chemical sputtering. Thus, our sputtering rates at low impact energies are smaller than in comparable non-cumulative studies. The sputtering yields of the Be2W alloy are generally lower than those of pure beryllium. We found a strong dependence of the sputtering yield on the incident angle with an increase by about a factor of 3 for larger incident angles at 100 eV impact energy. In the pristine surface, a large majority of the impacting hydrogen projectiles at perpendicular impact remains in the surface.
Uncertainty and complementarity: two key notions in Paul Busch’s studies at the heart of quantum mechanics
Authors: Lahti Pekka 
Published: November 2020

Abstract
The problem of approximate joint measurement of complementary observables, like position and momentum, and the relevance of the uncertainty relations to that question were at the heart of the investigations of Paul Busch into the foundations of quantum mechanics. A good third of his published work dealt with this and closely related questions. This paper is an attempt to survey some of the steps taken in that research starting with Paul’s first papers on the subject matter in the early 1980’s and reaching its height in recent years.
Subspace constraints for joint measurability
Authors: Kiukas Jukka 
Published: November 2020

Abstract
The structure of quantum effects, positive operators of norm at most one, played a central role in the work of Paul Busch on uncertainty, complementarity, and joint measurability in quantum measurement theory. Here we focus on one aspect of this structure, called “strength of an effect along a ray” [Lett. Math. Phys. 47 329 (1999)], presenting a few observations not explicit in the existing literature. In fact, the strength function turns out to be useful for characterising positivity and complementarity of quantum effects of a suitable block matrix form, and for studying extensions of joint measurements defined on a subspace of codimension one.
Sequential measurements and entropy
Authors: Schmidt Heinz-Jürgen , Gemmer Jochen 
Published: November 2020

Abstract
We sketch applications of the so-called J-equation to quantum information theory concerning fundamental properties of the von Neumann entropy. The J-equation has recently be proposed as a sort of progenitor of the various versions of the Jarzynski equation. It has been derived within a general framework of sequential measurements that is slightly generalised here.
A relational perspective on the Wigner-Araki-Yanase theorem
Authors: Loveridge Leon 
Published: November 2020

Abstract
We present a novel interpretation of the Wigner-Araki-Yanase (WAY) theorem based on a relational view of quantum mechanics. Several models are analysed in detail, backed up by general considerations, which serve to illustrate that the moral of the WAY theorem may be that in the presence of symmetry, a measuring apparatus must fulfil the dual purpose of both reflecting the statistical behaviour of the system under investigation, and acting as a physical reference system serving to define those quantities which must be understood as relative.
Localizability and elementary particles
Authors: Jaeger Gregg 
Published: November 2020

Abstract
The well-definedness of particles of any kind depends on the limits, approximations, or other conditions that may or may not be involved, for example, whether there are interactions and whether ostensibly related energy is localizable. In particular, their theoretical status differs between its non-relativistic and relativistic versions: One can properly define interacting elementary particles in single-system non-relativistic quantum mechanics, at least in the case of non-zero mass systems; by contrast, one is severely challenged to define even these properly in the relativistic quantum field theories that now underlie the study of particle physics. Here, the impact of localizability on this status is reviewed in relation to the work of Paul Busch on positive operator valued measures that significantly probes the relevance of quantum unsharpness to it.
Comparison of entangling protocols in ABC-type spin chains
Authors: Estarellas Marta P , Spiller Timothy P , D’Amico Irene 
Published: November 2020

Abstract
In this contribution we consider an advantageous building block with potential for various quantum applications: a device based on coupled spins capable of generating and sharing out an entangled pair of qubits. Our model device is a dimerized spin chain with three weakly coupled embedded sites (defects). Three different entangling protocols were proposed for this chain in [1] and [2], one producing a Cluster state building block and two generating a Bell state, depending on the initial state injection. Here we compare the robustness of such protocols as quantum entangling gates against different types of fabrication (static energy fluctuations) and operation (timing injection delays) errors.
Accurate numerical determination of a self-preserving quantum vortex ring
Authors: Zuccher Simone , Caliari Marco 
Published: November 2020

Abstract
We compute simultaneously the translational speed, the magnitude and the phase of a quantum vortex ring for a wide range of radii, within the Gross–Pitaevskii model, by imposing its self preservation in a co-moving reference frame. By providing such a solution as the initial condition for the time-dependent Gross–Pitaevskii equation, we verify a posteriori that the ring’s radius and speed are well maintained in the reference frame moving at the computed speed. Convergence to the numerical solution is fast for large values of the radius, as the wavefunction tends to that of a straight vortex, whereas a continuation technique and interpolation of rough solutions are needed to reach convergence as the ring tends to a disk. Comparison with other strategies for generating a quantum ring reveals that all of them seem to capture quite well the translational speed, whereas none of them seems to preserve the radius with the accuracy reached in the present work.
An approximate method for evaluating the fracture process zone near mode II dynamic crack tip
Authors: Ji Chenmeng , Qi Chengzhi 
Published: November 2020

Abstract
Fracture process zone is the key for understanding the nonlinear fracture of quasi-brittle materials. Evaluation of the shape and size of fracture process zone near mode II dynamic crack tip is still a problem unsolved completely at present. The analytical methods for study on dynamic crack like integral transformation method and Wiener-hopf method are not easy to be used to calculate the stress fields near dynamic crack tip. So far the studies on fracture process zone near dynamic crack tip mostly focused on the experimental and numerical simulations. An approximate method for evaluating the shape and the size of fracture process zone is proposed and the feasibility of the new method is demonstrated by comparing with the results calculated based on the well-known stress fields. The shape and size of the fracture process zone near the mode II dynamic crack tip in dependence on crack propagation velocity are determined based on the approximate method. The results show that the areas of fracture process zone calculated based on the new method are nearly the same with the results calculated based on the well-known stress fields under plane stress condition and plane strain condition by the Von Mises criterion. The approximate method can provide a good reference for determination of the fracture process zone near mode II dynamic crack tip since no analytic method has been found for evaluating the fracture process zone near dynamic crack tip to the authors’ knowledge. The fracture process zone near mode II dynamic crack tip is distributed symmetrically with respect to crack plane and increases with the crack propagation velocity. The area of fracture process zone changes more rapidly when the Rayleigh wave velocity is approached. The areas of fracture process zone calculated under plane stress condition are bigger than these calculated under plane strain condition.