bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterizing centrosymmetric two-ring PAHs using jet-cooled high resolution mid-infrared laser spectroscopy and anharmonic quantum chemical calculations
Authors: Chawananon S. , Pirali O. , Goubet M. , Asselin P. 
Published: July 2022

The presence of Polycyclic Aromatic Hydrocarbon (PAH) molecules in the interstellar medium, recently confirmed by the detection of cyano-naphthalenes, has renewed the interest of extensive spectroscopic and physical-chemistry studies on such large species. The present study reports the jet-cooled rovibrational infrared study of three centrosymmetric two-ring PAH molecules, viz., naphthalene (C10H8), [1,5] naphthyridine (C8H6N2), and biphenyl (C12H10), in the in-plane ring C–H bending (975–1035 cm−1) and C–C ring stretching (1580–1620 cm−1) regions. For the two most rigid PAHs, the accuracy of spectroscopic parameters derived in ground and several excited states (six for naphthalene and six for [1,5] naphthyridine) has significantly improved the literature values. In addition, comparison between experiments and quantum chemical calculations confirms the predictive power of the corrected calculated rotational parameters. The more flexible structure of biphenyl makes the analysis of high resolution jet-cooled spectra of ν19 and ν23 modes recorded at about 1601 and 1013 cm−1, respectively, particularly challenging. The presence of three torsional vibrations below 120 cm−1 together with small values of the rotational constants prevented us from determining the ground and v19 = 1 excited rotational constants independently. In the ν23 band region, the presence of two bands rotationally resolved and separated by only 0.8 cm−1 raises the question of possible splittings due to a large amplitude motion, most probably the torsion of the aliphatic bond between the two phenyl rings.
Hyper-Raman spectroscopy of benzene and pyridine revisited
Authors: Inoue Kazuki , Morimoto Tenri , Yokogawa Daisuke , Okuno Masanari 
Published: July 2022

Hyper-Raman (HR) spectra of benzene-h6, benzene-d6, and pyridine in the liquid phase excited at 1064 nm were measured by a picosecond laser with a high repetition rate. Although benzene and pyridine are important aromatic molecules, the qualities of the HR spectra previously reported were not high enough to be compared with those of IR and Raman spectroscopy. Our HR spectroscopic system significantly improves sensitivity that enables the detection of HR bands of benzene and pyridine not observed before. In addition to band assignments, we interpret HR bands of benzene based on the vibronic coupling theory of (pre-) resonance hyper-Raman scattering. Depolarization ratios of HR bands of benzene and pyridine, obtained from polarized-HR measurements, are first examined from a theoretical point of view of HR spectroscopy. Moreover, we evaluate quantum chemical calculations for HR spectra by comparing experimental and computational spectra. We show that the frequency-dependent polarizability and hyperpolarizability calculations using time-dependent density functional theory well reproduce the HR experiments for bulk aromatic compounds.
Phase-separating RNA-binding proteins form heterogeneous distributions of clusters in subsaturated solutions
Authors: Kar Mrityunjoy , Dar Furqan , Welsh Timothy J. , Vogel Laura T. , Kühnemuth Ralf , Majumdar Anupa , Krainer Georg , Franzmann Titus M. , Alberti Simon , Seidel Claus A. M. , Knowles Tuomas P. J. , Hyman Anthony A. , Pappu Rohit V. 
Published: July 2022

Macromolecular phase separation is thought to be one of the processes that drives the formation of membraneless biomolecular condensates in cells. The dynamics of phase separation are thought to follow the tenets of classical nucleation theory, and, therefore, subsaturated solutions should be devoid of clusters with more than a few molecules. We tested this prediction using in vitro biophysical studies to characterize subsaturated solutions of phase-separating RNA-binding proteins with intrinsically disordered prion-like domains and RNA-binding domains. Surprisingly, and in direct contradiction to expectations from classical nucleation theory, we find that subsaturated solutions are characterized by the presence of heterogeneous distributions of clusters. The distributions of cluster sizes, which are dominated by small species, shift continuously toward larger sizes as protein concentrations increase and approach the saturation concentration. As a result, many of the clusters encompass tens to hundreds of molecules, while less than 1% of the solutions are mesoscale species that are several hundred nanometers in diameter. We find that cluster formation in subsaturated solutions and phase separation in supersaturated solutions are strongly coupled via sequence-encoded interactions. We also find that cluster formation and phase separation can be decoupled using solutes as well as specific sets of mutations. Our findings, which are concordant with predictions for associative polymers, implicate an interplay between networks of sequence-specific and solubility-determining interactions that, respectively, govern cluster formation in subsaturated solutions and the saturation concentrations above which phase separation occurs.
Forces on hockey players and conservation laws: on the theoretical efficiency of different techniques
Authors: Persson Rasmus A X 
Published: July 2022

Abstract
With a more comprehensive, yet still idealized, take on the analysis by Nässén et al (2019 Eur. J. Phys.
40 065005) regarding the efficiency of different ice skating strides, we find no superiority of the ‘angular momentum skating’ technique within their model. The fundamental reason is that for the ‘angular momentum stride’, there is a force component opposing the forward motion during the latter part of the stride, but not so for the traditional skating technique. We conclude with a short pedagogical discussion regarding conservation laws in physics.
An application of the Lyapunov stability theorem: a bead on a rotating hoop
Authors: Cao Yuxuan , Zhou Wenquan , Jiang Jiangang 
Published: July 2022

Abstract
The motion of a bead on a rotating hoop is a classical problem in mechanics. The problem describes that a bead is placed on the track of a hoop rotating around a vertical axis. Although this issue is researched by lots of scholars, this system is usually analyzed without considering the friction. However, when considering friction, it becomes difficult to analyze the stability. The purpose of this study is to investigate the stability of the system with friction more easily. We derive the equation of motion of the bead and use the Lyapunov stability theorem to analyze the stability. The stability is determined by the angular velocity of the hoop. If the angular velocity is less than or equal to the critical value the bead is asymptotically stable at origin (the bottom of the hoop) otherwise it is asymptotically stable at a non-zero position. In addition, we study the difference between mass point bead and rigid body bead and find that both have identical bifurcation diagram and stability, whereas the trajectories have a difference on the phase plane. In the end, the numerical simulation method is used to verify the conclusion above.
Quantum carpets in leaky boxes
Authors: Berry M V 
Published: July 2022

Abstract
Quantum waves evolving or propagating inside one-dimensional boxes generate ‘quantum carpets’: intricate patterns in spacetime. The formally equivalent patterns in classical paraxial optics are observed as the Talbot effect. Boxes that are leaky, i.e. with penetrable walls, can be modelled by representing the walls as nonhermitian boundaries. The waves are superpositions of discrete eigenmodes with complex eigenvalues. Several different boundary conditions are explored, in which the Robin parameter—ratio of the mode derivatives and their values at the walls—may or may not depend on the eigenvalue. Nonhermitian models, which ignore the waves leaking outside the box, or represent them in simplified form, are approximations. For one physical model, the evolving wave in the full space can be calculated exactly, indicating that the nonhermitian model for the wave inside is highly accurate. Leaky boxes can be useful pedagogically: as introductory examples of nonhermiticity and biorthogonality (left and right eigenvectors), and as a rich source of postgraduate or advanced undergraduate student projects, exploring many variants.
Temperature-activated dielectric relaxation in lead-free halide perovskite single crystals
Authors: Paul Rajashik , Tailor Naveen Kumar , Mahaptra Apurba , Yadav Pankaj , Satapathi Soumitra 
Published: July 2022

Abstract
Lead-free metal-halide perovskites have recently appeared as a promising candidate in optoelectronics and photovoltaics because of their non-toxicity, stability, and unique photophysical properties. Much scientific research has been done on optoelectronic characteristics and photovoltaic applications of lead-free perovskites, but the dielectric characteristics and insight into the relaxation phenomenon remain elusive. Here, we study the dielectric relaxation and conduction mechanism in the single crystalline (SC) A3Bi2X9 (A = MA+/FA+) perovskite using temperature-dependent electrochemical impedance spectroscopy in correlation with the modulus spectroscopy. With increasing temperature, the peak of −Z″(ω) shifts toward a high-frequency regime which specifies the thermally dependent relaxation mechanism in both crystals. The activation energy was estimated as 381 meV for MA3Bi2I9 (MBI) crystal and 410 meV for the FA3Bi2I9 (FBI) crystal suggesting hopping of mobile ions between lattice sites. The connected orientational polarization with the thermal motion of molecules leads to the enhancement in the dielectric constant (ϵ′) with temperature. The ϵ″(ω) in these crystals shows the significant ionic conductivity with a typical 1/fγ
type characteristics (in the low-frequency regime) where γ is found to be in the range of 0.93–1.0 for MBI crystal and 0.88–0.98 for FBI crystal. The correlated imaginary part of impedance (−Z″) and modulus (M″) demonstrate the temperature-activated delocalized relaxation (non-Debye toward the Debye type) in these crystals. Stevels model suggests that the contribution of traps reduces with temperature rise and therefore conductivity enhances. Our study provides a comprehensive analysis and in-depth knowledge about the dielectric and conductivity relaxation mechanism in these lead-free perovskite SCs, which will help to implement efficient energy storage devices using these materials.
Current-driven periodic domain walls injection in a ferromagnetic nanostrip with a modified perpendicular magnetic anisotropy region
Authors: Zhou Xiuping , Ren Hanyu , Jiang Congying , Wang Fan , He Xinyan , Chen Zhenzhen , Qiu Yang , Zhu Mingmin , Yu Guoliang , Zhou Haomiao 
Published: July 2022

Abstract
Effective control of domain wall (DW) injection and motion in a ferromagnetic nanostrip is of great significance for the development of DW-based spintronic devices. In this work, we exploit the properties of 90° magnetization walls induced by a modified perpendicular magnetic anisotropy (PMA) between the out-of-plane and in-plane magnetized regions of Pt/Co, with spin-transfer torque (STT) being used to control the injection of DWs into a ferromagnetic nanostrip. We demonstrate that this STT stimulus combined with the modified PMA enables the continuous and synchronous injection of a series of head-to-head and tail-to-tail transverse in-plane DWs. Furthermore, micromagnetic simulation results show that the presence of a 90° magnetized transition region is a prerequisite for magnetic DW injection, and that the generation frequency can be controlled reversibly from the MHz to the multi-GHz range. Our findings demonstrate the feasibility of a highly tunable and direct-current-controlled transverse in-plane DW signal source, which could pave the way toward compact and integrated DW circuits and oscillators.
Sn2Pd: a possible superconducting material with topological surface states
Authors: Sharma M M , Awana V P S 
Published: July 2022

Abstract
In this article, we report the detailed magneto transport measurements of topological semimetal candidate, Sn2Pd. Single crystal of Sn2Pd is synthesized through self-flux method. Phase purity and crystalline morphology are confirmed through powder x-ray diffraction pattern and field emission scanning electron microscopy image. Signatures of superconducting transition are seen in both transport and magneto transport measurements, which are further supported by the AC magnetization studies. Sn2Pd is found to show superconductivity onset at below 2.8 K, but not the zero resistivity down to 2 K. Although, isothermal magneto resistivity measurements below superconducting onset (2.8 K) clearly exhibited superconductor like behavior, but is not observed in heat capacity measurements, indicating the same to be of weak nature. Magneto transport measurements performed in normal state of Sn2Pd show the presence of weak antilocalization effect, which is confirmed by modelling of low field magneto-conductivity through Hikami Larkin Nagaoka formalism. Here, it is worth mentioning that the present article is the first report on magneto transport measurements of Sn2Pd, which show the same to be a topological material with weak superconducting phase below around 2.8 K.
Birkhoff normal form and twist coefficients of periodic orbits of billiards*
Authors: Jin Xin , Zhang Pengfei 
Published: July 2022

Abstract
In this paper we study the Birkhoff normal form around elliptic periodic points for a variety of dynamical billiards. We give an explicit construction of the Birkhoff transformation and obtain explicit formulas for the first two twist coefficients in terms of the geometric parameters of the billiard table. As an application, we obtain characterizations of the nonlinear stability and local analytic integrability of the billiards around the elliptic periodic points.
A novel method to measure the thermal diffusivity of transparent materials
Authors: Lee Wen-Tang , Lin Fong-Feng , Lou Yu-You 
Published: July 2022

Abstract
The refractive index of a liquid is known to depend strongly on the temperature gradient of liquids. When a laser beam passes through a transparent material going through thermal diffusion, the light projected onto a screen will be displaced in relation to the thermal diffusivity. A simple apparatus is used to measure the time evolution t of the laser beam displacement h and/vs. the position of the laser beam on the liquid container y whose liquid medium is going through thermal diffusion. Thermal diffusion dynamics can then be revealed. The thermal diffusivity of glycerol, ethanol, DI water, and NaCl aqueous solution has been measured. This simple procedure can demonstrate refractive index and thermal diffusivity in advanced high school physics courses.
Observation of libration and change in apparent diameter of the Moon with a pinhole camera
Authors: Matsutani Akihiro 
Published: July 2022

Abstract
We demonstrated that an optimally designed pinhole camera can be used as an astronomical tool to observe the libration and apparent diameter change of the Moon at night. The libration and apparent diameter change of the Moon were observed using a handmade pinhole camera with a diameter of 0.65 mm and a focal length of 400 mm. It was found that the lunar mare with its characteristic pattern can be observed using this pinhole camera with a resolution of 2.5 arcmin. It was also found that the apparent diameter change of the Moon of about 10% can be observed with this pinhole camera. The pinhole camera used in this experiment is very useful as a handmade scientific educational material for learning the principles of optics and the movement of the Moon.
A zero power current and frequency sensor for smart grid applications
Authors: Aragonez Omar , Jackson Nathan 
Published: July 2022

Abstract
Obtaining real time feedback on the amplitude and frequency of current flowing through power lines is of significant importance to smart grids. This paper investigates the use of a zero power multifunctional device (sensor and energy harvester) to solve this challenging problem. The passive device combines a piezoelectric cantilever with a hard magnet mass in order to couple the AC magnetic field from the power line to the device to generate an oscillating kinetic force at the frequency of the current. The proposed device is passive, but the transmission of the data requires the use of wireless sensor nodes, which requires power. The piezoelectric cantilever acts as both a passive sensor and a kinetic energy harvester to power the wireless sensor nodes. This study investigates the effects on both the sensor sensitivity and energy harvesting power density as a function of the type of wire (stranded vs solid wires), stiffness of the cantilever, and pull strength of the magnet for high current applications. The results demonstrate that stranded wires have a slight reduction in sensitivity from 1.12 V A−1 to 0.98 V A−1 for solid and stranded wire. The stiffness of the cantilever also affects the sensitivity and energy harvesting performance, where stiffer beams resulted in high power density and sensitivity. Increasing the magnet thickness and pull strength resulted in increased power density and bandwidth but it also effects the optimal spatial location of the magnet in relation to the wire. The device was also validated as a frequency sensor with a resolution of <1 Hz, and could be further optimized in the future. The results of this study validate the potential use of the device as a multifunctional sensor/energy harvester for smart grid applications.
An optical transition-edge sensor with high energy resolution
Authors: Hattori Kaori , Konno Toshio , Miura Yoshitaka , Takasu Sachiko , Fukuda Daiji 
Published: July 2022

Abstract
Optical transition-edge sensors (TESs) have shown an energy resolution for resolving the number of incident photons at the telecommunication wavelength. However, a higher energy resolution is required for biological imaging and microscopic spectroscopy. In this study, we tested an Au/Ti (10/20 nm) bilayer TES that showed a high energy resolution. The high energy resolution was achieved by lowering the critical temperature

T

c

to 115 mK, and the resultant energy resolution was 67 meV full width at half maximum (FWHM) at 0.8 eV. When

T

c

was reduced to 115 mK, the theoretical resolution would scale up to 30 meV FWHM, considering that the typical energy resolution of optical TESs was 150 meV and

T

c

was 300 mK. To investigate the difference between the theoretical expectation (30 meV) and the measured value (67 meV), we measured the complex impedance and current noise of the TES. We found excess Johnson noise in the TES; the excess Johnson noise term M was 1.5 at a bias point where the resistance was 10% of the normal resistance. For reference, the above mentioned TES was compared with a TES showing typical energy resolution (156 meV FWHM). We also discussed factors that improved or inhibited the energy resolution.
Dynamics of charged aerosols relevant to transmission of airborne infections
Authors: Karimov A R , Stenflo L , Yu M Y 
Published: July 2022

Abstract
A simple model including the effects of initial velocity, air drag, gravity, and electrostatics on the dynamics of airborne droplets emitted from humans is presented. It is found that relatively large droplets can also travel far if their charge and/or the atmospheric electric field is sufficiently large.
Non-relativistic scattering by a shield barrier and by an elliptical aperture
Authors: Schmidt Alexandre G M , de Jesus Anderson L 
Published: July 2022

Abstract
We study the non-relativistic quantum mechanical scattering of a plane wave by a shield barrier and an elliptical aperture modeled as Dirac delta functions running along a coordinate surface of the sphero-conal coordinate system. The scattering problem is formulated via Lippmann-Schwinger (LS) equation in the position representation. In order to solve the LS equation, we first calculate the free Green's function of the problem and obtain its bilinear expansion in terms of the eigenfunctions of the scalar Helmholtz equation—which are products of spherical Bessel (or first kind Hankel) functions and Lamé polynomials. Such bilinear expansion allows us to obtain an integral equation with a separable kernel and solve the scattering problem. Then, we calculate the wavefunctions in the internal and external domains and the scattering amplitudes.
The QCD phase transition behind a PBH origin of LIGO/Virgo events?
Authors: Iguaz Joaquim , Serpico Pasquale D. , Franco-Abellán Guillermo 
Published: July 2022

AbstractThe best-motivated scenario for a sizable primordial black hole (PBH) contribution to the LIGO/Virgo binary black hole mergers invokes the QCD phase transition, which naturally enhances the probability to form PBH with masses of stellar scale. We reconsider the expected mass function associated not only to the QCD phase transition proper, but also the following particle antiparticle annihilation processes, and analyse the constraints on this scenario from a number of observations: the specific pattern in cosmic microwave background (CMB) anisotropies induced by accretion onto PBHs, CMB spectral distortions, gravitational wave searches, and direct counts of supermassive black holes (SMBHs) at high redshift. We find that the scenario is not viable, unless an ad hoc mass evolution for the PBH mass function and a cutoff in power-spectrum very close to the QCD scale are introduced by hand. Despite these negative results, we note that a future detection of coalescing binaries involving sub-solar PBHs has the potential to check the cosmological origin of SMBHs at thee±annihilation epoch, if indeed the PBH mass function is shaped by the changes to the equation of state driven by the thermal history of the universe.
Optical Observations of the Nearby Type Ia Supernova 2021hpr
Authors: Zhang Yu , Zhang Tianmeng , Danzengluobu  , Li Zhitong , Zhao Pinsong , Zhang Bingqing , Du Lin , Zhu Yinan , Wu Hong 
Published: July 2022

Abstract
We present the optical photometric and spectroscopic observations of the nearby Type Ia supernova (SN) 2021hpr. The observations covered the phase of −14.37 to +63.68 days relative to its maximum luminosity in the B band. The evolution of multiband light/color curves of SN 2021hpr is similar to that of normal Type Ia supernovae (SNe Ia) with the exception of some phases, especially a plateau phase that appeared in the V − R color curve before peak luminosity, which resembles that of SN 2017cbv. The first spectrum we observed at t ∼ −14.4 days shows a higher velocity for the Si ii
λ6355 feature (∼21,000 km s−1) than that of other normal velocity (NV) SNe Ia at the same phase. Based on the Si ii
λ6355 velocity of ∼12,420 km s−1 around maximum light, we deduce that SN 2021hpr is a transitional object between high velocity (HV) and NV SNe Ia. Meanwhile, the Si ii
λ6355 feature shows a high velocity gradient (HVG) of about 800 km s−1 day−1 from roughly −14.37 to −4.31 days relative to the B-band maximum, which indicates that SN 2021hpr can also be classified as an HVG SN Ia. Despite SN 2021hpr having a higher velocity for the Si ii
λ6355 and Ca ii near-IR (NIR) triplet features in its spectra, its evolution is similar to that of SN 2011fe. Including SN 2021hpr, there have been six supernovae observed in the host galaxy NGC 3147; the supernovae explosion rate in the last 50 yr is slightly higher for SNe Ia, while for SNe Ibc and SNe II it is lower than expected rate from the radio data. Inspecting the spectra, we find that SN 2021hpr has a metal-rich (12 + log(O/H) ≈ 8.648) circumstellar environment, where HV SNe tend to reside. Based on the decline rate of SN 2021hpr in the B band, we determine the distance modulus of the host galaxy NGC 3147 using the Phillips relation to be 33.46 ± 0.21 mag, which is close to that found by previous works.