bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum mechanical studies of 2D nanobiohybrids (Review Article)
Authors: Stepanian S. G. , Adamowicz L.
Published: April 2022

We considered the recent application of quantum mechanical methods for studying the structure, interaction energies, as well as vibrational and electronic spectra of complexes of 2D nanomaterials (graphene, graphene oxide) with biological molecules. We analyzed how to overcome the main problems arising in computational studies of 2D nanobiohybrids, namely, the large size of systems, the nonuniformity of 2D nanomaterials, the need to use methods that can correctly take into account dispersion interactions. An analysis of the results of quantum mechanical studies, published over the recent decade, showed that the development of theoretical calculation methods and a significant increase in the productivity of computing technology made it possible to calculate not only the structure and interaction energies of nanobiosystems, but also their vibrational and electronic spectra.
Spectroscopy analysis of the alignment of nanoassemblies of DNA-wrapped carbon nanotubes in stretched gelatin film
Authors: Glamazda A. Yu. , Plokhotnichenko A. M. , Karachevtsev V. A.
Published: April 2022

We present the polarized Raman studies and light absorption study of nanoassemblies of DNA-wrapped single-walled carbon nanotubes (SWNTs) incorporated into the gelatin film. Nanoassemblies are formed in aqueous suspension with SWNTs:DNA by positively charged 5,10,15,20-tetrakis-(N-methyl-4-pyridyl) porphyrin (TMPyP4). The gelatin film with embedded nanoassemblies was exposed to a mechanical stretching to about 300% tensile strain for making an alignment along a chosen direction. The analysis of the absorption spectra taken along and normal to the stretching direction revealed the strong polarized dependence. The polarized Raman spectra of the stretched gelatin film showed the angular dependence of the integrated intensity of tangential mode of SWNTs that allowed to estimate the alignment degree. It showed that about 60% of the SWNT nanoassemblies are aligned in the range of ± 15° to the direction of the stretching. The addition of the porphyrin derivative does not impede the orientation of the SWNTs:DNA nanohybrids along the stretching direction. The performed studies of embedded SWNTs:DNA:TMPyP4 nanoassemblies in the flexible gelatin film are intended to show the simple method for obtaining the controlled ordered biocompatible nanotube networks functionalized by the porphyrin derivatives inside a polymer matrix.
Design, development, and instrumentation of isopiestic experimental setup
Authors: Kumar S. Shyam , Prasad G. Rajendra , Rao J. Prabhakar , Kumar V. Suresh , Ganesan Rajesh , Jayaraman V.
Published: April 2022

An isopiestic experimental facility for the measurement of vapor pressures has been designed, fabricated, and commissioned. Using the vapor pressure data as a function of temperature, useful thermodynamic properties of alloys and compounds of interest can be derived. The isopiestic facility comprises a pair of furnaces, temperature controllers, thermocouple movement mechanism, user interface, and data collection. Four such experimental setups have been commissioned. This experimental facility is useful to determine the vapor pressures of a volatile component over the condensed phases as a function of temperature and composition. Using the vapor pressure data, the thermodynamic properties of various systems can be determined. The experimental setup was validated by a Pr–Cd isopiestic run, and the results are compared with the data reported in the literature.
Quantum symmetry on Potts model
Authors: Goswami Debashish , Hossain S. K. Asfaq
Published: April 2022

We formulate the notion of quantum group symmetry of the Hamiltonian corresponding to the Potts model and compute it for few simple models. Our examples illustrate how a slight change of the model parameter may result in a drastic change of the quantum symmetry group (in some cases, the classical symmetry group remains unaffected), signifying a case of phase transition.
Meat-, vegetarian-, and vegan sausages: Comparison of mechanics, friction, and structure
Authors: Ghebremedhin Marta , Baechle Mathias , Vilgis Thomas A.
Published: April 2022

Plant based meat surrogates attract increasing interest. Modern methods of biotechnology, food chemistry/technology, and process engineering allow for surrogates with high optical similarity. Nowadays, targeted molecular-sensory methods taste and smell to be largely approximated to the original products. Nevertheless, the products appear completely different on a molecular scale, which is clearly noticeable in texture, oral processing, friction, and bolus formation. A consequent physical consideration of the function and effects of the proteins of different origin reveals the strengths of the respective products and offers suggestions how sensory weak points can be understood better and avoided. This is illustrated here by means of exemplary examples and experiments joined with underpinned by molecular models. Meat sausages, vegetarian, and vegan surrogates are microscopically investigated by rheology, tribology, and tensile experiments. The interpretation of the results is illustrated and supported by simple models.
Wave propagation with longitudinal dust grain oscillations in dusty plasma crystals
Authors: Nkendji Kenkeu E. , Togueu Motcheyo A. B. , Kanaa Thomas , Tchawoua C.
Published: April 2022

Traveling waves are studied with a longitudinal dust grain oscillation in dusty plasma crystals modeled by α,β-Fermi Pasta Ulam Tsingou equation. Within the phonon band of the dispersion relation, the quasidiscrete approximation is applied to the relative displacement of the model to derive the nonlinear Schrödinger equation. The bright soliton solution is used as an initial condition for the full integration. The propagation of the robust bright wave is observed for the frequency far from the cutoff frequency while the localize wave is obtained at the cutoff frequency. In the forbidden bandgap, an analytical amplitude threshold of the nonlinear supratransmission phenomenon is derived. The numerical simulation confirms the validity of the analytical threshold, and the train of bright soliton is generated. Finally, by harmonically driving the equation of the longitudinal dusty plasma crystal, the traveling asymmetric bright soliton is generated for the first time from the plane wave.
Laser-driven, ion-scale magnetospheres in laboratory plasmas. I. Experimental platform and first results
Authors: Schaeffer D. B. , Cruz F. D. , Dorst R. S. , Cruz F. , Heuer P. V. , Constantin C. G. , Pribyl P. , Niemann C. , Silva L. O. , Bhattacharjee A.
Published: April 2022

Magnetospheres are a ubiquitous feature of magnetized bodies embedded in a plasma flow. While large planetary magnetospheres have been studied for decades by spacecraft, ion-scale “mini” magnetospheres can provide a unique environment to study kinetic-scale, collisionless plasma physics in the laboratory to help validate models of larger systems. In this work, we present preliminary experiments of ion-scale magnetospheres performed on a unique high-repetition-rate platform developed for the Large Plasma Device at the University of California, Los Angeles. The experiments utilize a high-repetition-rate laser to drive a fast plasma flow into a pulsed dipole magnetic field embedded in a uniform magnetized background plasma. 2D maps of the magnetic field with high spatial and temporal resolution are measured with magnetic flux probes to examine the evolution of magnetosphere and current density structures for a range of dipole and upstream parameters. The results are further compared to 2D particle-in-cell simulations to identify key observational signatures of the kinetic-scale structures and dynamics of the laser-driven plasma. We find that distinct 2D kinetic-scale magnetopause and diamagnetic current structures are formed at higher dipole moments, and their locations are consistent with predictions based on pressure balances and energy conservation.
Reorganization free energy of copper proteins in solution, in vacuum, and on metal surfaces
Authors: Kontkanen Outi Vilhelmiina , Biriukov Denys , Futera Zdenek
Published: April 2022

Metalloproteins, known to efficiently transfer electronic charge in biological systems, recently found their utilization in nanobiotechnological devices where the protein is placed into direct contact with metal surfaces. The feasibility of oxidation/reduction of the protein redox sites is affected by the reorganization free energies, one of the key parameters determining the transfer rates. While their values have been measured and computed for proteins in their native environments, i.e., in aqueous solution, the reorganization free energies of dry proteins or proteins adsorbed to metal surfaces remain unknown. Here, we investigate the redox properties of blue copper protein azurin, a prototypical redox-active metalloprotein previously probed by various experimental techniques both in solution and on metal/vacuum interfaces. We used a hybrid quantum mechanical/molecular mechanical computational technique based on density functional theory to explore protein dynamics, flexibility, and corresponding reorganization free energies in aqueous solution, vacuum, and on vacuum gold interfaces. Surprisingly, the reorganization free energy only slightly decreases when azurin is dried because the loss of the hydration shell leads to larger flexibility of the protein near its redox site. At the vacuum gold surfaces, the energetics of the structure relaxation depends on the adsorption geometry; however, significant reduction of the reorganization free energy was not observed. These findings have important consequences for the charge transport mechanism in vacuum devices, showing that the free energy barriers for protein oxidation remain significant even under ultra-high vacuum conditions.
N2, NO, and O2 molecules in LiGaO2 in both Ga and Li sites and their relation to the vacancies
Authors: Dabsamut Klichchupong , Boonchun Adisak , Lambrecht Walter R. L.
Published: April 2022

Doping of the ultrawide bandgap semiconductor LiGaO2 (Eg=5.6 eV) with N2, NO, and O2 molecules placed in either Ga or Li vacancies is studied using first-principles calculations. These molecular dopants are considered potential acceptors for p-type doping. Their optimal placement and orientation relative to the lattice is studied as well as their transition levels and energy of formation. Unfortunately, they are found to have deep acceptor level transition states. We discuss the relation of the transition levels to the one-electron levels, their spin state, and defect wave functions. They are found to be closely related to those of the corresponding vacancies.
Polymer-turbulence interactions in a complex flow and implications for the drag reduction phenomenon
Authors: Lin Che-Yu , Owolabi Bayode E. , Lin Chao-An
Published: April 2022

We present direct numerical simulation data for turbulent duct flow of a finite-extensibility non-linear elastic dumbbell model with the Peterlin approximation (FENE-P) fluid in the high drag reduction regime. While the secondary flow pattern is qualitatively similar to that in a Newtonian fluid, its magnitude is significantly reduced, resulting in a less uniformly distributed velocity profile and hence smaller gradients at the wall. The Reynolds stress tensor in the polymer-laden flow was found to be increasingly anisotropic with most of the turbulent kinetic energy retained in the streamwise component, u′u′¯. We introduce a novel approach for investigating polymer stretching using the anisotropy invariant map of the polymer stress tensor and observe the persistence of both uniaxial and biaxial extension. Analysis of the transport equation for the mean kinetic energy indicates that polymer stretching and relaxation is a highly dissipative process; hence, the introduction of an additional channel for dissipation in a flow is key to drag reduction.
How do discrete symmetries shape the stability of geophysical flows?
Authors: David Tomos W. , Delplace Pierre , Venaille Antoine
Published: April 2022

We examine the role discrete symmetries, time-reversal, and mirror symmetries play in the context of geophysical waves and instabilities. By looking at three special cases from the two-layer quasi-geostrophic model as well as developing a general framework for translating real-space transformations to Fourier space, we are able to (1) show that baroclinic instability is an example of spontaneous parity-time symmetry breaking; (2) show that pure parity symmetry for a fluid system is exactly analogous to charge-conjugation-parity symmetry in a condensed matter system; and (3) show that when a pure parity symmetry is broken, this is associated with the suppression of wave propagation. Furthermore, in the latter case, instability can arise without a corresponding symmetry breaking. This study highlights the role of symmetry breaking behind the dynamics of geophysical waves and instabilities.
Does the composition in PtGe clusters play any role in fighting CO poisoning?
Authors: Ugartemendia Andoni , Mercero Jose M. , de Cózar Abel , Jimenez-Izal Elisa
Published: April 2022

The high catalytic activity of Pt is accompanied by a high affinity for CO, making it extremely susceptible to poisoning. Such CO poisoning limits the use of proton exchange membrane fuel cells. In this work, using global minima search techniques and exhaustive electronic structure characterization, the dopant concentration is pinpointed as a crucial factor to improve the CO tolerance of Pt catalysts. By investigating the PtGe nanoclusters of different sizes and compositions, we found that, for those clusters with roughly the same amount of Pt and Ge, the binding to CO is weakened significantly. The uniqueness of the PtGe equimolar clusters is traced down to the electronic effects. The strong covalency and electrostatic stabilization arising from the advantageous Pt–Ge mixing make the equimolar clusters highly resistant toward CO poisoning and therefore more durable. Importantly, the novel catalysts not only are more resistant to deactivation but also remain catalytically active toward hydrogen oxidation. Representative clusters are additionally deposited on graphene with a pentagon–octagon–pentagon (5-8-5) reconstructed divacancy. The remarkable results of free-standing clusters hold true for surface mounted clusters, in which the interaction with CO is dramatically weakened for those compounds with a Pt:Ge ratio of 1:1. Our results demonstrate that Ge can be a promising alloying agent to mitigate the deactivation of Pt and that the dopant concentration is a critical factor in the design of advanced catalysts.
Perspectives on domain engineering for dielectric energy storage thin films
Authors: Liu Yiqian , Yang Bingbing , Lan Shun , Pan Hao , Nan Ce-Wen , Lin Yuan-Hua
Published: April 2022

Dielectric energy storage capacitors as emerging and imperative components require both high energy density and efficiency. Ferroelectric-based dielectric thin films with large polarizability, high breakdown strength, and miniaturization potential hold promises for competitive integrated and discrete energy storage devices. Since ferroelectric domains are central to polarization hysteresis loops and, hence, energy storage performances, domain engineering has been widely used in dielectric thin films. In this Perspective, we focus on the most state-of-the-art dielectric energy storage films in the framework of domain engineering. Generally applicable domain engineering strategies are overviewed, followed by articulative examples of their implementation in modulating domain sizes and symmetries that enhance the energy storage. Finally, we envision prospects of further improvements of dielectric thin films within domain engineering and beyond.
CFC-11 measurements in China, Nepal, Pakistan, Saudi Arabia and South Korea (1998–2018): Urban, landfill fire and garbage burning sources
Authors: Simpson Isobel J. , Barletta Barbara , Meinardi Simone , Aburizaiza Omar Siraj , DeCarlo Peter F. , Farrukh Muhammad Akhyar , Khwaja Haider , Kim Jinseok , Kim Younha , Panday Arnico , Siddique Azhar , Stone Elizabeth A. , Wang Tao , Woo Jung-Hun , Xue Likun , Yokelson Robert J. , Zeb Jahan , Blake Donald R.
Published: April 2022

Environmental context The production and consumption of chlorofluorocarbons (CFCs) is regulated under the Montreal Protocol and its amendments, due to their role in stratospheric ozone depletion. Global atmospheric levels of CFC-11 did not decline as rapidly as expected during 2012–2018, in large part due to emissions from eastern China. In order to further clarify global CFC-11 emissions, this work provides a rare set CFC-11 measurements from understudied countries and sources throughout Asia (1998–2018). Abstract Trichlorofluoromethane (CFC-11) is an ozone-depleting substance whose production and consumption are regulated under the Montreal Protocol. Global atmospheric CFC-11 levels declined less quickly than expected during 2012–2018, largely because of ongoing emissions from eastern Asia. Satellite measurements suggest additional CFC-11 hotspots in the Arabian Peninsula and north India/Nepal. Here we present CFC-11 levels measured in dozens of Asian cities during 1998–2018, including China and Pakistan before the 2010 phaseout of CFC-11, and China, Nepal, Pakistan, Saudi Arabia and South Korea after the phaseout. Surface measurements of CFCs in Nepal, Pakistan and Saudi Arabia are very rare, and these surveys provide important observational constraints from understudied regions. During pre-phaseout campaigns, higher CFC-11 levels were measured in Beijing than Karachi, despite much higher overall volatile organic compound (VOC) levels in Karachi. During post-phaseout campaigns, average CFC-11 levels were higher in inland Shandong Province and Seoul (1.11–1.23× background) than in western Saudi Arabia, Lahore and Kathmandu (1.02–1.11× background), despite higher levels of other VOCs in the latter regions. While China is known to emit excess CFC-11, elevated CFC-11 levels in Seoul, especially during stagnant meteorological conditions, suggest local emissions in 2015–2016. Rough emission estimates suggest that South Korea is likely a relatively minor global source of excess CFC-11. Hotspot CFC-11 levels were measured from a landfill fire in Mecca (average of 1.8× background) and from garbage burning in Nepal (1.5× background). Because garbage burning and open burning in dumps are common practices, further investigation of CFC-11 emissions at dumps and landfills worldwide is encouraged to determine their global impact.
Benthic foraminifera as bioindicators for assessing reef condition in Kāne‘ohe Bay, O‘ahu, Hawai‘i
Authors: Mathes Gregor H. , Steinbauer Manuel J. , Cotton Laura
Published: April 2022

Context Tropical coral reef environments provide a wide variety of goods and ecosystem services but are experiencing growing pressure from coastal development and tourism. Assessing the status of reef communities along gradients of human pressure is therefore necessary to predict recovery and resilience capacity of reefs. Aims First, to determine the overall water quality in Kāne‘ohe Bay, O’ahu, Hawai‘i, by employing a low-cost monitoring approach for anthropogenic stress on coral reef areas. Second, to assess the suitability of the monitoring approach to complement existing monitoring programmes. Methods Sediment samples containing benthic foraminifera were used to determine water quality and stressor sources in Kāne‘ohe Bay, O’ahu, Hawai‘i, by applying the Foram Index (FI) and Bayesian regression analysis. The FI is based on relative abundance of functional groups of larger benthic foraminifera. Key results Overall water quality in Kāne‘ohe Bay may support active growth and recovery of coral reefs in the northern sector but deteriorates around Kāne‘ohe City. Conclusions Benthic foraminifera can be used as bio-indicators in Hawaiian reefs, providing an easy and fast-to-apply method for assessing short-term changes in water quality and stress sources. Implementing benthic foraminifera studies within existing long-term monitoring programs of Hawaiian reefs can be beneficial for conservation efforts. Implications Within a historic context, our findings illustrate the modest recovery of an ecosystem following pollution control measures but highlight the need of conservation efforts for reef environments adjacent to major human settlements.
Chirped Bright and Kink Solitons in Nonlinear Optical Fibers with Weak Nonlocality and Cubic-Quantic-Septic Nonlinearity
Authors: Zhou Qin , Zhong Yu , Triki Houria , Sun Yunzhou , Xu Siliu , Liu Wenjun , Biswas Anjan
Published: April 2022

This work focuses on chirped solitons in a higher-order nonlinear Schrödinger equation, including cubic-quintic-septic nonlinearity, weak nonlocal nonlinearity, self-frequency shift, and self-steepening effect. For the first time, analytical bright and kink solitons, as well as their corresponding chirping, are obtained. The influence of septic nonlinearity and weak nonlocality on the dynamical behaviors of those nonlinearly chirped solitons is thoroughly addressed. The findings of the study give an experimental basis for nonlinear-managed solitons in optical fibers.
Laser-Induced Electron Fresnel Diffraction in Tunneling and Over-Barrier Ionization
Authors: Geng Lei , Liang Hao , Peng Liang-You
Published: April 2022

Photoelectron momentum distribution in strong-field ionization has a variety of structures that reveal the complicated dynamics of this process. Recently, we identified a low-energy interference structure in the case of a super-intense extreme ultraviolet (XUV) laser pulse and attributed it to the laser-induced electron Fresnel diffraction. This structure is determined by the laser-induced electron displacement [Geng et al.
Phys. Rev. A 104 (2021) L021102]. In the present work, we find that the Fresnel diffraction picture also appears in the tunneling and over-barrier regime of ionization by short pulses. However, the electron displacement is now induced by the electric field component of the laser pulse rather than the magnetic field component in the case of the super-intense XUV pulse. After corresponding modifications to our quantum and semiclassical models, we find that the same physical mechanism of the Fresnel diffraction governs the low-energy interference structures along the laser polarization. The results predicted by the two models agree well with the accurate results from the numerical solution to the time-dependent Schrödinger equation.
Fabrication of P(100) silicon macro-pore and pillar array by wet electrochemical etching
Authors: Li Xin , Shao Mengfan , Wang Hao , Tang Qian , Ren Ding
Published: April 2022

In this paper, pyramidal notch array was pre-etched on P(100) silicon wafer using anisotropic wet chemical etching, then macro-pore/pillar array were successfully processed in the pyramidal notch array by an anodic electrochemical etching. The formation mechanism of macro-pore and pillar in pyramidal notch were investigated, it indicates that the silicon dissolution rate is proportional to electric field, while electric field is mainly concentrated on the tip, edges and corners of the pyramidal notch. Therefore, there is an etching rate difference between the notch corner and planar regions in the pyramid notch. The notch corners are preferentially etched at first, then a pore is formed in the notch. If the shape of the open window is truncated and the bottom size is large enough, four pores would initiate at the notch angels due to etching rate difference between the truncated pyramidal notch corner and notch center, consequently, a pillar is formed in the notch center.
β-Ga2O3 nanowires: controlled growth, characterization, and deep-ultraviolet photodetection application
Authors: Ruan Wei , Wu Zhengyuan , Liu Jian , Chen Jing , Shan Yabing , Song Pengyu , Jiang Zhuoxun , Liu Ran , Zhang Guoqi , Fang Zhilai
Published: April 2022

We investigate the growth of (

2
ˉ

01

) β-Ga2O3 nanowires with a GaN seed crystal in detail. Growth of (

2
ˉ

01

) β-Ga2O3 nanowires starts with the formation of (001) Ga(II)–O chains of octahedral Ga2O6 structures, indicating the initial formation of (

2
ˉ

01

) and (001) atomic facets of β-Ga2O3 nanowires. Subsequent growth of Ga2O3 leads to the formation of (100) Ga(I)–O chains and energetically stable (100) and (010) sidewalls and octahedral Ga2O6 structures in the β-Ga2O3 nanowires. Energetically stable tetrahedral GaO4 structures are eventually formed in the β-Ga2O3 nanowires. High-quality N-doped (

2
ˉ

01

) β-Ga2O3 nanowires are synthesized and growth kinetics is clarified. The β-Ga2O3 nanowires deep-ultraviolet photodetectors show superior performance with high photoresponsivity (3.5 × 103 A W−1) and detectivity (9.6 × 1015 Jones) at −10 V bias.
Ultrananoporous supercapacitor with ionic liquid comprised of two-site cation: an Ising model study (II)
Authors: Zhou Shiqi , Zhou Run
Published: April 2022

A four-state one-dimension discrete spin model with the nearest neighbor and partial next nearest neighbor lattice interactions is proposed for describing electrical double layer formed by ionic liquid in cylindrical pore that can accommodate only one row of particles. The model, in which cation is modeled as a dimer formed by two hard spheres (HSs): one is positively charged with diameter

d
+

, while the other is neutral with diameter

d

+
0

, and anion is modeled by charged HS with diameter

d
−

, is designed to investigate effects of pore diameter

d

c
y
l
i
n

, ion transfer free energy, ion size and electrical valence on behaviors of specific differential capacitance

C
d

and specific energy storage

E

and its saturation value

E

s
a
t

. Relevant Kramers–Wannier transfer matrix is

16
×
16

, which gives system partition function by numerically solving maximum real root of the relevant characteristic equation. Main findings are briefly described below. (i) The ion valence has little effect on the

E

s
a
t

value, but does reduce the threshold voltage strength

U

s
a
t

, beyond which the energy storage reaches

E

s
a
t

. However, the ion valence (whether co- or counter-ion) raises both the

E

s
a
t

and

U

s
a
t

values as the relevant ion size decreases enough. (ii) Decreasing of the

d

c
y
l
i
n

value weakly reduces the

U

s
a
t

value, but raises the

C
d

peak height and the

E

s
a
t

value obviously; correlation between the

d

c
y
l
i
n

value and

E

s
a
t

value becomes stronger with the ions getting more pore hostile. (iii) With the counter-ion or co-ion charged site size decreasing, both the

E

s
a
t

value and

U

s
a
t

value rise. However, the effect of the co-ion charged site size is weakened as the co-ion gets more pore hostile, and the cation neutral site size influences on the

E

s
a
t

value less than the cation charged site size does. (iv) Pore friendly co-ion or pore hostile counter-ion always helps in raising the

E

s
a
t

value; the two have significant synergistic effect with the co-ion pore friendliness playing more important role than the counter-ion pore hostility.
Room temperature Szilard cycle and entropy exchange at the Landauer limit in a dopant atom double quantum dot silicon transistor
Authors: Durrani Zahid , Abualnaja Faris , Jones Mervyn
Published: April 2022

Room-temperature (RT) thermodynamics of a dopant-atom double quantum dot (DQD) silicon transistor are extracted using measurements of the dual gate charge stability diagram. Current traces corresponding to electron exchange in the Szilard one-electron gas ‘Maxwell Demon’ thermodynamic cycle are determined. Theoretical analysis, based on energy state shifts within the generalised DQD charge stability diagram, is used to map the Szilard cycle entropy exchange to the stability diagram. The restriction on the inter-QD coupling energy E
m > kT, necessary to observe DQD operation, is inherently seen to satisfy the Landauer limit, kTln2, for the minimum energy consumption per cycle for 1 bit. Associated entropy flows are extracted and simulated using single-electron Monte Carlo equivalent circuit simulations, from 4.2 to 290 K. An entropy valley, tending to the Szilard limit minimum of −kln2,

occurs at degeneracy between neighbouring electron states, with traces persisting to RT. Changes in gate cycle trajectory, device capacitance, and temperature are characterised to establish conditions for RT operation.
Superconductivity from repulsion in the doped 2D electronic Hubbard model: an entanglement perspective
Authors: Mukherjee Anirban , Lal Siddhartha
Published: April 2022

We employ the momentum space entanglement renormalization group (MERG) scheme developed in references (Mukherjee et al 2021 J. High Energy Phys. JHEP04(2021)148; Patra and Lal 2021 Phys. Rev. B 104 144514) for the study of various insulating, superconducting and normal phases of the doped and the undoped 2D Hubbard model on a square lattice found recently by us (Mukherjee and Lal 2020 New J. Phys.
22 063007; Mukherjee and Lal 2020 New J. Phys.
22 063008). At each MERG step, disentanglement of particular degrees of freedom, transforms the tensor network representation of the many-particle states. The MERG reveals distinct holographic entanglement features for the normal metallic, topologically ordered insulating quantum liquid and Neél antiferromagnetic symmetry-broken ground states of the 2D Hubbard model at half-filling, clarifying the essence of the entanglement phase transitions that separates the three phases. An MERG analysis of the quantum critical point of the hole-doped 2D Hubbard model reveals the evolution of the many-particle entanglement of the quantum liquid ground state with hole-doping, as well as how the collapse of Mottness is concomitant with the emergence of d-wave superconductivity.
Rolling bearing fault feature extraction via improved SSD and a singular-value energy autocorrelation coefficient spectrum
Authors: Xu Weiyang , Shen Yehu , Jiang Quansheng , Zhu Qixin , Xu Fengyu
Published: April 2022

It is usually difficult to extract weak fault features from rolling bearing vibration signals under noise pollution. To address this problem, a fault feature extraction approach for rolling bearings using improved singular spectrum decomposition (SSD) and a singular-value energy autocorrelation coefficient spectrum (SVEACS) is proposed. Firstly, to facilitate the determination of the optimal modal parameters in the SSD algorithm, the number of SSD layers is adaptively determined using an improved SSD algorithm based on permutation entropy. Then, the optimal modal components are selected, and the proposed SVEACS is used to determine the order of singular-value noise reduction. Finally, envelope analysis is used to extract the accurate shock characteristics of the denoised signal. The results of the experiments on simulated and real signals indicate that the proposed method can effectively extract the weak characteristics of the vibration signal under strong noise, and accurately diagnose the fault of a rolling bearing.
Application of artificial landmark in sonar detection
Authors: Li Jianda , Tang Zhijie , Wang Zhanhua , Huang Jingke , Wang Chi
Published: April 2022

Sonar is an important means of underwater target detection. However, the existing sonar measurement method does not use a third-party object as a reference, which makes it difficult to measure underwater targets. In this paper, we propose an angle measurement method and a 3D mapping algorithm based on sonar images and artificial landmarks. By combining acoustic and visual methods, using the known size information of artificial landmarks as a reference, we can calculate the target information to realize the mapping between real space and sonar images. Before verifying the feasibility, we processed the sonar image, denoised it with a median filter, enhanced the landmark image with the Sauvola algorithm, and finally introduced two data fitting methods to extract the edge information of artificial landmarks, so as to help us find the key points more accurately. The experimental results show that the accuracy of our method can reach the millimeter level, and the error range is within 5%. The technology proposed in this paper realizes the shape correction and precise length measurement of underwater targets.
Molecular dynamics simulation of nanofilament breakage in neuromorphic nanoparticle networks
Authors: Wu Wenkai , Pavloudis Theodoros , Verkhovtsev Alexey V , Solov’yov Andrey V , Palmer Richard E
Published: April 2022

Neuromorphic computing systems may be the future of computing and cluster-based networks are a promising architecture for the realization of these systems. The creation and dissolution of synapses between the clusters are of great importance for their function. In this work, we model the thermal breakage of a gold nanofilament located between two gold nanoparticles via molecular dynamics simulations to study on the mechanisms of neuromorphic nanoparticle-based devices. We employ simulations of Au nanowires of different lengths (20–80 Å), widths (4–8 Å) and shapes connecting two Au1415 nanoparticles (NPs) and monitor the evolution of the system via a detailed structural identification analysis. We found that atoms of the nanofilament gradually aggregate towards the clusters, causing the middle of wire to gradually thin and then break. Most of the system remains crystalline during this process but the center is molten. The terminal NPs increase the melting point of the NWs by fixing the middle wire and act as recrystallization areas. We report a strong dependence on the width of the NWs, but also their length and structure. These results may serve as guidelines for the realization of cluster-based neuromorphic computing systems.
Spectroscopic study of the 4f
n−15d transitions of LaPO4 doped with Pr3+ or co-doped with Pr3+ and Gd3+ in the vacuum ultra violet region
Authors: Hilario Eloísa G , Rodrigues Lucas C V , Caiut José Maurício A
Published: April 2022

The energy of f-d transitions depends on the crystalline field in which the lanthanide ion is inserted. Depending on the experimental setup, these transitions could occur at high energy, so several studies regarding theoretical data have been conducted. Here, we present the experimental determination of the energy of interconfigurational 4f

n
 → 4f

n−15d (f-d) transitions from Pr3+ ions to the lanthanum orthophosphate LaPO4 matrix; we have also determined the bandgap value for this host. The experiments were carried out at the Synchrotron setup of the Brazilian LNLS laboratory. Specifically, we synthesized LaPO4:Pr3+ and LaPO4:Pr3+/Gd3+ by the hydrothermal method under different pH conditions or by spray pyrolysis. The particles resulting from hydrothermal synthesis had different morphologies and the influence of pH value was showed: the reaction medium was controlled along the process, which changed the surface potential. On the basis of Raman spectroscopy and x-ray diffraction analyses, we found that the crystalline phase was monoclinic monazite for all the samples. We studied the 4f5d level and bandgap transitions at high energy by absorption analysis in the VUV range. The experimental results were 7.5 eV (LaPO4 bandgap) and 5 eV (4f

n
→ 4f

n−15d transition of the Pr3+ ion), which were close to the theoretical values reported in the literature for this ion and this matrix.
Shape dependent multiferroic behavior in Bi2Fe4O9 nanoparticles
Authors: Sahoo Aditi , Bhattacharya Dipten , Das Moumita , Mandal Prabhat
Published: April 2022

Ferroelectric and magnetic properties are investigated for Bi2Fe4O9 nanoparticles with different shapes (cuboid and sphere-like) synthesized by hydrothermal and sol-gel method. The magnetic study reveals that coercivity, Neel temperature and remanent magnetization strongly depend on shape of the particle. The nanoparticle with sphere-like shape exhibits magnetization curve of antiferromagnetic (AFM) ordering with ferromagnetic (FM) component. As the particle shape changes from sphere-like to cuboid, the AFM component is dominating over the ferromagnetic component. A small exchange bias is also observed at low temperature in both the sphere-like and cuboid nanoparticle. The coercivity, remanent magnetization and Neel temperature of sphere-like nanoparticle is greater than cuboid nanoparticle. Ferroelectric measurement shows the remanent polarization of cuboid is greater than sphere-like nanoparticle but the coercivity is almost same. This Bi2Fe4O9 nanoparticle shows a small change in polarization under magnetic field. The polarization value decreases with magnetic field increases. The magnetoelectric coupling-measured by change of remanent polarization under magnetic field are found to be greater in Bi2Fe4O9 sphere-like nanoparticles. These shape dependent magnetic and ferroelectric properties are coming because of shape anisotropy.
‘Astrophysics: history and theory’, an undergraduate, interdisciplinary, asynchronous astrophysics course taught in the physics program
Authors: Trout Joseph J , Jacobsen Tara , Buondonno Gracie , Weber Courtney
Published: April 2022

This project produced an online astronomy course based on the free, online OpenStax textbook. When this project was conceived, about a year before the Covid-19 pandemic, the authors had no idea that in a short period of time, most college and university classes would be online. This abrupt change in modalities of courses, from traditional, face-to-face lectures and laboratories to a more modern online format, sparked energetic discussions about the effectiveness of online courses. This paper describes the online astronomy course and its creation and evaluates the success of the course at conveying the concepts and theories studied in astronomy courses. The success of this course is examined using a 100-question pre-test and post-test based on content knowledge. A survey was also completed of the students to evaluate the perceived success of the online course and the acceptance of online courses. The survey was adjusted to include opinions about the in-person labs that were cancelled due to the Covid-19 pandemic.
What happens next? Non bubbles answer
Authors: Featonby David , Prolongo Marisa
Published: April 2022

At first sight, a bubble of soap solution looks very similar to a spherical drop of the same solution. This experiment explores this further.
Simple motor variants
Authors: Lee Heejin , Chen Yu , Lee Jiwon , Moon Su Jin , Kim Jung Bog
Published: April 2022

We have developed new rotors that can be classified into three groups by changing the rotors used in simple motors into various types. Group I has a semicircular shape rather than a perfect circle or square shape, group II has a structure consisting of several closed circles on one plane, and group III has a three-dimensional shape. We wanted to show students that a closed circular shape is not the only thing that can rotate in a magnetic field, and that various types of rotors are possible. Also, we think it would be good to give students an opportunity to envision different shapes of rotors.
An accelerator experiment for junior and senior high school students to improve students’ involvement in fundamental physics
Authors: Tanaka K S , Harada K , Hayamizu T , Kita R , Kono R , Maruta K , Nagahama H , Ozawa N , Sakemi Y , Sugimori R
Published: April 2022

In Japan, research activities by junior and senior high school students show an upward trend. However, there are limited examples of research activities in the field of elementary particles and atoms. This is due to the difficulty associated with procuring research tools such as accelerators or particle detectors. Therefore, we hosted the ‘Accel Kitchen’ in 2018 and 2019 at the Cyclotron and Radioisotope Center (CYRIC) in Tohoku University where junior and senior high school students could participate in ongoing research of particle and atomic physics. At each workshop, 12 junior and senior high school students participated in the beam experiment, including the production of francium atoms (Fr) by the fusion reaction of oxygen and gold, optimizing the transport of the ion beam and identifying the alpha decay nuclei, and laser trapping of Fr for two days. Each group that was involved in the experiment was supported by researchers and university students who acted as mentors. This was the first opportunity for junior and senior high school students to know about the particle beam experiment in Japan.
On the merits of a unified physics and engineering undergraduate programme of study
Authors: Nezhad Maziar P
Published: April 2022

The merits of a pedagogic and programmatic unification between physics and several engineering disciplines at the undergraduate level are discussed. Arguments for such a unification are presented, based on the strong overlap of core teaching material and the similarity of career trajectories in the modern job market for physics and engineering graduates. In addition to providing a level of robustness for academic institutions against external factors such as fluctuating student intake numbers, such a merger can also have positive dividends for increased inclusion of minority and female students in STEM fields. The widespread availability and affordability of advanced laboratory equipment, computing hardware/software and other technical infrastructure at the current time is also highlighted as a reason for the practical feasibility of this approach.
Microcontroller based study of diode thermometers for online demonstration of undergraduate laboratory classes in COVID-19 lockdown
Authors: Biswas Subhrajyoti , Roy Durjoy
Published: April 2022

At constant current (I) the forward bias potential (V) of a pn junction diode may be considered to vary linearly with temperature (t) within a temperature range. Based on this property we have constructed diode thermometer using germanium (Ge) and silicon (Si) diodes. The experimental

V

−

t

data at constant forward current have been fitted to a straight line for calibration of the diode thermometers using the least square method. Furthermore, the fitting parameters of the straight line have also been used to determine the band gap energy of germanium and silicon and experimental values of band gap for both the semiconductor materials are found to agree well with accepted values.
The little robot, black holes, and spaghettification
Authors: Pinochet Jorge
Published: April 2022

The tidal forces generated by a black hole can be so powerful that they cause unlimited stretching, known as spaghettification. A detailed analysis of this phenomenon requires the use of Einstein’s theory of general relativity. The aim of this paper is to offer an up-to-date and accessible analysis of spaghettification, in which the complex mathematics of Einstein’s theory are replaced with the simpler and more intuitive concepts of Newtonian gravity. The article can serve as educational material for undergraduate modern physics or astronomy courses.
Magnetic levitator fitted with the Hall sensor readings
Authors: Zvorykin Ilya Yu , Katkova Mariia R , Maslennikova Yulia V
Published: April 2022

In this article, we propose a simple and accessible model of a magnetic levitator fitted with a Hall sensor. This model also allows to determine the magnitude of the magnetic field within the levitator working volume. Students can also compare the experimental magnetic field values to reference values in magnetism textbooks. This Arduino-based levitator may be built by a student under teacher’s supervision as part of an individual project in high school or secondary school setting.
A teaching proposal for the didactics of Special Relativity: the spacetime globe
Authors: Leonardi Alessio Mattia , Mobilio Settimio , Fazio Claudio
Published: April 2022

Special Relativity introduces students to Modern Physics, whose importance in the high school is increasing. Nevertheless its teaching and learning is a critical issue. Different solutions have been developed to overcome the encountered difficulties. In this paper we describe the spacetime globe, a mechanical instrument that allows to experience Special Relativity hands-on. We show how it is possible to treat all the main phenomena foreseen by Special Relativity with simple laboratory experiences, using the idea of Minkowski’s spacetime diagrams. The aim is to develop the use of geometrical approach in learning Special Relativity in high schools.
On the operation of the Hanstead car
Authors: Persson Rasmus A X
Published: April 2022

We consider the operation of the hypothetical mechanical vehicle driven by an engine powered by small rockets introduced by P D Hanstead in the inaugural volume of this journal. Hanstead arrived at three contradictory conclusions regarding the change in velocity should some of the rockets malfunction at a particular time. This thought experiment constitutes an excellent, conceptual discussion, or even exam, question for an introductory mechanics course.
Building a digital barometer with Arduino to study forces due to atmospheric pressure and weather maps at schools
Authors: Moya Antonio Ángel , Merino Ana
Published: April 2022

We describe a simple STEM project for students to learn to measure atmospheric pressure by using a sensor of the type BMP180 together with the Arduino electronic platform. The collected experimental data, together with simple experiments, can be used to study the different pressure units and the relationship between pressure and force. Also, they can be used to study basic meteorology concepts associated with the movement of air on isobar maps, and to include transversal competences related to environmental education.
Limits of the simple pendulum formula for classroom use
Authors: Oliveira Vitor
Published: April 2022

We discuss the limits of the equation of the period of a simple pendulum,

T
s

=
2
π

l

/

g

, frequently used in high-school and university classrooms to measure the acceleration of gravity. We evaluate the relative error in determining the acceleration of gravity with this simple equation instead of a more realistic one, taking into account the string’s mass, the bob’s radius, and finite angular displacements. We show that the bob radius and finite angular displacements increase the period of oscillation of the pendulum and, hence, contribute to a positive deviation in the value of g calculated with the simple pendulum formula. On the other hand, the string’s mass decreases the pendulum’s period and induces a negative deviation in the value of g. As a result, it is possible to adapt the pendulum’s characteristics to use the simple pendulum formula and calculate g with accuracy.
Experimental characterisation of the magnetic field correction factor,

kB⃗,

for Roos chambers in a parallel MRI-linac
Authors: Begg Jarrad , Jelen Urszula , Keall Paul , Liney Gary , Holloway Lois
Published: April 2022

Objective. Reference dosimetry on an MRI-linac requires a chamber specific magnetic field correction factor,

k

B
⃗

.

This work aims to measure the correction factor for a parallel plate chamber on a parallel MRI-linac. Approach.

k

B
⃗

is defined as the ratio of the absorbed dose to water calibration coefficient in the presence of the magnetic field,

N

D
,
w

B
⃗

relative to that under 0 T conditions,

N

D
,
w

0
T

.

k

B
⃗

was measured via a

N

D
,
w

transfer to a field chamber at each magnetic field strength from a chamber with known

N

D
,
w

and

k

B
⃗

.

This was achieved on the parallel MRI-linac by moving the measurement set-up between a high magnetic field strength region at the MRI-isocentre and a low magnetic field strength region at the end of the bore whilst maintaining consistent set-up and scatter conditions. Three PTW 34001 Roos chambers were investigated as well as a PTW 30013 Farmer used to validate methodology. Main Results. The beam quality used for the measurements of

k

B
⃗

was TPR
20/10 = 0.632. The

k

B
⃗

for the PTW Farmer chamber at 1 T on a parallel MRI-linac was 0.993 ± 0.013 (k = 1). The average

k

B
⃗

factor measured for the three Roos chambers on a 1 T parallel MRI-linac was 0.999 ± 0.014 (k = 1). Significance. The results presented are the first measurements of

k

B
⃗

for a Roos chamber on a parallel MRI-linac. The Roos chamber results demonstrate the potential for the chamber as a reference dosimeter in parallel MRI-linacs.