bluuebunny/crossref_metadata_2025 huggingface dataset:
Die Dunkelfeld-Radiografie – ein neuer Weg zur Diagnostik von Gichterkrankungen bei Vögeln und Reptilien?
Authors: Roiser Nathalie , Scholz Josef , Kimm Melanie A. , Andrejewski Jana , Baumgartner Christine , Braig Eva , Herzen Julia , Pfeiffer Daniela , Korbel Rüdiger
Published: July 2022

Gegenstand und Ziel In der Studie soll evaluiert werden, ob die Dunkelfeld-Radiografie (DFR) zur Diagnostik der Gichterkrankung bei Vögeln und Reptilien angewendet werden kann und ob das Tiermodell für die Etablierung des neuen nicht invasiven Verfahrens für die Gichtdiagnostik in der Humanmedizin geeignet ist.

Material und Methoden Es wurden insgesamt 18 Gliedmaßen von 11 Vögeln (7 verschiedene Spezies aus den Ordnungen der Papageienvögel, Singvögel, Greifvögel, Hühnervögel und Taubenvögel) und 7 Reptilien (4 verschiedene Spezies aus den Ordnungen der Schuppenkriechtiere und Schildkröten) mit und ohne Verdacht auf Gelenksgicht vergleichend an einem gitterbasierten Dunkelfeld-Röntgen-Versuchsaufbau sowie mittels konventioneller Röntgenuntersuchung gemessen. Jede Bilderfassung erzeugte ein Dunkelfeld- und ein konventionelles Absorptionsröntgenbild. Die Ergebnisse der einzelnen Scans wurden jeweils mit den Ergebnissen einer pathologischen Untersuchung und der Arthrozentese verglichen.

Ergebnisse Bei 5 der untersuchten Vögel und bei 4 der untersuchten Reptilien wurde Gicht pathologisch-anatomisch nachgewiesen. Aus beiden Gruppen konnten bei jeweils 3 Tieren mittels Arthrozentese Harnsäurekristalle in den Gelenken gefunden werden. Im Dunkelfeldbild konnten die Kristalle in jeweils 2 Fällen detektiert werden. Die nadelförmigen Harnsäurekristalle hatten eine Länge von 2,6 μm bis 56 μm.

Schlussfolgerungen Es konnte gezeigt werden, dass die Harnsäurekristalle ein deutliches Dunkelfeldsignal erzeugen, wohingegen die Kristallablagerungen in den konventionellen Röntgenbildern nicht zu sehen waren.

Klinische Relevanz Die gewonnenen Ergebnisse zeigen, dass am Tiermodell von Vögeln und Reptilien eine Harnsäurekristalldetektion mittels nicht invasiver bildgebender Dunkelfeld Bildgebung möglich ist. Dies könnte die Gichtdiagnostik nicht nur in der Tiermedizin, sondern auch in der Humanmedizin erweitern und die Arthrozentese bei positivem DFR Befund ablösen. Präklinische Scanner, welche den Dunkelfeld- und Phasenkontrast nutzen, existieren bereits für Hände und Mammografie und werden im Humanbereich bereits klinisch erprobt.
Ursache, Verbreitung und evidenzbasierte Therapie sowie Prävention der peripartalen Hypokalzämie
Authors: Venjakob Peter Lennart , Borchardt Stefan
Published: July 2022

Die peripartale Hypokalzämie ist eine weit verbreitete Stoffwechselstörung, dessen klinische Form etwa 7 % der Milchkühe und dessen subklinische Form fast jede 2. multipare Kuh betrifft. Obwohl sich hinsichtlich Diagnostik und Therapie in den letzten 30 Jahren kaum etwas verändert hat, herrscht bei Landwirten und Tierärzten Unklarheit über die Prävalenz und den Risikozeitraum dieser Stoffwechselstörung. Darüber hinaus gibt es sehr unterschiedliche Angaben darüber, wieviel Kalzium einer Kuh mit klinischer Hypokalzämie substituiert werden sollte. Ziel dieses Übersichtsartikels ist es, die Entstehung und Verbreitung von Hypokalzämie evidenzbasiert darzustellen. Des Weiteren werden die Ergebnisse älterer und neuer Studien zusammengefast, mit dem Ziel eine möglichst genaue Empfehlung zur Behandlung von klinischer Hypokalzämie zu geben. Da in einer 2017 durchgeführten Studie gezeigt wurde, dass der überwiegende Teil deutscher Milchviehbetriebe keine Prophylaxe gegen Hypokalzämie betreibt, werden in dem letzten Teil dieser Arbeit die verschiedenen Prophylaxekonzepte, unter Berücksichtigung der aktuellen Literatur, dargestellt.
Kinetische und Kinematische Gangbildanalyse der Rückenbewegung chondrodystropher Rassen nach Hemilaminektomie im Vergleich zu einer gesunden Population
Authors: Balmer Sarah , Steigmeier-Raith Stephanie , Layer Anna , Reese Sven , Meyer-Lindenberg Andrea
Published: July 2022

Gegenstand und Ziel Die Erhebung kinetischer und kinematischer Daten der Rückenbewegung von gesunden Hunden im Vergleich zu Hunden chondrodystropher Rassen nach Hemilaminektomie im Schritt und im Trab.

Material und Methoden Bei 19 gesunden Hunden wurde ganganalytisch die Rückenbewegung untersucht und mit einer Gruppe von 21 chondrodystrophen Hunden, die aufgrund eines Bandscheibenvorfalles der Brust- oder Lendenwirbelsäule mittels Hemilaminektomie operativ versorgt wurden, verglichen.

Ergebnisse Die erkrankten Tiere zeigten sowohl in der Transversal- als auch in der Sagittalebene in beiden Gangarten (Schritt und Trab) über die gesamte Wirbelsäule hinweg einen vergrößerten Bewegungsumfang (Range of motion, ROM). Die Lokalisation der Hemilaminektomiestelle (Brust- oder Lendenwirbelsäule oder thorakolumbaler Übergang) wirkte sich sehr unterschiedlich auf den Bewegungsablauf der Rückenbewegung aus. Die Gruppe der erkrankten Tiere zeigte eine signifikant vergrößerte prozentuale Gewichtsverteilung auf die Vordergliedmaßen. Im direkten Vergleich der Hintergliedmaßen (ipsilaterale Seite der Hemilaminektomie zur kontralateralen Seite) in der Gruppe der erkrankten Tiere wurde eine reduzierte vertikale Spitzenkraft (peak vertical force, PVF) sowie ein reduzierter vertikaler Impuls (VI) für die ipsilaterale Gliedmaße festgestellt.

Schlussfolgerung Hunde nach Hemilaminektomie haben eine verminderte Stabilität im Bereich der Wirbelsäule, die sich je nach Lokalisation der Hemilaminektomie unterschiedlich auf die einzelnen Wirbelsäulenabschnitte auswirkt. Es kommt zudem zu einer verstärkten Gewichtsaufnahme auf die Vordergliedmaßen. Die zur Hemilaminektomie ipsilaterale Hintergliedmaße zeigt trotz subjektiv lahmheitsfreiem Gangbild eine verminderte Gewichtsaufnahme im Vergleich zur kontralateralen Seite.

Klinische Relevanz Operative Eingriffe im Sinne einer Hemilaminektomie beeinflussen bzw. verändern nachhaltig die Bewegungsabläufe der Wirbelsäule, jedoch scheinen die Hunde mit verschiedenen kompensatorischen Mechanismen im Alltag problemlos zurecht zu kommen.
One-Pot Synthesis of 1,2,3-Triazole-Fused Polycyclic Systems via Sequential Annulation of 1,n-Enynes with Tosyl Azide
Authors: Peng Shiyong , Zhou Ting , Yang Liangliang , Lang Ming
Published: July 2022

An efficient one-pot sequential annulation of 1,n-enynes with tosyl azide is reported, providing a series of novel N-alkyl 1,2,3-triazole-fused polycyclic scaffolds in moderate to excellent yields under mild reaction conditions.
Recent Advances in Transition-Metal-Catalyzed Asymmetric Functionalization of Enamides
Authors: Chen Yifeng , Xi Yang
Published: July 2022

Enamides, as prefunctionalized electron-rich heteroatom-substituted alkenes represent a powerful platform to synthesize useful nitrogen-containing natural products and bioactive molecules. This review discloses recent progress in the transition-metal-catalyzed enantioselective functionalization of enamides, including the Heck reaction, hydrofunctionalization, and difunctionalization, with a focus on the general scope, current limitations, stereochemical reaction control, and mechanistic aspects.

1 Introduction

2 Asymmetric Heck Reaction of Enamides

3 Asymmetric Hydrofunctionalization of Enamides

3.1 Nickel Catalysis

3.2 Copper Catalysis

3.3 Rhodium Catalysis

3.4 Iridium Catalysis

4 Asymmetric Difunctionalization of Enamides

4.1 Palladium Catalysis

4.2 Nickel Catalysis

4.3 Copper Catalysis

5 Summary and Outlook
α-Sulfenylation between 4-Hydroxydithiocoumarin and 1,3-Dicarbonyl Compounds: A Key Precursor for the Synthesis of New Pyrazole Derivatives
Authors: Khan Abu Taleb , Mondal Santa
Published: July 2022

An efficient synthetic protocol for the α-sulfenylation of 1,3-dicarbonyl compounds is reported through a cross dehydrogenative coupling reaction with 4-hydroxydithiocoumarins in the presence of 10 mol% KI and 1 equiv. TBHP in toluene under reflux conditions. Some of the products are utilized for the synthesis of substituted new pyrazole derivatives on reaction with phenylhydrazine in ethanol at room temperature. In addition, α-benzylation is also achieved on treatment with benzyl bromide using K2CO3/CH3CN under mild conditions. The salient features of the present protocol are good yields, mild reaction conditions, shorter reaction time, no byproducts were formed (sulfoxide/sulfone), and no deacylation occurs during the process. In the present protocol, 4-hydroxydithiocoumarin is converted into a suitable electrophile through a radical substitution pathway, which undergoes ultimately C–S bond formation with 1,3-dicarbonyl compounds by a nucleophilic substitution reaction.
Surface-reconstructed oxygen-vacancy-rich amorphous-crystalline Ni(Co) heterostructure for boosted oxygen evolution reaction
Authors: Liu Xue-jian , Chen Zhi-gang , Zhu Cheng-feng , Yang Guang , Weng Xue-fei , Cui Yi
Published: July 2022

The design of low-cost and robust electrocatalysts with rich active sites remains challenging for improving the efficiency of water oxidation. Herein, ternary Ni-Co-Mo oxide films were uniformly synthesized on Cu foil via simple electrochemical deposition method. After surface reconstruction, the robust amorphous-crystalline amorphous-crystalline Ni(Co) heterostructure with rich oxygen vacancies were achieved. Accordingly, the as-obtained surface-reconstructed heterostructure catalysts exhibited a superior oxygen evolution reaction activity with overpotential as low as 308 mV at 20 mA/cm2 and a small Tafel slope of 90 mV/dec. Moreover, a negligible activity degradation was observed for the heterostructure catalyst via continuously catalyzing OER process over 24 h, highlighting the structural robustness of the self-reconstructed Ni-Co-Mo catalyst for practical electrocatalytic applications.
Substituent effects on the photocatalytic properties of a symmetric covalent organic framework
Authors: Liu Ting-Ting , Wu Xin-Ping , Gong Xue-Qing
Published: July 2022

Symmetric covalent organic frame-work (COF) photocatalysts generally suffer from inefficient charge separation and short-lived photoexcited states. By performing density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations, we find that partial substitution with one or two substituents (N or NH2) in the linkage of the representative symmetric COF (N0-COF) gives rise to the separation of charge carriers in the resulting COFs (i.e., N1-COF, N2-COF, (NH2)1-N0-COF, and (NH2)2-N0-COF). Moreover, we also find that the energy levels of the highest occupied crystal orbital (HOCO) and the lowest unoccupied crystal orbital (LUCO) of the N0-COF can shift away from or toward the vacuum level, depending on the electron-withdrawing or electron-donating characters of the substituent. Therefore, we propose that partial substitution with carefully chosen electron-withdrawing or electron-donating substituents in the linkages of symmetric COFs can lead to efficient charge separation as well as appropriate HOCO and LUCO positions of the generated COFs for specific photocatalytic reactions. The proposed rule can be utilized to further boost the photocatalytic performance of many symmetric COFs.
A case study of using x-ray Thomson scattering to diagnose the in-flight plasma conditions of DT cryogenic implosions
Authors: Poole H. , Cao D. , Epstein R. , Golovkin I. , Walton T. , Hu S. X. , Kasim M. , Vinko S. M. , Rygg J. R. , Goncharov V. N. , Gregori G. , Regan S. P.
Published: July 2022

The design of inertial confinement fusion ignition targets requires radiation-hydrodynamics simulations with accurate models of the fundamental material properties (i.e., equation of state, opacity, and conductivity). Validation of these models is required via experimentation. A feasibility study of using spatially integrated, spectrally resolved, x-ray Thomson scattering measurements to diagnose the temperature, density, and ionization of the compressed DT shell of a cryogenic DT implosion at two-thirds convergence was conducted. Synthetic scattering spectra were generated using 1D implosion simulations from the LILAC code that were post processed with the x-ray scattering model, which is incorporated within SPECT3D. Analysis of two extreme adiabat capsule conditions showed that the plasma conditions for both compressed DT shells could be resolved.
Advanced design of a x-ray absorption spectroscopy setup for measuring transition metals speciation in molten carbonates, hydroxides and hydrogenosulfates
Authors: Safarzadeh Z. , Gomes J. C. , Sirieix-Plénet J. , Ruiz N. , Hamitouche L. , Michot L. , Carré L. , Barthe L. , Briois V. , Rollet A.-L.
Published: July 2022

Battery recycling is currently becoming a crucial issue. One possible treatment path involves the use of molten salts. A mechanistic understanding of the underlying processes requires being able to analyze in situ speciation in molten salts at various temperatures. This can be advantageously achieved using x-ray absorption spectroscopy, the use of Quick-EXAFS facilities being particularly appropriate. Consequently, this paper presents the design and development of a new setup allowing carrying out Quick-EXAFS experiments in oxidizing molten salts at high temperatures. We describe the different components of a cell and the performance of the heating device. We illustrate the capabilities of the setup by analyzing the temperature evolution of Co speciation upon dissolution of LiCoO2, a typical battery electrode material, in molten carbonates, hydroxides, and hydrogenosulphates.
Optimal maximal gaps of Dirichlet eigenvalues of Sturm–Liouville operators
Authors: Guo Shuyuan , Meng Gang , Yan Ping , Zhang Meirong
Published: July 2022

In this paper, we consider the gaps λ2n(q) − λ1(q) for the Dirichlet eigenvalues {λm(q)} of Sturm–Liouville operators with potentials q on the unit interval. By merely assuming that potentials q have the L1 norm r, we will explicitly give the solutions to the maximization problems of λ2n(q) − λ1(q), where n is arbitrary. As a consequence, the solutions can lead to the optimal upper bounds for these eigenvalue gaps. The proofs are extensively based on the eigenvalue theory of measure differential equations in Meng and Zhang [J. Differ. Equations 254, 2196–2232 (2013)] and on the known results of the optimization problems for single eigenvalues of ordinary differential equations in Wei, Meng, and Zhang [J. Differ. Equations 247, 364–400 (2009)].
Topological data analysis of truncated contagion maps
Authors: Klimm Florian
Published: July 2022

The investigation of dynamical processes on networks has been one focus for the study of contagion processes. It has been demonstrated that contagions can be used to obtain information about the embedding of nodes in a Euclidean space. Specifically, one can use the activation times of threshold contagions to construct contagion maps as a manifold-learning approach. One drawback of contagion maps is their high computational cost. Here, we demonstrate that a truncation of the threshold contagions may considerably speed up the construction of contagion maps. Finally, we show that contagion maps may be used to find an insightful low-dimensional embedding for single-cell RNA-sequencing data in the form of cell-similarity networks and so reveal biological manifolds. Overall, our work makes the use of contagion maps as manifold-learning approaches on empirical network data more viable.
Synchronization in the Kuramoto model in presence of stochastic resetting
Authors: Sarkar Mrinal , Gupta Shamik
Published: July 2022

What happens when the paradigmatic Kuramoto model involving interacting oscillators of distributed natural frequencies and showing spontaneous collective synchronization in the stationary state is subject to random and repeated interruptions of its dynamics with a reset to the initial condition? While resetting to a synchronized state, it may happen between two successive resets that the system desynchronizes, which depends on the duration of the random time interval between the two resets. Here, we unveil how such a protocol of stochastic resetting dramatically modifies the phase diagram of the bare model, allowing, in particular, for the emergence of a synchronized phase even in parameter regimes for which the bare model does not support such a phase. Our results are based on an exact analysis invoking the celebrated Ott–Antonsen ansatz for the case of the Lorentzian distribution of natural frequencies and numerical results for Gaussian frequency distribution. Our work provides a simple protocol to induce global synchrony in the system through stochastic resetting.
Effect of plasma boundary and electrode asymmetry in planar DC discharge system
Authors: Barnwal Prashant K. , Ganguli A. , Narayanan R. , Tarey R. D.
Published: July 2022

This paper present presents a detailed characterization and analysis of plasma formation using different anode sizes in two contrasting configurations in a planar DC discharge system. One configuration has a conducting boundary (CB) formed by the conducting wall of the vacuum chamber that acts as an extended cathode. The second configuration, the Small Volume Insulated Boundary (SVIB) with a volume 22.5 times smaller than the CB system, is realized by confining the plasma completely within a fully insulating boundary. Anode sizes may be equal to the cathode size (symmetric electrodes) or smaller (asymmetric electrodes). In general, CB discharges require much lower applied voltages, showing very little variation with the pressure. Although the symmetric CB discharges have only single electron population, the asymmetric electrode discharges exhibit two electron populations, a high-density bulk population (Te ∼ 2–3 eV) and a very low-density warm population (Tw ∼ 40 eV) that serves to enhance ionization and compensate for reduced anode size. In contrast, the SVIB discharges require high voltages, show considerable variation in discharge voltage both with pressure and anode size, and have higher densities. In addition, one finds two electron populations for all anode sizes. From estimates of the anode sheath drop, it is possible to show that all CB discharges have an electron-rich anode sheath for all anode sizes. In contrast, the SVIB discharges exhibit ion-rich anode sheaths for all anode sizes, although for small-sized anodes and high pressures the sheaths transform to an electron-rich sheath.
Concerning a hole trap in α-Al2O3:C,Mg
Authors: Kalita J. M. , Chithambo M. L.
Published: July 2022

We report the existence of a hole trap in α-Al2O3:C,Mg as determined using thermoluminescence (TL) and optically stimulated luminescence (OSL). The associated experiments are based on the hypotheses that if a TL glow peak is associated with a hole trap in the glow curve of α-Al2O3:C,Mg, that hole trap will not participate in any light-induced electron-transfer process and its removal will not cause the OSL intensity to decrease. To examine the first hypothesis, a TL glow curve was recorded at 1 °C/s to establish the position of glow peaks. There is a high intensity peak at 184 °C (labeled as peak IV) and eight secondary peaks at 48, 80, 108, 228, 288, 320, 386, and 426 °C (peaks I, II, III, and V–IX). The light-induced charge transfer between various electron traps associated with the peaks was studied. This study reveals that all peaks except the one at 228 °C (peak V) participate in the charge-transfer process. A test of the second hypothesis shows that peak V is also not reproduced by illumination (phototransfer), and the depletion of this peak does not influence the charge-transfer process. An additional study on the effect of temperature on the TL and OSL intensity was carried out to further assess the nature of the charge traps associated with the peaks. The depletion of peak V does not affect the OSL intensity. The results from both experiments are clear evidence consistent with the hypothesis that the charge trap associated with peak V is a hole trap.
Cross-correlation corrected friction in generalized Langevin models: Application to the continuous Asakura–Oosawa model
Authors: Klippenstein Viktor , van der Vegt Nico F. A.
Published: July 2022

The development of dynamically consistent coarse-grained models for molecular simulations is often based on generalized Langevin equations, motivated by the application of the projection operator formalism (Mori–Zwanzig theory). While Mori’s projection operator yields linear generalized Langevin equations that can be computationally efficiently implemented in numerical simulations, the downside is that Mori’s generalized Langevin equation does not encompass the multi-body potential of mean force required to correctly encode structural and thermodynamic properties in coarse-grained many-body systems. Zwanzig’s projection operator yields nonlinear generalized Langevin equations including the multi-body potential of mean force, while the remaining force contributions are not as cheap to implement in molecular simulation without making it formally hard to justify approximations. For many-particle coarse-grained models, due to computational and conceptual simplicity, an often used approach is to combine nonlinear conservative interactions with linear expressions to model dissipation. In a previous study [V. Klippenstein and N. F. A. van der Vegt, J. Chem. Phys. 154, 191102 (2021)], we proposed a method to parameterize such models to achieve dynamic consistency in coarse-grained models, allowing us to reconcile Mori’s and Zwanzig’s approach for practical purposes. In the current study, by applying the same strategy, we develop coarse-grained implicit solvent models for the continuous Asakura–Oosawa model, which under certain conditions allows us to develop very accurate coarse-grained potentials. By developing coarse-grained models for different reference systems with varying parameters, we test the broader applicability of the proposed procedure and demonstrate the relevance of accurate coarse-grained potentials in bottom-up derived dissipative models. We study how different system parameters affect the dynamic representability of the coarse-grained models. In particular, we find that the quality of the coarse-grained potential is crucial to correctly model the backscattering effect due to collisions on the coarse-grained scale. As hydrodynamic interactions are not explicitly modeled in the presented coarse-graining approach, deviations are observed in the long-time dynamics. The Asakura–Oosawa model allows for the tuning of system parameters to gain an improved understanding of this limitation. We also propose three new iterative optimization schemes to fine-tune the generalized Langevin thermostat to exactly match the reference velocity-autocorrelation function.
Initial transient stage of pin-to-pin nanosecond repetitively pulsed discharges in air
Authors: Wang Xingxing , Patel Adam , Shashurin Alexey
Published: July 2022

In this work, evolution of parameters of nanosecond repetitively pulsed (NRP) discharges in pin-to-pin configuration in air was studied during the transient stage of initial 20 discharge pulses. Gas and plasma parameters in the discharge gap were measured using coherent microwave scattering, optical emission spectroscopy, and laser Rayleigh scattering for NRP discharges at repetition frequencies of 1, 10, and 100 kHz. Memory effects (when perturbations induced by the previous discharge pulse would not decay fully until the subsequent pulse) were detected for the repetition frequencies of 10 and 100 kHz. For 10 kHz NRP discharge, the discharge parameters experienced significant change after the first pulse and continued to substantially fluctuate between subsequent pulses due to rapid evolution of gas density and temperature during the 100 μs inter-pulse time caused by intense redistribution of the flow field in the gap on that time scale. For 100 kHz NRP discharge, the discharge pulse parameters reached a new steady-state at about five pulses after initiation. This new steady-state was associated with well-reproducible parameters between the discharge pulses and substantial reduction in breakdown voltage, discharge pulse energy, and electron number density in comparison to the first discharge pulse. For repetition frequencies 1–100 kHz considered in this work, the memory effects can be likely attributed to the reduction in gas number density and increase in the gas temperature that cannot fully recover to ambient conditions before subsequent discharge pulses.
Significant variation of structural, electronic, magnetic, and polarized properties induced by strain in armchair MoSTe nanoribbon
Authors: Wang Xinxin , Li Gaojie , Liu Haobo , Shi Wenyu , Li Xiaohong , Wan Jianguo
Published: July 2022

Both the inner strain and external strain are considered to study the variation of structural, electronic, magnetic, and polarized properties of aMoSTe-nanoribbons (NRs). Our results show that the aMoSTe-NR presents direct bandgap and magnetism due to the inner strain. With the increase of width, the bandgaps, magnetic moments, and out-of-plane piezoelectronic coefficients present oscillation behavior independence of nanoribbon symmetry. However, the variation of in-plane piezoelectronic coefficients is strongly dependent on the edge type that the aMoSTe-NR with symmetric edges has larger piezoelectronic coefficients than that with asymmetric edges. When the external strain is applied to aMoSTe-NRs, the changes of bandgap, magnetic moment, and polarization are only influenced by the external strain, unrelative to the edge type. Especially, the in-plane polarization is increased accompanied with parabolic behavior in the range from 0 to 8%. The in-plane piezoelectric coefficient is enhanced to 14.072 × 10−10 C m−1 at 8%, about 2.7 times as much as aMoSTe-NRs without strain. The polarization along the out-of-plane direction presents linear character. The Born-effective charge indicates that the polarization of aMoSTe-NRs is mainly from S atoms near edge atoms. The significant variation provides guidance to the application of aMoSTe-NRs in designing electronic and piezoelectric devices.
The discrete Chebyshev–Meckler–Mermin–Schwarz polynomials and spin algebra
Authors: Garg Anupam
Published: July 2022

The polynomials discovered by Chebyshev and subsequently related to spin transition probabilities by Meckler [Meckler, Phys. Rev. 111, 1447 (1958)] and Mermin and Schwarz [Found. Phys. 12, 101 (1982)] are studied, and their application to phase space representations of spin states and operators is examined. In particular, a formula relating the end-point value of the polynomials to scale factors relating different phase space representations of spherical harmonic operators is found. This formula is applied to illustrative calculations of Wigner functions for a single spin and the singlet state of a pair of spins.
Structural heterogeneity in non-crystalline Tex Se1−x thin films
Authors: Sari Bengisu , Batiz Humberto , Zhao Chunsong , Javey Ali , Chrzan D. C. , Scott Mary C.
Published: July 2022

Rapid crystallization behavior of amorphous TexSe1−x thin films limits the use of these alloys as coatings and in optoelectronic devices. Understanding the short- and medium-range ordering of the amorphous structure and the fundamental physics governing the crystallization of the films is crucial. Although the lack of long range crystalline order restricts the characterization of the amorphous films, electron microscopy offers a way to extract information about the nanoscale ordering. In this paper, the local ordering of amorphous TexSe1−x thin films with x=0.22, 0.61, 0.70, 0.90, and 1 grown by thermal evaporation is investigated using radial distribution function (RDF) and fluctuation electron microscopy (FEM) analysis. RDF results show that the nearest-neighbor distances of selenium (Se) and tellurium (Te) in their crystalline structure are preserved, and their bond lengths increase with the addition of Te. Density functional theory (DFT) calculations predict structures with interatomic distances similar to those measured experimentally. Additionally, fluctuations in atomic coordination are analyzed. Medium range order (MRO) analysis obtained from FEM and DFT calculations suggests that there are at least two populations within the chain network structure, which are close to the Se–Se and Te–Te intrachain distances. For the binary alloy with x > 0.61, TexSe1−x, Te–Te like populations increase and Te fragments might form, suggesting that the glass forming ability decreases rapidly.
Dopant compensation in p-type doped MAPb1−xCuxI3 alloyed perovskite crystals
Authors: Liu Ting , Li Chen , Yuan Beilei , Chen Yang , Wei Haoming , Cao Bingqiang
Published: July 2022

Tuning the optical and electrical properties of semiconductors by designed doping is the basis of most energy-related semiconductor optoelectronic devices. In this Letter, we report the dopant compensation effect of P-type doped MAPb1−x CuxI3 alloyed perovskite crystals. MAPb1−xCuxI3 single crystals were prepared by the inverse temperature crystallization method using cupric chloride (CuCl2) as the doping source. By XRD, XPS, STEM, and photoluminescence (PL) spectra analyses, we demonstrate that the doped cupric (Cu2+) ions can partially substitute lead (Pb2+) ions and form Cu–Pb based crystal semiconductor alloys of MAPb1−xCuxI3 with tunable bandgap by controlling the Pb/Cu ratio. More detailed XPS analysis of the doped crystal shows that the Cu2+ ions in MAPb1−xCuxI3 are partially reduced by I− ions, and the coexistence of two valence states of Cu species (Cu2+ and Cu+) was observed in the doped crystals. Hall results of MAPb1−xCuxI3 semiconductors show that the presence of reduced Cu+ ions impels the change of conductive type from weak N-type to P-type obviously, while the resistivity of doped MAPb1−xCuxI3 increases significantly from 104 to 107 Ω cm. The defect-related optical fingerprints of cupric doped crystals were investigated in detail by temperature-dependent PL spectroscopy. The pristine MAPbI3 perovskite crystal exhibits intrinsic donor bound exciton (D0X) luminescence at low temperature (10 K), while the doped MAPb1−xCuxI3 perovskites exhibit donor-acceptor or bound exciton (A0X) peaks related to a Cu+ dopant in sequence with the increase in the Cu ion content. These results indicate that the doping of Cu2+/+ ions into the MAPb1−xCuxI3 crystal not only changes the semiconductor bandgap but also causes the dopant compensation.
Complex dynamics in a Hopfield neural network under electromagnetic induction and electromagnetic radiation
Authors: Wan Qiuzhen , Yan Zidie , Li Fei , Chen Simiao , Liu Jiong
Published: July 2022

Due to the potential difference between two neurons and that between the inner and outer membranes of an individual neuron, the neural network is always exposed to complex electromagnetic environments. In this paper, we utilize a hyperbolic-type memristor and a quadratic nonlinear memristor to emulate the effects of electromagnetic induction and electromagnetic radiation on a simple Hopfield neural network (HNN), respectively. The investigations show that the system possesses an origin equilibrium point, which is always unstable. Numerical results uncover that the HNN can present complex dynamic behaviors, evolving from regular motions to chaotic motions and finally to regular motions, as the memristors’ coupling strength changes. In particular, coexisting bifurcations will appear with respect to synaptic weights, which means bi-stable patterns. In addition, some physical results obtained from breadboard experiments confirm Matlab analyses and Multisim simulations.
Information evolution in complex networks
Authors: Tian Yang , Li Guoqi , Sun Pei
Published: July 2022

Many biological phenomena or social events critically depend on how information evolves in complex networks. However, a general theory to characterize information evolution is yet absent. Consequently, numerous unknowns remain about the mechanisms underlying information evolution. Among these unknowns, a fundamental problem, being a seeming paradox, lies in the coexistence of local randomness, manifested as the stochastic distortion of information content during individual–individual diffusion, and global regularity, illustrated by specific non-random patterns of information content on the network scale. Here, we attempt to formalize information evolution and explain the coexistence of randomness and regularity in complex networks. Applying network dynamics and information theory, we discover that a certain amount of information, determined by the selectivity of networks to the input information, frequently survives from random distortion. Other information will inevitably experience distortion or dissipation, whose speeds are shaped by the diversity of information selectivity in networks. The discovered laws exist irrespective of noise, but noise accounts for disturbing them. We further demonstrate the ubiquity of our discovered laws by analyzing the emergence of neural tuning properties in the primary visual and medial temporal cortices of animal brains and the emergence of extreme opinions in social networks.
Errors in approximate ionization energies due to the one-electron space truncation of the EKT eigenproblem
Authors: Cioslowski Jerzy
Published: July 2022

Unless the approximate wavefunction of the parent system is expressed in terms of explicitly correlated basis functions, the finite size of the generalized Fock matrix is unlikely to be the leading source of the truncation error in the ionization energy E produced by the EKT (extended Koopmans’ theorem) formalism. This conclusion is drawn from a rigorous analysis that involves error partitioning into the parent- and ionized-system contributions, the former being governed by asymptotic power laws when the underlying wavefunction is assembled from a large number of spinorbitals and the latter arising from the truncation of the infinite-dimensional matrix V whose elements involve the 1-, 2-, and 3-matrices of the parent system. Quite surprisingly, the decay of the second contribution with the number n of the natural spinorbitals (NOs) employed in the construction of the truncated V turns out to be strongly system-dependent even in the simplest case of the 1S states of two-electron systems, following the n−5 power law for the helium atom while exhibiting an erratic behavior for the H− anion. This phenomenon, which stems from the presence of the so-called solitonic natural spinorbitals among the NOs, renders the extrapolation of the EKT approximates of E to the complete-basis-set limit generally unfeasible. However, attaining that limit is not contingent upon attempted reproduction of the ill-defined one-electron function known as “the removal orbital,” which does not have to be invoked in the derivation of EKT and whose expansion in terms of the NOs diverges.
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.
Polarization modulation of 2DEG toward plasma-damage-free GaN HEMT isolation
Authors: Dai Yijun , Guo Wei , Chen Li , Xu Houqiang , AlQatari Feras , Guo Chenyu , Peng Xianchun , Tang Ke , Liao Che-Hao , Li Xiaohang , Ye Jichun
Published: July 2022

GaN electronics have hinged on invasive isolation such as mesa etching and ion implantation to define device geometry, which, however, suffer from damages, hence potential leakage paths. In this study, we propose a new paradigm of polarization isolation utilizing intrinsic electronic properties, realizing in situ isolation during device epitaxy without the need of post-growth processing. Specifically, adjacent III- and N-polar AlGaN/GaN heterojunctions were grown simultaneously on the patterned AlN nucleation layer on c-plane sapphire substrates. The two-dimensional electron gas (2DEG) was formed at III-polar regions but completely depleted in N-polar regions, thereby isolating the 2DEG channels with a large 3.5 eV barrier. Structures of polarization-isolated high electron mobility transistors (PI-HEMTs) exhibit significantly reduced isolation leakage currents by up to nearly two orders of magnitude at 50 V voltage bias compared to the state-of-the-art results. Aside from that, a high isolation breakdown voltage of 2628 V is demonstrated for the PI-HEMT structure with 3 μm isolation spacing, which is two-times higher than a conventional mesa-isolation HEMT. Moreover, the PI-HEMT device shows a low off-state leakage current of 2 × 10−8 mA/mm with a high Ion/Ioff ratio of 109 and a nearly ideal subthreshold slope of 61 mV/dec. This work demonstrates that polarization isolation is a promising alternative toward the plasma-damage-free isolation for GaN electronics.
Dispersion-tunable photonic topological waveguides
Authors: Zhang Zijian , Li Yuanzhen , Wang Chi , Xu Su , Wang Zuojia , Li Erping , Chen Hongsheng , Gao Fei
Published: July 2022

Dispersion-tunable photonic topological waveguides have recently attracted much attention, due to their promising applications on topological devices with tunable operational frequencies. Since dispersions of topological waveguides traverse the whole bandgaps of bulk structures, tuning the dispersions (especially the bandwidths) requires changing the whole bulk of corresponding photonic topological insulators. A previously reported material-modification approach provided a parallel tuning on such numerous lattices; however, the increased material loss deteriorated transmissions of the topological waveguide. Here, a parallel tuning approach on structures is theoretically proposed and demonstrated, which spawns dispersion-tunable photonic topological waveguides without increasing material loss. Based on the bilayer honeycomb model, a topological valley waveguide by utilizing bilayer designer plasmonic structures is constructed, accomplished with dispersion tunings by altering interlayer distance. Experimental results validate the theoretical model and display a 61%-relative-tuning range of frequency, with a tunable relative bandwidth up to 16%. This approach may promise applications in tunable topological lasers, robust delay lines, and intelligent photonic devices.
Is terahertz emission a good probe of the spin current attenuation length?
Authors: Gorchon Jon , Mangin Stéphane , Hehn Michel , Malinowski Gregory
Published: July 2022

Terahertz (THz) emission from magnetic films has recently become an important characterization tool of spintronic properties, particularly since no patterning is required. One such property of interest is the spin-current attenuation length. When separating a magnetic film from a spin-to-charge converter with a light metal, the emitted intensity reduces almost exponentially with the thickness of the spacer. However, the extracted characteristic length is more than an order of magnitude smaller than the spin diffusion length measured in equilibrium. In this work, we experimentally and theoretically demonstrate that most of the observed decay in the THz emission is of optical (THz) origin. We are able to estimate a spin current attenuation length for Cu of ∼50 nm in much closer agreement with spin diffusion length measurements. We conclude that THz emission remains a powerful characterization technique, but due to the high number of intricate conversion mechanisms, and most importantly, due to the high sensitivity to changes in the optical properties, extracting absolute numbers for spintronic phenomena remains extremely challenging.
The linear stability of slip channel flows
Authors: Ceccacci S. , Calabretto S. A. W. , Thomas C. , Denier J. P.
Published: July 2022

A linear stability investigation is undertaken on the two-dimensional flow that develops in a channel whose walls are coated with a superhydrophobic material. The surfaces are modeled as classical slip surfaces, exploiting a linear Navier slip condition imposed on the channel walls. Both symmetric and asymmetric slip walls are considered, whereby the linearized stability of the flow is determined via an Orr–Sommerfeld normal-mode approach. In both instances, the application of slip establishes a significant stabilizing effect and increases the critical Reynolds number associated with the onset of linearly unstable behavior. Indeed, for sufficiently large slip lengths, the upper and lower branches of the neutral stability curve coalesce. Consequently, the flow becomes linearly stable to all disturbances for all wavelengths and Reynolds numbers.
Semi-analytical theory of emission and transport in a LAFE-based diode
Authors: Biswas Debabrata , Rudra Rashbihari , Kumar Raghwendra
Published: July 2022

A large area field emitter (LAFE) typically consists of several thousands of nanoscale emitting tips. These are difficult to simulate using purely numerical methods based on finite/boundary element or finite difference methods. We show here that a semi-analytically obtained electrostatic field allows tracking of field emitted electrons of a LAFE fairly accurately using the knowledge of only the LAFE geometry. Using a single and a nine-emitter configuration, the beam parameters calculated using this method are compared with the results of tracking using fields generated by COMSOL. The net emission current, energy conservation, and the transverse trace-emittance are found to be reproduced with reasonable accuracy.
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.
Investigating the size effect on the electrical conductivity at nanoscale with solid spins
Authors: Wang En-Hui , Zang Han-Xiang , Wang Ze-Hao , Chen Xiang-Dong , Guo Guang-Can , Sun Fang-Wen
Published: July 2022

With the miniaturization of electrical components at nanoscale, the impact of dimension and shape on the electrical properties of the devices plays an important role in the applications. In this work, we used an ensemble of nitrogen-vacancy (NV) centers in diamond to noninvasively investigate the size effect on electric conductivity at nanoscale. The magnetic noise originated from the random movement of electrons in conductors, which is related to the conductivity, was detected by recording the spin relaxation of NV centers. The results indicate that the conductivity increases with the size of devices at the scale of electron mean free path. By further imaging the magnetic noise of the metallic structure with discontinuous thickness, we demonstrated that the spatial distribution of conductance at nanoscale can be revealed with high density NV center arrays. The results can help to understand the electron transport in nanomaterials. This technique can be used to optimize the design of nanoscale electrical devices.
An investigation of a gas–liquid swirling flow with shear-thinning power-law liquids
Authors: Liu Shuo , Zhang Jian , Xu Jing-yu
Published: July 2022

A gas–liquid swirling flow with shear-thinning liquid rheology exhibits complex behavior. In order to investigate its flow characteristics, experiments and computational fluid dynamics (CFD) simulations are conducted based on dimensional analysis. A Malvern particle size analyzer and electrical resistance tomography are applied to obtain the bubble size distribution and section void fraction. A Coriolis mass flowmeter is applied to obtain the mixture flow rate and mixture density for an entrance gas volume fraction smaller than 7%. The CFD coupled mixture multiphase model and large eddy simulation model are applied, considering the liquid shear-thinning power-law rheology. The results show that the swirling flow can be divided into developing and decaying sections according to the swirl intensity evolution in the axial direction. A gas–liquid swirl flow with shear-thinning liquid prohibits a core-annulus flow structure. A smaller index n contributes to maintaining the development of the swirl flow field and its core-annulus flow structure so that the swirl flow can form over a shorter distance with a stronger intensity. For a more uniform distribution of the apparent viscosity, the gas column in the pipe center is thinner. On the other hand, a larger consistency k enlarges the stress tensor. The amplitude of the velocity and the pressure of the core-annulus flow structure are reduced. A weaker swirl intensity appears with a wider gas column appearing as a consequence. Furthermore, the swirl number decays with an exponential behavior with parameters sensitive to the consistency k and index n of the decaying section of the swirling flow field. These are beneficial to gas–liquid separator design and optimization when encountering the shear-thinning power-law liquid phase in the petroleum industry.
Switching between symmetric and asymmetric separation-induced shock reflections in an oscillatory duct flow
Authors: Chen Hao , Zhang Qi-Fan , Luo Wei-Hang , Yue Lian-Jie
Published: July 2022

Separation-induced shock reflections in straight ducts are generally considered asymmetric for Mach numbers beyond 2.2, but our experiment shows that this is not always the case. A symmetric shock pattern, a proven outcome of following the free-interaction theory (FIT), is observed to appear in an oscillatory duct flow at a Mach number of 2.47. Interestingly, its existence is restricted to the period when the shocks move forward. Once a full retreat starts, it changes suddenly into an utterly asymmetric style that conforms to the past observation. This behavior indicates that the FIT fundamentally plays a limited role in supersonic duct flows.