bluuebunny/crossref_metadata_2025 huggingface dataset:
Knotting and adsorption of end-grafted active polymers
Authors: Shen Yi-Fan , Luo Meng-Bo
Published: February 2025

Increasing the rotational inertia of the active head in the active polymer enhances the knotting and weakens the adsorption of an end-grafted active polymer. Knotted polymers are less adsorbed than unknotted ones.
Phosphorus recovery from animal manures through pyrolysis: phosphorus transformations, release mechanisms, and applications of manure biochars in agriculture
Authors: Knijnenburg Jesper T. N. , Suwanree Siraprapa , Macquarrie Duncan , Kasemsiri Pornnapa , Jetsrisuparb Kaewta
Published: February 2025

Phosphorus recovery from animal manures by pyrolysis can effectively close the agricultural phosphorus cycle.
Broad-spectrum photothermal high-entropy alloy powders for efficient solar-driven antibacterial and dye degradation
Authors: An Bang , Yang Mengmeng , Shang Yuanyuan , Sun Chao , Wang Shuo , Qian Kun , Zou Xuexue , Dong Qiangsheng , Shao Yi , Chu Chenglin , Xue Feng , Wang Cheng , Bai Jing
Published: February 2025

The development of solar-driven photothermal materials for efficient wastewater treatment remains a significant challenge.
Optical and excitonic properties of calcite CaCO3
Authors: Janovec Jozef , Dolado Jorge S. , Ayuela Andrés
Published: February 2025

Calcite has been successfully used as a substrate or coating material in optical devices, but very little is known about its own optical properties.
Transparent photochromic Fe-doped W18O49 films with ultrahigh solar energy modulation for smart windows
Authors: Zhu Yongkang , Li Bin , Li Chenxu , Tian Shouqin
Published: February 2025

Fe3+ doping, as an electron transformed mediate, significantly increases the bleaching speed of photochromic W18O49 nanocomposite film and simultaneously improves its optical performance, with Tlum of 82.9% and ΔTsol of 60.2% for smart windows.
Development of MhOR1 as a chemogenetic tool for odorant-mediated regulation of insulin release
Authors: Li Hanbing , Chen Gaojun , Lou Xiayan , Hu Changyi , Zheng Ninghuai , He Lian , Yao Yuanfa
Published: February 2025

Here, we described a novel chemogenetic tool, MhOR1, which triggered calcium influx in response to odorant molecules. This mechanism could be harnessed for engineering β cells to regulate insulin secretion via odorant molecules.
A macroscopically homogeneous lipid phase exhibits leaflet-specific lipid diffusion in a glass-supported lipid bilayer
Authors: Otosu Takuhiro , Sakaguchi Miyuki , Yamaguchi Shoichi
Published: February 2025

Leaflet-specific lipid diffusion analysis revealed that the strength of interleaflet coupling is sensitive to the lipid composition even in the region where macroscopically homogeneous phase is observed.
Highly reactive iron/nickel bimetallic biochar composites for highly efficient remediation of Cr(vi)
Authors: Zhu Runhong , Shi Yunlong , Zhou Yi , Xia Yi , Qi Qin , Liang Xiaojie , Kuang Meijuan , Jia Zhenya , Wang Mengyue , Yu Changjiang
Published: February 2025

We prepared a biochar-embedded FeNi alloy to form core–shell type magnetic materials. BC@FeNi-900-3 exhibited superior corrosion performance, enhancing Cr(vi) reduction. Mechanistic studies revealed the Cr(vi) removal mechanism of BC@FeNi-900-3.
Metal- and base-free selective amidations of organoboronic acids with dioxazolones and isocyanates
Authors: Sun Hui , Chen Shuguang , Wang Hui
Published: February 2025

Metal- and base-free cross-coupling reactions of boronic acids with dioxazolones and isocyanates to selectively synthesize various amides are described.
A molecular strategy for creating functional vesicles with balancing structural stability and stimuli-responsiveness
Authors: Sasaki Shoi , Ueno Hibiki , Arai Noriyoshi , Asakura Kouichi , Banno Taisuke
Published: February 2025

Amphiphiles with amide linkages formed stable vesicles, surviving against osmotic shock. When amphiphiles with azobenzene moiety were added, the vesicles exhibited large deformation. The finding contributes to the development of functional vesicles.
A superior and accessible cavitand receptor for the binding of monoterpenes and sesquiterpenes in water
Authors: Marchi Luciano Hugo , López-Coll Ricard , Álvarez-Yebra Rubén , Lledó Agustí
Published: February 2025

An octacarboxylate cavitand receptor featuring improved solubility and an expanded binding site displays enhanced binding of monoterpenes and sesquiterpenes in water.
Multiple kernel‐enhanced encoder for effective herbarium image segmentation
Authors: Lee Sanghyuck , Moon Hyeonji , Kim Sangtae , Lee Jaesung
Published: February 2025

The neural network proposed here specializes in herbarium image segmentation. The encoder of the proposed model contains multiple kernels of different sizes to address the complex structures of plant components, such as tangled roots and stems. By employing multiple kernel sizes, the convolution block enables multiscale learning, which is underexplored in previous approaches. This design effectively extracts and fuses local and global features, enabling both broad and narrow perspectives on complex structures within herbarium images and thereby improves segmentation performance. The experimental results demonstrate that the proposed model outperforms three conventional models. The source code can be accessed at https://github.com/tkdgur658/herbarim_segmentation_network
Gamma-ray flares from the jet of the blazar CTA 102 in 2016–2018
Authors: Kim Sanghyun , Lee Sang-Sung , Algaba Juan Carlos , Rani Bindu , Park Jongho , Jeong Hyeon-Woo , Cheong Whee Yeon , D’Ammando Filippo , Lähteenmäki Anne , Tornikoski Merja , Tammi Joni , Ramakrishnan Venkatessh , Agudo Iván , Casadio Carolina , Escudero Juan , Fuentes Antonio , Traianou Efthalia , Myserlis Ioannis , Thum Clemens
Published: February 2025

CTA 102 is a γ-ray bright blazar that exhibited multiple flares in observations by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope during the period of 2016–2018. We present results from the analysis of multi-wavelength light curves with the aim of revealing the nature of γ-ray flares from the relativistic jet in the blazar. We analysed radio, optical, X-ray, and γ-ray data obtained in a period from 2012 September 29 to 2018 October 8. We identified six flares in the γ-ray light curve, showing a harder-when-brighter trend in the γ-ray spectra. We performed a cross-correlation analysis of the multi-wavelength light curves. We found nearly zero time lags between the γ-ray and optical and X-ray light curves, implying a common spatial origin for the emission in these bands. We found significant correlations between the γ-ray and radio light curves as well as negative or positive time lags with the γ-ray emission lagging or leading the radio during different flaring periods. The time lags between the γ-ray and radio emission propose the presence of multiple γ-ray emission sites in the source. As seen in 43 GHz images from the Very Long Baseline Array, two moving disturbances (or shocks) were newly ejected from the radio core. The γ-ray flares from 2016 to 2017 are temporally coincident with the interaction between a travelling shock and a quasi-stationary one at ∼0.1 mas from the core. The other shock was found to have emerged from the core nearly simultaneously with the γ-ray flare in 2018. Our results suggest that the γ-ray flares originated from shock-shock interactions.
PANOPTICON: A novel deep learning model to detect single transit events with no prior data filtering in PLATO light curves
Authors: Vivien H. G. , Deleuil M. , Jannsen N. , De Ridder J. , Seynaeve D. , Carpine M.-A. , Zerah Y.
Published: February 2025

Aims. To prepare for the analyses of the future PLATO light curves, we develop a deep learning model, PANOPTICON, to detect transits in high precision photometric light curves. Since PLATO’s main objective is the detection of temperate Earth-sized planets around solar-type stars, the code is designed to detect individual transit events. The filtering step, required by conventional detection methods, can affect the transit, which could be an issue for long and shallow transits. To protect the transit shape and depth, the code is also designed to work on unfiltered light curves.

Methods. The PANOPTICON model is based on the Unet family architecture, but it is able to more efficiently extract and combine features of various length scale, leading to a more robust detection scheme. We trained the model on a set of simulated PLATO light curves in which we injected, at the pixel level, planetary, eclipsing binary, or background eclipsing binary signals. We also included a variety of noises in our data, such as granulation, stellar spots, and cosmic rays. We then assessed the capacity of PANOPTICON to detect transits in a separate dataset.

Results. The approach is able to recover 90% of our test population, including more than 25% in the Earth-analog regime, directly in unfiltered light curves. We report that the model also recovers transits irrespective of the orbital period, and it is therefore able to reliably retrieve transits on a single event basis. These figures were obtained when accepting a false alarm rate of 1%. When keeping the false alarm rate low (<0.01%), PANOPTICON is still able to recover more than 85% of the transit signals. Any transit deeper than ~180 ppm is essentially guaranteed to be recovered.

Conclusions. This method is able to recover transits on a single event basis, and it does so with a low false alarm rate. Due to the nature of machine learning, the inference time is minimal, around 0.2 s per light curve of 126 720 points. Thanks to light curves being one dimensional, the model training is also fast, on the order of a few hours per model. This speed in training and inference, coupled with the recovery effectiveness and precision of the model, make this approach an ideal tool to complement or be used ahead of classical approaches.
The centimeter emission from planet-forming disks in Taurus
Authors: Garufi A. , Carrasco-González C. , Macías E. , Testi L. , Curone P. , Ricci L. , Facchini S. , Long F. , Manara C. F. , Pascucci I. , Rosotti G. , Zagaria F. , Clarke C. , Herczeg G. J. , Isella A. , Rota A. , Maucó K. , van der Marel N. , Tazzari M.
Published: February 2025

The last decade has witnessed remarkable advances in the characterization of the (sub-)millimeter emission from planet-forming disks. Conversely, the study of (sub-)centimeter emission has made more limited progress, to the point that only a few exceptional disk-bearing objects have been characterized in the centimeter regime. This work takes a broad view of the centimeter emission from a large sample with Karl G. Jansky Very Large Array (VLA) observations that is selected from previous Atacama Large (sub-)Millimeter Array (ALMA) surveys of more representative disks in brightness and extent. We report on the detection and characterization of flux at centimeter wavelengths from 21 sources in the Taurus star-forming region. Complemented by literature and archival data, the entire photometry from 0.85 mm to 6 cm is fit by a two-component model that determines the ubiquitous presence of free-free emission entangled with the dust emission. The flux density of the free-free emission is found to scale with the accretion rate but is independent of the outer-disk morphology depicted by ALMA. The dust emission at 2 cm is still appreciable and offers the possibility to extract an unprecedented large set of dust spectral indices in the centimeter regime. A pronounced change between the median millimeter indices (2.3) and centimeter indices (2.8) suggests that a large portion of the disk emission is optically thick up to 3 mm. The comparison of both indices and fluxes with the ALMA disk extent indicates that this portion can be as large as 40 au and suggests that the grain population within this disk region that emits the observed centimeter emission is similar in disks with different sizes and morphologies. All these results await confirmation and dedicated dust modeling once facilities such as next generation VLA (ngVLA) or Square Kilometre Array (SKA)-mid are able to resolve the centimeter emission from planet-forming disks and disentangle the various components.
Subependymal Giant Cell Astrocytoma in an Adult without Tuberous Sclerosis: Systematic Review and Illustrative Case Example
Authors: Holler Brandon M. , Evans Alexander R. , York Abigail , Graffeo Christopher S.
Published: February 2025

Background Subependymal giant cell astrocytoma (SEGA) is a rare neoplasm arising from subependymal tissue. Predominantly associated with the tuberous sclerosis complex (TSC), SEGA may present with a range of diverse symptoms, most commonly seizures or neurocutaneous features of TSC. We present a novel case of sporadic SEGA in a 59-year-old woman who presented with acute intraparenchymal hemorrhage (IPH).

Methods Systematic literature review and illustrative case example.

Results A 59-year-old woman presented with a headache decreased level of consciousness, and acute IPH involving the anterior septum pellucidum and right medial caudate head. MRI was concerning for an underlying neoplasm, which grew slowly on follow-up imaging, prompting microsurgical resection. A gross total resection was achieved, and postoperative pathology confirmed SEGA (WHO grade I) without TSC1/2 mutation. She remained disease-free and neurologically intact at 1-year follow-up. A systematic review identified seven publications that revealed pathologically confirmed SEGA in nine adult patients without TSC. Headache, papilledema, and visual disturbances were the most common presenting symptoms. Treatment protocols included microsurgical resection versus biopsy followed by radiographic surveillance, and the overall rate of symptom-free survival was at least 80% as of the last follow-up.

Conclusion We report the tenth case of sporadic SEGA in an adult patient without TSC, as well as an associated systematic review of this rare neoplastic entity. Further study is required to identify risk factors for the development of sporadic SEGA, as well as potential avenues for the management of this disease that may depart from the standard protocol in pediatric TSC patients.
One pot pyridinium ylide assisted tandem reaction for the diastereoselective synthesis of trans-2,3-dihydrofuran-chromone conjugate
Authors: Das Supratim , Mandal Subham , Mukhopadhyay Chhanda
Published: February 2025

An efficient synthetic procedure for the preparation of novel fused 2,3- dihydrofurans-chromone conjugates was developed with the assistance of in situ generated pyridinium ylide. Pyridine, 3-formylchromone, 1,3-diketo and phenacyl bromide with triethylamine acting as a catalyst, initiated a sequential one-pot, two-step tandem reaction that went smoothly in aqueous media.1H and 13CNMR spectroscopy and single-crystal analysis demonstrated the diastereoselective synthesis of trans-2,3-dihydrofurans.
Awareness of Antithyroid Drug-Induced Agranulocytosis in Patients with Thyrotoxicosis
Authors: Abunamous Nasser , Takaleh Akram , Abdelsalhen Mohamed , Alqedra Mohamed , Abbara Amena , Almazrouei Raya , Agha Adnan
Published: February 2025

Objective Anti-thyroid drugs (ATDS)-induced agranulocytosis is a serious side effect that can be treated by early management if the patient has been educated to promptly self-identify agranulocytosis based on its presenting features. We aimed to assess the knowledge of patients taking carbimazole for hyperthyroidism regarding suspected agranulocytosis.

Methods This questionnaire-based cross-sectional study with prospective follow-up analyzed adult patients with hyperthyroidism who visited an endocrine clinic, in a tertiary hospital in the UAE, between January 2023 and March 2024. They were asked about their knowledge about the symptoms of agranulocytosis and the immediate steps required upon symptom observation. They were then given bilingual agranulocytosis information cards and educated either face-to-face or telephonically. Their knowledge and awareness were re-evaluated 3-6 months later. Chi-squared tests were used to assess the differences before and after patient education.

Results The initial and follow-up surveys were answered by 68 patients (mean age: 43.7 ± 17.1 years). The cohort included 48 (70.6%) females and 58 (85.3%) Emiratis. Hypothyroidism was due to Graves' disease in 64 (94.1%) patients and toxic multinodular goiter in 4 (5.9%) patients. There were 41 (60.3%) participants who responded that they had received adequate information on ATD-related agranulocytosis upon treatment initiation, which improved to 67 (98.5%) following patient education. Similarly, their self-reported confidence in identifying ATD-related side effects significantly improved (50% [34/68] vs. 100% [68/68]; p < 0.00001) after receiving education.

Conclusion Patient education and information cards on ATD-induced agranulocytosis improve patient awareness regarding symptom identification and the next steps required for suspected agranulocytosis.
The Portuguese Muslim community: integration and its role against radicalization
Authors: de Carvalho Cátia Moreira , Neyroud Peter , Pinto Isabel R. , Pinto Marta
Published: February 2025

Portugal has never reported any case of violent radicalization from Islamist-inspired terrorism. To analyze some of the reasons why, this article sets two goals: understand the integration factors of the Muslim community and identify strategies to prevent radicalization implemented by its members. An exploratory qualitative study was conducted with interviews with 11 Muslim leaders. The results describe the characteristics of integration of the Muslim community and the strategies implemented by them to prevent radicalization. The results are important to inform policy and practice related to immigrants’ integration, and to understand how community resilience can be built to prevent radicalization.
Doped fullerite–the first three-dimensional organic superconductor (review)
Authors: Loktev V. M.
Published: February 2025

The results of investigations of fullerene (the C60 molecule), solid fullerene (fullerite), and doped fullerite are surveyed. The metallization (insulator–metal transition) of fullerite by doping with alkali metals and the mechanisms of the resulting superconductivity are discussed.
High-frequency response of metallic point contacts with small electron mean free path
Authors: Balkashin O. P. , Kulik I. I. , Moskalets M. V.
Published: February 2025

The effect of an external electromagnetic field on metallic point contacts (copper–copper, nickel–nickel) in the thermal regime of current flow has been studied. The frequency of the electromagnetic field varied from the acoustic to the optical region. A microscopic calculation has been carried out, within the framework of point contact spectroscopic theory, of the contact response as a function of the applied bias. Results of the calculation are convincingly confirmed by the experimental results at acoustic and microwave frequencies. In the range 4.3·1012 – 28·1012 Hz a change in the bias dependence of the signal was observed. The effect is explained by the heating of the pre-contact region by the radiation. Calculations made on this assumption gave satisfactory agreement with experiment. This result agrees with the change in the mechanism of the effect of a HF field on point contacts in the ballistic regime of current flow, observed previously.
Surface ferroelectricity and linear magnetoelectric effect in centrosymmetric magnets
Authors: Chupis I. E.
Published: February 2025

The existence of electric polarization and the linear magnetoelectric effect (LMEE) near the surface of a magnet of arbitrary symmetry in the magnetically ordered state is predicted. These phenomena are due to a change in the exchange energy and magnetic moment near the surface and can be described by a magnetoelectric energy of the form P(dM2/dn), where n is the normal to the crystal surface. The induced electric polarization and the LMEE susceptibility are calculated for a centrosymmetric ferromagnetic film.
Ballistic and nonballistic regimes in point-contact spectroscopy
Authors: Kulik I. O.
Published: February 2025

Current carrying states in point contacts provide information concerning quasiparticle scattering mechanisms in solids. If both the elastic, limp, and the inelastic, lε, mean free paths of electrons are larger than the contact diameter, then the non-Ohmic component of the contact current is related to the spectral electron-phonon interaction function g(ω) as d2I/dV2 = – C(limp/d)|ω=eV, where K is a kinematic factor. A similar regime in the diffusive relation holds with C~d/limp. The opposite regime of the small mean free path results in specific thermal PC spectroscopy, since the hot spot regime sets in the contact with the temperature controlled by the bias according to the relation eV = 3.63 kT. Modulation in V results in modulation of T and therefore in nonlinearity of the current. Elastic scattering of electrons by localized excitations as e.g., two-level systems, magnetic excitations, etc., results in population spectroscopy because the effective energy of excitation in a contact depends crucially on eV. Similarly, if the scattering is elastic, but energy-dependent (as e.g., in the Kondo effect), there appears a nonlinear component in the ICV resulting in energy-dependent elastic PC spectroscopy. Trapping of phonons in the contact influences that part of the PC spectrum which lies above the phonon energies. This part can be removed by increasing the modulation frequency up to 1010–1011 Hz. The frequency dependence of the IVC represents in itself a new kind of PC spectroscopy, namely that of phonon relaxation mechanisms in metals.
Low current-density point-contact spectroscopy by transverse electron focusing
Authors: Nowack A. , Hoevers H. , van Kempen H.
Published: February 2025

Energy-resolved transverse electron focusing (TEF) is used to supply a point contact with a very low current of excited electrons generated by an emitter point-contact. By this method, we have studied point contacts between Ag and the heavy-fermion system CeB6 and the type II superconductor NbZr, respectively. In the TEF, i.e., collector vs emitter voltage, characteristics of CeB6 only a pronounced asymmetry appears, but no other feature of usual point-contact characteristics of CeB6. In the case of NbZr, corresponding structures in TEF- and usual point-contact characteristics is observed.
Point-contact spectroscopy of LaCeAI2 and LaCeB6 alloys
Authors: Klug J. , Winzer K.
Published: February 2025

We have measured the dV/dI vs V characteristics of point contacts between a normal metal (W or Mo) and La1−xCexAl2 and La1−x CexB6 in the temperature range between 1.5 and 15 K for several concentrations x. Our curves show pronounced asymmetric zero-bias maxima and phonon structures at higher voltages, proving the spectroscopic origin of all these structures.
A non-Kondo maximum in electric resistivity of some heavy-fermion compounds and its dependence on pressure and magnetic field
Authors: Rozhavsky A. S. , Tuluzov I. G. , Zagoskin A. M.
Published: February 2025

A maximum on the R(T) curve, typical for some heavy-fermion compounds, can be explained by electron-phonon scattering in terms of a two-band hybridization model with self-consistent temperature-dependent chemical potential, without referring to the Kondo mechanism. The dependence of the maximum on pressure and magnetic field is in reasonable agreement with experimental data.
Theoretical models describing tunneling spectra measured on high temperature superconductors
Authors: Seidel P. , Hohn N. , Wohlleben D.
Published: February 2025

We report on point-contact measurements on the organic superconductor αt(BEDT-TTF)2I3 (Tc ≈ 8 K). The dv/dI vs V characteristics of homocontacts of this material show strong nonlinearities which, interpreted as a gap-structure, lead to extremely high values of Δ/kTdc. Among other possibilities, we discuss the anomaly in terms of a strongly enhanced McMillian–Rowell structure Δ(ε) at ε = ΔBCS + ωph. The enhancement is caused by deviations from the Eliashberg equations due to strong coupling (λ = 1−2) together with an Einstein phonon spectrum.
Observation of resonance structure on current-voltage characteristics of break junctions based on Bi–Sr–Ca–Cu–O:Pb
Authors: Leonyuk L. I. , Rakhimov H. T. , Sethupathi K.
Published: February 2025

Tunneling effects in polycrystalline (2212- and 2223-phases) and monocrystalline (2212-phase) samples of BiSrCaCuO:Pb compounds have been investigated. Equidistant oscillations of significant amplitude have been registered on dI/dV characteristics in a wide range of temperatures. In contrast with the gap structure, the period of oscillations ΔV of dynamic conductance is temperature independent, yet its amplitude is decreasing with temperature. The possible reasons for the “resonance” structure are discussed. On the d2I/dV2-characteristics of junctions based on monocrystalline samples at V ≥ 2Δ a well defined structure was observed, which may be connected with strong electron-phonon interactions.
Influence of the proximity effect in experimental conductance characteristics of high-T
c point-contact junctions
Authors: Di Chiara A. , Fontana F. , Peluso G. , Tafuri F.
Published: February 2025

The possible influence of the proximity effect on the conductance characteristics of point-contact junctions is discussed and a phenomenological model is proposed. The model is based on the application of the McMillan proximity model to the determination of the features of the order parameter in the basic electrode and on the use of the BTK model to determine the transition probability between the basic electrode and the needle. Experimental results and computed curves are also compared.
Tunneling measurements of Bi–Sr–Ca–Cu–O single crystals
Authors: Heinz E. , Klug J. , Seidel P.
Published: February 2025

Using the break-junction technique we have measured the conductance–voltage characteristics of contacts based on BSCCO single crystals, which consist mainly of 2-2-1-2 phase. Depending on the contact resistance the background shapes of the dI/dV(V) characteristics show tunneling or metallic behavior. Typically, a broadened gap-like feature at 50–60 meV and a zero bias anomaly due to the Josephson supercurrent were observed. The gap energy was almost temperature independent for temperatures up to Tc.
Andreev reflection from layered superconductors
Authors: Hahn Artur
Published: February 2025

For layered superconductors (e.g. HTS) with coherence length smaller than the layer periodicity length, a periodic pair potential is to be expected. As a consequence, band structure features appear in the quasiparticle excitation spectrum. We report some considerations on what is to be expected for the current transmission coefficient for quasiparticles injected from a normal metal and Andreev-backscattered by the superconductor. If normal scattering in the contact is modeled by a delta-function of strength Z, an unexpected result is obtained: in the tunneling limit, Z→∞, the current transmission coefficient is not proportional to the quasiparticle density of states in the superconductor but, instead, strongly depends on the location of the delta function with respect to the first layer.
Metallic point contacts in high frequency field
Authors: Baikashin O. P.
Published: February 2025

Frequency dispersion of the conductivity of metallic point contacts has been measured in a wide spectral range from sound to optical wavelengths. The nonstationary phenomena in the contacts are analyzed by using experimental data for the amplitude and the shape of the response signal at frequencies ωτi ∼ 1 (ω is external radiation frequency and τi is the characteristic relaxation time for the process that causes the I–V nonlinearity). The uniform and nonuniform nonequilibrium phonon kinetics are studied for pure contacts with ballistic electron transport. The temperature relaxation frequency is measured for the heating PC regime. New types of PC spectroscopy, viz., high frequency and laser heating modes, are presented.
Noise phenomena in metallic point contacts
Authors: Akimenko A. I.
Published: February 2025

Nonequilibrium fluctuations of the metallic point-contact conductivity are surveyed. It is shown that the electron transport character influences the noise spectra (V¯2(V)) singularities significantly. The anisotropy, frequency, current direction, and impurities effects are considered as well. Some models are presented to account for the effects. The influence of structural defects and impurities on the point-contact resistance fluctuations are studied and a possible role of two-level systems is discussed.
1/f noise and electron–phonon interaction in point contacts
Authors: Zagoskin A. M. , Kulik I. O. , Omelyanchouk A. N.
Published: February 2025

The 1/f voltage noise due to scattering of charge carriers by the two level tunnel systems (TLS) existing in the amorphized vicinity of a point contact is investigated. The electron–phonon interaction changes the occupation numbers of the TLS upper level and the fluctuation dynamics, thus giving rise to the peculiarities of the noise intensity vs the contact bias at characteristic phonon energies. The results obtained are in qualitative agreement with experimental data.
Dissipation mechanisms at the resistive transition of HTSC in magnetic field
Authors: Sergeeva G. G.
Published: February 2025

Experimental studies of the resistive transition in a magnetic field in single crystals with structure of YBa2Cu3O7, Bi2Sr2CaCu2O8 and in thin films are analyzed. Some phenomenological models describing the dissipation mechanism at the resistive transition are discussed and a comparative analysis of dissipation mechanisms is carried out for low-temperature and high-temperature superconductors. Attention is mainly paid to the dissipation mechanisms associated with superconducting fluctuations, viscous flow and creep of magnetic flux in HTSC with an account for the peculiarities of the vortex state in layered superconductors. The substantial temperature interval of the magnetic-field-induced resistive transition broadening is explained by the fact that the strong fluctuation effects in magnetic field entail absence of the phase transition at H = Hc2 (T) and the existence of a vortex fluid.
Structure and properties of condensed CO2–Kr films
Authors: Kovalenko S. I. , Solodovnik A. A.
Published: February 2025

The structure and radiation effects in condensed Co2–Kr films are investigated by using electron diffraction methods. Observations are carried out in the temperature range from 6 to 46 K. The upper boundary of the temperature interval is determined by intense sublimation of krypton. The composition of the mixture under investigation is varied from 0 to 100 mol.% Kr. An analysis of the experimental data leads to the conclusion that, in spite of the closeness of lattice parameters, the solubility of Kr in CO2 does not exceed 30 mol.%. The substitution of Kr atoms for CO2 molecules is accompanied by a considerable loosening of the matrix lattice. According to the results of observations, the solubility of CO2 molecules in Kr is beyond the accuracy of the electron diffraction technique. The lack of a noticeable solubility in this case is apparently due to a considerable difference in the molar volumes of activated CO2 particles and the inert gas. The effects of impurity atoms of the inert gas and of irradiation by electrons with an energy of tens of keV on the orientational ordering of Co2 molecules are also studied. The influence of radiation on the size of the region of existence of solid solutions is investigated. It is shown that this region is much smaller in irradiated and annealed samples than in unirradiated samples.
Effect of light impurities on the lattice dynamics of cryocrystals
Authors: Bagatskii M. I. , Syrkin E. S. , Feodos’ev S. B.
Published: February 2025

The influence of a defect atom that is lighter than the matrix atom on the heat capacity of a crystal is studied theoretically and experimentally by considering the example of Ar solution in Kr. It is shown that the dynamic interaction for light impurities affects only the high-frequency region of the phonon spectrum and does not exert a noticeable influence on the thermodynamic characteristics at low temperatures up to very high concentrations of impurity atoms.
On the measurement of low circular dichroism and experimental verification of anyon superconductivity
Authors: Mil’ner V. A. , Mil’ner A. A. , Miloslavskaya O. V.
Published: February 2025

The experiment on the observation of a weak circular dichroism [K. B. Lyons, J. Kwo, J. F. Dillon, Jr., et al., Phys. Rev. Lett. 64, 2949 (1990)] is simulated on a computer model. One of the possibilities of the emergence of a spurious result associated with the linear dichroism of the sample is revealed and estimated quantitatively. The method of rotation of the sample or the light polarization plane during measurement of the circular dichroism in anisotropic objects is considered.
Effect of superheating on the evolution of the Larkin–Ovchinnikov instability in thin Sn films
Authors: Volotskaya V. G. , Dmitrenko I. M. , Koretskaya O. A. , Musienko L. E.
Published: February 2025

The dynamic mixed state in thin films of thin is studied. It is found that the nonlinearity and jumps in IVC are associated with the dynamics of nonequilibrium quasiparticles. The experimental data are in accord with the theoretical dependences obtained in the theory of nonlinear conductivity, taking into account the finite rate of heat removal from the film. The energy relaxation time for Sn is estimated as τϵ = 1.2−2.10−10 s.
Origin of the cyclotron resonance in normal magnetic field in cadmium
Authors: Zimbovskaya N. A.
Published: February 2025

It is shown that the observed1 cyclotron resonance peak in the cadmium impedance derivative in a magnetic field perpendicular to the sample surface can be caused by curvature anomalies on the cyclotron orbit of the efficient electrons associated with the edge of the electron lens.
On the magnetic structure of β-oxygen
Authors: Vitebskii I. M. , Sobolev V. L. , Chabanov A. A. , Loktev V. M.
Published: February 2025

Within the framework of the symmetry approach we consider possible magnetic ordering types in the rhombohedral β phase of solid oxygen. It is shown that the most probable realization in this crystal is an orientationally disordered magnetic structure with alternating “polarizations” in neighboring antiferromagnetic X-Y planes. It is established that the “single-polar” model suggested till now for the β-oxygen antiferromagnetic structure is unstable against exchange-striction monoclinic distortions in the crystal lattice and contradicts x-ray data.
Acoustic and dielectric properties of supersaturated solutions of 3He in He II
Authors: Adamenko I. N. , Gusev O. E. , Nemchenko K. É. , Tsyganok V. I.
Published: February 2025

We study theoretically the metastable state of superfluid 3He–4He solutions containing droplets of virtually pure 3He. The calculated velocity, first-sound absorption coefficient, and dielectric permeability of this system allow obtaining detailed information about supersaturated solutions.
On the possible role of neutral oxygen in the formation of electron spectrum in high-T
c superconductors
Authors: Loktev V. M.
Published: February 2025

The microscopic mechanism of attraction between nearest-neighbor p-holes associated with the dynamic mixing of their states with those of neutral oxygen is studied. It is shown that the attraction is responsible for the formation of a branch of two-particle bound states of fermions in the CuO2-plane electron spectrum.
Fluctuation effects in multicontact Josephson systems: magnetic susceptibility in a weak ac field and magnetic flux noise
Authors: Demin A. V. , Khlus V. A.
Published: February 2025

A model of superconducting granular systems with weak links between the grains is considered. The model presumes the existence of N-contact closed loops and statistical ensembles of such loops. The dynamics of thermally activated decays of metastable current states of a loop, which are similar to a phase slip, is investigated. The temperature dependence of the imaginary component χ″ of the magnetic susceptibility is calculated for different frequencies of the external magnetic field. The importance of two-level states of the potential energy of a loop is demonstrated. The spectral density of the magnetic flux noise is calculated for the ensemble of independent loops by averaging over the distribution of local magnetic flux trapped by a loop and over the Josephson weak coupling energies. It is shown that the main contribution to the noise comes from “effective” loops corresponding to nearly symmetrical two-level systems. The spectral density of such a noise in a certain frequency range is of the form 1/f. The temperature dependence of the 1/f noise amplitude at a fixed frequency is obtained.
Investigation of relaxation processes in nonequilibrium states of quench-condensed copper films with hydrogen Impurities at temperatures below 5 K
Authors: Belevtsev B. I. , Fomin A. V. , Yatsuk L. A.
Published: February 2025

Relaxation processes in the nonequilibrium state of quench-condensed polycrystalline films of copper with hydrogen impurities are investigated. Films of thickness 50–250 Å were condensed under hydrogen pressures PH2=3.10−6−1.10−4 Torr on a substrate cooled by liquid helium to temperatures 1.4−2.5 K. The resistivity of the films was measured in situ, and electron diffraction patterns were recorded. The films exhibited high (nonequilibrium) values of hydrogen concentration (up to ∼30 at.%) and were in the labile state. It is shown that a transition of the films to a more equilibrium state is accompanied by a considerable displacement of hydrogen impurities at temperatures ≤5 K. The corresponding structural relaxation in the films is exhibited in the form of alternating increase and decrease in the crystallite lattice parameters, accompanied by large nonuniform deformation of the crystallites. The nature of observed relaxation processes in the nonequilibrium state bears the features of spinodal decomposition. The effect of two-dimensional nature and inhomogeneous (granular) structure on the mode of decomposition of inhomogeneous state of the films is considered.
Quasi-one-dimensional electron system over liquid helium
Authors: Kovdrya Yu. Z. , Nikolaenko V. A.
Published: February 2025

A quasi-one-dimensional electron system over liquid helium is realized for the first time by using the curved surface of helium flowing into parallel grooves of an optical diffraction grating. The conductivity of surface electrons moving along and across the grooves is found to be strongly anisotropic. The estimated values of the mobility of electrons moving along the grooves are close to the value of mobility for a bulk liquid.
Trapping of injected charges in solid parahydrogen samples
Authors: Levchenko A. A.
Published: February 2025

The trapping time for injected charges is estimated from transient characteristics of space-charge-limited current in solid parahydrogen samples. Typical values of depth of the traps are 60 K for negative charges and 25 K for positive charges.
Superconductivity of ultrathin beryllium films in the strong-localization state
Authors: Tutov V. I. , Semenenko E. E.
Published: February 2025

The effect of a magnetic field on the resistance of cold deposited beryllium films 6–10 Å thick has been investigated. In films about 10 Å thick, which are in the state of strong localization (R□ = 105 Ω), a local superconductivity has been discovered. It is caused by disordered (to various degree according to reduced Tc values) crystallites of the metastable superconducting phase of beryllium. Data of this report, along with those previously obtained, give evidence that the metastable superconducting phase of beryllium occurs as a result of phase size effect in a narrow interval of grain sizes (8–30 Å).
Thermopower and fluctuation effects in bismuth cuprate high-T
c crystals
Authors: Xiang Yu. N. , Shevchenko O. G. , Panfilov A. S.
Published: February 2025

Thermopower, conductivity and magnetic susceptibility were studied in high-Tc bismuth cuprate crystals of a unique stoichiometric composition Bi2Sr2CaCu2Ox. In the vicinity of the temperature Tc of the superconducting transition (approximately 10% Tc wide) a peak-shaped feature has been revealed in the temperature dependence of the thermopower along with a difference in the behavior of the thermopower outside the peak area, which is closely related with the defect (impurity) structure of the samples. Analysis shows that the observed peculiarities, as well as conductivity and magnetic susceptibility data, can be interpreted as a consequence of thermodynamic Gaussian fluctuations of the bi-component order parameter, the 2D/0D crossover in the two-band system with a narrow and wide band overlapping near the Fermi level.
Peculiarities in the behavior of point-contact spectrum during evolution of the structural state
Authors: Nikiforenko V. N.
Published: February 2025

Experimental data on the instability of point-contact spectra of zinc single crystals due to a destabilization of the basal dislocation network surrounding the point contact are considered. The spectra are characterized by the presence of zero-point anomalies for E > kT, and a considerable rise in the Fermi level and the current density.
Response to music on the nonlinear dynamics of human fetal heart rate fluctuations: A recurrence plot analysis
Authors: Reyes-Lagos José Javier , Mendieta-Zerón Hugo , Martínez-Madrigal Migdania , Santiago-Nuñez Juan Carlos , Reyes-Mendoza Luis Emilio , Gonzalez-Reyes Ximena , Echeverría Juan Carlos , Abarca-Castro Eric Alonso , Talavera-Peña Ana Karen , Avilés-Hernández Sara , Lerma Claudia
Published: February 2025

Music has been shown to influence physiological functions in humans, but its effects on fetal heart rate variability (fHRV) are not well understood. This study aimed to assess the response of classical music exposure on the nonlinear behavior of fetal heart rate fluctuations in fetuses between 32 and 40 weeks of gestation using recurrence quantification analysis (RQA). We collected R–R time series from 37 fetuses in the third trimester following a study into four stages: PRE (baseline), STIM1 (first musical piece), STIM2 (second musical piece), and POST (post-exposure). The fetal R–R time series from each stage were evaluated using RQA indices such as determinism (DET), average diagonal line length (L), maximum line length (LMAX), entropy (ENTR), and trapping time (TT), as well as conventional linear indices like SDRR (standard deviation of R–R intervals). Results revealed three main points. First, there was an increase in DET, L, LMAX, and TT, with a decrease in ENTR in the POST stage compared to PRE, indicating more regular and predictable patterns. Second, the STIM2 stage enhanced the predictability and stability of cardiac dynamics compared to PRE, as indicated by L, LMAX, and TT. Third, no significant changes were observed in conventional indices, except for an increase in SDRR in the POST stage compared to STIM1. These findings suggest a reduction in complexity and nonlinear behavior of fHRV patterns after musical stimulus. The increase in SDRR during the POST stage appears to coincide with fetal movements, as indicated by the number of fetal accelerations found.
Mechanical–chemical coupling in gas–surface interaction: A study of strain effects on the catalytic properties of SiO2
Authors: Gao Yue , Meng Songhe , Yang Qiang , Wang Zexuan , Gao Bo , Yang Fan
Published: February 2025

In actual flight conditions, the surface of thermal protection materials may experience stress, and the impact of surface strain on catalytic reaction and mechanical–chemical coupling has not been fully explored. In this study, a surface gas–solid interaction model was constructed using reaction molecular dynamics and density functional theory methods. The surface catalytic reaction characteristics of α-SiO2 (001) under up to 2% uniaxial and biaxial tensile strain were investigated. Results indicate that both uniaxial stretching along the X axis and biaxial stretching along the X and Y axes inhibit the catalytic recombination reaction at higher surface temperatures. For the uniaxial stretching model, when the strain reaches 2%, the catalytic coefficient decreases by 21.2%, whereas for the biaxial stretching model, it decreases by 34.3%. From the perspectives of surface morphology and energy, the study reveals that tensile strain reduces the undercoordination degree of Si atoms on the surface, reduces the surface energy of α-SiO2 (001), increases the activation energy of the atomic oxygen recombination reaction, alters the recombination pathways of oxygen atoms, strain-induced selective desorption of oxygen atoms reduces the recombination probabilities of both Eley–Rideal and Langmuir–Hinshelwood pathways, ultimately decreasing the catalytic recombination coefficient.
Flow transition and vortex evolution of a symmetric airfoil at low Reynolds number and high angle of attack
Authors: Chen Jichang , Lu Zhiwei , Wu Bin , He Sida , Xiao Tianhang , Tong Mingbo , Kan Kan
Published: February 2025

The flow around airfoil is a significant topic due to the complexities associated with separated structures and fluctuating forces. This study investigates flow transition and vortex evolution for a symmetric airfoil within the range of Reynolds number Re=800–2000 and angle of attack AoA=18∘–26∘. A series of numerical simulations are performed using a well-validated level-set based immersed boundary method. The effects of increasing Re and AoA on the near-profile flow and vortex structures are examined comprehensively through various physical results from the time-averaged, time-history and time-resolved perspectives, including lift and drag coefficients, Strouhal number, pressure and friction distributions, portrait phase map, and spectrum of lift coefficient and instantaneous vorticity. Within the adopted parameter space (Re=800–2000 and AoA=18∘–26∘), three distinct flow patterns, namely, single-period & single-amplitude, double-period & double-amplitude, and multi-period & multi-amplitude, are identified based on the time-history and spectrum of the lift coefficient. Comparative analyses reveal that the flow pattern is strongly influenced by both the Reynolds number and the angle of attack. A detailed analysis of these flow patterns is presented through the period time-evolution of the lift coefficient and vortex structures. The results indicate that the mechanisms of flow patterns are closely related to the formation, merging, splitting, and shedding of various vortices.
Discussion on pore-to-field scale evolution of invasive pattern in immiscible two-phase flow with pseudoplastic behavior in porous media
Authors: Li Yu , Liu Hui-Qing , Peng Chao , He Hong
Published: February 2025

The immiscible two-phase flow with non-Newtonian behavior presents many challenges for geoscience engineering applications. Due to the non-Darcy flow with pseudoplasticity in bitumen or heavy oil reservoir, the variable and velocity-affected viscous force leads to unstable and unpredictable evolution of invasive patterns in porous media. Primarily, drainage experiments, computational fluid dynamics, and analytical model analyses were conducted to track morphological variations of invasive interface, revealing the evolution mechanisms of invasive patterns with pseudoplasticity. Subsequently, the field-scale two-phase flow simulation, established by the blocked-centered finite difference method, quantitively investigates the impact of invasive patterns on the extraction of pseudoplastic oil. Ultimately, given previous methods for evaluation of invasive patterns, capillary number, and mobility ratio play a communicating role in the pore-scale and the field-scale study. Through the dual-scale framework, the capillary number and mobility ratio, serving as driving force and resistance, respectively, predictably improve the evolutionary diagram pore-scale invasive patterns and accurately evaluate the field-scale potential of pseudoplastic oil extraction. From both pore and field perspectives, our work holds promising application for optimizing invasive patterns by injection operation in the pseudoplastic oil reservoirs.