bluuebunny/crossref_metadata_2025 huggingface dataset:
Whole examination AI estimation of fetal biometrics from 20-week ultrasound scans
Authors: Venturini Lorenzo , Budd Samuel , Farruggia Alfonso , Wright Robert , Matthew Jacqueline , Day Thomas G. , Kainz Bernhard , Razavi Reza , Hajnal Jo V.
Published: January 2025

The current approach to fetal anomaly screening is based on biometric measurements derived from individually selected ultrasound images. In this paper, we introduce a paradigm shift that attains human-level performance in biometric measurement by aggregating automatically extracted biometrics from every frame across an entire scan, with no need for operator intervention. We use a neural network to classify each frame of an ultrasound video recording. We then measure fetal biometrics in every frame where appropriate anatomy is visible. We use a Bayesian method to estimate the true value of each biometric from a large number of measurements and probabilistically reject outliers. We performed a retrospective experiment on 1457 recordings (comprising 48 million frames) of 20-week ultrasound scans, estimated fetal biometrics in those scans and compared our estimates to real-time manual measurements. Our method achieves human-level performance in estimating fetal biometrics and estimates well-calibrated credible intervals for the true biometric value.
Improving 3D deep learning segmentation with biophysically motivated cell synthesis
Authors: Bruch Roman , Vitacolonna Mario , Nürnberg Elina , Sauer Simeon , Rudolf Rüdiger , Reischl Markus
Published: January 2025

Biomedical research increasingly relies on three-dimensional (3D) cell culture models and artificial-intelligence-based analysis can potentially facilitate a detailed and accurate feature extraction on a single-cell level. However, this requires for a precise segmentation of 3D cell datasets, which in turn demands high-quality ground truth for training. Manual annotation, the gold standard for ground truth data, is too time-consuming and thus not feasible for the generation of large 3D training datasets. To address this, we present a framework for generating 3D training data, which integrates biophysical modeling for realistic cell shape and alignment. Our approach allows the in silico generation of coherent membrane and nuclei signals, that enable the training of segmentation models utilizing both channels for improved performance. Furthermore, we present a generative adversarial network (GAN) training scheme that generates not only image data but also matching labels. Quantitative evaluation shows superior performance of biophysical motivated synthetic training data, even outperforming manual annotation and pretrained models. This underscores the potential of incorporating biophysical modeling for enhancing synthetic training data quality.
Effects of porous hedgehog-like morphology and graphene oxide on the cycling stability and rate performance of Co3O4/NiO microspheres
Authors: Zhu Guozhen , Xu Xinsong , Zhang Yiyao , Lian Jiale , Li Yuhan , Yang Zhen , Che Renchao
Published: January 2025

A porous hedgehog-like Co3O4/NiO/graphene oxide microsphere was prepared by a facile solvothermal method and annealing treatment in an argon atmosphere, and showed a good rate performance due to graphene oxide.
Amplification-free detection of Mycobacterium tuberculosis using CRISPR-Cas12a and graphene field-effect transistors
Authors: Wang Weiqi , Du Huanyu , Dai Changhao , Ma Hongwenjie , Luo Shi , Wang Xuejun , Guo Mingquan , Kong Derong , Wei Dacheng
Published: January 2025

In this work, we present a graphene field-effect transistor integrated with the CRISPR/Cas12a system for the ultrasensitive detection of Mycobacterium tuberculosis, achieving a detection limit of 2.42 × 10−18 M within 5 minutes.
New opportunities for emerging two-dimensional metastable-phase noble metal oxides in acidic electrocatalytic water splitting
Authors: Wang Qun , Shao Mingwang , Shao Qi
Published: January 2025

Metastable-phase materials possess unique structures, high Gibbs free energy, abundant active sites, and adjustable physicochemical properties, making them ideal candidates for optimizing electrocatalysis.
Asymmetric structure endows thermal radiation and heat conduction in graphene films for enhancing dual-mode heat dissipation
Authors: Niu Ruo-Han , Li Ye-Wen , Ma Shi-Long , Yi Zong-Lin , Xie Li-Jing , Su Fang-Yuan , Jia Hui , Chen Cheng-Meng
Published: January 2025

An asymmetric-structure graphene material was designed for both high thermal conductivity and enhanced radiation.
Instantaneous asymmetry of the Martian bow shock: A single- and dual-spacecraft study using MAVEN and Mars Express
Authors: Nesbit-Östman Sara , Gunell Herbert , Goetz Charlotte
Published: January 2025

Aims. We study the instantaneous asymmetry of the Martian bow shock during a change in the direction of the interplanetary magnetic field (IMF) and for steady-state conditions. Specifically, we study the asymmetry with regard to the convective electric field and to the crustal fields of Mars.

Methods. Two methods were used: First, a single-spacecraft method in which a switch in hemisphere in the Mars solar-electric (MSE) coordinate system was studied during a change in the direction of the interplanetary magnetic field. Second, we used a dual-spacecraft method wherein near simultaneous bow shock crossings on opposite hemispheres were studied. The dual bow shock crossings were then compared to a bow shock model, and the difference in the distance to the model was used as a measure of asymmetry.

Results. With the single-spacecraft method, an asymmetry with respect to the solar wind convective electric field, Esw, was found, wherein the bow shock was farther from the planet in the ZMSE <0 hemisphere, that is, the −E hemisphere. With the dual-spacecraft method, the mean of the magnitude of the asymmetries in the individual case was 0.13 RM. However, the standard deviation was as high as the mean, and no significant asymmetry could be attributed either to the solar wind convective electric field or to the Martian crustal fields. A strong asymmetry without a clear correlation to these factors was found nonetheless. Possible causes of the measured asymmetry are discussed.

Conclusions. The magnitude of the asymmetries in individual observations is larger than the average asymmetries. This indicates that the shape of the Martian bow shock is dynamic and influenced by fluctuations or wave phenomena.
Do tides play a role in the determination of the pre-stellar core mass function?
Authors: Dumond Pierre , Chabrier Gilles
Published: January 2025

Recent studies have examined the role of tides in the star formation process. They suggest, notably, that the tides determine the characteristic mass of the stellar initial mass function (IMF) by preventing the collapse of density fluctuations that would become gravitationally unstable in the absence of the tidal field generated by a neighboring central mass. However, most of these studies consider the tidal collapse condition as a 1D process or use a scalar virial condition and thus neglect the anisotropy of the tidal field and its compressive effects. In the present paper, we consider a turbulence-induced density perturbation formed in the envelope of a central core. This perturbation is subject to a tidal field generated by the central core. We study its evolution taking dynamical effects and the anisotropy of the tides into account. Based on the general tensorial virial equations, we determine a new collapse condition that takes these mechanisms into account. We identify two regimes: (i) a weak tidal regime in which the dynamics of the perturbation is only slightly modified by the action of the tides and (ii) a strong tidal regime in which the density threshold for collapse can potentially be increased due to the combined effects of the tides and the rotational support generated by the tidal synchronization of the perturbation with the orbital motion. In the case of a turbulence-induced density perturbation of mass Mp formed in the vicinity of a first Larson core, which is the case considered in some star formation scenarios, we show that the density threshold above which the perturbation collapses is increased only for low-mass perturbations (Mp ≲ 2.7 M⊙) and only by at most a factor of 1.5. We conclude that tides likely do not play a major role in the process of star formation or in the determination of the characteristic mass of the IMF. We propose an alternative explanation for the observed value of the characteristic mass of the IMF.
Endoscopic size measurement of colorectal polyps: a systematic review of techniques
Authors: Taghiakbari Mahsa , Djinbachian Roupen , Labelle Juliette , von Renteln Daniel
Published: January 2025

Accurate size measurement of colorectal polyps is critical for clinical decision making and patient management. This systematic review aimed to evaluate the current techniques used for colonic polyp measurement to improve the reliability of size estimations in routine practice.

A comprehensive literature search was conducted across PubMed, EMBASE, and MEDLINE to identify studies relevant to size measurement techniques published between 1980 and March 2024. The primary outcome was the accuracy of polyp sizing techniques used during colonoscopy.

61 studies were included with 34 focusing on unassisted and assisted endoscopic visual estimation and 27 on computer-based tools. There was significant variability in visual size estimation among endoscopists. The most accurate techniques identified were computer-based systems, such as virtual scale endoscopes (VSE) and artificial intelligence (AI)-based systems. The least accurate techniques were visual or snare-based polyp size estimation. VSE assists endoscopists by providing an adaptive scale for real-time, direct, in vivo polyp measurements, while AI systems offer size measurements independent of the endoscopist’s subjective judgment.

This review highlights the need for standardized, accurate, and accessible techniques to optimize sizing accuracy during endoscopic procedures. There is no consensus on a gold standard for measuring polyps during colonoscopy. While biopsy forceps, snare, and graduated devices can improve the accuracy of visual size estimation, their clinical implementation is limited by practical, time, and cost challenges. Computer-based techniques will likely offer improved accuracy of polyp sizing in the near future.
Cobalt-Catalyzed Regioselective Hydroformylation of Allylic Alcohol Esters
Authors: Lu Wenxin , Chong Qinglei , Meng Fanke , Du Zhenhao
Published: January 2025

Aliphatic aldehydes are important building blocks in organic synthesis due to their high reactivity and versatility. Herein, we report a simple, mild and efficient method for the hydroformylation of allyl alcohol esters under cobalt catalysis. This procedure offers good functional group tolerance, moderate to good product yields and exclusive chemo- and regioselectivity, making it an attractive method to prepare aldehydes with linear selectivity.
Doyle–Kirmse Reaction of S-Allyl and S-Propargyl Phosphorothioates
Authors: Tual Laurine , Rognan Charlou , Maujean Timothé , Gulea Mihaela , Pertschi Romain , Girard Nicolas , Blond Gaëlle
Published: January 2025

The Doyle–Kirmse reaction represents a powerful synthetic tool for forming both C–S and C–C bonds in a single process. The rhodium-catalyzed Doyle–Kirmse reaction of S-allyl and S-propargyl phosphorothioates with diazoesters has been developed and represents a rare example involving substrates bearing an electron-withdrawing group on the sulfur atom. The transformation takes place at room temperature, in only 5 minutes, and leads via a [2,3]-sigmatropic rearrangement of the sulfonium ylide intermediate to the corresponding S-homoallyl or S-homoallenyl phosphorothioates in yields ranging from 25% to 92% (19 examples).
Recyclable Copper-Catalyzed Cascade Coupling/Condensation/ Deacylation Reaction of 2′-Halotrifluoroacetanilides with β-Keto Esters toward 2-(Trifluoromethyl)indoles
Authors: Cai Mingzhong , Wang Yan , Ye Qian
Published: January 2025

An efficient heterogeneous copper-catalyzed cascade coupling/condensation/deacylation reaction of 2′-halotrifluoroacetanilides with β-keto esters has been developed. The reaction proceeds smoothly in anhydrous dimethyl sulfoxide at 80–90 °C using Cs2CO3 as base and 10–20 mol% SBA-15-immobilized l-proline–CuI complex [SBA-15–l-Proline–CuI] as catalyst and provides a general and practical method for the assembly of a variety of polysubstituted 2-(trifluoromethyl)indoles in good to high yields. This heterogenized copper catalyst can be easily recovered via a simple centrifugation process and reused more than seven cycles with almost consistent catalytic activity.
Impact of Vitamin D3 Deficiency on Quality of Life in Epilepsy: A Call for Routine Screening and Intervention
Authors: Sulena Sulena , Parkash Ishaan , Bansal Pir Dutt , Nagar Akanksha , Gupta Dipti , Bahetra Mamta
Published: January 2025

Background The association between vitamin D3 levels and quality of life (QoL) in people with epilepsy on long-term antiseizure medications is an area of ongoing research. This study aims to assess serum vitamin D3 levels in people with epilepsy and evaluate the effects of supplementation on their QoL.

Methods A prospective study was conducted at a tertiary hospital from June 2021 to July 2022. People with epilepsy aged 12 to 45 years, receiving antiseizure medications for at least 1 year, were recruited. Baseline serum vitamin D3 levels were measured, and epilepsy diagnoses were confirmed according to the International League Against Epilepsy guidelines (2017). QoL was evaluated using the Quality of Life in Epilepsy Scale (QOLIE-31) for adults and the Quality of Life in Epilepsy for Adolescents Scale (QOLIE-48) for adolescents. Patients with vitamin D3 deficiencies received supplementation, and their QoL were reassessed at 3 and 6 months. Data were analyzed using t-tests, multiple logistic regression, and analysis of variance.

Results At baseline, the mean serum vitamin D3 level was 17.99 ± 6.77 ng/mL, increasing to 21.46 ± 2.91 ng/mL at 3 months and 24.41 ± 3.19 ng/mL at 6 months. Patients with vitamin D3 deficiency exhibited significantly lower scores across multiple domains of the Quality of Life Inventory (QOLIE-31 and QOLIE-48). A significant improvement was seen in most of the QOLIE scores and serum vitamin D3 levels after vitamin D3 supplementation.

Conclusion People with epilepsy on long-term antiseizure medications have vitamin D3 deficiency, which negatively impacts their QoL. Regular screening and supplementation are recommended for better management of epilepsy.
Segmental versus Extended Resection for Colon Cancer in Lynch's Syndrome
Authors: Hendren Jared R. , Sommovilla Josh
Published: January 2025

Lynch's syndrome is a common cause of hereditary colorectal cancer (CRC), resulting in higher risk of CRC and development of subsequent, metachronous CRC (mCRC). Beyond treating the primary cancer, surgeons and patients must decide on whether performing an extended colectomy, to reduce the risk of mCRC, is worth the change in function that comes with the larger operation. Considerations include likelihood for mCRC, morbidity and quality of life after resection, impact of pathogenic variant, and certain other cancer risk reduction options. The contemporary evidence to guide these decisions is reviewed herein.
Efficacy of Amniotic Suspension Allografts in the Treatment of Knee Osteoarthritis: A Systematic Review
Authors: Ansari Ayub , Baig Mirza , Tanbour Yazan , Syed Kazi , Ahmed Yunus , Beutel Bryan G.
Published: January 2025

Knee osteoarthritis significantly impacts mobility and quality of life. This condition is a leading cause of disability in aging populations, with total knee replacement commonly sought in advanced cases. Traditional nonoperative management strategies, including anti-inflammatories, corticosteroid injections, and hyaluronic acid, often provide limited relief, especially in severe cases. Recently, regenerative therapies such as amniotic suspension allografts (ASA) have emerged as promising alternatives due to their anti-inflammatory and regenerative properties, which may counteract the catabolic effects of osteoarthritis. This systematic review evaluated the efficacy and safety of ASA in reducing pain and improving function among knee osteoarthritis patients. Following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines, a comprehensive search of PubMed and Embase databases initially identified 1,733 studies pertaining to ASA, of which 1,575 were screened, and 9 studies ultimately met the inclusion criteria for detailed analysis of ASA in the treatment of knee osteoarthritis. Data extraction and narrative synthesis focused on outcomes such as pain reduction and functional improvement using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), as well as safety profiles. The results demonstrated notable improvements in pain scores following ASA treatment, as shown by studies reporting increases in KOOS pain scores over 6 months, which generally outperformed hyaluronic acid and saline treatments in pain reduction. Similarly, ASA treatment was associated with substantial improvements in physical function outcome scores, enhancing patients' ability to perform daily activities. Patient-reported outcomes also indicated higher quality of life and functional status, with most patients experiencing high levels of satisfaction. Additionally, ASA's safety profile was favorable, with adverse events primarily mild to moderate in nature, including a few transient events such as knee stiffness and myalgias. This systematic review highlights ASA as an effective therapeutic option for knee osteoarthritis, although further studies focusing on long-term radiographic outcomes and mechanisms of action are recommended to fully establish its benefits and optimize treatment protocols.
Is It Safe to Use Tranexamic Acid for Chronic Subdural Hematoma: A Systematic Review and Meta-Analysis
Authors: Habibi Mohammad Amin , Naseri Alavi Seyed Ahmad , Boskabadi Amir Reza , Seraj Farid Qoorchi Moheb , Mirjnani Mohammad Sina , Benam Mohsen , Salehpour Firooz , Koets Andrew J.
Published: January 2025

Trans-4-(aminomethyl)-cyclohexane-1-carboxylic acid, also known as tranexamic acid (TXA), has occasionally been used to prevent postoperative recurrence of chronic subdural hematoma (CSDH) after burr hole craniotomy (BC). However, there is a lack of data about the safety and efficacy of TXA administration after BC. This systematic review and meta-analysis adhered to the Cochrane Handbook Standards Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and searching databases up to January 2024 for randomized controlled trials and cohort studies evaluating TXA. The primary outcome was CSDH recurrence and reoperation. The secondary outcome was thrombosis risk and mortality rate. Ten studies were included, comprising 14,836 patients with CSDH who underwent surgical treatment. Five studies were randomized controlled trials, while the other two case series and three cohort studies. The overall pooled hematoma recurrence rate in the group of patients who used TXA as an adjuvant treatment to the surgical intervention (TXA group), compared with patients who only used surgery to treat CSDH (control group), was 0.05 (95% confidence interval [0.03–0.08], p < 0.01), indicating a significant reduction in recurrence with TXA treatment. TXA, as an adjuvant treatment to the surgical intervention, reduces the risk of postoperative hematoma recurrence, reoperation, thromboembolic complication, and mortality related to CSDH after BC in elderly patients.
How Do MRI Findings Influence Rectal Cancer Management?
Authors: Ramakrishnan Ayloor Seshadri , Pradeep Jeyakumar
Published: January 2025

Treatment of rectal cancer is currently guided by the need to reduce local recurrence, improve survival, reduce treatment-related toxicity, and improve the patient's quality of life (QoL). Magnetic resonance imaging (MRI) scan is now the imaging modality of choice for rectal cancer. However, the role of MRI in rectal cancer has transformed beyond describing the local stage of cancer to becoming a tool to predict the prognosis of a patient by its ability to detect features associated with a high risk of recurrence and poor survival. This greatly helps the multidisciplinary team (MDT) responsible for treating patients with rectal cancer to stratify them based on the potential for recurrence and decide on the need for and type of preoperative treatment to be offered. MRI also has the ability to assess the response to such treatments, based on which the MDT can tailor the subsequent treatment. This has the potential to spare the patient from unnecessary treatment, thus improving the QoL. MRI provides a roadmap to the surgeon while planning the surgery. In this review, we give a brief overview of the current management strategies for rectal cancer and highlight the role of MRI in the decision-making process.
On the NMR theory for bounded diffusion of arbitrary dimensions. Application to the phase-separation kinetics of 3He–4He solid solutions
Authors: Kontor K. N. , Maksimov L. A.
Published: January 2025

The theory of attenuation of a pulsed NMR spin-echo signal is constructed for the defect structure of a crystal when the spin diffusion is bounded and low-dimensional. It is shown that the phase distribution of spins diffusing in a nonuniform magnetic field is Gaussian both for small damping times when an unlimited diffusion is realized, and for large damping times when diffusion is considerably restricted under the condition that the magnetic field gradient is not very large. The dependence of the echo-signal on the magnetic field gradient is obtained for different models of bounded diffusion of arbitrary dimensions. The results are applied for interpreting experiments on the phase-separation kinetics of solid 3He–4He solutions.
Zero-order Fermi-defectons in two-dimensional quantum crystals
Authors: Arutyunyan M. Z. , Vardanyan G. Z. , Mkrtchyan G. S. , Saakyan A. S.
Published: January 2025

A method is proposed for observing zero-order Fermi-defectons in 2D-quantum crystals formed as a result of absorption of helium isotopes (3He, 4He) on a graphite substrate. The 2D-quantum crystal is subjected to a constant uniform magnetic field. It is shown that for a certain value of the magnetic field strength, the susceptibility of the system exhibits an anomalous behavior due to a phase transition which is an analog of Lifshits’ 2.5-order phase transition.
Structure and peculiarities of the superconducting transition in weakly orthorhombic YBa2Cu3−xO7−y crystals
Authors: Mitkevich V. V. , Demirskii V. V. , Vasil’chenko S. A. , Dotsenko V. I.
Published: January 2025

Comprehensive structural investigations are carried out directly in a crystal in which a transition to the superconducting state has been registered. Inductive measurements using alternating current in a single crystal reveal a double superconducting transition with Tcl = 92 K and Tc2 = 40 K. For the observed orthorhombicity of 0.019(1) Å in the investigated crystal, the filling of positions O2 and O3 by oxygen is 0.4 and 0.3 respectively, so that the formation of Cu–O chains of an appreciable length is not possible along any axis.
Thermopower of a homogeneous metal circuit containing a point contact
Authors: Shklyarevskii O. I. , Jansen A. G. M. , Wyder P.
Published: January 2025

Thermoelectric size effect has been studied in a homogeneous circuit containing a point contact as one of its branches. It is shown that if the condition d≪lϵ, lpc is satisfied, the diffusive thermopower and the drag thermopower in the point contact are suppressed considerably in comparison with the corresponding quantities for the bulk material. It is found that Spc(d) dependence is preserved at least up to Debye temperatures. A comparison is made with the theoretical results.
Local fields on 57Fe nuclei in UFe2
Authors: Checherskii V. D. , Eremenko V. V. , Kaner N. É.
Published: January 2025

The Mössbauer spectra of UFe2 are measured and analyzed below the Curie temperature. It is found that the magnetic ordering produces a gradient of electric fields associated with the anisotropy of the spatial distribution of electrons around Fe atoms. The procedure for analyzing Mössbauer spectra is described briefly for the case when the energies of magnetic electric field gradient in a general form. The obtained local field parameters are discussed against the background of the works published earlier.
Exchange field distribution in anisotropic spin glass
Authors: Khazan M. V.
Published: January 2025

The distribution function of exchange field in anisotropic spin glass is determined in the Sherrington–Kirkpatrick model. It is found that this function is of Ising type in the longitudinal phase of spin glass at T = 0.
Electromagnetic excitation of sound in YBa2Cu3O7−x ceramic
Authors: Gantmakher V. F. , Dolgopolov V. T. , Murzin S. S. , Nikolaev R. K. , Ovchinnikova L. V. , Sidorov N. S.
Published: January 2025

It is shown that standing acoustic waves can be excited electromagnetically in superconducting plates of YBa2Cu3O7−x ceramic. The velocity of sound is found to be a multiple-valued function of the ceramic density and strongly dependent on thermal treatment of the samples.
Magnetoplasmons in two-dimensional electron systems with elliptic profile
Authors: Nazin S. S. , Shikin V. B.
Published: January 2025

The general problem on the spectrum of magnetoplasma oscillations in an individual multielectron dimple on liquid helium surface is solved. The equilibrium electron density distribution in such dimples is called elliptic. The vibrational spectrum of edge magnetoplasmons contains three types of modes, the first of which is characterized by an increase in frequency with the magnetic field H; the frequency of the second mode decreases with increasing H, while for the third mode the frequency is a nonmonotonic function of H, which vanishes both when H →0 and H → ∞. The role of mobile boundaries of the electron disk in the formation of the magnetoplasmon spectrum is investigated and the peculiarities of attenuation of edge magnetoplasmons are considered. The theory is in qualitative agreement with experiments on excitation of edge magnetoplasmons on two-dimensional conducting disks in the absence of screening.
Influence of correlation effects on relaxation processes in a two-dimensional electron system on helium surface
Authors: Vil’k Yu. M. , Monarkha Yu. P.
Published: January 2025

Relaxation processes in a two-dimensional electron system are investigated without using the quasi-classical description under the conditions when the autocorrelation time τee, for the electron velocity is much shorter than the relaxation time of the system. A relation between the low-frequency conductivity and the energy loss rate of surface electrons, and the dynamic form factor of the two-dimensional electron liquid is established. It is shown that for the same values of the fundamental parameter Γ, equal to the ratio of the mean Coulomb energy to temperature, the contribution of correlation effects to the pulsed collision frequency increases with the electron concentration. The obtained theoretical results make it possible to explain the experimentally observed concentration dependence of the mobility of surface electrons and considerably broaden the region of applicability of the formulas describing energy relaxation.
Topology of the phase diagram of H2–D2 in the region of high-temperature phase transition
Authors: Bereznyak N. G. , Sheinina A. A.
Published: January 2025

The topology of the phase diagram of the binary system hydrogen-deuterium is determined in the temperature range 12−20 K under pressures up to 100 atm by taking into account the phase transformation in the solid phase. The experimental data on high-temperature phase transition are given a special consideration and a non-controversial interpretation of the results is presented.
On the band structure of metaloxide superconductors
Authors: Antsygina T. N. , Slyusarev V. A.
Published: January 2025

The electron energy spectrum of metaloxide superconductors is analyzed proceeding from their crystalline structure. It is shown that the band spectrum of these compounds has a number of peculiarities. The relation between the model under consideration and the models of narrow-band superconductors/V. P. Galaiko, Fiz. Nizk. Temp. 13, 1102 (1987)/and local pairs/I. O. Kulik, Fiz. Nizk. Temp. 13, 879 (1987)/is investigated.
Manifestation of generalized topological transition in conductivity of finite samples (plates)
Authors: Kaganov M. I. , Kamshilin D. V. , Nurmagambetov A. A.
Published: January 2025

Peculiarities in the conductivity of thin metal plates due to the existence (or emergence) of points of flattening on the Fermi surface are investigated.
Suppression of high-temperature superconductivity of oxide ceramics in longitudinal and transverse magnetic fields
Authors: Aliev F. G. , Buzdin A. I. , Balashov V. A. , Moshchalkov V. V. , Kolotyrkina N. A. , Eremina E. A. , Oleinikov N. N. , Pryadun V. V. , Tret’yakov Yu. D.
Published: January 2025

The anisotropy in superconducting properties and geometrical size of monocrystallites must lead to an anisotropy in the magnetoresistance of polycrystalline samples. Such an effect is observed in YBa2Cu3O7–x high-temperature superconductor near the critical temperature.
Calculation of electron and phonon characteristics of materials with a high-temperature superconducting transition
Authors: Davydov S. Yu. , Leonov E. I.
Published: January 2025

The values of electrons and phonon dispersion in the two-dimensional lattice of CuO2 are determined by using the bonding orbital method. The obtained results are in good agreement with the results of computer experiments. It is shown that the electron phonon interaction constant is ∼ 3 eV/Å and the Debye temperature is ∼ 1340 K.
The influence of inhomogeneity of YBaCuO thin films on their interaction with electromagnetic radiation
Authors: Afanas’ev A. S. , Volkov A. F. , Gubankov V. N. , Divin Yu. Ya. , Shadrin P. M.
Published: January 2025

The effect of electromagnetic radiation of the millimeter range on electric parameters of YBaCuO films is studied. It is shown that with an improvement of the film structure, the mechanism of interaction with the radiation can change from the percolation mechanism in the system of weak bonds between grains to the heating mechanism in the grains of the films.
The sequence of low-temperature phase transitions in the CsDy0.9Gd(Eu)0.1(MoO4)2 system
Authors: Zherlitsyn S. V. , Zvyagina G. A. , Fil’ V. D.
Published: January 2025

Temperature dependences of relative changes in the sound velocities along the principal axes of the CsDy0.9Gd(Eu)0.1(MoO4)2 crystal are investigated in the region of the structural second-order phase transition at Tc ∼ 30 K. The absence of a noticeable softening of the transverse moduli indicates the nonferrodistortion type of the transition. Another structural first-order transition is detected in the temperature range between 27 and 24 K.
On the possibility of liquid helium isotope separation in narrow capillaries
Authors: Monarkha Yu. P. , Sokolov S. S.
Published: January 2025

The possibility of helium isotope separation in narrow capillaries is investigated theoretically. The dispersion relation for collective vibrations of an inhomogeneous liquid in a cylindrical capillary is analyzed. It is found that for a sufficiently small outer or inner radius of the separated phase, the light isotope distribution, which is uniform along the cyclinder axis, is unstable. The stability region for the separated phase is determined for various Van der Waals constants of the capillary wall material.
Investigation of ferromagnetic ordering in liquid 3He by using polarized neutrons
Authors: Zhuchenko N. K. , Kuz’mina S. M. , Tarovik É. G. , Trunov V. A. , Yagud R. Z.
Published: January 2025

Ferromagnetic ordering in liquid 3He is investigated at ultralow temperatures. No ferromagnetic ordering has been discovered in 3He contained in pores of size ∼900Å at a temperature ∼0.3 K in a magnetic field of 18 kOe. The height of the potential barrier separating the metastable polarized state from the equilibrium nonpolarized state exceeds 5 erg/cm3.
Electrodynamics of a screw-symmetry superconductor
Authors: Dubrovskii I. M.
Published: January 2025

The superconductor under consideration is a hollow cylinder for which the tensor of proportionality factors between the current density and the difference between the phase gradient and the vector potential of the magnetic field has in cylindrical coordinates nondiagonal components connecting the axial and azimuthal components of the corresponding vectors. It is shown that an axial current passing through such a semiconductor gives rise to an azimuthal component of current and an axial component of magnetic field. If the cylinder has the form of a thin film, the axial field flux in the cavity will be frozen after the disconnection of the axial current circuit. In other words, such a superconductor has a memory. If there is an axial magnetic field in the superconductor cavity, and hence an azimuthal current flows through it, the emerging distribution of axial and radial current produces an azimuthal magnetic field which is equal to zero outside the superconducting material and is mainly localized near its inner surface. The possibilities of experimentally obtaining and investigating such systems is considered.
Current–voltage characteristics and energy gap in high-temperature YBaCuO compounds
Authors: Dmitriev V. M. , Solov’ev A. L. , Dmitrenko A. I.
Published: January 2025

Point contacts formed by metal (steel, niobium) and high-temperature superconductors (HTS) YBaCuOx are investigated in the temperature range from the helium temperature to Tc≃70 K. The magnitude (Δ(0)∼17 MeV, 2 Δ(0)/kTc≃5.5) and the temperature dependence of the energy gap are determined; it is found that they match with the values predicted by the BCS theory in the strong-bond limit. The discovered peaks on the dV/dI (V) dependence, which weakly depend on temperature, point towards the strong electron-phonon interaction in HTS. The effects associated with a change in conductivity of HTS upon a transition through Tc are considered.
Two-band model of a superconductor with a high critical temperature
Authors: Poluéktov Yu. M.
Published: January 2025

The model of a superconductor with two overlapping conduction bands is considered for the case when interband scattering processes play a leading role in the emergence of superconductivity. The effect of electron–phonon attraction as well as the Coulomb repulsion of electrons from different bands on the critical temperature is taken into account. It is shown that when the Coulomb interaction plays the decisive role, the critical temperature can be considerably higher than that possible in the case of the electron–phonon interaction.
The theory of electron–exciton interaction in high-temperature superconductors
Authors: Pedan A. G. , Kulik I. O.
Published: January 2025

The mechanism of high-temperature superconductivity in the Y–Ba–Cu–O ceramic involving the formation of local pairs on copper oxide CuO chains and their interaction with band states in copper oxide (CuO2) planes is considered. The local pairs are formed by holes in filled shells of oxygen ions O2− which are the “bridges” between the chains and conducting planes. The attraction between the holes in neighboring oxygen ions emerges as a result of the exciton transition of Cu2+ and O2− ions to the virtual state Cu+O−.
High-temperature superconductivity in terms of the two-band model
Authors: Moskalenko V. A. , Palistrant M. E. , Vakalyuk V. M.
Published: January 2025

An attempt is made to explain thermodynamic characteristics of high-temperature superconductors by using the two-band model. The possibility of obtaining high values of Tc, small values of the relative jump in the electron heat capacity and the ratios 2 Δ1/Tc ≥ 3.5 and 2 Δ2/Tc < 3.5 (or ≪ 3.5) in the weak bond approximation is demonstrated. It is found that the thermodynamic critical magnetic field differs considerably from the critical field in the BCS theory.
Phase transition in one-dimensional mixed state in thin superconducting films
Authors: Cherkasova V. G. , Fogel’ N. Ya.
Published: January 2025

The temperature dependence of the field corresponding to the formation of a one-dimensional mixed state is determined for vanadium thin films in a magnetic field H‖ parallel to their surface. The phase diagram of the films is studied by measuring the temperature and field dependences of the critical current Ic. The field corresponding to the penetration of a vortex chain is determined by the kinks on the Ic (H‖) curves. For samples with rough surfaces, the experimental Hc1 (T) curves are in good agreement with the theoretical ones. The values of Hcl for films with d ≲ 1000 Å are approximately one order of magnitude higher than the typical values for type II bulk superconductors. For films with smooth boundaries, the vortex penetration is inhibited by a surface barrier, and the corresponding field Hs is appreciably higher than Hcl. The influence of the Bean-Livingston barrier increases in the temperature interval where the relation between the film thickness and the coherence length ξ (T) satisfies the condition d ≫ 2 ξ (T).
Nonlinear electrical conductivity of metal point contacts in the dirty limit
Authors: Kulik I. O. , Moskalets M. V.
Published: January 2025

Nonlinear electrical conductivity of dirty metal point contacts is considered for an arbitrary ratio of the electron energy scattering length λε to the contact size d. It is shown that in the absence of phonon reabsorption, the d2I/dV2(V) dependence has clearly manifested spectral properties corresponding to characteristic decreases with increasing ratio d/λε. The dependence of the amplitude of the principal (| eV | = ħω0) and multiphonon (| eV | = ħω0) peaks of the point contact spectrum and background on the ratio d/λε is calculated by using Einstein’s model.
Structure and properties of Kr–O2 condensed films
Authors: Kovalenko S. I. , Solodovnik A. A.
Published: January 2025

Electron diffraction studies of the structure of condensed Kr–O2 films have been carried out. Measurements were made in the temperature range 5−35 K on samples whose effective thickness varied from 30−40 to 400 Å. A considerable solubility (up to 40 mol % O2) was reported for the components on the Kr side below 35 K. This was facilitated by the closeness of the volumes corresponding to a partially oriented-disordered O2 molecule and a Kr atom. The solubility of Kr in α- and β-O2 was found to be negligible. The addition of small amounts of an inert gas initiated the formation of α′-phase which was transformed into β-modification near the sublimation temperature of O2. For Kr concentrations ≳ 10%, a decomposition into α and β phases was observed. Solutions with a γ-O2-structure were found to border the solidus line in the cases when the Kr concentration was <30%.
Nonlinear phenomena in normal metal–superconducting ceramic contacts
Authors: Sinchenko A. A.
Published: January 2025

The current–voltage characteristics of point contacts formed by a normal metal and a superconducting ceramic are studied. Measurements of dV/dI(V) have led to the value Δ(0) = 18−22 meV of the energy gap for the high-temperature superconductors YBa2Cu3O7−x corresponding to the ratio 2Δ(0)/kTc = 4.7−5.2. Under a certain pressure of the counterelectrode, the IVC of contacts displayed singularities associated with the Josephson nature of conductivity between granules of the ceramic.
Neutron studies of zero-point oscillations in a parahydrogen crystal under pressure
Authors: Vindryaevskii B. A. , Ishmaev S. N. , Kobelev G. V. , Sadikov I. P. , Sukhoparov V. A , Telepnev A. S. , Chernyshov A. A.
Published: January 2025

Inelastic noncoherent scattering of slow neutrons was measured on parahydrogen polycrystals in a pressure range up to p = 10.6 kbar, over which its density is almost doubled. The mean-square displacements 〈u02〉 corresponding to the zero-point vibrations of molecules in the crystal were found in the harmonic approximation from the angular dependence of the intensity of the peak corresponding to the rotational para–ortho transformation of the hydrogen molecules. The molar volume dependence of 〈u02〉 can be presented in the form 〈u02(p)〉=〈u02(0)〉[v(p)/v(0)]γ where the Grtineisen parameter γ = 2.0 ± 0.1 The magnitude of the zero-point vibrations relative to the hcp lattice parameter a for hydrogen remains significant in the investigated pressure range, varying from 18 to 12%.
Effect of dissipation on dynamic characteristics of small tunnel junctions in terms of the polaron model
Authors: Odintsov A. A.
Published: January 2025

The impedance and the current–voltage characteristic are calculated by using the approximate kinetic equation obtained on the basis of the polaron model of tunnel junction in the presence of an external harmonic microwave signal. The results are exact for a strongly shunted junction.
Nonlinear effects in bcc metal conductivity in multichannel specular reflection of electrons
Authors: Kovtun E. A. , Manzhelii E. V.
Published: January 2025

Quantum nonlinear effects emerging in the conductivity of metal plates with a bcc lattice upon the multichanel specular reflection (MSR) of electrons from the plate boundary are considered. It is assumed that the plate thickness d ≲ l0 (l0 is the mean free path). The current-voltage characteristic (IVC) of the plates is calculated in terms of a quasirandom MSR spectrum for arbitrary values of the nonlinearity parameter γ = e.ℰ⋅l0/(ℏνF/d) (ε is the electric field strength and νF the characteristic Fermi velocity). It is found that Zener breakdown in an electric field becomes significant in view of the double degeneration of the MSR spectral term, which is typical of bcc metals. This leads to additional nonlinear anomalies on the IVC of the plate.
Possibility of superconducting type correlations in repulsive Fermi systems
Authors: Antsygina T. N. , Slyusarev V. A.
Published: January 2025

The possibility of the existence of superconducting correlations is analyzed by using the Hubbard model with repulsion on the basis of the generalized self-consistent field method (without resorting to the auxiliary field formalism or equivalent approximations based on the “spherical” type uncontrollable approximations). It is shown that a superconducting solution does not exist in this method under the condition forbidding a double occupancy of a lattice site. The results are compared with the recent data.
Helium adsorption by synthetic activated carbons at liquid helium temperature
Authors: Dikina L. S. , Ivantsov V. G. , Kartel’ N. T. , Lukashev V. N. , Maidanov V. A. , Mikheev V. A.
Published: January 2025

The adsorptivity of new synthetic activated carbons to helium is investigated experimentally at liquid helium temperature under pressures ranging between 0.005 and 10 torr.
Acoustic losses in the system YBa2Cu3O7–δ+ xZrO2
Authors: Bar’yakhtar V. G. , Bereza S. Yu. , Varyukhin V. N. , Loboda S. N. , Strongin S. B.
Published: January 2025

The system YBa2Cu3O7–δ + xZrO2 has been synthesized with x = 1 to 50 mol %. It is shown that the addition of ZrO2 considerably improves the elastic and mechanical parameters at room temperature. The temperature spectrum of acoustic losses is studied at temperatures between 77 and 300 K. The maximum internal friction is observed in the superconducting state near the transition temperature. The effect of Zr concentration on the inelastic properties of the system YBa2Cu3O7–δ + xZrO2 is studied. A possible interpretation for the observed anomalies is offered.
Temperature dependence of the heat capacity of YBa2Cu3O7–δ single crystals with twin structure near superconducting transition point
Authors: Kopasov A. P.
Published: January 2025

The effect of twinning planes forming a periodic structure on the heat capacity of YBa2Cu3O7–δ single crystals at temperatures close to the superconducting transition point is analyzed theoretically and compared with experiment [S.E. Inderhees et al., Phys. Rev. Lett. 60, 1178 (1988)]. It is shown that the inclusion of the contribution proportional to | ψ |6 (ψ is the order parameter) in the Ginzburg-Landau free energy removes the considerable discrepancy between the experimental results obtained by Inderhees et al. and the theoretical results obtained at temperatures slightly lower than 89 K by A.A. Abrikosov and A.I. Buzdin [Pis’ma Zh. Eksp. Teor. Fiz. 47, 204 (1988)], who disregarded the contribution proportional to | ψ |6, which contribution was possibly due to the effect of fluctuations.
Effect of oxygen impurities on conversion of β-methane
Authors: Akulenko V. G. , Lokotosh T. V.
Published: January 2025

The conversion time for CH4 molecules in the librational and free sublattices (LS and FS) of β-methane due to the effect of paramagnetic oxygen impurity is measured. It is shown that oxygen catalyzes conversion in LS much more strongly since the interaction between CH4 and O2 molecules is of quasi-resonance nature in this case, and the coupling constants of translational and angular motion for this pair of molecules are increased. As regards FS, O2 affects only the conversion rate of CH4 molecules nearest to it, while more distant molecules are converted in the same way as in pure methane.
Effect of high frequency current on Nb superconducting film in the resistive state
Authors: Elant’ev A. I. , Karasik B. S.
Published: January 2025

The conductivity of thin and narrow Nb films in the resistive state is studied in the frequency range 1−400 MHz. The features of the frequency dependence of conductivity due to electron heating are determined. The heating influence on the current–voltage characteristics is studied. The experimental data are found to be in agreement with the theory of homogeneous electron heating.
Current states in superconductors with local-pair condensate
Authors: Beloborod’ko S. I. , Kulik I. O. , Omel’yanchuk A. N.
Published: January 2025

Superconducting current states are studied with the model of superconductivity with local pairs. The depairing curve in a homogeneous current state is constructed. The Ginzburg–Landau set of equations is derived, which describe the behavior of a superconductor in a spatially inhomogeneous current state in a magnetic field. Near the transition point, the temperature dependences are found for the critical current, order parameter Δ (T) and the penetration depth of the magnetic field λ (T).
Anomalous penetration of short acoustic pulses into metal
Authors: Gokhfel’d V. M.
Published: January 2025

The propagation of acoustic pulses shorter than the electron relaxation time in a conductor is studied theoretically. It is shown that the nonlocal deformation interaction between the electron and ion subsystems creates a pulse in the metal forerunning the main signal, which propagates at the maximum electron velocity in the given direction and penetrates into the sample to the macroscopic depth of about the electron mean free path. The experimental procedure to measure directly the Fermi velocities using the above effect is developed. The nature of attenuation of the main signal and the shape of the forerunner are analyzed as functions of parameter ωt0 (t0 is pulse duration and ω the carrier frequency).
New group of Shubnikov–de Haas oscillations in Bi–0.02 at. % Te thin single crystal filaments
Authors: Gitsu D. V. , Dolma V. A.
Published: January 2025

A new group of low-frequency Shubnikov–de Haas (SdH) oscillations with a frequency about half that of the Shubnikov oscillations from the minima ellipsoid cross-section of L-electrons is observed along with the SdH oscillations related to L-electrons in thin single crystal wires of diameter d > 1 μ m made of the electronic alloy Bi–0.02 at. % Te. It is assumed that the physical nature of the new group of carriers may be related to impurity states in doped bismuth.