bluuebunny/crossref_metadata_2025 huggingface dataset:
Tracing hierarchical star formation out to kiloparsec scales in nearby spiral galaxies with UVIT
Authors: Shashank Gairola , Subramanian Smitha , Muraleedharan Sreedevi , Menon Shyam H. , Mondal Chayan , Krishna Sriram , Das Mousumi , Subramaniam Annapurni
Published: December 2024

Molecular clouds fragment under the action of supersonic turbulence and gravity, which results in a scale-free hierarchical distribution of star formation within galaxies. Recent studies suggest that the hierarchical distribution of star formation in nearby galaxies shows a dependence on host galaxy properties. In this context, we study the hierarchical distribution of star formation from a few tens of parsecs up to several kiloparsecs in four nearby spiral galaxies: NGC 1566, NGC 5194, NGC 5457, and NGC 7793, by leveraging large-field-of-view and high-resolution far-ultraviolet (FUV) and near-ultraviolet (NUV) observations from the UltraViolet Imaging Telescope (UVIT). Using the two-point correlation function, we infer that the young star-forming clumps (SFCs) in the galaxies are arranged in a fractal-like hierarchical distribution, but only up to a maximum scale. This largest scale of hierarchy (lcorr) is ubiquitous in all four galaxies and ranges from 0.5 kpc to 3.1 kpc. The flocculent spiral NGC 7793 has roughly five times smaller lcorr than the other three grand design spirals, possibly due to its lower mass, lower pressure environment, and a lack of strong spiral arms. lcorr being much smaller than the galaxy size suggests that the star formation hierarchy does not extend to the full galaxy size and it is likely an effect set by multiple physical mechanisms in the galaxy. The hierarchical distribution of SFCs dissipates almost completely within 10−50 Myr in our galaxy sample, signifying the migration of SFCs away from their birthplaces with increasing age. The fractal dimension of the hierarchy for our galaxies is found to be between 1.05 and 1.50. We also find that depending upon the star formation environment, significant variations can exist in the local and global hierarchy parameters of a galaxy. Overall, our results suggest that the global hierarchical properties of star formation in galaxies are not universal. This study also demonstrates the capabilities of UVIT in characterising the star formation hierarchy in nearby galaxies. In the future, a bigger sample can be employed to better understand the role of large-scale galaxy properties such as morphology and environment as well as physical processes like feedback, turbulence, shear, and interstellar medium conditions in determining the non-universal hierarchical properties of star formation in galaxies.
A broadband X-ray view of the ultraluminous sources in the galaxies ESO 501–023 and IC 5052
Authors: Cruz-Sanchez N. , Fogantini F. A. , Saavedra E. A. , Abaroa L. , García F. , Combi J. A. , Romero G. E.
Published: December 2024

We report the results obtained from the analysis of XMM-Newton and NuSTAR observations of two ultraluminous X-ray sources (ULXs) located in the galaxies ESO 501–023 and IC 5052. To better understand their nature, we studied the spectral and timing behavior of these sources. We used spectral-timing techniques to investigate the presence of possible pulsations in the data. We did not detect any significant pulsations and set upper limits on the pulsed fraction of < 9% for ESO 501–023 ULX and < 11% for IC 5052 X-1. These sources exhibit typical ULX X-ray spectra and can be well fitted with two thermal components plus a Comptonization tail at high energies. To classify the sources, we compared their spectral parameters with those of other well-known ULXs. Our results show that ESO 501–023 ULX is in the broadened disk state and IC 5052 X-1 is in the hard ultraluminous state. Finally, our results suggest that the sources are likely nonmagnetic, supercritically accreting objects fed by companion stars.
Current Developments from Silicon Valley – How Artificial Intelligence is Changing Gynecology and Obstetrics
Authors: Griewing Sebastian , Gremke Niklas , Wagner Uwe , Wallwiener Markus , Kuhn Sebastian ,   Commission Digital Medicine of the German Society for Gynecology and Obstetrics
Published: December 2024

Artificial intelligence (AI) has become an omnipresent topic in the media. Lively discussions are being held on how AI could revolutionize the global healthcare landscape. The development of innovative AI models, including in the medical sector, is increasingly dominated by large high-tech companies. As a global technology epicenter, Silicon Valley hosts many of these technological giants which are muscling their way into healthcare provision with their advanced technologies. The annual conference of the American College of Obstetrics and Gynecology (ACOG) was held in San Francisco from 17 – 19 May 2024. ACOG celebrated its AI premier, hosting two sessions on current AI topics in gynecology at their annual conference. This paper provides an overview of the topics discussed and permits an insight into the thinking in Silicon Valley, showing how technology companies grow and fail there and examining how our American colleagues perceive increased integration of AI in
gynecological and obstetric care. In addition to the classification of various, currently popular AI terms, the article also presents three areas where artificial intelligence is being used in gynecology and looks at the current developmental status in the context of existing obstacles to implementation and the current digitalization status of the German healthcare system.
Ernährungsmedizinische Versorgung an deutschen Krankenhäusern – Ergebnisse einer Umfrage unter Ärzten
Authors: Rau Monika , Ferschke Melanie , Mühling Ramona , Fromhold-Treu Sophie , Geier Andreas , Pirlich Matthias , Hahn Sigrid
Published: December 2024

Mangelernährung betrifft 20–30% der Krankenhauspatienten und geht mit einer erhöhten Morbidität und Mortalität einher. Ein regelmäßiges Screening sowie multiprofessionelle Ernährungsteams sind für das Erkennen und die Behandlung entscheidend. Ziel dieser Umfrage ist es, die ernährungsmedizinische Versorgungssituation in deutschen Akutkliniken zu erfassen.

Die Onlineumfrage wurde zwischen 11/2022–08/2023 über medizinische Fachgesellschaften und personalisiert an Chefärzte des deutschen Krankenhausregisters verschickt. Die Umfrage basiert auf einem Instrument der Hochschule Fulda.

An der Befragung nahmen 182 Ärzte teil, von denen 53% angaben, dass ihr Krankenhaus ein Ernährungsteam hat, das am häufigsten organisatorisch der Gastroenterologie angegliedert war. In 88% der Ernährungsteams ist ein Facharzt – meistens ein Facharzt für Gastroenterologie – tätig. Zu den häufigsten Fragestellungen an das Ernährungsteam gehören die Mangelernährung, die parenterale/enterale Ernährung und der Überleitungsprozess. Krankenhäuser mit Ernährungsteam führen zu 83%, Krankenhäuser ohne Ernährungsteam nur zu 47% ein regelmäßiges Screening auf Mangelernährung durch. Als häufigstes Screeninginstrument wird der NRS-2002 verwendet. Bei positivem Screening wird in Kliniken mit Ernährungsteam in 57% automatisch das Team hinzugezogen. In Einrichtungen ohne Ernährungsteam sind standardisierte Abläufe aufgrund von Personalmangel oft nicht möglich.

Die Umfrage zeigt eine ungleiche ernährungsmedizinische Versorgungssituation in deutschen Krankenhäusern. Krankenhäuser mit Ernährungsteam screenen häufiger auf Mangelernährung. Eine verbesserte Finanzierung und Standardisierung sind erforderlich, um die ernährungsmedizinische Versorgungssituation zu optimieren.
Der Effekt interpersoneller Fähigkeiten von Therapeut:innen auf die
therapeutische Allianz
Authors: Schwartz Brian , Rubel Julian A. , Lutz Wolfgang , Schöttke Henning
Published: December 2024

Ziel der Studie Interpersonelle Fähigkeiten von Therapeut:innen spielen
eine zentrale Rolle bei Therapeutenunterschieden im Therapieergebnis. Ebenso
wird die Stärke der therapeutischen Allianz von Therapeutenvariablen
beeinflusst. Das Ziel der Studie war es daher, Therapeutenunterschiede in der
Allianz zu erfassen und den Effekt interpersoneller Fähigkeiten von
Therapeut:innen auf die therapeutische Allianz zu untersuchen.

Methodik Interpersonelle Fähigkeiten von 99 angehenden Therapeut:innen
wurden in einer Gruppendiskussion mit der Skala Therapie-Relevante
Interpersonelle Verhaltensweisen (TRIB) gemessen. Die Therapeut:innen
behandelten n=1031 ambulante Psychotherapiepatient:innen im Rahmen der
Ausbildung zum/zur Psychologischen Psychotherapeut:in. Die Allianz wurde zum
Therapieende mit dem Assessment for Signal Clients (ASC) erfasst. Mit
hierarchisch linearen Modellen wurde die Allianz, unter Kontrolle von weiteren
Patienten- und Therapeutenvariablen, aus den interpersonellen Fähigkeiten
vorhergesagt. Zudem wurde die Ausgangsbelastung als Moderator des Effekts
untersucht.

Ergebnisse Der Therapeuteneffekt (TE) in der Allianz betrug 7,3%.
Interpersonelle Fähigkeiten waren ein signifikanter Prädiktor der Allianz
(b=0,104, p<0,001) und konnten 1,8% der Gesamtvarianz über alle
Kontrollvariablen hinaus aufklären. Der TE wurde auf 5,7% reduziert, was
bedeutet, dass 23,0% der Therapeutenunterschiede in der Allianz auf
interpersonelle Fähigkeiten zurückzuführen waren. Der Moderationseffekt durch
die Ausgangsbelastung wurde zwar nur marginal signifikant (b=0,069,
p=0,061), der Zusammenhang zwischen interpersonellen Fähigkeiten und
Allianz verschwand aber bei geringer Patientenbelastung.

Diskussion Mit der TRIB Skala können interpersonelle Fähigkeiten bereits
vor Ausbildungsbeginn erfasst werden. Die Vorhersage ist vor dem Hintergrund der
mehrjährigen zeitlichen Distanz zwischen den Erhebungen von interpersonellen
Fähigkeiten und Allianz zu betrachten, wobei sie für die selektive Stichprobe
von für die Ausbildung ausgewählten Therapeut:innen gilt.

Schlussfolgerung Interpersonelle Fähigkeiten können die Allianz
vorhersagen. Der Einfluss interpersoneller Fähigkeiten von Therapeut:innen auf
die Allianz steigt mit zunehmender Ausgangsbelastung der Patient:innen an,
während bei gering belasteten Patient:innen kein signifikanter Zusammenhang
besteht. Mittels videobasierter Ratingsysteme können die interpersonellen
Fähigkeiten individueller Therapeut:innen automatisiert gemessen,
Therapeut:innen mit Defiziten identifiziert und gezielt trainiert werden.
Assessment of Ophthalmology Residency Training in Switzerland: A Trainee-Based Survey
Authors: Khamsy Lilly , Turgut Ferhat , Saad Amr , Vicini Rino , Foa Nastasia , Villard Frédéric , Vez Sarah , Karal-Biechl Anne Catherine , Bühler Virginie
Published: December 2024

Background This study aimed to evaluate the current status of ophthalmology residency training in Switzerland and provide insights for enhancing training programs.

Materials and Methods The survey covered demographic data such as gender, age, workplace, and year of residency, as well as working conditions, current practical and diagnostic skills, interest in scientific work, and future plans. It consisted of 16 multiple choice questions (MCQ), 5 multiple select questions (MSQ), 8 free-text, 6 Net Promoter Score (NPS), and 4 Likert scale questions. All Young Swiss Ophthalmologists (YSO) members received an invitation to participate in the survey using an online form. All collected data were anonymized, and participants provided their consent for data collection, analysis, and publication.

Results The survey assessed the perspectives of 63 Swiss ophthalmology residents on their training experiences. Respondents indicated the greatest interest in specializing in cataract and vitreoretinal surgery, followed by cornea, glaucoma, refractive surgery, and lid surgery. They also expressed a great need for improved supervision, structured curricula, and alignment of clinical and research duties. While pursuing additional surgical training and private practice autonomy, residents also expressed a preference for balanced workloads that emphasize patient care over full-time academic work.

Conclusion The survey indicates a need to standardize ophthalmology residency training in Switzerland to ensure comprehensive and uniform education. It also highlights specific areas for improvement, such as the absence of surgical training. Ongoing assessments are necessary to evaluate future developments.
Neoadjuvante Therapie des resektablen, nicht-kleinzelligen Lungenkarzinoms
Authors: Welcker Katrin , Jonigk Danny , Kropf-Sanchen Cornelia , Tufman Amanda , Draube Andreas , Stenzinger Albrecht , Zaatar Mohamed , Thomas Michael
Published: December 2024

Die Behandlungsaussichten beim nicht-kleinzelligen Lungenkarzinom (NSCLC) haben sich durch die Integration von Immuncheckpoint-Inhibitoren in multimodale Therapiekonzepte deutlich erweitert. Aktuell rücken kombinierte, Immuncheckpoint-Inhibitor-basierte Therapiekonzepte auch in frühe, resektable Stadien des NSCLC vor. Die neoadjuvante und perioperative Chemoimmuntherapie eröffnet einen vielversprechenden neuen präoperativen Behandlungsansatz, impliziert aber auch einige neue Fragen und Herausforderungen. Mit den erweiterten perioperativen Therapiemöglichkeiten und der Aussicht auf eine weitere mögliche Verbesserung der Rezidivfreiheit nach Tumorresektion verschiebt sich damit auch die Notwendigkeit, therapierelevante Befunde zur Bildgebung, molekularen und histopathologischen Diagnostik frühzeitig und umfassend zu erheben, weiter nach vorne: Alle Patienten mit Lungenkarzinom sollen unabhängig von der Therapieintention in einem interdisziplinären Tumorboard mit thoraxonkologischer Schwerpunktexpertise vorgestellt werden. Dies ist regelhaft in zertifizierten Lungenkrebszentren gegeben.

Ein standardisiertes Vorgehen trägt zur optimierten prätherapeutischen Diagnostik bei und erleichtert die Abstimmung für das bestmögliche multimodale Vorgehen im interdisziplinären Tumorboard. Bei zentral gelegenen resektablen Tumoren erhöhen sich durch die neoadjuvante Behandlung z.B. die Aussichten auf ein möglichst parenchymsparendes Vorgehen. Einige Fragestellungen lassen sich noch nicht abschließend beantworten. Die perioperative Systemtherapie mit molekular-zielgerichteten und Immuncheckpoint-Inhibitoren ist Gegenstand zahlreicher laufender Studien. Die erhebliche Dynamik bei den Neuzulassungen und die Entwicklung perioperativer Therapiekonzepte macht eine kontinuierliche Anpassung der diagnostischen Algorithmen und Standards erforderlich. Die Integration in die prächirurgische Standardroutine macht eine zügige Einordnung der relevanten Befunde sowie enge Abstimmung zwischen den diagnostischen und interventionellen Fachdisziplinen unerlässlich.
Tenodese de bíceps proximal – Análise biomecânica em ovinos: Comparação entre âncora metálica, âncora sem nós bioabsorvível onlay e parafuso de interferência
Authors: Orso Amauri João , Dallanora Mateus Franceschi , Piluski Paulo Cesar Faiad , Rodriguez Carlos Humberto Castillo , Bonadiman João Artur , Lech Osvandré
Published: December 2024

Objetivo Avaliar biomecanicamente diferentes dispositivos de fixação do bíceps proximal no úmero de ovinos, comparando sua força de fixação até a falha, deslocamento do tendão e local de falha em cada técnica.

Métodos Foram realizados 27 ensaios em úmero de ovinos, separando-os em 3 grupos: grupo A com tenodese com âncoras metálicas (n = 11), grupo B com âncoras bioabsorvíveis sem nós (n = 8) e grupo C com parafusos de interferência metálicos (n = 8), realizando a tenodese com o próprio bíceps dos ovinos mantendo sua inserção distal nativa. Os três métodos foram submetidos a máquina universal de ensaio de tração.

Resultados Não se observou diferença estatisticamente significativa quanto à força de fixação até a falha e deslocamento entre os tendões fixados pelas diferentes técnicas. Em relação ao padrão de rupturas, observou-se que a maioria das rupturas das âncoras metálicas aconteceu ao nível da junção miotendínea, a maioria âncoras de suturas sem nós teve falha por escorregamento da interface fio-parafuso e todos os parafusos de interferência tiveram falha via escorregamento do tendão.

Conclusão As três técnicas com âncora metálica, âncora bioabsorvível sem nós e parafuso de interferência mostraram-se amplamente resistentes às cargas de tração para tenodese do cabo longo do bíceps em ovinos. Não houve diferença estatisticamente significativa entre os três grupos. Estudos com resistência em carga cíclica podem fornecer dados mais valiosos para a comparação dos grupos.
Precisão da ressonância magnética na detecção de rupturas do ligamento cruzado anterior e do ligamento cruzado posterior e correlações artroscópicas subsequentes: Uma investigação
Authors: Yadav Vijendra , Chandrashekhar Chidanand Kaudki Janekunte , Ram Rishi Pothuri , Mohammed Rafeeq
Published: December 2024

Objetivo Este estudo examinou a precisão da ressonância magnética (RM) como modalidade diagnóstica para detecção da ruptura de ligamentos do joelho, em que a artroscopia é o padrão-ouro. O estudo investigou a sensibilidade, especificidade, valor preditivo positivo e valor preditivo negativo dos resultados da RM em uma coorte de 200 pacientes em comparação à artroscopia diagnóstica.

Métodos Nossa instituição realizou um exame clínico abrangente de todos os pacientes com lesões no joelho e aqueles com achados afirmativos sugestivos de ruptura ligamentar foram submetidos à RM. O estudo incluiu 200 pacientes com rupturas do ligamento cruzado anterior (LCA) e do ligamento cruzado posterior (LCP) confirmadas por RM que, posteriormente, foram submetidos à artroscopia para fins diagnósticos e terapêuticos. Os resultados foram submetidos a vários testes estatísticos para comparação e análise dos desfechos.

Resultados O estudo demonstrou sensibilidade e especificidade notavelmente altas, com acurácia quase ideal para o diagnóstico de lesões do LCA e do LCP por meio de RM em comparação à artroscopia. Os pacientes com resultados afirmativos à RM poderiam ser submetidos a procedimentos artroscópicos diagnósticos ou terapêuticos.

Conclusão O estudo enfatiza a importância da RM como método não invasivo e altamente preciso para avaliação das lesões ligamentares do joelho. Embora a RM possa ser usada na investigação de primeira linha, deve-se enfatizar que a artroscopia continua a ser o padrão-ouro para o diagnóstico de rupturas do LCA e do LCP. Este estudo recomenda o uso da RM como uma valiosa ferramenta de triagem em pacientes com suspeita de ruptura de ligamentos do joelho, com potencial para reduzir o número de artroscopias diagnósticas em indivíduos com achados clínicos inconclusivos, o que minimiza o desconforto do paciente e os custos de saúde.
Comparação entre métodos de fixação externa circular e de fixação com placa e parafuso nas fraturas do pilão tibial
Authors: Schueda Marco Antonio , Gubert Leonardo Maranhão , Dal Vesco Yan Celuppi , Dal Piva Fernanda Fossa , Niada Felipe Guglielmi , Mehanna Ryad Fayez
Published: December 2024

Objetivo Comparar os métodos de fixação de fraturas do pilão tibial entre pacientes atendidos em um hospital.

Métodos Foram analisados os prontuários de 28 pacientes que realizaram procedimento cirúrgico para fratura do pilão tibial, sendo 15 deles tratados com fixador externo circular e 13 com fixação interna por placa e parafusos. Foram analisados idade, sexo, fatores agravantes, energia do trauma (alta ou baixa), presença de lesão de tecidos moles, ocorrência de fraturas associadas e desfechos clínicos.

Resultados O sexo mais acometido foi o masculino, na faixa etária entre 40 e 60 anos. O mecanismo de trauma em sua maioria foi acidentes automobilísticos e a lesão associada em 100% dos casos foi a fratura do terço distal da fíbula. O padrão de fratura observado nos pacientes tratados com fixador externo circular foram AO 43C3 e 43C2. Já os padrões de fratura prevalentes observado no grupo de fixação interna foram AO 43C1, 43C2 e 43C3.

Conclusão A escolha terapêutica individualizada é de extrema importância para um melhor desfecho funcional. Também é imprescindível ressaltar que o perfil da fratura e dos pacientes do grupo fixador externo circular e de fixação interna por placa e parafusos tende a ser bastante heterogêneo, pois as fraturas de pior classificação e mais frequentemente associadas a lesões de partes moles costumam ser manejadas com fixação externa circular, enquanto aqueles com fraturas de menor gravidade e menor incidência de lesão de partes moles tendem a ser manejados por redução aberta e fixação interna. Observa-se que os desfechos clínicos e radiográficos tendem a ser similares entre ambos os grupos apesar das particularidades de cada método.
Imaging of Pleural Tuberculosis: A Narrative Review
Authors: Rai Santosh P.V. , K. Livingstone Yvette , Alok Kale , Akshita Goel
Published: December 2024

Pleural tuberculosis is the second most common type of extrapulmonary tuberculosis (TB) after TB lymphadenitis and presents secondary to pulmonary TB in most cases. TB pleuritis develops due to a delayed hypersensitivity response precipitated by the discharge of tubercular bacilli in the pleural space typically within 6 to 9 months of the initial TB infection. TB empyema on the other hand is multibacillary and purulent, often seen in cases of pulmonary TB. Longstanding pleural TB can also present as fibrothorax, chylothorax, or empyema necessitans. It shows features similar to pleural mesothelioma in later stages and is important to be considered as a differential, especially in endemic regions. This review article aims to provide an in-depth knowledge into the basic anatomy of pleural space, pathophysiology of pleural TB, and imaging features helpful in making a diagnosis.
Guiding Device for Subdurostomy Catheters in the Management of Chronic Subdural Hematoma: Moscote–Agrawal Subdurostomy Catheter Introducer
Authors: Moscote-Salazar Luis Rafael , Agrawal Amit , Florez William , Chacon Ariana
Published: December 2024

The drainage of chronic subdural hematoma is a very frequently performed neurosurgical procedure. The management often requires subdurostomy with catheter placement for hematoma drainage. Sometimes, the catheter misplacement can lead to complications that could be catastrophic. This technical note introduces the Moscote–Agrawal guiding device, a tool designed to enhance the accuracy and safety of catheter placement during subdurostomy. We hope that this concept can be adapted by neurosurgeons around the world to minimize procedural risks, improve outcomes, and ensure the safety of neurosurgical practices.
Challenges in the Management of Dislodged Coronary Stent Embolization: A Case Report
Authors: Bekler Ozkan
Published: December 2024

Although device embolization is a rare complication in percutaneous coronary interventions (PCI), its mortality and morbidity are serious complications. With the increasing prevalence of complicated procedures, invasive cardiologists encounter device embolization daily. Different devices and techniques are utilized to retrieve these devices. Most devices used during PCIs are infection stents. More infrequently, the tip of diverting wires, angioplasty balloons, or balloon holders may break and embolize distally into the arteries. A 51-year-old man with non-ST elevation myocardial infarction was presented for restoration of the ring of the stent, which was stripped in the first diagonal ostium, with snare communication. The patient had an anterior myocardial infarction and underwent stent implantation in the left anterior descending artery (LAD) 1 month ago. While the stripped stent was being retracted, the LAD stent had been inserted, causing the stent implanted a month ago to be retracted. Additionally, the dissection was observed in the proximal LAD, and the procedure was terminated by stenting the LAD-Diagonal bifurcation lesion using the mini-crush technique. This case report highlights the importance of constant vigilance that invasive cardiologists must show when removing the embolized device. The maturity of the technique depends on the operator's experience with the methods of use and the material possibilities in the laboratory.
Experimental study of He4P-ρ-T data near the critical vaporization point
Authors: Kukarin V. F. , Martynets V. G. , Matizen É. V. , Sartakov A. G.
Published: December 2024

Dielectric permittivity measurements with a planar capacitor are used to determine P-ρ-T data for He4 near the critical vaporization point. Approximately 620 experimental points on 23 isotherms are obtained. Temperature, pressure, and density ranges comprise 5.062–5.381 °K, 1530–2028 torr, and 42–104 g/liter respectively. The data obtained coincide well with those of other authors in regions where comparison is possible.
Toward the theory of cyclotron resonance of two-dimensional electrons on a liquid helium surface
Authors: Dykman M. I.
Published: December 2024

It is demonstrated that in describing quantum cyclotron resonance of two-dimensional electrons on a helium surface in the one-electron approximation, the interaction with ripplons cannot be considered weak. The cyclotron resonance peak in this approximation is formed because of transitions between Landau levels with generation or annihilation of large numbers of ripplons. The method of moments is used to calculate the peak half-width. General expressions for the cyclotron resonance peak half-width and shift, as obtained in Refs. 1, 2 in the one-electron approximation (for weak and strong coupling to oscillations of the medium), and in Ref. 3 in many electron theory (for the relatively weak concentration range), are compared. An explanation is offered for the qualitative peculiarities of the peak half-width and shift which appeared in the experiments of Ref. 4 at low concentration levels.
Dependence of the critical current of two-band superconductors on the external magnetic field
Authors: Botoshan N. I. , Deyu V. I. , Kolpazhiu M. K.
Published: December 2024

Green’s current functions for two-band superconductors are used to derive a complete system of equations describing a current-carrying, thin-walled superconducting cylinder in a parallel external magnetic field. The critical current density calculated for high concentrations of paramagnetic impurities proves to be a periodic function of the external magnetic field parallel to the generatrix of the cylinder.
Nonequilibrium superconductor states in the case of “narrow” nonequilibrium sources
Authors: Kirichenko I. K. , Novikov V. E. , Seminozhenko V. P. , Shestopalov V. L.
Published: December 2024

Stationary nonequilibrium states of superconductors are examined when nonequilibrium is caused by the effect of a microwave electromagnetic field of frequency Ω > 2Δ as well as tunnel injection of excitations in a S-I-S contact at the voltage V>2Δ/e (Δ is the magnitude of the superconductor energy gap). Solutions of the kinetic equations for the nonequilibrium quasiparticle distribution function fϵ are obtained by numerical methods. Cases when an analytic solution is impossible (strong nonequilibrium) are examined and analyzed in detail. The spectral dependences of such quantities as ultrasound attenuation in a nonequilibrium superconductor and generation of “2Δ phonons” are investigated. The self-blocking effect of the tunnel current in a nonsymmetric S1-I-S2 tunnel contact is examined.
The isotope effect in the PdHx (Dx) system
Authors: Ginodman V. B. , Zherikhina L. N.
Published: December 2024

The superconducting transition temperatures in PdDx samples were measured in the deuterium concentration interval 0.72 ≤ x ≤ 0.85. These results are compared with similar data for PdHx so as to obtain the isotope effect ΔTc in this concentration region. It is shown that the observed ΔTc (x) is in qualitative agreement with theory, but the experimental values of ΔTc (x) are slightly larger than the theoretical ones.
Critical fields in superconducting periodic structures
Authors: Minenko E. V. , Shekhter R. I. , Kulik I. O.
Published: December 2024

The Ginzburg–Landau equations derived in this paper for doped superconducting superstructures containing both normal and magnetic impurities are used to investigate critical magnetic fields. In the temperature range where the superstructure period a is much shorter than the coherence length ξ(T), the angular dependence of Hc2 has been found to be universal and to depend on the anisotropy coefficient α only. Effects of disorder (i.e., deviations of the superstructure potential from periodicity) on the results obtained are discussed in terms of localized states.
Cyclotron resonance on open electron orbits
Authors: Peschanskii V. G. , Yung O. V. , Yasemidis K.
Published: December 2024

We study the absorption of electromagnetic waves by metals in an oblique magnetic field when the extremal number of electrons in the open cross-section of the Fermi surface drifts along the sample. The interaction of these electrons with the electromagnetic wave under conditions of the anomalous skin effect leads to the cyclotron resonance when the wave frequency ω is a multiple of the Larmor frequency Ω of the conduction electrons in the magnetic field. The intensity of the resonance is approximately equal to the resonance intensity in a parallel magnetic field. In both cases, the impedance for ω = nΩ has a fractional-power singularity. It is shown that this result, obtained by Lekhtsier and one of the authors {V.G. Peschanskii, and V.S. Lekhtsier, Zh. Éksp. Teor. Fiz. 46, 764 (1964) [Sov. Phys. JETP 19, 520 (1964)]}, is correct for frequencies ω for which r/δ≫ωτ > 1, where δ is the skin depth, and r is the radius of curvature of the electron trajectory in the magnetic field. As either ω or the electron mean free time τ increase, the resonance weakens, and for ωτ≫r/δ, the character of the resonance singularity changes. In thin metallic films when the film thickness d is smaller than the electron orbit diameter D, the orbit is cut off. For d>D +δ, the resonance line shape is the same as in the bulk material. In a narrow range of magnetic fields such that δ >(d–D)> 0, the resonance undergoes substantial changes and vanishes. This last condition gives the accuracy of determination of the diameter of the electron resonance orbit.
Low energy electron-magnon states localized at the surface of a ferromagnetic semiconductor
Authors: Petrova T. G.
Published: December 2024

Low-energy surface states are studied which belong to the magnetic-polaron type. These states occur in the spectrum of a ferromagnetic semiconductor for positive s-d exchange integrals in the volume of the system and negative at the surface. Using the Jacobian matrix method we calculate the energy of the localized states and construct the corresponding wave functions. We also find the average values of the z projections of the electron spin, and of the total spin of the surface layer of atoms in these states. It is shown that these states affect the magnetic ordering of the surface by lowering its magnetization, and also lead to mainly antiparallel orientation of the electron spin at the surface of the system relative to the spontaneous moment of the lattice.
Mechanisms of exciton–magnon absorption of light by the two-sublattice noncollinear antiferromagnet CoCO3
Authors: Verdyan A. I. , Eremenko V. V. , Kaner N. É. , Litvinenko Yu. G. , Shapiro V. V.
Published: December 2024

The region from 16,000 to 26,000 cm−1 of the light absorption spectrum of the antiferromagnet CoCO3 was studied in external magnetic fields of up to 300 kOe at temperatures of 1.8 to 35 °K. The electronic transitions in the frequency range studied were identified and the fine structure of the 4Γ4−2Γ4 transition was examined in detail. After investigating the mechanisms of exciton–magnon light absorption in CoCO3 we found values of 33.5 and 22.5 cm−1 for the spin-wave energies at the Brillouin zone boundary.
Measurement of Kapitsa resistance using second sound in He II
Authors: Tsoi A. N. , Nemirovskii S. K.
Published: December 2024

The effect of the Kapitsa resistance on the boundary conditions in acoustic experiments is discussed. We show that the correct calculation of the temperature resistance and of the thermal balance leads to a relaxation type of process of thermal energy transfer into the bulk helium, with a characteristic time τ = RC(R is the Kapitsa resistance, C is the specific heat per unit surface). This fact can be used to measure R in the following way: As is known, the speed of second sound depends on the signal amplitude which, in turn, is a function of τ(R); consequently, the speed of the second sound signal is connected to the boundary resistance R in a unique way.
Relationship of electrical resistance of polycrystalline tin films to structural characteristics
Authors: Belevtsev B. I. , Komnik Yu. F. , Kopina V. E. , Yatsuk L. A.
Published: December 2024

Change of electrical resistance with temperature is studied in tin films of various thicknesses, produced by condensation on a substrate at helium temperature and subjected to heating up to various temperatures (between helium and room). A parallel electron diffraction study of crystallite size during heating is performed. Using the Mayadas-Shatzkes theory and approximate linearized expressions obtained therefrom for the temperature coefficient of polycrystalline film resistance, the values of the specularity coefficient for reflection of electrons from external surfaces and the reflection coefficient from intercrystallite boundaries’ together with their changes due to recrystallization are determined. The temperature behavior of these characteristics is also determined.
The steady-state Josephson effect in microbridges with paramagnetic impurities
Authors: Cheishvili O. D.
Published: December 2024

Josephson tunneling in superconducting S–c–S junctions is investigated in the “dirty” limit, when the weak link of the junction contains paramagnetic impurities. It is shown that Josephson tunneling can occur in such a system over the entire temperature range.
Effect of twinning planes on the potential distribution in finite conductors
Authors: Bogod Yu. A. , Krasovitskii Vit. B.
Published: December 2024

It has been found that in strong transverse magnetic fields the interaction of the charge carriers with twinning planes leads to the nonreproducibility of the longitudinal-voltage signals when the magnetic field is reversed. It can generally be concluded on the basis of the data obtained that the discrepancy in a number of cases between the measured dependences and the predicted asymptotic forms of the magnetoresistivity tensor components is due to the crystal-lattice defects, which distort the current lines in the samples.
Features of phase equilibrium in liquid Ne−H2 solutions
Authors: Marinin V. S. , Pashkov V. V.
Published: December 2024

Special features of phase equilibrium in liquid Ne−H2 solutions are examined using the thermodynamic perturbation theory. In the 26−31.14 °K temperature interval, the pressure and composition of the azeotropic mixture are determined, as are the phase separation curve and the parameters of the upper critical separation (consolute) temperature. An analog is established for the well-known “law of equal areas,” which allows calculation of the composition of heterogeneous phases.
Raising the critical temperature of a superconductor by means of microwave radiation
Authors: Aslamazov L. G. , Gavrilov V. I.
Published: December 2024

It is demonstrated that suppression of superconductivity by the current limits the rise of the critical temperature of a superconductor in a microwave field.
Surface impedance of tungsten and cadmium plates in a strong magnetic field at radio frequencies
Authors: Zherebchevskii D. É. , Naberezhnykh V. P. , Chabanenko V. V.
Published: December 2024

The frequency-and-field dependence of the impedance, its resistive and reactive components, of tungsten and cadmium plates were studied experimentally over the 2−7 MHz frequency range under antisymmetric excitation, with the depth δ of the skin layer close to or larger than the plate thickness d. Here the behavior of the experimental curves is shown to follow closely a relation based on the assumption that most of the impedance is due to the skin effect. A comparison of experimental and theoretical results yields an estimate of the mean free path length for electrons in metals.
Quadratic low-temperature contribution to the electrical resistivity of transition metals
Authors: Cherepanov V. I. , Startsev V. E. , Volkenshtein N. V.
Published: December 2024

The temperature dependence of the electrical resistivity of high-purity single crystal samples of tungsten, rhenium, molybdenum and ruthenium are studied in the range 2−40 °K. It is shown that the quadratic contribution to the electrical resistivity of pure tungsten is due mainly to the interference between surface and electron–phonon scattering, rather than to direct electron–electron collisions. A similar conclusion is also made for rhenium. The quadratic contribution to the electrical resistivity of bulk samples of molybdenum correlates with the experimental results on the radio-frequency size effect, and is at least an order of magnitude larger than in tungsten and in rhenium. It is established that an increase in the impurity content in ruthenium increases the quadratic temperature-dependent contribution to the electrical resistivity.
Effect of intercalation on the low-temperature specific heat of the layered crystal Pbl2
Authors: Gurevich A. M. , Sukharevskii B. Ya. , Alapina A. V.
Published: December 2024

Investigations of the temperature dependences of the specific heats of lead iodide samples intercalated by different organic molecules (piperidine, aniline, pyridine) have revealed that these molecules interact differently with the matrix layers. It is suggested, on the basis of investigations of a number of PbI2 (piperidine) samples differing in their organic-molecule contents, that a single-phase PbI2 (piperidine) sample can exist in a narrow region near the stoichiometric composition. Measurements of the CP(T) of a completely deintercalated sample have shown that the intercalation process is reversible, and that the specific heat is insensitive to the surface of the intercalated samples.
Thermal conductivity of low-density solid 4He
Authors: Golub A. A. , Svatko S. V.
Published: December 2024

Measurements of the thermal conductivity of helium crystals with a molar volume of 20.56 cm3/mole are reported for the temperature interval 0.4−1.8 °K. Analysis of the results has disclosed a possible significant influence of dislocations on the thermal conductivity of helium in the regime of Poiseuille phonon gas flow. The values of the dislocation density and the time for normal phonon–phonon collisions are estimated. An explanation is proposed for the discrepancies among the results of various investigators in the Poiseuille flow regime.
Critical magnetic field intensities and critical currents in thin niobium films
Authors: Pan V. M. , Prokhorov V. G. , Kaminskii G. G.
Published: December 2024

In this study the temperature dependences of the critical magnetic field intensities and the critical currents in superconducting niobium films of various thicknesses are investigated.
Phase-slip dynamics and excess current in long superconducting bridges
Authors: Kulik I. O. , Omel’yanchuk A. N. , Khlus V. A.
Published: December 2024

Dynamic two-fluid equations are formulated which describe the nonlinear penetration of a longitudinal electric field into a superconductor. Some properties of phase-slip centers in long channels are examined. The occurrence of a phase-slip center, localized in the center of a superconducting bridge which leads to the jump condition in the hysteretic current–phase relation I(φ), is analyzed in detail. The dependence of the excess current on the bridge length is analyzed. For limitingly long lengths (which are, nevertheless, small in comparison with the penetration depth) the excess current is 5/8 of the critical current.
Quantum temperature size effect and magnetism in CuzS compounds
Authors: Aliev F. Yu. , Asadov Yu. G. , Mamedov M. Sh. , Khakimov K. , Ibragimov S. G. , Godzhaev F. R.
Published: December 2024

At temperatures below 130°K, CuzS films have been found to exhibit temperature oscillations in their electrical conductivity and coefficient of thermal expansion and at 160°K, to undergo a second-order phase transition. Susceptibility measurements on compounds of the system CuzS (1 ≤ z ≤ 2) have led to the detection of weak ferromagnetism in CuS, due, apparently, to the interaction of the electrons with the paramagnetic copper atoms.
Anomalous transparency of the metal–dielectric interface during thermal emission of phonons by thin metal films
Authors: Volotskaya V. G. , Shklovskii V. A. , Musienko L. E.
Published: December 2024

We report measurements of the thermal resistivity of the metal–dielectric interface for tin films in good thermal contact with a single-crystal quartz substrate. There is an anomalous increase in the transparency of the interface at Te ≲ 10 °K. We discuss the possible causes of this increase.
Magnetic field splitting of exciton absorption lines in α-oxygen
Authors: Prikhot’ko A. F. , Ostrovskii V. S. , Pikus Yu. G. , Shanskii L. I.
Published: December 2024

We have studied the influence of a magnetic field up to 60 kOe on the optical absorption of polycrystalline antiferromagnetic oxygen, α − O2, in the vicinity of the exciton and vibronic 1Σg+←3Σg− transitions. A general expression is obtained for the matrix element of the intersublattice resonant interaction in magnetic dielectrics. In addition to the contribution due to the isotropic mechanism associated only with the mutual orientation (cant) of the spins on the inequivalent sublattices, it is shown that when a single-ion anisotropy exists there is a significant additional contribution to this interaction arising from an anisotropic mechanism, caused by the “nonclassical” nature of the ground state. The contribution of this mechanism is determined by the crystal symmetry and the orientation of the antiferromagnetism vector. It is shown that for α − O2 the anisotropic mechanism for the intersublattice resonant interaction is dominant and that, for a reasonable value of 70 cm−1 for the exchange interaction of an excited oxygen molecule with its neighbors, satisfactorily explains the observed behavior of the exciton line — namely the nonlinearity and the magnitude of its splitting in a magnetic field and also the intensities of the split components. The roles of the isotropic and anisotropic components of the resonant interaction are considered for various ranges of magnetic field strength both for the case of polycrystalline α − O2 and for the basic types of ionic antiferromagnets.
Hysteresis of elastic characteristics of V3Si in the mixed state
Authors: Kuznetsov Yu. S. , Shtol’ts A. K. , Gel’d P. V. , Marchenko V. A.
Published: December 2024

The results of investigations of the temperature dependences of the elastic modulus C11 of a V3Si single-crystal specimen in a magnetic field are reported. The hysteresis effects observed are explained by proceeding from the assumption that Abrikosov vortices are pinned on defects in the specimen.
Flow of helium II in narrow channels
Authors: Krasnov Yu. K. , Matyushkina L. V.
Published: December 2024

A quantitative description of the first-order transition from nondissipative isothermal flow of He II in a narrow slot to dissipative flow is presented on the basis of the dynamic theory of quantum vortices in a two-component liquid. The velocity profile is described and values of the lifetime, effective viscosity, and vortex intensity as functions of temperature and flow rate are obtained. A detailed study is performed of He II flow out of a narrow channel in a gravitational field. The dependence of such flow on the differences in level, length and width of such channels and on temperature are found.
Thermal conductivity of low-density weak solid solutions of He3 in He4
Authors: Golub A. A. , Svatko S. V.
Published: December 2024

Crystals of helium isotopes in solid solution, with 0.05, 0.15, and 0.5 at. % He3 concentrations, respectively, have been grown under a constant pressure of 31.1 atm and their thermal conductivity then measured over the 0.4−1.8 °K temperature range. In an analysis of the results, a component of the thermal resistence has been isolated which is proportional to T−2 and corresponds to the mechanism of phonon scattering by stress fields around dislocations. The possibility is considered that the impurity component of thermal resistance could be weakly anisotropic.
Investigation of the surface electron mobility in liquid He4 and weak solutions of He3 in He4
Authors: Esel’son B. N. , Rybalko A. S. , Sokolov S. S.
Published: December 2024

The mobility of electrons localized near a liquid He4 surface has been investigated experimentally by different methods in the 0.1−1 °K temperature interval. The mobility increases according to a law close to T−1 as the temperature is lowered. The results obtained are in good agreement with available theoretical ideas. Preliminary investigations of surface electron mobility have been conducted in He3−He4 solutions with He3 concentrations less than 0.1%.
Investigation of the liquid crystal phase transition in a system of electrons localized on the surface of liquid helium
Authors: Esel’son B. N. , Rybalko A. S. , Sokolov S. S.
Published: December 2024

The liquid–crystal phase diagram is investigated experimentally for a system of electrons localized near the surface of liquid He4 in the temperature range 0.4−0.5 °K. The point of the phase transition was determined by the discontinuity in the curves showing the mobility of surface electrons as a function of the pressing electric field. Resonant absorption of energy was observed in the crystalline phase for different electronic concentrations. The results obtained agree well with theoretical considerations.
Critical characteristics of a thin superconducting film
Authors: Gvozdikov V. M. , Manninen É.
Published: December 2024

The free energy of a thin superconducting film in a magnetic field is computed taking into account the damping of levels arising from spatial quantization. The Ginzburg-Landau expansion, the coefficients of which α and β differ from the corresponding quantities in bulk samples, is obtained. The phase transition is studied as a function of the field H, temperature T, and film thickness d with the help of the coefficients α and β. An expression is obtained for the critical current. A correlation is established between Tc and the normal resistance of the film. The experimental significance of this correlation is discussed.
Impedance of a metallic film under conditions of the anomalous skin effect
Authors: Katsnel’son M. I. , Okulov V. I. , Ustinov V. V.
Published: December 2024

The impedance of a metallic film symmetrically or antisymmetrically excited under conditions of the anomalous skin effect is computed for the case in the which the film thickness is small compared to the mean free path of the conduction electrons. The contribution of the dc resistance of the film to the impedance is separated out, and it is shown that the remaining part of the impedance can be expanded in powers of the ratio of the skin depth to the mean free path, using the fact that the probability of scattering of the near-glancing electrons at the boundaries is low. The dependence of the various contributions to the impedance on the film thickness is analyzed.
On the quantum theory of dislocation dragging by electrons in a magnetic field
Authors: Grishin A. M. , Humen L. N. , Kaner É. A. , Fel’dman É. P.
Published: December 2024

We investigated the quantum oscillations of the electron drag acting on a line dislocation whose axis is nearly parallel to the magnetic field. The quasiclassical situation was considered, when a large number of Landau levels are situated below the Fermi level. The contribution made to the drag force by electron transitions which involve no change in the level number is analyzed in detail. This contribution is decisive in the range of small angles between the magnetic field and the axis of the dislocation.