bluuebunny/crossref_metadata_2025 huggingface dataset:
How much is the effective dose from medical imaging in pediatric patients in the neurosurgery department?
Authors: Zeinali-Rafsanjani B. , Haseli S. , Jalli R. , Saeedi-Moghadam M.
Published: July 2021

Medical imaging with ionizing radiation in pediatric patients is rising, and their radiation sensitivity is 2–3 times more than adults. The objective of this study was to estimate the total effective dose (ED) of all medical imaging by CT scan and plain radiography in patients in pediatric neurosurgery department. Patients with at least one brain CT scan and recorded dose length product (DLP) were included. Patients’ imaging data were collected from the picture-archiving-and-communicating system (PACS) using their national code to find all their medical imaging. Total ED (mSv) from CT scans and plain radiographs were calculated. A total of 300 patients were included, of which 129 were females and 171 males with a mean age of 5.45 ± 4.34 years. Mean DLPs of brain, abdomen, and chest CT were 329.16, 393.06, 284.46 mGy.cm. The most frequent CT scans in these children were brain CT scans with ED range of 0.09 to 47.09 mSv. Total ED due to all CT scans and plain radiographs were in the range of 0.38 to 63.41 mSv. Although the mean DLP of each brain, chest, and abdomen CT of patients was in the range of DRLs reported by previous studies, the patients with numerous CT scans received more radiation doses than mean ED (6.21 mSv between all age groups). The most frequent CT scan was the brain, and the most frequent plain radiographs were chest and lower extremities. It can be concluded that reducing the number of CT scans or plain radiographs by appropriate physical exams or replacing them with modalities that do not use ionizing radiation can reduce ED.
Digitale Technologien in der Kieferorthopädie
Authors: Koos Bernd
Published: July 2021

Liebe Kolleginnen und Kollegen,

das Spektrum der kieferorthopädischen Behandlung ist geprägt von einer ausgesprochenen Breite und Komplexität, bei der regelmäßig interdisziplinäre Aspekte von entscheidender Bedeutung sind. Dabei gilt auch für die Kieferorthopädie, dass in zunehmendem Maße die digitalen Techniken zu einer Steigerung der Effizienz, aber vor allem auch zu einer Verbesserung der kieferorthopädischen Behandlung im Sinne der Steigerung der medizinischen Qualität, insbesondere auch durch die Vermeidung von unerwünschten Nebenwirkungen, führen können.
Digitale Kiefermodelle – Erstellung und kieferorthopädisch-diagnostische Anwendungen
Authors: Gerhart Catrin , Radeke Johanna , Elkholy Fayez , Schramm Elena , Lapatki Bernd G.
Published: July 2021

Die digitale Kieferorthopädie erfuhr besonders in den letzten Jahren sowohl in der Diagnostik als auch in der Therapie großen Zuspruch. Digitale Kiefermodelle können entweder direkt mittels Einscannen der Gipsmodelle oder indirekt mittels Intraoralscan erstellt werden. Auf längere Sicht setzt sich hier sicherlich das Intraoralscanning durch. Die digitalisierten und gegenseitig registrierten Kiefermodelle können mit ausgereiften Softwaretools mittlerweile sehr genau und ohne zeitlichen Mehraufwand ausgewertet werden. Zudem ergeben sich zahlreiche neue Applikationsmöglichkeiten, wie z. B. die Integration mit 3D-Gesichtsscans für dento-faziale 3D-Analysen. Auch das digitale Setup von Kiefermodellen zur Behandlungssimulationen, z. B. bei der Fragestellung Ex- oder Non-Ex-Therapie oder vor kieferchirurgisch-kieferorthopädisch kombinierter Behandlung, ist ein attraktives Anwendungsfeld. Darüber hinaus ergeben sich durch die Verfügbarkeit von digitalen Kiefermodellen faszinierende therapeutische Anwendungen, z. B. im Bereich des indirekten Bracketings oder der Alignertherapie, die in diesem mehr diagnostisch fokussierten Beitrag jedoch nicht näher thematisiert werden.
Digitale Fortschritte in der kombiniert kieferorthopädisch-kieferchirurgischen Therapie erwachsener Patienten
Authors: Quast Anja , Kauffmann Philipp , Trautmann Johanna , Klenke Daniela , Santander Petra , Meyer-Marcotty Philipp
Published: July 2021

Im Zuge der Digitalisierung hat sich auch die Fallplanung im Rahmen kieferorthopädisch-kieferchirurgischer Therapien verändert. Dabei wird die klassische Modelloperation auf Basis von 2-dimensionalen Röntgenbildern und einartikulierten Gipsmodellen zunehmend durch eine digitale Planung mittels digitaler Volumentomografie, Stereofotogrammetrie und 3-dimensionalen Druckverfahren ersetzt. Als Vorteile werden eine Reduktion von Laborschritten, die damit einhergehende Zeitersparnis und Eliminierung potenzieller Fehlerquellen sowie die verbesserte Visualisierung präoperativer Asymmetrien und des postoperativen Ergebnisses beschrieben. Der Artikel stellt die digitalen Fortschritte und einen möglichen Workflow für die klinische Praxis exemplarisch dar.
Hygienische Aufbereitung von Hilfsmitteln in der außerklinischen Intensivpflege
Authors: Ziech Patrick , Zinken Anika
Published: July 2021

Die hygienische Aufbereitung von verwendeten Medizinprodukten ist für Patienten, die außerhalb eines Krankenhauses ambulant gepflegt werden, von enormer Wichtigkeit. Doch nicht immer gibt es dafür klare und unmissverständliche Regelungen seitens der Hersteller – wie das Beispiel einer Betroffenen zeigt.
MDR-Tuberkulose, Alpha-1-Antitrypsin-Mangel, Husten bei Altenpflegerin
Authors: Hoheisel Andreas , Vogt Geert , Nagel Stephan , Bonitz Andreas , Müller Christian , Köhnlein Thomas , Hoheisel Gerhard
Published: July 2021

Multiresistente Tuberkulosen (MDR-TB) machen zwar einen nur geringen Anteil an der Gesamtzahl aller TB-Erkrankungen aus, durch die erforderliche komplexe Medikation mit potenziell schweren und lebensbedrohlichen Nebenwirkungen, Langzeitfolgen und ungünstigem Verlauf ist jedoch besondere Sorgfalt geboten. Wir berichten über eine 30-jährige Altenpflegerin mit chronischem Husten und angeborenem Alpha-1-Antitrypsin-Mangel (AATM), die an einer MDR-TB erkrankte und erhebliche Medikamenten-Nebenwirkungen erlitt.
Immunmodulation im Cholesteatom
Authors: Leichtle Anke , Leffers David , Daerr Markus Georg , Draf Clara , Kurabi Arwa , Ryan Allen F , Rupp Jan , Bruchhage Karl-Ludwig
Published: July 2021

Einleitung Die Ätiopathogenese der chronischen Otitis media epitympanalis bzw. des Cholesteatoms und ihr proliferierender destruierender Verlauf mit möglichen Komplikationen wie Destruktion der knöchernen Strukturen mit Hörverlust, vestibulärer Dysfunktion, Gesichtsnervenlähmung und intrakraniellen Komplikationen sind immer noch ungeklärt. Die Therapie der Wahl ist nach wie vor die operative Sanierung. Aktuelle Studien befassen sich immer mehr mit dem angeborenen Immunsystem.

Methoden Unsere Untersuchungen erfolgten im Mausmodell an WT-Mäusen und immundefizienten KO-Mäusen sowie an Gewebeproben vom Cholesteatom, gesunder Gehörgangshaut und gesunder Mittelohrschleimhaut, die während sanierenden Ohroperationen entnommen wurden. Die Expressionsanalysen erfolgten auf Gen- und Proteinebene mit TNF als Major Target zur Therapieevaluation. Mittels TUNEL-Färbung und Immunhistochemie an Kryoschnitten wurde die Apoptose-Rate durch TNF bestimmt.

Ergebnisse Das ungerichtet-expansive Cholesteatomwachstum zeigt ein immunmodulatorisches Profil mit Hoch- und Runterregulation von verschiedenen Gen-Netzwerken, vor allem Molekülen der TNF-Down- und -Upstream-Signalwege. Dabei wird TNF sowohl inflammatorisch als auch apoptotisch moduliert und eignet sich als möglicher Therapieansatz in verschiedenen Modellen.

Schlussfolgerungen Es gibt Hinweise auf eine immunmodulatorische Regulation im Cholesteatom.
The Relationship Between Intact Parathyroid Hormone and
25-Hydroxyvitamin D in United Kingdom Resident South Asians and Whites: A
Comparative, Cross-Sectional Observational Study
Authors: Coley-Grant Deon , Jawad Mohammed , Ashby Helen L. , Cornes Michael P. , Kumar Bharan , Hallin Magnus , Nightingale Peter G. , Ford Clare , Gama Rousseau
Published: July 2021

Ethnic differences in intact parathyroid hormone (iPTH) at similar total 25
hydroxyvitamin D [25(OH)D] concentrations have been reported between US resident
Whites, Blacks, and Hispanics, but this has not been studied between South
Asians and Whites. We, therefore, compared the iPTH relationship to 25(OH)D in
UK resident South Asians and Whites. A comparative, cross-sectional
observational study in which demographic and laboratory data on South Asian and
White residents of Wolverhampton, UK were analyzed. Log-log models measured the
association between 25(OH)D and the interaction term of ethnicity and iPTH.
Seven hundred and seventy-two patients consisting of 315 white subjects (208
women) and 457 South Asian subjects (331 women) were studied. Compared to South
Asians, White subjects were older, had higher serum concentrations of 25(OH)D,
creatinine (lower eGFR), adjusted calcium and magnesium, but similar
concentrations of iPTH and phosphate. In an adjusted model, variables
significantly associated with 25(OH)D included age, creatinine, adjusted calcium
and ethnicity; but not iPTH and the interaction term of ethnicity and iPTH (beta
coefficient –0.071, 95% CI –0.209, 0.067,
p=0.32). In our study cohort, iPTH was not, per se, influenced by 25
(OH)D. We found no ethnic differences in the association between iPTH and
25(OH)D between South Asians and White UK residents
Recent Advance in Iminyl Radical Triggered C–H and C–C Bond Functionalization of Oxime Esters via 1,5-HAT and β-Carbon Scission
Authors: Guo Li-Na , Liu Le , Duan Xin-Hua
Published: July 2021

The direct functionalization of C(sp3)–H and C(sp3)–C(sp3) bonds is considered as one of the most valuable synthetic strategies because of its high efficiency and step-economy for the rapid assembly of complex molecules. However, the relatively high bond disassociation energies (BDEs) and similar chemical environment lead to large obstacles in terms of low reactivity and selectivity. Using a radical-based strategy has proved to be an efficient approach to overcome these difficulties via a hydrogen atom transfer (HAT) process for selective C(sp3)–H functionalization and β-carbon scission for C(sp3)–C(sp3) bond derivatization. Oxime esters have emerged as outstanding precursors of iminyl radicals for versatile chemical transformations. This short review summaries the recent advances in site-specific C(sp3)–H functionalization and C(sp3)–C(sp3) bond cleavage starting from oxime esters by our group and pioneering work by others, mainly focusing on the reaction design as well as the reaction mechanism.

1 Introduction

2 C(sp3)–H Bond Functionalization via 1,5-HAT of Acyclic Oxime Esters­

2.1 1,5-HAT/Cyclization

2.2 1,5-HAT/C–C or C–Heteroatom Bond Formation

3 C(sp3)–C(sp3) Bond Functionalization via β-Carbon Scission of Cyclic Oxime Esters

3.1 β-Carbon Scission/C–C or C–Heteroatom Bond Formation

3.2 β-Carbon Scission/Cyclization

4 Conclusion and Outlook
A Convenient Approach to meso-Uracil–4,4-Difluoro-4-bora-3a, 4a-diaza-s-indacene Derivatives
Authors: Cordaro M. , Trapani M. , Castriciano M. A. , Elemans J. A. A. W. , Nicosia A. , Mineo P.
Published: July 2021

An effective and convenient protocol for the synthesis of 1-substituted uracil-6-carbaldehyde derivatives has been developed. A three-step sequence permits the preparation of uracil-6-carbaldehydes with various substituents at the N-1 in large quantities by using low-cost precursors. The aldehyde-functionalized uracils served as useful precursors for the preparation of meso-(1-substituted 6-uracil)-derivatives of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY). In this way, regioselectively functionalized BODIPYs with a direct connection to a nucleobase were prepared in yields of 30–45%. MALDI-TOF mass spectrometry, NMR, UV/vis absorption, and steady-state and time-­resolved fluorescence spectroscopies were used to characterize the structures and the spectroscopic/photophysical properties of the resultant dyes.
Synthesis of Dibenzo[a,e]cyclooctene-5,11(6H,12H)-diones via the Elusive Benzocyclobutenone Anion
Authors: Liu Yu , Lu Ping , Huang Yingchao , Chen Jun
Published: July 2021

We reported here a facile synthesis of dibenzo[a,e]cyclo­octene-5,11(6H,12H)-diones via dimerization of benzocyclobutenones in the presence of simple base via the elusive benzocyclobutenone anion­. The temperature effect played a crucial role in the dimerization reaction­. Further synthesis of 5,11-disubstituted dibenzo[a,e]cyclo­octenes (dibenzo[a,e][8]annulenes) from dibenzo[a,e]cyclooctene-5,11(6H,12H)-diones was also explored.
Relation Between Insertion Torque and Implant Stability Quotient: A Clinical Study
Authors: do Vale Souza João Paulo , de Moraes Melo Neto Clóvis Lamartine , Piacenza Lucas Tavares , Freitas da Silva Emily Vivianne , de Melo Moreno André Luiz , Penitente Paulo Augusto , Brunetto Juliana Lujan , dos Santos Daniela Micheline , Goiato Marcelo Coelho
Published: July 2021

Objectives This study aimed to assess the relation between the insertion torque and implant stability quotient (ISQ recorded immediately and 6 months after implant placement).

Materials and Methods Twenty-five patients over the age of 18 years were selected for this study. One implant was placed per patient after tooth extraction. All implants had the same size (11.5 × 3.75 mm) and brand (Hexagonal Morse cone, DSP Biomedical). The insertion torque (Ncm) and resonance frequency analysis (ISQ value) (Osstell Mentor) were used to assess the primary stability (on the day of surgery). After 6 months, resonance frequency analysis was used to assess the secondary stability of each implant.

Statistical Analysis The insertion torque data were correlated with ISQ measurements by using Pearson’s correlation. The significance level was 5%.

Results There was a positive correlation between insertion torque and initial ISQ (correlation: 0.457; p = 0.022); however, no correlation was found between insertion torque and final ISQ (p = 0.308).

Conclusion The present study demonstrated that there is a positive correlation between the insertion torque and the initial ISQ. Therefore, the higher the insertion torque, the higher the initial ISQ (and vice versa).
Comparative Evaluation of Flexural Strength and Modulus of Elasticity of Three Adhesive Luting Cements at Different Time Intervals under Oral Simulated Conditions: An In Vitro Study
Authors: Dewan Sumedha , Kalra Tarun , Kumar Manjit , Bansal Ajay , Avasthi Abhishek
Published: July 2021

Aim The purpose of this study was to compare and evaluate the flexural strength and modulus of elasticity of three adhesive luting cements as a function of specimen age, effect of storage media, and effect of curing through porcelain.

Materials and Methods Twenty samples fabricated for self-cure resin-modified glass ionomer cement (GIC; RelyX Luting 2, 3M ESPE, United States) were classified as group 1, whereas 40 samples fabricated for two dual-cure resin cements (20 samples each), Universal Resin Cement (Ammdent, Italy) and Maxcem Elite (Kerr Australia Pty. Ltd.), were classified as groups 2 and 3, respectively. The dual-cure cements were photo-activated using light cure unit with an intensity of 550 mW/cm2 in nine overlapping sections for 20 seconds per section on both sides. A total of 60 samples (20 samples in each group) were fabricated and tested using universal testing machine to compare flexural strength and modulus of elasticity of resin-modified GIC with two dual-cure adhesive resin cements, to determine the influence of storage of the specimens in artificial saliva at 37°C for 24 hours and to determine the influence of curing through porcelain disk of 2 mm thickness on these properties.

Results The overall mean flexural strength and modulus of elasticity of resin-modified GIC was less than the dual-cure resin cements. The values reduced for resin-modified GIC when the samples were tested after 24 hours of storage in saliva, whereas an increase in the strength was seen for dual-cure cements. The curing through porcelain disk reduced the properties of dual-cure cements. Maxcem Elite showed better overall mean flexural strength and modulus of elasticity in all the parameters.

Conclusion When comparing all three cements, both dual-cure cements showed better flexural strength and modulus of elasticity compared to resin-modified GIC, which indicates their use in cementation of fixed restorations.
A Scoping Review of Health Information Technology in Clinician Burnout
Authors: Wu Danny T. Y. , Xu Catherine , Kim Abraham , Bindhu Shwetha , Mah Kenneth E. , Eckman Mark H.
Published: July 2021

Background Clinician burnout is a prevalent issue in healthcare, with detrimental implications in healthcare quality and medical costs due to errors. The inefficient use of health information technologies (HIT) is attributed to having a role in burnout.

Objective This paper seeks to review the literature with the following two goals: (1) characterize and extract HIT trends in burnout studies over time, and (2) examine the evidence and synthesize themes of HIT's roles in burnout studies.

Methods A scoping literature review was performed by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines with two rounds of searches in PubMed, IEEE Xplore, ACM, and Google Scholar. The retrieved papers and their references were screened for eligibility by using developed inclusion and exclusion criteria. Data were extracted from included papers and summarized either statistically or qualitatively to demonstrate patterns.

Results After narrowing down the initial 945 papers, 36 papers were included. All papers were published between 2013 and 2020; nearly half of them focused on primary care (n = 16; 44.4%). The most commonly studied variable was electronic health record (EHR) practices (e.g., number of clicks). The most common study population was physicians. HIT played multiple roles in burnout studies: it can contribute to burnout; it can be used to measure burnout; or it can intervene and mitigate burnout levels.

Conclusion This scoping review presents trends in HIT-centered burnout studies and synthesizes three roles for HIT in contributing to, measuring, and mitigating burnout. Four recommendations were generated accordingly for future burnout studies: (1) validate and standardize HIT burnout measures; (2) focus on EHR-based solutions to mitigate clinician burnout; (3) expand burnout studies to other specialties and types of healthcare providers, and (4) utilize mobile and tracking technology to study time efficiency.
Achondroplasia: Clinical, Radiological and Molecular Profile from Rare Disease Centre, India
Authors: Goyal Manisha , Gupta Ashok , Bhandari Anu , Faruq Mohammed
Published: July 2021

Achondroplasia is the most common autosomal dominant form of skeletal dysplasia and is caused by heterozygous mutations of the fibroblast growth factor receptor 3 (FGFR3) gene at region 4p16.3. This study highlights the data of achondroplasia cases, clinical spectrum, and their outcome from small cities and the region around Rajasthan. The data for analysis were collected retrospectively from genetic records of rare disease clinic in Rajasthan. Clinical profile, radiographic features, molecular test results, and outcome were collected. There were 15 cases, including eight males and seven females, in this cohort. All had facial hypoplasia, depressed nasal bridge, prominent forehead, and characteristic radiographic features. A total of 14 cases were sporadic and one case was inherited from the mother. Mutation analysis showed 13 out of 15 cases with the p.Gly380Arg mutation in the FGFR3 gene. Hydrocephalus was developed in three cases, required shunting in two cases.
The Mechanism of Interleukin-35 in Chronic Hepatitis B
Authors: Tang Ying , Ma Tianyi , Jia Shengnan , Zhang Qian , Liu Siqi , Qi Ling , Yang Lanlan
Published: July 2021

Interleukin-35 (IL-35) is a newly identified inhibitory cytokine. It has recently been found to play an extremely important role in chronic hepatitis B disease, which makes it likely to be a target for new therapies for hepatitis B malady. IL-35 modulates a variety of immune mechanisms to cause persistent viral infections, such as affecting the ratio of helper T cells, reducing the activity of cytotoxic T cells, hindering the antigen presentation capacity for dendritic cells, and increasing the transcription level of hepatitis B virus. On the other hand, IL-35 can control the inflammation caused by hepatitis B liver injury. Therefore, to seek a breakthrough in curing hepatitis B disease, the contradictory part of IL-35 in the occurrence and development of this sickness is worthy of further discussion and research. This article will systematically review the biological effects of IL-35 and the specific mechanisms affecting the disease.
Entre abstraction et réalité dans la mise en œuvre du conseil agricole en Afrique subsaharienne: leçons apprises des expériences du département de l’Atlantique au Bénin
Authors: Aplogan Aristophane , Zossou Espérance , Zoundji Gérard C. , Vodouhe Simplice D.
Published: July 2021

Agricultural advisory, a learning and decision-making approach, is an important part of the agricultural policies in Sub-saharan Africa. This study aims to analyse the agricultural advisory service provided by comparing the organizational framework and implementation strategies with the realities observed in practice. Using simple random sampling method, 6 groups of 30 farmers from 6 different villages and 30 agricultural advisers were selected in the south of Benin, “Atlantique” department. Data were collected through focus group discussion and semi-structured interviews. Data were analysed using an analytical framework integrating the institutional and social environment as well as the various modalities used for the provision of agricultural advice. Results highlighted four main categories of factors limiting farmers’ access to agricultural advisory service: (i) agricultural advisory service-oriented towards large farms; (ii) individualized and overly specialized advice; (iii) limited number and unskilled agricultural advisers; and (iv) a “gendarme” monitoring and evaluation system little oriented towards the quality of the advice. This critical analysis of the implementation of the agricultural advice service offers some guidelines for strengthening agricultural innovation systems.
Specialized magnetic tweezers developed for piconewton force manipulation
Authors: Green Leigh Ann
Published: July 2021

Ultrasensitive magnetic tweezers allow for exploration of the fluctuation dynamics among biomolecules.
Enhancing flexoelectricity in PEDOT:PSS polymer films with soft treatments
Authors: Saadeh M. , Aceta Y. , Frère P. , Guiffard B.
Published: July 2021

We report the use of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as a transducing material in the fabrication of mechanical-to-electrical conversion devices based on the flexoelectric-like response of this polymer. Devices are made in a cantilever-based three-layer stainless-steel/PEDOT:PSS/top metal electrode configuration to assess the effective transverse flexoelectric coefficient μ12′. We investigated the influence of the nature of the top electrode in the flexoelectric response comparing samples with gold and aluminum top electrodes and demonstrated the huge impact of adding a small fraction of a second dopant such as xylitol to the PEDOT:PSS polymer blend and the benefits of a post-treatment of the polymer film with ethanol and methanol on the flexoelectric coefficient. The combination of xylitol addition and the rinsing of the polymer films with ethanol and methanol, along with the use of gold as a top electrode, led to a significant improvement of μ12′ to ca. 24 μC m−1, which is in the range of those reported for high permittivity oxide materials. These findings support the use of conjugated polymers as an alternative to inorganic materials in flexoelectric-based applications, where large flexibility is required.
Design of a high-throughput bio-ferrograph for isolation of cancer cells from whole blood
Authors: Svetlizky D. , Levi O. , Eliaz N.
Published: July 2021

Enumeration and morphological characterization of circulating tumor cells (CTCs) can be useful in diagnosis and prognosis of metastatic cancer patients. The bio-ferrograph (BF) with its five flow channels, which was developed in the late 1990s for magnetic isolation of biological cells and tissue fragments from fluids, is a modification of the analytical ferrograph. Its use for isolation of rare CTCs from human whole blood (HWB) is a novel approach for the detection of cancer at a cellular level. The isolation process is facilitated by the interaction of specifically magnetized cells with a strong external magnetic field, yielding high recovery rates with no morphological alternation of cells that are isolated on a coverslip glass slide, thus allowing complementary microscopic, chemical, biological, and mechanical analyses. Here, a full mechanical and magnetostatic design of a novel high-throughput BF is presented. The system design is based on an optimized procedure for bio-ferrographic isolation of CTCs from HWB. It incorporates a semi-automated CTC separation system consisting of sample preparation, labeling, and staining; magnetic isolation; and system recovery. The design process was optimized based on experimental feasibility tests and finite element analyses. The novel bench-top system consists of 100 flow channels, allowing simultaneous analysis of multiple samples from 20 patients in each run, with the potential to become a decision-making tool for medical doctors when monitoring patients in a hospital setting. It opens a new route for early diagnosis, prognosis, and treatment of cancers, as well as other diseases, such as osteoarthritis.
Beam-driven ECH waves: A parametric study
Authors: Zhang Xu , Angelopoulos Vassilis , Artemyev Anton V. , Zhang Xiao-Jia
Published: July 2021

Electron cyclotron harmonic (ECH) waves play a significant role in driving the diffuse aurora, which constitutes more than 75% of the particle energy input into the ionosphere. ECH waves in magnetospheric plasmas have long been thought to be excited predominantly by the loss cone anisotropy (velocity–space gradients) that arises naturally in a planetary dipole field. Recent THEMIS observations, however, indicate that an electron beam can also excite such waves in Earth's magnetotail. The ambient and beam plasma conditions under which electron beam excitation can take place are unknown. Knowledge of such conditions would allow us to further explore the relative contribution of this excitation mechanism to ECH wave scattering of magnetospheric electrons at Earth and the outer planets. Using the hot plasma dispersion relation, we address the nature of beam-driven ECH waves and conduct a comprehensive parametric survey of this instability. We find that growth is provided by beam electron cyclotron resonances of both first and higher orders. We also find that these waves are unstable under a wide range of plasma conditions. The growth rate increases with beam density, beam velocity, and hot electron temperature; it decreases with increasing beam temperature and beam temperature anisotropy (T⊥/T∥), hot electron density, and cold electron density and temperature. Such conditions abound in Earth's magnetotail, where magnetospheric electrons heated by earthward convection and magnetic reconnection coexist with colder ionospheric electrons.
Gradual conductance modulation of Ti/WOx/Pt memristor with self-rectification for a neuromorphic system
Authors: Shin Jiwoong , Kang Myounggon , Kim Sungjun
Published: July 2021

In this study, we present an analysis of the gradually modulated conductance of the Ti/WOx/Pt memristor. The deposited material layers were verified by transmission electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray photoelectron spectroscopy. The results revealed that the current level and the rectification behavior differed depending on the presence or absence of the compliance current (CC). If the current is controlled low at a CC of 100 μA, the current is suppressed at the positive voltage bias. It was verified through array simulation that this can mitigate the sneak current in the crossbar array structure. Finally, we conduct the potentiation and depression characteristics for an in-mode and a self-compliance mode and evaluate the pattern recognition accuracy of Modified National Institute of Standards and Technology database through neuromorphic simulation. The synaptic device with a self-rectifying behavior has considerable potential for the synapse array structure in a neuromorphic system.
Analytic and numerical vibronic spectra from quasi-classical trajectory ensembles
Authors: Provazza Justin , Tempelaar Roel , Coker David F.
Published: July 2021

The truncated Wigner approximation to quantum dynamics in phase space is explored in the context of computing vibronic line shapes for monomer linear optical spectra. We consider multiple model potential forms including a shifted harmonic oscillator with both equal and unequal frequencies on the ground and excited state potentials as well as a shifted Morse potential model. For the equal-frequency shifted harmonic oscillator model, we derive an analytic expression for the exact vibronic line shape that emphasizes the importance of using a quantum mechanical distribution of phase space initial conditions. For the unequal-frequency shifted harmonic oscillator model, we are no longer able to obtain an exact expression for the vibronic line shape in terms of independent deterministic classical trajectories. We show how one can rigorously account for corrections to the truncated Wigner approximation through nonlinear responses of the line shape function to momentum fluctuations along a classical trajectory and demonstrate the qualitative improvement in the resulting spectrum when the leading-order quantum correction is included. Finally, we numerically simulate absorption spectra of a highly anharmonic shifted Morse potential model. We find that, while finite quantization and the dissociation limit are captured with reasonable accuracy, there is a qualitative breakdown of the quasi-classical trajectory ensemble’s ability to describe the vibronic line shape when the relative shift in Morse potentials becomes large. The work presented here provides clarity on the origin of unphysical negative features known to contaminate absorption spectra computed with quasi-classical trajectory ensembles.
Mesoscopic model reduction for the collective dynamics of sparse coupled oscillator networks
Authors: Smith Lauren D. , Gottwald Georg A.
Published: July 2021

The behavior at bifurcation from global synchronization to partial synchronization in finite networks of coupled oscillators is a complex phenomenon, involving the intricate dynamics of one or more oscillators with the remaining synchronized oscillators. This is not captured well by standard macroscopic model reduction techniques that capture only the collective behavior of synchronized oscillators in the thermodynamic limit. We introduce two mesoscopic model reductions for finite sparse networks of coupled oscillators to quantitatively capture the dynamics close to bifurcation from global to partial synchronization. Our model reduction builds upon the method of collective coordinates. We first show that standard collective coordinate reduction has difficulties capturing this bifurcation. We identify a particular topological structure at bifurcation consisting of a main synchronized cluster, the oscillator that desynchronizes at bifurcation, and an intermediary node connecting them. Utilizing this structure and ensemble averages, we derive an analytic expression for the mismatch between the true bifurcation from global to partial synchronization and its estimate calculated via the collective coordinate approach. This allows to calibrate the standard collective coordinate approach without prior knowledge of which node will desynchronize. We introduce a second mesoscopic reduction, utilizing the same particular topological structure, which allows for a quantitative dynamical description of the phases near bifurcation. The mesoscopic reductions significantly reduce the computational complexity of the collective coordinate approach, reducing from O(N2) to O(1). We perform numerical simulations for Erdős–Rényi networks and for modified Barabási–Albert networks demonstrating remarkable quantitative agreement at and close to bifurcation.
Radiometric force on a sphere in a rarefied gas based on the Cercignani–Lampis model of gas–surface interaction
Authors: Kalempa D. , Sharipov F.
Published: July 2021

The radiometric force on a sphere due to its thermal polarization in a rarefied gas flow being in equilibrium is investigated on the basis of a kinetic model to the linearized Boltzmann equation. The scattering kernel proposed by Cercignani and Lampis to model the gas–surface interaction using two accommodation coefficients, namely, the tangential momentum accommodation coefficient and the normal energy accommodation coefficient, is employed as the boundary condition. The radiometric force on the sphere, as well as the flow field of the gas around it, is calculated in a wide range of the gas rarefaction, defined as the ratio of the sphere radius to an equivalent free path of gaseous particles, covering the free molecular, transition, and continuum regimes. The discrete velocity method is employed to solve the kinetic equation numerically. The calculations are carried out for values of accommodation coefficients considering most situations encountered in practice. To confirm the reliability of the calculations, the reciprocity relation between the cross phenomena is verified numerically within a numerical error of 0.1%. The temperature drop between two diametrically opposite points of the spherical surface in the direction of the gas flow stream, which characterizes the thermal polarization effect, is compared to experimental data for a spherical particle of Pyrex glass immersed in helium and argon gases.
Enhanced piezoelectric effect in MoS2 and surface-engineered GaN bilayer
Authors: Wang Xinxin , Shi Wenyu , Wan Jianguo
Published: July 2021

The piezoelectric effect of MoS2 and surface-engineered GaN bilayers is systematically investigated using the density functional perturbation theory based on first-principles calculations. The results show that the piezoelectric coefficients increased in the stacking with same polarization orientation between MoS2 and of surface-engineered GaN monolayers. We further find that the increment extent is also affected by different stacking configurations. Furthermore, the uniaxial and normal strains can effectively modulate the piezoelectric coefficients in a reasonable range. Such variations can be revealed by analyzing the charge distribution at different strain states. Our results show that MoS2 and surface-engineered GaN bilayers have potential applications in nanosensors and piezotronics.
Transient circulant clusters in two-population network of Kuramoto oscillators with different rules of coupling adaptation
Authors: Kasatkin D. V. , Nekorkin V. I.
Published: July 2021

We considered a network consisting of two populations of phase oscillators, the interaction of which is determined by different rules for the coupling adaptation. The introduction of various adaptation rules leads to the suppression of splay states and the emergence of each population complex non-stationary behavior called transient circulant clusters. In such states, each population contains a pair of anti-phase clusters whose size and composition slowly change over time as a result of successive transitions of oscillators between clusters. We show that an increase in the mismatch of the adaptation rules makes it possible to stop the process of rearrangement of clusters in one or both populations of the network. Transitions to such modes are always preceded by the appearance of solitary states in one of the populations.
Measurement and modeling of bulk viscosity for polystyrene melts
Authors: Chang Yuan-Jung , Chang Rong-Yeu , Osswald Tim A.
Published: July 2021

Bulk viscosity describes the irreversible resistance to the rate of volume change. Bulk viscosity, which is more than ten thousand times higher than shear viscosity, has been ignored in the field of polymer processing for the past decades. Bulk viscosity may play an important role for compressible polymer melts undergoing strong compression during processing, especially during the packing and holding stage in injection molding. In this study, bulk viscosity of an amorphous Polystyrene melt is investigated through measurements, modeling, and implementation in an injection molding simulation. The results demonstrated that bulk viscosity can be derived from a cooling rate-controlled PVT (pressure-specific volume–temperature) measurement. A new pressure-specific volume–temperature–cooling rate model was developed to obtain smooth and reliable bulk viscosity results. Furthermore, a Cross-William–Landel–Ferry–Arrhenius model was found capable of describing the dependence of temperature, rate of volume change, and mechanical pressure on bulk viscosity of this polymer melt. The proposed modeling was first verified using the non-equilibrium PVT and then was implemented into an injection molding simulation. Simulation results showed that the effects of bulk viscosity not only prevent the material from changing its size but also reduce mechanical pressure variations during the injection molding packing stage.
Observation of enhanced pedestal turbulence during ELM mitigation with resonant magnetic perturbation on EAST
Authors: Zhong Fubin , Zhang Tao , Wang Yumin , Wen Fei , Huang Jia , Wu Mingfu , Li Gongshun , Liu Yukai , Geng Kangning , Xiang Haoming , Ye Kaixuan , Zhou Zhen , Han Xiang , Meng Lingyi , Wang Liang , Sun Youwen , Gao Xiang
Published: July 2021

Edge localized mode (ELM) mitigation accompanied by density pump-out has been achieved during the application of resonant magnetic perturbation (RMP) with a toroidal mode number of n = 4 on EAST recently. The mean ELM frequency increases by a factor of 2.7 from 86 to 235 Hz with a decreased reduction in ELM loss. The evolution of pedestal electron density measured by a profile reflectometer before and after turning on the RMP current is presented. Both the pedestal density and density gradient show a decrease with application of RMP. The density fluctuation in the pedestal region has been measured by an O-mode fluctuation reflectometer. The broadband density fluctuation with a frequency range of 20–115 kHz is enhanced at the later period of the inter-ELM phase during ELM mitigation. This phenomenon is also observed for magnetic fluctuation measured by magnetic probes mounted in the vacuum vessel. A further study shows that the enhanced broadband fluctuations lead to a decrease in the growth rate of the pedestal density and an increase in divert or particle flux. This result implies that these enhanced broadband fluctuations could lead to an enhancement of outward particle transport. The possible roles of the enhanced fluctuations observed in ELM mitigation are also discussed.
Deterministic modeling of the diffusive memristor
Authors: Akther A. , Ushakov Y. , Balanov A. G. , Savel’ev S. E.
Published: July 2021

Recently developed diffusive memristors have gathered a large amount of research attention due to their unique property to exhibit a variety of spiking regimes reminiscent to that found in biological cells, which creates a great potential for their application in neuromorphic systems of artificial intelligence and unconventional computing. These devices are known to produce a huge range of interesting phenomena through the interplay of regular, chaotic, and stochastic behavior. However, the character of these interplays as well as the instabilities responsible for different dynamical regimes are still poorly studied because of the difficulties in analyzing the complex stochastic dynamics of the memristive devices. In this paper, we introduce a new deterministic model justified from the Fokker–Planck description to capture the noise-driven dynamics that noise has been known to produce in the diffusive memristor. This allows us to apply bifurcation theory to reveal the instabilities and the description of the transition between the dynamical regimes.
A perspective on the hydrodynamic phonon transport in two-dimensional materials
Authors: Yu Cuiqian , Ouyang Yulou , Chen Jie
Published: July 2021

Thermal transport in two-dimensional (2D) materials has attracted great attention since the discovery of high thermal conductivity in graphene, which is closely related to the hydrodynamic phonon transport. In this Perspective, we briefly summarize the recent progresses in studying hydrodynamic phonon transport in 2D materials, including both theoretical and experimental works. First, the criterion and numerical methods for studying hydrodynamic phonon transport are reviewed. We then discuss the physical mechanism and peculiar phenomena related to hydrodynamic phonon transport in 2D materials and finally present the challenge for future studies. This Perspective aims to provide the physical understanding of the hydrodynamic phonon transport, which might be beneficial to the exploration of novel thermal transport behaviors in 2D materials.
Sensitization and desensitization of PBXs stemming from microcrack and microvoid in responses to pressure-time loading
Authors: Yang Kun , Wu Yanqing , Duan Hongzheng , Huang Fenglei
Published: July 2021

Comprehensively understanding the main differences exhibited in the ignition stage of high-intensity shock and low-intensity impact initiation processes of polymer bonded explosives (PBXs), including defect-related hotspot formation, ignition threshold, and sensitization or desensitization, is necessary for the safety evaluation of PBXs. The roles of shear-crack and void-collapse hotspots in the ignition for single-impacted PBXs are first studied using a physically based thermomechanical model. The variations of sensitivity for pre-impacted PBXs are further reported. Results show that a crack hotspot dominates in a low pressure range (90–200 MPa) with a relatively long ramp time (∼1.0 μs). High pressure will cause a friction-locked crack, while low pressure will lead to the insufficient frictional heating, thus resulting in a slight increase in hotspot temperature. Moreover, a long duration (∼10.0 μs) is required for satisfying the hotspot temperature-size criterion of ignition. The void hotspot dominates in high pressure (≥350 MPa) with a short ramp time (<0.1 μs). The dominant range of crack hotspots is extended (70–240 MPa) after a pre-impact load, while that of the void hotspot reduces (≥550 MPa). If the secondary loading is high-intensity shock, the explosives are desensitized due to the pre-elimination of voids. In contrast, if the secondary loading is low-intensity impact, the explosives are sensitized due to the pre-increase in crack-related damage.
Shock wave in series connected Josephson transmission line: Theoretical foundations and effects of resistive elements
Authors: Kogan Eugene
Published: July 2021

We analytically study the shock wave in the Josephson transmission line (JTL) in the presence of ohmic dissipation. When ohmic resistors shunt the Josephson junctions (JJ) or are introduced in series with the ground capacitors, the shock is broadened. When ohmic resistors are in series with the JJ, the shock remains sharp, as it was in the absence of dissipation. In all the cases considered, ohmic resistors do not influence the shock propagation velocity. We study an alternative to the shock wave—an expansion fan—in the framework of the simple wave approximation for the dissipationless JTL and formulate the generalization of the approximation for the JTL with ohmic dissipation.
Effects of propagation delay in coupled oscillators under direct–indirect coupling: Theory and experiment
Authors: Hui Nirmalendu , Biswas Debabrata , Banerjee Tanmoy , Kurths Jürgen
Published: July 2021

Propagation delay arises in a coupling channel due to the finite propagation speed of signals and the dispersive nature of the channel. In this paper, we study the effects of propagation delay that appears in the indirect coupling path of direct (diffusive)–indirect (environmental) coupled oscillators. In sharp contrast to the direct coupled oscillators where propagation delay induces amplitude death, we show that in the case of direct–indirect coupling, even a small propagation delay is conducive to an oscillatory behavior. It is well known that simultaneous application of direct and indirect coupling is the general mechanism for amplitude death. However, here we show that the presence of propagation delay hinders the death state and helps the revival of oscillation. We demonstrate our results by considering chaotic time-delayed oscillators and FitzHugh–Nagumo oscillators. We use linear stability analysis to derive the explicit conditions for the onset of oscillation from the death state. We also verify the robustness of our results in an electronic hardware level experiment. Our study reveals that the effect of time delay on the dynamics of coupled oscillators is coupling function dependent and, therefore, highly non-trivial.
Heterogeneous selection on exploration behavior within and among West European populations of a passerine bird
Authors: Mouchet Alexia , Cole Ella F. , Matthysen Erik , Nicolaus Marion , Quinn John L. , Roth Allison M. , Tinbergen Joost M. , van Oers Kees , van Overveld Thijs , Dingemanse Niels J.
Published: July 2021

Significance

A key question in behavioral ecology is whether individual differences in behavior are adaptive rather than merely representing “noise around an adaptive mean.” We show strong evidence for spatial and temporal variation in survival and recruitment selection both within and among West European great tit (
Parus major
) populations, implying that spatiotemporal variation in environmental conditions contributes to the maintenance of animal personality variation. The majority of the variance in selection was attributable to large-scale geographical variation, selecting for local adaptation in behavior. Temporal variation was also important, counteracting spatially driven local adaptation. Our study thereby demonstrates the importance of acknowledging both large- and small-scale geographical and temporal variation to understand the biological processes maintaining variation in animal behavior.
Pressure-induced high-temperature superconductivity retained without pressure in FeSe single crystals
Authors: Deng Liangzi , Bontke Trevor , Dahal Rabin , Xie Yu , Gao Bin , Li Xue , Yin Ketao , Gooch Melissa , Rolston Donald , Chen Tong , Wu Zheng , Ma Yanming , Dai Pengcheng , Chu Ching-Wu
Published: July 2021

To raise the superconducting-transition temperature (T
c
) has been the driving force for the long-sustained effort in superconductivity research. Recent progress in hydrides with T
c
s up to 287 K under pressure of 267 GPa has heralded a new era of room temperature superconductivity (RTS) with immense technological promise. Indeed, RTS will lift the temperature barrier for the ubiquitous application of superconductivity. Unfortunately, formidable pressure is required to attain such high T
c
s. The most effective relief to this impasse is to remove the pressure needed while retaining the pressure-induced T
c
without pressure. Here, we show such a possibility in the pure and doped high-temperature superconductor (HTS) FeSe by retaining, at ambient pressure via pressure quenching (PQ), its T
c
up to 37 K (quadrupling that of a pristine FeSe at ambient) and other pressure-induced phases. We have also observed that some phases remain stable without pressure at up to 300 K and for at least 7 d. The observations are in qualitative agreement with our ab initio simulations using the solid-state nudged elastic band (SSNEB) method. We strongly believe that the PQ technique developed here can be adapted to the RTS hydrides and other materials of value with minimal effort.