bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonthermal processes in hot accretion flows onto supermassive black holes: An inhomogeneous model
Authors: Gutiérrez E. M. , Vieyro F. L. , Romero G. E.
Published: February 2021

Context.Many low-redshift active galactic nuclei harbor a supermassive black hole accreting matter at low or medium rates. At such rates, the accretion flow usually consists of a cold optically thick disk, plus a hot, low density, collisionless corona. In the latter component, charged particles can be accelerated to high energies by various mechanisms.

Aims.We aim to investigate, in detail, nonthermal processes in hot accretion flows onto supermassive black holes, covering a wide range of accretion rates and luminosities.

Methods.We developed a model consisting of a thin Shakura-Sunyaev disk plus an inner hot accretion flow or corona, modeled as a radiatively inefficient accretion flow, where nonthermal processes take place. We solved the transport equations for relativistic particles and estimated the spectral energy distributions resulting from nonthermal interactions between the various particle species and the fields in the source.

Results.We covered a variety of scenarios, from low accretion rates up to 10% of the Eddington limit, and identified the relevant cooling mechanisms in each case. The presence of hadrons in the hot flow is decisive for the spectral shape, giving rise to secondary particles and gamma-ray cascades. We applied our model to the source IC 4329A, confirming earlier results which showed evidence of nonthermal particles in the corona.
Fast rotating and low-turbulence discs atz ≃ 4.5: Dynamical evidence of their evolution into local early-type galaxies
Authors: Fraternali F. , Karim A. , Magnelli B. , Gómez-Guijarro C. , Jiménez-Andrade E. F. , Posses A. C.
Published: February 2021

Massive starburst galaxies in the early Universe are estimated to have depletion times of ∼100 Myr and thus be able to convert their gas very quickly into stars, possibly leading to a rapid quenching of their star formation. For these reasons, they are considered progenitors of massive early-type galaxies (ETGs). In this paper, we study two high-zstarbursts, AzTEC/C159 (z ≃ 4.57) and J1000+0234 (z ≃ 4.54), observed with ALMA in the [C II] 158-μm emission line. These observations reveal two massive and regularly rotating gaseous discs. A 3D modelling of these discs returns rotation velocities of about 500 km s−1and gas velocity dispersions as low as ≈ 20 km s−1, leading to very high ratios between regular and random motion (V/σ ≳ 20), at least in AzTEC/C159. The mass decompositions of the rotation curves show that both galaxies are highly baryon-dominated with gas masses of ≈1011 M⊙, which, for J1000+0234, is significantly higher than previous estimates. We show that these high-zgalaxies overlap withz = 0 massive ETGs in the ETG analogue of the stellar-mass Tully-Fisher relation once their gas is converted into stars. This provides dynamical evidence of the connection between massive high-zstarbursts and ETGs, although the transformation mechanism from fast rotating to nearly pressure-supported systems remains unclear.
Bunt wie der Regenbogen
Authors: Herbertz-Floßdorf Michaela
Published: February 2021

Regenbogenfamilien sind bisher kein selbstverständlicher Teil der Gesellschaft. Für die meisten Menschen gilt die Konstellation Vater-Mutter-Kind als Familie. Diese heteronormative Vorstellung zwingt Regenbogenfamilien dazu, sich zu erklären, was im Alltag zu einer Belastung werden kann. Im vorliegenden Beitrag erläutert die Autorin verschiedene Familien-modelle, setzt sich mit Vorurteilen auseinander und vermittelt Handlungsansätze für den Umgang mit Regenbogeneltern.
Behandlungsevaluation in der stationären Psychiatrie: Transdiagnostische Faktoren als Korrelate des Behandlungsergebnisses
Authors: Wyssen Andrea , Balsiger Nora , Djurdjevic Arabela , Munsch Simone , Trier Stephan
Published: February 2021

Ziel Eine stationäre psychiatrisch-psychotherapeutische Behandlung wurde in einem naturalistischen Setting im Sinne der Effectiveness-Forschung evaluiert. Transdiagnostische Faktoren wurden als Korrelate des Behandlungsergebnisses untersucht.

Methoden Die Datenerhebung mit Selbstberichtsfragebogen fand zum Eintritts- und Austrittszeitpunkt statt. Die Patientenpopulation (N = 378) bestand aus Frauen und Männern (16–80 Jahre; M = 40,4; SD = 15,8) mit Primärdiagnosen einer depressiven, Angst- oder Essstörung. Die durchschnittliche Behandlungsdauer betrug 8,2 Wochen (SD = 3,8). Primäre Ergebnisvariablen waren die Symptomausprägung und das psychosoziale Funktionsniveau. Als transdiagnostische Korrelate wurden Selbstwert, Selbstwirksamkeitserwartung und Emotionsregulation in die Regressionsanalysen einbezogen.

Ergebnisse Die Veränderung der transdiagnostischen Faktoren erklärte einen signifikanten Anteil der Varianz am Behandlungsergebnis auf (Varianzaufklärung: 8–27 % Selbstwirksamkeit, 23–42 % Selbstwert, 10–26 % Emotionsregulation).

Diskussion/Schlussfolgerung Diese Studie zeigt, dass die Evaluation der Wirksamkeit von Behandlungen in einem naturalistischen klinischen Setting praktikabel ist. Transdiagnostisch bedeutsame Faktoren klärten störungsübergreifend einen substanziellen Teil der statistischen Varianz am Behandlungsergebnis auf. Aussagen über Kausalität sind anhand des vorliegenden Studiendesigns zwar nicht möglich, dennoch unterstreichen die Ergebnisse die Relevanz störungsübergreifender Trainings (z. B. der Emotionsregulation) zur Verbesserung der Wirksamkeit von Behandlungsansätzen.
The effect of train-the-colonoscopy-trainer course on colonoscopy quality indicators
Authors: Hoff Geir , Botteri Edoardo , Huppertz-Hauss Gert , Kvamme Jan Magnus , Holme Øyvind , Aabakken Lars , Dahler Stein , Medhus Asle W. , Blomgren Ingrid , Sandvei Per , Darre-Næss Ole , Kjellevold Øystein , Seip Birgitte
Published: February 2021

Background Systematic training in colonoscopy is highly recommended; however, we have limited knowledge of the effects of “training-the-colonoscopy-trainer” (TCT) courses. Using a national quality register on colonoscopy performance, we aimed to evaluate the effects of TCT participation on defined quality indicators.

Methods This observational study compared quality indicators (pain, cecal intubation, and polyp detection) between centers participating versus not participating in a TCT course. Nonparticipating centers were assigned a pseudoparticipating year to match their participating counterparts. Results were compared between first year after and the year before TCT (pseudo)participation. Time trends up to 5 years after TCT (pseudo)participation were also compared. Generalized estimating equation models, adjusted for age, sex, and bowel cleansing, were used.

Results 11 participating and 11 nonparticipating centers contributed 18 555 and 10 730 colonoscopies, respectively. In participating centers, there was a significant increase in detection of polyps ≥ 5 mm, from 26.4 % to 29.2 % (P = 0.035), and reduction in moderate/severe pain experienced by women, from 38.2 % to 33.6 % (P = 0.043); no significant changes were found in nonparticipating centers. Over 5 years, 20 participating and 18 nonparticipating centers contributed 85 691 and 41 569 colonoscopies, respectively. In participating centers, polyp detection rate increased linearly (P = 0.003), and pain decreased linearly in women (P = 0.004). Nonparticipating centers did not show any significant time trend during the study period.

Conclusions Participation in a TCT course improved polyp detection rates and reduced pain experienced by women. These effects were maintained during a 5-year follow-up.
Sex-specific Association of Antipsychotic-induced Weight Gain and Treatment Response for Antipsychotic-Naive First Episode Schizophrenia Patients: A Prospective 8-week Longitudinal Study
Authors: Shi Hui , Guan Xiao Ni , Liu Dian Ying , Zhu Lin , Wu Zhi Wei , Luo Guo Zhi , Wang Jun , Xiu Mei Hong , Zhang Xiang Yang
Published: February 2021

Background Patients with antipsychotic-naïve first-episode (ANFE) schizophrenia (SZ) can help clarify many confounding factors in determining sex differences in antipsychotic drug induced weight gain and its association with symptom improvement.

Methods This 8-week longitudinal trial of ANFE patients with SZ enrolled 526 patients and 313 healthy controls. We evaluated bodyweight and the efficacy of antipsychotics on the Positive and Negative Syndrome Scale (PANSS) at baseline and at the end of week 8.

Results Males and females after treatment showed no sex difference in weight gain, BMI increase, and percentage of weight gain. However, at baseline, male patients had more positive symptoms than female patients, and decreases in positive symptoms, general psychopathology, and total PANSS scores were less in male than female patients. Adjusting for confounding factors using multiple linear regression confirmed that weight gain was significantly associated with these decreases in PANSS symptoms only in men not women.

Conclusions The relationship between weight gain and symptom reduction after 8 weeks of antipsychotic treatment exists only in male patients with ANFE SZ and not in female patients.
Zusammenhang zwischen Stresserleben und Stressverhalten – gemessen mit dem Differenziellen Stress Inventar und Burnout-Symptomatik im MBI
Authors: Thielmann Beatrice , Zavgorodnii Igor , Böckelmann Irina
Published: February 2021

Ziel der Studie war es, den Zusammenhang zwischen den unterschiedlichen DSI-Kategorien und DSI-Typen des Stresserlebens und -verhaltens zum Burnout zu ermitteln.

Methodik Es wurde 185 Probanden das Maslach Burnout Inventory (MBI) und das Differenzielle Stress Inventar (DSI) vorgelegt. Daraus resultierend erfolgte eine Einteilung in DSI-Typen, um die Ausprägung der Dimensionen „Emotionale Erschöpfung“, „Zynismus/Depersonalisierung“ und „Leistungsfähigkeit“ aus dem MBI zu vergleichen.

Ergebnisse Verschiedene Typen des Stressverhaltens zeigen Unterschiede in den Burnout-Dimensionen. Nur 4 Probanden (2,2 %) hatten eine ausgeprägte Burnout-Symptomatik. Der DSI-Typ II ist besonders gefährdet, eine Burnout-Symptomatik zu entwickeln.

Schlussfolgerungen Personen mit verschiedenen Ausprägungen von Stressauslösern und Stressmanifestation sowie Copingstrategien bzw. Risiken der Stressstabilisierung haben unterschiedlich starke Ausprägungen der MBI-Dimensionen und somit unterschiedliche Risiken für Burnout. Erkenntnisse über den DSI-Typ könnten bei Vorschlägen für Präventionsmaßnahmen zur Vermeidung der Beeinträchtigung psychischer Gesundheit einbezogen werden.
Behandlungsstrategien bei oromandibulärer Dystonie
Authors: Yoshida Kazuya
Published: February 2021

Eine oromandibuläre Dystonie ist charakterisiert durch unwillkürliche tonische oder klonische Spasmen der Kau- und / oder Zungenmuskulatur bzw. der Muskeln im stomatognathen System. Sie wird oft fälschlicherweise als kraniomandibuläre Dysfunktion oder psychiatrische Erkrankung diagnostiziert. Aufgrund der klinischen Bilder wird die oromandibuläre Dystonie in 6 Subtypen (Kieferschluss-, Kieferöffnungs-, Zungen-, Kieferdeviations-, Kieferprotrusions-, und Lippendystonie) eingeteilt. Es gibt verschiedene Behandlungsmethoden, z. B. Injektion von Botulinum-Toxin, Muskelafferenzblockierung (Injektionen von Lidocain und Äthanol in die Kau- oder Zungenmuskulatur zur Blockierung der Afferenzen der Muskelspindeln), Aufbissschiene und chirurgische Eingriffe (Coronoidotomie). In vielen Fällen können aufgrund des Subtyps die Symptome durch eine Kombination dieser Methoden erfolgreich behandelt werden. In diesem Leitthema werden spezielle Therapieempfehlungen für jeden Subtyp beschrieben. Eine genaue Diagnose und Behandlung einer oromandibulären Dystonie erfordert umfassende Kenntnisse und Fähigkeiten sowohl in der Mund-, Kiefer- und Gesichtschirurgie als auch in der Neurologie. Daher ist die Zusammenarbeit zwischen diesen Abteilungen sehr wichtig.
Special Situations in the Management of Diverticular Disease
Authors: Wood Elizabeth H. , Sigman Michael M. , Hayden Dana M.
Published: February 2021

Diverticular disease affects a large percentage of the US population, affecting over 30% among those older than 45 years old. It is responsible for ∼300,000 hospitalizations per year in the United States and can lead to serious complications such as hemorrhage, obstruction, abscess, fistulae, or bowel perforation.2 It is an extremely common reason for emergency room and outpatient visits and evaluations by general and colorectal surgeons. In the US, patients usually present with sigmoid diverticulitis in the setting of a normal immune system so surgeons will follow well-established practice guidelines for treatment. However, there may be special circumstances in which the management of diverticulitis is not as straightforward. In this article, we will address patients who present with multifocal disease, giant colonic diverticulum, right-sided diverticulitis, and diverticulitis in the setting of immunosuppression and hopefully provide guidance for treatment in these special circumstances.
Safety and Accuracy of Ultrasound-guided Burr Hole Brain Abscess Aspiration
Authors: Allouch Hassan , Kassem Majed El Sayed , Behnke-Mursch Julianne , Mursch Kay
Published: February 2021

Background Ultrasound-guided burr hole biopsies or catheter placements are quick and safe procedures. The use of these procedures for treatment of brain abscesses has been reported, but larger series are missing. The aim of our study was to evaluate the accuracy and safety of the methods.

Patients Twenty-five brain abscess aspirations in 17 patients were analyzed. Fourteen procedures were performed to evacuate abscesses in eloquent regions; another 3 were located deeply in the cerebellar hemispheres.

Results In all the procedures, a histopathologic diagnosis could be established. Only one transient deterioration of a hemiparesis occurred; other operative complications were not observed. Six patients needed more than one operation due to a relapse of the abscess. Two out of three cerebellar abscesses could be cured with one aspiration. Thirteen patients had an excellent outcome, and 2 remained severely disabled. One patient died from cerebritis and another from a neoplasm. In every procedure, a proper visualization of the abscess and monitoring of the penetration and aspiration could easily be performed.

Conclusion Ultrasound-guided burr hole aspiration is minimally invasive, quick, and has a very low complication rate. It offers the advantage to adapt to intraoperatively changing anatomy. The rate of recurrence is not lower than in other treatment modalities.
COVID-19: The Dentists’ Perceived Impact on the Dental Practice
Authors: Amato Alessandra , Ciacci Carolina , Martina Stefano , Caggiano Mario , Amato Massimo
Published: February 2021

Objectives The present study aimed to investigate the dentists’ knowledge of the risks from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, and how it will impact their practice.

Materials and Methods An ad hoc self-administered anonymous questionnaire was submitted to Italian dentists.

Statistical Analysis Differences in rates were calculated using the chi-square test. The level of significance was set at p < 0.05.

Results A total of 849 dentists fully completed the survey. Eighty-eight per cent of Italian dentists are worried about the health of their families, with no difference in high-risk (red zone) and low-risk (orange zone) regions. About 86% of professionals report some income loss and 94% fear a drop in patients after the quarantine phase, with the dentists working the red zone claiming a greater economic loss and fearing a reduced practice after the end of the lockdown.

Discussion A large majority of the Italian dentists appears to be aware of the need for changes in their dental practices by planning specific sterilization processes between appointments, testing patients for SARS-CoV-2 serology, asking patients not to be accompanied, and reducing the number of visits per day.

Conclusion The survey expresses the serious concern of the dentists for the pandemic’s effects on their profession.
The Short-Term Effect of Active Skeletonized Sutural Distractor Appliance on Temporomandibular Joint Morphology of Class III Malocclusion Subjects
Authors: Huqh Mohamed Zahoor Ul , Hassan Rozita , Rahman Roselinda Abdul , Yusof Asilah , Narmada Ida Bagus , Ahmad Wan Muhamad Amir W
Published: February 2021

Objectives The purpose of this study was to evaluate the short-term effect of active skeletonized sutural distractor (ASSD) appliance on temporomandibular joint morphology of class III malocclusion subjects.

Materials and Methods This was a prospective interventional study. Cone-beam computerized tomography (CBCT) images of 22 patients were taken before and after treatment by using Planmeca Promax 3D CBCT machine version 2.9.2 (Planmeca OY Helsinki, Finland). The condylar width, height, length, roof of glenoid fossa thickness, and all joint spaces were measured. The condylar position was determined based on Pullinger and Hollander formula. The condylar shape was determined as per Kinzinger et al. The condylar volume was calculated by using Mimics software (Materialize, Belgium).

Statistical Analysis Data analysis was performed by using SPSS software version 24. Wilcoxon paired signed-rank test was used to compare the difference in temporomandibular joint morphology and condylar volume between pre- and post-treatment measurements. Chi-square test was used to compare the condylar position and shape.

Results The superior (p = 0.000 on the right side, p = 0.005 on the left side) and posterior joint spaces (p = 0.000 on both sides) were decreased after the treatment, respectively. The condyles were rotated upward and backward, thereby increasing the anterior joint spaces (p = 0.000 on both sides) after the treatment. The condylar volume increases after treatment, but no significant differences were observed (p = 0.903 on the right side, p = 0.062 on the left side).

Conclusion The significant changes were observed in joint spaces. The condyles were more anteriorly placed before treatment. Condylar position and shape alter in response to ASSD treatment. The condylar volume did not show any significant change.
In Vitro Enamel Remineralization Efficacy of Calcium Silicate-Sodium Phosphate-Fluoride Salts versus NovaMin Bioactive Glass, Following Tooth Whitening
Authors: El-Damanhoury Hatem M. , Elsahn Nesrine A. , Sheela Soumya , Bastaty Talal
Published: February 2021

Objectives This study aimed to evaluate the effect of in-office bleaching on the enamel surface and the efficacy of calcium silicate-sodium phosphate-fluoride salt (CS) and NovaMin bioactive glass (NM) dentifrice in remineralizing bleached enamel.

Materials and Methods Forty extracted premolars were sectioned mesio-distally, and the facial and lingual enamel were flattened and polished. The samples were equally divided into nonbleached and bleached with 38% hydrogen peroxide (HP). Each group was further divided according to the remineralization protocol (n = 10); no remineralization treatment (nontreated), CS, or NM, applied for 3 minutes two times/day for 7 days, or CS combined with NR-5 boosting serum (CS+NR-5) applied for 3 minutes once/day for 3 days. The average Knoop hardness number (KHN) and surface roughness (utilizing atomic force microscopy) were measured. Surface topography/elemental analysis was analyzed by using scanning electron microscopy/energy dispersive X-ray analysis. All the tests were performed at baseline, after bleaching, and following each remineralization protocol. Data were statistically analyzed by two-way analysis of variance and Bonferroni post hoc multiple comparison tests (α = 0.05).

Results HP significantly reduced KHN and increased roughness (p < 0.05). All remineralization materials increased the hardness and reduced the surface roughness after bleaching except NM, which demonstrated significantly increased roughness (p < 0.05). Ca/P ratio decreased after bleaching (p < 0.05), and following treatment, CS and CS+NR-5 exhibited higher remineralization capacity in comparison to NM (p < 0.05).

Conclusion Although none of the material tested was able to reverse the negative effect of high-concentration in-office HP on enamel completely, the remineralization efficacy of CS and CS+NR-5 was superior to that of NM.
Risk Factors, Pattern and Outcome of Motorcycle-associated Head Injury in Sokoto: An Analysis of 184 Cases
Authors: Obanife Henry Olayere , Ismail Nasiru Jinjiri , Lasseini Ali , Shehu Bello B. , Otorkpa Ega J.
Published: February 2021

Background Road traffic accident (RTA) is the eighth leading cause of death worldwide. Motorcycle-associated head injury is the leading cause of road traffic associated morbidity and mortality in developing countries. Even though the incidence and mortality of head injury from motor cycle crash is on the increase in developing countries, especially in the African continent, most of the studies published in the literature on this subject matter took place in the developed Western countries.

Materials and Methods This was a retrospective cross-sectional study of data from patients managed in our institution between December 2014 and November 2016.

Results One hundred and eighty-four patients were analyzed. None of the patients used safety helmet for protection. The mean age was 27.6 ± 17.2 years with male female ratio of 6.7:1. Lone crash by cyclists and collisions accounted for 66.8% and 33.1% of the cases, respectively. Passengers and riders comprised 75% of the patients, while 25% were vulnerable pedestrians. The most frequently abused substance by the patients was tramadol (65.52%). Severe head injury and pupillary abnormality were found in 23.9% and 45.5% of the patients, respectively. Cranial CT scan showed abnormalities in 40.2% of the patients. Surgery was done in 28.3% of the patients with mortality rate of 20.7%.

Conclusions The use of motorcycle as a mean of transportation has caused significant negative impact on the society. Young people, who constitute the workforce, are majorly affected, and this invariably leads to a serious economic burden on the concerned families and communities.
Plasma treatments help lentil seeds improve water uptake and germination
Authors: Bandari Anashe
Published: February 2021

With a suitable plasma treatment, seeds can get a boost in their growth parameters that can be retained for at least 45 days.
Giving the slip to a metal deformation mystery
Authors: Patrick Chris
Published: February 2021

A kinematic model uses X-ray diffraction patterns to identify active slip systems during the dynamic compression of metals.
Teaching a large-scale crystallography school with Zoom Webinar
Authors: Ferrara Joseph D. , Cochran Amanda , Del Campo Mark , Göb Christian R. , Le Maguerès Pierre , Meyer Mathias , Puschmann Horst , Schürmann Christian , Stanley Alexandra , Swepston Paul N. , Tripathi Akhilesh , White Fraser , Wojciechowski Jakub
Published: February 2021

In order to address the loss of crystallographic training opportunities resulting from the cancelation of conventional schools around the world due to the COVID-19 pandemic, we have started an online crystallography school with live lectures and live Q&A using Zoom Webinar. Since we were trying to reach a large audience in a relatively short period, we have limited the school to ten 1 h lectures covering practical aspects of small molecule crystallography including data collection, data processing, and structure solution. In the school, we also covered some advanced topics that students commonly see in their work: absolute structure determination, twinning, and disorder. To round out the education, we provided lectures on macromolecular crystallography and powder diffraction. For students to practice on their own, we used freely available data reduction and structure solution software, as well as datasets with which to practice. To give students credit for course completion, we provided an online exam and an electronic certificate of completion. In this editorial, we will provide some insight into the issues of holding lectures with up to 750 students of very diverse backgrounds and review the efficacy of the school in teaching crystallography for the two cohorts of students.
An apparatus for the continuous measurement of thickness during the electropolishing of superconducting cavities
Authors: Bertucci M. , Bosotti A. , Campari R. , D’Ambros A. , Gresele A. , Grimaldi A. T. , Michelato P. , Monaco L. , Pagani C. , Paparella R. , Pistoni N. C. , Rizzi M. , Sertore D. , Torri A.
Published: February 2021

An apparatus allowing continuous acquisition of thickness measurements during electropolishing of superconducting cavities is described. The instrument is based on the ultrasound thickness measurement technique and allows the connection of up to six probes. The apparatus has been employed to monitor the surface treatment of PIP-II low beta single cell prototypes developed and manufactured by LASA-INFN and specifically to measure surface removal at different points of interest on the cavity surface. The apparatus facilitated the development and optimization of electropolishing parameters for incorporation into the cavity manufacturing process.
Lattice stability and point defect energetics of TiSi2 and TiGe2 allotropes from first-principles calculations
Authors: Brown David L. , Jones Kevin S. , Phillpot Simon R.
Published: February 2021

This work determines the phase stabilities and point defect energetics of TiSi2 and TiGe2 allotropes using density functional theory. The primary focus is on the C49 and C54 allotropes, which compete during TiSi2 phase formation. It is found that the ground state structure for TiGe2 is the C54 allotrope, desirable for its low sheet resistance, while the less desirable, higher resistance C49 allotrope forms the ground state structure of TiSi2. A first attempt to understand the Ge atom's role in lowering the enthalpy of formation for the C54 structure is made from the perspective of the extended Born model. Charge density differences, the density of states, and Bader charge analysis show that these systems are predominantly ionically bonded, with the Ge atoms introducing additional covalent bond stability for the C54 allotrope. It is known that higher temperatures favor C54 formation in TiSi2. Helmholtz free energy calculations for TiSi2 suggest that the vibrational free energy does not drive the system to the C54 phase. The formation energies of certain point defects within the C49 structure of TiSi2 are less than 1 eV, which is consistent with experiments that show high defect concentrations. Thus, the driving force for C54 formation at higher temperatures may be related to the high defect concentration in the C49 allotrope.
Oscillatory flow around a vertical wall-mounted cylinder: Dynamic mode decomposition
Authors: Jang H. K. , Ozdemir C. E. , Liang J.-H. , Tyagi M.
Published: February 2021

This study applies the Dynamic Mode Decomposition (DMD) to better understand and model the oscillatory flow across a vertical wall-mounted cylinder. At different Keulegan–Carpenter numbers, three-dimensional direct numerical simulations are performed to provide the flow details such as the snapshots of the coherent structures around the cylinder, vorticity fields, and bed shear stress. The selected fields are decomposed into dynamic modes. The characteristic flow features with relevant information including spatial mode shape, frequency, and mode amplitude are systematically investigated. The time series of flow fields is also reconstructed using the DMD analysis and compared against the original data to assess the efficacy of information in the low-dimensional system. The results show that the DMD analysis can capture the dynamic and nonlinear features of the oscillatory flow past the vertical wall-mounted cylinder and also efficiently reconstruct the relevant fields with reasonable accuracy. It provides a basis for the data-driven model of scour near the cylinder–wall junction relevant to coastal engineering applications.
Dynamically consistent coarse-grain simulation model of chemically specific polymer melts via friction parameterization
Authors: Johnson Lilian C. , Phelan Frederick R.
Published: February 2021

Coarse-grained (CG) models of polymers involve grouping many atoms in an all-atom (AA) representation into single sites to reduce computational effort yet retain the hierarchy of length and time scales inherent to macromolecules. Parameterization of such models is often via “bottom-up” methods, which preserve chemical specificity but suffer from artificially accelerated dynamics with respect to the AA model from which they were derived. Here, we study the combination of a bottom-up CG model with a dissipative potential as a means to obtain a chemically specific and dynamically correct model. We generate the conservative part of the force-field using the iterative Boltzmann inversion (IBI) method, which seeks to recover the AA structure. This is augmented with the dissipative Langevin thermostat, which introduces a single parameterizable friction factor to correct the unphysically fast dynamics of the IBI-generated force-field. We study this approach for linear polystyrene oligomer melts for three separate systems with 11, 21, and 41 monomers per chain and a mapping of one monomer per CG site. To parameterize the friction factor, target values are extracted from the AA dynamics using translational monomer diffusion, translational chain diffusion, and rotational chain motion to test the consistency of the parameterization across different modes of motion. We find that the value of the friction parameter needed to bring the CG dynamics in line with AA target values varies based on the mode of parameterization with short-time monomer translational dynamics requiring the highest values, long-time chain translational dynamics requiring the lowest values, and rotational dynamics falling in between. The friction ranges most widely for the shortest chains, and the span narrows with increasing chain length. For longer chains, a practical working value of the friction parameter may be derived from the rotational dynamics, owing to the contribution of multiple relaxation modes to chain rotation and a lack of sensitivity of the translational dynamics at these intermediate levels of friction. A study of equilibrium chain structure reveals that all chains studied are non-Gaussian. However, longer chains better approximate ideal chain dimensions than more rod-like shorter chains and thus are most closely described by a single friction parameter. We also find that the separability of the conservative and dissipative potentials is preserved.
Azimuthal equatorial flows in spherical coordinates with discontinuous stratification
Authors: Martin Calin I.
Published: February 2021

We are concerned here with an exact solution to the governing equations for geophysical fluid dynamics in spherical coordinates, which incorporates discontinuous fluid stratification. This solution represents a steady, purely azimuthal equatorial flow with an associated free surface and an interface separating two fluid regions, each of which has its own continuous distribution of density. However, the two density functions do not match along the interface. Following the derivation of the solution, we demonstrate that there is a well-defined relationship between the imposed pressure at the free surface and the resulting distortion of the surface's shape. Moreover, imposing the continuity of the pressure along the interface generates an equation that describes (implicitly) the shape of the interface. Interestingly, it turns out that the interface defining function has infinite regularity.
Onset of thermal convection of a weakly rarefied Maxwellian gas: A continuum-slip approach
Authors: Wang Yunpeng , Khayat Roger E. , Zobaer Md Asif
Published: February 2021

The onset of the Rayleigh–Bénard convection for a monatomic rarefied gas of Maxwellian type is investigated at small Knudsen numbers. Density variations due to compressibility have been considered without any restriction imposed on the magnitude of temperature difference. The steady-state conduction problem has been solved both analytically and numerically using a continuum approach with velocity-slip and temperature-jump conditions at the solid boundaries. The influence of the Froude number and the Knudsen number is comprehensively studied. To examine the onset of thermal convection, a linear temporal stability analysis is performed for the conduction state and the dispersion relation is calculated by a Chebyshev collocation method. The neutral stability curve obtained in the Froude–Knudsen number plane marks transition to convection from a pure conduction state. The critical wave number for the onset of convection is found to be close to 3.14, agreeing well with the existing findings. The convection only occurs for Knudsen numbers smaller than 0.027. A comparison between the Maxwellian model and the hard-sphere model is given and discussed. The encouraging results suggest the use of more realistic gas models in future studies.
Jumping liquid metal droplets controlled electrochemically
Authors: Song Minyung , Mehrabian Nazgol , Karuturi Sahil , Dickey Michael D.
Published: February 2021

Jumping droplets are interesting because of their applications in energy harvesting, heat transfer, anti-icing surfaces, and displays. Typically, droplets “jump” from a surface when two or more drops coalesce. Here, we demonstrate an approach to get a single droplet of liquid metal (eutectic gallium indium) to jump by using electrochemistry in a solution of 1M NaOH. Applying a positive potential to the metal (∼1 V relative to the open circuit potential) drives electrochemical surface oxidation that lowers the interfacial tension from ∼450 mN/m to ∼0 mN/m. In the low interfacial tension state, the droplet flattens due to gravity. Rapid switching to a negative potential (relative to the open circuit potential) reduces the surface oxide, returning the deformed droplet to a state of high interfacial tension. This rapid change in interfacial tension in the flattened state generates excess surface energy, which drives the droplet to return to a spherical shape with enough momentum that the liquid droplet jumps. This work is unique because (1) the jumping is controlled and tuned electrically, (2) the approach works with a single droplet, (3) it does not require a superhydrophobic surface, which is typically used to prevent droplets from adhering to the substrate, (4) the drops jump through a viscous medium rather than air, and (5) the potential energy obtained by the jumping drops is one order of magnitude higher than previous approaches. Yet, a limitation of this approach relative to conventional jumping drops is the need for electrolyte and a source of electricity to enable jumping. Herein, we characterize and optimize the jumping height (∼6 mm for a 3.6 mm diameter drop) by changing the reductive and oxidative potential and time.
Direct formation of nitrogen-vacancy centers in nitrogen doped diamond along the trajectories of swift heavy ions
Authors: Lake Russell E. , Persaud Arun , Christian Casey , Barnard Edward S. , Chan Emory M. , Bettiol Andrew A. , Tomut Marilena , Trautmann Christina , Schenkel Thomas
Published: February 2021

We report depth-resolved photoluminescence measurements of nitrogen-vacancy (NV−) centers formed along the tracks of swift heavy ions (SHIs) in type Ib synthetic single crystal diamonds that had been doped with 100 ppm nitrogen during crystal growth. Analysis of the spectra shows that NV− centers are formed preferentially within regions where electronic stopping processes dominate and not at the end of the ion range where elastic collisions lead to the formation of vacancies and defects. Thermal annealing further increases NV yields after irradiation with SHIs preferentially in regions with high vacancy densities. NV centers formed along the tracks of single swift heavy ions can be isolated with lift-out techniques for explorations of color center qubits in quasi-1D registers with an average qubit spacing of a few nanometers and of order 100 color centers per micrometer along 10 to 30-μm-long percolation chains.
Sustainable improvement of seeds vigor using dry atmospheric plasma priming: Evidence through coating wettability, water uptake, and plasma reactive chemistry
Authors: Dufour T. , Gutierrez Q. , Bailly C.
Published: February 2021

Lentil seeds have been packed in a dielectric barrier device and exposed for several minutes to a cold atmospheric plasma generated in helium with/without a reactive gas (nitrogen or oxygen). While no impact is evidenced on germination rates (caping nearly at 100% with/without plasma exposure), seeds’ vigor is clearly improved with a median germination time decreasing from 1850 min (31 h) to 1500 min (26 h), hence representing a time saving of at least 5 h. We show that the admixture of nitrogen to helium can further increase this time saving up to 8 h. Contrarily, we demonstrate that the addition of molecular oxygen to the helium discharge does not promote seeds’ vigor. Whatever the plasma chemistry utilized, these biological effects are accompanied with strong hydrophilization of the seed coating (with a decrease in contact angles from 118° to 25°) as well as increased water absorption (water uptakes measured 8 h after imbibition are close to 50% for plasma-treated seeds instead of 37% for seeds from the control group). A follow-up of the seeds over a 45-days aging period shows the sustainability of the plasma-triggered biological effects: whatever the plasma treatment, seeds’ vigor remains stable and much higher than for seeds unexposed to plasma. For these reasons, the seed-packed dielectric barrier device supplied with a He–N2 gas mixture can be considered as a relevant dry atmospheric priming plasma in the same way as those used in routine by seed companies.
Bloch–Landau–Zener dynamics induced by a synthetic field in a photonic quantum walk
Authors: D’Errico Alessio , Barboza Raouf , Tudor Rebeca , Dauphin Alexandre , Massignan Pietro , Marrucci Lorenzo , Cardano Filippo
Published: February 2021

Quantum walks are processes that model dynamics in coherent systems. Their experimental implementations proved to be key to unveiling novel phenomena in Floquet topological insulators. Here, we realize a photonic quantum walk in the presence of a synthetic gauge field, which mimics the action of an electric field on a charged particle. By tuning the energy gaps between the two quasi-energy bands, we investigate intriguing system dynamics characterized by the interplay between Bloch oscillations and Landau–Zener transitions. When both gaps at quasi-energy values of 0 and π are vanishingly small, the Floquet dynamics follows a ballistic spreading.
Asymptotic behavior of non-autonomous stochastic complex Ginzburg–Landau equations on unbounded thin domains
Authors: Chen Zhang , Li Lingyu
Published: February 2021

This paper mainly investigates the asymptotic behavior of non-autonomous stochastic complex Ginzburg–Landau equations on unbounded thin domains. We first prove the existence and uniqueness of random attractors for the considered equation and its limit equation. Due to the non-compactness of Sobolev embeddings on unbounded domains, the pullback asymptotic compactness of such a stochastic equation is proved by the tail-estimate method. Then, we show the upper semi-continuity of random attractors when thin domains collapse onto the real space R.
Double quantum dot-like transport in controllably doped graphene nanoribbon
Authors: Wang Zhongwang , Yuan Yahua , Liu Xiaochi , Muruganathan Manoharan , Mizuta Hiroshi , Sun Jian
Published: February 2021

In this Letter, we demonstrate coupled double-quantum dot (DQD)-like transport in an ∼30 nm-wide controllably doped graphene nanoribbon (GNR). Controlled doping is introduced from hydrogen silsesquioxane by changing its electron exposure dose. The proximity effect, which brings in additional dose accumulation, is utilized to introduce two charge puddles with stronger p-doping at the two ends of the moderately p-doped GNR, which act as two quantum dots. By electrostatically isolating these two charge puddles with simplified overlapping dual gates, DQD-like transport features are measured in the doped GNR at a temperature of 5 K. Moreover, the transition from strongly to weakly coupled DQDs is observed due to electrically tunable inter-dot coupling.
Six degrees of freedom vibration isolation with Euler springs
Authors: Leandri G. L. , Sunderland A. , Winterflood J. , Ju L.
Published: February 2021

A novel design allows column springs in Euler buckling mode to be laterally stable and thus provides vibration isolation in six degrees of freedom. Analytical models of the stiffness were used to develop a design with a vertical resonance of 1.13 Hz, a horizontal resonance of 1.68 Hz, and a roll resonance of 2.58 Hz. A prototype vibration isolator reduces vertical vibration by a factor of 2 at 2 Hz. Vertical, horizontal, and roll vibrations are reduced by a factor of 100 at frequencies above 20 Hz.
The effect of areal density asymmetries on scattered neutron spectra in ICF implosions
Authors: Crilly A. J. , Appelbe B. D. , Mannion O. M. , Forrest C. J. , Chittenden J. P.
Published: February 2021

Scattered neutron spectroscopy is a diagnostic technique commonly used to measure areal density in inertial confinement fusion experiments. Deleterious areal density asymmetries modify the shape of the scattered neutron spectrum. In this work, a novel analysis is developed, which can be used to fit the shape change. This will allow experimental scattered neutron spectroscopy to directly infer the amplitude and mode of the areal density asymmetries, with little sensitivity to confounding factors that affect other diagnostics for areal density. The model is tested on spectra produced by a neutron transport calculation with both isotropic and anisotropic primary fusion neutron sources. Multiple lines of sight are required to infer the areal density distribution over the whole sphere—we investigate the error propagation and optimal detector arrangement associated with the inference of mode 1 asymmetries.
Fast dynamics in a model metallic glass-forming material
Authors: Zhang Hao , Wang Xinyi , Yu Hai-Bin , Douglas Jack F.
Published: February 2021

We investigate the fast β- and Johari–Goldstein (JG) β-relaxation processes, along with the elastic scattering response of glass-forming (GF) liquids and the boson peak, in a simulated Al–Sm GF material exhibiting a fragile–strong (FS) transition. These dynamical processes are universal in “ordinary” GF fluids and collectively describe their “fast dynamics,” and we find these relaxation processes also arise in a GF liquid exhibiting a FS transition. String-like particle motion, having both an irreversible and a reversible nature (stringlets) component, occurs in the fast-dynamics regime, corresponding to a ps timescale. String-like collective motion associated with localized unstable modes facilitates irreversible and intermittent particle “jumping” events at long times associated with the JG β-relaxation process, while stringlets associated with localized stable modes and corresponding perfectly reversible atomic motion give rise to the boson peak. To further clarify the origin of the boson peak, we calculate the density of states for both the stringlet particles and the “normal” particles and find that the stringlet particles give rise to a boson peak, while the normal atoms do not. The growth of stringlets upon heating ultimately also leads to the “softening” of these excitations, and the boson peak frequency and shear modulus drop in concert with this softening. The growth of string-like collective motion upon heating in the fast-dynamics regime is further shown to be responsible for the growth in the intensity of the fast relaxation process. Relaxation in cooled liquids clearly involves a hierarchy of relaxation processes acting on rather different timescales and spatial scales.
Correlation between internal states and creep resistance in metallic glass thin films
Authors: Li M. , Tan J. , Qin X. M. , Lu D. H. , Feng Z. X. , Li C. J. , Ketov S. V. , Calin M. , Eckert J.
Published: February 2021

Some mechanisms of creep, especially those involving dislocations for many crystalline materials, can be verified by direct microstructural examination. However, metallic glass thin films (MGTFs) are disordered materials lacking the long-range order of crystals. Even today, the creep mechanisms for amorphous alloys are far from being fully understood. The physical factors governing localization and instability during creep deformation are still elusive. In this work, Ni60Nb40 alloys with high kinetic stability were prepared by magnetron sputtering at different substrate temperatures to obtain MGTFs with different internal states. We report a close correlation between the internal states and the creep resistance of the MGTFs and reveal that altering the substrate temperature during magnetron sputtering can induce changes in the surface morphologies, plastic deformation resistance, and creep resistance of Ni60Nb40 MGTFs. The creep deformation mechanism is interpreted based on the shear transformation zone (STZ) model of amorphous alloys, and our results may have implications for understanding the role of STZs during creep deformation of MGTFs.
Introduction of Sr into Bi2Se3 thin films by molecular beam epitaxy
Authors: Riney L. , Bunker C. , Bac S.-K. , Wang J. , Battaglia D. , Park Yun Chang , Dobrowolska M. , Furdyna J. K. , Liu X. , Assaf B. A.
Published: February 2021

SrxBi2Se3 is a candidate topological superconductor, but its superconductivity requires the intercalation of Sr into the van der Waals gaps of Bi2Se3. We report the synthesis of SrxBi2Se3 thin films by molecular beam epitaxy, and we characterize their structural, vibrational, and electrical properties. X-ray diffraction and Raman spectroscopy show evidence of substitutional Sr alloying into the structure, while transport measurements allow us to correlate the increasing Sr content with an increased n-type doping, but do not reveal superconductivity down to 1.5 K. Our results suggest that Sr predominantly occupies sites within a quintuple layer, simultaneously substituting for Bi and as an interstitial. We, thus, motivate future density functional theory studies to further investigate the energetics of Sr substitution into Bi2Se3.
A simple model for the entropy of melting of monatomic liquids
Authors: Lilley Drew , Jain Anubhav , Prasher Ravi
Published: February 2021

We present an analytical model for calculating the entropy at melt of monatomic liquids. The model is motivated by the concept of a rough potential energy surface. It offers a simple, physical explanation for Richard's melting rule and provides a material-dependent correction to Trouton's vaporization rule. Without employing any adjustable parameters, the model agrees closely with experimental entropy of melting values for monatomic liquids. When combined with the phonon theory of liquids, it allows for estimation of entropy over the entire liquid range.