bluuebunny/crossref_metadata_2025 huggingface dataset:
Das thorakale Aortenaneurysma – Diagnostik und Behandlungsstrategien
Authors: Fiorucci Beatrice , Banafsche Ramin , Jerkku Thomas , Pichlmaier Maximilian , Kölbel Tilo , Rantner Barbara , Tsilimparis Nikolaos
Published: January 2019

Was ist neu?

Diagnostik Die CTA hat sich mit der kontinuierlichen Verbesserung der Qualität, Geschwindigkeit und Verfügbarkeit als optimales diagnostisches Verfahren für die thorakale Aorta etabliert. Daneben gewinnt die MRT zunehmend an Wichtigkeit, hauptsächlich wegen der exakten Darstellung von Wandveränderungen der Aorta und der Möglichkeit, durch innovative Protokolle dynamische Fluss-Phänomene abzubilden.

Behandlungsstrategien Nachdem sich die TEVAR als Therapie der Wahl für die Versorgung von thorakalen Aortenpathologien durchgesetzt hat, fokussiert sich die Entwicklung dieser Technik nun auf den total endovaskulären Ansatz durch die Rekrutierung einer suffizienten proximalen Landezone im Aortenbogen, proximal der LSA mittels gebranchter oder fenestrierter Aortenbogen-Prothesen, die supraaortale Gefäße mit einbeziehen. Da neurologische Komplikationen wie der perioperative Schlaganfall oder die spinale Ischämie derzeit die größte Herausforderung bei endovaskulären Verfahren darstellen, ist intensive Forschung und stetige Optimierung der Techniken die Grundlage für eine sichere endovaskuläre Zukunft in der Versorgung thorakaler Aortenpathologien.
Refractory Bergmann type A bile leak: the need to strike a balance
Authors: Mutignani Massimiliano , Forti Edoardo , Larghi Alberto , Dokas Stefanos , Pugliese Francesco , Cintolo Marcello , Bonato Giulia , Tringali Alberto , Dioscoridi Lorenzo
Published: January 2019

Background and study aims Endoscopic therapy for postoperative Bergmann type A bile leaks is based on biliary sphincterotomy ± stent insertion. However, recurrent or refractory bile leaks can occur.

Patients and methods This was retrospective study including all consecutive patients who were referred to our center with a Bergmann type A bile leak refractory to previous conventional endoscopic treatments.

Results Seventeen patients with post-cholecystectomy-refractory Bergmann type A bile leak were included. All had received prior endoscopic biliary sphincterotomy with biliary stent or nasobiliary catheter placement and all had a percutaneous or surgical abdominal drainage. Repeat endoscopic retrograde cholangiopancreatography (ERCP) confirmed a Bergmann type A bile leak and in all patients we observed that the abdominal drainage was placed adjacent to the origin of the fistula. Our treatment consisted of pulling the drain away from the fistulous site, with extension of the previous sphincterotomy when needed. The treatment was successful in all cases. Mild complications occurred in three patients.

Conclusions Our retrospective study shows that refractory Bergmann type A bile leak may be a consequence of an unfavorable position of the abdominal drainage tube, which can be corrected by pulling the drain away from the origin of the fistula. This establishes a favorable pressure gradient that leads the bile flowing from the bile duct into the duodenum.
Die laryngotracheale Resektion als Alternative zum permanenten Tracheostoma
Authors: Aleksanyan A. , Stoelben E.
Published: January 2019

Einleitung Zervikale Tracheastenosen als Folge von Tracheotomien oder Tumoren sowie idiopathischer Genese können in der Regel durch eine Tracheaquerresektion unterhalb des Ringknorpels dauerhaft geheilt werden. Im Falle einer Beteiligung des Ringknorpels erhöhen sich die Komplexität und das Risiko des Eingriffs. Wir berichten über die Technik der laryngotrachealen Resektion und Rekonstruktion und vergleichen in unserem eigenen Patientengut die Ergebnisse der zervikalen Tracheaquerresektion und der laryngotrachealen Resektion in Bezug auf ihre perioperativen Ergebnisse.

Patienten und Methode In unserer Klinik wurden im Zeitraum von 01/2005 bis 12/2015 über 800 Tracheaeingriffe durchgeführt. Davon waren 111 zervikale Trachearesektionen mit 76 Tracheaquerresektionen und 35 laryngotracheale Resektionen. Die Resektion erfolgte immer mit primärer Anastomose ohne Anlage eines intraoperativen Tracheostomas oder einer intralaryngealen Schiene. Die perioperativen Daten wurden retrospektiv aus den Patientenakten erhoben.

Ergebnisse Bei der Indikationsstellung überwiegt in beiden Gruppen die Stenose oder Defektbildung nach Tracheotomie, gefolgt von idiopathischer Stenose, Tumoren und Morbus Wegener. Es traten keine Wundheilungsstörungen an der Anastomose auf. Postoperative Tracheotomien waren mit 3 bzw. 2 Eingriffen nach Tracheaquer- bzw. laryngotrachealer Resektion selten notwendig. Pulmonale Komplikationen und die N. recurrens-Parese waren mit 5/4 und 2/2 Fällen in beiden Gruppen ähnlich häufig. Kein Patient musste mit einem definitiven Tracheostoma weiterleben. Es verstarb jeweils ein Patient im postoperativen Verlauf. Somit ergab sich kein signifikanter Unterschied in der Komplikationsrate zwischen den beiden Gruppen.

Schlussfolgerung Die laryngotracheale Resektion ist ein relevanter Bestandteil der zervikalen Trachearesektion. Sie kann ohne signifikant erhöhte Morbidität durchgeführt werden und erhält so die pulmonale und Stimmfunktion des Patienten auch bei komplexen Stenosen mit Beteiligung des unteren Kehlkopfes.
Nutzende und Nicht-/Nicht-mehr-Nutzende Berliner Drogenkonsumräume im Vergleich
Authors: Stöver Heino , O´Reilly Maike-Sinead , Förster Stefan , Jurković Larissa
Published: January 2019

Eine im Jahr 2005 von der Senatsverwaltung Berlin in Auftrag gegebene Evaluation der Berliner Drogenkonsumräume ergab, dass ein großer Teil der Drogengebrauchenden in Berlin die niedrigschwelligen Angebote der Drogenkonsumräume (DKR) nicht regelmäßig oder nur selten nutzte. Die Studie „Evaluation der Nutzungsprofile der Drogenkonsumraumnutzer im Land Berlin“, die 2015 vom Institut für Suchtforschung Frankfurt durchgeführt wurde, analysiert daher die Gründe für die Nutzung bzw. Nicht-/Nicht-mehr-Nutzung von DKR in Berlin. Dieser Artikel stellt die wichtigsten Ergebnisse des Berichts vor und vergleicht diese im Anschluss mit Ergebnissen aus DKR in Frankfurt und NRW. Im Zentrum steht dabei die Frage, wie sich existierende niedrigschwellige Angebote in Berlin im Sinne der Qualitätssicherung bedarfsgerecht ausbauen lassen. Die Untersuchung zeigt, dass die DKR die definierte Zielgruppe (Opioidkonsumierende außerhalb von Substitutionsbehandlungen) überwiegend erreicht. Jedoch zeigt die Studie auch existierende Problemlagen auf und weist auf Verbesserungsbedarfe hin. So werden sowohl von den Nicht-/Nicht-mehr-Nutzenden, als auch seitens der befragten Fachkräfte die knapp bemessenen Öffnungszeiten sowie das Nutzungsverbot für Substituierte thematisiert.
Supervised Short-term High-intensity Training on Plasma Irisin Concentrations in Type 2 Diabetic Patients
Authors: Dünnwald Tobias , Melmer Andreas , Gatterer Hannes , Salzmann Karin , Ebenbichler Christoph , Burtscher Martin , Schobersberger Wolfgang , Grander Wilhelm
Published: January 2019

Irisin is a myokine involved in adipocyte transformation. Its main beneficial effects arise from increased energy expenditure. Irisin production is particularly stimulated by physical exercise. The present study investigates the changes of plasma irisin in type 2 diabetic patients performing 2 different training modalities. Fourteen type 2 diabetic patients underwent 4 week of supervised high-intensity interval training (HIT; n=8) or continuous moderate-intensity training (CMT; n=6), with equivalent total amounts of work required. Plasma samples were collected in the resting state atbaseline and one day after the exercise intervention to analyse resting plasma irisin, blood lipids, blood glucose, hsCRP, Adiponectin, Leptin and TNF-α concentrations. In addition, body composition and VO2peak were determined Resting plasma irisin increased after HIT (p=0.049) and correlated significantly with plasma fasting glucose at follow-up (r=0.763; p=0.006). CMT did not significantly change the amount of plasma irisin, although follow-up values of plasma irisin correlated negatively with fat-free mass (r=−0.827, p=0.002) and with fasting plasma glucose (r = − 0.934, p=0.006). Plasma irisin was found to increase with higher training intensity, confirming the assumption that exercise intensity, in addition to the type of exercise, may play an important role in the stimulation of the irisin response.
Effects of Different Percentages of Blood Flow Restriction on Energy Expenditure
Authors: Pfeiffer Patrick , Cirilo-Sousa Maria , Santos Heleodório
Published: January 2019

The study aimed to analyze the effect of different levels of blood flow restriction (BFR) on energy expenditure (EE) and subjective perceptions of discomfort (SPD) during aerobic exercises. A sample group of 24 young men was required to walk on a treadmill for 14 min at 40% of their maximum speed, with 4 different percentages of BFR (0, 50, 80 and 100%) applied in the lower limbs (LL) once a week with a 7-day interval between the 4 evaluations. EE data were collected during the exercise periods; SPD data were collected after the exercises. There was a significant increase in EE at 50, 80 and 100% BFR compared to the condition without BFR, and between 50 and 100% BFR; however, there were no differences between 50 and 80% and 80 and 100% BFR. Discomfort showed a significant increase according to the increase in BFR. During the walking exercises with BFR, the EE strongly increased until 50% of BFR; after this level the additional increases slowed. It can be concluded that when performing aerobic exercises with BFR, there is no need to use BFR levels above 50% to reach satisfying level of EE with only a moderate level of discomfort to the practitioner. This study was registered in the Brazilian Registry of Clinical Trials (REBEC) under number RBR-3XHSJX.
Systematic Review and Meta-Analysis of Randomised, Other-than-Placebo Controlled, Trials of Non-Individualised Homeopathic Treatment
Authors: Mathie Robert , Fok Yvonne , Viksveen Petter , To Aaron , Davidson Jonathan
Published: January 2019

Introduction This study focuses on randomised controlled trials (RCTs) of non-individualised homeopathic treatment (NIHT) in which the control (comparator) group was other than placebo (OTP).

Objectives To determine the comparative effectiveness of NIHT on health-related outcomes in adults and children for any given condition that has been the subject of at least one OTP-controlled trial. For each study, to assess its risk of bias and to determine whether its study attitude was predominantly ‘pragmatic’ or ‘explanatory’.

Methods Systematic review. For each eligible trial, published in the peer-reviewed literature up to the end of 2016, we assessed its risk of bias (internal validity) using the seven-domain Cochrane tool, and its relative pragmatic or explanatory attitude (external validity) using the 10-domain PRECIS tool. We grouped RCTs by whether these examined IHT as alternative treatment (study design 1a), adjunctively with another intervention (design 1b), or compared with no intervention (design 2). RCTs were sub-categorised as superiority trials or equivalence/non-inferiority trials. For each RCT, we designated a single ‘main outcome measure’ to use in meta-analysis: ‘effect size’ was reported as odds ratio (OR; values > 1 favouring homeopathy) or standardised mean difference (SMD; values < 0 favouring homeopathy).

Results Seventeen RCTs, representing 15 different medical conditions, were eligible for study. Three of the trials were more pragmatic than explanatory, two were more explanatory than pragmatic, and 12 were equally pragmatic and explanatory. Fourteen trials were rated ‘high risk of bias’ overall; the other three trials were rated ‘uncertain risk of bias’ overall. Ten trials had data that were extractable for analysis. Significant heterogeneity undermined the planned meta-analyses or their meaningful interpretation. For the three equivalence or non-inferiority trials with extractable data, the small, non-significant, pooled effect size (SMD = 0.08; p = 0.46) was consistent with a conclusion that NIHT did not differ from treatment by a comparator (Ginkgo biloba or betahistine) for vertigo or (cromolyn sodium) for seasonal allergic rhinitis.

Conclusions The current data preclude a decisive conclusion about the comparative effectiveness of NIHT. Generalisability of findings is restricted by the limited external validity identified overall. The highest intrinsic quality was observed in the equivalence and non-inferiority trials of NIHT.
Role of Elbow Incongruity in Canine Elbow Dysplasia: Advances in Diagnostics and Biomechanics
Authors: Ginja Mário , Colaço Bruno , Alves-Pimenta Sofia
Published: January 2019

Elbow incongruity plays an important role in the development of elbow dysplasia and its diagnosis can be challenging. The objectives of this systematic review were to discuss elbow biomechanics and recent advances in the assessment of incongruity, to revise the diagnostic protocols suggested, debate advantages and disadvantages of measurements proposed to characterize the joint and improve screening.

In spite of advances in the understanding of elbow incongruity, the exact mechanisms involved are not fully elucidated. The elbow is a complex joint and structures in contact differ in different phases of the gait cycle. Advances in the biomechanical field allowed new discoveries and a physiological type of incongruity was described. The next challenge is to unravel the dynamic incongruity. Radiology and computed tomography (CT) are nowadays the imaging tools more applied in clinical practice to quantify incongruity. But a CT standardized screening protocol is required. Most reported findings of incongruity were increased articular joint spaces. The proximity of joint structures and standardization of elbow positioning are identified as the main obstacles to a good interpretation. This review serves to highlight controversy between physiological types of cartilage covering described and pathological changes reported in arthroscopic studies. Radioulnar incongruity was reported more often than humeroulnar incongruity, yet prevalence studies are lacking. Sensitive and reproducible methodologies are in development, which seem primordial to assess the phenotypic heterogeneity.
Mindfulness Training among Parents with Preterm Neonates in the Neonatal Intensive Care Unit: A Pilot Study
Authors: Marshall Alyssa , Guillén Úrsula , Mackley Amy , Sturtz Wendy
Published: January 2019

Objective To evaluate the feasibility of a mindfulness-based training session (MBTS) for parents of neonates born at ≤32 weeks' gestation in a level 3 neonatal intensive care unit (NICU).

Study Design Within 14 days of admission, parents completed the Parental Stressor Scale: Neonatal Intensive Care Unit Questionnaire (PSS:NICU), Cognitive and Affective Mindfulness Scale (CAMS-R), and a survey on stress management techniques. Parents then participated in a MBTS with instruction in mindfulness-based practices and were asked to practice the techniques during the NICU stay. At discharge, parents repeated the surveys to evaluate their mindfulness-based practice experience.

Results Of the 98 parents approached, 51 consented to participate (52%). Of these, 28 completed MBTS, initial, and discharge surveys. One parent had previously practiced mindfulness. The majority of parents (79%) reported that mindfulness practice was helpful, and 71% stated that they would continue their practice after NICU discharge. There was no difference in PSS:NICU or CAMS-R at discharge.

Conclusion An MBTS was feasible to provide to parents in our NICU. Parents practiced the mindfulness-based techniques and reported benefit from their mindfulness-based practice. Future studies are needed to evaluate if an MBTS is a valuable resource for NICU parents' coping.
Optical calcium test for measurement of multiple permeation pathways in flexible organic optoelectronic encapsulation
Authors: Boldrighini Patrick , Fauveau Aurélie , Thérias Sandrine , Gardette Jean Luc , Hidalgo Manuel , Cros Stéphane
Published: January 2019

Organic photovoltaic (OPV) devices and other organic electronics have the promise to provide lightweight, flexible alternatives to traditional rigid semiconductor technologies. However, organic electronics often degrade rapidly upon exposure to oxygen, water, light, and combinations thereof, as well as upon exposure to elevated temperatures. This requires the use of high gas barrier packaging in order for devices to have operational lifetimes on the order of years. To meet the challenge of transparent high gas barrier materials which maintain the flexibility of organic optoelectronics, many different materials and encapsulation schemes have been developed including the lamination of devices between flexible multi-layer barrier films. Because of their excellent barrier properties, these materials often require specialized testing for permeation measurements which evaluate materials independently. In this work, we demonstrate the use of an optical calcium test, which uses a sample geometry that closely mimics an OPV device, to evaluate a complete encapsulation scheme and to elucidate the relative importance of different permeation pathways. Using an encapsulation scheme of laminating a device between two multi-layer barrier films using an adhesive, measurements were made for water vapor permeation through the barrier film, the bulk adhesive, and along the adhesive-to-barrier film interface. The results show that the combined lateral permeation, including through the bulk adhesive and along the adhesive-to-barrier film interface, can constitute over 50% of the total permeation for small devices (4.5 cm × 4.5 cm). The adhesive-to-barrier film interface was also found to be a very important pathway as it was deemed responsible for more permeation than the bulk adhesive. The technique was also used to evaluate encapsulation design variables such as the effects of adhesive thickness and surface treatments on the lateral water permeation. We demonstrate that decreasing the adhesive thickness leads to a decrease in the lateral water permeation.
On the near-optimality of one-shot classical communication over quantum channels
Authors: Anshu Anurag , Jain Rahul , Warsi Naqueeb Ahmad
Published: January 2019

We study the problem of transmission of classical messages through a quantum channel in several network scenarios in the one-shot setting. We consider both the entanglement assisted and unassisted cases for the point to point quantum channel, the quantum multiple-access channel, the quantum channel with a state, and the quantum broadcast channel. We show that it is possible to near-optimally characterize the amount of communication that can be transmitted in these scenarios, using the position-based decoding strategy introduced in a prior study (A. Anshu, R. Jain, and N. Warsi, https://ieee.org/document/8399830). In the process, we provide a short and elementary proof of the converse for entanglement-assisted quantum channel coding in terms of the quantum hypothesis testing divergence [obtained earlier in the work of W. Matthews and S. Wehner, IEEE Trans. Inf. Theory 60, 7317–7329 (2014)]. Our proof has the additional utility that it naturally extends to various network scenarios mentioned above. Furthermore, none of our achievability results require a simultaneous decoding strategy, existence of which is an important open question in quantum Shannon theory.
Mean-field analysis of directed modular networks
Authors: Moriya Satoshi , Yamamoto Hideaki , Akima Hisanao , Hirano-Iwata Ayumi , Kubota Shigeru , Sato Shigeo
Published: January 2019

We considered a modular network with a binomial degree distribution and related the analytical relationships of the network properties (modularity, average clustering coefficient, and small-worldness) with structural parameters that define the network, i.e., number of nodes, number of modules, average node degree, and ratio of intra-modular to total connections. Even though modular networks are universally found in real-world systems and are consequently of broad interest in complex network science, the relationship between network properties and structural parameters has not yet been formulated. Here, we show that a series of equations for predicting the network properties can be related using a mean-field connectivity matrix that is defined on the basis of the structural parameters in the network generation algorithm. The theoretical results are then compared with values calculated numerically using the original connectivity matrix and are found to agree well, except when the connections between modules are sparse. Representation of the structure of the network using simple parameters is expected to be conducive for elucidating the structure–dynamics relationship.
High efficiency and low roll-off hybrid white organic light emitting diodes by strategically introducing multi-ultrathin phosphorescent layers in blue exciplex emitter
Authors: Zhao Chenyang , Yan Donghang , Ahamad Tansir , Alshehri Saad M. , Ma Dongge
Published: January 2019

Because of the low exciton utilization of fluorescent emitters and inadequately stable blue phosphorescent emitters, hybrid white organic light emitting diodes (WOLEDs) are considered as the most effective way to achieve good white emission. Nevertheless, the serious efficiency roll-off is still a big challenge to be addressed. Generally, the high density and long lifetime of radiative triplet excitons are the main causes. Thus, broadening the exciton distribution region, decreasing the local exciton density, and accelerating the triplet excitons radiated by low-energy emitters will improve this roll-off problem. In this paper, we proposed a hybrid WOLED by simply introducing multi-ultrathin phosphorescent layers in a blue exciplex emitting layer (EML). Compared to the common multi-EML hybrid WOLEDs, the proposal device demonstrates higher efficiency and lower efficiency roll-off at high luminance. The maximum external quantum efficiency, current efficiency, and power efficiency reach 20.4%, 62.8 cd A−1, and 75.9 lm W−1, respectively, and remain 16.5%, 50.7 cd A−1, and 47.1 lm W−1, respectively, at the luminance of 1000 cd m−2. By the analysis of exciton utilization processes, it can be inferred that the improved performance benefits from the energy transfer and wider exciton distribution, thus reducing the exciton density and energy loss due to more efficient exciton utilization.
Direct observation of fast surface dynamics in sub-10-nm nanoglass particles
Authors: Chen Na , Wang Di , Guan Peng Fei , Bai Hai Yang , Wang Wei Hua , Zhang Zheng Jun , Hahn Horst , Gleiter Herbert
Published: January 2019

Preventing the crystallization of metallic glasses is a challenging task, primarily because of their non-equilibrium nature. In this paper, we show that a reduction in size significantly increases the surface dynamics of metallic glasses, thereby favoring the formation of a surface liquid-like layer with near-equilibrium minimum energy. The fast atomic mobility at the surface of sub-10-nm nanoglass particles is directly observed and found to be consistent with the existing theoretical predictions. Our results suggest that the devitrification of glass can be avoided if the nucleation of crystals is too difficult. These results help to elucidate the underlying mechanisms of glass dynamics at the nanoscale, which are useful for designing ultrastable glasses and furthering our understanding of the nature of glass.
Numerical research on a 4 MW 170 GHz coaxial gyrotron with a double electron beam
Authors: Hou Shenyong , Yu Shen , Li Hongfu
Published: January 2019

In this paper, a coaxial gyrotron with a double electron beam is investigated on the ohmic loss, starting current, mode competition, and beam wave interaction. Its beam-wave interaction equation and dependence of the starting current on the static magnetic field and parameter K (the ratio of the current of an electron beam to the total current of a double electron beam) are given. On this basis, a 4 MW 170 GHz coaxial gyrotron with a double electron beam is studied. By the numerical calculation, the influence of K on the starting current is analyzed under a given static magnetic field and at different guiding center radii of the double electron beam. Studies show that the ability of the gyrotron to suppress the mode competition has a relation with the selection of the guiding center radii of the two electron beams. Then, the investigation of a time-dependent multi-mode competition of the gyrotron is performed, which shows that the gyrotron can stably operate in the TE38,18− mode. The results show that by considering the ohmic loss, the gyrotron can operate at 170.4 GHz with the output power of 4.04 MW and the beam-wave interaction efficiency of 35.47% when B = 6.82 T, U = 88 KV, I = 129 A, and K = 0.4. Each of the two electron beams in the gyrotron has different beam-wave interaction efficiencies. Compared to the coaxial gyrotron with one electron beam, the beam-wave interaction efficiency of each electron beam in the coaxial gyrotron with a double electron beam has a different increase.
Experimental examination of a method to estimate temporal effect by neutrons and γ-rays on scintillation light in scintillator-based soft x-ray diagnostic of experimental advanced superconducting tokamak and large helical device
Authors: Bando T. , Ohdachi S. , Zhou R. J. , Zhong G. Q. , Yuan Y. , Hu L. Q. , Ling B. L.
Published: January 2019

Scintillators, which are more tolerant of neutrons or γ-rays than semiconductors, are a promising candidate for soft X-ray (SX) diagnostics in high neutron flux environments such as JT-60SA or ITER. Although scintillators are tolerant of radiations, neutrons and γ-rays can cause scintillation light and become noise on SX signals. Therefore, a method to estimate the temporal effect by the radiations on SX signals and an appropriate design of the radiation shield based on the estimation are required. In previous studies, it has been proposed for estimating the effect by the radiations to calculate the absorption powers due to SXs, neutrons, and γ-rays in scintillators assuming that amplitudes of scintillation light are proportional to the absorption powers. In this study, an experimental examination of this proposal is conducted in the Experimental Advanced Superconducting Tokamak (EAST). It is shown that the proposal may be valid in the examination of EAST. In addition to results in EAST, initial results of a multi-channel scintillator-based SX diagnostic in the Large Helical Device (LHD) are introduced. Although a scintillator-based SX diagnostic in LHD observes oscillations of SXs by magnetohydrodynamic (MHD) phenomena successfully, the observed temporal effect on SX signals by neutrons or γ-rays is more significant than the expected effect, which is estimated by calculating the absorption powers. One of the possible reasons for the contradiction between the results in EAST and LHD is unexpected γ-rays around the scintillators in LHD. Although the temporal effect by the radiations is significant in the current system of LHD, the degradation of amplitudes of SX signals after the deuterium plasma experiments is not observed with the current level of the fluence. The scintillator-based SX diagnostic in LHD may work as a diagnostic to research MHD instabilities in deuterium plasma experiments without additional maintenance during an experimental campaign by making the pinhole larger or setting an additional radiation shield.
Computational analysis of the electron beam source with hollow anode
Authors: Levko Dmitry
Published: January 2019

The computational analysis of the plasma source with the hollow anode is performed using the two-dimensional Particle-in-Cell Monte Carlo collisions model. This source operates in two molecular gases (CO2 and N2) in the abnormal glow mode, i.e., it is supported by the secondary electron emission from the cathode. It is obtained that this plasma source can be used for the generation of high-energy electrons (energy > 100 eV) only if the cathode potential exceeds 500 V. Otherwise, the high-energy electrons generated in the high-voltage cathode sheath dissipate almost all their energy in the plasma column and get thermalized.
Sensitivity analysis of the electrostatic interaction between the atomic force microscopy probe and a thin dielectric film with 3D-localized charge cloud
Authors: Azib M. , Baudoin F. , Binaud N. , Villeneuve-Faure C. , Teyssedre G. , Bugarin F. , Segonds S.
Published: January 2019

Recent experimental studies have demonstrated that the Electrostatic Force Distance Curve (EFDC) can be used for space charge probing in thin dielectric layers. Experiments highlight that this method seems to be sensitive to charge localization. However, the relative contributions of charge distribution parameters (density, lateral/in-depth spreading) remain unknown. The aim of this paper is to determine the contribution of each charge distribution parameters to EFDC. To reach this aim, we have developed an electrostatic and an electromechanical model to simulate EFDC over a charge cloud trapped in a thin dielectric layer. Hence, the EFDC sensitivity to charge localization could be investigated through the shape parameters of the charge cloud and by extracting the respective contributions from the atomic force microscopy tip and the cantilever.
Uncertainty in linewidth quantification of overlapping Raman bands
Authors: Saltonstall Christopher B. , Beechem Thomas E. , Amatya Jatin , Floro Jerrold , Norris Pamela M. , Hopkins Patrick E.
Published: January 2019

Spectral linewidths are used to assess a variety of physical properties, even as spectral overlap makes quantitative extraction difficult owing to uncertainty. Uncertainty, in turn, can be minimized with the choice of appropriate experimental conditions used in spectral collection. In response, we assess the experimental factors dictating uncertainty in the quantification of linewidth from a Raman experiment highlighting the comparative influence of (1) spectral resolution, (2) signal to noise, and (3) relative peak intensity (RPI) of the overlapping peaks. Practically, Raman spectra of SiGe thin films were obtained experimentally and simulated virtually under a variety of conditions. RPI is found to be the most impactful parameter in specifying linewidth followed by the spectral resolution and signal to noise. While developed for Raman experiments, the results are generally applicable to spectroscopic linewidth studies illuminating the experimental trade-offs inherent in quantification.
Structural, optical, and electrical properties of ferroelectric copolymer of vinylidenefluoride doped with Rhodamine 6G dye
Authors: Kochervinskii V. V. , Gradova M. A. , Gradov O. V. , Kiselev D. A. , Ilina T. S. , Kalabukhova A. V. , Kozlova N. V. , Shmakova N. A. , Bedin S. A.
Published: January 2019

An effect of Rhodamine 6G dye introduced into vinylidenefluoride and tetrafluoroethylene copolymer on a number of its structural and electrical characteristics has been detected. It was shown that at film crystallization, the inserted dopant shifts the equilibrium distribution of isomers to the side of increasing concentrations of chains with the conformation of a planar zigzag. The dye introduced strongly increases ac conductivity, especially at high electric fields. The investigation of high voltage polarization under bipolar external field conditions shows slow switching of gigantic current which is observed at fields lower than coercive ones. The estimation of the charge density indicates the non-ferroelectric nature of the phenomenon observed. The analysis of the data shows that in the system, Maxwell–Wagner relaxation processes take place, which lead to the space charge formation in the polymer matrix. It is established that current switching observed must be attributed to the relaxation of the space charge field.
Modeling heterogeneous melting in phase change memory devices
Authors: Scoggin J. , Woods Z. , Silva H. , Gokirmak A.
Published: January 2019

We present thermodynamic crystallization and melting models and calculate phase change velocities in Ge2Sb2Te5 based on kinetic and thermodynamic parameters with a focus on the impacts of grain boundary melting. The calculated phase change velocities are strong functions of grain size, with smaller grains beginning to melt at lower temperatures. Phase change velocities are continuous functions of temperature which determine crystallization and melting rates. Hence, set and reset times as well as power and peak current requirements for switching are strong functions of grain size. Grain boundary amorphization can lead to a sufficient increase in cell resistance for small-grain phase change materials even if the whole active region does not completely amorphize. Isolated grains left in the amorphous regions, the quenched-in nuclei, facilitate templated crystal growth and significantly reduce set times for phase change memory cells. We demonstrate the significance of heterogeneous melting through 2-D electrothermal simulations coupled with a dynamic material phase change model. Our results show reset and set times on the order of ∼1 ns for 30 nm wide confined nanocrystalline (7.5 nm–25 nm radius crystals) phase change memory cells.
Non-invasive time-resolved measurements of anomalous collision frequency in a Hall thruster
Authors: Dale Ethan T. , Jorns Benjamin A.
Published: January 2019

The time-resolved cross-field electron anomalous collision frequency in a Hall thruster is inferred from minimally invasive laser-based measurements. This diagnostic is employed to characterize the relationship between the dominant low-frequency “breathing” oscillations and anomalous electron transport mechanisms. The ion Boltzmann equation combined with a generalized Ohm's law is used to infer key quantities including the ionization rate and axial electric field strength which are necessary in computing the total electron cross-field collision frequency. This is accomplished by numerically integrating functions of velocity moments of the ion velocity distribution function measured with laser-induced fluorescence, in conjunction with current density measurements at a spatial boundary. Estimates of neutral density are used to compute the classical collision frequency profile and the difference in the total collision frequency, and this quantity describes the anomalous collision frequency. This technique reveals the anticipated trends in electron transport: few collisions in the acceleration region but a collision frequency approaching the cyclotron frequency farther downstream. The time-resolved transport profiles indicate that the anomalous collision frequency fluctuates by several orders of magnitude during a breathing cycle. At troughs in the discharge current, classical collisions may dominate; at peaks in the discharge current, anomalous collisions dominate. These results show that the breathing mode and electron transport are directly correlated. This finding is discussed with regard to existing numerical models for the breathing mode and interpretations of anomalous electron transport.
Shape transformation and manipulation of a vesicle by active particles
Authors: Wang Chao , Guo Yong-kun , Tian Wen-de , Chen Kang
Published: January 2019

Langevin dynamics simulations are employed to study the shape transformation of a two-dimensional vesicle induced by active particles both inside and outside. We find that the shape of the vesicle changes from circle, to capsule, and eventually to dumbbell with the enhancement of the particle activity. Under the cooperation between the inside and the outside active particles, such significant shape transformation is realized by tuning the activity in a small range. And unexpectedly, the fluctuations of the capsule and the dumbbell shapes are not completely random but mostly along the direction of the short axis. In the situation of strong activity, the inside of the dumbbell vesicle is analogous to a system of two chambers, which are connected by a narrow channel. Intriguingly, we observe the vibration of the channel width, accompanied with the exchange of active particles between the two chambers. We also find that dynamical manipulation of the vesicle shape is possible through tuning the particle activity dynamically. This work provides new ideas to the control of the vesicle morphology and new insights into the dynamics in the vesicle’s shape transformation.
Evolutionary design algorithm for optimal light trapping in solar cells
Authors: Gouvêa Rogério Almeida , Moreira Mário Lúcio , Souza Jeferson Avila
Published: January 2019

Light scattering at rough interfaces is a standard approach to enhance absorption of light in the absorber layers of solar cells due to light trapping. In this work, an automata optimization algorithm, based on the Constructal Theory, is proposed for the heuristic geometric design to enhance light trapping of silicon solar cell surface textures. Surface textures were investigated computationally for light absorption of a normally incident simulated solar spectrum, under constraints of transverse area of the texture. The photogenerated current density was calculated for textures to estimate light trapping. In the automata optimization, Elemental Constructals, consisting of dielectric material blocks, were assembled on top of the solar cell forming a texture. Three variations of the proposed automata algorithm were tested and their capabilities were determined. The best result for this optimization was a photocurrent J=17.48mA/cm2 for grid periodicity above the wavelength and J=18.31mA/cm2 for grid periodicity in the sub-wavelength range. The evolutionary algorithm was also applied to assemble a periodic-disordered texture from fixed shape gratings to better harness incident light. Different textures with fixed shapes of gratings had been investigated to determine optimal geometric parameters. Optimized triangular, trapezoidal, and rounded-tip textures achieved the best results in this phase and were implemented to assemble the periodic-disordered texture which reached J=19.75mA/cm2 for triangular gratings. Results found with this pristine evolutionary algorithm corroborate its efficiency in finding, practically, geometries that lead to greater light absorption with a minimum amount of dielectric materials.
Impact of interfacial structure on the charge dynamics in nanocomposite dielectrics
Authors: Kubyshkina Elena , Unge Mikael
Published: January 2019

We demonstrate that the chemistry at the interface between nanoparticle and polymer matrix influence charge dynamics in polymer nanocomposite. Applying density functional theory, we investigate the influence of crystal surface termination, silicon treatment, and water and carboxyl defect on the electronic properties of interfaces in MgO-polyethylene nanocomposite. The band offsets between the nanofiller and base matrix materials show a strong dependence on the chemical composition at the interface. Based on the calculated electronic structure, we propose a band alignment model for charge dynamics in nanocomposite dielectrics. The model not only provides a mechanism of reduction of space charge and conductivity but also predicts an increase in thermal stress and susceptibility to the chemical additives. It is suggested that the suppression mechanisms of space charge and conductivity in nanocomposites can be inherently unstable and promote material aging. The results of the study show a need for long-term performance tests of nanocomposite dielectrics.
Nonlinear dynamics of a chemically-active drop: From steady to chaotic self-propulsion
Authors: Morozov Matvey , Michelin Sébastien
Published: January 2019

Individual chemically active drops suspended in a surfactant solution were observed to self-propel spontaneously with straight, helical, or chaotic trajectories. To elucidate how these drops can exhibit such strikingly different dynamics and “decide” what to do, we propose a minimal axisymmetric model of a spherical active drop, and show that simple and linear interface properties can lead to both steady self-propulsion of the droplet as well as chaotic behavior. The model includes two different mobility mechanisms, namely, diffusiophoresis and the Marangoni effect, which convert self-generated gradients of surfactant concentration into the flow at the droplet surface. In turn, surface-driven flow initiates surfactant advection that is the only nonlinear mechanism and, thus, the only source of dynamical complexity in our model. Numerical investigation of the fully coupled hydrodynamic and advection-diffusion problems reveals that strong advection (e.g., large droplet size) may destabilize a steadily self-propelling drop; once destabilized, the droplet spontaneously stops and a symmetric extensile flow emerges. If advection is strengthened even further in comparison with molecular diffusion, the droplet may perform chaotic oscillations. Our results indicate that the thresholds of these instabilities depend heavily on the balance between diffusiophoresis and the Marangoni effect. Using linear stability analysis, we demonstrate that diffusiophoresis promotes the onset of high-order modes of monotonic instability of the motionless drop. We argue that diffusiophoresis has a similar effect on the instabilities of a moving drop.
Generation of two-photon orbital-angular-momentum entanglement with a high degree of entanglement
Authors: Li Wei , Zhao Shengmei
Published: January 2019

An important problem in the practical application of high-dimensional two-photon orbital angular momentum (OAM) entanglement generated by spontaneous down conversion is a lower degree of entanglement, where the amplitudes of modes are not uniformly distributed. In contrast to the previously raised entanglement concentration protocol, we here report on an experimental scheme that addresses this problem by tuning the two-photon quantum angular position correlation. An opaque mask with N evenly distributed angular slits having a radius r is inserted in the two-photon down-conversion light path. The number N should be such that the separation of adjacent angular slits is larger than the scale of the two-photon angular position correlation. The OAM entanglement for the two-photon state after the opaque mask is cast into a set of folded subbands with a dimension of N, owing to the reduction of rotational symmetry from continuous invariance to discrete invariance. Almost maximum OAM entanglement can be realized by properly setting the width of the angular slits.
Ir4+ ions in β-Ga2O3 crystals: An unintentional deep donor
Authors: Lenyk C. A. , Giles N. C. , Scherrer E. M. , Kananen B. E. , Halliburton L. E. , Stevens K. T. , Foundos G. K. , Blevins J. D. , Dorsey D. L. , Mou S.
Published: January 2019

Electron paramagnetic resonance (EPR) and infrared absorption are used to detect Ir4+ ions in β-Ga2O3 crystals. Mg and Fe doped crystals are investigated, and concentrations of Ir4+ ions greater than 1 × 1018 cm−3 are observed. The source of the unintentional deep iridium donors is the crucible used to grow the crystal. In the Mg-doped crystals, the Ir4+ ions provide compensation for the singly ionized Mg acceptors and thus contribute to the difficulties in producing p-type behavior. The Ir4+ ions replace Ga3+ ions at the Ga(2) sites, with the six oxygen neighbors forming a distorted octahedron. A large spin-orbit coupling causes these Ir4+ ions to have a low-spin (5d5, S = 1/2) ground state. The EPR spectrum consists of one broad line with a significant angular dependence. Principal values of the g matrix are 2.662, 1.815, and 0.541 (with principal axes near the crystal a, b, and c directions, respectively). Ionizing radiation at 77 K decreases the Ir4+ EPR signal in Mg-doped crystals and increases the signal in Fe-doped crystals. In addition to the EPR spectrum, the Ir4+ ions have an infrared absorption band representing a d-d transition within the t2g orbitals. At room temperature, this band peaks near 5153 cm−1 (1.94 μm) and has a width of 17 cm−1. The band is highly polarized: its intensity is maximum when the electric field E is parallel to the b direction in the crystal and is nearly zero when E is along the c direction.
Liquid crystal enabled dynamic cloaking of terahertz Fano resonators
Authors: Shen Zhi-Xiong , Zhou Sheng-Hang , Ge Shi-Jun , Hu Wei , Lu Yan-Qing
Published: January 2019

Terahertz (THz) metadevices featured by high-Q Fano resonance are applicable for ultrasensitive biodetection. The active tuning of Fano resonance further extends their applications to switching and filtering. Here, we propose a dynamic Fano cloaking in a liquid crystal (LC) integrated THz metasurface. The metasurface is composed of two-gap asymmetric split rings. Its Fano resonance is intensively dependent on the incident polarization. The Fano resonance occurs when illuminated by THz waves with polarization perpendicular to the gaps, while for parallel polarization, the Fano resonance vanishes, namely, the cloaking of Fano resonators. A 250-μm-thick LC layer functions as an integrated tunable polarization converter. Thus, the device can be electrically switched between the sharp Fano state and the high-transmission state. The modulation depth reaches over 50% in a broad frequency range of 660 GHz. This work may inspire various advanced active THz apparatuses for biosensing, switching, and filtering.
Magnetic contributions to the low-temperature specific heat of Sc79Fe21 nanoglass
Authors: Wang Chaomin , Palit Mithun , Yin Nan , Shi Quan , Ivanisenko Yulia , Gleiter Herbert , Hahn Horst
Published: January 2019

The specific heat (Cp) of the Sc79Fe21 nanoglass and Sc75Fe25 melt-spun ribbons was measured in zero and non-zero applied magnetic fields for a temperature range of 1.9 to 7 K. The plots for the Cp/T-vs-T2 without an applied magnetic field show an “upturn” at lower temperatures. Based on the variations of the “upturn” with applied magnetic fields and the magnetism of the alloys, the “upturn” was attributed to the effect of the ferromagnetic clusters. The calculated number of ferromagnetic clusters within the Sc79Fe21 nanoglass was much smaller than that within the Sc75Fe25 melt-spun ribbon, most likely because of the chemically heterogeneous structure of the nanoglass.
Fractional modeling of blood ethanol concentration system with real data application
Authors: Qureshi Sania , Yusuf Abdullahi , Shaikh Asif Ali , Inc Mustafa , Baleanu Dumitru
Published: January 2019

In this study, a physical system called the blood ethanol concentration model has been investigated in its fractional (non-integer) order version. The three most commonly used fractional operators with singular (Caputo) and non-singular (Atangana-Baleanu fractional derivative in the Caputo sense—ABC and the Caputo-Fabrizio—CF) kernels have been used to fractionalize the model, whereas during the process of fractionalization, the dimensional consistency for each of the equations in the model has been maintained. The Laplace transform technique is used to determine the exact solution of the model in all three cases, whereas its parameters are fitted through the least-squares error minimization technique. It is shown that the fractional versions of the model based upon the Caputo and ABC operators estimate the real data comparatively better than the original integer order model, whereas the CF yields the results equivalent to the results obtained from the integer-order model. The computation of the sum of squared residuals is carried out to show the performance of the models along with some graphical illustrations.