bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-linear optical response in disordered 2D materials
Authors: João Simão M. , Viana Parente Lopes João M.
Published: April 2020

Using KITE [1], a quantum transport software developed by ourselves, we explore the effect of disorder in the second-order con¬ductivity, aiming to reproduce mesoscopic samples under more realistic models of disorder. This work will be concerned about our most recent results with KITE. We will showcase and examine how different mod¬els of disorder affect the same system, experimenting with Anderson disorder and vacancies in gapped Graphene.
Energy loss by fast-travelling charged particles traversing two-dimensional materials
Authors: Santos Jaime E. , Vasilevskiy Mikhail , Peres Nuno M.R. , Jauho Antti-Pekka
Published: April 2020

We consider the problem of the radiation losses by fast-traveling particles traversing two-dimensional (2d) materials or thin films. After review¬ing the screening of electromagnetic fields by two dimensional conducting ma¬terials, we obtain the energy loss by a fast particle traversing such a material or film. In particular, we discuss the pattern of radiation emitted by monolayer graphene treated within a hydrodynamic approximation. These results are com¬pared with recent published results using similar approximations and, having in mind a potential application to particle detection, we briefly discuss how one can improve on the signals obtained by using other two-dimensional materials.
Ion beam induced current analysis in GaN microwires
Authors: Verheij Dirkjan , Peres Marco , Cardoso Susana , Alves Luís Cerqueira , Alves Eduardo , Durand Cristophe , Eymery Joël , Fernandes Jorge , Lorenz Katharina
Published: April 2020

GaN is a wide bandgap semiconductor which is expected to withstand high radiation doses. Consequently, it is considered a promising material for new generation particle detectors in radiation related applications. We report on the fabrication and electrical characterization under proton irradiation of single microwire sensors based on a back-to-back Schottky contact configuration. The microwires are grown by metal-organic vapor phase epitaxy and processed into sensors by using optical lithography on dispersed wires. We investigate the impact of the contacts and the semiconductor bulk on the ion beam induced current (IBIC) by irradiating specific areas of the sensor and simultaneously measuring the change in conductivity. We observed that the contribution of the excess charge carriers generated in the depletion regions formed at the contact interfaces is of low influence when compared to the excess charge carriers generated in the microwire bulk.
Orthorhombic GdMnO3 Epitaxial Thin Film Grown onto SrTiO3 (110)
Authors: Machado P. , Figueiras F.G. , Vilarinho R. , Fernandes J.R.A. , Tavares P.B. , Rosário Soares M. , Cardoso S. , Almeida A. , Agostinho Moreira J.
Published: April 2020

GdMnO3 epitaxial thin films were deposited onto (110)-oriented SrTiO3 substrates by RF magnetron sputtering. The structure, microstructure, dielectric and magnetic properties were investigated in detail. The XRD results revealed that the GdMnO3 thin films exhibit an epitaxial strained orthorhombic symmetry and grow preferably in off-plane (001) orientation, wherein the basal lattice parameters are strained by the substrate lattice. A dielectric relaxation process was ascertained, whose activation energy is sensitive to the magnetic phase transitions, occurring at 41 K and at 20 K, respectively. The canted nature of the low temperature magnetic phase is discussed.
Experimental dynamic analysis of the existing footbridge in Dobřichovice town
Authors: Polák Michal , Plachý Tomáš , Čítek Adam , Berková Karolína , Hájková Petra , Čáp Miroslav
Published: April 2020

The paper presents an experimental dynamic analysis of the existing footbridge across the Berounka River in Dobřichovice town, Czech Republic. The experiment was realized in two stages. The main purpose of the first one was the vibration response determination of the footbridge induced by pedestrians. At first, the natural frequencies and mode shapes of its horizontal load-bearing structure were measured and then the footbridge was loaded by different groups of pedestrians. The response was observed and dynamic behaviour of the footbridge was evaluated. In the course of the second stage of the experiment, the dynamic response of the footbridge deck to pedestrian traffic was measured by two different methods using radar interferometry and classical approach realized by piezoelectric accelerometers. Basic objectives of the second stage were to evaluate the fundamental modal characteristics of the footbridge and to verify new approach to dynamic response measurement – radar interferometry realized by two synchronized radars.
Solution of a high bridge pillar under wind effects taking into account the real properties of reinforced concrete
Authors: Tvrdá Katarína
Published: April 2020

The current standard is that the calculation of a reinforced concrete structure is carried out using the theory of elasticity and its design is based on the requirements of EC2. In this paper, a computational method based on direct numerical integration and Gaussian or Newton-Cotes cubicles that directly reflect the material properties determined by EC2 is presented. The deviations in the internal forces and deformations achieved compared to the classical theory of elasticity are demonstrated in the calculation of the high bridge pillar.
Investigation of dynamic acting of a technological equipment on a building construction
Authors: Polach Pavel , Hajžman Michal
Published: April 2020

This paper deals with the analysis of acting a dynamically loaded technological equipment on a building construction. The Cyclone 18 cyclotron was selected as a demonstrator of the technological equipment. Two cyclotron loading modes are simulated: excitation by a harmonic sinusoidal force and a seismic excitation. Mounting the cyclotron in the building construction is considered absolutely rigid. To create the cyclotron finite element model and to calculate the cyclotron dynamic acting on the building construction the ANSYS software was used, in which the cyclotron calculation model including its concrete chamber was created.
Transmission of transport vibrations from the ground to the building - case study
Authors: Kowalska-Koczwara Alicja , Pachla Filip
Published: April 2020

Transport vibrations are transmitted from the ground the foundations and building walls to the building and received by its construction and by people in the buildings. During the vibration of buildings, inertia forces generate an additional (apart from the static one) loading of the structure. In the diagnosis and design of buildings, these forces are taken into account by analyzing the requirements for stiffness and strength of the building structure. Exceedance of these requirements may lead to accelerated wear and even structural damages of the building. In this paper a simple relationship between ground and building vibration was made. The building chosen for analysis is light-weight wooden building located close to Cracow near Zakopianka road. What is worth noting that building is so called passive building. The excitation which was simulated on the dynamical polygon was car (bus) and truck lorry passages. The sensors were accelerations in three orthogonal directions, one sensor was placed about 2.5 m far from the building and the second on the foundation wall. The different types of excitation were compared and the conclusion from the analysis was made.
Analysis and evaluation of the effect of vibrations on historical buildings
Authors: Urushadze Shota , Pirner Miroš
Published: April 2020

Continued exposure of human induced vibrations contributes to the degradation of materials and joints, causing the initiation of cracks or the growth of existing ones, such that they may endanger the structure. Loads, which an undamaged structure could safely resist, can be critical if repeated numerous times. This risk is present in various types of historical buildings, and is influenced by changes in vibration magnitude, by the distance from their source, and by the quality of the building’s maintenance. Good maintenance, which includes regular inspections, allows early detection of any emerging damage and its subsequent repair. This article describes the methods and results of the measurement of dynamic response to road traffic and other types of technical seismicity in four historic buildings. The goal of this paper is to present some examples of analysis and evaluation of the effects of such human activity.
Structural health monitoring and structural modifications of industrial building subjected to dynamic loading
Authors: Soltys Robert , Tomko Michal , Demjan Ivo
Published: April 2020

A complex structural, static and dynamic review of an existing steel ceiling has been realised after two years of service and the completion of subsequent construction work. The construction work involved the reconstruction of a steel structure and structural modifications to the ceiling, which is part of the production hall. The construction work was realised in order to reduce the vibration response of the ceiling. The interior of the steel structure was supplemented by steel structural elements to share the load transfer of automatic washing machines. The structural behaviour of the ceiling was monitored before and after the modification. Accelerations of the ceiling were time-domain-monitored at specific locations. Measured data was transformed to the spectral-domain which is represented by power spectral densities.
Example of analysis of climatic data series with respect to the testing of reinforcement concrete corrosion in a climate chamber
Authors: Lehner Petr , Konečný Petr , Walentyński Ryszard
Published: April 2020

The paper presents a possible statistical evaluation of the climate data, namely temperature and relative humidity, with respect to the rapid evaluation of the risk of reinforced concrete corrosion in the laboratory conditions. Data on temperature and humidity from Leoš Janáček Ostrava Airport over the last ten years are analysed. The processed data will be used as the set up for the climate chamber where the concrete samples with steel rods will be placed.
Influence of the clay on mechanical properties of construction made of rammed earth
Authors: Padevět Pavel , Mužíkovát Barbora , Otcovská Tereza
Published: April 2020

The article is focused on the monitoring of mechanical properties of rammed earth made from two types of clays. Due to a change in the composition of the mixture, there are changes in the material properties that are important for the design of the rammed earth structures. The resulting values of the properties of the individual are compared with each other. The mechanical properties of compression and bending compression are compared in the paper.
Aerodynamic interference of wind flow around three cylindrical bodies with surface roughness
Authors: Macháček Michael , Urushadze Shota , Pospíšil Stanislav , Trush Arsenii , Pirner Miroš
Published: April 2020

The aerodynamic interference effect is an important and complex phenomenon that can modified wind flow around structures in a group and wind loading on structures can significantly increase. Three cylindrical buildings in one row with a rough surface and surrounding lower minor buildings were studied by experimental measurement in wind tunnel with a turbulent boundary layer. The experimental study was focused on aerodynamical forces, local dynamic pressure on a facade of the buildings, and visualization of wind flow around buildings.
Optimierung der Langzeitbetreuung von neurologischen Patienten durch internet- und mobile-basierte Interventionen ohne und mit persuasiven Elementen einschließlich der Gamification
Authors: Lohse Peter , Steinmetzer Tobias , Reichmann Heinz , Reckhardt Markus , Bönninger Ingrid , Reinhardt Fritjof
Published: April 2020

In einer Pilotstudie an 60 neurologischen Langzeitpatienten (degenerative zerebrale Mikroangiopathie mit reduzierter sensomotorischer Stabilität) erfolgt eine erste Überprüfung der Praxistauglichkeit eines eigens entwickelten Konzeptes, das in dem Kommunikationsaspekt einen Schwerpunkt der medizinischen Langzeitbehandlung sieht. Zunächst werden die Präferenzen des Patienten und weitere seine Adhärenz bestimmenden Faktoren analysiert. Neben Verständigung und sachlich-argumentativem Austausch bedarf es dabei einer affektiv-emotionalen vielschichtigen Botschaftsübermittlung, die sich auf den Rezipienten umfassend und in Echtzeit einstellt. Persuasion ist das gezielte Ansprechen von Verhaltensmustern. Gamification überführt spielerische Elemente in einen spielfremden Kontext. Dabei bieten technologiebasierte Ansätze eine Möglichkeit, Aspekte von Gesundheit, Lebensqualität und positiver Krankheitsbewältigung, z. B. durch den Einsatz von internet- und mobile-basierten Interventionen (IMI), zu optimieren. Auf diesem informationstheoretischen und gesundheitskommunikativen Hintergrund wurde eine Pilotstudie mit 60 neurologischen Langzeitpatienten mit symptomatischer zerebraler Mikroangiopathie durchgeführt, die wegen einer bestehenden sensomotorischen Inkompetenz stationär aufgenommen worden waren. Noch während des einwöchigen stationären Aufenthaltes bekamen die Patienten eine Einführung in eine standardisierte sensomotorische Trainingstherapie, die sie dann nach Entlassung aus dem stationären Setting über sechs Wochen hinweg als vierarmige Interventionsstudie ambulant am Klinikcampus oder häuslich, jeweils ohne und mit Gamification, weiterführten. Die Patienten wurden am Anfang und am Ende der Trainingsphase mit motorisch-funktionellen Verfahren und testpsychologisch untersucht. Anschließend wurden sie einem standardisierten Leitfadeninterview unterzogen. Als wichtigste Ergebnisse fanden sich:

– Die computergestützte Trainingstherapie war wirksam und wurde von den Patienten angenommen. Ihnen war besonders wichtig: hohe Anwenderfreundlichkeit, hohe Präzision in der Widerspiegelung des Beherrschungsgrades auch subtiler Trainingselemente durch den Patienten und eine persönliche Fortschrittsbewertung in Echtzeit.

– Die häuslichen Trainingsergebnisse waren besser als die in der Campusambulanz.

– Training mit und ohne Gamification ist vergleichbar, es werden über sechs Wochen hinweg ähnliche Therapieeffekte erzielt, allerdings verbessert sich die subjektive Lebensqualität unter Gamification signifikant.
„Haben wir noch Sex oder schläfst du schon?“
Authors: Miorin-Bellermann Juliane
Published: April 2020

Hauptverantwortlich für Libido, Fertilität und sexuelle Aktivität ist ein fragiles Gleichgewicht von Hormonen wie Testosteron, Östradiol, Kortisol, T3 und T4. Einflüsse wie Dauerstress, Adipositas, Kontrazeptiva, Xeno- oder Phytohormone können die Hormonbalance empfindlich stören, unter anderem in Form von Östrogendominanz, Kortisolüberschuss und Testosteronmangel. In drei vorgestellten Fällen kann durch gezielte Hormondiagnostik, phytotherapeutische und homöopathische Therapie sowie eine Änderung des Lebensstils die Lebensfreude und Libido – in einem Fall auch die Fertilität – wieder in hohem Maße hergestellt werden.
Der Tag, der alles änderte
Authors: Kormer von Baerle Dörte
Published: April 2020

Krebs im Beckenraum und seine Therapien bedeuten nicht nur für Körperfunktionen eine Zäsur, sondern auch für das Selbstbild, Sexualleben und Rollenverständnis. In vielen Fällen kommen Sexualität und Partnerschaft zum Erliegen, weil Betroffene sich ihrem Körper entfremden, sich hilflos und wertlos fühlen – häufig verstärkt durch Unfruchtbarkeit, erektile Dysfunktion oder Körperveränderungen. Wer gemeinsam mit dem Patienten den Fokus auf dessen Kräfte, Selbstwirksamkeit und Ressourcen lenkt und diese durch Übungen stärkt, unterstützt seinen Weg zu einem neuen Selbstverständnis und mehr Eigeninitiative.
Helferin für Lust und Lunge
Authors: Rosenhauer von Löwensprung Natalie
Published: April 2020

Damiana war schon im alten Mexiko bei Libidostörungen und Asthmaerkrankungen bewährt.
Optical coherence tomography of the pancreatic and bile ducts: are we ready for prime time?
Authors: Tyberg Amy , Raijman Isaac , Novikov Aleksey A. , Sejpal Divyesh V. , Benias Petros C. , Trindade Arvind J. , Das Ananya , Sachdev Mankanwal , Khosravi Farhoud , Tarnasky Paul , Kedia Prashant , Gaidhane Monica , Kahaleh Michel , Joshi Virendra
Published: April 2020

Background and study aims First-generation optical coherence tomography (OCT) has been shown to increase diagnostic sensitivity for malignant biliary and pancreatic-duct strictures. A newer OCT imaging system, NVision Volumetric Laser Endomicroscopy (VLE), allows for in vivo cross-sectional imaging of the ductal wall at the microstructure level during endoscopic retrograde cholangiopancreatography (ERCP). The aim of this study was to identify and evaluate characteristics on OCT that are predictive of benign and malignant strictures.

Patients and methods Consecutive patients from six centers who underwent OCT between September 2016 and September 2017 were included in a dedicated registry. OCT images were analyzed, and nine recurring characteristics were further assessed. Final diagnosis was based on histology and/or surgical pathology.

Results 86 patients were included (49 % male, mean age 64.7). OCT was performed in the bile duct in 79 patients and the pancreatic duct in seven. Nine OCT characteristics were identified: dilated hypo-reflective structures (n = 7), onion-skin layering (n = 8), intact layering (n = 17), layering effacement (n = 25), scalloping (n = 20), thickened epithelium (n = 42), hyper-glandular mucosa (n = 13), prominent blood vessels (n = 6), and a hyper-reflective surface (n = 20). Presence of hyper-glandular mucosa, hyper-reflective surface and scalloping significantly increased the odds of malignancy diagnosis by 6 times more (P = 0.0203; 95 % CI 1.3 to 26.5), 4.7 times more (P = 0.0255; 95 % CI 1.2 to 18.0) and 7.9 times more (P = 0.0035; 95 % CI 1.97 to 31.8) respectively.

Conclusion By providing in-vivo cross-sectional imaging of the pancreatic and biliary duct wall, OCT technology may improve sensitivity in diagnosing malignant strictures and provide standardizable criteria predictive of malignancy.
Diagnostic yield of EUS-guided through-the-needle microforceps biopsy versus EUS-FNA of pancreatic cystic lesions: a systematic review and meta-analysis
Authors: Westerveld Donevan R. , Ponniah Sandeep A. , Draganov Peter V. , Yang Dennis
Published: April 2020

Background and study aims Accurate diagnosis and risk stratification of pancreatic cysts (PCs) is challenging. The aim of this study was to perform a systematic review and meta-analysis to assess the feasibility, safety, and diagnostic yield of endoscopic ultrasound-guided through-the-needle biopsy (TTNB) versus fine-needle aspiration (FNA) in PCs.

Methods Comprehensive search of databases (PubMed, EMBASE, Cochrane, Web of Science) for relevant studies on TTNB of PCs (from inception to June 2019). The primary outcome was to compare the pooled diagnostic yield and concordance rate with surgical pathology of TTNB histology and FNA cytology of PCs. The secondary outcome was to estimate the safety profile of TTNB.
Results: Eight studies (426 patients) were included. The diagnostic yield was significantly higher with TTNB over FNA for a specific cyst type (OR: 9.4; 95 % CI: [5.7–15.4]; I2 = 48) or a mucinous cyst (MC) (OR: 3.9; 95 % CI: [2.0–7.4], I2 = 72 %). The concordance rate with surgical pathology was significantly higher with TTNB over FNA for a specific cyst type (OR: 13.5; 95 % CI: [3.5–52.3]; I2 = 48), for a MC (OR: 8.9; 95 % [CI: 1.9–40.8]; I2 = 29), and for MC histologic severity (OR: 10.4; 95 % CI: [2.9–36.9]; I2 = 0). The pooled sensitivity and specificity of TTNB for MCs were 90.1 % (95 % CI: [78.4–97.6]; I2 = 36.5 %) and 94 % (95 % CI: [81.5–99.7]; I2 = 0), respectively. The pooled adverse event rate was 7.0 % (95 % CI: [2.3–14.1]; I2 = 82.9).

Conclusions TTNB is safe, has a high sensitivity and specificity for MCs and may be superior to FNA cytology in risk-stratifying MCs and providing a specific cyst diagnosis.
Uptake and barriers for implementation of the resect and discard strategy: an international survey
Authors: Willems Philippe , Djinbachian Roupen , Ditisheim Saskia , Orkut Sinan , Pohl Heiko , Barkun Alan , Bouin Mickael , Faulques Bernard , von Renteln Daniel
Published: April 2020

Background and study aims Optical real-time diagnosis (= resect-and-discard strategy) is an alternative to histopathology for diminutive colorectal polyps. However, clinical adoption of this approach seems sparse. We were interested in evaluating potential clinical uptake and barriers for implementation of this approach.

Methods We conducted an international survey using the “Google forms” platform. Nine endoscopy societies distributed the survey. Survey questions measured current clinical uptake and barriers for implementing the resect-and-discard strategy, perceived cancer risk associated with diminutive polyps and potential concerns with using CT-colonography as follow-up, as well as non-resection of diminutive polyps.

Results Eight hundred and eight endoscopists participated in the survey. 84.2 % (95 % CI 81.6 %–86.7 %) of endoscopists are currently not using the resect-and-discard strategy and 59.9 % (95 % CI 56.5 %–63.2 %) do not believe that the resect-and-discard strategy is feasible for implementation in its current form. European (38.5 %) and Asian (45 %) endoscopists had the highest rates of resect-and-discard practice, while Canadian (13.8 %) and American (5.1 %) endoscopists had some of the lowest implementation rates. 80.3 % (95 % CI 77.5 %–83.0 %) of endoscopists believe that using the resect-and-discard strategy for diminutive polyps will not increase cancer risk. 48.4 % (95 % CI 45.0 %–51.9 %) of endoscopists believe that leaving diminutive polyps in place is associated with increased cancer risk. This proportion was slightly higher (54.7 %; 95 % CI 53.6 %–60.4 %) when asked if current CT-colonography screening practice might increase cancer risks.

Conclusion Clinical uptake of resect-and-discard is very low. Most endoscopists believe that resect-and-discard is not feasible for clinical implementation in its current form. The most important barriers for implementation are fear of making an incorrect diagnosis, assigning incorrect surveillance intervals and medico-legal consequences.
The International Academy of Health Sciences Informatics (IAHSI): IMIAs Academy is Now Established and on Track
Authors: Haux Reinhold , Ball Marion J. , Kimura Michio , Martin-Sanchez Fernando , Otero Paula , Huesing Elaine , Koch Sabine , Lehmann Christoph U.
Published: April 2020

Objectives: To summarize the major activities of the International Academy of Health Sciences Informatics (IAHSI) from 2018 until 2019, and to provide an outline of actions planned for 2020.

Method: Reporting about these activities and actions by the members of the Academy's first Board.

Results: Academy bylaws were accepted by the Academy Plenary and the IMIA General Assembly on August 25th, 2019 and August 26th, 2019, respectively. Academy's strategy and focus areas were developed. Based on the Academy's eligibility criteria, the 2018/2019 Class made of 26 new Academy Fellows was elected. Future activities will concentrate on building taskforces for developing and implementing major Academy focus areas.

Conclusions: We are glad to report that the Academy is strong and thriving.
Methylene Blue versus Coil-Based Computed Tomography-Guided Localization of Lung Nodules
Authors: Zhang Ze-Dong , Wang Hua-Long , Liu Xian-Yan , Xia Feng-Fei , Fu Yu-Fei
Published: April 2020

Background Preoperative computed tomography (CT)-guided localization has been shown to significantly improve lung nodule video-assisted thoracoscopic surgery (VATS)-based wedge resection technical success rates. However, at present, there was insufficient research regarding the optimal approaches to localization of these nodules prior to resection. We aimed to compare the relative clinical efficacy of preoperative CT-guided methylene blue and coil-based lung nodule localization.

Methods In total, 91 patients with lung nodules were subjected to either CT-guided methylene blue (n = 34) or coil (n = 57) localization and VATS resection from January 2014 to December 2018. We compared baseline data, localization-associated complication rates, as well as the technical success of localization and resection between these two groups of patients.

Results In total, 42 lung nodules in 34 patients underwent methylene blue localization, with associated localization and wedge resection technical success rates of 97.6 and 97.6%, respectively. A total of 71 lung nodules in 57 patients underwent coil localization, with associated localization and wedge resection technical success rates of 94.4 and 97.2%, respectively. There were no significant differences in technical success rates of localization or wedge resection between these groups (p = 0.416 and 1.000, respectively). The coil group sustained a longer duration between localization and VATS relative to the methylene blue group (13.2 vs. 2.5 hours, p = 0.003).

Conclusion Both methylene blue and coil localization can be safely and effectively implemented for conducting the diagnostic wedge resection of lung nodules. The coil-based approach is compatible with a longer period of time between localization and VATS procedures.
Enhanced brightness of a laser-driven x-ray and particle source by microstructured surfaces of silicon targets
Authors: Ebert Tina , Neumann Nico W. , Döhl Leonard N. K. , Jarrett Jonathan , Baird Christopher , Heathcote Robert , Hesse Markus , Hughes Aasia , McKenna Paul , Neely David , Rusby Dean , Schaumann Gabriel , Spindloe Christopher , Tebartz Alexandra , Woolsey Nigel , Roth Markus
Published: April 2020

The production of intense x-ray and particle sources is one of the most remarkable aspects of high energy laser interaction with a solid target. Wide application of these laser-driven secondary sources requires a high yield, which is partially limited by the amount of laser energy absorbed by the target. Here, we report on the enhancement of laser absorption and x-ray and particle flux by target surface modifications. In comparison to targets with flat front surfaces, our experiments show exceptional laser-to-target performance for our novel cone-shaped silicon microstructures. The structures are manufactured via laser-induced surface structuring. Spectral and spatial studies of reflectance and x-ray generation reveal significant increases of the silicon Kα line and a boost of the overall x-ray intensity, while the amount of reflected light decreases. Also, the proton and electron yields are enhanced, but both temperatures remain comparable to those of flat foil targets. We support the experimental findings with 2D particle in cell simulations to identify the mechanisms responsible for the strong enhancement. Our results demonstrate how custom surface structures can be used to engineer high power laser-plasma sources for future applications.
Direct measurement of the ionization source rate and closure of the particle balance in a helicon plasma using laser induced fluorescence
Authors: Green Jonathan , Schmitz Oliver , Zepp Michael
Published: April 2020

A detailed study of the flows of ion and neutral argon populations in a helicon plasma was carried out. Understanding the principle ion sinks and sources of neutral fueling is essential to understanding the ability of helicon wave heating to create high density plasmas. This heating mechanism and the neutral fueling required to sustain it and perhaps manipulate the axial density profile in long cylindrical plasmas are an active research topic for advanced plasma wakefield accelerator concepts. Using laser induced fluorescence (LIF) of ion and neutral argon species, an ion flux of up to 2.5×1021 m−2 s−1 was measured leaving the core of a helicon plasma with a peak electron density of 4.0×1018 m−3. Taking the divergence of the axial ion flux profile yields a minimum ionization rate estimate of 2×1021 m−3 s−1, and including the radial divergence increases the estimated ionization rate to approximately 1022 m−3 s−1. Neutral flow velocities measured using LIF reveal a circulatory fueling and loss mechanism with distinct zones where radial or axial sources and sinks dominate.
A novel 3D non-autonomous system with parametrically excited abundant dynamics and bursting oscillations
Authors: Wang Mengjiao , Li Jianhui , Yu Samson Shenglong , Zhang Xinan , Li Zhijun , Iu Herbert H. C.
Published: April 2020

In this paper, a novel non-autonomous chaotic system with rich dynamical behaviors is proposed by introducing parametric excitation to a Lorenz-like system, and the effect of the initial value of the excitation system on the resulting system dynamics is then thoroughly investigated. The attractors resulting from the proposed chaotic system will enter different oscillating states or have topological change when the initial value varies. Furthermore, some novel bursting oscillations and bifurcation mechanism are revealed. Stability and bifurcation of the proposed 3D non-autonomous system are comprehensively investigated to analyze the causes of the observed dynamics through a range of analytical methods, including bifurcation diagram, Lyapunov exponent spectrum, and sequence and phase diagrams. Software simulation and hardware experimentation are conducted in this study, which verify the dynamic behaviors of the proposed chaotic system. This study will create a new perspective and dimension of perceiving non-autonomous chaotic systems and exploring their applicability in real-world engineering applications.
Two super Camassa–Holm equations: Reciprocal transformations and applications
Authors: Tian Kai , Liu Q. P. , Yue Wen Jun
Published: April 2020

Reciprocal transformations are introduced for two super Camassa–Holm (CH) equations. Under these transformations and appropriate changes of dependent variables, the super CH equation, proposed by Geng et al. [Stud. Appl. Math. 130, 1 (2013)], is converted to a negative member of the super Korteweg–de Vries (KdV) hierarchy studied by Geng and Wu in 2010 [Appl. Math. Lett. 23, 716 (2010)], while the other super CH equation, due to Zhang and Zuo [J. Math. Phys. 52, 073503 (2011)], is related to a new super KdV hierarchy. In the latter case, algebraic properties of this new super KdV hierarchy are established, including Hamiltonian operators, a recursion operator, and conserved quantities.
Thermal transport exceeding bulk heat conduction due to nonthermal micro/nanoscale phonon populations
Authors: Chiloyan Vazrik , Huberman Samuel , Maznev Alexei A. , Nelson Keith A. , Chen Gang
Published: April 2020

While classical size effects usually lead to a reduced effective thermal conductivity, we report here that nonthermal phonon populations produced by a micro/nanoscale heat source can lead to enhanced heat conduction, exceeding the prediction from Fourier's law. We study nondiffusive thermal transport by phonons at small distances within the framework of the Boltzmann transport equation (BTE) and demonstrate that the transport is significantly affected by the distribution of phonons emitted by the source. We discuss analytical solutions of the steady-state BTE for a source with a sinusoidal spatial profile, as well as for a three-dimensional Gaussian “hot spot,” and provide numerical results for single crystal silicon at room temperature. If a micro/nanoscale heat source produces a thermal phonon distribution, it gets hotter than that predicted by the heat diffusion equation; however, if the source predominantly produces low-frequency acoustic phonons with long mean free paths, it may get significantly cooler than that predicted by the heat equation, yielding an enhanced heat transport beyond bulk heat conduction.
Modeling and analysis for thermal management in gallium oxide field-effect transistors
Authors: Yuan Chao , Zhang Yuewei , Montgomery Robert , Kim Samuel , Shi Jingjing , Mauze Akhil , Itoh Takeki , Speck James S. , Graham Samuel
Published: April 2020

Increased attention has been paid to the thermal management of β-Ga2O3 devices as a result of the large thermal resistance that can present itself in part due to its low intrinsic thermal conductivity. A number of die-level thermal management approaches exist that could be viable for thermal management. However, they have not been assessed for β-Ga2O3 devices exclusively. Here, we explore the limits of various die level thermal management schemes on a β-Ga2O3 metal–semiconductor field-effect transistor using numerical simulations. The effects of the various cooling approaches on the device channel temperature were comprehensively investigated, along with guidance for material selection to enable the most effective thermal solutions. Among various cooling strategies, double side cooling combined with a heat spreader used in the active region of the device can suppress the device thermal resistance to as low as 11 mm °C/W, achieving a maximum dissipated power density as high as 16 W/mm for a junction temperature limit of 200 °C. A multi-finger transistor thermal model was also developed to assess the potential of β-Ga2O3 devices for higher output power applications. Overall, this numerical study shows that it is possible to achieve high power β-Ga2O3 device operation with appropriate die-level thermal management solutions.
Microstructure and properties of 9Cr-3W-3Co steel joint by shielded metal arc welding
Authors: Zhang Youyi , Gou Guoqing
Published: April 2020

In the view of the application of 9Cr-3W-3Co new martensitic heat-resistant steel as the material of ultra-supercritical thermal power, the welding material (deposited metal) for the shielded metal arc welding is designed and multi-layer and multi-pass welding is carried out. The microstructure of the 9Cr-3W-3Co joint was analyzed by optical microscopy and scanning electron microscopy. The hardness, tensile strength, and impact absorption energy of the joints were investigated. The results show that the microstructure of the upper and middle parts of the welded metal is tempered martensite, carbide particles, and M-A components, and the lower part of the welded metal is composed of tempered martensite, acicular δ ferrite, and carbide particles. The micro-hardness distribution of the different parts of the joint is basically the same. From the welded metal through the HAZ to the base metal, its hardness gradually decreases, and the average hardness of the joint is 288 HV. The average tensile strength of the joint is 631 MPa, which is 0.84 of the base metal. The fracture position is in the welded metal area, and the fracture behavior is brittle fracture. The average impact absorption energy of the 9Cr-3W-3Co steel joint is 17 J, which is lower than that of the base metal.
Atomic microwave-to-optical signal transduction via magnetic-field coupling in a resonant microwave cavity
Authors: Tretiakov A. , Potts C. A. , Lee T. S. , Thiessen M. J. , Davis J. P. , LeBlanc L. J.
Published: April 2020

Atomic vapors offer many opportunities for manipulating electromagnetic signals across a broad range of electromagnetic spectra. Here, a microwave signal with an audio frequency modulation encodes information in an optical signal by exploiting an atomic microwave-to-optical double resonance and magnetic-field coupling that is amplified by a resonant high-Q microwave cavity. Using this approach, audio signals are encoded as amplitude or frequency modulations in a GHz carrier, transmitted through a cable or over free space, demodulated through cavity-enhanced atom-microwave interactions, and, finally, optically detected to extract the original information. This atom-cavity signal transduction technique provides a powerful means by which to transfer information between microwave and optical fields, all using a relatively simple experimental setup without active electronics.
Metamaterials and Cesàro convergence
Authors: Nellambakam Yuganand , Shiv Chaitanya K. V. S.
Published: April 2020

In this paper, we show that the linear dielectrics and magnetic materials in matter obey a special kind of mathematical property known as Cesàro convergence. Then, we also show the analytical continuation of permittivity and permeability to the complex plane in terms of the Riemann zeta (ζ) function. The nontrivial zeros on the half-line of the Riemann zeta (ζ) function correspond to permittivity ξe = 0 and permeability ξm = 0. The permittivity ξe = 0 and permeability ξm = 0 in the literature are known as zero index materials.
On the error in the two-term Weyl formula for the Dirichlet Laplacian
Authors: Frank Rupert L. , Larson Simon
Published: April 2020

We study the optimality of the remainder term in the two-term Weyl law for the Dirichlet Laplacian within the class of Lipschitz regular subsets of Rd. In particular, for the short-time asymptotics of the trace of the heat kernel, we prove that the error term cannot be made quantitatively better than little-o of the second term.
Geometric and electronic structures of pyrazine molecule chemisorbed on Si(100) surface by XPS and NEXAFS spectroscopy
Authors: Song Xiu-neng , Ji Huan-yu , Lin Juan , Wang Ruo-yu , Ma Yong , Wang Chuan-kui
Published: April 2020

The geometric and electronic structures of several possible adsorption configurations of the pyrazine (C4H4N2) molecule covalently attached to Si(100) surface, which is of vital importance in fabricating functional nano-devices, have been investigated using X-ray spectroscopies. The Carbon K-shell (1s) X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy of predicted adsorbed structures have been simulated by density functional theory with cluster model calculations. Both XPS and NEXAFS spectra demonstrate the structural dependence on different adsorption configurations. In contrast to the XPS spectra, it is found that the NEXAFS spectra exhibiting conspicuous dependence on the structures of all the studied pyrazine/Si(100) systems can be well utilized for structural identification. In addition, according to the classification of carbon atoms, the spectral components of carbon atoms in different chemical environments have been investigated in the NEXAFS spectra as well.
O2-oxidation of cyanomethylene radical: Infrared identification of criegee intermediates syn- and anti-NCC(H)OO
Authors: Lu Bo , Qin Yuan-yuan , Song Chao , Qian Wei-yu , Wang Li-na , Zeng Xiao-qing
Published: April 2020

Cyanomethylene radical (HCCN) is an important intermediate in the nitrile chemistry in both the earth’s and the Titan’s atmosphere. Despite that the mechanism for the oxidation of HCCN has been already computationally explored, the key Criegee intermediate, NCC(H)OO, remains unobserved yet. By photolyzing mixtures (1:50:1000) of either HC(N2)CN/O2/N2 (266 nm) or HCCNCO/O2/N2 (193 nm) at 15.0 K, the elusive carbonyl oxides NCC(H)OO, in syn- and anti-conformations, have been generated and characterized with IR spectroscopy. The spectroscopic identification is supported by 18O-labeling experiments and the quantum chemical calculations at the BP86/6-311++G(3df,3pd) level. Upon subsequent UV-light irradiation, both conformers of NCC(H)OO further react with O2 and yield NCC(O)H and O3, whereas, the dioxirane isomer HC(O2)CN, which is lower than syn-NCC(H)OO by 23.7 kcal/mol at the CCSD(T)-F12a/aug-cc-pVTZ//BP86/6-311++G(3df,3pd) level, was not observed experimentally.
Two-photon dissociation dynamics of hydroxyl radical
Authors: Sun Ge , Zheng Xian-feng , Qin Yuan , Song Yu , Zhang Jingsong , Amero Jose Martin , Vázquez Gabriel J.
Published: April 2020

Two-photon dissociation dynamics of the OH radical is studied using the high-n Rydberg atom time-of-flight (HRTOF) technique. The H(2S)+O(1D) and H(2S)+O(1S) product channels are observed in the dissociation of the OH radical on the 22Π and B2Σ+ repulsive states, respectively, from sequential two-photon excitation via the A2Σ+ (v′=2, J′=0.5−2.5) state. Both H+O product channels have anisotropic angular distributions, with β=−0.97 for H(2S)+O(1D) and 1.97 for H(2S)+O(1S). The anisotropic angular distributions are consistent with a mechanism of OH direct dissociation on the repulsive potential energy curves (PECs) leading to the H+O products. The OH bond dissociation energy D0(O−H) is determined to be 35580±15 cm−1.
PLD-derived Ge2Sb2Te5 phase-change films with extreme bending stability for flexible device applications
Authors: Li Ming , Xie Mingzhang , Ji Huan , Zhou Jiaoyan , Jiang Kai , Shang Liyan , Li Yawei , Hu Zhigao , Chu Junhao
Published: April 2020

Ge 2 Sb 2 Te 5 phase-change films on flexible mica substrates are prepared by pulsed laser deposition (PLD). X-ray diffraction measurements determine the crystallographic phase of the as-deposited films and confirm that the ⟨111⟩ is the preferential orientation of growth. Temperature-dependent Raman and electrical measurements show that phase transitions from the amorphous to rock salt and hexagonal structures occur at 420 K and 550 K, respectively. Here, we have assembled a flexible electronic device with aluminum alloy sheet and silver glue for fixing after bending. Two significant resistance drops, encompassing four orders and two orders of magnitude, can be observed at the transition temperatures ranging from 420 K to 550 K. The switching ratio of the flexible devices is maintained at six orders of magnitude under different bending states. The present results demonstrate an excellent potential for applications of these PLD-deposited Ge2Sb2Te5 films on mica substrates in flexible data storage and neuro-inspired computing.
Stochastic resonance induced by an unknown linear frequency modulated signal in a strong noise background
Authors: Wu Chengjin , Yang Jianhua , Sanjuán Miguel A. F. , Liu Houguang
Published: April 2020

Stochastic resonance (SR) is widely used as a signal enhancement technique in recovering and enhancing periodic or aperiodic signals submerged in noise. However, system parameters and noise intensity tend to influence the SR performance. To achieve better resonance performance, several indices are often used to determine these parameters, including signal-to-noise, amplification factor, and cross-correlation coefficient. Nevertheless, for a linear frequency modulated (LFM) signal, such indices may no longer work and consequently make SR unable to recover the unknown LFM signal from raw signals. Thus, this limits the application of SR to some extent. To deal with this problem, we define here a new index to characterize the unknown LFM signal with the help of the fractional Fourier transform. Guided by this index, SR is thus able to recover the unknown LFM signal from the raw signal. In addition, a cloud model based genetic algorithm is used to achieve an adaptive SR in order to improve the effectiveness of signal processing.
Shape evolutions of moving fluid threads under asymmetrical confinements
Authors: Wang Bo , Zhang Shuai , Chen Xiaodong
Published: April 2020

This paper presents a combined experimental and numerical investigation designed to improve our understanding of how the shape of moving fluid threads evolves under asymmetrical confinements in both circular and square microchannels. Microfluidic devices with two junctions are designed to control the length of the fluid thread at the first junction and the deformation of the fluid thread at the second junction. Three different flow modes: nonbreakup, loosely confined breakup, and tightly confined breakup, are identified for varying lengths of fluid threads and capillary number, and two boundaries are identified between the three modes. The deformation dynamics of the fluid threads evolving as difference modes are addressed to consider the effects of thread length and capillary number. Numerical simulations are carried out to determine how the curvature evolves for different flow modes in the square microchannel. The evolution of interface profiles is obtained numerically over a wide range of capillary number. Stop-flow simulations are then carried out to identify both the critical shape for the onset of the capillary instability during tightly confined breakup and the corresponding curvature distribution. This critical shape is found to be corresponding to the fluid thread with the critical length at the transitive boundary between the loosely confined and tightly confined situations.
Engineering optical anisotropy in nonlinear crystals with ultrafast light
Authors: Karpinski Pawel , Shvedov Vladlen , Krolikowski Wieslaw , Hnatovsky Cyril
Published: April 2020

Photonic technology is widely based on anisotropic (and) nonlinear materials, which allow light modulation and parametric light conversion. Because the number of naturally occurring crystals is limited, there is a growing demand for artificial metamaterials with optical properties specifically tailored to a given application. Here, we utilize the top-down method to synthesize sub-wavelength periodic nanostructures inside a uniaxial optically nonlinear crystal (lithium niobate, LiNbO3) by irradiating it with multiple femtosecond laser pulses. By superimposing form-birefringence associated with the light-induced nanostructures onto natural birefringence of the host crystal we create macroscopic domains of a biaxial metamaterial embedded into otherwise uniaxial medium.
Variation in guided streamer propagation along a DBD plasma jet by tailoring the applied voltage waveform
Authors: Pinchuk M. E. , Stepanova O. M. , Gromov M. , Leys Ch. , Nikiforov A.
Published: April 2020

Experimental data on the evolution of a helium atmospheric pressure plasma jet driven by two different voltage waveforms are presented. The characteristics of directed ionization waves (guided streamers) were compared for a sinusoidal voltage waveform with a frequency of 52 kHz and a voltage waveform that was formed via the superposition of 41.6 kHz bipolar square pulses and 300 kHz oscillations. With the sinusoidal voltage, two consecutive ionization waves were observed. With a special tailoring voltage, control of the guided streamer propagation in a stepwise mode was achieved. The observed second streamer and the second step of propagation could be regarded as a secondary ionization wave for both voltages. A change in the voltage waveform led to significant variations in the secondary ionization wave formation and streamer parameters. The voltage waveform enabled the number of ionization waves and their propagation to change, which provided the possibility of controlling the plasma parameters of the jet.
Pulsed optically pumped atomic clock with a medium- to long-term frequency stability of 10−15
Authors: Shen Qian , Lin Haixiao , Deng Jianliao , Wang Yuzhu
Published: April 2020

Herein, we report a significant improvement in the medium- to long-term frequency stability of our pulsed optically pumped (POP) vapor-cell rubidium clock. Such an achievement is established with the better control of our system and the environment. An integrated optical module, including a distributed Bragg reflector laser and an acousto-optic modulator, is developed to improve the stability of the laser. The physics package is sealed in a vacuum chamber with a vacuum of 4 × 10−4 Pa to significantly reduce the impacts of the barometric effect. An AC-driven heater is placed much closer to the cell to enable a better temperature control. The resolution of the servo control voltage is also optimized. With all these improvements, a frequency stability of 4.7 × 10−15 at 104 s in terms of the Allan deviation is obtained. We also estimate the main noise sources that limit the frequency stability of the POP atomic clock.