bluuebunny/crossref_metadata_2025 huggingface dataset:
Monte Carlo calculations of the atmospheric sputtering yields on Titan
Authors: Gu H. , Cui J. , Niu D.-D. , Wellbrock A. , Tseng W.-L. , Xu X.-J.
Published: February 2019

Context. Sputtering serves as an important mechanism of atmospheric escape in the solar system.

Aims. This study is devoted to atmospheric sputtering on Titan, with a special focus on how the N2 and CH4 sputtering yields respond to varying ion incidence energy and angle, and varying ion mass.

Methods. A Monte Carlo model was constructed to track the energy degradation of incident ions and atmospheric recoils from which the sputtering yields were obtained. A large number of model runs were performed, taking into account three categories of incident ion with representative masses of 1, 16, and 28 Da, as well as two collision models both characterized by a strongly forward scattering angle distribution, but different in terms of the inclusion or exclusion of electronic excitation of ambient neutrals.

Results. Our model calculations reveal substantial increases in both the N2 and CH4 sputtering yields with increasing ion incidence energy and angle, and increasing ion mass. The energy distribution of escaping molecules is described reasonably well by a power law, with an enhanced high energy tail for more energetic incident ions and less massive atmospheric recoils. The CH4-to-N2 sputtering yield ratio is found to range from 10 to 20%, increasing with increasing incidence angle and also increasing with decreasing incidence energy. An approximate treatment of ion impact chemistry is also included in our model, predicting N2 sputtering yields on Titan that are in broad agreement with previous results.
Eruptions from quiet Sun coronal bright points
Authors: Galsgaard Klaus , Madjarska Maria S. , Mackay Duncan H. , Mou Chaozhou
Published: February 2019

Context. Our recent observational study shows that the majority of coronal bright points (CBPs) in the quiet Sun are sources of one or more eruptions during their lifetime.

Aims. Here, we investigate the non-potential time-dependent structure of the magnetic field of the CBP regions with special emphasis on the time-evolving magnetic structure at the spatial locations where the eruptions are initiated.

Methods. The magnetic structure is evolved in time using a non-linear force-free field (NLFFF) relaxation approach based on a time series of helioseismic and magnetic imager (HMI) longitudinal magnetograms. This results in a continuous time series of NLFFFs. The time series is initiated with a potential field extrapolation based on a magnetogram taken well before the time of the eruptions. This initial field is then evolved in time in response to the observed changes in the magnetic field distribution at the photosphere. The local and global magnetic field structures from the time series of NLFFF field solutions are analysed in the vicinity of the eruption sites at the approximate times of the eruptions.

Results. The analysis shows that many of the CBP eruptions reported in a recent publication contain a twisted flux tube located at the sites of eruptions. The presence of flux ropes at these locations provides in many cases a direct link between the magnetic field structure, their eruption, and the observation of mini coronal mass ejections (mini-CMEs). It is found that all repetitive eruptions are homologous.

Conclusions. The NLFFF simulations show that twisted magnetic field structures are created at the locations hosting eruptions in CBPs. These twisted structures are produced by footpoint motions imposed by changes in the photospheric magnetic field observations. The true nature of the micro-flares remains unknown. Further 3D data-driven magnetohydrodynamic modelling is required to show how these twisted regions become unstable and erupt.
Speckle decorrelation with wavelength shift as a simple way to image transport mean free path
Authors: Mikhailovskaya Alesya , Fade Julien , Crassous Jérôme
Published: February 2019

We present an experimental scheme for determining the light transport properties of random disordered materials. The sample is illuminated with a laser and the speckle patterns obtained at different wavelengths are recorded with a camera. The transport mean free path is then deduced from the correlation functions of the scattered intensities. This method is tested on two kinds of random materials: colloidal particles dispersed into a polymeric matrix and on granular material made of glass beads. The possibility to image a material with a disorder varying at large scale is finally presented.
Neue Rollen in der Pflege
Authors: Maier Julia
Published: February 2019

Seit drei Jahren arbeitet die Selbstverwaltung mit viel Energie daran, die
Vorgaben in puncto Qualität aus dem Krankenhausstrukturgesetz umzusetzen. Eine
wichtige Rolle dabei spielt das Institut für Qualitätssicherung und Transparenz
im Gesundheitswesen – IQTIG.
Arbeitgeberattraktivität: Machbare Kunststücke
Authors: Dernedde Jutta
Published: February 2019

Es ist vermutlich kein Geheimnis, dass Krankenhäuser zu den Unternehmen gehören, denen auch in diesem Jahr das ein oder andere Kunststück abverlangt werden wird. Zum Beispiel gibt es da diesen besonderen Spagat, bereits vorhandene Stellen auf Stationen mit Fachkräften zu besetzen, die es in dem erforderlichen Maße bundesweit heute gar nicht mehr gibt.
Telemedizin: Medgate Deutschland will Marktführer werden
Authors: Kucera Martin
Published: February 2019

Das Schweizer Unternehmen Medgate betreibt das größte ärztliche telemedizinische Zentrum Europas. Jetzt hat die Rhön-Klinikum AG eine Absichtserklärung zur Gründung einer gemeinsamen Gesellschaft mit dem Telemedizinanbieter unterzeichnet. Erklärtes Ziel beider Unternehmen ist die Marktführerschaft in Deutschland.
35-Stunden-Woche: Frankfurter „Image-Pflege“
Authors: Kohrs Jens
Published: February 2019

Im Ringen um Fachkräfte haben die Frankfurter Rotkreuz-Kliniken die nächste Runde eingeläutet. Für alle stationären Pflegekräfte gilt die 35-Stunden-Woche bei vollem Gehaltsausgleich. Ein Gespräch mit der Vorstandsvorsitzenden Karin Schoppet und dem Geschäftsführer Finanzen und Strategie, Gunnar Sevecke.
med.Logistica: Die Zukunft der Krankenhauslogistik im Fluss
Authors: Nöllgen Karolin
Published: February 2019

Am 5. und 6. Juni 2019 versammelt sich die internationale Expertise der Krankenhauslogistik in Leipzig. Auf dem Programm des Kongresses mit Fachmesse für Logistik und Prozessmanagement im Krankenhaus stehen aktuelle Best-Practices von der Bauplanung bis zur OP-Logistik.
Hauptstadtkongress: Der Patient im Zentrum
Authors: Dorner Carola
Published: February 2019

„Kerngeschäft ist der Patient“ heißt eine Session beim diesjährigen Hauptstadtkongress. Eigentlich sollte Patientenzentrierung im Gesundheitssystem eine Selbstverständlichkeit sein. Tatsächlich bedeutet das nichts anderes als einen Paradigmenwechsel, sagt Prof. Dr. Volker Penter von der KPMG AG.
Manager des Jahres 2018: Alexander Schmidtke: Keine Angst vor Mammutaufgaben
Authors: Kohrs Jens
Published: February 2019

Wirtschaftlich konsolidieren, Generalsanierung einleiten, Übergang zur Uniklinik vorbereiten – die Erwartungen waren hoch, als Alexander Schmidtke vor neun Jahren das Klinikum Augsburg übernahm. Seitdem hat sich viel verändert. Zwei Phasen hat der umtriebige Manager erfolgreich abgeschlossen – und mittlerweile schon die nächste Herausforderung für sich gefunden.
Senkrechtstarter 2018: PD Dr. Felix Nensa: Vorreiter der Medizin von morgen
Authors: Doelfs Guntram
Published: February 2019

Während andere weiter über die Digitalisierung im Gesundheitswesen reden, forscht der Radiologe PD Dr. Felix Nensa von der Uniklinik Essen längst an der Medizin der Zukunft. Er entwickelt mithilfe künstlicher Intelligenz Anwendungen, von denen Mediziner wie Patienten gleichermaßen profitieren werden.
Ausländische Mitarbeiter: Integration mit Tücken
Authors: Holldorf Lars
Published: February 2019

Viele Krankenhäuser versuchen, ihre Personalnot mithilfe ausländischer Ärzte und Pflegekräfte zu lindern. Bei den Medizinern ist das nicht neu, doch bei Pflegekräften sind die Erfahrungen noch sehr begrenzt. Deshalb passieren meistens teure Fehler, die schon vorab vermieden werden könnten.
Sprechstunde in der PR-Ambulanz: Warum brauche ich für meine Klinik eine Vision?
Authors: Endele Kerstin
Published: February 2019

Kerstin Endele ist zur Hälfte Journalistin und zur Hälfte Biochemikerin. Seit mehr als 15Jahren ist sie Expertin für Gesundheitskommunikation und war fünf Jahre Kommunikationschefin und Pressesprecherin der Charité. Wenn sie nicht Klinikvorstände aus Krisen rettet und Pressesprechern diverser Krankenhäuser dabei hilft, ein bisschen Strategie ins übliche Chaos zu bringen, betreibt sie mit der PR-Ambulanz (www.pr-ambulanz.com) einen der größten Blogs zur Klinikkommunikation in Deutschland.
Evidence for a Radical Mechanism in Cu(II)-Promoted SnAP
Reactions
Authors: Luescher Michael , Bode Jeffrey
Published: February 2019

Saturated nitrogen heterocycles can be found with increasing abundance in bioactive molecules despite a limited number of methods to access these scaffolds. However, the coupling of recently introduced SnAP [tin (Sn) amine protocol] reagents with a wide range of aldehydes and ketones has proven to be a reliable, practical, and versatile one-step approach to saturated N-heterocycles. While effective, the lack of mechanistic understanding limits efforts to develop new catalytic and enantioselective variants. To distinguish between a polar or radical mechanism, we assessed Lewis and Brønsted acids, radical trapping experiments, and radical clock SnAP reagents reinforcing the current understanding of the SnAP protocol as a radical cyclization.
A “Green” Primary Explosive: Design, Synthesis, and Testing
Authors: Tang Jie , Chen Dan , Zhang Gen , Yang Hongwei , Cheng Guangbin
Published: February 2019

This account presents the synthesis and the characterization of triazine-tetrazine nitrogen heterocyclic compounds. Some compounds were characterized by NMR and IR spectroscopy, mass spectrometry, differential scanning calorimetry (DSC), and single-crystal X-ray diffraction. The physical and chemical properties were obtained by EXPLO5 v6.01, gas pycnometer, BAM Fallhammer, BAM Friction tester, and several detonation tests. The results show that the new metal-free polyazido compound 3,6-bis-[2-(4,6-diazido-1,3,5-triazin-2-yl)-diazenyl]-1,2,4,5-tetrazine (4) with high heat of formation (2820 kJ mol–1/6130.2 kJ kg–1) and excellent detonation velocity and pressure (D = 8602 m s–1, P = 29.4 GPa) could be used as ingredient in secondary explosives. 3,6-Bis-[2-(4,6-diazido-1,3,5-triazin-2-yl)-hydrazinyl]-1,2,4,5-tetrazine (3) can detonate research department explosive (RDX, cyclonite) as a primer (Δf
H
m = 2114 kJ mol–1/4555.2 kJ kg–1, D = 8365 m s–1, P = 26.8 GPa), whose initiation capacity is comparable to that of the traditional primary explosive Pb(N3)2. Therefore, the metal-free compound 3 can potentially replace lead-based-primary explosives, which would be advantageous for the environment.

1 Introduction

2 Strategies to Form High-Nitrogen Compounds with High Heat of Formation

3 Metal-Free Strategies to Prepare Primary Explosives

4 Concluding Remarks
Organoselenium-Catalyzed Polymerization of Aniline with Hydrogen Peroxide as Oxidant
Authors: Gao Ge , Han Jie , Yu Lei , Xu Qing
Published: February 2019

A convenient method for the synthesis of polyanilines was developed through the organoselenium-catalyzed oxidation of anilines with H2O2. Unlike reported methods, this reaction generates no wastes other than water. These green features make the method much more practical in terms of large-scale preparation. Moreover, it is the first example of an application of organoselenium catalysis techniques in aniline polymerization reactions and might be an important advance in the fields of both organoselenium catalysis and polyanilines.
Rock-Hard Chronic Thrombotic Occlusion and Its Management in Endovascular Interventions
Authors: Madassery Sreekumar
Published: February 2019

Endovascular recanalization for patient with peripheral arterial disease and the end of its spectrum critical limb ischemia (CLI) has become a preferred method of revascularization due to advancement of techniques and equipment, allowing reduction of limb amputations while maintaining a minimally invasive approach compared to surgical approaches. Interventionalists have undertaken a progressively increasing complexity of diseased vessels in the hopes of providing inline unobstructed flow through occlusions for patients with claudication as well as direct flow to a nonhealing wound in patients with CLI. One of the major roadblocks encountered in lower extremity recanalization procedures is managing severely calcified chronic thrombotic occlusions which decrease luminal revascularization, ultimately increasing use of adjunctive interventions such as subintimal tracking, reentry device utilization, and stent placement. Understanding the histopathology and classification of lower extremity calcifications, imaging findings, and escalation of equipment use provides a thorough background in dealing with these specific cases.
Multidisciplinary Approach to PAD: Who's on Your Team?
Authors: Dhand Sabeen
Published: February 2019

The complexity of peripheral arterial disease (PAD) and its multiorgan involvement requires the utilization of a multispecialty team approach. Members of this team include a vascular specialty (interventional radiology, cardiology, and vascular surgery), podiatry, orthopedic surgery, primary care, infectious disease, endocrinology, plastic surgery, wound care nursing, and dietetics. A team approach has been proven to significantly improve patient outcomes as well as decreasing amputation rates. In order to promote collaboration and avoid duplication of care, the team can be broken down into three main pillars: medical management, wound care, and revascularization. A complete team approach is vital for this population, with an overall goal to treat all manifestations of the disease and prevent further progression and risk of major sequelae of the disease.
Clinical Assessment of Peripheral Arterial Disease in the Office: What Do the Guidelines Say?
Authors: Scherbel Derek , Tummala Srini
Published: February 2019

Lower extremity peripheral arterial disease (PAD) is the manifestation of atherosclerotic disease within the lower extremities. The presentation of PAD is diverse ranging from asymptomatic disease to claudication or to debilitating rest pain, nonhealing ulcers, and gangrene. PAD is associated with significant morbidity, mortality, and healthcare costs. Proper diagnosis and management of PAD is important so as to maintain quality of life and reduce the risk of cardiovascular disease and adverse limb events such as amputation. This document provides a comprehensive outpatient approach to the clinical assessment of PAD that includes risk factors, diagnosis, treatment, and follow-up options.
Evidence-Based Interventions for Adult Aural Rehabilitation: That Was Then, This Is Now
Authors: Maidment David , Henshaw Helen , Heffernan Eithne , Ferguson Melanie
Published: February 2019

More than a decade after Arthur Boothroyd published “Adult Aural Rehabilitation: What Is It and Does It Work?,” the four cornerstones of adult aural rehabilitation are re-examined in terms of research that we and others in the field have undertaken. The focus is on novel advances in high-quality research relating to interventions to support self-management for hearing aids and other listening devices (sensory management), knowledge and skill (instruction), auditory and cognitive training (perceptual training), and motivational engagement (counseling). Much of this new research has a theoretical underpinning (e.g., behavior change theory) to better guide the development and evaluation of interventions, with a focus on self-management and patient-centered approaches. New and emerging technologies that support e- and m-health delivery of interventions provide greater personalization and interactivity to promote self-management of hearing loss. Looking to the future, there remains a requirement for a set of relevant and appropriate outcome measures to evaluate the effectiveness of interventions trialed in clinical studies. There is a continuing need for high-quality evidence, underpinned by contemporary theory, to increase the likelihood that translational adult aural rehabilitation research that aims to benefit patients will be applied in future clinical practice.
Potential of Multidimensional, Large-scale Biodatabases to Elucidate Coagulation and Platelet Pathways as an Approach towards Precision Medicine in Thrombotic Disease
Authors: Panova-Noeva Marina , Eggebrecht Lisa , Prochaska Jürgen H. , Wild Philipp S.
Published: February 2019

Cardiovascular and especially thrombotic diseases remain a major cause of morbidity and mortality worldwide. In past years, significant improvements in understanding disease processes, risk assessment, and prediction of clinical outcome in the field of thrombosis and haemostasis have been made by using large-scale biodatabases. These important research resources enable a comprehensive research approach by integrating clinical, environmental, genomic, and molecular information. Cutting edge, high throughput technologies open new data dimensions for clinical large-scale investigations. Joining multiple information levels from several pathophysiological pathways in contrast to a single marker approach might better model the complexity of disease pathogenesis. This review focuses on the possibilities that ultimately allow conducting wide-scale analyses for unravelling the multifaceted interplay between coagulation and cellular (e.g., platelets) elements in the development of thrombotic disease. It further provides examples for the use of biodatabases in the field of venous thromboembolism, explores the links between venous and arterial thrombotic diseases, and finally informs on the current use of platelet biomarkers in the thrombosis and haemostasis field.
Teaching digital fiction: integrating experimental writing and current technologies
Authors: Skains R. Lyle
Published: February 2019

Today’s creative writers are immersed in a multiplicative, multimodal—digital—universe. It requires “multiliteracies”, all in a constantly and rapidly evolving technological environment, which are not yet fundamentally integrated into the basic literacy skills entrenched in school learning. How can creative writing instructors in higher education best prepare their students for the real-world contexts of their creative practice? One approach is to integrate the creative writing workshop with a focus on digital and interactive design. This paper outlines a module incorporating multiple literacies into a creative writing course, Playable Fiction, noting the affordances, limitations, and benefits of teaching workshops for writing digital fiction (“born-digital” fiction, composed for and read on digital devices). The researcher took an ethnographical approach to the question, designing a module to encourage creative writing students to experiment with digital fiction, and observing the effects on the students’ attitudes and their coursework. Included is a discussion of the benefits to students of developing multiliteracies and considerations for teaching, including issues of technical know-how and the lack of infrastructural support. Finally, the paper describes the model class taught to second-year and third-year undergraduates in the ‘Games Design and Professional Writing' programs at Bangor University, in the UK, including marking recommendations and reading list advice.
Second harmonic generation by crossed surface plasma waves over a metallic surface
Authors: Jatav Priyanka , Parashar Jetendra
Published: February 2019

Excitation of second harmonic radiation by nonlinear mixing of two surface plasma waves (SPWs), propagating at an angle to each other over an air–metal interface, is investigated. The SPWs exert a ponderomotive force on electrons, driving a nonlinear surface current and producing the second harmonic. Depending upon the angle between the SPWs and the electron density of metals, the excited radiation could be a radiation mode or a surface mode. The latter requires a surface ripple for phase matching. The efficiency of radiative second harmonic increases with the free electron density of the metal. It is sensitive to the angle between the interacting SPWs. The surface mode second harmonic is relatively more efficient.
Elastic-plastic deformation of molybdenum single crystals shocked to 12.5 GPa: Crystal anisotropy effects
Authors: Mandal A. , Gupta Y. M.
Published: February 2019

To understand crystal anisotropy effects on shock-induced elastic-plastic deformation of molybdenum (Mo), results from high-purity single crystals shocked along [110] and [111] orientations to an elastic impact stress of 12.5 GPa were obtained and compared with the [100] results previously reported [A. Mandal and Y. M Gupta, J. Appl. Phys. 121, 045903 (2017)]. Measured wave profiles showed a time-dependent response, and strong anisotropy was observed in the elastic wave attenuation with the propagation distance, elastic limits, shock speeds, and overall structure of the wave profiles. Resolved shear stresses on {110}〈111〉 and {112}〈111〉 slip systems provided insight into the observed anisotropy in elastic wave attenuation and elastic limits and showed that shear stresses, and not longitudinal stresses, are a better measure of strength in shocked single crystals. Under shock compression, resolved shear stresses at elastic limits were comparable to the Peierls stress of screw dislocations in Mo. Elastic wave attenuation was rapid when shear stresses were larger than the Peierls stress. Large differences in the elastic limits under shock and quasi-static loading are likely a consequence of the large Peierls stress value for Mo. Numerically simulated wave profiles, obtained using the dislocation-based plasticity model described in the [100] work, showed good agreement with all measured wave profiles but could not differentiate between the {110}〈111〉 and {112}〈111〉 slip systems. Overall, experimental results and corresponding numerical simulations for the three crystal orientations have provided a comprehensive insight into shock-induced elastic-plastic deformation of Mo single crystals, including the development of a continuum material model.
Direct observation of long distance lateral transport in InGaN/GaN quantum wells
Authors: Dróżdż Piotr A. , Korona Krzysztof P. , Sarzyński Marcin , Grzanka Szymon , Czernecki Robert , Suski Tadeusz
Published: February 2019

The horizontal excitation energy transport in the range of tens of micrometers was measured in high quality homoepitaxial InGaN quantum wells (QWs) with the use of time and space resolved micro-photoluminescence as a function of (i) applied vertical electric field, (ii) temperature, and (iii) linear density of atomic steps. The investigated structure consisted of InGaN QWs inside a p-n junction. The indium content in QWs was designed to be different in defined areas of the sample (due to mastering of different off-cuts and atomic steps density) so that the wells could emit at energies from 2.6 to 2.86 eV. The horizontal transport range was sensitive to the vertical electric field, which means that it could not be just a radiation transfer, but charge carriers must have been involved as well. We found that the transport range decreased for higher slope angles, possibly due to stronger scattering on atomic steps when their linear density became higher. The diffusion coefficients reached 6 cm2/s and due to long lifetime of even 2 μs, the diffusion length was even LD = 30 μm in areas of low off-cut angles. We discuss possible mechanisms of transport and conclude that for such high diffusion constant, the most probable is the excitonic transport. The LD was maximum at 40 K and then decreased significantly with temperature, which was probably caused by thermal dissociation of excitons.
Influence of water quality on the tip vortex cavitation inception
Authors: Chen Linya , Zhang Lingxin , Peng Xiaoxing , Shao Xueming
Published: February 2019

Tip vortex cavitation (TVC) is an important type of cavitation. There is an urgent need for the accurate prediction of its inception condition. The water quality, i.e., the distribution of nuclei, is one of the main contributors to the TVC inception. Since there is no available cavitation model involving the effect of water quality, a new model suitable for TVC prediction is investigated based on the bubble dynamics. The migration and growth of nuclei are simulated in a tip vortex flow. An analytic method is developed to calculate the capture time of nuclei so that we can determine the critical nucleus in a vortex flow according to a filtering principle. The comparisons of the effect of water quality obtained in simulations and analytics are performed. It validates that the embodiment of water quality is rational and the analytical method is applicable for engineering purpose. Finally, the prediction model is quantitatively improved by considering the effect of water quality, and it is a new model for the prediction of tip vortex cavitation inception.
Modeling cardiac complexity: Advancements in myocardial models and analytical techniques for physiological investigation and therapeutic development in vitro
Authors: Callaghan Neal I. , Hadipour-Lakmehsari Sina , Lee Shin-Haw , Gramolini Anthony O. , Simmons Craig A.
Published: February 2019

Cardiomyopathies, heart failure, and arrhythmias or conduction blockages impact millions of patients worldwide and are associated with marked increases in sudden cardiac death, decline in the quality of life, and the induction of secondary pathologies. These pathologies stem from dysfunction in the contractile or conductive properties of the cardiomyocyte, which as a result is a focus of fundamental investigation, drug discovery and therapeutic development, and tissue engineering. All of these foci require in vitro myocardial models and experimental techniques to probe the physiological functions of the cardiomyocyte. In this review, we provide a detailed exploration of different cell models, disease modeling strategies, and tissue constructs used from basic to translational research. Furthermore, we highlight recent advancements in imaging, electrophysiology, metabolic measurements, and mechanical and contractile characterization modalities that are advancing our understanding of cardiomyocyte physiology. With this review, we aim to both provide a biological framework for engineers contributing to the field and demonstrate the technical basis and limitations underlying physiological measurement modalities for biologists attempting to take advantage of these state-of-the-art techniques.
Thermophotonic cooling in GaAs based light emitters
Authors: Radevici Ivan , Tiira Jonna , Sadi Toufik , Ranta Sanna , Tukiainen Antti , Guina Mircea , Oksanen Jani
Published: February 2019

Fundamental thermodynamic considerations reveal that efficient emission from an electrically injected light emitting diode (LED) can lead to the cooling of the device. This effect, known as electroluminescent (EL) cooling, has been identified decades ago, but it has not been experimentally demonstrated in semiconductors at practical operating conditions due to the extreme requirements set for the efficiency of the light emission. To probe the conditions of EL cooling in GaAs based light emitters, we have designed and fabricated LED structures with integrated photodiodes (PDs), where the optically mediated thermal energy transport between the LED and the PD can be easily monitored. This allows characterization of the fundamental properties of the LED and a path for eliminating selected issues encountered in conventional approaches for EL cooling, such as the challenging light extraction. Despite several remaining nonidealities, our setup demonstrates a very high directly measured quantum efficiency of 70%. To characterize the bulk part of the LED, we also employ a model for estimating the power conversion efficiency (PCE) of the LED, without the contribution of non-fundamental nonidealities such as photodetection losses. Our results suggest that the PCE of the LED peaks at around 105–115%, exceeding the 100% barrier required to reach the EL cooling regime by a clear margin. This implies that the LED component in our device is in fact cooling down by transporting thermal energy carried by the emitted photons to the PD. This provides a compelling incentive for further study to confirm the result and to find ways to extend it for practically useful EL cooling.
Helical vortex core dynamics and flame interaction in turbulent premixed swirl combustion: A combined experimental and large eddy simulation investigation
Authors: Taamallah S. , Dagan Y. , Chakroun N. , Shanbhogue S. J. , Vogiatzaki K. , Ghoniem A. F.
Published: February 2019

In this study, a combined experimental and Large Eddy Simulation (LES) investigation is performed to identify the vortical structures, their dynamics, and interaction with a turbulent premixed flame in a swirl-stabilized combustor. Our non-reacting flow experiment shows the existence of large scale precessing motion, commonly observed for such flows. This off-axis precessing dynamics disappears with combustion but only above a critical equivalence ratio at which the flame attaches to the swirler centerbody and vortex breakdown changes from a cone to a bubble type. For compact flames stabilized along the inner shear layer (ISL), no precessing is seen, but large scale vortices along the ISL are observed; these structures interact with the ISL-stabilized flame and contribute to its wrinkling as revealed by laser-induced fluorescence data. After validating the LES results in terms of low order statistics and point temperature measurements in relevant areas of the flow, we show that it can capture the precessing motion in the non-reacting flow and its suppression with combustion. The simulations show that the ISL vortices in the reacting case originate from a vortex core that is formed at the swirler’s centerbody. This vortex core has a conical helical shape that interacts—as it winds out—with the ISL and the flame stabilized along it. The simulated helical vortex core (HVC) exists in both reacting and non-reacting flows; in the latter, it is dominated by the off-axis motion, whereas in the reacting case, that motion is damped and only remains the cork-screw type solid body rotation of the HVC.
An ultra-flexible modular high vacuum setup for thin film deposition
Authors: Götsch Thomas , Wernig Eva-Maria , Klötzer Bernhard , Schachinger Thomas , Kunze-Liebhäuser Julia , Penner Simon
Published: February 2019

A modular high vacuum chamber dedicated to thin film deposition is presented. We detail the vacuum and gas infrastructure required to operate two highly flexible chambers simultaneously, with a focus on evaporation techniques (thermal and electron beam) and magnetron sputtering, including baking equipment to remove residual water from the chamber. The use of O-ring-sealed flat flanges allows a tool-free assembly process, in turn enabling rapid changes of the whole setup. This leads to a high flexibility regarding the deposition techniques as the chamber can be adapted to different sources within minutes, permitting the formation of multilayer systems by consecutive depositions onto the same substrate. The central piece of the chamber is a flat flange ground glass tube or cross. The glass recipient permits optical monitoring of the deposition process. Further equipment, such as for the introduction of gases, additional pressure gauges, or evaporators, can be incorporated via specifically designed stainless steel/aluminum interconnectors and blank flanges. In the end, we demonstrate the preparation of an unsupported thin film system consisting of electron-beam-evaporated platinum nanoparticles embedded in magnetron-sputtered zirconia (ZrO2), deposited onto NaCl single crystals, which subsequently can be removed by dissolution. These films are further analyzed by means of transmission electron microscopy, X-ray photoelectron spectroscopy, and atomic force microscopy.
Magneto-mechanical trapping of micro-diamonds at low pressures
Authors: O'Brien M. C. , Dunn S. , Downes J. E. , Twamley J.
Published: February 2019

A number of quantum technologies require macroscopic mechanical oscillators possessing ultra-high motional Q-factors. These can be used to explore the macroscopic limits of quantum mechanics, to develop quantum sensors and to test the quantum nature of gravity. One approach is to trap nanometer to micron-sized particles in 3D; however, the use of ion or optical traps suffers from a number of difficulties including electrodynamic noise due to patch fields, damage to the particles due to unwanted laser heating, or difficulty in reaching low pressures due to particle loss. In this work, we report a completely passive, magnetic trap which confines a micro-diamond in 3D and which requires no active power—optical or electrical. We design, model, fabricate, and test the operation of our magneto-mechanical trap and experimentally demonstrate trapping down to ∼0.1 Torr. We measure the position fluctuation of the trapped micro-diamond as a function of pressure and find good agreement with Brownian theory.
Effect of compressibility on small scale statistics in homogeneous shear turbulence
Authors: Chen Song , Wang Jianchun , Li Hui , Wan Minping , Chen Shiyi
Published: February 2019

The effect of compressibility on the small scale properties of stationary homogeneous shear turbulence (HST) is studied in a rectangular domain of size 4π × 2π × 2π by numerical simulations at four turbulent Mach numbers of Mt = 0.14, 0.2, 0.4, and 0.6. Compared to the compressible homogeneous isotropic turbulence (HIT), the small scale properties of HST are more sensitive to Mach number change and the velocity derivatives show a clear deviation from isotropy. At Mt = 0.14, the preferred eigenvalue ratio of the strain rate tensor is very close to −4:1:3 reported in incompressible turbulence. As Mt increases, the conditional probability density functions of the normalized eigenvalues become more dependent on the dilatation, and its ratio tends to −1:0:0 in the strong compression regions at Mt = 0.6, indicating the sheet-like structures of localized shock waves. The alignments between vorticity and eigenvectors are similar to the observations in HIT. After the Helmholtz decomposition, it is found that the compressible vortex stretching term is the primary cause for the enhancement of enstrophy production at high turbulent Mach numbers.
In situ beta radiation monitoring system with enhanced efficiency for water samples from decommissioned nuclear environment
Authors: Lee UkJae , Choi Woo Nyun , Kim Min Ji , Kim Hee Reyoung
Published: February 2019

A nuclear environment, including decommissioning activity contains various radioactive nuclides such as pure beta emitters. These radionuclides should be monitored to ensure radiological safety. In particular, beta radionuclides, such as 3H and 14C, can cause internal exposures and should be managed more strictly in terms of health physics. For beta radionuclides, the measurement is carried out in a laboratory through sampling rather than on-site because of the short range. This method is time consuming, laborious, and costly and can also generate secondary waste. In this study, a system for the in situ monitoring of beta radionuclides in water samples is proposed for nuclear facilities and decommissioned environments. A plastic scintillator with low sensitivity to gamma rays and good reactivity with beta radionuclides was used. The detection efficiency was increased by using a detection part, whereby the water sample is made to directly contact the scintillator by utilizing the characteristic of plastic scintillators (i.e., they do not react with water). A coincidence circuit was constructed by using multiple photomultiplier tubes (PMTs) and applied to gross beta activity measurements. The values obtained from a single PMT were used in the spectral analysis to determine the effect of each beta radionuclide. Beta radionuclides in water samples in the field can be monitored by using plastic scintillators and multiple PMTs.
Analytic band-to-trap tunneling model including band offset for heterojunction devices
Authors: Gao Xujiao , Kerr Bert , Huang Andy
Published: February 2019

We present an analytic band-to-trap tunneling model based on the open boundary scattering approach. The new model has three major advantages: (i) It includes not only the well-known electric field effect, but more importantly, the effect of heterojunction band offset. This feature allows us to simulate both electric field and band offset enhanced carrier recombination near a heterojunction in heterostructures. (ii) Its analytic form enables straightforward implementation into a parallel Technology Computer Aided Design device and circuit simulators. (iii) The developed method can be used for any potentials which can be approximated to a good degree such that the Schrödinger equation with open boundary conditions results in piecewise analytic wave functions. Simulation results of an InGaP/GaAs heterojunction bipolar transistor (HBT) reveal that the proposed model predicts significantly increased base currents, because the tunneling of holes in the base to traps in the emitter is greatly enhanced by the emitter-base band offset. This finding, which is not captured by existing band-to-trap tunneling models, is consistent with the experimental observation for an InGaP/GaAs HBT after neutron irradiation.
Acceleration region dynamics in a magnetically shielded Hall thruster
Authors: Cusson Sarah E. , Dale Ethan T. , Jorns Benjamin A. , Gallimore Alec D.
Published: February 2019

The influence of the cathode flow fraction and facility background pressure on the acceleration region of a magnetically shielded Hall thruster is experimentally characterized. The location of the acceleration region is measured using laser-induced fluorescence on H9, a 9-kW class Hall thruster, for six different facility background pressures and four different cathode flow fractions. The results show that when the facility pressure is increased from 7.1 × 10– 6 to 3.0 × 10– 5 Torr-Xe, the acceleration region shifts inward 1.6 ± 0.5 mm. Similarly, when the cathode flow fraction is increased from 7% to 15%, the acceleration region shifts inward 0.9 ± 0.5 mm. This experiment leads to two conclusions. First, introducing neutrals in the cathode region can directly impact the acceleration mechanism in the thruster. Second, changing the cathode flow fraction affects the acceleration region of the thruster in a similar manner as the background pressure. This result is discussed in the context of the neutral density environment created by both injection schemes. Calculations of this parameter show that the increase in neutral density in the proximity of the acceleration region is similar when varying the background pressure and changing the cathode flow fraction. This provides correlational evidence linking the role of neutral density to the acceleration region shift.
Thermodynamic picture of vitrification of water through complex specific heat and entropy: A journey through “no man’s land”
Authors: Saito Shinji , Bagchi Biman
Published: February 2019

We investigate thermodynamic properties of supercooled water across the “no man’s land” onto the formation of amorphous ice. The calculations are aided by very long computer simulations, often more than 50 μs long, with the TIP4P/2005 model potential. Density fluctuations that arise from the proximity to a putative liquid-liquid (LL) transition at 228 K, cast a long shadow on the properties of water, both above and below the LL transition. We carry out the calculations of the quantum mechanical static and frequency-dependent specific heats by combining seminal studies of Lebowitz, Percus, and Verlet and Grest and Nagel with the harmonic approximation for the density of states. The obtained values are in quantitative agreement with all available experimental and numerical results of specific heats for both supercooled water and ice. We calculate the entropy at all the state points by integrating the specific heat. We find that the quantum corrected-contributions of intermolecular vibrational entropy dominate the excess entropy of amorphous phases over the crystal over a wide range of temperatures. Interestingly, the vibrational entropy lowers the Kauzmann temperature, TK, to 130 K, just below the experimental glass-to-liquid water transition temperature, Tg, of 136 K and the calculated Tg of 135 K in our previous study. A straightforward extrapolation of high temperature entropy from 250 K to below however would give a much higher value of TK ∼ 190 K. The calculation of Lindemann ratios shows the melting of amorphous ice ∼135 K. The amorphous state exhibits an extremely short correlation length for the distance dependence of orientational correlation.
Diffusion processes in microwave discharge ion source and consequences on the upgrade of existing ion sources
Authors: Castro G. , Mascali D. , Miracoli R. , Celona L. , Gammino S.
Published: February 2019

Several experiments have shown that the insertion of insulator materials within the plasma chamber may lead to a general improvement of microwave discharge ion source performances. In particular, the insertion of alumina into the chamber walls and borum nitride into extraction and injection flanges permits to increase the extracted current and the proton fraction and leads to a general decrease in the beam ripple. These beneficial effects have been usually explained by considering the secondary electron emission of insulators hit by plasma electrons. This paper tries to illustrate that these effects can be explained by taking into account the modification of the diffusion regime induced by the insulator materials. This approach will be used to comment on the results obtained with the versatile ion source by changing the wall conditions.
Motion, deformation, and aggregation of multiple red blood cells in three-dimensional microvessel bifurcations
Authors: Ye Ting , Peng Lina
Published: February 2019

Vessel bifurcation is a place where many diseases start, such as the atherosclerosis, because the flow in this place is complex involving secondary flow and/or stagnation regions, and the cells are often blocked to aggregate together. A numerical study has been conducted to analyze three-dimensional motion, deformation, and aggregation of multiple red blood cells (RBCs) in a microvessel bifurcation. A smoothed dissipative particle dynamics model is used to simulate the fluids inside and outside of the RBCs. The RBC membrane is modeled as a triangular network, associated with a deformation potential energy and an aggregation potential energy to describe the RBC deformation and aggregation, respectively. The interaction between the fluid and the RBCs is modeled by the immersed boundary method. The numerical models are first validated by examining the rheology of multiple RBCs in a cylindrical tube. Then, we investigate the effect of number of RBCs, mechanical properties, and interaction strength on their motion, deformation, and aggregation. The simulation results showed that the leading RBC has more deformation, compared with subsequent RBCs. The larger the RBC number, the easier the RBCs aggregate. The RBC deformation has an obvious effect on the RBC aggregation, whereas the RBC aggregation has a slight effect on the RBC deformation. Both the RBC deformation and aggregation can cause the RBC centroid to deviate at the apex of bifurcation, and this determines which branch the RBCs move into.
Opencage radio frequency coil for magnetic resonance imaging
Authors: Nikulin A. , de Rosny J. , Haliot K. , Larrat B. , Ourir A.
Published: February 2019

We present a volume radio frequency coil for Magnetic Resonance Imaging that provides access to the region of interest. While the conventional birdcage coil is composed of a periodic array of similar unit cells making a cylindrical structure, the proposed coil, called “opencage,” is made of an aperiodic array of metamaterial based unit cells presenting different geometries and characteristics. We develop here a dedicated approach based on Bloch impedance matching and phase balance for the design of the opencage coil. We perform full-wave numerical simulations to validate this concept. An experimental demonstration of the opencage coil for small animal imaging at 7 Tesla is presented. The results of the in-vitro, in-vivo imaging and B1+ map reconstruction achieved with a preclinical MRI scanner are presented. We show that B1+ field homogeneity and amplitude generated by the opencage coil are comparable to those of a conventional birdcage coil of the same size.
Nonlinear optical properties of benzylamine lead(II) bromide perovskite microdisks in femtosecond regime
Authors: Mushtaq Aamir , Kushavah Dushyant , Ghosh Supriya , Pal Suman Kalyan
Published: February 2019

Organometal halide perovskites, an emerging class of direct bandgap semiconductors, are attractive candidates for many optoelectronic device applications. Herein, we have reported the nonlinear optical (NLO) properties of layered benzylamine lead(II) bromide perovskite microdisks (MDs) having a lateral dimension of a few micrometers and an average thickness of 35 nm, featuring narrow deep blue emission using the Z-scan technique. The NLO behavior switches over from saturable absorption to reverse saturable absorption under femtosecond laser pulse excitation. Our NLO studies have demonstrated tunable nonlinear behavior, which is attributed to the interplay between single and two-photon absorption by the carriers in the conduction band. Perovskite MDs exhibit an optical limiting behavior originating from the two-photon absorption mechanism.
The interaction between volume discharges and surface discharges in spot-line white-eye hexagonal superlattice pattern in dielectric barrier discharge
Authors: Yu Guanglin , Dong Lifang , Dou Yaya , Mi Yanlin , Liu Binbin , Li Caixia , Pan Yuyang
Published: February 2019

We report on the interaction between surface discharges (SDs) and volume discharges (VDs) in the spot-line white-eye hexagonal superlattice pattern in dielectric barrier discharge using an intensified charge-coupled device camera, a high-speed video camera, and a spectrograph. The small spot-lines and halos discharge in the first pulse and the second pulse at the rising edge of the voltage, respectively. The central spots discharge at the falling edge of voltage. The small spots are VDs whose discharge time is incompletely simultaneous. The lines are direction-selective SDs induced by small spots. It is found that the above phenomena result from the interaction between SDs and VDs. The incompletely simultaneous discharge of the small spots is due to the different quantities of wall charges transported by the SDs induced by small spots. The directional selectivity of the SDs results from that the SDs are extinguished when they are close to halos due to the neutralization of the wall charge of halos (VDs) and the wall charge of SDs, while they can stretch to other small spots.