bluuebunny/crossref_metadata_2025 huggingface dataset:
Effectiveness of two field methods of saturating near surface concrete on the water permeability of in situ concrete
Authors: Yang Kai , Basheer Muhammed , Nanukuttan Sreejith , Bai Yun , Long Adrian
Published: August 2019

Determining the water permeability of concrete in structures remains a challenge because of difficulties in removing the influence of its moisture content. Saturating concrete with water could be one option, but this is not easy to achieve on site. This paper reports a testing programme carried out to assess the reliability and effectiveness of two field saturation methods, viz. vacuum saturation and ponding. The water permeability test results after applying the vacuum saturation and ponding were compared with that obtained after incremental immersion. It was found that ponding was unable to remove the influence of moisture, whilst vacuum saturation was effective for wet concretes. The results obtained from the electrical resistance measurements after incremental immersion suggested that the water permeability of concretes can be accurately determined by carrying out in situ permeability tests if the near surface region up to a depth of 25 mm is fully saturated.
Investigation of the prestressed beams and glass-window panels at a shopping centre
Authors: Mircea Andreea-Terezia
Published: August 2019

In today’s rapidly changing demands of commercial buildings, designers, manufacturers, contractors, and installers face the necessity to advance their methods, to improve techniques, and generally to stay competitive under all constraints of time, budget, codes and client desires. Building with precast concrete elements provides quick and cost-efficient production, along with flexible, independent interior design. The show-window of the investigated commercial building is divided into several glass panels. Having only upper and lower grip, the glass window panels with very tall heights, are subject to deformation. In order to resist, panels are provided with U-shaped profiles or/ and perimeter rails. The critical points are the glass panels’ support, so the ceiling and floor fastenings have to be very solid, as well as qualitatively superior designed and executed. This paper aims to highlight some relevant aspects regarding the investigation of the metal fixing system designed to connect show-window panels to prestressed concrete ceiling beams at a commercial building.
Mechanical properties of alkali activated geopolymer paste using different Romanian fly ash sources – experimental results
Authors: Lăzărescu Adrian , Mircea Călin , Szilagyi Henriette , Baeră Cornelia
Published: August 2019

As concrete demand is constantly increasing in recent years and also considering that cement production is both a consumer of natural resources and a source of carbon dioxide release into the atmosphere, there have been worldwide investigations into green alternatives for making concrete environmentally friendlier and simultaneously to satisfy the development of infrastructure facilities. The use of fly ash as a component of cementitious binders is not new but when considering the specific case of alkaline activation and fly ash representing the only source for the binder formation, it necessitates a more complete understanding of its specific reactions during the alkaline activation process. Since the fly ash varies dramatically, not only from one source to another, but also from one batch to another even when provided by the same power plant, its chemistry in obtaining alkali-activated materials during the geopolymerisation process and the final mechanical properties are considered crucial for the performance of geopolymer concrete. This paper will provide a review of the experimental results concerning the physical and mechanical evaluation of the alkali-activated fly ash-based geopolymer materials, developed with different types of fly ash, for a better understanding of geopolymer concrete production control.
Vorsorgeuntersuchungen und Check-ups in der Pneumologie
Authors: Kroenig Johannes , Holland Angélique , Vogelmeier Claus Franz
Published: August 2019

In pneumology, preventive check-ups have played a subordinate role so far. Current research results could change this. In the following article the focus is on lung cancer and COPD, diseases that have a considerable influence on mortality and morbidity in modern society. Approaches will be discussed that will allow earlier diagnosis of COPD or identify patients at risk. In particular Capture, a questionnaire that significantly increases the pre-test probability in COPD diagnostics, should be mentioned here. Lung carcinoma screening is a controversial topic in Germany. In an American study, the relative mortality rate from lung cancer was significantly reduced by CT screening. Results of a European study (Nelson trial) are still pending. A high pre-test probability will also be decisive for lung cancer screening. In this way, the cost-benefit ratio could be optimized. Since COPD patients have a significantly increased risk of lung cancer, there might be overlaps in the screening procedures.
Demenz und metabolisch-vaskuläre Risikofaktoren: Möglichkeiten der Prävention
Authors: Gonder Ulrike , von Schacky Clemens , Worm Nicolai , Lechner Benjamin , Bock Markus , Lechner Katharina
Published: August 2019

Die Prävalenz der Demenz ist in den letzten Jahren gestiegen und nimmt mit dem Alter exponentiell zu. In Deutschland sind ca. 1,7 Mio. Menschen betroffen, die jährliche Neuerkrankungsrate wird auf 300 000 geschätzt. Der Begriff Demenz umfasst verschiedene Krankheitsformen mit unterschiedlichen Ätiologien. Dem demenziellen Syndrom des höheren Lebensalters liegen meist vaskuläre und metabolische Risikofaktoren zugrunde, die der klinischen Demenzmanifestation um Dekaden vorausgehen. Dies bietet ein enormes Zeitfenster für die Prävention, welche insbesondere vor dem Hintergrund weitgehend fehlender kurativer pharmakologischer Ansätze eine große Bedeutung erlangt. Lebensstilmaßnahmen, die eine hohe Nahrungsqualität und eine ausreichende Versorgung mit Omega-3-Fettsäuren, körperliche Aktivität und erholsamen Schlaf beinhalten, verbessern metabolische und vaskuläre Risikofaktoren und mindern das Demenzrisiko. Da multimodale Konzepte synergistisch wirken, versprechen sie den größten präventiven Nutzen.
Multidisziplinärer anonymer Survey zur Vertrautheit von Ärztinnen und Ärzten eines Universitätsklinikums mit gängigen Termini und Kenngrößen der evidenzbasierten Medizin
Authors: Baulig Christine , Ahrens Sünje-Theresa , Tulka Sabrina , Krummenauer Frank
Published: August 2019

Hintergrund Eine Patientenversorgung nach den Grundsätzen der evidenzbasierten Medizin (EbM) ist im Sozialgesetzbuch (u. a. § 137f SGB V) festgelegt. Im Rahmen der Qualitätssicherung in der Medizin wird deshalb immer wieder eine Pflicht-Weiterbildung für Ärztinnen und Ärzte im Bereich EbM gefordert. Es stellt sich die Frage, inwieweit aktuell klinisch tätige Ärztinnen und Ärzten bereits mit gängigen Termini und Kenngrößen der EbM vertraut sind. Ebenso ist die optimale zeitliche Ansiedlung einer möglichen Weiterbildung während der ärztlichen Ausbildung unklar.

Material und Methoden Im Februar 2017 wurde an 4 Kliniken der Universität Witten/Herdecke ein anonymer Survey (Papier-Fragebogen) durchgeführt. Der Fragebogen bestand aus 12 ausformulierten Aufgaben zu klassischen Methoden der EbM. Alle Aufgaben waren mit „richtig“ oder „falsch“ zu beantworten; das Nichtbeantworten einzelner Aufgaben war gestattet. Primärer Endpunkt der Untersuchung war der individuelle Anteil korrekt beantworteter unter den gegebenen Antworten. Die primäre Fragestellung des Surveys bestand in der Schätzung des medianen Anteils korrekter unter den vorliegenden Antworten der Teilnehmenden mittels eines 2-seitigen 95 %-Konfidenzintervalls.

Ergebnisse Aus den 4 Kliniken resultierten 70 auswertbare Fragebögen (15–19 pro Klinik). Der mediane Anteil korrekter unter den gegebenen Antworten lag bei 47 % (95 %-KI [40 %; 50 %]). Die 4 Kliniken unterschieden sich zum Niveau 5 % bezüglich des Anteils korrekter Antworten nicht signifikant (p = 0,388), konkret zeigten sich mediane Anteile zwischen 40 % und 50 % korrekter unter den gegebenen Antworten in den 4 Kliniken.

Diskussion Dem klinisch tätigen Personal an Universitätskliniken kann eine gewisse Vertrautheit mit gängigen Methoden der klinischen Forschung unterstellt werden. Der Anteil korrekter Antworten lag jedoch unter 50 %, sodass eine Weiterbildung zu EbM-spezifischen Methoden indiziert erscheint. Hinweise zum optimalen Zeitpunkt solcher Angebote während der ärztlichen Ausbildung konnten nicht aus dem Survey abgeleitet werden.
Palliativdienste in den deutschen onkologischen Spitzenzentren
Authors: Gahr Susanne , Berendt Julia , Lödel Sarah , Ostgathe Christoph , Simon Steffen T. , Tewes Mitra , Zader Kirsten , Schwartz Jacqueline , Neukirchen Martin
Published: August 2019

Hintergrund Ein Palliativdienst ist in der Beratung und Versorgung von Patienten mit einer Tumorerkrankung als Qualitätsindikator anerkannt und in National Cancer Institutes, Vorbild der deutschen Comprehensive Cancer Center (CCC), flächendeckend (92 %) umgesetzt. Daher stellt sich die Frage, wie die Palliativdienste aktuell in die CCCs integriert sind.

Methode Durch eine papierbasierte quantitative Befragung an 16 Standorten der bisher geförderten CCCs wurden von Juli bis August 2017 Angaben zum Vorhandensein, zur personellen Situation, Inanspruchnahme und zu Perspektiven eines Palliativdienstes erfasst. Die Befragung richtete sich an die Leiter der palliativmedizinischen Einheiten der CCCs. Die Daten wurden in SPSS ausgewertet (Häufigkeit, Median, Mittelwert, Spannweite).

Ergebnisse 15 CCCs haben an der Befragung teilgenommen (Rücklauf 94 %). 13 der 15 CCCs verfügen über einen Dienst, der Palliativpatienten mitbehandelt. In 12 von 13 CCCs sind diese in den Regelarbeitszeiten (wochentags 8–16 Uhr) erreichbar. Alle Dienste sind ärztlich besetzt, 11 zusätzlich pflegerisch. 7 Dienste sind neben Arzt und Pflege mit einer weiteren Profession besetzt. Es wurden im Jahr 2016 im Median 4482 Mitbehandlungen durch die Dienste erbracht, davon 80 % als Zusatzentgelte (ZE) ohne Erlös und ohne kodierbaren OPS. Im Jahr 2017 planen 5 Zentren das ZE 2017-133, 2 Zentren das ZE 60 und 3 Zentren beide ZE abzurechnen.

Diskussion Dienste für Palliativpatienten sind in den deutschen CCCs regelhaft vorhanden, erfüllen jedoch nur zur Hälfte die in der S3-Leitlinie geforderte Bedingung der Multiprofessionalität. Das im Jahr 2017 neu eingeführte, stundengenau abrechenbare Zusatzentgelt könnte hier Verbesserungen schaffen und zur Kostendeckung beitragen. Dadurch können entgegen der bisherigen Regelung notwendige und sinnvolle Leistungen mit einer Behandlungsdauer auch unter 7 Tagen abgerechnet werden.
Iron-Catalyzed Radical Methylation of Activated Alkenes with tert-Butanol as the Methyl Source
Authors: Xu Zhengbao , Jia Rui , Ma Zhiwei , Cao Shouhao , Shen Liang , Ji Hongfang
Published: August 2019

A free-radical-initiated methylation/addition/cyclization of N-arylacrylamides and a methylation/addition/elimination of quinines have been developed in which t-BuOH is used as a methyl source. These reactions provide effective and selective methods for the synthesis of various methylated oxindoles and quinones in moderate to good yields.
Conversion of Thesis to Peer-Reviewed Publication
Authors: Shukla Dhaval , Tripathi Manjul , Devi Bhagavatula Indira
Published: August 2019

Introduction Writing a thesis or dissertation during a postgraduate medical or surgical training is a part of curriculum, which is considered a major component of training during residency. We aimed to analyze and find out the fate of thesis of our residents, their outcome, and impact. We have also evaluated the reasons for not publishing the thesis in a peer-reviewed paper.

Methods This study was conducted at a neurosurgical department of a premier training institute. PubMed and Google Scholar were searched for the topics of thesis and names of residents to find out whether any paper was published similar to topic of thesis. The faculties and residents were also personally contacted to evaluate the publication status of their thesis. A questionnaire was sent to the students who did not publish their thesis to find out the reasons for not submitting for publication.

Results Total 56 residents submitted 85 thesis. The conversion rate to peer-reviewed publication was 32.5%. There was decreasing trend of conversion to publication over 10 years. The most common reasons for not publishing was a bad design of study, or deemed worthless for publication.

Conclusion Conversion rate of thesis to paper is poor. In addition to writing thesis, candidates should be encouraged to have publications in indexed journal as full-length articles. Such publications carry more significance in long-term career of a resident.
Botulism in the Pediatric Intensive Care Units in the United States: Interrogating a National Database
Authors: Howes Cynthia , Hiatt Kerith , Turlington Katherine , Foster Cortney , Holloway Adrian , Graciano Ana Lia , Custer Jason , Bhutta Adnan , Bagdure Dayanand
Published: August 2019

Botulism in children can have severe complications necessitating intensive care. The current literature lacks data of children with botulism requiring critical care. We aim to describe the outcomes of pediatric botulism in the pediatric intensive care unit (PICU). Retrospective cohort data from Virtual Pediatric Systems (VPS, LLC, Los Angeles, California), from 2009 to 2016 including all PICU admissions among children with botulism, were analyzed. Characteristics and outcomes were compared with similar studies. A total of 380 children were identified over 8 years. Our cohort had the shortest length of stay (median 4.6 days), the smallest percent requiring mechanical ventilation (40%), and the highest median age (120 days) amongst comparable studies. Length of mechanical ventilation and PICU stay has decreased among children with botulism. Advances in PICU care may have contributed to these improved outcomes.
Venous Flaps for Revascularization and Soft-Tissue Coverage in Traumatic Hand Injuries: A Systematic Review of the Literature
Authors: Roberts John M. , Carr Logan W. , Haley Christopher T. , Hauck Randy M. , Michelotti Brett F.
Published: August 2019

Background The use of the venous flap for simultaneous revascularization and coverage of soft tissue defects has been documented in the literature for over 30 years. First described in 1981, Nakayama et al demonstrated that a vein and overlying skin, or a venous flap, may be transposed from one area of the body to another with complete survival of the graft. The aim of this study was to conduct a systematic review of the literature to determine predictors of venous flap survival in traumatic hand injuries.

Methods A literature search of PubMed, MEDLINE, and Cochrane Library was performed with emphasis on venous flap use in traumatic hand injuries. MeSH terms included: vein graft, revascularization, venous flow through flap, arterialized venous flap, bypass, replantation, amputation, avulsion, trauma, injury, amputate, finger, hand, and thumb.

Results Forty-three articles were collected that contained data on 626 free venous flaps. Most patients were males (73.9) and injured their right hand (52.3%). The forearm was the most commonly used venous flap donor site (83.6%), and most of the skin paddles were 10 to 25 cm2 (41.1%). Arterial inflow was used in 93.1% of the flaps. Most venous flaps (79.6%) healed without superficial tissue loss or necrosis. Ninety-two (14.7%) flaps had partial loss while 36 (5.8%) flaps did not survive.

Conclusion The use of venous flaps for concomitant revascularization and soft tissue coverage of the hand permits good results with limited morbidity. The overall flap survival rate is nearly 95%. Younger patients whose flaps have arterial inflow and skin paddles of medium size (10–25 cm2) have the best chance for survival.
Acute Spinal Cord Compression due to Chloroma as the Initial Presenting Feature of Acute Myeloid Leukemia
Authors: Patro Sushant Kumar , Nayak Biswaranjan , Kumar Arun , Krishnamurthy Balappa Holeppagol , Biswal Debabrata , Sahoo Prafulla Kumar
Published: August 2019

Chloroma is the deposits in leukemic cells outside the bone marrow and is not common. It is extremely rare to find a chloroma compressing the spinal cord causing paraplegia without any prior symptoms. Only few case reports have been found in the literature till date. We report an interesting case of a 7-year-old boy who presented with acute back pain and paraplegia with a dorsal extradural mass, and with a previous diagnosis of tuberculosis of the dorsal spine, treated with antitubercular drugs without any other signs of systemic illness. After surgical decompression and histopathologic examination of the tissue, it was found to be chloroma. There are only few reported cases of this disease initially presented as paraplegia without any systemic signs of malignancy in the literature, and chloroma presents as a diagnostic challenge to the surgeon. Chloromas are a rare cause of acute spinal cord compression but should be diagnosed and treated promptly to prevent neurologic dysfunction.
Distal Metaphyseal Osteotomy Allows for Greater Ulnar Shortening Compared to Diaphyseal Osteotomy for Ulnar Impaction Syndrome: A Biomechanical Study
Authors: Luo T. David , De Gregorio Michael , Zuskov Andrey , Khalil Mario , Li Zhongyu , Nuñez Fiesky A. , Nuñez Fiesky A.
Published: August 2019

Purpose To compare the biomechanical characteristics between diaphyseal and metaphyseal ulnar-shortening osteotomy with respect to (1) maximal shortening achieved at each osteotomy site and (2) force required to achieve shortening at each site.

Methods Nine fresh frozen cadaveric upper extremities were affixed through the proximal ulna to a wooden surgical board. A metaphyseal 20-mm bone wedge was resected from the distal ulna and sequential shortening was performed. A load cell was attached to a distal post that was clamped to the surgical board and used to measure the force required for each sequential 5-mm of shortening until maximal shortening was achieved. The resected bone was reinserted, and plate fixation was used to restore normal anatomy. A 20-mm diaphyseal osteotomy was performed, and force measurements were recorded in the same manner with (1) interosseous membrane intact, (2) central band released, and (3) extensive interosseous membrane and muscular attachments released.

Results Metaphyseal osteotomy allowed greater maximal shortening than diaphyseal osteotomy with the interosseous membrane intact and with central band release but similar shortening when extensive interosseous membrane and muscle release was performed. Force at maximal shortening was similar between metaphyseal and diaphyseal osteotomy. Sequential soft tissue release at the diaphysis allowed for increased shortening with slightly decreased shortening force with sequential release.

Conclusion Metaphyseal ulnar osteotomy allows greater maximal shortening but requires similar force compared with diaphyseal osteotomy. Sequential release of the interosseous membrane permits increased shortening at the diaphysis but requires extensive soft tissue release.

Clinical Relevance Both sites of osteotomy can achieve sufficient shortening to decompress the ulnocarpal joint for most cases of ulnar impaction syndrome. The greater shortening from metaphyseal ulnar osteotomy may be reserved for severe cases of shortening, especially after distal radius malunion or in the setting of distal radius growth arrest in the pediatric population.

Level of Evidence This is a Level V, basic science study.
Principles of Orthoplastic Surgery for Lower Extremity Reconstruction: Why Is This Important?
Authors: Azoury Saïd C. , Stranix John T. , Kovach Stephen J. , Levin L. Scott
Published: August 2019

Background Regardless of the antecedent etiology, lower extremity salvage and reconstruction attempts to avoid amputation, restore limb function, and improve quality of life outcomes. This goal requires a treatment team well versed in neurovascular pathology, skeletal and soft tissue reconstruction, and physical rehabilitation.

Methods A review was performed of historical milestones that lead to the development of orthoplastic extremity reconstruction, principles of current management and the evidence that supports an orthoplastic approach. Based on available evidence and expert opinion, the authors further sought to provide insight into the future of the field centered around the importance of a multidisciplinary management protocol.

Results Historically, orthopaedic and plastic surgeons worked separately when faced with challenging reconstructive cases involving lower extremity skeletal and soft tissue reconstruction. With time, many embraced that their seemingly separate skill-sets and knowledge could be unified in a collaborative orthoplastic approach in order to offer patients the best possible chance for success. First coined by the senior author (LSL) in the early 1990s, the collaborative orthoplastic approach between orthopaedic and plastic surgeons in limb salvage for the past several decades has resulted in a unique field of reconstructive surgery. Benefits of the orthoplastic approach include decreased time to definitive skeletal stabilization/soft tissue coverage, length of hospital stay, post-operative complications, need for revision procedures and improved functional outcomes.

Conclusion The orthoplastic approach to lower extremity reconstruction is a collaborative model of orthopaedic and plastic surgeons working together to expedite and optimize care of patients in need of lower extremity reconstruction. The implementation of protocols, systems, and centers that foster this approach leads to improve outcomes for these patients. We encourage centers to embrace the orthoplastic approach when considering limb salvage, as the decision to amputate is irreversible.
Mapping the composition-dependence of the energy bandgap of GaAsNBi alloys
Authors: Occena J. , Jen T. , Mitchell J. W. , Linhart W. M. , Pavelescu E.-M. , Kudrawiec R. , Wang Y. Q. , Goldman R. S.
Published: August 2019

We have examined the alloy composition dependence of the energy bandgap and electronic states in GaAsNBi alloys. Using direct measurements of N and Bi mole fractions, via ion beam analysis, in conjunction with direct measurements of the out-of-plane misfit via x-ray rocking curves, we determine the “magic ratio” for lattice-matching of GaAsNBi alloys with GaAs substrates. In addition, using a combination of photoreflectance and photoluminescence spectroscopy, we map the composition- and misfit-dependence of the energy bandgaps, along with revealing the energetic position of Bi-related states at approximately 0.18 eV above the valence band maximum.
Initial-boundary value problem for the spin-1 Gross-Pitaevskii system with a 4 × 4 Lax pair on a finite interval
Authors: Yan Zhenya
Published: August 2019

In this paper, we explore the initial-boundary value (IBV) problem for an integrable spin-1 Gross-Pitaevskii system with a 4 × 4 Lax pair on the finite interval x ∈ [0, L] by extending the Fokas unified approach. The solution of this three-component system can be expressed by means of the solution of a 4 × 4 matrix Riemann-Hilbert (RH) problem formulated in the complex spectral k-plane. Furthermore, the relevant jump matrices with explicit (x, t)-dependence of the matrix RH problem can be explicitly obtained using three spectral functions {s(k), S(k), SL(k)} arising from the initial data and Dirichlet-Neumann boundary conditions at x = 0, L, respectively. The global relation is also presented and used to deduce two distinct but equivalent types of representations [i.e., one via the large k of asymptotics of the eigenfunctions and another one in terms of the Gel’fand-Levitan-Marchenko (GLM) approach] for the Dirichlet and Neumann boundary value problems. In particular, the formulae for IBV problem on the finite interval can be extended to the ones on a half-line as the length L of the interval approaches to infinity. Moreover, we also give the linearizable boundary conditions for the GLM representations.
Characterization of electric-field enhancement leading to circuit-layout dependent damage of low-k films when exposed to processing plasma
Authors: Ikeda Taro , Tanihara Akira , Yamamoto Nobuhiko , Eriguchi Koji
Published: August 2019

We investigated the effects of Cu-line layouts on plasma-induced radiation damage (PRD) to interline low-k dielectric films. We carried out a finite-element-method-based three-dimensional (3D) electromagnetic simulation (EMS), in which a Drude free-electron model was implemented for the dielectric function of Cu lines. The 3D EMS analysis revealed that the electric field in the low-k films was enhanced for specific Cu-line layouts exposed to N2 plasma irradiation, while no clear electric-field enhancement was observed for Ar plasma exposure. The specific optical emission lines produced in N2 plasmas are the root cause of damage creation in the low-k dielectric films with embedded Cu lines. The 3D EMS analysis predicted that the electric field was enhanced with decreasing the line and space (L/S) widths. The prediction implies that the Cu-line-layout dependent PRD should be more prominent as device dimensions shrink. We verified the predicted results experimentally using devices with low-k films between various L/S Cu lines, in addition to a blanket wafer—without Cu lines. We found that an increasing peak in the low-k dielectric constant appeared at a specific L/S width after N2 plasma exposure and no clear increase in the dielectric constant was observed after Ar plasma exposure. The obtained experimental results are consistent with the 3D EMS analysis. We propose a damage model, where the electric field enhancement plays an important role in the low-k dielectric films with embedded Cu lines. The proposed damage model is indispensable for minimizing PRD and designing Cu layouts in future devices.
Selection of a stochastic Landau-Lifshitz equation and the stochastic persistence problem
Authors: Cresson Jacky , Kheloufi Yasmina , Nachi Khadra , Pierret Frederic
Published: August 2019

In this article, we study the persistence of properties of a given classical deterministic differential equation under a stochastic perturbation of two distinct forms: external and internal. The first case corresponds to add a noise term to a given equation using the framework of Itô or Stratonovich stochastic differential equations. The second case corresponds to consider parameter dependent differential equations and to add a stochastic dynamics on the parameters using the framework of random ordinary differential equations. Our main concerns for the preservation of properties are stability/instability of equilibrium points and symplectic/Poisson Hamiltonian structures. We formulate persistence theorem in these two cases and prove that the cases of external and internal stochastic perturbations are drastically different. We then apply our results to develop a stochastic version of the Landau-Lifshitz equation. We discuss, in particular, previous results obtained by Étoré et al. [J. Differ. Equations 257, 2115–2135 (2014)] and we finally propose a new family of stochastic Landau-Lifshitz equations.
IShTAR: A test facility to study the interaction between RF wave and edge plasmas
Authors: Shesterikov I. , Crombe K. , Kostic A. , Sitnikov D. A. , Usoltceva M. , Ochoukov R. , Heuraux S. , Moritz J. , Faudot E. , Fischer F. , Faugel H. , Fünfgelder H. , Siegl G. , Noterdaeme J.-M.
Published: August 2019

Existence of high electric fields near an RF antenna launcher causes a number of parasitic phenomena, such as arcing and impurity release, which seriously deteriorate the performance of an Ion Cyclotron Range of Frequencies (ICRF) heating scheme in fusion devices. Limited accessibility of the near antenna region in large-scale fusion experiments significantly complicates the associated experimental studies. The IShTAR test facility has been developed with the requirement to provide a better accessibility and diagnosability of plasmas in the direct vicinity of an ICRF antenna. The purpose of this work is to give a detailed description on the experimental setup and the available diagnostics. Furthermore, the paper will demonstrate the capability of the experiment to study phenomena near an ICRF antenna launcher which are relevant for large-scale fusion ion cyclotron resonance heating systems.
Long-term evolution of spherical shell with boron carbide layer after explosive compression
Authors: Andriyash A. V. , Arinin V. A. , Dyachkov S. A. , Karpenko G. Ya , Kovaldov V. V. , Korotaev P. Yu , Kuratov S. E. , Medin S. A. , Mikhailov A. L. , Murzov S. A. , Nefedov A. V. , Panov K. N. , Parshikov A. N. , Sogrin S. Yu , Yanilkin A. V. , Zhakhovsky V. V.
Published: August 2019

Predictive simulation of the long-term response of multilayer targets with ceramics layers to shock compression demands appropriate material models. Because ceramics are complex brittle materials, which tend to lose their strength under heavy loads, such simulation requires the failure models well-proven for a wide range of strains and strain rates. Standard plate impact experiments provide the main data utilized for developing and validating the mechanical models of material response to shock compression. However, apart from the fact that such experimental data are inherently one-dimensional, they can be insufficient to verify the failure model at relatively low strain rates typical for long unloading waves. Here, we present the experimental results for explosive compression of a spherical multilayer shell initiated by a single detonator. The explosive-coated shell consists of the nested spherical layers: the outer made of boron carbide and the inner of lead. X-ray images showing the evolution of those layers after detonation are then compared with simulation results. Propagation of the compression wave through the layers resulting in ceramics damage is analyzed in detail. We demonstrate that the failure model of boron carbide should be adjusted for compressions below 10 GPa to achieve a good agreement with our experimental images. Such an improved failure model provides the predictive simulation of long-term dynamics of targets after unloading, and it has almost no effect on wave profiles after plate impact.
Anomalous spin Hall angle of a metallic ferromagnet determined by a multiterminal spin injection/detection device
Authors: Wimmer T. , Coester B. , Geprägs S. , Gross R. , Goennenwein S. T. B. , Huebl H. , Althammer M.
Published: August 2019

We report on the determination of the anomalous spin Hall angle in the ferromagnetic metal alloy cobalt-iron (Co25Fe75, CoFe). This is accomplished by measuring the spin injection/detection efficiency in a multiterminal device with nanowires of platinum (Pt) and CoFe deposited onto the magnetic insulator yttrium iron garnet (Y3Fe5O12, YIG). Applying a spin-resistor model to our multiterminal spin transport data, we determine the magnon conductivity in YIG, the spin conductance at the YIG/CoFe interface, and finally the anomalous spin Hall angle of CoFe as a function of its spin diffusion length in a single device. Our experiments clearly reveal a negative anomalous spin Hall angle of the ferromagnetic metal CoFe, but a vanishing ordinary spin Hall angle. This work, therefore, adds new observations to the results reported in Tian et al. [Phys. Rev. B 94, 020403 (2016)] and Das et al. [Phys. Rev. B 96, 220408(R) (2017)] , where the authors found finite contributions of the ordinary spin Hall angle in the ferromagnetic metals Co and Permalloy.
Perfect acoustic absorption by subwavelength metaporous composite
Authors: Zhou Yukun , Li Dongting , Li Yong , Hao Tong
Published: August 2019

We present a design of a low-frequency perfect acoustic absorption metaporous composite with frequency tunability and the insensitivity to the incident angle based on a critical coupling mechanism. The metaporous composite is constructed by embedding an Archimedean spiral structure in traditional porous materials. We verified the tunable balance of the dissipation and leakage of the metaporous composite by adjusting the slit orientation of the embedded spiral and the width and depth of the porous materials. Our simulations show that the composite's thickness is 1/20th of the corresponding wavelength at the perfect absorption (PA). Experiment and complex frequency plane analysis confirm the perfect acoustic absorption. The simulations show that the acoustic absorption of the system is highly efficient (0.95), up to a large oblique incidence, e.g., 60°. We also achieve the dual-band PA by embedding two spirals or using the higher order mode of a single spiral. The proposed composite absorber provides promising potential for low-frequency noise reduction applications.
Control of etch pit formation for epitaxial growth of graphene on germanium
Authors: Becker Andreas , Wenger Christian , Dabrowski Jarek
Published: August 2019

Graphene epitaxy on germanium by chemical vapor deposition is a promising approach to integrate graphene into microelectronics, but the synthesis is still accompanied by several challenges such as the high process temperature, the reproducibility of growth, and the formation of etch pits during the process. We show that the substrate cleaning by preannealing in molecular hydrogen, which is crucial to successful and reproducible graphene growth, requires a high temperature and dose. During both substrate cleaning and graphene growth, etch pits can develop under certain conditions and disrupt the synthesis process. We explain the mechanisms how these etch pits may form by preferential evaporation of substrate, how substrate topography is related to the state of the cleaning process, and how etch pit formation during graphene growth can be controlled by choice of a sufficiently high precursor flow. Our study explains how graphene can be grown reliably on germanium at high temperature and thereby lays the foundation for further optimization of the growth process.
Mean-field theory based on the Jacobi hsp ≔ semidirect sum hN⋊sp(2N,R)C algebra of boson operators
Authors: Nishiyama Seiya , da Providência João
Published: August 2019

In this paper, we give an expression for canonical transformation group with Grassmann variables, basing on the Jacobi hsp ≔ semidirect sum hN⋊sp(2N,R)C algebra of boson operators. We assume a mean-field Hamiltonian (MFH) linear in the Jacobi generators. We diagonalize the boson MFH. We show a new aspect of eigenvalues of the MFH. An excitation energy arisen from additional self-consistent field parameters has never been seen in the traditional boson mean-field theory. We derive this excitation energy. We extend the Killing potential in the Sp(2N,R)CU(N) coset space to the one in the Sp(2N+2,R)CU(N+1) coset space and make clear the geometrical structure of Kähler manifold, a non-compact symmetric space Sp(2N+2,R)CU(N+1). The Jacobi hsp transformation group is embedded into an Sp(2N+2,R)C group and an Sp(2N+2,R)CU(N+1) coset variable is introduced. Under such mathematical manipulations, extended bosonization of Sp(2N+2,R)C Lie operators, vacuum function and differential forms for extended boson are presented by using integral representation of boson state on the Sp(2N+2,R)CU(N+1) coset variables.
Draining of films on a quasivertical plate using viscous dissipation
Authors: Peralta Juan Manuel , Meza Bárbara E. , Zorrilla Susana E.
Published: August 2019

This work focused on obtaining an improved and expanded general theoretical analysis of a two-dimensional film draining on a quasivertical plate, solving rigorous mass, momentum, and energy balances. A dimensional analysis and scaling was used to simplify the mathematical description, and a generalized Newtonian fluid was assumed as the film-forming material. A new quantity that governs the draining flow and film characteristics, called viscous dissipation, was proposed as part of the novel analytical expressions obtained in this work. Velocity profile, average velocity, flow rate, and local and average film thickness expressions can be obtained, allowing to simplify the overall calculation complexity and to find new potential analytical expressions using more complex rheological models.
Static characteristics of CMOS digital circuit based on transition metal dichalcogenide transistors
Authors: Mao F. F. , Jin Z. , Shang L. Y. , Hu Z. G. , Chu J. H.
Published: August 2019

Static characteristics of digital combinational logic circuits and Schmitt triggers based on two-dimensional (2D) transition metal dichalcogenides (TMDs) have been systematically explored. Selenide tungsten (WSe2) transistors act as the P type metal oxide semiconductor (PMOS). Molybdenum disulfide (MoS2) transistors play the role as N type metal oxide semiconductor (NMOS). Based on the circuit simulations, we find that the output of the complementary metal oxide semiconductor (CMOS) inverters and Schmitt triggers can approach the supply voltage (VDD) and ground (GND), respectively. The key performance indexes of the two digital circuits have been studied with the change of the device parameters. The simulation results indicate that a thinner gate oxide thickness and a higher dielectric permittivity gate oxide material can increase the noise margin of the inverters. Besides, different width ratios of PMOS and NMOS can influence the noise margin of inverters. An inverter with a large PMOS whose width is 64 nm and a small NMOS whose width is 32 nm can improve the low level noise margin, but reduce the high level noise margin. In addition, a gate oxide thickness of 2.8 nm can broaden the hysteresis window of the Schmitt triggers obviously. The output curves of the Schmitt triggers change slightly with different gate oxide materials. The hysteresis window of the Schmitt triggers becomes narrow with decreasing of the supply voltage. The present work could help to design the standard cells with different requirements and improve the performance of digital integrated circuits using TMDs transistors.
Absorption in ultrathin GaN-based membranes: The role of standing wave effects
Authors: Amargianitakis E. A. , Jayaprakash R. , Kalaitzakis F. G. , Delamadeleine E. , Monroy E. , Pelekanos N. T.
Published: August 2019

A methodology is described to extract the absorption coefficient spectrum and exciton oscillator strength of GaN layers and GaN/AlGaN quantum wells by analyzing microtransmittance experiments in high-quality, free-standing membranes with thicknesses in the 160–230 nm range. The absorbance of a subwavelength GaN membrane is found to be an oscillating function of its thickness, in keeping with the standing wave effect. We analyze our results using two alternative models including interference effects and extract identical absorption coefficient values. The room-temperature absorption coefficient of bulk GaN membranes at the main exciton peak is found to be 9 × 104 cm−1. In the case of GaN/AlGaN quantum wells, the enhancement and blue shift of the excitonic absorption are observed, as a result of quantum confinement.
Mechanism and characteristics on the electric explosion of Al/Ni reactive multilayer foils
Authors: Zeng Qingxuan , Wang Tao , Li Mingyu , Ren Yangyang
Published: August 2019

Al/Ni multilayer foils were integrated with high voltage initiators using conventional microelectronic processing techniques and electrically exploded at an extremely high heating rate. In order to increase the knowledge about the electric explosion process of Al/Ni foils, several samples with different bilayer thicknesses, bridge dimensions, and capacitor voltages were tested. Time dependent voltage and current waveforms, energy depositions, and average flier velocities were measured and compared. The application of Al/Ni multilayers significantly increased the flier velocity and energy deposition of the device. The stored chemical energy of Al/Ni multilayer foils indeed contributed to the flier velocity increase, according to the experimental observations that the 225 nm bilayer bridges with the largest heat of reaction resulting in the highest flier velocities of all. Analysis of the experimental results allows us to prove that the electric explosion process of Al/Ni foils consisted of three stages. First, the Al layers were heated to vaporize. Then, the condensed AlNi grains started to nucleate due to exothermic mixing and subsequently evaporated with continuous energy deposition. Finally, the metal vapors ionized and formed plasma. These results provide fundamental understanding about electric explosion of Al/Ni reactive multilayer foils, and also enable us to improve the reliability and energy efficiency of electrically exploded Al/Ni multilayers for specific applications.
Crystallization kinetics with fragile-to-strong crossover in Zn-Sb-Te supercooled phase-change liquids
Authors: Gu Jierong , Chen Yimin , Zhang Qian , Wang Guoxiang , Wang Rongping , Shen Xiang , Wang Junqiang , Xu Tiefeng
Published: August 2019

Understanding crystallization kinetics is essential to select the high-performance materials for phase-change memory. By ultrafast differential scanning calorimetry, we found the distinct fragile-to-strong crossover crystallization kinetics in ZnSb and Zn28Sb54Te18 supercooled liquids. Zn28Sb54Te18 inherits the excellent thermal stability around glass transition from ZnSb and exhibits faster crystal growth rate close to melting temperature (Umax is 9.1 m s−1) and larger crossover magnitude f (2.3), compared to the typical fragile-to-strong crossover material Ag-In-Sb2Te. Such a material with a distinct fragile-to-strong crossover is helpful to improve their thermal stability nearby glass transition temperature and accelerate the phase transition speed close to melting temperature.
Nanoscale ballistic diodes made of polar materials for amplification and generation of radiation in the 10 THz-range
Authors: Kochelap V. A. , Korotyeyev V. V. , Lyashchuk Yu. M. , Kim K. W.
Published: August 2019

We investigate ultrahigh frequency electrical properties of nanoscale n+−i−n+ diodes made of polar semiconductors. The calculations show that the coupling between optical vibrations of the lattice and the ballistic electrons strongly modifies and enhances the time-of-flight effects giving rise to narrow resonances of the diode impedance in the reststrahlen frequency range. Particularly, negative dynamic resistance is induced in close proximity to the optical phonon frequency. The resonant effects in the dynamic resistance of nanoscale GaAs and InP diodes are studied in detail. The obtained magnitudes of the negative dynamic resistance effect indicate that the nanoscale diodes are capable of generating electromagnetic radiation in the far-infrared spectral range under electric pumping.
Initial-boundary value problems for a reaction-diffusion equation
Authors: Himonas A. Alexandrou , Mantzavinos Dionyssios , Yan Fangchi
Published: August 2019

A novel approach that utilizes Fokas’s unified transform is employed for studying a reaction-diffusion equation with power nonlinearity formulated either on the half-line or on a finite interval with data in Sobolev spaces. This approach was recently introduced for initial-boundary value problems involving dispersive nonlinear equations such as the nonlinear Schrödinger and the Korteweg-de Vries equations. Thus, the present work extends the new approach from dispersive equations to diffusive ones, demonstrating the universality of the unified transform in the analysis of nonlinear evolution equations on domains with a boundary.
Global well-posedness to some modified 2-D nonhomogeneous Navier-Stokes equations
Authors: Liu Xiaofeng
Published: August 2019

In this paper, we are concerned with the global well-posedness of modified 2D nonhomogeneous Navier-Stokes equations. Our results improve the results of Zhang [Int. Math. Res. Not. 2008(1), rnn098] to some extent.
Optimism is associated with exceptional longevity in 2 epidemiologic cohorts of men and women
Authors: Lee Lewina O. , James Peter , Zevon Emily S. , Kim Eric S. , Trudel-Fitzgerald Claudia , Spiro Avron , Grodstein Francine , Kubzansky Laura D.
Published: August 2019

Significance

Optimism is a psychological attribute characterized as the general expectation that good things will happen, or the belief that the future will be favorable because one can control important outcomes. Previous studies reported that more optimistic individuals are less likely to suffer from chronic diseases and die prematurely. Our results further suggest that optimism is specifically related to 11 to 15% longer life span, on average, and to greater odds of achieving “exceptional longevity,” that is, living to the age of 85 or beyond. These relations were independent of socioeconomic status, health conditions, depression, social integration, and health behaviors (e.g., smoking, diet, and alcohol use). Overall, findings suggest optimism may be an important psychosocial resource for extending life span in older adults.
Endogenous fluctuations in the dopaminergic midbrain drive behavioral choice variability
Authors: Chew Benjamin , Hauser Tobias U. , Papoutsi Marina , Magerkurth Joerg , Dolan Raymond J. , Rutledge Robb B.
Published: August 2019

Human behavior is surprisingly variable, even when facing the same problem under identical circumstances. A prominent example is risky decision making. Economic theories struggle to explain why humans are so inconsistent. Resting-state studies suggest that ongoing endogenous fluctuations in brain activity can influence low-level perceptual and motor processes, but it remains unknown whether endogenous fluctuations also influence high-level cognitive processes including decision making. Here, using real-time functional magnetic resonance imaging, we tested whether risky decision making is influenced by endogenous fluctuations in blood oxygenation level-dependent (BOLD) activity in the dopaminergic midbrain, encompassing ventral tegmental area and substantia nigra. We show that low prestimulus brain activity leads to increased risky choice in humans. Using computational modeling, we show that increased risk taking is explained by enhanced phasic responses to offers in a decision network. Our findings demonstrate that endogenous brain activity provides a physiological basis for variability in complex human behavior.
Dynamical formation of a strongly correlated dark condensate of dipolar excitons
Authors: Mazuz-Harpaz Yotam , Cohen Kobi , Leveson Michael , West Ken , Pfeiffer Loren , Khodas Maxim , Rapaport Ronen
Published: August 2019

Significance

Interactions between many quantum particles are known to trigger exotic collective phenomena such as superconductivity and superfluidity. Here we present a theoretical model and experimental results for a collective quantum phenomenon in an interacting Bose gas of electronic quasi-particles, known as dipolar excitons. We show that a dense Bose–Einstein condensate can be formed in an optically inactive state, previously believed to be unstable, due to short-range exchange interactions between excitons. However, long-range dipolar repulsion leads to strong correlations, suppressing the exchange interaction and allowing dark condensation at very high densities. The formation of this dark condensate results in a sharp dynamical buildup in the number of particles, a surprising out-of-equilibrium phenomenon in quantum gases.