bluuebunny/crossref_metadata_2025 huggingface dataset:
Life-time prediction for aviation GTE compressor disk based on mixed-mode and multi-axial fracture resistance parameters
Authors: Shlyannikov Valery , Ishtyryakov Ivan , Yarullin Rustam
Published: December 2019

This study is concerned with analysis of fatigue crack growth and life-time prediction for aviation GTE compressor disk under operation conditions. For consideration were different combinations of rotational speed, temperature, surface flaw form and sizes as well as elastic-plastic titanium alloy BT3-1 properties are employed. A crack growth rate equation is derived involving the fracture process zone size and nonlinear stress intensity factor. The assessments of the structural integrity of the rotating disk are compared for elastic and elastic-plastic solutions. It is stated that the traditional elastic crack growth models overestimate the residual fatigue lifetime with respect to the nonlinear fracture mechanics approach.
Investigation of mixed mode fatigue crack propagation in SEN-specimen under in-phase and out-of-phase conditions due to tension-compression and torsional loading
Authors: Koester Paul , Benz Christopher , Sander Manuela
Published: December 2019

Numerous cases of damage by fatigue in structures are related to mechanical stresses due to mixed mode loading conditions. To prevent such cases of failure a precise knowledge of the corresponding theoretical background is indispensable. Unfortunately, it is not yet possible to describe the crack propagation considering a superposition of all three crack modes satisfactory. For this purpose, experiments on single-edge notched specimens made of 34CrNiMo6 using a tension-torsion testing machine under different mixed mode ratios and phase angles were performed. The focus of the investigations is especially on the kinking and the twisting angle of the crack as well as on the influence on the residual lifetime. Further, existing concepts concerning the prediction of the crack growth under mixed mode are evaluated.
Multiaxial high-cycle fatigue modelling for random loading
Authors: Wei Haoyang , Chen Jie , Carrion Patricio , Imanian Anahita , Shamsaei Nima , Iyyer Nagaraja , Liu Yongming
Published: December 2019

In this paper, a multiaxial fatigue life prediction model is proposed under general multiaxial random loadings. First, a brief review for existing multiaxial fatigue models is given and special focus is on the LiuMahadevan critical plane concept, which can be applied to both brittle and ductile materials. Next, new model development based on the Liu-Mahadevan critical plane concept for random loading is presented. The key concept is to use two-steps to identify the critical plane: identify the maximum damage plane due to normal stress and calculate the critical plane orientation with respect to the maximum damage plane due to normal stress. Multiaxial rain-flow cycle counting method with mean stress correction is used to estimate the damage on the critical plane. Equivalent stress transformation is proposed to convert the multiaxial random load spectrum to an equivalent constant amplitude spectrum. The equivalent stress is used for fatigue life prediction. Following this, experimental design and testing is performed for Al 7075-T6 under various different random uniaxial and multiaxial spectrums. The developed model is validated with both literature and in-house testing data. Very good agreement is observed for the investigated material. Finally, conclusion and future work is given based on the proposed study.
Short cracks observations on surfaces of specimens made of three materials, subjected to synchronous and asynchronous multiaxial loadings
Authors: Pejkowski Łukasz , Seyda Jan , Skibicki Dariusz
Published: December 2019

In this paper analysis of short cracks observed on surfaces of specimens subjected to axial, torsional, synchronous in-phase and out-of-phase as well as a number of asynchronous loadings was performed. The tests were conducted on PA38-T6 aluminum alloy, E235 non-alloy steel and 1.4301 austenitic stainless steel thin-walled specimens, in strain-control mode. It was concluded that for PA38-T6 aluminum alloy and E235 steel, fatigue cracks initiated and propagated on the plane of maximum shear strain, regardless of the loading case. Fatigue cracks observed on the surface of 1.4301 steel specimens developed predominantly on the levels of maximum normal strain. For this material, the surface condition resulting from the machining had a significant impact on the cracks growth. In the case of non-proportional loadings, at high levels of strain, cracks often propagated along the machining marks.
Evaluation of fatigue strength criteria for thick-walled nodular cast iron components from EN-GJS-400 under multiaxial load
Authors: Fass Markus , Störzel Klaus , Baumgartner Jörg
Published: December 2019

This paper discusses the quality of common methods for estimating the fatigue strength of EN-GJS-400-18-LT specimens under multiaxial stress. This is particularly important for the lightweight design of wind turbines. Experimental fatigue tests with axial, torsional and combined loads with a load ratio of R = -1 were performed. The results of these fatigue tests are used to validate commonly used multi-axial stress hypotheses. The investigated methods are the von Mises hypothesis, the Findley-criterion, the modified Gough-Pollard method and the critical plane nominal stress hypothesis.
An efficient procedure to speed up critical plane search in multiaxial fatigue: Application to the Carpinteri-Spagnoli spectral criterion
Authors: Benasciutti Denis , Marques Julian Marcell Enzveiler
Published: December 2019

A more efficient procedure is proposed to speed up the Carpinteri-Spagnoli (CS) algorithm in numerical computations. The goal is accomplished by deriving the exact solution for the spectral moments and expected maximum peak of normal/shear stress in any rotated plane orientation. The algorithm then avoid the use of “for/end” loops to identify the five rotations that locate the critical plane in CS method. The procedure is especially advantageous if applied to three-dimensional finite element analysis, in which the stress spectra in thousands of nodes need to be processed iteratively. The procedure is based on theoretical results that have, however, a more general validity, being applicable to any multiaxial criterion that makes use of angular rotations to identify the critical plane.
Smart Data Analytics in SME Manufacturing – an Axiomatic Design based Conceptual Framework
Authors: Vickery Andrew R. , Rauch Erwin , Rojas Rafael A. , Brown Christopher A.
Published: December 2019

The objective of this paper is to go a step further introducing the concept of Industry 4.0 (I4.0) using Axiomatic Design as a research methodology. The rationale for this work is to increase the performance of SMEs allowing a better utilization of resources, using tools coming to the foreground of industry enabled by the Fourth Industrial Revolution (also known as Industry 4.0). This would improve the competitive position of SMEs on the global market. The state-of-the-art shows that only few companies andespecially few small and medium sized enterprises (SMEs) are using data analytics to take advantage of new technological achievements to compete with one another. The method used in this paper for deriving aconceptual framework how SMEs can exploit the advantages of smart data analytics in manufacturing is axiomatic design, using inputs collected from a field study at SMEs. The results show that SMEs are challenged in implementing advanced data analytics instruments and need to define strategies for collecting, analysing and interpreting data for improving their performance and provide framework which should help SMEs to implement data analytics on the shop floor.
Chinolon-Toxizität – Neues und neu Bewertetes
Authors: Kern Winfried V.
Published: December 2019

Was ist neu?

Neue bzw. neu bewertete Nebenwirkungen Eine Reihe von unerwünschten Wirkungen der Fluorchinolone wurde neu bewertet. Die meisten dieser Nebenwirkungen sind bereits bekannt und im Vergleich zu den häufigen zentralnervösen Störungen relativ selten. Zu neuen unerwünschten Wirkungen der Fluorchinolone gehören erhöhte Risiken für Aortananeurysmata/Aortendissektion und für sehr seltene lang anhaltende, möglicherweise nicht reversible periphere Neuropathien, Muskelschmerzen, Bewegungs- und Gangstörungen, deren Assoziation mit Fluorchinolonen unsicher und deren Genese und Behandlung unklar sind.

Risiko zusätzlicher Fälle mit Nebenwirkungen Basierend auf Hochrechnungen werden auf 100 000 Fluorchinolon-Behandelte (im Vergleich zu anderen Antibiotika) mehr als 1000 zusätzliche Fälle mit Nebenwirkungen geschätzt, vor allem Fälle mit neuropsychiatrischen Nebenwirkungen sowie an zweiter Stelle Tendinopathien/Sehnenrupturen sowie Arzneimittelhepatitis.

Indikationseinschränkungen Sie betreffen in Deutschland vor allem die Behandlung von Pneumonien und Atemwegsinfektionen, bei denen alternative, ähnlich wirksame Substanzen zur Verfügung stehen. In der Behandlung der unkomplizierten Zystitis sind in Deutschland sowieso andere Substanzen empfohlen. Vorbeugende Behandlungen mit Fluorchinolonen sollten nicht durchgeführt (Reisediarrhoe, rezidivierende Zystitis) oder kritisch überdacht werden (febrile Neutropenie, spontan bakterielle Peritonitis). Eine vermehrte Aufklärung der Patienten erscheint sinnvoll und notwendig.
Optimal number of endoscopic biopsies for diagnosis of early gastric cancer
Authors: Nishitani Masaki , Yoshida Naohiro , Tsuji Shigetsugu , Masunaga Teppei , Hirai Hirokazu , Miyajima Saori , Dejima Akihiro , Nakashima Takashi , Wakita Shigenori , Takemura Kenichi , Minato Hiroshi , Kaneko Shuichi , Doyama Hisashi
Published: December 2019

Background and study aims No recommendations are available for optimal number of endoscopic biopsies for early gastric cancer (GC), and whether detection of early GC is improved by increasing the number of biopsy is unclear. We therefore evaluated the relationship between number of biopsies and diagnostic accuracy.

Materials and methods We retrospectively evaluated 858 early GCs (623 from endoscopic submucosal dissection and 235 surgical specimens), which we classified as obtained after one, two, or three or more biopsies. We assessed diagnostic accuracy by number of biopsies, and in subgroups by tumor diameter, gross type, and surface color.

Results Almost half the lesions were obtained after one biopsy each, 30 % after two biopsies, and 20 % after three or more biopsies. Although diagnostic accuracy increased with biopsy number, it was significantly greater for the two-biopsy group than the one-biopsy group, (92.5 % vs. 83.9 %, P = 0.0009), but did not significantly differ between the two- and three or more-biopsy groups. This finding was seen when tumors were evaluated by size, but not by elevated type and surface color, for which more biopsies did not improve diagnostic accuracy. Multivariate analysis demonstrated that two or more biopsies was the independent significant factors for diagnostic accuracy.

Conclusions Two biopsies are the optimal number required to diagnose early GC.
Metastasiertes kastrationsresistentes Prostatakarzinom
Authors: Pohlmann Birgit-Kristin
Published: December 2019

Bei der Behandlung von Patienten mit metastasiertem kastrationsresistentem Prostatakarzinom (mCRPC) sollten im Therapieverlauf alle lebensverlängernden Therapien, also Chemo- und endokrine Therapien eingesetzt werden. Verschiedene Kriterien sind hier zu beachten. Zudem beeinflusst die Vorbehandlung im noch hormonnaiven Stadium die Therapiesequenz in der metastasierten Situation. Die Kombinationstherapie aus Androgendeprivation (ADT) plus Chemotherapie (Docetaxel) bzw. ARTA (Androgenrezeptor-gerichtete Substanz) ist hier ein neuer Standard.
Efficient Straightforward Synthesis of Amidopiperazinophanes as Versatile Novel Supramolecular Scaffolds
Authors: Thirunarayanan Ayyavu , Selvarani Sivasamy , Francisco Gracia , Rajakumar Perumal
Published: December 2019

A simple one-pot synthesis of amidopiperazinophanes with a combination of electron-deficient amide groups and electron-rich alkyne and piperazine functionalities has been achieved by using multicomponent reaction (MCR) methodology with the Mannich reaction. Herein, we demonstrate the synthesis of macrocyclic amide structures in good yields. These macrocycles, with electron donor/acceptor sites, are versatile molecules for host–guest and binding.
The Complexity of the Homeopathic Healing Response Part 1: The Role of the Body as a Complex Adaptive System in Simillimum-Initiated Recovery from Disease
Authors: Bell Iris R.
Published: December 2019

Background The concepts of complex systems science enhance the understanding of how people develop and recover from disease. Living systems (human beings, animals, and plants) are self-organizing complex adaptive systems (CAS): that is, interconnected networks. CAS maintain life by initiating and carrying out non-linear dynamical changes to optimize survival fitness and function in the context of an ever-changing environment.

Aims In Part 1 of this two-part paper, we relate concepts from complex systems science to homeopathic healing. The systemic changes of homeopathic healing involve adaptive patterns of responses to salient signals (similia) for reversing disease patterns and generating emergent multi-symptom healing over time.

Methods and Results This narrative review relates homeopathic clinical practice theory to complex systems and network research. Homeopathic medicines communicate individually salient environmental information to the organism, with effects that are multi-system and indirect. The body's defense mechanisms recognize the self-similar information that the correctly chosen simillimum medicine at low dose conveys as a weak external/internal environmental stressor or danger signal (hormetin) to mobilize neural and cellular defenses. The body networks then use endogenous cell to cell signaling and amplify the small magnitude signal information. The results are disproportionately large: that is, non-linear, adaptive, modifications across the inter-connected self-organized biological networks/sub-systems of the body. CAS amplification mechanisms for small or weak signals include stochastic resonance, time-dependent sensitization, and hormesis.

Conclusions The body as a complex system has the capacity for self-organization, emergence and self-similarity over global (overall health and wellbeing) and local (organ) levels of organization. These features are key for future research on the systemic healing that evolves over time during individualized homeopathic treatment.
Thermal Ablation of T1a Renal Cell Carcinoma: The Clinical Evidence
Authors: Young Shamar , Golzarian Jafar , Anderson J. Kyle
Published: December 2019

Renal cell carcinoma (RCC) is most commonly diagnosed at an early (T1a) stage and is typically amenable to several effective treatments. The current gold standard therapy is partial nephrectomy, given its decreased morbidity and similar oncologic outcomes when compared with radical nephrectomy. Thermal ablation is an evolving definitive therapy for T1a RCC which is even less invasive than partial nephrectomy. This article reviews the evidence for thermal ablation in the treatment of T1a RCC and compares outcomes of existing ablation modalities with surgical management.
Intraoperative Irreversible Electroporation in Locally Advanced Pancreatic Cancer: A Guide for the Interventional Radiologist
Authors: Frey Gregory T. , Padula Carlos A. , Stauffer John A. , Toskich Beau B.
Published: December 2019

Efforts to improve mortality associated with locally advanced pancreatic cancer (LAPC) have shown minimal gains despite advances in surgical technique, systemic treatments, and radiation therapy. Locoregional therapy with ablation has not been routinely adopted due to the high risk of complications associated with thermal destruction of the pancreas. Irreversible electroporation (IRE) is an emerging, nonthermal, ablative technology that has demonstrated the ability to generate controlled ablation of LAPC while preserving pancreatic parenchymal integrity. IRE may be performed percutaneously or via laparotomy and will commonly involve multidisciplinary treatment teams. This article will describe the technical aspects of how multidisciplinary IRE is performed during laparotomy at a single tertiary care institution.
Triptycene End-Capped Quinoxalinophenanthrophenazines with Aromatic Substituents – Synthesis, Characterization, and Single-Crystal Structure Analysis
Authors: Ueberricke Lucas , Wieland Sonja , Rominger Frank , Mastalerz Michael
Published: December 2019

In a previous study, we found that one-fold triptycene end-capped quinoxalinophenanthrophenazines (QPPs) arrange in crystals preferably in a coplanar fashion providing high overlap of the π-planes. Thus, resulting in high calculated charge transfer integrals. Most interestingly, this motif was observed for a variety of QPPs derivatives, independently of the nature of their peripheral substituents, e.g. bromide, methoxy, cyano, or triisopropylsilylethynyl groups, and of the crystallization conditions. Here, we describe the synthesis of another small series of three QPPs containing different aromatic substituents at the same position to get an insight, whether these aromatic substituents disturb the otherwise preferred π stacking of the QPP planes.
MDR, Brexit & Co: Worauf Sie sich in 2020 einstellen müssen
Authors: Freye Carolin
Published: December 2019

Klinikeinkäufer müssen sich im Jahr 2020 auf die neuen Gegebenheiten des Medizinproduktemarktes einstellen – dazu gehören u. a. die neue europäische Medical Device Regulation (MDR), der Brexit und als Konsequenz daraus: drohende Lieferabrisse.
Electrostatic Langmuir waves and spin-electron-acoustic waves in spin polarized plasma double layer
Authors: Andreev Pavel A. , Golubeva (Kiriltseva) T. G. , Kumar Punit , Kuz'menkov L. S.
Published: December 2019

The quantum hydrodynamic model for the electrostatic wave in the two parallel layers of two dimensional electron gases is developed. It is considered for two regimes: classic regime and quantum regime with the separate spin evolution. There are two Langmuir-like waves in the classic regime. Their frequency (ω) dependencies have an interferencelike pattern on concentrations ω2∼(n01+n02 ± 2n01n02), where 01 and n02 are the equilibrium concentrations of the electrons in each layer of electron gas and ± refers to the spectrum of two waves. This spectrum appears instead of the couple of Langmuir waves in two noninteracting two-dimensional electron gases. In the quantum regime, the separate spin evolution leads to the spectrum of four waves instead of the two Langmuir waves present in two noninteracting two-dimensional electron gases. Two extra waves are related to the separate spin evolution of electrons. They are associated with the spin-electron acoustic waves. The contribution of the quantum Bohm potential has also been considered. The influence of the concentrations of electrons, the interlayer distance, and the spin polarization on the spectrum of waves is studied numerically.
Morphology-selective preparation and formation mechanism of few-layer graphene on Cu substrate by liquid-phase pulsed laser ablation
Authors: Ren Xudong , Ma Fuhui , Wang Rihong , Qian Lei , Ma Wenxun
Published: December 2019

This paper presented a morphology-selective preparation and formation mechanism of few-layer graphene (FLG) on a Cu substrate by pulsed laser ablation in liquid. It is a simple and controllable route to grow FLG directly on the surface of a copper foil at ambient temperature and normal pressure, which does not need other precursor materials. FLG with 3–10 layers of thickness and continuous hundreds of micrometers in lateral size is obtained. The morphology and structure of FLG were investigated by using a Raman spectrometer, scanning electron microscope, high-resolution transmission electron microscope, and atomic force microscope. The formation mechanism of FLG and the role of the plasma-produced carbon species are put forward based on the interaction between the laser, material, and substrate. Our finding, the direct deposition of FLG on the Cu substrate by pulsed laser ablation in liquid, will open a door to apply this green route to the production of FLG with controlled morphology.
About the cyclotron resonance conditions in magnetized current-carrying plasmas
Authors: Grishanov N. I. , Azarenkov N. A.
Published: December 2019

The resonant cyclotron wave-particle interactions in a cylindrical current-carrying plasma and in two-dimensional axisymmetric toroidal plasma models for tokamaks with D-shaped, elliptic and circular magnetic surfaces are discussed. The corresponding phase resonance conditions are derived by solving the linearized Vlasov equations as a boundary-value problem for perturbed plasma particle distribution functions, accounting for the geometry of a confinement magnetic field in the zero-order over magnetization parameters. It is shown that the Doppler shifts under the cyclotron resonance conditions in the current-carrying plasmas differ from those for a plasma in a uniform magnetic field due to the rotational transformation (including the shear-effects) of the helical magnetic field lines. As for elongated tokamaks, the cyclotron wave-particle resonance conditions in the general case, along with helicity-corrections, involve the bounce-resonances of the untrapped (circulating, passing) and two groups of so-called t-trapped and d-trapped particles.
Two-dimensional carbon nitride (2DCN) nanosheets: Tuning of novel electronic and magnetic properties by hydrogenation, atom substitution and defect engineering
Authors: Bafekry Asadollah , Shayesteh Saber Farjami , Peeters Francois M.
Published: December 2019

By employing first-principles calculations within the framework of density functional theory, we investigated the structural, electronic, and magnetic properties of graphene and various two-dimensional carbon-nitride (2DNC) nanosheets. The different 2DCN gives rise to diverse electronic properties such as metals (C3N2), semimetals (C4N and C9N4), half-metals (C4N3), ferromagnetic-metals (C9N7), semiconductors (C2N, C3N, C3N4, C6N6, and C6N8), spin-glass semiconductors (C10N9 and C14N12), and insulators (C2N2). Furthermore, the effects of adsorption and substitution of hydrogen atoms as well as N-vacancy defects on the electronic and magnetic properties are systematically studied. The introduction of point defects, including N vacancies, interstitial H impurity into graphene and different 2DCN crystals, results in very different band structures. Defect engineering leads to the discovery of potentially exotic properties that make 2DCN interesting for future investigations and emerging technological applications with precisely tailored properties. These properties can be useful for applications in various fields such as catalysis, energy storage, nanoelectronic devices, spintronics, optoelectronics, and nanosensors.
Floquet topological insulator laser
Authors: Ivanov Sergey K. , Zhang Yiqi , Kartashov Yaroslav V. , Skryabin Dmitry V.
Published: December 2019

We introduce a class of topological lasers based on the photonic Floquet topological insulator concept. The proposed system is realized as a truncated array of lasing helical waveguides, where the pseudomagnetic field arises due to twisting of the waveguides along the propagation direction that breaks the time-reversal symmetry and opens up a topological gap. When sufficient gain is provided in the edge channels of the array, the system lases into topological edge states. Topological lasing is stable only in certain intervals of the Bloch momenta that ensure a dynamic, but stable balance between the linear amplification and nonlinear absorption leading to the formation of breathing edge states. We also illustrate topological robustness of the edge currents by simulating lattice defects and triangular arrangements of the waveguides.
On the origin of oscillatory interactions between surfaces mediated by polyelectrolyte solution
Authors: Jiang Jian , Ginzburg Valeriy V. , Wang Zhen-Gang
Published: December 2019

We use a numerical implementation of polymer classical density functional theory with an incompressibility condition to study the system consisting of nonadsorbing polyelectrolytes confined by two planar surfaces and quantify the effective interaction between the two planar surfaces as a function of the polyelectrolyte and salt concentrations. Our results indicate that for the uncharged surfaces (and weakly charged surfaces), the effective interaction primarily consists of a short-range attraction due to the depletion followed by repulsion due to the electric double layer overlapping and electrostatic correlations. For salt-free and low salt concentration systems, the magnitude of the repulsion barrier is determined by the overlap between the electric double layers, while at relatively high salt concentrations, the magnitude of the repulsion barrier is determined by the electrostatic correlations. Due to the competition between the electric double layer and the electrostatic correlations, the magnitude of the repulsion barrier varies nonmonotonically. In contrast, a mean-field Poisson-Boltzmann treatment of the electrostatics predicts a monotonically decreasing repulsion barrier with increasing salt concentration. At moderate salt concentrations, our theory predicts oscillatory interaction profiles. A comparison with the mean-field Poisson-Boltzmann treatment of electrostatics suggests that the oscillations are due primarily to electrostatic correlations.
Suppression of high-power microwave window breakdown by the sweeping-out-electron effect with an external dc bias electric field
Authors: Zhang Jianwei , Luo Wei , Wang Hongguang , Liu Chunliang , Li Yongdong , Lin Shu
Published: December 2019

To suppress microwave window breakdown, an external parallel dc bias electric field is applied to sweep out the electrons from the discharge zone. The development of microwave window breakdown under an external dc electric field is investigated using particle-in-cell and Monte Carlo collision simulation. The results show that the number of multipactor electrons decreases with the strength of the external unidirectional dc electric field when the size of the microwave window is finite. In addition, the threshold of breakdown is strongly influenced by the direction of the external bidirectional dc electric field. When the electric field is directed from the center to the edge of the microwave window, breakdown occurs more readily than in the absence of the electric field. However, when the electric field is directed toward the center of the microwave window, the discharge process starts at the edge of the window and develops to the center of the window. This is because a smaller density of electrons at the window edge results in a smaller gas pressure and the low gas pressure above the dielectric surface thus makes formation of the plasma more difficult. As a result, the early stage of breakdown is suppressed and the maximum transmitting power is enhanced.
Effects of off-stoichiometry and Ti doping on thermoelectric performance of Fe2VAl Heusler compound
Authors: Nishino Y. , Kamizono S. , Miyazaki H. , Kimura K.
Published: December 2019

Improvement of p-type thermoelectric performance for Heusler-type Fe2V1.08−yTiyAl0.92 alloys with y = 0–0.34 has been investigated, focusing on the valence electron concentration (VEC) effect for tuning the Fermi level across the center of the pseudogap via Ti doping, combined with a constructive modification of the electronic structure around the pseudogap through the off-stoichiometric V/Al composition change. The Seebeck coefficient changes its sign from negative to positive at around VEC = 6.0 due to Ti doping, and the peak value reaches approximately 120 μV/K at 350 K for y = 0.22. As a result of a drastic reduction in the electrical resistivity at 300–600 K, the power factor enhances up to 3.7 × 10−3 W/mK2 at 300 K for y = 0.30. The thermal conductivity increases with Ti doping to 15.5 W/mK at 350 K for y = 0.16, because of an increased stability of the L21 structure for VEC closer to 6.0, but then decreases to approximately 12 W/mK for y = 0.34. While the dimensionless figure of merit ZT = 0.13 is achieved at 500 K for y = 0.34, the codoping of Ta (Fe2V0.69Ti0.34Ta0.05Al0.92) leads to a further enhancement of up to ZT = 0.18 at 500 K.
Electroreflectance study on optical anisotropy in β-Ga2O3
Authors: Onuma T. , Tanaka K. , Sasaki K. , Yamaguchi T. , Honda T. , Kuramata A. , Yamakoshi S. , Higashiwaki M.
Published: December 2019

Electroreflectance (ER) spectra of β-Ga2O3 were measured using Schottky barrier diodes. The ER spectra were well fitted to a third derivative line shape function by assuming three excitonic transitions. The transition energies exhibited moderate blueshifts with an external reverse bias by reflecting the contribution of transitions at M0 type critical points. Optical anisotropy was selectively observed in the polarized ER spectra. The fittings for the third derivative line shape function gave relatively large broadening parameters (0.11–0.89 eV) due mainly to the large exciton-longitudinal-optical-phonon interaction in β-Ga2O3. The ER spectra exhibited a third derivative line shape with a Franz-Keldysh oscillation superimposed on it. The results demonstrate that ER measurements are useful for investigating optical anisotropy in β-Ga2O3 and related alloys.
Effects of eddy shocklets on the segregation and evaporation of droplets in highly compressible shear layers
Authors: Ren Zhaoxin , Wang Bing , Zhang Fan , Zheng Longxi
Published: December 2019

Numerical studies of droplet-laden spatially developing shear layers are conducted with a high convective Mach number (Mc = 1.0), in which a high-order hybrid weighted essentially nonoscillatory scheme is used for the turbulence as well as shock capturing. The evaporating droplets are tracked as point mass in the Lagrangian manner, and the two-way coupling between the flow and droplets is considered by adding the source terms to the governing equations of the gas-phase. This research focuses on the preferential concentration of droplets and the interactions between droplets and eddy shocklets in the shear layers with high flow compressibility and analyzes the underlying mechanisms of momentum and thermal response behaviors of droplets to eddy shocklets. The segregation of droplets exhibits the strongest spatial preference in the highly compressible shearing vortices, and droplets tend to accumulate as stripes behind the shocklets, associated with the coherent structures. The high flow compressibility results in the strong spatiotemporal variations of pressure and temperature, and the distributions of the expansion zones with low temperature and the compression zones with high temperature occur alternately in the shear layer. The relaxation response behaviors of the droplets to the change of momentum and thermal features of the surrounding carrier gas result in the delay of droplet evaporation in the high temperature region and then the enhancement of droplet-vapors in the low temperature region. The present observations can be ascribed to the interactions between the dispersed droplets and the distributed eddy shocklets in the shear flows with high compressibility.
Electroluminescence of Cr3+ and pseudo-Stark effect in β-Ga2O3 Schottky barrier diodes
Authors: Fiedler A. , Galazka Z. , Irmscher K.
Published: December 2019

Bright, red electroluminescence is generated in reverse biased Schottky barrier diodes (SBDs) based on β-Ga2O3 single crystals codoped with chromium and silicon. It is due to intracenter transitions of octahedrally coordinated Cr3+ ions excited by electron impact in the depletion layer of the diodes. The electroluminescence spectrum around 700 nm in wavelength is nearly identical to the spectrum of the well-known photoluminescence of Cr3+ in β-Ga2O3, which is featured by the two lines R1 and R2. In contrast to the photoluminescence, however, in the electroluminescence, each of the R1 and R2 lines is additionally split by 1.5–3 meV. Since the R1/R2 lines correspond to transitions from two Kramers-degenerate states (split 2E excited state) to the ground state 4A2, this splitting cannot be ascribed to the normal Stark effect in the strong electric field of the Schottky barrier diode's depletion layer. Instead, we explain the splitting by the pseudo-Stark effect that occurs because the Cr3+ ions replace Ga3+ at two kinds of energetically equivalent octahedral sites that differ crystallographically by an inversion at the Cr ion. Superposition of the dominating R1 doublet radiation would result in a tunable beat frequency of about 0.4–0.7 THz and might be utilized for a terahertz light source. Moreover, the electroluminescence of chromium is representative of the ability to excite the luminescent states of other transition metals. Hence, high temperature light-emitting SBDs in different colors are a potential application for β-Ga2O3.
Solitary sound waves in weakly dispersive neutron stars
Authors: Tsintsadze L. N. , Rozina Ch. , Tsintsadze N. L.
Published: December 2019

We examine the degenerate characteristics of the weakly ionized neutron stars (WINSs), while considering magnetic field quantization. A new set of quantum (QMHD) equations is obtained, which describes the homogeneous, weakly ionized, collisional degenerate neutron star. Then, using the obtained QMHD model, we have shown that in a WINS, electrons are responsible for the appearance of an additional term in momentum equations of neutrons, and hence, we formulate the linear dispersive properties of the medium. It is found that the nonlinear dispersive effects cause the broadening of the wave profile to balance the nonlinear steepening, so that the nonlinear stationary waves can be formed in the dispersive neutrino stars. In this context, it is demonstrated that neutron sound waves of WINS are described by two different modified Korteweg–de Vries equations. The present astrophysical plasma is highly recommended to investigate the propagation of proper waves in a strongly magnetized, ionized hydrogen atom.
Self-formed PbI2-DMSO adduct for highly efficient and stable perovskite solar cells
Authors: Liu Jingjing , Chen Bingbing , Wang Qi , Li Renjie , Shi Biao , Li Yucheng , Hou Fuhua , Cui Xinghua , Wang Pengyang , Li Yuelong , Zhao Ying , Zhang Xiaodan
Published: December 2019

Currently, chemical vapor deposition (CVD) has attracted widespread attention for preparing high efficiency and large-scale perovskite solar cells (PSCs). The surface morphology and crystallinity of precursor lead iodide (PbI2) films play a critical role in the subsequent CVD process. Here, we use a self-formed PbI2-dimethyl sulfoxide adduct in precursor PbI2 for fabricating a high quality perovskite film. The results show that a larger grain size and excessive PbI2 in the perovskite film effectively suppress carrier recombination, which is helpful to improve the device stability and efficiency. It is noted that the device maintained an excellent stability with almost the same efficiency after 1000 h (in a dry N2 glovebox, 25 °C). Finally, the PSC by using the CVD method exhibits a high power conversion efficiency of 17.9% with a bandgap of 1.60 eV, an open voltage (VOC) of 1140 mV, a short-circuit current density (JSC) of 20.1 mA/cm2, and a fill factor of 78%. This method provides guidance for preparing large-area solar cells or applications in tandem solar cells.
Magnesium oxide at extreme temperatures and pressures studied with first-principles simulations
Authors: Soubiran François , González-Cataldo Felipe , Driver Kevin P. , Zhang Shuai , Militzer Burkhard
Published: December 2019

We combine two first-principles computer simulation techniques, path integral Monte Carlo and density functional theory molecular dynamics, to determine the equation of state of magnesium oxide in the regime of warm dense matter, with densities ranging from 0.35 to 71 g cm−3 and temperatures ranging from 10 000 K to 5 × 108 K. These conditions are relevant for the interiors of giant planets and stars as well as for shock wave compression measurements and inertial confinement fusion experiments. We study the electronic structure of MgO and the ionization mechanisms as a function of density and temperature. We show that the L-shell orbitals of magnesium and oxygen hybridize at high density. This results in a gradual ionization of the L-shell with increasing density and temperature. In this regard, MgO behaves differently from pure oxygen, which is reflected in the shape of the MgO principal shock Hugoniot curve. The curve of oxygen shows two compression maxima, while that of MgO shows only one. We predict a maximum compression ratio of 4.66 to occur for a temperature of 6.73 × 107 K. Finally, we study how multiple shocks and ramp waves can be used to cover a large range of densities and temperatures.
Global existence of weak solutions to the compressible quantum Navier-Stokes equations with degenerate viscosity
Authors: Lü Boqiang , Zhang Rong , Zhong Xin
Published: December 2019

We study the compressible quantum Navier-Stokes (QNS) equations with degenerate viscosity in the three dimensional periodic domains. On the one hand, we consider QNS with additional damping terms. Motivated by the recent works of Li and Xin [e-print arXiv:1504.06826] and P. Antonelli and S. Spirito [Arch. Ration. Mech. Anal. 225, 1161–1199 (2017)], we construct a suitable approximate system which has smooth solutions satisfying the energy inequality and the BD entropy estimate. Using this system, we obtain the global existence of weak solutions to the compressible QNS equations with damping terms for large initial data. Moreover, we obtain some new a priori estimates, which can avoid using the assumption that the gradient of the velocity is a well-defined function, which was indeed used directly in the work of Vasseur and Yu [SIAM J. Math. Anal. 48, 1489–1511 (2016); Invent. Math. 206, 935–974 (2016)]. On the other hand, in the absence of damping terms, we also prove the global existence of weak solutions to the compressible QNS equations without the lower bound assumption on the dispersive coefficient, which improves the previous result of P. Antonelli and S. Spirito [Arch. Ration. Mech. Anal. 225, 1161–1199 (2017)].
Single-shot curvature sensing with non-coaxial Fibonacci-sieve filter in telescope
Authors: Zhang Xiuping , Zhang Yingge , Zhang Junyong , Yang Pengqian , Zhu Jianqiang
Published: December 2019

Wavefront curvature sensing is considered a promising method for measuring wavefront aberrations, which has widespread applications ranging from adaptive optics to optical testing. Here, a single-shot curvature sensing with a noncoaxial Fibonacci-sieve filter in the telescope was proposed to reconstruct the wavefront distribution of tiny transmissive objects fabricated on a chrome plate. A noncoaxial Fibonacci-sieve filter in the telescope was designed to realize simultaneously triplanar diffraction patterns at a recording plane; thus, the wavefront can be quantitatively retrieved by a single exposure. A trifocal Fibonacci sieve was fabricated, and its feasibility was verified in the optical region experimentally. With the advantages of simple operation in real-time and reducing the effects of vibration, this method makes it possible to be applied to various imaging and detection techniques, especially for biological imaging and wavefront detection.
Synthesis of PEG-grafted boron doped Si nanocrystals
Authors: Greenhagen Jesse R. , Andaraarachchi Himashi P. , Li Zhaohan , Kortshagen Uwe R.
Published: December 2019

Silicon nanocrystals are intriguing materials for biomedical imaging applications because of their unique optical properties and biological compatibility. We report a new surface functionalization route to synthesize biological buffer soluble and colloidally stable silicon nanocrystals, which is enabled by surface boron doping. Harnessing the distinctive Lewis acidic boron surface sites, postsynthetic modifications of plasma synthesized boron doped nanocrystals were carried out with polyethylene glycol (PEG-OH) ligands in dimethyl sulfoxide under photochemical conditions. The influence of PEG concentration, PEG molecular weight, and boron doping percentage on the nanocrystal solubility in a biological buffer has been investigated. The boron doping facilitates the surface functionalization via two probable pathways, by providing excellent initial dispersiblity in polar solvents and providing available acidic boron surface sites for bonding. These boron doped silicon nanocrystals have nearly identical absorption features as intrinsic silicon nanocrystals, indicating that they are promising candidates for biological imaging applications.
Double-core ionization photoelectron spectroscopy of C6H6: Breakdown of the “intuitive” ortho-meta-para binding energy ordering of K−1K−1 states
Authors: Carniato S. , Selles P. , Ferté A. , Berrah N. , Wuosmaa A. H. , Nakano M. , Hikosaka Y. , Ito K. , Žitnik M. , Bučar K. , Andric L. , Palaudoux J. , Penent F. , Lablanquie P.
Published: December 2019

Single-site Double-Core Hole (ss-DCH or K−2) and two-site Double-Core Hole (ts-DCH or K−1K−1) photoelectron spectra including satellite lines were experimentally recorded for the aromatic C6H6 molecule using the synchrotron radiation and multielectron coincidence technique. Density functional theory and post-Hartree-Fock simulations providing binding energies and relative intensities allow us to clearly assign the main K−2 line and its satellites. K−1K−1 states’ positions and assignments are further identified using a core-equivalent model. We predict that, contrary to what has been observed in the C2H2n series of molecules, the K−1K−1 energy-level ordering in C6H6 does not reflect the core-hole distances between the two holes.
Three-step growth of highly photoresponsive BaSi2 light absorbing layers with uniform Ba to Si atomic ratios
Authors: Yamashita Yudai , Sato Takuma , Saitoh Noriyuki , Yoshizawa Noriko , Toko Kaoru , Suemasu Takashi
Published: December 2019

Barium disilicide (BaSi2) shows great promise as a light absorbing material for solar cell applications. Thus, it is important to form high-quality BaSi2 films with a low defect density. We previously found that the photoresponsivity of a-axis-oriented BaSi2 epitaxial films was enhanced drastically when formed under Si-rich conditions by molecular beam epitaxy. However, the degree of a-axis crystal orientation normal to the sample surface was degraded. In this work, we investigated the origin of this degradation by cross-sectional transmission electron microscopy (X-TEM). It was found that excess Si atoms in BaSi2 films diffused out and precipitated around the BaSi2/Si interface, resulting in the formation of Si layers with an interface roughness of 0.2–0.3 μm when grown under Si-rich conditions. Furthermore, extended defects stemming from such rough interface regions were detected by deep level transient spectroscopy, and they acted as hole trap defects. To achieve high photoresponsivity in BaSi2 films under Si-rich conditions while avoiding such Si precipitation, we proposed a three-step growth method for BaSi2 films. X-TEM observations confirmed uniform Ba to Si atomic ratios throughout the entire layer and smooth BaSi2/Si interfaces. In addition, relative to films grown by the conventional two-step method, the a-axis orientation was improved significantly, and the photoresponsivity increased by approximately five times to reach 0.5 A/W at a wavelength of 800 nm under a bias voltage of −0.1 V. This corresponds to an external quantum efficiency above 90%.
A portable rotating disc as blood rheometer
Authors: Agarwal Rahul , Sarkar Arnab , Paul Subhechchha , Chakraborty Suman
Published: December 2019

Abnormalities in biophysical properties of blood are often strong indicators of life threatening infections. However, there is no existing device that integrates the sensing of blood hematocrit (or equivalently, packed cell volume), viscosity, and erythrocyte sedimentation rate (ESR) in a unified paradigm for point-of-care diagnostics. In an effort to develop a rapid, integrated, accurate, portable, and inexpensive sensing platform to diagnose the corresponding pathophysical parameters, we develop a simple and portable spinning disk capable of yielding these results in a few minutes instead of the traditional duration of hours. The device requires only 40 μl of unprocessed freshly drawn blood treated with an anticoagulant ethylenediaminetetraacetic acid, instead of the traditional requirement of 2 ml of blood for just the ESR measurement and still more for hematocrit determination. In contrast to the sophisticated instrumentation required to determine these parameters by the previously proposed microfluidic devices, our device requires minimal infrastructure. The measurement of hematocrit is accomplished by means of a simple 15 cm ruler. Additionally, a simple measurement of the blood flow rate enables the determination of the ESR value. The rapidity, ease, accuracy, portability, frugality, and possible automation of the overall measurement process of some of the most important parameters of blood under infection pinpoint its utility in extreme point-of-care settings.
Polarizabilities, dispersion coefficients, and retardation functions at the complete basis set CCSD limit: From Be to Ba plus Yb
Authors: Visentin Giorgio , Buchachenko Alexei A.
Published: December 2019

Static and dynamic polarizabilities of alkaline earth metal atoms Be-Ba and of the Yb atom, as well as dispersion coefficients and retardation functions for their long-range interactions, are used as a benchmark for the restricted coupled cluster method with singles and doubles (CCSD) and noniterative triples added [CCSD(T)] and related polarization propagator CCSD(3) methods at the complete basis set limit. The latter is attained through the sequence of the augmented correlation-consistent polarized weighted core valence n-zeta basis sets with the exact 2-component approximation for the scalar relativistic effects and with the small-core effective core potentials (for Ca, Sr, and Ba). At the converged level of core correlation treatment, the finite-field CCSD(T) method reproduces the best available data for the static dipole and quadrupole polarizabilities better than 1% and 4%, respectively. Systematic cancelation of the triple contribution in the CCSD(3) calculations of the dynamic polarizabilities of alkaline earth metal atoms makes their dispersion coefficients accurate within 3%. The retardation functions are computed and used for the analysis of the long-range interactions in the homonuclear dimers. Implications to accurate ab initio calculations of the global interaction potentials are discussed.
Detection of nitric oxide with Faraday rotation spectroscopy at 5.33 µm
Authors: Fang Bo , Yang Na-na , Wang Chun-hui , Zhao Wei-xiong , Xu Xue-zhe , Zhang Yang , Zhang Wei-jun
Published: December 2019

We report the development of a static magnetic field Faraday rotation spectrometer for NO detection. A 5.33 µm continuous-wave quantum cascade laser was used as the probing laser. Line absorption at 1875.81 cm−1 (2Π3/2Q(3/2), υ=1←0) was chosen for the detection. By using a Chernin type multipass cell, a detection precision of 1.15 ppbv (1σ, 1s) was achieved with an absorption pathlength of 108 m. This value was reduced to 0.43 ppbv by increasing the data-acquisition time to 15 s.
John Wheeler’s H-bomb blues
Authors: Wellerstein Alex
Published: December 2019

In 1953, as a political battle raged over the US’s nuclear future, the eminent physicist lost a classified document, about the hydrogen bomb, on an overnight train from Philadelphia to Washington, DC.