bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of cosmic ray dynamics and ionospheric parameters during increased solar activity and magnetic storms
Authors: Mandrikova Oksana , Polozov Yuryi , Mandrikova Bogdana
Published: November 2019

Based on the ground station data, the paper investigates the dynamics of space rays and ionospheric parameters during strong and moderate magnetic storms 2018. The research was carried out applying new methods for modeling and data analysis suggested by the authors. In the course of investigation, anomalous changes in ionospheric parameters preceding and accompanying magnetic storms were detected. When they were compared with the data of cosmic rays and interplanetary magnetic field, correlation was observed. It confirms the solar nature of the detected ionospheric effects. Application of regression methods confirmed the assumption on statistically significant effect of interplanetary magnetic field parameters on ionospheric parameter dynamics during increased solar activity. The results are of interest in the tasks of space weather forecast.
Diagnostics of geomagnetically-induced currents in high-tension electric transmission lines
Authors: Sivokon Vladimir , Cherneva Nina , Malkin Evgeniy
Published: November 2019

The problem of geomagnetically-induced currents (GIC) effect on electrotechnical systems is topical as long as uninterrupted power distribution is critically important for all the spheres of human activity. Our investigations showed the possibility of GIC diagnostics based on the estimates of industrial current higher harmonics and showed that even harmonics correlate with the Earth magnetic field changes in a greater degree. However, the measurements carried out in 220 V network showed low and not always univocal correlation of the processes. Thus, we propose a technique for diagnostics of geomagnetically-induced currents in high-tension electric transmission lines**.
Magnetic field of the Hot Earth. Reversals, magnetic anomalies and mechanism of the magnetic poles drift.
Authors: Kuznetsov Vladimir
Published: November 2019

Principally new model of the magnetic field of the Hot Earth is proposed. Unlike the commonly accepted approach which considers that the Earth’s temperature doesn’t increase because heat released under selfgravitation is removed through radiation our model assumes that early substance of the Earth heated up to 30 000 K was a superheated and overcompressed vapour.

Cooling the Earth substance was condensing. The system was expanding adiabatically that governed the character of the Earth enlargement. This scheme origins from the phase transition (PT) of condensation-evaporation under the benefit of condensation. PT provides the heat, geodynamics of expansion and the Earth’s magnetic field (EMF).

The high temperature of the substance causes its thermoionization, whereas PT operation relating to mass transfer initiates charges separation and generation of the double electric layer (DEL). A diurnal rotation of DEL induces a weak initial EMF which enhances then at the expense of the Hall dynamo (Hall current) inside PT area. The benefit of evaporation causes the Earth compression and reversal of the EMF polarity.

The approach we develop provides an insight into features of the magnetic field of the planets and satellites at the Sun system.
On the question of the relationship of variations in geophysical fields, lunar-solar tidal effects and seismic events
Authors: Bataleva Elena
Published: November 2019

Based on the results of instrumental observations made in the Tien Shan, the interrelation of time variations of a number of geophysical fields and seismic events is established. According to the results of the correlation analysis, it was concluded that the fault zones are characterized by significantly higher variations of geophysical fields, an intense response to weak external influences in the form of a solid moon-solar tide.
Search for geophysical structures by their mathematical models and samples
Authors: Mochalov Vladimir , Mochalova Anastasia
Published: November 2019

When we analyze geophysical data, the task of searching for structures by their samples and mathematical models often appears. We propose to use deep neural networks (DNN) to search and detect the forms of geophysical structures. At the same time, both the structure samples themselves and the synthesized structure samples according to their mathematical models act as a training dataset. End-to-end demonstration examples of the highlighting of reflection traces from different layers of the ionosphere in the ionograms, as well as the highlighting of whistler forms in the VLF spectrograms are presented.
Solar cosmic rays by the ground level observation: anisotropy
Authors: Balabin Yury , Germanenko Aleksei , Gvozdevsky Boris
Published: November 2019

Nine large GLE events have been studied by the improved methodic of the inverse problem solution. The problems of the SCR anisotropy form setting have been in detail worked out in the new methodic. The SCR pitch-angle distribution form is automatically selected in solution search. It significantly improves the solutions convergence.
Development of a methodology to estimate a region and waiting period for strong Kamchatka earthquakes based on seismic and ionospheric predictive signs
Authors: Bogdanov Vadim , Pavlov Aleksey
Published: November 2019

In this paper, an attempt is made to combine seismological and ionospheric predictive signs formed on the eve of earthquakes in order to develop a methodology for assessing the region and the time period of waiting for strong Kamchatka earthquakes with energy class KS ≥ 13:5 (M ≥ 6:0). The seismological parameter determined on the basis of the probabilistic model of the seismicity of Kamchatka region and allowing to estimate the region and the probability of occurrence of a strong earthquake in it is proposed as a mediumterm precursor. The complex of ionospheric disturbances is considered as a short-term precursor with a waiting period of up to 5 days for earthquakes. The estimation of their prognostic efficiency for the considered precursors is carried out by methods A. A. Gusev and G. M. Molchan, and their joint analysis was performed on the eve of earthquakes with KS ≥ 13:5 (M ≥ 6:0), that occurred in the period 2009–2018.
Perioperative management of patients undergoing antithrombotic treatment in oral surgery in France: a survey
Authors: Touny Marion , Catros Sylvain , Fricain Jean-Christophe , Fénelon Mathilde
Published: November 2019

Introduction: The prevention and treatment of thromboembolic events is generally based on the prescription of antithrombotics. These drugs are associated with an increased hemorrhagic risk. The procedures for the management of patients under antithrombotic treatment are described in the recommendations of the Société Française de Chirurgie Orale (SFCO), published in 2015. The main objective of this study was to describe dentists' knowledge and practices regarding the perioperative management of patients under antithrombotic agents in oral surgery in France. Materials and methods: A national cross-sectional study was conducted between June and September 2018. An electronic questionnaire was created on Google Forms and sent through social networks. Results: In total, 185 responses were collected. Two-thirds of the respondents reported that they were aware of the 2015 recommendations. Ten respondents reported that they did not manage patients treated with antithrombotic drugs. Among the respondents who managed such patients, 25% and 16% ordered hemostasis tests for patients treated with direct anticoagulants and antiplatelet agents, respectively. Discussion: Although 71% of dentists considered themselves properly informed, one-third stated that they were not aware of SFCO's 2015 recommendations. Among those who were aware of these recommendations, 47% correctly ordered hemostasis tests before surgery in patients on antithrombotic medication. Conclusion: This study indicates that there is a lack of knowledge and noncompliance with the recommendations among at least half the sample population regarding perioperative management of patients on antithrombotic therapy.
Einfluss der beruflichen Tätigkeit auf den Therapieerfolg von
Patienten mit primär extrinsischem Impingement der
Schulter
Authors: Köhler Hans-Christian , Hacke Claudia , Gutcke André , Tischer Thomas , Schulze Christoph
Published: November 2019

Ziel der Studie Schulterbeschwerden sind eine bedeutende Ursache
für Arbeitsunfähigkeit. Bei zugrundeliegendem subakromialem
Impingementsyndrom wurde der Erfolg unterschiedlicher Therapieformen kaum
getrennt nach unterschiedlicher beruflicher Tätigkeit untersucht. Diese
prospektive vergleichende klinische Verlaufsbeobachtung untersucht den Einfluss
der beruflichen Tätigkeit bei konservativer und operativer Therapie auf
das Therapieergebnis hinsichtlich Funktion, Schmerz und
Arbeitsfähigkeit.

Methodik In diese Studie konnten 97 Patienten (Frauen: n=22,
Männer: n=75; Durchschnittsalter: 43,1±10,1 Jahre) mit
einem primär extrinsischem Impingementsyndrom der Schulter
eingeschlossen werden. Die Patienten wurden primär in die beiden
Berufsgruppen der körperlich Arbeitenden und Bürotätigen
unterteilt. Im Weiteren wurden auch jeweils die Subgruppen konservative bzw.
operative Therapie betrachtet. Es erfolgte entweder eine rein konservative
Therapie oder eine operative Therapie mit physiotherapeutischer Nachbehandlung.
Die konservative Therapie erfolgte durch strukturierte physiotherapeutisch
angeleitete Neukoordination der Schultergürtelmuskulatur. Operativ wurde
eine arthroskopische subakromiale Dekompression durchgeführt. Die
Patienten wurden 3, 6 und 12 Monate nach Interventionsbeginn nachuntersucht und
Schulterfunktion (Constant-Score), Schmerz (NRS) sowie
Arbeitsunfähigkeitsdauer erfasst. Die statistische Auswertung erfolgte
mittels mixed ANOVA um die Effekte einer konservativen bzw. operativen Therapie
auf die Zielparameter zwischen unterschiedlich beruflich tätigen
Personen im Nachbeobachtungszeitraum von 3, 6 und 12 Monaten zu berechnen
(Therapieform*Berufstätigkeit*Zeit). Die Modelle wurden
zusätzlich für Alter, Geschlecht und BMI adjustiert.

Ergebnisse Die beiden Berufsgruppen zeigten hinsichtlich Funktion und
Schmerzniveau keinen statistisch signifikanten Unterschied sowohl nach
konservativer als auch nach operativer Therapie. Bürotätige
waren 3 Monate nach operativer Versorgung signifikant länger
arbeitsunfähig als nach konservativer Therapie (7,3±0,8 Wochen
gegenüber 0,5±7,3 Wochen; p<0,001). Auch war die Gruppe
der operierten Bürotätigen gegenüber operierten
körperlich Arbeitenden 3 Monate nach Operation signifikant
länger arbeitsunfähig (3,0±1,1 Wochen gegenüber
7,3±0,8 Wochen; p=0,002).

Schlussfolgerung Zum einen zeigte sich Bürotätigkeit als
negativer Prädiktor, da operativ behandelte Bürotätige
gegenüber operativ behandelten körperlich Arbeitenden eine
statistisch signifikant längere Arbeitsunfähigkeit hatten. Zum
anderen war aber auch die operative Versorgung ein negativer Prädiktor,
weil operativ behandelte Bürotätige gegenüber
konservativ behandelten Bürotätigen eine statistisch signifikant
längere Arbeitsunfähigkeit hatten. Darüber hinaus zeigte
sich keine langfristige Überlegenheit einer Therapieform unter
Berücksichtigung der Berufsgruppe.
Copper-Mediated One-Pot Synthesis of Indoles through Sequential Hydroamination and Cross-Dehydrogenative Coupling Reaction
Authors: Sun Peng , Yang Jiaojiao , Song Zirui , Cai Yichao , Liu Yajie , Chen Chunxia , Chen Xin , Peng Jinsong
Published: November 2019

Starting from simple anilines and ester arylpropiolates, an efficient one-pot synthesis of 2-arylindole-3-carboxylate derivatives has been developed through copper-mediated sequential hydroamination and cross-dehydrogenative coupling (CDC) reaction. The initial hydroamination of anilines to ester arylpropiolates in benzene can proceed in a stereoselective manner to give ester (Z)-3-(arylamino)acrylates in the presence of CuCl2/phenanthroline, KMnO4, and KHCO3 at 120 °C. Sequentially, these in situ functionalized adducts can undergo direct intramolecular oxidative alkenylation of aromatic C–H bond in mixed solvents (benzene/DMSO 1:1) at 130 °C affording multi-substituted­ indoles in good to high yields.
BF3·OEt2-Catalyzed Synthesis of anti-β-(N-Arylamino)-α-hydroxynitriles by Regio- and Diastereospecific Ring Opening of 3-Aryloxirane-2-carbonitriles with Anilines
Authors: Xu Chuangchuang , Lu Yang , Xu Kaini , Xu Jiaxi
Published: November 2019

A safe and convenient synthetic method to anti-β-(N-arylamino)-α-hydroxynitriles from 3-aryloxirane-2-carbonitriles and anilines was developed under the catalysis of BF3·OEt2 in ethanol. In this method, BF3·OEt2 first reacts with ethanol to produce the true catalyst of super­ acid H[B(OEt)F3], followed by an acid-catalyzed regio- and diastereospecific ring opening of oxirane-2-carbonitriles with anilines, generating anti-β-(N-arylamino)-α-hydroxynitriles. The method features the advantages of non-metal catalysis, short reaction times, and easy operation, and uses an environmentally friendly solvent.
Total Synthesis of 1-Oxomiltirone and Arucadiol
Authors: Oh Chang Ho , Seong Chaehyeon , Kang Juyeon , Chai Uiseong , Mac Dinh Hung
Published: November 2019

A practical and efficient approach for the total synthesis of arucadiol and 1-oxomiltirone is reported. The key step which involves an intramolecular [4+2] cycloaddition catalyzed by gold(III) bromide or copper(II) triflate leads to the formation of 6-6-6-fused aromatic abietane core.
Short-Term Complications Associated with Surgical Ligation of Patent Ductus Arteriosus in ELBW Infants: A 25-Year Cohort Study
Authors: Foster Megan , Mallett Lea H. , Govande Vinayak , Vora Niraj , Castro Abel , Raju Muppala , Cantey Joseph B.
Published: November 2019

Objective This article aims to determine the incidence of short-term complications of surgical patent ductus arteriosus (PDA) ligations, the factors associated with those complications, and whether complications are associated with poor long-term outcomes.

Study Design Retrospective cohort study of all extremely low birth weight (ELBW, < 1,000 g) infants who underwent surgical PDA ligation at a single-center neonatal intensive care unit from 1989 to 2015. Demographic, clinical, and laboratory data were reviewed. The primary outcome was development of a short-term (< 2 weeks from ligation) surgical complication. Secondary outcomes include bronchopulmonary dysplasia (BPD), length of stay, and mortality.

Results A total of 180 ELBW infants were included; median gestational age and birth weight was 24 weeks and 683 g, respectively, and 44% of infants had at least one short-term complication. Need for vasopressors (33%) was the most common medical complication and vocal cord paralysis (9%) was the most common surgical complication. Younger corrected gestational age at time of repair was associated with increased risk for complications. Mortality, length of stay, and BPD rates were similar between infants with and without complications.

Conclusion Serious complications were seen in a minority of infants. Additional research is needed to determine if short-term complications are associated with long-term adverse outcomes.
Manejo de la fractura-luxación Interfalángica proximal mediante fijador externo tipo Suzuki. Protocolo de tratamiento y resultados preliminares
Authors: Laredo Rivero Rafael , Fabra Bárbara Maria Pérez , Delgado Alcalá Victor , Cibantos Martínez Roberto , Gomez Garrido David , Cervera Irima Javier
Published: November 2019

Introducción La fractura-luxación de la articulación interfalángica proximal de la mano es frecuente en la práctica clínica, sin embargo, no existe un consenso ni indicaciones definidas para cada tipo de fractura, lo que supone un importante campo de confusión y su tratamiento continúa siendo hoy en día un reto no resuelto. Nos preguntamos si es posible simplificar este algoritmo y utilizar el fijador tipo Suzuki de forma protocolizada para manejar la gran mayoría de lesiones con indicación quirúrgica.

Métodos Se recogieron 15 pacientes con patrones de fractura de tipo 1 (66,6%), tipo 2 (6,6%), tipo 3 (20%) y tipo 5 (6,6%) según la clasificación de Seno entre 2011 y 2019 operados mediante esa técnica y evaluamos sus resultados clínicos y funcionales.

Resultados La media de rango articular metacarpofalángico fue de 97°/-3°, interfalángico proximal de 93°/3° e interfalángico distal de 82°/1°. El EVA medio fue de 2 y el Quick DASH de 13.

Conclusiones Los resultados obtenidos son comparables con el resto de las técnicas quirúrgicas sin aumento de las complicaciones, lo que nos plantea la posibilidad de comenzar un estudio prospectivo con una sola técnica para tratar la mayoría de los patrones de fractura.
Epidermoid Cyst of the Fourth Ventricle: A Case Report
Authors: Kumar Sushil , Sharma Sandeep , Misra Rajneesh , Kumar Kundan
Published: November 2019

Epidermoid cysts of the fourth ventricle are slow-growing benign rare lesions. We report a case of fourth ventricle epidermoid in a young lady with short duration of symptoms.
Removal of Well-Fixed Tibial Cone in Revision Total Knee Arthroplasty—A Uniquely Challenging Yet Necessary Scenario
Authors: Scully William F. , Deren Matthew E. , Sultan Assem A. , Samuel Linsen T. , Nageotte William , Molloy Robert M. , Krebs Viktor E.
Published: November 2019

The number of revision total knee arthroplasties (TKA) performed in the United States continues to increase. While advancements in implant design and surgical technique have led to improved outcomes compared with historical data, these cases remain technically demanding with high rates of aseptic failure and worse patient reported outcome scores compared with primary total knee arthroplasty. One particular problem commonly encountered in revision knee arthroplasty is bone loss, particularly in the epiphyseal region, which negatively impacts the structural integrity of the implants. Various modular metaphyseal sleeves and cones in conjunction with stemmed implants have been designed to enhance metaphyseal fixation, corroborated by multiple studies demonstrating excellent midterm results involving cones, and sleeves. Commercially available revision systems that incorporate metaphyseal cones are currently widely utilized in revision TKA. For tibial defects, both symmetric and asymmetric cone options are available. Excellent midterm results have been reported with use of this device in the setting of severe proximal tibial bone loss in revision TKA surgery. With the enhanced fixation provided by various sleeve and cone augments, implant removal in the setting of recurrent infection or implant failure can be extremely challenging. Consequently, in this work, we sought to describe an algorithmic approach for removing a tibial cone in conjunction with the overlying tibial baseplate. A review of the literature has also been conducted for complex surgical techniques regarding removal of well-fixed implants in revision total knee arthroplasty.
Generation of electromagnetic effect and flash in hypervelocity impact of aluminum projectile on aluminum target
Authors: Xu Mingyang , Song Weidong
Published: November 2019

A 3D Smoothed Particle Hydrodynamics (SPH) code was developed to investigate the generation of electromagnetic effect and flash during hypervelocity impact of an aluminum projectile on an aluminum target. The Arrhenius equation and the Biot-Savart law were incorporated into the SPH code for calculating the plasma charge and the magnetic field intensity from the plasma. Planck's law for the blackbody spectral radiance was introduced into the SPH code to determine the flash radiation intensities of different characteristic wavelengths. By using the SPH code, the effect of impact velocities and angles on the magnetic field intensity and flash intensity was explored. The numerical results show that the magnetic field intensity and flash intensity increase significantly with the impact velocity. By decreasing the incident angle from 90° to 45°, the magnetic field intensity and flash intensity decrease. Finally, based on the numerical simulations, two semiempirical formulae were proposed to accurately describe the variation of magnetic field intensity and the evolution of the flash radiation intensity with the impact velocity and the impact angle.
Fully experiment-based evaluation of few digital volume correlation techniques
Authors: Powierza Bartosz , Gollwitzer Christian , Wolgast Dagmar , Staude Andreas , Bruno Giovanni
Published: November 2019

Digital Volume Correlation (DVC) is a powerful set of techniques used to compute the local shifts of 3D images obtained, for instance, in tomographic experiments. It is utilized to analyze the geometric changes of the investigated object as well as to correct the corresponding image misalignments for further analysis. It can therefore be used to evaluate the local density changes of the same regions of the inspected specimens, which might be shifted between measurements. In recent years, various approaches and corresponding pieces of software were introduced. Accuracies for the computed shift vectors of up to about 1‰ of a single voxel size have been reported. These results, however, were based either on synthetic datasets or on an unrealistic setup. In this work, we propose two simple methods to evaluate the accuracy of DVC-techniques using more realistic input data and apply them to several DVC programs. We test these methods on three materials (tuff, sandstone, and concrete) that show different contrast and structural features.
Normal-mode splitting in coupled high-Q microwave cavities
Authors: Castelli A. R. , Martinez L. A. , Pate J. M. , Chiao R. Y. , Sharping J. E.
Published: November 2019

Three-dimensional radio frequency cavities demonstrate excellent frequency selectivity and, as such, are known for their use in RF filters. These cavities have potential applications in quantum information science, precision displacement metrology, and quantum electrodynamics. Additionally, coupled cavities that form a spectral doublet allow for parametric gain when incorporating mechanical elements. Here, we investigate normal-mode splitting in a pair of quarter-wave stub microwave cavities at room temperature and cryogenic environments in order to identify coupling mechanics for normal and superconducting systems. Superconducting quarter-wave stub cavities with a resonant frequency of 10 GHz are made from reactor-grade niobium and exhibit Q ranging from 105 to 109. We varied cavity-to-cavity coupling to observe several normal-mode splittings of increasing peak separation until we observed a mode crossing. The minimum observed peak separation was 7 MHz for room temperature tests and 200 kHz for cryogenic tests. We also report on values of an intrinsic quality factor for the tuning cavity as a dielectric rod is translated along its symmetry axis. The realization of coupled superconducting radio frequency (SRF) cavities of this type is a necessary step toward implementation of parametric SRF-mechanical gain.
Soft X-ray spectroscopy with transition-edge sensors at Stanford Synchrotron Radiation Lightsource beamline 10-1
Authors: Lee Sang-Jun , Titus Charles J. , Alonso Mori Roberto , Baker Michael L. , Bennett Douglas A. , Cho Hsiao-Mei , Doriese William B. , Fowler Joseph W. , Gaffney Kelly J. , Gallo Alessandro , Gard Johnathon D. , Hilton Gene C. , Jang Hoyoung , Joe Young Il , Kenney Christopher J. , Knight Jason , Kroll Thomas , Lee Jun-Sik , Li Dale , Lu Donghui , Marks Ronald , Minitti Michael P. , Morgan Kelsey M. , Ogasawara Hirohito , O’Neil Galen C. , Reintsema Carl D. , Schmidt Daniel R. , Sokaras Dimosthenis , Ullom Joel N. , Weng Tsu-Chien , Williams Christopher , Young Betty A. , Swetz Daniel S. , Irwin Kent D. , Nordlund Dennis
Published: November 2019

We present results obtained with a new soft X-ray spectrometer based on transition-edge sensors (TESs) composed of Mo/Cu bilayers coupled to bismuth absorbers. This spectrometer simultaneously provides excellent energy resolution, high detection efficiency, and broadband spectral coverage. The new spectrometer is optimized for incident X-ray energies below 2 keV. Each pixel serves as both a highly sensitive calorimeter and an X-ray absorber with near unity quantum efficiency. We have commissioned this 240-pixel TES spectrometer at the Stanford Synchrotron Radiation Lightsource beamline 10-1 (BL 10-1) and used it to probe the local electronic structure of sample materials with unprecedented sensitivity in the soft X-ray regime. As mounted, the TES spectrometer has a maximum detection solid angle of 2 × 10−3 sr. The energy resolution of all pixels combined is 1.5 eV full width at half maximum at 500 eV. We describe the performance of the TES spectrometer in terms of its energy resolution and count-rate capability and demonstrate its utility as a high throughput detector for synchrotron-based X-ray spectroscopy. Results from initial X-ray emission spectroscopy and resonant inelastic X-ray scattering experiments obtained with the spectrometer are presented.
On the dynamics of a simplified canonical Chua’s oscillator with smooth hyperbolic sine nonlinearity: Hyperchaos, multistability and multistability control
Authors: Fonzin Fozin T. , Megavarna Ezhilarasu P. , Njitacke Tabekoueng Z. , Leutcho G. D. , Kengne J. , Thamilmaran K. , Mezatio A. B. , Pelap F. B.
Published: November 2019

A simplified hyperchaotic canonical Chua’s oscillator (referred as SHCCO hereafter) made of only seven terms and one nonlinear function of type hyperbolic sine is analyzed. The system is found to be self-excited, and bifurcation tools associated with the spectrum of Lyapunov exponents reveal the rich dynamical behaviors of the system including hyperchaos, torus, period-doubling route to chaos, and hysteresis when turning the system control parameters. Wide ranges of hyperchaotic dynamics are highlighted in various two-parameter spaces based on two-parameter Lyapunov diagrams. The analysis of the hysteretic window using a basin of attraction as argument reveals that the SHCCO exhibits three coexisting attractors. Laboratory measurements further confirm the performed numerical investigations and henceforth validate the mathematical model. Of most/particular interest, multistability observed in the SHCCO is further controlled based on a linear augmentation scheme. Numerical results show the effectiveness of the control strategy through annihilation of the asymmetric pair of coexisting attractors. For higher values of the coupling strength, only a unique symmetric periodic attractor survives.
Category O for Takiff sl2
Authors: Mazorchuk Volodymyr , Söderberg Christoffer
Published: November 2019

We investigate various ways to define an analog of Bernstein-Gelfand-Gelfand category O for the nonsemisimple Takiff extension of the Lie algebra sl2. We describe Gabriel quivers for blocks of these analogs of category O and prove the extension fullness of one of them in the category of all modules.
Force driven transition of a globular polyelectrolyte
Authors: Radhakrishnan Keerthi , Singh Sunil P.
Published: November 2019

We have systematically studied behavior of a flexible polyelectrolyte (PE) chain with explicit counterions, subjected to a constant force at the terminal ends. Our simulations reveal that in the hydrophobic regime, a PE globule abruptly opens to a coil state beyond a critical force Fc. At the transition point, the polymer shape shows large scale fluctuations that are quantified in terms of end-to-end distance Re. These fluctuations suggest that the system coexists in globule and coil states at the transition, which is also confirmed from the bimodal distribution of Re. Moreover, the critical force associated with the globule coil transition exhibits a nonmonotonic behavior, where surprisingly, Fc decreases with Bjerrum length lB in the limit of small lB, followed by an increase in the larger lB limit. Furthermore, this behavior is also validated from a theory adopted for the PE. From the free energy analysis, we have demonstrated that predominantly, the competition between the intrachain repulsive energy, counterion’s translational entropy, and adsorption energy leads to the novel feature of nonmonotonic behavior of force.
Optimized commercial desktop cutter technique for rapid-prototyping of microfluidic devices and application to Taylor dispersion
Authors: Taylor Abigail W. , Harris Daniel M.
Published: November 2019

Microfluidics provides a platform for efficient and transportable microanalysis, catalyzing advancements in fields such as biochemistry, materials science, and microbial ecology. While the analysis is cost-effective, standard device fabrication techniques are disproportionately expensive and specialized. A commercially available desktop cutting plotter provides an accessible method for rapidly fabricating microfluidic devices at extremely low costs. The optimized technique described in the present work enables fabrication of microchannels with dimensions as small as ∼100 μm. Straightness of channel walls is comparable to other common fabrication techniques but achieved here at a fraction of the cost and fabrication time. Solute dispersion experiments are performed using the rapidly prototyped channels to measure the effective dispersion coefficient in laminar flow through rectangular channels. The results of these experiments compare favorably to predictions from classical Taylor-Aris dispersion theory. This note provides all necessary tools for researchers and educators to seamlessly apply the desktop cutter fabrication technique. Materials list, fabrication instructions, and detailed channel characterization results are available in the supplementary material.
Hetero-integration of quasi two-dimensional PbZr0.2Ti0.8O3 on AlGaN/GaN HEMT and non-volatile modulation of two-dimensional electron gas
Authors: Chen Lixiang , Wang He , Hou Bin , Liu Ming , Shen Lvkang , Lu Xiaoli , Ma Xiaohua , Hao Yue
Published: November 2019

In theory, two-dimensional electron gas (2DEG) density in AlGaN/GaN heterostructures can be modulated via the polarization of a ferroelectric material. Therefore, the integration of ferroelectric materials with AlGaN/GaN high electron mobility transistors (HEMTs) is a very attractive method for exploring further applications of electronic devices. This paper reports on the integration of single crystal PbZr0.2Ti0.8O3 (PZT) thin films (20 nm) and AlGaN/GaN HEMT via a substrate transfer technique. Continuous and nonvolatile modulation of 2DEG density in the AlGaN/GaN heterojunction interface is achieved in accordance with the theory. By poling the PZT/AlGaN/GaN HEMT from 2 V to 7 V, the device exhibits different threshold voltages (from −3 V to 1 V). A modulation of 2DEG density up to 300% is achieved. Moreover, the retention characteristic of the device is excellent, and the variation of the threshold voltage is less than 0.25 V after 105 s. Compared to the conventional method of depositing PZT directly on AlGaN/GaN HEMT, the transfer technique can achieve better quality in a much thinner film and prevent the interdiffusion during growth. At the same time, the excellent quality of the transferred PZT film has a good ability to modulate the 2DEG. The generality of our approach paves the way for integrating ferroelectric materials on the GaN-based devices, and this is promising for using the device in more application fields.
Thermal transport and energy dissipation in two-dimensional Bi2O2Se
Authors: Yang Fang , Wang Ridong , Zhao Weiwei , Jiang Jie , Wei Xin , Zheng Ting , Yang Yutian , Wang Xinwei , Lu Junpeng , Ni Zhenhua
Published: November 2019

Thermal transport and energy dissipation are important for a material in both thermoelectric and electronic devices. Here, we investigate the lateral and interfacial thermal transport of two-dimensional (2D) Bi2O2Se by Raman spectroscopy. It is found that thin Bi2O2Se flakes have a low in-plane thermal conductivity while maintaining an appropriate interfacial thermal conductance. The in-plane thermal conductivity of Bi2O2Se decreases with decreasing thickness, to as low as 0.92 ± 0.18 W⋅m−1⋅K−1 at a thickness of ∼8 nm. Such a low thermal conductivity is derived from the low phonon group velocity, strong anharmonicity, and large surface scattering of acoustic phonons of the Bi2O2Se thin layer. Simultaneously, thinner Bi2O2Se presents a higher thermal dissipation to the substrate than the thicker counterparts in the device. The interfacial thermal conductance increases with decreasing thickness, and reaches ∼21 MW⋅m−2⋅K−1 at ∼8 nm. These results provide critical information for the design of thermoelectric devices with high figures of merit and electronics with low-power consumption based on 2D materials.
The role of water models on the prediction of slip length of water in graphene nanochannels
Authors: Celebi Alper Tunga , Nguyen Chinh Thanh , Hartkamp Remco , Beskok Ali
Published: November 2019

Slip lengths reported from molecular dynamics (MD) simulations of water flow in graphene nanochannels show significant scatter in the literature. These discrepancies are in part due to the used water models. We demonstrate self-consistent comparisons of slip characteristics between the SPC, SPC/E, SPC/Fw, TIP3P, TIP4P, and TIP4P/2005 water models. The slip lengths are inferred using an analytical model that employs the shear viscosity of water and channel average velocities obtained from nonequilibrium MD simulations. First, viscosities for each water model are quantified using MD simulations of counterflowing, force-driven flows in periodic domains in the absence of physical walls. While the TIP4P/2005 model predicts water viscosity at the specified thermodynamic state with 1.7% error, the predictions of SPC/Fw and SPC/E models exhibit 13.9% and 23.1% deviations, respectively. Water viscosities obtained from SPC, TIP4P, and TIP3P models show larger deviations. Next, force-driven water flows in rigid (cold) and thermally vibrating (thermal) graphene nanochannels are simulated, resulting in pluglike velocity profiles. Large differences in the flow velocities are observed depending on the used water model and to a lesser extent on the choice of rigid vs thermal walls. Depending on the water model, the slip length of water on cold graphene walls varied between 34.2 nm and 62.9 nm, while the slip lengths of water on thermal graphene walls varied in the range of 38.1 nm–84.3 nm.
Ultrafast hole extraction from photoexcited colloidal CdSe quantum dots coupled to nitroxide free radicals
Authors: Dutta Poulami , Tang Yanhao , Mi Chenjia , Saniepay Mersedeh , McGuire John A. , Beaulac Rémi
Published: November 2019

Organic free radicals related to the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical are known as photoluminescence-quenchers when coupled to group II-chalcogenide colloidal quantum dots (QDs), but the mechanism responsible for this phenomenon has so far remained unresolved. Using a combination of time-resolved photoluminescence and transient absorption spectroscopies, we demonstrate that photoexcited colloidal CdSe QDs coupled to 4-amino-TEMPO undergo highly efficient reductive quenching, that is, hole transfer from the valence band of the quantum dot to the organic paramagnetic species. Interestingly, the process is shown to occur on a subpicosecond time scale for bound 4AT; such a large rate constant for the extraction of holes from photoexcited CdSe QD by a molecular species is rare and underlines the potential that TEMPO derivatives can play in mediating efficient redox processes involving colloidal CdSe QDs.
Size dependence of photocatalytic hydrogen generation for CdTe quantum dots
Authors: Yin Jiajia , Cogan Nicole M. B. , Burke Rebeckah , Hou Zhentao , Sowers Kelly L. , Krauss Todd D.
Published: November 2019

CdTe quantum dots (QDs) are attractive photosensitizers for photocatalytic proton reduction due to their broad absorbance profile that can extend from the ultraviolet to near-infrared regions, providing access to a larger portion of the solar spectrum than possible with analogous CdSe and CdS QD photosensitizers. Here, the photocatalytic hydrogen (H2) generation from various sizes of dihydrolipoic acid (DHLA)-capped CdTe QDs, ranging from 2.5 to 7.5 nm in diameter, and a molecular Ni-DHLA catalyst in aqueous solutions was evaluated, and an unusual size-dependent photocatalytic activity with CdTe QDs was observed. Under optimized conditions, using 3.4 nm CdTe-DHLA and a 1:20 ratio of QD/Ni-DHLA catalyst, as many as 38 000 turnover numbers (mol H2 per mol QD) were achieved. However, below this critical size, the H2 production efficiency decreased; this behavior is attributed to the rapid oxidation of the QD surface, resulting in detrimental surface trap states. These results are consistent with ultrafast transient absorption spectroscopic measurements, which suggest the presence of extremely fast charge-trapping processes in the oxidized CdTe-DHLA QDs. While fast electron transfer from CdTe-DHLA QDs is observed in the presence of the Ni-DHLA catalyst, the charge trapping processes occur on a competitive time scale, thus lowering the efficiency of the CdTe/Ni-DHLA H2 production system. Understanding rapid charge trapping in CdTe QDs may help suggest potential improvements for the overall CdTe photocatalytic system.
Direct numerical simulations of multi-mode immiscible Rayleigh-Taylor instability with high Reynolds numbers
Authors: Liang Hong , Hu Xiaoliang , Huang Xuefeng , Xu Jiangrong
Published: November 2019

In this paper, we conduct the high-resolution direct numerical simulations of multimode immiscible Rayleigh-Taylor instability (RTI) with a low Atwood number (At = 0.1) using an improved phase field lattice Boltzmann method. The effect of the Reynolds number on the evolutional interfacial dynamics and bubble/spike amplitudes is first investigated by considering its wide range, from 100 up to a high value of 30 000. The numerical results show that, for sufficiently large Reynolds numbers, a sequence of distinguishing stages in the immiscible RTI can be observed, which includes the linear growth, saturated velocity growth, and chaotic development stages. At the late stage, the RTI induces a complex topology structure of the interface and a mass of dissociative drops can be significantly observed in the system. The accelerations of the bubble and spike front are also measured, and it is reported that their normalized values at the late time are, respectively, approximate to the constant values of around 0.025 and 0.027, exhibiting a terminally quadratic growth. As the Reynolds number is reduced to small ones, the multiple disturbances of the RTI are found to merge into a larger one at the initial stage. Then, the evolutional interfaces display the patterns familiar from the single-mode RTI. The phase interfaces in the whole process become very smooth without the appearance of the breakup phenomenon, and the spike and bubble velocities at the late time approach constant values. Furthermore, we also analyze the effects of the initial conditions in terms of the perturbation wavelength and amplitude, and it is found that the instability undergoes a faster growth at the intermediate stage for a larger wavelength, while the late-time bubble and spike growth rates are insensitive to the changes of the initially perturbed wavelength and amplitude.
Optimally graded porous material for better sound absorption
Authors: Gasparini Allison
Published: November 2019

Researchers present process to design, optimize and manufacture continuously graded acoustic porous materials with near-perfect noise absorption in given frequency range.
Optimal design of a single-mode trench-assisted homogeneous multicore fibre with a minimum crosstalk level
Authors: Kumar Dablu , Ranjan Rakesh
Published: November 2019

We have proposed an optimal design of five different core structures (St1 – St5) for a seven-core trench-assisted multicore fibre, whose core radius and relative core/cladding refractive index difference Δ
1 are optimal for single-mode propagation. The crosstalk performance and its reduction (in dB) with respect to variations in fibre design parameters, such as cladding/trench (Δ
2) depth and trench width W
t are investigated. It is shown that some fibre operational parameters, like, fibre bending radius, operating wavelength and fibre length, affect the crosstalk performance. It is found that the crosstalk and its reduction amount are extremely dependent on the values of Δ
1 and Δ
2. The dispersion characteristics of the cores are investigated for all the proposed core structures and the observed dispersion is found to be about – 6 ps nm−1 km−1 at an operating wavelength of 1550 nm. An ultralow crosstalk (less than –100 dB per 100 km) can be achieved mainly with two proposed core structures (St4 and St5) having a suitably higher values of Δ
1 along with a small core radius for single-mode propagation. The multicore fibre design with many cores (up to 55) is demonstrated to ensure a high transmission capacity.
Formation of light with controlled rotation of the polarisation plane by superposing linearly polarised waves
Authors: Kotov V.M.
Published: November 2019

A method is proposed for generating linearly polarised light, whose polarisation plane rotates at a given frequency. The method is based on the double passage of the light through an acousto-optic modulator made of an anisotropic crystal. An experimental prototype based on a paratellurite crystal is fabricated, with the help of which rotation of linearly polarised light of a He – Ne laser (λ = 0.63 μm) is obtained with the frequency controlled by the frequency of sound.
Coherent combining of diode laser beams in a master oscillator – zigzag slab power amplifier system
Authors: Bogatov A.P. , Drakin A.E. , Mikaelyan G.T.
Published: November 2019

An integrated zigzag laser diode amplifier, with each segment (zigzag) consisting of three sections, is considered. The operation of this amplifier is analysed. It is shown that the presence of three sections with independent pump currents makes it possible to combine coherently all amplifier output beams. The first two sections in this configuration play the role of a phase shifter, and the third serves as a power amplifier. The influence of fluctuations of the output radiation phase in each segment on the resulting brightness of total output beam of the entire amplifier is investigated.
Mid-IR reflectance spectrum of multilayer graphene: Influence of adsorbate at the graphene – substrate interface
Authors: Frolov V.D. , Pivovarov P.A. , Plotnichenko V.G. , Konov V.I.
Published: November 2019

Water adsorbate at the interface between graphene and SiO2/Si substrate is found to affect the reflectance spectra of (3 – 6)-layer graphene in the mid-IR range (λ = 2 – 16 μm). The sample under study was previously kept in acetone vapour to remove water adsorbate from the graphene – substrate interface. The graphene reflectance in the range of 8 – 16 μm tends to decrease with recovery of water adsorbate layer at the graphene – substrate interface at room temperature and relative air humidity RH = 40 % – 60 %. The observed effect is most likely caused by the blue shift of the absorption edge at interband transitions due to the change in the Fermi level position in the graphene valence band under the influence of the charge induced in graphene by the water adsorbate film.
Normal modes of strictly resonant and quasi-resonant regimes of electromagnetically induced transparency
Authors: Parshkov O.M.
Published: November 2019

We report the results of a theoretical study of the evolution of a probe pulse under electromagnetically induced transparency conditions in the lambda scheme of degenerate inhomogeneously broadened quantum transitions. It is assumed that the interacting fields are elliptically polarised, and their effect on the medium can be either strictly resonant or quasi-resonant. It is shown that probe light in a medium can be represented as the sum of two normal modes, i.e. quasi-monochromatic elliptically polarised fields propagating independently of each other. The major axis of the polarisation ellipse of the normal mode of the first type is parallel, and that of the second type is perpendicular to the major axis of the polarisation ellipse of the control light. Due to the fact that velocities of normal-mode pulses are different, a single probe pulse entering a medium splits into individual pulses inside the medium, each of which transfers the energy of one of the normal modes. In the case of quasi-resonance, the splitting occurs at a shorter distance than in the case of strict resonance. If normal modes are not phase modulated at the input surface of the medium, then in the case of quasi-resonance they become phase modulated during their propagation inside the medium, whereas this does not occur in the case of strict resonance. It is shown that in the case of quasi-resonance, the phase modulation value of the mode of the second of the above types significantly exceeds that of the first type. The medium transparency for the normal mode of the first type slightly decreases with the transition from the case of strict resonance to the case of quasi-resonance, while the medium transparency for the mode of the second type decreases significantly. The total probe field, which is the sum of the normal modes, has phase modulation before it splits into mode pulses in cases of both strict resonance and quasi-resonance, even if it does not have it on the input surface.
Double integrated laser-thyristor
Authors: Bagaev T.A. , Ladugin M.A. , Padalitsa A.A. , Marmalyuk A.A. , Kurnyavko Yu.V. , Lobintsov A.V. , Danilov A.I. , Sapozhnikov S.M. , Krichevskii V.V. , Zverkov M.V. , Konyaev V.P. , Simakov V.A. , Slipchenko S.O. , Podoskin A.A. , Pikhtin N.A.
Published: November 2019

Comparative experiments are performed on a semiconductor laser with different numbers (one or two) of emitting sections monolithically integrated with an electronic switch (thyristor). It is shown that the functional integration of a laser with a thyristor in one heterostructure makes it possible to achieve efficient operation of the laser in a pulsed regime (up to 50 W), while the use of vertical integration of two laser sections in this device additionally increases the optical output power to 90 W with all other conditions being the same.
Growth of Yb : Na2SO4 crystals and study of their spectral – luminescent characteristics
Authors: Tsvetkov V.B. , Proydakova V.Yu. , Kuznetsov S.V. , Subbotin K.A. , Lis D.A. , Yapryntsev A.D. , Ivanov V.K. , Fedorov P.P.
Published: November 2019

Ytterbium-doped single crystals of the high-temperature hexagonal sodium sulphate modification are grown by the Czochralski method. It is found by energy dispersive analysis that the crystallisation occurs congruently. The Yb : Na2SO4 crystals have additional (with respect to Yb3+ ions) absorption bands in the regions of 650, 850 and 1150 nm, which obviously belong to colour centres. The luminescence spectrum of the Yb : Na2SO4 single crystal noticeably differs from the luminescence spectrum of Yb : YAG crystals by the presence of a broad band without a prominent peak. The luminescence decay curve for the powder is single-exponential with a time constant of 1175 μs, which is somewhat larger than that for the Yb : YAG crystal. The lifetime of the ytterbium excited state does not change during storage of the samples in air for a week.
Magic wavelengths near 800 nm for precision spectroscopy of an inner-shell transition in thulium atoms
Authors: Tregubov D.O. , Golovizin A.A. , Fedorova E.S. , Khabarova K.Yu. , Sorokin V.N. , Kolachevsky N.N.
Published: November 2019

Differential dynamic polarisability of the inner-shell clock transition at a wavelength of 1.14 μm in the thulium atom is measured by the method of precision laser spectroscopy in the spectral range of 800 – 860 nm. Experimental data approximated by a theoretical model yield the probability of the transition at λ = 809.5 nm: A809.5 = 460(70) s−1. The values of two magic wavelengths are obtained experimentally, namely, λ
m1 = 807.727(18) nm and λ
m2 = 813.3(2) nm, the wavelength of λ
m1 being determined for the first time. Main parameters of an optical lattice at these wavelengths are compared and a conclusion is made that trapping thulium atoms in an optical lattice at λ
m2 is preferable for optical clock operation.