bluuebunny/crossref_metadata_2025 huggingface dataset:
Streaming instability of multiple particle species
Authors: Schaffer Noemi , Johansen Anders , Lambrechts Michiel
Published: July 2021

The streaming instability provides an efficient way of overcoming the growth barriers in the initial stages of the planet formation process. Considering the realistic case of a particle size distribution, the dynamics of the system is altered compared to the outcome of single size models. In order to understand the outcome of the multispecies streaming instability in detail, we perform a large parameter study in terms of particle number, particle size distribution, particle size range, initial metallicity, and initial particle scale height. We study vertically stratified systems and determine the metallicity threshold for filament formation. We compare these with a system where the initial particle distribution is unstratified and find that its evolution follows that of its stratified counterpart. We find that a change in the particle number does not result in significant variation in the efficiency and timing of filament formation. We also see that there is no clear trend for how varying the size distribution in combination with the particle size range changes the outcome of the multispecies streaming instability. Finally, we find that an initial metallicity of Zinit = 0.005 and Zinit = 0.01 both result in similar critical metallicity values for the start of filament formation. Our results show that the inclusion of a particle size distribution into streaming instability simulations, while changing the dynamics as compared to mono-disperse systems, does not result in overall unfavorable conditions for solid growth. We attribute the subdominant role of multiple species to the high-density conditions in the midplane, conditions under which linear stability analysis also predict little difference between single and multiple species.
The CARMENES search for exoplanets around M dwarfs
Authors: Sabotta S. , Schlecker M. , Chaturvedi P. , Guenther E. W. , Muñoz Rodríguez I. , Muñoz Sánchez J. C. , Caballero J. A. , Shan Y. , Reffert S. , Ribas I. , Reiners A. , Hatzes A. P. , Amado P. J. , Klahr H. , Morales J. C. , Quirrenbach A. , Henning Th. , Dreizler S. , Pallé E. , Perger M. , Azzaro M. , Jeffers S. V. , Kaminski A. , Kürster M. , Lafarga M. , Montes D. , Passegger V. M. , Zechmeister M.
Published: July 2021

Context. The CARMENES exoplanet survey of M dwarfs has obtained more than 18 000 spectra of 329 nearby M dwarfs over the past five years as part of its guaranteed time observations (GTO) program.

Aims. We determine planet occurrence rates with the 71 stars from the GTO program for which we have more than 50 observations.

Methods. We use injection-and-retrieval experiments on the radial-velocity time series to measure detection probabilities. We include 27 planets in 21 planetary systems in our analysis.

Results. We find 0.06−0.03+0.04 giant planets (100 M⊕ < Mpl sin i < 1000 M⊕) per star in periods of up to 1000 d, but due to a selection bias this number could be up to a factor of five lower in the whole 329-star sample. The upper limit for hot Jupiters (orbital period of less than 10 d) is 0.03 planets per star, while the occurrence rate of planets with intermediate masses (10 M⊕ < Mpl sin i < 100 M⊕) is 0.18−0.05+0.07 planets per star. Less massive planets with 1 M⊕ < Mpl sin i < 10 M⊕ are very abundant, with an estimated rate of 1.32−0.31+0.33 planets per star for periods of up to 100 d. When considering only late M dwarfs with masses M⋆ < 0.34 M⊙, planets more massive than 10 M⊕ become rare. Instead, low-mass planets with periods shorter than 10 d are significantly overabundant.

Conclusions. For orbital periods shorter than 100 d, our results confirm the known stellar mass dependences from the Kepler survey: M dwarfs host fewer giant planets and at least two times more planets with Mpl  sin i < 10 M⊕ than G-type stars. In contrast to previous results, planets around our sample of very low-mass stars have a higher occurrence rate in short-period orbits of less than 10 d. Our results demonstrate the need to take into account host star masses in planet formation models.
Solar chromosphere heating and generation of plasma outflows by impulsively generated two-fluid Alfvén waves
Authors: Pelekhata M. , Murawski K. , Poedts S.
Published: July 2021

Context. We address the heating of the solar chromosphere and the related generation of plasma inflows and outflows.

Aims. We attempt to detect variations in ion temperature and vertical plasma flows, which are driven by impulsively excited two-fluid Alfvén waves. We aim to investigate the possible contribution of these waves to solar chromosphere heating and plasma outflows.

Methods. We performed numerical simulations of the generation and evolution of Alfvén waves with the use of the JOANNA code, which solves the two-fluid equations for ions+electrons and neutrals, coupled by collision terms.

Results. We confirm that the damping of impulsively generated small-amplitude Alfvén waves slightly affects the temperature of the chromosphere and generates slow plasma flows. In contrast, the Alfvén waves generated by large-amplitude pulses increase the chromospheric plasma temperature more significantly and result in faster plasma outflows. The maximum heating occurs when the pulse is launched from the central photosphere, and the magnitude of the related plasma flows grows with the amplitude of the pulse.

Conclusions. Large-amplitude two-fluid Alfvén waves can contribute significantly to the heating of the solar chromosphere and to the generation of plasma outflows.
Study of mechanochemical interaction of tungsten with liquid gallium
Authors: Grigoryev Vladimir M. , Vosmerikov Sergey V.
Published: July 2021

Mechanochemical interaction of tungsten with gallium was studied. Using x-ray diffraction and electron microscopy, it was shown that after mechanical activation of a W-Ga mixture for 1 min, gallium is completely spread, as a thin layer, onto the tungsten surface, while the longer activation leads to the formation of W(Ga) solid solution. Moreover, gallium was shown to be incorporated into tungsten lattice only if the grains reach a certain critical nanosize.
Processing of propane-butane fraction on zeolite-containing catalysts
Authors: Tuktin B.T. , Temirova A.M. , Omarova A.A.
Published: July 2021

Abstarct.

Processing of propane-butane and propane-propylene fractions in light hydrocarbons on the zeolite catalysts modified by zinc, manganese, cobalt, lanthanum was studied. It was shown that the degree of conversion on the Zn-La-Co-ZSM-AI2O3 catalyst increases from 40.2 to 99.0% as the temperature increasesfrom450to600 °C. The maximum yield of aromatic hydrocarbons was 31.4%. As the temperature increases from 450 to 600С, the cracking of hydrocarbons intensifies resulting in the formation of methane and ethane. New generation catalysts based on zeolites have the prospect of being used in technologies for processing various types of hydrocarbon raw materials. The activity of catalysts in the processing of light hydrocarbons depends on the structure and state of the active centers. The physicochemical characteristics of the developed catalysts have been studied. One of the possible ways to control the catalytic properties is to introduce a variable valence catalyst as modifiers into the composition.
Composite catalysts for the catalytic processing of fuel oil
Authors: Shakiyeva Tatyana , Sassykova Larissa , Khamlenko Anastassiya , Dossumova Binara , Sassykova Albina , Muratova Albina , Zhumagali Madina , Zhakirova Nurbubi , Abildin Tleutai
Published: July 2021

The paper describes the catalytic cracking of heavy petroleum feedstock on catalysts based natural Taizhuzgen zeolite and Narynkol clay (Kazakhstan). Catalytic cracking was studied on fuel oil of the M-100 brand taken from the LLP Pavlodar Oil Chemistry Refinery (Kazakhstan). Air was added into the reaction medium. It was found that under optimal conditions, the conversion of the heavy residue of M-100 fuel oil reaches 46.2%, when cracking the initial fuel oil, the yield of the middle distillate fraction is 85.7 wt. % due to the content of 41.1 wt. % residual light gas oil in the resulting products. The optimal composite catalyst allows carry out the cracking of heavy oil residues without preliminary purification and with a high degree ofconversion to diesel fraction.
Technology for transformation of high-viscosity and high-paraffin oil raw materials using electromagnetic processing
Authors: Zhakirova N.K. , Salakhov R.Kh. , Nasima Zh.K. , Bakyt A.M. , Sassykova L.R.
Published: July 2021

The article presents the results of electromagnetic activation of petroleum raw materials in the vortex layer apparatus. It is shown that under electromagnetic influence, there is a significant increase in the proportion of straight-run gasoline fraction distillate, as well as a change in the physicochemical parameters of the light fractions obtained. It is established that the processes of wave action on oil, which take place in the zone of the electromagnetic field, lead to a change in the group hydrocarbon composition of the distillates obtained. NMR spectroscopy was used to study the effect of electromagnetic radiation on the properties of oil raw materials on the physicochemical properties and structure of the oil.
Influence of Chromium Concentration on Corrosion Resistance of Surface Layers of Stainless Steel
Authors: Bushueva Evdokiya , Turlo Yevgeny , Khamgushkeeva Galina
Published: July 2021

Phase transformations occurring during the non-vacuum electron-beam surfacing using a mixture of amorphous boron and chromium powder (from 5 to 30 wt%) as well as the effect of the resulting structure on the corrosion resistance of the surface layers of chromium-nickel austenitic steel have been investigated. It has been found that when processing a powder mixture with a minimum chromium content (5 and 10 wt%), layers with a dense arrangement of borides are formed. Further increase in chromium concentration (20 and 30 wt%) leads to the formation of solid solutions in the modified layer. It has been shown that an increase in the concentration of chromium in the surface layer leads to a twofold increase in the corrosion resistance of the 12Х18Н9T (AISI 302) steel surface.
Cavitation method of intensification of processing of hydrocarbon raw materials
Authors: Barshabayeva Aigerim , Aubakirov Yermek
Published: July 2021

The article describes the success of research and application of wave methods in the process of processing hydrocarbon raw materials. A promising direction for intensifying the processing of hydrocarbon raw materials is wave technologies implemented on the basis of physical principles: electrical, magnetic, radiation, acoustic, cavitation, microwave, vibration, laser effects. The hydrodynamic cavitation unit and the instrumental-technological scheme of the unit are presented. Two main groups of hypotheses are presented -thermal and electrical. The studies on the change in the physicochemical and rheological characteristics of oil during its processing in a rotary impulse apparatus are shown.
Preparation of nanocomposite silver/kaolin with antibacterial properties
Authors: Baltabayeva Balnur , Ospanova Aliya , Kubasheva Zhanar
Published: July 2021

In this study, a nanocomposite based on kaolin from the Alekseevsky deposit (Kazakhstan), containing nano-silver particles, was synthesized. Kaolin has good physical and chemical properties and is an effective carrier for medicines. The synthesis of AgNPs/kaolin nanocomposites was carried out by chemical reduction. Impregnation of silver nanoparticles into silica matrix can prevent the agglomeration of mobile ions, and thereby preserve the antibacterial activity of the compound. The composition and structure of the resulting nanocomposite were studied using SEM/EDS analysis to study the morphology and elemental composition of natural and silver-modified kaolin, the specific surface was determined by the BET method, and functional groups were identified by IR spectroscopy. The resulting composite was tested for antibacterial activity against Gram-negative and Gram-positive bacteria (E.Сoli, S. Aureus).
Study of the synthesis of a copolymer of isodecyl- and benzylmethacrylates after radiation initiation
Authors: Antonov Ilya , Tolochko Boris , Varand Alexandr , Mikhailenko Mikhail , Eltsov Ilya , Bryazgin Alexandr , Smirnov Eugene
Published: July 2021

Polymerization was carried out using the method of radiation initiation. Experiments were carried out on methacrylic acid derivatives with bulky substituents (isodecyl and benzyl). The regularities of its formation are investigated. The conditions for obtaining a homogeneous copolymer are determined. A polymer with a molecular weight of more than 106 g/mol was obtained. An increase in the viscosity of the copolymer with an increase in the temperature of the solution was shown.
High conductive hybrid polymer CsH5(PO4)2-Butvar compounds
Authors: Gus’kov Rostislav , Ponomareva Valentina
Published: July 2021

Hybrid polymer compounds (1–х)CsH5(PO4)2-хButvar (х=0– 0.3), synthesized with different solvents (ethanol and isopropanol) were first synthesized and investigated. Fundamental possibility of creating new highly conductive thin polymer electrolytes based on CsH5(PO4)2 was shown. An optimal synthesis method was determined. The crystal structure of CsH5(PO4)2 (P21/c) remains unchanged in the polymer system. The thickness of the electrolyte is no more than 50-100 μm. Proton conductivity increases by 2 orders of magnitude and depends on the composition. The highest conductivity was 10-1 S/cm at 135 °C. Changes in conductivity are caused by dispersion of the salt, as well as by the presence of insignificant amounts of residual water under the synthesis conditions.
Circulating Rotavirus Genotypes among Children Younger than 5 Years with Acute Gastroenteritis in Zaria, Northwestern Nigeria
Authors: Giwa Fatima Jummai , Garba Maria , Mukhtar Abdulaziz , Idris Mukhtar , Lartey Belinda , Damanka Susan , Samaila Modupeola , Muktar Hassan , Olayinka Adebola , Armah George
Published: July 2021

Objective This study aimed to determine the circulating rotavirus genotypes among children 0 to 59 months with acute gastroenteritis in Zaria, Northwestern Nigeria.

Methods A cross-sectional hospital-based study was performed from November 2015 to April 2017 on 415 stool samples of children 0 to 59 months with acute gastroenteritis presenting at the pediatric clinics in five selected health care facilities in Zaria, Northwestern Nigeria. The stool samples were tested for group A rotavirus antigen by enzyme-linked immunosorbent assay (ELISA) using the ProSpecT™ Rotavirus Microplate Assay (Thermo Scientific Oxoid, United Kingdom). Rotavirus-positive strains were further characterized using seminested multiplex reverse transcriptase polymerase chain reaction.

Results Of the 415 diarrheal stool samples collected from children with acute gastroenteritis, 12.3% (n = 51) tested positive by ELISA. Five rotavirus G genotypes (G1, G2, G3, G9, and G12) and three P genotypes (P[4], P[6], and P[8]) were detected. Eight genotype combinations were detected with G1P[8], G12P[8], and G3P[6] being the most prevalent (9.8% each) followed by G1P[6], G2P[4], and G9P[8] (5.9% each). G/P mix types representing 25.5% (n = 13) of strains were detected during the study period.

Conclusion This study found a high diversity of rotavirus strains with emerging unusual rotavirus genotypes and a concurrent high proportion of mixed infections. This increased antigenic diversity of rotavirus strains may impact on vaccine effectiveness and rotavirus epidemiology and highlights the importance of continuous surveillance.
Management and Outcomes of Isolated Distal Deep Vein Thromboses: A Questionable Trend toward Long-Lasting Anticoagulation Treatment. Results from the START-Register
Authors: Palareti Gualtiero , Legnani Cristina , Antonucci Emilia , Testa Sophie , Mastroiacovo Daniela , Cosmi Benilde , Poli Daniela , Bucherini Eugenio , Dentali Francesco , Fontanella Andrea , Mumoli Nicola , Imberti Davide , Falanga Anna , Ageno Walter , Pomero Fulvio
Published: July 2021

Background Isolated distal deep vein thromboses (IDDVT) are frequently diagnosed; however, their natural history and real risk of complications are still uncertain. Though treatment is still not well standardized, international guidelines recommend no more than 3 months of anticoagulation therapy. We investigated how Italian clinicians treat IDDVT patients in their real life in our country.

Methods Baseline characteristics and clinical history of the patients enrolled in the prospective, observational, multicenter START-Register for a first IDDVT or proximal DVT (PDVT) were analyzed.

Results Overall, 412 IDDVT patients were significantly younger, with better renal function, and more frequent major transient risk factors, when compared with 1,173 PDVT patients. The anticoagulation duration was >180 days in 52.7% of IDDVT patients (70.7% in PDVT). During treatment, bleeding occurred in 5.6 and 2.8% patient-years in IDDVT and PDVT, respectively (p = 0082). Bleeding was more frequent in IDDVT than PDVT patients treated with warfarin (6.8 vs. 3.2 patient-years, p = 0.0228, respectively). Thrombotic complications occurred in 1.1 and 2.4% patient-years in IDDVT and PDVT patients, respectively. Analyzing together the two groups, 66.1% of bleeds and 86.1% thrombotic complications occurred after 90 days anticoagulation treatment.

Conclusion The large majority of IDDVT patients received anticoagulation for more than 3 months. Most bleeding and thrombotic complications occurred after the first 90 days of anticoagulation therapy. These results indicate that an extended anticoagulation beyond 90 days in IDDVT patients is associated with increased risk of complications. Whether an extended treatment may lower recurrences after anticoagulation withdrawal should be assessed by specifically designed studies.
Comparison with Navigation of a Novel Three-Step Technique for Improving Accuracy of the Distal Femoral Resection during Conventional TKA: A Case–Control Study
Authors: Mullaji Arun B. , Khalifa Ahmed A. , Shetty Gautam , Thakur Harshad
Published: July 2021

Correct placement of the femoral component in the coronal plane during primary total knee arthroplasty (TKA) is related to long-term survival. The aim of this radiographic study was to determine the accuracy of a novel three-step technique for improving the accuracy of the distal femoral cut during conventional technique and compare it with computer navigation during TKA. A total of 458 TKAs were retrospectively analyzed (178 conventional TKAs with the novel technique and 280 navigated TKAs) for postoperative femoral component coronal alignment and compared between the two groups. Mean femoral component coronal alignment was not significantly different (p = 0.314) between the two groups. There was no significant difference in the mean femoral component coronal alignment between varus and valgus knees. The number of outliers (90 ± 3 degrees) for femoral component coronal alignment was not significantly different between the two groups when assessed separately for varus and valgus deformities. The mean value of femoral component alignment using the conventional technique in knees with varus deformity <10 degrees was 88.8 degrees, in knees with varus deformity 10 to 20 degrees was 89.4 degrees, and in those with varus deformity >20 degrees was 90.2 degrees. Femoral component alignment in knees with varus <10 degrees was significantly different from those >20 degrees (p = 0.006); there was no significant difference between knees with varus <10 degrees and those with 10 to 20 degrees varus (p = 0.251), nor between 10 and 20 degrees varus knees and those with varus >20 degrees (p = 0.116). Using the novel three-step technique during conventional TKA to perform the distal femoral cut can help achieve femoral component coronal alignment comparable to the navigation technique.
Radioembolization for Hepatocellular Carcinoma
Authors: Gunduz Seyda , Saini Gia , Segaran Nicole , Naidu Sailen , Patel Indravadan , Alzubaidi Sadeer , Oklu Rahmi
Published: July 2021

Hepatocellular carcinoma (HCC) is the fastest-growing cancer worldwide, causing significant morbidity and mortality. Surgical resection, ablation, or transplantation is the best treatment option for patients with HCC. However, only about one-fifth of patients are suitable for such primary curative treatments due to underlying liver disease or rapid extension of the tumor. Image-guided locoregional therapies may prove an important alternative in this scenario, particularly transarterial radioembolization (TARE) with yttrium-90 (Y-90). Based on many studies, TARE can be considered a curative treatment option for patients with early-stage HCC, a bridge to transplantation, and a method for downstaging tumors to give patients with unresectable HCC a chance to potentially receive a curative treatment. TARE can be also combined with other treatment modalities to provide a better quality of life in patients when compared with systemic therapy in patients with unresectable HCC. Here, we discuss the use of TARE in the approach to HCC patients who are in early, intermediate, or advanced stages.
Simulations of semi-rigid tailfins pave the way for easier to construct underwater robot designs
Authors: Liebendorfer Adam
Published: July 2021

An analysis discerns the effects of shape and torsional spring on hydrodynamic properties of caudal fins with low-order flexibility.
Advances in design position push-button mechanisms for future use in biomicrofluidic applications
Authors: Liebendorfer Adam
Published: July 2021

Approaches incorporating microvalves look to make microfluidic-based diagnostic devices more accessible for point-of-care users.
Replace and repair: Biomimetic bioprinting for effective muscle engineering
Authors: Blake Cooper , Massey Oliver , Boyd-Moss Mitchell , Firipis Kate , Rifai Aaqil , Franks Stephanie , Quigley Anita , Kapsa Robert , Nisbet David R. , Williams Richard J.
Published: July 2021

The debilitating effects of muscle damage, either through ischemic injury or volumetric muscle loss (VML), can have significant impacts on patients, and yet there are few effective treatments. This challenge arises when function is degraded due to significant amounts of skeletal muscle loss, beyond the regenerative ability of endogenous repair mechanisms. Currently available surgical interventions for VML are quite invasive and cannot typically restore function adequately. In response to this, many new bioengineering studies implicate 3D bioprinting as a viable option. Bioprinting for VML repair includes three distinct phases: printing and seeding, growth and maturation, and implantation and application. Although this 3D bioprinting technology has existed for several decades, the advent of more advanced and novel printing techniques has brought us closer to clinical applications. Recent studies have overcome previous limitations in diffusion distance with novel microchannel construct architectures and improved myotubule alignment with highly biomimetic nanostructures. These structures may also enhance angiogenic and nervous ingrowth post-implantation, though further research to improve these parameters has been limited. Inclusion of neural cells has also shown to improve myoblast maturation and development of neuromuscular junctions, bringing us one step closer to functional, implantable skeletal muscle constructs. Given the current state of skeletal muscle 3D bioprinting, the most pressing future avenues of research include furthering our understanding of the physical and biochemical mechanisms of myotube development and expanding our control over macroscopic and microscopic construct structures. Further to this, current investigation needs to be expanded from immunocompromised rodent and murine myoblast models to more clinically applicable human cell lines as we move closer to viable therapeutic implementation.
Machine learning on neutron and x-ray scattering and spectroscopies
Authors: Chen Zhantao , Andrejevic Nina , Drucker Nathan C. , Nguyen Thanh , Xian R. Patrick , Smidt Tess , Wang Yao , Ernstorfer Ralph , Tennant D. Alan , Chan Maria , Li Mingda
Published: July 2021

Neutron and x-ray scattering represent two classes of state-of-the-art materials characterization techniques that measure materials structural and dynamical properties with high precision. These techniques play critical roles in understanding a wide variety of materials systems from catalysts to polymers, nanomaterials to macromolecules, and energy materials to quantum materials. In recent years, neutron and x-ray scattering have received a significant boost due to the development and increased application of machine learning to materials problems. This article reviews the recent progress in applying machine learning techniques to augment various neutron and x-ray techniques, including neutron scattering, x-ray absorption, x-ray scattering, and photoemission. We highlight the integration of machine learning methods into the typical workflow of scattering experiments, focusing on problems that challenge traditional analysis approaches but are addressable through machine learning, including leveraging the knowledge of simple materials to model more complicated systems, learning with limited data or incomplete labels, identifying meaningful spectra and materials representations, mitigating spectral noise, and others. We present an outlook on a few emerging roles machine learning may play in broad types of scattering and spectroscopic problems in the foreseeable future.
Respiratory droplet resuspension near surfaces: Modeling and analysis
Authors: Nikfar Mehdi , Paul Ratul , Islam Khayrul , Razizadeh Meghdad , Jagota Anand , Liu Yaling
Published: July 2021

Knowing the environmental spreading pathway of COVID-19 is crucial for improving safety practices, particularly for health care workers who are more susceptible to exposure. This paper focuses on the possible secondary transmission due to resuspension of virus-laden droplets from common surfaces, which several studies have shown to be possible under external disturbances. Such disturbances could be body motion during walking, running, clothes removal, or airflow in the environment. In this paper, a three-dimensional two-phase model is utilized to study respiratory droplet resuspension dynamics on various surfaces due to sudden agitation. The velocity range and variation during walking, surgical glove removal, and dropping an object are studied experimentally. A parametric study is performed to characterize the effects of droplet size and surface wettability on the minimum initial droplet velocity required for detachment from surfaces. The results are reported as average droplet velocity during the detachment process, total detachment time, and detached droplet volume. The obtained results indicate that respiratory droplets larger than 200 μm can detach from typical surfaces due to normal daily activities. Droplets are partially separated from hydrophilic surfaces with contact angle ≤90°, while the entire droplet is detached from hydrophobic surfaces with contact angle >90°. Furthermore, the minimum initial droplet velocity to induce the resuspension depends on the droplet size. Droplet velocity immediately after detachment is a function of droplet size, initial droplet velocity, and surface wettability. Bigger droplets have larger detached volume percentage as well as higher velocity after detachment compared to smaller droplets. Finally, a higher initial velocity is needed to separate droplets from hydrophilic surfaces as compared to hydrophobic surfaces. In accordance with the results, the droplet minimum initial velocity to cause detachment is 2 m s−1, while our experiments show that surface velocity can reach up to 3 m s−1 during normal human activities. We also develop an analytical model to predict the required kinetic energy to detach droplets from different surfaces, which is in good agreement with numerical results. The mechanism of droplet detachment is dictated by a competition between droplet kinetic energy induced by surface motion and surface energy due to droplet–surface interaction as well as droplet–vapor and surface–vapor interactions. We believe that the results of this fundamental study can potentially be used to suggest proper surface wettability and safe motion that reduce respiratory droplet resuspension from various surfaces.
In situ water radiolysis in a scanning electron microscope and observation of micro- and nanobubbles formation
Authors: Takahara Koji , Suzuki Satoru
Published: July 2021

Nanobubble formation by radiolysis of water has been observed in a transmission electron microscope using very high electron dose ratios. Here, surface micro- and nanobubbles were formed in situ in a conventional scanning electron microscope at relatively low magnifications of ∼1000. Bubble formation was observed at a low dose ratio of 1.3 × 1011 electrons/cm2 s, which is 5–7 orders of magnitude smaller than in previous studies using transmission electron microscopes. Our observations suggest that the pressure in the liquid cell is one of the important factors for the formation of bubbles. The contact angles obtained by direct observation of 69 bubbles were 50°–90°, with an average of 69°. These angles are much larger than those of the bubbles previously observed using an atomic force microscope. Despite the large contact angles (and large Laplace pressures), the micro- and nanobubble lifetimes were at least three days. Scanning electron microscopy shows potential as an important analytical tool for micro- and nanobubbles.
Fluid dispersion relation of dust acoustic wave with ion flow
Authors: Saitou Yoshifumi
Published: July 2021

The fluid dispersion relation of the dust acoustic wave in a plasma, which consists of electrons, an ion flow, and a dust fluid, is investigated. The dispersion relation has a form similar to that of the conventional one of the ion acoustic wave. It can be transformed into a form that includes the energy exchange factor between the ion flow and dust fluid. The dust acoustic wave can be controlled by varying the ion flow velocity. Varying the ion flow velocity is equivalent to varying the energy exchange factor. In the region where the energy exchange factor is negative, the dust acoustic wave does not propagate and the net energy of the dust fluid is expected to be transferred to the ion flow. In contrast, in the regions where the exchange factor is positive, the dust acoustic wave propagates.
Predicting different turbulent mixing problems with the same k–ɛ model and model coefficients
Authors: Xie Han-song , Xiao Meng-juan , Zhang You-sheng
Published: July 2021

In the foreseeable future, the Reynolds-averaged Navier–Stokes (RANS) method will remain the most viable approach for simulating practical flows. The RANS method mainly comprises two parts: a physical model and model coefficients. Hitherto, although researchers have made great effort to improve them, there is still much room for improving the satisfaction of RANS prediction. Given an available but possibly non-accurate physical model, is it possible to achieve a satisfactory RANS prediction? Our recent work on determination of k–L mixing model coefficients [Zhang et al., J. Fluid Mech. 905, A26 (2020)] sheds light on this problem. In that study, a satisfactory RANS prediction is achieved by systematically setting the values of model coefficients to match the given model. In this paper, we further extend this methodology to the widely used k–ɛ model. Consequently, with the same k–ɛ model and the same model coefficients, we successfully predict different turbulent mixing problems induced by various interface instabilities, which broadly occur in both nature and engineering. The investigated problems include both basic mixing problems, e.g., classical Rayleigh–Taylor (RT), Richtmyer–Meshkov (RM), and Kelvin–Helmholtz mixing, and complex mixing problems, e.g., reshocked RM mixing, RT mixing with initial tilted interface, and spherical implosion mixing. The successful predictions of the k–ɛ model, as well as those of the k–L model, indicate that the idea mentioned above may be applied to other RANS models and bring hope for predicting engineering problems with the same physical model and the same model coefficients.
Unity quantum efficiency in III-nitride quantum wells at low temperature: Experimental verification by time-resolved photoluminescence
Authors: Farr Philipp , Sidikejiang Shawutijiang , Horenburg Philipp , Bremers Heiko , Rossow Uwe , Hangleiter Andreas
Published: July 2021

Using time-resolved photoluminescence (PL) measurements, we present an experimental verification for 100% internal quantum efficiency (IQE) of III-N quantum wells at low temperatures. Conventional IQE measurements, such as temperature- and power-dependent PL, require a low-temperature normalization, where usually an IQE of 100% is assumed. This assumption neglects remaining nonradiative recombination that may be present even at cryogenic temperatures. From time-resolved PL measurements, the effective charge carrier decay time and the lifetime of radiative recombination can be evaluated separately. We state that the low-temperature IQE of a quantum well corresponds to 100%, whenever the effective charge carrier decay is dominated only by a radiative recombination. In this case, the temperature-dependent measurements show a synchronous rise of the effective lifetimes together with the radiative lifetimes, since only the radiative lifetime increases with temperature in a 2D system. At the same time, nonradiative processes are thermally activated, which results in a decreasing lifetime with temperature. Thereby, absolute IQE measurements become possible, since we provide a robust indicator for the absence of nonradiative recombination in quantum wells at low temperature.
Exploiting random phenomena in magnetic materials for data security, logics, and neuromorphic computing: Challenges and prospects
Authors: Navau C. , Sort J.
Published: July 2021

Random phenomena are ubiquitous in magnetism. They include, for example: the random orientation of magnetization in an assembly of non-interacting isotropic magnets; arbitrary maze domain patterns in magnetic multilayers with out-of-plane anisotropy, random polarization, and chirality of an array of magnetic vortices; or Brownian skyrmion motion, among others. Usually, for memory applications, randomness needs to be avoided to reduce noise and enhance stability and endurance. However, these uncontrolled magnetic effects, especially when incorporated in magnetic random-access memories, offer a wide range of new opportunities in, e.g., stochastic computing, the generation of true random numbers, or physical unclonable functions for data security. Partial control of randomness leads to tunable probabilistic bits, which are of interest for neuromorphic computing and for new logic paradigms, as a first step toward quantum computing. In this Perspective, we present and analyze typical materials that exhibit stochastic magnetic phenomena and we show some examples of emerging applications. The current challenges in terms of material development, as well as new strategies to tune stochasticity, enhance energy efficiency, and improve operation speeds are discussed, aiming to provide new prospects and opportunities in this compelling research field.
Propeller–duct interaction on the wake dynamics of a ducted propeller
Authors: Gong Jie , Ding Jiangming , Wang Lianzhou
Published: July 2021

The propeller–duct interaction on the wake dynamics of a ducted propeller is numerically investigated via detached eddy simulations. The blade–blade interference and blade–duct interaction are analyzed through different configurations under non-ducted and ducted conditions. It is found that the blade–blade interference benefits the loading stability, and the duct leads to a faster efficiency decrease in a single blade with the increasing blade number. The short-wave instability dominates the wake as the unstable secondary vortices accelerates the vortex evolution. The multi-induction effect stabilizes the two tip vortices system in a two-bladed configuration, while the tip vortex grouping occurs early in a four-bladed propeller due to the combined effect of the duct retardation and smaller spiral-to-spiral distance. Additionally, the enhanced wake instability leads to the fast decline of the power spectral density peaks of kinetic energy at blade passing frequency and shaft frequency harmonics toward the far field under ducted conditions.
Efficiency of pulsed-jet propulsion via thrust-drag decomposition
Authors: Bi Xiaobo , Zhu Qiang
Published: July 2021

By using an axisymmetric immersed-boundary model, fluid dynamics of a cephalopod-inspired propeller undergoing periodic inflation–deflation deformation in background flow is numerically studied in a low Reynolds number regime. A thrust-drag decoupling method based on physical analysis is proposed, in which the jet-related thrust is obtained as the summation of three parts: the jet momentum flux, the normal stress at the exit plane, and the flow acceleration inside the body. This method enables the calculation of the propulsive efficiency, especially the efficiency at the steady-swimming state. Systematic simulations are then conducted to study the effects of the Reynolds number and stroke ratio on force generation and efficiency. Two Reynolds numbers, the incoming-flow Reynolds number Re∞ and the jet-flow Reynolds number Rej, are involved. When Re∞ is fixed, the thrust generation is found to depend mostly on jet-flow velocity at high Rej, while the effect of incoming-flow velocity is pronounced at relatively low Rej, mostly through its influence on the excessive pressure at the nozzle. Within the range of incoming-flow Reynolds number considered in this study (40–150), our results show that the whole-cycle propulsive efficiency of the propeller lies in the range of 11%–30%.
Second language learners’ engagement with written feedback
Authors: Liu Kailin , Storch Neomy
Published: July 2021

Studies on feedback given to second language (L2) learners have focused primarily on learners’ response to feedback on language. This study explores how L2 learners in one university EAP class respond to teacher written feedback on all aspects of writing and the factors that may affect their response. Using data from student initial and revised texts, the study first looks at nine learners’ uptake of feedback. Then, adopting a case study approach and using data from retrospective interviews, the study examines how three learners engage with feedback on different dimensions of their writing. Findings show that learners took up almost all feedback suggestions regardless of form or focus. Yet, learners’ engagement with the feedback differed. Using activity theory (AT), we explain the learners’ engagement with the feedback received by reference to the interaction of context and individual-related factors. Our findings highlight the complexity of learner behavior in response to feedback.
Exploring the Case The Heritage of a Historic Farmhouse in Rural Catalonia
Authors: Louis Oriane , Pi Marta Valls I , Rajerinera Samuel , Sanjivy Agnès , Zhu Chuhong
Published: July 2021

Introduction

An interesting aspect of the L’Avenc de Tavertet Case Study is the restoration of this ancient building to turn it into a centre for tourism. This Exploring the Case is written for researchers and students in the specifics of such a process and in the challenges that have to be overcome.
Criminal Problem-Solving and Civil Dependency Court Policies regarding Medications for Opioid use Disorder
Authors: Andraka-Christou Barbara , Clark MH , Atkins Danielle N. , del Pozo Brandon
Published: July 2021

Background: Criminal problem-solving courts and civil dependency courts often have participants with substance use disorder (SUD), including opioid use disorder (OUD). These courts refer participants to treatment and set treatment-related requirements for court participants to avoid incarceration or to regain custody of children. Medications for opioid use disorder (MOUD) are the most effective treatment for OUD but are underutilized by court system participants. Little is known about variation in court policies for different MOUDs. Also, more information is needed about types of policies for each MOUD, including whether participants may begin MOUD, continue previously begun MOUD, or complete the court program with MOUD. Methods: An online survey was distributed to criminal problem-solving and civil dependency judges in Florida in 2019 and 2020, yielding data from 58 judges (a 24% response rate). We used nonparametric statistics to test hypotheses with ordinal data. A Friedman's test for related samples or Cochran's Q was used to make within-group comparisons between policies and MOUDs. Results: We found considerable policy variation, with more permissive policies for naltrexone than buprenorphine or methadone, and more permissive policies for continuing MOUD than for initiating MOUD or completing a court program with MOUD. For each medication, less than one quarter of judges indicated their court always permits MOUD, with most indicating that MOUD is permitted sometimes or usually. Conclusion: Because respondents rarely chose “never” or “always” for any MOUD policy, most courts appear to be making MOUD decisions on a case-by-case basis. A clearer understanding of this decision-making process is needed. Some court participants may be required to discontinue MOUD before completing a court program, even if they were permitted to start or continue MOUD treatment. Discontinuation of MOUD without medical justification is contrary to the standard of care for individuals with OUD and increases their risk of overdose.
From Finite Nuclei to Neutron Stars: The Essential Role of High-Order Density Dependence in Effective Forces
Authors: Jiang Chong-Ji , Qiang Yu , Guan Da-Wei , Chai Qing-Zhen , Qiao Chun-Yuan , Pei Jun-Chen
Published: July 2021

A unified description of finite nuclei and equation of state of neutron stars presents both a major challenge and also opportunities for understanding nuclear interactions. Inspired by the Lee–Huang–Yang formula of hard-sphere gases, we develop effective nuclear interactions with an additional high-order density dependent term. While the original Skyrme force SLy4 is widely used in studies of neutron stars, there are not satisfactory global descriptions of finite nuclei. The refitted SLy4’ force can improve descriptions of finite nuclei but slightly reduces the radius of neutron star of 1.4M⊙withM⊙being the solar mass. We find that the extended SLy4 force with a higher-order density dependence can properly describe properties of both finite nuclei and GW170817 binary neutron stars, including the mass-radius relation and the tidal deformability. This demonstrates the essential role of high-order density dependence at ultrahigh densities. Our work provides a unified and predictive model for neutron stars, as well as new insights for the future development of effective interactions.
Particle charge distributions in the effluent of a flow-through atmospheric pressure low temperature plasma
Authors: Husmann Eric , Thimsen Elijah , Chen Xiaoshuang
Published: July 2021

Atmospheric pressure low-temperature plasmas are often utilized to perform particle synthesis, treatment, and removal. It is well-known that dust particles are highly negatively charged in these plasmas; however, little is known about dust particle charging behavior as particles leave the plasma volume and pass through the spatial afterglow region. In this work, monodisperse particles of various sizes and work functions were introduced into an atmospheric pressure radiofrequency capacitively coupled flow-through plasma. Dust particle electrical mobility distributions downstream of the flow-through plasma were measured utilizing a differential mobility analyzer in conjunction with a condensation particle counter at various gas flow velocities. Charge distributions were determined from the measured electrical mobility distributions. Experiments confirm that particles become less negatively charged, and even net-positively charged after leaving the plasma volume, with a distribution that follows a shifted Boltzmann charge distribution. Additionally, particle charge in the effluent of the flow-through plasma is negligibly dependent on work function but highly size and flow velocity dependent. Larger particles were shown to have a higher magnitude of charge under all studied conditions; however, particle polarity was switchable by varying gas flow velocity. The charging dynamics were simulated utilizing a constant number Monte Carlo model that accounts for electron temperature decay and the transition from ambipolar to free diffusion of electrons and ions in the spatial afterglow. Simulation results also suggest that, at the same flow velocity, larger particles obtain a greater magnitude of charge, negative or positive. The decrease in electron mobility and the difference between ion and electron convective loss rates create an ion-rich region in the plasma effluent that promotes ion–particle collisions and drives particle charge removal and even reversal of polarity. Larger particles more favorably collide with energetic species in these environments, which results in higher charge states.
Time-domain optics for atomic quantum matter
Authors: Kanthak Simon , Gebbe Martina , Gersemann Matthias , Abend Sven , Rasel Ernst M , Krutzik Markus
Published: July 2021

We investigate time-domain optics for atomic quantum matter. Within a matter-wave analog of the thin-lens formalism, we study optical lenses of different shapes and refractive powers to precisely control the dispersion of Bose–Einstein condensates. Anharmonicities of the lensing potential are incorporated in the formalism with a decomposition of the center-of-mass motion and expansion of the atoms, allowing to probe the lensing potential with micrometer resolution. By arranging two lenses in time formed by the potentials of an optical dipole trap and an atom-chip trap, we realize a magneto-optical matter-wave telescope. We employ this hybrid telescope to manipulate the expansion and aspect ratio of the ensembles. The experimental results are compared to numerical simulations that involve Gaussian shaped potentials to accommodate lens shapes beyond the harmonic approximation.
Sudden singularities in generalized hybrid metric-Palatini cosmologies
Authors: Rosa João Luís , Lobo Francisco S.N. , Rubiera-Garcia Diego
Published: July 2021

In this work, we explore cosmological sudden singularities
arising in the dynamically equivalent scalar-tensor representation
of generalized hybrid metric-Palatini gravity. Using a FLRW
background, we show that the structure of the field equations
prevents sudden singularities from arising at time derivatives of
the scale factor of orders lower than four, but that they are
allowed to appear for time derivatives of higher orders. Imposing an
ansatz for the scale factor, we provide an explicit solution where
these sudden singularities appear in the fourth-order time
derivative of the scale factor. A comparison of the Hubble and
deceleration parameters arising from this model with the
experimental measurements from the Planck Satellite allow us to
impose constraints on the time span for which the occurrence of
sudden singularities becomes likely in our universe, as measured
from the Big Bang.