bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethics in Surgical Innovations from the Patient Perspective
Authors: Eyers Tony , Krastev Yordanka
Published: August 2020

Objective: Surgical innovation (SI) can place patients at risk. We sought to explore what clinical information is readily available to patients who have been offered innovative surgical procedures, using two examples drawn from our recent experience: one a surgical technique, and the other a prosthetic material. We wanted to determine from our review the extent to which information available on the Internet might augment the medical literature and help satisfy the ethical requirements for patients to be adequately informed before they proceed with innovative surgery.

Methods: A scoping review of the medical literature was performed to look for studies addressing the review aims; targeted searches on Google, YouTube, and patient websites were carried out to find readily available patient information on two chosen innovative surgical procedures. We conducted a content analysis of the selected references to determine the availability, relevance, and the utility of the published information to a layperson.

Results: Medical database searches identified 614 records, 91 were screened and only six were relevant. The Internet searches returned thousands of results; however, we limited our screening to the first five pages of results for those sources. From both types of searches, 348 references were excluded because they did not meet the inclusion criteria and 51 were included in the analysis. The findings are presented in four themes: safety and feasibility of the technique, availability and accessibility to a layperson, relevance and utility to a layperson, and commercial information.

Conclusion: The review has shown that lay people seeking to find out more about the two innovations would get very little useful information from Google, YouTube, or patient websites. Practitioners offering SI should provide sufficient information to allow their patients to make an autonomous decision about whether to proceed. For major SI, we encourage innovators to develop a plain language statement that would be made available on the Internet to the mutual advantage of both innovators and patients.
Advancing Medical Imaging Informatics by Deep Learning-Based Domain Adaptation
Authors: Choudhary Anirudh , Tong Li , Zhu Yuanda , Wang May D.
Published: August 2020

Introduction: There has been a rapid development of deep learning (DL) models for medical imaging. However, DL requires a large labeled dataset for training the models. Getting large-scale labeled data remains a challenge, and multi-center datasets suffer from heterogeneity due to patient diversity and varying imaging protocols. Domain adaptation (DA) has been developed to transfer the knowledge from a labeled data domain to a related but unlabeled domain in either image space or feature space. DA is a type of transfer learning (TL) that can improve the performance of models when applied to multiple different datasets.

Objective: In this survey, we review the state-of-the-art DL-based DA methods for medical imaging. We aim to summarize recent advances, highlighting the motivation, challenges, and opportunities, and to discuss promising directions for future work in DA for medical imaging.

Methods: We surveyed peer-reviewed publications from leading biomedical journals and conferences between 2017-2020, that reported the use of DA in medical imaging applications, grouping them by methodology, image modality, and learning scenarios.

Results: We mainly focused on pathology and radiology as application areas. Among various DA approaches, we discussed domain transformation (DT) and latent feature-space transformation (LFST). We highlighted the role of unsupervised DA in image segmentation and described opportunities for future development.

Conclusion: DA has emerged as a promising solution to deal with the lack of annotated training data. Using adversarial techniques, unsupervised DA has achieved good performance, especially for segmentation tasks. Opportunities include domain transferability, multi-modal DA, and applications that benefit from synthetic data.
Transparency of Health Informatics Processes as the Condition of Healthcare Professionals’ and Patients’ Trust and Adoption: the Rise of Ethical Requirements
Authors: Séroussi Brigitte , Hollis Kate Fultz , Soualmia Lina F.
Published: August 2020

Objectives: To provide an introduction to the 2020 International Medical Informatics Association (IMIA) Yearbook by the editors.

Methods: This editorial provides an introduction and overview to the 2020 IMIA Yearbook which special topic is: “Ethics in Health Informatics”. The keynote paper, the survey paper of the Special Topic section, and the paper about Donald Lindberg’s ethical scientific openness in the History of Medical Informatics chapter of the Yearbook are discussed. Changes in the Yearbook Editorial Committee are also described.

Results: Inspired by medical ethics, ethics in health informatics progresses with the advances in biomedical informatics. With the wide use of EHRs, the enlargement of the care team perimeter, the need for data sharing for care continuity, the reuse of data for the sake of research, and the implementation of AI-powered decision support tools, new ethics requirements are necessary to address issues such as threats on privacy, confidentiality breaches, poor security practices, lack of patient information, tension on data sharing and reuse policies, need for more transparency on apps effectiveness, biased algorithms with discriminatory outcomes, guarantee on trustworthy AI, concerns on the re-identification of de-identified data.

Conclusions: Despite privacy rules rooted in the Health Insurance Portability and Accountability Act of 1996 (HIPAA) in the USA and even more restrictive new regulations such as the EU General Data Protection Regulation published in May 2018, some people do not believe their data will be kept confidential and may not share sensitive information with a provider, which may also induce unethical situations. Transparency on healthcare data processes is a condition of healthcare professionals’ and patients’ trust and their adoption of digital tools.
Ethical Issue as the Limiting Factor for Epilepsy Surgery
Authors: Gedela Satyanarayana , Korff Christian
Published: August 2020

Epilepsy is one of the most common neurological disorders with almost one-third of these patients becoming intractable to medical treatments. For some of these patients, epilepsy surgery could be the best option. There are lot of disparities in caring of the epilepsy patients. There are multiple limitations in offering epilepsy surgery for the medically intractable epilepsy patients, resulting in almost 19 years gap from the diagnosis of intractable epilepsy to epilepsy surgery. These limitations range from patient or parental fear to lack of available resources. Sometimes we face an ethical issue being the limitation from doing the right thing for the patient. We want to share our experience with one of our patients with symptomatic medically intractable focal epilepsy from Rasmussen’s encephalitis who could not get the epilepsy surgery treatment because of an ethical issue.
Is Rhinoplasty Surgery a Risk Factor for Low Back Pain among Otorhinolaryngologists?
Authors: Kaplama Mehmet Erkan , Ak Semih , Yukkaldiran Ahmet
Published: August 2020

This study aimed to investigate the relationship between low back pain and performing rhinoplasty and presents the data related to the prevalence of low back pain among the otorhinolaryngologists included in a sample. The questionnaire prepared by the researchers was completed by volunteer otorhinolaryngologists who participated in the 22nd International Rhinocamp Congress. The questionnaire prepared to investigate low back problems contained items to obtain the demographic features of the participants, whether they were performing septorhinoplasty, how many years they had been performing this procedure, whether they had any problem (ache, pain, or discomfort) in the lumbar region, whether they had been hospitalized or had surgery due to this problem, low back pain frequency and intensity, and the presence of low back pathologies (e.g., protrusion, perforated disc, and bulging) detected by magnetic resonance imaging. The research was performed with the participation of 110 otorhinolaryngologists, of whom 37.3% (n = 41) were women and 62.7% (n = 69) were men, 79.1% (n = 87) were performing rhinoplasty surgery, and 69.1% (n = 76) had low back pain. Low back pain was reported in 72.4% (n = 63) of the doctors performing rhinoplasty and 56.5% (n = 13) of those who did not perform this surgery. There was a statistically significant relationship between the presence of low back pain and whether the doctors performed rhinoplasty surgery (χ2 = 4.151; p = 0.042 [< 0.05]). In addition, the complaints of low back pain were affected by the number of years the doctors had been performing rhinoplasty (p = 0.001 < 0.01). Low back pain was found to be frequent among otorhinolaryngologists performing rhinoplasty. Training, exercises, and performing the operation in a position that will prevent the occurrence of lower back pain can improve quality of life and minimize labor loss caused by pain among rhinoplasty surgeons.
Various Types of Medial Tibial Bone Resorption after Total Knee Arthroplasty Using a Thick Cobalt Chromium Tibial Baseplate
Authors: Song Sang Jun , Lee Hyun Woo , Kang Se Gu , Bae Dae Kyung , Park Cheol Hee
Published: August 2020

Recent literature has implicated a thick cobalt chromium baseplate as a potential source of stress shielding and medial tibial bone resorption after total knee arthroplasty (TKA) in a Western population. The purpose was to calculate the incidence of various types and severity of medial tibial bone resorption utilizing a novel classification system after TKA with a thick cobalt chromium baseplate in Asian patients. Five hundred TKAs using Attune prostheses with mean follow-up of 3.4 years were evaluated, using the prospective radiographic data. The mean age was 71.3 years. The preoperative mechanical axis was varus, 11.2 degrees. The type and severity of medial tibial bone resorption were categorized as type U (resorption under the tibial baseplate up to 50% [U1] or beyond 50% [U2] of medial tibial tray width), C (resorption around the penetrated cement under the baseplate), and M (resorption on the medial tibial cortex without extension to the baseplate). Bone resorption of medial proximal tibia was observed in 96 knees (19.2%). Types U1 and U2 were seen in 46 and 28 knees, respectively. Type C was observed in 12 knees and type M in 10 knees. The type U resorption group had significantly more preoperative varus deformity (varus 12.9 vs. 10.9 degrees, p = 0.017). Medial tibial bone resorption after TKAs using a thick cobalt chromium baseplate is not uncommon and has various locations, types, and severities. The medial tibial bone resorption might be related to various causes, including stress shielding, thermal necrosis from cement in the bony hole, and bony devascularization. The type-U resorption has to be closely observed in patients with preoperative severe varus deformity. This is a Level IV study.
Clinical Outcomes, Health Care Costs and Prognostic Factors for Total Knee Arthroplasty: A Multilevel Analysis of a National Cohort Study Using Administrative Claims Data
Authors: Buitrago Giancarlo , Ortiz Jorge R. , Camacho Felipe
Published: August 2020

Total knee arthroplasty (TKA) is one of the most frequent orthopaedic surgeries. The purpose of this study was to determine the 30-day postoperative mortality rate, total episode-of-care costs, and prognostic factors associated with these outcomes, for adult patients who underwent TKA in Colombia's contributory health care system. A retrospective cohort study of all adult patients enrolled in Colombia's contributory health system, who underwent TKA between January 1, 2012 and November 30, 2015 was performed. Thirty-day postoperative mortality rates, 30-day ICU admissions rates, 30-day hospital readmission rates, 1-year arthroplasty revision rates, and total episode-of-care costs were estimated. Multilevel, generalized linear models were generated, to determine the prognostic factors associated with outcomes presented. A total of 12,453 patients were included. The 30-day mortality rate was 0.13 per 100 surgeries and the ICU admissions rate at 30 days postoperative was 4.44 per 100 surgeries. The 30-day hospital readmission rate was 4.28 per 100 surgeries and the 1-year arthroplasty revision rate was 1.22 per 100 surgeries. The prognostic factors associated with mortality were age, Charlson Index, and type of insurer. The prognostic factors associated with hospital readmission were age category, Charlson Index, and geographic region; younger age and higher Charlson Index were found to be associated with a higher 1-year arthroplasty revision rate. The median of total episode-of-care costs was USD$ 6,190.07 (interquartile range: 2,299–7,282). The multivariate model found that age, the Charlson Index, the Atlantic region, and type of insurer were associated with the costs incurred by the health system. For patients undergoing TKA in Colombia, age, the Charlson Index, insurers, and geographic region are associated with mortality, ICU admissions, 30-day hospital readmissions, 1-year arthroplasty revisions, and total costs incurred by the health system.
Effect of Local Infiltration Analgesia on Functional Outcomes in Total Knee Arthroplasty: A Randomized, Placebo-Controlled, Double-Blind Clinical Trial
Authors: Unver Bayram , Yuksel Ertugrul , Eymir Musa , Maltepe Fikret , Karatosun Vasfi
Published: August 2020

Local infiltration analgesia (LIA) is a simple, surgeon-administered technique for the treatment of postoperative pain after total knee arthroplasty (TKA). The aim of the study was to investigate the efficacy of LIA and its effects on functional outcomes in TKA. A total of 135 patients with primary TKA were recruited and randomized either to receive LIA or to receive placebo injection (PI). Pain, active range of motion (ROM), knee function score, functional activities, and hospital length of stay (LOS) were assessed before surgery and from postoperative day (POD) 1 to at discharge. Lower pain scores at rest were recorded on POD1 and POD2 in the LIA group (p = 0.027 and p = 0.020, respectively). Lower pain score on walking was recorded on POD1 in the LIA group (p = 0.002). There was a statistically significant difference in active knee flexion between groups on POD1 (p = 0.038). There was a significant difference in LOS between LIA and PI groups. Shorter stay was seen in LIA group. There were no statistically significant differences between the groups in terms of knee function score and functional outcomes. LIA technique is effective for pain management in the early postoperative period. LIA added benefit for knee function in terms of active knee flexion ROM after TKA. A shorter hospital LOS was observed in LIA group. However, we did not find any differences in groups in terms of functional assessment such as ability to rise from a chair and walking capacity.The level of evidence is randomized controlled trial, level I.
Preoperative Meniscal Extrusion Predicts Unsatisfactory Clinical Outcomes and Progression of Osteoarthritis after Isolated Partial Medial Meniscectomy: A 5-Year Follow-Up Study
Authors: Novaretti João V. , Astur Diego C. , Cavalcante Elton L.B. , Kaleka Camila C. , Amaro Joicemar T. , Cohen Moisés
Published: August 2020

The objective of this study was to examine the association between preoperative meniscal extrusion of patients undergoing partial medial meniscectomy with clinical outcomes and progression of osteoarthritis and to determine the extent of meniscal extrusion associated with unsatisfactory clinical outcomes and progression of osteoarthritis. Ninety-five patients who underwent partial medial meniscectomy with a minimum follow-up of 5 years were retrospectively reviewed. Preoperative meniscal extrusion was evaluated with magnetic resonance imaging. Patients were assessed preoperatively and postoperatively with Lysholm and International Knee Documentation Committee (IKDC) subjective scores for clinical outcomes and with IKDC radiographic scale for osteoarthritis. An ANOVA (Analysis of Variance) was used to analyze the variations in meniscal extrusion and the clinical and radiological outcomes. A regression analysis was performed to identify factors that affect preoperative medial meniscus extrusion and that influence results after partial meniscectomy. An optimal cutoff value for meniscal extrusion associated with unsatisfactory clinical outcomes and progression of osteoarthritis was established. Significance was set at p < 0.05. The mean ± SD preoperative and postoperative Lysholm scores were 59.6 ± 15.5 versus 83.8 ± 13.1 (p < 0.001) and the mean preoperative and postoperative IKDC subjective scores were 59.4 ± 16.8 versus 82.0 ± 15.8 (p < 0.001). Meniscal extrusion greater than 2.2 mm (sensitivity, 84%; specificity, 81%) and 2.8 mm (sensitivity, 73%; specificity, 85%) was associated with unsatisfactory (poor/fair) Lysholm and IKDC subjective scores, respectively. The progression of osteoarthritis, characterized as a change of at least one category on the IKDC radiographic scale, occurred when meniscal extrusion was greater than 2.2 mm (sensitivity, 63%; specificity, 75%). Patients with higher body mass index (BMI) had significantly greater meniscal extrusion that patients with normal BMI (p < 0.001). The medial meniscus was more extruded in patients with horizontal and root tears. In conclusion, patients with preoperative meniscal extrusion of 2.2 mm or greater had unsatisfactory clinical outcomes and progression of osteoarthritis after partial medial meniscectomy at a minimum of 5 years follow-up. Higher BMI and horizontal and root tears were associated with greater preoperative meniscal extrusion.
A Risk Score for Predicting the Incidence of Hemorrhage in Critically Ill Neonates: Development and Validation Study
Authors: Sokou Rozeta , Piovani Daniele , Konstantinidi Aikaterini , Tsantes Andreas G. , Parastatidou Stavroula , Lampridou Maria , Ioakeimidis Georgios , Gounaris Antonis , Iacovidou Nicoletta , Kriebardis Anastasios G. , Politou Marianna , Kopterides Petros , Bonovas Stefanos , Tsantes Argirios E.
Published: August 2020

The aim of the study was to develop and validate a prediction model for hemorrhage in critically ill neonates which combines rotational thromboelastometry (ROTEM) parameters and clinical variables. This cohort study included 332 consecutive full-term and preterm critically ill neonates. We performed ROTEM and used the neonatal bleeding assessment tool (NeoBAT) to record bleeding events. We fitted double selection least absolute shrinkage and selection operator logit regression to build our prediction model. Bleeding within 24 hours of the ROTEM testing was the outcome variable, while patient characteristics, biochemical, hematological, and thromboelastometry parameters were the candidate predictors of bleeding. We used both cross-validation and bootstrap as internal validation techniques. Then, we built a prognostic index of bleeding by converting the coefficients from the final multivariable model of relevant prognostic variables into a risk score. A receiver operating characteristic analysis was used to calculate the area under curve (AUC) of our prediction index. EXTEM A10 and LI60, platelet counts, and creatinine levels were identified as the most robust predictors of bleeding and included them into a Neonatal Bleeding Risk (NeoBRis) index. The NeoBRis index demonstrated excellent model performance with an AUC of 0.908 (95% confidence interval [CI]: 0.870–0.946). Calibration plot displayed optimal calibration and discrimination of the index, while bootstrap resampling ensured internal validity by showing an AUC of 0.907 (95% CI: 0.868–0.947). We developed and internally validated an easy-to-apply prediction model of hemorrhage in critically ill neonates. After external validation, this model will enable clinicians to quantify the 24-hour bleeding risk.
Coagulopathy and Thrombosis as a Result of Severe COVID-19 Infection: A Microvascular Focus
Authors: Katneni Upendra K. , Alexaki Aikaterini , Hunt Ryan C. , Schiller Tal , DiCuccio Michael , Buehler Paul W. , Ibla Juan C. , Kimchi-Sarfaty Chava
Published: August 2020

Coronavirus disease of 2019 (COVID-19) is the clinical manifestation of the respiratory infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While primarily recognized as a respiratory disease, it is clear that COVID-19 is systemic illness impacting multiple organ systems. One defining clinical feature of COVID-19 has been the high incidence of thrombotic events. The underlying processes and risk factors for the occurrence of thrombotic events in COVID-19 remain inadequately understood. While severe bacterial, viral, or fungal infections are well recognized to activate the coagulation system, COVID-19-associated coagulopathy is likely to have unique mechanistic features. Inflammatory-driven processes are likely primary drivers of coagulopathy in COVID-19, but the exact mechanisms linking inflammation to dysregulated hemostasis and thrombosis are yet to be delineated. Cumulative findings of microvascular thrombosis has raised question if the endothelium and microvasculature should be a point of investigative focus. von Willebrand factor (VWF) and its protease, a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS-13), play important role in the maintenance of microvascular hemostasis. In inflammatory conditions, imbalanced VWF-ADAMTS-13 characterized by elevated VWF levels and inhibited and/or reduced activity of ADAMTS-13 has been reported. Also, an imbalance between ADAMTS-13 activity and VWF antigen is associated with organ dysfunction and death in patients with systemic inflammation. A thorough understanding of VWF-ADAMTS-13 interactions during early and advanced phases of COVID-19 could help better define the pathophysiology, guide thromboprophylaxis and treatment, and improve clinical prognosis.
Reducibility of the quantum harmonic oscillator in d-dimensions with finitely differentiable perturbations
Authors: Jian Wenwen
Published: August 2020

In this paper, the d-dimensional quantum harmonic oscillator with a pseudo-differential time quasi-periodic perturbation iψ̇=(−Δ+V(x)+ϵW(ωt,x,−i∇))ψ,x∈Rd is considered, where ω ∈ (0,2π)n, V(x)≔∑j=1dvj2xj2,vj≥v0>0, and W(θ, x, ξ) is a real polynomial in (x, ξ) of degree at most two, with coefficients belonging to Cℓ in θ∈Tn for the order ℓ satisfying ℓ ≥ 2n + β, 0 < β < 1. Using the techniques developed by Bambusi et al. [Anal. PDE 11(3), 775–799 (2018)] and Rüssmann [“On optimal estimates for the solutions of linear partial differential equations of first order with constant coefficients on the torus,” in Dynamical Systems, Theory and Applications, Lecture Notes in Physics Vol. 38 (Rencontres, Battelle Research Institute, Seattle, WA, 1975), pp. 598–624], this paper shows that for any ϵ small enough, there is a set Dϵ⊂(0,2π)n with a big Lebesgue measure such that for any ω∈Dϵ, the system is reducible.
What conditions ensure that nonlinear systems will synchronize?
Authors: Bandari Anashe
Published: August 2020

A set of coupled oscillators is guaranteed to achieve global synchrony if a threshold level of connectivity is exceeded.
Sandwich device ensures rapid and even spreading of biofluids for analysis
Authors: Bandari Anashe
Published: August 2020

Changes in pressure drive fluids toward a filter paper, ensuring faster and more even spread.
Effect of texture on the electrical and electrocaloric properties of 0.90Pb(Mg1/3Nb2/3)O3–0.10PbTiO3 relaxor ceramics
Authors: Mensur-Alkoy Ebru , Okatan M. Baris , Aydin Ecem , Kilic Yusuf , Misirlioglu I. Burc , Alkoy Sedat
Published: August 2020

Functional properties of ferroelectric compositions depend strongly on the type of stable crystalline phase at a given temperature and texturing. In addition to defining a governing crystallographic axis among the grains with respect to a global reference axis, texturing in these systems is also often meant to imply the relationship between an external applied field and the polar axis. Here, we synthesize randomly oriented and ⟨001⟩pc textured 0.90Pb(Mg1/3Nb2/3)O3–0.10PbTiO3 solid solutions that fall into the relaxor category. A >95% degree of ⟨001⟩pc texturing was achieved by the use of single crystal BaTiO3 template crystallites whose volume fraction does not exceed 5% of the entire sample volume. Electrical measurements made on random and textured samples reveal the impact of texture on the hysteresis and the dielectric response. A Curie–Weiss analysis of the temperature dependent dielectric data shows the degree of relaxor behavior in random and textured samples. As similar compositions have recently been getting interest for electrothermal management applications, we compute the electrocaloric (EC) response of the random and textured samples using indirect methods followed by an estimation of the EC response with a subsequent thermodynamic analysis to shed light on the effect of texture on the observed differences between the textured and the random oriented samples. We finally compare and contrast on the desirability of texturing in these systems for use as EC components for thermal management applications.
Thermohydraulic performance of a novel curved serpentine coil
Authors: Reddy Desireddy Shashidhar , Khan Mohd. Kaleem , Awasthi Kuldeep
Published: August 2020

Conventional coil designs, such as helical and flat serpentine (FS) coils, are commonly employed for heat transfer applications due to their higher heat transfer performance and compactness. In the last few decades, chaotic coil designs have attracted the attention of a few researchers due to their superior thermohydraulic performance. In this paper, we present a novel and simple chaotic coil design termed the curved serpentine (CS-θ) coil, which is a modified version of the conventional FS coil. The straight tubes of length L in the FS coil are bent as arcs of radius R1 and subtended angle θ (i.e., L = R1 × θ), which are interconnected with U-bends of radius R2. The laminar flow of water through the CS-θ coil is numerically investigated, and the peaks and valleys in the local Nusselt number and friction factor at various axial locations are explained with the help of velocity and temperature contours and secondary flow patterns. The chaotic nature of flow through these coils is explained with the help of streamlines and transverse flow vectors, transversal intersection of the trajectories, and the Lyapunov spectrum. The thermohydraulic performance (η) of this coil is found superior to conventional FS and helical coils. It is found that the CS-θ coils, in which the flow is fully developed just before entering the U-bend, can achieve the best thermohydraulic performance. We also propose generalized correlations for predicting the average Nusselt number and friction factor in the CS-θ coils with a maximum deviation of ±10% and ±7.5%, respectively.
Flow-structure interactions of two tandem inverted flags in a water tunnel
Authors: Hu Yao-Wei , Feng Li-Hao , Wang Jin-Jun
Published: August 2020

The dynamic behaviors and vortex interaction modes of two tandem inverted flags at different gap distances and flow velocities are investigated experimentally in this paper. The results show that the straight, flapping, and deflected modes can still be observed with a successive increase in the flow velocity. The fixed-phase, different-frequency, changing-phase, alternating-phase, and aperiodic flapping modes are further found in the flapping mode. Considering the fixed phase difference and predominance of the fixed-phase mode, we mainly focus on this mode. The amplitude of the front flag is almost similar to that of an isolated flag due to the unaffected leading-edge vortex when they are both in the flapping mode, while it is smaller for the rear flag, indicating the great significance of the rear flag amplitude for studying the dynamic behaviors of two tandem inverted flags. First, the relation between the amplitude of the rear flag and the phase difference contains two linear segments with almost the same slope and a constant segment, fully demonstrating their strong correlation rather than the irrelevance. Second, the rear flag and the trailing-edge vortex (TEV) of the front flag are found to interact via the strong and weak interaction modes. Only in the strong interaction mode can the rear flag extract energy from the TEV of the front flag at lower critical flow velocity, resulting in a larger amplitude than that of the front flag. In general, a small gap distance is more conducive to energy harvesting at low flow velocity, while a large gap distance is more beneficial at high flow velocity.
Stabilization of metallic phases through formation of metallic/semiconducting lateral heterostructures
Authors: Canton-Vitoria Ruben , Hotta Takato , Liu Zheng , Inoue Tsukasa , Kitaura Ryo
Published: August 2020

In this study, we develop a new approach for stabilization of metallic phases of monolayer MoS2 through the formation of lateral heterostructures composed of semiconducting/metallic MoS2. The structure of metallic (a mixture of T and T′) and semiconducting (2H) phases was unambiguously characterized by Raman spectroscopy, x-ray photoelectron spectroscopy, photoluminescence imaging, and transmission electron microscope observations. The amount of NaCl, reaction temperature, reaction time, and locations of substrates are essential for controlling the percentage of metallic/semiconducting phases in lateral heterostructures; loading a large amount of NaCl at low temperatures with short reaction times prefers metallic phases. The existence of the semiconducting phase in MoS2 lateral heterostructures significantly enhances the stability of the metallic phases through passivation of reactive edges. The same approach can be applied to other transition metal dichalcogenides (TMDs), such as WS2, leading to boosting of basic research and application of TMDs in metallic phases.
Nonplanar ion acoustic waves in dusty plasma with two temperature electrons: Application to Saturn's E ring
Authors: Bansal Sona , Aggarwal Munish , Gill Tarsem S
Published: August 2020

In the present paper, we have studied the cylindrical/spherical ion acoustic waves in dusty plasma consisting of positive ions, immobile dust particles, and q nonextensive distributed cold and hot electrons. A multiple scale expansion method is employed to derive a modified Korteweg–de Vries (mKdV) equation. Exact analytical solution for the mKdV equation in nonplanar geometry is obtained using the weighted residual method. This solution is, then, plotted for different physical parameters relevant to Saturn's E ring through 2D figures. We show that the amplitude of the wave decreases faster as one departs away from the axis of the cylinder or the center of the sphere. Such a decaying behavior continues as time progresses. This is expected from the obtained solution where the cylindrical (spherical) amplitude component (τ∞/τ)m decreases as the time progresses. We have also studied the role of the nonadiabatic dust charging fluctuating dissipation process and analyzed the resulting damped mKdV equation. Furthermore, the parametric dependence of wave properties (amplitude and width) on the q nonextensive parameter, density, and temperature of cold and hot electrons, concentration of dust particles, and thermal effects of ions has been studied in detail, and findings obtained here will be beneficial to further astrophysical investigations.
Decorated membrane resonators as underground seismic wave barriers against high magnitude earthquakes
Authors: Xu Feilong , Sun Liang , Zhen Liang , He X. , Yang Z.
Published: August 2020

We report a framework of underground barriers against seismic waves from high-magnitude earthquakes, which consist of the deep subwavelength decorated membrane resonators (DMR's) modeled as a type of artificial soil, the meta-soil, which is buried in the host soil. The meta-soil has the same elastic properties as the host soil but with a dynamic effective mass density that mimics the functionality of the DMR's mixed with the host soil. Metallic membrane DMR's with multiple working frequencies down to 7 Hz are experimentally demonstrated. Transmission attenuation exceeding 20 dB and absorption above 98% are numerically demonstrated for the 1 Hz Rayleigh waves using about 12 rows of underground meta-soil columns. The findings obtained from the meta-soil are validated by using discrete generic tuned mass dampers buried in the soil. A scaling law similar to the mass density law for acoustic waves that relates the meta-soil mass density to the wave frequency for a given transmission attenuation has been analytically derived and numerically verified. The main mechanism for the wave attenuation is the resonant enhancement of scattering and dissipation by the resonators in the meta-soil. The findings for attenuating the 1 Hz seismic waves serve as a benchmark and design platform for the broadband seismic wave barriers due to the following findings. (1) It is a representative frequency for high magnitude earthquakes. The practical lower frequency limit is about 0.5 Hz, so the dimension and weight of the dampers for 0.5 Hz will be comparable to that for 1 Hz, while the dampers for higher frequencies will be smaller in size and lighter in weight. (2) The length of the wells will be comparable to that of the 1 Hz ones and proportionally shorter for higher frequency waves. Our findings provide a viable solution that could fill the gap between the maximum earthquake resistance capability of most modern buildings and infrastructures (∼seventh magnitude) and the need to resist the highest (∼eighth) magnitude earthquakes recorded in human history, and remedy one of the main shortcomings in the literature on the local resonators for underground seismic wave barriers, which is the gross over-estimation of the seismic wave blocking power of the barriers due to the omission or unrealistic under-estimation of the intrinsic dissipation of the elastic components of the local resonators.
The north–south orientation of Australian termite mounds is due to the Sun and local wind: A heat transfer investigation
Authors: Fagundes Tadeu Mendonca , Ordonez Juan C. , Yaghoobian Neda
Published: August 2020

The Australian “magnetic” termite mounds are famously known for their systematic wedge-shape and north–south alignment. Although the longer axis of the mound wedge is mainly aligned north-to-south, depending on their locations, they might have slight deviations from true north, exhibiting consistent east or westward orientations. The structural characteristics of Australian mounds have been the subject of many in situ investigations in the past, suggesting that the orientation of these structures might be a response to termites’ need for having a sort of thermal regulation within their habitat. Using the foundations based by the observational studies, this study develops a thermo-physics based predictive model, founded on the principles of heat transfer and thermodynamics, to fundamentally investigate the reason behind the shape and orientation of magnetic mounds. Using the typical environmental conditions of the locations where these mounds are found, the shape and orientation of the thermally optimized structures were successfully predicted by the model, indicating that their structural characteristics arise as a response to the combined effects of the local solar irradiance received on the mound body and the local wind condition. These combined effects result in a thermally regulated medium within the mound (i.e., uniform temperatures throughout the structure with minimum fluctuations throughout the day) that provides a suitable microclimate for the residing termites. The effects of different environmental conditions on the mound structural characteristics are also investigated.
Kinetics of cluster formation in active suspension: Coarsening regime
Authors: Kichatov Boris , Korshunov Alexey , Sudakov Vladimir , Kolobov Andrey , Gubernov Vladimir , Golubkov Alexandr , Kiverin Alexey
Published: August 2020

The active suspension has an amazing property to undergo a phase transition into dense and dilute gas phases, even in the absence of the interparticle forces of attraction. In this work, the phase transition in active suspension is considered within a minimal model, in which self-propelled particles are moving with a constant speed, while their direction of propagation is governed by mutual collisions. The final stage of cluster formation in active suspension is studied when the larger clusters grow by consuming the smaller ones. The analysis of kinetic equation for the evolution of the number of particles in a cluster and conservation of particles law in active suspension shows that the number of clusters decreases with time according to a power of minus three fifths and the average number of particles in a cluster depends on their speed and time in the power of three fifths. The size distribution function of clusters is obtained, which is found to be asymmetric with respect to the average number of particles in clusters.
Tolerance of spin-Seebeck thermoelectricity against irradiation by swift heavy ions
Authors: Okayasu Satoru , Harii Kazuya , Kobata Masaaki , Yoshii Kenji , Fukuda Tatsuo , Ishida Masahiko , Ieda Jun’ichi , Saitoh Eiji
Published: August 2020

The ion-irradiation tolerance of thermoelectric devices based on the spin Seebeck effect (SSE) was investigated by using 320 MeV gold ion (Au24+) beams modeling cumulative damages due to fission products emitted from the surface of spent nuclear fuels. For this purpose, prototypical Pt/Y3Fe5O12/Gd3Ga5O12 SSE elements were irradiated with varying the dose level at room temperature and measured the SSE voltage of them. We confirmed that the thermoelectric and magnetic properties of the SSE elements are not affected by the ion-irradiation up to 1010 ions/cm2 fluence and that the SSE signal is extinguished around 1012 ions/cm2, in which the ion tracks almost fully cover the sample surface. We also performed the hard X-ray photoemission spectroscopy (HAXPES) measurements to understand the effects at the interface of Pt/Y3Fe5O12. The HAXPES measurements suggest that the chemical reaction that diminishes the SSE signals is enhanced with the increase of the irradiation dose. The present study demonstrates that SSE-based devices are applicable to thermoelectric generation even in harsh environments for a long time period.
Trifunctional metasurface for manipulating linearly and circularly polarized waves in transmission and reflection modes
Authors: Fang Quanhai , Wu Liangpei , Pan Weikang , Li Minhua , Dong Jianfeng
Published: August 2020

Integration of multiple functionalities into a single, planar, and ultra-compact device has become an emerging research area in photonics. In this work, we design, fabricate, and experimentally demonstrate a trifunctional metasurface integrated by meta-atoms with resonant and geometrical phase cells. By changing the polarization and incident direction of electromagnetic (EM) waves, the wavefronts of the transmitted and reflected waves can be reshaped. The metasurface exhibits the strong capability to manipulate both the linearly polarized (LP) wave and circularly polarized (CP) wave at different frequencies. Therefore, the designed trifunctional metasurface can achieve three distinct functionalities including beam deflecting for X-linearly polarized (X-LP) wave at 13 GHz impinging from below, and diverging and focusing lens for CP waves at 9 GHz impinging from above. Both far-field and near-field microwave experiments demonstrate the predicted functionalities of the fabricated device, which can advance research and applications related to other distinct functionalities of photonics integration.
Prediction of the electron kinetics relevant for CO2 splitting using in situ propellant production technology: Effect of the gas composition
Authors: Zhang Bin , Zhang Xiaobing
Published: August 2020

Electron kinetics plays an essential role in CO2 splitting in non-equilibrium plasmas. Indigenous resources, particularly CO2 rich in the Martian atmosphere, are utilized as the feedstock for the technology of in situ propellant production (ISPP) in Mars missions. To obtain electron kinetics including electron energy distribution function (EEDF) and transport coefficients, a Boltzmann analysis is adopted. In view of ISPP in the upper Martian atmosphere, the complicated variation of the gas composition with the altitude in both dayside and nightside is considered. The composition of gas mixture is derived from the previous measurement data through site survey and numerical models. According to the results of calculation, altitude affects the behavior of EEDFs and transport coefficients in both dayside and nightside. The rapid drop in CO2 content and the rise in O content with altitude lead to a broader EEDF. The reduction of the critical breakdown electric field strength with the increasing altitude is ascribed to the combined effects of the decline of the attachment coefficient and enhancement of the ionization coefficient. The electron energy loss mechanism is presented for the analysis of energy efficiency. At low mean electron energy, electron energy is mostly transferred to vibrational levels of CO2. With the increasing electron energy, more energy-demanding processes, like ionization and electronic excitation, become essential pathways of energy loss.
2N-rule: Searching topological phases and robust edge modes in carbon nanotubes
Authors: Hu Chen , Guo Hong
Published: August 2020

We theoretically report an explicit and robust scheme, 2N-rule, for systematically searching topological phases in carbon nanotubes (CNTs) of all diameters. By investigating the topological Zak phase based on both analytical model and first-principles approaches, such a 2N-rule of insulating CNT(n,0) is generally established: when n=2N, where N is an integer (an even n), it is a topological insulator; otherwise, it is a normal insulator. For finite-length topological CNTs, topologically protected quantum modes naturally occur at the tube ends, which hold significant robustness against external environment perturbations, taking advantage over fragile edge states in conventional systems. The topological CNTs can provide a platform for potential applications in reliable carbon nanoelectronics as well as exploring fundamental science of one-dimensional topological materials.
Nonlinear elastic imaging with amplitude and frequency modulated low frequency sources
Authors: Bentahar M. , Mechri C. , Scalerandi M.
Published: August 2020

The use of low frequency waves is the most practical means to investigate nonlinear elastic properties of hysteretic media, such as the strain dependence of wave velocity. Indeed, the rapid increase in damping as a function of frequency makes high frequency waves unable to provide sufficient strain energy to successfully excite nonlinearity. The drawback is that low frequency waves are not suitable for imaging, due to their long wavelength and resulting intrinsic averaging of nonlinear effects over large spatial scales. To address this, we propose here an amplitude modulation of swept sources that allows us to correlate the frequency at which harmonics are detected with the position of the source of nonlinearity, taking advantage of the different strain distributions in the sample at different frequencies.
p-type conductivity and damage recovery in implanted GaN annealed by rapid gyrotron microwave annealing
Authors: Meyers V. , Rocco E. , Anderson T. J. , Gallagher J. C. , Ebrish M. A. , Jones K. , Derenge M. , Shevelev M. , Sklyar V. , Hogan K. , McEwen B. , Shahedipour-Sandvik F.
Published: August 2020

We demonstrate p-type activation of GaN doped by Mg ion implantation, and in situ during metalorganic chemical vapor deposition through sequential short-duration gyrotron microwave heating cycles at temperatures of 1200–1350 °C. GaN is implanted with 1019 cm−3 Mg ions, capped with AlN, and annealed under 3 MPa N2 overpressure in 5 s heating cycles for less than 60 s total using a high-power gyrotron microwave heating source. Through I–V characterization, photoluminescence spectroscopy, and Raman spectroscopy, we study the evolution of electrical properties, optically active point defects, and material strain in response to implantation and annealing. For Mg-implanted samples, increasing annealing temperature is characterized by an increase in the PL substitutional Mg-related peak (UVL) relative to the shallow-donor vacancy-related peak (GL2). Through comparison of implanted and in situ doped samples, it is demonstrated that the origin of compensating VN lies primarily in implantation rather than degradation from the annealing process. Transmission line measurements and diode I–V measurements show a sheet resistance of 1083 kΩ/□ and a hole concentration of 1.23 × 1015 cm−3, respectively, in the Mg-implanted material annealed at 1350 °C. We conclude that temperature-cycled gyrotron annealing at 1350 °C decreases implant-induced compensating point defects and activates Mg to obtain selective p-type conduction.
Derivation of ρ-dependent coordinate transformations for nonrigid molecules in the Hougen–Bunker–Johns formalism
Authors: Viglaska Dominika , Rey Michael , Nikitin Andrei V. , Tyuterev Vladimir G.
Published: August 2020

In this paper, we report a series of transformations for the construction of a Hamiltonian model for nonrigid polyatomic molecules in the framework of the Hougen–Bunker–Johns formalism (HBJ). This model is expressed in normal mode coordinates for small vibrations and in a specific coordinate ρ to describe the large amplitude motion. For the first time, a general procedure linking the “true” curvilinear coordinates to ρ is proposed, allowing the expression of the potential energy part in the same coordinate representation as the kinetic energy operator, whatever the number of atoms. A Lie group-based method is also proposed for the derivation of the reference configuration in the internal axis system. This work opens new perspectives for future high-resolution spectroscopy studies of nonrigid, medium-sized molecules using HBJ-type Hamiltonians. Illustrative examples and computation of vibrational energy levels on semirigid and nonrigid molecules are given to validate this method.
Impact of electron injection on carrier transport and recombination in unintentionally doped GaN
Authors: Modak Sushrut , Chernyak Leonid , Xian Minghan , Ren Fan , Pearton Stephen J. , Khodorov Sergey , Lubomirsky Igor , Ruzin Arie , Dashevsky Zinovi
Published: August 2020

The impact of electron injection on minority carrier (hole) diffusion length and lifetime at variable temperatures was studied using electron beam-induced current, continuous, and time-resolved cathodoluminescence techniques. The hole diffusion length increased from 306 nm to 347 nm with an electron injection charge density up to 117.5 nC/μm3, corresponding to the lifetime changing from 77 ps to 101 ps. Elongation of the diffusion length was attributed to the increase in the non-equilibrium carrier lifetime, which was determined using ultrafast time-resolved cathodoluminescence and related to non-equilibrium carrier trapping on gallium vacancy levels in the GaN forbidden gap.