bluuebunny/crossref_metadata_2025 huggingface dataset:
An Evaluation of the Learning Curve in Pulmonary Endarterectomy Using Propensity Score Matching
Authors: Miyahara Shunsuke , Schröder Tom A. , Wilkens Heinrike , Karliova Irem , Langer Frank , Kunihara Takashi , Schäfers Hans-Joachim
Published: September 2020

Objective Pulmonary endarterectomy (PEA) is the only causative, but demanding treatment of choice for chronic thromboembolic pulmonary hypertension (CTEPH). We analyzed our results with PEA to evaluate the learning curve.

Methods Consecutive 499 patients who underwent PEA between 1995 and 2014 were divided into two groups according to the temporal order: early cohort (n = 200, December 1995–March 2006), and late cohort (n = 299, March 2006–December 2014). We assessed perioperative outcomes after PEA as compared between the early and the late cohort also in propensity-score–matched cohorts.

Results Age at the surgery was older in the late cohort (p = 0.042). Preoperative mean pulmonary artery pressure (mPAP) was 46.8 ± 11.0 mm Hg in the early cohort and 43.5 ± 112.7 mm Hg in the late cohort (p = 0.0035). The in-hospital mortality in the early and late cohorts was 14.0% (28/200) and 4.7% (14/299), respectively (p = 0.00030). The duration of circulatory arrest (CA) became much shorter in the late cohort (42.0 ± 20.5 min in the early and 24.2 ± 11.6 min in the late cohort, respectively, p < .0001). In matched cohorts, the in-hospital mortality showed no significant difference (8.7% in the early cohort and 5.2% in the late cohort, < 0.0001). The CA duration, however, was still shorter in the late cohort (p <0.0001).

Conclusions Over time, older patients have been accepted for surgery, more patients were operated for lesser severity of CTEPH. Duration of CA and mortality decreased even beyond the first 200 patients, indicating a long learning curve.
A Multidisciplinary Management Framework for the Treatment of Benign Prostatic Hyperplasia with Focus on Homoeopathy: A Review
Authors: Karso Liyi
Published: September 2020

Background Benign prostatic hyperplasia (BPH) is a globally prevailing urological condition among ageing men. In India, a few epidemiological studies conducted on BPH patients suggest it as the most common pathological condition with an incidence of around 93.3%. Although non-malignant, the condition adversely impacts the quality of life (QoL) in a way similar to that of other non-communicable diseases like diabetes, hypertension and cardiovascular diseases.

Objective This article aims to review the comprehensive management of BPH with focus on homoeopathic treatment.

Methods PubMed, EMBASE, Google Scholar, AYUSH PORTAL and leading homoeopathic journals were searched for articles on BPH and its homoeopathic management.

Results The review offers a holistic framework for management of BPH that is inclusive of modifiable lifestyle factors alongside homoeopathic treatments. It further underscores that the condition may be cost-effectively managed through homoeopathy to bring about better QoL among people with BPH.

Conclusion Lifestyle optimisation and management of metabolic risk factors may reduce the progression of BPH. Homoeopathic medicines are not only useful in effective management of BPH but also cost-effective, safe and non-surgical. However, randomised controlled trials and double-blind studies can be further taken up in future for more precise authentication.
Iron Deficiency Anemia and Serum Hepcidin Level in Children with Typhoid Fever: A Case–Control Study
Authors: Mohamed Ghada , Aboelhassan Samir , Zaki Maysaa El Sayed , Wahba Yahya
Published: September 2020

Objective Typhoid fever is a common systemic bacterial infection in children with a complex interplay between serum hepcidin and iron. We investigated the relationship between iron deficiency anemia (IDA) and serum hepcidin level in children with acute typhoid fever.

Methods We conducted a preliminary case–control study in Mansoura University Children's Hospital, Egypt from April 2017 to May 2019 including 30 children aged 5 to 15 years with confirmed acute typhoid fever. We recruited 15 healthy nonanemic children, of comparable ages and sex as controls from the same hospital while attending for nonfebrile complaints. Typhoid fever cases were subdivided according to IDA existence into 16 cases with IDA and 14 non-IDA cases. We excluded all children having diseases which may affect serum iron and hepcidin levels, for example, liver, blood, gastrointestinal, and kidney diseases, and patients receiving drugs interfering with iron metabolism. All participants were subjected to complete blood count, serum ferritin, iron, hepcidin levels, and total iron-binding capacity (TIBC).

Results In non-IDA typhoid fever group, serum iron level was significantly low, while serum hepcidin level was significantly high when compared with controls (p < 0.001 and p = 0.02, respectively). In IDA typhoid fever group, no statistically significant difference existed as regards serum hepcidin level when compared with controls (p = 0.53). No significant correlations were detected between serum hepcidin levels and hemoglobin, serum iron, ferritin, and TIBC values in each group.

Conclusion Preexisting iron status could affect serum hepcidin level in patients with acute typhoid fever. Coexistence of IDA might oppose the up-regulatory effect of acute typhoid fever on serum hepcidin level.
Detrimental Results of COVID-19 Fear to Child Health
Authors: Yazici Mutlu Uysal , Akkaya Bilge , Torun Emine Gulsah , Azapagasi Ebru , Senel Saliha
Published: September 2020

The outbreak of coronavirus disease 2019 (COVID-19) and its consequences have led to fear and anxiety among individuals worldwide. The risk of coronavirus transmission frightens people more than any other health problem they face. Parents have concerns about being infected with COVID-19 and delay accessing hospitals even in an emergency which can be very detrimental to child health. Here, in this article, we would like to present eight patients delayed in admission to the hospital to draw attention to the harmful consequences of COVID-19 fear in the community. Although anxiety and fear are encouraging to take necessary precautions, exaggeration of these emotions may cause greater health problems.
Simultaneous Use of Two Different Tools to Assess Compliance with Antiepileptic Drugs: Experience in A Community-Based Study
Authors: Singh Paramjit , Gupta Kanchan , Singh Gagandeep , Kaushal Sandeep
Published: September 2020

Objective Antiepileptic drug (AED) therapy remains the primary form of treatment for epilepsy, noncompliance to which can result in breakthrough seizure, emergency department visits, fractures, head injuries, and increased mortality. Various tools like self-report measures, pill-counts, medication refills, and frequency of seizures can assess compliance with varying extent. Thus, assessment of compliance with AEDs is crucial to be studied.

Materials and Methods Compliance was assessed using pill-count and Morisky medication adherence scale (MMAS) during home visits. A pill-count (pills dispensed–pills remaining)/(pills to be consumed between two visits) value of 0.85 to ≤1.15 was recorded as appropriate compliance. Underdose (<0.85) and overdose (>1.15) was labeled as noncompliance. Score of 1 was given to each positive answer in MMAS. Score of ≥1 was labeled as noncompliance.

Statistical analysis: Relationship of demographic factors between compliant and noncompliant patients was analyzed using Chi-square test (SPSS version 21.0, IBM). Rest of the data was analyzed with the help of descriptive statistics using Microsoft Excel. p< 0.05 was considered statistically significant.

Results Out of 105 patients, 54 patients were noncompliant with both pill-count and MMAS. 10 patients were noncompliant with pill-count only, while 10 were noncompliant with MMAS.

Conclusion Both tools complement each other when used in combination, as use of a single tool was not able to completely detect compliance.
Stabilization of cycles with stochastic prediction-based and target-oriented control
Authors: Braverman E. , Kelly C. , Rodkina A.
Published: September 2020

We stabilize a prescribed cycle or an equilibrium of a difference equation using pulsed stochastic control. Our technique, inspired by Kolmogorov’s law of large numbers, activates a stabilizing effect of stochastic perturbation and allows for stabilization using a much wider range for the control parameter than would be possible in the absence of noise. Our main general result applies to both prediction-based and target-oriented controls. This analysis is the first to make use of the stabilizing effects of noise for prediction-based control; the stochastic version has previously been examined in the literature, but only the destabilizing effect of noise was demonstrated. A stochastic variant of target-oriented control has never been considered, to the best of our knowledge, and we propose a specific form that uses a point equilibrium or one point on a cycle as a target. We illustrate our results numerically on the logistic, Ricker, and Maynard Smith models from population biology.
Hydrophobic surfaces help reduce harmful protein fibril formation
Authors: Mandel Savannah
Published: September 2020

Molecular dynamics simulation reveals key insights on the formation of amyloid fibril formation and potentially how to develop treatments against it.
Unified first-principles equations of state of deuterium-tritium mixtures in the global inertial confinement fusion region
Authors: Kang Dongdong , Hou Yong , Zeng Qiyu , Dai Jiayu
Published: September 2020

Accurate knowledge of the equation of state (EOS) of deuterium–tritium (DT) mixtures is critically important for inertial confinement fusion (ICF). Although the study of EOS is an old topic, there is a longstanding lack of global accurate EOS data for DT within a unified theoretical framework. DT fuel goes through very wide ranges of density and temperature from a cold condensed state to a hot dense plasma where ions are in a moderately or even strongly coupled state and electrons are in a partially or strongly degenerate state. The biggest challenge faced when using first-principles methods for obtaining accurate EOS data for DT fuel is the treatment of electron–ion interactions and the extremely high computational cost at high temperatures. In the present work, we perform extensive state-of-the-art ab initio quantum Langevin molecular dynamics simulations to obtain EOS data for DT mixtures at densities from 0.1 g/cm3 to 2000 g/cm3 and temperatures from 500 K to 2000 eV, which are relevant to ICF processes. Comparisons with average-atom molecular dynamics and orbital-free molecular dynamics simulations show that the ionic strong-coupling effect is important for determining the whole-range EOS. This work can supply accurate EOS data for DT mixtures within a unified ab initio framework, as well as providing a benchmark for various semiclassical methods.
Relativistic two-component projection-based quantum embedding for open-shell systems
Authors: Hoyer Chad E. , Li Xiaosong
Published: September 2020

In this work, we present a relativistic quantum embedding formalism capable of variationally treating relativistic effects, including scalar-relativity and spin–orbit coupling. We extend density functional theory (DFT)-in-DFT projection-based quantum embedding to a relativistic two-component formalism, where the full spin magnetization vector form is retained throughout the embedding treatment. To benchmark various relativistic embedding schemes, spin–orbit splitting of the nominally t2g valence manifold of W(CO)6, exchange coupling of [(H3N)4Cr(OH)2Cr(NH3)4]4+, and the dissociation potential curve of WF6 are investigated. The relativistic embedding formalism introduced in this work is well suited for efficient modeling of open-shell systems containing late transition metal, lanthanide, and actinide molecular complexes.
Experimental and theoretical study of capacitive memory of metal-oxide-semiconductor devices based on Er-doped In2O3 nano-column arrays
Authors: Ghosh Anupam , Lahiri Rini , Dhar Dwivedi Shyam Murli Manohar , Mondal Aniruddha
Published: September 2020

The enhanced electronic memory performance of glancing angle deposited erbium-doped indium oxide (In2O3:Er) transparent nano-column (NCol) based metal-oxide-semiconductor (MOS) structured memory devices is reported. The fabricated MOS devices are Au/In2O3/p-Si, Au/0.26 at. % In2O3:Er/p-Si, and Au/0.48 at. % In2O3:Er/p-Si. The capacitance–voltage (C–V), conductance–voltage (G–V), C–V hysteresis, endurance, and retention properties from the cyclic current–voltage (I–V) curve of the fabricated devices were investigated in detail. The overall interface state density (Dit) for the devices at the different applied frequency (f) decreases with the increase in Er doping. The observations obtained from C–V, G–V, and Dit–f curves were theoretically explained considering a modified delta depletion model. It was found that Au/0.48 at. % In2O3:Er/p-Si does not go to inversion even at a high applied voltage. The constant capacitive memory window (MW) for Au/In2O3/p-Si is ∼1 V at the depletion region. MW increases from ∼0.6 V (sweep voltage ±6 V) to ∼2.5 V (sweep voltage ±16 V) and ∼1.4 V (sweep voltage ±6 V) to ∼6.8 V (sweep voltage ±16 V), respectively, for Au/0.26 at. % In2O3:Er/p-Si and Au/0.48 at. % In2O3:Er/p-Si. The increased MWs despite reduced Dit is explained in detail by primarily considering increased polarization switching of the In-O-Er material, asymmetric charge injection from the top electrode, and the presence of the oxygen-rich environment. The I–V hysteresis performance of the devices under a reverse bias was also improved with Er doping due to the migration of O2− inside the oxide layer. The whole analysis indicates that the gate-controlled Au/0.48 at. % In2O3:Er/p-Si MOS device is appropriate for capacitive memory applications.
Wide-field Raman spectroscopic imaging with frequency modulation based spatially encoded light illumination
Authors: Ren Shenghan , Yan Tianyu , Wang Lin , Wang Nan , Liang Jimin , Zeng Qi , Chen Xueli
Published: September 2020

Raman spectroscopic imaging (RSI) can simultaneously measure the spectra and spatial information of samples. The measured data include two-dimensional spatial images and one-dimensional Raman spectra. Traditionally, RSI can be obtained by point scanning, line scanning, and wide-field illumination schemes. The point scanning scheme provides the best resolution but a lower imaging speed. On the contrary, wide-field illumination can image fast but provides a lower spatial resolution. To integrate the advantages of the two schemes, a complementary scheme for wide-field RSI was proposed, which uses frequency modulation based spatially encoded (FMSE) light as the excitation. In this scheme, all the beams of wide-field illumination are modulated at different frequencies. Thus, each excitation beam has its own modulation frequency, and the excited Raman signal will carry this modulation information. For the detection module, a single point detector was used to collect time series Raman signals carrying the unique modulation information. Using a sparse reconstruction-based demodulation strategy, the Raman image can be recovered effectively. The feasibility of the method was verified with numerical simulations. The reconstruction results showed that it is feasible to conduct Raman spectroscopic imaging with high-resolution and high speed under the illumination of FMSE light and detection of a single-point detector.
High-efficiency cross-polarization conversion metamaterial using spiral split-ring resonators
Authors: Yang Tian , Liu Xiaoming , Wang Chen , Wang Feilou , Zhou Ji
Published: September 2020

We report on a high-efficiency cross-polarization conversion metamaterial design consisting of novel spiral split-ring resonators (SRRs). Numerical simulations on the resonant electric field and surface current distributions demonstrate that the cross-polarization response is attributed to the charge accumulation in the horizontal SRR gap. The dependencies of resonance frequency on the structural parameters of the SRR reveal that an inductive-capacitive resonance dominates the SRR. We further show that the polarization conversion efficiency can be significantly enhanced by integrating two orthogonal gratings, which enable a linear polarization wave to be rotated to its orthogonal direction with a high efficiency of ∼90%. These results offer a way to engineer novel high-performance metamaterial polarization devices.
Experimental evidence on photo-assisted O− ion production from Al2O3 cathode in cesium sputter negative ion source
Authors: Tarvainen O. , Kronholm R. , Laitinen M. , Reponen M. , Julin J. , Toivanen V. , Napari M. , Marttinen M. , Faircloth D. , Koivisto H. , Sajavaara T.
Published: September 2020

The production of negative ions in cesium sputter ion sources is generally considered to be a pure surface process. It has been recently proposed that ion pair production could explain the higher-than-expected beam currents extracted from these ion sources, therefore opening the door for laser-assisted enhancement of the negative ion yield. We have tested this hypothesis by measuring the effect of various pulsed diode lasers on the O− beam current produced from Al2O3 cathode of a cesium sputter ion source. It is expected that the ion pair production of O− requires populating the 5d electronic states of neutral cesium, thus implying that the process should be provoked only with specific wavelengths. Our experimental results provide evidence for the existence of a wavelength-dependent photo-assisted effect but cast doubt on its alleged resonant nature as the prompt enhancement of beam current can be observed with laser wavelengths exceeding a threshold photon energy. The beam current transients observed during the laser pulses suggest that the magnitude and longevity of the beam current enhancement depends on the cesium balance on the cathode surface. We conclude that the photo-assisted negative ion production could be of practical importance as it can more than double the extracted beam current under certain operational settings of the ion source.
Improved description of ligand polarization enhances transferability of ion–ligand interactions
Authors: Wineman-Fisher Vered , Al-Hamdani Yasmine , Nagy Péter R. , Tkatchenko Alexandre , Varma Sameer
Published: September 2020

The reliability of molecular mechanics (MM) simulations in describing biomolecular ion-driven processes depends on their ability to accurately model interactions of ions simultaneously with water and other biochemical groups. In these models, ion descriptors are calibrated against reference data on ion–water interactions, and it is then assumed that these descriptors will also satisfactorily describe interactions of ions with other biochemical ligands. The comparison against the experiment and high-level quantum mechanical data show that this transferability assumption can break down severely. One approach to improve transferability is to assign cross terms or separate sets of non-bonded descriptors for every distinct pair of ion type and its coordinating ligand. Here, we propose an alternative solution that targets an error-source directly and corrects misrepresented physics. In standard model development, ligand descriptors are never calibrated or benchmarked in the high electric fields present near ions. We demonstrate for a representative MM model that when the polarization descriptors of its ligands are improved to respond to both low and high fields, ligand interactions with ions also improve, and transferability errors reduce substantially. In our case, the overall transferability error reduces from 3.3 kcal/mol to 1.8 kcal/mol. These improvements are observed without compromising on the accuracy of low-field interactions of ligands in gas and condensed phases. Reference data for calibration and performance evaluation are taken from the experiment and also obtained systematically from “gold-standard” CCSD(T) in the complete basis set limit, followed by benchmarked vdW-inclusive density functional theory.
Evaluation of CMIP6 AMIP climate simulations with the ACCESS-AM2 model
Authors: Bodman R. W. , Karoly D. J. , Dix M. R. , Harman I. N. , Srbinovsky J. , Dobrohotoff P. B. , Mackallah C.
Published: September 2020

The most recent version of the ACCESS-AM2 atmosphere-only climate model is introduced with results from the CMIP6 Atmospheric Model Intercomparison Project (AMIP) experiments configured with two land-surface models: CABLE and JULES. AMIP simulations are required as part of the CMIP6 core experiments. They are forced by prescribed time-varying observed sea surface temperature and sea-ice variations as well as variations in natural and anthropogenic external forcings. We evaluate the performance of the two configurations using three historical realisations for each. Model biases are estimated both globally and for the Australian region. The model shows close agreement with observed interannual variations of global-mean temperature across the latitude range 65°N–65°S. This is also true for the land-only temperature for 65°N–65°S, and a more stringent test of the model is driven by specified observed sea surface temperatures. Patterns of mean precipitation are simulated reasonably well, although there are biases in the amount and distribution of precipitation, typical of longstanding problems in representing this aspect of the climate. Selected features of the atmospheric circulation are discussed, including air temperatures and wind speeds. For the Australian region, in addition to examining the climatological patterns of temperature and precipitation, important drivers of climate variability are reviewed: El Niño-Southern Oscillation, the Indian Ocean Dipole and the Southern Annular Mode. In general, the correlation patterns for precipitation simulated by ACCESS-AM2 are somewhat weaker than in observations, although the ensemble means show better agreement than individual ensemble members. Overall, the two different land-surface schemes perform similarly. ACCESS-AM2 has reduced root mean square errors for both temperature and precipitation of around 15–20% at the global scale compared to the older CMIP5 versions of the model: ACCESS 1.0 and ACCESS 1.3.
MAC5, an RNA-binding protein, protects pri-miRNAs from SERRATE-dependent exoribonuclease activities
Authors: Li Shengjun , Li Mu , Liu Kan , Zhang Huimin , Zhang Shuxin , Zhang Chi , Yu Bin
Published: September 2020

Significance

In
Arabidopsis
, MAC5, a component of the conserved MOS4-associated complex, is required for development and immunity. This study shows that MAC5 interacts with Serrate (SE) and the stem loop of pri-miRNAs, facilitates pri-miRNA processing, and protects pri-miRNAs from SE-dependent 5′-to-3′ exoribonuclease activities. Consequently, this study provides insights into the mechanism regulating miRNA biogenesis. Since MAC5 is a conserved protein, this study may have a broader impact.
Acquisition of null objects in Mandarin Chinese by heritage speakers
Authors: Chou Chao-Ting Tim , Chen Tsung-Ying , Pires Acrisio
Published: September 2020

The acquisition of the grammatical knowledge related to inflectional morphology and syntax-pragmatics interface have both been shown to be challenging for heritage speakers (e.g.,Montrul et al. 2008;Polinsky 2006,2008;Sorace et al. 2009;Montrul 2009;Benmamoun et al. 2013a;Laleko & Polinsky 2016). In these previous work on heritage language acquisition, the acquisition of inflectional morphology (e.g. either agreement morphology or topic marking) is also a relevant acquisition task associated with the syntax-discourse phenomena under investigation. In this paper we focus on the acquisition of discourse-conditioned structures by heritage speakers when inflectional morphology is not part of the learning task. Specifically, we report results of a picture-verification experiment focusing on English-dominant heritage Chinese speakers’ grammatical knowledge of null objects. As a topic-prominent language lacking verbal tense/agreement morphology, the licensing and identification of null arguments in Chinese has nothing to do with agreement morphology. In addition, unlike other topic-prominent pro-drop languages, Chinese has no inflectional morphology associated with grammatical subjects/objects and topic phrases. Without the interference of co-occurring inflectional morphology, we found that there is no significant difference between heritage Chinese speakers and the monolingual baseline in their acceptance of null objects in contextually appropriate contexts. The results of our study cast doubt on the thesis that heritage speakers are unable to acquire discourse-related knowledge (cf.Sorace & Serratrice 2009;Laleko 2010;Laleko & Polinsky 2016) and supportYuan’s (2010)claim that interface categories should not be considered holistically.
Narratives as discursive practices in interviews
Authors: Perrino Sabina
Published: September 2020

Humans are prone to tell stories when they interact with each other. Knowing how many stories we tell in a day could be a difficult endeavor, especially because what counts as “a story” varies across disciplines and cultures. Narratives have always been primary modes in human communication and engagement across cultures, however, and have been used as key analytical tools across numerous disciplines in the social sciences and beyond. While defining narratives has been a daunting task in narratological studies, it is important to appreciate that narratives have also been studied for their pragmatic effects in the here-and-now of speech participants’ interactions and across various spatiotemporal configurations. Through an analysis of a set of narrative practices that I collected in Senegal (West Africa) and in Northern Italy in interview settings, I demonstrate that narratives are also performative interactional events in which their sociocultural surrounding is always fluid and can influence the story in unpredictable ways as it unfolds in interaction.
Síandhocin the history of Catalan
Authors: Pujol i Campeny Afra
Published: September 2020

Old Catalan presents two affirmative particles competing for the same function between the 13th and the 17th centuries:síandhoc. This article explores their syntax and the factors that contributed to the rise of the former and the disappearance of the latter and accounts for their distribution in the written record. Traditionally, it was believed thathocwas the only positive sentential proform active in the language until the 15th century. However,síhad already been grammaticalised as such by the 13th century, its new function being obscured in the written record by the pervasive use of the official koine established by the Crown of Aragon’sCancelleriain learned prose. Nevertheless, in documents closer to speech,símakes a much earlier appearance and shows great vitality before the 15th century, the last century whenhocwas still hegemonic before finally disappearing as a consequence of external and internal factors.
Quantum effects across dynamical horizons
Authors: Giavoni Cecilia , Schneider Marc
Published: September 2020

We present a generalization of the Hawking effect for dynamical trapping horizons by calculating the tunneling rate in the Hamilton–Jacobi formalism. It turns out that all horizons classified by Hayward are subjected to thermal quantum effects. While the Hawking effect for future outer and past inner trapping horizons is given as a particle emission, we show that the Hawking effect for future inner and past outer trapping horizons translates to an absorption. The universality of the treatment allows a natural transfer to the static case.
Quasi-normal mode of a regular Schwarzschild black hole
Authors: Villani Mattia
Published: September 2020

Some quantum gravity theories, like loop quantum gravity, predict that quantum mechanical effects will avoid the formation of a singularity inside a black hole. From the general relativity point of view, this means that the metric will differ from the ones of Schwarzschild or Kerr at least inside the event horizon. If the metric is not that of Schwarzschild or Kerr, the potential of the Regge–Wheeler equation is modified, therefore it is possible to peek inside a black hole using the quasi-normal modes to find out if there is indeed a singularity. We address this problem for a regular Schwartzchild black hole using an effective metric first introduced by Hayward.
Josephson AC effect induced by weak gravitational field
Authors: Ummarino Giovanni Alberto , Gallerati Antonio
Published: September 2020

In this paper we examine the possibility of a Josephson AC effect between two superconductors induced by the Earth’s gravitational field, making use of the gravito-Maxwell formalism. The theoretical framework exploits the symmetry between the weak field expansion of the gravitational field and the standard Maxwell formulation, combined with the Josephson junction physics. We also suggest a suitable experimental setup, analysing also the related possible difficulties in measurements.
Impact dynamics for gravity-driven motion of a particle
Authors: Villegas Cesar E P , Rojas Wudmir Y , Bravo Carlos , Rocha Alexandre R
Published: September 2020

Introductory mechanics courses use the bouncing ball model to familiarize students with the principles of binary inelastic collisions. Nonetheless, in undergraduate courses, the modeling of binary systems typically disregards the time of contact and the effects of gravity, which yields to a constant coefficient of restitution (COR) and, as a consequence, prevents students from elucidating the real dependence of COR with impact speed. In this work, we proposed a simple experimental setup to investigate the impact dynamics of a spring-mass body that bounces on a rigid plate as well as a theoretical framework that captures the velocity dependence of the COR for low-impact speeds. Our analytical expression for the COR highlights the role-played by gravity, impact speed and collision time on the collision dynamics. Our results suggest that the inclusion of gravity force allows an adequate estimation of the critical impact speed and maximum deformation distance, crucial parameters to differentiate between repulsive and attractive interaction regimes. Our experimental setup enables the clarification of several key concepts of mechanics while it is easy to be performed in most undergraduate laboratories.
An ADMM-LAP method for total variation myopic deconvolution of adaptive optics retinal images
Authors: Chen Xiaotong , Herring James L , Nagy James G , Xi Yuanzhe , Yu Bo
Published: September 2020

Adaptive optics corrected flood imaging of the retina is a popular technique for studying the retinal structure and function in the living eye. However, the raw retinal images are usually of poor contrast and the interpretation of such images requires image deconvolution. Different from standard deconvolution problems where the point spread function (PSF) is completely known, the PSF in these retinal imaging problems is only partially known which leads to the more complicated myopic (mildly blind) deconvolution problem. In this paper, we propose an efficient numerical scheme for solving this myopic deconvolution problem with total variational (TV) regularization. First, we apply the alternating direction method of multipliers (ADMM) to tackle the TV regularizer. Specifically, we reformulate the TV problem as an equivalent equality constrained problem where the objective function is separable, and then minimize the augmented Lagrangian function by alternating between two (separated) blocks of unknowns to obtain the solution. Due to the structure of the retinal images, the subproblems with respect to the fidelity term appearing within each ADMM iteration are tightly coupled and a variation of the linearize and project method is designed to solve these subproblems efficiently. The proposed method is called the ADMM-LAP method. Theoretically, we establish the subsequence convergence of the ADMM-LAP method to a stationary point. Both the theoretical complexity analysis and numerical results are provided to demonstrate the efficiency of the ADMM-LAP method.
Thermal oxidation of AlGaN nanowires for sub-250 nm deep ultraviolet photodetection
Authors: Zhang Xiaodong , He Tao , Tang Wenbo , Ma Yongjian , Wei Xing , Wang Danhao , Zhang Haochen , Sun Haiding , Fan Yaming , Cai Yong , Zhang Baoshun
Published: September 2020

In this work, we demonstrated a thermal oxidation process for AlGaN nanowires and revealed the underlying mechanism of AlGaN to AlGaO transition for sub-250 nm deep ultraviolet photodetection. When the AlGaN nanowires were exposed to oxygen atmosphere below a temperature of 700 °C, only the Al–N bond was oxidized while the Ga–N bond remained intact, and thereafter, the AlGaN nanowires were slowly oxidized to AlGaON complex. However, as the oxidation temperature was elevated to above 700 °C, the AlGaN complex was transformed into AlGaO complex. Using this method, photodetectors based on AlGaON nanowires were fabricated and compared with its AlGaN counterpart. The AlGaON photodetector showed a response peak at deep ultraviolet of 242 nm with a high responsivity of 726 mA W−1, compared with the response peak at 276 nm in AlGaN nanowires. This work offers an alternative method towards the realization of high performance sub-250 nm deep ultraviolet photodetection.
Optical characterization of nanostructured β − FeSi2 layers obtained by Fe+ implantation
Authors: Salinas-Fuentes Cecilia , Hernández-Zanabria Angélica , Kudriavtsev Yuriy , Cheang-Wong Juan-Carlos
Published: September 2020

In this work, we present a comprehensive analysis of nanostructured β − FeSi2 layers obtained by 40 keV Fe ion implantation in silicon, followed by rapid thermal annealing. A series of chemical, structural and optical characterizations of the samples were performed. Our results establish the formation of a 26.6 nm thick layer consisting of β − FeSi2 nanocrystals, with an average size of 4.8 nm, embedded in the Si substrate. Optical excitation of the sample leads to a photoluminescence signal with an extremely narrow peak (1 nm full width at half maximum) at 1456 nm. This sharp emission is comparable with the radiation of semiconductor lasers and therefore, this β − FeSi2 nanostructured layer is of interest for the fabrication of new optoelectronic devices in the near-infrared region.
Tunable strain effects on the electronic structures and mobility properties of InP/InAs lateral heterostructure
Authors: Lin Long , Li Shaofei , Yao Linwei , Yu Weiyang , Cai Xiaolin , Zhang Liwei , Zhang Wei-Bing , Zhang Zhanying , Tao Hualong
Published: September 2020

Two-dimensional lateral heterostructures (LHSs) carry unconventional physical properties due to their excellent adjustable band-offset and sensitive interface characteristics. In this paper, we have designed two kinds of seamless LHSs with excellent stabilities, the zigzag-zigzag (Z-Z) InP/InAs LHS and the armchair-armchair (A-A) InP/InAs LHS, and the changes in lattice structures and electronic properties under different strains are studied systematically by employing first-principles calculations based on density functional theory. Our results indicate that the Z-Z and A-A InP/InAs LHSs are indirect-bandgap semiconductors with a moderate bandgap. Surprisingly, it is found that the carrier mobility of holes for the Z-Z InP/InAs LHS is as high as 6.954 × 103cm2· V−1· s−1. The established Z-Z and A-A InP/InAs LHSs exhibit superior properties under uniaxial strains (a-direction and b-direction) and biaxial strain (ab-direction). It is found that the conduction bands of Z-Z and A-A InP/InAs LHSs occur with an intriguing downward (upward) transfer under compressive (tensile) strain along the b- and ab-directions, respectively. Moreover, when more than 2% of the tensile strain along the ab-direction is applied, the Z-Z and A-A InP/InAs LHS change from an indirect bandgap semiconductor to a direct bandgap semiconductor, and the Z-Z InAs/InP LHS changes into type-II heterostructure. Based on the calculated band structures, the effect of uniaxial strain on effective mass is anisotropic. Especially when tensile strain is applied, the effective mass of electrons in Z-Z and A-A InP/InAs LHSs will be reduced, which is consistent with the change in band structures under strain. The strain tunability of direct bandgap, type-II band alignment, and high carrier mobility mean Z-Z and A-A InP/InAs LHSs have potential applications in optoelectronic, photovoltaic, and flexible electronic devices.
No evidence for room temperature ferromagnetism in the high temperature metal-organic material: Ni2TCNQ
Authors: Berlie Adam , Terry Ian , Szablewski Marek , Quinn Kimberly
Published: September 2020

The search for ferromagnetic organic-based compounds has been a particular challenge to both chemists and physicists over the past few decades. The synthesis of the Ni2A, where A is an organic acceptor; tetracyanoethene (TCNE), 3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) (Jain et al 2007 Nature
445 291), was reported to be a great advancement with claims that the ferromagnetism persisted to well above room temperature. There were, however some substantial flaws in the methodology associated with the synthesis and physical characterisation. Our work solely studies the Ni2TCNQ compound where we find no evidence for the existence of inherent ferromagnetism within the material that was reported in the original paper. Instead, we find that the magnetism is due to superparamagnetic nickel nanoparticles embedded in an amorphous matrix. It is hoped that our work will also show that one must be careful when using Ni(COD)2 as a precursor in the synthesis of magnetic materials and that the usefulness of the reported synthetic method is extremely limited.
Dimension of Gibbs measures with infinite entropy
Authors: Pérez Pereira Felipe
Published: September 2020

We study the Hausdorff dimension of Gibbs measures with infinite entropy with respect to maps of the interval with countably many branches. We show that under simple conditions, such measures are symbolic-exact dimensional, and provide an almost sure value for the symbolic dimension. We also show that the lower local dimension dimension is almost surely equal to zero, while the upper local dimension is almost surely equal to the symbolic dimension. In particular, we prove that a large class of Gibbs measures with infinite entropy for the Gauss map have Hausdorff dimension zero and packing dimension equal to 1/2, and so such measures are not exact dimensional.
A sufficient and necessary condition of PS-ergodicity of periodic measures and generated ergodic upper expectations
Authors: Feng Chunrong , Qu Baoyou , Zhao Huaizhong
Published: September 2020

This paper contains two parts. In the first part, we study the ergodicity of periodic measures of random dynamical systems on a separable Banach space. We obtain that the periodic measure of the continuous time skew-product dynamical system generated by a random periodic path is ergodic if and only if the underlying noise metric dynamical system at discrete time of integral multiples of the period is ergodic. For the Markov random dynamical system case, we prove that the periodic measure of a Markov semigroup is PS-ergodic if and only if the trace of the random periodic path at integral multiples of period either entirely lies on a Poincaré section or completely outside a Poincaré section almost surely. In the second part of this paper, we construct sublinear expectations from periodic measures and obtain the ergodicity of the sublinear expectations from the ergodicity of periodic measures. We give some examples including the ergodicity of the discrete time Wiener shift of Brownian motions. The latter result would have some independent interests.
Dynamic modelling and control of shear-mode rotational MR damper for mitigating hazard vibration of building structures
Authors: Yu Yang , Royel Sayed , Li Yancheng , Li Jianchun , Yousefi Amir M , Gu Xiaoyu , Li Shaoqi , Li Huan
Published: September 2020

Magneto-rheological (MR) materials and their devices are being rapidly developed and have drawn surge of interest for the potential application in vibration control. Among them, a novel shear-mode rotational MR damper (SM-RMRD) with adaptive variable stiffness and damping was developed for adaptive structural control in real-time against different types of earthquakes. To make use of this innovative device perfectly, a robust and reliable model should be developed to simulate the nonlinear and hysteretic behaviours for the application in adaptive control. Accordingly, this research initially presents a new phenomenological model to describe the force response of the SM-RMRD. Then, model parameters are estimated based on experimental data of force, displacement and velocity, which were directly or indirectly obtained from the device under different loading protocols. The field dependence of each model parameter is also investigated so that a general model with current-related parameters is acquired for designing the control strategy. Using the current-dependent model of SM-RMRD, a semi-active controller is developed and implemented to the SM-RMRD to produce the feedback control for the structures in real-time. Finally, the effectiveness of proposed control method is appraised by a numerical study, in which an SM-RMRDs-incorporated three-storey building model with different control strategies are subjected to various scaled benchmark earthquakes. The comparison result verifies the excellent capacity of the proposed controller based on the developed phenomenological model in terms of reducing the storey acceleration and inter-storey drift.
Mechanically robust, intrinsically self-healing crosslinked polymer enabled by dynamic urea bond exchange reaction
Authors: Zhou Zhongqun , Zeng Yanning , Yu Caili , Chen Haibo , Zhang Faai
Published: September 2020

Designing a crosslinked polymer with self-healing, recyclable, and mechanical properties is a significant challenge in the field of self-healing chemistry. Herein, robust, intrinsically self-healing, crosslinked polyureas (C-PUs) are prepared via a facile one-pot photo-induced copolymerization to address the aforementioned limitation. The key strategy involves the introduction of a synthetic monomer with reversible urea bonds into the polymer network as a versatile dynamic crosslinker. The resultant C-PUs are a class of resource-saving materials with a combination of excellent intrinsic self-healing capability with outstanding mechanical robustness. Notably, the properties of the materials can be easily tuned by simply adjusting the dynamic crosslinker content. In addition, an environmentally friendly polymer reprocessing is achieved and the potential of the materials in the smart anticorrosion application is investigated. These desirable properties are attributed to the underlying topological network rearrangement enabled by the dynamic urea bond exchange reaction, which is confirmed by stress relaxation tests. Therefore, the resulting self-healing C-PUs can serve as models to extend the scope of applications in smart protective materials or ocean engineering.
Data augmentation for enhancing EEG-based emotion recognition with deep generative models
Authors: Luo Yun , Zhu Li-Zhen , Wan Zi-Yu , Lu Bao-Liang
Published: September 2020

Objective. The data scarcity problem in emotion recognition from electroencephalography (EEG) leads to difficulty in building an affective model with high accuracy using machine learning algorithms or deep neural networks. Inspired by emerging deep generative models, we propose three methods for augmenting EEG training data to enhance the performance of emotion recognition models. Approach. Our proposed methods are based on two deep generative models, variational autoencoder (VAE) and generative adversarial network (GAN), and two data augmentation ways, full and partial usage strategies. For the full usage strategy, all of the generated data are augmented to the training dataset without judging the quality of the generated data, while for the partial usage, only high-quality data are selected and appended to the training dataset. These three methods are called conditional Wasserstein GAN (cWGAN), selective VAE (sVAE), and selective WGAN (sWGAN). Main results. To evaluate the effectiveness of these proposed methods, we perform a systematic experimental study on two public EEG datasets for emotion recognition, namely, SEED and DEAP. We first generate realistic-like EEG training data in two forms: power spectral density and differential entropy. Then, we augment the original training datasets with a different number of generated realistic-like EEG data. Finally, we train support vector machines and deep neural networks with shortcut layers to build affective models using the original and augmented training datasets. The experimental results demonstrate that our proposed data augmentation methods based on generative models outperform the existing data augmentation approaches such as conditional VAE, Gaussian noise, and rotational data augmentation. We also observe that the number of generated data should be less than 10 times of the original training dataset to achieve the best performance. Significance. The augmented training datasets produced by our proposed sWGAN method significantly enhance the performance of EEG-based emotion recognition models.
Deep brain stimulation: a review of the open neural engineering challenges
Authors: Vissani Matteo , Isaias Ioannis U , Mazzoni Alberto
Published: September 2020

Objective. Deep brain stimulation (DBS) is an established and valid therapy for a variety of pathological conditions ranging from motor to cognitive disorders. Still, much of the DBS-related mechanism of action is far from being understood, and there are several side effects of DBS whose origin is unclear. In the last years DBS limitations have been tackled by a variety of approaches, including adaptive deep brain stimulation (aDBS), a technique that relies on using chronically implanted electrodes on ‘sensing mode’ to detect the neural markers of specific motor symptoms and to deliver on-demand or modulate the stimulation parameters accordingly. Here we will review the state of the art of the several approaches to improve DBS and summarize the main challenges toward the development of an effective aDBS therapy. Approach. We discuss models of basal ganglia disorders pathogenesis, hardware and software improvements for conventional DBS, and candidate neural and non-neural features and related control strategies for aDBS. Main results. We identify then the main operative challenges toward optimal DBS such as (i) accurate target localization, (ii) increased spatial resolution of stimulation, (iii) development of in silico tests for DBS, (iv) identification of specific motor symptoms biomarkers, in particular (v) assessing how LFP oscillations relate to behavioral disfunctions, and (vi) clarify how stimulation affects the cortico-basal-ganglia-thalamic network to (vii) design optimal stimulation patterns. Significance. This roadmap will lead neural engineers novel to the field toward the most relevant open issues of DBS, while the in-depth readers might find a careful comparison of advantages and drawbacks of the most recent attempts to improve DBS-related neuromodulatory strategies.