bluuebunny/crossref_metadata_2025 huggingface dataset:
Cr Doped MoS2 Films: Tribological Properties, Microstructure, and Electronic Structure
Authors: Liu Jian , Sui Xudong , Yan Zhen , Huang Guosheng , Hao Junying
Published: February 2021

Cr doped MoS2 films were deposited by magnetron sputtering. The tribological properties of Cr doped MoS2 films under vacuum (VC) and air (AR) environments were investigated. The results show that Cr doped MoS2 film with Cr target power of 0.2 A (0.2 A Cr:MoS2 film) exhibits low friction coefficient and long wear life under both VC and AR environments. The chemical compositions of the films were analyzed by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). With the increases of Cr target power, the content of Cr increases. The cross-sectional field emission scanning electron microscopy (FESEM) morphologies show that the structure of the films changed from granular particles to column when the Cr target power increases from 0.2 A to 0.4 A. The wear mechanism has also been discussed based on the characteristics of worn surface. The 0.4 A Cr:MoS2 film has the lowest wear volume among these films, which can be attributed to the compact microstructure. The bandgap of Cr doped MoS2 films were measured by XPS and the tribological performance of the film is found to be best when there is a modest bandgap. It can be speculated that the tribological performance of Cr doped MoS2 films are closely related to the width of bandgap.
Nonlinear Stability Analysis of a Generic Fan With Distorted Inflow Using Passage-Spectral Method
Authors: Romera David , Corral Roque
Published: February 2021

The dependence of the aerodynamic stability of fan blades with the nodal diameter and amplitude of the inlet perturbations is studied. The analysis is conducted using a block-wise spatial Fourier decomposition of reduced passages to reconstruct the full-annulus solution. The method represents very efficiently the unsteady flow generated by inlet non-uniformities. The explicit spatial Fourier approximation is exploited to characterize the relevance of each nodal diameter of the inlet perturbation in the fan stall process and study the nonlinear stability in a harmonic by harmonic basis. This approximation allows studying the contribution to stall of each circumferential mode separately. The methodology has been assessed for the NASA rotor 67. The maximum amplitude of total pressure distortion at which the compressor becomes unstable and triggers a stall process has been mapped. It has been proven that despite the complexity of a screen-induced total pressure distortion the only relevant parameter for the nonlinear stability of the fan is the most unstable nodal diameter. The equivalence in terms of stability between realistic distortion screens and single harmonic distortions has been assessed. Full-annulus simulations have been conducted to assess the accuracy of the simplified nonlinear stability limit. It is concluded that performing a nonlinear simulation with the proper single harmonic perturbation is enough to assess fan stability. The total pressure error with respect the full annulus simulation including a screen-induced pressure deficit at the intake is below 10%. It is shown that for the NASA rotor 67 running at the nominal speed, the most unstable nodal diameter is the first. This study not only shows a reduction in computational time to assess nonlinear fan stability by a factor of 7 but also creates an efficient methodology for understanding the nonlinear instability of fans due to inlet distortion profiles.
Contribution of Somatosensory and Parietal Association Areas in Improving Standing Postural Stability Through Standing Plantar Perception Training in Community-Dwelling Older Adults
Authors: Matsuno Satoshi , Yoshiike Takuya , Yoshimura Atsushi , Morita Sachiyo , Fujii Yusuke , Honma Motoyasu , Ozeki Yuji , Kuriyama Kenichi
Published: February 2021

Although standing plantar perception training (SPPT) may improve standing postural stability, the underlying neural mechanisms remain unclear. The authors investigated the relationship between regional cortical responses to SPPT using a balance pad and training outcomes in 32 older participants (mean ± SD:72.2 ± 6.0, range:60–87). Regional cortical activity was measured in the bilateral supplementary motor area, primary sensorimotor area, and parietal association area using near-infrared spectroscopy. Postural sway changes were compared before and after SPPT. Changes in two-point plantar discrimination and regional cortical activity during SPPT, associated with standing postural stability improvements, were examined using multiple regression and indicated improved standing postural stability after SPPT (p < .0001). Changes in right parietal association area activity were associated with standing postural stability improvements while barefoot. Overall, the results suggest that right parietal association area activation during SPPT plays a crucial role in regulating standing postural stability and may help develop strategies to prevent older adults from falling.
The Influence of Cognitive Dual Tasks on Concussion Balance Test Performance
Authors: Morelli Nathan , Heebner Nicholas R. , DeFeo Courtney J. , Hoch Matthew C.
Published: February 2021

Objective: To determine the influence of a cognitive dual task on postural sway and balance errors during the Concussion Balance Test (COBALT). Methods: Twenty healthy adults (12 females, eight males; aged 21.95 ± 3.77 years; height = 169.95 ± 9.95 cm; weight = 69.58 ± 15.03 kg) partook in this study and completed single- and dual-task versions of a reduced COBALT. Results: Sway velocity decreased during dual-task head rotations on foam condition (p = .021, ES = −0.57). A greater number of movement errors occurred during dual-task head rotations on firm surface (p = .005, ES = 0.71), visual field flow on firm surface (p = .008, ES = 0.68), and head rotations on foam surface (p < .001, ES = 1.61) compared with single-task conditions. Cognitive performance was preserved throughout different sensory conditions of the COBALT (p = .985). Discussion: Cognitive dual tasks influenced postural control and destabilized movements during conditions requiring advanced sensory integration and reweighting demands. Dual-task versions of the COBALT should be explored as a clinical tool to identify residual deficits past the acute stages of concussion recovery.
Water heavily fractionated as it ascends on Mars as revealed by ExoMars/NOMAD
Authors: Villanueva Geronimo L. , Liuzzi Giuliano , Crismani Matteo M. J. , Aoki Shohei , Vandaele Ann Carine , Daerden Frank , Smith Michael D. , Mumma Michael J. , Knutsen Elise W. , Neary Lori , Viscardy Sebastien , Thomas Ian R. , Lopez-Valverde Miguel Angel , Ristic Bojan , Patel Manish R. , Holmes James A. , Bellucci Giancarlo , Lopez-Moreno Jose Juan ,   NOMAD team
Published: February 2021

Following water isotopes as they ascend on Mars.
High-resolution terahertz-driven atom probe tomography
Authors: Vella Angela , Houard Jonathan , Arnoldi Laurent , Tang Mincheng , Boudant Matthias , Ayoub Anas , Normand Antoine , Da Costa Gerald , Hideur Ammar
Published: February 2021

High-amplitude terahertz single-cycle pulses enable direct control of ion emission from nanostructures.
High-performance wearable thermoelectric generator with self-healing, recycling, and Lego-like reconfiguring capabilities
Authors: Ren Wei , Sun Yan , Zhao Dongliang , Aili Ablimit , Zhang Shun , Shi Chuanqian , Zhang Jialun , Geng Huiyuan , Zhang Jie , Zhang Lixia , Xiao Jianliang , Yang Ronggui
Published: February 2021

A self-healable, recyclable, Lego-like reconfigurable thermoelectric generator enables wearable energy harvesting.
Human neurons from Christianson syndrome iPSCs reveal mutation-specific responses to rescue strategies
Authors: Lizarraga Sofia B. , Ma Li , Maguire Abbie M. , van Dyck Laura I. , Wu Qing , Ouyang Qing , Kavanaugh Brian C. , Nagda Dipal , Livi Liane L. , Pescosolido Matthew F. , Schmidt Michael , Alabi Shanique , Cowen Mara H. , Brito-Vargas Paul , Hoffman-Kim Diane , Gamsiz Uzun Ece D. , Schlessinger Avner , Jones Richard N. , Morrow Eric M.
Published: February 2021

Neurons from patient-derived iPSCs demonstrate mutation-specific responses to potential therapeutic strategies for Christianson syndrome.
Quantifying Potential N Turnover Rates in Hypersaline Microbial Mats by Using
15
N Tracer Techniques
Authors: Coban Oksana , Rasigraf Olivia , de Jong Anniek E. E. , Spott Oliver , Bebout Brad M.
Published: February 2021

Nitrogen is essential for life. The nitrogen cycle on Earth is mediated by microbial activity and has had a profound impact on both the atmosphere and the biosphere throughout geologic time.
Evaluating Specimen Quality and Results from a Community-Wide, Home-Based Respiratory Surveillance Study
Authors: Kim Ashley E. , Brandstetter Elisabeth , Wilcox Naomi , Heimonen Jessica , Graham Chelsey , Han Peter D. , Starita Lea M. , McCulloch Denise J. , Casto Amanda M. , Nickerson Deborah A. , Van de Loo Margaret M. , Mooney Jennifer , Ilcisin Misja , Fay Kairsten A. , Lee Jover , Sibley Thomas R. , Lyon Victoria , Geyer Rachel E. , Thompson Matthew , Lutz Barry R. , Rieder Mark J. , Bedford Trevor , Boeckh Michael , Englund Janet A. , Chu Helen Y.
Published: February 2021

While influenza and other respiratory pathogens cause significant morbidity and mortality, the community-based burden of these infections remains incompletely understood. The development of novel methods to detect respiratory infections is essential for mitigating epidemics and developing pandemic-preparedness infrastructure.
Complete Genome Sequence of Exfoliative Toxin-Producing Staphylococcus aureus Strain MSSA_SSSS_01, Obtained from a Case of Staphylococcal Scalded-Skin Syndrome
Authors: Cella Eleonora , David Michael Z. , Jubair Mohammad , Baines Sarah L. , Pegues David A. , Azarian Taj
Published: February 2021

Here, we announce the complete genome sequence of an exfoliative toxin-producing strain of
Staphylococcus aureus
sequence type 582 (ST582), isolated from a case of staphylococcal scalded-skin syndrome. The genome consists of a single circularized unitig with a total length of 2,792,190 bp carrying 2,699 genes. The genome is the basis for future epidemiological and genomic studies.
Acute hypertensive crisis due to newly diagnosed pheochromocytoma in the ninth decade of life: an unusual presentation
Authors: Cartwright Carmen , Ucciferro Peter , Anastasopoulou Catherine
Published: February 2021

The patient is an 85-year-old man with multiple comorbidities, including hypertension and coronary artery disease with recent myocardial infarction who underwent cardiac catheterisation. During the procedure, the patient developed profound hypertensive crisis with flash pulmonary oedema, requiring significant intervention for blood pressure (BP) control. His crisis was also marked by wide excursions in his BP. The patient was found to have a large left adrenal mass measuring 9.4×8.7×8.1 cm, with biochemical testing confirming the suspicion of pheochromocytoma. Alpha-blockade was started prior to availability of lab results due to high index of suspicion. Surgical removal, the mainstay of treatment, has yet to transpire as he has no family, and due to his underlying dementia, he was not felt to have capacity for decision-making at the time of diagnosis. The case elucidates the vast presentations of this tumour, the means of diagnosis and the difficulties of treatment.
Associations of pre-pregnancy impaired fasting glucose and body mass index among pregnant women without pre-existing diabetes with offspring being large for gestational age and preterm birth: a cohort study in China
Authors: Tang Jie , Chen Ruoling , Yu Yizhen , Bao Wei , Tiemeier Henning , Rodney Amanda , Zhu Xinhong , Li Mingzhen , Huang Dongming , Zhao Qingguo
Published: February 2021

Introduction

Associations of pre-pregnancy impaired fasting glucose (IFG) and body mass index (BMI) with large for gestational age (LGA) and preterm birth (PTB) have been poorly understood. We aimed to investigate the associations of maternal BMI, separately and together with pre-pregnancy IFG, with LGA and PTB in Chinese population. We also aimed to quantify these associations by maternal age.

Research design and methods

This was a retrospective cohort study of women from the National Free Preconception Health Examination Project with singleton birth from 121 counties/districts in 21 cities of Guangdong Province, China, from January 1, 2013 to December 31, 2017. Women were included if they did not have pre-existing chronic diseases (diabetes, hypertension, etc). Participants were divided into eight groups according to their BMI (underweight (BMI <18.5 kg/m2), normal weight (18.5–23.9 kg/m2), overweight (24.0–27.9 kg/m2), and obesity (≥28.0 kg/m2)) and pre-pregnancy fasting glucose status (normoglycemia (fasting glucose concentration <6.1 mmol/L) and IFG (6.1–7.0 mmol/L)). Adjusted incidence risk ratios (aIRRs) and 95% CIs of LGA, severe LGA, PTB and early PTB were estimated.

Results

We included 634 030 women. The incidences of LGA, severe LGA, PTB and early PTB for the study population were 7.1%, 2.5%, 5.1% and 1.1%, respectively. Compared with normal weight mothers with normoglycemia, overweight and obese mothers irrespective of IFG had a higher risk of LGA (eg, obesity with IFG aIRR 1.85 (1.60–2.14)) and severe LGA (eg, obesity with IFG 2.19 (1.73–2.79)). The associations of BMI and pre-pregnancy fasting glucose status with LGA were similar found among women of all age groups. Underweight with normoglycemia had 6.0% higher risk of PTB (1.06 (1.03–1.09)) and 8.0% higher risk of early PTB (1.08 (1.02–1.17)), underweight with IFG had 14.0% higher risk of PTB (1.14 (1.02–1.27)), and obese mothers with IFG had 45.0% higher risk of PTB (1.45 (1.18–1.78)). The associations of BMI and pre-pregnancy fasting glucose status with PTB differed by maternal age.

Conclusion

Overweight and obesity regardless of IFG were associated with an increased risk of LGA, and these associations were similarly observed among mothers of all age groups. Underweight regardless of IFG, and obesity with IFG were associated with an increased risk of PTB, but the associations differed by maternal age. Findings from this study may have implications for risk assessment and counselling before pregnancy.
Chronic kidney disease detection, staging and treatment in cardiovascular disease prevention
Authors: Lamprea-Montealegre Julio Alejandro , Shlipak Michael G , Estrella Michelle M
Published: February 2021

Globally, nearly 10% of the population has chronic kidney disease (CKD), defined as a glomerular filtration rate less than 60 mL/min/1.73 m2and/or a urinary albumin to creatinine ratio greater than 30 mg/g (3 mg/mmol). Persons with CKD have a substantially high risk of cardiovascular disease. Indeed, most persons with CKD are far more likely to develop a cardiovascular event than to progress to end-stage kidney disease. Although early detection and staging of CKD could help prevent its cardiovascular consequences, current rates of testing for CKD are very low, even among high-risk populations such as persons with diabetes, hypertension and cardiovascular disease. In this review, we first describe the need to test for both estimated glomerular filtration rate and albuminuria among persons at high risk of CKD in order to properly stage CKD and enhance cardiovascular risk stratification. We then discuss how detection and staging for CKD could help prioritise patients at high risk of atherosclerotic cardiovascular disease and heart failure who could derive the largest benefit from cardiovascular preventive interventions. In addition, we discuss the central role of CKD detection and staging in the initiation of cardiorenal preventive therapies, such as the sodium–glucose cotransporter 2 inhibitors, which have shown overwhelming evidence of cardiorenal protection. We conclude by discussing strategies to overcome historical barriers to CKD detection and treatment.
An examination of contributions of animal- and plant-based dietary patterns on the nutrient quality of diets of adult Canadians
Authors: Fabek Hrvoje , Sanchez-Hernandez Diana , Ahmed Mavra , Marinangeli Christopher P.F. , House James D. , Anderson G. Harvey
Published: February 2021

Dietary guidance and Canada’s 2019 Food Guide encourage increased consumption of plant-based foods as a source of dietary protein. However, there is an absence of recent data on protein and nutrient intakes and quality of Canadian dietary patterns that might occur with increased plant protein intakes. This study compared food sources and nutrient intakes of Canadian adults within groups of increasing plant protein-containing diets. The CCHS 2015 Public-Use Microdata File of single 24-hour dietary recalls of males and females ≥19 years (n = 6498) or ≥70 years (n = 1482) were examined. Respondents were allocated into 4 groups defined by their protein intake percentage coming from plant-based foods (i.e., group 1: 0–24.9%, group 2: 25–49.9%, group 3: 50–74.9%, group 4: 75–100%). Protein intake in adults averaged 63.3% animal and 36.7% plant protein. Where plant protein contributed >50% protein, higher intakes of carbohydrate, dietary fibre, folate, dietary folate equivalents, iron and magnesium (p < 0.001) but lower intakes of total and saturated fat, protein, vitamin D, vitamin B12, riboflavin and niacin (p < 0.0001) were reported. In contrast, group 1 had higher total and saturated fat, protein, vitamin B12, thiamin, niacin, and zinc, but lower carbohydrate, dietary fibre, and magnesium. Balancing plant- with animal-based protein foods leads to healthier dietary patterns with more favourable nutritional properties when compared with diets based on either high animal or high plant protein content.

Novelty: Combinations of animal- and plant-based proteins improve nutrient quality of Canadian diets. The source of protein influences diet quality.
Piezo-photo-thermoelasticity transport process for hyperbolic two-temperature theory of semiconductor material
Authors: Lotfy Kh. , Elidy E. S. , Tantawi Ramdan S.
Published: February 2021

A general solution for propagating waves in a generalized piezo-photo-thermoelastic medium for the one-dimensional (1D) problem under the hyperbolic two-temperature theory is investigated. The governing equations of the elastic waves, carrier density (plasma wave), quasi-static electric field, heat conduction equation, hyperbolic two temperature coefficient and constitutive relationships for the peizo-thermoelastic medium are obtained using Laplace transformation method in 1D. On the interface adjacent to the vacuum, mechanical stress loads, thermal and plasma boundary conditions are applied to obtain the main basic physical quantities in the Laplace domain. The inversion of Laplace transform by a numerical method is applied to obtain the complete solutions in the Laplace time domain for the main physical fields in this phenomenon. The effects on the force stress, displacement component, temperature distribution and carrier density of the thermoelastic, thermoelectric and hyperbolic two-temperature parameters by the applied force were graphically discussed.
Quantum transport, electronic properties and molecular adsorptions in graphene
Authors: Fujimoto Yoshitaka
Published: February 2021

Molecular sensor applications are used in different fields including environmental monitoring and medical diagnosis. Graphene, a single atomic layer consisting of the hexagonally arranged carbon material, is one of the most promising materials for ideal channels in field-effect transistors to be used as electronic sensing applications owing to its lightweight, mechanical robustness, high electronic conductivity and large surface-to-volume ratio. This paper provides a review of molecular adsorptions, electronic properties and quantum transport of graphene based on the first-principles density-functional study. The adsorption properties of environmentally polluting or toxic molecules and electronic transport of graphene are revealed. The possibility of detecting these molecules selectively is also discussed for designing the graphene-based sensor applications.
Coexistence of type-II and type-IV Dirac fermions in SrAgBi
Authors: Ma Tian-Chi , Hu Jing-Nan , Chen Yuan , Shao Lei , Hu Xian-Ru , Deng Jian-Bo
Published: February 2021

Relativistic massless Weyl and Dirac fermions have isotropic and linear dispersion relations to maintain Poincaré symmetry, which is the most basic symmetry in high-energy physics. The situation in condensed matter physics is less constrained; only certain subgroups of Poincaré symmetry — the 230 space groups that exist in 3D lattices — need be respected. Then, the free fermionic excitations that have no high-energy analogues could exist in solid state systems. Here, We discovered a type of nonlinear Dirac fermion without high-energy analogue in SrAgBi and named it type-IV Dirac fermion. The type-IV Dirac fermion has a nonlinear dispersion relationship and is similar to the type-II Dirac fermion, which has electron pocket and hole pocket. The effective model for the type-IV Dirac fermion is also found. It is worth pointing out that there is a type-II Dirac fermion near this new Dirac fermion. So we used two models to describe the coexistence of these two Dirac fermions. Topological surface states of these two Dirac points are also calculated. We envision that our findings will stimulate researchers to study novel physics of type-IV Dirac fermions, as well as the interplay of type-II and type-IV Dirac fermions.
A wideband receiver front-end with low noise and high linearity by exploiting reconfigurable dual paths in 180 nm CMOS
Authors: Guo Benqing , Chen Hongpeng , Wang Xuebing , Li Lei , Zhou Wanting
Published: February 2021

In this paper, a wideband receiver front-end including the flexible reconfigurable main and auxiliary paths is proposed. Therein, the main path has the low-noise advantage thanks to the low-noise transconductance amplifier (LNTA) preceding the mixer and baseband. Meanwhile, by utilizing a mixer-first structure, the auxiliary path renders a high in-band and out-of-band linearity. Furthermore, an inductor resonance structure is also designed to mitigate the baseband noise crosstalk issue which is disclosed by a charging/discharging mechanism via the tail capacitance of passive mixers. Both of the receiving paths have shared a common baseband circuit while loading a commonly-shared 25% duty-cycle LO source generator. Simulation results by a 180 nm CMOS have demonstrated that the main path provides a low noise figure (NF) of 2.7 dB, while the auxiliary path obtains the in-band and out-of-band IIP3 of 9.2 and 21 dBm under typical LO excitation frequency of [Formula: see text] GHz. The power consumption of the main path of the dual-path front-end is 57 mW and that of the auxiliary path is 26 mW under a supply voltage of 1.8 V.
Spatial and Frequency Approaches for Audio File Protection
Authors: Salah Euschi , Amine Khaldi , Redouane Kafi Med , Fares Kahlessenane
Published: February 2021

In order to protect audio files, we propose in this paper a new integration scheme for blind audio file watermarking. The goal is to find a compromise between capacity and imperceptibility in order to hide as much data as possible while minimizing file degradation. This integration scheme is implemented in the three insertion domains: spatial, frequency and multi-resolution domains. For the spatial-domain integration, the mark is inserted directly into the data samples. For the frequency-domain integration, a Discrete Cosine Transform is applied to the audio frames; after the thresholding and quantification step, the watermark is inserted into the Discrete Cosine Transform coefficients to obtain the watermarked file. For the multi-resolution-domain insertion, a single-level Discrete Wavelet Transform is applied using the scaling low-pass filter and wavelet high-pass filter. The watermark integration is then performed using the obtained AC coefficients. The proposed concealment process combines three values to integrate two bits and only one may be modified, which reduces the probability of change unlike other approaches. This implies less modification and therefore less distortion of the host file; this explains the good Signal-to-Noise Ratio obtained of more than 59[Formula: see text]dB for the spatial-domain integration and therefore a reasonable imperceptibility. An evaluation of the watermark’s robustness demonstrates that the proposed schemes generate reasonably robust watermarked samples against various attacks with a high-quality watermark with normalized cross-correlation greater than 0.9 for the three insertion domains.
Semiclassical level density parameter with collective enhancements in nuclei
Authors: Monga Saniya , Kaur Harjeet
Published: February 2021

In this work, we calculate the level density parameter for several nuclei by deploying the semiclassical trace formula for spherically symmetric harmonic oscillator potential with spin-orbit interactions, which describes the quantum shell effects in terms of the classical periodic orbits. With the usage of recently proposed Laplace like formula of level density parameter by Canbula et al., the effects of collective rotations and vibrations as well as deformations in nuclei are incorporated. The comparison of our results with the experimental ones show a good agreement. Later on, the study is also extended to the calculation of nuclear level density and survival probability in several superheavy nuclei (SHN).
TWO STAGE DECUMULATION STRATEGIES FOR DC PLAN INVESTORS
Authors: FORSYTH PETER A.
Published: February 2021

Optimal stochastic control methods are used to examine decumulation strategies for a defined contribution (DC) plan retiree. An initial investment horizon of 15 years is considered, since the retiree will attain this age with high probability. The objective function reward measure is the expected sum of the withdrawals. The objective function tail risk measure is the expected linear shortfall with respect to a desired lower bound for wealth at 15 years. The lower bound wealth level is the amount which is required to fund a lifelong annuity 15 years after retirement, which generates the required minimum cash flows. This ameliorates longevity risk. The controls are the withdrawal amount each year, and the asset allocation strategy. Maximum and minimum withdrawal amounts are specified. Specifying a short initial decumulation horizon, results in the optimal strategy achieving: (i) median withdrawals at the maximum rate within 2–3 years of retirement (ii) terminal wealth larger than the desired lower bound at 15 years, with greater than [Formula: see text] probability and (iii) median terminal wealth at 15 years considerably larger than the desired lower bound. The controls are computed using a parametric model of historical stock and bond returns, and then tested in bootstrap resampled simulations using historical data. At the 15 year investment horizon, the retiree has the option of (i) continuing to self-manage the decumulation policy or (ii) purchasing an annuity.
Regularity for the fully nonlinear parabolic thin obstacle problem
Authors: Chatzigeorgiou Georgiana
Published: February 2021

We prove [Formula: see text] regularity (in the parabolic sense) for the viscosity solution of a boundary obstacle problem with a fully nonlinear parabolic equation in the interior. Following the method which was first introduced for the harmonic case by L. Caffarelli in 1979, we extend the results of I. Athanasopoulos (1982) who studied the linear parabolic case and the results of E. Milakis and L. Silvestre (2008) who treated the fully nonlinear elliptic case.
Strange star with Krori–Barua potential in the presence of anisotropy
Authors: Bhar Piyali
Published: February 2021

In this paper, a well-behaved new model of anisotropic compact star in (3+1)-dimensional spacetime has been investigated in the background of Einstein’s general theory of relativity. The model has been developed by choosing [Formula: see text] component as Krori–Barua (KB) ansatz [Krori and Barua in J. Phys. A, Math. Gen. 8 (1975) 508]. The field equations have been solved by a proper choice of the anisotropy factor which is physically reasonable and well behaved inside the stellar interior. Interior spacetime has been matched smoothly to the exterior Schwarzschild vacuum solution and it has also been depicted graphically. Model is free from all types of singularities and is in static equilibrium under different forces acting on the system. The stability of the model has been tested with the help of various conditions available in literature. The solution is compatible with observed masses and radii of a few compact stars like Vela X-1, 4U [Formula: see text], PSR J[Formula: see text], LMC X [Formula: see text], EXO [Formula: see text].
Why My Code Summarization Model Does Not Work
Authors: Chen Qiuyuan , Xia Xin , Hu Han , Lo David , Li Shanping
Published: February 2021

Code summarization aims at generating a code comment given a block of source code and it is normally performed by training machine learning algorithms on existing code block-comment pairs. Code comments in practice have different intentions. For example, some code comments might explain how the methods work, while others explain why some methods are written. Previous works have shown that a relationship exists between a code block and the category of a comment associated with it. In this article, we aim to investigate to which extent we can exploit this relationship to improve code summarization performance. We first classify comments into six intention categories and manually label 20,000 code-comment pairs. These categories include
“what,”
“why,”
“how-to-use,”
“how-it-is-done,”
“property,”
and
“others.”
Based on this dataset, we conduct an experiment to investigate the performance of different state-of-the-art code summarization approaches on the categories. We find that the performance of different code summarization approaches varies substantially across the categories. Moreover, the category for which a code summarization model performs the best is different for the different models. In particular, no models perform the best for
“why”
and
“property”
comments among the six categories. We design a composite approach to demonstrate that comment category prediction can boost code summarization to reach better results. The approach leverages classified code-category labeled data to train a classifier to infer categories. Then it selects the most suitable models for inferred categories and outputs the composite results. Our composite approach outperforms other approaches that do not consider comment categories and obtains a relative improvement of 8.57% and 16.34% in terms of
ROUGE-L
and
BLEU-4
score, respectively.
Using Spectral Graph Theory to Map Qubits onto Connectivity-limited Devices
Authors: Lin Joseph X. , Anschuetz Eric R. , Harrow Aram W.
Published: February 2021

We propose an efficient heuristic for mapping the logical qubits of quantum algorithms to the physical qubits of connectivity-limited devices, adding a minimal number of connectivity-compliant SWAP gates. In particular, given a quantum circuit, we construct an undirected graph with edge weights a function of the two-qubit gates of the quantum circuit. Taking inspiration from spectral graph drawing, we use an eigenvector of the graph Laplacian to place logical qubits at coordinate locations. These placements are then mapped to physical qubits for a given connectivity. We primarily focus on one-dimensional connectivities and sketch how the general principles of our heuristic can be extended for use in more general connectivities.
Mental Models of a Mobile Shoe Rack
Authors: Rueben Matthew , Klow Jeffrey , Duer Madelyn , Zimmerman Eric , Piacentini Jennifer , Browning Madison , Bernieri Frank J. , Grimm Cindy M. , Smart William D.
Published: February 2021

Most people do not have direct access to knowledge about the inner workings of robots. Instead, they must develop mental models of the robot, a process that is not well understood. This article presents findings from a long-term, in-the-wild, qualitative, hypothesis-generating study of the mental model formation process. The focus was on how (qualitatively) users form mental models of the robot—specifically its perceptual capabilities, rules of behavior, and communication with other humans. Participants of diverse ages had multiple interactions with the robot over six weeks in a non-laboratory setting. The robot’s rules of behavior were changed every two weeks. A novel, non-anthropomorphic robot was created for the study with a realistic use case: storing people’s shoes during a yoga class.

This article reports findings from a case study analysis of 28 interviews conducted over six weeks with six participants. These findings are organized into six topics: (1) variability in the rate at which mental models are updated to be more predictive, (2) types of reasoning and hypothesizing about the robot, (3) borrowing from existing mental models and use of imagination, (4) attributing sensing capabilities where there are no visible sensors, (5) judgments about whether the robot is autonomous or teleoperated, and (6) experimenting with the robot. Specific suggestions for future research are given throughout, culminating in a set of study design recommendations. This work demonstrates the fruitfulness of long-term, in-the-wild studies of human-robot interaction, of which mental model formation is a foundational aspect.
A Non-Intrusive Tool Chain to Optimize MPSoC End-to-End Systems
Authors: France-Pillois Maxime , Martin Jérôme , Rousseau Frédéric
Published: February 2021

Multi-core systems are now found in many electronic devices. But does current software design fully leverage their capabilities? The complexity of the hardware and software stacks in these platforms requires software optimization with end-to-end knowledge of the system.

To optimize software performance, we must have accurate information about system behavior and time losses. Standard monitoring engines impose tradeoffs on profiling tools, making it impossible to reconcile all the expected requirements: accurate hardware views, fine-grain measurements, speed, and so on. Subsequently, new approaches have to be examined.

In this article, we propose a non-intrusive, accurate tool chain, which can reveal and quantify slowdowns in low-level software mechanisms. Based on emulation, this tool chain extracts behavioral information (time, contention) through hardware side channels, without distorting the software execution flow. This tool consists of two parts. (1) An online acquisition part that dumps hardware platform signals. (2) An offline processing part that consolidates meaningful behavioral information from the dumped data. Using our tool chain, we studied and propose optimizations to MultiProcessor System on Chip (MPSoC) support in the Linux kernel, saving about 60% of the time required for the release phase of the GNU OpenMP synchronization barrier when running on a 64-core MPSoC.
Events
Authors: Dennis Louise A.
Published: February 2021

This section features information about upcoming events relevant to the readers of AI Matters, including those supported by SIGAI. We would love to hear from you if you are are organizing an event and would be interested in cooperating with SIGAI.For more information about conference support visit sigai.acm.org/activities/requesting_sponsorship.html.
Multiscale Models for Light-Driven Processes
Authors: Nottoli Michele , Cupellini Lorenzo , Lipparini Filippo , Granucci Giovanni , Mennucci Benedetta
Published: February 2021

Multiscale models combining quantum mechanical and classical descriptions are a very popular strategy to simulate properties and processes of complex systems. Many alternative formulations have been developed, and they are now available in all of the most widely used quantum chemistry packages. Their application to the study of light-driven processes, however, is more recent, and some methodological and numerical problems have yet to be solved. This is especially the case for the polarizable formulation of these models, the recent advances in which we review here. Specifically, we identify and describe the most important specificities that the polarizable formulation introduces into both the simulation of excited-state dynamics and the modeling of excitation energy and electron transfer processes.
Modeling Spin-Crossover Dynamics
Authors: Mukherjee Saikat , Fedorov Dmitry A. , Varganov Sergey A.
Published: February 2021

In this article, we review nonadiabatic molecular dynamics (NAMD) methods for modeling spin-crossover transitions. First, we discuss different representations of electronic states employed in the grid-based and direct NAMD simulations. The nature of interstate couplings in different representations is highlighted, with the main focus on nonadiabatic and spin-orbit couplings. Second, we describe three NAMD methods that have been used to simulate spin-crossover dynamics, including trajectory surface hopping, ab initio multiple spawning, and multiconfiguration time-dependent Hartree. Some aspects of employing different electronic structure methods to obtain information about potential energy surfaces and interstate couplings for NAMD simulations are also discussed. Third, representative applications of NAMD to spin crossovers in molecular systems of different sizes and complexities are highlighted. Finally, we pose several fundamental questions related to spin-dependent processes. These questions should be possible to address with future methodological developments in NAMD.
Role of Dynamic Susceptibility Contrast Perfusion MRI in Glioma Progression Evaluation
Authors: Quan Guanmin , Zhang Kexin , Liu Yawu , Ren Jia-Liang , Huang Deyou , Wang Weiwei , Yuan Tao
Published: February 2021

Accurately and quickly differentiating true progression from pseudoprogression in glioma patients is still a challenge. This study aims to explore if dynamic susceptibility contrast- (DSC-) MRI can improve the evaluation of glioma progression. We enrolled 65 glioma patients with suspected gadolinium-enhancing lesion. Longitudinal MRI follow-up (mean 590 days, range: 210–2670 days) or re-operation (n = 3) was used to confirm true progression (n = 51) and pseudoprogression (n = 14). We assessed the diagnostic performance of each MRI variable and the different combinations. Our results showed that the relative cerebral blood volume (rCBV) in the true progression group (1.094, 95%CI: 1.135–1.636) was significantly higher than that of the pseudoprogression group (0.541 ± 0.154)

p
<
0.001

. Among the 18 patients who had serial DSC-MRI, the rCBV of the progression group (0.480, 95%CI: 0.173–0.810) differed significantly from pseudoprogression (-0.083, 95%CI: −1.138–0.620) group

p
=
0.015

. With an rCBV threshold of 0.743, the sensitivity and specificity for discriminating true progression from pseudoprogression were 76.5% and 92.9%, respectively. The Cho/Cr and Cho/NAA ratios of the true progression group (2.520, 95%CI: 2.331–2.773; 2.414 ± 0.665, respectively) were higher than those of the pseudoprogression group (1.719 ± 0.664; 1.499 ± 0.500, respectively) (

p
=
0.001

,

p
<
0.001

, respectively). The areas under ROC curve (AUCs) of enhancement pattern, MRS, and DSC-MRI for the differentiation were 0.782, 0.881, and 0.912, respectively. Interestingly, when combined enhancement pattern, MRS, and DSC-MRI variables, the AUC was 0.965 and achieved sensitivity 90.2% and specificity 100.0%. Our results suggest that DSC-MRI can significantly improve the diagnostic performance for identifying glioma progression. DSC-MRI combined with conventional MRI may promptly distinguish true gliomas progression from pseudoprogression when the suspected gadolinium-enhancing lesion was found, without the need for a long-term follow-up.
Facial Image Segmentation Based on Gabor Filter
Authors: Li Hong-An , Fan Jiangwen , Zhang Jing , Li Zhanli , He Dandan , Si Ming , Zhang Yun
Published: February 2021

As an important part of face recognition, facial image segmentation has become a focus of human feature detection. In this paper, the AdaBoost algorithm and the Gabor texture analysis algorithm are used to segment an image containing multiple faces, which effectively reduces the false detection rate of facial image segmentation. In facial image segmentation, the image containing face information is first analyzed for texture using the Gabor algorithm, and appropriate thresholds are set with different thresholds of skin-like areas, where skin-like areas in the image’s background information are removed. Then, the AdaBoost algorithm is used to detect face regions, and finally, the detected face regions are segmented. Experiments show that this method can quickly and accurately segment faces in an image and effectively reduce the rate of missed and false detections.
Experiment and Failure Analysis of Rock‐Like Material Affected by Different Excavation Depths
Authors: Tian Yuan , Zhu Zhende , Liu Xinyu , He Yanxin
Published: February 2021

In order to increase the understanding of the strength and failure mechanism of rock mass during tunnel excavation, a series of uniaxial compression tests were conducted on mortar specimen with cracks and holes by using a rock mechanics servo‐controlled testing system. And by monitoring the experimental process, the initiation, propagation, and coalescence process of cracks were observed and characterized. According to the experimental results, the influences of the excavation depth on the mechanical parameters and fracture characteristics of mortar specimens with single hole and the ones with single‐hole crack were analyzed in detail. In the specimens with single hole, the peak strength decreases with the increase of hole depth, but the peak strain and elastic modulus have no obvious linear correlation with the hole depth. And the position and angle of initial crack change differently with the increase of the hole depth. The position of initial crack moves from the side of the hole to the top of the hole. When the hole depth exceeds 50%, the crack initiation angle is no longer inclined to the axial stress direction, but parallel to the axial stress direction. In the specimens with single prefabricated crack, the wing‐shaped secondary cracks are generated at the tip of the precrack, and the antiwing‐shaped secondary cracks are generated at the tip when approaching the peak stress. However, in the specimens with single‐hole crack, no antiwing‐shaped crack appears. And when the hole depth reaches 80%, two wing‐shaped cracks appear at the precrack tip. One of the new wing‐shaped cracks appears in the direction of the extension line of the precrack.
How Did the COVID-19 Pandemic Affect Higher Education Learning Experience? An Empirical Investigation of Learners’ Academic Performance at a University in a Developing Country
Authors: El Said Ghada Refaat
Published: February 2021

COVID-19 has dramatically reshaped the way global education is delivered. Millions of learners were affected by educational institution closures due to the pandemic, which resulted in the largest online movement in the history of education. With this sudden shift away from classrooms in many parts of the globe, universities had to rapidly shift to virtual and digital strategies. Many believe that the adoption of online distance learning will persist after pandemic. A new hybrid model of education is expected to emerge, and, given the digital divide, new shifts in education approaches could widen equality gaps. This is one of the first empirical studies investigating the effect of the sudden shift from face-to-face to online distance learning due to COVID-19 lockdown at one of the universities in Egypt. Comparison of grades was made between 376 business students who completed a face-to-face course in spring 2019 and 372 students who completed the same course but fully online via distance learning mode in spring 2020 during the lockdown. T-test was conducted to compare grades of quizzes, course work, and final exam for the two groups. Chi-square test was used to compare grade distribution for both groups. The effect of gender, credit hours, age, and CGPA was assessed. The results suggested that there was no statistically significant difference in students’ grades. In addition, the unplanned and rapid move to online distance learning at the time of pandemic did not result in a poor learning experience as was expected. The study also included a survey of 435 students and interviews with a sample of professors about their learning and teaching experience during the lockdown. The results of this study provide specific recommendations for universities, instructors, and higher education portal designers about future application of online distance learning. Since Egypt decided to make the shift to online distant learning in all future higher education plans, the results of this research would be especially vital for universities in Egypt and other developing countries. If administered correctly, this shift could lead to a larger learner population, more cost efficiencies, and more university revenue.
Total Oxidation of Isopropanol in Its Liquid Phase, at a Low Temperature in the Presence of Prepared and Characterized Zinc Oxide
Authors: Dehmani Younes , Amhoud Abdellatif , Abouarnadasse Sadik
Published: February 2021

The complete oxidation of isopropanol in its liquid phase at a low temperature was studied in the presence of zinc oxide (ZnO). This solid was prepared with the precipitation method. Structural analysis (infrared in Fourier transform and diffraction of X-rays) and textured (adsorption/desorption of N2) were conducted for the wurtzite structure results, an IV type isotherm with a type H3 hysteresis. This solid presents a good catalytic activity against the complete oxidation of isopropanol, a constant of selectivity equal to 1; however, the studied temperatures were 40, 60, and 80°C. In addition, a kinetic study of the oxidation was performed and showed that the reaction follows a successive mechanism isopropanol-acetone-carbon dioxide. The low value of the apparent energy of the activation of this solid confirms the high value of the initial rate of the catalytic oxidation reaction of isopropanol in the temperature range studied.