bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon-Based Multi-Phase Rotating Detonation Engine
Authors: Dunn Ian , Flores Wilmer , Morales Anthony , Malik Vidhan , Ahmed Kareem 
Published: June 2021

Abstract
This article focuses on extending an H2/air rotating detonation engine's detonability limits by introducing solid carbon particles into the combustor. Carbon black particles consisting of 1% volatility and a carbon concentration of 99% were used as a solid-phase mixing agent for enhanced reaction wave dynamics. Carbon black was found to sustain detonations over multiple operational regimes formerly unattainable without carbon particles. The experiments confirm that detonations were attainable over a wide range of operational parameters, including the total mass flux flowing through the annulus (≅120–270 kg/s m2), the hydrogen/air equivalence ratios (0.65–1.0), and carbon additions (0–20 g). Chemiluminescence imaging was used to visualize the detonation wave within the annulus, quantify detonation wave velocities, and define a detonability map. The detonability map demonstrates the advantage of carbon addition, shows that detonation-based combustion can be sustained at leaner equivalence ratios, reduces hydrogen consumption dependency. The detonation wave velocities decreased as the H2/air equivalence ratio was reduced, where, in general, the detonation wave velocities decreased with respect to the Chapman–Jouguet velocity, suggesting a decrease in the detonation waves efficiency with reduced H2 concentrations. However, an extraordinary phenomenon was witnessed at very lean H2/air equivalence ratios and low mass flux conditions, where the detonation wave velocity increased upward of 100 m/s. This variation is a direct effect of the carbon particles, which drive the detonation wave. Thus, the results demonstrate that carbon particles’ addition provides an economically feasible solution to sustain high-efficiency energy production.
Numerical Investigation of Pressure-Cycling-Induced Fatigue Failure of Wrinkled Energy Pipelines
Authors: Singh Navjot , Das Sreekanta , Song Peter , Yoosef-Ghodsi Nader 
Published: June 2021

Abstract
Wrinkle defects can be complex pipeline deformities to assess and can present the potential to initiate a pipeline release incident as a result of fatigue failure due to pressure cycling, if not dealt with accordingly. Specifically, the stress distribution arising due to applied loads such as internal pressure can vary rapidly due to the complex shape along the wrinkle profile, which may introduce complexities in subsequent assessments such as fatigue life analysis. This paper presents a methodology using numerical simulation for evaluating stress concentration factors of wrinkle defects of varying geometries. A nonlinear finite element model is developed to evaluate stress concentration factors induced by wrinkle defects within steel pipelines subjected to internal pressure. Afterward, data from full-scale laboratory tests for the wrinkled pipe specimens subjected to cyclic pressure fatigue loading are analyzed to evaluate stress concentration factors for comparable wrinkle profiles. Lastly, a comparison between the results of the stress concentration factors evaluated using the finite element method and test data is provided, followed by a brief discussion of potential sources of discrepancies between results obtained from these methods.
Basic Constraints for Design Optimization of Cubic and Bistable Nonlinear Energy Sink
Authors: Wu Zhenhang , Seguy Sébastien , Paredes Manuel 
Published: June 2021

Abstract
This work mainly concentrates on the optimization of cubic and bistable nonlinear energy sink (NES) to find the maximum efficiency point under harmonic excitation. The conservative system is considered to reveal the inner property of the damping system. With the application of the multiple scales method and the complex variables method, the threshold of excitation and different response regimes are distinguished under the assumption of 1:1 resonance. The maximum efficiency point of cubic and bistable NES occurs when strongly modulated response disappears. The factors that affect the optimal efficiency limit are explored. The result indicates that the maximum absorption efficiency level is mainly determined by the damping parameters. Compared with the cubic case, the bistable case involves more complex regimes in terms of chaos oscillation. The influence of damping parameters on the chaos threshold is discussed to adopt different energy levels. With the help of analytical predictions, the proper nonlinear stiffness is determined for certain harmonic excitation. This study offers some fundamental insights into the optimal design of cubic and bistable NES.
Analysis and Experimental Study on Dynamic Characteristics of an Integrated Quasi-Zero Stiffness Isolator
Authors: Liu Haiping , Xiao Kaili , Lv Qi , Ma Yunlong 
Published: June 2021

Abstract
The dynamic performance of an integrated quasi-zero stiffness (IQZS) isolator which is constructed by a single elastic structure is investigated in this study. This prototype exhibits the characteristics of the best simplicity, high reliability, and without friction by using the minimum number of elements. For completeness, the static properties of the IQZS isolator are provided at first. And then, the dynamic behavior is analyzed and the frequency response under harmonic excitation is derived by using an equivalent mechanical model. Frequency response curves (FRCs) under force excitation condition are obtained by using the harmonic balance method (HBM). Moreover, the dynamic performance of the nonlinear isolator supporting a lumped mass is investigated, and the vibration isolation performance is evaluated by utilizing force transmissibility and comparing with an equivalent linear system with the same design parameter setting. It can be concluded that the effective isolation range of the nonlinear isolator is broader than the linear counterpart. The effects of system parameters on the transmissibility are also examined. At last, the comparison between the analytical and experimental results under force excitation shows that the analytical model of the IQZS isolator is accurate in terms of force transmissibility. The calculation results may provide a theoretical basis for designing this class of IQZS isolator in engineering practice.
Multidrug-Resistant Klebsiella pneumoniae Clones from Wild Chimpanzees and Termites in Senegal
Authors: Baron Sophie Alexandra , Mediannikov Oleg , Abdallah Rim , Kuete Yimagou Edmond , Medkour Hacène , Dubourg Gregory , Elamire Youssouf , Afouda Pamela , Ngom Issa Isaac , Angelakis Emmanouil , Davoust Bernard , Diatta Georges , Barciela Amanda , Hernandez-Aguilar R. Adriana , Sokhna Cheikh , Caputo Aurelia , Levasseur Anthony , Rolain Jean-Marc , Raoult Didier 
Published: June 2021

Antibiotic resistance genes exist naturally in various environments far from human usage. Here, we investigated multidrug-resistant
Klebsiella pneumoniae
, a common pathogen of chimpanzees and humans. We screened antibiotic-resistant
K. pneumoniae
from 48 chimpanzee stools and 38 termite mounds (
n
= 415 samples) collected in protected areas in Senegal.
Child mortality in England during the COVID-19 pandemic
Authors: Odd David , Stoianova Sylvia , Williams Tom , Sleap Vicky , Blair Peter , Fleming Peter , Wolfe Ingrid , Luyt Karen 
Published: June 2021

ObjectivesUsing the National Child Mortality Database (NCMD), this work aims to investigate and quantify the characteristics of children dying of COVID-19, and to identify any changes in rate of childhood mortality during the pandemic.DesignWe compared the characteristics of the children who died in 2020, split by SARS-CoV-2 status. A negative binomial regression model was used to compare mortality rates in lockdown (23 March–28 June), with those children who died in the preceding period (6 January–22 March), as well as a comparable period in 2019.SettingEngland.ParticipantsChildren (0–17 years).Main outcome measuresCharacteristics and number of the children who died in 2020, split by SARS-CoV-2 status.Results1550 deaths of children between 6th of January and 28 June 2020 were notified to the NCMD; 437 of the deaths were linked to SARS-CoV-2 virology records, 25 (5.7%) had a positive PCR result. PCR-positive children were less likely to be white (37.5% vs 69.4%, p=0.003) and were older (12.2 vs 0.7 years, p<0.0006) compared with child deaths without evidence of the virus. All-cause mortality rates were similar during lockdown compared with both the period before lockdown in 2020 (rate ratio (RR) 0.93 (0.84 to 1.02)) and a similar period in 2019 (RR 1.02 (0.92 to 1.13)).ConclusionsThere is little to suggest that there has been excess mortality during the period of lockdown. The apparent higher frequency of SARS-CoV-2-positive tests among children from black, Asian and minority ethnic groups is consistent with findings in adults. Ongoing surveillance is essential as the pandemic continues.
Mental healthcare for children with chronic conditions: a qualitative study
Authors: Jones Renee , Hiscock Harriet , Wurzel Danielle , Kao Kung-Ting , Freeman Jeremy L , Ride Jemimah 
Published: June 2021

ObjectiveTo explore parent perspectives on accessing mental healthcare for children with a chronic physical health condition.DesignQualitative research using semistructured interviews and Framework Analysis. Rankings were used to select attributes for a Discrete Choice Experiment (DCE).SettingFour specialty outpatient clinics (diabetes, epilepsy, bronchiectasis unrelated to cystic fibrosis and epidermolysis bullosa) at an Australian tertiary paediatric hospital.ParticipantsEighteen parents of children with a chronical physical health condition.ResultsMost parents identified the child’s general practitioner and/or hospital team as an initial pathway to seek help if they were worried about their child’s mental health. Parents see mental healthcare as part of care for the whole child and want the outpatient clinics to proactively discuss child and family mental health, as well as refer to appropriate services as needed. The hospital being a familiar, child-friendly environment was identified as a key reason the hospital might be a desired place to access mental healthcare, as previous research has found. Six attributes of mental health services were identified as important and will be included in an upcoming DCE: travel time, cost, wait time, available hours, knowledge of physical health condition, and recommendation.ConclusionsThis study highlights the opportunity presented in specialist outpatient clinics to address the often unmet mental healthcare needs of children with chronic physical health conditions. Parents identified practical ways for outpatient clinics to better facilitate access to mental healthcare. These will be further explored through a quantitative study of parent preferences.
Individual participant data systematic reviews with meta-analyses of psychotherapies for borderline personality disorder
Authors: Storebø Ole Jakob , Ribeiro Johanne Pereira , Kongerslev Mickey T , Stoffers-Winterling Jutta , Sedoc Jørgensen Mie , Lieb Klaus , Bateman Anthony , Kirubakaran Richard , Dérian Nicolas , Karyotaki Eirini , Cuijpers Pim , Simonsen Erik 
Published: June 2021

IntroductionThe heterogeneity in people with borderline personality disorder (BPD) and the range of specialised psychotherapies means that people with certain BPD characteristics might benefit more or less from different types of psychotherapy. Identifying moderating characteristics of individuals is a key to refine and tailor standard treatments so they match the specificities of the individual participant. The objective of this is to improve the quality of care and the individual outcomes. We will do so by performing three systematic reviews with meta-analyses of individual participant data (IPD). The aim of these reviews is to investigate potential predictors and moderating patient characteristics on treatment outcomes for patients with BPD.Methods and analysisWe performed comprehensive searches in 22 databases and trial registries up to October 6th 2020. These will be updated with a top-up search up until June 2021. Our primary meta-analytic method will be the one-stage random-effects approach. To identify predictors, we will use the one-stage model that accounts for interaction between covariates and treatment allocation. Heterogeneity in case-mix will be assessed with a membership model based on a multinomial logistic regression where study membership is the outcome. A random-effects meta-analysis is chosen to account for expected levels of heterogeneity.Ethics and disseminationThe statistical analyses will be conducted on anonymised data that have already been approved by the respective ethical committees that originally assessed the included trials. The three IPD reviews will be published in high-impact factor journals and their results will be presented at international conferences and national seminars.PROSPERO registration numberCRD42021210688.
COVID-19-related state-wise racial and ethnic disparities across the USA: an observational study based on publicly available data from The COVID Tracking Project
Authors: Xian Zhaoying , Saxena Anshul , Javed Zulqarnain , Jordan John E , Alkarawi Safa , Khan Safi U , Shah Karan , Vahidy Farhaan S , Nasir Khurram , Dubey Prachi 
Published: June 2021

ObjectiveTo evaluate COVID-19 infection and mortality disparities in ethnic and racial subgroups in a state-wise manner across the USA.MethodsPublicly available data from The COVID Tracking Project at The Atlantic were accessed between 9 September 2020 and 14 September 2020. For each state and the District of Columbia, % infection, % death, and % population proportion for subgroups of race (African American/black (AA/black), Asian, American Indian or Alaska Native (AI/AN), and white) and ethnicity (Hispanic/Latino, non-Hispanic) were recorded. Crude and normalised disparity estimates were generated for COVID-19 infection (CDI and NDI) and mortality (CDM and NDM), computed as absolute and relative difference between % infection or % mortality and % population proportion per state. Choropleth map display was created as thematic representation proportionate to CDI, NDI, CDM and NDM.ResultsThe Hispanic population had a median of 158% higher COVID-19 infection relative to their % population proportion (median 158%, IQR 100%–200%). This was followed by AA, with 50% higher COVID-19 infection relative to their % population proportion (median 50%, IQR 25%–100%). The AA population had the most disproportionate mortality, with a median of 46% higher mortality than the % population proportion (median 46%, IQR 18%–66%). Disproportionate impact of COVID-19 was also seen in AI/AN and Asian populations, with 100% excess infections than the % population proportion seen in nine states for AI/AN and seven states for Asian populations. There was no disproportionate impact in the white population in any state.ConclusionsThere are racial/ethnic disparities in COVID-19 infection/mortality, with distinct state-wise patterns across the USA based on racial/ethnic composition. There were missing and inconsistently reported racial/ethnic data in many states. This underscores the need for standardised reporting, attention to specific regional patterns, adequate resource allocation and addressing the underlying social determinants of health adversely affecting chronically marginalised groups.
Adenovirus and RNA-based COVID-19 vaccines’ perceptions and acceptance among healthcare workers in Saudi Arabia: a national survey
Authors: Temsah Mohamad-Hani , Barry Mazin , Aljamaan Fadi , Alhuzaimi Abdullah , Al-Eyadhy Ayman , Saddik Basema , Alrabiaah Abdulkarim , Alsohime Fahad , Alhaboob Ali , Alhasan Khalid , Alaraj Ali , Halwani Rabih , Alamro Nurah Maziad , Al-Shahrani Fatimah S , Jamal Amr , Alsubaie Sarah , Memish Ziad A , Al-Tawfiq Jaffar A 
Published: June 2021

ObjectivesThe aim of this study was to compare the perception, confidence, hesitancy and acceptance rate of various COVID-19 vaccine types among healthcare workers (HCWs) in Saudi Arabia, a nation with Middle East respiratory syndrome coronavirus experience.DesignNational cross-sectional, pilot-validated questionnaire.SettingOnline, self-administered questionnaire among HCWs.ParticipantsA total of 2007 HCWs working in the Kingdom of Saudi Arabia participated; 1512 (75.3%) participants completed the survey and were included in the analysis.InterventionData were collected through an online survey sent to HCWs during 1–15 November 2020. The main outcome measure was HCW acceptance of COVID-19 candidate vaccines. The associated factors of vaccination acceptance were identified through a logistic regression analysis and via measurement of the level of anxiety, using the Generalised Anxiety Disorder 7 scale.ResultsAmong the 1512 HCWs who were included, 62.4% were women, 70.3% were between 21 and 40 years of age, and the majority (62.2%) were from tertiary hospitals. In addition, 59.5% reported knowing about at least one vaccine; 24.4% of the participants were sure about their willingness to receive the ChAdOx1 nCoV-19 vaccine, and 20.9% were willing to receive the RNA BNT162b2 vaccine. However, 18.3% reported that they would refuse to receive the Ad5-vectored vaccine, and 17.9% would refuse the Gam-COVID-Vac vaccine. Factors that influenced the differential readiness of HCWs included their perceptions of the vaccine’s efficiency in preventing the infection (33%), their personal preferences (29%) and the vaccine’s manufacturing country (28.6%).ConclusionsAwareness by HCWs of the several COVID-19 candidate vaccines could improve their perceptions and acceptance of vaccination. Reliable sources on vaccine efficiency could improve vaccine uptake, so healthcare authorities should use reliable information to decrease vaccine hesitancy among frontline healthcare providers.
Chiral magnetic properties of QCD phase-diagram
Authors: Tawfik Abdel Nasser , Diab Abdel Magied 
Published: June 2021

AbstractThe QCD phase-diagram is studied, at finite magnetic field. Our calculations are based on the QCD effective model, the SU(3) Polyakov linear-sigma model (PLSM), in which the chiral symmetry is integrated in the hadron phase and in the parton phase, the up-, down- and strange-quark degrees of freedom are incorporated besides the inclusion of Polyakov loop potentials in the pure gauge limit, which are motivated by various underlying QCD symmetries. The Landau quantization and the magnetic catalysis are implemented. The response of the QCD matter to an external magnetic field such as magnetization, magnetic susceptibility and permeability has been estimated. We conclude that the parton phase has higher values of magnetization, magnetic susceptibility, and permeability relative to the hadron phase. Depending on the contributions to the Landau levels, we conclude that the chiral magnetic field enhances the chiral quark condensates and hence the chiral QCD phase-diagram, i.e. the hadron-parton phase-transition likely takes place, at lower critical temperatures and chemical potentials.
Neutrino trapping in extremely compact Tolman VII spacetimes
Authors: Stuchlík Zdeněk , Hladík Jan , Vrba Jaroslav , Posada Camilo 
Published: June 2021

AbstractExtremely compact objects trap gravitational waves or neutrinos, assumed to move along null geodesics in the trapping regions. The trapping of neutrinos was extensively studied for spherically symmetric extremely compact objects constructed under the simplest approximation of the uniform energy density distribution, with radius located under the photosphere of the external spacetime; in addition, uniform emissivity distribution of neutrinos was assumed in these studies. Here we extend the studies of the neutrino trapping for the case of the extremely compact Tolman VII objects representing the simplest generalization of the internal Schwarzschild solution with uniform distribution of the energy density, and the correspondingly related distribution of the neutrino emissivity that is thus again proportional to the energy density; radius of such extremely compact objects can overcome the photosphere of the external Schwarzschild spacetime. In dependence on the parameters of the Tolman VII spacetimes, we determine the “local” and “global” coefficients of efficiency of the trapping and demonstrate that the role of the trapping is significantly stronger than in the internal Schwarzschild spacetimes. Our results indicate possible influence of the neutrino trapping in cooling of neutron stars.
Stringy-running-vacuum-model inflation: from primordial gravitational waves and stiff axion matter to dynamical dark energy
Authors: Mavromatos Nick E. , Solà Peracaula Joan 
Published: June 2021

AbstractIn previous works, we have derived a Running Vacuum Model (RVM) for a string Universe, which provides an effective description of the evolution of 4-dimensional string-inspired cosmologies from inflation till the present epoch. In the context of this “stringy RVM” version, it is assumed that the early Universe is characterised by purely gravitational degrees of freedom, from the massless gravitational string multiplet, including the antisymmetric tensor field. The latter plays an important role, since its dual gives rise to a ‘stiff’ gravitational axion “matter”, which in turn couples to the gravitational anomaly terms, assumed to be non-trivial at early epochs. In the presence of primordial gravitational wave (GW) perturbations, such anomalous couplings lead to an RVM-like dynamical inflation, without external inflatons. We review here this framework and discuss potential scenarios for the generation of such primordial GW, among which the formation of unstable domain walls, which eventually collapse in a non-spherical-symmetric manner, giving rise to GW. We also remark that the same type of “stiff” axionic matter could provide, upon the generation of appropriate potentials during the post-inflationary eras, (part of) the Dark Matter (DM) in the Universe, which could well be ultralight, depending on the parameters of the string-inspired model. All in all, the new (stringy) mechanism for RVM inflation preserves the basic structure of the original (and more phenomenological) RVM, as well as its main advantages: namely, a mechanism for graceful exit and for generating a huge amount of entropy capable of explaining the horizon problem. It also predicts axionic DM and the existence of mild dynamical Dark Energy (DE) of quintessence type in the present universe, both being “living fossils” of the inflationary stages of the cosmic evolution. Altogether the modern RVM appears to be a theoretically sound (string-based) approach to cosmology with a variety of phenomenologically testable consequences.