bluuebunny/crossref_metadata_2025 huggingface dataset:
Transient Response of Distributed Parameter Systems
Authors: Zhou Jianping , Feng Zhigang
Published: February 2021

A semi-analytic method is presented for the analysis of transient response of distributed parameter systems which are consist of one dimensional subsystems. The system is first divided into one dimensional sub-systems. Within each subsystem, replacing differentials on time t by finite difference, the governing partial differential equations are reduced to difference-differential equations. The solution of derived ordinary differential equations is obtained in an exact and closed form by distributed transfer function method and represented in nodal displacement parameters. Assemling global equilibrium equations at each nodes according to displacement continuity and force equilibrium requirements gives simutaneous linear algebraic equations. Numerical results are illustrated and compared with that of finite element method.
Floating Slab Railway Track for Isolation of Vibration: Models of Infinite Length
Authors: Forrest James A.
Published: February 2021

Vibration transmitted from underground railways into nearby buildings is an increasingly significant problem affecting high-value residential and commercial developments. Various forms of vibration isolation are used in underground railways, one of which is the ‘floating slab track’. Rails are fixed directly to a massive concrete slab which in turn rests on a resilient mounting (usually rubber bearings or steel springs) so isolating the track from the tunnel invert. The effectiveness of vibration attenuation does not compare well with the simple mass-spring models typically used in the design of floating slab track.

This paper develops a model for floating slab track by conceptualising the track as two infinite beams (representing the rail and the concrete slab) separated by elastic layers representing the resilient elements used in floating slab track construction. A dynamic model for a finite-length unit of track is obtained from this physical model by the dynamic-stiffness-matrix method. A repeating unit method is utilised to create track models of infinite length from the finite track unit, an approach which much reduces the computation required. A concept of total force transmitted to the ground for a given set of inputs on the rail is developed, and the effect of various track parameters on the transmitted force is examined.
Self-Excited Harmonic and Solitary Waves in a Spinning Disk (With Video Presentation)
Authors: Boulahbal Djamil , Crandall Stephen H.
Published: February 2021

Solitary waves have been reported in many applications in physics and engineering. While these waves are of relatively simple shape, the mechanisms that control them are highly nonlinear and often not completely understood. In this study a flexible disk spinning against a stationary base plate and interacting with the surrounding air-field exhibits both harmonic as well as solitary waves and this, depending on the spin rate of the disk. Preliminary experimental results indicate that-in contrast with harmonic waves, the speed with which the solitary waves propagate does not depend upon the spin rate of the disk. This appears to be a lock-in phenomenon that is characteristic of well known nonlinear fluid-structure interaction problems. Furthermore, and despite the presence of dispersion in the fluid/disk medium, all solitary waves propagate with the same speed. While a full model capable of predicting these solitons has yet to be developed, a discussion is presented on both the linear model that is currently accepted in the literature, as well as on the nonlinear mechanisms that may control such interesting waves.
Stability and Bifurcations in a Model of Phase Transitions With Order Parameter
Authors: Sikora Janusz , Cusumano Joseph P. , Jester William A.
Published: February 2021

A one-dimensional model of phase transitions with convex strain energy is investigated within the limits of nonlinear bar theory. The model is a special case of a coupled field theory that has been developed by Fried and Gurtin to study the nucleation and propagation of phase boundaries. The system of governing equations studied here consists of a wave equation coupled to a nonlinear reaction-diffusion equation. Using phase plane methods, the equilibria of the system have been constructed in order to obtain the macroscopic response of the bar and the bifurcation diagram. It is demonstrated that a large number of coexisting spatially periodic, inhomogeneous solutions can occur, with the number of these solutions being inversely proportional to the diffusion coefficient in the reaction-diffusion subsystem. A stability analysis of the equilibria is presented.
Commercialization of Active Isolation for Jet Aircraft
Authors: Southward Steve C. , Ivers Douglas E. , Nicholson Geoff C.
Published: February 2021

Active Noise and Vibration Control (ANVC) technology is a proven solution for noise and vibration problems in aircraft. The challenges in commercializing this solution range from the development issues of choosing the best actuation, sensor, and control technology to obtaining sufficient flight test time and satisfying FAA requirements. This paper examines significant case histories in the progression of the Lord active vibration control program from conception to market. Throughout the development program, several important discoveries were made regarding the performance, reliability, and economics of Active Isolation Systems (AIS) in jet aircraft. First, practical speaker-based solutions cannot achieve global acoustic noise cancellation for engine tones above about 200 Hz. A comparatively small array of structural actuators placed in the dominant transmission path, such as in or near the engine mounts, are capable of global cancellation in the cabin up to at least 500 Hz. Second, the performance is generally better when cabin microphones are used as error sensor inputs because the AIS control system can compensate for flanking paths better than if accelerometers are used as error sensors. Third, when the actuators are placed in the dominant transmission path and close to the vibration source, the control system will simultaneously achieve global acoustic noise reduction in the cabin and vibration reduction in the aircraft structure without affecting the engine casing vibration levels.
Identification of Fault Signals in Rotating Machinery Using Higher Order Time Frequency Analysis
Authors: Lee Sang-Kwon , White Paul R.
Published: February 2021

Impulsive acoustic and vibration signals within rotating machinery are often induced by irregular impacting. Thus the detection of these impulses can be useful for fault diagnosis. Recently there is an increasing trend towards the use of higher order statistics for fault detection within mechanical systems based on the observation that impulsive signals tend to increase the kurtosis values. We show that the fourth order Wigner Moment Spectrum, called the Wigner Trispectrum, has superior detection performance to second order Wigner distribution for typical impulsive signals found in a condition monitoring application. These methods are also applied to data sets measured within a car engine and industrial gearbox.
A Singular-Value Decomposition Method for Updating the Analytical Model
Authors: Xianmin Zhang
Published: February 2021

Based on the theory of singular-value decomposition and the matrix approximation technique, an analytical model updating method using the identified model parameters is developed. Firstly, The identified modal matrix is decomposed by means of singular-value decomposition technique. The general updating equations for the analytical model are obtained according to the decomposition results, the eigenequation of the system, and the modal orthogonality relations. Secondly, the best matrix approximation solution for the updating equations is definited. The existence and uniqueness of the best approximation relative to the analytical model are studied. The concrete form of the best modification and two algorithms are presented. Examples demonstrate that the analytical model modification method developed in this paper possesses high modificatory accuracy comparing with some other methods. The method possesses the ability to modify the large error models.
Direct Estimation of Nonlinear Joint Parameters
Authors: Zhang X.-N. , Fritzen C.-P. , Jennewein D.
Published: February 2021

A method is proposed to identify nonlinear joint characteristics of a structure by means of measured data. The relation between the joint force function and the response of the system is established by use a position index matrix. The parameters of the joint force function are estimated by means of a least squares strategy. The parameter estimation can be done in time domain and also in frequency domain. Especially, when there is no excitation on the joint degrees of freedom only a part of the responses of the system are needed to identify the nonlinear joint parameters. The validity of the method is demonstrated by computer simulations.
Mathematical Model of a Buckled Spring for Vehicle Active Suspension
Authors: Yao Shiping , Morgan Colin , Leighton Nigel J.
Published: February 2021

The basic characteristic of a conventional spring is that of a constant rate, that is a linear force-displacement relationship. If, however, a flat, thin leaf spring is end-loaded past its buckling point it will deform into a curve and the resulting force-displacement relationship can be made virtually flat; that is a very low effective rate is seen, once the buckling force is exceeded.

A novel form of automotive active suspension system proposed by Leighton & Pullen (1994) relies upon the “buckled spring” element acting through a variable geometry wishbone assembly to provide wheel to body forces that are controllable by a low power actuator but are virtually independent of wheel to body displacement.

The dynamic behavior of the spring element is also significant, since resonance effects may affect the vibration isolating properties of the suspension system and may result in unstable modes of motion. This paper presents a rigorous derivation of the static and dynamic characteristic of the spring element and of the effect of design compromises that are essential for practical application.

Comparison of the experimental and simulation results shows that the simulation can be used to predict the static and dynamic performance of the spring.
Investigation of Stick-Slip Phenomenon Using a Two-Disk Friction System Vibration Model
Authors: Larsson Henric , Farhang Kambiz
Published: February 2021

A lumped parameter model is presented for studying the dynamic interaction between two disks in relative rotational motion and in frictional contact. The contact elastic and dissipative characteristics are represented by equivalent stiffnesses and damping coefficients in the axial as well as torsional directions. The formulation accounts for the coupling between the axial and angular motions by viewing the contact normal force to be the result of axial behavior of the system.

The model is used to investigate stick-slip behavior of a two-disk friction system. In this effort the friction coefficient is represented as an exponentially decaying function of relative angular velocity, varying from its static value at zero relative velocity to its kinetic value at very high velocities. This investigation result in establishment of critical curve defining two parameter regions: one in which stick-slip occurs and that in which stick-slip does not occur. Moreover, the onset and termination of stick-slip, when it occurs, is related to the highest component frequency in the system. It is found that stick-slip starts at a period nearly equal to that of the highest component frequency and terminates at a period almost three times that of the highest component frequency.
An Algorithm for Systematic Generation of Subscales With Application to a Two-Disk Friction System
Authors: Zargar Yasir S. , Farhang Kambiz
Published: February 2021

In this paper we propound an algorithm for development of scale models of complex physical systems. The algorithm systematically treats the three sub-tasks of scaling, which includes creation of dimensionless parameters, application of scaling law and similitude requirements, and determination of scale factors. Optimum set of dimensionless parameters are obtained in which the pertinent variables with only integer powers appear. This is achieved by seeking integer solutions to appropriate set of linear algebraic equations in the powers, using a simple iterative technique.

Application of the scaling law and similitude requirements along with a logarithmic transformation leads to a set of linear algebraic equations in the scale factors. In many applications, over-constrained systems are resulted for which true scaling can not be achieved. Two techniques are introduced in the proposed algorithm which circumvent the difficulty in treating over-constrained systems. The first method is based on a relaxation technique, whereas the second method introduces the concept of auxiliary variables to obtain the least squares solutions to the new set of linear equations. The effectiveness of the algorithm is demonstrated through its application in finding scale models of a two disk friction system.
Dynamic Response of Compliant Mechanisms Using the Pseudo-Rigid-Body Model
Authors: Lyon Scott M. , Evans Mark S. , Erickson Paul A. , Howell Larry L.
Published: February 2021

The pseudo-rigid-body modeling technique is used to simplify the nonlinear analysis of compliant mechanisms. This paper presents the first work that investigates the possibility of using the pseudo-rigid-body model to predict the dynamic response of compliant mechanisms. Four different configurations of the parallel-guiding mechanism are modeled and tested, as well as two configurations of compliant straight-line mechanisms. The model predictions of the first natural frequencies were compared with experimental results for all six mechanism configurations. The model predictions are within 9% of the experimental results for all cases.
Distortion Energy Based Design of Structures Under Random Excitations
Authors: Chen Mu-Tsang
Published: February 2021

Random vibration analysis (RVA) of structural systems is a rapidly growing branch of engineering mechanics. The theory of random vibration is central to the analysis and design of structures in a variety of engineering fields. In recent years, RVA in conjunction with finite element methods has been available in several commercial computer-aided-engineering software, such as ANSYS, NASTRAN, etc. The finite element-based RVA is being widely adopted for computing stochastic responses, such as displacements, stresses and strains in terms of statistical quantities, i.e., root-mean-square responses. However, these statistical responses from RVA are limited to Cartesian responses which depend on the coordinate system of use. In structural design, a failure criterion using distortion energy known as the von Mises theory is more appropriate and of interest in this paper. The statistics of von Mises stress can not be obtained in terms of the statistics of Cartesian stresses. Simulation-based von Mises stress responses corresponding to a covariance matrix of Cartesian stresses are used to perform scatter and failure analyses. Based on a sufficient number of stress samples, a probability distribution of von Mises stress response may be obtained. Given a specified design criterion, statistical moments of safety margin as well as a safety index can be computed. In addition, a required design strength corresponding to a desired probability of failure can be provided in this study.
Prediction of Modal Characteristics due to Design Change
Authors: Yi Tong Y. , Nikravesh Parviz E.
Published: February 2021

This paper presents a method for predicting modal characteristics of a structure that is considered to undergo a design change. It is assumed that for the original structure the modal data is available either as a complete or as an incomplete set. Based on the available modal data and the known data on the design change, this paper discusses methodologies for determining the vibration characteristics of the modified structure. By considering practical situations, the emphasis of this paper is on structures for which a finite element model, and hence a stiffness matrix, is not available.
A General Method of Multibody System Motion Optimization
Authors: Zakhariev Evtim V.
Published: February 2021

The present paper suggests a general off-line numerical algorithm for optimization of motion of multibody systems. The nonlinear dynamics model is numerically derived as Ordinary Differential Equations for the minimal set of the generalized coordinates. The trajectory is discretized of small intervals (nodes) where the robot motion is assumed to be with constant general coordinate accelerations. The mathematical description of the problem for optimal motion planning is presented as nonlinear programming problem. The characteristics of motion and discretized generalized forces in every node are parameters of the optimization problem. The convergence of the algorithm is tested in case of a five degrees of freedom redundant robot achieving point-to-point time optimal motion.
Dynamic Modelling and Solutions for a Transmission Mechanism With Flexible Support
Authors: Hongzhao Liu , Appleton E. , Zhixiao Su , Shengning Zhang , Weiqing Cao
Published: February 2021

In this work, the motion differential equations for a multiple-point meshing mechanism with flexible support are established by the Lagrange formula, and solved using a Laplace transform approach. The stable conditions and the formula for calculating this system’s natural frequencies are given and the general dynamic responses, in analytical form, are developed. The analysis pays special attention to the zero state response to a step function and constant loading inputs. Furthermore, the dynamic torques acting on the basic shaft and torsional bar are also discussed. This research lays the foundation for the analysis and design of this new type of transmission mechanism.
Dynamics of Nonlinear Mechanical Systems and Virtual Reality: An Educational Tool for Engineering
Authors: Santos Ilmar F. , Ferretti Alexandre P. , Schmidek Eduardo
Published: February 2021

This work has significant practical applications in the area of Dynamics of nonlinear systems. Here, one of these applications is presented: a methodology based on Dynamics principles and axioms and animation techniques, which yield the visualization of the dynamic behavior of nonlinear systems. Three theoretical and experimental examples are shown, illustrating mechanical systems modeled as systems of particles, as a rigid body and as multibody systems. Three laboratory prototypes were created: a double pendulum (system of particles), a top (rigid body) and a satellite with internal rotors (multibody system). The purpose of comparing the motions of these prototypes with the ones obtained by numerical simulations is to make learning easier and to show the physical meaning of equations of motion obtained through Dynamics principles and axioms formulated by Newton, Euler, D’Alembert, Jourdain and Lagrange.
Solution Numerical of Stiff ODEs and DAEs in Mechanical and Other Systems
Authors: Pasic H.
Published: February 2021

Presented is a formal solution of the initial-value problem of the system of general implicit differential-algebraic equations (DAEs) F(x, y, y’) = 0 of index zero or higher, based on perturbations of the polynomial coefficients of the vector y(x). The equation is linearized with respect to the coefficients and brought into a form suitable for implementation of the weighted residual methods. The solution is advanced by a single-step multi-stage collocation qadrature formula which is stiffly accurate and suitable for solving stiff differential equations and DAEs that arise in many mechanical and other systems. The algorithm is illustrated by two index-2 and index-3 examples — one of which is the well known pendulum problem.
Modelling of a Passenger Coach As Elastic Multibody System
Authors: Haug Jürgen , Piram Udo , Schiehlen Werner , Schirle Thomas
Published: February 2021

In this paper the multibody model of a railroad passenger coach consisting of two rigid bogies and an elastic car body is presented. The elastic body is introduced by a floating reference frame and superimposed elastic deformations linearized with respect to the reference frame. The governing equations of motion are presented in symbolical form, where the time-invariant matrices describing the elastodynamical behavior are computed numerically in a preprocessor. To increase the computational efficiency, condensation techniques are applied and ten modes are chosen to describe the elastic behavior. Simulations of high speed travelling have been carried out with excitation from measured data of a real track. As a measure of ride comfort the acceleration at characteristic points on the coach are computed. Comparison with results obtained using a less sophisticated rigid body model show significant higher accelerations, depending on the position on the coach, too.
Performance Assessment of Flexure Fixture for Payload Modal Survey
Authors: Chung Y. T.
Published: February 2021

A modal survey was conducted on a large orbiter payload supported by flexure assemblies to extract its dynamic characteristics for math model validation. The structural test article weighed 31500 lb (14.3 tons) and was supported by a flexure fixture at each of the four sill trunnions and one keel location. The primary design objective of the flexure fixture is to provide test boundary conditions which simulate the flight interfaces between the orbiter and its payload during modal testing. At the time this test was conducted, the test article was the heaviest payload ever tested using the flexure fixture since its introduction in 1991. Therefore, the test results could provide valuable feedback to the design concepts and the performance of the flexure fixture. Furthermore, difficulties such as exciting the true flight modes, non-linearity and adding extra mass to the flight configuration may be minimized by using flexure fixture.
Model Correlation Issues in Residual Flexibility Testing
Authors: Tinker Michael L. , Cutchins Malcolm A.
Published: February 2021

Application of the free-suspension residual flexibility modal test method raises some interesting issues and problems for the correlation of finite element models to test data. This paper presents a discussion of some of those issues as related to testing and analysis of two structures. One of these test articles is the International Space Station Pathfinder, a large structure similar in size and weight to the Space Station Resource Node.

The approach used by the authors to correlate models to residual flexibility data is presented, along with mode shape and frequency response results which illustrate the structural dynamic behavior of the models before and after the updating process. Frequency response functions (FRF) for the regions of the structure that interface with the environment (a test fixture or another structure) are shown to be the primary tools for model correlation that distinguish or characterize the residual flexibility approach.

A number of critical issues related to use of the structure interface FRF for correlating the model are then identified and discussed, including (1) the requirement of prominent stiffness lines, (2) overcoming problems with measurement noise which makes the antiresonances or minima in the functions difficult to identify, and (3) the use of interface stiffness and lumped mass perturbations to bring the analytical responses into agreement with test data. It is shown that good comparison of analytical-to-experimental FRF is the key to obtaining good agreement of the residual flexibility values.
Ultrasonographic imaging of supinator injury and hematoma after a fall
Authors: Chiu Yi-Hsiang , Wang Tyng-Guey
Published: February 2021

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Plantar vein thrombosis: an unexpected cause of posttraumatic foot pain explained with ultrasound
Authors: Mezian Kamal , Hrehová Laura , Sobotová Karolína
Published: February 2021

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Cerebral hypoperfusion as assessed by transcranial duplex in posterior reversible encephalopathy syndrome
Authors: Alberte-Woodward Miguel , García-Pazos Olga , Guijarro-del Amo Mónica
Published: February 2021

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Ultrasonography techniques in the preoperative diagnosis of parotid gland tumors – an updated review of the literature
Authors: Psychogios Georgios
Published: February 2021

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Dynamic ultrasonography for assessing the nerve-fasciae relationship in entrapment syndromes
Authors: Pirri Carmelo , Stecco Carla , Fede Caterina , De Caro Raffaele , Özçakar Levent
Published: February 2021

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Three-dimensional echocardiography in rapid differentiation of the left ventricular mass – a case of left ventricular myxoma
Authors: Fabijanic Damir , Kardum Duško , Lukšić Bruno , Carević Vedran
Published: February 2021

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Advances in the application of Doppler ultrasonography in the newborn
Authors: Johnson Peter Anto , Johnson John Christy
Published: February 2021

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True hero of the trade: On the critical contributions of Art Gossard to modern device techonology
Authors: Muhowski Aaron J. , Skipper Alec M. , March Stephen D. , Rodwell Mark J. W. , Bank Seth R.
Published: February 2021

Professor Arthur Gossard’s seminal contributions to fundamental physics often overshadow the immense impact he has had on advancing the performance and functionality of electronic and photonic devices. This paper attempts to, at least in part, capture this important aspect of Gossard’s continuing research contributions by reviewing three disparate examples, along with their device applications: epitaxial regrowth, digital alloy growth, and metal:semiconductor nanocomposites.
Acoustics Apps: Interactive simulations for digital teaching and learning of acoustics
Authors: Moheit Lennart , Schmid Johannes D. , Schmid Jonas M. , Eser Martin , Marburg Steffen
Published: February 2021

This paper presents the Acoustics Apps, an e-learning platform that offers an interactive and playful environment for teaching and learning the principles of acoustics and vibration. The Acoustics Apps address the increasing demand for digitized teaching methods, which might be suitable for home schooling or as a complement to physical experiments by adding interactive simulation. The apps combine learning by experimenting, observing, and exploring using state-of-the-art scientific methods and numerical simulations. The ability to visualize and control acoustic phenomena facilitates understanding of the relevant physical principles. The apps are designed to be used intuitively and can be tailored to suit the existing knowledge of the user. As such, a wide range of users can benefit from this learning aid. It has been developed to allow barrier-free access to modern educational tools, requiring only a device with a browser and Internet access. The necessary computing power is provided by an external server using the COMSOL ServerTM technology. The Acoustics Apps are freely available for academic and teaching purposes at apps.vib.mw.tum.de.
Cygnus X-1 contains a 21–solar mass black hole—Implications for massive star winds
Authors: Miller-Jones James C. A. , Bahramian Arash , Orosz Jerome A. , Mandel Ilya , Gou Lijun , Maccarone Thomas J. , Neijssel Coenraad J. , Zhao Xueshan , Ziółkowski Janusz , Reid Mark J. , Uttley Phil , Zheng Xueying , Byun Do-Young , Dodson Richard , Grinberg Victoria , Jung Taehyun , Kim Jeong-Sook , Marcote Benito , Markoff Sera , Rioja María J. , Rushton Anthony P. , Russell David M. , Sivakoff Gregory R. , Tetarenko Alexandra J. , Tudose Valeriu , Wilms Joern
Published: February 2021

A heavy black hole in an x-ray binary

If a black hole interacts with a binary companion star, the system emits x-rays and can form a radio jet. The masses of black holes in these x-ray binaries are all lower than those detected using gravitational waves, challenging models of black hole formation from massive stars. Miller-Jones
et al.
used radio astrometry to refine the distance to Cygnus X-1, a well-studied x-ray binary. They found a larger distance than previous estimates, raising the mass of the black hole in the system to 21 solar masses. The results challenge the wind mass loss rates implemented in stellar evolution models.

Science
, this issue p.
1046
“
Sifarchaeota
,” a Novel Asgard Phylum from Costa Rican Sediment Capable of Polysaccharide Degradation and Anaerobic Methylotrophy
Authors: Farag Ibrahim F. , Zhao Rui , Biddle Jennifer F.
Published: February 2021

The exploration of deep marine sediments has unearthed many new lineages of microbes. The finding of this novel phylum of Asgard archaea is important, since understanding the diversity and evolution of Asgard archaea may inform also about the evolution of eukaryotic cells. The comparison of metabolic potentials of the Asgard archaea can help inform about selective pressures the lineages have faced during evolution.
Laboratory Evolution and Reverse Engineering of
Clostridium thermocellum
for Growth on Glucose and Fructose
Authors: Yayo Johannes , Kuil Teun , Olson Daniel G. , Lynd Lee R. , Holwerda Evert K. , van Maris Antonius J. A.
Published: February 2021

C. thermocellum
is an important candidate for sustainable and cost-effective production of bioethanol through consolidated bioprocessing. In addition to unsurpassed cellulose deconstruction, industrial application and fundamental studies would benefit from improvement of glucose and fructose consumption.
HIV-1 Nef-Induced Secretion of the Proinflammatory Protease TACE into Extracellular Vesicles Is Mediated by Raf-1 and Can Be Suppressed by Clinical Protein Kinase Inhibitors
Authors: Zhao Zhe , Fagerlund Riku , Baur Andreas S. , Saksela Kalle
Published: February 2021

Chronic immune activation contributes to the immunopathogenesis of human immunodeficiency virus type 1 (HIV-1) infection and is associated with poor recovery of the immune system despite potent antiretroviral therapy, which is observed in 10% to 40% drug-treated patients depending on the definition of immune reconstitution. We have previously shown that the HIV pathogenicity factor Nef can promote loading of the proinflammatory protease TACE into extracellular vesicles (EVs), and the levels of such TACE-containing EVs circulating in the blood correlate with low CD4 lymphocyte counts in HIV patients receiving antiretroviral therapy.
Supplemental Material: Detrital-zircon analyses, provenance, and late Paleozoic sediment dispersal in the context of tectonic evolution of the Ouachita orogen
Authors: Thomas W.A. , al. et
Published: February 2021

Table S2. Hf isotopic data.
Supplemental Material: Origin and age of the Shenshan tectonic mélange in the Jiangshan-Shaoxing-Pingxiang Fault and late Early Paleozoic juxtaposition of the Yangtze Block and the West Cathaysia terrane, South China
Authors: Wang Lijun , Lin Shoufa , al. et
Published: February 2021

Photos of acritarchs, table of U-Pb zircon data and results of mixture modeling of U-Pb zircon data from the Shenshan tectonic mélange of South China.
Global trends in adolescents’ road traffic injury mortality, 1990–2019
Authors: Khan Uzma Rahim , Razzak Junaid A , Wärnberg Martin Gerdin
Published: February 2021

Objective

The aim of this study was to determine the trends of road traffic injury (RTI) mortality among adolescents aged 10–14 years and 15–19 years across different country income levels with respect to the type of road users from 1990 to 2019.

Methods

We conducted an ecological study. Adolescents’ mortality rates from RTIs at the level of high-income countries (HICs), upper-income to middle-income countries (UMICs), lower-income to middle-income countries and low-income countries were extracted from the Global Burden of Disease study. Time series were plotted to visualise the trends in mortality rates over the years. We also conducted Poisson regression using road traffic mortality rates as the dependent variable and year as the independent variable to model the trend of the change in the annual mean mortality rate, with incidence rate ratios (IRRs) and 95% CIs.

Results

There were downward mortality trends in all types of road users and income levels among adolescents from 1990 to 2019. HICs had more pronounced reductions in mortality rates than countries of any other income level. For example, the reduction in pedestrians in HICs was IRR 0.94 (95% CI 0.90 to 0.98), while that in UMICs was IRR 0.97 (95% CI 0.95 to 0.99) in adolescents aged 10-14 years.

Conclusions

There are downward trends in RTI mortality in adolescents from 1990 to 2019 globally at all income levels for all types of road users. The decrease in mortality rates is small but a promising finding. However, prevention efforts should be continued as the burden is still high.
Unexpected death in children with severe congenital heart defects in Norway 2004–2016
Authors: Wik Gunnar , Jortveit Jarle , Sitras Vasileios , Døhlen Gaute , Rønnestad Arild E , Holmstrøm Henrik
Published: February 2021

Aims

Updated knowledge on the rates and causes of death among children with severe congenital heart defects (CHDs) is needed to further improve treatment and survival. This study investigated nationwide mortality rates in children with severe CHDs with an emphasis on unexpected mortality unrelated to cardiac intervention.

Methods and results

Data on all pregnancies and live-born children in Norway from 2004 to 2016 were obtained from national registries, the Oslo University Hospital’s Clinical Registry for CHDs and medical records. Among 2359 live-born children with severe CHDs, 234 (10%) died before 2 years of age. Of these, 109 (46%) died in palliative care, 58 (25%) died of causes related to a cardiac intervention and 67 (29%) died unexpectedly and unrelated to a cardiac intervention, either before (n=26) or following (n=41) discharge after a cardiac intervention. Comorbidity (38/67, 57%), persistent low oxygen saturation (SaO2; <95%; 41/67, 61%), staged surgery (21/41, 51%), residual cardiac defects (22/41, 54%) and infection (36/67, 54%) were frequent in children who died unexpectedly unrelated to an intervention. Two or more of these factors were present in 62 children (93%). The medical reports at hospital discharge lacked information on follow-up in many patients who died unexpectedly.

Conclusions

The numbers of unexpected deaths unrelated to cardiac intervention in children <2 years of age without comorbidity were low in Norway. However, close follow-up is recommended for infants with comorbidities, persistent low oxygen saturation, staged surgery or residual cardiac defects, particularly when an infection occurs.
Usefulness of video recordings for validating neonatal encephalopathy exams: a population-based cohort study
Authors: Arnaez Juan , Vega-Del-Val Cristina , Hortigüela Montesclaros , Benavente-Fernández Isabel , Martínez-Biarge Miriam , Ochoa Sangrador Carlos , Garcia-Alix Alfredo
Published: February 2021

Objective

To determine the usefulness of video recordings for validating neonatal encephalopathy (NE) exams.

Design

Population-based prospective cohort study. NE was assessed and recorded at 1, 3 and 5 hours after birth by the attending physician. Recordings were reviewed blindly after the recruitment period by two specialists. Outcome was assessed at 36 months of age.

Setting

Twelve intensive care units in Spain.

Patients

Infants of ≥35 weeks’ gestational age with perinatal asphyxia.

Main outcomes measures

Weighted kappa to measure disagreement between the two specialists and between the attending physician and the specialists’ classification agreed on by consensus. Regression models to test the association of disagreement on NE assessment and outcome.

Results

Of the 32 325 liveborn infants, 217 met the inclusion criteria. Video-recordings were not available for 43 infants (20%). Weighted kappa statistic was 0.74 (95% CI 0.67 to 0.81) between the specialists and the attending physicians. Disagreement occurred in 93 of the 417 (22%) videos, specifically in 39 (14%), 43 (47%), 11 (34%) and 0 exams categorised as no, mild, moderate and severe NE, respectively. According to the specialist consensus assessment, there was disagreement on the therapeutic hypothermia decision in 10 infants.

When there was consensus among the specialists assessing a more severe NE degree compared with the attending physicians in 170 infants, those infants had lower cognitive scores with a median of −5.33 points (95% CI −9.85 to −8.16; p=0.02).

Conclusions

This study supports the feasibility and benefit of using video recordings to identify NE in infants with perinatal asphyxia.
Tear secretion from the lacrimal gland: variations in normal versus dry eyes
Authors: Singh Swati , Shanbhag Swapna S , Basu Sayan
Published: February 2021

Purpose

To investigate the secretory status of the main lacrimal gland in healthy and dry eye disease (DED) via fluorescein-assisted direct assessment of tear secretion from the palpebral lobes.

Methods

Included were 25 healthy subjects (50 lobes) and 75 subjects with DED (cicatrising conjunctivitis (CC, n=27), evaporative dry eyes (EDE, n=25) and Sjogren’s syndrome (SS, n=23)). Analysed parameters included number and location of ductular openings, tear flow rate per gland and per ductule, and the time lag for the initiation of secretion.

Results

Ductular openings could be observed in all patients with EDE and healthy subjects whereas only 33% (18/54) glands of CC patients and 67% glands (31/46) patients with SS revealed ductules. The median number of ductules per lobe was 4 in normal (range 3–5), 3 in EDE (3–6), 1 in SS (0–3) and 0 in CC group (0–3) (p<0.000001). The median tear flow rate per lobe in CC (0.00 μL/min) and SS (0.21 μL/min) was significantly lesser than normal lobes (1.05 μL/min, and EDE (0.99 μL/min eyes. The tear flow rate differed significantly between SS and CC group (p<0.0001). The maximum time lag occurred in the CC group (median, 20 s), followed by the SS group (median, 1.5 s) whereas the EDE group had similar time lag (<1 s) as of normal glands (p<0.0001).

Conclusion

Direct assessment of tear secretion from the palpebral lobe demonstrates significant differences between EDE, aqueous deficient dry eye and dry eye in CC.
Review of de novo uveitis in older adults presenting to a large tertiary centre
Authors: Samalia Priya , Hawley Luke Jeffrey , Niederer Rachael L , Sims Joanne
Published: February 2021

Background/aims

The primary aim of this study was to describe the causes of de novo uveitis in individuals 60 years and older. Secondary objectives were to determine the incidence of intraocular lymphoma and the clinical predictors of lymphoma.

Methods

Retrospective chart review of all subjects presenting to the uveitis service at Auckland District Health Board (Auckland, New Zealand) between January 2006 and October 2020

Results

686 subjects (900 eyes) were aged ≥60 years at first presentation with uveitis, representing 23.4% of all subjects with uveitis during the study period. Non-infectious aetiology occurred in 631 (70.1%) eyes and infectious etiologies occurred in 269 (29.9%) eyes. The most frequent causes were idiopathic (36.3%), herpes zoster (14.8%), HLAB27 (8.7%) and sarcoidosis (4.8%). Twenty (2.2%) eyes of 13 (1.9%) subjects had a diagnosis of lymphoma. Lymphoma represented 11.2% of all intermediate uveitis. Subjects diagnosed with lymphoma did not develop posterior synechiae, epiretinal membrane, cystoid macular oedema or ocular hypertension.

Conclusions

Intraocular lymphoma was uncommon in the overall cohort, but an important cause of intermediate uveitis. A diagnosis of lymphoma needs to be considered in any older subject with de novo intermediate uveitis. The lack of posterior synechiae, cystoid macular oedema, epiretinal membrane and ocular hypertension further increases the suspicion for lymphoma.
Food anaphylaxis in the United Kingdom: analysis of national data, 1998-2018
Authors: Baseggio Conrado Alessia , Ierodiakonou Despo , Gowland M Hazel , Boyle Robert J , Turner Paul J
Published: February 2021

Objective

To describe time trends for hospital admissions due to food anaphylaxis in the United Kingdom over the past 20 years.

Design

Analysis of national data, 1998-2018.

Setting

Data relating to hospital admissions for anaphylaxis and deaths, and prescription data for adrenaline autoinjector devices.

Participants

UK population as a whole and devolved nations (England, Scotland, Wales, and Northern Ireland).

Main outcome measures

Time trends, age, and sex distributions for hospital admissions for anaphylaxis due to food and non-food triggers, and how these admission rates compare with the case fatality rate (number of fatalities as a proportion of hospital admissions).

Results

Between 1998 and 2018, 101 891 people were admitted to hospital for anaphylaxis. Of these admissions, 30 700 (30.1%) were coded as due to a food trigger. Food anaphylaxis admissions increased from 1.23 to 4.04 per 100 000 population per year (from 1998 to 2018), an annual increase of 5.7% (95% confidence interval 5.5% to 5.9%, P<0.001). The largest increase in hospital admissions was observed in children younger than 15 years, with an increase from 2.1 to 9.2 admissions per 100 000 population per year (an annual increase of 6.6%, 95% confidence interval 6.3% to 7.0%). For comparison, the annual increase was 5.9% (5.6% to 6.2%) in people aged 15-59 years and 2.1% (1.8% to 3.1%) in those aged 60 years and older. 152 deaths were identified where the fatal event was probably caused by food induced anaphylaxis. The case fatality rate decreased from 0.7% to 0.19% for confirmed fatal food anaphylaxis (rate ratio 0.931, 95% confidence interval 0.904 to 0.959, P<0.001) and to 0.30% for suspected fatal food anaphylaxis (0.970, 0.945 to 0.996, P=0.024). At least 46% (86 of 187, which also includes 35 deaths in 1992-98) of deaths were triggered by peanut or tree nut. Cow’s milk was responsible for 17 of 66 (26%) deaths in school aged children. Over the same time period, prescriptions for adrenaline autoinjectors increased by 336% (estimated rate ratio 1.113, 95% confidence interval 1.112 to 1.113; an increase of 11% per year).

Conclusions

Hospital admissions for food induced anaphylaxis have increased from 1998 to 2018, however the case fatality rate has decreased. In school aged children, cow’s milk is now the most common single cause of fatal anaphylaxis.
Menstrual experience of adolescents in the USA: protocol for a scoping review
Authors: Olowojesiku Ronke , Shim Deborah J , Moppins Bryanna , Park Daye , Patterson Jasmine O , Schoenl Samantha A , Gaines Julie K , Sperr Edwin V , Baldwin Amy
Published: February 2021

Introduction

In recent years, there has been a growing desire to address issues related to menstruation, particularly for adolescent girls. In low-income and middle-income countries, prior literature review of the adolescent menstrual experience suggests the need for further research into the impact and efficacy of interventions with this population. There is evidence to suggest the need for initiatives and research in higher-income countries like the USA. To date, the body of research on adolescent menstrual experience in the USA remains uncharacterised. Therefore, we propose a scoping review of the literature on this subject to better inform on areas for future primary study.

Methods and analyses

Using the framework proposed by Arksey and O’Malley and expounded on by Levacet aland the Joanna Briggs Institute, we will search electronic databases (MEDLINE, CINAHL, PsycINFO, Web of Science, ProQuest Public Health Database, Social Science Citation Index, Social Services Abstracts and SocINDEX) and grey literature for relevant studies in consultation with experienced librarians. The abstracts and full-text from each reference will be screened by two independent reviewers for inclusion. Bibliographic data, study characteristics and themes will be extracted from studies selected for inclusion using a rubric created by the research team. Findings will be summarised and a list of subject areas for future primary research will be generated in consultation with stakeholders. The review will be conducted using the Preferred Reporting Items from Systematic Reviews and Meta-Analyses extension for Scoping Reviews guidelines.

Ethics and dissemination

Formal ethics training for this study is not required, as the research team will review publicly available studies. Stakeholders working in adolescent and menstrual health were consulted in designing this review. We will share key findings with stakeholders and in scholarly journals at the conclusion of the review.
Countermeasures against COVID-19: how to navigate medical practice through a nascent, evolving evidence base — a European multicentre mixed methods study
Authors: Eibensteiner Fabian , Ritschl Valentin , Stamm Tanja , Cetin Asil , Schmitt Claus Peter , Ariceta Gema , Bakkaloglu Sevcan , Jankauskiene Augustina , Klaus Günter , Paglialonga Fabio , Edefonti Alberto , Ranchin Bruno , Shroff Rukshana , Stefanidis Constantinos J , Vandewalle Johan , Verrina Enrico , Vondrak Karel , Zurowska Aleksandra , Alper Seth L , Aufricht Christoph
Published: February 2021

Objectives

In a previously published Delphi exercise the European Pediatric Dialysis Working Group (EPDWG) reported widely variable counteractive responses to COVID-19 during the first week of statutory public curfews in 12 European countries with case loads of 4–680 infected patients per million. To better understand these wide variations, we assessed different factors affecting countermeasure implementation rates and applied the capability, opportunity, motivation model of behaviour to describe their determinants.

Design

We undertook this international mixed methods study of increased depth and breadth to obtain more complete data and to better understand the resulting complex evidence.

Setting

This study was conducted in 14 paediatric nephrology centres across 12 European countries during the COVID-19 pandemic.

Participants

The 14 participants were paediatric nephrologists and EPDWG members from 12 European centres.

Main outcome measures

52 countermeasures clustered into eight response domains (access control, patient testing, personnel testing, personal protective equipment policy, patient cohorting, personnel cohorting, suspension of routine care, remote work) were categorised by implementation status, drivers (expert opinion, hospital regulations) and resource dependency. Governmental strictness and media attitude were independently assessed for each country and correlated with relevant countermeasure implementation factors.

Results

Implementation rates varied widely among response domains (median 49.5%, range 20%–71%) and centres (median 46%, range 31%–62%). Case loads were insufficient to explain response rate variability. Increasing case loads resulted in shifts from expert opinion-based to hospital regulation-based decisions to implement additional countermeasures despite increased resource dependency. Higher governmental strictness and positive media attitude towards countermeasure implementation were associated with higher implementation rates.

Conclusions

COVID-19 countermeasure implementation by paediatric tertiary care centres did not reflect case loads but rather reflected heterogeneity of local rules and of perceived resources. These data highlight the need of ongoing reassessment of current practices, facilitating rapid change in ‘institutional behavior’ in response to emerging evidence of countermeasure efficacy.