bluuebunny/crossref_metadata_2025 huggingface dataset:
An Historical View of Mechanical Failure Prevention
Authors: Pusey Henry C.
Published: March 2021

This paper provides a general overview of developments and progress in mechanical failure prevention technology, primarily over, the last three decades. The principal reference sources used are the proceedings of the 50 conferences of the Mechanical Failures Prevention Group (MFPG), now the Society for Machinery Failure Prevention Technology (MFPT). Since many technical disciplines are involved in this complex technology, an attempt is made to place mechanical failure prevention in perspective. Discussion of the evolving technology is presented under four topic areas that serve to cover most of the elements of this broad-based field. These topics are Diagnostics and Prognostics, Failure Analysis, Life Extension and Durability, and Sensors Technology. Selected subtopics and methodologies are also discussed. The importance of the relationship and interaction of the numerous technical disciplines involved in mechanical failure prevention technology is stressed. Significant advancements in the technology are emphasized. Some technological gaps and problems that are yet to be solved are identified.
Damage Tolerance Assessment of a Paper Pulp Refiner Disk
Authors: Cartwright D. J. , Orbison J. G. , Kohler G. , Shah H.
Published: March 2021

As long as materials continue to have imperfections in their structure, failure by cracking will continue to be a consideration in design. Cracks may be the result of material in homogeneity, service loading and may also be introduced during the manufacturing of either, the material itself or the structure in which the material is used. In the presence of a crack, a structure is more prone to fail at stress levels lower than those based on standard yield criteria. Components such as rotating machinery store large amounts of energy during operation and a fracture resulting from cracks in the rotating parts can be especially dangerous. Thus it is necessary to consider the failure mode of fracture when designing the disk and this requires a knowledge of the stress intensity factor of the crack in the disk and the fracture toughness of the disk material. In the present work the Boundary Element Method combined with Subtraction of Bueckner Singular Fields is used to obtain weight functions for an internal radial crack in an annular disk. A previously developed, general representation, of the weight function leads to integrals that can be evaluated analytically to obtain the stress intensity factor. Stress intensity factors are determined for the disk, containing a radial crack in a typical pulp refiner and the minimum level of fracture.
Aggregation Functions for Engineering Design Trade-Offs
Authors: Scott Michael J. , Antonsson Erik K.
Published: March 2021

The Method of Imprecision (MoI) is a formal theory for the manipulation of preliminary design information that represents preferences among design alternatives with the mathematics of fuzzy sets. Using the MoI, different design tradeoff strategies can be applied. To date, two aggregation functions have been developed for the MoI, one representing a compensating strategy and one a non-compensating strategy. Other research on aggregation functions on fuzzy sets has focused on two classes of functions that are not suitable for engineering design. The general restrictions on design-appropriate aggregation functions are discussed, and a family of functions ranging from the non-compensating min to the compensating product of powers is presented. An application to preliminary engineering design is given.
Theoretical and Numerical Validation of the Stochastic Interrogation Experimental Method
Authors: Kimble Bart W. , Cusumano Joseph P.
Published: March 2021

Stochastic interrogation is an experimental method that uses transient trajectories starting at numerous pseudo-random initial conditions to obtain detailed information about the flow of a dynamical system in phase space. From this flow information, various global dynamical phenomena can be studied, such as the transition to complex basin boundaries, chaotic transients, and strange non-attracting sets. The existence of these features in turn allows the occurrence of a homoclinic bifurcation to be inferred, even when all attractors in a system are nonchaotic. In this paper, the validity of inferences made using the stochastic interrogation experimental method is checked with the aid of a numerical model, using theoretical predictions from Melnikov theory and direct computations of invariant manifolds.
Dynamic Response and Stability of Pressurized Gas Squeeze-Film Dampers
Authors: Arakere Nagaraj K. , Ravichandar B. C.
Published: March 2021

Compressible squeeze films, an important and interesting area in gas lubrication, have been relatively neglected in recent times. Aircraft engines are being designed with light weight flexible rotors operating at high speeds and temperatures that may eventually eliminate the use of oil lubrication. A gas or air SFD might be a viable alternative to a conventional oil damper, in high temperature applications that preclude the use of oil lubrication. Oil squeeze-film dampers currently being used for rotordynamic control will not be viable at temperatures above 350 °F, due to limitations on lubricant oil temperature. Gas SFD’s are well suited for use in high temperature gas lubricated foil bearings. This paper presents an analysis of pressurized air dampers, similar to a hydrostatic gas bearing. Pressurized air is supplied through a series of orifices in the bearing midplane. Air flows through the orifices and the resulting pressure forces are calculated using a simple gas-flow model, as in orifice compensated hydrostatic bearings.

A small perturbation analysis of the shaft center yields the stiffness and damping coefficients, for centered circular motions. Damping characteristics are studied for a range of parameters such as supply pressure, orifice diameter, pocket volume, orbit size, number of orifices and shaft speed. Results show that maximum damping forces are generated for near choking flow conditions. The damping force becomes negligible at frequencies above 350 Hz. For damping force to be present, the gas pressurization has to exert a force on the rotor opposing the instantaneous velocity, or, 90 degrees out of phase with displacement Linear stability of unbalanced dampers undergoing centered circular orbits, is also investigated, in view of their relevance to rotordynamics. Damper design curves are presented for various parameters.
Stability of Time Varying Systems
Authors: Colonius Fritz , Kliemann Wolfgang
Published: March 2021

The stability behavior of time varying systems can be studied using the concept of Lyapunov exponents and their corresponding Lyapunov subspaces. For linear time varying systems the entire Lyapunov spectrum can be approximated by the Floquet exponents of periodic systems. This leads to a variety of stability results, including the characterization of stability radii. Furthermore, a structural stability type theorem shows that stability features of time varying hyperbolic systems persist under small perturbations. For nonlinear time varying systems a stable manifold theorem allows us to interpret the linear results for the nonlinear system locally around an equilibrium point.
Vibration Suppression of a Flexible Beam Using Center Manifold Theory
Authors: Khajepour Amir , Golnaraghi Farid , Morris K. A.
Published: March 2021

In this paper we develop a nonlinear control strategy based on modal coupling using the center manifold theory. As an example we use the technique for vibration suppression of a flexible beam. The controller in this case is a mass-spring-dashpot mechanism which is free to slide along the beam. The equations of the plant/controller are coupled and nonlinear, and the linearized equations of the system have two uncontrollable modes. As a result, the performance of the system can not be improved by linear control theory or by most conventional nonlinear control techniques.

We use the normal forms method to simplify the center manifold equations and derive a relation which includes all system parameters. We then show that there exists a set of optimal controller parameters (feedback gains, controller damping and frequency) which maximized the energy dissipation. Finally we consider the stability and design issues, and use numerical simulation to verify the results.
On the Non-Linear Dynamics of a Traveling Cable With Small Sag
Authors: Reuter Christoph G. , Hagedorn Peter
Published: March 2021

Traveling cables or threadlines appear in a number of technical applications such as textile machinery, V-belts, ski lifts, funiculars and also in simple models of traveling webs in paper machinery. The mechanical models used so far, most often neglect the effect of sag due to the weight of the cable, although it is well known that in some cases it may be quite important. In this paper, the authors develop a particularly simple model for translating cables using the assumption that the longitudinal inertia forces are negligible in comparison to the transversal inertia forces if the sag of the cable is sufficiently small. This assumption has already been made in a study of linear vibrations of stationary cables in 1970 by Irvine & Caughey. This lead to surprising results which have also been verified experimentally in the laboratory.

The extended model presented in this paper includes gyroscopic and nonlinear terms in the equations of motion, related to the cable transport velocity and geometric nonlinearities. As a particular case (zero longitudinal speed and linear theory) the model of Irvine & Caughey is again contained in the present analysis. The linear and non-linear vibrations about a steady state solution are studied. The results show some interesting features which may also be relevant to technical systems if the transport speed is sufficiently high.
Spectral Analyses of Nonlinear Interactions
Authors: Balachandran Balakumar , Khan Khalil A.
Published: March 2021

Signals pertaining to motions of nonlinearly coupled oscillators are studied using higher-order spectral analyses. The analyses is used to understand the role of phase coupling in nonlinear interactions between two or more Fourier components. For certain motions of weakly nonlinear systems, analytical approximations are obtained for relevant higher-order spectra and coherence functions. Numerical studies are conducted to verify analytical predictions and to illustrate the usefulness of spectral analyses for different cases.
Dynamics of Geometrically Exact Sandwich Beams/1-D Plates: Computational Aspects
Authors: Vu-Quoc L. , Deng H.
Published: March 2021

A Galerkin projection of the equation of motion of geometrically-exact sandwich beams, applicable to 1-D plates, formulated in Vu-Quoc & Ebcioğlu [1995] is presented here. The beam could take any arbitrary initial position in the 2-D space. Each layer of the beam could have different material constants with no restriction on the mass distribution and layer thickness; further, each layer could take on different length, thus allows the modeling of multilayer structures with ply drop-off. Finite rotations and shear deformation are accommodated for in each layer. The deformed cross section of the beam is continuous, piecewise linear. The continuity of displacement across the interlayer boundaries is exactly enforced. Extensive numerical examples including sandwich structures with ply drop-off, free flying and spin up maneuver of sandwich beams are presented to illustrate the applicability and versatility of the proposed formulation.
Analysis of a Nonlinear Friction Damping Mechanism in a Fluid-Structure Interaction System
Authors: Gottlieb Oded , Feldman Michael , Yim Solomon C. S.
Published: March 2021

Analysis of a nonlinear friction damping mechanism in a fluid-structure interaction system is performed by combining a generalized averaging procedure with a recently developed identification algorithm based on the Hilbert transform. The system considered includes a nonlinear restoring force and a nonlinear dissipation force incorporating both viscous and structural damping. Frequency and damping response backbone curves obtained from simulated data are compared with analytical and approximate solutions and are found to be accurate. An example large scale experiment exhibiting viscous and Coulomb damping is also analyzed resulting in identification of system parameters.
Experimental Investigation of Friction Dynamics Associated With Normal Load
Authors: Dupont Pierre E. , Kasturi Prakash S.
Published: March 2021

In the last five years, it has become clear that for a broad range of systems which exhibit significant friction, the dynamics of the friction itself must be included to reach a complete understanding of system stability and control issues. Dynamics associated with variations in velocity have received most of the attention while those associated with variations in normal load have been largely ignored. This paper presents results of ongoing research in the experimental identification of friction dynamics due to variations in both normal load and velocity for a line contact in boundary lubrication. Tests were conducted with inputs consisting of step changes in velocity and normal force. Our analyses indicate that a first or second order model is necessary to represent dynamic friction behavior associated with these inputs.
Matrix-Free Iterative Methods for Parallel Finite Element Computations in Acoustics
Authors: Malhotra Manish , Pinsky Peter M.
Published: March 2021

In this paper we consider the iterative solution of non-Hermitian, indefinite and complex-valued matrix problems arising from finite element discretization of time-harmonic acoustics problems in exterior domains. The computational model is based on using Galerkin least squares finite element methods for the acoustic fluid, combined with the non-local Dirichlet-to-Neumann map as the radiation boundary condition. The emphasis here is to develop efficient computational procedures that are suitable for parallel iterative solution of large-scale problems. In this context, we develop a low-storage implementation of the non-local DtN map which allows the use of this exact boundary condition without any storage penalties related to its non-local nature. In order to accelerate iterative convergence, we consider a multilevel preconditioning approach based on the h-version of the hierarchical finite element method. Finite element formulations that employ hierarchical shape functions yield better conditioned matrices than formulations based on the usual Lagrange functions. This improved conditioning translates into a faster rate of convergence if projections between nodal and hierarchical basis functions are used to construct the preconditioning operator. We present numerical results for the solution of two-dimensional scattering problems to examine convergence rates that are realized on practical discretizations.
Transient and Time-Harmonic Infinite Elements for Near-Surface Computations of Three-Dimensional Structures Submerged in a Half-Space
Authors: Kallivokas Loukas F. , Bielak Jacobo
Published: March 2021

This paper is concerned with the numerical solution by the finite element method of transient and time-harmonic three-dimensional acoustic scattering problems in infinite and semi-infinite domains. Its main objective is to illustrate how a local second-order surface-only infinite element — either transient or time-harmonic — developed recently for the three-dimensional wave equation in a full-space can be applied readily to scattering problems with penetrable objects near a planar free surface. Taking a problem in structural acoustics as a prototype, the combined infinite element-finite element method is used here to determine the total and scattered pressure patterns generated when a traveling plane wave impinges upon a structure of general geometry submerged in an acoustic fluid in half-space. One key feature of this methodology is that the ordinary differential equations that result from the spatial discretization maintain the symmetry and sparsity associated with problems defined only over interior domains; the resulting equations can then be solved by standard step-by-step time integration techniques. Thus, the combination of low bandwidth matrices with the ease of use of the infinite elements places the method in an ideal position to meet the large computational demands typically associated with large-scale underwater acoustics problems.
The Modified Boundary Element Method for Vibration and Sound Radiation Prediction of Fluid-Loaded Structures
Authors: Bernblit Michael V.
Published: March 2021

The objective of this study is to modify the conventional Boundary Element Method (BEM) to enable rigorous account of fluid loading. For this purpose the two-level BEM has been developed which allows to split structural and acoustical phases of the problem into two sequential stages. At first step fluid loading is ignored and the in-vacuo normal component of the surface velocity and structural Green’s function are calculated. Then surface pressure distribution is computed from the modified Boundary Integra] Equation with perturbated kernel. Secondly, vibration velocity of fluid-loaded surface is calculated using convolution of the surface pressure and the in-vacuo Green’s function. After that sound pressure is predicted for any control point by Helmholtz formula. The method is applied for volume and planar fluid-loaded radiators as well as to sound scattering by elastic bodies.
A Review of the Developments in the Boundary Element Method for Time-Domain Elastodynamics
Authors: Kaljević Igor , Saigal Sunil
Published: March 2021

The boundary element formulations for two-dimensional time-domain transient elastodynamics are reviewed in this paper. Several improvements of present formulations regarding the numerical integration of boundary element kernels and analysis of symmetric domains are presented. The deterministic transient formulations are next applied for analyzing problems with spatially random boundary conditions. The deficiencies of the present formulations are summarized and possible improvements are suggested.
Analysis and Experimental Evaluation of Inherent Instability in Electromagnetic Eddy-Current Dampers Intended for Reducing Lateral Vibration of Rotating Machinery
Authors: Kligerman Yuri , Grushkevich Asif , Darlow Mark S. , Zuckerberger Adrian
Published: March 2021

There have been a number of papers published that concern the design and operation of electromagnetic, eddy-current dampers for controlling lateral vibration of rotating machinery. Many of these papers have included analysis approaches and all have been generally effective for low-speed operations. There have been a few reports concerning high-speed (supercritical) operations and many of these have indicated instability problems, but none of these have provided a valid analysis to account for instability. That is, all of the analytical approaches have ignored the disk rotation, relative to the magnetic field, and no obvious sources of instability have been found. In this paper, we will present our work in which we have rederived the analyses of this system in which we have not made the common assumption of no rotation between the disk and the magnetic field. In this case, the potential of instability for supercritical speed operation is clear and, in fact, the equivalent negative damping contribution of the eddy-current damper, under these conditions, has a negative effect on the system even if not fully unstable. We have carefully performed a series of experimental tests which corroborate this analytical approach. Finally, we briefly discuss alternative eddy-current damper design approaches that could be considered to provide effective damping at all speeds and avoid these instability problems.
Vibration Analysis of Metal/Polymer/Metal Components
Authors: Mignery Lezza A.
Published: March 2021

In this report, a practical finite element design method is developed for metal/polymer/metal laminated components. An analysis is presented which will predict the damping characteristics of laminated structures. Predictions of natural frequencies, loss factors, and frequency responses are compared to experimental data and closed form solutions for simple geometries. The analysis is then used to determine the damping characteristics of a laminated design. It is then shown how to use the analysis to improve the damping quality of the component. With the methods presented here, components may be designed which reduce vibrations, noise, and fatigue wear by means of a practical finite element approach.
Complete Balancing of Multicylinder Engines Without Requiring Harmonic Balancers
Authors: Bagci Cemil
Published: March 2021

Presently used balancing methods for multicylinder engines and pumps are for partial balancing. As a result the complete shaking force, shaking torque, and shaking moment balancings of engines require the use of harmonic force and harmonic torque and moment balancers. This article presents a new method for complete shaking force and shaking moment balancing of multicylinder engines that requires no harmonic balancers. This is achieved by keeping the total center of mass of each slider crank loop stationary, where the design equations are developed using a linearly independent mass vector method. Balancing the shaking force also balances the shaking moment. Shaking torque is balanced by eliminating the angular momentum of each mechanism loop and by arranging the phase angles of the crank throws. Four-, six-, and eight-cylinder engines are balanced in the numerical examples given. Two methods of completely balancing single-cylinder engines are also given.
On the Number of Modes Required to Observe Forces in Flexible Structures
Authors: Clark William W. , Kim Joo Hyung , Marangoni Roy D.
Published: March 2021

The number of required modes to provide accurate force information in a truncated model of a flexible structure is investigated. In the context of modal truncation of a distributed parameter system, the difference in convergence rates between displacements and forces is discussed. The residual flexibility, a term from past literature, is used to recapture some of the lost force information in a truncated model. This paper presents numerical and experimental results of a study where the residual flexibility is used in conjunction with a Kalman filter so that accurate force information may be obtained from a small set of displacement measurements with a reduced-order model. The motivation for this paper is to be able to obtain accurate information about dynamic bearing loads in a rotating machine for diagnostic and control purposes.
Regularization of Some One-Dimensional Inverse Problems for Identification of Nonlinear Surface Phenomena
Authors: Groetsch C. W. , Hanke Martin
Published: March 2021

A simple numerical method for some one-dimensional inverse problems of model identification type arising in nonlinear heat transfer is discussed. The essence of the method is to express the nonlinearity in terms of an integro-differential operator, the values of which are approximated by a linear spline technique. The inverse problems are mildly ill-posed and therefore call for regularization when data errors are present. A general technique for stabilization of unbounded operators may be applied to regularize the process and a specific regularization technique is illustrated on a model problem.
Determination of Modal Residues and Residual Flexibility for Time-Domain System Realization
Authors: Alvin Kenneth F. , Peterson Lee D.
Published: March 2021

A linear least-squares procedure for the determination of modal residues using time-domain system realization theory is presented. The present procedure is shown to be theoretically equivalent to residue determination in realization algorithms such as the Eigen-system Realization Algorithm (ERA) and Q-Markov COVER. However, isolating the optimal residue estimation problem from the general realization problem affords several advantages over standard realization algorithms for structural dynamics identification. Primary among these are the ability to identify data sets with large numbers of sensors using small numbers of reference point responses, and the inclusion of terms which accurately model the effects of residual flexibility. The accuracy and efficiency of the present realization theory-based procedure is demonstrated for both simulated and experimental data.
Convergence and Large Deviations in a Bayesian Approach to Functional Estimation Problems
Authors: Fitzpatrick B. G. , Yin G.
Published: March 2021

We examine the large sample behavior of Bayesian posterior distributions in a nonlinear regression model for statistical inference in distributed parameter identification. Under suitable conditions, we prove the consistency of the parameter identification algorithm via Bayesian approach. We then derive large deviations results for independent, identically distributed error models. The large deviations ascertain the rate of convergence. We show that the convergence mentioned above is exponentially fast. That is, there exists a nonnegative function I defined on the parameter set such that πn(dq) ∼ exp(−nI(q))dp for almost all ω, where πn is the conditional distribution of the parameter, given the observations.
Identification of Parameters in Hereditary Systems
Authors: Hartung Ferenc , Turi Janos , Herdman Terry L.
Published: March 2021

In this paper we study the numerical performance of a parameter identification technique, based on approximation by equations with piecewise constant arguments, on various classes of hereditary systems. The examples considered here include delay equations with state-dependent delays and neutral equations.
Moderate- and High-Intensity Inspiratory Muscle Training Equally Improves Inspiratory Muscle Strength and Endurance—A Double-Blind Randomized Controlled Trial
Authors: Rehder-Santos Patricia , Abreu Raphael M. , Signini Étore De F. , da Silva Claudio D. , Sakaguchi Camila A. , Dato Carla C. , Catai Aparecida M.
Published: March 2021

Background and Objective: Inspiratory muscle training (IMT) produced outstanding results in the physical performance of active subjects; however, little is known about the best training intensity for this population. The objective was to investigate the impact of an IMT of high intensity, using the critical inspiratory pressure (CIP), on inspiratory muscle strength (IMS), inspiratory muscle endurance (IME), peak power, and oxygen uptake of recreational cyclists; and to compare these results with moderate-intensity IMT (60% of maximal inspiratory pressure [MIP]). Methods: Thirty apparently healthy male recreational cyclists, 20–40 years old, underwent 11 weeks of IMT (3 times per week; 55 min per session). Participants were randomized into 3 groups: sham group (6 cmH2O; n = 8); 60% MIP (MIP60; n = 10) and CIP (n = 12). All participants performed the IMS test and incremental IME test at the first, fifth, ninth, and 13th weeks of the experimental protocol. Cardiopulmonary exercise testing was performed on an electromagnetic braking cycle ergometer pre-IMT and post-IMT. Data were analyzed using a 2-way repeated measures ANOVA (group and period factors). Results: IMS increased in CIP and MIP60 groups at the ninth and 13th weeks compared with the sham group (P < .001; β = 0.99). Regarding IME, there was an interaction between the CIP and MIP60 groups in all periods, except in the initial evaluation (P < .001; β = 1.00). Peak power (in watts) increased after IMT in CIP and MIP60 groups (P = .01; β = 0.67). Absolute oxygen uptake did not increase after IMT (P = .49; β = 0.05). Relative oxygen uptake to lean mass values did not change significantly (P = .48; β = 0.05). Conclusion: High-intensity IMT is beneficial on IMS, IME, and peak power, but does not provide additional gain to moderate intensity in recreational cyclists.
Tapering and Repeated High-Intensity Effort Ability in Young Elite Rugby Union Players: Influence of Pretaper Fatigue Level
Authors: Vachon Adrien , Berryman Nicolas , Mujika Iñigo , Paquet Jean-Baptiste , Bosquet Laurent
Published: March 2021

Purpose: To assess the effects of a short-term taper on the ability to perform repeated high-intensity efforts, depending on players’ fatigue level following an intensive training block. Method: After a 3-day off-season camp, 13 players followed the same 3-week preseason training block followed by a 7-day exponential taper. Performance was assessed by a repeated high-intensity effort test before and after the taper. Total sprint time, percentage of decrement, and the number of sprints equal to or higher than 90% of the best sprint were retained for analysis. Players were a posteriori classified in normal training or acute fatigue groups based on their readiness to perform prior to the taper, assessed through the magnitude of difference in psychological (Profile of Mood State Questionnaire), cardiovascular (submaximal constant-duration cycling), and neuromuscular (countermovement jump) tests between the preintensive and postintensive training blocks. Results: Training load declined by 55% (9%) during the taper (P = .001, g = −2.54). The overall group showed a small improvement in total sprint time (−3.40% [3.90%], P = .04, g = −0.39) following the taper. Relative changes tended to be higher in the acute fatigue compared with the normal training group (−5.07% [4.52%] vs −1.45% [1.88%], respectively; P = .08; d = 1.01). No taper-induced improvement was observed in percentage of decrement or number of sprints equal to or higher than 90% of the best sprint. Conclusion: A 7-day taper consisting of 55% training load reduction improved repeated high-intensity effort performance in young elite rugby union players. Pretaper level of fatigue seems to be a key determinant in the taper supercompensation process, as acutely fatigued players at the end of the intensive training block tended to benefit more from the taper.
Reallocating Time From Sedentary Behavior to Physical Activity in Patients With Peripheral Artery Disease: Analyzing the Effects on Walking Capacity Using Compositional Data Analysis
Authors: Germano-Soares Antonio Henrique , Tassitano Rafael M. , Farah Breno Quintela , Andrade-Lima Aluísio , Correia Marília de Almeida , Gába Aleš , Štefelová Nikola , Puech-Leao Pedro , Wolosker Nelson , Cucato Gabriel Grizzo , Ritti-Dias Raphael Mendes
Published: March 2021

Background: To examine the associations between physical activity (PA) and sedentary behavior (SB) with walking capacity and the effects of reallocating time from SB to PA in patients with symptomatic peripheral artery disease (PAD) using compositional data analysis.Methods: This cross-sectional study included 178 patients (34% females, mean age = 66 [9] y, body mass index = 27.8 [5.0] kg/m2, and ankle-brachial index = 0.60 [0.18]). Walking capacity was assessed as the total walking distance (TWD) achieved in a 6-minute walk test, while SB, light-intensity PA, and moderate to vigorous-intensity PA (MVPA) were measured by a triaxial accelerometer and conceptualized as a time-use composition. Associations between time reallocation among wake-time behaviors and TWD were determined using compositional isotemporal substitution models.Results: A positive association of MVPA with TWD (relative to remaining behaviors) was found in men (βilr = 66.9, SE = 21.4,P = .003) and women (βilr = 56.5, SE = 19.8;P = .005). Reallocating 30 minutes per week from SB to MVPA was associated with higher TWD in men (6.7 m; 95% confidence interval, 2.6–10.9 m) and women (4.5 m; 95% confidence interval, 1.5–7.5 m).Conclusions: The findings highlight, using a compositional approach, the beneficial and independent association of MVPA with walking capacity in patients with symptomatic PAD, whereas SB and light-intensity PA were not associated.
Primordial GATA6 macrophages function as extravascular platelets in sterile injury
Authors: Zindel J. , Peiseler M. , Hossain M. , Deppermann C. , Lee W. Y. , Haenni B. , Zuber B. , Deniset J. F. , Surewaard B. G. J. , Candinas D. , Kubes P.
Published: March 2021

Macrophages seal 'em in the coelom

GATA6
+
macrophages resident in body cavities exhibit both phagocytic and repair functions. However, the mechanisms by which these cells can identify and migrate to sites of injury have remained unclear. Using intravital imaging of mouse peritoneal cavities, Zindel
et al.
report that GATA6
+
macrophages rapidly assemble clot-like structures in a process strongly analogous to thrombosis (see the Perspective by Herrick and Allen). The formation of these aggregates requires the expression of macrophage scavenger receptor domains and acts to plug wounds and promote healing. This pathway can be inadvertently activated during medical procedures, when macrophage aggregates can promote the generation of abdominal scar tissue known as adhesions. Inhibition of macrophage scavenger receptors may therefore be a useful therapeutic approach after surgeries that cause injury to body cavities.

Science
, this issue p.
eabe0595
; see also p.
993
Whirls and swirls of polarization
Authors: Martin Lane W.
Published: March 2021

Exotic toroidal polarization textures in a polymer ferroelectric interact with terahertz radiation
Whole-Genome Enrichment and Sequencing of Chlamydia trachomatis Directly from Patient Clinical Vaginal and Rectal Swabs
Authors: Bowden Katherine E. , Joseph Sandeep J. , Cartee John C. , Ziklo Noa , Danavall Damien , Raphael Brian H. , Read Timothy D. , Dean Deborah
Published: March 2021

Chlamydia trachomatis
is an obligate intracellular bacterium that is not easily cultured, which limits our understanding of urogenital and rectal
C. trachomatis
transmission and impact on morbidity. To provide a publicly available workflow for whole-genome target enrichment and sequencing of
C. trachomatis
directly from clinical urine, vaginal, conjunctival, and rectal specimens, we developed and report on an RNA bait library to enrich the organism from clinical samples for sequencing.
Serum Antibody Responses against Carbapenem-Resistant Klebsiella pneumoniae in Infected Patients
Authors: Banerjee Kasturi , Motley Michael P. , Diago-Navarro Elizabeth , Fries Bettina C.
Published: March 2021

Carbapenem-resistantKlebsiella pneumoniaeis a rapidly emerging public health threat that can cause fatal infections in up to 50% of affected patients. Due to its resistance to nearly all antimicrobials, development of alternate therapies like antibodies and vaccines is urgently needed.
Periprosthetic joint infection withUreaplasma parvumdetected by 16S rRNA PCR
Authors: Ball Nicola Diane , Snape Susan Elizabeth
Published: March 2021

Usual culture methods to identify pathogenic bacteria can be unsuccessful, particularly when working with fastidious organisms. We present a case of early periprosthetic knee joint infection withUreaplasma parvumonly identified using 16S ribosomal RNA PCR. This case represents the impact molecular methods of bacterial identification can have on clinical care allowing for more targeted antimicrobial therapy; something which is imperative in an era of increasing antimicrobial resistance.
Methylation status of vault RNA 2-1 promoter is a predictor of glycemic response to glucagon-like peptide-1 analog therapy in type 2 diabetes mellitus
Authors: Lin Chia-Hung , Lee Yun-Shien , Huang Yu-Yao , Tsai Chi-Neu
Published: March 2021

Introduction

Therapeutic efficiency of glucagon-like peptide-1 (GLP-1) analog is about 50%–70% in type 2 diabetes mellitus (T2DM). Discovery of potential genetic biomarkers for prediction of treatment efficiency of GLP-1 analog before therapy is still necessary. We assess whether DNA methylation was associated with glycemic response to GLP-1 analog therapy in patients with poorly controlled T2DM.

Research design and methods

Genomic DNA was extracted from the peripheral blood of training (n=10) and validation (n=128) groups of patients with T2DM receiving GLP-1 analogs. DNA methylome was analyzed using Infinium Human Methylation EPIC Bead Chip in the training group. The candidate genes were examined using a pyrosequencing platform in the validation group. The association between DNA methylation status and glycemic response to GLP-1 was analyzed in these patients.

Results

The most differential methylation region between those with a good (responsive) and poor (unresponsive) glycemic response to GLP-1 analog therapy was located on chromosome 5q31.1 (135415693 to 135416613), the promoter ofVTRNA2-1in the training group. The methylation status of theVTRNA2-1promoter was examined in the validation group via pyrosequencing reaction, and the hypomethylation ofVTRNA2-1(<40% methylation) was significantly associated with poor glycemic response to GLP-1 treatment (OR 2.757, 95% CI 1.240 to 6.130, p=0.011). Since theVTRNA2-1promoter region was previously reported maternal imprinting extended to the adjacent centromeric CCCTC-binding factor site that contained an A/C polymorphism (rs2346018), which was associated with methylation density ofVTRNA2-1, this A/C polymorphism was also integrated to analyze association with glycemic response to GLP-1 analog therapy. In patients with the A allele of rs2346018 and hypomethylation (<40%) on theVTRNA2-1promoter, the OR increased to 4.048 (95% CI 1.438 to 11.389, p=0.007).

Conclusions

The glycemic response to GLP-1 analog treatment is associated with the methylation status of theVTRNA2-1promoter and polymorphism of rs2346018.
In-Motion-App for remote General Movement Assessment: a multi-site observational study
Authors: Adde Lars , Brown Annemette , van den Broeck Christine , DeCoen Kris , Eriksen Beate Horsberg , Fjørtoft Toril , Groos Daniel , Ihlen Espen Alexander F , Osland Siril , Pascal Aurelie , Paulsen Henriette , Skog Ole Morten , Sivertsen Wiebke , Støen Ragnhild
Published: March 2021

Objectives

To determine whether videos taken by parents of their infants’ spontaneous movements were in accordance with required standards in the In-Motion-App, and whether the videos could be remotely scored by a trained General Movement Assessment (GMA) observer. Additionally, to assess the feasibility of using home-based video recordings for automated tracking of spontaneous movements, and to examine parents’ perceptions and experiences of taking videos in their homes.

Design

The study was a multi-centre prospective observational study.

Setting

Parents/families of high-risk infants in tertiary care follow-up programmes in Norway, Denmark and Belgium.

Methods

Parents/families were asked to video record their baby in accordance with the In-Motion standards which were based on published GMA criteria and criteria covering lighting and stability of smartphone. Videos were evaluated as GMA ‘scorable’ or ‘non-scorable’ based on predefined criteria. The accuracy of a 7-point body tracker software was compared with manually annotated body key points. Parents were surveyed about the In-Motion-App information and clarity.

Participants

The sample comprised 86 parents/families of high-risk infants.

Results

The 86 parent/families returned 130 videos, and 121 (96%) of them were in accordance with the requirements for GMA assessment. The 7-point body tracker software detected more than 80% of body key point positions correctly. Most families found the instructions for filming their baby easy to follow, and more than 90% reported that they did not become more worried about their child’s development through using the instructions.

Conclusions

This study reveals that a short instructional video enabled parents to video record their infant’s spontaneous movements in compliance with the standards required for remote GMA. Further, an accurate automated body point software detecting infant body landmarks in smartphone videos will facilitate clinical and research use soon. Home-based video recordings could be performed without worrying parents about their child’s development.

Trials registration number

NCT03409978.
Patients’ and healthcare professionals’ beliefs, perceptions and needs towards chronic kidney disease self-management in China: a qualitative study
Authors: Shen Hongxia , van der Kleij Rianne M J J , van der Boog Paul J M , Wang Wenjiao , Song Xiaoyue , Li Zhengyan , Lou Xiaoping , Chavannes Niels
Published: March 2021

Objectives

To support the adaptation and translation of an evidence-based chronic kidney disease (CKD) self-management intervention to the Chinese context, we examined the beliefs, perceptions and needs of Chinese patients with CKD and healthcare professionals (HCPs) towards CKD self-management.

Design

A basic interpretive, cross-sectional qualitative study comprising semistructured interviews and observations.

Setting

One major tertiary referral hospital in Henan province, China.

Participants

11 adults with a diagnosis of CKD with CKD stages G1–G5 and 10 HCPs who worked in the Department of Nephrology.

Results

Four themes emerged: (1) CKD illness perceptions, (2) understanding of and motivation towards CKD self-management, (3) current CKD practice and (4) barriers, (anticipated) facilitators and needs towards CKD self-management. Most patients and HCPs solely mentioned medical management of CKD, and self-management was largely unknown or misinterpreted as adherence to medical treatment. Also, the majority of patients only mentioned performing disease-specific acts of control and not, for instance, behaviour for coping with emotional problems. A paternalistic patient–HCP relationship was often present. Finally, the barriers, facilitators and needs towards CKD self-management were frequently related to knowledge and environmental context and resources.

Conclusions

The limited understanding of CKD self-management, as observed, underlines the need for educational efforts on the use and benefits of self-management before intervention implementation. Also, specific characteristics and needs within the Chinese context need to guide the development or tailoring of CKD self-management interventions. Emphasis should be placed on role management and emotional coping skills, while self-management components should be tailored by addressing the existing paternalistic patient–HCP relationship. The use of electronic health innovations can be an essential facilitator for implementation.
Description of symptom course in a telemedicine monitoring clinic for acute symptomatic COVID-19: a retrospective cohort study
Authors: O'Keefe James B , Tong Elizabeth J , O'Keefe Ghazala D , Tong David C
Published: March 2021

Objective

Describe the disease course in a cohort of outpatients with COVID-19 and evaluate factors predicting duration of symptoms.

Design

Retrospective cohort study.

Setting

Telemedicine clinic at a large medical system in Atlanta, Georgia.

Participants

337 patients with acute COVID-19. Exclusion criteria included intake visit more than 10 days after symptom onset and hospitalisation prior to intake visit.

Main outcome measures

Symptom duration in days.

Results

Common symptoms at intake visit are upper respiratory (73% cough, 55% loss of smell or taste, 57% sinus congestion, 32% sore throat) and systemic (66% headache, 64% body aches, 53% chills, 30% dizziness, 36% fever). Day of symptom onset was earliest for systemic and upper respiratory symptoms (median onset day 1 for both), followed by lower respiratory symptoms (day 3, 95% CI 2 to 4), with later onset of gastrointestinal symptoms (day 4, 95% CI 3 to 5), when present. Cough had the longest duration when present with median 17 days (95% CI 15 to 21), with 42% not resolved at final visit. Loss of smell or taste had the second longest duration with 14 days (95% CI 12 to 17), with 38% not resolved at final visit. Initial symptom severity is a significant predictor of symptom duration (p<0.01 for multiple symptoms).

Conclusions

COVID-19 illness in outpatients follows a pattern of progression from systemic symptoms to lower respiratory symptoms and persistent symptoms are common across categories. Initial symptom severity is a significant predictor of disease duration for most considered symptoms.
Drivers and mediators of healthcare workers’ anxiety in one of the most affected hospitals by COVID-19: a qualitative analysis
Authors: Fang Mengling , Xia Bo , Tian Tian , Hao Yan , Wu Zhenghao
Published: March 2021

Objective

To report the driving and mediating factors of healthcare workers’ anxiety during the COVID-19 pandemic.

Design

Qualitative indepth interview study.

Setting

The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.

Participants

53 healthcare workers who were or were not diagnosed with COVID-19.

Results

During the COVID-19 pandemic, healthcare workers were initially not sufficiently psychologically prepared. Then they suffered from severe anxiety and apprehension during the peak stage, regardless of whether they were infected with SARS-CoV-2 or not. These negative emotions were exacerbated by four drivers, namely infection risk, supplies, isolation and media. As the epidemic gradually came under control, healthcare workers experienced less anxiety from these factors, but became concerned about their low financial status. To reduce anxiety, healthcare workers diverted their attention from the risk of infection through personal entertainment and religious beliefs and focused on treating their patients. Furthermore, assistance from other people, including colleagues, families, friends, patients and society, helped protect healthcare workers from anxiety.

Conclusions

Personal and social support can relieve healthcare workers’ anxiety to some extent during the different stages of an epidemic. Both protective equipment and financial allowance motivate healthcare workers to focus on patient care, although the latter matters more as the epidemic comes under control.
Development of a convolutional neural network to differentiate among the etiology of similar appearing pathological B lines on lung ultrasound: a deep learning study
Authors: Arntfield Robert , VanBerlo Blake , Alaifan Thamer , Phelps Nathan , White Matthew , Chaudhary Rushil , Ho Jordan , Wu Derek
Published: March 2021

Objectives

Lung ultrasound (LUS) is a portable, low-cost respiratory imaging tool but is challenged by user dependence and lack of diagnostic specificity. It is unknown whether the advantages of LUS implementation could be paired with deep learning (DL) techniques to match or exceed human-level, diagnostic specificity among similar appearing, pathological LUS images.

Design

A convolutional neural network (CNN) was trained on LUS images with B lines of different aetiologies. CNN diagnostic performance, as validated using a 10% data holdback set, was compared with surveyed LUS-competent physicians.

Setting

Two tertiary Canadian hospitals.

Participants

612 LUS videos (121 381 frames) of B lines from 243 distinct patients with either (1) COVID-19 (COVID), non-COVID acute respiratory distress syndrome (NCOVID) or (3) hydrostatic pulmonary edema (HPE).

Results

The trained CNN performance on the independent dataset showed an ability to discriminate between COVID (area under the receiver operating characteristic curve (AUC) 1.0), NCOVID (AUC 0.934) and HPE (AUC 1.0) pathologies. This was significantly better than physician ability (AUCs of 0.697, 0.704, 0.967 for the COVID, NCOVID and HPE classes, respectively), p<0.01.

Conclusions

A DL model can distinguish similar appearing LUS pathology, including COVID-19, that cannot be distinguished by humans. The performance gap between humans and the model suggests that subvisible biomarkers within ultrasound images could exist and multicentre research is merited.