bluuebunny/crossref_metadata_2025 huggingface dataset:
Electro-Rheological-Fluid-Based Articulating Robotic Systems
Authors: Gandhi M. V. , Thompson B. S. , Shakir S.
Published: April 2021

The limitations of the current generation of robotic systems has triggered a new research thrust for predicting the elastodynamic response of assemblages of articulating flexible-bodied systems. This research thrust is extended herein by proposing the fabrication of robotic systems in either monolithic or ultra-advanced composite laminated high-strength, high-stiffness materials in which are incorporated electrorheological fluids. These multi-phase fluid systems, which change their rheological behavior instantaneously when subjected to an externally applied electrical field, provide a potential for tailoring the vibrational characteristics of these hybrid materials from which the structural members of the proposed robotic systems are fabricated.

This paper is focused on developing the necessary design tools for predicting the vibrational response of flexible multibodied articulating systems fabricated with this new class of advanced materials. A variational theorem is developed herein as a basis for finite element formulations which can be employed to predict the elastodynamic response of these systems. A coherent combination of experimental and theoretical work on cantilevered beams is presented to demonstrate the viability of the proposed design methodology. In addition, computer simulation results are presented to demonstrate the potential payoffs in terms of superior performance characteristics of a new generation of robotic systems capitalizing on this innovative and revolutionary design philosophy.
Structural Kinematics of Partially-Parallel Robotic Mechanisms
Authors: Mohamed M. Gaber
Published: April 2021

This paper introduces a new generation of robotic mechanisms. Such mechanisms are intermediate between the familiar serial and the fully-parallel robotic mechanisms. They usually comprise several subassemblies that are serially connected to one another. Each subassembly is basically an over constrained fully parallel kinematic chain. Such mechanisms are called “Partially-Parallel Robotic Mechanisms.” A type synthesis of planar and spatial partially-parallel robotic mechanisms is performed. Several practical designs are then introduced and studied for future robotic applications. Several performance criteria of this type of mechanisms are discussed and compared with those of serial as well as fully-parallel robotic mechanisms. Partially-parallel mechanisms are superior than serial mechanisms in rigidity, strength precision positioning and load carrying capacity. Furthermore, they are relatively less complex and have larger range of motion than fully-parallel mechanisms.
On the Workspace of Closed-Loop Manipulators With Ground-Mounted Rotary-Linear Actuators and Finite Size Platform
Authors: Weng Tzu-Chen , Sandor G. N. , Xu Yongxian , Kohli D.
Published: April 2021

This paper deals with the workspace of a closed-loop manipulator having three rotary-linear (R-L) actuators on ground-mounted cylindric joints, plus three revolute and three spheric pairs [1]. The workspace is defined as the reachable region of the origin of the moving coordinate system embedded in the six-degree-of-freedom platform of the manipulator. The regions in the workspace where the platform can rotate in any direction, cannot rotate or can rotate in only some directions have been defined as complete rotatability workspace (CRW), nonrotatability workspace (NRW) and partial rotatability workspace (PRW). Equations of the workspace of the platform which has a) complete theoretical rotatability and b) nonrotatability (when its center is on the boundary of the workspace) are respectively derived. The reachable region of the center of the platform, where this center remains in a plane with a given platform orientation, is also studied.
Primary Workspace of Simple Six-Link Robots
Authors: Lin E. Y. , Yang D. C. H. , Cheng S. Y.
Published: April 2021

This paper presents an analytical study on the primary workspace of some simple six-link robots. The approach is to divide the structure of a six-link robot into two subsystems, the regional structure and the wrist. Taking advantage of the kinematic simplicity of three-link subsystems, we at the same time are able to solve the problem of reassemblage of the subsystems by using the concept of vector fields at the connection. Two types of wrist, the Euler Angle wrist and the Roll-Pitch-Yaw wrist are considered. (For Roll-Pitch-Yaw wrist, only Cartesian and articulated regional structures are included). Criteria for these robots to access points from specific directions are firstly developed. The theorems regarding accessing points from all directions are then derived. Finally clean statements on the boundaries of primary workspace are made.
Cam Motion Synthesis Using Spline Functions: Part I — Basic Theory and Elementary Applications
Authors: Tsay D. M. , Huey C. O.
Published: April 2021

The application of spline functions to the general synthesis of cam motion programs is presented. The approach provides a single, systematic, easily automated method of accommodating discrete constraints on follower displacements, velocities, and accelerations, even when the set of constraints becomes large. It also allows the designer to develop refined motion characteristics while still satisfying the discrete constraints. A series of examples is presented to illustrate application of the method and to compare it to the more traditional techniques.
Cycloid Drives With Machining Tolerances: Part I — Kinematic Analysis
Authors: Blanche J. G. , Yang D. C. H.
Published: April 2021

The cycloidal speed reducer, or cycloid drive, is an epicyclic gear train in which the profile of the planet gear is an epitrochoid and the annular sun gear has rollers as its teeth. The cycloid drive has very high efficiency and small size, in comparison with a conventional gear mechanism, making it an attractive candidate for limited space applications. On the other hand, in this type of transmissions there exist two major drawbacks, namely, backlash and torque ripple Backlash, the angle through which the output shaft can rotate when the input shaft is held fixed, has a degrading effect on the output accuracy. Torque ripple, the variation in mechanical advantage as the input shaft rotates, causes vibrations and could lead to dynamic instability of the machinery. If the cycloid drive were manufactured to the ideal dimensions, there would be no backlash nor torque ripple. However, in reality, there will always be some machining tolerances. In this paper an analytical model is developed which models the cycloid drive with machining tolerances. This model is used in Part II of this investigation to determine the effect of machining tolerances on backlash and torque ripple. As a result, simple and practical equations for design synthesis of this type of drives are formulated.
Cycloid Drives With Machining Tolerances: Part II — Computer-Aided Design
Authors: Yang D. C. H. , Blanche J. G.
Published: April 2021

In this paper a computer-aided design package is developed for analyzing cycloid drives with machining tolerance. It is found that both the backlash and the torque ripple are periodic functions of the input crank angle. The frequency is equal to the number of teeth on the ring gear times the input shaft frequency. Also, simple and practical formulas for design synthesis of these types of transmissions are developed with the consideration of tolerance, drive parameters (gear ratio, normalized tooth height and pitch diameter) and performance indices (backlash and torque ripple).
Kinematic Displacement Analysis of a Double-Cardan-Joint Driveline
Authors: Fischer I. S. , Paul R. N.
Published: April 2021

The input-output displacement relations of two Cardan joints arranged in series on a driveline has been investigated in detail, including the effects of unequal joints angles, the phase angle between the two Cardan joints and also such manufacturing tolerance errors as non-rigth angle link lengths and offset joint axes.

A combined Newton-Raphson and Davidson-Fletcher-Powell optimization algorithm using dual-number coordinate-transformation matrices was employed to perform the analysis.

An experiment was conducted to validate the results of the analysis. The apparatus consisted of a double-Cardan-joint driveline whose rotations were measured by optical shaft encoders that were sampled by a computer data-acquisition system. The equipment was arranged so that the phase angle between the joints and the offset angles between the shafts at each of the two joints could be readily varied.

The “relative phase angle”, the difference between the phase angle of the two joints and the angle between the planes defined by the input and intermediate and the intermediate and output shafts, was found to be the significant factor. If the offset angles at both Cardan joints are equal, the double-Cardan-joint driveline function as a constant-velocity coupling when the magnitude of the relative phase angle is zero. If the offset angles at the two Cardan joints are unequal, a condition prevailing in the important front-wheel-drive automobile steering column, then fluctuation in output velocity for a constant input velocity is minimized although not eliminated for zero relative phase angle.
Singularities in Motion and Displacement Functions for the RCRCR RCRRC and RSRC Linkages: Part I — Basic Concepts
Authors: Litvin F. L. , Tan J. , Fanghella P. , Wu S.
Published: April 2021

A new approach for the determination of singularities in motion of spatial linkages, displacement functions and the number of linkage configurations is proposed. Singularities in motion occur at positions where an overconstrained group of links become movable at least locally while the driving link is fixed. The determination of displacement functions is based on modeling of the linkage by two open kinematic chains formed: (i) by links of an overconstrained group of links and (ii) the driving link and the frame. Conditions of “assembly” of the open chains provide invariants-scalar products-that yield the appropriate equations that relate the parameters in motion of the driving link and the overconstrained group of links. The number of linkage configurations is proposed to determine through the number of singularity positions that are simulated with a certain combination of the linkage design parameters. Applications of the proposed approach to the RCRCR, RCRRC and RSRC linkages are represented in the following parts 2, 3 and 4 of the paper.
Singularities in Motion and Displacement Functions for the RCRCR, RCRRC and RSRC Linkages: Part II — The RCRCR Linkage
Authors: Litvin F. L. , Tan J.
Published: April 2021

The general approach for the determination of singularities in motion and displacement functions for spatial linkages has been developed by Litvin, et al. (1986) and represented in the first part of this paper. Applications of the developed methods for the RCRCR linkage are given in this paper. The authors have determined the singularities in motion, displacement functions and the configurations of the linkage. Numerical examples are given.
Singularities in Motion and Displacement Functions for the RCRCR, RCRRC and RSRC Linkages: Part IV — The RSRC Linkage
Authors: Litvin F. L. , Wu S.
Published: April 2021

The basic ideas of this paper are based on the following considerations (see Litvin, et al., 1986, and Part I of this paper): (i) Singularities in motion occur at positions where the overconstrained group that is formed by links 2 and 3 becomes movable with respect to links 1 and 4 while the driving link 1 is held at rest (link 4 is the frame). (ii) The displacement functions are determined by modeling the linkage by two open kinematic chains. Configurations of the linkage are discussed. Numerical examples are given.
The Image Curve of the Motion of the Planet in a Spherical Epicyclic Gear Train
Authors: Ge Q. , McCarthy J. M.
Published: April 2021

This paper uses the Euler parameters of the motion of the planet of a spherical epicyclic gear train to obtain a curve on the surface of a hypersphere in four dimensions. This curve, called the image curve, represents the rotational motion of the planet as it rolls without slipping on the fixed gear. Two image curves are obtained for two different choices of moving and fixed reference frames and it is shown that they are related by an orthogonal transformation in four dimensional space. The differential properties of the image curve are computed and it is found that the curvature is constant and the torsion is periodic in the motion parameter. A reference position is chosen and the canonical frame and instantaneous invariants of the motion are determined in terms of the dimensions of the gear train.
A Substructure Technique for Dynamics of Flexible Mechanical Systems With Contact-Impact
Authors: Wu S.-C. , Haug E. J.
Published: April 2021

A substructure synthesis method is proposed to account for contact-impact effects in flexible components of mechanical systems. Components that may come into contact is divided into substructures, on each of which local deformation modes are defined to described deformation fields of components. Constraint modes and fixed interface normal modes are used to account for elastic deformation within each substructure. A constraint addition-deletion technique is used to account for contact between impacting bodies. Lagrange multipliers associated with the constraints, which represent constraint forces, are used to determine separation of contacting nodes. Use of the method is illustrated on problems of longitudinal and transverse impact of bodies.
Selection of Deformation Modes for Flexible Multibody Dynamics
Authors: Kim S.-S. , Haug E. J.
Published: April 2021

This paper presents a method of selecting boundary conditions and deformation modes for redundantly constrained flexible components in mechanical system dynamics. Gaussian elimination is used to partition the coefficient matrix in equilibrium equations for each flexible component, leading to definition of a retained statically determinate set and a redundant set of boundary conditions. Methods for selection of deformation modes is presented, to account for deformation due to constraint reaction forces. A door closing mechanism and a moving flexible beam illustrate the method of selecting boundary conditions and the effectiveness of constraint modes for approximation for system dynamic response.
Some Issues in the Generation of the Topology of Systems With Constant Power-Flow Input-Output Requirements
Authors: Prabhu D. R. , Taylor D. L.
Published: April 2021

In this paper, we examine design problems in which requirements consist of constant power-flows with constant effort and flow variables in various domains. The use of an outgrowth of bond graph structure for design is explored. A spanning set of functional primitives is determined which can assemble an arbitrary system meeting the above functional requirements. Some basic theorems are developed regarding generic assembly algorithms to build systems using elements belonging to the chosen set. Maximum and minimum bounds on complexity are determined. An optimal partitioning of specified requirements is obtained to minimize the number of primitives needed. Power-flows through each primitive used is subsequently minimized to obtain a minimal power-flow graph.
A Separating Channel Decomposition Algorithm for Non-Convex Polygons With Application in Interference Detection
Authors: Ku T. S. , Ravani B.
Published: April 2021

An algorithm for efficient decomposition of interface channels between non-convex polygons in a Computer-Aided Design (CAD) environment is presented. This algorithm forms the computational basis for the solution of several design automation problems. In this paper, the channel decomposition algorithm is presented and applied to the problem of interference detection between non-convex polygons. The resulting interference detection algorithm does not require preprocessing of the data and uses a simple data structure. In a companion paper (Ku and Ravani 1988), the channel decomposition algorithm is applied to the problem of model-based rigid-body guidance in presence of geometric constraints.
Optimal Design of Wind Turbines Using BIAS, A Method of Multipliers Code
Authors: Vick B. D. , Wrigglesworth W. , Scott L. B. , Ragsdell K. M.
Published: April 2021

A method has been developed and is demonstrated which determines the chord and twist distribution for a wind turbine with maximum power coefficient. Only small wind turbines (less than 10 kilowatts) are considered in this study, but the method could be used for larger wind turbines. Glauert determined a method for estimating the chord and twist distribution that will maximize the power coefficient if there is no drag. However, the method proposed here determines the chord and twist distribution which will maximize the power coefficient with the effect of drag included. Including drag in the analysis does not significantly affect the Glauert chord and twist distribution for airfoils with a high lift coefficient at the maximum lift to drag ratio. However, if the airfoil has a fairly low lift coefficient at its maximum lift to drag ratio due to its shape or a rough surface then significant improvement can be obtained in power coefficient by altering the Glauert chord and twist distribution according to the method proposed herein.
Part Layout Optimization Using a Quadtree Representation
Authors: Sandgren E. , Dworak T.
Published: April 2021

A nonlinear programming formulation is developed for minimizing the area required to position a set of pre-defined objects without overlap. The objects consist of polygons with an arbitrary number of edges. Nonconvex polygons are assumed which allows for the modelling of complex parts, including parte with holes. A quadtree representation is formed for each polygon and intersections are determined by traversing quadtrees for the potentially intersecting objects. The design variables are selected to be the x and y location and the rotation for each polygon that is to be positioned. An exterior penalty function method is used to generate the solution to the resulting nonlinear programming problem. A nongradient search technique is used due to the discrete nature of the overlap constraints. Example problems are presented and extensions to other classes of problems are discussed.
Optimal Design of Mechanisms Using Simulated Annealing: Theory and Applications
Authors: Jain P. , Agogino A. M.
Published: April 2021

A new approach to optimization in kinematic synthesis of mechanisms is presented which is based on simulated annealing, a probabilistic combinatorial optimization technique. The advantage of this technique is that it converges to the global optimum asymptotically. Simulated annealing has been successfully applied to solve several combinatorial optimization problems in the fields of computer-aided design of VLSI chips, image processing and graph theory. However, it has not been used as an optimization tool in the field of mechanical design. We solve three problems in kinematic synthesis using simulated annealing and the results show that the method is fast and obtains solutions at least as good as and in some cases better than those obtained by conventional optimization techniques.
Optimum Synthesis of Thin-Walled Vibrating Beams With Coupled Bending and Torsion
Authors: Grandhi R. V. , Moradmand J. K.
Published: April 2021

This paper considers the optimum structural design of vibrating beams in which the inertial axes and the elastic axes are non-collinear. The condition of non-collinear axes exists in structures having unsymmetric cross-sections. For unsymmetric crose-sections the centroid and the shear center do not coincide. This results in coupling between some of the bending and torsional modes. This paper presents results for the simply supported and cantilever beams with a thin-walled channel cross-section. The minimization of the structural volume subject to multiple frequency constraints and its dual problem of maximization of the fundamental frequency subject to a volume constraint are considered. A quadratic extended interior penalty function with Newton’s method of unconstrained minimization is used in structural optimization. The structures considered have non-structural masses besides their own mass.
A Generalized Expert System Shell for Implementing Mechanical Design Applications: Review, Introduction and Fundamental Concepts
Authors: Premkumar P. , Kramer S. N.
Published: April 2021

The foundations for an expert system shell for implementing mechanical design applications are presented in this paper. The shell supports facilities for knowledge acquisition, quasi-reactive planning, design evaluation, and subjective explanation. The underlying philosophy of each of these facilities and some preliminary implementation issues are discussed. A brief summary of a recent research effort and its implications on the development of a generalized expert system shell for implementing mechanical design applications are also presented.
A Graphical, User-Driven Newton-Raphson Technique for Use in the Analysis and Design of Compliant Mechanisms
Authors: Hill T. C. , Midha A.
Published: April 2021

The analysis and design of compliant mechanisms, undergoing large (geometrically nonlinear) deflections, have been assisted by the Newton-Raphson method to find the loads which satisfy a prescribed set of force and displacement boundary conditions. This paper introduces a graphical, user-driven Newton-Raphson technique that allows easy access to good initial design variable estimates, and subsequently accurate and expeditious solutions. These design variables may include loads as well as material and geometric properties of the beam segments composing the mechanism. A line search step-restriction technique is included to enhance the stability of the method. The method uses six-degree-of-freedom planar beam elements in a chain calculation that cumulatively evaluates the large deflections corresponding to a given load set.
Limitations of Conjugate Gear Tooth Surfaces in Order to Avoid Undercutting and Appearance of Envelope of Lines of Contact
Authors: Litvin F. L. , Kin D. J. , Zhang Y.
Published: April 2021

Gear tooth surfaces being in line contact at every instant are considered. The dimensions of the contacting surfaces must be limited in order to avoid: (i) the appearance of the envelope of lines of contact on the generating surface Σ1 and (ii) the appearance of singular points on the generated surface Σ2. The relations between the developed concepts and the Wildhaber’s concept of the limiting pressure angle are investigated. Applications to the worm-gear drive and the generation of a pinion of a formate gear drive are considered. Computer graphics have been used to illustrate the results of computation.
A Recursive Formulation for Real-Time Dynamic Simulation
Authors: Bae D.-S. , Hwang R. S. , Haug E. J.
Published: April 2021

A new recursive algorithm for real-time, interactive dynamic simulation, animated graphics, and design variation analysis is presented for mechanical systems with closed loops. State vector kinematic relations that represent translational and rotational motion are defined, to simplify the formulation and to relieve computational burden. Recursive equations of motion are first derived for a single loop multi-body system. Faster than real-time performance is demonstrated for a closed loop robot, using an Alliant FX/8 multiprocessor. The algorithm is extended to multi-loop, multi-body systems for parallel processing real-time simulation in companion papers [1,2]. Performance of the algorithm on a shared memory multi-processor is compared with that achieved with other dynamic simulation algorithms. A vehicle example is used to demonstrate efficiency of the algorithm for real-time simulation and graphics rendering in a network environment, for use as an interactive design tool.
N-type doping of low-pressure chemical vapor deposition grown β-Ga2O3 thin films using solid-source germanium
Authors: Ranga Praneeth , Bhattacharyya Arkka , Whittaker-Brooks Luisa , Scarpulla Michael A. , Krishnamoorthy Sriram
Published: April 2021

We report on the growth and characterization of Ge-doped β-Ga2O3 thin films using a solid germanium source. β-Ga2O3 thin films were grown using a low-pressure chemical vapor deposition reactor with either an oxygen or a gallium delivery tube. Films were grown on 6° offcut sapphire and (010) β-Ga2O3 substrates with growth rates between 0.5 and 22 μm/h. By controlling the germanium vapor pressure, a wide range of Hall carrier concentrations between 1017 and 1019 cm−3 were achieved. Low-temperature Hall data revealed a difference in donor incorporation depending on the reactor configuration. At low growth rates, germanium occupied a single donor energy level between 8 and 10 meV. At higher growth rates, germanium doping predominantly results in a deeper donor energy level at 85 meV. This work shows the effect of reactor design and growth regime on the kinetics of impurity incorporation. Studying donor incorporation in β-Ga2O3 is important for the design of high-power electronic devices.
Rheology of macro- and nano-emulsions in the presence of micellar depletion attraction
Authors: Sanatkaran Neda , Zhou Muchu , Foudazi Reza
Published: April 2021

In this work, we investigate the effect of interdroplet interaction on the rheological behavior of oil-in-water emulsions within a range of macro- to nano-droplet sizes and various volume fractions from dilute to concentrated regimes. We determine the total interdroplet interaction from electrostatic, van der Waals, and depletion attraction contributions. At constant surfactant concentration, the depth of attractive potential is much higher than kBT for submicron emulsions and macroemulsions, whereas it is on the order of thermal energy for nanoemulsions. Thus, as the droplet size decreases in systems with considerable yield stress below jamming transition, the emulsions undergo a gel-to-glass transition. The yield strain ranges of gel and glassy systems overlap, although the droplets in gels undergo the dissipative rearrangement before macroscopic translational motion.
‘Superagency’ may further politicize Indonesian research
Authors: Rochmyaningsih Dyna
Published: April 2021

New National Research and Innovation Agency will have broad powers to fund, execute, and control science.
Dynamic remodeling of host membranes by self-organizing bacterial effectors
Authors: Hsieh Ting-Sung , Lopez Victor A. , Black Miles H. , Osinski Adam , Pawłowski Krzysztof , Tomchick Diana R. , Liou Jen , Tagliabracci Vincent S.
Published: April 2021

Bacterial effectors manipulate membranes

Many pathogenic bacteria use molecular syringes to translocate proteins called effectors into the host cell to hijack the cellular machinery for their proliferation.
Legionella pneumophila
, the causative bacteria of Legionnaires' disease, uses a large effector arsenal and harnesses the host membrane system to establish a specialized vacuole where it replicates. Hsieh
et al.
show that, within this effector arsenal, the phospholipid kinase MavQ and the phosphatase SidP work together and self-organize on the intracellular membrane network of its eukaryotic host to promote membrane remodeling. The interactions between MavQ and SidP constitute positive and negative feedback loops, respectively, that orchestrate their spatiotemporal oscillation during infection.

Science
, aay8118, this issue p.
935
Electric field control of natural optical activity in a multiferroic helimagnet
Authors: Masuda Ryoji , Kaneko Yoshio , Tokura Yoshinori , Takahashi Youtarou
Published: April 2021

An optically active spiral

The material cupric oxide exhibits magnetoelectric coupling, meaning that its magnetic properties can be controlled by electric fields. In its spin spiral phase, cupric oxide has a spiral magnetic ordering that can be right- or left-handed. Masuda
et al.
used electric fields to create purely left- or right-handed samples and then studied their optical activity. The samples exhibited natural optical activity, which the researchers were then able to control with electric fields.

Science
, this issue p.
496
Imaging translation dynamics in live embryos reveals spatial heterogeneities
Authors: Dufourt Jeremy , Bellec Maelle , Trullo Antonio , Dejean Matthieu , De Rossi Sylvain , Favard Cyril , Lagha Mounia
Published: April 2021

Quantifying translation in space and time

During development, precise control of gene expression establishes reproducible patterns, leading to the formation of organs at the right time and place. The emergence of developmental patterns has been primarily studied at the transcriptional level, but the fate of these transcripts has received little attention. Dufourt
et al.
used the SunTag labeling method to image the dynamics of translation of individual messenger RNA (mRNA) molecules in living fruit fly embryos. This work revealed “translation factories”—clusters of mRNA and translation machinery—and heterogeneities in the efficiency of translation between identical mRNAs.

Science
, abc3483, this issue p.
840
Chronoculture, harnessing the circadian clock to improve crop yield and sustainability
Authors: Steed Gareth , Ramirez Dora Cano , Hannah Matthew A. , Webb Alex A. R.
Published: April 2021

The daily rhythms of agriculture

Sunlight drives agriculture, and plant circadian rhythms tune the plant's response to daily light-dark cycles. Steed
et al.
discuss how agricultural productivity might be improved by consideration of how the plant's circadian rhythm alters plant responses to the challenges posed by its environment.

Science
, this issue p.
eabc9141
The human dimension of biodiversity changes on islands
Authors: Nogué Sandra , Santos Ana M. C. , Birks H. John B. , Björck Svante , Castilla-Beltrán Alvaro , Connor Simon , de Boer Erik J. , de Nascimento Lea , Felde Vivian A. , Fernández-Palacios José María , Froyd Cynthia A. , Haberle Simon G. , Hooghiemstra Henry , Ljung Karl , Norder Sietze J. , Peñuelas Josep , Prebble Matthew , Stevenson Janelle , Whittaker Robert J. , Willis Kathy J. , Wilmshurst Janet M. , Steinbauer Manuel J.
Published: April 2021

Accelerating ecosystem disruption

Oceanic islands are among the most recent areas on Earth to have been colonized by humans, in many cases in just the past few thousand years. Therefore, they are important laboratories for the study of human impacts on natural vegetation and biodiversity. Nogué
et al.
provide a quantitative palaeoecological study of 27 islands around the world, focusing on pollen records of vegetation composition before and after human arrival. The authors found a consistent pattern of acceleration of vegetation turnover after human invasion, with median rates of change increasing by a factor of six. These changes occurred regardless of geographical and ecological features of the island and show how rapidly ecosystems can change and how island ecosystems are set on new trajectories.

Science
, this issue p.
488
Extreme oxidant amounts produced by lightning in storm clouds
Authors: Brune W. H. , McFarland P. J. , Bruning E. , Waugh S. , MacGorman D. , Miller D. O. , Jenkins J. M. , Ren X. , Mao J. , Peischl J.
Published: April 2021

Cleaning in a flash

Hydroxyl radicals (OH) are the most important oxidizing species in the atmosphere and provide much of its ability to cleanse itself. It is known that nitric oxide production by lightning leads to the formation of OH and other atmospheric oxidants, such as ozone and hydroperoxyl radicals (HO
2
), through a variety of chemical reactions. Brune
et al.
used airborne measurements of OH and HO
2
to show that lightning also produces them directly and in amounts much greater than expected. They found that this mechanism may be responsible for as much as one-sixth of the oxidizing capacity of Earth's atmosphere.

Science
, this issue p.
711
Determination of MIC Quality Control Parameters for Exebacase, a Novel Lysin with Antistaphylococcal Activity
Authors: Traczewski Maria M. , Ambler Jane E. , Schuch Raymond
Published: April 2021

Exebacase (CF-301), a novel, antistaphylococcal lysin (cell wall hydrolase) is the first agent of this class to enter late-stage clinical development (phase 3, NCT04160468) for the treatment of
Staphylococcus aureus
bacteremia, including right-sided endocarditis. A multilaboratory Clinical and Laboratory Standards Institute (CLSI) M23-defined tier 2 quality control (QC) study was conducted to establish exebacase QC ranges for a new reference broth microdilution method.
S. aureus
ATCC 29213 and
Enterococcus faecalis
ATCC 29212 were selected as reference QC strains.
Clinical characteristics of full thickness macular holes that closed without surgery
Authors: Uwaydat Sami H , Mansour Ahmad , Ascaso Francisco J , Parodi Maurizio Battaglia , Foster Robert , Smiddy William E , Schwartz Stephen G , Charbaji Abdulrazzak , Belotto Silvana , Jürgens Ignasi , Mateo Javier , Ellabban Abdallah A , Wu Lihteh , Figueroa Marta , Olivier Pascual Nuria , Lima Luiz H , Alsakran Wael A , Caliskan Kadayifcilar Sibel , Sinawat Suthasinee , Assi Alexandre , Mansour Hana A , Casella Antonio Marcello , Navea Amparo , Neila Elena Rodríguez , Saatci A Osman , Govindahari Vishal , Esteban Floria Olivia , Agarwal Komal , Bakkali El Bakkali Ismael , Alaman Angel Salinas , Larripa Sofia Fernandez , Rey Amanda , Pera Patricia , Bruix Lluís , Lopez-Guajardo Lorenzo , Pérez-Salvador Eduardo , Lara Medina Francisco Javier , Hrisomalos Frank N , Chhablani Jay , Arevalo J Fernando
Published: April 2021

Purpose

To ascertain the anatomic factors that help achieve non-surgical sealing in full thickness macular hole (FTMH).

Methods

Retrospective collaborative study of FTMH that closed without surgical intervention.

Results

A total of 78 patients (mean age 57.9 years) included 18 patients with blunt ocular trauma, 18 patients that received topical or intravitreal therapies and 42 patients with idiopathic FTMH. Mean±SD of the initial corrected visual acuity (VA) in logMAR improved from 0.65±0.54 to 0.34±0.45 (p<0.001) at a mean follow-up of 33.8±37.1 months. FTMH reopened in seven eyes (9.0%) after a mean of 8.6 months. Vitreomacular traction was noted in 12 eyes (15.8%), perifoveal posterior vitreous detachment in 42 (53.8%), foveal epiretinal membrane in 10 (12.8%), cystoid macular oedema (CME) in 49 (62.8%) and subretinal fluid (SRF) in 20 (25.6%). By multivariate analysis, initial VA correlated to the height (p<0.001) and narrowest diameter of the hole (p<0.001) while final VA correlated to the basal diameter (p<0.001). Time for closure of FTMH (median 2.8 months) correlated to the narrowest diameter (p<0.001) and the presence of SRF (p=0.001). Mean time for closure (in months) was 1.6 for eyes with trauma, 4.3 for eyes without trauma but with therapy for CME, 4.4 for eyes without trauma and without therapy in less than 200 µm in size and 24.7 for more than 200 µm.

Conclusion

Our data suggest an observation period in new onset FTMH for non-surgical closure, in the setting of trauma, treatment of CME and size <200 µm.
Perception of obesity and overweight among adults living in suburban Nepal: a qualitative study
Authors: Shrestha Sachita , Asthanee Shanta , Karmacharya Biraj Man , Subedi Seema , Koju Rajendra
Published: April 2021

Objective

To explore the perception of obesity and overweight among Nepalese adults living in a suburban community.

Design

A qualitative study composed of focus group discussion (FGD) and in-depth interview (IDI).

Setting

Community and healthcare facilities in Dhulikhel, Nepal.

Participants

Four FGDs were conducted with community members (n=22) and four IDIs were conducted with healthcare providers (HCPs).

Results

Obesity is a rising problem in this suburban community. Participants had inadequate knowledge regarding the consequences of obesity, and they perceived overweight as normal, healthy and attractive. The participants above 40 years of age did not perceive themselves to be overweight or obese. Despite participants’ awareness of the importance of diet control and exercise to prevent obesity, these were not translated into practice.

Conclusions

This study provided insight into perceptions of obesity in a suburban Dhulikhel community through both community members’ and HCPs’ perspective. Misconceptions and inadequate knowledge of obesity among people in this community indicate the need for health education and intervention programme to increase health awareness and preventive practices.
Influence of childhood trauma on the treatment outcomes of pharmacological and/or psychological interventions for adolescents and adults with bipolar disorder: protocol for a systematic review and meta-analysis
Authors: Wrobel Anna , Russell Samantha E , Dean Olivia M , Cotton Sue , Berk Michael , Turner Alyna
Published: April 2021

Introduction

Despite available pharmacological and psychological treatments, remission rates for bipolar disorder remain relatively low. Current research implicates the experience of childhood trauma as a potential moderator of poor treatment outcomes among individuals with bipolar disorder. To date, the evidence reporting the influence of childhood trauma on the treatment outcomes of pharmacological and/or psychological interventions for adolescents and adults with bipolar disorder has not been systematically reviewed.

Method and analysis

MEDLINE Complete, Embase, PsycINFO and the Cochrane Central Register of Controlled Trials will be searched to identify randomised and nonrandomised studies of pharmacological and/or psychological interventions for bipolar disorder, which also assessed childhood trauma. To be eligible for inclusion, studies must have been conducted with adolescents or adults (≥10 years). Data will be screened and extracted by two independent reviewers. The methodological quality of the included studies will be assessed with the Cochrane Collaboration’s Risk of Bias tool and the Newcastle-Ottawa Scale. If deemed viable, a meta-analysis will be conducted using a random effects model. Heterogeneity of evidence will be estimated with the I² statistics.

Ethics and dissemination

This systematic review will use only previously published data. Therefore, ethical approval is not required. The results will be written in concordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines, published in peer-reviewed journals and presented at relevant conferences.

PROSPERO registration number

CRD42020201891.
Cost-effectiveness of emergency preparedness measures in response to infectious respiratory disease outbreaks: a systematic review and econometric analysis
Authors: Vardavas Constantine , Nikitara Katerina , Zisis Konstantinos , Athanasakis Konstantinos , Phalkey Revati , Leonardi-Bee Jo , Johnson Helen , Tsolova Svetla , Ciotti Massimo , Suk Jonathan E
Published: April 2021

Objectives

Respiratory infectious disease outbreaks pose a threat for loss of life, economic instability and social disruption. We conducted a systematic review of published econometric analyses to assess the direct and indirect costs of infectious respiratory disease outbreaks that occurred between 2003 and 2019.

Setting

Respiratory infectious disease outbreaks or public health preparedness measures or interventions responding to respiratory outbreaks in OECD countries (excluding South Korea and Japan) so as to assess studies relevant to the European context. The cost-effectiveness of interventions was assessed through a dominance ranking matrix approach. All cost data were adjusted to the 2017 Euro, with interventions compared with the null. We included data from 17 econometric studies.

Primary and secondary outcome measures

Direct and indirect costs for disease and preparedness and/or response or cost-benefit and cost-utility were measured.

Results

Overall, the economic burden of infectious respiratory disease outbreaks was found to be significant to healthcare systems and society. Indirect costs were greater than direct costs mainly due to losses of productivity. With regard to non-pharmaceutical strategies, prehospitalisation screening and the use of protective masks were identified as both an effective strategy and cost-saving. Community contact reduction was effective but had ambiguous results for cost saving. School closure was an effective measure, but not cost-saving in the long term. Targeted antiviral prophylaxis was the most cost-saving and effective pharmaceutical intervention.

Conclusions

Our cost analysis results provide evidence to policymakers on the cost-effectiveness of pharmaceutical and non-pharmaceutical intervention strategies which may be applied to mitigate or respond to infectious respiratory disease outbreaks.
International clinical practice guidelines for gender minority/trans people: systematic review and quality assessment
Authors: Dahlen Sara , Connolly Dean , Arif Isra , Junejo Muhammad Hyder , Bewley Susan , Meads Catherine
Published: April 2021

Objectives

To identify and critically appraise published clinical practice guidelines (CPGs) regarding healthcare of gender minority/trans people.

Design

Systematic review and quality appraisal using AGREE II (Appraisal of Guidelines for Research and Evaluation tool), including stakeholder domain prioritisation.

Setting

Six databases and six CPG websites were searched, and international key opinion leaders approached.

Participants

CPGs relating to adults and/or children who are gender minority/trans with no exclusions due to comorbidities, except differences in sex development.

Intervention

Any health-related intervention connected to the care of gender minority/trans people.

Main outcome measures

Number and quality of international CPGs addressing the health of gender minority/trans people, information on estimated changes in mortality or quality of life (QoL), consistency of recommended interventions across CPGs, and appraisal of key messages for patients.

Results

Twelve international CPGs address gender minority/trans people’s healthcare as complete (n=5), partial (n=4) or marginal (n=3) focus of guidance. The quality scores have a wide range and heterogeneity whichever AGREE II domain is prioritised. Five higher-quality CPGs focus on HIV and other blood-borne infections (overall assessment scores 69%–94%). Six lower-quality CPGs concern transition-specific interventions (overall assessment scores 11%–56%). None deal with primary care, mental health or longer-term medical issues. Sparse information on estimated changes in mortality and QoL is conflicting. Consistency between CPGs could not be examined due to unclear recommendations within the World Professional Association for Transgender Health Standards of Care Version 7 and a lack of overlap between other CPGs. None provide key messages for patients.

Conclusions

A paucity of high-quality guidance for gender minority/trans people exists, largely limited to HIV and transition, but not wider aspects of healthcare, mortality or QoL. Reference to AGREE II, use of systematic reviews, independent external review, stakeholder participation and patient facing material might improve future CPG quality.

PROSPERO registration number

CRD42019154361.
Area under the expiratory flow-volume curve: predicted values by regression and deep learning methods and recommendations for clinical practice
Authors: Ioachimescu Octavian C , Ramos José A , Hoffman Michael , Stoller James K
Published: April 2021

Background

In spirometry, the area under expiratory flow-volume curve (AEX-FV) was found to perform well in diagnosing and stratifying physiologic impairments, potentially lessening the need for complex lung volume testing. Expanding on prior work, this study assesses the accuracy and the utility of several models of estimating AEX-FV based on forced vital capacity (FVC) and several instantaneous flows. These models could be incorporated in regular spirometry reports, especially when actual AEX-FV measurements are not available.

Methods

We analysed 4845 normal spirometry tests, performed on 3634 non-smoking subjects without known respiratory disease or complaints. Estimated AEX-FV was computed based on FVC and several flows: peak expiratory flow, isovolumic forced expiratory flow at 25%, 50% and 75% of FVC (FEF25,FEF50and FEF75, respectively). The estimations were based on simple regression with and without interactions, by optimised regression models and by a deep learning algorithm that predicted the response surface of AEX-FV without interference from any predictor collinearities or normality assumption violations.

Results

Median/IQR of actual square root of AEX-FV was 3.8/3.1–4.5 L2/s. The per cent of variance (R2) explained by the models selected was very high (>0.990), the effect of collinearities was negligible and the use of deep learning algorithms likely unnecessary for regular or routine pulmonary function testing laboratory usage.

Conclusions

In the absence of actual AEX-FV, a simple regression model without interactions between predictors or use of optimisation techniques can provide a reasonable estimation for clinical practice, thus making AEX-FV an easily available additional tool for interpreting spirometry.
Advanced cancer and COVID-19 comorbidity: medical oncology-palliative medicine ethics meetings in a comprehensive cancer centre
Authors: Thery Laura , Vaflard Pauline , Vuagnat Perrine , Soulie Ophélie , Dolbeault Sylvie , Burnod Alexis , Laouisset Céline , Marchal Timothée , Massiani Marie-Ange , Bozec Laurence , Bidard François-Clément , Cottu Paul , Angellier Elisabeth , Bouleuc Carole
Published: April 2021

Objectives

In managing patients with cancer in the COVID-19 era, clinical oncologists and palliative care practitioners had to face new, disrupting and complex medical situations, challenging the quality of the shared decision-making process. During the first lockdown in France, we developed an onco-palliative ethics meeting to enhance the quality of the decision-making process for patients with advanced cancer treated for COVID-19.

Methods

A least one of the institutional ethics committee members was present along with oncologists, palliative care teams, psycho-oncologists, radiologists and intensive care specialists. Specific medical parameters were systematically collected to form a standardised framework for the discussions.

Results

The main raised issues were the definition of new criteria for the implementation of invasive resuscitation techniques, optimal ways to adapt or delay anticancer treatment and best procedures to address terminal respiratory failure and end-of-life care. The main clinical and ethical guidelines that emerged during these debates are presented. The palliative care team played a major role in assessing and reporting patients’ awareness of cancer-related prognosis and their wishes concerning invasive therapies or transfer to intensive care units, enabling an individualised benefit–risk balance assessment. The ethics committee members ensured continuous monitoring during the discussions. Their function was to recall the main ethical principles including dignity, which is conferred on people when there are treated as having equal status.

Conclusions

The onco-palliative ethics meeting provided a powerful avenue for improvement of collegiality and reinforcement of teamwork, which could be a major protection against burnout for healthcare professionals facing an epidemic onslaught.