bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical Expression of the Damping Characteristics of Air-Lubricated Slideways for Machine Tools
Authors: Kato Shigeo
Published: March 2022

Analytical expression of the damping ratio and the natural frequency of air-lubricated slideways are presented. By the research, the damping characteristics of air-lubricated slideways is represented by a transfer function which has a first-order formula in the numerator and a third-order formula in the denominator. The third-order denominator of the transfer function which shows damping characteristics of air-lubricated slideways is analytically resolved to factors, a first-order delay system with the fast decay (time constant T3) and a second-order vibration system with damping. Air-lubricated slideway has two time constants T1 and T2 which represent the damping characteristics of the slideway. The damping ratio of the slideway ζ0 is analytically expressed by the time constant T2, the natural frequency of the slideway ωn, and dimensionless number k that is the ratio of T2 and T3 as ζ0 = k(1 − k)/(2T2ωn).
Crash Worthiness of Automobile Mechanisms
Authors: Salmon J. L. , Nayfeh A. H.
Published: March 2022

Two methods for performing transient inertia analysis of vehicle mechanism systems are presented in this paper. The analysis techniques are used to predict the response of automotive mechanisms to the accelerations associated with vehicle impacts. General analytical methods for evaluating rotational system dynamics are presented. The utility of the techniques are demonstrated by evaluation of a vehicle outside door handle. The methods, along with time dependent accelerations associated with vehicle impact, are used in a specific example to perform a dynamic analysis of an automobile outside door handle. The first method utilizes generalized Lagrange equations for a non-conservative system to formulate a second order nonlinear differential equation that defines the response of the handle components to the transient input. The differential equation is solved numerically by employing a fourth order Runge-Kutta method. The second method uses commercially available two dimensional rigid body dynamics software to evaluate the events. The results predicted using the analytical techniques are compared to experimental data generated by high speed film analysis of latch tests performed on a high G acceleration sled at Ford Motor Company.
Some Studies for the Application of Explicit FE Codes in Simulation of Quasi-Static Tests
Authors: Lu David X. , Shahidi Behrooz K. , Rivard Cliff M. , Li Rihua
Published: March 2022

Explicit algorithms have been applied to study quasi-static large deformation contact problems with the use of some non-physical acceleration methods for the improvement of computation efficiency. Numerical errors caused by those non-physical acceleration methods are studied in this paper. It is found that oscillation will be introduced if one uses dynamic approach to study a quasi-static problem. Numerical errors caused by dynamic approach will be increased when non-physical acceleration techniques, such as Speed-Up-Loading and Mass-Scaling, are applied.
Front End Design of Vehicle Structure Subjected to Frontal Crash Load
Authors: Mahmood Hikmat F. , Li Chunhui
Published: March 2022

This paper describes a straightforward and effective development process to formulate a frontal end structure to meet the crash safety requirements. The process developed provides a progressive localized buckling behavior for maximum energy absorption. The design and analysis are implemented by using a finite element collapsible beam theory to predict the strength and mode of collapse of the front end components and subsystem. A simplified lumped mass-spring system is proposed for predicting crash performance using the various components characteristic. The springs used in the model representing major energy absorption components and their stiffness are analytically obtained from FEA beam code. The effects of the crash on occupant response are simulated by a MADYMO model. The final designs are experimentally verified using dynamic test of full scale structure. Correlation between analysis and test is good and the structure achieves the desired crush characteristics in crush length, peak, and mean loads. This process provides a rapid develop tool toward an efficient structure for frontal crash energy absorption early in the vehicle program.
Computational Modeling of Axial Neck Impact: Influence of Head Motion and Cervical Spine Buckling on Dynamic Behavior
Authors: Camacho Daniel L. A. , Nightingale Roger W. , Myers Barry S.
Published: March 2022

A computational head-neck model was developed to better understand the influence of head motion and cervical spine buckling on dynamic responses to near-vertex head impact. The model consisted of rigid vertebrae interconnected by assemblies of nonlinear springs and dashpots, and a finite element shell model of the skull. Model parameters were based upon quasi-static pure moment testing of cadaveric cervical spine motion segments and existing data reported in the literature. Geometric and inertial characteristics were derived from three-dimensional reconstructions of skull and vertebral CT images. The model correctly reproduced the complex cervical spine buckling deformations observed in high speed video of near-vertex impacts to cadaveric head-neck specimens, including a buckle at 6 msec and subsequent local post-buckled regions of both flexion and extension. Head and neck load histories agreed with those reported in the cadaveric studies. Sensitivity analyses of the cervical spine modeling parameters revealed that head and neck responses were most sensitive to changes in flexion-extension properties, consistent with structural stability theory for a slender column buckling under compressive loads. A sensitivity analysis of head mass demonstrated that even in the absence of a pocketing impact surface, the head inertia can oppose translational motion of the upper cervical spine during impact, resulting in increased neck loads.
Modeling and Analysis of Passive Moving Seat for Improved Safety
Authors: Tarabishy M. Nabeel , Dollar Anna , Cammino Roberto A.
Published: March 2022

Although current safety systems in passenger cars which include seat belts, frontal airbags, and more recently side airbags, are effective means in reducing injury in the case of accidents, there is still much room for improvement on existing systems, or addition of new ones. This paper introduces a novel system that can be added to existing designs to further reduce the injuries sustained in automobile accidents. The design calls for absorbing some of the crash energy by allowing the seat to move with respect to the chassis through a limited distance. As a result, the impact profile is affected, and therefore, the severity of the crash is reduced. Simulation runs on a simple passenger model at 35 mph have shown a reduction of HIC (Head Injury Criteria) from 1300 to 450 when this design is implemented.
Natural Convection Heat Sink With Heated Shroud
Authors: Morrison Andrew T. , You S. M.
Published: March 2022

Numerical solutions for laminar natural convection in a vertical shrouded fin array are presented. Analysis of a physically realizable configuration is compared to published results for an adiabatic shroud. The effect of a uniform heat flux on the heat sink shroud representing an incident solar heat load is also examined for a vertical heat sink with natural convection and radiation. Comparison to closed form relations for laminar flow between plates lends some insight into the influence of the developing boundary layer on the heat sink thermal performance. Some heat transfer enhancement beyond that of an adiabatic shroud was observed at high Grashof numbers. At low Grashof numbers the Nusselt number was lower than for an adiabatic shroud. However, compared to no shroud, the presence of a shroud at any distance from the fin tip improved the transfer of heat from the fin array. The benefit of the shroud when a heat load is present appears to be greatest for a shroud clearance of C = 0.5 to 1.0.
Contact Area and Thermal Contact Resistance in an Ideal Bolted Joint: Part 2 — Study of Thermal Contact Resistance
Authors: Park Chang J. , Kaminski Deborah A.
Published: March 2022

The thermal contact resistance at the interface of a bolted joint was investigated analytically, experimentally and numerically. Consideration was restricted to an ideal two-plate model for which the interface was perfectly flat. The two bolted plates made circular contact under uniform axisymmetric normal loading. The effect of important system parameters such as plate thickness, material property and loading radius were investigated.

In the analytical study, a closed form solution for the thermal contact resistance for a bolted joint was derived. A three-dimensional heat conduction equation was applied to a model which had a circular geometry and isoflux boundary conditions. The model was solved by the method of separation of variables and superposition. The results showed that an isoflux condition at the interface was valid when thermal conductivities and thicknesses of the top and bottom plates were equal or close to each other.

In the experimental study, the temperature drops were measured across a bolted piece with an interface and these were compared with drops across one solid piece without the interface at low air pressure. Only copper was used and all the copper plates had mirror-like surface finishes. The values of thermal contact resistance obtained from the experiment were consistently lower than those from the numerical analysis, due to air pressure in the vacuum chamber.

In the numerical study, isothermal and isoflux boundary conditions were used. The results of this investigation would be useful in the design of cooling for high power electronic devices bolted on heat sinks.
Analytical Feasibility of Laser Induced Stress Wave Thermometry Applied to Silicon Wafers
Authors: Rabroker G. Andrew , Suh C. Steve , Burger Christian P. , Chona Ravinder
Published: March 2022

A model correlating the group velocity of guided plate waves to temperature in anisotropic silicon substrate is presented. The model is developed through numerical solution and manipulation of the dispersion relations while elastic constants are treated as functions of temperature. Results demonstrate that adequate thermal resolution is provided by both the lowest order antisymmetric and symmetric dispersive Lamb wave modes to serve as an effective diagnostic in a non contact thermometry scheme in rapid thermal processing (RTP) of silicon wafers.
Measurement of Solder-Copper Interfacial Fracture Parameters Using u2-Displacement Fields
Authors: Tippur H. V. , Krishnamoorthy H.
Published: March 2022

Moiré interferometry is used for mapping elasto-plastic deformations in 63/37 solder-copper bimaterials subjected to predominantly tensile loading. A method for quantifying the fracture parameter — the J-integral — using full-field measurement of u2-displacements has been developed. A linear relationship between crack tip opening displacements (CTOD) and the J-integral is demonstrated. The crack growth resistance curve and hence crack initiation toughness JC for the bimaterial is obtained. Full-field optical information has also suggested the possibility of using a simpler method for the J-integral estimation using a single strain gage.
Testing and Measurement Techniques Applied to Electronic Packaging Development
Authors: Guo Yifan , Sarihan Vijay
Published: March 2022

Electronic packages are complicated material systems operating under thermal and mechanical loading conditions. The package design and reliability analysis requires knowledge in many technical disciplines and specialized experimental methods and tools. Recently, many advanced techniques are adopted from other technical areas to be applied to the packaging applications and many experimental tools are developed correspondingly. In this paper advanced experimental techniques in electronic packaging are reviewed. The techniques and methods for mechanical analysis are emphasized as well as the new development in equipment and tools. The applications of these techniques are introduced by numerous reference publications. Most of the applications are directly related to new product development and have made significant impact in the electronics industries by assisting product designs, qualifications, reliability predictions and cycle time reductions.
Moiré Interferometric Analysis of Crack Nucleation From Bimaterial Corners
Authors: Mohammed I. , Liechti K. M.
Published: March 2022

Bimaterial corners arise in many modem structural components from structural adhesively bonded joints to line structures in microelectronics devices. The elasticity problem has been extensively analyzed (Williams, 1952, Bogy, 1971, Hein and Erdogan, 1971) and it has been shown that singularities in stress can arise, depending on the properties of the materials and the corner geometry. These singularities (or eigenvalues) may be complex in nature and a number of them may co-exist for a particular configuration. Various schemes have been developed for extracting the stress intensity factors (or eigenvectors) associated with each singular term (Stem et al, 1976, Carpenter and Byers, 1987).
Advances in Tensile Testing of Polysilicon Thin Films
Authors: Sharpe William N. , Yuan Bin , Edwards Richard L.
Published: March 2022

Polysilicon is the most widely used material in current commercial MEMS products, yet its mechanical properties are not fully determined. Vapor deposited polysilicon is thin — on the order of a few microns — which makes handling and testing difficult. It is desirable to use mechanical tests similar to those standardized by ASTM, but this requires special techniques and procedures.

Tensile tests of 3.5 micron thick polysilicon film have been conducted and these are briefly described. Two advances in mechanical property testing are then presented. A preliminary investigation of the effect of hydrofluoric acid on the tensile properties of polysilicon shows no deleterious effect of this acid which is commonly used as a release agent. Fracture toughness testing of polysilicon, in which crack opening displacement is measured (an approach similar to that specified by ASTM), yields a preliminary value of 1.6 MPa-m1/2.
Hydrodynamic Coupling Between a Viscoelastic Gas/Liquid Interface and a Swirling Vortex Flow
Authors: Lopez J. M. , Chen Jinghong
Published: March 2022

While the structure and dynamics of boundary layers on rigid no-slip walls in rotation dominated enclosed flows are still an area of active research, the interactions between rotating or swirling flows with a free surface have received comparatively less attention. For the most part, investigations in this area have been focused on clean free surfaces, which may be treated as stress-free. However, in most practical situations the surface is rarely clean, and even under laboratory conditions, it is quite difficult to achieve a clean free surface. Most impurities in fluids are surface active, and hence the name surface active agent or surfactant. These surfactants tend to establish an equilibrium surface concentration which alters the interfacial tension and interfacial viscoelastic properties of the gas/liquid interface. The coupling between the bulk swirling flow and the interface is provided via the stress boundary conditions, and these are dependent upon the surface concentration of surfactant, which in turn is altered by the interfacial flow. Forces acting on the interface include surface tension gradients (elastic) and the viscous resistance to shear and dilation. These viscoelastic properties are functions of the surfactant concentration on the surface. Here, we present numerical studies of flow in a cylinder driven by the constant rotation of the bottom endwall with the top free surface being contaminated by a Newtonian surfactant. Comparisons with a clean free surface and a no-slip top endwall provide added insight into the altered dynamics that result from the presence of a small amount of surfactant.
Nonlinear Spin-Up of a Rotating Stratified Fluid: Theory
Authors: Hewitt Richard E. , Duck Peter W. , Foster Michael R. , Davis Peter A.
Published: March 2022

We consider the boundary layer that forms on the wall of a rotating container of stratified fluid when altered from an initial state of rigid body rotation. The container is taken to have a simple axisymmetric form with sloping walls. The introduction of a non-normal component of buoyancy into the velocity boundary-layer is shown to have a considerable effect for certain geometries.

We introduce a similarity-type solution and solve the resulting unsteady boundary-layer equations numerically for three distinct classes of container geometry. Computational and asymptotic results are presented for a number of parameter values. By mapping the parameter space we show that the system may evolve to either a steady state, a double-structured growing boundary-layer, or a finite-time breakdown depending on the container type, rotation change and stratification. In addition to extending the results of Duck, Foster & Hewitt (1997) to a more general container shape, we present evidence of a new finite-time breakdown associated with higher Schmidt/Prandtl numbers.
Modelling and Simulation of Rotating Buoyant Suspensions: Fundamentals and Challenges
Authors: Ungarish M.
Published: March 2022

The methodology used in the analysis of the flow-field of non-colloidal suspensions in a rotating system, accompanied by separation under the action of a centrifugal or gravitational field, is discussed. Some results for centrifugal separation and rotating particle-driven gravity currents are reviewed, and some new challenging questions that appear in the context of these problems are pointed out.
Particle Entrainment in a Bounded Rotating Flow With a Drain
Authors: Mang J. , Minkov E. , Schaflinger U. , Ungarish M.
Published: March 2022

A bathtub vortex is usually formed at the axis of a drain. In the presence of such a vortex, gravity separation of solid impurities lighter than the embedding fluid is counteracted by centrifugal separation and viscous resuspension. Both mechanisms are responsible for the agglomeration of impurities at the axis of the vortex. From there the impurities are easily sucked into the outlet.

In the investigated case, a viscous fluid with a given initial rotation is spinning down in a container with endplates both at the bottom and the top. The amount of fluid withdrawn through a circular hole in the center of the vortex is constantly replaced by a radial influx.

The resulting time-dependent flow was solved by means of a finite difference method taking into account the influence of Ekman layers at the bottom and the top. Subsequently, the process of centrifugal separation of particles lighter than the embedding fluid was studied according to the aforementioned flow field. The results were compared with the particle motion in a classical Oseen vortex. For a simplified case an analytical solution was derived and compared with the corresponding numerical solution. Both results were found to be in good agreement.
Particle Motion in Taylor Couette Flow
Authors: Wereley Steven T. , Lueptow Richard M.
Published: March 2022

Supercritical circular Couette flow devices with a suspension in the annulus between an inner rotating cylinder and an outer fixed cylinder are used for continuous mixing of suspensions and for rotating filtration. The motion of particles in suspension depends on both centrifugal sedimentation and transport due to the vortical motion of Taylor vortices, a centrifugal flow instability that results in a stack of toroidal vortices in the annulus. We have modeled the motion of particles in Taylor Couette flow using computational particle tracking in an analytic velocity field. The fluid velocity field was based on an analytic model that has been shown to accurately represent the flow field just above the transition to supercritical Taylor vortex flow. Particles of various densities were computationally placed in the analytic flow field and tracked to determine the preferential steady state particle positions. Since the centrifugal field goes to zero near the outer cylinder, particles near the outer cylinder are easily carried by the Taylor vortices toward the inner cylinder where they are exposed to the centrifugal field. Due to their density, particles near the inner cylinder centrifugally sediment outward. As a result, particles that start near the inner cylinder or the outer cylinder both tend toward a limit cycle orbit resulting in a region of clear fluid near the inner and outer cylinders and at the centers of the vortices.
Experimental Investigation of the Thermal Plumes in a Thick Layer Cooled From Above
Authors: Volino Ralph J. , Smith Geoffrey B.
Published: March 2022

Simultaneous measurements of surface temperature and the underlying velocity field are presented for a thick horizontal layer evaporatively cooled from above. The convection is characterized by meandering, descending sheet-like plumes which form where cool fluid at the surface collects and plunges into the warmer bulk fluid below. Previous studies have documented the temperature field at the cooled surface and a few have provided point measurements of velocity in the fluid below the surface, but simultaneous measurements of surface temperature and the velocity field were lacking. In the present study, the instantaneous, free surface temperature field has been documented with an infrared (IR) sensing camera. Simultaneous two-dimensional velocity measurements in planes perpendicular and parallel to the free surface were acquired using digital particle image velocimetry (DPIV). Data from cases using room temperature water with Ra* = 1.3 × 109, and heated water with Ra* = 8.5 × 109 are presented. In planes perpendicular to the free surface, velocities were quantified in the convective plumes and the surrounding fluid. The plumes were correlated with the low temperature lines in the free surface temperature field. The velocities in the plumes were about ten times those in the surrounding fluid. In planes parallel to the free surface, horizontal motions toward the descending sheets were observed and quantified. The present measurements provide needed documentation of the relationship between the surface temperature and the underlying hydrodynamics, that is, the velocity fields associated with the convective plumes.
Experiments on Czochralski Convection Model
Authors: Nakano Akifumi , Koyama Hide S. , Sung Hyung Jin
Published: March 2022

A laboratory experiment of critical transition flow modes in Czochralski convection model was performed. The time period of temperature oscillation tp and the interval of temperature oscillation ΔT were scrutinized to capture the critical transition regime. The effects of the rotation of a model crystal rod and a model crucible were examined for three Prandtl number flows (9.10 × 102, 4.45 × 103 and 8.89 × 103). Liquid crystal flow visualization was carried out. Experiment was extended to suppress the temperature oscillation by varying the rotation rate of model crystal rod Ω = Ω0 (1 + A sin (2πft/tp)), where A denotes the rotation amplitude and f the frequency. Based on the inherent time period of oscillation tp, the oscillatory flow modes were characterized in a range of mixed convection parameter 24.3 ≤ Ra/PrRe2 ≤ 950 at Rayleigh number Ra = 4.84 × 106.
All Angle-of-Attack Hydrodynamic Model for Underwater Vehicles Validated by Tank Test Data
Authors: Chhabra Narender K. , Scholten James R.
Published: March 2022

An underwater vehicle’s design and operation requires prediction of its performance at various velocities and angles-of-attack or of sideslip. Traditional models based upon headway motion at substantial speeds use coefficient-based equations of motion. Simulations based upon these coefficients are not valid for hover, low speeds, or high angles-of-attack or of sideslip.

To remedy this severe limitation, nonlinear hydrodynamic models valid for all attitudes of underwater vehicles have been developed and are presented here. These models are derived from the physics of hydrodynamic phenomena. Forces and moments for the total vehicle are obtained by relying on body-buildup techniques. For the vehicle’s hull, the models are profile drag, lift, crossflow force, and added mass. For appendages such as fins, the models are lift and drag when unstalled, normal force when stalled, transition between unstalled and stalled conditions, and hull interference effects. Whenever the equations contain parametric coefficients such as added-mass, drag, and lift, values are specified for all angles-of-attack and sideslip with a minimal use of empirical look-up tables. These models represent the state-of-the-art in low speed hydrodynamics at all angles-of-attack.

The hydrodynamic models presented here have been improved and validated by analysis and comparison with test data. Sub-scale versions of two different vehicles have been tested in tow-tanks at all angles-of-attack.

The models have been implemented in a C language computer code which runs at high speed with no iteration required. This code is utilized regularly in faster-than-real-time vehicle performance simulations.
Coupled Lagrangian-Eulerian Analysis of Submerged Shells Subjected to Ballistic Shock Waves
Authors: Lee M. , Shin Y. S.
Published: March 2022

The coupled Lagrangian-Eulerian analysis has been performed to investigate the transient fluid-structure interaction of underwater ballistic waves and submerged elastic spherical shells. The ballistic waves are formed when a high speed solid body strikes the water surface and penetrates underwater. With the validation of this approach, analyses are first conducted for the problems of an elastic shell subjected to an acoustic step wave. Then, a series of numerical simulations has been conducted using the ballistic waves which are defined from the pressure wave generation model.
Innovative Concepts in Diver Thermal Protection
Authors: Zoulias James B. , Nuckols M. L.
Published: March 2022

Passive methods of protecting a diver from cold exposures are constantly being sought as alternatives to active heating systems. All passive thermal protection techniques share one common advantage over their active heating counterparts; they have no requirement for energy storage or energy distribution. This advantage tends to make passive protection less complex and usually less expensive. Unfortunately in severe cold water, passive systems have customarily required divers to use thick, layered insulating garments worn beneath waterproof diving suits to reduce the loss of body heat to the surrounding cold water. These suits tend to be excessively bulky — inhibiting diver mobility; inherently buoyant — requiring 40–60 pounds of lead weights to make the diver neutrally buoyant; difficult to keep waterproof — an uncertainty that could fatally reduce the diver’s thermal protection during long duration missions; and only minimally effective in protecting the divers’ extremities. Even the best conventional drysuits have been found to be inadequate to meet the full requirements for long duration missions in near freezing waters.

The objective of the research reported in this paper has been to provide the diving community with improvements in thermal protection for long duration, cold water missions. The unconventional approach proposed here, the use of liquids as an insulating medium for divers’ suits, shows promise as a means of significantly surpassing the performance, and acceptable durations, of conventional drysuits. Laboratory testing of conceptual insulating concepts are reported.
Combustion System Design for a Stirling Engine Powered Diver Propulsion Vehicle
Authors: Potter Ian J. , Reader Graham T. , Clavelle Eric , Bowen Caroline E. , Gorin Steve
Published: March 2022

The selection and design of a power system for any form of underwater vehicle is an extremely complex and difficult task. The system must be capable of providing the vehicle with the required mission performance in terms of power and energy and also be volumetrically and gravimetrically compact.

When the vehicle to be used is a newly designed U.S. Navy Diver Propulsion Vehicle (DPV), other power system constraints are highlighted. These constraints include limited vehicle diameter, high performance operation, low power requirements, safety and a non-magnetic signature. Of the many power systems available, very few can fulfil the design criteria for the DPV. One system that can is the hydrocarbon fuelled Stirling engine — a dynamic heat engine using an external combustion system.

This paper describes the design of the combustion system for the Stirling engine powered DPV. Details are given of the design evaluation and the development of a combustion gas recirculation system to enable pure gaseous oxygen to be used as the combustion oxidant In addition, details are given of the restrictions imposed on component design and manufacture by the low vehicle power requirements.
Selection of an Engine and Power Source for a Low Signature Diver Propulsion Vehicle
Authors: Gorin Steven E. , Gavin William , Schreck David , Reader Graham T. , Potter Ian J. , Fauvel O. R.
Published: March 2022

The selection of an engine and power source for a small, one-man, diver propulsion vehicle (DPV) for potential use in a minefield is the topic of this paper. The stringent requirements of minimal magnetic and acoustic signatures, low detectability, diver safety, and operation in a wide range of environmental conditions prevented the use of standard engine configurations. Other system requirements include two man portability, 10 mile range, 2 knot minimum speed, variable speed control, multiple start/stop capability, 0–300 fsw depth range, 29 °F to 95 °F operating temperature range, and −40°F to 140°F storage temperature range.

Several different engine technologies were considered, including electric motors, internal combustion engines, external combustion engines, piezoelectric motors, magneto hydrodynamic engines, and pneumatic engines. Most contenders were quickly eliminated because of their magnetic and/or acoustic signatures. Diesel, Rankine, and Stirling engines were determined to be the best candidates.

Candidate power sources were also evaluated. These included batteries, fuel cells, nuclear, and chemical power. Many of these were eliminated because of the safety consideration and others were eliminated because of the incompatibility with the engine. Hydrocarbon combustion was chosen because of its high specific energy and compatibility with candidate engines.

Candidate engine and power source technologies were evaluated for their ability to meet system requirements. The Stirling engine and the hydrocarbon combustor were selected as the most promising technologies for engine and power source prototype development This paper discusses the reason for the selection of these technologies.
Does Physical Conditioning Influence Performance Attenuation and Recovery in Gaelic Football?
Authors: Daly Lorcan S. , Ó Catháin Ciarán , Kelly David T.
Published: March 2022

Purpose: This study investigated the influence of components of fitness on measures of performance attenuation and recovery following Gaelic football match play. Methods: Measurements of players’ anthropometric characteristics, body composition, running speed, lower-body strength and power, blood lactate concentrations, running economy, and maximal aerobic capacity () were taken over 2 separate days 1 week prior to a competitive match. Creatine kinase, countermovement jump height, drop jump height, contact time, reactive strength index, and perceptual responses were tested prematch, at full time, 24 hours postmatch, and 48 hours postmatch. Results: Multiple components of fitness were associated with reduced performance attenuation and improved recovery responses (adjusted R2 = 9.8%–27.6%; P < .05). Players were divided into higher-standard and lower-standard (higher standard: 57.4 [4.2] mL·kg−1·min−1; lower standard: 45.3 [3.8] mL·kg−1·min−1) and relative squat (higher standard: 1.46 [0.11] 1-repetition-maximum kg·body mass−1; lower standard: 1.20 [0.08] 1-repetition-maximum kg·body mass−1) groups. After adjusting for prematch baseline differences, there were significant differences between groups in drop jump height at 24 hours postmatch (; P < .05) and countermovement jump height at 48 hours postmatch (; P < .05), where the lower-standard group displayed larger decrements. In addition, there were significant differences between relative squat groups at all postmatch time points in contact time (; P < .05) and reactive strength index (; P < .05) and in perceptual responses at 24 hours postmatch (; P < .05), where the lower-standard group expressed larger decrements. Conclusion: Coaches should prioritize the development of aerobic capacity and neuromuscular function as an effective method of reducing performance attenuation and enhancing recovery kinetics in Gaelic football.
A Mixed-Method Study of Athletes’ Experiences With Mindfulness Across Stages of Readiness
Authors: Minkler Thomas O. , Zizzi Sam , Costalupes Blake , Follmer D. Jake
Published: March 2022

Existing mindfulness literature in sport primarily focuses on manualized mindfulness protocols, while less is known about athlete experiences with mindfulness outside of interventions. The purpose of the present study was to explore student-athlete experiences with and readiness to practice mindfulness. Using convenience and snowball sampling, 205 collegiate athletes completed a mixed-method survey that assessed readiness, trait mindfulness, social support for mindfulness practice, and mindfulness’ perceived effect on performance. Participants were invited to comment on benefits, barriers, or adverse experiences during their practice. Athletes with long-term experience had significantly higher mindfulness scores than those with less experience; they also perceived that mindfulness had significantly greater effects on performance than those not practicing. Various benefits and barriers were expressed across stages of readiness, though roughly 6%–10% of participants reported an adverse effect of mindfulness practice. It is thus important for practitioners to consider readiness levels and previous experiences in implementing mindfulness interventions.
Control of reactive collisions by quantum interference
Authors: Son Hyungmok , Park Juliana J. , Lu Yu-Kun , Jamison Alan O. , Karman Tijs , Ketterle Wolfgang
Published: March 2022

In this study, we achieved magnetic control of reactive scattering in an ultracold mixture of
23
Na atoms and
23
Na
6
Li molecules. In most molecular collisions, particles react or are lost near short range with unity probability, leading to the so-called universal rate. By contrast, the Na + NaLi system was shown to have only ~4% loss probability in a fully spin-polarized state. By controlling the phase of the scattering wave function via a Feshbach resonance, we modified the loss rate by more than a factor of 100, from far below to far above the universal limit. The results are explained in analogy with an optical Fabry-Perot resonator by interference of reflections at short and long range. Our work demonstrates quantum control of chemistry by magnetic fields with the full dynamic range predicted by our models.
Toward a coherent ultracold chemistry
Authors: Cornish Simon L. , Hutson Jeremy M.
Published: March 2022

Magnetic fields can be used to change chemical reaction rates by a factor of 100
A new Hall for quantum protection
Authors: Rubio Angel
Published: March 2022

Long-range vacuum fluctuations break the integer quantum Hall topological protection
Catalyst coaxed to make branched α-olefins
Authors: Rosen Mari S.
Published: March 2022

Process conditions allow a titanium catalyst to add just two ethylene molecules to an α-olefin
Biden doesn’t get it
Authors: Thorp H. Holden
Published: March 2022

It has been a rough 2 weeks for the US science community. After 4 years of bludgeoning by the Trump administration, hope resurged a year ago as a new White House promised to value science. But there have been missteps, the most recent taking place on the heels of another blunder that many saw coming. Eric Lander, who just stepped down as President Biden’s science adviser and director of the Office of Science and Technology Policy (OSTP), was a prominent research figure with a well-known record of bullying and callous actions. With the notable exception of the 500 Women Scientists organization, the scientific community was embarrassingly silent about Lander’s nomination. Not surprisingly, he is out of the White House because of the same behavioral issues. And yet, in another tone deaf move, the administration just named Francis Collins, the recently retired director of the National Institutes of Health (NIH), as Lander’s interim replacement as science adviser while asking Alondra Nelson, the OSTP’s deputy director for science and society and an experienced administrator and scholar, to temporarily direct OSTP. Apparently, Biden doesn’t think Nelson is capable of doing both jobs. I disagree and am not staying silent this time.
Worldwide Control and Management of Chagas Disease in a New Era of Globalization: a Close Look at Congenital Trypanosoma cruzi Infection
Authors: Abras Alba , Ballart Cristina , Fernández-Arévalo Anna , Pinazo María-Jesús , Gascón Joaquim , Muñoz Carmen , Gállego Montserrat
Published: March 2022

Population movements have turned Chagas disease (CD) into a global public health problem. Despite the successful implementation of subregional initiatives to control vectorial and transfusionalTrypanosoma cruzitransmission in Latin American settings where the disease is endemic, congenital CD (cCD) remains a significant challenge.
Life with a field geologist: Improbable adventures on five continents
Authors: Alvarez* Milly
Published: March 2022

As the wife and field assistant of geologist Walter Alvarez for the past 56 years, I have shared in adventures on five different continents. The quest to explore the history of our planet has given us insight and understanding of human history and culture as well. From the semi-arid Guajira desert of Colombia to the network of bike paths in Holland, to witnessing the September 1969 Revolution in Libya, from living in a medieval Italian hill town, visiting the Silk Road cities in Soviet Central Asia, participating in the plate tectonic revolution, helping found the Geological Observatory of Coldigioco, and continuing in the stimulating environment of the University of California, Berkeley, our lives have been rich in experiences. Linking it all together reminds us of the nearly infinite number of contingencies and decisions that shape each of our lives and contribute to our shared human history.
Oceanic productivity after the Cretaceous/Paleogene impact: Where do we stand? The view from the deep
Authors: Alegret Laia , Arreguín-Rodríguez Gabriela J. , Thomas Ellen
Published: March 2022

More than four decades have passed since Walter Alvarez helped to bring mass extinctions to the attention of a broad audience and inspired extensive multidisciplinary research on a wide variety of topics ranging from the Cretaceous/Paleogene (K/Pg) and other impact events to astronomy, climate modeling, and the centuries-long debate on the extent to which apparent extinctions are a real phenomenon or due to incompleteness of the fossil record. Many questions about ecosystems in the aftermath of extinctions remain, and we summarize knowledge about an integral part of this discussion, i.e., oceanic productivity after the K/Pg mass extinction. We compiled new and published benthic foraminiferal data across the K/Pg boundary globally, at geographically and bathymetrically diverse sites, to contribute to the understanding of environmental consequences of the K/Pg impact through analysis of extinction patterns in Earth’s largest habitat: the deep seafloor.

We find no significant links between the severity of extinction of benthic foraminiferal species or their global decrease in diversity and factors such as the distance from the Chicxulub crater, paleo-water depth, and paleolatitude. Benthic foraminiferal populations show strong post-impact variability in space and time, supporting the hypothesis of heterogeneous oceans with extensive, local-to-regional plankton blooms, but we suggest that the apparent geographic variability may at least in part be due to incompleteness of the geological record at high time resolution. Additional high-resolution studies are necessary to enable us to evaluate the rates of past extinctions and compare these to the rates of present and future extinctions.
Pulmonary lymphangitis sarcomatosis: a rare cause of severe progressive dyspnoea
Authors: Quigley David , O Donnell Rory , McDonnell Caoimhe
Published: March 2022

Pulmonary lymphangitis carcinomatosis is a complication of malignancy with a poor prognosis. We describe an unusual case in which it caused ventilatory failure and unfortunately death in a previously well male in his 70s. Abnormal chest imaging led to a wide differential diagnosis with Bronchoscopy confirming malignant cells. MRI of his pelvis and biopsy was done diagnosis of metastatic leiomyosarcoma, a particularly aggressive malignancy. Sarcoma-related lymphangitis carcinomatosis is rarely described in the literature and this is the first case to our knowledge of its association with leiomyosarcoma.
Generalised oedema as a presenting manifestation of inflammatory myopathy
Authors: Ray Aritra Kumar , Karmakar Poulami , Chandra Atanu , Ghosh Sudip Kumar , Karmakar Partha Sarathi
Published: March 2022

Polymyositis is an immune-mediated inflammatory myopathy usually presenting with weakness of proximal muscles in a symmetric pattern. Generalised subcutaneous oedema as presenting feature of inflammatory myopathy, especially polymyositis, has rarely been reported. We report here a case of a young woman who was admitted to our facility with generalised severe subcutaneous oedema. During hospital stay, she gradually developed significant proximal muscle weakness with bulbar symptoms. The initial presentation of the patient masqueraded with other causes of anasarca. However, detailed clinical features, laboratory evaluation, electromyography and muscle biopsy clinched the diagnosis of polymyositis. She was treated with systemic corticosteroids and azathioprine. The patient responded well to treatment and the swelling gradually subsided.
Spontaneous postpartum lateral rectus haemorrhage
Authors: Hurley Daire John , Murphy Rory , Farrell Stephen
Published: March 2022

A postpartum woman presented with sudden-onset left eyelid swelling and severe pain. Clinical examination revealed left exophthalmos and ophthalmoplegia with marked resistance to retropulsion of the left globe. The patient was not able to perceive light in the affected left eye and a relative afferent pupillary defect was present. CT orbits showed an enhancing lesion in the left retrobulbar space, suggestive of a lateral rectus haemorrhage. An emergency left lateral canthotomy and inferior cantholysis was performed. A day later, an MRI showed expansion of the left lateral rectus with significant mass effect on the globe. As the visual acuity remained reduced at counting fingers and there was a persistent relative afferent pupillary defect (RAPD), an exploratory orbitotomy and haematoma evacuation was performed. Three days postoperatively, the visual acuity had returned to 6/6. Eye movements normalised within 2 weeks and follow-up imaging revealed near complete resolution of the haematoma.
Association between Olympic Games and children’s growth: evidence from China
Authors: Guo Chao , Hu Xiyuan , Xu Chaofan , Zheng Xiaoying
Published: March 2022

Objectives

To estimate the association between the 2008 Beijing Olympic Games (BOG) and growth of children in China.

Methods

A total sample of 6 951 children aged 3–10 years were included, among which 3 201 were interviewed in 2014 and 3 750 were interviewed in 2018. The BOG was used as a natural experiment. Exposure to the BOG was established by triple differences measured by age group, survey period and whether child participants were living in BOG areas or not, respectively. Children’s growth was assessed by binary variables of stunting, underweight, overweight and obesity. The difference-in-difference-in-differences (DDD) method was used to estimate the association between the BOG and children’s growth.

Results

DDD estimates showed that the BOG was significantly associated with decreased risks of children’s underweight (OR 0.12; 95% CI 0.02 to 0.69) and overweight (OR 0.43; 95% CI 0.19 to 0.98) after controlling for multiple covariates in fractional polynomial models. There was significant sex heterogeneity with regard to the association between BOG and obesity, that is, lower odds of obesity (OR 0.24; 95% CI 0.06 to 0.94) were found in female children but not in male children.

Conclusion

The BOG was positively associated with healthier growth of children including decreased risks of both undernutrition and overnutrition. More attention should be given to the improvement of health surveillance and services before and after sporting events so that the active role of such mega-events in the lasting well-being of the public can be determined in more detail.
Rest-activity circadian rhythm and impaired glucose tolerance in adults: an analysis of NHANES 2011–2014
Authors: Xu Yanyan , Su Shaoyong , McCall William V , Isales Carlos , Snieder Harold , Wang Xiaoling
Published: March 2022

Introduction

Circadian rhythm disturbance occurs in type 2 diabetes, yet it is unknown whether it also exists in the prediagnostic phase of the disease. Thus, we examined the association of rest-activity circadian rhythm with 2-hour glucose levels and the risk of impaired glucose tolerance (IGT) in a nationally representative sample of adults without diabetes using a cross-sectional design.

Research design and methods

We analyzed data from 2760 adults without diabetes (age ≥20) with at least 4 days of validated accelerometer recordings and a valid oral glucose tolerance test from the National Health and Nutrition Examination Survey 2011–2014. Non-parametric rest-activity circadian rhythm parameters were derived from the accelerometer recordings.

Results

In the models adjusting for multiple covariates, a one-quantile increase in relative amplitude (ie, increased circadian rhythmicity) was associated with 2.66 mg/dL decrease in 2-hour glucose level (95% CI −3.94 to −1.38, p<0.001) and a decreased odds of IGT (OR 0.75, 95% CI 0.63 to 0.89, p=0.002). A one-quantile increase in intradaily variability (ie, increased rhythm fragmentation) was associated with 3.01 mg/dL increase in 2-hour glucose level (95% CI 1.52 to 4.49, p=0.001) and an increased odds of IGT (OR 1.37, 95% CI 1.19 to 1.58, p<0.001).

Conclusions

Circadian disruption is significantly associated with impaired glucose homeostasis in a general population of adults without diabetes. The association of circadian rhythm abnormalities with indicators of the pre-diabetic state suggests that circadian dysfunction may contribute to early disease pathogenesis.