bluuebunny/crossref_metadata_2025 huggingface dataset:
“If the Woman Doesn't Prevent, You Will Become Pregnant”: Exploring Male Involvement in Contraceptive Use Preceding Unplanned Pregnancy in Sierra Leone
Authors: McLean Kristen E. , Thulin Elyse J.
Published: March 2022

Globally, millions of unintended pregnancies occur each year resulting in a host of social, economic, and health‐related problems. Improving knowledge of and access to family planning services is an effective way to prevent unintended pregnancy, and research suggests that men's involvement promotes greater contraceptive uptake. To explore this issue, we assess contraceptive knowledge, attitudes, and behaviors among Sierra Leonean men who experienced an unplanned pregnancy. Findings indicate that men's participation in family planning was limited due to barriers including inadequate knowledge about contraception, poor access to services, and gender norms that consider family planning a woman's responsibility. As a result, men often resorted to a pattern of control that put the onus of contraceptive use on women and blamed women when they became pregnant, without considering their own role in pregnancy prevention. We suggest that family planning policies and interventions both engage men and address the barriers to their participation in reproductive health.
Soft maximin estimation for heterogeneous data
Authors: Lund Adam , Wengel Mogensen Søren , Richard Hansen Niels
Published: March 2022

Extracting a common robust signal from data divided into heterogeneous groups is challenging when each group—in addition to the signal—contains large, unique variation components. Previously, maximin estimation was proposed as a robust method in the presence of heterogeneous noise. We propose soft maximin estimation as a computationally attractive alternative aimed at striking a balance between pooled estimation and (hard) maximin estimation. The soft maximin method provides a range of estimators, controlled by a parameter , that interpolates pooled least squares estimation and maximin estimation. By establishing relevant theoretical properties we argue that the soft maximin method is statistically sensible and computationally attractive. We demonstrate, on real and simulated data, that soft maximin estimation can offer improvements over both pooled OLS and hard maximin in terms of predictive performance and computational complexity. A time and memory efficient implementation is provided in the R package SMME available on CRAN.
Patient-generated data in epilepsy care decisions: a scoping review protocol
Authors: Jylhä Virpi , Rosenlund Milla , Kuusisto Hanna , Saranto Kaija
Published: March 2022

Objective:

This scoping review will explore the meaning and content of patient-generated data in epilepsy care decisions.

Introduction:

Clinical decisions about management of long-term conditions such as epilepsy are based on multiple factors, including efficacy and safety of interventions, experiences of professionals as well as patient preferences and values. Patient-generated data integrates patient values and preferences into clinical decision-making. However, more information is needed about the meaning and content of patient-generated data when making clinical decisions in epilepsy care.

Inclusion criteria:

This scoping review will consider studies focusing on patient-generated data and clinical decision-making in epilepsy management. Studies will be included if they concern adult patients with epilepsy, their family members/guardians, or health professionals who treat patients with epilepsy in any health care facility or eHealth services. All studies will be included regardless of methodology. Text and opinion papers will also be considered. Study protocols will be excluded.

Methods:

The databases to be searched include MEDLINE, CINAHL, Scopus, PsycINFO, and Cochrane Central Register of Controlled Trials. Sources of unpublished studies and gray literature will include websites of relevant epilepsy organizations and DART-Europe E-theses Portal. The data will be extracted by two independent reviewers using a tool created for the study purpose. Along with a narrative summary, the results will be presented in tabular or graphical format in a manner that aligns with the review objective and questions. There will be no time limit on the search. Studies published in English, Finnish, Swedish, and German will be included.
CLONING AND EXPRESSION OF RECOMBINANT PROTEIN OF SUMO, FUSED WITH BIOTIN ACCEPTOR PEPTIDE
Authors: Kulyyassov A.T. , Ramankulov Ye.M. , Ogryzko V.V.
Published: March 2022

Post-translation modifications by SUMO are involved in a plethora of biological processes, including cell proliferation. Since SUMOylation is an essential regulatory mechanism in signal transduction, violation of the processes associated with SUMOylation can lead to various diseases, including cancer.

We adopted the proximity utilizing biotinylation method, based on co-expression of recombinant proteins within a single cell: the protein of interest fused with the biotin ligase BirA and its partner with the biotin acceptor peptide (BAP). This co-expression allows for accurate quantitative assessment of the extent of the interaction of various molecules in vivo.

Using this approach, the aim of this work was to construct a new plasmid vector containing a SUMO gene fused with a BAP and to implement its expression in HEK293T cells.

Co-expression of the BAP–SUMO and BirA-HP1g (BirA-HP1a) recombinant proteins in HEK293T cells resulted in protein biotinylation, which are SUMOylated proximal proteins (or interaction partners) of the proteins of interest BirA-HP1g and BirA-HP1a.
Projection-Based Model Reduction for Coupled Conduction—Enclosure Radiation Systems
Authors: Brunini Victor , Parish Eric J. , Tencer John , Rizzi Francesco
Published: March 2022

A projection-based reduced order model (pROM) methodology has been developed for transient heat transfer problems involving coupled conduction and enclosure radiation. The approach was demonstrated on two test problems of varying complexity. The reduced order models demonstrated substantial speedups (up to 185×) relative to the full order model with good accuracy (less than 3% L∞ error). An attractive feature of pROMs is that there is a natural error indicator for the ROM solution: the final residual norm at each time-step of the converged ROM solution. Using example test cases, we discuss how to interpret this error indicator to assess the accuracy of the ROM solution. The approach shows promise for many-query applications, such as uncertainty quantification and optimization. The reduced computational cost of the ROM relative to the full-order model (FOM) can enable the analysis of larger and more complex systems as well as the exploration of larger parameter spaces.
Thermophysical Investigations of Mango Seed Oil as a Novel Cutting Fluid: A Sustainable Approach Toward Waste to Value Addition
Authors: Naik Dungavath Narayana Swamy , Sharma Varun
Published: March 2022

In the present work, a novel cutting fluid has been extracted from mango (Mangifera indica L.) seeds using the soxhlet technique. Cutting fluid from agricultural waste can reduce the shortage of edible oils and eliminate the need to dispose them. Therefore, nonedible oils are economically comparable with edible oils. In order to validate the effectiveness of extracted cutting fluid, thermophysical characterization and tribology tests were performed. The obtained results were compared with edible and nonedible oils, such as sunflower oil (SFO) and mahua seed oil (MaSO), respectively. Friction tests were conducted using a tribometer with pin-on-disk (WC-Co/Ti-3Al-2.5V) at different tribological conditions. The worn surface and wear mechanism of disks were examined using a scanning electron microscope (SEM) associated with energy-dispersive spectroscopy (EDS) for comparing the elemental composition quantitatively. These findings showed that mango seed oil (MSO) exhibited the lowest coefficient of friction (COF) and wear volume followed by MaSO, SFO, and dry, respectively. SEM analysis showed that no plowing was observed; however, small pits and cracks were found on wear track under MSO. Further, the abovementioned oils were used as a cutting fluid in the machining of Ti-3Al-2.5V (grade 9 alloy). In this regard, MSO has shown a similar effect in turning operation with minimum quantity lubrication (MQL) system.
Petri Net Modeling for Disassembly Process Planning
Authors: Xirouchakis Paul , Kiritsis Dimitris
Published: March 2022

A generic Petri-Net model is presented for the modelling of disassembly planning operations. This is of interest for developing decision support systems within the context of planning for recyclability. The proposed modelling methodology could allow the identification and assessment of cost-effective characteristics of disassembly. The proposed approach for the evaluation and the optimisation of the disassembly process for components, part and subassemblies recovery could be used for optimal disassembly sequence generation by considering the precedence constraints between assembly components. The proposed approach is based upon the Petri Net modelling technology already developed at the CAD/CAM laboratory (LICP) at the Swiss Federal Institute of Technology. In this work a generic dynamic model was developed based on Petri Net technology. The Petri Net model (i) represented manufacturing knowledge of the type of precedence constraints (ii) represented dynamically the process planning procedure itself and (iii) encapsulated all possible process planning solutions (process plans). Furthermore, process planning simulation was performed directly on the Petri Net and reachability analysis of the model gave the complete set of solutions (process plans).
Interaction of Process Mechanisms and Environmental Effects in Secondary Finishing
Authors: Bauer D. , Sheng P.
Published: March 2022

This paper presents a modeling framework to enable environmental evaluation of surface finishing processes. The formulation integrates sub-models analyzing energy use, cutting fluid vaporization, cutting fluid aerosol formation, wheel wear, and chip and workpiece fluid carry-off. The overall model can be used to compare and evaluate the energy use and waste stream mass flux for different design and process specifications. This waste stream output mass flux can then serve as input into models predicting the fate, transport, toxicity, and exposure-based risk of the waste streams from this process alone or in conjunction with the waste streams from other processes at the manufacturing facility. A test case is presented to illustrate use of the model.
Probabilistic Analysis of Accidents Involving Pyrophoric Particle Accumulation in a Closed System Containing High Explosives
Authors: Bott Terrence F. , Eisenhawer Stephen W.
Published: March 2022

This paper describes a probabilistic analysis of an unusual safety concern encountered during safety analysis of a closed system containing high explosive (HE). In this application, a pyrophoric material could be generated inside the system by corrosion of system components. This pyrophore may form extremely small particles that could be transported through a complex path to a high explosive component, where they could collect on exposed surfaces as a result of routine handling operations. A potentially serious accident could be initiated if the system is opened for maintenance and oxygen reaches the pyrophoric particles that are resting on the surface of the high explosive. The pyrophoric particles react vigorously in the presence of oxygen and will ignite the high explosive if there is a sufficient concentration of the particles in a localized area. This paper reports on models for estimating the probability of achieving hazardous concentrations of pyrophoric particles on the explosive surface. These probability estimates are based on occupancy likelihood and geometric models. The probability models provide a means for exploring the effects of material behavior, heat transfer, and material transport on the likelihood of achieving unwanted concentrations of pyrophoric particles on the explosive surface.
Explosive Noise and Radioactivity Risk: French Nuclear Tests
Authors: Margulies T.
Published: March 2022

A one-dimensional nonlinear elastic wave model was used to compute sound transmission through the tuff which was coupled to an ocean transmission calculation of pressure versus distance. Sound levels that are greater than those used for marine mammal protection harassment are received hundreds of kilometers away from the source near areas of U.S. interests. These geoacoustic estimates were also compared to poroelastic Biot model predictions. Furthermore, the ionizing radioactivity released to the lagoon has been assessed obtaining levels of concern for those that would swim in the water in the future if the testing is forgotten or ignored.
Fluid Flow-Induced Vibration of Suspended Nonlinear Cables
Authors: Chang W. K. , Pilipchuk V. , Ibrahim R. A.
Published: March 2022

The nonlinear interaction of the first two in-plane modes of a suspended cable with a moving fluid along the plane of the cable is studied. The governing equations of motion for two-mode interaction are derived based on a general continuum model. The interaction causes the modal differential equations of the cable to be non-self-adjoint. As the flow speed increases above a certain critical value, the cable experiences oscillatory motion similar to the flutter of aeroelastic structures. A coordinate transformation in terms of the transverse and stretching motions of the cable is introduced to reduce the two nonlinearly coupled differential equations into a linear ordinary differential equation governing the stretching motion, and a strongly nonlinear differential equation for the transverse motion. For small values of gravity-to-stiffness ratio the dynamics of the cable is examined using a two-time-scale approach. Numerical integration of the modal equations shows that the cable experiences stretching oscillations only when the flow speed exceeds a certain level. Above this level both stretching and transverse motions take place. The influences of system parameters such as gravity-to stiffness ratio, density ratio, and the fluid flow randomness on the response characteristics are also reported.
Identification of Linearised Parameters for Fluidelastic Instability
Authors: Meskell C. , Fitzpatrick J. A.
Published: March 2022

A method for estimating the parameters of a linearized model of the fluidelastic forces in an array of cylinders is described. The behaviour of a tube on a flexible mount in the third row of an otherwise rigid 5 row normal triangular array, with pitch-to-diamter ratio of 1.58, has been investigated. The fluid stiffness and damping over a range of flow velocities has been estimated from experimental data. The results are then used to predict a stability threshold which is in agreement with previously published data for critical velocities. The damping in the flexible mount has been varied and shown not to effect the estimated fluid parameters.
Computation of Vortex Shedding and Radiated Sound for a Circular Cylinder
Authors: Cox Jared S. , Rumsey Christopher L. , Brentner Kenneth S. , Younis Bassam A.
Published: March 2022

The Lighthill acoustic analogy approach combined with Reynolds-averaged Navier Stokes is used to predict the sound generated by unsteady viscous flow past a circular cylinder assuming a correlation length of ten cylinder diameters. The two-dimensional unsteady flow field is computed using two Navier-Stokes codes at a low Mach number over a range of Reynolds numbers from 100 to 5 million. Both laminar flow as well as turbulent flow with a variety of eddy viscosity turbulence models are employed. Mean drag and Strouhal number are examined, and trends similar to experiments are observed. Computing the noise within the Reynolds number regime where transition to turbulence occurs near the separation point is problematic: laminar flow exhibits chaotic behavior and turbulent flow exhibits strong dependence on the turbulence model employed. Comparisons of far-field noise with experiment at a Reynolds number of 90,000, therefore, vary significantly, depending on the turbulence model. At a high Reynolds number outside this regime, three different turbulence models yield self-consistent results.
Turbulence-Induced Tube Vibration in a Parallel Steam-Water Two-Phase Flow
Authors: Kawamura Koji , Yasuo Akira , Inada Fumio
Published: March 2022

This paper is concerned with the fluid force acting on a tube placed in a parallel steam-water two-phase flow. Based on experiments on the tube vibration induced by the turbulence of two-phase flow, the relationships between the hydrodynamic mass, damping ratio, excitation force, and the fluid flow conditions were evaluated. Mass flow rate, pressure, and void fraction were varied in the experiment to measure random vibration of the tube caused by turbulence in the stream. The hydrodynamic mass and damping ratio were derived by analyzing the vibration data. The excitation force was calculated using a transfer function to represent the relationship between the intensity and excitation force of the vibration given by random statistical theory. It was found that the hydrodynamic mass and damping ratio are little affected by the mass flow rate and pressure but are significantly affected by the void fraction and frequency. In contrast, the vibration excitation force is affected by the pressure as well as the effects of void fraction and frequency. The relationships between them were evaluated.
Margins of Uncertainty in the Prediction of Fluidelastic Instability in Heat Exchanger Tube Bundles
Authors: Goyder H. G. D.
Published: March 2022

During the design and operation of a heat exchanger it is necessary to check for the possibility of fluidelastic vibration. The usual approach is to allow for some pessimism so that there is a margin between the prediction and actual occurrence of damaging vibration. This paper deals with some of the factors that control this margin.
Vibration Damping in Multispan Heat Exchanger Tubes
Authors: Taylor C. E. , Pettigrew M. J. , Dickinson T. J. , Currie I. G. , Vidalou P.
Published: March 2022

Heat exchanger tubes can be damaged or fail if subjected to excessive flow-induced vibration, either from fatigue or fretting-wear. Good heat exchanger design requires that the designer understands and accounts for the vibration mechanisms that might occur, such as vortex shedding, turbulent excitation or fluidelastic instability. To incorporate these phenomena into a flow-induced vibration analysis of a heat exchanger requires information about damping.

Damping in multispan heat exchanger tubes largely consists of three components: viscous damping along the tube, and friction and squeeze-film damping at the supports. Unlike viscous damping, squeeze-film damping and friction damping are poorly understood and difficult to measure. In addition, the effect of temperature-dependent fluid viscosity on tube damping has not been verified.

To investigate these problems a single vertical heat exchanger tube with multiple spans was excited by random vibration. Tests were conducted in air and in water at three different temperatures (25, 60 and 90 °C). At room temperature, tests were carried out at five different preloads. Frequency response spectra and resonant peak-fitted damping ratios were calculated for all tests. Energy dissipation rates at the supports and the rate of excitation energy input were also measured.

Results indicate that damping does not change over the range of temperatures tested and friction damping is very dependent on preload.
Flow-Induced Acoustic Resonance With Various Finned Tube Banks
Authors: Nemoto A. , Takakuwa A. , Tsutsui M.
Published: March 2022

Experimental investigations were earned out on flow induced acoustic resonance with tube banks composed of various tubes such as bare, solid fin, serrated fin, and plate-fin tubes.

Tube banks contained in ducts were connected to a silent wind tunnel and installed in an anechoic room. Sound emitted from the tube bank was measured by microphones on the duct wall and at the duct outlet.

The results clarified the effects of the fins on tube banks. In a wide longitudinal pitch of tube bank geometry, there were no great differences in resonant effect, although fins help to emit flow noise. In a narrow geometry, it was revealed that the characteristics of the fin participate in resonance and damping effect. With a complicated geometry, such as serrated fin and plate-fin tubes, there is a greater damping effect and less resonance is generated. In any case, the baffle plates dividing duct width could suppress the resonance.
Identification of Non-Linear Rotor Dynamic Coefficients Using Multiple Circumferential Pressure Measurements
Authors: Spirig Michael , Staubli Thomas
Published: March 2022

A new approach to determine rotor dynamic coefficients based on multiple circumferential pressure measurements is proposed. With the newly introduced procedure, the identification of all, even non-linear, rotor dynamic coefficients can be achieved with one single test run.

The advantage of this procedure is the enormous reduction of test runs and a much simpler and faster identification procedure. A necessary condition for the proposed procedure — besides the simultaneous pressure measurements at multiple positions — is that there are mechanical means to achieve an orbit motion of the rotor (e.g. an eccentric ellipse, Fig. 7.) and that this orbit motion is measured with appropriate accuracy.
Activities in Aeroelasticity at NASA Langley Research Center
Authors: Perry Boyd , Noll Thomas E.
Published: March 2022

This paper presents the results of recently-completed research and presents status reports of current research being performed within the Aeroelasticity Branch of the NASA Langley Research Center. Within the paper this research is classified as experimental, analytical, and theoretical aeroelastic research. The paper also describes the Langley Transonic Dynamics Tunnel, its features, capabilities, a new open-architecture data acquisition system, ongoing facility modifications, and the subsequent calibration of the facility.
Fluid-Structure Coupling Requirements for Time-Accurate Aeroelastic Simulations
Authors: Bendiksen Oddvar O.
Published: March 2022

In this paper we study the requirements that must be satisfied by a fluid-structure coupling scheme, in order to obtain a dynamically consistent aeroelastic code. Both spatial compatibility and time synchronization requirements must be met, to assure that the time-marching simulations exhibit the physically correct stability behavior. Inconsistent or inaccurate implementation of the fluid-structure boundary conditions can cause the aeroelastic code to converge to an incorrect aeroelastic solution. It is shown that CFD codes based on linear interpolations for the velocities cannot be fully compatible with structural FE codes that use plate or shell elements to model the wing skin. Numerical examples are presented for three different nonlinear aeroelastic models, using Euler-based aerodynamics and two different fluid-structure coupling schemes. The results indicate that for Mach numbers in the upper transonic range, past the transonic dip, the aeroelastic solution appears very sensitive to the fluid-structure coupling scheme used. In the case of the NACA 0012 model, the two different schemes studied predicted entirely different stability behaviors.
Aeroservoelasticity in Compressible Flow and Aeroelastic Scaling Considerations
Authors: Presente Eyal H. , Friedmann Peretz P.
Published: March 2022

Active flutter suppression of a two dimensional wing section in subsonic flow is studied. The equations of motion of a typical section are presented in nondimensional form. A two degree of freedom system, with pitch and plunge dynamics, combined with a trailing-edge control surface is considered. Aerodynamic loads are expressed in time-domain using Roger’s approximation. Linear optimal control is used to design a full-state feedback regulator for flutter suppression. Constraints on actuator deflection and rate limit the flutter envelope expansion. Aeroservoelastic scaling is addressed and parameters required for maintaining similarity between a full-scale system and its model are identified. Results illustrate system behavior in compressible flow. Approximate relations comparing an actively controlled flap with a continuously deforming airfoil, using piezoelectric actuation, are obtained and used to compare the performance of these two systems.
Multidisciplinary Optimization of Composite Wings Using Refined Structural and Aeroelastic Analysis Methodologies
Authors: Chattopadhyay Aditi , Jha Ratneshwar
Published: March 2022

An integrated multidisciplinary procedure has been developed for structural and aeroelastic optimization of composite wings based on refined analysis technique. A refined higher-order theory is used to analyze composite box beam, which represents the load carrying member of the wing. Unsteady aerodynamic computations are performed using a panel code based on the Doublet Lattice Method. Flutter/divergence dynamic pressure is obtained by the Laplace domain method through rational function approximation of unsteady aerodynamic loads. The objective of the optimization procedure is to minimize wing structural weight with constraints on flutter/divergence speed and stresses at the root due to the static load. Composite ply orientations and laminate thicknesses are used as design variables. The Kreisselmeier-Steinhauser function approach is used to efficiently integrate the objective function and constraints into a single envelope function. The resulting unconstrained optimization problem is solved using the Davidon-Fletcher-Powell algorithm. Numerical results are presented showing significant improvements, after optimization, compared to a reference design.
Integrated Electromechanical Devices for Active Control of Vibration and Sound
Authors: Anderson Eric H. , Holcomb Mark D. , Leo Donald J. , Bogue Adam X. , Russo Farla R.
Published: March 2022

Advances in transducers and electronics have made possible integrated electromechanical devices for active vibration and noise control. This paper describes one such system which makes use of piezoelectric materials. An integrated device employing piezoceramic actuators and sensors, analog electronic signal conditioning, programmable control components, and a voltage amplifier is described. Issues driving design of each functional subsystem are addressed. The device is packaged using flex circuit technology and other electronics industry methods. The means of integrating transducers and other components are noted. Test results indicating the vibration suppression capability are presented, and the considerably greater possibilities for more sophisticated control designs using the same system are summarized. Potential applications in active vibration and sound control are described, and uses of the broader technology, beyond the specific device design, are summarized.
Biomechanics of the Total Knee Replacement: Theoretical and Computational Modeling of Biomechanical Response to the Tibial Insert
Authors: Sathyamoorthy Mohan
Published: March 2022

Degenerative bone disease is a condition that often affects the articulating joints in the body by compromising the normal range of movement in those areas. As the condition progresses, the patient experiences a more painful and reduced level of mobility, often requiring joint replacement therapy. As the use of orthopaedic implants has become commonplace, the need to adequately understand and characterize the body’s biomechanical response to such implants is necessary to assist patients in achieving a more complete recovery, and more importantly, to optimize the design of biocompatible implants. The total knee replacement (TKR), a modular assembly comprising of femoral, tibial, and patellar components, has demonstrated great benefit to patients in terms of pain management and restoration of mobility. However, with reported disadvantages including stem loosening and bone fracture [1], correlating three dimensional stress concentrations to bone resorption may be an effective predictor of potential bone fracture site in TKR patients. The relationship between stress adaptive theories, stress concentrations predicted by computational modeling, and bone resorption has previously not been studied in great detail. This paper develops a continuum relationship that relates stress adaptive bone remodeling in response to stress concentrations, and presents a basic finite element model to quantify stress concentrations to help verify the proposed relationship. Results could eventually be used recursively to optimize TKR implant design and performance.
Modelling of Oxygen Diffusion in Pulmonary Capillaries
Authors: Frank Andreas O. , Chuong C. J. Charles
Published: March 2022

Oxygen (O2) uptake by the lungs occurs from the alveolar air space to hemoglobin (Hb) in the red blood cell (RBC), which can conceptually be separated into membrane and red cell segments (Roughton and Forster Equation) [8]. The objective of this study was to determine O2 uptake using the finite element method (FEM) and assess the effects of geometry. We developed a modified 2D model representing the sheet flow characteristics of the pulmonary capillaries [2]. Analysis of an axisymmetric model of comparable hematocrit (Hct) was also carried out. The Nusselt number was used to assess the efficiency in oxygen transport of these two geometric configurations.
Gel Compression Considerations for Chromatography Scale-Up for Protein C Purification
Authors: He Weiwei , Bruley Duane F. , Drohan William N.
Published: March 2022

Protein C is a vitamin K dependent glycoprotein which is synthesized by the liver [1]. It is the zymogen of a serine protease which acts as an anticoagulant by inhibiting activated factors V and VIII thus enhancing fibrinolysis. An increased risk for the development of venous thrombosis has been attributed to Protein C deficiency[2]. This work is to establish theoretical and experimental relationships for the scale up of Immobilized Metal Affinity Chromatography (IMAC) and Immuno Affinity Chromatography for the low cost production of large quantities of Protein C. Gel matrices for Protein C separation are being analyzed to determine the relationship between the materials properties of the gel and column collapse characteristics.
An Analysis of Hemodialysis Catheter Fluid Mechanics
Authors: Siegel John M. , Makhijani Vinod B.
Published: March 2022

Hemodialysis catheters are primarily used in instances of acute renal failure and poisonings, although there is increasing use of these catheters for long-term access, particularly in the elderly population. The typical hemodialysis catheter consists of a polymer tube with either a single or double lumen. This tube is inserted into one of three preferred catheter access sites: the femoral vein, subclavian vein, or internal jugular vein (the femoral vein is typically used for acute access only). Once in place, the catheter is available for vascular access during hemodialysis.
Altered Swelling-Induced Strain Fields in Articular Cartilage Following Periods of Immobilization
Authors: Narmoneva D. A. , Wang J. Y. , Patel S. S. , Howell D. S. , Setton L. A.
Published: March 2022

Swelling effects in cartilage arise from a high density of negatively-charged proteoglycans which generate a large swelling pressure. Swelling effects in cartilage are regulated by a balance between this swelling pressure and elastic forces generated within the cartilage solid matrix (1,2). Increased swelling is a characteristic of osteoarthritic cartilage and reflects a pathological alteration in the balance between swelling pressure and elastic restraining forces (3). Recently, we have developed a new technique to measure the nonuniform swelling-induced strain fields in samples of articular cartilage in situ, i.e., while attached to the subchondral bone (4). We observed variations in swelling behavior of cartilage with depth from the articular surface, reflecting the nonhomogeneous composition and structure of the material. In this study, we apply our newly-developed experimental technique to measure the swelling-induced strain fields in cartilage following removal of weight-bearing forces with cast immobilization. Periods of joint immobilization have been shown to produce compositional changes characteristic of osteoarthritis including a decreased proteoglycan content and changes in proteoglycan conformation (5, 6). We hypothesize that the changes associated with joint immobilization will alter the swelling behavior of articular cartilage, which will be detected as a change in swelling-induced strain fields in cartilage in situ.
Confined and Unconfined Stress Relaxation of Cartilage: A Transversely Isotropic Analysis
Authors: Bursać Predrag M. , Obitz Toby W. , Eisenberg Solomon R. , Stamenović Dimitrije
Published: March 2022

It has been shown that the stress relaxation response of articular cartilage in unconfined compression is not adequately described by an isotropic biphasic model [1,2]. Two possible explanations have been advanced to account for this observed disagreement between theory and experiment:

(i) friction at the indenter/tissue interface that the model assumes to be negligible [3];

(ii) cartilage behaves as a transversely isotropic material [4,5].

In the present study, stress-relaxation experiments were performed in both confined and unconfined compression on immature bovine knee cartilage. High aspect ratio (height/diameter) specimens were used to minimize the effect of friction at the indenter/tissue interface [3]. The data obtained from these tests were used with a transversely isotropic biphasic model to estimate material parameters.
Effects of Varying Strain Amplitudes and Cyclic Loads on the Tensile Behavior of the IGHL
Authors: Wang Vincent M. , Huang Chun-Yuh , Cohen Nathaniel P. , Pawluk Robert J. , Bucchieri John S. , Flatow Evan L. , Bigliani Louis U. , Pollock Roger G. , Mow Van C.
Published: March 2022

Cyclic tensile testing of soft collagenous tissues is a useful tool for studying their mechanical response in situ as well as for simulating repetitive joint motion [2,5]. It has been hypothesized that the cumulative effects of repetitive microtrauma may contribute to acquired instability in the glenohumeral joint [3]. Many investigations have focused on the inferior glenohumeral ligament (IGHL) which is the primary restraint of the joint in the most common position of shoulder dislocation [4,8]. Not until recently, however, has an experimental protocol addressed repetitive loading of the capsular ligaments at subfailure levels of strain [6,9], The objectives of this study are to examine the effects of increasing: 1) the number of repetitive loading cycles, and 2) strain magnitudes, on the tensile load response and induced laxity in the IGHL.
In Situ Mechanical Behavior of a Repaired Articular Surface
Authors: Wayne Jennifer S. , Mukherjee Nilay
Published: March 2022

Once damaged, articular cartilage in diarthrodial joints is difficult to repair. Altered mechanical conditions around the repair site and inferior material properties of the repair tissue may be possible reasons for its ultimate degeneration (1). Understanding and quantifying this mechanical environment would provide valuable information to help improve protocols in the management of damaged articular surfaces. In this study, the in situ mechanical conditions on a repaired articular surface were examined.
Effect of Strain Rate on Failure Behaviour of the Annulus Fibrosus in Tension
Authors: Kasra M. , Parnianpour M. , Wang J. L. , Shirazi-Adl A. , Grynpas M. D.
Published: March 2022

A large proportion of overexertion injuries in sport and work related activities occur during high strain rate loading. The disc is known to have time dependent material properties (1). The joint load and stiffness may increase and the mode of failure may change from a location to another when higher loading rates are sustained (2). In order to quantify the response of the spine to dynamic loads, we need to account for the rate dependencies of the intervertebral disc in tension as well as other loading conditions. Bending tasks stretch the annulus fibrosus in the vertical direction and render the disc vulnerable to prolapse if the hydrostatic pressure in the nucleus pulposus is raised at the same time. Thus, the ability of the annulus to resist repeated vertical stretching may have a decisive influence on a disc’s susceptibility to prolapse. Tensile properties of the annulus fibrosus have been reported in the literature (3). However, to what extent loading rate can affect annulus tensile properties still needs to be clarified. The objective of this study was to investigate the loading rate sensitivity and regional variations in tensile mechanical properties of the annulus fibrosus, using disc annulus specimens from sheep.
A Cervical Spine Model to Predict Vertebral Stresses in High Acceleration
Authors: Sadegh Ali M. , Tchako Abraham
Published: March 2022

A cervical spine model was developed to investigate the stresses in each vertebra when subjected to high G-z and G-y accelerations. The experimental data used were collected from the biodynamic responses of human volunteers. The model accounts for the biodynamic viscoelastic characteristics of the neck. The results indicated that high stress occurred in C2 and C4 for G-z acceleration cases, while for G-y the high stresses were at C1 and C7.
Intervertebral Disc Pressure Changes During a Chiropractic Procedure
Authors: Gudavalli Maruti R. , Cox James M. , Baker James A. , Cramer Gregory D. , Patwardhan Avinash G.
Published: March 2022

Some of the treatments for low back pain use traction as the loading mechanism to the spine. One such treatment protocol used by chiropractic physicians in the treatment of low back pain is the Cox flexion-distraction procedure (1). The Cox procedure consists of placing the patient in a prone position on a flexion-distraction table and then creating traction and flexion motions at the joint of interest. The treatment is based on the hypothesis that the intradiscal pressure decreases during the procedure and may provide an opportunity for the disc bulge to reduce. However, no data exist to support this hypothesis. The purpose of the present study was to measure the changes in the intradiscal pressures in the lumbar spine on unembalmed cadavers during the flexion-distraction procedure.
Evaluation of a Modular Polyaxial Spinal Component With Interlocking Tapers
Authors: Needham Dusty A. , Rouleau Jeffrey P. , Buchanan Dennis J. , Conta Robert L. , Parr Jack E.
Published: March 2022

The use of tapers in orthopaedic applications for the fixation of one implant component to another is well documented, such as in femoral head fixation to a hip stem. By providing sufficient interference between the two components, hoop stresses and friction forces are generated which hold the assembly together. Under normal physiological conditions, the spine is subjected to a variety of loading regimes, including tension, compression, torsion, bending, and combinations of all four. With the addition of instrumentation, these spinal loads are shared with the fixation device. The resulting construct must be strong enough to maintain correction of the spinal deformity during healing. To examine the strength of a spinal instrumentation system which includes the new locking mechanism of tapers, several tests were utilized, including flexion-extension, axial rod gripping capacity, torsional rod gripping capacity, anterior-posterior pull, and fatigue flexion-extension tests.
Biofidelity of the Hybrid III Neck for Spinal Trauma Assessment
Authors: Sances Anthony , Voo Liming
Published: March 2022

The objective of this study was to delineate the dynamic axial compressive responses of the Hybrid head-neck system and compare with the intact human cadaver head-neck complex responses. The Hybrid III head-neck preparation was tested under dynamic loading at rates to 8.0 m/sec. Inertially compensated forces, axial deformations, and distal generalized six-axis load cell histories were gathered at dynamic sampling rates. The localized axial compressions of the neck were obtained using retroreflective target information and high-speed photography. The Hybrid III dummy responded with non-linear and rate stiffening characteristics with minimal initial softening. This was in contrast to the human cadaver tissues wherein initial softening characteristics were present in the force-deformation curves. The Hybrid III neck was found to be at least two times stiffer compared to the human under dynamic axial compressive loading. Furthermore, the shape of the Hybrid III force-deformation response was different from the human cadaver tissues. These differences must be included to properly extrapolate the results from the Hybrid III to predict injury in real-world vehicular crash environments.
Design Optimization of a Composite Splint Material for Strength and Thermoformability
Authors: Ainsworth Stephen D. , Latour Robert A.
Published: March 2022

The development of a short fiber reinforced, low temperature thermoplastic splint material has potential to improve the ease, cost and efficiency of splinting and casting musculoskeletal problems. Design optimization of the fiber/matrix system is a key step in the development process of this new material. The tensile strength, flexural strength, and elastic moduli were found for 2-D randomly oriented short E-glass fiber reinforced polycaprolactone at both room temperature and at 170°F. The effect of fiber length and fiber volume fraction on the previously mentioned properties were studied by testing a range of fiber volume fractions (0.0 to 0.10) with fiber lengths of 3 mm and 7 mm. The results of this study show potential for increasing strength and rigidity of the low temperature thermoplastic through fiber reinforcement, while maintaining some degree of thermoformability.
A Surgeon’s Perspective on MEMS for Surgery
Authors: Treat M. R.
Published: March 2022

Surgery has changed a great deal in the past decade. The change is denoted by the term “minimally invasive surgery”. The essence of minimally invasive surgery is the use of technology to enable the surgeon to perform his therapeutic tasks in ways which are less physically and physiologically harmful to the patient. At present, the technologies principally in use are imaging technologies (chiefly video and x-ray) coupled with some very basic mechanical devices which allow the surgeon to manipulate organs in various body cavities without opening the body cavity. There is still a long way to go in achieving the full potential of minimally invasive surgery. MEMS technologies can definitely play a role here. I envision the main use for MEMS technology to be in allowing us to design surgical instruments which incorporate various kinds of sensors. Placing micro sensors on the instruments will restore for the surgeon the tactile immediacy of operating with his hands directly on the tissue, instead of through the intermediary of an insensitive and awkward mechanical device. The sensor types which will probably be useful for surgical instruments fall into two overall categories: the first category is sensors which give the surgeon some force feedback as he goes about the job of placing various types of tissue fasteners (staples or sutures). Many surgical complications arise because there is insufficient or inaccurate force feedback to regulate the closing pressure of staples or sutures. Excessive closing pressures can result in tissue necrosis while insufficient pressures may result in leakage through the staple/suture line. The other category of sensors would be various chemo sensors, which can detect the pH, oxygen and carbon dioxide levels in tissue, as well as other chemical entities of clinical importance such as lactic acid.
A New Linear Stepper Motor Within a Hand Held Surgical Device
Authors: Rizq Raed N. , Wulfman David R. , Peichel David , Erdman Arthur G. , Polla Dennis L.
Published: March 2022

A new hand held surgical device intended to aid physicians in microsurgery is reported. This device provides a means for delivering small implants through the use of a precision motion linear stepper motor fabricated from silicon and piezoelectric components. Test instruments have delivered over fifty implants with consistent performance. Typically the test instruments have attained 1.2 mm/s advancement speeds against 3 Newton resistance loads, a maximum output force of 4.6 Newtons, and maximum total displacement of 38 mm.
Hip Implant With Metal-on-Metal Articulation: Some Design Aspects
Authors: Shareef Nazeer H. , Levine Danny L. , Laurent Michel , Hamman Gary
Published: March 2022

One of the main concerns in the orthopaedic community today is the generation of UHMWPE wear debris causing aseptic loosening and osteolysis in total hip arthroplasties. Consequently, there is a growing interest among researchers in this area to explore the use of alternate bearing surfaces in hip implants (1). The performance of total hip replacements can possibly be improved by using metal-on-metal articulating surfaces as is supported by the clinical findings (2). Proper characterization of the prosthetic implants with metal-on-metal bearing surfaces necessitates appropriate material screening and examination of the wear properties of the material in use (3,4).
Maneuverable NURBS Models Within a Haptic Virtual Environment
Authors: Thompson Thomas V. , Nelson Donald D. , Cohen Elaine , Hollerbach John
Published: March 2022

Haptic rendering should not be limited to immobile polygonal models. This paper presents a system that performs Direct Parametric Tracing (DPT) on maneuverable Non-Uniform Rational B-Splines (NURBS) models without the use of an intermediate representation. The system distributes computation between an advanced CAD modeling system and a microprocessor controller for a Sarcos force-reflecting exo-skeleton arm. Methods ranging from model manipulation to simulation of the dynamics of simple assemblies are discussed. Solutions to synchronicity issues that arise in such a distributed system are also described.
A Ray-Based Haptic Rendering Technique for Displaying Shape and Texture of 3D Objects in Virtual Environments
Authors: Basdogan Cagatay , Ho Chih-Hao , Srinivasan Mandayam A.
Published: March 2022

In this paper, we propose a new ray-based haptic rendering method for displaying 3D objects in virtual environments. We have developed a set of software algorithms that work with a force reflecting haptic interface and enable the user to touch and feel arbitrary 3D polyhedral virtual objects. Using the interface device and the suggested model, the user feels as if exploring the shape and surface details of objects such as textures. The components of the model include a hierarchical database for storing geometrical and material properties of objects, collision detection algorithms, a simple mechanistic model for computing the forces of interaction between the 3D virtual objects and the force-reflecting device, and a haptic filtering technique for simulating surface details of objects such as smoothness and texture. The developed algorithms together with a haptic interface device have several applications in areas such as medicine, education, computer animation, teleoperation, entertainment, and rehabilitation.